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3,854,313 | https://en.wikipedia.org/wiki/Waveguide%20%28optics%29 | An optical waveguide is a physical structure that guides electromagnetic waves in the optical spectrum. Common types of optical waveguides include optical fiber waveguides, transparent dielectric waveguides made of plastic and glass, liquid light guides, and liquid waveguides.
Optical waveguides are used as components in integrated optical circuits or as the transmission medium in local and long-haul optical communication systems. They can also be used in optical head-mounted displays in augmented reality.
Optical waveguides can be classified according to their geometry (planar, strip, or fiber waveguides), mode structure (single-mode, multi-mode), refractive index distribution (step or gradient index), and material (glass, polymer, semiconductor).
Total internal reflection
The basic principles behind optical waveguides can be described using the concepts of geometrical or ray optics, as illustrated in the diagram.
Light passing into a medium with higher refractive index bends toward the normal by the process of refraction (Figure a.). Take, for example, light passing from air into glass. Similarly, light traveling in the opposite direction (from glass into air) takes the same path, bending away from the normal. This is a consequence of time-reversal symmetry. Each ray in air (black) can be mapped to a ray in the glass (blue), as shown in Figure b. There's a one-to-one correspondence. But because of refraction, some of the rays in the glass are left out (red). The remaining rays are trapped in the glass by a process called total internal reflection. They are incident on the glass-air interface at an angle above the critical angle. These extra rays correspond to a higher density of states in more-advanced formulations based on the Green's function.
Using total internal reflection, we can trap and guide the light in a dielectric waveguide (Figure c). The red rays bounce off both the top and bottom surface of the high index medium. They're guided even if the slab curves or bends, so long as it bends slowly. This is the basic principle behind fiber optics in which light is guided along a high index glass core in a lower index glass cladding (Figure d).
Ray optics only gives a rough picture of how waveguides work. Maxwell's equations can be solved by analytical or numerical methods for a full-field description of a dielectric waveguide.
Dielectric slab waveguide
Perhaps the simplest optical waveguide is the dielectric slab waveguide, also called a planar waveguide. Owing to their simplicity, slab waveguides are often used as toy models but also find application in on-chip devices like arrayed waveguide gratings and acousto-optic filters and modulators.
The slab waveguide consists of three layers of materials with different dielectric constants, extending infinitely in the directions parallel to their interfaces. Light is confined in the middle layer by total internal reflection if the refractive index of the middle layer is larger than that of the surrounding layers.
The slab waveguide is essentially a one-dimensional waveguide. It traps light only normal to the dielectric interfaces. For guided modes, the field in domain II in the diagram is propagating and can be treated as a plane wave. The field in domains I and III evanescently decay away from the slab. The plane wave in domain II bounces between the top and bottom interfaces at some angle typically specified by the , the wave vector in the plane of the slab. Guided modes constructively interfere on one complete roundtrip in the slab. At each frequency, one or more modes can be found giving a set of eigenvalues which can be used to construct a band diagram or dispersion relation.
Because guided modes are trapped in the slab, they cannot be excited by light incident on the top or bottom interfaces. Light can be end-fire or butte coupled by injecting it with a lens in the plane of the slab. Alternatively a coupling element may be used to couple light into the waveguide, such as a grating coupler or prism coupler.
There are 2 technologies: diffractive waveguides and reflective waveguides.
Two-dimensional waveguide
Strip waveguide
A strip waveguide is basically a strip of the layer confined between cladding layers. The simplest case is a rectangular waveguide, which is formed when the guiding layer of the slab waveguide is restricted in both transverse directions rather than just one. Rectangular waveguides are used in integrated optical circuits and in laser diodes. They are commonly used as the basis of such optical components as Mach–Zehnder interferometers and wavelength division multiplexers. The cavities of laser diodes are frequently constructed as rectangular optical waveguides. Optical waveguides with rectangular geometry are produced by a variety of means, usually by a planar process.
The field distribution in a rectangular waveguide cannot be solved analytically, however approximate solution methods, such as Marcatili's method, Extended Marcatili's method and Kumar's method, are known.
Rib waveguide
A rib waveguide is a waveguide in which the guiding layer basically consists of the slab with a strip (or several strips) superimposed onto it. Rib waveguides also provide confinement of the wave in two dimensions and near-unity confinement is possible in multi-layer rib structures.
Segmented waveguide and photonic crystal waveguide
Optical waveguides typically maintain a constant cross-section along their direction of propagation. This is for example the case for strip and of rib waveguides. However, waveguides can also have periodic changes in their cross-section while still allowing lossless transmission of light via so-called Bloch modes. Such waveguides are referred to as segmented waveguides (with a 1D patterning along the direction of propagation) or as photonic crystal waveguides (with a 2D or 3D patterning).
Laser-inscribed waveguide
Optical waveguides find their most important application in photonics. Configuring the waveguides in 3D space provides integration between electronic components on a chip and optical fibers. Such waveguides may be designed for a single mode propagation of infrared light at telecommunication wavelengths, and configured to deliver optical signal between input and output locations with very low loss.
One of the methods for constructing such waveguides utilizes photorefractive effect in transparent materials. An increase in the refractive index of a material may be induced by nonlinear absorption of pulsed laser light. In order to maximize the increase of the refractive index, a very short (typically femtosecond) laser pulses are used, and focused with a high NA microscope objective. By translating the focal spot through a bulk transparent material the waveguides can be directly written. A variation of this method uses a low NA microscope objective and translates the focal spot along the beam axis. This improves the overlap between the focused laser beam and the photorefractive material, thus reducing power needed from the laser.
When transparent material is exposed to an unfocused laser beam of sufficient brightness to initiate photorefractive effect, the waveguides may start forming on their own as a result of an accumulated self-focusing. The formation of such waveguides leads to a breakup of the laser beam. Continued exposure results in a buildup of the refractive index towards the centerline of each waveguide, and collapse of the mode field diameter of the propagating light. Such waveguides remain permanently in the glass and can be photographed off-line (see the picture on the right).
Light pipe
Light pipes are tubes or cylinders of solid material used to guide light a short distance. In electronics, plastic light pipes are used to guide light from LEDs on a circuit board to the user interface surface. In buildings, light pipes are used to transfer illumination from outside the building to where it is needed inside.
Optical fiber waveguide
Optical fiber is typically a circular cross-section dielectric waveguide consisting of a dielectric material surrounded by another dielectric material with a lower refractive index. Optical fibers are most commonly made from silica glass, however other glass materials are used for certain applications and plastic optical fiber can be used for short-distance applications.
See also
ARROW waveguide
Cutoff wavelength
Dielectric constant
Digital planar holography
Electromagnetic radiation
Equilibrium mode distribution
Erbium-doped waveguide amplifier
Leaky mode
Lightguide display
Photonic crystal
Photonic-crystal fiber
Prism coupler
Transmission medium
Waveguide (radio frequency)
Waveguide
Zero-mode waveguide
References
13. Yao Zhou, Jufan Zhang, Fengzhou Fang. Design of a dual-focal geometrical waveguide near-eye see-through display. Optics and Laser Technology, 2022, Volume 156, https://doi.org/10.1016/j.optlastec.2022.108546.
14. Yao Zhou, Jufan Zhang, Fengzhou Fang. Design of a large field-of-view two-dimensional geometrical waveguide. Results in Optics, Volume 5, 2021, 100147, https://doi.org/10.1016/j.rio.2021.100147.
External links
AdvR nonlinear waveguides in rubidium-doped potassium titanyl phosphate (KTP)
Optical components
Photonics
pl:Światłowód
ta:அலைநடத்தி | Waveguide (optics) | [
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21,462,430 | https://en.wikipedia.org/wiki/Hydraulic%20splitter | A hydraulic splitter, also known as rock splitter or darda splitter, is a type of portable hydraulic tool. It is used in demolition jobs which involve breaking large blocks of concrete or rocks. Its use in geology was first popularized by volcanologist David Richardson.
Following the darda splitters, the second type hydraulic splitter, known as piston splitter began to be used in large rock demolition sites like tunneling sites or building foundation sites. This type of piston splitter produces much stronger splitting forces than darda splitters. The piston splitter requires a larger hole size diameters (usually 90mm, 95mm, 105mm and rarely 150mm or 200mm) than the darda splitter, which requires holes usually under 50mm. The cylinder diameters of the piston splitters are smaller than the holes by 10~15mm in diameter. Hwacheon HRD-tech introduced this piston splitter in late 1990 for industrial application and improved its minute details in Korea. Many others began to manufacture them as the demand rose.
The darda splitters have been manufactured by a German company, Darda and by many other manufacturers. Large size darda splitters mounted on excavator is manufactured by Yamamoto Rock international and Splitstone.
Splitstone manufactures both portable and larger splitters.
The darda splitters consist of two wedges which are inserted in a pre-drilled hole and a hydraulic cylinder driven by a hydraulic power pack.
The piston splitter consists of one hydraulic power pack and one or more cylinders which has(have) one or multiple pistons on cylinder body and connecting hoses between the power pack and the cylinders.
Piston splitters have been used for demolition of rocks in building foundation, tunnels, shaft digging, trench work, quarrying and zoo areas. Large size piston splitters are mounted on an excavator for more efficient demolition.
The splitting performance is very efficient in comparison with the predrilled hole-making. As the spacing between hole is near to front and side, the number of holes required are quite many. With manual type splitter, the wedge type splitter requires 20~25 cm space, while piston type splitter requires 40~50 cm.
Larger size wedge splitter requires large spacing as much as 50~70 cm. Large size piston splitter requires 60~100 cm spacing . Large size wedge splitter or
piston splitter is mounted on a vehicle like excavator.
More and more strict environmental regulation( noise or vibration, dust, flying rock) increases the demand for hydraulic rock ( or concrete) splitting across the world.
External links
Demolition
Hydraulic tools | Hydraulic splitter | [
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27,717,039 | https://en.wikipedia.org/wiki/LY-293284 | LY-293284 is a research chemical developed by the pharmaceutical company Eli Lilly and used for scientific studies. It acts as a potent and selective 5-HT1A receptor full agonist. It was derived through structural simplification of the ergoline based psychedelic LSD, but is far more selective for 5-HT1A with over 1000× selectivity over other serotonin receptor subtypes and other targets. It has anxiogenic effects in animal studies.
See also
8-OH-DPAT
RDS-127
RU-28306
References
Serotonin receptor agonists
Anxiogenics
Drugs developed by Eli Lilly and Company
Tryptamines
Ketones | LY-293284 | [
"Chemistry"
] | 145 | [
"Ketones",
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27,721,459 | https://en.wikipedia.org/wiki/Centrifugal%20water%E2%80%93oil%20separator | A centrifugal water–oil separator, centrifugal oil–water separator or centrifugal liquid–liquid separator is a device designed to separate oil and water by centrifugation. It generally contains a cylindrical container that rotates inside a larger stationary container. The denser liquid, usually water, accumulates at the periphery of the rotating container and is collected from the side of the device, whereas the less dense liquid, usually oil, accumulates at the rotation axis and is collected from the center.
Centrifugal oil–water separators are used for waste water processing and for cleanup of oil spills on water bodies.
Centrifugal oil–water separators are also used for filtering diesel and lubricating oils by removing waste particles and impurities.
Mechanism
A mix of oil and water is pumped constantly into a cone-shaped separating apparatus at an angle, which creates a spinning vortex. The filtration is a result of the force balance that occurs on fluids in a vortex. High-density liquids will move to the outside, along with any contaminant, displacing the lower-density liquids to the inside (center of rotation). Water, being the more dense liquid, sits on the outside and is removed through a discharge outlet. Any segregated oil can now safely be recovered through a suction orifice at the center. The process will continue to function in this fashion as long as sufficient oil is added to maintain coverage of the suction orifice.
Comparison to other types of separators
There are other types of separators that use gravitational forces to separate mixtures, but these other types of forces are not as strong as the centrifugal force in the centrifugal separator. Other types of separators are coalescing plate pack separators and petrol interceptor separators.
Coalescing plate pack separators work very differently from centrifugal separators. With the plate packs, water is fed into the separator through gravity through the inlet pipe, then the mixture is spread evenly through the separation chamber where the coalescing plate packs are. In the plate packs the oil will rise because of their buoyancy and coalesce on the underside of the plates and form globules of oil that rise to the surface. From there the waste oil globules go into the clean water chamber and are discharged through the lower portion of the separator.
With the interceptors the dirty water mixture enters the first tank of the interceptor where that tanks builds up hydrocarbons and other hazardous material in a layer. Then comes the second and third tanks of the interceptor that are all connected through pipes called "dip pipes" which don't allow the hydrocarbons and other contaminants to pass through. The same process that happened in the first tank will happen in the second and third tanks just with less and less contaminants.
In a centrifugal oil and water separator, the force of gravity is one-thousand times greater that of the coalescing plate pack separator or the petrol interceptor, so the separation is much greater. Not only is the force of separation greater, but there are fewer working parts so maintenance is much easier and cheaper.
More advantages of the centrifugal oil and water separator include compact equipment size, versatility, ease of use, low cost, and high performance.
Disadvantages
Centrifugal oil and water separators do have their disadvantages. One known disadvantage of these separators is that they tend to have low powered suction. For example, when the pump end is dry and the impeller is rotating at high speeds, it is simply not powerful enough to lift the oily water mixture into the separator. For this reason, these separators must always be primed before use.
Design and features
Materials and metals used
The bowl of the separator is generally made up of stainless steel, brass, and bronze. The structural parts are usually where the stainless steel is and the parts on the inside that come into contact with mixtures are either made of bronze or brass depending on the mixture going through the centrifugal separator. The housing and gearbox of the separator is made of aluminum or stainless steel and cast iron. The gearbox in particular is cast iron with stainless steel coating it.
Transmission
The rotation of the separator bowl is usually powered by an electric motor, the power of which is transferred to the bowl by a transmission which may include a clutch, flexible coupling and worm gear or a centrifugal clutch connected to the vertical driving device with a flat belt.
Suction and discharging of the liquids
The suction process of the separator takes place as stationary feed pipe suctions the mixture liquid into the cone-shaped pipe that feeds into the vortex. After the filtration of the liquids occur the unwanted contaminants are discharged either through an overflow or through one or two centripetal pumps. In case of a (combined) clarifier the solids are trapped at the outer edge of the bowl and will be discharged at intervals, except for purifiers in use for very clean liquids which may not have an opening mechanism and need to be cleaned manually.
See also
Centrifuge
References
Centrifuges
Oil spill remediation technologies
Liquid-liquid separation | Centrifugal water–oil separator | [
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27,721,700 | https://en.wikipedia.org/wiki/Industrial%20computed%20tomography | Industrial computed tomography (CT) scanning is any computer-aided tomographic process, usually X-ray computed tomography, that uses irradiation to produce three-dimensional internal and external representations of a scanned object. Industrial CT scanning has been used in many areas of industry for internal inspection of components. Some of the key uses for industrial CT scanning have been flaw detection, failure analysis, metrology, assembly analysis and reverse engineering applications. Just as in medical imaging, industrial imaging includes both nontomographic radiography (industrial radiography) and computed tomographic radiography (computed tomography).
Types of scanners
Line beam scanning is the traditional process of industrial CT scanning. X-rays are produced and the beam is collimated to create a line. The X-ray line beam is then translated across the part and data is collected by the detector. The data is then reconstructed to create a 3-D volume rendering of the part.
In cone beam scanning, the part to be scanned is placed on a rotary table. As the part rotates, the cone of X-rays produce a large number of 2D images that are collected by the detector. The 2D images are then processed to create a 3D volume rendering of the external and internal geometries of the part.
History
Industrial CT scanning technology was introduced in 1972 with the invention of the CT scanner for medical imaging by Godfrey Hounsfield. The invention earned him a Nobel Prize in medicine, which he shared with Allan McLeod Cormack. Many advances in CT scanning have allowed for its use in the industrial field for metrology in addition to the visual inspection primarily used in the medical field (medical CT scan).
Analysis and inspection techniques
Various inspection uses and techniques include part-to-CAD comparisons, part-to-part comparisons, assembly and defect analysis, void analysis, wall thickness analysis, and generation of CAD data. The CAD data can be used for reverse engineering, geometric dimensioning and tolerance analysis, and production part approval.
Assembly
One of the most recognized forms of analysis using CT is for assembly, or visual analysis. CT scanning provides views inside components in their functioning position, without disassembly. Some software programs for industrial CT scanning allow for measurements to be taken from the CT dataset volume rendering. These measurements are useful for determining the clearances between assembled parts or the dimension of an individual feature.
Void, crack and defect detection
Traditionally, determining defects, voids and cracks within an object would require destructive testing. CT scanning can detect internal features and flaws displaying this information in 3D without destroying the part. Industrial CT scanning (3D X-ray) is used to detect flaws inside a part such as porosity, an inclusion, or a crack. It has been also used to detect the origin and propagation of damages in concrete.
Metal casting and moulded plastic components are typically prone to porosity because of cooling processes, transitions between thick and thin walls, and material properties. Void analysis can be used to locate, measure, and analyze voids inside plastic or metal components.
Geometric dimensioning and tolerancing analysis
Traditionally, without destructive testing, full metrology has only been performed on the exterior dimensions of components, such as with a coordinate-measuring machine (CMM) or with a vision system to map exterior surfaces. Internal inspection methods would require using a 2D X-ray of the component or the use of destructive testing. Industrial CT scanning allows for full non-destructive metrology. With unlimited geometrical complexity, 3D printing allows for complex internal features to be created with no impact on cost, such features are not accessible using traditional CMM. The first 3D printed artefact that is optimised for characterisation of form using computed tomography CT
Image-based finite element methods
Image-based finite element method converts the 3D image data from X-ray computed tomography directly into meshes for finite element analysis. Benefits of this method include modelling complex geometries (e.g. composite materials) or accurately modelling "as manufactured" components at the micro-scale.
Trends and Developments
The industrial computed tomography market is forecast to reach a size of USD 773.45 million to USD 1,116.5 million between 2029 and 2030. Regional trends show that strong market growth is expected, particularly in the Asia-Pacific region, but also in North America and Europe, due to strict safety regulations and preventive maintenance of industrial equipment. Growth is being driven primarily by the ongoing development of CT devices and services that enable precise and non-destructive testing of components. Innovations such as the use of artificial intelligence for automated fault analyses and the development of mobile CT systems are expanding the possibilities.
See also
CT scan
Industrial radiography
Cone beam computed tomography, applications in quality control and metrology.
PCB reverse engineering, an application of industrial CT to image printed circuit boards non-destructively.
References
Tomography
Materials science
Microtomography
Microtechnology
Nondestructive testing
Reverse engineering
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27,723,967 | https://en.wikipedia.org/wiki/Tivozanib | Tivozanib, sold under the brand name Fotivda, is a medication used for the treatment of advanced renal cell carcinoma (kidney cancer). It is an oral VEGF receptor tyrosine kinase inhibitor.
The most common side effects include fatigue (tiredness), hypertension (high blood pressure), diarrhea, decreased appetite, nausea, dysphonia (voice changes), hypothyroidism, cough, and stomatitis.
Tivozanib was approved for medical use in the European Union in August 2017, and in the United States in March 2021.
Medical uses
In the United States, tivozanib is indicated for the treatment of adults with relapsed or refractory advanced renal cell carcinoma following two or more prior systemic therapies.
In the European Union, it is indicated for the treatment of adults with advanced renal cell carcinoma; and for the first line treatment of adults with advanced renal cell carcinoma and for adults who are VEGFR and mTOR pathway inhibitor-naïve following disease progression after one prior treatment with cytokine therapy for advanced renal cell carcinoma.
Contraindications
Tivozanib must not be combined with St. John's Wort, an inducer of the liver enzyme CYP3A4. It should not be taken during pregnancy as it is teratogenic, embryotoxic and fetotoxic in rats.
Adverse effects
The most common side effects in studies were hypertension (high blood pressure, in 48% of patients), dysphonia (hoarse voice, 27%), fatigue and diarrhea (both 26%). A hypertensive crisis occurred in 1% of patients.
Interactions
Administration of a single dose of tivozanib with rifampicin, a strong inducer of the enzyme CYP3A4, cuts the biological half-life and total exposure (area under the curve) of tivozanib in half, but has no relevant influence on highest concentrations in the blood. Combination with ketoconazole, a strong CYP3A4 inhibitor, has no relevant effects. The clinical significance of these findings is not known.
Pharmacology
Mechanism of action
A quinoline urea derivative, tivozanib suppresses angiogenesis by being selectively inhibitory against vascular endothelial growth factor (VEGF). It is designed to inhibit all three VEGF receptors.
Pharmacokinetics
After tivozanib is taken by mouth, highest blood serum levels are reached after 2 to 24 hours. The total area under the curve is independent of food intake. When in the bloodstream, over 99% of the substance are bound to plasma proteins, predominantly albumin. Although the enzymes CYP3A4 and CYP1A1 and several UGTs are capable of metabolising the drug, over 90% circulate in unchanged form. The metabolites are demethylation, hydroxylation and N-oxidation products and glucuronides.
The biological half-life is 4.5 to 5.1 days; 79% being excreted via the feces, mostly unchanged, and 12% via the urine, completely unchanged.
Chemistry
Tivozanib is used in form of the hydrochloride monohydrate, which is a white to light brown powder. It is practically insoluble in water and has low solubility in aqueous acids, ethanol and methanol. It is not hygroscopic and not optically active.
History
It was discovered at Kyowa Kirin and developed by Aveo Pharmaceuticals.
The US Food and Drug Administration (FDA) approved tivozanib based on evidence from one clinical trial of 350 adult participants with advanced kidney cancer (renal cell carcinoma) that had been treated with two or more prior medicines and has come back or did not respond to treatment. The trial compared participants who were randomly assigned to receive either tivozanib or sorafenib. Both the participants and the health care providers knew which treatment was being given. The treatment continued until the disease progression or the side effects became too toxic. The trial compared the length of time participants were alive without progression between the two groups. The trial was conducted at 120 of sites in 12 of countries in North America and Europe. The number of participants representing efficacy findings may differ from the number of patients representing safety findings due to different pools of study participants analyzed for efficacy and safety.
Clinical trials
Phase III results on advanced renal cell carcinoma suggested a 30% or 3 months improvement in median progression-free survival compared to sorafenib but showed an inferior overall survival rate of the experimental arm versus the control arm. The Food and Drug Administration's Oncologic Drugs Advisory Committee voted in May 2013 13 to 1 against recommending approval of tivozanib for renal cell carcinoma. The committee felt the drug failed to show a favorable risk-benefit ratio and questioned the equipose of the trial design, which allowed control arm patients who used sorafenib to transition to tivozanib following progression disease but not those on the experimental arm using tivozanib to transition to sorafenib. The application was formally rejected by the FDA in June 2013, saying that approval would require additional clinical studies.
In 2016, Aveo Oncology announced the start of a second Phase III clinical study in third line advanced RCC patients.
Society and culture
Legal status
In August 2017, the European Commission approved tivozanib for medical use in the European Union.
References
External links
Angiogenesis inhibitors
Cancer treatments
Isoxazoles
Phenol ethers
Quinolines
Receptor tyrosine kinase inhibitors
Ureas
Chloroarenes | Tivozanib | [
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27,724,442 | https://en.wikipedia.org/wiki/Aurecon | Aurecon Group Pty Ltd is an Australian engineering, management, design, planning, project management, consulting and advisory company based in Docklands, Victoria, with operations in Australia, New Zealand and Southeast Asia.
History
Formed through the merger of three engineering consultancies, Africon, Connell Wagner and Ninham Shand. Aurecon has over 6,500 staff members. The company operates in 28 countries across Africa, Asia-Pacific and the Middle East.
Africon was formed in 1935. The original business, Van Wyk en Louw Consulting, grew as one of the 'top 5' engineering consulting firms under apartheid, winning lucrative government contracts including management of 'townships' before changing its name to Africon during South Africa's transformation to democracy. At the time of the merger, Africon was ranked amongst the world’s top 200 international design firms and was South Africa’s largest engineering company. The organisation operated in both the public and private sectors within the fields of transportation, property, municipal services, energy and mining.
Connell Wagner was one of Asia Pacific’s largest multi-disciplinary engineering consultancies, with a history spanning more than 75 years. The firm provided a broad range of professional technical services across several market sectors, namely buildings, industrial, transportation, urban development, water, international development, environment, energy, telecommunications and defence.
Established in 1935, Ninham Shand was one of South Africa’s leading, privately owned companies of consulting engineers and environmental scientists. The organisation offered consulting services in areas including water resources and supply, heavy engineering, purification, infrastructure services, structures and buildings, transportation and roads, and environmental science.
In October 2019, Aurecon decided to demerge its African business.
References
External links
Aurecon Official Website
Australian companies established in 2009
Construction and civil engineering companies of Australia
Construction and civil engineering companies established in 2009
International engineering consulting firms
Engineering consulting firms of Australia | Aurecon | [
"Engineering"
] | 394 | [
"Engineering consulting firms",
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27,725,921 | https://en.wikipedia.org/wiki/Weather%20of%202009 | Global weather activity of 2009 profiles the major worldwide storms, including blizzards, tornadoes, ice storms, tropical cyclones and other meteorogical events, from January 1, 2009, to December 31, 2009. Wintery storms are events in which the dominant varieties of precipitation are forms that only occur at cold temperatures, such as snow or sleet, or a rainstorm where ground temperatures are cold enough to allow ice to form (i.e. freezing rain). It may be marked by strong wind, thunder and lightning (a thunderstorm), heavy precipitation, such as ice (ice storm), or wind transporting some substance through the atmosphere (as in a dust storm, snowstorm, hailstorm, etc.). Summer storms including flooding, severe thunderstorms and extratropical cyclones (which can occur in summer or winter) are also included in this list to a certain extent.
As this occurred a heat wave and/or unforeseen monsoon weather also hit parts of Australia in 2009 and 2010. Victoria, the scene of horrific bushfires the year before, had a far colder summer, with hot weather arriving more than a month later than usual in 2009. August 17 saw a dust storm at Laguna Mar Chiquita as a major drought hit Argentina, and flooding and hailstorms hit southeastern Australia and Queensland in March 2010. The lack of winter precipitation in parts of China, however, contributed to a severe drought in the southwest. Bolivia, Venezuela, Mali, Mauritania, Morocco and Spain have also seen periods of drought in 2009 and 2010. On between May 12 and 26, both Mauritania, the Sénégal River Area and neighbouring parts of both Senegal and Mali faced both a drought and famine in 2010.
A storm (from Proto-Germanic *sturmaz "noise, tumult") is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather.
Storms are created when a centre of low pressure develops, with a system of high pressure surrounding it. This combination of opposing forces can create winds and result in the formation of storm clouds, such as the cumulonimbus. Small, localized areas of low pressure can form from hot air rising off hot ground, resulting in smaller meteorological disturbances such as dust devils and whirlwinds.
January
December 30, 2008—January 1, 2009
An Alberta clipper affected regions around the Great Lakes, Midwestern United States and Northeastern United States. The storm strengthened over the Atlantic, and in turn the Northeastern United States saw about 10–20 cm of snow as compared to the 7-10 cm of snow in the Greater Toronto Area. The Atlantic provinces were in a Blizzard for New Year's Day, with 49 cm recorded in Charlottetown, Prince Edward Island, and 25 cm in Halifax, Nova Scotia. Blizzard warnings and storm surge warnings were posted as winds were sustained more than , out of the North. Newfoundland and Labrador saw about 15–25 cm of snow, with blowing snow. Another 15–20 cm fell through the province, and 5-15 cm of heavy snowfall occurred in and around Vancouver.
Amounts of 5–15 cm of heavy wet snow fell in Metro Vancouver and the surrounding Fraser Valley.
January 2–4
January 2 saw a blizzard hit the Swiss–Liechtenstein border, killing an Italian tourist, when his car skidded into a tree due to black ice on the nearby road.
Yet another winter storm developed and brought about 10–25 cm across Alberta, Saskatchewan and through the Northern Great Plains. 10–20 cm also fell through Northern Ontario, with freezing rain, ice pellets (sleet) and rain to the south. Northeastern United States can expect ice and snow, with rain down south. Traveling will not be easy.
On the west coast, Vancouver and the surrounding Fraser Valley got 5–20 cm of wet snow, with heavier accumulation towards in the interior of British Columbia, about 10–20 cm of dryer, more powdery snow.
January 5–7
A major winter storm is developing near the Gulf. It is slowly moving north, and it will be a complex of two lows. Toronto, Ontario, recorded about 13 cm. Niagara region saw snow mixing with ice pellets and Freezing rain. Eastern Ontario and Southern Quebec saw amounts of 15–30 cm. Similar amounts fell in New England. The Atlantic provinces saw snow to start then mixing, and rain was reported in some areas.
Snow continued in Metro Vancouver with accumulations of 2–15 cm of heavy wet snow.
Metro Vancouver and the Fraser Valley were stuck with continuing snow from the 1st-5th with accumulations for those 5 days anywhere from 15 to 30 cm of heavy wet snow pile up. As the temperatures rose (up to 10 °C), heavy rains came to the area starting on the 6th. Rain amounts on the 6th and the 7th were anywhere from 30 to even 150 mm on Western Vancouver Island, the north shore of Vancouver, and sections of the Fraser Valley. In the city of Chilliwack in the Fraser Valley a very deep snow cover, mostly sub-freezing temperatures since December 13, 2008, warm temperatures and heavy rain created flooding concerns for residents living near or on the edge of the Fraser River.
January 8
Four died on January 8 during a heavy blizzard in the Indian state of Jammu and Kashmir and the North West Frontier.
January 9–11
A storm brought 5–15 cm across the Canadian Prairies and through the Great Plains. Midwest U.S. and Southwestern Ontario could see amounts of 5–25 cm. Many areas are reporting heavy amounts of snowfall.
On the west coast, up to 120 mm could fall in some areas, as a low pressure area comes in. These latest storms have caused flooding in many areas. Due to excessive snow melt courtesy from the large amounts produced by the December Snowstorms with the Pineapple Express storm along with heavy rain fall lead to epic flooding. More than 18 rivers went beyond Major Flood stage and a couple went over Record Stage. These floods led the closure of I-5 in Centralia when the Chehalis and Skookumchuck Rivers overflowed. This was the second time in two consecutive years when that Section of I-5 was closed due to flooding.
January 17–19
A major winter storm swept across the Great Lakes region and the U.S. Northeast. Areas of Toronto recorded between 15 and 25 cm, with 10 cm in Windsor, Ontario, & higher amounts towards the Lakes. Some areas reported more than 20 cm of accumulation. This same storm affected Northeastern United States with 10–30 cm, and the Atlantic provinces of Canada. Some areas have reported freezing rain and ice pellets, and even rain mixing in. U.S. Southeast saw mostly rain.
January 25–30
On January 21, heavy rain cause worst floods in 40 years in Brunei Darussalam. Heavy rains started late on Tuesday in the oil-rich capital of Bandar Seri Begawan, causing flash floods and landslides, interrupting power supply and shutting some telephone lines. About 145.8 millimetres of rainfall was recorded during the 24-hour period from 8 am Tuesday to 8 am Wednesday, according to the weather department, which expects more rain in the coming days but not as heavy as on Tuesday. Two casualties were reported.
In late January 2009, severe winter storm developed over the Midwest, after having already brought more than an inch of ice to many areas in the United States. The system moved eastward across the Midwest into the Northeast. Many places expected a major ice storm, and areas to the north expected significant snowfall accumulations. Over 2 million people were without power throughout the Midwest and Northeastern United States. About 500,000 people in Kentucky were left without electricity. Ice reached8 cm thick in some areas. The storm caused 23 deaths, with 6 deaths in Texas. Regions of Southern Ontario received between 5–20 cm, with 20–30 cm in Eastern Ontario and Southern Quebec. Similar amounts fell in the Atlantic Provinces, with some rain/snow mixing in at times, as some areas got above the 0 C (32 F) mark.
On the January 27, up to 10 cm of heavy wet snow fell in Eastern Metro Vancouver, the surrounding Fraser Valley in British Columbia, and Kitsap Country in Washington. At this point, the winter of 2008-2009 was one of the snowiest in years for Southwestern British Columbia and the pacific northwest as winter storm after winter storm pounded the region from mid-December through to early January. Some locations received up to 125 cm of snow during that period and snowcover for Vancouver exceeded 60 cm at one point in late December pointing to flood concerns on the then ice-jammed Fraser river.
February
February 1–2
A warm, moist Mediterranean cyclone began to move (unusually?) northwards over France, against a cold continental high pressure ridge, causing the cyclone to discharge its moisture as snow over large areas of western Europe. The system was vigorous enough to produce a winter-time tornado in Málaga.
On February 1 and 2, heavy snow fell overnight across large parts of the United Kingdom, causing widespread disruption to transport and education. London received its heaviest snowfalls in 18 years. Many roads, including the M25 London Orbital motorway, were blocked in the morning rush hour, whilst train services are disrupted and many airport runways closed. Transport for London suspended all London Buses and the London Underground was severely disrupted. Hundreds of schools were forced to close.
Temperatures fell below seasonal averages with Chesham, Buckinghamshire recording -10 degrees Celsius at night.
Airports were affected included London's Heathrow and Gatwick airports. Charles de Gaulle Airport and Orly Airport were affected.
Spain, Germany, Portugal and Ireland were also affected. In Ireland, snowstorms disrupted road and rail transport, including the M50 and M1. Dublin Airport and Cork Airport were severely disrupted, as were ferry services in the Irish Sea throughout February 2.
Ireland was affected in a similar way to the UK. In the Republic, the South and East were the worst affected. Due to black ice, driving was very treacherous, with ice and snow blocking many major routes such as the M1 and M50. Dublin Airport and Cork Airport were seriously affected, with many flights to Britain and Europe delayed and cancelled. The major rail routes across Ireland were closed down, as a result of bad ice and snow. Temperatures across Ireland fell below average everywhere, with temperatures of -8 and -9 degrees Celsius recorded in places.
The snow was a result of wind blowing across from West Siberia, and reacted with the low pressure system approaching across from the Atlantic. This created unusually large amounts of snow, which fell across England, Wales and Eastern Ireland. This weather type is rare in Ireland, and is normally confined to small amounts; however, the total amount of snowfall in this storm was the highest since 1981.
A winter storm developing over the Gulf states and through the Gulf of Mexico, is bringing widespread Heavy Rain to the South Eastern States of the US. Up to 100 mm is possible in some areas. Coastal areas of North Eastern United States can expect snowfall of up to in some areas, local amounts may be higher. Atlantic Canada will see strong winds and snowfall amounts of .
A small weather system carrying snow that developed in North France reached South East England and the Midlands which brought of snow in some parts of Gloucestershire. Further snow came in from the south and east throughout the week. The worst places affected was the Forest of Dean and The Cotswolds. On 6 February a few small towns in Devon reported around of lying snow (Okehampton). The Severn Bridge, the main link between England and Wales closed due to falling ice for the first time. Some 321 schools in Buckinghamshire, 300 schools in Gloucestershire and 307 schools in Wales also closed on the 6th.
February 6–12
About 3,000 people were killed as a storm complex paced over Haiti on the 6th
A winter storm from the Atlantic reached southern Britain and the Midlands on 9–10 causing heavy rain and flooding. Across the midlands and further north, it was cold enough for it to fall as snow. Coupled with the strong winds, it made blizzard conditions. The Met office issued an extreme winter storm warning for many counties in Great Britain. Meanwhile, a temperature of was recorded in the Scottish Highlands — the coldest UK temperature since 2003. Smaller outbreaks of snow occurred across parts of the north and east of England on 12–13 February.
A major storm developing over Texas is affecting many communities in North America. Areas like Oklahoma City were hit hard with heavy rain, hail and a tornado in western Oklahoma City. There have been numerous spottings of funnel clouds. Heavy rain continues through Texas and Kansas, which will extend into Missouri, Arkansas and Louisiana. Areas of Michigan, Illinois and SW Ontario could see pop-up thunderstorms, but likely not as severe. Northern Ontario will see mostly an ice-rain event. While areas to the South could see .
February 16–20
A major storm affected Newfoundland with strong winds gusting to 100 km/h in some areas. Bitterly cold conditions, strong winds and heavy snowfall caused a blizzard through parts of Newfoundland. Some areas of Newfoundland received between 20 and 40 cm. Local areas and local drifts were locally higher.
A winter storm that developed over Colorado brought messy weather across the Great plains, Midwest U.S., the Great Lakes and Northeast United States. Some areas had a messy mix of snow, ice and rain. Toronto had seen about 10 cm. South Western Ontario saw between 1–10 cm. Northern Areas of Ontario and Quebec received between 10 and 25 cm. Eastern Ontario received between 10 and 20 cm. The northeast saw local amounts of over 15 cm. From Midwestern sections of the U.S. to the Southern Lakes messy mix was reported with rain at times. Southern United States saw heavy amounts of rainfall, Thunderstorms and Tornado warnings were issued in some areas.
The Atlantic provinces are seeing heavy snowfall and some mixed precipitation. Areas could exceed 10 cm. Newfoundland could get more heavy snowfall.
February 21–23
An Alberta clipper, which picked up moisture from the Gulf, dumped about 5–20 cm across the Midwest, and the Great lakes area. Areas like Windsor saw close to 15 cm, Toronto saw about 5–12 cm. Eastern Ontario and Southern Quebec could see slightly higher amounts as a coastal low develops, and gives heavier snow. Northeastern United States are seeing snow, mix precipitation and rainfall. The heavier snowfall is towards New England and Maine.
Atlantic Canada is seeing blizzard like conditions. 15–40 cm is possible is some areas. Winter storm warnings and snowfall warnings are in place.
March
March 1–4
A major winter storm which brought up to 16" of snow to parts of West Tennessee and Arkansas and up to 7" of snow to parts of Georgia (including the Atlanta area), Alabama (including Birmingham) and Mississippi gathered strength and moved northeastward, in the process crossing the Washington, D.C. metropolitan area before impacting the greater New York and greater Philadelphia areas. The storm was a large, widespread storm, with snow totals exceeding across most of the tri-state area. as well as 3–7 inches north of Rockland County, as well as scattered amounts of 17–20 inches in New Jersey and Pennsylvania.
On March 1 to 2 a heavy dust storm hits N.E. China and parts of Mongolia. It then parses over the Bohai Sea and the Yellow Sea, finally dispersing over North Korea and South Korea in the 4th
March 7
On the 7th, heavy rain induced floods killed 52 in Bolivia, 19 in Peru, and 16 in Ecuador, said news reports.
March 9
A quick late winter storm caused about 5–15 cm of snow in Metro Vancouver, British Columbia, Canada with cold wind chills as low as -10 °C and with sustained winds at about 20 km/h.
March 13
Snow storm strands 2 busses, 53 cars and 83 people on the Ust-Kamenogorsk-Georgiyevka highway in Kazakhstan on March 13.
March 22
Heavy snow and ice hits the Sea of Okhotsk, Sakhalin Island and Primorsky Krai in Russia far east on March 22.
March 26–28
A major blizzard hit Denver and other counties around the area on Thursday, March 26. Parts of the Front Range saw of snow and schools around Denver were closed early. Denver International Airport canceled more than 400 planes departing and arriving. On Friday, March 27, the storm impacted Kansas, northwestern Oklahoma, and the Texas Panhandle, with 12 to of snow and blizzard conditions. Some areas around Pratt County, Kansas and Kiowa County, Kansas received 28" of Snowfall. Snow Drifts reached high in Dalhart, Texas. On Friday night and into Saturday, March 28, the storm system impacted the Kansas City area and northern parts of Missouri, before moving into the Quad Cities area, Northern Illinois and Southern Wisconsin on Saturday night. Numerous areas here saw between 4 and 8" of snow. Waukegan, Illinois, saw around half a foot from this late-season winter blast.
April
April 12–13
A late major winter storm coming from New England was expected to hit the Maritime Provinces on Easter. 15–30 cm of snow was expected in most areas, and Halifax and southern areas were expected to see heavy rain.
June
June 2
Another 15 people and 10,000 head of cattle had died by this date in Mongolia. Snow also fell on Russia's Sakhalin island.
June 6
Heavy rain and storm with twister in Czech Republic
July
July 1
Heavy rain falls in parts of Ukraine.
July 11
July 11 saw heavy storms flood the Chinese city of Shuzou, in Jiangsu Province.
July 17
On July 17, flooding caused by heavy rain and hailstorms hit Nanaimo village, and its environs as bad weather sweeps over most of Mongolia, killing 24 people as it did so.
July 24
On July 24, the Dakar Rally stage in Mauritania due to heavy sandstorms and high winds.
August
August 5–6
August 5 and 6 saw the Maritime affairs department in Hainan province issued an emergency tropical storm warning to 20,000 fishing vessels in the South China Sea as Typhoons Morakot and Goni, approached China's Guangdong Province. Heavy storms hit the cities of Guangzhou,
Zhuhai and Haikou. More than 953,000 residents and more than 35,000 boats were evacuated back to shore in the eastern and southeastern provinces of the People's Republic of China as Typhoons Morakot approached A fishing boat capsized with nine fishermen missing. 3 people died in the China and 462 died in Taiwan.
August 4–10
Blizzards in southern Brazil, reached 1,000,000 people, closing roads. Maximum accumulation of snow and a minimum temperature of .
August 21–28
A stream of moisture that emerged from the Gulf of California brought rain to Southern California. A flash flood warning was issued for Central and Eastern San Diego County as a result of the rain. Later on, the system moved north and started to move towards the east coast on Sunday, August 23. The remaining thunderstorms lingered around in Central and Eastern San Diego County until Friday, August 28 before finally moving towards the east coast.
September
September 2–8
A heavy and rainy cyclone hit the Bering Sea, Choris Peninsula and parts of the Aleutian Islands on September 2. A heavy storm hit parts of the Beaufort Sea and parts of the Chukchi Sea on September 4.
Heavy rain and floods on the 4th also lead to both cars were under water and bales of wheat are floating down the swollen river past Mr A.J. Duncan's farms at Muirden Farm, Turriff, Aberdeenshire. Both Oxbridge and Publican spring barley planting was at risk if the flood waters did not clear quickly.
On the 8th unusually heavy rain hit Argentina, and storms hit Argentina, Brazil and Uruguay, killing 14 or 15 people (reports varied). Tornados his Argentina to. A town official in Santa Rosa, Paulo Alvez appealed for help for both the town of Santa Rosa and El Progreso.
Arkansas witnessed heavy flooding on the 7th and 8th.
October
October 1–5
A heavy and snowy cyclone hit the Kedrovaya River in Primorsky Krai and parts of the Aleutian Islands on October 1.
A heavy and rainy cyclone hit the Bering Sea and parts of the Chukchi Sea on October 3. 21 people were confirmed dead following rainstorms and landslides in Sicily. A fishing boat was damaged at sea off the coast of Sicily. Austria saw heavy flooding, with lesser levels in the Czech Republic, Poland, Slovenia, Slovakia, Romania, Moldova and southern parts of Ukraine. Two Ukrainians and a Moldovan died in the storm.
5 days of unusually heavy rain left 205 dead, 125 injured and 750,000 homeless in southern India by October the 5th. Indian and Sri Lankan medical teams managed to save many lives across Tamil Nadu and Kerala states.
October 7–20
Late on October 11, the disorganized remnants of Super Typhoon Melor were absorbed by another low-pressure system just north of it, similar to how Typhoon Kujira's remnants were absorbed by another extratropical system. The extratropical cyclone rapidly intensified as it neared the Pacific Northwest. Several wind and flood watches/warnings were issued on October 17 in advance for the expected arrival of the winter storm. A high wave advisory was issued for the entire western seaboard. Just before midnight of October 18, the powerful winter storm struck California with gale-force winds and torrential rainfall. In Northern California, the rainfall was seemingly endless. The San Francisco Bay area suffered the most damage, from high waves and reported gusts of . A rare storm warning was posted for San Francisco Bay and subsequently, wind gusts were clocked at on Angel Island. While the main system remained offshore, the storm's moisture split into two new systems over the Western United States, which rapidly moved eastward across the US, bringing strong winds and heavy rain. On December 20, after looping back north into the Gulf of Alaska, the storm complex was absorbed by another stronger extratropical cyclone approaching from the west. The damage that the storm complex caused is currently estimated at $1.18 million (2009 USD).
Heavy snow fell in parts of Pennsylvania between October 15 and 16. State College, Pennsylvania saw of wet snow, causing a very memorable Penn State homecoming game, and breaking numerous records, such as earliest recorded snowfall, most severe October snowstorm, and most snow in the month of October. Moderate snow fell between October 15 and 18 in the Northeastern United States, as far as the suburbs of New York City, with light snow being reported in the city itself. Boston suburbs saw moderate, wet snow fall on the morning of October 16, in spots accumulating up to . The area was then hit on October 18, when in the afternoon, heavy rain turned to heavy snow and almost white-out conditions. The ground was too warm for any significant accumulation, but up to were reported at spots between Boston and Lowell. All of the snow melted by October 20.
October 12–13
On 12 October 2009, Just over 200 herdsmen and 1,000 heads of livestock had been stranded by heavy snowfalls in Ali prefecture. The week-long snowfall had accumulated to about 30 centimetres in Pulan County in Ali, with some areas reaching as much as 1 meter depth, according to Xing Xiuyin, head of an armed police detachment stationed in the Tibetan region. 30 soldiers and two snow-clearing machines were sent on the way to Ali, according to Xing Xiuyin.
Thousands of people were trapped as heavy snow fell in Tibet's Lhunze County, but rescue services managed to minimize the casualties and damage to homes. The rescue services also managed to provide shelter and emergency fodder for 200 head of cattle. By October 13, snow was reported by Chinese authorities to be falling in both Qinghai and Heilongjiang Provinces.
October 15–16
On 15 October 2009, Germany, Austria and Poland were hit by heavy snowstorms. One person died after falling in a Tyrolian lake by accident.
27,000 lightning strikes and heavy rainstorms hit parts of Spain in just over 12 hours on 16 October.
On October 16 the cold weather in Poland kills 4 people and the Czech power company CEZ Group declared a state of emergency in 8 regions due to the widespread reports of fallen power lines. The town of Jablonec nad Nisou was mostly blacked out by a power outage. Heavy snow was reported in Poland, the Czech Republic, Slovakia, Liechtenstein and the Austrian province of Styria.
October 29–30
Between October 29 and 30 a very powerful winter storm battered the west coast of the US, although it did not affect Southern California. It was very windy in the places that it hit, but the storm only stayed there for two days. The storm left and traveled towards the east coast after that day. The only affect the storm had on Southern California was bringing a cloudy day with very cold temperatures.
October 31
Heavy snowfall hit Russia's Primorsky Territory on October 31, as the cold windstorm moved from the Sea of Okhotsk to the coast of the Kamchatka Peninsula, bringing heavy snow and rain to the region that meteorologists expected to last another 24 hours. They also warned that temperatures would fall by up to 15 degrees and that weather conditions could make traveling difficult as snowfall in the Vladivostok area had already significantly impeded travel by larger vehicles. The city administration's official Yevgeny Kolpinets told the Russian news agency Itar-Tass that the inclement weather had stopped bus traffic in the city, but luckily no energy supply service problems had been reported. Weather forecasters expected more cyclone-generated snow fall over the next few days.
November
November 3–18
On November 3, the Harbin Snow Festival in Harbin, Heilongjiang, China, experienced unusually heavy snow.
The festival was first started in 1985 and had never before seen such heavy snowfall. Harbin is China's tenth-largest city with a population of about 4,500,000, so planned electricity rationing would hit this usually busy city hard, as would the planned rationing in Beijing. The worst snowstorms in Northeastern China since 1949 claimed 40 lives, destroyed thousands of buildings and destroyed almost of winter crops, according to the Civil Affairs Ministry. The snowfall was the heaviest in the provinces of Hebei, Shanxi, Shaanxi, Shandong and Henan since the founding of the People's Republic of China in 1949.
On November 4, Tropical Storm Ida hits Nicaragua and later the Gulf of Mexico. The Lower Mississippi River Forecast Center puts out a flood alert on the Mississippi River By November the 7th, a storm waning was also out in Pinar del Río, in western Cuba, as it headed out of Central America and in to southern Mexico. Winds of were forecast for Yucatán Peninsula and Yucatán Channel. Heavy rain was reported in parts of Haiti. A rainfall of 3 to is predicted by local authorities and the Lower Mississippi River Forecast Center for both the Yucatán Peninsula and western Cuba. By the 10th, it had virtually died out and was only a bad storm in New Orleans and Pensacola. 35-45 M.P.H. winds and heavy rain battered the rest of Florida‘s Gulf Coast and Alabama's Dauphin Island. The remnants of the storm then caused some more snow to fall in the southern parts the Great Plains on region the 11th and 12th.
On November 10, heavy rain and intermittent snow hit the Cheviot Hills, Pennines, Dee Valley in Wales and The Wash. Light snow fell in the Grampian Mountains and Aberdeenshire. Passing sleet was also recorded in Lincolnshire on the 10th. A flood watch was put on the River Tay and the River Dee. Minor surface flooding had already occurred in parts of Lincolnshire and Cumbria after the previous two days flooding.
11 November 2009, saw snow and/or rain storms menacing Hungary, Iceland, India's part of the Himalayas (rain and snow), parts of Indonesia (rain only), north western Iran, northern Iraq, Mount Fuji in Japan and in Armenia. Yet more snow storms hit the People's Republic of China, disrupting traffic across the northeastern provinces, Beijing and Tibet on November the 10th and 11th. Most of Bulgaria's poor drainage systems and second-rate storm drains failed during the day's heavy rain and windstorms. Snow was also present in most of the mountain regions.
Heavy snowfall in China caused school building collapses and the deaths of 38 people on the 18th.
November 10–13
Floods on the 10th and 11th killed 8 in Brazil's Rio Grande do Sul, according to the state's Civil Defence Department. 4 others were killed in Argentina and Uruguay. 22,000 people were evacuated in each nation as heavy rain made the rivers between Uruguay and Argentina to overflow its banks.
November 11 – December 30
After a rather snowy November 11, Iceland's weather became rather unusual. From November 12 to December 30, Iceland's abnormally warm and dry November weather gave way and December became very snowy with the town of Akureyri receiving 35 cm of snow over the night of December 1–2. Snow fell and blizzards occurred intermittently throughout a windy December.
On December 12, heavy snow hit Dimmuborgir, Iceland.
November 14
A blizzard and about half a foot of snow fell on the 1,040 m high Peak Chekhov, near Yuzhno, Sakhalin Island, on November 14, 2009.
November 18–25
Many properties were flooded in Ambleside on November 18, leaving the main road impassible for most vehicles. Over 200 people in Cockermouth were rescued from their homes by the emergency services.
On the Isle of Man, there were brief power cuts on the 18th, in Ballaragh and Laxey but Manx Electricity restored power to all affected properties by the afternoon.
On the 20th, all services on the West Coast Main Line were still temporarily suspended after a landslip between Carlisle and Penrith. The West Coast Main Line was flooded between Carlisle and Carstairs and was closed as a result. Services were reduced between Edinburgh and Glasgow and also Edinburgh and Dunblane.
In Workington, the collapse of Northside Bridge carrying the A597 road and the condemnation of Calva Bridge carrying the A596 resulted in a journey from Northside to the town centre. Network Rail are constructed a temporary railway station, Workington North, to help Northside residents get into and out of town. The 170 members of the Royal Engineers from 170 (Infrastructure Support Unit) installed a temporary footbridge upstream of Calva Bridge, which opened as scheduled, on 5 December 2009.
As a result of the loss of all road and footbridges in Workington on November 19, it was announced that a new railway station, Workington North, would be built on wasteland leased for two years from Allerdale Council. The station was scheduled to open by 28 November with services provided by Northern Rail. Workington North opened on 30 November 2009.
The government pledged £1,000,000 to the reconstruction of the shattered town, but deemed any new (permanent) road or a (temporary) rail bridge unnecessary and only allowed the army engineers to build a temporary foot bridge at state expense to begin with. Northern Rail, Network Rail and a local contractor all helped in the building of Workington North station. The Department for Transport announced that it would fund the service until 31 December 2009, at a cost of £216,000. All trains between Workington, Workington North, Flimby and Maryport would be free of charge until 31 December 2009.
Heavy sandstorms hit Mauritania on Nov 22.
County Fermanagh was hit by heavy rain on November the 23rd. Many roads were flooded or hit by landslides. The B36 Dernawilt Road between Enniskillen and Killyfole was one of many that were affected by the storm. Both Lough Erne and the Colebrooke River were put on flood alert.
A mini-tornado tore through Maypole Lane in the Derbyshire village of Littleover the next day, November 24. Derbyshire Fire and Rescue Service reported moderate damage in the Village
on the 24th. A small waterspout was reported off the coast of Aberdeenshire.
25 November saw fierce winds rattling Dublin Airport and parts of the east coast of Ireland, leading to the diversion of ten aircraft—seven aircraft to Shannon Airport and three aircraft to Manchester Airport. Some of the affected aircraft were transatlantic flights from destinations such as Chicago and New York.
November 21 – December 3
Early on November 21 the Joint Typhoon Warning Center (JTWC) reported that an area of convection had persisted within a monsoon trough about to the southeast of Guam.
The typhoon later weakened to a category four, before re-strengthening to a category five on November 27, remaining quasi-stationary for more than two days. It weakened to a tropical depression on December 2, after sending bursts of moisture into the jet stream. The storm dissipated on December 3.
November 25–30
On November 25, a cold extratropical cyclone tracked into Russia's Primorsky Territory from the Yellow Sea. Weather forecasters correctly predicted snow, gale-force wind and temperatures between 0 and −2 °C, with one night's temperature drop reaching −25°С. Over the next week the daytime temperature was predicted to be between 2°С to -10°С, with a nighttime temperature between −24 and −25 °C. The wind speed was expected to be between 0 and . Both ice and avalanche warnings were issued for a week (to December 2) as heavy snow was predicted for both Primorsky Krai and Amur Krai, but significantly less than expected actually occurred over the week and the storm finally cleared up on 30 November, rather than on December 2.
A powerful storm (probably the earlier one from Primorsky Krai) stalled in the Gulf of Alaska on November 25. On the 26th, its wind field produced high tides on the western seaboard. The storm weakened significantly on the 27th and moved towards Southern California, bringing heavy rainfall starting early in the morning and causing strong winds. The storm left Southern California and moved on to batter the east coast during the afternoon of Sunday, November 29, 2009. A heavy and snowy cyclone hit the Aleutian Islands on November 30.
By November 27 heavy rain was moving over the Irish Sea is set to give some heavy rain then turning to snow over parts of the Peak District, with altitudes above , dropping over of snow in some places. This is the usual snowfall for parts of Scotland, including the West Highlands and the East Highlands.
In the U.K., Cumbria's Workington North Temporary Station was officially opened on 30 November 2009.
On the 30th more than 100 people died as heavy rain flood Jeddah, Saudi Arabia. The poorly designed and built local infrastructure and mismanagement of city works construction have been blamed, as well as the effects of Global Warming.
December
December 1–2
On December 1 and 2 heavy rain fell in the British Isles, and into the night, the rain band hit the cold air and turned to snow giving about on some hilltops and mountains across Scotland.
On 2 December, thousands of acres of Irish farmland remained underwater, floodwaters were still rising in some County Galway villages and roads in County Clare and Galway were still impassable. Floods were still in situ across the UK and both bus and train services were disrupted in Essex, Cumbria and Pembrokeshire. The River Severn and River Derwent were put on flood watch by the Environment Agency.
December 3, 2009 – January 1, 2010
Toronto, Ontario, Canada was hit by both a cold front and two extreme cold weather warnings between December 3 and January 1. A strong arctic cold front moved through Alberta from the northwest, bringing from of snowfall. Winds gusted to , causing whiteout and blizzard conditions across most of Alberta. The southern half of the province got the worst of the storm. The winds blew the snow into massive drifts and snow banks up to in height. Numerous communities in Calgary were completely snowed in for three days, from December 5 to 7. Numerous cars and trucks were abandoned, with many of them buried up to their roofs in snow.
December 4–7
Between December 4–7 a heavy snow storm hit Calgary and disrupted travel in general Canada.
December 6–14
The December 2009 North American snowstorms were a meteorological event in North America that started on December 11. The snowstorms brought record amounts of snow to the Midwest and contributed to deaths of 16 people. The storms affected a number of US states, including Arizona, Wisconsin and New York, as well as Canada. Although the initial storm had virtually subsided by December 11, further snow was expected to fall.
A weak disturbance that started overnight on December 6 stalled over the western United States and intensified rapidly. Heavy downpours began early in the morning of December 7 and continued non-stop until the evening, triggering flash-flood watches. The storm dropped as much as of rain in Cuyamaca, San Diego, causing blackouts in some locations. This storm was followed by a small semi-tropical winter storm which started overnight on December 10 and then stalled over Southern California and intensified, causing heavy downpours. In addition to of rain, this storm gave pea-sized-hail and gusty winds before weakening and moving away from Southern California on December 13.
Heavy snow hit Wisconsin, New York, Washington, D.C., and parts of Maryland on the 10th and 14th. Heavy rain hit parts of Arizona on the 11th.
In Vancouver, BC a strong winter storm deposited anywhere from 10 to 30 cm of heavy snow from the night of the 12th through to the morning of the 15th after a frigid arctic air that had been over the region for days with as low as -15 °C temperatures met with moist Pacific air.
December 8–16
Light snow began to fall in the Grampian Mountains on December 8. On the 8th more heavy snow showers followed on the 18th. Heavy overnight snow caused widespread disruption across England in the South East, East Anglia, the East Midlands and Yorkshire and the Humber. East Winds brought further snowfalls in the northern half of the UK.
Overnight, five Eurostar trains were stuck in the Channel Tunnel, trapping 2,000 people for 16 hours after electrical failures due to cold temperatures. Many schools in England were closed on the 9th. During the December 2009 European snowfall, four Eurostar trains broke down inside the Channel Tunnel, after leaving France, and one in Kent on 18 December. Although the trains had been winterised, the systems had not coped with the conditions. Over 2,000 passengers were stuck inside failed trains inside the tunnel, and over 75,000 had their services disrupted. All Eurostar services were cancelled from Saturday 19 December to Monday 21 December 2009. An independent review, published on 12 February 2010, was critical of the contingency plans in place for assisting passengers stranded by the delays, calling them "insufficient".
The cold weather began in earnest on December 10, with temperatures in Braemar, Aberdeenshire reaching a low of −4.9 °C on the 10th, −7 °C on the 11th, and −8.9 °C on the 12th. This was the beginning of the "Big Freeze". Between December 11 and 16, cold air from the north and east brought subzero temperatures to many northern parts of the UK and the southern county of Oxfordshire, along with dense fog.
December 14–21
A major blizzard killed 11 people in Romania between December 14 and 21.
Wintery showers of rain, sleet, and heavy snow affected East and South-East parts of the United Kingdom. On 18 December, heavy snowfall caused widespread disruption and travel chaos across large parts of Lancashire, South East England, East Anglia, the East Midlands and Yorkshire and the Humber, forcing schools to close early for the upcoming Christmas holiday and cutting power supplies in some areas. The heaviest snowfall in 20 years also caused temperatures to fall as low as in the Scottish Highlands.
More heavy snow showers followed on December 18. Heavy overnight snow caused widespread disruption across England in the South East, East Anglia, the East Midlands, Yorkshire, and the Humber. Five Eurostar trains were stuck in the Channel Tunnel after electrical failures due to cold temperatures, trapping 2,000 people for up to 16 hours. Many schools in England were closed on December 18.
Heavy snowfall and sub-zero temperatures killed at least 290 people across Europe. Temperatures fell to as low as in Germany, suspending and cancelling flights and stranding thousands of Christmas passengers. As many as 40% of flights from Paris's two airports, Orly and Charles de Gaulle, were cancelled. Berlin Tegel Airport, Amsterdam's Schiphol Airport, and Frankfurt International Airport were forced to close due to ice on the runway.
Heavy snow fell in both the Russian territories of Krasnodar Krai and in the Russian Far East on December the 18th. The Far Eastern storm had heavy snow flurries occurred across the Sea of Okhotsk, Cape Lopatka, Avacha Bay, Petropavlovsk-Kamchatsky, Volcanoes of Kamchatka, which a UNESCO World Heritage Site in the Kamchatka Peninsula's Central Range Mountains on December the 18th.
On December 20, 3 people froze to death in Steiermark, Austria, while blizzards hit S.W. Norway. December 21 and 22 saw 20 cm of snow fall in Moscow and nearby towns Temperatures of as low as −20 °C killed 47 people in Poland on December 20. In northern Italy, some locations recorded the lowest temperature since 1985, with one low reaching . Finland, the UK, Belgium, and the Netherlands also recorded record low temperatures.
In the United Kingdom, many major motorways, including the M25, M4, M40 and M1, were brought to a standstill due to snow drifts, cold, and ice, leaving many towns gridlocked. The UK's Highways Agency tried to grit the M11 and M1, only to have a gritter van skid off the M11 and into a deep snow drift. Some people were able to travel from London Victoria Station to Ashford International railway station courtesy of a steam train hauled by Tornado. Widespread transport disruption to roads, railways, buses, and airports affected much of England, Wales, Scotland and Northern Ireland.
In Zagreb, Croatia, around 50 passengers were injured when a train travelling from Sisak to Zagreb failed to stop due to black ice on the rails and hit a buffer at the city's main railway station. One person suffered life-threatening injuries, while some 40 others required medical attention. A homeless man froze to death in southern Kosovo during a localized snowstorm. In Bosnia and Herzegovina, 3 people were found dead from hypothermia in Sarajevo and Teslić.
December 16–19
A powerful nor'easter brought blizzard conditions to the northeastern and mid-atlantic United States, as well as Nova Scotia in Canada on 16 December. Washington, D.C., received nearly two feet (over 60 cm) of snow, setting a city record for December snowfall. New York City and southern New England were forecast to receive over a foot of snow. The snow covered most of New England, disrupting travel in New York and Pennsylvania as local record low temperatures are recorded as snow falls in Florida on the 17th. Seven people were killed as a result of the storm.
19 December 2009 also saw a meeting of both meteorological , provincial and governmental officials from across Eastern Siberia and the neighbouring provinces of Northeast China on how to cope with any future severe storms in southern Sakhalin Island and Heilongjiang Province. 8 people had died on the island by this date
December 20–22
On December 20, nearly a foot and a half of snow fell in parts of Buncombe County and around other parts of North Carolina, with the highest amounts seen north and east of Transylvania County. This was the most snow seen in the region since 1996. Two feet of snow was recorded on Mt. Mitchell. National Guard units were mobilized to help stranded drivers and clear roads. Red Cross and National Guard shelters were opened in Buncombe, Madison and McDowell counties to accommodate travellers stranded by miles-long backups on the congested and debris-strewn I-40 and I-26. Hundreds of trees and limbs fell under the weight of the snow, blocking roads and leaving tens of thousands without power or phones. On December 22, blizzard conditions also struck Washington, D.C. Snow fall would be widely spread across the north eastern USA and most of the Eastern Seaboard.
On December 20 snow near the city of Hanover caused miles-long traffic jams on the Autobahn.
There had been road 50 accidents reported on the stretch of Autobahn, which only has 5-6 accident a day in normal weather. The trains running between Warsaw and Poznań were delayed by at least an hour due to snow drifts on the tracks and fallen power lines. The Polish Meteorological Institute predicted the weather would not change for the next few days and temperatures would stay at -10C for the next couple of days. Poland, northern Germany, Scandinavia, Lithuania and Hungary would all see at least some heavy snow in places that day. Light snow was reported in most parts on continental Europe and the UK by the 22nd. Twenty-three football matches and two horse races were called off in the UK.
December 21, 2009—January 3, 2010
In Mongolia, heavy December snowstorms killed 2,000 cattle and 2 people. The worst of the snowstorms occurred between December 21 and January 3.
December 21–22
On December 21 blizzards disrupted New England, south western Ukraine, Düsseldorf, Frankfurt, Bosnia, Serbia, Paris, the Netherlands and London.
On December 22, a blanket of heavy snow fell upon large parts of Japan and South Korea, causing the deaths of 10 Japanese and 3 South Korean people. Snow was piled up to 184 cm high in parts of Niigata. Up to 650,000 homes and businesses lost electricity, and local trains were also halted by the power outage. In Fukui, two nuclear power plants automatically shut down due to technical problems caused by the unusually heavy snowfalls. South Korea deployed several thousand troops to clear highways and remove snow from the roofs of weak buildings after up to a metre of snow had fallen over the past two weeks. Although the storm certainly affected North Korea as well, no reports are available.
Also on the 22nd, snowstorms hit Leicestershire and Warsaw. At the same time, a Winter storm hit Moscow, Saint Petersburg, and parts of Tannu Tuva, while a Siberian cyclone started up over Yakutia and headed for Khabarovsk Krai.
December 22–28
Starting on December 22, a large winter storm began moving across the Great Plains and Midwest. It claimed 21 lives, canceled hundreds of flights and knocked out power across most of West Virginia. The storm stalled and spun around itself for a few days before continuing northeast. Many parts of the Great Plains experienced heavy snowfall, while places further north such as Chicago and Ottawa received freezing rain. As the snow and rain subsided on the 27th, it left record rainfalls in Texas to the Upper Midwest. The storm dumped of snow in Grand Forks, North Dakota, and near Norfolk, Nebraska. In the East, higher temperatures and rains have started melting and washing away last week's record-setting snowfalls, threatening the region with flooding. The National Weather Service also of flooding in parts of the South and Midwest, and winter weather advisories were in effect in sections of Nebraska, Illinois, Indiana and Michigan through the Sunday. A man drowned after slipping into the Kennebec River, near Moosehead Lake in Maine. Over of snow fell in South Dakota. Several inches of snow also fell in the Las Vegas Valley, Nevada. In southern Ontario, snowsqualls fed into a cold front behind the main low pressure center of the storm to produce a rapid drop in temperatures on December 28.
An outbreak of 28 tornadoes also occurred in the Southeastern United States. One EF3 tornado caused major damage in Lufkin, Texas, injuring two people.
December 23, 2009—January 1, 2010
December 23 to 26 saw heavy snow hit both Primorsky (Primorye) Krai, Khabarovsk Krai, Sakhalin Oblast and Kamchatka Krai. The weekend saw a migratory cyclone bringing a warm spell and snowstorms reaching Primorsky on the Friday. Heavy snow badly disrupted life in Vladivostok in December as sleet and gale-force wind occurred on Primorsky Krai's south coast. Over two days, temperatures rose from -4 °C up to -2 °C. On the night of December 26 the strengthening cyclone began drifting to the southern coast of Primorsky and over Sakhalin Krai. Snow also fell in Amur Oblast. President Vladimir Putin visited Vladivostok on the 25th.
Heavy snowfall also began in Saint Petersburg, Russia. By December 26, the city was under 35 cm of snow, creating the most December snowfall seen in the city since 1881. A snowstorm also occurred in parts of the Barents Sea.
On December 30, an emergency warning about the passage of another powerful cyclone was issued to all the territories and population centres along Russia's Pacific Coast. The gales, heavy snowfall, blizzards and a sharp fall in air temperatures hit the Sea of Okhotsk and the surrounding territories of Primorsky Krai, Sakhalin Oblast, Khabarovsk Krai and Magadan Oblast. The Far Eastern territorial centre of the federal Ministry for Emergency Situations and Civil Defence (E.M.E.R.C.O.M.) warned that the cyclone would produce snow banks, icy conditions on roads, as well as snow bringing down phone and power transmission lines in Primorsky territory. The temperatures reckoned to have fallen near the expected −7 °C. The temperature was that which usually occurs in a Siberian cyclone, when it reaches the Russian Far East. Forecasters said there was a strong possibility of heavy snowfall and blizzards along the eastern districts of the Khabarovsk Krai, in parts of the Sakhalin Island and on the southern Kuril Islands December 31 and January 1.
The last week of 2009 saw an Arctic storm bearing down on Sakhalin Island, and local officials told people not to drive their cars outside any city limits and banned the rather dangerous practice of ice fishing, due to the purported death of a Nivkh fisherman, until the storm had passed. Nonetheless, dozens of cars were buried in snow and in one village, rescuers dug out 56 cars, freeing 74 passengers and giving aid to those who were haplessly trapped. People in cars that remained stuck were being provided with both water, bread and fuel via snowmobile. The towns of Korsakov and Poronaysk were worst hit, and parts of the local taiga forests of fir and birch had been entirely up-rooted and buried by the blizzard conditions.
December 25–30
About 60% of the Italian city of Venice was flooded by a heavy rainstorm on December the 25th.
Parts of England again suffered repeated power cuts, and Scotland experienced fresh snowfall overnight on 26–27 December with the worst affected area being Perthshire, where between fell.
Temperatures dropped to in parts of the Highlands overnight on 28–29 December, with Braemar recording Britain's lowest temperature of the winter. Fresh travel warnings were issued on 29 December as the wintry conditions continued to cause problems on Scotland's roads.
The runway of Inverness Airport was briefly closed because of snow and ice, and First ScotRail reduced services to and from Glasgow Central because of the severe conditions.
The snow and icy conditions were good for the Scottish ski industry, which said the weather helped it to experience its best start to the season for several years.
Warnings of heavy snow were issued for Wales, the Midlands, north-west England, eastern and southern England, and Yorkshire and Humber. More snow began falling across parts of Wales and central and northern England on the evening of 29 December, with Wales recording the heaviest of the snow showers where some rural areas were cut off by of up to . Snow was also reported in parts of the West Midlands region and Yorkshire.
In Italy, December 30 saw hundreds of homes in Tuscany evacuated because of flooding and Spain's rescue services were on yellow danger alert after flash floods destroyed roads and landslides swept railways away. Transport Links between Almeria, Granada, Málaga and Sevilla were severed. Drought-blighted Andalusia has had its fifth day of rain, and Portugal was on orange flood alert. Authorities said the rain had destroyed millions of Euros worth of agricultural produce. The harbours were closed and the Madeira archipelago islands were also under threat of both flooding and gale-force winds, as 110 km/h whipped up six-metre -high waves.
December 28, 2009—January 3, 2010
At least two of the Russian Far East storms stacked up over the Gulf of Alaska during December 28. Various weather forecasts suggested that one would spread valley rain and mountain snow across Northern California and drop up to half an inch of rain across the northern Sacramento Valley over the next few days. The National Weather Service issued a Winter Weather Advisory warning for the Mount Shasta area, where forecasters expected 1 to of snow in town and up to above . The second cold front, and its related storm, would bring more rain and high country snow to the north state by New Year's Eve or New Year's Day.
The blizzards began on New Year's Eve, and lasted until January 3. The worst of the blizzards occurred on December 31, when an avalanche derailed a diesel locomotive fitted with a railway snowplough off its railway tracks. The storm continued through 1 January, when three workers sent to repair the damage were swept away by the howling blizzard that was ripping through Sakhalin Island according to the RIA Novosti news service. One worker was found alive and rescue teams retrieved the body of a second Sunday morning. The situation worsened to the point that 140 soldiers were ordered to help dig the train out from beneath of snow. A local man, Andrei Sukhonosov, trying to return home to the city of Tomari was on the buried train.
Authorities and rescue services in Sakhalin Oblast were put on alert, and warned of a high risk of avalanches on the island's numerous hills and mountains. Another avalanche warning was issued on the 2nd, for Sakhalin Island, due to hazardous levels of snowfall during yet another Siberian snow cyclone and blizzard, emergency officials said. The authorities in Primorsky and Khabarovsk Krai were also put on alert, just in case things got ant worse. The last two Russian Far Eastern storms dissipated in the Gulf of Alaska on January 5 and 6 respectively.
December 29–31
Following the deadly 2009 North American Christmas winter storm, a medium-sized nor'easter formed in Texas and brought moderate snow to the western portion of the state on December 29. In anticipation of the event Texas Governor Rick Perry activated his resources ahead of the winter storm. It then moved through the Southeast and brought heavy rain and freezing rain to higher altitudes. Some snow was reported in Clayton, Georgia, but did not accumulate. It then moved quickly up the East Coast of the United States, bringing freezing rain and sleet to the Mid-Atlantic and moderate to heavy snow to the Tri-State Area (New York, New Jersey, Connecticut). at the most was reported in White Plains in Hartford. It then brought about to Boston and southeastern New England. Overnight January 1, it strengthened explosively over water and looped back around to create a blizzard in northern New England. Up to was on the ground in Lubec, Maine, by Sunday, and on Saturday it moved to southern New England. fell in Lexington, Massachusetts, making that the most fallen in southern New England in the season. Boston received . The storm moved into the Labrador Sea by Sunday afternoon, leaving behind a pattern where multiple storms within the broader low undergo cyclogenesis to track north of Newfoundland.
Sportscotland Avalanche Information Service (SAIS) issued warnings about conditions on Scottish mountains on December 30. However, three people died in three large avalanches. Two climbers were killed as a result of an avalanche on Ben Nevis, while a man was airlifted from Liathach, a mountain in Torridon, after getting into trouble, and died in hospital.
Continued icy weather in Scotland on New Year's Eve led to the cancellation of Hogmanay celebrations in Inverness amid concerns over public safety. New Year celebrations in other parts of Scotland went ahead as planned. North-east Scotland experienced fresh snowfall during the afternoon and evening of 31 December. For a second time that week Inverness Airport was closed forcing several hundred passengers to make alternative arrangements. In Batley, West Yorkshire of water leaked into the local gas network, leaving 400 homes in Dewsbury and Batley without gas during sub-zero temperatures. The final homes were reconnected on 7 January.
December 31 to January 5 saw heavy flooding in southern Spain and heavy snow in northern Spain.
Fatalities
The death toll finally stood at:
Political impact
Much of the snowstorm activity coincided with Copenhagen Summit of December 2009 as well as the Climatic Research Unit email controversy one month prior. The unusual weather patterns that year (particularly in the Southern United States) provided an opportunity to promote or question the theory of global warming, and led to an increasing use of the phrase "climate change" as opposed to "global warming."
Gallery
See also
Winter storm
Winter of 2009–10 in Europe
2009 West Africa floods
2013–14 North American winter
Global storm activity of 2008
Global storm activity of 2010
Winter storms of 2009–10 in East Asia
2010 Northern Hemisphere heat waves
Global storm activity of 2008
Winter of 1946–47 in the United Kingdom
Winter of 1962–63 in the United Kingdom
February 2009 Great Britain and Ireland snowfall
Winter of 1990–91 in Western Europe
Cyclogenesis
Jet stream
Arctic oscillation
North Atlantic oscillation
Pacific–North American teleconnection pattern
El Niño–Southern Oscillation
Gulf Stream
European windstorm
Global storm activity of 2007
Global storm activity of 2006
References
2009 meteorology
2009 natural disasters
Weather events
Power outages
Blizzards
Ice storms
Weather by year | Weather of 2009 | [
"Physics"
] | 11,940 | [
"Weather",
"Physical phenomena",
"Weather by year"
] |
27,725,953 | https://en.wikipedia.org/wiki/Johnson%20Matthey%20Technology%20Review | Johnson Matthey Technology Review, known as Platinum Metals Review before 2014, is a quarterly, open access, peer-reviewed scientific journal publishing reports on scientific research on the platinum group metals and related industrial developments.
History
The journal was established in 1957 under the name Platinum Metals Review and was published by Johnson Matthey and Co., with the support of the Rustenburg Platinum Mines. This was done in the hopes of increasing the availability of information on the properties of Platinum and to link both academic and industrial research with "the aims of finding practical solutions to the material problems of modern technology (McDonald/Hunt)". From the July 2004 issue onward, it was published in electronic format only. In 2014 the journal was relaunched as Johnson Matthey Technology Review.
Aims and scope
The journal included reviews of research, books, and academic conferences, as well as primary results in the form of brief reports. It also reviewed what it considered to be notable aspects of patents and relevant scientific literature. Occasionally articles on the history, geological occurrences, and exploitation of platinum group metals were also published.
While between 2016 and October 2022 the journals content was published as CC BY-NC-ND 4.0, the journal is now published under CC-BY 4.0 from January 2023 onward, in accordance with the definition of open access given by the Budapest Open Access Initiative.
Abstracting and indexing
Currently, Johnson Matthey Technology Review was abstracted and indexed by:
Chemical Abstracts Service
CAS SciFinder
Web of Science
Science Citation Index Expanded
Journal Citation Reports
ProQuest Current Contents
ProQuest SciSearch
SciTech Premium Collection
Technology Research Database
Scopus
CNKI
EBSCO
While it was still known as Platinum Metals Review, it was abstracted and indexed by:
Chemical Abstracts Service
Chemical Engineering and Biotechnology Abstracts
Compendex
Corrosion Abstracts
Current Contents/Physical, Chemical & Earth Sciences
Environment Abstracts
Metals Abstracts/METADEX
Metal Finishing Abstracts
Science Citation Index Expanded
Scopus
World Textile Abstracts
References
External links
Materials science journals
Academic journals established in 1957
Quarterly journals
English-language journals
journals
Chemistry journals
Geology journals
Engineering journals
Metallurgical processes | Johnson Matthey Technology Review | [
"Chemistry",
"Materials_science",
"Engineering"
] | 422 | [
"Metallurgical processes",
"Materials science journals",
"Metallurgy",
"Materials science"
] |
33,074,786 | https://en.wikipedia.org/wiki/Nuclear%20spectroscopy | Nuclear spectroscopy is a superordinate concept of methods that uses properties of a nucleus to probe material properties. By emission or absorption of radiation from the nucleus information of the local structure is obtained, as an interaction of an atom with its closest neighbours. Or a radiation spectrum of the nucleus is detected. Most methods base on hyperfine interactions, which are the interaction of the nucleus with its interaction of its atom's electrons and their interaction with the nearest neighbor atoms as well as external fields. Nuclear spectroscopy is mainly applied to solids and liquids, rarely in gases. Its methods are important tools in condensed matter physics, solid state chemistry., and analysis of chemical composition (analytical chemistry).
Methods
In nuclear physics these methods are used to study properties of the nucleus itself.
Methods for studies of the nucleus:
Gamma spectroscopy
Hypernuclear spectroscopy
Methods for condensed matter studies:
Nuclear magnetic resonance (NMR)
Mössbauer spectroscopy
Perturbed angular correlation (PAC, TDPAC, PAC spectroscopy)
Muon spin spectroscopy
Nuclear orientation
Channeling
Nuclear reaction analysis
Nuclear quadrupole resonance (NQR)
Methods for trace element analysis:
Neutron activation analysis (NAA)
Associated particle imaging (API)
References
Spectroscopy
Scientific techniques | Nuclear spectroscopy | [
"Physics",
"Chemistry",
"Astronomy"
] | 243 | [
"Spectroscopy stubs",
"Molecular physics",
"Spectrum (physical sciences)",
"Instrumental analysis",
"Astronomy stubs",
"Molecular physics stubs",
"Spectroscopy",
"Physical chemistry stubs"
] |
33,075,099 | https://en.wikipedia.org/wiki/Boiler%20design | Boiler design is the process of designing boilers used for various purposes. The main function of a boiler is to heat water to generate steam. Steam produced in a boiler can be used for a variety of purposes including space heating, sterilisation, drying, humidification and power generation. The temperature or condition of steam required for these applications is different, so boiler designs vary accordingly.
Modern design benefits
Modern boiler design offers several benefits. In the past, improper design of boilers has caused explosions which led to loss of life and property. Modern designs attempt to avoid such mishaps. Further, mathematical modeling can determine how much space a boiler will need and the type of materials to be used. When the design specifications of a boiler are determined, design engineers can estimate a cost and time schedule for the construction.
Boiler design may be based upon:
Production of a maximum quantity of steam with minimal fuel consumption
Economic feasibility of installation
Minimal operator attention required during operation
Capability for quick starting
Conformity to safety regulations
Quality of raw water : how hard or soft the water is will determine the material of the boiler.
Heat source - the fuel to be burned and its ash properties or the process material from which the heat is to be recovered.
Capacity/steam output required, usually measured in tonnes per hour or kg/s.
Steam condition - pressure, temperature, etc.
Safety considerations
Mechanical constraints
Cost restrictions
Monetary cost
Tensile strength of material must be considered while using any joining processes.
Accessories and mountings are devices which form an integral part of boiler but are not mounted on it. They include economizers, superheaters, feed pumps and air pre-heaters. Accessories help in controlling and running the boiler efficiently. Certain common mountings (specifically those required by the Indian Boiler Act) include:
Feed check valve - regulates the flow of water into the boiler and prevents the back flow of water in case of failure of the feed pump.
Steam stop valve - regulates the flow of steam that is produced in the boiler to the steam pipe, and may also be used to stop the supply of steam from the boiler
Fusible plug - placed at the lowest level of water and above the combustion chamber, its function is to extinguish the fire as soon as the water level in the shell of the boiler falls below a certain marked level.
Blow-off cock - removes water from the shell at regular intervals to remove the various impurities that may be settled at the bottom of the shell.
Safety valves - automatically prevent the steam pressure from exceeding safe levels
Water-level indicators - indicate the level of water in the shell.
References
Bibliography
Malek, Mohammad A. (2005.) "Power boiler design, inspection, and repair: ASME code simplified." McGraw-Hill. ISBN
Stromeyer, C.E. (1893.) "Marine boiler management and construction." Longmans, Green, and Co.
Outdoor wood-fired boiler
Boilers
Design | Boiler design | [
"Chemistry",
"Engineering"
] | 590 | [
"Boilers",
"Design",
"Pressure vessels"
] |
33,077,295 | https://en.wikipedia.org/wiki/Almgren%20regularity%20theorem | In geometric measure theory, a field of mathematics, the Almgren regularity theorem, proved by , states that the singular set of a mass-minimizing surface has codimension at least 2. Almgren's proof of this was 955 pages long. Within the proof many new ideas are introduced, such as monotonicity of a frequency function and the use of a center manifold to perform a more intricate blow-up procedure.
A streamlined and more accessible proof of Almgren's regularity theorem, following the same ideas as Almgren, was given by Camillo De Lellis and Emanuele Spadaro in a series of three papers.
References
Theorems in measure theory
Theorems in geometry | Almgren regularity theorem | [
"Mathematics"
] | 150 | [
"Theorems in mathematical analysis",
"Mathematical analysis",
"Theorems in measure theory",
"Mathematical analysis stubs",
"Geometry",
"Theorems in geometry",
"Mathematical problems",
"Mathematical theorems"
] |
33,082,485 | https://en.wikipedia.org/wiki/Suspension%20%28dynamical%20systems%29 | Suspension is a construction passing from a map to a flow. Namely, let be a metric space, be a continuous map and be a function (roof function or ceiling function) bounded away from 0. Consider the quotient space:
The suspension of with roof function is the semiflow induced by the time translation .
If , then the quotient space is also called the mapping torus of .
References
Dynamical systems | Suspension (dynamical systems) | [
"Physics",
"Mathematics"
] | 86 | [
"Mechanics",
"Dynamical systems"
] |
926,601 | https://en.wikipedia.org/wiki/Cinnamic%20acid | Cinnamic acid is an organic compound with the formula C6H5-CH=CH-COOH. It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents. Classified as an unsaturated carboxylic acid, it occurs naturally in a number of plants. It exists as both a cis and a trans isomer, although the latter is more common.
Occurrence and production
Biosynthesis
Cinnamic acid is a central intermediate in the biosynthesis of a myriad of natural products including lignols (precursors to lignin and lignocellulose), flavonoids, isoflavonoids, coumarins, aurones, stilbenes, catechin, and phenylpropanoids. Its biosynthesis involves the action of the enzyme phenylalanine ammonia-lyase (PAL) on phenylalanine.
Natural occurrence
It is obtained from oil of cinnamon, or from balsams such as storax. It is also found in shea butter. Cinnamic acid has a honey-like odor; and its more volatile ethyl ester, ethyl cinnamate, is a flavor component in the essential oil of cinnamon, in which related cinnamaldehyde is the major constituent. It is also found in wood from many diverse tree species.
Synthesis
Cinnamic acid was first synthesized by the base-catalysed condensation of acetyl chloride and benzaldehyde, followed by hydrolysis of the acid chloride product. In 1890, Rainer Ludwig Claisen described the synthesis of ethyl cinnamate via the reaction of ethyl acetate with benzaldehyde in the presence of sodium as base. Another way of preparing cinnamic acid is by the Knoevenagel condensation reaction. The reactants for this are benzaldehyde and malonic acid in the presence of a weak base, followed by acid-catalyzed decarboxylation. It can also be prepared by oxidation of cinnamaldehyde, condensation of benzal chloride and sodium acetate (followed by acid hydrolysis), and the Perkin reaction. The oldest commercially used route to cinnamic acid involves the Perkin reaction, which is given in the following scheme
Metabolism
Cinnamic acid, obtained from autoxidation of cinnamaldehyde, is metabolized into sodium benzoate in the liver.
Uses
Cinnamic acid is used in flavorings, synthetic indigo, and certain pharmaceuticals. A major use is as a precursor to produce methyl cinnamate, ethyl cinnamate, and benzyl cinnamate for the perfume industry. Cinnamic acid is a precursor to the sweetener aspartame via enzyme-catalysed amination with phenylalanine. Cinnamic acid can dimerize in non-polar solvents resulting in different linear free energy relationships.
References
Flavors
Enoic acids
Phenylpropanoids | Cinnamic acid | [
"Chemistry"
] | 630 | [
"Biomolecules by chemical classification",
"Phenylpropanoids"
] |
926,641 | https://en.wikipedia.org/wiki/Centrifuge%20Accommodations%20Module | The Centrifuge Accommodations Module (CAM) is a cancelled element of the International Space Station (ISS). Although the module was planned to contain several parts, the centrifuge still was considered the most important capability of the module.
History
The centrifuge would have provided controlled acceleration rates (artificial gravity) for experiments and the capability to:
Expose a variety of biological specimens that are less than tall to artificial gravity levels between 0.01g and 2g.
Simultaneously provide two different artificial gravity levels.
Provide partial g and hyper g environment for specimens to investigate altered gravity effects and g-thresholds.
Provide short duration and partial g and hyper g environment for specimens to investigate temporal effects of gravity exposure.
Provide Earth simulation environment on ISS to isolate microgravity effects on specimens.
Provide Earth simulation environment on ISS to allow specimens to recover from microgravity effects.
Provide in situ 1g controls for specimens in micro-gravity.
It was built by JAXA's predecessor, NASDA, but owned by NASA, who obtained ownership of the CAM by trading in a free launch of the Japanese Experiment Module Kibo to the ISS. The CAM flight model along with the engineering model of the centrifuge rotor were manufactured. The CAM would have been attached to the zenith port on the Harmony module of the ISS.
It was cancelled in 2005 alongside the Habitation Module and the Crew Return Vehicle, because of ISS cost overruns and scheduling problems in Space Shuttle assembly flights.
It is now on display in an outdoor exhibit at the Tsukuba Space Center in Japan.
See also
Artificial gravity
Space adaptation syndrome
Space colonization
Nautilus-X#ISS centrifuge demonstration
References
External
Centrifuge, Japan Aerospace Exploration Agency (JAXA)
Centrifuges
Cancelled spacecraft
Components of the International Space Station | Centrifuge Accommodations Module | [
"Chemistry",
"Engineering"
] | 367 | [
"Chemical equipment",
"Centrifugation",
"Centrifuges"
] |
927,421 | https://en.wikipedia.org/wiki/Molecular%20lesion | A molecular lesion or point lesion is damage to the structure of a biological molecule such as DNA, RNA, or protein. This damage may result in the reduction or absence of normal function, and in rare cases the gain of a new function. Lesions in DNA may consist of breaks or other changes in chemical structure of the helix, ultimately preventing transcription. Meanwhile, lesions in proteins consist of both broken bonds and improper folding of the amino acid chain. While many nucleic acid lesions are general across DNA and RNA, some are specific to one, such as thymine dimers being found exclusively in DNA. Several cellular repair mechanisms exist, ranging from global to specific, in order to prevent lasting damage resulting from lesions.
Causes
There are two broad causes of nucleic acid lesions, endogenous and exogenous factors. Endogenous factors, or endogeny, refer to the resulting conditions that develop within an organism. This is in contrast with exogenous factors which originate from outside the organism. DNA and RNA lesions caused by endogenous factors generally occur more frequently than damage caused by exogenous ones.
Endogenous Factors
Endogenous sources of specific DNA damage include pathways like hydrolysis, oxidation, alkylation, mismatch of DNA bases, depurination, depyrimidination, double-strand breaks (DSS), and cytosine deamination. DNA lesions can also naturally occur from the release of specific compounds such as reactive oxygen species (ROS), reactive nitrogen species (RNS), reactive carbonyl species (RCS), lipid peroxidation products, adducts, and alkylating agents through metabolic processes. ROS is one of the major endogenous sources of DNA damage and the most studied oxidative DNA adduct is 8-oxo-dG. Other adducts known to form are etheno-, propano-, and malondialdehyde-derived DNA adducts. The aldehydes formed from lipid peroxidation also pose another threat to DNA. Proteins such as "damage-up" proteins (DDPs) can promote endogenous DNA lesions by either increasing the amount of reactive oxygen by transmembrane transporters, losing chromosomes by replisome binding, and stalling replication by transcription factors. For RNA lesions specifically, the most abundant types of endogenous damage include oxidation, alkylation, and chlorination. Phagocytic cells produce radical species that include hypochlorous acid (HOCl), nitric oxide (NO•), and peroxynitrite (ONOO−) to fight infections, and many cell types use nitric oxide as a signaling molecule. However, these radical species can also cause the pathways that form RNA lesions.
Exogenous Factors
Ultraviolet Radiation
UV light, specifically non-ionizing shorter-wavelength radiation such as UVC and UVB, causes direct DNA damage by initiating a synthesis reaction between two thymine molecules. The resulting dimer is very stable. Although they can be removed through excision repairs, when UV damage is extensive, the entire DNA molecule breaks down and the cell dies. If the damage is not too extensive, precancerous or cancerous cells are created from healthy cells.
Chemotherapy drugs
Chemotherapeutics, by design, induce DNA damage and are targeted towards rapidly dividing cancer cells. However, these drugs can not tell the difference between sick and healthy cells, resulting in the damage of normal cells.
Alkylating agents
Alkylating agents are a type of chemotherapeutic drug which keeps the cell from undergoing mitosis by damaging its DNA. They work in all phases of the cell cycle. The use of alkylating agents may result in leukemia due to them being able to target the cells of the bone marrow.
Cancer causing agents
Carcinogens are known to cause a number of DNA lesions, such as single-strand breaks, double- strand breaks, and covalently bound chemical DNA adducts. Tobacco products are one of the most prevalent cancer-causing agents of today. Other DNA damaging, cancer-causing agents include asbestos, which can cause damage through physical interaction with DNA or by indirectly setting off a reactive oxygen species, excessive nickel exposure, which can repress the DNA damage-repair pathways, aflatoxins, which are found in food, and many more.
Lesions of Nucleic Acids
Oxidative lesions
Oxidative lesions are an umbrella category of lesions caused by reactive oxygen species (ROS), reactive nitrogen species (RNS), other byproducts of cellular metabolism, and exogenous factors such as ionizing or ultraviolet radiation. Byproducts of oxidative respiration are the main source of reactive species which cause a background level of oxidative lesions in the cell. DNA and RNA are both affected by this, and it has been found that RNA oxidative lesions are more abundant in humans compared to DNA. This may be due to cytoplasmic RNA having closer proximity to the electron transport chain. Known oxidative lesions characterized in DNA and RNA are many in number, as oxidized products are unstable and may resolve quickly. The hydroxyl radical and singlet oxygen are common reactive oxygen species responsible for these lesions. 8-oxo-guanine (8-oxoG) is the most abundant and well characterized oxidative lesion, found in both RNA and DNA. Accumulation of 8-oxoG may cause dire damage within the mitochondria and is thought to be a key player in the aging process. RNA oxidation has direct consequences in the production of proteins. mRNA affected by oxidative lesions is still recognized by ribosome, but the ribosome will undergo stalling and dysfunction. This results in proteins having either decreased expression or truncation, leading to aggregation and general dysfunction.
Structural rearrangements
Depurination is caused by hydrolysis and results in loss of the purine base of a nucleic acid. DNA is more prone to this, as the transition state in the depurination reaction has much greater energy in RNA.
Tautomerization is a chemical reaction that is primarily relevant in the behavior of amino acids and nucleic acids. Both of which are correlated to DNA and RNA. The process of tautomerization of DNA bases occurs during DNA replication. The ability for the wrong tautomer of one of the standard nucleic bases to mispair causes a mutation during the process of DNA replication which can be cytotoxic or mutagenic to the cell. These mispairings can result in transition, transversion, frameshift, deletion, and/or duplication mutations. Some diseases that result from tautomerization induced DNA lesions include Kearns-Sayre syndrome, Fragile X syndrome, Kennedy disease, and Huntington's disease.
Cytosine deamination commonly occurs under physiological conditions and essentially is the deamination of cytosine. This process yields uracil as its product, which is not a base pair found within DNA. This process causes extensive DNA damage. The rate of this process is slowed down significantly in double-stranded DNA compared to single-stranded DNA.
Single and Double Stranded Breaks
Single-strand breaks (SSBs) occur when one strand of the DNA double helix experiences breakage of a single nucleotide accompanied by damaged 5’- and/or 3’-termini at this point. One common source of SSBs is due to oxidative attack by physiological reactive oxygen species (ROS) such as hydrogen peroxide. H2O2 causes SSBs three times more frequently than double-strand breaks (DSBs). Alternative methods of SSB acquisition include direct disintegration of the oxidized sugar or through DNA base-excision repair (BER) of damaged bases. Additionally, cellular enzymes may perform erroneous activity leading to SSBs or DSBs by a variety of mechanisms. One such example would be when the cleavage complex formed by DNA topoisomerase 1 (TOP1) relaxes DNA during transcription and replication through the transient formation of a nick. While TOP1 normally reseals this nick shortly after, these cleavage complexes may collide with RNA or DNA polymerases or be proximal to other lesions, leading to TOP1-linked SSBs or TOP1-linked DSBs.
Chemical Adducts
A DNA adduct is a segment of DNA that binds to a chemical carcinogen. Some adducts that cause lesions to DNA included oxidatively modified bases, propano-, etheno-, and MDA-induced adducts. 5‐Hydroxymethyluracil is an example of an oxidatively modified base where oxidation of the methyl group of thymine occurs. This adduct interferes with the binding of transcription factors to DNA which can trigger apoptosis or result in deletion mutations. Propano adducts are derived by species generated by lipid peroxidation. For example, HNE is a major toxic product of the process. It regulates the expression of genes that are involved in cell cycle regulation and apoptosis. Some of the aldehydes from lipid peroxidation can be converted to epoxy aldehydes by oxidation reactions. These epoxy aldehydes can damage DNA by producing etheno adducts. An increase in this type of DNA lesion exhibits conditions resulting in oxidative stress which is known to be associated with an increased risk of cancer. Malondialdehyde (MDA) is another highly toxic product from lipid peroxidation and also in the synthesis of prostaglandin. MDA reacts with DNA to form the M1dG adduct which causes DNA lesions.
Disease Effects
Many systems are in place to repair DNA and RNA lesions but it is possible for lesions to escape these measures. This may lead to mutations or large genome abnormalities, which can threaten the cell or organism's ability to live. Several cancers are a result of DNA lesions. Even repair mechanisms to heal the damage may end up causing more damage. Mismatch repair defects, for example, cause instability that predisposes to colorectal and endometrial carcinomas.
DNA lesions in neurons may lead to neurodegenerative disorders such as Alzheimer's, Huntington's, and Parkinson's diseases. These come as a result of neurons generally being associated with high mitochondrial respiration and redox species production, which can damage nuclear DNA. Since these cells often cannot be replaced after being damaged, the damage done to them leads to dire consequences. Other disorders stemming from DNA lesions and their association with neurons include but are not limited to Fragile X syndrome, Friedreich's ataxia, and Spinocerebellar ataxias.
During replication, usually DNA polymerases are unable to go past the lesioned area, however, some cells are equipped with special polymerases which allow for translesion synthesis (TLS). TLS polymerases allow for the replication of DNA past lesions and risk generating mutations at a high frequency. Common mutations that occur after undergoing this process are point mutations and frameshift mutations. Several diseases come as a result of this process including several cancers and Xeroderma pigmentosum.
The effect of oxidatively damaged RNA has resulted in a number of human diseases and is especially associated with chronic degeneration. This type of damage has been observed in many neurodegenerative diseases such as Amyotrophic lateral sclerosis, Alzheimer's, Parkinson's, dementia with Lewy bodies, and several prion diseases. It is important to note that this list is rapidly growing and data suggests that RNA oxidation occurs early in the development of these diseases, rather than as an effect of cellular decay. RNA and DNA lesions are both associated with the development of diabetes mellitus type 2.
Repair Mechanisms
DNA Damage Response
When DNA is damaged such as due to a lesion, a complex signal transduction pathway is activated which is responsible for recognizing the damage and instigating the cell's response for repair. Compared to the other lesion repair mechanisms, DDR is the highest level of repair and is employed for the most complex lesions. DDR consists of various pathways, the most common of which are the DDR kinase signaling cascades. These are controlled by phosphatidylinositol 3-kinase-related kinases (PIKK), and range from DNA-dependent protein kinase (DNA-PKcs) and ataxia telangiectasia-mutated (ATM) most involved in repairing DSBs to the more versatile Rad3-related (ATR). ATR is crucial to human cell viability, while ATM mutations cause the severe disorder ataxia-telangiectasia leading to neurodegeneration, cancer, and immunodeficiency. These three DDR kinases all recognize damage via protein-protein interactions which localize the kinases to the areas of damage. Next, further protein-protein interactions and posttranslational modifications (PTMs) complete the kinase activation, and a series of phosphorylation events takes place. DDR kinases perform repair regulation at three levels - via PTMs, at the level of chromatin, and at the level of the nucleus.
Base Excision Repair
Base excision repair (BER) is responsible for removing damaged bases in DNA. This mechanism specifically works on excising small base lesions which do not distort the DNA double helix, in contrast to the nucleotide excision repair pathway which is employed in correcting more prominent distorting lesions. DNA glycosylases initiate BER by both recognizing the faulty or incorrect bases and then removing them, forming AP sites lacking any purine or pyrimidine. AP endonuclease then cleaves the AP site, and the single-strand break is either processed by short-patch BER to replace a single nucleotide long-patch BER to create 2-10 replacement nucleotides.
Single Stranded Break Repair
Single stranded breaks (SSBs) can severely threaten genetic stability and cell survival if not quickly and properly repaired, so cells have developed fast and efficient SSB repair (SSBR) mechanisms. While global SSBR systems extract SSBs throughout the genome and during interphase, S-phase specific SSBR processes work together with homologous recombination at the replication forks.
Double Stranded Break Repair
Double stranded breaks (DSB) are a threat to all organisms as they can cause cell death and cancer. They can be caused exogenously as a result of radiation and endogenously from errors in replication or encounters with DNA lesions by the replication fork. DSB repair occurs through a variety of different pathways and mechanisms in order to correctly repair these errors.
Nucleotide Excision and Mismatch Repair
Nucleotide excision repair is one of the main mechanisms used to remove bulky adducts from DNA lesions caused by chemotherapy drugs, environmental mutagens, and most importantly UV radiation. This mechanism functions by releasing a short damage containing oligonucleotide from the DNA site, and then that gap is filled in and repaired by NER. NER recognizes a variety of structurally unrelated DNA lesions due to the flexibility of the mechanism itself, as NER is highly sensitive to changes in the DNA helical structure. Bulky adducts seem to trigger NER. The XPC-RAD23-CETN2 heterotrimer involved with NER has a critical role in DNA lesion recognition. In addition to other general lesions in the genome, UV damaged DNA binding protein complex (UV-DDB) also has an important role in both recognition and repair of UV-induced DNA photolesions.
Mismatch repair (MMR) mechanisms within the cell correct base mispairs that occur during replication using a variety of pathways. It has a high affinity for targeting DNA lesions with specificity, as alternations in base pair stacking that occur at DNA lesion sites affect the helical structure. This is likely one of many signals that triggers MMR.
References
Molecular biology | Molecular lesion | [
"Chemistry",
"Biology"
] | 3,345 | [
"Biochemistry",
"Molecular biology"
] |
928,203 | https://en.wikipedia.org/wiki/Jabil | Jabil Inc. is an American multinational manufacturing company involved in the design, engineering, and manufacturing of electronic circuit board assemblies and systems, along with supply chain services, primarily serving original equipment manufacturers. It is headquartered in the Gateway area of St. Petersburg, Florida. It is one of the largest companies in the Tampa Bay area.
History
Founded in 1966 in the Detroit area, Jabil initially focused on circuit board assembly production and repair for Control Data Systems. The company name, Jabil, derives from the combination of the first names of its founders, James Golden and Bill Morean. After Golden exited the business, Bill Morean's son, William, joined the company and gradually began to shape its direction by signing new contracts, including an offer to purchase a majority stake in the company.
In 1979, Jabil established a high-volume manufacturing partnership with General Motors (GM), moving towards automated manufacturing and advanced assembly technology.
In 1981, Jabil introduced independent test engineering and development services. A year later, the company started volume production of circuit boards with manual surface-mount technology (SMT) processes. By 1984, Jabil had implemented computer-aided design services for production. A year later, the company transitioned to highly automated volume production using SMT processes. Towards the end of the 1980s, Jabil adopted the automated tape-automated bonding (TAB) process for circuit board production.
In 1982, Jabil moved its headquarters from Detroit to St. Petersburg, Florida.
In April 1993, Jabil became a publicly traded company, listing its shares on the New York Stock Exchange.
In 1997, Jabil expanded its manufacturing capacity and workforce, completing a new 120,000-square-foot building in St. Petersburg.
In 2001, Jabil was added to the S&P 500 Index.
In 2013, William D. Morean retired and was succeeded by Timothy Main as board chairman. Later, William E. Peters was named president and Mark Mondello was appointed CEO.
In 2014, Jabil was moved from the S&P 500 Index to the S&P MidCap 400 Index.
In 2017, Jabil announced that it would be closing its first European international plant in Livingston, United Kingdom, by the end of the year. Two hundred sixty-six employees in Livingston would lose their jobs. Jabil laid off approximately 400 people in September 2016, 100 of those being corporate employees located in St. Petersburg Florida. In March 2024, the company announced it would lay off 120 workers in Vancouver, Washington.
In January 2023, it was reported that Jabil had started manufacturing components for AirPods in India. In December 2023, Jabil rejoined the S&P 500 index.
On 19 April 2024, Jabil announced that CEO Kenny Wilson would take paid leave pending an investigation related to company policies, although not affecting the company's financial statements or reporting. Following Wilson's leave, which began on April 15, CFO Michael Dastoor was appointed as interim CEO by the board of directors. Following the completion of the investigation, Wilson resigned from the company and Dastoor was named CEO.
Acquisitions and mergers
Jabil has acquired numerous companies and arms of companies. Their acquisitions have expanded their presence in countries such as China, Mexico, India, Spain, the Netherlands and Russia.
In 1999, Jabil began its operations in China by acquiring GET Manufacturing.
In 2001, Jabil expanded its manufacturing capability and acquired Intel's manufacturing facility in Malaysia. A year later, the company acquired a factory of Lucent Technologies in Shanghai. In 2002, the company also acquired contract manufacturing services of Philips.
In 2005, Jabil acquired Varian's electronics manufacturing business for $195 million. A year later, Jabil expanded its operations to Taiwan and acquired Green Point for $881 million through its subsidiary Jabil Circuit Taiwan.
In 2011, Jabil acquired Telmar Network, a communication network service provider based in Texas.
In February 2013, Jabil acquired Nypro for $665 million in cash. The purchase was completed in July 2013.
In 2015, Jabil acquired Shemer Group, an Israeli metal fabrication company specializing in contract manufacturing for high-tech capital equipment manufacturers. In the same year, the company acquired Plasticos Castella, a Spain-based food and consumer packaging manufacturer.
In 2018, Jabil acquired the medical devices business of Johnson & Johnson.
In 2021, Jabil acquired Ecologic Brands.
In August 2023, Jabil sold its mobility business in China to BYD. In November 2023, Jabil acquired the Silicon Photonics business of Intel.
In November 2023, Jabil acquired ProcureAbility.
References
External links
Companies based in St. Petersburg, Florida
Manufacturing companies based in Florida
Electronics companies established in 1966
Companies listed on the New York Stock Exchange
Electronics manufacturing
Electronics companies of the United States
1966 establishments in Michigan
1993 initial public offerings
Electronics manufacturing companies | Jabil | [
"Engineering"
] | 990 | [
"Electronic engineering",
"Electronics manufacturing"
] |
929,147 | https://en.wikipedia.org/wiki/Moonlight | Moonlight consists of mostly sunlight (with little earthlight) reflected from the parts of the Moon's surface where the Sun's light strikes.
History
The ancient Greek philosopher Anaxagoras was aware that "the sun provides the moon with its brightness".
Illumination
The intensity of moonlight varies greatly depending on the lunar phase, but even the full moon typically provides only about 0.05–0.1 lux illumination. When a full Moon around perigee (a "supermoon") is viewed around upper culmination from the tropics, the illuminance can reach up to 0.32 lux. From Earth, the apparent magnitude of the full Moon is only about that of the Sun.
The color of moonlight, particularly around full moon, appears bluish to the human eye compared to other, brighter light sources due to the Purkinje effect. The blue or silver appearance of the light is an illusion.
The Moon's Bond albedo averages 0.136, meaning only 13.6% of incident sunlight is reflected from the lunar surface. Moonlight takes approximately 1.26 seconds to reach Earth's surface. Scattered in Earth's atmosphere, moonlight generally increases the brightness of the night sky, reducing contrast between dimmer stars and the background. For this reason, many astronomers usually avoid observing sessions around a full moon.
Gallery
Folklore
In folklore, moonlight sometimes has a harmful influence. For example, sleeping in the light of a full Moon on certain nights was said to transform a person into a werewolf. The light of the Moon was thought to worsen the symptoms of lunatics, and to sleep in moonlight could make one blind, or mad. Nyctalopia (night blindness caused by a lack of vitamin A) was thought to be caused by sleeping in moonlight in the tropics.
"Moon blindness" is a name for equine recurrent uveitis. Moonlight is no longer thought of as the cause.
In the 16th century, moonmilk, a soft white limestone precipitate found in caves, was thought to be caused by the rays of the Moon.
Selenoplexia was a supposed medical condition caused by the rays of the moon.
Art
In 2008 Katie Paterson produced an artwork titled Light bulb to Simulate Moonlight. It consists of 289 lightbulbs coated to produce a similar spectrum to the light of the full Moon.
See also
Airglow
Daylight
Diffuse reflection
Earthlight (astronomy)
Lunar effect
Scotobiology
Starlight
Night in paintings (Western art)
Night in paintings (Eastern art)
References
External links
Phases of the Moon at USNO
Strange Moonlight at Science@NASA
Moonlight Brightness at LunarLight Photography
Lunar observation
Light
Light sources | Moonlight | [
"Physics"
] | 545 | [
"Physical phenomena",
"Spectrum (physical sciences)",
"Electromagnetic spectrum",
"Waves",
"Light"
] |
929,631 | https://en.wikipedia.org/wiki/Ski%20wax | Ski wax is a material applied to the bottom of snow runners, including skis, snowboards, and toboggans, to improve their coefficient of friction performance under varying snow conditions. The two main types of wax used on skis are glide waxes and grip waxes. They address kinetic friction—to be minimized with a glide wax—and static friction—to be achieved with a grip wax. Both types of wax are designed to be matched with the varying properties of snow, including crystal type and size, and moisture content of the snow surface, which vary with temperature and the temperature history of the snow. Glide wax is selected to minimize sliding friction for both alpine and cross-country skiing. Grip wax (also called "kick wax") provides on-snow traction for cross-country skiers, as they stride forward using classic technique.
Modern plastic materials (e.g. high-modulus polyethylene and Teflon), used on ski bases, have excellent gliding properties on snow, which in many circumstances diminish the added value of a glide wax. Likewise, uni-directional textures (e.g. fish scale or micro-scale hairs) underfoot on cross-country skis can offer a practical substitute for grip wax for those skiers, using the classic technique.
History
Johannes Scheffer in Argentoratensis Lapponiæ (History of Lapland) in 1673 gave what is probably the first recorded instruction for ski wax application He advised skiers to use pine tar pitch and rosin. Ski waxing was also documented in 1761. In 1733 the use of tar was described by Norwegian colonel Jens Henrik Emahusen. In the 1740s Sami people use of resin and tallow under their skis is recorded in writing.
Beginning around 1854, California gold rush miners held organized downhill ski races. They also discovered that ski bases, smeared with lubricants brewed from vegetable and/or animal compounds, increased speed. This led to some of the first commercial ski lubricants, such as Black Dope and Sierra Lighting; both were mainly composed of sperm oil, vegetable oil and pine pitch. However, some instead used paraffin candle wax that melted onto ski bases, and these worked better under colder conditions.
Pine tar on wooden ski bases proved effective for using skis as transport over the centuries, because it fills the pores of the wood and creates a hydrophobic surface that minimizes suction from water in the snow, yet has sufficient roughness to allow traction for forward motion. In the 1920s and 30s, new varnishes were developed by European companies as season-long ski bases. A significant advance for cross country racing was the introduction of klister, for good traction in granular snow, especially in spring conditions; klister was invented and patented in 1913 by Peter Østbye. In the early 1940s Astra AB, a Swedish chemical company, advised by Olympic crosscountry skier Martin Matsbo, started the development of petroleum-based waxes, using paraffin wax and other admixtures. By 1952, such noted brands as Toko, Swix and Rex were providing an array of color-coded, temperature-tailored waxes.
In the last quarter of the 20th century, researchers addressed the twin problems of water and impurities adhering to skis during spring conditions. Terry Hertel addressed both problems, first with the novel use of a surfactant that interacted with the wax matrix in such a way as to repel water effectively, a product introduced in 1974 by Hertel Wax. Hertel also developed the first fluorocarbon product and the first spring-time wax that repels and makes the running surface slick for spring time alpine ski and snowboard. This technology was introduced to the market in 1986 by Hertel Wax. In 1990, Hertel filed for a U.S. patent on a "ski wax for use with sintered-base snow skis", containing paraffin, a hardener wax, roughly 1% per-fluoroether diol, and 2% SDS surfactant. Trademarks for Hertel waxes are Super HotSauce, Racing FC739, SpringSolution and White Gold. In the 1990s, Swix chief chemist Leif Torgersen found a glide wax additive to repel pollen and other snow impurities—a problem with soft grip waxes during distance races—in the form of a fluorocarbon that could be ironed into the ski base. The solution was based on the work of Enrico Traverso at Enichem SpA, who had developed a fluorocarbon powder with a melting temperature just a few degrees below that of sintered polyethylene, patented in Italy as a "ski lubricant comprising paraffinic wax and hydrocarbon compounds containing a perfluorocarbon segment".
Science of sliding on snow
The ability of a ski or other runner to slide over snow depends on both the properties of the snow and the ski to result in an optimum amount of lubrication from melting the snow by friction with the ski—too little and the ski interacts with solid snow crystals, too much and capillary attraction of meltwater retards the ski.
Friction
Before a ski can slide, it must overcome the maximum value static friction, , for the ski/snow contact, where is the coefficient of static friction and is the normal force of the ski on snow. Kinetic (or dynamic) friction occurs when the ski is moving over the snow. The coefficient of kinetic friction, , is less than the coefficient of static friction for both ice and snow. The force required for sliding on snow is the product of the coefficient of kinetic friction and the normal force: . Both the static and kinetic coefficients of friction increase with colder snow temperatures (also true for ice).
Snow properties
Snowflakes have a wide range of shapes, even as they fall; among these are: six-sided star-like dendrites, hexagonal needles, platelets and icy pellets. Once snow accumulates on the ground, the flakes immediately begin to undergo transformation (called metamorphism), owing to temperature changes, sublimation, and mechanical action. Temperature changes may be from the ambient temperature, solar radiation, rainwater, wind, or the temperature of the material beneath the snow layer. Mechanical action includes wind and compaction. Over time, bulk snow tends to consolidate—its crystals become truncated from breaking apart or losing mass with sublimation directly from solid to gas and with freeze-thaw, causing them to combine as coarse and granular ice crystals. Colbeck reports that fresh, cold, and man-made snow all interact more directly with the base of a ski and increase friction, indicating the use of harder waxes. Conversely, older, warmer, and denser snows present lower friction, in part due to increased grain size, which better promotes a water film and a smoother surface of the snow crystals for which softer waxes are indicated.
Ski friction properties
Colbeck offers an overview of the five friction processes of skis on snow. They are the: 1) resistance due to plowing of snow out of the way, 2) deformation of the snow over which the ski is traveling, 3) lubrication of the ski with a thin layer of melt water, 4) capillary attraction of water in the snow to the ski bottom, and 5) contamination of the snow with dust and other non-slippery elements. Plowing and deformation pertain to the interaction of the ski, as a whole, with the snow and are negligible on a firm surface. Lubrication, capillary attraction and contamination are issues for the ski bottom and the wax that is applied to reduce sliding friction or achieve adequate grip.
Typically, a sliding ski melts a thin and transitory film of lubricating layer of water, caused by the heat of friction between the ski and the snow in its passing. Colbeck suggests that the optimum water film thickness is in the range between 4 and 12 μm. However, the heat generated by friction can be lost by conduction to a cold ski, thereby diminishing the production of the melt layer. At the other extreme, when the snow is wet and warm, heat generation creates a thicker film that can create increased capillary drag on the ski bottom. Kuzmin and Fuss suggest that the most favorable combination of ski base material properties to minimize ski sliding friction on snow include: increased hardness and lowered thermal conductivity of the base material to promote meltwater generation for lubrication, wear resistance in cold snow, and hydrophobicity to minimize capillary suction. These attributes are readily achievable with a PTFE base, which diminishes the value added by glide waxes. Lintzén reports that factors other than wax are much more important in reducing friction on cross-country skate skis—the curvature of the ski and snow conditions.
Glide wax
Glide wax can be applied to alpine skis, snowboards, skate skis, classic skis, back-country skis, and touring skis. Traditional waxes comprise solid hydrocarbons. High-performance "fluorocarbon" waxes also contain fluorine, which substitutes some fraction of the hydrogen atoms in the hydrocarbons with fluorine atoms to achieve lower coefficients of friction and higher water repellency than the pure hydrocarbon wax can achieve. Wax is adjusted for hardness to minimize sliding friction as a function of snow properties, which include the effects of:
Age: Reflects the metamorphism of snow crystals that are sharp and well-defined, when new, but with aging become broken or truncated with wind action or rounded into ice granules with freeze-thaw, all of which affects a ski's coefficient of friction.
Moisture content: The percentage of mass that is liquid water and may create suction friction with the base of the ski as it slides.
Temperature: Affects the ease with which sliding friction can melt snow crystals at the interface between ski and snow.
Properties
A variety of glide waxes are tailored for specific temperature ranges and other snow properties with varying wax hardness and other properties that address repellence of moisture and dirt. The hardness of the glide wax affects the melting of the snow to lubricate its passage over the surface and its ability to avoid suction from meltwater in the snow. Too little melting and sharp edges of snow crystals or too much suction impede the passage of the ski. A tipping point between where crystal type dominates sliding friction and moisture content dominates occurs around . Harder waxes address colder, drier or more abrasive snow conditions, whereas softer waxes have a lower coefficient of friction, but abrade more readily. Wax formulations combine three types of wax to adjust coefficient of friction and durability. From hard to soft, they include synthetic waxes with 50 or more carbon atoms, microcrystalline waxes with 25 to 50 carbon atoms and paraffin waxes with 20 to 35 carbon atoms. Additives to such waxes include graphite, teflon, silicon, fluorocarbons, and molybdenum to improve glide and/or reduce dirt accumulation.
Application
Glide wax can be applied cold or hot. Cold applications include, rubbing hard wax like a crayon, applying a liquid wax or a spray wax. Hot applications of wax include the use of heat from an iron, infrared lamp, or a "hot box" oven.
Base material
The role of glide wax is to adapt and improve the friction properties of a ski base to the expected snow properties to be encountered on a spectrum from cold crystalline snow to saturated granular snow. Modern ski bases often are made from ultra-high-molecular-weight polyethylene (UHMWPE). Kuzmin asserts that UHMWPE is non-porous and can hold neither wax nor water, so there is no possibility for filling pores; furthermore, he asserts that UHMWPE is very hydrophobic, which means that wet snow does not appreciably retard the ski and that glide wax offers little additional ability to repel water. He notes that clear bases are more durable and hydrophobic than those with carbon content. The same author asserts that texture is more important than surface chemistry for creating the optimum balance between a running surface that's too dry (not slippery enough) and too wet (ski subject to suction forces). In warm, moist snow, texture can help break the retarding capillary attraction between the ski base and the snow. Giesbrecht agrees that low wetting angle of the ski base is key and also emphasizes the importance of the degree of surface roughness at the micrometre scale as a function of snow temperature—cold snow favoring a smoother surface and wetter, warmer snow favoring a textured surface. Some authors question the necessity to use any glide waxes on modern ski bases.
Grip wax
Cross-country skiers use a grip wax (also called "kick wax") for classic-style waxable skis to provide traction with static friction on the snow that allows them to propel themselves forward on flats and up hills. They are applied in an area beneath the skier's foot and extending, somewhat forward, that is formed by the camber of the classic ski, called the "grip zone" (or "kick zone"). The presence of camber allows the skis to grip the snow, when the weight is on one ski and the ski is fully flexed, but minimize drag when the skis are weighted equally and are thus less than fully flexed. Grip waxes are designed for specific temperature ranges and types of snow; a correctly selected grip wax does not appreciably decrease the glide of skis that have proper camber for the skier's weight and for the snow conditions. There are two substances used for grip wax: hard wax and klister.
Hard wax: a traditionally paraffin wax-based substance with admixtures—for snow comprising crystals that are relatively intact and not substantially changed by packing or freeze-thaw. The admixtures, which include a dye, rubber, rosin, resin and colophony, adjust the hardness of the wax to tailor the effectiveness of its grip for specific, discrete temperature ranges (from approximately -25 °F to +35 °F); waxes are graded and color-coded according to these temperature ranges. Harder grip waxes are designed for colder snow temperatures, but grip poorly in warm temperatures. Conversely, softer waxes in cold temperatures create enough friction and melting that the melt layer may accumulate and promote frozen accretion of snow.
Klister: a sticky ointment, which may contain a combination of rosins, waxes, solvents and fats—with the formulation tailored for snow that comprises coarse crystals, having been transformed through freeze-thaw or being wind-blown, and adjusted for specific temperature ranges. Spray-on klister is more convenient than klister applied from a tube. An incorrect match of klister to snow conditions can also cause icing.
Some skis are "waxless", having a fish-scale or other texture to prevent the ski from sliding backwards. Ski mountaineers use temporarily adhered climbing skins to provide uphill grip, but typically remove them for descent.
Wax solvents
Wax can be dissolved by non-polar solvents like mineral spirits. However, some commercial wax solvents are made from citrus oil, which is less toxic, harder to ignite, and gentler on the ski base.
Health and environmental effects
Health
Ski wax may contain chemicals with potential health affects including per- and polyfluoroalkyl substances (PFASs). Levels of perfluorinated carboxylic acids, especially perfluorooctanoic acid (PFOA), have been shown to increase in ski wax technicians during the ski season.
Environment
When skiing, the friction between the snow and skis causes wax to abrade and remain in the snow pack until spring thaw. Then the snowmelt drains into watersheds, streams, lakes and rivers, thereby changing the chemistry of the environment and the food chain. PFASs in ski wax are heat resistant, chemically and biologically stable, and thus environmentally persistent. They have been shown to accumulate in animals that are present at ski venues. The International Ski Federation (FIS) announced to introduce a ban on PFASs in waxes in all competitive ski disciplines from the winter season of 2020/21.
References
Further reading
Non-petroleum based lubricants
Skiing equipment
Waxes | Ski wax | [
"Physics"
] | 3,422 | [
"Materials",
"Matter",
"Waxes"
] |
930,016 | https://en.wikipedia.org/wiki/Ascidiacea | Ascidiacea, commonly known as the ascidians or sea squirts, is a paraphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer test or "tunic" made of the polysaccharide cellulose.
Ascidians are found all over the world, usually in shallow water with salinities over 2.5%. While members of the Thaliacea (salps, doliolids and pyrosomes) and Appendicularia (larvaceans) swim freely like plankton, sea squirts are sessile animals after their larval phase: they then remain firmly attached to their substratum, such as rocks and shells.
There are 2,300 species of ascidians and three main types: solitary ascidians, social ascidians that form clumped communities by attaching at their bases, and compound ascidians that consist of many small individuals (each individual is called a zooid) forming large colonies.
Sea squirts feed by taking in water through a tube, the oral siphon. The water enters the mouth and pharynx, flows through mucus-covered gill slits (also called pharyngeal stigmata) into a water chamber called the atrium, then exits through the atrial siphon.
Some authors now include the thaliaceans in Ascidiacea, making it monophyletic.
Anatomy
Sea squirts are rounded or cylindrical animals ranging from about in size. One end of the body is always firmly fixed to rock, coral, or some similar solid surface. The lower surface is pitted or ridged, and in some species has root-like extensions that help the animal grip the surface. The body wall is covered by a smooth thick tunic, which is often quite rigid. The tunic consists of cellulose, along with proteins and calcium salts. Unlike the shells of molluscs, the tunic is composed of living tissue and often has its own blood supply. In some colonial species, the tunics of adjacent individuals are fused into a single structure.
The upper surface of the animal, opposite to the part gripping the substratum, has two openings, or siphons. When removed from the water, the animal often violently expels water from these siphons, hence the common name of "sea squirt". The body itself can be divided into up to three regions, although these are not clearly distinct in most species. The pharyngeal region contains the pharynx, while the abdomen contains most of the other bodily organs, and the postabdomen contains the heart and gonads. In many sea squirts, the postabdomen, or even the entire abdomen, are absent, with their respective organs being located more anteriorly.
As its name implies, the pharyngeal region is occupied mainly by the pharynx. The large buccal siphon opens into the pharynx, acting like a mouth. The pharynx itself is ciliated and contains numerous perforations, or stigmata, arranged in a grid-like pattern around its circumference. The beating of the cilia sucks water through the siphon, and then through the stigmata. A long ciliated groove, or endostyle, runs along one side of the pharynx, and a projecting ridge along the other. The endostyle may be homologous with the thyroid gland of vertebrates, despite its differing function.
The pharynx is surrounded by an atrium, through which water is expelled through a second, usually smaller, siphon. Cords of connective tissue cross the atrium to maintain the general shape of the body. The outer body wall consists of connective tissue, muscle fibres, and a simple epithelium directly underlying the tunic.
Digestive system
The pharynx forms the first part of the digestive system. The endostyle produces a supply of mucus which is then passed into the rest of the pharynx by the beating of flagella along its margins. The mucus then flows in a sheet across the surface of the pharynx, trapping planktonic food particles as they pass through the stigmata, and is collected in the ridge on the dorsal surface. The ridge bears a groove along one side, which passes the collected food downwards and into the oesophageal opening at the base of the pharynx.
The esophagus runs downwards to a stomach in the abdomen, which secretes enzymes that digest the food. An intestine runs upwards from the stomach parallel to the oesophagus and eventually opens, through a short rectum and anus, into a cloaca just below the atrial siphon. In some highly developed colonial species, clusters of individuals may share a single cloaca, with all the atrial siphons opening into it, although the buccal siphons all remain separate. A series of glands lie on the outer surface of the intestine, opening through collecting tubules into the stomach, although their precise function is unclear.
Circulatory system
The heart is a curved muscular tube lying in the postabdomen, or close to the stomach. Each end opens into a single vessel, one running to the endostyle, and the other to the dorsal surface of the pharynx. The vessels are connected by a series of sinuses, through which the blood flows. Additional sinuses run from that on the dorsal surface, supplying blood to the visceral organs, and smaller vessels commonly run from both sides into the tunic. Nitrogenous waste, in the form of ammonia, is excreted directly from the blood through the walls of the pharynx, and expelled through the atrial siphon.
Unusually, the heart of sea squirts alternates the direction in which it pumps blood every three to four minutes. There are two excitatory areas, one at each end of the heart, with first one being dominant, to push the blood through the ventral vessel, and then the other, pushing it dorsally.
There are four different types of blood cell: lymphocytes, phagocytic amoebocytes, nephrocytes and morula cells. The nephrocytes collect waste material such as uric acid and accumulate it in renal vesicles close to the digestive tract. The morula cells help to form the tunic, and can often be found within the tunic substance itself. In some species, the morula cells possess pigmented reducing agents containing iron (hemoglobin), giving the blood a red colour, or vanadium (hemovanadin) giving it a green colour. In that case the cells are also referred to as vanadocytes.
Nervous system
The ascidian central nervous system is formed from a plate that rolls up to form a neural tube. The number of cells within the central nervous system is very small. The neural tube is composed of the sensory vesicle, the neck, the visceral or tail ganglion, and the caudal nerve cord. The anteroposterior regionalization of the neural tube in ascidians is comparable to that in vertebrates.
Although there is no true brain, the largest ganglion is located in the connective tissue between the two siphons, and sends nerves throughout the body. Beneath this ganglion lies an exocrine gland that empties into the pharynx. The gland is formed from the nerve tube, and is therefore homologous to the spinal cord of vertebrates.
Sea squirts lack special sense organs, although the body wall incorporates numerous individual receptors for touch, chemoreception, and the detection of light.
Life history
Almost all ascidians are hermaphrodites and conspicuous mature ascidians are sessile. The gonads are located in the abdomen or postabdomen, and include one testis and one ovary, each of which opens via a duct into the cloaca. Broadly speaking, the ascidians can be divided into species which exist as independent animals (the solitary ascidians) and those which are interdependent (the colonial ascidians). Different species of ascidians can have markedly different reproductive strategies, with colonial forms having mixed modes of reproduction.
Solitary ascidians release many eggs from their atrial siphons; external fertilization in seawater takes place with the coincidental release of sperm from other individuals. A fertilized egg spends 12 hours to a few days developing into a free-swimming tadpole-like larva, which then takes no more than 36 hours to settle and metamorphose into a juvenile.
As a general rule, the larva possesses a long tail, containing muscles, a hollow dorsal nerve tube and a notochord, both features clearly indicative of the animal's chordate affinities. One group though, the molgulid ascidians, have evolved tailless species on at least four separate occasions, and even direct development. A notochord is formed early in development and always consists of a row of exactly 40 cells. The nerve tube enlarges in the main body, and will eventually become the cerebral ganglion of the adult. The tunic develops early in embryonic life and extends to form a fin along the tail in the larva. The larva also has a statocyst and a pigmented cup above the mouth, which opens into a pharynx lined with small clefts opening into a surrounding atrium. The mouth and anus are originally at opposite ends of the animal, with the mouth only moving to its final (posterior) position during metamorphosis.
The larva selects and settles on appropriate surfaces using receptors sensitive to light, orientation to gravity, and tactile stimuli. When its anterior end touches a surface, papillae (small, finger-like nervous projections) secrete an adhesive for attachment. Adhesive secretion prompts an irreversible metamorphosis: various organs (such as the larval tail and fins) are lost while others rearrange to their adult positions, the pharynx enlarges, and organs called ampullae grow from the body to permanently attach the animal to the substratum. The siphons of the juvenile ascidian become orientated to optimise current flow through the feeding apparatus. Sexual maturity can be reached in as little as a few weeks. Since the larva is more advanced than its adult, this type of metamorphosis is called 'retrogressive metamorphosis'. This feature is a landmark for the 'theory of retrogressive metamorphosis or ascidian larva theory'; the true chordates are hypothesized to have evolved from sexually mature larvae.
Direct development in ascidians
Some ascidians, especially in Molgulidae family, have direct development in which the embryo develops directly into the juvenile without developing a tailed larva.
Colonial species
Colonial ascidians reproduce both asexually and sexually. Colonies can survive for decades. An ascidian colony consists of individual elements called zooids. Zooids within a colony are usually genetically identical and some have a shared circulation.
Sexual reproduction
Different colonial ascidian species produce sexually derived offspring by one of two dispersal strategies – colonial species are either broadcast spawners (long-range dispersal) or philopatric (very short-range dispersal). Broadcast spawners release sperm and ova into the water column and fertilization occurs near to the parent colonies. Some species are also viviparous. Resultant zygotes develop into microscopic larvae that may be carried great distances by oceanic currents. The larvae of sessile forms which survive eventually settle and complete maturation on the substratum- then they may bud asexually to form a colony of zooids.
The picture is more complicated for the philopatrically dispersed ascidians: sperm from a nearby colony (or from a zooid of the same colony) enter the atrial siphon and fertilization takes place within the atrium. Embryos are then brooded within the atrium where embryonic development takes place: this results in macroscopic tadpole-like larvae. When mature, these larvae exit the atrial siphon of the adult and then settle close to the parent colony (often within meters). The combined effect of short sperm range and philopatric larval dispersal results in local population structures of closely related individuals/inbred colonies. Generations of colonies which are restricted in dispersal are thought to accumulate adaptions to local conditions, thereby providing advantages over newcomers.
Trauma or predation often results in fragmentation of a colony into subcolonies. Subsequent zooid replication can lead to coalescence and circulatory fusion of the subcolonies. Closely related colonies which are proximate to each other may also fuse if they coalesce and if they are histocompatible. Ascidians were among the first animals to be able to immunologically distinguish self from non-self as a mechanism to prevent unrelated colonies from fusing to them and parasitizing them.
Fertilization
Sea squirt eggs are surrounded by a fibrous vitelline coat and a layer of follicle cells that produce sperm-attracting substances. In fertilization, the sperm passes through the follicle cells and binds to glycosides on the vitelline coat. The sperm's mitochondria are left behind as the sperm enters and drives through the coat; this translocation of the mitochondria might provide the necessary force for penetration. The sperm swims through the perivitelline space, finally reaching the egg plasma membrane and entering the egg. This prompts rapid modification of the vitelline coat, through processes such as the egg's release of glycosidase into the seawater, so no more sperm can bind and polyspermy is avoided. After fertilization, free calcium ions are released in the egg cytoplasm in waves, mostly from internal stores. The temporary large increase in calcium concentration prompts the physiological and structural changes of development.
The dramatic rearrangement of egg cytoplasm following fertilization, called ooplasmic segregation, determines the dorsoventral and anteroposterior axes of the embryo. There are at least three types of sea squirt egg cytoplasm: ectoplasm containing vesicles and fine particles, endoderm containing yolk platelets, and myoplasm containing pigment granules, mitochondria, and endoplasmic reticulum. In the first phase of ooplasmic segregation, the myoplasmic actin-filament network contracts to rapidly move the peripheral cytoplasm (including the myoplasm) to the vegetal pole, which marks the dorsal side of the embryo. In the second phase, the myoplasm moves to the subequatorial zone and extends into a crescent, which marks the future posterior of the embryo. The ectoplasm with the zygote nucleus ends up at the animal hemisphere while the endoplasm ends up in the vegetal hemisphere.
Promotion of out-crossing
Ciona intestinalis is a hermaphrodite that releases sperm and eggs into the surrounding seawater almost simultaneously. It is self-sterile, and thus has been used for studies on the mechanism of self-incompatibility. Self/non-self-recognition molecules play a key role in the process of interaction between sperm and the vitelline coat of the egg. It appears that self/non-self recognition in ascidians such as C. intestinalis is mechanistically similar to self-incompatibility systems in flowering plants. Self-incompatibility promotes out-crossing, and thus provides the adaptive advantage at each generation of masking deleterious recessive mutations (i.e. genetic complementation).
Ciona savignyi is highly self-fertile. However, non-self sperm out-compete self-sperm in fertilization competition assays. Gamete recognition is not absolute allowing some self-fertilization. It was speculated that self-incompatibility evolved to avoid inbreeding depression, but that selfing ability was retained to allow reproduction at low population density.
Botryllus schlosseri is a colonial tunicate able to reproduce both sexually and asexually. B. schlosseri is a sequential (protogynous) hermaphrodite, and in a colony, eggs are ovulated about two days before the peak of sperm emission. Thus self-fertilization is avoided, and cross-fertilization is favored. Although avoided, self-fertilization is still possible in B. schlosseri. Self-fertilized eggs develop with a substantially higher frequency of anomalies during cleavage than cross-fertilized eggs (23% vs. 1.6%). Also, a significantly lower percentage of larvae derived from self-fertilized eggs metamorphose, and the growth of the colonies derived from their metamorphosis is significantly lower. These findings suggest that self-fertilization gives rise to inbreeding depression associated with developmental deficits that are likely caused by expression of deleterious recessive mutations.
Asexual reproduction
Many colonial sea squirts are also capable of asexual reproduction, although the means of doing so are highly variable between different families. In the simplest forms, the members of the colony are linked only by rootlike projections from their undersides known as stolons. Buds containing food storage cells can develop within the stolons and, when sufficiently separated from the 'parent', may grow into a new adult individual.
In other species, the postabdomen can elongate and break up into a string of separate buds, which can eventually form a new colony. In some, the pharyngeal part of the animal degenerates, and the abdomen breaks up into patches of germinal tissue, each combining parts of the epidermis, peritoneum, and digestive tract, and capable of growing into new individuals.
In yet others, budding begins shortly after the larva has settled onto the substrate. In the family Didemnidae, for instance, the individual essentially splits into two, with the pharynx growing a new digestive tract and the original digestive tract growing a new pharynx.
DNA repair
Apurinic/apyrimidinic (AP) sites are a common form of DNA damage that inhibit DNA replication and transcription. AP endonuclease 1 (APEX1), an enzyme produced by C. intestinalis, is employed in the repair of AP sites during early embryonic development. Lack of such repair leads to abnormal development. C. intestinalis also has a set of genes that encode proteins homologous to those employed in the repair of DNA interstrand crosslinks in humans.
Ecology
The exceptional filtering capability of adult sea squirts causes them to accumulate pollutants that may be toxic to embryos and larvae as well as impede enzyme function in adult tissues. This property has made some species sensitive indicators of pollution.
Over the last few hundred years, most of the world's harbors have been invaded by non-native sea squirts that have been introduced by accident from the shipping industry. Several factors, including quick attainment of sexual maturity, tolerance of a wide range of environments, and a lack of predators, allow sea squirt populations to grow rapidly. Unwanted populations on docks, ship hulls, and farmed shellfish cause significant economic problems, and sea squirt invasions have disrupted the ecosystem of several natural sub-tidal areas by smothering native animal species.
Sea squirts are the natural prey of many animals, including nudibranchs, flatworms, molluscs, rock crabs, sea stars, fish, birds, and sea otters. Some are also eaten by humans in many parts of the world, including Japan, Korea, Chile, and Europe (where they are sold under the name "sea violet"). As chemical defenses, many sea squirts intake and maintain an extremely high concentration of vanadium in the blood, have a very low pH of the tunic due to acid in easily ruptured bladder cells, and (or) produce secondary metabolites harmful to predators and invaders. Some of these metabolites are toxic to cells and are of potential use in pharmaceuticals.
Evolution
Fossil record
Ascidians are soft-bodied animals, and for this reason, their fossil record is almost entirely lacking. The earliest reliable ascidians is Shankouclava shankouense from the Lower Cambrian Maotianshan Shale (Yunnan, South China). There are also two enigmatic species from the Ediacaran period with some affinity to the ascidians – Ausia from the Nama Group of Namibia and Burykhia from the Onega Peninsula, White Sea of northern Russia.
They are also recorded from Lower Jurassic (Bonet and Benveniste-Velasquez, 1971; Buge and Monniot, 1972) and the Tertiary from France (Deflandre-Riguard, 1949, 1956; Durand, 1952; Deflandre and Deflandre-Rigaud, 1956; Bouche, 1962; Lezaud, 1966; Monniot and Buge, 1971; Varol and Houghton, 1996). Older (Triassic) records are ambiguous. From the Early Jurassic, the species Didemnum cassianum, Quadrifolium hesselboi, Palaeoquadrum ullmanni and other indet genera are recorded. The representatives of the genus Cystodytes (family Polycitoridae) have been described from the Pliocene of France by Monniot (1970, 1971) and Deflandre-Rigaud (1956), and from Eocene of France by Monniot and Buge (1971), and lately from the Late Eocene of S Australia by Łukowiak (2012).
Phylogeny
The ascidians were on morphological evidence treated as sister to the Thaliacea and Appendicularia, but molecular evidence has suggested that ascidians could be polyphyletic within the Tunicata, as shown in the following cladogram.
In 2017 and 2018, two studies were published, which suggested an alternate phylogeny, placing Appendicularia as sister to the rest of Tunicata, and Thaliacea nested inside Ascidiacea. A grouping of Thaliacea and Ascidiacea to the exclusion of Appendicularia had already been suggested for a long time, under the name of Acopa. Brusca et al. treat Ascidiacea as a monophyletic group including pelagic Thaliacea.
Uses
Culinary
Various ascidians are eaten by humans around the world as delicacies.
Sea pineapple (Halocynthia roretzi) is cultivated in Japan (hoya, maboya) and Korea (meongge). When served raw, they have a chewy texture and peculiar flavor likened to "rubber dipped in ammonia" which has been attributed to a naturally occurring chemical known as cynthiaol. Styela clava is farmed in parts of Korea where it is known as mideoduk and is added to various seafood dishes such as agujjim. Tunicate bibimbap is a specialty of Geoje Island, not far from Masan.
Microcosmus species from the Mediterranean Sea are eaten in France (figue de mer, violet), Italy (limone di mare, uova di mare) and Greece (fouska, φούσκα), for example, raw with lemon, or in salads with olive oil, lemon and parsley.
The piure (Pyura chilensis) is used in the cuisine of Chile – it is consumed both raw and in seafood stews similar to bouillabaisse.
Pyura praeputialis is known as cunjevoi in Australia. It was once used as a food source by Aboriginal people living around Botany Bay, but is now used mainly for fishing bait.
Ciona is being developed in Norway as a potential substitute meat protein, after processing to remove its 'marine taste' and to make its texture less 'squid-like'.
Model organisms for research
Several factors make sea squirts good models for studying the fundamental developmental processes of chordates, such as cell-fate specification. The embryonic development of sea squirts is simple, rapid, and easily manipulated. Because each embryo contains relatively few cells, complex processes can be studied at the cellular level, while remaining in the context of the whole embryo.
The eggs of some species contain little yolk and are therefore transparent making them transparency ideal for fluorescent imaging. Its maternally-derived proteins are naturally associated with pigment (in a few species only), so cell lineages are easily labeled, allowing scientists to visualize embryogenesis from beginning to end.
Sea squirts are also valuable because of their unique evolutionary position: as an approximation of ancestral chordates, they can provide insight into the link between chordates and ancestral non-chordate deuterostomes, as well as the evolution of vertebrates from simple chordates. The sequenced genomes of the related sea squirts Ciona intestinalis and Ciona savignyi are small and easily manipulated; comparisons with the genomes of other organisms such as flies, nematodes, pufferfish and mammals provides valuable information regarding chordate evolution. A collection of over 480,000 cDNAs have been sequenced and are available to support further analysis of gene expression, which is expected to provide information about complex developmental processes and regulation of genes in vertebrates. Gene expression in embryos of sea squirts can be conveniently inhibited using Morpholino oligos.
References
Citations
General and cited references
External links
The Dutch Ascidians Homepage
Encyclopedia of Marine Life of Britain and Ireland
A fate map of the ascidian egg
Ciona savignyi Database
ANISEED Ascidian Network for In Situ Expression and Embryological Data
Chordate classes
Cambrian Series 2 first appearances
Extant Cambrian first appearances
Paraphyletic groups | Ascidiacea | [
"Biology"
] | 5,524 | [
"Phylogenetics",
"Paraphyletic groups"
] |
5,202,850 | https://en.wikipedia.org/wiki/Stirling%20radioisotope%20generator | A Stirling radioisotope generator (SRG) is a type of radioisotope generator based on a Stirling engine powered by a large radioisotope heater unit. The hot end of the Stirling converter reaches high temperature and heated helium drives the piston, with heat being rejected at the cold end of the engine. A generator or alternator converts the motion into electricity. Given the very constrained supply of plutonium, the Stirling converter is notable for producing about four times as much electric power from the plutonium fuel as compared to a radioisotope thermoelectric generator (RTG).
The Stirling generators were extensively tested on Earth by NASA, but their development was cancelled in 2013 before they could be deployed on actual spacecraft missions. A similar NASA project still under development, called Kilopower, also utilizes Stirling engines, but uses a small uranium fission reactor as the heat source.
History
Stirling and Brayton-cycle technology development has been conducted at NASA Glenn Research Center (formerly NASA Lewis) since the early 1970s. The Space Demonstrator Engine (SPDE) was the earliest 12.5 kWe per cylinder engine that was designed, built and tested. A later engine of this size, the Component Test Power Converter (CTPC), used a "Starfish" heat-pipe heater head, instead of the pumped-loop used by the SPDE. In the 1992-93 time period, this work was stopped due to the termination of the related SP-100 nuclear power system work and NASA's new emphasis on "better, faster, cheaper" systems and missions.
In 2020, a free-piston Stirling power converter reached 15 years of maintenance-free and degradation-free cumulative operation in the Stirling Research Laboratory at NASA Glenn. This duration equals the operational design life of the MMRTG, and is representative of typical mission concepts designed to explore the outer planets or even more distant Kuiper Belt Objects. This unit, called the Technology Demonstration Converter (TDC) #13, is the oldest of several converters that have shown no signs of degradation. Since 2017, the NASA Radioisotope Power Systems Program at NASA Glenn has continued developing several candidate technologies for the first dynamic RPS to fly in space, including designs based on the record-setting TDC #13 and the gas-bearing-based Stirling converter that was used in the ASRG. A small turbo-Brayton system is also under technology development. Several viable generator designs in the range of 100-500 Watts have emerged from the ongoing dynamic conversion technology development effort. In the near-term, a lunar demonstration mission using a dynamic RPS as part of NASA's Artemis Program could be the first opportunity for a DRPS to be used in spaceflight. The use of DRPS in a lunar-landed payload would enable it to survive and operate productively during the frigidly cold, two-week lunar nights, or in permanently shadowed craters near the moon's poles.
In the early 21st century, a major project using this concept was undertaken: the Advanced Stirling Radioisotope Generator (ASRG), a power source based on a 55-watt electric converter. The thermal power source for this system was the General Purpose Heat Source (GPHS). Each GPHS contained four iridium-clad Pu-238 fuel pellets, stood 5 cm tall and 10 cm square, and weighed 1.44 kg. The hot end of the Stirling converter reached 650 °C and heated helium drove a free piston reciprocating in a linear alternator, heat being rejected at the cold end of the engine. The alternating current (AC) generated by the alternator was then converted to 55 watts direct current (DC). Each ASRG unit would use two Stirling converter units with about 500 watts of thermal power supplied by two GPHS units and would deliver 100-120 watts of electric power. The ASRG underwent qualification testing at NASA Glenn as a power supply for a future NASA mission.
The ASRG was designed into many mission proposals in this era, but was cancelled in 2013, due to NASA budget constraints.
See also
Advanced Stirling radioisotope generator
Radioisotope heater unit
Radioisotope thermoelectric generator
References
External links
NASA's Radioisotope Power Systems Program News
Radio Isotope Power Systems for the New Frontier
Why Develop a Stirling Radioisotope Generator?
Free Piston Stirling Converter sets record at NASA Glenn Research Center
Nuclear technology
Electrical generators
Nuclear power in space
Stirling engines | Stirling radioisotope generator | [
"Physics",
"Technology"
] | 925 | [
"Electrical generators",
"Machines",
"Nuclear technology",
"Physical systems",
"Nuclear physics"
] |
5,205,878 | https://en.wikipedia.org/wiki/Computational%20mechanics | Computational mechanics is the discipline concerned with the use of computational methods to study phenomena governed by the principles of mechanics. Before the emergence of computational science (also called scientific computing) as a "third way" besides theoretical and experimental sciences, computational mechanics was widely considered to be a sub-discipline of applied mechanics. It is now considered to be a sub-discipline within computational science.
Overview
Computational mechanics (CM) is interdisciplinary. Its three pillars are mechanics, mathematics, and computer science.
Mechanics
Computational fluid dynamics, computational thermodynamics, computational electromagnetics, computational solid mechanics are some of the many specializations within CM.
Mathematics
The areas of mathematics most related to computational mechanics are partial differential equations, linear algebra and numerical analysis. The most popular numerical methods used are the finite element, finite difference, and boundary element methods in order of dominance. In solid mechanics finite element methods are far more prevalent than finite difference methods, whereas in fluid mechanics, thermodynamics, and electromagnetism, finite difference methods are almost equally applicable. The boundary element technique is in general less popular, but has a niche in certain areas including acoustics engineering, for example.
Computer Science
With regard to computing, computer programming, algorithms, and parallel computing play a major role in CM. The most widely used programming language in the scientific community, including computational mechanics, is Fortran. Recently, C++ has increased in popularity. The scientific computing community has been slow in adopting C++ as the lingua franca. Because of its very natural way of expressing mathematical computations, and its built-in visualization capacities, the proprietary language/environment MATLAB is also widely used, especially for rapid application development and model verification.
Process
Scientists within the field of computational mechanics follow a list of tasks to analyze their target mechanical process:
A mathematical model of the physical phenomenon is made. This usually involves expressing the natural or engineering system in terms of partial differential equations. This step uses physics to formalize a complex system.
The mathematical equations are converted into forms which are suitable for digital computation. This step is called discretization because it involves creating an approximate discrete model from the original continuous model. In particular, it typically translates a partial differential equation (or a system thereof) into a system of algebraic equations. The processes involved in this step are studied in the field of numerical analysis.
Computer programs are made to solve the discretized equations using direct methods (which are single step methods resulting in the solution) or iterative methods (which start with a trial solution and arrive at the actual solution by successive refinement). Depending on the nature of the problem, supercomputers or parallel computers may be used at this stage.
The mathematical model, numerical procedures, and the computer codes are verified using either experimental results or simplified models for which exact analytical solutions are available. Quite frequently, new numerical or computational techniques are verified by comparing their result with those of existing well-established numerical methods. In many cases, benchmark problems are also available. The numerical results also have to be visualized and often physical interpretations will be given to the results.
Applications
Some examples where computational mechanics have been put to practical use are vehicle crash simulation, petroleum reservoir modeling, biomechanics, glass manufacturing, and semiconductor modeling.
Complex systems that would be very difficult or impossible to treat using analytical methods have been successfully simulated using the tools provided by computational mechanics.
See also
Scientific computing
Dynamical systems theory
Movable cellular automaton
References
External links
United States Association for Computational Mechanics
Santa Fe Institute Comp Mech Publications
Computational science
Mechanics
Computational fields of study
Computational physics | Computational mechanics | [
"Physics",
"Mathematics",
"Technology",
"Engineering"
] | 731 | [
"Computational fields of study",
"Applied mathematics",
"Computational physics",
"Computational science",
"Mechanics",
"Computing and society",
"Mechanical engineering"
] |
5,207,969 | https://en.wikipedia.org/wiki/P-Toluenesulfonic%20acid | p-Toluenesulfonic acid (PTSA, pTSA, or pTsOH) or tosylic acid (TsOH) is an organic compound with the formula CH3C6H4SO3H. It is a white extremely hygroscopic solid that is soluble in water, alcohols, and other polar organic solvents. The CH3C6H4SO2 group is known as the tosyl group and is often abbreviated as Ts or Tos. Most often, TsOH refers to the monohydrate, TsOH.H2O.
As with other aryl sulfonic acids, TsOH is a strong organic acid. It is about one million times stronger than benzoic acid. It is one of the few strong acids that is solid and therefore is conveniently weighed and stored.
Preparation and uses
TsOH is prepared on an industrial scale by the sulfonation of toluene. Common impurities include benzenesulfonic acid and sulfuric acid. TsOH is most often supplied as the monohydrate, and it may be necessary to remove the complexed water before use. Impurities can be removed by recrystallization from its concentrated aqueous solution followed by azeotropic drying with toluene.
TsOH finds use in organic synthesis as an "organic-soluble" strong acid. Examples of uses include:
Acetalization of an aldehyde.
Fischer–Speier esterification
Transesterification reactions
Tosylates
Alkyl tosylates are alkylating agents because tosylate is electron-withdrawing as well as a good leaving group. Tosylate is a pseudohalide. Toluenesulfonate esters undergo nucleophilic attack or elimination. Reduction of tosylate esters gives the hydrocarbon. Thus, tosylation followed by reduction allows for the deoxygenation of alcohols.
In a famous and illustrative use of tosylate as a leaving group, the 2-norbornyl cation was formed by an elimination reaction of 7-norbornenyl tosylate. The elimination occurs 1011 times faster than the solvolysis of anti-7-norbornyl p-toluenesulfonate.
Tosylates are also protecting groups for alcohols. They are prepared by combining the alcohol with 4-toluenesulfonyl chloride in the presence of a base. These reactions are usually performed in an aprotic solvent, often pyridine, which additionally acts as a base.
Reactions
TsOH may be converted to p-toluenesulfonic anhydride by heating with phosphorus pentoxide.
When heated with acid and water, TsOH undergoes hydrolysis to toluene:
CH3C6H4SO3H + H2O → C6H5CH3 + H2SO4
This reaction is general for aryl sulfonic acids.
See also
Tosyl
Collidinium p-toluenesulfonate
References
Benzenesulfonic acids
Reagents for organic chemistry
Acid catalysts
Sulfonic acids
P-Tosyl compounds | P-Toluenesulfonic acid | [
"Chemistry"
] | 643 | [
"Sulfonic acids",
"Acids",
"Acid catalysts",
"Functional groups",
"Reagents for organic chemistry"
] |
5,208,165 | https://en.wikipedia.org/wiki/Torsion%20constant | The torsion constant or torsion coefficient is a geometrical property of a bar's cross-section. It is involved in the relationship between angle of twist and applied torque along the axis of the bar, for a homogeneous linear elastic bar. The torsion constant, together with material properties and length, describes a bar's torsional stiffness. The SI unit for torsion constant is m4.
History
In 1820, the French engineer A. Duleau derived analytically that the torsion constant of a beam is identical to the second moment of area normal to the section Jzz, which has an exact analytic equation, by assuming that a plane section before twisting remains planar after twisting, and a diameter remains a straight line.
Unfortunately, that assumption is correct only in beams with circular cross-sections, and is incorrect for any other shape where warping takes place.
For non-circular cross-sections, there are no exact analytical equations for finding the torsion constant. However, approximate solutions have been found for many shapes.
Non-circular cross-sections always have warping deformations that require numerical methods to allow for the exact calculation of the torsion constant.
The torsional stiffness of beams with non-circular cross sections is significantly increased if the warping of the end sections is restrained by, for example, stiff end blocks.
Formulation
For a beam of uniform cross-section along its length,
the angle of twist (in radians) is:
where:
T is the applied torque
L is the beam length
G is the modulus of rigidity (shear modulus) of the material
J is the torsional constant
Inverting the previous relation, we can define two quantities; the torsional rigidity,
with SI units N⋅m2/rad
And the torsional stiffness,
with SI units N⋅m/rad
Examples
Bars with given uniform cross-sectional shapes are special cases.
Circle
where
r is the radius
This is identical to the second moment of area Jzz and is exact.
alternatively write:
where
D is the Diameter
Ellipse
where
a is the major radius
b is the minor radius
Square
where
a is half the side length.
Rectangle
where
a is the length of the long side
b is the length of the short side
is found from the following table:
Alternatively the following equation can be used with an error of not greater than 4%:
where
a is the length of the long side
b is the length of the short side
Thin walled open tube of uniform thickness
t is the wall thickness
U is the length of the median boundary (perimeter of median cross section)
Circular thin walled open tube of uniform thickness
This is a tube with a slit cut longitudinally through its wall. Using the formula above:
t is the wall thickness
r is the mean radius
References
External links
Torsion constant calculator
Continuum mechanics
Structural analysis | Torsion constant | [
"Physics",
"Engineering"
] | 585 | [
"Structural engineering",
"Continuum mechanics",
"Structural analysis",
"Classical mechanics",
"Mechanical engineering",
"Aerospace engineering"
] |
5,208,463 | https://en.wikipedia.org/wiki/Ferredoxin%20fold | In protein structure, a ferredoxin fold is a common α+β protein fold with a signature βαββαβ secondary structure along its backbone. Structurally, the ferredoxin fold can be regarded as a long, symmetric hairpin that is wrapped once around, so that its two terminal β-strands hydrogen-bond to the central two β-strands, forming a four-stranded, antiparallel β-sheet covered on one side by two α-helices.
External links
SCOP list of proteins with a ferredoxin-like fold
References
Protein folds | Ferredoxin fold | [
"Chemistry"
] | 121 | [
"Biochemistry stubs",
"Protein stubs"
] |
5,208,618 | https://en.wikipedia.org/wiki/TIM%20barrel | The TIM barrel (triose-phosphate isomerase), also known as an alpha/beta barrel, is a conserved protein fold consisting of eight alpha helices (α-helices) and eight parallel beta strands (β-strands) that alternate along the peptide backbone. The structure is named after triose-phosphate isomerase, a conserved metabolic enzyme. TIM barrels are ubiquitous, with approximately 10% of all enzymes adopting this fold. Further, five of seven enzyme commission (EC) enzyme classes include TIM barrel proteins. The TIM barrel fold is evolutionarily ancient, with many of its members possessing little similarity today, instead falling within the twilight zone of sequence similarity.
The inner beta barrel (β-barrel) is in many cases stabilized by intricate salt-bridge networks. Loops at the C-terminal ends of the β-barrel are responsible for catalytic activity while N-terminal end loops are important for the stability of the TIM-barrels. Structural inserts ranging from extended loops to independent protein domains may be inserted in place of these loops or at the N-terminus/C-terminals. TIM barrels appear to have evolved through gene duplication and domain fusion events of half-barrel proteins, with a majority of TIM barrels originating from a common ancestor. This led many TIM barrels to possess internal symmetries. Further gene duplication events of this ancestral TIM barrel led to diverging enzymes possessing the functional diversity observed today. TIM barrels have also been a longstanding target for protein designers. Successful TIM barrel designs include both domain fusions of existing proteins and de novo designs. Domain fusions experiments have resulted in many successful designs, whereas de novo designs only yielded successes after 28 years of incremental development.
Structure
Topology
The TIM barrel gets its name from the enzyme triose-phosphate isomerase (TIM), which was the first protein possessing the fold to be crystallized. TIM barrels contain 200-250 amino acid residues, folded into 8 alpha helices (α-helices) and 8 beta strand (β-strands). The β-strands are arranged into a parallel beta barrel (β-barrel), and are surrounded by the 8 α-helices. The defining property of TIM β-barrels is that they always possess a shear number of 8. The shear number is determined by picking a residue x on β-strand-1, and moving along the β-barrel, in a perpendicular direction to the direction of the strands, until residue y on the original β-strand-1 is reached. The number of residues between the start and end positions (|y−x|) is the shear number. Since the number of strands is equal to the shear number, side-chains point alternatively towards the pore and the core, giving a 4-fold symmetry. The α-helices surround and completely enclose the inner β-barrel. Short loops typically connect the α and β secondary structures, forming a (βα)8 repeat topology. In some cases, structures ranging from extended loops to independent domains may be inserted in place of these loops, or may be attached to the N/C-terminals. All TIM barrel enzymes possess catalytic sites at the C-terminal end of the β-barrel, and structural inserts present close to this end may aid in catalytic activity.
Core and pore regions
TIM barrels contain two distinct buried regions, where amino acid residues are completely enveloped by their neighbors and lack access to solvent. The term 'pore' is a misnomer, as no solvent channels exist within this region. The core region consists of all residues constituting the α-β interface, and lies exterior to the central β-barrel. The pore region consists of all interior β-barrel residues, which are surrounded and enclosed by the β-barrel backbone.
Due to the pleated nature of β-strands, alternate residues along a strand are almost evenly split between the pore (53%) and core (47%). For β-barrels, 95% of their core residues are buried. Only 11% of their core residues are polar, possessing an affinity for water, and possessing the ability to form hydrogen bonds or salt bridges. Similarly, 84% of β-strand pore residues are buried. However, 42% of their pore residues are polar. These residues form intricate salt bridge networks to compensate for their lack of solvent accessibility.
TIM barrel stabilizing elements
Salt bridges within TIM barrel pores are thought to contribute to the overall stability of the fold. An example of a large salt bridge network can be found in 2-deoxyribose-5-phosphate aldolase. This network was found to be conserved across the Class I aldolase family.
The exact reason for the overrepresentation of polar residues and salt bridges within the pore remains unclear. One study proposes that they improve foldability rather than thermodynamic stability of TIM barrels. During the folding process, inner pore residues on β-strands would be exposed to water. Partially-folded βαβα modules, called foldons, would be energetically stabilized by polar pore residues during this stage of folding.
In another study involving the S. solfataricus indole-3-glycerol phosphate synthase TIM barrel protein, a conserved βαβαβ module was found to be an essential folding template, which guided the folding of other secondary structures. β-barrel closure only occurred at the end of the folding process. In this case however, the authors credited branched aliphatic amino acids (valine, leucine, and isoleucine) for foldon stability.
Another stabilizing element in TIM barrels is the beta hairpin clamp. Side chain H-bond donors at the N-termini of even-numbered β-strands often form H-bonds with main chain amide hydrogens in preceding odd-numbered β-strands. These clamps (or hydrophobic side chain bridge analogs) are conserved in 3 indole-3-glycerolphosphate synthase TIM barrel orthologs from the bacterial and archaeal kingdoms, implying they arose in their last common ancestor and have been preserved for over a billion years.
Structural inserts
The N/C-terminal and loop regions on TIM barrel proteins are capable of hosting structural inserts ranging from simple secondary structural motifs to complete domains. These domains aid in substrate recognition and catalytic activity. Four diverse examples of TIM barrels containing additional motifs and domains are discussed below.
Bacillus subtilis Orotidine 5'-phosphate decarboxylase () is a TIM barrel protein displaying 4 α-helices in place of the βα loops typically present at the C-terminal of the β-barrel (residues 35-42, 89-91, 126-133, and 215-219). One of these helices (R215→K219) contains a conserved arginineresidue (R215) required for interacting with a phosphate moiety on orotidine 5′-monophosphate. The other helices were not found to host residues critical for catalytic activity, and may serve in structural roles.
Mycobacterium tuberculosis bifunctional histidine/tryptophan biosynthesis isomerase (PriA) () possesses the ability to catalyse two reactions: (i) HisA reaction: the conversion of N-[(5-phosphoribosyl) formimino]-5-aminoimidazole-4-carboxamide ribonucleotide (ProFAR) to N-[(5-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamide ribonucleotide (PRFAR), and (ii) TrpF reaction: N-(5’-phosphoribosyl)-anthranilate (PRA) to 1-(O-carboxyphenylamino)- 1’-deoxyribulose-5’-phosphate (CdRP). PriA is a TIM barrel enzyme that accommodates both substrates using active site loops (loops 1, 5, and 6, extended βα loops at the C-terminal end of the β-barrel) that change conformation depending on the reactant present. Loop 1 wraps over the active site only in the presence of ProFAR. Loop5 wraps over the active site, adopting a β-sheet conformation in the presence of CdRP, or a knot-like conformation in the presence of ProFAR. Loop 6 wraps over the active site for all reactants.
Lactococcus lactis Dihydroorotate dehydrogenase A (DHODA) () is an example of a TIM barrel possessing β-sheets and extended loops over the C-terminal end of the β-barrel. DHODA catalyzes the oxidation of dihydroorotate to orotate, which is part of the de novo uridine 5'-monophosphate (UMP) synthesis pathway. This oxidation is mediated by flavin mononucleotide (FMN). Here, β-sheets and extended loops enclose the active site forming a cavity, while also hosting several catalytic residues.
The Methylophilus methylotrophus trimethylamine dehydrogenase () TIM barrel is an example of a complete domain insertion. Here, a Rossmann fold domain is inserted at the C-terminal end of the TIM-barrel. Trimethylamine dehydrogenase catalyzes the conversion of trimethylamine to formaldehyde. This reaction requires both a reduced 6-S-cysteinyl Flavin mononucleotide (FMN) cofactor and a reduced iron-sulphur ([4Fe-4S]+) center. FMN is covalently bound within the C-terminal region of the β-barrel. The [4Fe-4S]+ center is too large to be accommodated within the TIM barrel, and is instead placed in close proximity, 7 Å away, at the interface between the TIM barrel and Rossmann fold domains.
Folding mechanisms
The conservation of the TIM barrel fold is mirrored by the conservation of its equilibrium and kinetic folding mechanisms in bacterial paralogs with phylogenetically distinct lineages. Chemical denaturation of several natural and 2 designed TIM barrel variants invariably involves a highly populated equilibrium intermediate. The kinetic intermediates that appear after dilution from highly denaturing solutions involve an early misfolded species that must at least partially unfold to access the productive folding pathway. The rate-limiting step in folding is the closure of the 8-stranded β-barrel, with the preceding, open barrel form corresponding to the equilibrium intermediate. Native-centric molecular dynamics simulations recapitulate the experimental results and point the way to testable computational models for complex folding mechanisms.
Conserved fitness landscapes
TIM barrel proteins possess an unusually high sequence plasticity, forming large families of orthologous and paralogous enzymes in widely divergent organisms. This plasticity suggests a sequence landscape that allows for protein adaptation to a variety of environmental conditions, largely independent of phylogenetic history, while maintaining function. A deep mutational scanning approach and a competition assay was used to determine the fitness of all possible amino acid mutants across positions in 3 hyperthermophilic indole-3-glycerolphosphate synthase (IGPS) TIM barrel enzymes in supporting the growth of a yeast host lacking IGPS. Although the 2 bacterial and 1 archaeal IGPS enzymes were only 30-40% identical in sequence, their fitness landscapes were strongly correlated: the same amino acids at the same positions in the three different proteins had very similar fitness. The correlation can be thought of as the conservation of the fitness landscape for a TIM barrel enzyme across evolutionary time.
Loop regions
Of the approximately 200 residues required to fully form a TIM barrel, about 160 are considered structurally equivalent between different proteins sharing this fold. The remaining residues are located on the loop regions that link the helices and strands; the loops at the C-terminal end of the strands tend to contain the active site, which is one reason this fold is so common: the residues required to maintain the structure and the residues that effect enzymatic catalysis are for the most part distinct subsets: The linking loops can, in fact, be so long that they contain other protein domains. Recently, it has been demonstrated that catalytic loops can be exchanged between different TIM barrel enzymes as semiautonomous units of functional groups.
Evolution and origins
The predominant theory for TIM barrel evolution involves gene duplication and fusion, starting with a half- barrel that eventually formed a full TIM barrel. Multiple studies support the theory of divergent evolution from a single ancestor, and are discussed below.
Evolution from a common ancestor
In the early 1990s, it was noted that all TIM barrel structures solved at the time were enzymes, indicating divergence from a common ancestor. Further, all TIM barrels possessed active sites at the C-terminal end of β-barrels. suggested that A common phosphate binding site, formed by a small α-helix and TIM barrel loops-7/8, strongly indicated divergent evolution. Further studies of these phosphate groups, concluding that 12 of 23 SCOP TIM barrel families diverged from a common ancestor. Similarly there were hints for common ancestry for 17 of the 21 CATH TIM barrel families. Based on these reports, it is considered plausible that the majority of TIM barrel proteins evolved from a common ancestor.
Origin through gene duplication and domain fusion
Many TIM barrel proteins possess 2-fold, 4-fold or 8-fold internal symmetry, suggesting that TIM barrels evolved from ancestral (βα)4, (βα)2, or βα motifs through gene duplication and domain fusion. A good example of 2-fold internal symmetry is observed in the enzymes ProFAR isomerase (HisA) and imidazole glycerol phosphate synthase (HisF) of the Thermotoga maritima histidine biosynthesis pathway. They catalyze 2 successive reactions in the pathway, possess 25% sequence homology, and possess root-mean-square deviations (RMSDs) between 1.5-2 Å, suggesting divergence from a common ancestor. More interestingly, the loops on the C terminal ends of both HisA and HisF showed a twofold repeated pattern, suggesting that their common ancestor also possessed 2-fold internal symmetry. Using these observations, a model was constructed for the evolution of the TIM barrels. An ancestral half-barrel would have undergone a gene duplication and fusion event, resulting in a single protein containing two half-barrel domains. Structural adaptations would have occurred, resulting in the merging of these domains to form a closed β-barrel, and forming an ancestral TIM barrel. Functional adaptations would have also occurred, resulting in the evolution of new catalytic activity at the C terminal end of the β-barrel. At this point, the common ancestor of HisA and HisF would have undergone a second gene duplication event. Divergent evolution of the duplicated genes of the ancestral TIM barrel would have resulted in the formation of HisA and HisF.
Interestingly, this evolutionary model has been experimentally validated using rational protein design and directed evolution. Höcker et al. first fused two C-terminal halves of HisF, yielding HisF-CC. This construct was then stabilized by the insertion of an internal salt-bridge, yielding HisF-C*C. Further stepwise stabilization and solubilization of HisF-C*C was achieved by optimizing the half-barrel interface, generating HisF-C**C and HisF-C***C, respectively. The crystal structure of HisF-C***C revealed a 2-fold symmetric TIM barrel, validating the possibility of natural domain fusion. Moreover, Höcker created the first chimeric HisAF and HisFA TIM barrels using HisA and HisF half-barrels. These experiments led to the proposal of a novel means of diversification and evolution of TIM-barrel enzymes through the exchange of (βα)4 half-barrel domains amongst preexisting TIM barrels. In accordance with this idea, a high catalytic activity on the HisAF construct was established. Similarly, chimeric βα5-flavodoxin-like fold (CheY)/HisF TIM barrels, and a perfectly 2-fold symmetric HisF-based TIM barrel have also been created.
The existence of 4/8-fold internal symmetry was suggested based on a computational analysis of TIM barrel sequences. For example, Escherichia coli KDPG aldolase () was suggested to possess a distinct 4-fold symmetry, with discernible 8-fold symmetry. The design of a 4-fold symmetric TIM barrel confirmed the possibility of higher orders of internal symmetry in natural TIM barrels, and will be discussed in detail in the next section. No experimental evidence for the existence of 8-fold symmetric TIM barrels has been reported to date.
De novo TIM barrel design
The TIM barrel fold has been a long-standing target for de novo protein designers. As previously described, numerous TIM barrels have been successfully designed based on preexisting natural half-barrels. In contrast, the de novo design of TIM barrels occurred in incremental steps over a period of 28 years.
The Octarellin series of proteins (Octarellin I→VI) were the first attempts to create a de novo TIM barrel. As the field of protein design was still in its infancy, these design attempts were only met with limited success. Although they displayed circular dichroism spectra consistent with αβ proteins and some cooperative folding characteristics, all Octarellin series peptides were insoluble, and had to be resolubilized from inclusion bodies for further characterization. Interestingly, Octarellin V.1 displayed a Rossmann-like fold under co-crystal conditions.
The Symmetrin series of proteins (Symmetrin-1→4) displayed more favorable biophysical characteristics. Symmetrin-1 was readily soluble, displayed circular dichroism spectra consistent with αβ proteins, and displayed excellent cooperative unfolding and refolding characteristics. Despite these advances, all proteins in this family displayed molten characteristics when analyzed using NMR (nuclear magnetic resonance), and further work to solve their structures could not be pursued.
Proteins of the sTIM series represented the first successful de novo TIM barrel design. sTIM-11 () was designed with an internal 4-fold symmetry, to reduce the complexity of computational design using the Rosetta software suite. Previously-derived first principles were used to delineate secondary structure topologies and lengths. sTIM-11 proved to be a highly thermostable, cooperatively folding design that adopted its intended structure.
See also
Protein folding
Triosephosphate isomerase
References
External links
SCOP list of proteins adopting the TIM barrel fold
Protein folds
Protein superfamilies
Protein tandem repeats
Protein domains | TIM barrel | [
"Biology"
] | 3,924 | [
"Protein tandem repeats",
"Protein superfamilies",
"Protein domains",
"Protein classification"
] |
5,208,918 | https://en.wikipedia.org/wiki/DGLAP%20evolution%20equations | The Dokshitzer–Gribov–Lipatov–Altarelli–Parisi (DGLAP) evolution equations are equations in QCD describing the variation of parton distribution functions with varying energy scales. Experimentally observed scaling violation in deep inelastic scattering is important evidence for the correctness of the equations and of QCD in general. The equations were first published in the western world by Guido Altarelli and Giorgio Parisi in 1977, and so are still sometimes called the Altarelli–Parisi equations. Only later did it become known that an equivalent formula had been published in Russia by in 1977, and by Vladimir Gribov and Lev Lipatov in 1972.
The DGLAP QCD evolution equations are widely used in global determinations of parton distributions, like those from the CTEQ or NNPDF collaborations.
See also
Jet (particle physics)
HERA
APFEL (Software)
References
Further reading
External links
Guido Altarelli (2009) QCD evolution equations for parton densities. Scholarpedia, 4(1):7124.
Quantum chromodynamics | DGLAP evolution equations | [
"Physics"
] | 227 | [
"Particle physics stubs",
"Particle physics"
] |
5,209,604 | https://en.wikipedia.org/wiki/Harnack%27s%20curve%20theorem | In real algebraic geometry, Harnack's curve theorem, named after Axel Harnack, gives the possible numbers of connected components that an algebraic curve can have, in terms of the degree of the curve. For any algebraic curve of degree in the real projective plane, the number of components is bounded by
The maximum number is one more than the maximum genus of a curve of degree , attained when the curve is nonsingular. Moreover, any number of components in this range of possible values can be attained.
A curve which attains the maximum number of real components is called an M-curve (from "maximum") – for example, an elliptic curve with two components, such as or the Trott curve, a quartic with four components, are examples of M-curves.
This theorem formed the background to Hilbert's sixteenth problem.
In a recent development a Harnack curve is shown to be a curve whose amoeba has area equal to the Newton polygon of the polynomial , which is called the characteristic curve of dimer models, and every Harnack curve is the spectral curve of some dimer model.()
References
Dmitrii Andreevich Gudkov, The topology of real projective algebraic varieties, Uspekhi Mat. Nauk 29 (1974), 3–79 (Russian), English transl., Russian Math. Surveys 29:4 (1974), 1–79
Carl Gustav Axel Harnack, Ueber die Vieltheiligkeit der ebenen algebraischen Curven, Math. Ann. 10 (1876), 189–199
George Wilson, Hilbert's sixteenth problem, Topology 17 (1978), 53–74
Real algebraic geometry
Theorems in algebraic geometry | Harnack's curve theorem | [
"Mathematics"
] | 353 | [
"Theorems in algebraic geometry",
"Theorems in geometry"
] |
25,853,619 | https://en.wikipedia.org/wiki/Luttinger%27s%20theorem | In condensed matter physics, Luttinger's theorem is a result derived by J. M. Luttinger and J. C. Ward in 1960 that has broad implications in the field of electron transport. It arises frequently in theoretical models of correlated electrons, such as the high-temperature superconductors, and in photoemission, where a metal's Fermi surface can be directly observed.
Definition
Luttinger's theorem states that the volume enclosed by a material's Fermi surface is directly proportional to the particle density.
While the theorem is an immediate result of the Pauli exclusion principle in the case of noninteracting particles, it remains true even as interactions between particles are taken into consideration provided that the appropriate definitions of Fermi surface and particle density are adopted. Specifically, in the interacting case the Fermi surface must be defined according to the criteria that
or
where is the single-particle Green function in terms of frequency and momentum. Then Luttinger's theorem can be recast into the form
,
where is the real part of the above Green function and is the differential volume of -space in dimensions.
See also
Fermi liquid
Fermi surface
Luttinger–Ward functional
References
Inline
General
Condensed matter physics
Eponymous theorems of physics
Fermions | Luttinger's theorem | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 260 | [
"Equations of physics",
"Fermions",
"Phases of matter",
"Materials science",
"Eponymous theorems of physics",
"Subatomic particles",
"Condensed matter physics",
"Matter",
"Physics theorems"
] |
25,854,285 | https://en.wikipedia.org/wiki/Digifold | Digifold is a new generation of four and six corner folding device for box gluers and associated machinery. Development began in the late 1990s, and was first exhibited at IPEX 2002 trade show. A system using Siemens S7-200 PLC and Siemens Servo controllers was developed throughout the late 1990s, into the year 2000. It was the first system, in the box folding industry, to use carbon fibre as a construction material (used in the drive shafts), and advanced aluminium (aluminum) alloys in the clamping devices. Although it was not the first servo driven backfolding system, it used advanced materials to improve speed and reduce cost over comparable systems (notably from Jagenberg, Bobst and others)
References
Jez Abbott (30 May 2008) Morgana quadruples the speed of its latest DigiFold creaser-folder, printweek.com
Morgana DigiFold infiltrates the CIA, ProPrint, Jan 21, 2009
External links
Product page
Machines | Digifold | [
"Physics",
"Technology",
"Engineering"
] | 203 | [
"Physical systems",
"Machines",
"Mechanical engineering"
] |
2,870,898 | https://en.wikipedia.org/wiki/Cocycle | In mathematics a cocycle is a closed cochain. Cocycles are used in algebraic topology to express obstructions (for example, to integrating a differential equation on a closed manifold). They are likewise used in group cohomology. In autonomous dynamical systems, cocycles are used to describe particular kinds of map, as in Oseledets theorem.
Definition
Algebraic Topology
Let X be a CW complex and be the singular cochains with coboundary map . Then elements of are cocycles. Elements of are coboundaries. If is a cocycle, then , which means cocycles vanish on boundaries.
See also
Čech cohomology
Cocycle condition
References
Algebraic topology
Cohomology theories
Dynamical systems | Cocycle | [
"Physics",
"Mathematics"
] | 151 | [
"Algebraic topology",
"Topology stubs",
"Fields of abstract algebra",
"Topology",
"Mechanics",
"Dynamical systems"
] |
2,871,265 | https://en.wikipedia.org/wiki/List%20of%20spherical%20symmetry%20groups | Finite spherical symmetry groups are also called point groups in three dimensions. There are five fundamental symmetry classes which have triangular fundamental domains: dihedral, cyclic, tetrahedral, octahedral, and icosahedral symmetry.
This article lists the groups by Schoenflies notation, Coxeter notation, orbifold notation, and order. John Conway uses a variation of the Schoenflies notation, based on the groups' quaternion algebraic structure, labeled by one or two upper case letters, and whole number subscripts. The group order is defined as the subscript, unless the order is doubled for symbols with a plus or minus, "±", prefix, which implies a central inversion.
Hermann–Mauguin notation (International notation) is also given. The crystallography groups, 32 in total, are a subset with element orders 2, 3, 4 and 6.
Involutional symmetry
There are four involutional groups: no symmetry (C1), reflection symmetry (Cs), 2-fold rotational symmetry (C2), and central point symmetry (Ci).
Cyclic symmetry
There are four infinite cyclic symmetry families, with n = 2 or higher. (n may be 1 as a special case as no symmetry)
Dihedral symmetry
There are three infinite dihedral symmetry families, with n = 2 or higher (n may be 1 as a special case).
Polyhedral symmetry
There are three types of polyhedral symmetry: tetrahedral symmetry, octahedral symmetry, and icosahedral symmetry, named after the triangle-faced regular polyhedra with these symmetries.
Continuous symmetries
All of the discrete point symmetries are subgroups of certain continuous symmetries. They can be classified as products of orthogonal groups O(n) or special orthogonal groups SO(n). O(1) is a single orthogonal reflection, dihedral symmetry order 2, Dih1. SO(1) is just the identity. Half turns, C2, are needed to complete.
See also
Crystallographic point group
Triangle group
List of planar symmetry groups
Point groups in two dimensions
References
Further reading
Peter R. Cromwell, Polyhedra (1997), Appendix I
On Quaternions and Octonions, 2003, John Horton Conway and Derek A. Smith
The Symmetries of Things 2008, John H. Conway, Heidi Burgiel, Chaim Goodman-Strauss,
Kaleidoscopes: Selected Writings of H.S.M. Coxeter, edited by F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss, Wiley-Interscience Publication, 1995,
(Paper 22) H.S.M. Coxeter, Regular and Semi Regular Polytopes I, [Math. Zeit. 46 (1940) 380–407, MR 2,10]
(Paper 23) H.S.M. Coxeter, Regular and Semi-Regular Polytopes II, [Math. Zeit. 188 (1985) 559–591]
(Paper 24) H.S.M. Coxeter, Regular and Semi-Regular Polytopes III, [Math. Zeit. 200 (1988) 3–45]
N.W. Johnson: Geometries and Transformations, (2018) Chapter 11: Finite symmetry groups, Table 11.4 Finite Groups of Isometries in 3-space
External links
Finite spherical symmetry groups
Simplest Canonical Polyhedra of Each Symmetry Type, by David I. McCooey
Polyhedra
Symmetry
Group theory
Spherical symmetry groups, Finite | List of spherical symmetry groups | [
"Physics",
"Mathematics"
] | 735 | [
"Group theory",
"Fields of abstract algebra",
"Geometry",
"Symmetry"
] |
2,871,908 | https://en.wikipedia.org/wiki/Pohlmeyer%20charge | In theoretical physics Pohlmeyer charge, named for Klaus Pohlmeyer, is a conserved charge invariant under the Virasoro algebra or its generalization. It can be obtained by expanding the holonomies (generating functions)
with respect to the constant matrices T. The gauge field is defined as a combination of and its conjugate.
According to the logic of loop quantum gravity and algebraic quantum field theory, these charges are the right physical quantities that should be used for quantization. This logic is however incompatible with the standard and well-established methods of quantum field theory based on Fock space and perturbation theory.
References
Quantum field theory
Conformal field theory | Pohlmeyer charge | [
"Physics"
] | 137 | [
"Quantum field theory",
"Theoretical physics",
"Quantum mechanics",
"Theoretical physics stubs",
"Quantum physics stubs"
] |
2,875,647 | https://en.wikipedia.org/wiki/Energy%E2%80%93momentum%20relation | In physics, the energy–momentum relation, or relativistic dispersion relation, is the relativistic equation relating total energy (which is also called relativistic energy) to invariant mass (which is also called rest mass) and momentum. It is the extension of mass–energy equivalence for bodies or systems with non-zero momentum.
It can be formulated as:
This equation holds for a body or system, such as one or more particles, with total energy , invariant mass , and momentum of magnitude ; the constant is the speed of light. It assumes the special relativity case of flat spacetime and that the particles are free. Total energy is the sum of rest energy and relativistic kinetic energy:
Invariant mass is mass measured in a center-of-momentum frame.
For bodies or systems with zero momentum, it simplifies to the mass–energy equation , where total energy in this case is equal to rest energy.
The Dirac sea model, which was used to predict the existence of antimatter, is closely related to the energy–momentum relation.
Connection to E = mc2
The energy–momentum relation is consistent with the familiar mass–energy relation in both its interpretations: relates total energy to the (total) relativistic mass (alternatively denoted or ), while relates rest energy to (invariant) rest mass .
Unlike either of those equations, the energy–momentum equation () relates the total energy to the rest mass . All three equations hold true simultaneously.
Special cases
If the body is a massless particle (), then () reduces to . For photons, this is the relation, discovered in 19th century classical electromagnetism, between radiant momentum (causing radiation pressure) and radiant energy.
If the body's speed is much less than , then () reduces to ; that is, the body's total energy is simply its classical kinetic energy () plus its rest energy.
If the body is at rest (), i.e. in its center-of-momentum frame (), we have and ; thus the energy–momentum relation and both forms of the mass–energy relation (mentioned above) all become the same.
A more general form of relation () holds for general relativity.
The invariant mass (or rest mass) is an invariant for all frames of reference (hence the name), not just in inertial frames in flat spacetime, but also accelerated frames traveling through curved spacetime (see below). However the total energy of the particle and its relativistic momentum are frame-dependent; relative motion between two frames causes the observers in those frames to measure different values of the particle's energy and momentum; one frame measures and , while the other frame measures and , where and , unless there is no relative motion between observers, in which case each observer measures the same energy and momenta. Although we still have, in flat spacetime:
The quantities , , , are all related by a Lorentz transformation. The relation allows one to sidestep Lorentz transformations when determining only the magnitudes of the energy and momenta by equating the relations in the different frames. Again in flat spacetime, this translates to;
Since does not change from frame to frame, the energy–momentum relation is used in relativistic mechanics and particle physics calculations, as energy and momentum are given in a particle's rest frame (that is, and as an observer moving with the particle would conclude to be) and measured in the lab frame (i.e. and as determined by particle physicists in a lab, and not moving with the particles).
In relativistic quantum mechanics, it is the basis for constructing relativistic wave equations, since if the relativistic wave equation describing the particle is consistent with this equation – it is consistent with relativistic mechanics, and is Lorentz invariant. In relativistic quantum field theory, it is applicable to all particles and fields.
Origins and derivation of the equation
The energy–momentum relation goes back to Max Planck's article
published in 1906.
It was used by Walter Gordon in 1926 and then by Paul Dirac in 1928 under the form , where V is the amount of potential energy.
The equation can be derived in a number of ways, two of the simplest include:
From the relativistic dynamics of a massive particle,
By evaluating the norm of the four-momentum of the system. This method applies to both massive and massless particles, and can be extended to multi-particle systems with relatively little effort (see below).
Heuristic approach for massive particles
For a massive object moving at three-velocity with magnitude in the lab frame:
is the total energy of the moving object in the lab frame,
is the three dimensional relativistic momentum of the object in the lab frame with magnitude . The relativistic energy and momentum include the Lorentz factor defined by:
Some authors use relativistic mass defined by:
although rest mass has a more fundamental significance, and will be used primarily over relativistic mass in this article.
Squaring the 3-momentum gives:
then solving for and substituting into the Lorentz factor one obtains its alternative form in terms of 3-momentum and mass, rather than 3-velocity:
Inserting this form of the Lorentz factor into the energy equation gives:
followed by more rearrangement it yields (). The elimination of the Lorentz factor also eliminates implicit velocity dependence of the particle in (), as well as any inferences to the "relativistic mass" of a massive particle. This approach is not general as massless particles are not considered. Naively setting would mean that and and no energy–momentum relation could be derived, which is not correct.
Norm of the four-momentum
Special relativity
In Minkowski space, energy (divided by ) and momentum are two components of a Minkowski four-vector, namely the four-momentum;
(these are the contravariant components).
The Minkowski inner product of this vector with itself gives the square of the norm of this vector, it is proportional to the square of the rest mass of the body:
a Lorentz invariant quantity, and therefore independent of the frame of reference. Using the Minkowski metric with metric signature , the inner product is
and
so
or, in natural units where = 1,
General relativity
In general relativity, the 4-momentum is a four-vector defined in a local coordinate frame, although by definition the inner product is similar to that of special relativity,
in which the Minkowski metric is replaced by the metric tensor field :
solved from the Einstein field equations. Then:
Units of energy, mass and momentum
In natural units where , the energy–momentum equation reduces to
In particle physics, energy is typically given in units of electron volts (eV), momentum in units of eV·−1, and mass in units of eV·−2. In electromagnetism, and because of relativistic invariance, it is useful to have the electric field and the magnetic field in the same unit (Gauss), using the cgs (Gaussian) system of units, where energy is given in units of erg, mass in grams (g), and momentum in g·cm·s−1.
Energy may also in theory be expressed in units of grams, though in practice it requires a large amount of energy to be equivalent to masses in this range. For example, the first atomic bomb liberated about 1 gram of heat, and the largest thermonuclear bombs have generated a kilogram or more of heat. Energies of thermonuclear bombs are usually given in tens of kilotons and megatons referring to the energy liberated by exploding that amount of trinitrotoluene (TNT).
Special cases
Centre-of-momentum frame (one particle)
For a body in its rest frame, the momentum is zero, so the equation simplifies to
where is the rest mass of the body.
Massless particles
If the object is massless, as is the case for a photon, then the equation reduces to
This is a useful simplification. It can be rewritten in other ways using the de Broglie relations:
if the wavelength or wavenumber are given.
Correspondence principle
Rewriting the relation for massive particles as:
and expanding into power series by the binomial theorem (or a Taylor series):
in the limit that , we have so the momentum has the classical form , then to first order in (i.e. retain the term for and neglect all terms for ) we have
or
where the second term is the classical kinetic energy, and the first is the rest energy of the particle. This approximation is not valid for massless particles, since the expansion required the division of momentum by mass. Incidentally, there are no massless particles in classical mechanics.
Many-particle systems
Addition of four momenta
In the case of many particles with relativistic momenta and energy , where (up to the total number of particles) simply labels the particles, as measured in a particular frame, the four-momenta in this frame can be added;
and then take the norm; to obtain the relation for a many particle system:
where is the invariant mass of the whole system, and is not equal to the sum of the rest masses of the particles unless all particles are at rest (see for more detail). Substituting and rearranging gives the generalization of ();
The energies and momenta in the equation are all frame-dependent, while is frame-independent.
Center-of-momentum frame
In the center-of-momentum frame (COM frame), by definition we have:
with the implication from () that the invariant mass is also the centre of momentum (COM) mass–energy, aside from the factor:
and this is true for all frames since is frame-independent. The energies are those in the COM frame, not the lab frame. However, many familiar bound systems have the lab frame as COM frame, since the system itself is not in motion and so the momenta all cancel to zero. An example would be a simple object (where vibrational momenta of atoms cancel) or a container of gas where the container is at rest. In such systems, all the energies of the system are measured as mass. For example, the heat in an object on a scale, or the total of kinetic energies in a container of gas on the scale, all are measured by the scale as the mass of the system.
Rest masses and the invariant mass
Either the energies or momenta of the particles, as measured in some frame, can be eliminated using the energy momentum relation for each particle:
allowing to be expressed in terms of the energies and rest masses, or momenta and rest masses. In a particular frame, the squares of sums can be rewritten as sums of squares (and products):
so substituting the sums, we can introduce their rest masses in ():
The energies can be eliminated by:
similarly the momenta can be eliminated by:
where is the angle between the momentum vectors and .
Rearranging:
Since the invariant mass of the system and the rest masses of each particle are frame-independent, the right hand side is also an invariant (even though the energies and momenta are all measured in a particular frame).
Matter waves
Using the de Broglie relations for energy and momentum for matter waves,
where is the angular frequency and is the wavevector with magnitude , equal to the wave number, the energy–momentum relation can be expressed in terms of wave quantities:
and tidying up by dividing by throughout:
This can also be derived from the magnitude of the four-wavevector
in a similar way to the four-momentum above.
Since the reduced Planck constant and the speed of light both appear and clutter this equation, this is where natural units are especially helpful. Normalizing them so that , we have:
Tachyon and exotic matter
The velocity of a bradyon with the relativistic energy–momentum relation
can never exceed . On the contrary, it is always greater than for a tachyon whose energy–momentum equation is
By contrast, the hypothetical exotic matter has a negative mass and the energy–momentum equation is
See also
Mass–energy equivalence
Four-momentum
Mass in special relativity
References
Momentum
Special relativity | Energy–momentum relation | [
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"Mathematics"
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2,875,651 | https://en.wikipedia.org/wiki/ASML%20Holding | ASML Holding N.V. (commonly shortened to ASML, originally standing for Advanced Semiconductor Materials Lithography) is a Dutch multinational corporation founded in 1984. ASML specializes in the development and manufacturing of photolithography machines which are used to produce computer chips.
it is the largest supplier for the semiconductor industry and the sole supplier in the world of extreme ultraviolet lithography (EUVL) photolithography machines that are required to manufacture the most advanced chips. , ASML was the fourth most valuable company in Europe, and the second most valued European tech company, with a market capitalization of about US$264 billion.
ASML's corporate headquarters is in Veldhoven, Netherlands and the location for research, development, manufacturing and assembly. ASML employs more than 42,000 people from 143 nationalities and relies on a network of nearly 5,000 tier 1 suppliers. ASML has a worldwide customer base and over sixty service points in sixteen countries. It has offices in the Netherlands, the United States, Belgium, France, Germany, Ireland, Israel, Italy, the United Kingdom, China, Hong Kong, Japan, South Korea, Malaysia, Singapore, and Taiwan.
The company is listed on both the AEX and Nasdaq stock exchanges, as ASML. It is also a component of the Euro Stoxx 50 and Nasdaq-100.
Products
ASML produces the photolithography machines used in the production of computer chips. In these machines, patterns are optically imaged onto a silicon wafer that is covered with a film of light-sensitive material (photoresist). This procedure is repeated dozens of times on a single wafer. The photoresist is then further processed to create the actual electronic circuits on the silicon. The optical imaging that ASML's machines deal with is used in the fabrication of nearly all integrated circuits and, as of 2011, ASML had 67 percent of the worldwide sales of lithography machines.
ASML's earlier competition consisted of Ultratech, Canon and Nikon, MKS Instruments, Lam Research and Cadence Design Systems.
Immersion lithography
Since immersion lithography was first proposed by Burn-Jeng Lin in the 1970s, ASML cooperated with Taiwan Semiconductor Manufacturing (TSMC). In 2004, TSMC began commercial production of 90 nanometer semiconductor nodes using ASML immersion lithography. As of 2011, their high-end TWINSCAN NXT:1950i system was used for producing features down to 32 nanometres at up to 200 wafers per hour, using a water immersion lens and an argon fluoride laser that produces light at a wavelength of 193 nm. , an average lithography machine cost .
DUV lithography
Deep ultraviolet (DUV) lithography devices from ASML use light that penetrates the UV spectrum to print the tiny features that form the microchip's structure.
EUV lithography
EUV lithography is a critical technology used to create the smallest and most complex chip designs. ASML holds a near-monopoly in the EUV market, with no significant direct competitors. The company's machines are capable of etching patterns as small as 8 nanometers, a remarkable achievement given that human hair is approximately 80,000 nanometers thick.
Extreme ultraviolet lithography (EUV) machines produce light in the 13.5 nm wavelength range when a high-energy laser is focused on microscopic droplets of molten tin to produce a plasma, which then emits EUV light. The light is bounced off Zeiss mirrors onto the surface of a silicon wafer to deliver the designs for the chip.
In 2009, the IMEC research center in Belgium produced the world's first functional 22 nm CMOS Static random-access memory memory cells with a prototype EUV lithography machine. After decades of development, ASML shipped the first production extreme ultraviolet lithography machine in either 2011 or 2013.
, ASML has shipped around 140 EUV systems, and it is the only company to manufacture them. ASML's best-selling EUV product has been the TWINSCAN NXE:3600D, which costs up to $200 million. Shipping the machine the size of a truck requires moving 180 tons with three Boeing 747s.
ASML is working on the next generation of EUV systems, with the first shipments for R&D purposes shipped to Intel in December 2023, and TSMC in late 2024. The platform is designated High-NA as it increases the numerical aperture (NA) from 0.33 to 0.55, and each system costs approximately $370 million.
ASML's EUV machines have experienced a significant surge in demand in recent years, driven by modern electronics' increasing complexity and performance requirements. This surge in demand has translated into steady revenue growth for the company, reaching $30 billion in 2023, up from $13 billion five years earlier.
History
ASM Lithography was founded in 1984 as a joint venture between the Dutch companies ASM and Philips. The company became an independent publicly-traded entity in 1988 and was renamed to ASML, which is its official name and not an abbreviation.
In 1991, ASML released the lithography system PAS 5500, which became an extremely successful platform for the company. The PAS 5500 was first utilized by Micron Technology, which was one of the world's largest producers of computer memory and storage, and ASML's largest customer at that time. The success of the PAS 5500 line propelled ASML into strong competition with Canon and Nikon, who were the leaders in that era of the lithography market.
In 1997, ASML began studying a shift to using extreme ultraviolet and in 1999 joined a consortium, including Intel and two other U.S. chipmakers, in order to exploit fundamental research conducted by the US Department of Energy. Because the CRADA it operates under is funded by the US taxpayer, licensing must be approved by Congress. It collaborated with the Belgian IMEC and Sematech and turned to Carl Zeiss in Germany for its need of mirrors.
In 2000, ASML acquired the Silicon Valley Group (SVG), a US lithography equipment manufacturer also licensed for EUV research results, in a bid to supply 193 nm scanners to Intel Corp.
In 2002, it became the largest supplier of photolithography systems.
At the end of 2008, ASML experienced a large drop in sales, which led management to cut the workforce by about 1000 worldwide, mostly contract workers and to apply for support from the Dutch national unemployment fund to prevent even larger layoffs. Two and a half years later, ASML expected a record-high revenue.
In July 2012, Intel announced a deal to invest $4.1 billion into ASML in exchange for 15% ownership, in order to speed up the transition from 300 mm to 450 mm wafers and further development of EUV lithography. This deal was without exclusive rights to future ASML products and, as of July 2012, ASML was offering another 10% of the shares to other companies. As part of their EUV strategy, ASML announced the acquisition of DUV and EUV sources manufacturer Cymer in October 2012.
In November 2013, ASML paused development of 450 mm lithography equipment, citing uncertain timing of chipmaker demand.
In 2015, ASML suffered intellectual property theft. A number of employees had been found stealing confidential data from its Silicon Valley software subsidiary that develops software for machine optimization.
In June 2016, ASML announced their plans to acquire Taiwan-based Hermes Microvision Inc. for about $3.1 billion to add technology for creating smaller and more advanced semiconductors.
In 2018, the Trump administration tried to block the sale of ASML technology to China, but as of 2021, the ongoing global chip shortage as well as the "technological cold war" between the US and China had been a business opportunity for ASML.
In November 2020, ASML revealed that it had acquired the German optical glassmaking firm Berliner Glas Group in order to meet increasing need for components for its EUV systems.
In July 2021, European Commissioner Thierry Breton, visited ASML and announced a goal of at least 20% of world production of semiconductors in Europe by 2030, and support via a European Alliance on semiconductors. After reporting earnings in July 2021, the company said they had a near monopoly for machines used by TSMC and Samsung Electronics to make the advanced chips.
In February 2023, ASML claimed that a former worker in China "allegedly" stole information about the company's technology. This was not the first time that ASML was allegedly linked with an intellectual property breach connected to China. In its 2021 annual report, ASML mentioned that Dongfang Jingyuan Electron Limited "was actively marketing products in China that could potentially infringe on ASML's IP rights." At the time, the United States Department of Commerce expressed concern about economic espionage against ASML. In October 2023, Dutch newspaper NRC Handelsblad reported that the former employee who "allegedly" stole data about ASML's technology subsequently went to work for Huawei.
In March 2023, the Dutch government placed restrictions on chip equipment exports in order to protect national security. This measure affected ASML as one of the most important companies in the global microchip supply chain. Export license requirements came into effect in September 2023.
In June 2023, the Netherlands' Institute for Human Rights ruled that despite the country's constitution prohibiting discrimination based on nationality, ASML was allowed to reject job applications from residents of countries subject to sanctions under the U.S. Export Administration Regulations (such as China, Cuba, Iran, North Korea, and Syria) in order to remain compliant with U.S. law.
In January 2024, the Dutch government placed further restrictions on the shipment of some advanced chip-making equipment to China. On 6 September 2024, the Dutch government tightened export controls on certain ASML chipmaking equipment, aligning its policy with U.S. restrictions to limit China's access to advanced technology amid safety and geopolitical concerns. These restrictions were expanded for tighter export controls in January 2025, with ASML required to apply for export licenses with the Dutch government instead of the U.S.
Finances
Shareholder
Sponsorships
ASML became a sponsor of the PSV soccer club in 2019 together with Philips. VDL Groep, Royal Swinkels Family Brewers and Jumbo Supermarkets from the Brainport region. Together they run various initiatives like soccer training camps for school children, the development of interactive programs for teaching, assisting community members in need or who are new to the region, as well as supporting a vitality program that is online.
Awards
The IEEE Spectrum Emerging Technology 2018 Award was given to ASML for its Extreme Ultraviolet Lithography system. ASML is currently the top supplier of photolithography systems to the semiconductor industry.
In the category for Popular Prize, Vadim Banine received the 2018 European Inventor Award for shaping the future of microchip manufacturing.
The largest independent microelectronics research center in Europe is called IMEC (Interuniversity Micro Electronics Centre). Martin van den Brink of ASML was given the 2019 IMEC Lifetime of Innovation Award.
The Netherlands Association for Investor Relations (NEVIR), where listed companies and professionals in investor relations had the chance to be recognized for their outstanding work in the sector, presented awards to ASML in the categories: "Best Company in the field of Investor Relations" during the Dutch IR Awards 2019 annual award ceremony.
ASML received the SEMI Americas Award at the 2020 edition of the microelectronics conference SEMICON West for its collaborative approach to extreme ultraviolet lithography (EUV), which helped it become commercially viable and opened the door to new technological possibilities.
The Intel Preferred Quality Supplier (PQS) Award for 2020 was awarded to ASML. ASML has attained a level of performance that continuously surpasses Intel's expectations for the commitment to continual quality improvement.
The Dutch Innovation Prize 2021 was awarded to ASML at the 4th National BID AVROTROS Innovation Dinner held at Kasteel Wittenburg in Wassenaar.
ASML received the first CoSta Award for the most successful and impactful innovative partnership between a corporate company and a startup.
References
External links
"The Silicon Age: Trends in Semiconductor Devices Industry", 2022
Electronics companies of the Netherlands
Equipment semiconductor companies
Nanotechnology companies
Technology companies of the Netherlands
Multinational companies headquartered in the Netherlands
Holding companies of the Netherlands
Companies based in North Brabant
Organisations based in Veldhoven
Computer companies established in 1984
Electronics companies established in 1984
Holding companies established in 1984
Technology companies established in 1984
Dutch companies established in 1984
Companies listed on Euronext Amsterdam
Companies in the Euro Stoxx 50
Companies in the AEX index
Companies listed on the Nasdaq
Dutch brands
Photonics companies | ASML Holding | [
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30,528,077 | https://en.wikipedia.org/wiki/Annual%20Review%20of%20Chemical%20and%20Biomolecular%20Engineering | Annual Review of Chemical and Biomolecular Engineering is an annual peer-reviewed scientific journal published by Annual Reviews, covering chemical and biomolecular engineering. The co-editors are Michael F. Doherty and Rachel A. Segalman. As of 2024, Journal Citation Reports, gives the journal an impact factor of 7.6.
History
The Annual Review of Chemical and Biomolecular Engineering was first published in 2010 by nonprofit publisher Annual Reviews. Its founding editor was John Prausnitz. In 2018, Prausnitz was succeeded by Michael F. Doherty and Rachel A. Segalman as co-editors. Though it was initially published in print, as of 2021 it is only published electronically.
As of 2023, it is being published as open access, under the Subscribe to Open model.
Scope and indexing
The Annual Review of Chemical and Biomolecular Engineering defines its scope as covering significant developments relevant to chemical engineering. It includes disciplines such as applied chemistry and biology, physics, and engineering with a focus on the development of chemical products and processes. As of 2024, Journal Citation Reports lists the journal's impact factor as 7.6, ranking it seventh of 74 journal titles in the category "Chemistry, Applied" and seventeenth of 170 titles in "Engineering, Chemical". It is abstracted and indexed in Scopus, Science Citation Index Expanded, CAB Abstracts, EMBASE, and MEDLINE, among others.
Editorial processes
The Annual Review of Chemical and Biomolecular Engineering is helmed by the editor or the co-editors. The editor is assisted by the editorial committee, which includes associate editors, regular members, and occasionally guest editors. Guest members participate at the invitation of the editor, and serve terms of one year. All other members of the editorial committee are appointed by the Annual Reviews board of directors and serve five-year terms. The editorial committee determines which topics should be included in each volume and solicits reviews from qualified authors. Unsolicited manuscripts are not accepted. Peer review of accepted manuscripts is undertaken by the editorial committee.
Current editorial board
As of 2022, the editorial committee consists of the two co-editors and the following members:
Ravi S. Kane
Linda J. Broadbelt
Kookheon Char
Wilfred Chen
Lydia Contreras
Christopher W. Jones
Sanat K. Kumar
Joseph B. Powell
Irina Smirnova
Levi T. Thompson
See also
List of engineering journals and magazines
References
Chemical and Biomolecular Engineering
Annual journals
Academic journals established in 2010
Chemical engineering journals
Biochemistry journals
English-language journals | Annual Review of Chemical and Biomolecular Engineering | [
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30,528,084 | https://en.wikipedia.org/wiki/Annual%20Review%20of%20Condensed%20Matter%20Physics | The Annual Review of Condensed Matter Physics is an annual peer-reviewed review journal published by Annual Reviews. It was established in 2010 and covers advances in condensed matter physics and related subjects. The co-editors are M. Cristina Marchetti and Andrew P. Mackenzie. As of 2023, Annual Review of Condensed Matter Physics is being published as open access, under the Subscribe to Open model. As of 2024, Journal Citation Reports lists the journal's impact factor of 14.3, ranking it sixth of 79 journal titles in the category "Physics, Condensed Matter" in 2023.
History
The Annual Review of Condensed Matter Physics was first published in 2010 by the nonprofit publisher Annual Reviews. Its founding editor was James S. Langer. He was joined by James P. Eisenstein in 2014. M. Cristina Marchetti and Subir Sachdev were co-editors in 2016 and 2017; in 2018, Andrew P. Mackenzie joined as the third co-editor. As of 2021, the co-editors were Marchetti and Mackenzie. Though it was initially published in print, as of 2021 it is only published electronically.
Scope and indexing
The Annual Review of Condensed Matter Physics defines its scope as covering significant developments relevant to condensed matter physics. It is abstracted and indexed in Scopus, Science Citation Index Expanded, Compendex, and INSPEC.
Editorial processes
The Annual Review of Condensed Matter Physics is helmed by the editor or the co-editors. The editor is assisted by the editorial committee, which includes associate editors, regular members, and occasionally guest editors. Guest members participate at the invitation of the editor, and serve terms of one year. All other members of the editorial committee are appointed by the Annual Reviews board of directors and serve five-year terms. The editorial committee determines which topics should be included in each volume and solicits reviews from qualified authors. Unsolicited manuscripts are not accepted. Peer review of accepted manuscripts is undertaken by the editorial committee.
Current editorial board
As of 2022, the editorial committee consists of the two co-editors and the following members:
Daniel F. Agterberg
Emily S. C. Ching
Eduardo H. Fradkin
Yong Baek Kim
Silvia Picozzi
Leo Radzihovsky
Kathleen J. Stebe
Masahito Ueda
Vincenzo Vitelli
See also
List of physics journals
References
Condensed Matter Physics
Annual journals
Condensed matter physics
Physics review journals
Academic journals established in 2010
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] | 499 | [
"Phases of matter",
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"Matter",
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30,530,797 | https://en.wikipedia.org/wiki/Magnonics | Magnonics is an emerging field of modern magnetism, which can be considered a sub-field of modern solid state physics. Magnonics combines the study of waves and magnetism. Its main aim is to investigate the behaviour of spin waves in nano-structure elements. In essence, spin waves are a propagating re-ordering of the magnetisation in a material and arise from the precession of magnetic moments. Magnetic moments arise from the orbital and spin moments of the electron, most often it is this spin moment that contributes to the net magnetic moment.
Following the success of the modern hard disk, there is much current interest in future magnetic data storage and using spin waves for things such as 'magnonic' logic and data storage. Similarly, spintronics looks to utilize the inherent spin degree of freedom to complement the already successful charge property of the electron used in contemporary electronics. Modern magnetism is concerned with furthering the understanding of the behaviour of the magnetisation on very small (sub-micrometre) length scales and very fast (sub-nanosecond) timescales and how this can be applied to improving existing or generating new technologies and computing concepts. A magnon torque device was invented and later perfected at the National University of Singapore's Electrical & Computer Engineering department, which is based on such potential uses, with results published on November 29, 2019, in Science.
A magnonic crystal is a magnetic metamaterial with alternating magnetic properties. Like conventional metamaterials, their properties arise from geometrical structuring, rather than their bandstructure or composition directly. Small spatial inhomogeneities create an effective macroscopic behaviour, leading to properties not readily found in nature. By alternating parameters such as the relative permeability or saturation magnetisation, there exists the possibility to tailor 'magnonic' bandgaps in the material. By tuning the size of this bandgap, only spin wave modes able to cross the bandgap would be able to propagate through the media, leading to selective propagation of certain spin wave frequencies. See Surface magnon polariton.
Theory
Spin waves can propagate in magnetic media with magnetic ordering such as ferromagnets and antiferromagnets. The frequencies of the precession of the magnetisation depend on the material and its magnetic parameters, in general precession frequencies are in the microwave from 1–100 GHz, exchange resonances in particular materials can even see frequencies up to several THz. This higher precession frequency opens new possibilities for analogue and digital signal processing.
Spin waves themselves have group velocities on the order of a few km per second. The damping of spin waves in a magnetic material also causes the amplitude of the spin wave to decay with distance, meaning the distance freely propagating spin waves can travel is usually only several 10's of μm. The damping of the dynamical magnetisation is accounted for phenomenologically by the Gilbert damping constant in the Landau-Lifshitz-Gilbert equation (LLG equation), the energy loss mechanism itself is not completely understood, but is known to arise microscopically from magnon-magnon scattering, magnon-phonon scattering and losses due to eddy currents. The Landau-Lifshitz-Gilbert equation is the 'equation of motion' for the magnetisation. All of the properties of the magnetic systems such as the applied bias field, the sample's exchange, anisotropy and dipolar fields are described in terms of an 'effective' magnetic field that enters the Landau–Lifshitz–Gilbert equation. The study of damping in magnetic systems is an ongoing modern research topic.
The LL equation was introduced in 1935 by Landau and Lifshitz to model the precessional motion of magnetization in a solid with an effective magnetic field and with damping. Later, Gilbert modified the damping term, which in the limit of small damping yields identical results. The LLG equation is,
The constant is the Gilbert phenomenological damping parameter and depends on the solid, and is the electron gyromagnetic ratio. Here
Research in magnetism, like the rest of modern science, is conducted with a symbiosis of theoretical and experimental approaches. Both approaches go hand-in-hand, experiments test the predictions of theory and theory provides explanations and predictions of new experiments. The theoretical side focuses on numerical modelling and simulations, so called micromagnetic modelling. Programs such as OOMMF or NMAG are micromagnetic solvers that numerically solve the LLG equation with appropriate boundary conditions. Prior to the start of the simulation, magnetic parameters of the sample and the initial groundstate magnetisation and bias field details are stated.
Experiment
Experimentally, there are many techniques that exist to study magnetic phenomena, each with its own limitations and advantages. The experimental techniques can be distinguished by being time-domain (optical and field pumped TR-MOKE), field-domain (ferromagnetic resonance (FMR)) and frequency-domain techniques (Brillouin light scattering (BLS), vector network analyser - ferromagnetic resonance (VNA-FMR)). Time-domain techniques allow the temporal evolution of the magnetisation to be traced indirectly by recording the polarisation response of the sample. The magnetisation can be inferred by the so-called 'Kerr' rotation. Field-domain techniques such as FMR tickle the magnetisation with a CW microwave field. By measuring the absorption of the microwave radiation through the sample, as an external magnetic field is swept provides information about magnetic resonances in the sample. Importantly, the frequency at which the magnetisation precesses depends on the strength of the applied magnetic field. As the external field strength is increased, so does the precession frequency. Frequency-domain techniques such as VNA-FMR, examine the magnetic response due to excitation by an RF current, the frequency of the current is swept through the GHz range and the amplitude of either the transmitted or reflected current can be measured.
Modern ultrafast lasers allow femtosecond (fs) temporal resolution for time-domain techniques, such tools are now standard in laboratory environments. Based on the magneto-optic Kerr effect, TR-MOKE is a pump-probe technique where a pulsed laser source illuminates the sample with two separate laser beams. The 'pump' beam is designed to excite or perturb the sample from equilibrium, it is very intense designed to create highly non-equilibrium conditions within the sample material, exciting the electron, and thereby subsequently the phonon and the spin system. Spin-wave states at high energy are excited and subsequently populate the lower lying states during their relaxation path's. A much weaker beam called a 'probe' beam is spatially overlapped with the pump beam on the magnonic material's surface. The probe beam is passed along a delay line, which is a mechanical way of increasing the probe path length. By increasing the probe path length, it becomes delayed with respect to the pump beam and arrives at a later time on the sample surface. Time-resolution is built in the experiment by changing the delay distance. As the delay line position is stepped, the reflected beam properties are measured. The measured Kerr rotation is proportional to the dynamic magnetisation as the spin-waves propagate in the media. The temporal resolution is limited by the temporal width of the laser pulse only. This allows to connect ultrafast optics with a local spin-wave excitation and contact free detection in magnonic metamaterials, photomagnonics.
Since 2009 "Magnonics" conferences are organised every second year. The next conference takes place in July-August 2025 in Cala Millor, Mallorca, Spain.
References
External links
Magnetic ordering | Magnonics | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 1,629 | [
"Magnetic ordering",
"Condensed matter physics",
"Electric and magnetic fields in matter",
"Materials science"
] |
38,541,620 | https://en.wikipedia.org/wiki/Web%20IDL | Web IDL is an interface description language (IDL) format for describing APIs (application programming interfaces) that are intended to be implemented in web browsers. Its adoption was motivated by the desire to improve the interoperability of web programming interfaces by specifying how languages such as ECMAScript should bind these interfaces.
Description
Web IDL is an IDL variant with:
A number of features that allow one to more easily describe the behavior of common script objects in a web context.
A mapping of how interfaces described with Web IDL correspond to language constructs within an ECMAScript execution environment.
Web specifications had been specified using OMG IDL since 1998, first with the DOM Level 1 specification. However, interfaces defined using OMG IDL were not able to specify behavior for JavaScript precisely, leading to issues with interoperability. WebIDL improved on this status quo by providing data types and binding specifications that make the intended behavior in JavaScript clearer.
Status of Web IDL specifications
The first edition of the Web IDL specification became a Candidate Recommendation on 19 April 2012 and a W3C Recommendation on 15 December 2016. For many years the Editor's Draft of a potential second edition, was what most new web specifications referenced. On 5 October 2021, the Editor's Draft was moved to the WHATWG as the Web IDL Living Standard per an update to the agreement between the W3C and WHATWG.
Usage
The W3C Wiki has a list of W3C Specifications that use Web IDL, and nearly all WHATWG specifications use it.
The Chromium Project has a page about using WebIDL to specify interfaces in Blink.
Mozilla uses Web IDL in their software creation process, mapping implementations to Web IDL specs.
When WebKit is built, the IDL files are parsed, creates the code to bind interfaces to implementations.
In the ES operating system, every system API is defined in Web IDL, and can be invoked from JavaScript directly.
References
External links
List of standards that use Web IDL
Web IDL syntax checker
Specification languages
Web browsers | Web IDL | [
"Engineering"
] | 432 | [
"Software engineering",
"Specification languages"
] |
38,542,576 | https://en.wikipedia.org/wiki/Young%27s%20convolution%20inequality | In mathematics, Young's convolution inequality is a mathematical inequality about the convolution of two functions, named after William Henry Young.
Statement
Euclidean space
In real analysis, the following result is called Young's convolution inequality:
Suppose is in the Lebesgue space and is in and
with Then
Here the star denotes convolution, is Lebesgue space, and
denotes the usual norm.
Equivalently, if and then
Generalizations
Young's convolution inequality has a natural generalization in which we replace by a unimodular group If we let be a bi-invariant Haar measure on and we let or be integrable functions, then we define by
Then in this case, Young's inequality states that for and and such that
we have a bound
Equivalently, if and then
Since is in fact a locally compact abelian group (and therefore unimodular) with the Lebesgue measure the desired Haar measure, this is in fact a generalization.
This generalization may be refined. Let and be as before and assume satisfy Then there exists a constant such that for any and any measurable function on that belongs to the weak space which by definition means that the following supremum
is finite, we have and
Applications
An example application is that Young's inequality can be used to show that the heat semigroup is a contracting semigroup using the norm (that is, the Weierstrass transform does not enlarge the norm).
Proof
Proof by Hölder's inequality
Young's inequality has an elementary proof with the non-optimal constant 1.
We assume that the functions are nonnegative and integrable, where is a unimodular group endowed with a bi-invariant Haar measure We use the fact that for any measurable
Since
By the Hölder inequality for three functions we deduce that
The conclusion follows then by left-invariance of the Haar measure, the fact that integrals are preserved by inversion of the domain, and by Fubini's theorem.
Proof by interpolation
Young's inequality can also be proved by interpolation; see the article on Riesz–Thorin interpolation for a proof.
Sharp constant
In case Young's inequality can be strengthened to a sharp form, via
where the constant
When this optimal constant is achieved, the function and are multidimensional Gaussian functions.
See also
Notes
References
External links
Young's Inequality for Convolutions at ProofWiki
Inequalities
Lp spaces | Young's convolution inequality | [
"Mathematics"
] | 524 | [
"Binary relations",
"Mathematical relations",
"Inequalities (mathematics)",
"Mathematical problems",
"Mathematical theorems"
] |
38,544,280 | https://en.wikipedia.org/wiki/Ballast | Ballast is dense material used as a weight to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship, submarine, or other floating structure that holds water is called a ballast tank. Water should be moved in and out from the ballast tank to balance the ship. In a vessel that travels on the water, the ballast will be kept below the water level, to counteract the effects of weight above the water level. The ballast may be redistributed in the vessel or disposed of altogether to change its effects on the movement of the vessel.
History
The basic concept behind the ballast tank can be seen in many forms of aquatic life, such as the blowfish or members of the argonaut group of octopus. The concept has been invented and reinvented many times by humans to serve a variety of purposes.
In the fifteenth and sixteenth century, the ballast "did not consist entirely of leakage, but of urine, vomit, and various foul food leavings that lazy sailors discharged into the ballast contrary to orders, in the belief that the pumps would take care of it." In the nineteenth century, cargo boats returning from Europe to North America would carry quarried stone as ballast, contributing to the architectural heritage of some east coast cities (for example Montreal), where this stone was used in building.
During World War 2 ships returning from Great Britain to the United States used rubble as ballast. The ballast would be dumped in New York and used for construction projects such as FDR Drive and an outcrop colloquially named Bristol Basin since it was made from rubble from bombed-out Bristol.
Uses
Ballast takes many forms, for example:
Sailing ballast, or ship's ballast, used to lower the centre of gravity of a ship to increase stability
Ballast tank, a device used on ships and submarines and other submersibles to control buoyancy and stability
Ballast (car racing), metallic plates used to bring auto racing vehicles up to the minimum mandated weight
in underwater diving, a diver weighting system comprises blocks of heavy material, usually lead, used to compensate for excess buoyancy of the diver and their equipment.
in gliding, weights added to maximise the average speed in cross-country competition, especially when thermal convection is strong
in a balloon, as part of a buoyancy compensator
Sailing ballast is used in sailboats to provide righting moment to resist the overturning moment generated by lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of little or no value would be loaded to keep the vessel upright. Some or all of this ballast would then be discarded when cargo was loaded.
Ballast weight is also added to a race car to alter its performance. In most racing series, cars have a minimum allowable weight. Often, the actual weight of the car is lower, so ballast is used to bring it up to the minimum. The advantage is that the ballast can be positioned to affect the car's handling by changing its load distribution. This is near-universal in Formula 1. It is also common in other racing series that ballast may only be located in certain positions on the car. In some racing series, for example the British Touring Car Championship, ballast is used as a handicap, the leading drivers at the end of one race being given more ballast for the next race.
Ballast may also be carried aboard an aircraft. For example, in gliding it may be used to increase speed and/or adjust the aircraft's center of gravity, or in a balloon as a buoyancy compensator.
References
Sources
Mechanisms (engineering)
Weights | Ballast | [
"Physics",
"Engineering"
] | 796 | [
"Matter",
"Weights",
"Physical objects",
"Mechanical engineering",
"Mechanisms (engineering)"
] |
38,545,126 | https://en.wikipedia.org/wiki/Water%20supply%20terrorism | Water supply terrorism involves acts of sabotage to a water supply system, through chemical or biological warfare or infrastructural sabotage. Throughout military history and the history of terrorism, water supply
attacks have been perpetrated by political groups, intending to scare, cause death, or drought.
Chemical and biological attacks
Examples
In 1984, members of the Rajneeshee religious cult contaminated a city water supply tank in The Dalles, Oregon, using Salmonella and infected 750 people.
In 1992 The Kurdistan Workers' Party (PKK) put lethal concentrations of potassium cyanide in the water tanks of a Turkish Air Force compound in Istanbul.
In 2000, workers at the Cellatex chemical plant in northern France dumped 5000 liters of sulfuric acid into a tributary of the Meuse River when they were denied workers’ benefits.
In 2000, Queensland police arrested a man for using a computer and a radio transmitter to take control of the Maroochy Shire wastewater system and release sewage into parks, rivers and property.
In 2024 there were two cases of possible drinking water sabotage at German army bases and one at the municipality of Mechernich where a local water treatment plant supplies water to a local army base.
LSD threats to the water supply
Despite the fact that it is impractical and very unlikely to produce any effect at large scale, during the 1960s a great deal of attention was paid to the notion that counter-culture figures could intoxicate a whole city by putting a small dose of LSD in the water supply.
On 19 March 1966 London Life ran an interview claiming that anyone could take control of London in under eight hours by putting 'acid' in the water system. Dr Donald Johnson claimed: "It is quite feasible that LSD could be used to take over a city or even a country. I agree if it were put into reservoirs, it would disable people sufficiently for an enemy to take control."
In November 1966 Vue magazine ran "Why They Had to Outlaw LSD", in which writer WH Carr claimed that "[A] few ounces of it, dumped in the water supply of a major city, could shake up millions."
Counter-culture icon Abbie Hoffman threatened to put LSD in Chicago's water-supply to protest the Vietnam War during the Democratic convention.
Infrastructural or resource-based attacks
History
In 1999, a bomb destroyed the main water pipeline in Lusaka, Zambia, cutting off water for 1.1 million people in the city.
In 2001, water flow to Kumanovo (population 100,000) was cut off for 12 days in conflict between ethnic Albanians and Macedonian forces.
The Revolutionary Armed Forces of Colombia (FARC) detonated a bomb inside a tunnel in the Chingaza Dam, which provides most of Bogotá’s water.
Four incendiary devices were found in the pumping station of a Michigan water-bottling plant. The Earth Liberation Front (ELF) claimed responsibility, accusing Ice Mountain Water Company of stealing water for profit.
In 2003 Jordanian authorities arrested Iraqi agents in connection with a failed plot to poison the water supply that serves American troops in the eastern Jordanian desert near the border with Iraq.
In 2006 Tamil Tiger rebels cut the water supply to government-held villages in northeastern Sri Lanka. Sri Lankan government forces then launched attacks on the reservoir, declaring the Tamil actions to be terrorism.
Draining of the Mesopotamian Marshes
The draining of the Mesopotamian Marshes occurred in Iraq and to a smaller degree in Iran between the 1950s and 1990s to clear large areas of the marshes in the Tigris-Euphrates river system. Formerly covering an area of around , the main sub-marshes, the Hawizeh, Central, and Hammar Marshes were all drained at different times for different reasons. Initial draining of the Central Marshes was intended to reclaim land for agriculture but later all three marshes became a tool of war and revenge.
Many international organizations such as the U.N. Human Rights Commission, the Supreme Council of the Islamic Revolution in Iraq (SCIRI), the International Wildfowl and Wetlands Research Bureau, and Middle East Watch have described the draining as a political attempt to force the Ma'dan people out of the area through water diversion tactics.
In popular culture
Kurt Vonnegut's book Cat's Cradle (1963) describes a fictional chemical that freezes water at room temperature and ends up destroying the world.
In 1966, Robert Thom published the short story called "The Day It All Happened, Baby!", which became the film Wild in the Streets, directed by Barry Shear in 1968 and in which LSD added to the water supply of Washington, D.C. is a crucial plot device.
The film The Tuxedo, starring Jackie Chan, features a power-hungry bottled-water mogul trying to destroy the world's natural water supply to force everyone to drink his bottled water.
The film Batman Begins portrays a terrorist's attempt to introduce a vapor-borne hallucinogen into the water system.
The film Waterborne is set in the aftermath of a bio-terrorist attack on the water supply of Los Angeles.
The film V for Vendetta (2006) features corrupt government leaders contaminating London's water supply.
In the video game Final Fantasy VI (1994), a siege on the fictional kingdom of Doma by an army of the Gestahlian Empire is broken when Kefka Palazzo releases a deadly poison into Doma's water supply. This not only breaks the siege, but kills most of Doma's inhabitants in the process.
See also
Well poisoning
Water privatisation
Water industry
Water diversion
Drought
References
Terrorism by method
Water supply
Water conflicts | Water supply terrorism | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 1,154 | [
"Hydrology",
"Water supply",
"Environmental engineering"
] |
38,549,290 | https://en.wikipedia.org/wiki/Soler%20model | The soler model is a quantum field theory model of Dirac fermions interacting via four fermion interactions in 3 spatial and 1 time dimension. It was introduced in 1938 by Dmitri Ivanenko
and re-introduced and investigated in 1970 by Mario Soler as a toy model of self-interacting electron.
This model is described by the Lagrangian density
where is the coupling constant,
in the Feynman slash notations, .
Here , , are Dirac gamma matrices.
The corresponding equation can be written as
,
where , ,
and are the Dirac matrices.
In one dimension,
this model is known as the massive Gross–Neveu model.
Generalizations
A commonly considered generalization is
with , or even
,
where is a smooth function.
Features
Internal symmetry
Besides the unitary symmetry U(1),
in dimensions 1, 2, and 3
the equation has SU(1,1) global internal symmetry.
Renormalizability
The Soler model is renormalizable by the power counting for and in one dimension only,
and non-renormalizable for higher values of and in higher dimensions.
Solitary wave solutions
The Soler model admits solitary wave solutions
of the form
where is localized (becomes small when is large)
and is a real number.
Reduction to the massive Thirring model
In spatial dimension 2, the Soler model coincides with the massive Thirring model,
due to the relation
,
with
the relativistic scalar
and
the charge-current density.
The relation follows from the identity
,
for any .
See also
Dirac equation
Gross–Neveu model
Nonlinear Dirac equation
Thirring model
References
Quantum field theory | Soler model | [
"Physics"
] | 341 | [
"Quantum field theory",
"Quantum mechanics"
] |
38,549,774 | https://en.wikipedia.org/wiki/Nonlinear%20Dirac%20equation | See Ricci calculus and Van der Waerden notation for the notation.
In quantum field theory, the nonlinear Dirac equation is a model of self-interacting Dirac fermions. This model is widely considered in quantum physics as a toy model of self-interacting electrons.
The nonlinear Dirac equation appears in the Einstein–Cartan–Sciama–Kibble theory of gravity, which extends general relativity to matter with intrinsic angular momentum (spin). This theory removes a constraint of the symmetry of the affine connection and treats its antisymmetric part, the torsion tensor, as a variable in varying the action. In the resulting field equations, the torsion tensor is a homogeneous, linear function of the spin tensor. The minimal coupling between torsion and Dirac spinors thus generates an axial-axial, spin–spin interaction in fermionic matter, which becomes significant only at extremely high densities. Consequently, the Dirac equation becomes nonlinear (cubic) in the spinor field, which causes fermions to be spatially extended and may remove the ultraviolet divergence in quantum field theory.
Models
Two common examples are the massive Thirring model and the Soler model.
Thirring model
The Thirring model was originally formulated as a model in (1 + 1) space-time dimensions and is characterized by the Lagrangian density
where is the spinor field, is the Dirac adjoint spinor,
(Feynman slash notation is used), is the coupling constant, is the mass, and are the two-dimensional gamma matrices, finally is an index.
Soler model
The Soler model was originally formulated in (3 + 1) space-time dimensions. It is characterized by the Lagrangian density
using the same notations above, except
is now the four-gradient operator contracted with the four-dimensional Dirac gamma matrices , so therein .
Other models
Besides the Soler model, extensive work has been done where nonlinear versions of Dirac’s equation are used to describe purely classical, nonlinear particle-like solutions (PLS) in (3 + 1) space-time dimensions. Rañada has given a review of the subject. Although a more recent review specifically devoted to purely classical, nonlinear PLS has apparently not appeared, pertinent references are available in various more recent publications.
The models reviewed by Rañada are meant to be entirely classical in nature and should properly be regarded as having nothing to do with quantum mechanics, but the dependent variable in the Dirac equation is still typically taken as a spinor. When a purely classical model of this nature is to be considered, the use of a spinor as the dependent variable seems inappropriate.
If a minor modification of the underlying Dirac equation is used, the problem can be avoided in a relatively straightforward way. Instead of using the usual column vector as the dependent variable in Dirac’s equation, one can use a 4 × 4 matrix. When there is no transformation of coordinates, the leftmost column of the matrix is used in Dirac’s equation in the usual manner, but when there is to be a transformation in space-time, the four components of the dependent variable are sometimes allowed to appear in various different positions in the 4 × 4 matrix.
The result can be understood in terms of a Clifford algebra since the dependent variable in Dirac’s equation can be represented as a 4 dimensional left ideal of a Clifford algebra. In this case one simply allows the dependent variable to lie in a different left ideal when there is a transformation in space-time.
Einstein–Cartan theory
In Einstein–Cartan theory the Lagrangian density for a Dirac spinor field is given by ()
where
is the Fock–Ivanenko covariant derivative of a spinor with respect to the affine connection, is the spin connection, is the determinant of the metric tensor , and the Dirac matrices satisfy
The Einstein–Cartan field equations for the spin connection yield an algebraic constraint between the spin connection and the spinor field rather than a partial differential equation, which allows the spin connection to be explicitly eliminated from the theory. The final result is a nonlinear Dirac equation containing an effective "spin-spin" self-interaction,
where is the general-relativistic covariant derivative of a spinor, and is the Einstein gravitational constant, . The cubic term in this equation becomes significant at densities on the order of .
See also
Dirac equation
Dirac equation in the algebra of physical space
Dirac–Kähler equation
Gross–Neveu model
Higher-dimensional gamma matrices
Nonlinear Schrödinger equation
Pokhozhaev's identity for the stationary nonlinear Dirac equation
Soler model
Thirring model
References
Quantum field theory
Dirac equation | Nonlinear Dirac equation | [
"Physics"
] | 977 | [
"Quantum field theory",
"Equations of physics",
"Eponymous equations of physics",
"Quantum mechanics",
"Dirac equation"
] |
28,996,847 | https://en.wikipedia.org/wiki/Geophysical%20fluid%20dynamics | Geophysical fluid dynamics, in its broadest meaning, refers to the fluid dynamics of naturally occurring flows, such as lava flows, oceans, and planetary atmospheres, on Earth and other planets.
Two physical features that are common to many of the phenomena studied in geophysical fluid dynamics are rotation of the fluid due to the planetary rotation and stratification (layering). The applications of geophysical fluid dynamics do not generally include the circulation of the mantle, which is the subject of geodynamics, or fluid phenomena in the magnetosphere.
Fundamentals
To describe the flow of geophysical fluids, equations are needed for conservation of momentum (or Newton's second law) and conservation of energy. The former leads to the Navier–Stokes equations which cannot be solved analytically (yet). Therefore, further approximations are generally made in order to be able to solve these equations. First, the fluid is assumed to be incompressible. Remarkably, this works well even for a highly compressible fluid like air as long as sound and shock waves can be ignored. Second, the fluid is assumed to be a Newtonian fluid, meaning that there is a linear relation between the shear stress and the strain , for example
where is the viscosity. Under these assumptions the Navier-Stokes equations are
The left hand side represents the acceleration that a small parcel of fluid would experience in a reference frame that moved with the parcel (a Lagrangian frame of reference). In a stationary (Eulerian) frame of reference, this acceleration is divided into the local rate of change of velocity and advection, a measure of the rate of flow in or out of a small region.
The equation for energy conservation is essentially an equation for heat flow. If heat is transported by conduction, the heat flow is governed by a diffusion equation. If there are also buoyancy effects, for example hot air rising, then natural convection, also known as free convection, can occur. Convection in the Earth's outer core drives the geodynamo that is the source of the Earth's magnetic field. In the ocean, convection can be thermal (driven by heat), haline (where the buoyancy is due to differences in salinity), or thermohaline, a combination of the two.
Buoyancy and stratification
Fluid that is less dense than its surroundings tends to rise until it has the same density as its surroundings. If there is not much energy input to the system, it will tend to become stratified. On a large scale, Earth's atmosphere is divided into a series of layers. Going upwards from the ground, these are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
The density of air is mainly determined by temperature and water vapor content, the density of sea water by temperature and salinity, and the density of lake water by temperature. Where stratification occurs, there may be thin layers in which temperature or some other property changes more rapidly with height or depth than the surrounding fluid. Depending on the main sources of buoyancy, this layer may be called a pycnocline (density), thermocline (temperature), halocline (salinity), or chemocline (chemistry, including oxygenation).
The same buoyancy that gives rise to stratification also drives gravity waves. If the gravity waves occur within the fluid, they are called internal waves.
In modeling buoyancy-driven flows, the Navier-Stokes equations are modified using the Boussinesq approximation. This ignores variations in density except where they are multiplied by the gravitational acceleration .
If the pressure depends only on density and vice versa, the fluid dynamics are called barotropic. In the atmosphere, this corresponds to a lack of fronts, as in the tropics. If there are fronts, the flow is baroclinic, and instabilities such as cyclones can occur.
Rotation
Coriolis effect
Circulation
Kelvin's circulation theorem
Vorticity equation
Thermal wind
Geostrophic current
Geostrophic wind
Taylor–Proudman theorem
Hydrostatic equilibrium
Ekman spiral
Ekman layer
General circulation
Atmospheric circulation
Ocean current
Ocean dynamics
Thermohaline circulation
Boundary current
Sverdrup balance
Subsurface currents
Waves
Barotropic
Kelvin wave
Rossby wave
Sverdrup wave (Poincaré wave)
Baroclinic
Gravity wave
See also
Geophysical Fluid Dynamics Laboratory
References
Further reading
External links
Geophysical Fluid Dynamics Program (Woods Hole Oceanographic Institution)
Geophysical Fluid Dynamics Laboratory (University of Washington)
Atmospheric dynamics
Geophysics
Fluid dynamics
Physical oceanography | Geophysical fluid dynamics | [
"Physics",
"Chemistry",
"Engineering"
] | 963 | [
"Applied and interdisciplinary physics",
"Atmospheric dynamics",
"Chemical engineering",
"Physical oceanography",
"Geophysics",
"Piping",
"Fluid dynamics"
] |
29,000,170 | https://en.wikipedia.org/wiki/Trash%20Inc%3A%20The%20Secret%20Life%20of%20Garbage | Trash Inc: The Secret Life of Garbage is a one-hour television documentary film that aired on CNBC on September 29, 2010 about trash/garbage, what happens to it when it's "thrown away", and its impact on the world. The film is hosted by CNBC Squawk Box co-anchor Carl Quintanilla as he reports from various landfills (such as the largest in the United States, the Apex Landfill in Clark County, Nevada), business, and other locations in the United States (New York, New Jersey, Hawaii, South Carolina) and China (mostly Beijing).
The idea for Trash, Inc was born of the 2008 recession and the relative stability of publicly traded waste management companies.
References
External links
CNBC original programming
American documentary television films
Waste
2010 in the environment
2010 television films
2010 films
Documentary films about environmental issues
2010s English-language films
2010s American films
English-language documentary films | Trash Inc: The Secret Life of Garbage | [
"Physics"
] | 189 | [
"Materials",
"Waste",
"Matter"
] |
29,002,911 | https://en.wikipedia.org/wiki/Macron%20%28physics%29 | In physics, macrons are microscopic (dust-sized) particles, accelerated to high speeds. The term was first used in the late 1960s, when it was believed that macrons could be accelerated cheaply in small particle accelerators as a way of achieving low-cost fusion power.
References
Fusion power | Macron (physics) | [
"Physics",
"Chemistry"
] | 62 | [
"Nuclear fusion",
"Nuclear chemistry stubs",
"Fusion power",
"Plasma physics"
] |
29,008,381 | https://en.wikipedia.org/wiki/Periodic%20graph%20%28crystallography%29 | In crystallography, a periodic graph or crystal net is a three-dimensional periodic graph, i.e., a three-dimensional Euclidean graph whose vertices or nodes are points in three-dimensional Euclidean space, and whose edges (or bonds or spacers) are line segments connecting pairs of vertices, periodic in three linearly independent axial directions. There is usually an implicit assumption that the set of vertices are uniformly discrete, i.e., that there is a fixed minimum distance between any two vertices. The vertices may represent positions of atoms or complexes or clusters of atoms such as single-metal ions, molecular building blocks, or secondary building units, while each edge represents a chemical bond or a polymeric ligand.
Although the notion of a periodic graph or crystal net is ultimately mathematical (actually a crystal net is nothing but a periodic realization of an abelian covering graph over a finite graph
), and is closely related to that of a Tessellation of space (or honeycomb) in the theory of polytopes and similar areas, much of the contemporary effort in the area is motivated by crystal engineering and prediction (design), including metal-organic frameworks (MOFs) and zeolites.
History
A crystal net is an infinite molecular model of a crystal. Similar models existed in Antiquity, notably the atomic theory associated with Democritus, which was criticized by Aristotle because such a theory entails a vacuum, which Aristotle believed nature abhors. Modern atomic theory traces back to Johannes Kepler and his work on geometric packing problems. Until the twentieth century, graph-like models of crystals focused on the positions of the (atomic) components, and these pre-20th century models were the focus of two controversies in chemistry and materials science.
The two controversies were (1) the controversy over Robert Boyle’s corpuscular theory of matter, which held that all material substances were composed of particles, and (2) the controversy over whether crystals were minerals or some kind of vegetative phenomenon. During the eighteenth century, Kepler, Nicolas Steno, René Just Haüy, and others gradually associated the packing of Boyle-type corpuscular units into arrays with the apparent emergence of polyhedral structures resembling crystals as a result. During the nineteenth century, there was considerably more work done on polyhedra and also of crystal structure, notably in the derivation of the Crystallographic groups based on the assumption that a crystal could be regarded as a regular array of unit cells. During the early twentieth century, the physics and chemistry community largely accepted Boyle's corpuscular theory of matter—by now called the atomic theory—and X-ray crystallography was used to determine the position of the atomic or molecular components within the unit cells (by the early twentieth century, unit cells were regarded as physically meaningful).
However, despite the growing use of stick-and-ball molecular models, the use of graphical edges or line segments to represent chemical bonds in specific crystals have become popular more recently, and the publication of encouraged efforts to determine graphical structures of known crystals, to generate crystal nets of as yet unknown crystals, and to synthesize crystals of these novel crystal nets. The coincident expansion of interest in tilings and tessellations, especially those modeling quasicrystals, and the development of modern Nanotechnology, all facilitated by the dramatic increase in computational power, enabled the development of algorithms from computational geometry for the construction and analysis of crystal nets. Meanwhile, the ancient association between models of crystals and tessellations has expanded with Algebraic topology. There is also a thread of interest in the very-large-scale integration (VLSI) community for using these crystal nets as circuit designs.
Basic formulation
A Euclidean graph in three-dimensional space is a pair (V, E), where V is a set of vertices (sometimes called points or nodes) and E is a set of edges (sometimes called bonds or spacers) where each edge joins two vertices. There is a tendency in the polyhedral and chemical literature to refer to geometric graphs as nets (contrast with polyhedral nets), and the nomenclature in the chemical literature differs from that of graph theory.
Symmetries and periodicity
A symmetry of a Euclidean graph is an isometry of the underlying Euclidean space whose restriction to the graph is an automorphism; the symmetry group of the Euclidean graph is the group of its symmetries. A Euclidean graph in three-dimensional Euclidean space is periodic if there exist three linearly independent translations whose restrictions to the net are symmetries of the net. Often (and always, if one is dealing with a crystal net), the periodic net has finitely many orbits, and is thus uniformly discrete in that there exists a minimum distance between any two vertices.
The result is a three-dimensional periodic graph as a geometric object.
The resulting crystal net will induce a lattice of vectors so that given three vectors that generate the lattice, those three vectors will bound a unit cell, i.e. a parallelepiped which, placed anywhere in space, will enclose a fragment of the net that repeats in the directions of the three axes.
Symmetry and kinds of vertices and edges
Two vertices (or edges) of a periodic graph are symmetric if they are in the same orbit of the symmetry group of the graph; in other words, two vertices (or edges) are symmetric if there is a symmetry of the net that moves one onto the other. In chemistry, there is a tendency to refer to orbits of vertices or edges as “kinds” of vertices or edges, with the recognition that from any two vertices or any two edges (similarly oriented) of the same orbit, the geometric graph “looks the same”. Finite colorings of vertices and edges (where symmetries are to preserve colorings) may be employed.
The symmetry group of a crystal net will be a (group of restrictions of a) crystallographic space group, and many of the most common crystals are of very high symmetry, i.e. very few orbits. A crystal net is uninodal if it has one orbit of vertex (if the vertices were colored and the symmetries preserve colorings, this would require that a corresponding crystal have atoms of one element or molecular building blocks of one compound – but not vice versa, for it is possible to have a crystal of one element but with several orbits of vertices). Crystals with uninodal crystal nets include cubic diamond and some representations of quartz crystals. Uninodality corresponds with isogonality in geometry and vertex-transitivity in graph theory, and produces examples objective structures. A crystal net is binodal if it has two orbits of vertex; crystals with binodal crystal nets include boracite and anatase. It is edge-transitive or isotoxal if it has one orbit of edges; crystals with edge-transitive crystal nets include boracite but not anatase – which has two orbits of edges.
Geometry of crystal nets
In the geometry of crystal nets, one can treat edges as line segments. For example, in a crystal net, it is presumed that edges do not “collide” in the sense that when treating them as line segments, they do not intersect. Several polyhedral constructions can be derived from crystal nets. For example, a vertex figure can be obtained by subdividing each edge (treated as a line segment) by the insertion of subdividing points, and then the vertex figure of a given vertex is the convex hull of the adjacent subdividing points (i.e., the convex polyhedron whose vertices are the adjacent subdividing points).
Another polyhedral construction is to determine the neighborhood of a vertex in the crystal net. One application is to define an energy function as a (possibly weighted) sum of squares of distances from vertices to their neighbors, and with respect to this energy function, the net is in equilibrium (with respect to this energy function) if each vertex is positioned at the centroid of its neighborhood, this is the basis of the crystal net identification program SYSTRE. (mathematicians
use the term ``harmonic realiaztions" instead of ``crystal nets in equilibrium positions" because the positions are characterized by the discrete Laplace equation; they also introduced the notion of standard realizations which are special harmonic realizations characterized by a certain minimal principle as well;see ). Some crystal nets are isomorphic to crystal nets in equilibrium positions, and since an equilibrium position is a normal form, the crystal net isomorphism problem (i.e., the query whether two given crystal nets are isomorphic as graphs; not to be confused with crystal isomorphism) is readily computed even though, as a subsumption of the graph isomorphism problem, it is apparently computationally difficult in general.
Active areas of crystal design using crystal nets
It is conjectured that crystal nets may minimize entropy in the following sense. Suppose one is given an ensemble of uniformly discrete Euclidean graphs that fill space, with vertices representing atoms or molecular building blocks and with edges representing bonds or ligands, extending through all space to represent a solid. For some restrictions, there may be a unique Euclidean graph that minimizes a reasonably defined energy function, and the conjecture is that that Euclidean graph may necessarily be periodic. This question is still open, but some researchers observe crystal nets of high symmetry tending to predominate observed Euclidean graphs derived from some classes of materials.
Historically, crystals were developed by experimentation, currently formalized as combinatorial chemistry, but one contemporary desideratum is the synthesis of materials designed in advance, and one proposal is to design crystals (the designs being crystal nets, perhaps represented as one unit cell of a crystal net) and then synthesize them from the design. This effort, in what Omar Yaghi described as reticular chemistry is proceeding on several fronts, from the theoretical to synthesizing highly porous crystals.
One of the primary issues in annealing crystals is controlling the constituents, which can be difficult if the constituents are individual atoms, e.g., in zeolites, which are typically porous crystals primarily of silicon and oxygen and occasional impurities. Synthesis of a specific zeolite de novo from a novel crystal net design remains one of the major goals of contemporary research. There are similar efforts in sulfides and phosphates.
Control is more tractable if the constituents are molecular building blocks, i.e., stable molecules that can be readily induced to assemble in accordance with geometric restrictions. Typically, while there may be many species of constituents, there are two main classes: somewhat compact and often polyhedral secondary building units (SBUs), and linking or bridging building units. A popular class of examples are the Metal-Organic Frameworks (MOFs), in which (classically) the secondary building units are metal ions or clusters of ions and the linking building units are organic ligands. These SBUs and ligands are relatively controllable, and some new crystals have been synthesized using designs of novel nets. An organic variant are the Covalent Organic Frameworks (COFs), in which the SBUs might (but not necessarily) be themselves organic. The greater control over the SBUs and ligands can be seen in the fact that while no novel zeolites have been synthesized per design, several MOFs have been synthesized from crystal nets designed for zeolite synthesis, such as Zeolite-like Metal-Organic Frameworks (Z-MOFs) and zeolitic imidazolate framework (ZIFs).
See also
Periodic graphs as Euclidean graphs
Hypothetical zeolite
Metal–organic framework
Molecular graph
References
External links
Crystallography | Periodic graph (crystallography) | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 2,374 | [
"Crystallography",
"Condensed matter physics",
"Materials science"
] |
34,565,362 | https://en.wikipedia.org/wiki/Flory%E2%80%93Rehner%20equation | In polymer science Flory–Rehner equation is an equation that describes the mixing of polymer and liquid molecules as predicted by the equilibrium swelling theory of Flory and Rehner.
It describes the equilibrium swelling of a lightly crosslinked polymer in terms of crosslink density and the quality of the solvent.
The Flory–Rehner equation is written as:
where, is the volume fraction of polymer in the swollen mass, the molar volume of the solvent, is the number of network chain segments bounded on both ends by crosslinks, and is the Flory solvent-polymer interaction term.
In its full form, the Flory–Rehner equation is written as:
where, is the specific volume of the polymer, is the primary molecular mass, and is the average molecular mass between crosslinks or the network parameter.
Flory–Rehner theory
The Flory–Rehner theory gives the change of free energy upon swelling of the polymer gel similar to the Flory–Huggins solution theory:
.
The theory considers forces arising from three sources:
The entropy change caused by mixing of polymer and solvent
The heat of mixing of polymer and solvent , which may be positive, negative, or zero so, that
The entropy change caused by reduction in numbers of possible chain conformations via swelling
The Flory–Rehner equation was used to model the cooking of steaks in a journal article in 2020
References
Bibliography
Polymer physics
Soft matter
Materials science
Polymers
Equations
Rubber properties | Flory–Rehner equation | [
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"Soft matter",
"Mathematical objects",
"Materials science",
"Equations",
"Condensed matter physics",
"Polymer chemistry",
"nan",
"Polymers"
] |
34,568,491 | https://en.wikipedia.org/wiki/Crystal%20model | A crystal model is a teaching aid used for understanding concepts in crystallography and the morphology of crystals. Models are ideal to learn recognizing symmetry elements in crystals.
Romé de l'Isle
The first real collections of crystal models were produced by Romé de l'Isle. He actually offered sets of small (ca 3 cm) models made of "terra cotta" in order to stimulate the sales of the expensive four-volume set of his book "Cristallographie" (1783). The models were manufactured by his co-workers Arnould Carangeot, Lhermina and Swebach-Desfontaines, who produced numerous large sets (up to 448 models in each set). In order to exactly transfer interplanar angles from natural crystals to the terra cotta models, Carangeot invented and designed a prototype of a contact goniometer. This instrument, that proved to be an invaluable tool in geometric crystallography, enabled the measurement of interplanar angles with a precision of about half a degree.
Teylers Museum in Haarlem has a complete set of these terracotta models that were bought in Paris (in 1785) by Martin van Marum, the first director of the museum. After over 200 years, this collection is still complete and in perfect condition at Teylers Museum.
René Just Haüy
Almost two decades later, René Just Haüy introduced wooden crystal models to illustrate the two-dimensional drawings in the atlas volume of his "Traité de Minéralogie" (1801). For the production of crystal models, wood appeared to be much more convenient than clay. Especially pear wood permitted getting smooth faces, sharp edges and accurate dihedral angles required for the production of these three-dimensional objects. In general, the angular accuracy was very high and some models, especially those illustrating crystal twins and Haüy's figures of decrement, still appear as masterpieces of fine woodwork and carving. Skilful craftsmen such as Pleuvin, Beloeuf and Lambotin (to name only a few) became specialists in this field and the models they offered were highly esteemed.
Between 1802 and 1804, Martin van Marum bought 597 of these pear wood models, 550 of these are still present in the collection of Teylers Museum. Each model is labeled, mentioning a number and the name of the crystal form. This set is the most complete collection of Haüy crystal models that still survives. That Van Marum was able to acquire such a unique collection was due to his networking. Van Marum allowed Haüy as a member of the Hollandsche Maatschappij, a nomination to which Haüy attached great value. Haüy mentioned this membership in all of his publications.
After their introduction by Romé de l'Isle and Haüy, crystal models were increasingly demanded both by scholars for teaching purposes as well as by mineral collectors. The quality of the models improved due to the technical progress in their production. Several mineralogists and crystallographers started designing their own series of models. Although pear wood kept a prominent place, models were also manufactured using materials like plaster, cast iron, lead, brass, glass, porcelain, cardboard, etc.
The Krantz Company
In 1833, Adam August Krantz (who studied pharmacy and later "Geognosie" at the Bergakademie Freiberg) founded the Krantz company in Bonn. Four years later, Krantz moved to Berlin and sold minerals, fossils, rocks and basically acquired a monopoly in the production of crystal models made of pear wood or walnut. Ever since its foundation, the firm was always in contact with renowned scientists and important collectors. Hence in 1880, Krantz proposed a series of 743 pear wood models compiled for teaching purposes by the crystallographer Paul Groth. Seven years later, a supplementary collection of 213 models was available.
At the onset of the 20th century, Friedrich Krantz (a nephew of August Krantz, with a degree in mineralogy) supported by his teacher the crystallographer Carl Hintze, offered a collection of 928 models including most of the Groth models. Later, and along with many other productions, a Dana collection of 282 models was manufactured. Krantz offered a choice of collections of wooden models in different sizes (5, 10, 15–25 cm). In addition, he sold a variety of glass models having the crystallographic axes illustrated by colored silk threads or with the holohedral form made of cardboard inside. Also available were models in massive cut and polished glass (colored and uncolored), cardboard models, wire crystal models, crystal lattice models, models with rotating parts, etc.
Over the years, Krantz published numerous detailed catalogues of the collections he offered; they constitute a precious documentation.
External links
Teylers Universum
Early Crystal Models
References
Mineralogy
Crystallography
Teylers Museum | Crystal model | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 1,014 | [
"Crystallography",
"Condensed matter physics",
"Materials science"
] |
37,100,405 | https://en.wikipedia.org/wiki/Triakis%20truncated%20tetrahedron | In geometry, the triakis truncated tetrahedron is a convex polyhedron made from 4 hexagons and 12 isosceles triangles. It can be used to tessellate three-dimensional space, making the triakis truncated tetrahedral honeycomb.
The triakis truncated tetrahedron is the shape of the Voronoi cell of the carbon atoms in diamond, which lie on the diamond cubic crystal structure. As the Voronoi cell of a symmetric space pattern, it is a plesiohedron.
Construction
For space-filling, the triakis truncated tetrahedron can be constructed as follows:
Truncate a regular tetrahedron such that the big faces are regular hexagons.
Add an extra vertex at the center of each of the four smaller tetrahedra that were removed.
See also
Quarter cubic honeycomb
Truncated tetrahedron
Triakis tetrahedron
References
Space-filling polyhedra
Truncated tilings | Triakis truncated tetrahedron | [
"Physics"
] | 197 | [
"Tessellation",
"Truncated tilings",
"Symmetry"
] |
37,102,865 | https://en.wikipedia.org/wiki/Chemically%20induced%20dimerization | Chemically induced dimerization (CID) is a biological mechanism in which two proteins bind only in the presence of a certain small molecule, enzyme or other dimerizing agent. Genetically engineered CID systems are used in biological research to control protein localization, to manipulate signalling pathways and to induce protein activation.
History
The first small molecule CID system was developed in 1993 and used FK1012, a derivative of the drug tacrolimus (FK506), to induce homo-dimerization of FKBP. This system was used in vivo to induce binding between cell surface receptors which could not bind in the normal way because they lacked the transmembrane and extracellular domain. Addition of FK1012 to the cells caused signal transduction.
Chemically induced dimerization systems
Applications
CID has been used for a number of applications in biomedical research. In most applications each dimerizing protein is expressed as part of a fusion construct with other proteins of interest. Adding the chemical dimerizing agent brings both constructs into proximity with each other and induces interactions between the proteins of interest. CID has been used to regulate and monitor gene transcription, signal transduction and post translational modifications in proteins.
Recently, CID has also been used to create a basic component of biocomputers, logic gates, from genetically manipulated cells. In this application, two independent CID systems, one based on plant proteins and one based on bacterial proteins are expressed in the same cell. Each set of proteins can be induced to dimerize by the addition of a separate chemical. By creating fusion proteins with the dimerizing proteins, membrane bound proteins and proteins that activate cell ruffling an AND gate and OR gate can be created that take chemical dimerizing agents as inputs and returns a ruffled or unruffled state as output.
References
Biotechnology
Genetic engineering
Biochemistry methods
Protein–protein interaction assays
Cell biology | Chemically induced dimerization | [
"Chemistry",
"Engineering",
"Biology"
] | 380 | [
"Biochemistry methods",
"Protein–protein interaction assays",
"Biological engineering",
"Cell biology",
"Genetic engineering",
"Biotechnology",
"nan",
"Molecular biology",
"Biochemistry"
] |
37,106,074 | https://en.wikipedia.org/wiki/Chen%E2%80%93Gackstatter%20surface | In differential geometry, the Chen–Gackstatter surface family (or the Chen–Gackstatter–Thayer surface family) is a family of minimal surfaces that generalize the Enneper surface by adding handles, giving it nonzero topological genus.
They are not embedded, and have Enneper-like ends. The members of the family are indexed by the number of extra handles i and the winding number of the Enneper end; the total genus is ij and the total Gaussian curvature is . It has been shown that is the only genus one orientable complete minimal surface of total curvature .
It has been conjectured that continuing to add handles to the surfaces will in the limit converge to the Scherk's second surface (for j = 1) or the saddle tower family for j > 1.
References
External links
The Chen–Gackstatter Thayer Surfaces at the Scientific Graphics Project
Chen–Gackstatter Surface in the Minimal Surface Archive
Xah Lee's page on Chen–Gackstatter
Minimal surfaces | Chen–Gackstatter surface | [
"Chemistry"
] | 215 | [
"Foams",
"Minimal surfaces"
] |
37,108,522 | https://en.wikipedia.org/wiki/Tetraethylammonium%20chloride | Tetraethylammonium chloride (TEAC) is a quaternary ammonium compound with the chemical formula , sometimes written as . In appearance, it is a hygroscopic, colorless, crystalline solid. It has been used as the source of tetraethylammonium ions in pharmacological and physiological studies, but is also used in organic chemical synthesis.
Preparation and structure
TEAC is produced by alkylation of triethylamine with ethyl chloride.
TEAC exists as either of two stable hydrates, the monohydrate and tetrahydrate. The crystal structure of has been determined, as has that of the tetrahydrate, .
Details for the preparation of large, prismatic crystals of are given by Harmon and Gabriele, who carried out IR-spectroscopic studies on this and related compounds. These researchers have also pointed out that, although freshly-purified is free of triethylamine hydrochloride, small quantities of this compound form on heating of TEAC as the result of a Hofmann elimination:
Synthetic applications
To a large extent, the synthetic applications of TEAC resemble those of tetraethylammonium bromide (TEAB) and tetraethylammonium iodide (TEAI), although one of the salts may be more efficacious than another in a particular reaction. For example, TEAC produces better yields than TEAB or TEAI as a co-catalyst in a reaction to prepare diarylureas from arylamines, nitroaromatics and carbon monoxide.
In other examples, such as the following, TEAC is not as effective as TEAB or TEAI:
2-Hydroxyethylation (attachment of ) by ethylene carbonate of carboxylic acids and certain heterocycles bearing an acidic N-H.
Phase-transfer catalyst in geminal di-alkylation of fluorene, N,N-dialkylation of aniline and N-alkylation of carbazole using aqueous sodium hydroxide and alkyl halides.
Biology
In common with tetraethylammonium bromide and tetraethylammonium iodide, TEAC has been used as a source of tetraethylammonium ions for numerous clinical and pharmacological studies, which are covered in more detail under the entry for Tetraethylammonium. Briefly, TEAC has been explored clinically for its ganglionic blocking properties, although it is now essentially obsolete as a drug, and it is still used in physiological research for its ability to block channels in various tissues.
Toxicity
The toxicity of TEAC is primarily due to the tetraethylammonium ion, which has been studied extensively. The acute toxicity of TEAC is comparable to that of tetraethylammonium bromide and tetraethylammonium iodide. These data are provided for comparative purposes; additional details may be found in the entry for Tetraethylammonium.
See also
Tetraethylammonium
Tetraethylammonium bromide
Tetraethylammonium iodide
Tetramethylammonium chloride
References
Tetraethylammonium salts
Chlorides | Tetraethylammonium chloride | [
"Chemistry"
] | 673 | [
"Chlorides",
"Inorganic compounds",
"Salts"
] |
37,110,728 | https://en.wikipedia.org/wiki/Exosortase | Exosortase refers to a family of integral membrane proteins that occur in Gram-negative bacteria that recognizes and cleaves the carboxyl-terminal sorting signal PEP-CTERM. The name derives from a predicted role analogous to sortase, despite the lack of any detectable sequence homology, and a strong association of exosortase genes with exopolysaccharide or extracellular polymeric substance biosynthesis loci. Many archaea have an archaeosortase, homologous to exosortases rather than to sortases. Archaeosortase A recognizes the signal PGF-CTERM, found at the C-terminus of some archaeal S-layer proteins. Following processing by archaeosortase A, the PGF-CTERM region is gone, and a prenyl-derived lipid anchor is present at the C-terminus instead.
Exosortase has not itself been characterized biochemically. However, site-directed mutagenesis work on archaeosortase A, an archaeal homolog of exosortases, strongly supports the notion of a Cys active site and convergent evolution with sortase family transpeptidases. A recent study on Zoogloea resiniphila, a bacterium found in activated sludge wastewater treatment plants, has shown that PEP-CTERM proteins (and by implication, exosortase as well) are essential to floc formation in some systems.
References
Membrane proteins
Enzymes | Exosortase | [
"Biology"
] | 318 | [
"Protein classification",
"Membrane proteins"
] |
37,113,247 | https://en.wikipedia.org/wiki/Empagliflozin | Empagliflozin, sold under the brand name Jardiance ( ), among others, is an antidiabetic medication used to improve glucose control in people with type2 diabetes. It is taken by mouth.
Common side effects include hyperventilation, anorexia, abdominal pain, nausea, vomiting, lethargy, mental status changes, hypotension, acute kidney injury, and vaginal yeast infections. Rarer but more serious side effects include a skin infection of the groin called Fournier's gangrene and a form of diabetic ketoacidosis with normal blood sugar levels. Use during pregnancy or breastfeeding is not recommended. Empagliflozin sometimes causes a transient decline in kidney function, and on rare occasions causes acute kidney injury, so use should be monitored in those with kidney dysfunction. But some trials have indicated that empagliflozin can be used in people with an eGFR as low as 20 mL/min/1.73 m², without increasing adverse kidney outcomes.
The use of empagliflozin has been shown to improve outcomes in people with established cardiovascular disease. There is evidence from high quality studies that empagliflozin can also help to slow the rate of kidney function decline. Irrespective of diabetes status, benefit was observed in those with mild, moderate or severe loss of kidney function. People started on empagliflozin may first see a decrease in kidney function before their glomerular filtration rate stabilises. Greatest benefit was demonstrated in those who had severe loss of kidney function, higher risk of kidney function worsening and background of diabetes.
Empagliflozin is an inhibitor of the sodium glucose co-transporter-2 (SGLT-2), and works by increasing sugar loss in urine.
Empagliflozin was approved for medical use in the United States and in the European Union in 2014. It is on the World Health Organization's List of Essential Medicines. In 2022, it was the 56th most commonly prescribed medication in the United States, with more than 12million prescriptions. It has received approval as a generic medication from the US Food and Drug Administration (FDA).
Medical uses
In the United States, empagliflozin is indicated to reduce the risk of cardiovascular death and hospitalization for heart failure in adults with heart failure; to reduce the risk of sustained decline in eGFR, end-stage kidney disease, cardiovascular death, and hospitalization in adults with chronic kidney disease at risk of progression; to reduce the risk of cardiovascular death in adults with type2 diabetes and established cardiovascular disease; and as an adjunct to diet and exercise to improve glycemic control in people aged ten years of age and older with type2 diabetes.
In the European Union, empagliflozin is indicated in people aged ten years of age and older for the treatment of insufficiently controlled type 2 diabetes as an adjunct to diet and exercise; as monotherapy when metformin is considered inappropriate due to intolerance; in addition to other medicinal products for the treatment of diabetes. It is indicated in adults for the treatment of symptomatic chronic heart failure; and it is indicated in adults for the treatment of chronic kidney disease.
Empagliflozin lowers risk of hospitalization and death in people with reduced heart function, when added to standard heart failure treatment with or without type2 diabetes. It is indicated in adults with type2 diabetes and established cardiovascular disease to reduce the risk of cardiovascular death; and as an adjunct to diet and exercise to improve glycemic control in adults with type2 diabetes.
In June 2023, the US Food and Drug Administration (FDA) expanded the indication, as an addition to diet and exercise, to improve blood sugar control in children 10 years and older with type2 diabetes.
Contraindications
History of a severe allergic reaction to empagliflozin
End-stage kidney disease
Diabetic ketoacidosis
Side effects
Common
Empagliflozin increases the risk of genital fungal infections. The risk is highest in people with a prior history of genital fungal infections.
Empagliflozin has been thought to be associated with increased risk of urinary tract infections. Reviews of clinical trials have shown there is no significant risk of developing urinary tract infections while taking empagliflozin when compared to placebo or other diabetic medications.
Empagliflozin reduces systolic and diastolic blood pressure and can increase the risk of low blood pressure, which can cause fainting and/or falls. The risk is higher in older people, people taking diuretics, and people with reduced kidney function.
Slight increases in Low-density lipoprotein (LDL) cholesterol can be seen with empagliflozin, in the range of 2–4% from baseline.
Serious
Diabetic ketoacidosis, a rare but potentially life-threatening condition, may occur more commonly with empagliflozin and other SGLT-2 inhibitors. While diabetic ketoacidosis is usually associated with elevated blood glucose levels, in people taking SGLT-2 inhibitors diabetic ketoacidosis may be seen with uncharacteristically normal blood glucose levels, a phenomenon called euglycemic diabetic ketoacidosis. The absence of elevated blood glucose levels in people on an SGLT-2 inhibitor may make it more difficult to diagnose diabetic ketoacidosis. The risk of empagliflozin-associated euglycemic diabetic ketoacidosis may be higher in the setting of illness, dehydration, surgery, and/or alcohol consumption. It is also seen in type1 diabetes who take empagliflozin, which notably is an unapproved or "off-label" use of the medication. To lessen the risk of developing ketoacidosis (a serious condition in which the body produces high levels of blood acids called ketones) after surgery, the FDA has approved changes to the prescribing information for SGLT2 inhibitor diabetes medicines to recommend they be stopped temporarily before scheduled surgery. Empagliflozin should each be stopped at least three days before scheduled surgery. Symptoms of diabetic ketoacidosis include nausea, vomiting, abdominal pain, tiredness, and trouble breathing.
Fournier's gangrene, a rare but serious infection of the groin, occurs more commonly in people taking empagliflozin and other SGLT-2 inhibitors. Symptoms include feverishness, a general sense of malaise, and pain or swelling around the genitals or in the skin behind them. The infection progresses quickly and urgent medical attention is recommended.
Empagliflozin can increase the risk of low blood sugar when it is used together with a sulfonylurea or insulin. When used by itself or in addition to metformin it does not appear to increase the risk of hypoglycemia.
Mechanism of action
Empagliflozin is an inhibitor of the sodium glucose co-transporter-2 (SGLT-2), which is found almost exclusively in the proximal tubules of nephronic components in the kidneys. SGLT-2 accounts for about 90percent of glucose reabsorption into the blood. Blocking SGLT-2 reduces blood glucose by blocking glucose reabsorption in the kidney and thereby excreting glucose (i.e., blood sugar) via the urine. Of all the SGLT-2 Inhibitors currently available, empagliflozin has the highest degree of selectivity for SGLT-2 over SGLT-1, SGLT-4, SGLT-5 and SGLT-6.
History
It was developed by Boehringer Ingelheim and is co-marketed by Eli Lilly and Company. It is also available as the fixed-dose combinations empagliflozin/linagliptin, empagliflozin/metformin, and empagliflozin/linagliptin/metformin.
For cardiovascular death, the FDA based its decision on a postmarketing study it required when it approved empagliflozin in 2014, as an adjunct to diet and exercise to improve glycemic control in adults with type2 diabetes. Empagliflozin was studied in a postmarket clinical trial of more than 7,000 participants with type2 diabetes and cardiovascular disease. In the trial, empagliflozin was shown to reduce the risk of cardiovascular death compared to a placebo when added to standard of care therapies for diabetes and atherosclerotic cardiovascular disease.
For heart failure, the safety and effectiveness of empagliflozin were evaluated by the FDA as an adjunct to standard of care therapy in a randomized, double-blind, international trial comparing 2,997 participants who received empagliflozin, 10 mg, once daily to 2,991 participants who received the placebo. The main efficacy measurement was the time to death from cardiovascular causes or need to be hospitalized for heart failure. Of the individuals who received empagliflozin for an average of about two years, 14% died from cardiovascular causes or were hospitalized for heart failure, compared to 17% of the participants who received the placebo. This benefit was mostly attributable to fewer participants being hospitalized for heart failure.
The FDA granted the application for empagliflozin priority review and granted the approval of Jardiance to Boehringer Ingelheim.
Legal status
As of May 2013, Boehringer and Lilly had submitted applications for marketing approval to the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA). Empagliflozin was approved in the European Union in May 2014, and was approved in the United States in August 2014. The FDA required four postmarketing studies: a cardiovascular outcomes trial, two studies in children, and a toxicity study in animals related to the pediatric trials.
Research
A meta-analysis of short-term randomized controlled trials has shown similar efficacy on glycemic control between empagliflozin 10mg and 25mg in people with type2 diabetes. While there may be a higher reduction in HbA1c with higher doses, this difference is more clinically significant when the patients' baseline HbA1c is ≥ 8.5%.
Weight and blood pressure
Empagliflozin causes moderate reductions in blood pressure and body weight. These effects are likely due to the excretion of glucose in the urine and a slight increase in urinary sodium excretion.
In clinical trials, participants with type2 diabetes taking empagliflozin with other diabetic medications lost an average of 2% of their baseline body weight. A higher percentage of people taking empagliflozin achieved weight loss greater than 5% from their baseline, which has been associated with improved glucose control. The same extent of weight loss was also observed in a study with heart failure patients taking empagliflozin.
Empagliflozin has been shown to reduce systolic blood pressure by 3 to 5millimeters of mercury (mmHg) without changes in pulse rate. A greater percentage of people with uncontrolled blood pressure at baseline, achieved controlled blood pressure (i.e. systolic blood pressure <130 mmHg and diastolic blood pressure <80 mmHg) after taking empagliflozin at 24 weeks. The effects on blood pressure and body weight are generally viewed as favorable, as many people with type2 diabetes have high blood pressure or are overweight or obese.
References
Drugs developed by Boehringer Ingelheim
Drugs developed by Eli Lilly and Company
Ethers
Glucosides
World Health Organization essential medicines
Wikipedia medicine articles ready to translate
SGLT2 inhibitors | Empagliflozin | [
"Chemistry"
] | 2,492 | [
"Organic compounds",
"Functional groups",
"Ethers"
] |
22,933,005 | https://en.wikipedia.org/wiki/Ratio%20detector | The ratio detector is a type of detector circuit, commonly used in radio receivers for demodulating frequency modulated (FM) signal.
The ratio detector is a variant of the Foster–Seeley discriminator, but one diode conducts in an opposite direction, and using a tertiary winding in the preceding transformer. The output in this case is taken between the sum of the diode voltages and the center tap. The output across the diodes is connected to a large value capacitor, forming a dynamic limiter. The ratio detector has the advantage over the Foster–Seeley discriminator that it does not respond to amplitude modulation (AM) signals, thus potentially saving a limiter stage; however, the output is only 50% of the output of a discriminator for the same input signal. The ratio detector has wider bandwidth, but more distortion than the Foster–Seeley discriminator.
Amplitude noise suppression
The suppression of the effect of amplitude variation of the incoming signal on the output of the ratio detector is based on the principle of RF dynamic limiting:
A large value reservoir capacitor (C4) and bleeding resistor(s) (R1, R2) are connected across the diodes. The RF signal is rectified by the diodes and the rectified DC voltage charges the reservoir capacitor, while a small steady current bleeds through the resistor(s), continuously discharging it. This results in a constant steady load and a moderate damping effect on the tuned circuit.
As the amplitude of the signal increases, the higher rectified voltage results in an inrush current towards the reservoir capacitor; the increased load results in an increased damping of the tuned circuit, resulting in nearly constant amplitude on the output despite the amplitude increase of the incoming signal.
Similarly, a decrease in the input signal amplitude results in decreased (or ceased) current flow towards the charged reservoir capacitor, resulting in decreased- or no damping on the tuned circuit.
The values of the reservoir capacitor and the bleeding resistor(s) are chosen so that the combined time constant of these components is below the audio spectrum.
References
Detectors | Ratio detector | [
"Engineering"
] | 448 | [
"Radio electronics",
"Demodulation"
] |
22,938,559 | https://en.wikipedia.org/wiki/Demolition%20waste | Demolition waste is waste debris from destruction of buildings, roads, bridges, or other structures. Debris varies in composition, but the major components, by weight, in the US include concrete, wood products, asphalt shingles, brick and clay tile, steel, and drywall. There is the potential to recycle many elements of demolition waste.
Composition
In 2014, 505.1 million tons of demolition debris was generated in the US. Out of the 505.1 million tons, the debris was composed of 353.6 million tons of concrete, 76.6 million tons of asphalt concrete, 35.8 million tons of wood product, 12.7 million tons of asphalt shingles, 11.8 million tons of brick and clay tile, 10.3 million tons of drywall and plaster, and 4.3 million tons of steel.
Disposal
Before demolition debris is extracted, contamination from lead, asbestos or other hazardous materials must be resolved. Hazardous materials must be disposed of separately, according to federal regulation. Demolition debris can be disposed of in either Construction and Demolition Debris landfills or municipal solid waste landfills. Alternatively, debris may also be sorted and recycled. Sorting may happen as deconstruction on the demolition site, off-site at a sorting location, or at a Construction and Demolition recycling center. Once sorted, materials are managed separately and recycled accordingly.
Recycling
Concrete and Brick
Concrete and brick can be recycled by crushing it into rubble. Once sorted, screened and contaminants are removed, reclaimed concrete or brick can be used in concrete aggregate, fill, road base, or riprap. Mobile concrete crushers also allow for recycling of concrete on-site.
Wood
Wood can be reused, repurposed, recycled, or burned as bioenergy. Reused wood can eliminate the need for full-size new lumber if used for smaller building components. Repurposed or recycled wood can be used in pathways, coverings, mulches, compost, animal bedding, or particleboard. Using recycled wood as a bioenergy feedstock is advantageous because it has lower water content, about 20% water, compared to virgin lumber, about 60% water.
Drywall
Drywall is made primarily of gypsum. Once the gypsum is depapered, it can be added in cement production, as a soil amendment, used in aerated composting, or recycled into new drywall. Gypsum recycling can be particularly beneficial because in landfill conditions gypsum will release hydrogen sulfide, a toxic gas.
Asphalt
Asphalt, from shingles or asphalt concrete, is typically recycled and used in pavement.
Metal
Scrap metal is an established industry focused on the collection, buying, selling, and recycling of salvaged materials.
See also
References
Waste
Demolition
cs:Suť
de:Bauschutt | Demolition waste | [
"Physics",
"Engineering"
] | 573 | [
"Demolition",
"Construction",
"Materials",
"Waste",
"Matter"
] |
22,938,591 | https://en.wikipedia.org/wiki/Differential%20screw | A differential screw is a mechanism used for making small, precise adjustments to the spacing between two objects (such as in focusing a microscope, moving the anvils of a micrometer, or positioning optics). A differential screw uses a spindle with two screw threads of differing leads (in case of a single lead equal to the thread pitch), and possibly opposite handedness, on which two nuts move. As the spindle rotates, the space between the nuts changes based on the difference between the threads. These mechanisms allow extremely small adjustments using commonly available screws. A differential screw mechanism using two nuts incurs higher friction and therefore requires more torque to turn than a simple, single lead screw with an equivalent pitch.
History
The first known use of a differential screw was on Towneley’s version of Gascoigne’s Micrometer.
Flamsteed’s Preface to the Historia Coelestis Britannica:
"Richard Towneley ... carried forward and completed his instrument (the micrometer) and made it perform with one screw, what on Gascoigne’s instrument had required two.”
A drawing by Robert Hooke in 1667 clearly shows Towneley’s Micrometer with the single screw with two different pitch threads on it. With this differential screw, one thread was half the pitch of the other, Towneley was able to keep the micrometer's indicating pointers centered in the field of view as they opened and closed.
Examples
Many differential screw configurations are possible. The micrometer adjuster pictured uses a nut sleeve with different inner and outer thread pitches to connect a screw on the adjusting rod end with threads inside the main barrel; as the thimble rotates the nut sleeve, the rod and barrel move relative to each other based on the differential between the threads.
Another arrangement holds the two "nuts" co-axially in a single fixture and has two separate screws with slightly different pitches (distance from the crest of one thread to the next) entering from opposite ends. The "heads" of the screws are fixed to the two objects whose spacing is to be adjusted. Each rotation of the fixture holding the nuts moves one screw into its nut by a small amount and moves the other screw out of its nut by a slightly larger amount. The total spacing between the screws, and thus the objects, will be slightly changed based on the difference in travel between the two screws.
More arrangements are possible. Two nuts can be fixed to each of two objects to be adjusted and the two screw heads attached to each other in the middle. The combined screws would be turned to adjust the spacing in that case.
Calculating motion and effective thread pitch
For single start threads, each turn changes the distance between the nuts by the effective pitch, . For a bolt with a given thread per inch, on one end and a second thread per inch, on the other, the change in distance (or ), and the effective thread per inch , is calculated by:
For example, a bolt with coarse threads (16 tpi, per turn) on one end and fine threads (24 tpi, per turn) on the other changes the distance between the nuts by about per revolution and is equivalent to a 48 tpi (0.53 mm/thread) thread:
For single start Metric threads, the effective pitch is simply the difference between the two thread pitches:
For example, an M5×0.80 thread paired with an M4×0.70 thread will produce a differential motion of 0.1 mm, or 100 μm per revolution.
Mixing metric and imperial threads can result in finer differentials while still using standard threads, they can be calculated in the same way as a metric differential but the TPI of the imperial thread must be converted to a metric pitch measurement. For example a 26 TPI thread has a pitch of ~0.977 mm and when paired with a 1.0 mm pitch metric thread the differential motion will be approximately 0.023 mm per revolution.
References
Mechanisms (engineering)
Metalworking
Screws | Differential screw | [
"Engineering"
] | 829 | [
"Mechanical engineering",
"Mechanisms (engineering)"
] |
22,940,609 | https://en.wikipedia.org/wiki/Soil%20gas | Soil gases (soil atmosphere) are the gases found in the air space between soil components. The spaces between the solid soil particles, if they do not contain water, are filled with air. The primary soil gases are nitrogen, carbon dioxide and oxygen. Oxygen is critical because it allows for respiration of both plant roots and soil organisms. Other natural soil gases include nitric oxide, nitrous oxide, methane, and ammonia. Some environmental contaminants below ground produce gas which diffuses through the soil such as from landfill wastes, mining activities, and contamination by petroleum hydrocarbons which produce volatile organic compounds.
Gases fill soil pores in the soil structure as water drains or is removed from a soil pore by evaporation or root absorption. The network of pores within the soil aerates, or ventilates, the soil. This aeration network becomes blocked when water enters soil pores. Not only are both soil air and soil water very dynamic parts of soil, but both are often inversely related.
Composition
The composition of gases present in the soil's pores, referred to commonly as the soil atmosphere or atmosphere of the soil, is similar to that of the Earth's atmosphere. Unlike the atmosphere, moreover, soil gas composition is less stagnant due to the various chemical and biological processes taking place in the soil. The resulting changes in composition from these processes can be defined by their variation time (i.e. daily vs. seasonal). Despite this spatial- and temporal-dependent fluctuation, soil gases typically boast greater concentrations of carbon dioxide and water vapor in comparison to the atmosphere. Furthermore, concentration of other gases, such as methane and nitrous oxide, are relatively minor yet significant in determining greenhouse gas flux and anthropogenic impact on soils.
Processes
Gas molecules in soil are in continuous thermal motion according to the kinetic theory of gases, and there is also collision between molecules – a random walk process. In soil, a concentration gradient causes net movement of molecules from high concentration to low concentration, which gives the movement of gas by diffusion. Numerically, it is explained by the Fick's law of diffusion. Soil gas migration, specifically that of hydrocarbon species with one to five carbons, can also be caused by microseepage.
The soil atmosphere's variable composition and constant motion can be attributed to chemical processes such as diffusion, decomposition, and, in some regions of the world, thawing, among other processes. Diffusion of soil air with the atmosphere causes the preferential replacement of soil gases with atmospheric air. More significantly, moreover, variation in soil gas composition due to seasonal, or even daily, temperature and/or moisture change can influence the rate of soil respiration.
According to the USDA, soil respiration refers to the quantity of carbon dioxide released from soil. This excess carbon dioxide is created by the decomposition of organic material by microbial organisms, in the presence of oxygen. Given the importance of both soil gases to soil life, significant fluctuation of carbon dioxide and oxygen can result in changes in rate of decay, while changes in microbial abundance can inversely influence soil gas composition.
In regions of the world where freezing of soils or drought is common, soil thawing and rewetting due to seasonal or meteorological changes influences soil gas flux. Both processes hydrate the soil and increase nutrient availability leading to an increase in microbial activity. This results in greater soil respiration and influences the composition of soil gases.
Studies and Research
Soil gases have been used for multiple scientific studies to explore topics such as microseepage, earthquakes, and gaseous exchange between the soil and the atmosphere. Microseepage refers to the limited release of hydrocarbons on the soil surface and can be used to look for petroleum deposits based on the assumption that hydrocarbons vertically migrate to the soil surface in small quantities. Migration of soil gases, specifically radon, can also be examined as earthquake precursors. Furthermore, for processes such as soil thawing and rewetting, for example, large sudden changes in soil respiration can cause increased flux of soil gases such as carbon dioxide and methane, which are greenhouse gases. These fluxes and interactions between soil gases and atmospheric air can further be analyzed by distance from the soil surface.
References
Soil physics
Geochemistry
Soil
Environmental science
Environmental chemistry | Soil gas | [
"Physics",
"Chemistry",
"Environmental_science"
] | 881 | [
"Environmental chemistry",
"Applied and interdisciplinary physics",
"nan",
"Soil physics"
] |
24,444,105 | https://en.wikipedia.org/wiki/NUTS%20statistical%20regions%20of%20Portugal | The Nomenclature of Territorial Units for Statistics (NUTS) is developed by Eurostat, and employed in both Portugal and the entire European Union for statistical purposes. The NUTS branch extends from NUTS1, NUTS2 and NUTS3 regions, with the complementary LAU (Local Administrative Units) sub-categorization being used to differentiate the local areas, of trans-national importance.
Developed by Eurostat and implemented in 1998, the Nomenclature of Territorial Units for Statistics (NUTS) regions, which comprises three levels of the Portuguese territory, are instrumental in European Union's Structural Fund delivery mechanisms. The standard was developed by the European Union and extensively used by national governments, Eurostat and other EU bodies for statistical and policy matters. Until 4 November 2002, the Sistema Estatístico Nacional (SEN) used a NUTS codification system that was distinct from the Eurostat system. With the enactment of Decree Law 244/2002 (5 November 2002), published in the Diário da República, this system was abandoned in order to harmonize the national system with that of Eurostat.
Subdivisions
The NUTS system subdivides the nation into three levels: NUTS I, NUTS II and NUTS III. In some European partners, as is the case with Portugal, a complementary hierarchy, respectively LAU I and LAU II (posteriorly referred to as NUTS IV and NUTS V) is employed. The LAU, or Local Administrative Units, in the Portuguese context pertains to the 308 municipalities (LAU I) and 3092 civil parishes (LAU II) respectively. In the broadest sense, the NUTS hierarchy, while they may follow some of the borders (municipal or parish) diverge in their delineation.
Changes NUTS 2-3 (1986—2024)
NUTS I
The first and broadest subdivision of Portugal is between continental Portugal and the two autonomous regions of the Azores and Madeira.
NUTS II
Although the districts are still the most socially relevant subdivision, their function is being phased in favour of locally oriented regional units, and regions are growing in importance. Since the creation of Oeste e Vale do Tejo in 2024, Portugal is divided into seven regions, in continental Portugal, plus the two autonomous regions that are their own NUTS II regions.
NUTS III
The nine regions of Portugal are likewise subdivided into 25 subregions () that, from 2015, represent the 2 metropolitan areas, the 21 intermunicipal communities and the 2 autonomous regions. Therefore, since the 2013 revision (enforced in 2015), the Portuguese subregions have a statutory and administrative relevance.
The two autonomous regions () in the Atlantic, correspond to their own NUTS I, II and III categories.
NUTS Codes
The regions, subregions and their NUTS codes are:
LAUs
Municipalities and civil parishes were at NUTS IV and V levels, but these nomenclature units have been abolished and substituted by LAUs: the municipality is classified as LAU 1, while the civil parish is LAU level 2. Below the NUTS levels, the two LAU (Local Administrative Unit) levels are:
The LAU codes of Portugal can be downloaded at:
See also
Administrative divisions of Portugal
ISO 3166-2 codes of Portugal
FIPS region codes of Portugal
List of Portuguese regions by Human Development Index
Subdivisions of Portugal
References
Sources
Hierarchical list of the Nomenclature of territorial units for statistics - NUTS and the Statistical regions of Europe
Overview map of EU Countries - NUTS level 1
PORTUGAL - NUTS level 2
PORTUGAL - NUTS level 3
Correspondence between the NUTS levels and the national administrative units
List of current NUTS codes
Download current NUTS codes (ODS format)
Regions of Portugal, Statoids.com
Municipalities of Portugal, Statoids.com
Regiões de Portugal, LOCAL.PT
Portugal
Nuts | NUTS statistical regions of Portugal | [
"Mathematics"
] | 744 | [
"Nomenclature of Territorial Units for Statistics",
"Statistical concepts",
"Statistical regions"
] |
24,444,233 | https://en.wikipedia.org/wiki/Comparison%20of%20pumps | This article lists different types of pump and provides a comparison of certain key design features. Different types of pumps are suitable for different applications, for example: a pump's maximum lift height also determines the applications it can be used for. Low-lift pumps are only suitable for the pumping of surface water (e.g., irrigation, drainage of lands, ...), while high-lift pumps allow deep water pumping (e.g., potable water pumping from wells).
Direct lift devices
Displacement pumps
Velocity pumps
Buoyancy pumps
Impulse Pumps
Note: reciprocating pumps are cyclic, rotary pumps are typically continuous.
References
Technological comparisons | Comparison of pumps | [
"Physics",
"Chemistry",
"Technology"
] | 134 | [
"Pumps",
"Turbomachinery",
"Physical systems",
"Hydraulics",
"nan"
] |
24,445,978 | https://en.wikipedia.org/wiki/AV.link | AV.link, also known under the trade names nexTViewLink, SmartLink, Q-Link, EasyLink, etc., is a protocol to carry control information between audio-visual devices connected via the SCART (EIA Multiport) connector.
It is standardised as CENELEC EN 50157-1.
The Consumer Electronics Control (CEC) communication channel in HDMI and PDMI is based on AV.link.
Electrical characteristics
AV.Link uses a single wire in an open collector configuration. It is passively pulled up to 3 or 3.3 V, and may be pulled down by any device on the bus. Total bus capacitance is a maximum of 7300 pF (ten devices at 100 pF each, plus nine cables at 700 pF), and signal transitions are correspondingly slow: 333 bit/s, with 50 μs fall time and 250 μs rise time.
Each bit transferred begins with a falling edge. The duration of the low period determines the value.
Data bits are 2.4±0.35 ms long, with 1 bits having a low period of 0.6±0.2 ms, and 0 bits having a low period of 1.5±0.2 ms. Receivers observe the data line at 1.05±0.2 ms after the falling edge to determine the bit's value.
Every message begins with a special start bit, 4.5±0.2 ms long, with a low period of 3.7±0.2 ms.
A transmitter must listen to the bus as it transmits; the receiver may hold it low, turning a transmitted 1 bit into a 0 bit. This is done, for example, to acknowledge a transmission.
If a receiver detects an error in the received data, it holds the bus low for 3.6±0.24 ms; this causes the transmitter to abort the message and retry from the beginning.
A message consists of a start bit, followed by a series of data bytes. Each byte is actually transmitted as 10 bits:
8 data bits, most significant bit first,
An end-of-message bit is 0 to indicate that more bytes are being transmitted, or 1 to indicate not, and
An acknowledge bit is transmitted as 1, but overwritten to a 0 bit by the receiver to acknowledge receipt.
For broadcast messages, the acknowledge bit is inverted: it is overwritten to 0 if any receiver rejects the message.
Each message begins with an address byte specifying the 4-bit initiator and recipient addresses. If two initiators begin transmitting at the same time, one of them will transmit a 0 bit while the other transmits a 1 bit, and the latter will observe the conflict and cease transmitting until the bus is idle again. (Note that it must be prepared for the case that the incoming message is addressed to it.)
An address byte sent with EOM=1 is a simple "ping" to check if the addressed device exists and is powered on. Otherwise, it is followed by an opcode byte, and parameters as required by the opcode.
When a device is powered on, it chooses an address and sends a ping to see if that address is claimed by another device. If no acknowledge is received, the address is free and may be kept. Otherwise, the device tries another address.
See also
Consumer Electronics Control
References
Designing CEC into your next HDMI Product
HDMI Specification Version 1.3a, Supplement 1: Consumer Electronics Control (CEC)
Audiovisual connectors
Television technology | AV.link | [
"Technology"
] | 725 | [
"Information and communications technology",
"Television technology"
] |
24,446,770 | https://en.wikipedia.org/wiki/Biotechnic%20%26%20Histochemistry | Biotechnic & Histochemistry is a peer-reviewed scientific journal that covers all aspects of histochemistry and microtechnic in the biological sciences from botany to cell biology to medicine. It is published by Taylor & Francis on behalf of the Biological Stain Commission. The journal was established in 1926 as Stain Technology by Harold J. Conn. It obtained its current title in 1991. The editor-in-chief is G. S. Nettleton.
Abstracting and indexing
The journal is abstracted and indexed in Index Medicus/MEDLINE/PubMed, Current Contents/Life Sciences, Science Citation Index, and EMBASE/Excerpta Medica. According to the Journal Citation Reports, the journal has a 2020 impact factor of 1.718.
References
External links
Academic journals established in 1926
Biotechnology journals
Histology
Taylor & Francis academic journals
English-language journals | Biotechnic & Histochemistry | [
"Chemistry",
"Biology"
] | 179 | [
"Histology",
"Biotechnology literature",
"Biotechnology journals",
"Microscopy"
] |
24,453,994 | https://en.wikipedia.org/wiki/Marschalk%20reaction | The Marschalk reaction in chemistry is the sodium dithionite promoted reaction of a phenolic anthraquinone with an aldehyde to yield a substituted phenolic anthraquinone after the addition of acid.
The mechanism can be found in the book Named Reactions in Organic Chemistry, and its more intuitive version is provided below:
One of the first applications of this reaction was reported in 1985.
References
Organic reactions
Name reactions | Marschalk reaction | [
"Chemistry"
] | 90 | [
"Name reactions",
"Organic reactions"
] |
24,454,427 | https://en.wikipedia.org/wiki/Optic%20axis%20of%20a%20crystal | An optic axis of a crystal is a direction in which a ray of transmitted light suffers no birefringence (double refraction). An optic axis is a direction rather than a single line: all rays that are parallel to that direction exhibit the same lack of birefringence.
Crystals may have a single optic axis, in which case they are uniaxial, or two different optic axes, in which case they are biaxial. Non-crystalline materials generally have no birefringence and thus, no optic axis. A uniaxial crystal (e.g. calcite, quartz) is isotropic within the plane orthogonal to the optic axis of the crystal.
Explanation
The internal structure of crystals (the specific structure of the crystal lattice, and the specific atoms or molecules of which it is composed) causes the speed of light in the material, and therefore the material's refractive index, to depend on both the light's direction of propagation and its polarization. The dependence on polarization causes birefringence, in which two perpendicular polarizations propagate at different speeds and refract at different angles in the crystal. This causes a ray of light to split into an ordinary ray and an extraordinary ray, with orthogonal polarizations. For light propagating along an optic axis, though, the speed does not depend on the polarization, so there is no birefringence although there can be optical activity (a rotation of the plane of polarization).
The refractive index of the ordinary ray is constant for any direction in the crystal. The refractive index of the extraordinary ray varies depending on its direction.
Liquid crystal directors
The mobile axis of a liquid crystal is called a director. It is the space and time average of the orientation of the long molecular axis within a small volume element of material demonstrating a mesophase. Electrical manipulation of the director enables liquid-crystal displays.
See also
Crystal optics
Index ellipsoid
Notes and references
Polarization (waves)
Optical mineralogy | Optic axis of a crystal | [
"Physics"
] | 419 | [
"Polarization (waves)",
"Astrophysics"
] |
6,836,056 | https://en.wikipedia.org/wiki/HBsAg | HBsAg (also known as the Australia antigen) is the surface antigen of the hepatitis B virus (HBV). Its presence in blood indicates existing hepatitis B infection.
Structure and function
The viral envelope of an enveloped virus has different surface proteins from the rest of the virus which act as antigens. These antigens are recognized by antibody proteins that bind specifically to one of these surface proteins.
The full-length HBsAg is called the L (for "large") form. It consists of a preS loop, a first transmembrane helix (TM1), a cytosolic loop (CYL), another TM helix (TM2), an antigenic loop (AGL), followed by two TM helices (TM3 and TM4). The preS loop can either be on the outside (lumen), or be located in the cytosol with the TM1 helix not actually penetrating the membrane. The M ("medium") form has a truncated preS; the part of preS1 unique to L is called preS1, while the part shared by L and M is called preS2. preS2 is always located in the lumen. The S ("small") form has no preS2.
HBsAg forms the shell of the virus. Furthermore, it contains parts that are recognized by the cellular receptor of the virus NTCP in preS1, which causes the causes the virus to tightly bind to the cell. How the virus convinces the cell to take the virus in after binding via endocytosis is unknown. It also serves to release the contents of the virion into the cell through membrane fusion. The part responsible for fusion is also located in preS1.
HBsAg self-assembles into viral shells even when no contents are present. Such an empty shell is called a virus-like particle or a small spherical subviral particle.
Immunoassay
Today, these antigen-proteins can be genetically manufactured (e.g. transgene E. coli) to produce material for a simple antigen test, which detects the presence of HBV.
It is present in the sera of patients with viral hepatitis B (with or without clinical symptoms). Patients who developed antibodies against HBsAg (anti-HBsAg seroconversion) are usually considered non-infectious. HBsAg detection by immunoassay is used in blood screening, to establish a diagnosis of hepatitis B infection in the clinical setting (in combination with other disease markers) and to monitor antiviral treatment.
In histopathology, the presence of HBsAg is more commonly demonstrated by the use of the Shikata orcein technique, which uses a natural dye to bind to the antigen in infected liver cells.
Positive HBsAg tests can be due to recent vaccination against Hepatitis B virus but this positivity is unlikely to persist beyond 14 days post-vaccination.
Applications
HBsAg made through recombinant DNA is used to make the hepatitis B vaccine. It has a very good efficacy of about 95%, with protection lasting for more than 30 years, even after the anti-HbsAg antigen titers have fallen.
The RTS,S also makes use of HBsAg. It is a mixture of a version of malaria surface antigen grafted to HBsAg (RTS) and ordinary HBsAg (S), both made through recombinant DNA. Much like ordinary HBsAg, these two are able to assemble into virus-like particles that are soluble in water.
History
It is commonly referred to as the Australia Antigen. This is because it was first isolated by the American research physician and Nobel Prize winner Baruch S. Blumberg in the serum of an Australian Aboriginal person. It was discovered to be part of the virus that caused serum hepatitis by virologist Alfred Prince in 1968.
Heptavax, a "first-generation" hepatitis B vaccine in the 1980s, was made from HBsAg extracted from the blood plasma of hepatitis patients. More modern vaccines are made from recombinant HBsAg grown in yeast.
See also
HBcAg
HBeAg
References
Viral structural proteins
Hepatitis B virus
Antigens | HBsAg | [
"Chemistry"
] | 880 | [
"Antigens",
"Biomolecules"
] |
6,837,693 | https://en.wikipedia.org/wiki/Bass%20diffusion%20model | The Bass model or Bass diffusion model was developed by Frank Bass. It consists of a simple differential equation that describes the process of how new products get adopted in a population. The model presents a rationale of how current adopters and potential adopters of a new product interact. The basic premise of the model is that adopters can be classified as innovators or as imitators, and the speed and timing of adoption depends on their degree of innovation and the degree of imitation among adopters. The Bass model has been widely used in forecasting, especially new product sales forecasting and technology forecasting. Mathematically, the basic Bass diffusion is a Riccati equation with constant coefficients equivalent to Verhulst—Pearl logistic growth.
In 1969, Frank Bass published his paper on a new product growth model for consumer durables. Prior to this, Everett Rogers published Diffusion of Innovations, a highly influential work that described the different stages of product adoption. Bass contributed some mathematical ideas to the concept. While the Rogers model describes all four stages of the product lifecycle (Introduction, Growth, Maturity, Decline), The Bass model focuses on the first two (Introduction and Growth). Some of the Bass model extensions present mathematical models for the last two (Maturity and Decline).
Model formulation
Where:
is the installed base fraction
is the rate of change of the installed base fraction, i.e.
is the coefficient of innovation
is the coefficient of imitation
Expressed as an ordinary differential equation,
Sales (or new adopters) at time is the rate of change of installed base, i.e., multiplied by the ultimate market potential. Under the condition, we have that
We have the decomposition where is the number of innovators at time, and is the number of imitators at time.
The time of peak sales:
The times of the inflection points at the new adopters' curve:
or in another form (related to peak sales):
The peak time and inflection points' times must be positive. When is negative, sales have no peak (and decline since introduction). There are cases (depending on the values of and) when the new adopters curve (that begins at 0) has only one or zero inflection points.
Explanation
The coefficient is called the coefficient of innovation, external influence or advertising effect. The coefficient is called the coefficient of imitation, internal influence or word-of-mouth effect.
Typical values of and when time is measured in years:
The average value of has been found to be 0.03, with a typical range between 0.01 and 0.03.
The average value of has been found to be 0.38, with a typical range between 0.3 and 0.5.
Derivation
The Bass diffusion model is derived by assuming that the hazard rate for the uptake of a product or service may be defined as:where is the probability density function and is the survival function, with being the cumulative distribution function. From these basic definitions in survival analysis, we know that:Therefore, the differential equation for the survival function is equivalent to:Integration and rearrangement of terms gives us that:For any survival function, we must have that and this implies that . With this condition, the survival function is:Finally, using the fact that , we find that the Bass diffusion model for product uptake is:
Extensions to the model
Generalised Bass model (with pricing)
Bass found that his model fit the data for almost all product introductions, despite a wide range of managerial decision variables, e.g. pricing and advertising. This means that decision variables can shift the Bass curve in time, but that the shape of the curve is always similar.
Although many extensions of the model have been proposed, only one of these reduces to the Bass model under ordinary circumstances. This model was developed in 1994 by Frank Bass, Trichy Krishnan and Dipak Jain:
where is a function of percentage change in price and other variables
Unlike the Bass model which has an analytic solution, but can also be solved numerically, the generalized bass models usually do not have analytic solutions and must be solved numerically. Orbach (2016) notes that the values of p,q are not perfectly identical for the continuous-time and discrete-time forms. For the common cases (where p is within the range of 0.01-0.03 and q within the range of 0.2-0.4) the discrete-time and continuous-time forecasts are very close. For other p,q values the forecasts may divert significantly.
Successive generations
Technology products succeed one another in generations. Norton and Bass extended the model in 1987 for sales of products with continuous repeat purchasing. The formulation for three generations is as follows:
where
is the incremental number of ultimate adopters of the ith generation product
is the average (continuous) repeat buying rate among adopters of the ith generation product
is the time since the introduction of the ith generation product
It has been found that the p and q terms are generally the same between successive generations.
Relationship with other s-curves
There are two special cases of the Bass diffusion model.
The first special case occurs when q=0, when the model reduces to the exponential distribution.
The second special case reduces to the logistic distribution, when p=0.
The Bass model is a special case of the Gamma/shifted Gompertz distribution (G/SG): Bemmaor (1994)
Use in online social networks
The rapid, recent (as of early 2007) growth in online social networks (and other virtual communities) has led to an increased use of the Bass diffusion model. The Bass diffusion model is used to estimate the size and growth rate of these social networks. The work by Christian Bauckhage and co-authors shows that the Bass model provides a more pessimistic picture of the future than alternative model(s) such as the Weibull distribution and the shifted Gompertz distribution.
The ranges of the p, q parameters
Bass (1969) distinguished between a case of p<q wherein periodic sales grow and then decline (a successful product has a periodic sales peak); and a case of p>q wherein periodic sales decline from launch (no peak).
Jain et al. (1995) explored the impact of seeding. When using seeding, diffusion can begin when p + qF(0) > 0 even if p’s value is negative, but a marketer uses seeding strategy with seed size of F(0) > -p/q . The interpretation of a negative p value does not necessarily mean that the product is useless: There can be cases wherein there are price or effort barriers to adoption when very few others have already adopted. When others adopt, the benefits from the product increase, due to externalities or uncertainty reduction, and the product becomes more and more plausible for many potential customers.
Moldovan and Goldenberg (2004) incorporated negative word of mouth (WOM) effect on the diffusion, which implies a possibility of a negative q. Negative q does not necessarily mean that adopters are disappointed and dissatisfied with their purchase. It can fit a case wherein the benefit from a product declines as more people adopt. For example, for a certain demand level for train commuting, reserved tickets may be sold to those who like to guarantee a seat. Those who do not reserve seating may have to commute while standing. As more reserved seating are sold, the crowding in the non-reserved railroad car is reduced, and the likelihood of finding a seat in the non-reserved car increases, thus reducing the incentive to buy reserved seating. While the non-cumulative sales curve with negative q is similar to those with q=0, the cumulative sales curve presents a more interesting situation: When p > -q, the market will reach 100% of its potential, eventually, as for a regular positive value of q. However, if p < -q, at the long-range, the market will saturate at an equilibrium level –p/q of its potential.
Orbach (2022) summarized the diffusion behavior at each portion of the p,q space and maps the extended (p,q) regions beyond the positive right quadrant (where diffusion is spontaneous) to other regions where diffusion faces barriers (negative p), where diffusion requires “stimuli” to start, or resistance of adopters to new members (negative q), which might stabilize the market below full adoption, occur.
Adoption of this model
The model is one of the most cited empirical generalizations in marketing; as of August 2023 the paper "A New Product Growth for Model Consumer Durables" published in Management Science had (approximately) 11352 citations in Google Scholar.
This model has been widely influential in marketing and management science. In 2004 it was selected as one of the ten most frequently cited papers in the 50-year history of Management Science. It was ranked number five, and the only marketing paper in the list. It was subsequently reprinted in the December 2004 issue of Management Science.
The Bass model was developed for consumer durables. However, it has been used also to forecast market acceptance of numerous consumer and industrial products and services, including tangible, non-tangible, medical, and financial products. Sultan et al. (1990) applied the Bass model to 213 product categories, mostly consumer durables (in a wide range of prices) but also to services such as motels and industrial/farming products like hybrid corn seeds.
See also
Diffusion of innovation
Forecasting
Lazy user model
Shifted Gompertz distribution
References
Applied mathematics
Innovation
Market segmentation
Product lifecycle management | Bass diffusion model | [
"Mathematics"
] | 1,958 | [
"Applied mathematics"
] |
6,838,909 | https://en.wikipedia.org/wiki/Opus%20tessellatum | Opus tessellatum is the Latin name for the normal technique of Greek and Roman mosaic, made from tesserae that are larger than about 4 mm. It is distinguished from the finer opus vermiculatum which used tiny tesserae, typically cubes of 4 millimetres or less, and was produced in workshops in relatively small panels which were transported to the site glued to some temporary support.
Opus tessellatum was used for larger areas and laid down at the final site. The two techniques were often combined, with small panels of opus vermiculatum called emblemata at the centre of a larger design in opus tessellatum. The tiny tesserae of opus vermiculatum allowed very fine detail, and an approach to the illusionism of painting. There was a distinct native Italian style of opus tessellatum using only black on a white background, which was no doubt cheaper than fully coloured work.
Opus tessellatum is usually used for backgrounds consisting of horizontally or vertically arranged lines, but not both in a grid, which would be opus regulatum.
See also
Mosaic
Mosaics of Delos
Opus regulatum
Opus sectile
Opus vermiculatum
Notes
References
Mosaic
Italian mosaic
Roman mosaics
Ancient Roman construction techniques | Opus tessellatum | [
"Engineering"
] | 250 | [
"Architecture stubs",
"Architecture"
] |
35,760,325 | https://en.wikipedia.org/wiki/Rayleigh%E2%80%93Plesset%20equation | In fluid mechanics, the Rayleigh–Plesset equation or Besant–Rayleigh–Plesset equation is a nonlinear ordinary differential equation which governs the dynamics of a spherical bubble in an infinite body of incompressible fluid. Its general form is usually written aswhere
is the density of the surrounding liquid, assumed to be constant
is the radius of the bubble
is the kinematic viscosity of the surrounding liquid, assumed to be constant
is the surface tension of the bubble-liquid interface
, in which, is the pressure within the bubble, assumed to be uniform and is the external pressure infinitely far from the bubble
Provided that is known and is given, the Rayleigh–Plesset equation can be used to solve for the time-varying bubble radius .
The Rayleigh–Plesset equation can be derived from the Navier–Stokes equations under the assumption of spherical symmetry. It can also be derived using an energy balance.
History
Neglecting surface tension and viscosity, the equation was first derived by W. H. Besant in his 1859 book with the problem statement stated as An infinite mass of homogeneous incompressible fluid acted upon by no forces is at rest, and a spherical portion of the fluid is suddenly annihilated; it is required to find the instantaneous alteration of pressure at any point of the mass, and the time in which the cavity will be filled up, the pressure at an infinite distance being supposed to remain constant (in fact, Besant attributes the problem to Cambridge Senate-House problems of 1847). Besant predicted the time required to fill an empty cavity of initial radius to be
Lord Rayleigh found a simpler derivation of the same result, based on conservation of energy. The kinetic energy of the inrushing fluid is where is the time-dependent radius of the void, and the radial velocity of the fluid there. The work done by the fluid pressing in at infinity is , and equating these two energies gives a relation between and . Then, noting that , separation of variables gives Besant's result. Rayleigh went further than Besant, in evaluating the integral (Euler's beta function) in terms of gamma functions. Rayleigh adapted this approach to the case of a cavity filled with an ideal gas (a bubble) by including a term for the work done compressing the gas.
For the case of the perfectly empty void, Rayleigh determined that the pressure in the fluid at a radius is given by:
When the void is at least one quarter of its initial volume, then the pressure decreases monotonically from at infinity to zero at . As the void shrinks further a pressure maximum, greater than appears at
very rapidly growing and converging on the void.
The equation was first applied to traveling cavitation bubbles by Milton S. Plesset in 1949 by including effects of surface tension.
Derivation
The Rayleigh–Plesset equation can be derived entirely from first principles using the bubble radius as the dynamic parameter. Consider a spherical bubble with time-dependent radius , where is time. Assume that the bubble contains a homogeneously distributed vapor/gas with a uniform temperature and pressure . Outside the bubble is an infinite domain of liquid with constant density and dynamic viscosity . Let the temperature and pressure far from the bubble be and . The temperature is assumed to be constant. At a radial distance from the center of the bubble, the varying liquid properties are pressure , temperature , and radially outward velocity . Note that these liquid properties are only defined outside the bubble, for .
Mass conservation
By conservation of mass, the inverse-square law requires that the radially outward velocity must be inversely proportional to the square of the distance from the origin (the center of the bubble). Therefore, letting be some function of time,
In the case of zero mass transport across the bubble surface, the velocity at the interface must be
which gives that
In the case where mass transport occurs and assuming the bubble contents are at constant density, the rate of mass increase inside the bubble is given by
with being the volume of the bubble. If is the velocity of the liquid relative to the bubble at , then the mass entering the bubble is given by
with being the surface area of the bubble. Now by conservation of mass , therefore . Hence
Therefore
In many cases, the liquid density is much greater than the vapor density, , so that can be approximated by the original zero mass transfer form , so that
Momentum conservation
Assuming that the liquid is a Newtonian fluid, the incompressible Navier–Stokes equation in spherical coordinates for motion in the radial direction gives
Substituting kinematic viscosity and rearranging gives
whereby substituting from mass conservation yields
Note that the viscous terms cancel during substitution. Separating variables and integrating from the bubble boundary to gives
Boundary conditions
Let be the normal stress in the liquid that points radially outward from the center of the bubble. In spherical coordinates, for a fluid with constant density and constant viscosity,
Therefore at some small portion of the bubble surface, the net force per unit area acting on the lamina is
where is the surface tension. If there is no mass transfer across the boundary, then this force per unit area must be zero, therefore
and so the result from momentum conservation becomes
whereby rearranging and letting gives the Rayleigh–Plesset equation
Using dot notation to represent derivatives with respect to time, the Rayleigh–Plesset equation can be more succinctly written as
Solutions
More recently, analytical closed-form solutions were found for the Rayleigh–Plesset equation for both an empty and gas-filled bubble and were generalized to the N-dimensional case. The case when the surface tension is present due to the effects of capillarity were also studied.
Also, for the special case where surface tension and viscosity are neglected, high-order analytical approximations are also known.
In the static case, the Rayleigh–Plesset equation simplifies, yielding the Young–Laplace equation:
When only infinitesimal periodic variations in the bubble radius and pressure are considered, the RP equation also yields the expression of the natural frequency of the bubble oscillation.
References
Fluid dynamics
Equations of fluid dynamics
Ordinary differential equations | Rayleigh–Plesset equation | [
"Physics",
"Chemistry",
"Engineering"
] | 1,269 | [
"Equations of fluid dynamics",
"Equations of physics",
"Chemical engineering",
"Piping",
"Fluid dynamics"
] |
35,761,226 | https://en.wikipedia.org/wiki/Chemical%20plant%20cost%20indexes | Chemical plant cost indexes are dimensionless numbers employed to updating capital cost required to erect a chemical plant from a past date to a later time, following changes in the value of money due to inflation and deflation. Since, at any given time, the number of chemical plants is insufficient to use in a preliminary or predesign estimate, cost indexes are handy for a series of management purposes, like long-range planning, budgeting and escalating or de-escalating contract costs.
A cost index is the ratio of the actual price in a time period compared to that in a selected base period (a defined point in time or the average price in a certain year), multiplied by 100. Raw materials, products and energy prices, labor and construction costs change at different rates, and plant construction cost indexes are actually a composite, able to compare generic chemical plants capital costs.
Calculations methods
Although the available indexes are compiled in several ways, they are defined to encompass a specific set of conditions and items. Prices for these items can be obtained either through company’s purchasing department data or through published indexes, like those published by the Bureau of Labor Statistics (BLS). Both the CE and the IC indexes, from Chemical Engineering and Intratec, respectively, employs BLS’ data.
The weighting of such factors, which is defined by the realized degree of importance of each component in the specific index (or sub-index), aims to represent the costs variations typically found for chemical plants.
Using a cost index
To update an item cost (equipment, projects) from period A to period B, is necessary to multiply period A’s cost by the ratio of period B’s index over period A’s index, according to the following equation:
As a rule-of-thumb, cost indexes permit fairly accurate estimates for cost escalation if the difference between period A and period B is less than 10 years. Differences between the actual equipment and labor prices and those predicted by the index tend to grow over the years, surpassing the typical error verified in budget-level estimates.
Cost indexes in engineering
The selection of the proper index to use depends on the industry in which it is applied. For example, while CE, M&S or IC Index are typically employed for chemical process industries, the ENR (Engineering News-Record) construction index is used for general industrial construction and takes in account the prices for fixed amounts of structural steel, cement, lumber and labor.
The majority of cost indexes demonstrate a time lag, due to data collection and its compilation for publishing. As stated before, some indexes use information published by other organizations and a delay in data may be verified (like those provide by the BLS). Exceptions to this are the ENR construction and the IC indexes, which present relatively current values.
The main indexes available for process industries include:
Chemical Engineering Index, CE: composed of 4 major components – for equipment and other bulk items, the others relevant to construction labor, buildings, and engineering and supervision – the index is employed primary as a process plant construction index, was established using a base period of 1957-1959 as 100. The CE Index is updated monthly and it lags in time by about 3 months. The CE Index was revised in 1982, to account for changes in labor productivity and, again, in 2002. Published in each issue of Chemical Engineering.
Marshall and Swift Cost Index, M&S (originally known as Marshall and Stevens Index): a composite of two major components - process-industry equipment average and all-industry equipment average - was established in 1926 with a value of 100. Some industries considered in the process-industry equipment average are chemicals, petroleum products, rubber and paper. The all-industry average encompasses 47 different types of industrial, commercial and housing equipment. Published monthly in each issue of Chemical Engineering until April 2012.
Intratec Chemical Plant Construction Index, IC: a process plant construction index developed by Intratec, a chemical consulting company. Although cost indexes do not usually forecast future escalation, the IC Index stands out for presenting a smaller delay between release date and index date, besides a 12 months forecast. On the other hand, the index is only available from January 2000 (with a value of 100). A sample is available at Intratec’s website.
Nelson-Farrar Indexes, NF (originally known as the Nelson Refinery Construction Indexes): established in 1946 with a value of 100, the index is more suitable for petroleum or petrochemical business. Published once a month in the Oil and Gas Journal.
Cost Indexes for different locations
The standard indexes available are usually restricted to a particular region, as in the case of NF Index, which is accurate only to the region of the US Gulf coast (USGC). Likewise most of the data available for plant and equipment costs are mostly either in
US Gulf Coast Basis (USGC)
Northwest Europe Basis (NWE)
Hence the Index values cannot be used to get accurate results in other regions of the world. This variation might be due various factors such as
Cost and availability of materials
Cost and availability of labor
Cost of transportation of equipment and labor
Import duties and local taxes
Currency exchange rates
Of all these factors currency exchange rates is said to have the greatest impact in the variation of results.
Cost indexes for international locations is published in "Process Engineering" journal as well as in the "International Journal of Production Economics" (formerly "Engineering Costs and Production Economics"). As of 2012 "Process Engineering" has not been publishing new indexes viewable by full access from EbscoHost. They mentioned in May/June 2012 that their analyst had fallen sick.
Location Factor
In order to be able to use the available standard indexes to locations where index data is not available we have to incorporate a new term called the Location Factor (LF) to the standard index value. It is a dimensionless value for a particular location relative to either of the above-mentioned basis.
Cost in A = Cost in USGC x LF(A)
where A is the location for which cost is being evaluated and LF(A) is the location factor for the location A relative to USGC
Location factors are greatly influenced by currency exchange rates due to their significant effect on Index value and hence vary drastically with time. Over the past couple of decades the location factors for various locations are trending close to the value 1. However location factor for a particular region within a country can be easily determined by adding 10% to the index of the reference location for every 1000 miles. The reference location is usually a major industrial location closest to the location where the index is being determined. Location factors for various locations have been published and updated in various journals as in Aspen Richardson's "International Construction Cost Factor Location Manual (2003)".
References
Chemical process engineering
Chemical industry
Manufacturing plants | Chemical plant cost indexes | [
"Chemistry",
"Engineering"
] | 1,404 | [
"Chemical process engineering",
"Chemical engineering",
"nan"
] |
35,764,498 | https://en.wikipedia.org/wiki/Fuzzy%20complex | Fuzzy complexes are protein complexes, where structural ambiguity or multiplicity exists and is required for biological function. Alteration, truncation or removal of conformationally ambiguous regions impacts the activity of the corresponding complex. Fuzzy complexes are generally formed by intrinsically disordered proteins. Structural multiplicity usually underlies functional multiplicity of protein complexes following a fuzzy logic. Distinct binding modes of the nucleosome are also regarded as a special case of fuzziness.
Historical background
For almost 50 years molecular biology was based on two dogmas: (i) equating biological function of the protein with a unique three-dimensional structure and (ii) assuming exquisite specificity in protein complexes. Specificity/selectivity is ensured by unambiguous set of interactions formed between the protein and its ligand (another protein, DNA, RNA or small molecule). Many protein complexes however, contain functionally important/critical regions, which remain highly dynamic in the complex or adopt different conformations. This phenomenon is defined fuzziness. The most pertinent example is the cyclin-dependent kinase inhibitor Sic1, which binds to the SCF subunit of Cdc4 in a phosphorylation dependent manner. No regular secondary structures are gained upon phosphorylation and the different phosphorylation sites interchange in the complex.
Classification of fuzzy complexes
Structural ambiguity in protein complexes covers a wide spectrum. In a polymorphic complex, the protein adopts two or more different conformations upon binding to the same partner, and these conformations can be resolved. Clamp, flanking and random complexes are dynamic, where ambiguous conformations interchange with each other and cannot be resolved. Interactions in fuzzy complexes are usually mediated by short motifs. Flanking regions are tolerant to sequence changes as long as the amino acid composition is maintained, for example in case of linker histone C-terminal domains and H4 histone N-terminal domains.
Regulatory pathways via fuzzy regions
Fuzzy regions modulate the conformational equilibrium or flexibility of the binding interface via transient interactions. Dynamic regions can also compete with binding sites or tether them to the target. Modifications of fuzzy regions by further interactions, or posttranslational modifications impact binding affinity or specificity. Alternative splicing can modulate the length of fuzzy regions resulting in context-dependent binding (e.g. tissue-specificity) on the complex. EGF/MAPK, TGF-β and WNT/Wingless signaling pathways employ tissue-specific fuzzy regions.
References
Protein structure
Stereochemistry | Fuzzy complex | [
"Physics",
"Chemistry"
] | 512 | [
"Stereochemistry",
"Space",
"Structural biology",
"nan",
"Spacetime",
"Protein structure"
] |
35,766,427 | https://en.wikipedia.org/wiki/Mechanical%20metamaterial | Mechanical metamaterials are rationally designed artificial materials/structures of precision geometrical arrangements leading to unusual physical and mechanical properties. These unprecedented properties are often derived from their unique internal structures rather than the materials from which they are made. Inspiration for mechanical metamaterials design often comes from biological materials (such as honeycombs and cells), from molecular and crystalline unit cell structures as well as the artistic fields of origami and kirigami. While early mechanical metamaterials had regular repeats of simple unit cell structures, increasingly complex units and architectures are now being explored. Mechanical metamaterials can be seen as a counterpart to the rather well-known family of optical metamaterials and electromagnetic metamaterials. Mechanical properties, including elasticity, viscoelasticity, and thermoelasticity, are central to the design of mechanical metamaterials. They are often also referred to as elastic metamaterials or elastodynamic metamaterials. Their mechanical properties can be designed to have values that cannot be found in nature, such as negative stiffness, negative Poisson’s ratio, negative compressibility, and vanishing shear modulus.
Classical mechanical metamaterials
3D printing, or additive manufacturing, has revolutionized the field in the past decade by enabling the fabrication of intricate mechanical metamaterial structures. Some of the unprecedented and unusual properties of classical mechanical metamaterials include:
Negative Poisson's ratio (auxetics)
Poisson's ratio defines how a material expands (or contracts) transversely when being compressed longitudinally. While most natural materials have a positive Poisson's ratio (coinciding with our intuitive idea that by compressing a material, it must expand in the orthogonal direction), a family of extreme materials known as auxetic materials can exhibit Poisson's ratios below zero. Examples of these can be found in nature, or fabricated, and often consist of a low-volume microstructure that grants the extreme properties. Simple designs of composites possessing negative Poisson's ratio (inverted hexagonal periodicity cell) were published in 1985. In addition, certain origami folds such as the Miura fold and, in general, zigzag-based folds are also known to exhibit negative Poisson's ratio.
Negative stiffness
Negative stiffness (NS) mechanical metamaterials are engineered structures that exhibit a counterintuitive property: as an external force is applied, the material deforms in a way that reduces the applied force rather than increasing it. This is in contrast to conventional materials that resist deformation. NS metamaterials are typically constructed from periodically arranged elements that undergo elastic instability under load. This instability leads to a negative stiffness behavior within a specific deformation range. The overall effect is a material that can absorb energy more efficiently and exhibit unique mechanical properties compared to traditional materials.
Negative thermal expansion
These mechanical metamaterials can exhibit coefficients of thermal expansion larger than that of either constituent. The expansion can be arbitrarily large positive or arbitrarily large negative, or zero. These materials substantially exceed the bounds for thermal expansion of a two-phase composite. They contain considerable void space.
High strength to density ratio
A high strength-to-density ratio mechanical metamaterial is a synthetic material engineered to possess exceptional mechanical properties relative to its weight. This is achieved through carefully designed internal microstructures, often periodic or hierarchical, which contribute to the material's overall performance.
Negative compressibility
In a closed thermodynamic system in equilibrium, both the longitudinal and volumetric compressibility are necessarily non-negative because of stability constraints. For this reason, when tensioned, ordinary materials expand along the direction of the applied force. It has been shown, however, that metamaterials can be designed to exhibit negative compressibility transitions, during which the material undergoes contraction when tensioned (or expansion when pressured). When subjected to isotropic stresses, these metamaterials also exhibit negative volumetric compressibility transitions.
In this class of metamaterials, the negative response is along the direction of the applied force, which distinguishes these materials from those that exhibit negative transversal response (such as in the study of negative Poisson's ratio).
Negative bulk modulus
Mechanical metamaterials with negative effective bulk modulus exhibit intriguing and counterintuitive properties. Unlike conventional materials that compress under pressure, these materials expand. This anomalous behavior stems from their carefully engineered microstructure, which allows for internal deformation mechanisms that counteract the applied stress. Potential applications for these materials are vast. They could be employed to design acoustic or phononic metamaterials,advanced shock absorbers, and energy dissipation systems. Furthermore, their unique elastic properties may find utility in creating novel structural components with enhanced resilience and adaptability to dynamic loads.
Vanishing shear modulus
A pentamode metamaterial is an artificial three-dimensional structure which, despite being a solid, ideally behaves like a fluid. Thus, it has a finite bulk but vanishing shear modulus, or in other words it is hard to compress yet easy to deform. Speaking in a more mathematical way, pentamode metamaterials have an elasticity tensor with only one non-zero eigenvalue and five (penta) vanishing eigenvalues. Pentamode structures have been proposed theoretically by Graeme Milton and Andrej Cherkaev in 1995 but have not been fabricated until early 2012. According to theory, pentamode metamaterials can be used as the building blocks for materials with completely arbitrary elastic properties. Anisotropic versions of pentamode structures are a candidate for transformation elastodynamics and elastodynamic cloaking.
Chiral micropolar elasticity
Very often Cauchy elasticity is sufficient to describe the effective behavior of mechanical metamaterials. When the unit cells of typical metamaterials are not centrosymmetric it has been shown that an effective description using chiral micropolar elasticity (or Cosserat ) was required. Micropolar elasticity combines the coupling of translational and rotational degrees of freedom in the static case and shows an equivalent behavior to the optical activity.
Infinite mechanical tunability
In addition to the well-known unprecedented mechanical properties of mechanical metamaterials, "infinite mechanical tunability" is another crucial aspect of mechanical metamaterials. This is particularly important for structural materials as their microstructure and stiffness can be tuned to effectively achieve theoretical upper bounds for specific stiffness and strength. While theoretical composites that achieve the same upper bound have existed for some time, they have been impractical to fabricate as they require features on multiple length scales. Single length scale designs are amenable to additive manufacturing, where they can enable engineered systems that maximize lightweight stiffness, strength and energy absorption.
Active Mechanical Metamaterials
To date, most mainstream studies on mechanical metamaterials have focused on passive structures with fixed properties, lacking active sensing or feedback capabilities. Deep integration of advanced functionalities is a critical challenge in exploring the next generation of metamaterials. Composite mechanical metamaterials could be the key to achieving this goal. However, the entire concept of composite mechanical metamaterials is still in its infancy. Obtaining programmable behavior through the interplay between material and structure in composite mechanical metamaterials enables integrating advanced functionalities into their texture beyond their mechanical properties. The “mechanical metamaterial tree of knowledge” implies that chiral, lattice and negative metamaterials (e.g., negative bulk modulus or negative elastic modulus) are ripe followed by origami and cellular metamaterials.
Recent research trends have been entering a space beyond merely exploring unprecedented mechanical properties. Emerging directions envisioned are sensing, energy harvesting, and actuating mechanical metamaterials.The tree of knowledge reveals that digital computing, digital data storage, and micro/nano-electromechanical systems (MEMS/NEMS) applications are one of the pillars of the mechanical metamaterials future research. Along this direction of evolution, the final target can be active mechanical metamaterials with a level of cognition. Cognitive abilities are crucial elements in a truly "intelligent mechanical metamaterials". Similar to complex living organisms, intelligent mechanical metamaterials can potentially deploy their cognitive abilities for sensing, self-powering, and information processing to interact with the surrounding environments, optimizing their response, and creating a sense–decide–respond loop.
Programmable mechanical metamaterials
Programmable response is an emerging direction for mechanical metamaterials beyond mechanical properties. Electrical responsiveness is an important functionality for designing adaptive, actuating, and autonomous mechanical metamaterials. For example, research ideas have been opened by active and adaptive mechanical metamaterials that design electrical materials into the microstructural units of metamaterials to autonomously convert mechanical-strain input into electrical-signal output.
Responsive mechanical metamaterials
Integrating functional materials and mechanical design is an emerging research area to explore responsive mechanical metamaterials. Recent studies explore new classes of mechanical metamaterials that can response to different excitation types such acoustic, thermophotovoltaic and magnetic.
Sensing and energy harvesting mechanical metamaterials
Recent studies have explored the integration of sensing and energy harvesting functionalities into the fabric of mechanical metamaterials. Meta-tribomaterials proposed in 2021 are a new class of multifunctional composite mechanical metamaterials with intrinsic sensing and energy harvesting functionalities. These material systems are composed of finely tailored and topologically different triboelectric microstructures. Meta-tribomaterials can serve as nanogenerators and sensing media to directly collect information about its operating environment. They naturally inherit the enhanced mechanical properties offered by classical mechanical metamaterials. Under mechanical excitations, meta-tribomaterials generate electrical signals which can be used for active sensing and empowering sensors and embedded electronics.
Electronic mechanical metamaterials
Electronic mechanical metamaterials are active mechanical metamaterials with digital computing and information storage capabilities. They have built the foundation for a new scientific field of meta-mechanotronics (mechanical metamaterial electronics) proposed in 2023. These material systems are created via integrating mechanical metamaterials, digital electronics and nano energy harvesting (e.g. triboelectric, piezoelectric, pyroelectric) technologies. Electronic mechanical metamaterials hold the potential to function as digital logic gates, paving the way for the development of mechanical metamaterial computers (MMCs) that could complement traditional electronic systems. Such computing metamaterial systems can be particularly useful under extreme loads and harsh environments (e.g. high pressure, high/low temperature and radiation exposure) where traditional semiconductor electronics cannot maintain their designed logical functions.
References
Metamaterials | Mechanical metamaterial | [
"Materials_science",
"Engineering"
] | 2,276 | [
"Metamaterials",
"Materials science"
] |
35,767,402 | https://en.wikipedia.org/wiki/Ternary%20cubic | In mathematics, a ternary cubic form is a homogeneous degree 3 polynomial in three variables.
Invariant theory
The ternary cubic is one of the few cases of a form of degree greater than 2 in more than 2 variables whose ring of invariants was calculated explicitly in the 19th century.
The ring of invariants
The algebra of invariants of a ternary cubic under SL3(C) is a polynomial algebra generated by two invariants S and T of degrees 4 and 6, called Aronhold invariants. The invariants are rather complicated when written as polynomials in the coefficients of the ternary cubic, and are given explicitly in
The ring of covariants
The ring of covariants is given as follows.
The identity covariant U of a ternary cubic has degree 1 and order 3.
The Hessian H is a covariant of ternary cubics of degree 3 and order 3.
There is a covariant G of ternary cubics of degree 8 and order 6 that vanishes on points x lying on the
Salmon conic of the polar of x with respect to the curve and its Hessian curve.
The Brioschi covariant J is the Jacobian of U, G, and H of degree 12, order 9.
The algebra of covariants of a ternary cubic is generated over the ring of invariants by U, G, H, and J, with a relation that the square of J is a polynomial in the other generators.
The ring of contravariants
The Clebsch transfer of the discriminant of a binary cubic is a contravariant F of ternary cubics of degree 4 and class 6, giving the dual cubic of a cubic curve.
The Cayleyan P of a ternary cubic is a contravariant of degree 3 and class 3.
The quippian Q of a ternary cubic is a contravariant of degree 5 and class 3.
The Hermite contravariant Π is another contravariant of ternary cubics of degree 12 and class 9.
The ring of contravariants is generated over the ring of invariants by F, P, Q, and Π, with a relation that Π2 is a polynomial in the other generators.
The ring of concomitants
and described the ring of concomitants, giving 34 generators.
The Clebsch transfer of the Hessian of a binary cubic is a concomitant of degree 2, order 2, and class 2.
The Clebsch transfer of the Jacobian of the identity covariant and the Hessian of a binary cubic is a concomitant of ternary cubics of degree 3, class 3, and order 3
See also
Ternary quartic
Invariants of a binary form
References
Invariant theory | Ternary cubic | [
"Physics"
] | 581 | [
"Invariant theory",
"Group actions",
"Symmetry"
] |
35,767,957 | https://en.wikipedia.org/wiki/C14H12O3S | {{DISPLAYTITLE:C14H12O3S}}
The molecular formula C14H12O3S (molar mass: 260.31 g/mol, exact mass: 260.0507 u) may refer to:
Suprofen
Tiaprofenic acid
Molecular formulas | C14H12O3S | [
"Physics",
"Chemistry"
] | 63 | [
"Molecules",
"Set index articles on molecular formulas",
"Isomerism",
"Molecular formulas",
"Matter"
] |
35,768,238 | https://en.wikipedia.org/wiki/Ternary%20quartic | In mathematics, a ternary quartic form is a degree 4 homogeneous polynomial in three variables.
Hilbert's theorem
showed that a positive semi-definite ternary quartic form over the reals can be written as a sum of three squares of quadratic forms.
Invariant theory
The ring of invariants is generated by 7 algebraically independent invariants of degrees 3, 6, 9, 12, 15, 18, 27 (discriminant) , together with 6 more invariants of degrees 9, 12, 15, 18, 21, 21, as conjectured by . discussed the invariants of order up to about 15.
The Salmon invariant is a degree 60 invariant vanishing on ternary quartics with an
inflection bitangent.
Catalecticant
The catalecticant of a ternary quartic is the resultant of its 6 second partial derivatives. It vanishes when the ternary quartic can be written as a sum of five 4th powers of linear forms.
See also
Ternary cubic
Invariants of a binary form
References
.
External links
Invariants of the ternary quartic
Invariant theory | Ternary quartic | [
"Physics"
] | 231 | [
"Invariant theory",
"Group actions",
"Symmetry"
] |
2,070,045 | https://en.wikipedia.org/wiki/Heun%20function | In mathematics, the local Heun function is the solution of Heun's differential equation that is holomorphic and 1 at the singular point z = 0. The local Heun function is called a Heun function, denoted Hf, if it is also regular at z = 1, and is called a Heun polynomial, denoted Hp, if it is regular at all three finite singular points z = 0, 1, a.
Heun's equation
Heun's equation is a second-order linear ordinary differential equation (ODE) of the form
The condition is taken so that the characteristic exponents for the regular singularity at infinity are α and β (see below).
The complex number q is called the accessory parameter. Heun's equation has four regular singular points: 0, 1, a and ∞ with exponents (0, 1 − γ), (0, 1 − δ), (0, 1 − ϵ), and (α, β). Every second-order linear ODE on the extended complex plane with at most four regular singular points, such as the Lamé equation or the hypergeometric differential equation, can be transformed into this equation by a change of variable.
Coalescence of various regular singularities of the Heun equation into irregular singularities give rise to several confluent forms of the equation, as shown in the table below.
{| class="wikitable"
|+Forms of the Heun Equation
|-
! Form !! Singularities !! Equation
|-
| General
| 0, 1, a, ∞
|
|-
| Confluent
| 0, 1, ∞ (irregular, rank 1)
|
|-
| Doubly Confluent
| 0 (irregular, rank 1), ∞ (irregular, rank 1)
|
|-
| Biconfluent
| 0, ∞ (irregular, rank 2)
|
|-
| Triconfluent
| ∞ (irregular, rank 3)
|
|}
q-analog
The q-analog of Heun's equation has been discovered by and studied by .
Symmetries
Heun's equation has a group of symmetries of order 192, isomorphic to the Coxeter group of the Coxeter diagram D4, analogous to the 24 symmetries of the hypergeometric differential equations obtained by Kummer.
The symmetries fixing the local Heun function form a group of order 24 isomorphic to the symmetric group on 4 points, so there are 192/24 = 8 = 2 × 4 essentially different solutions given by acting on the local Heun function by these symmetries, which give solutions for each of the 2 exponents for each of the 4 singular points. The complete list of 192 symmetries was given by using machine calculation. Several previous attempts by various authors to list these by hand contained many errors and omissions; for example, most of the 48 local solutions listed by Heun contain serious errors.
See also
Heine–Stieltjes polynomials, a generalization of Heun polynomials.
References
A. Erdélyi, F. Oberhettinger, W. Magnus and F. Tricomi Higher Transcendental functions vol. 3 (McGraw Hill, NY, 1953).
Hahn W.(1971) On linear geometric difference equations with accessory parameters.Funkcial. Ekvac., 14, 73–78
.
Ordinary differential equations
Special functions | Heun function | [
"Mathematics"
] | 705 | [
"Special functions",
"Combinatorics"
] |
2,070,470 | https://en.wikipedia.org/wiki/Piping%20and%20instrumentation%20diagram | A Piping and Instrumentation Diagram (P&ID) is a detailed diagram in the process industry which shows process equipment together with the instrumentation and control devices. It is also called as mechanical flow diagram (MFD).
Superordinate to the P&ID is the process flow diagram (PFD) which indicates the more general flow of plant processes and the relationship between major equipment of a plant facility.
Contents and function
A piping and instrumentation diagram (P&ID) is defined as follows:
A diagram which shows the interconnection of process equipment and the instrumentation used to control the process. In the process industry, a standard set of symbols is used to prepare drawings of processes. The instrument symbols used in these drawings are generally based on International Society of Automation (ISA) Standard S5.1
The primary schematic drawing used for laying out a process control installation.
They usually contain the following information:
Mechanical equipment, including:
Pressure vessels, columns, tanks, pumps, compressors, heat exchangers, furnaces, wellheads, fans, cooling towers, turbo-expanders, pig traps (see 'symbols' below)
Bursting discs, restriction orifices, strainers and filters, steam traps, moisture traps, sight-glasses, silencers, flares and vents, flame arrestors, vortex breakers, eductors
Process piping, sizes and identification, including:
Pipe classes and piping line numbers
Flow directions
Interconnections references
Permanent start-up, flush and bypass lines
Pipelines and flowlines
Blinds and spectacle blinds
Insulation and heat tracing
Process control instrumentation and designation (names, numbers, unique tag identifiers), including:
Valves and their types and identifications (e.g. isolation, shutoff, relief and safety valves, valve interlocks)
Control inputs and outputs (sensors and final elements, interlocks)
Miscellaneous - vents, drains, flanges, special fittings, sampling lines, reducers and swages
Interfaces for class changes
Computer control system
Identification of components and subsystems delivered by others
P&IDs are originally drawn up at the design stage from a combination of process flow sheet data, the mechanical process equipment design, and the instrumentation engineering design. During the design stage, the diagram also provides the basis for the development of system control schemes, allowing for further safety and operational investigations, such as a Hazard and operability study (HAZOP). To do this, it is critical to demonstrate the physical sequence of equipment and systems, as well as how these systems connect.
P&IDs also play a significant role in the maintenance and modification of the process after initial build. Modifications are red-penned onto the diagrams and are vital records of the current plant design.
They are also vital in enabling development of;
Control and shutdown schemes
Safety and regulatory requirements
Start-up sequences
Operational understanding.
P&IDs form the basis for the live mimic diagrams displayed on graphical user interfaces of large industrial control systems such as SCADA and distributed control systems.
Identification and reference designation
Based on STANDARD ANSI/ISA S5.1 and ISO 14617-6, the P&ID is used for the identification of measurements within the process. The identifications consist of up to 5 letters. The first identification letter is for the measured value, the second is a modifier, 3rd indicates passive/readout function, 4th - active/output function, and the 5th is the function modifier. This is followed by loop number, which is unique to that loop. For instance FIC045 means it is the Flow Indicating Controller in control loop 045. This is also known as the "tag" identifier of the field device, which is normally given to the location and function of the instrument. The same loop may have FT045 - which is the flow transmitter in the same loop.
For reference designation of any equipment in industrial systems the standard IEC 61346 (Industrial systems, installations and equipment and industrial products — Structuring principles and reference designations) can be applied. For the function Measurement the reference designator B is used, followed by the above listed letter for the measured variable.
For reference designation of any equipment in a power station the KKS Power Plant Classification System can be applied.
Symbols of chemical apparatus and equipment
Below are listed some symbols of chemical apparatus and equipment normally used in a P&ID, according to ISO 10628 and ISO 14617.
Historical use
Prior to the advent of computer-aided design (CAD) in the late 1980s, P&IDs were drawn by hand. The drawing template shown below, actual size 225.mm by 111 mm, is typical of those used to draw P&IDs.
Piping and instrumentation diagram manual drawing template (1980s). Symbol key:
See also
Instrumentation in petrochemical industries
External links
Learn How to Read P&ID Drawings – A Complete Guide
Interpreting Piping and Instrumentation Diagrams-Symbology
Commons:Category:Chemical engineering symbols - A list of P&ID symbols in SVG format
References
Process engineering
Piping
Diagrams
Industrial automation | Piping and instrumentation diagram | [
"Chemistry",
"Engineering"
] | 1,027 | [
"Process engineering",
"Building engineering",
"Chemical engineering",
"Industrial engineering",
"Automation",
"Mechanical engineering by discipline",
"Mechanical engineering",
"Piping",
"Industrial automation"
] |
2,071,466 | https://en.wikipedia.org/wiki/Rate%20of%20heat%20flow | The rate of heat flow is the amount of heat that is transferred per unit of time in some material, usually measured in watts (joules per second). Heat is the flow of thermal energy driven by thermal non-equilibrium, so the term 'heat flow' is a redundancy (i.e. a pleonasm). Heat must not be confused with stored thermal energy, and moving a hot object from one place to another must not be called heat transfer. However, it is common to say ‘heat flow’ to mean ‘heat content’.
The equation of heat flow is given by Fourier's law of heat conduction.
Rate of heat flow = - (heat transfer coefficient) * (area of the body) * (variation of the temperature) / (length of the material)
The formula for the rate of heat flow is:
where
is the net heat (energy) transfer,
is the time taken,
is the difference in temperature between the cold and hot sides,
is the thickness of the material conducting heat (distance between hot and cold sides),
is the thermal conductivity of the material conducting heat, and
is the surface area of the surface emitting heat.
If a piece of material whose cross-sectional area is and thickness is with a temperature difference between its faces is observed, heat flows between the two faces in a direction perpendicular to the faces. The time rate of heat flow, , for small and small , is proportional to . In the limit of infinitesimal thickness , with temperature difference , this becomes , where is the time rate of heat flow through the area , is the temperature gradient across the material, and , the proportionality constant, is the thermal conductivity of the material. People often use , , or the Greek letter to represent this constant. The minus sign is there because the rate of heat flow is always negative—heat flows from the side at higher temperature to the one at lower temperature, not the other way around.
See also
Heat transfer coefficient
Heat transfer
Thermal conduction
Thermal conductivity
Heat flux
Watt
Flux
References
Thermodynamic properties
Heat flow | Rate of heat flow | [
"Physics",
"Chemistry",
"Mathematics"
] | 426 | [
"Thermodynamics stubs",
"Temporal quantities",
"Thermodynamic properties",
"Physical quantities",
"Quantity",
"Temporal rates",
"Thermodynamics",
"Physical chemistry stubs"
] |
2,071,900 | https://en.wikipedia.org/wiki/Causal%20dynamical%20triangulation | Causal dynamical triangulation (CDT), theorized by Renate Loll, Jan Ambjørn and Jerzy Jurkiewicz, is an approach to quantum gravity that, like loop quantum gravity, is background independent.
This means that it does not assume any pre-existing arena (dimensional space) but, rather, attempts to show how the spacetime fabric itself evolves.
There is evidence
that, at large scales, CDT approximates the familiar 4-dimensional spacetime but shows spacetime to be 2-dimensional near the Planck scale, and reveals a fractal structure on slices of constant time. These interesting results agree with the findings of Lauscher and Reuter, who use an approach called Quantum Einstein Gravity, and with other recent theoretical work.
Introduction
Near the Planck scale, the structure of spacetime itself is supposed to be constantly changing due to quantum fluctuations and topological fluctuations. CDT theory uses a triangulation process which varies dynamically and follows deterministic rules, to map out how this can evolve into dimensional spaces similar to that of our universe.
The results of researchers suggest that this is a good way to model the early universe, and describe its evolution. Using a structure called a simplex, it divides spacetime into tiny triangular sections. A simplex is the multidimensional analogue of a triangle [2-simplex]; a 3-simplex is usually called a tetrahedron, while the 4-simplex, which is the basic building block in this theory, is also known as the pentachoron. Each simplex is geometrically flat, but simplices can be "glued" together in a variety of ways to create curved spacetimes. Whereas previous attempts at triangulation of quantum spaces have produced jumbled universes with far too many dimensions, or minimal universes with too few, CDT avoids this problem by allowing only those configurations in which the timelines of all joined edges of simplices agree.
Derivation
CDT is a modification of quantum Regge calculus where spacetime is discretized by approximating it with a piecewise linear manifold in a process called triangulation. In this process, a d-dimensional spacetime is considered as formed by space slices that are labeled by a discrete time variable t. Each space slice is approximated by a simplicial manifold composed by regular (d − 1)-dimensional simplices and the connection between these slices is made by a piecewise linear manifold of d-simplices. In place of a smooth manifold there is a network of triangulation nodes, where space is locally flat (within each simplex) but globally curved, as with the individual faces and the overall surface of a geodesic dome. The line segments which make up each triangle can represent either a space-like or time-like extent, depending on whether they lie on a given time slice, or connect a vertex at time t with one at time t + 1. The crucial development is that the network of simplices is constrained to evolve in a way that preserves causality. This allows a path integral to be calculated non-perturbatively, by summation of all possible (allowed) configurations of the simplices, and correspondingly, of all possible spatial geometries.
Simply put, each individual simplex is like a building block of spacetime, but the edges that have a time arrow must agree in direction, wherever the edges are joined. This rule preserves causality, a feature missing from previous "triangulation" theories. When simplexes are joined in this way, the complex evolves in an orderly fashion, and eventually creates the observed framework of dimensions. CDT builds upon the earlier work of Barrett, Crane, and Baez, but by introducing the causality constraint as a fundamental rule (influencing the process from the very start), Loll, Ambjørn, and Jurkiewicz created something different.
Related theories
CDT has some similarities with loop quantum gravity, especially with its spin foam formulations. For example, the Lorentzian Barrett–Crane model is essentially a non-perturbative prescription for computing path integrals, just like CDT. There are important differences, however. Spin foam formulations of quantum gravity use different degrees of freedom and different Lagrangians. For example, in CDT, the distance, or "the interval", between any two points in a given triangulation can be calculated exactly (triangulations are eigenstates of the distance operator). This is not true for spin foams or loop quantum gravity in general. Moreover, in spin foams the discreteness is thought to be fundamental, while in CDT it is viewed as a regularization of the path integral, to be removed by the continuum limit.
Another approach to quantum gravity that is closely related to causal dynamical triangulation is called causal sets. Both CDT and causal sets attempt to model the spacetime with a discrete causal structure. The main difference between the two is that the causal set approach is relatively general, whereas CDT assumes a more specific relationship between the lattice of spacetime events and geometry. Consequently, the Lagrangian of CDT is constrained by the initial assumptions to the extent that it can be written down explicitly and analyzed (see, for example, hep-th/0505154, page 5), whereas there is more freedom in how one might write down an action for causal-set theory.
In the continuum limit, CDT is probably related to some version of Hořava–Lifshitz gravity. In fact, both theories rely on a foliation of spacetime, and thus they can be expected to lie in the same universality class. In 1+1 dimensions they have actually been shown to be the same theory, while in higher dimensions there are only some hints, as understanding the continuum limit of CDT remains a difficult task.
See also
Asymptotic safety in quantum gravity
Causal sets
Fractal cosmology
Loop quantum gravity
5-cell
Planck scale
Quantum gravity
Regge calculus
Simplex
Simplicial manifold
Spin foam
References
Notes
Bibliography
Quantum gravity: progress from an unexpected direction
Jan Ambjørn, Jerzy Jurkiewicz, and Renate Loll – "The Self-Organizing Quantum Universe", Scientific American, July 2008
Alpert, Mark "The Triangular Universe" Scientific American page 24, February 2007
Ambjørn, J.; Jurkiewicz, J.; Loll, R. – Quantum Gravity or the Art of Building Spacetime
Loll, R.; Ambjørn, J.; Jurkiewicz, J. – The Universe from Scratch – a less technical recent overview
Loll, R.; Ambjørn, J.; Jurkiewicz, J. – Reconstructing the Universe – a technically detailed overview
Markopoulou, Fotini; Smolin, Lee – Gauge Fixing in Causal Dynamical Triangulations – shows that varying the time-slice gives similar results
Loll, R – Quantum Gravity from Causal Dynamical Triangulations: A Review A review from May 2019, focusing on results that were recent at that time
Early papers on the subject:
R. Loll, Discrete Lorentzian Quantum Gravity, arXiv:hep-th/0011194v1 21 Nov 2000
J Ambjørn, A. Dasgupta, J. Jurkiewicz, and R. Loll, A Lorentzian cure for Euclidean troubles, arXiv:hep-th/0201104 v1 14 Jan 2002
External links
Renate Loll's talk at Loops '05
John Baez' talk at Loops '05
Pentatope: from MathWorld
(Re-)Constructing the Universe from Renate Loll's homepage
Renate Loll on the Quantum Origins of Space and Time as broadcast by TVO
Physical cosmology
Astrophysics
Quantum gravity
Physics beyond the Standard Model | Causal dynamical triangulation | [
"Physics",
"Astronomy"
] | 1,656 | [
"Astronomical sub-disciplines",
"Theoretical physics",
"Unsolved problems in physics",
"Astrophysics",
"Quantum gravity",
"Particle physics",
"Physics beyond the Standard Model",
"Physical cosmology"
] |
31,566,537 | https://en.wikipedia.org/wiki/Photomagnetic%20effect | The photomagnetic effect is a theoretical quantum mechanical effect discovered by the researchers Samuel L. Oliveira and Stephen C. Rand at University of Michigan 2007–2011. The researchers have discovered a powerful magnetic interaction between the photon's dynamic magnetic field – and certain isolator materials' atom's magnetic moment, that is 100 million times stronger than formerly anticipated. Under the proper circumstances, the photon's magnetic fields effect is as strong as their electric field – as e.g. in solar cells.
The discovery is a surprise, because it is not straightforward to derive the strong magnetic effect from the physical equations, and thereby indicate that this quantum mechanical effect would be interesting enough. That is why the photomagnetic effect has been neglected for more than 100 years.
The researchers have theoretically calculated that incoherent light as e.g. sunlight, is almost as efficient as laserlight, to be converted by the photomagnetic effect.
The power density should be 10 million watt per square centimeter, but the researchers will look for new photomagnetic materials, that can work with lower light intensities.
See also
Photoelectric effect
Photomagnetism
References
Solar power
Energy conversion
University of Michigan
Magneto-optic effects | Photomagnetic effect | [
"Physics",
"Chemistry",
"Materials_science"
] | 253 | [
"Optical phenomena",
"Physical phenomena",
"Electric and magnetic fields in matter",
"Magneto-optic effects"
] |
31,573,758 | https://en.wikipedia.org/wiki/Bredig%27s%20arc%20method | Bredig's arc method or electrical disintegration is a method of preparation of colloidal solution, of metals such as gold, silver or platinum.
This method consists of both dispersion and condensation. An arc is struck between electrodes of the desired metal, under the surface of water containing some stabilizing agent such as traces of potassium hydroxide. The intense heat of the arc vaporizes some of the metal which then condenses under cold water. The water is kept cold with an ice bath.
This method is not suitable when the dispersion medium is an organic liquid as considerable charring occurs.
References
Colloids | Bredig's arc method | [
"Physics",
"Chemistry",
"Materials_science"
] | 135 | [
"Chemical mixtures",
"Condensed matter physics",
"Colloids"
] |
31,575,438 | https://en.wikipedia.org/wiki/Cohomology%20of%20algebras | In mathematics, the homology or cohomology of an algebra may refer to
Banach algebra cohomology of a bimodule over a Banach algebra
Cyclic homology of an associative algebra
Group cohomology of a module over a group ring or a representation of a group
Hochschild homology of a bimodule over an associative algebra
Lie algebra cohomology of a module over a Lie algebra
Supplemented algebra cohomology of a module over a supplemented associative algebra
See also
Cohomology
Ext functor
Tor functor
Homological algebra | Cohomology of algebras | [
"Mathematics"
] | 123 | [
"Fields of abstract algebra",
"Mathematical structures",
"Category theory",
"Homological algebra"
] |
31,575,736 | https://en.wikipedia.org/wiki/TMEM229B | Transmembrane protein 229b is a protein that in humans is encoded by the TMEM229b gene.
Nomenclature
The TMEM229B gene is also known as C14orf83, FLJ33387, Q8NBD8, Hs.509707, Hs.712258, IPR010540, and CN083_HUMAN.
Gene
The TMEM229B gene is located on the sense strand (-) of chromosome 14 at location 14q24.1 and spans the chromosomal locus 67,936,983—67,982,021. Covering a total of 45,038 base pairs (bp) along the chromosome, the TMEM229B gene has a total of 3 exons in its primary unspliced transcript mRNA of 4,068 bp. There are a total of 7 transcript variants for TMEM229B ranging in mRNA size from 519 bp to 5008 bp. The TMEM229B gene is flanked by phosphatidylinositol glycan anchor class H (PIGH), a protein associated with the endoplasmic reticulum specifically GPI-anchor biosynthesis, and PLEK2 on its left. See Figure 1.0. The gene is highly conserved in vertebrates, including portions of the approximately 3,000 base pairs of 3'UTR.
Tissue distribution
Expressed sequence tag mapping of TMEM229B gene expression indicates that it is ubiquitously expressed throughout the body. TMEM229B is more heavily expressed in the parathyroid, skin, and thyroid tissues, and moderately expressed in bone marrow, trachea, spleen, eye, brain, pancreas, mammary gland, intestine, liver, thymus, lymph node, ovarian, muscle, lung, blood, and kidney tissues.
Protein
The translated TMEM229B protein is a total of 167 amino acids long, with a predicted molecular weight of 19,531 daltons. The TMEM229B protein contains a domain of unknown function, part of the domain family DUF1113, spanning from amino acids 87 to 135.
Based on predicted structure TMEM229b is highly resemblant of a connexin subunit. A highly conserved phosphorylation site exists at the Threonine-139 position. See multiple sequence alignment below.
Clinical relevance
Expression of the TMEM229B gene increases in several disease states including amelanotic skin melanoma, B-cell neoplasm, breast carcinoma, Burkitt's lymphoma, colorectal adenocarcinoma, carcinoma, cutaneous T cell lymphoma, esophageal carcinoma, gastric carcinoma, glioblastoma, liver carcinoma, lymphoma, melanoma, small cell lung carcinoma, T-cell acute lymphoblastic leukemia, thyroid carcinoma and Wilms' tumor as found in several microarray experiments. Over-expression of the TMEM229B gene has not been linked as a causal factor in any of these disease states.
References
Proteins
Genes on human chromosome 14 | TMEM229B | [
"Chemistry"
] | 699 | [
"Biomolecules by chemical classification",
"Proteins",
"Molecular biology"
] |
21,471,974 | https://en.wikipedia.org/wiki/Barth%C3%A9l%C3%A9my%20Bisengimana | Barthélémy Bisengimana Rwema (born 12 May 1935) was a Zairean official who served as head of the Bureau of the President under Mobutu Sese Seko from May 1969 to February 1977. Bisengimana was a member of the Tutsi ethnic group whose rise to prominence was largely the result of the complete dependence of the Banyarwanda upon the central government for power, which made them reliable supporters. A native of Cyangugu Province in Rwanda, in 1961 Bisengimana was the first graduate with a degree in electrical engineering from Lovanium University in Kinshasa.
Bisengima's aided many Congolese Tutsis in North and South Kivu to acquire land and start lucrative businesses. Andre Kalinda, a chief of the Hunde and territorial administrator of Masisi, became the most powerful chief due to his connections with both Bisengimana and the Acogenoki. At his height in 1972, Bisengimana managed to get the Political Bureau of the ruling Mouvement Populaire de la Révolution (MPR) to pass a citizenship decree in which everyone originating from "Ruanda-Urundi" and residing in then-Belgian Congo on or before January 1950 was automatically granted citizenship. This Law 72-002 amended the MPR's statutes and became referred to as "Article 15". When the law, which further allowed the new citizens to claim land rights, went into effect in 1973, a number of Tutsi refugees legally received plantations and ranches that had been previously owned by Belgian settlers. Among these was Bisengimana, who claimed the Osso concession, which contained the largest number of cattle owned by white settlers in Masisi.
Bisengimana was dismissed in 1977, followed allegations of getting kickbacks from a textile plant in Kisangani. Following his removal, there was increasing pressure to reverse Article 15, resulting in the passing of Law 81-002 on 29 June 1981.
Footnotes
References
1935 births
Living people
People from Western Province, Rwanda
Tutsi people
Rwandan exiles
Rwandan refugees
Electrical engineers
Popular Movement of the Revolution politicians
Lovanium University alumni
Democratic Republic of the Congo people of Rwandan descent
Rwandan emigrants to the Democratic Republic of the Congo
21st-century Democratic Republic of the Congo people | Barthélémy Bisengimana | [
"Engineering"
] | 477 | [
"Electrical engineering",
"Electrical engineers"
] |
21,474,044 | https://en.wikipedia.org/wiki/Wireless%20identification%20and%20sensing%20platform | A wireless identification and sensing platform (WISP) is an RFID (radio-frequency identification) device that supports sensing and computing: a microcontroller powered by radio-frequency energy.
That is, like a passive RFID tag, WISP is powered and read by a standard off-the-shelf RFID reader, harvesting the power it uses from the reader's emitted radio signals. To an RFID reader, a WISP is just a normal EPC gen1 or gen2 tag; but inside the WISP, the harvested energy is operating a 16-bit general purpose microcontroller. The microcontroller can perform a variety of computing tasks, including sampling sensors, and reporting that sensor data back to the RFID reader. WISPs have been built with light sensors, temperature sensors, and strain gauges. Some contain accelerometers.
WISPs can write to flash and perform cryptographic computations. The WISP was originally developed by Intel Research Seattle, but after their closure development work has continued at the Sensor Systems Laboratory at the University of Washington in Seattle.
Implementation
The WISP consists of a board with power harvesting circuitry, demodulator, modulator, microcontroller, external sensors, and other components such as EEPROM and LED.
Applications
WISPs have been used for light level measurement, acceleration sensing, cold chain monitoring (passive data logging), and cryptography and security applications.
See also
Indian Institute of Remote Sensing
Intel Research Lablets
Remote sensing in mobile telecommunications
NODE platform
Quality control system (QCS) for web and papers
SWARM
Wireless sensor network nodes
References
External links
Wireless sensor network
Ubiquitous computing
Automatic identification and data capture
Radio-frequency identification | Wireless identification and sensing platform | [
"Technology",
"Engineering"
] | 351 | [
"Radio electronics",
"Wireless networking",
"Wireless sensor network",
"Data",
"Automatic identification and data capture",
"Radio-frequency identification"
] |
21,477,359 | https://en.wikipedia.org/wiki/Falling%20cat%20problem | The falling cat problem is a problem that consists of explaining the underlying physics behind the observation of the cat righting reflex.
Although amusing and trivial to pose, the solution of the problem is not as straightforward as its statement would suggest. The apparent contradiction with the law of conservation of angular momentum is resolved because the cat is not a rigid body, but instead is permitted to change its shape during the fall owing to the cat's flexible backbone and non-functional collar-bone. The behavior of the cat is thus typical of the mechanics of deformable bodies.
Several explanations have been proposed for this phenomenon since the late 19th century:
Cats rely on conservation of angular momentum.
The rotation angle of the front body is larger than that of the rear body.
The dynamics of the falling cat have been explained using the Udwadia–Kalaba equation.
History
The falling cat problem has elicited interest from scientists including George Gabriel Stokes, James Clerk Maxwell, and Étienne-Jules Marey. In a letter to his wife, Katherine Mary Clerk Maxwell, Maxwell wrote, "There is a tradition in Trinity that when I was here I discovered a method of throwing a cat so as not to light on its feet, and that I used to throw cats out of windows. I had to explain that the proper object of research was to find how quick the cat would turn round, and that the proper method was to let the cat drop on a table or bed from about two inches, and that even then the cat lights on her feet."
Whereas the cat-falling problem was regarded as a mere curiosity by Maxwell, Stokes, and others, a more rigorous study of the problem was conducted by Étienne-Jules Marey who applied chronophotography to capture the cat's descent on film using a chronophotographic gun. The gun, capable of capturing 12 frames per second, produced images from which Marey deduced that, as the cat had no rotational motion at the start of its descent, the cat was not "cheating" by using the cat handler's hand as a fulcrum. This in itself posed a problem as it implied that it was possible for a body in free fall to acquire angular momentum. Marey also showed that air resistance played no role in facilitating the righting of the cat's body.
His investigations were subsequently published in Comptes Rendus, and a summary of his findings were published in the journal Nature. The article's summary in Nature appeared thus:
Despite the publication of the images, many physicists at the time maintained that the cat was still "cheating" by using the handler's hand from its starting position to right itself, as the cat's motion would otherwise seem to imply a rigid body acquiring angular momentum.
Solution
The problem was initially solved in 1969 by modelling the cat as a pair of cylinders (the front and back halves of the cat) capable of changing their relative orientations and has been described in terms of a connection in the configuration space that encapsulates the relative motions of the two parts of the cat permitted by the physics. We can model the simplified "cat" as two cylinders connected by a flexible spine in the middle. We also assume that the flexible spine disallows twisting, so both cylinders can only rotate by the same degree. Thus, the configuration space of the system has only three dimensions:
, the overall angle of the cat around the horizontal axis.
, the bending angle of the spine
, the turning angle of the cylinders
Framed in this way, the dynamics of the falling cat problem is a prototypical example of a nonholonomic system, the study of which is among the central preoccupations of control theory. A solution of the falling cat problem is a curve in the configuration space that is horizontal with respect to the connection (that is, it is admissible by the physics) with prescribed initial and final configurations. Finding an optimal solution is an example of optimal motion planning.
In the language of physics, Montgomery's connection is a certain Yang–Mills field on the configuration space, and is a special case of a more general approach to the dynamics of deformable bodies as represented by gauge fields, following the work of Shapere and Wilczek.
See also
Buttered cat paradox
Momentum wheel
Parallel parking problem
References
Works cited
Further reading
Lagrangian Reduction and the Falling Cat Theorem
Biophysics
Cat behavior
Classical mechanics
Control theory
Rotation | Falling cat problem | [
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21,478,904 | https://en.wikipedia.org/wiki/Border%20blaster | A border blaster is a broadcast station that, though not licensed as an external service, is, in practice, used to target another country. The term "border blaster" is of North American origin, and usually associated with Mexican AM stations whose broadcast areas cover large parts of the United States, and United States border AM stations covering large parts of Canada. Conceptually similar European broadcasting included some pre-World War II broadcasting towards the United Kingdom, "radio périphérique" around France and the U.S. government-funded station Radio Free Europe, targeting European countries behind the Iron Curtain.
With broadcasting signals far more powerful than those of U.S. stations, the Mexican border blasters could be heard over large areas of the U.S. from the 1940s to the 1970s, often to the great irritation of American radio stations, whose signals could be overpowered by their Mexican counterparts. These are also sometimes referred to as X stations for their call letters: Mexico assigns callsigns beginning with XE or XH to broadcast stations.
On November 9, 1972, in Washington, D.C., the United States and Mexico signed an "Agreement Concerning Frequency Modulation Broadcasting in the 87.5 to 108 MHz Band". Since then, in the FM band power levels and frequency assignments have been set by mutual agreement between the two countries. AM radio border blasters still exist, though they are largely ignored due to the decline of AM radio in the U.S. and in Mexico. There are several such stations licensed by Mexico's Secretariat of Communications and Transportation using transmitters with an effective radiated power similar to those of major licensed commercial stations located within the U.S.
Background
In contrast to pirate radio stations which broadcast illegally, border blasters are generally licensed by the government upon whose soil they are located. Pirate radio stations are freebooters from offshore, outside the territorial waters of the nation they target, or ones that are illegally operating in defiance of national law within its sovereign territory. They also contrast with shortwave radio broadcasters, which operate on frequencies expressly designated for international broadcasts, whereas border blasters use frequencies designated for domestic broadcasts.
Mexico to U.S.
In Mexico and the US, while the federal government of the US did not particularly like them, the stations were allowed to flourish. W. Lee O'Daniel used a border blaster in his successful campaign for governor of Texas. The US, unlike the UK, has never required a license to listen to broadcast radio or television. The only restriction placed upon border-blasters was a law which prohibited studios in the US from linking by telephone to border-blaster transmitters in Mexico. This law, part of the Brinkley Act, was introduced in the wake of John R. Brinkley's fraudulent medical advice program on XERA. The Brinkley Act remains on the books in the US, but licenses under that act are now routinely granted as long as the station follows applicable US and Mexican regulations.
The pop culture inspired by the border blaster stations is extensive: the 1971 Doors song "The WASP (Texas Radio and the Big Beat)", ZZ Top's song "Heard It on the X" (1975), "The Wolfman of Del Rio" by Terry Allen on his 1979 album Lubbock (On Everything), 1983's "Mexican Radio" by Wall of Voodoo, and 1987's "Border Radio" movie theme by The Blasters.
Europe
A similar situation developed in Europe, beginning with Radio Luxembourg after World War II. The British government identified these stations as pirates because the Sunday broadcast was reserved for British listeners (deliberately coinciding with the BBC Sundays of religious programmes). The broadcasts were considered illegal on British soil as these stations were breaking the monopoly of the non-commercial BBC. (Coincidentally, a large percent of the Republic of Ireland could receive spillover from Northern Ireland, Wales and the west of England BBC TV and radio broadcasts for decades.) Listening to the broadcasts was technically a violation of UK radio-license laws of the day. The same "radio périphérique" , or "peripheral radio", phenomenon existed in France from the 1930s until the legalization of private broadcasting in the early 1980s, which allowed Radio Luxembourg from Luxembourg, Radio Andorre and Sud Radio from Andorra, Radio Monte Carlo from Monaco, and Europe 1 from Saarland, Germany, to begin legally broadcasting signals across international borders.
The British government created countermeasures after World War II: the state-owned telephone monopoly prevented studios in Britain from linking by telephone to the transmitters of Radio Luxembourg. These restrictions were mostly lifted following the privatisation and demonopolisation of the UK telephone system.
Northern U.S. and Canada
Signals of many US and Canada radio stations (and to a lesser extent television outlets) encroach on neighboring territory. Such stations are usually not deemed "border blasters," as their programming is not primarily targeted at listeners and viewers across the border. US and Canadian stations adhere to comparable maximum power levels, and the encroachment is regarded as unintentional and largely unavoidable. However, in areas where a US radio station is close to a significantly larger Canadian metropolitan area (or vice versa), true border blasters do exist.
An exception to that general rule is KRPI located in Ferndale, Washington. It is owned by BBC Broadcasting, Inc., a Washington state company with studios in Richmond, British Columbia. The station airs a mixture of music, news and talk focused on the South Asian communities in Metro Vancouver. To improve reception of the station within its target market, KRPI applied and received an FCC construction permit to increase its nighttime power from 10 to 50 kilowatts, change the community it served and move its transmitter from Ferndale to Point Roberts, a community adjacent to the Canada–US border. The move has attracted much criticism from the local citizens of Point Roberts and the adjacent densely populated community of Tsawwassen, British Columbia, because it would cause harmful blanketing interference.
Another possible exception to that general rule on the Canadian side was CKLW in Windsor, Ontario, across the river from Detroit. Originally licensed as a Class II-B (now Class B) station and always operating in full compliance with the technical specifications and operating rules of its CRTC licence (i.e., protection of the entire Mexican border nights and protection of co-channel Canadian stations days and nights), CKLW's 50,000-watt directional signal blanketed much of Michigan and northern Ohio east to Cleveland days and nights, and south to Toledo, Lima and Dayton in the daytime. American-owned until 1970 as part of the RKO General chain (along with such other top 40 powerhouses as KHJ in Los Angeles and KFRC in San Francisco), it functioned essentially as a Detroit-market station during the 1960s and 1970s. Its Motown-flavored personality Top 40 format made it one of the most highly rated stations in the Midwestern US. The decline of AM radio as a music source in the 1970s, combined with new Canadian government rules imposing domestic ownership of and minimum domestic music content on Canadian-based stations, made it difficult for CKLW to continue to compete for listeners with Detroit-based, US-licensed FM music stations, which offered clean stereo sound and faced no program content or music playlist restrictions. CKLW abandoned the Top 40 format and its efforts to compete in the Detroit market in the 1980s. Today it is a news/talk station aimed largely at an Ontario audience, though still containing a significant amount of American syndicated talk.
WLYK is another example of a border blaster, broadcasting from a transmitter in New York State and serving the adjacent Kingston, Ontario, area; its operator Rogers Communications holds an ownership stake in its U.S.-based licensee. Numerous stations in northern New York target larger cities in Ontario and Quebec in addition to their local areas of New York, including (but not limited to) WYSX targeting Brockville; WRCD, WVLF and WMWA targeting Cornwall; and WQLR and WBTZ targeting Montreal. By contrast under CRTC regulations, Canadian radio stations must be operated from studios within the country.
Attempts at border-blasting were somewhat more common on the other side of the border, where smaller markets in the United States could find lucrative larger markets in Canada within their broadcast range. WIVB-TV, prior to the digital television transition, could be seen as a U.S. border blaster into Canada (as Western New York is a smaller market than Southern Ontario, which boasts the major world city of Toronto); it operated with 100,000 watts of power on the VHF low band (channel 4), even after the Federal Communications Commission reduced the maximum allowed power for that band to 80,000 watts. (WIVB did not make significant attempts to reach the Canadian market, although rival station WKBW-TV did.) Another famous U.S.-based border blaster into Canada was KCND-TV in Pembina, North Dakota; Pembina was a small border town of less than 1,000 residents, which normally would be far too small a market to support a television station, but spent its fifteen-year existence targeting Winnipeg, a much larger city sixty miles north of Pembina. Likewise, the small market of Burlington, Vermont, and Plattsburgh, New York, found it could reach a larger audience in Montreal. Canadian regulators put in simultaneous substitution requirements to prevent losing revenue to these American border-blasters (this forced KCND's owners to sell the station to Canadian interests, who transformed the station into modern-day Winnipeg, Manitoba-based CKND-TV; Burlington station WFFF-TV entered into a famous cross-border scheduling feud over the simsub problems, while WKBW, after unsuccessfully suing to bar the CRTC from enforcing it on systems that only operate in one province in 1977, competed mainly by focusing on its unique brand of local news, which could not be simsubbed). Also in Western New York, radio station WTOR is licensed to the northwesternmost municipality in the region (Youngstown), operates with a directional signal covering Southern Ontario but very little American territory, and is brokered to a Canadian ethnic broadcaster based in Mississauga; it maintains its U.S. license and transmitter site as a legal fiction, with ethnic broadcaster Sima Birach holding the station's license and claiming himself as "operations manager" even as he seldom appears at the station's nominal U.S. studio in person.
In the west, KVOS-TV in Bellingham, Washington, targeted an audience in Vancouver and Victoria for many years. In fact, KVOS' inaugural broadcast, in June of 1953, was a kinescope film of the Coronation of Queen Elizabeth II, which was broadcast over KVOS as Vancouver's CBC Television station, CBUT, had yet to sign on.
At least one border blaster targets the Russian Far East: KICY broadcasts its religious programming on a 50,000-watt clear-channel directional signal pointed due west from the Seward Peninsula, one of the westernmost land masses in North America.
Programming
Most border blaster stations today program Spanish-language programming targeted at the Mexican side of the border. Some of the Spanish language border blasters target the growing Latino audience living in the southwestern US. Some target both.
As was the case between the 1930s and the 1970s, some border blaster stations in areas near larger American border cities such as San Diego are leased out by American broadcasting companies and air English-language programming targeting American audiences, although the AM stations have sometimes been supplanted by FM signals just over the border and able to reach major American cities like San Diego or El Paso with city-grade signals. During those decades border radio was used by preachers who solicited donations, and advertisers who sold products of dubious value. The American side leases the station from the Mexican station owners/license holders and feeds programming from their American studios to the Mexican transmitters via satellite.
Due to Mexican government regulations, these stations must air the Mexican national anthem at midnight and 6 a.m. daily, the government-produced radio magazine La Hora Nacional on Sunday nights, and 48 minutes of tiempos oficiales (public service announcements from the Mexican government, which include campaign ads during elections) per-day, and give station identification in Spanish. This is usually done softly or during commercial breaks so the listeners on the American side won't usually notice it. The PSA requirement has produced controversy even amongst officials in Mexico, for reasons including reinforcing negative perceptions of the country, taking up airtime that could be used to promote cross-border tourism and interactions instead, and their poor quality.
Geographical list of border blasters
Baja California
Tijuana / Rosarito
XEPRS-AM: This is the radio station, formerly known as XERB, featured in the George Lucas movie American Graffiti starring Wolfman Jack as the disc jockey. He moved to this station following his work on XERF.
XHPRS-FM: This is the FM counterpart to XEPRS-AM.
XETRA-FM
XETRA-AM
XEAK-AM
XELO-AM
XHITZ-FM: Broadcasts with an English top 40 format targeted exclusively at San Diego.
XHMORE-FM
XHRM-FM
XHRST-FM
XETV-TDT: Owned and operated by Televisa. From the station's launch in 1953 to 2017, programming and sales rights were managed by Bay City Television, Inc. (a California-based corporation). Afterwards, it converted to a Canal 5 relay, with signal remained to cover the Spanish community on the American side of the border.
XHAS-TDT: programming originates in San Diego but is sent to a transmitter in Tijuana
Sonora
San Luis Río Colorado
XHLPS-FM: Targeted exclusively at San Luis, Arizona
XHSLR-FM: Targeted to listeners In Yuma County, Arizona
Heroica Nogales
XHRZ-FM
Agua Prieta
XHNNO-FM
XHSAP-FM
XHSOS-FM
Chihuahua
Ciudad Juárez
XEROK-AM
XEJ-AM
XHGU-FM
XHH-FM
XHPX-FM
XHUAR-FM
XHNZ-FM
XHTO-FM - Broadcasts in the English language with a Top 40/CHR format targeted to listeners in El Paso, Texas
Coahuila
Ciudad Acuña
XER: "Sunshine Station between the Nations" broadcasting on AM at 735kHz. This was the original station licensed to John R. Brinkley in Mexico as the Villa Acuña Broadcasting Company. It first signed on August 18, 1932 with a 50 kW transmitter and claimed 75 kW ERP via an omnidirectional antenna. The engineering was by Will Branch of Fort Worth who had engineered WBAP for Amon Carter, owner of the Fort Worth Star-Telegram. It was shut down by the Mexican authorities on February 24, 1933 and the Villa Acuña Broadcasting Company was dissolved.
XERA: In September 1935 Brinkley gained a new license for Villa Acuña from the Government of Mexico with new call letters of XERA. His new operating company was Cía Mexicana Radiodifusora Fronteriza and the station came on the air from the same location as the old XER but with a directional antenna. His new transmitter power was 500 kW, but with his new antenna he claimed an output of 1MW. XERA called itself "the world's most powerful broadcasting station" and Variety magazine claimed that it could be heard in New York City. Following the signing of various treaties, the Government of Mexico revoked the license of XERA in the closing days of 1939.
XERF-AM: from 1947. The station that made Wolfman Jack world famous for his disc jockey and sales presentations between 1962 and 1964. This station came on the air long after the era of both XERA and Brinkley, but it initially used his old facilities although the powerful transmitter of XERA had been dismantled and shipped elsewhere. The station later moved to a new building where a 250kW RCA main transmitter was installed. The RCA "Ampliphase" transmitter has not been operational for many decades.
Piedras Negras
XEPN-AM was sister station to XER/XERA, and was also controlled by John Brinkley.
XELO-AM
Nuevo León
Monterrey
XEG-AM: In 1950 the advertising time of this station came under the control of Harold Schwartz of Chicago, who also came to represent XERB near Tijuana/Rosarito (the station made famous in the movie American Graffiti.) From the late 1960s through the early 1980s, XEG was known for its nighttime Black/R&B/Disco music programming block, transcribed from KGFJ, Los Angeles. XEG ran a huge 150kW signal at night, with 50kW daytime, on 1050 kHz.
XET-AM, nicknamed La T Grande, went on the air in 1930, made the Carter Family music well known in the 1930s.
Tamaulipas
Matamoros
XELD-TV: This station, owned in a joint venture between Romulo O'Farrill and Emilio Azcárraga, signed on in 1951 as Mexico's third television station on air, the first outside Mexico City and the first TV border blaster. It held affiliations with all major American networks, though its primary connection was with CBS. It was the only station in the area until 1953; weakened by economic conditions, new stations in the US and the deterioration and destruction of its physical plant, the station was gone by the middle of 1954.
Nuevo Laredo
XENT-AM: Operated by Norman G. Baker from 1933 until forced off the air in 1940; "The Calliaphone Station" (for an air-operated calliope invented by Baker) promoted a cancer-cure clinic of Baker's, essentially continuing his former station KTNT ("Know The Naked Truth") of Muscatine, Iowa, as was itself forced off the air in 1931. Brochures for the clinic urged patients to "phone 666 upon arrival in Laredo," attracting many complaints to the American Medical Association as invoked reference to Revelation 13:18, citing 666 as the Mark of the Beast. When the original XENT was dismantled, the callsign was assigned to a new and unrelated station at La Paz, Baja California Sur.
Reynosa
XED-AM: The first radio station in Mexico to be considered a border-blaster. XED was originally located at Reynosa, Tamaulipas, and was under the advertising sales management of the International Broadcasting Company. Located across the Rio Grande from McAllen, Texas, the station broadcast with a power of 10 kilowatts that was the most powerful transmitter in Mexico at that time.
XEAW-AM: Another station that came under the management control of John R. Brinkley. (See XER and XERA.)
Tampico
XEFW-AM
See also
Atlantic 252
City of license
List of international radio broadcasters
List of international television broadcasters
List of international religious radio broadcasters
LM Radio
MW DX
Pirate radio
Rimshot
Signal overspill
External links
Dedication of the Wolfman Jack Memorial in Del Rio, Texas
Official Ciudad Acuña municipal website – (in Spanish)
Investigation of radio operations in Tijuana, BC, conducted by broadcast engineer Donald Mussell
References
"Border Radio" by Fowler, Gene and Crawford, Bill. Texas Monthly Press, Austin. 1987
"Una radio entre dos reinos", by José Luis Ortiz Garza, Mexico, Ed. Ruz, 2010. .
Mass Media Moments in the United Kingdom, the USSR and the USA, by Gilder, Eric. – "Lucian Blaga" University of Sibiu Press, Romania. 2003
"Agreement Between the Government of the United States of America and the Government of the United Mexican States Relating to the FM Broadcasting Services in the Band 88–108 MHz", dated August 11, 1992. This agreement implies the existence of an earlier agreement, dated November 9, 1972. (Article 10) Link to Texts of Broadcast Agreements with Mexico
Radio in Mexico
Radio in the United States
United States communications regulation
Broadcast engineering
International relations
Broadcast transmitters | Border blaster | [
"Engineering"
] | 4,183 | [
"Broadcast engineering",
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21,479,365 | https://en.wikipedia.org/wiki/Tolyl%20group | In organic chemistry, tolyl groups are functional groups related to toluene. They have the general formula , the change of the relative position of the methyl and the R substituent on the aromatic ring can generate three possible structural isomers 1,2 (ortho), 1,3 (meta), and 1,4 (para). Tolyl groups are aryl groups which are commonly found in the structure of diverse chemical compounds. They are considered nonpolar and hydrophobic groups.
The functionalization to include tolyl groups into compounds is often done by Williamson etherification, using tolyl alcohols as reagents, or by C-C coupling reactions. Tolyl sulfonates are excellent leaving groups in nucleophilic substitutions, for this reason, they are commonly generated as intermediaries to activate alcohols. To this end, 4-toluenesulfonyl chloride is reacted in the presence of a base with the corresponding alcohol.
References
Aryl groups | Tolyl group | [
"Chemistry"
] | 212 | [
"Substituents",
"Aryl groups",
"Functional groups",
"Organic chemistry stubs"
] |
21,481,156 | https://en.wikipedia.org/wiki/Pitch%20drop-back | Pitch drop-back is the phenomena by which an aircraft which is perturbed in flight path angle from its trim position by a step input exhibits an output which is indicative of a second order system.
A pilot who actuates an elevator input may find that the aircraft then "droops" or "drops back" to a position further toward the start position. The phenomenon is particularly marked in tilt-rotor aircraft. Pitch drop-back may be controlled using a Stability Augmentation System or Stability Control and Augmentation System.
See also
List of aviation, avionics, aerospace and aeronautical abbreviations
Index of aviation articles
References
Aerospace engineering | Pitch drop-back | [
"Physics",
"Engineering"
] | 132 | [
"Physical systems",
"Transport",
"Transport stubs",
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21,481,649 | https://en.wikipedia.org/wiki/Institute%20of%20Nuclear%20Materials%20Management | The Institute of Nuclear Materials Management (INMM) is an international technical and professional organization that works to promote safe handling of nuclear material and the safe practice of nuclear materials management through publications, as well as organized presentations and meetings.
The INMM's headquarters is located in Deerfield, Illinois in the United States, but its members are located around the world including Europe, Asia, South America and North America. There are more than 1,100 members and 32 chapters.
Les Shephard, vice president of Sandia National Laboratories' Energy, Security, and Defense Technology Center, said in February 2009 of the INMM and the American Nuclear Society,
Structure
INMM is led by an executive committee of nine members, including a president, vice president, secretary, treasurer, four members-at-large, and the immediate past president. In addition, INMM has several standing and two technical committees. Many organizations, such as Los Alamos National Laboratory and Brookhaven National Laboratory, are Sustaining Members of the INMM.
Technical divisions
In 2010, the INMM Executive Committee approved a restructuring of the Institute. This included changes in the technical divisions. Some were merged and a new division was created. The technical divisions are:
Facility Operations
International Safeguards
Materials Control and Accountability
Nonproliferation and Arms Control
Nuclear Security and Physical Protection
Packaging, Transportation and Disposition
The division is the focal point for information and activities related to the physical protection of nuclear materials, nuclear facilities, and other high-value assets and facilities.
Until 2010, the INMM had six technical divisions:
International Safeguards, focusing on the development of effective international nuclear material safeguards, and working to advance safeguard procedures and technology
Materials Control and Accountability, promoting and communicating the need for development of technology for the control and accountability of nuclear materials
Nonproliferation and Arms Control, promoting research to further international stability with regard to nonproliferation and international arms control
Packaging and Transportation and Disposition, promoting technology and research aimed at the packaging and transportation of radioactive materials, including all levels of radioactive waste
Nuclear Security and Physical Protection, focusing on research to advance technology for the physical protection of nuclear materials and nuclear facilities
Waste Management, promoting research to help find a solution for the worldwide waste management issues, focusing on each step of waste management including handling, processing, storing, and disposal for all radioactive waste
Best practices
The INMM develops and promotes global "best practices" for nuclear materials management. Best practices are based on past events, lessons learned, and ways to effectiveness and efficiency. They are focused on the six technical divisions and should be applicable to all countries with nuclear capabilities, both civilian and military.
In 2008, the INMM joined with Nuclear Threat Initiative, the United States Department of Energy, and the International Atomic Energy Agency to establish a new international organization called the World Institute for Nuclear Security (WINS) aimed at strengthening physical protection and security of the world's nuclear and radioactive materials and facilities. This organization's focus is on collecting information on best management practices from professionals responsible for on-the-ground security and sharing that information with their peer professionals around the world. These security professionals are in the best position to know where the vulnerabilities are, how to improve security, and how to ensure that improvements are implemented quickly and effectively. WINS will place a high priority on protecting sensitive information that may be discussed between members. Initial funding for the WINS included $3 million each from the Peter G. Peterson Foundation and the U.S. Department of Energy plus $100,000 from Norway.
Chapters
The INMM has 32 chapters around the world, including six regional chapters in the United States and international chapters in Japan, South Korea, Morocco, Nigeria, Obninsk Regional in Russia, Russian Federation, South Africa, the United Kingdom, Ukraine, Urals, and Vienna.
The INMM also has 16 student chapters that offer opportunities including participation in a mentor program, meetings and workshops, publication subscriptions, and professional networking. Student chapters currently exist at Federal University of Rio de Janeiro, Georgia Institute of Technology, Idaho State University, Ibn Tofail University, Jordan University of Science and Technology, Mercyhurst College Institute for Intelligence Studies, Middlebury Institute of International Studies at Monterey, North Carolina State University and other Triangle Area universities, Oregon State University, Pandit Deendayal Petroleum University, Pennsylvania State University, Texas A&M University, the University of Michigan, University of Missouri, University of New Mexico, University of Tennessee, University of Utah,
University of Washington, and Universitas Gadjah Mada
Meetings and workshops
INMM holds an annual meeting, an annual Spent Fuel Management Seminar, and a number of other workshops each year. These educational/networking events allow professionals in nuclear materials management to learn new strategies, keep abreast of the science and technology, and to meet with colleagues from around the world. In June 2005, INMM held two workshops in Prague, Czech Republic, sponsored by the Nuclear Threat Initiative (NTI).
Publications
INMM publishes the Journal of Nuclear Materials Management, a quarterly, peer-reviewed technical journal. In addition, the "Communicator", online newsletter is posted three times annually.
American physicist William Higginbotham served as technical editor of the Journal from 1974 until his death in 1994.
See also
American National Standards Institute
U.S. Department of Energy
U.S. Nuclear Regulatory Commission
Brazilian-Argentine Agency for Accounting and Control of Nuclear Materials (ABACC)
European Nuclear Society
International Atomic Energy Agency
American Nuclear Society
Nuclear Threat Initiative
World Nuclear Association
Nuclear Energy Institute
References
External links
Institute of Nuclear Materials Management
World Institute for Nuclear Security
International nuclear energy organizations
Nuclear materials
Nuclear proliferation
Nuclear technology
Professional associations based in the United States
Companies based in Deerfield, Illinois
Organizations based in Illinois | Institute of Nuclear Materials Management | [
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"Nuclear physics",
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21,482,414 | https://en.wikipedia.org/wiki/Architectural%20drawing | An architectural drawing or architect's drawing is a technical drawing of a building (or building project) that falls within the definition of architecture. Architectural drawings are used by architects and others for a number of purposes: to develop a design idea into a coherent proposal, to communicate ideas and concepts, to convince clients of the merits of a design, to assist a building contractor to construct it based on design intent, as a record of the design and planned development, or to make a record of a building that already exists.
Architectural drawings are made according to a set of conventions, which include particular views (floor plan, section etc.), sheet sizes, units of measurement and scales, annotation and cross referencing.
Historically, drawings were made in ink on paper or similar material, and any copies required had to be laboriously made by hand. The twentieth century saw a shift to drawing on tracing paper so that mechanical copies could be run off efficiently. The development of the computer had a major impact on the methods used to design and create technical drawings, making manual drawing almost obsolete, and opening up new possibilities of form using organic shapes and complex geometry. Today the vast majority of drawings are created using CAD software.
History
The oldest architectural elevation drawing was found in a piece of white terracotta crucibles unearthed in China, dated 7400 years ago. It shows 2 stilted watch towers (or light houses) with spiral staircase above water.
Size and scale
The size of drawings reflects the materials available and the size that is convenient to transport – rolled up or folded, laid out on a table, or pinned up on a wall. The drafting process may impose limitations on the size that is realistically workable. Sizes are determined by a consistent paper size system, according to local usage. Normally the largest paper size used in modern architectural practice is ISO A0 () or in the USA Arch E () or Large E size ().
Architectural drawings are drawn to scale so that relative sizes are correctly represented. The scale is chosen both to ensure the whole building will fit on the chosen sheet size and to show the required amount of detail. On the scale of one-eighth of an inch to one foot (1:96) or the metric equivalent of 1 to 100, walls are typically shown as simple outlines corresponding to the overall thickness. At a larger scale, half an inch to one foot (1:24) or the nearest common metric equivalent 1 to 20, the layers of different materials that make up the wall construction are shown. Construction details are drawn to a larger scale, in some cases full size (1 to 1 scale).
Scale drawings enable dimensions to be "read" off the drawing, i.e. measured directly. Imperial scales (feet and inches) are equally readable using an ordinary ruler. On a one-eighth inch to one-foot scale drawing, the one-eighth divisions on the ruler can be read off as feet. Architects normally use a scale ruler with different scales marked on each edge. A third method, used by builders in estimating, is to measure directly off the drawing and multiply by the scale factor.
Dimensions can be measured off drawings made on a stable medium such as vellum. All processes of reproduction introduce small errors, especially now that different copying methods mean that the same drawing may be re-copied, or copies made in several different ways. Consequently, dimensions need to be written ("figured") on the drawing. The disclaimer "Do not scale off dimensions" is commonly inscribed on architects' drawings, to guard against errors arising in the copying process.
Standard views used in architectural drawing
This section deals with the conventional views used to represent a building or structure. See the Types of architectural drawing section below for drawings classified according to their purpose.
Floor plan
A floor plan is the most fundamental architectural diagram, a view from above showing the arrangement of spaces in a building in the same way as a map, but showing the arrangement at a particular level of a building. Technically it is a horizontal section cut through a building (conventionally at four feet / one metre and twenty centimetres above floor level), showing walls, windows and door openings, and other features at that level. The plan view includes anything that could be seen below that level: the floor, stairs (but only up to the plan level), fittings, and sometimes furniture. Objects above the plan level (e.g. beams overhead) can be indicated as dashed lines.
Geometrically, plan view is defined as a vertical orthographic projection of an object onto a horizontal plane, with the horizontal plane cutting through the building.
Site plan
A site plan is a specific type of plan, showing the whole context of a building or group of buildings. A site plan shows property boundaries and means of access to the site, and nearby structures if they are relevant to the design. For a development on an urban site, the site plan may need to show adjoining streets to demonstrate how the design fits into the urban fabric. Within the site boundary, the site plan gives an overview of the entire scope of work. It shows the buildings (if any) already existing and those that are proposed, usually as a building footprint; roads, parking lots, footpaths, hard landscaping, trees, and planting. For a construction project, the site plan also needs to show all the services connections: drainage and sewer lines, water supply, electrical and communications cables, exterior lighting, etc.
Site plans are commonly used to represent a building proposal prior to detailed design: drawing up a site plan is a tool for deciding both the site layout and the size and orientation of proposed new buildings. A site plan is used to verify that a proposal complies with local development codes, including restrictions on historical sites. In this context the site plan forms part of a legal agreement, and there may be a requirement for it to be drawn up by a licensed professional: architect, engineer, landscape architect or land surveyor.
Elevation
An elevation is a view of a building seen from one side, a flat representation of one façade. This is the most common view used to describe the external appearance of a building. Each elevation is labelled in relation to the compass direction it faces, e.g. looking toward the north you would be seeing the southern elevation of the building. Buildings are rarely a simple rectangular shape in plan, so a typical elevation may show all the parts of the building that are seen from a particular direction.
Geometrically, an elevation is a horizontal orthographic projection of a building onto a vertical plane, the vertical plane normally being parallel to one side of the building.
Architects also use the word elevation as a synonym for façade, so the "north elevation" is the north-facing wall of the building.
Cross section
A cross section, also simply called a section, represents a vertical plane cut through the object, in the same way as a floor plan is a horizontal section viewed from the top. In the section view, everything cut by the section plane is shown as a bold line, often with a solid fill to show objects that are cut through, and anything seen beyond generally shown in a thinner line. Sections are used to describe the relationship between different levels of a building. In the Observatorium drawing illustrated here, the section shows the dome which can be seen from the outside, a second dome that can only be seen inside the building, and the way the space between the two accommodates a large astronomical telescope: relationships that would be difficult to understand from plans alone.
A sectional elevation is a combination of a cross section, with elevations of other parts of the building seen beyond the section plane.
Geometrically, a cross section is a horizontal orthographic projection of a building on to a vertical plane, with the vertical plane cutting through the building.
Isometric and axonometric projections
Isometric and axonometric projections are a simple way of representing a three dimensional object, keeping the elements to scale and showing the relationship between several sides of the same object, so that the complexities of a shape can be clearly understood.
There is some confusion over the distinction between the terms isometric and axonometric. "Axonometric is a word that has been used by architects for hundreds of years. Engineers use the word axonometric as a generic term to include isometric, diametric and trimetric drawings." This article uses the terms in the architecture-specific sense.
Despite fairly complex geometrical explanations, for the purposes of practical drafting the difference between isometric and axonometric is simple (see diagram above). In both, the plan is drawn on a skewed or rotated grid, and the verticals are projected vertically on the page. All lines are drawn to scale so that relationships between elements are accurate. In many cases a different scale is required for different axes, and again this can be calculated but in practice was often simply estimated by eye.
An isometric uses a plan grid at 30 degrees from the horizontal in both directions, which distorts the plan shape. Isometric graph paper can be used to construct this kind of drawing. This view is useful to explain construction details (e.g. three dimensional joints in joinery). The isometric was the standard view until the mid twentieth century, remaining popular until the 1970s, especially for textbook diagrams and illustrations.
Cabinet projection is similar, but only one axis is skewed, the others being horizontal and vertical. Originally used in cabinet making, the advantage is that a principal side (e.g. a cabinet front) is displayed without distortion, so only the less important sides are skewed. The lines leading away from the eye are drawn at a reduced scale to lessen the degree of distortion. The cabinet projection is seen in Victorian engraved advertisements and architectural textbooks, but has virtually disappeared from general use.
An axonometric uses a 45-degree plan grid, which keeps the original orthogonal geometry of the plan. The great advantage of this view for architecture is that the draftsman can work directly from a plan, without having to reconstruct it on a skewed grid. In theory the plan should be set at 45 degrees, but this introduces confusing coincidences where opposite corners align. Unwanted effects can be avoided by rotating the plan while still projecting vertically. This is sometimes called a planometric or plan oblique view, and allows freedom to choose any suitable angle to present the most useful view of an object.
Traditional drafting techniques used 30–60 and 45 degree set squares, and that determined the angles used in these views. Once the adjustable square became common those limitations were lifted.
The axonometric gained in popularity in the twentieth century, not just as a convenient diagram but as a formal presentation technique, adopted in particular by the Modern Movement. Axonometric drawings feature prominently in the influential 1970's drawings of Michael Graves, James Stirling and others, using not only straightforward views but worms-eye view, unusually and exaggerated rotations of the plan, and exploded elements.
Detail drawings
Detail drawings show a small part of the construction at a larger scale, to show how the component parts fit together. They are also used to show small surface details, for example decorative elements. Section drawings at large scale are a standard way of showing building construction details, typically showing complex junctions (such as floor to wall junction, window openings, eaves and roof apex) that cannot be clearly shown on a drawing that includes the full height of the building. A full set of construction details needs to show plan details as well as vertical section details. One detail is seldom produced in isolation: a set of details shows the information needed to understand the construction in three dimensions. Typical scales for details are 1/10, 1/5 and full size.
In traditional construction, many details were so fully standardized, that few detail drawings were required to construct a building. For example, the construction of a sash window would be left to the carpenter, who would fully understand what was required, but unique decorative details of the façade would be drawn up in detail. In contrast, modern buildings need to be fully detailed because of the proliferation of different products, methods and possible solutions.
Architectural perspective
Perspective in drawing is an approximate representation on a flat surface of an image as it is perceived by the eye. The key concepts here are:
Perspective is the view from a particular fixed viewpoint.
Horizontal and vertical edges in the object are represented by horizontals and verticals in the drawing.
Lines leading away into the distance appear to converge at a vanishing point.
All horizontals converge to a point on the horizon, which is a horizontal line at eye level.
Verticals converge to a point either above or below the horizon.
The basic categorization of artificial perspective is by the number of vanishing points:
One-point perspective where objects facing the viewer are orthogonal, and receding lines converge to a single vanishing point.
Two-point perspective reduces distortion by viewing objects at an angle, with all the horizontal lines receding to one of two vanishing points, both located on the horizon.
Three-point perspective introduces additional realism by making the verticals recede to a third vanishing point, which is above or below depending upon whether the view is seen from above or below.
The normal convention in architectural perspective is to use two-point perspective, with all the verticals drawn as verticals on the page.
Three-point perspective gives a casual, photographic snapshot effect. In professional architectural photography, conversely, a view camera or a perspective control lens is used to eliminate the third vanishing point, so that all the verticals are vertical on the photograph, as with the perspective convention. This can also be done by digital manipulation of a photograph taken with a standard lens.
Aerial perspective is a technique in painting, for indicating distance by approximating the effect of the atmosphere on distant objects. In daylight, as an ordinary object gets further from the eye, its contrast with the background is reduced, its color saturation is reduced, and its color becomes more blue. Not to be confused with aerial view or bird's eye view, which is the view as seen (or imagined) from a high vantage point. In J M Gandy's perspective of the Bank of England (see illustration at the beginning of this article), Gandy portrayed the building as a picturesque ruin in order to show the internal plan arrangement, a precursor of the cutaway view.
A montage image is produced by superimposing a perspective image of a building on to a photographic background. Care is needed to record the position from which the photograph was taken, and to generate the perspective using the same viewpoint. This technique is popular in computer visualization, where the building can be photorealistically rendered, and the final image is intended to be almost indistinguishable from a photograph.
Sketches and diagrams
A sketch is a rapidly executed freehand drawing, a quick way to record and develop an idea, not intended as a finished work. A diagram could also be drawn freehand but deals with symbols, to develop the logic of a design. Both can be worked up into a more presentable form and used to communicate the principles of a design.
In architecture, the finished work is expensive and time consuming, so it is important to resolve the design as fully as possible before construction work begins. Complex modern buildings involve a large team of different specialist disciplines, and communication at the early design stages is essential to keep the design moving towards a coordinated outcome. Architects (and other designers) start investigating a new design with sketches and diagrams, to develop a rough design that provides an adequate response to the particular design problems.
There are two basic elements to a building design, the aesthetic and the practical. The aesthetic element includes the layout and visual appearance, the anticipated feel of the materials, and cultural references that will influence the way people perceive the building. Practical concerns include space allocated for different activities, how people enter and move around the building, daylight and artificial lighting, acoustics, traffic noise, legal matters and building codes, and many other issues. While both aspects are partly a matter of customary practice, every site is different. Many architects actively seek innovation, thereby increasing the number of problems to be resolved.
Architectural legend often refers to designs made on the back of an envelope or on a napkin. Initial thoughts are important, even if they have to be discarded along the way, because they provide the central idea around which the design can develop. Although a sketch is inaccurate, it is disposable and allows for freedom of thought, for trying different ideas quickly. Choice becomes sharply reduced once the design is committed to a scale drawing, and the sketch stage is almost always essential.
Diagrams are mainly used to resolve practical matters. In the early phases of the design architects use diagrams to develop, explore, and communicate ideas and solutions. They are essential tools for thinking, problem solving, and communication in the design disciplines. Diagrams can be used to resolve spatial relationships, but they can also represent forces and flows, e.g. the forces of sun and wind, or the flows of people and materials through a building.
An exploded view diagram shows component parts dis-assembled in some way, so that each can be seen on its own. These views are common in technical manuals, but are also used in architecture, either in conceptual diagrams or to illustrate technical details. In a cutaway view parts of the exterior are omitted to show the interior, or details of internal construction. Although common in technical illustration, including many building products and systems, the cutaway is in fact little-used in architectural drawing.
Types
Architectural drawings are produced for a specific purpose, and can be classified accordingly. Several elements are often included on the same sheet, for example a sheet showing a plan together with the principal façade.
Presentation drawings
Drawings intended to explain a scheme and to promote its merits. Working drawings may include tones or hatches to emphasize different materials, but they are diagrams, not intended to appear realistic. Basic presentation drawings typically include people, vehicles and trees, taken from a library of such images, and are otherwise very similar in style to working drawings. Rendering is the art of adding surface textures and shadows to show the visual qualities of a building more realistically. An architectural illustrator or graphic designer may be employed to prepare specialist presentation images, usually perspectives or highly finished site plans, floor plans and elevations etc.
Survey drawings
Measured drawings of existing land, structures and buildings. Architects need an accurate set of survey drawings as a basis for their working drawings, to establish exact dimensions for the construction work. Surveys are usually measured and drawn up by specialist land surveyors.
Record drawings
Historically, architects have made record drawings in order to understand and emulate the great architecture known to them. In the Renaissance, architects from all over Europe studied and recorded the remains of the Roman and Greek civilizations, and used these influences to develop the architecture of the period. Records are made both individually, for local purposes, and on a large scale for publication. Historic surveys worth referring to include:
Colen Campbell's Vitruvius Brittanicus, illustrations of English buildings by Inigo Jones and Sir Christopher Wren, as well as Campbell himself and other prominent architects of the era.
The Survey of London, founded in 1894 by Charles Robert Ashbee and now available through English Heritage. A record of notable streets and individual buildings in the former County of London.
Historic American Buildings Survey, records of notable buildings drawn up during the 1930s Depression, this collection is held by the Library of Congress and is available copyright-free on the internet.
Record drawings are also used in construction projects, where "as-built" conditions of the completed building are documented to take account of all the variations made during the course of construction.
Working drawings
A comprehensive set of drawings used in a building construction project: these will include not only architect's drawings, but structural and other engineering drawings as well. Working drawings logically subdivide into location, assembly and component drawings.
Location drawings, also called general arrangement drawings, include floor plans, sections and elevations: they show where the construction elements are located.
Assembly drawings show how the different parts are put together. For example, a wall detail will show the layers that make up the construction, how they are fixed to structural elements, how to finish the edges of openings, and how prefabricated components are to be fitted.
Component drawings enable self-contained elements e.g. windows and doorsets, to be fabricated in a workshop, and delivered to site complete and ready for installation. Larger components may include roof trusses, cladding panels, cupboards and kitchens. Complete rooms, especially hotel bedrooms and bathrooms, may be made as prefabricated pods complete with internal decorations and fittings.
Formerly, working drawings would typically combine plans, sections, elevations and some details to provide a complete explanation of a building on one sheet. That was possible because little detail was included, the building techniques involved being common knowledge amongst building professionals. Modern working drawings are much more detailed and it is standard practice to isolate select areas of the project on separate sheets. Notes included on drawings are brief, referring to standardized specification documents for more information. Understanding the layout and construction of a modern building involves studying an often-sizeable set of drawings and documents.
Drafting
Until the latter part of the 20th century, all architectural drawings were manually produced, if not by the architects, then by trained (but less skilled) draftsmen (or drafters), who did not generate the design, but did make many of the less important decisions. This system has continued with CAD drafting: many design architects have little or no knowledge of CAD software programmes, relying upon others to take their designs beyond the sketch stage. Draftsmen often specialize in a type of structure, such as residential or commercial, or in a type of construction: timber frame, reinforced concrete, prefabrication, etc.
The traditional tools of the architect were the drawing board or drafting table, T-square and set squares, protractor, compasses, pencil, and drawing pens of different types. Drawings were made on vellum, coated linen, and tracing paper. Lettering would either be done by hand, mechanically using a stencil, or a combination of the two. Ink lines were drawn with a ruling pen, a relatively sophisticated device similar to a dip-in pen, but with adjustable line width, capable of producing a very fine controlled line width. Ink pens had to be dipped into ink frequently. Draftsmen worked standing up, keeping the ink on a separate table to avoid spilling ink on the drawing.
Developments in the 20th century included the parallel motion drawing board, as well as more complex improvements on the basic T-square. The development of reliable technical drawing pens allowed for faster drafting and stenciled lettering. Letraset dry transfer lettering and half-tone sheets were popular from the 1970s until computers made those processes obsolete.
CGI and computer-aided design
Computer-aided design (generally referred to by the acronym CAD) is the use of computer software to create drawings. Today the vast majority of technical drawings of all kinds are made using CAD. Instead of drawing lines on paper, the computer records equivalent information electronically. There are many advantages to this system: repetition is reduced because complex elements can be copied, duplicated and stored for re-use. Errors can be deleted, and the speed of drafting allows many permutations to be tried before the design is finalized. On the other hand, CAD drawing encourages a proliferation of detail and increased expectations of accuracy, aspects which reduce the efficiency originally expected from the move to computerization.
Professional CAD software such as AutoCAD is complex and requires both training and experience before the operator becomes fully productive. Consequently, skilled CAD operators are often divorced from the design process. Simpler software such as SketchUp and Vectorworks allows for more intuitive drawing and is intended as a design tool.
CAD is used to create all kinds of drawings, from working drawings to photorealistic perspective views. Architectural renderings (also called visualizations) are made by creating a three-dimensional model using CAD. The model can be viewed from any direction to find the most useful viewpoints. Different software (for example Autodesk 3ds Max) is then used to apply color and texture to surfaces, and to represent shadows and reflections. The result can be accurately combined with photographic elements: people, cars, background landscape.
Building information modeling
Building information modeling (BIM) is the logical development of CAD drawing, a relatively new technology but fast becoming mainstream. The design team collaborates to create a three-dimensional computer model, and all plans and other two-dimensional views are generated directly from the model, ensuring spatial consistency. The key innovation here is to share the model via the internet, so that all the design functions (site survey, architecture, structure and services) can be integrated into a single model, or as a series of models associated with each specialism that are shared throughout the design development process. Some form of management, not necessarily by the architect, needs to be in place to resolve conflicting priorities. The starting point of BIM is spatial design, but it also enables components to be quantified and scheduled directly from the information embedded in the model.. Building information modelling can be characterized into 3 different levels ranging from 0–3. These levels represent BIM maturity and distinguishes the amount of cooperation in projects. They gauge information being shared throughout the whole process.
Level 0 is individualized with no collaboration. Individuals are working on their own CAD files separately and working using their own standards. These are known to be more traditional ways which are being phased out therefore no longer being used today.
Level 1 is a mixture of 3D and 2D work. Project teams are required to manage and share data amongst the team. Aspects such as "naming conventions" should be adopted.
Level 2 involves all team members using 3D models. Although they might not being using the same information, the built environment is shared through a similar file formats. This level also introduces construction sequencing and cost.
Level 3 involves working on a shared project model. The model exists in a central environment and can be modified by everyone. Conflicting information is reduced due to real time update on models. Later levels include sequencing components, cost estimation and accounting for upfront costs.
Parametric design
Parametric design is an example of computer intelligence rising in the field of architecture. It is the creation of complex relationships between models. Measurements in parametric design connect by scripts. Users can adjust and adapt their models based on measurements. Changing one measurement will affect other measurements based on the set parameters. The parametric design uses scalability and adjustments which involve complex organic shapes. It allows for the creation of forms that would not be possible with regular 3d modeling or would take copious amounts of time. Models can decrease production time, therefore, allowing for the time allotted to other times of the design process. An argument with parametric design is the question of practicality. At times, it is unsure whether or not these styles properly comply with users wants and needs. Real-life examples of parametric designs would be The Metropol Parasol in Seville or the Canton in Guangzhou China. These forms have a commonality with complex repetitive patterns which twist, bend and curve in dramatic ways. These lattices are unique and there is a complexity tied with how they look. This is coined as "parametricism" by Zaha Hadid which is a style based on digital animation techniques.
Architectural animation
An architectural animation is a short film showing how a proposed building will look: the moving image makes three-dimensional forms much easier to understand. An animation is generated from a series of hundreds or even thousands of still images, each made in the same way as an architectural visualization. A computer-generated building is created using a CAD programs, and that is used to create more or less realistic views from a sequence of viewpoints. The simplest animations use a moving viewpoint, while more complex animations can include moving objects: people, vehicles, and so on.
Digital era
Schools are producing well-versed architecture students who perform in computer assisted collaboration, construction automation and intelligent buildings which promise to have as much impact before the adaptation of technologies. It’s important to understand that architects are problem solvers and critical thinking which has been used since the dawn of man is still being carried on. The idea of innovation, responsiveness and critical thinking will never be "phased out" and always relevant today. Although pure drafting, which involves manually drawing plans for construction, is not being used as often because of CAD, they are training architects to exercise human-centered designers and to dive deeper into culture to ultimately understand clientele. Human-centered design involves the human perspective in all steps of the design process. The unpredictability and complexity of humans is unmatched with any pre-programmed systems.
Virtual reality
Virtual reality in architectural projects helps designers understand spaces from a cognitive perspective. VR stands for virtual reality and explains an experience in a world that doesn't exist. Virtual reality creates an experience generated by a computer program. The use of motion tracking allows for quick manipulation. It creates an individual, secluded experience. Architecture firms are using this as a tool to allow employees to learn and create a more engaging experience for both clients and employees. Benefits of VR for architecture include: low start-up costs, gaining a competitive edge, avoiding revision, and the duplication of real-world scenarios. By placing a client into a virtual world, the feedback is often more straightforward, as the client can walk through the environment, according to their needs and aesthetic choices.
Online practices
Due to COVID-19. architecture firms have increasingly shifted to a digital environment for collaboration. Video conferencing is proving to be a popular way of meeting with clients and simulating the studio environment. Collaboration and communication using programs like Zoom are common consistently being used. Since the beginning of the epidemic, people are expected to be increasingly well versed with technology. Although coordination is often difficult, programs like BIM help improve workflow between both architects clients. However, relationships with clients are harder to facilitate because clients are not able to touch or feel the work. Adaptation is critical as more and more programs are being implemented among the studio to support staff.
Architectural reprographics
Reprographics or reprography covers a variety of technologies, media, and support services used to make multiple copies of original drawings. Prints of architectural drawings are still sometimes called blueprints, after one of the early processes which produced a white line on blue paper. The process was superseded by the dye-line print system which prints black on white coated paper (Whiteprint). The standard modern processes are the ink-jet printer, laser printer and photocopier, of which the ink-jet and laser printers are commonly used for large-format printing. Although colour printing is now commonplace, it remains expensive above A3 size, and architect's working drawings still tend to adhere to the black and white / greyscale aesthetic.
See also
Architectural model
Copyright in architecture in the United States
Drawing
Engineering drawing
Layers in a standard architectural drawing
Linear scale
List of museums with major collections of European prints and drawings
Museum for Architectural Drawing, Berlin, Germany
Multiview orthographic projection
Preservation: Library and Archival Science
Structural drawing
Technical drawing
References
Drawing
Technical drawing | Architectural drawing | [
"Engineering"
] | 6,357 | [
"Design engineering",
"Construction",
"Civil engineering",
"Technical drawing",
"Architecture"
] |
25,864,995 | https://en.wikipedia.org/wiki/Proline%20rich%20protein | Proline-rich proteins (PRPs) are a class of intrinsically disordered proteins (IDPs) containing several repeats of a short proline-rich sequence.
Many tannin-consuming animals secrete a tannin-binding protein (mucin) in their saliva. Tannin-binding capacity of salivary mucin is directly related to its proline content. Advantages in using salivary proline-rich proteins (PRPs) to inactivate tannins are :
PRPs inactivate tannins to a greater extent than do dietary proteins; this results in reduced fecal nitrogen losses,
PRPs contain non specific nitrogen and nonessential amino acids; this makes them more convenient for an animal to exploit rather than using up valuable dietary protein.
Example of this class of protein is IB5, a human parotid salivary protein known to bind with polyphenols (binding responsible for the astringency mouth feel). Other examples include Proline-Rich 12, Proline-Rich Protein 30, and Proline-Rich Protein 21.
References | Proline rich protein | [
"Chemistry"
] | 221 | [
"Biochemistry stubs",
"Protein stubs"
] |
25,866,517 | https://en.wikipedia.org/wiki/C24H25ClN2O | {{DISPLAYTITLE:C24H25ClN2O}}
The molecular formula C24H25ClN2O (molar mass: 392.921 g/mol) may refer to:
RTI-336
RTI-371, or 3β-(4-Methylphenyl)-2β-[3-(4-chlorophenyl)isoxazol-5-yl]tropane
Molecular formulas | C24H25ClN2O | [
"Physics",
"Chemistry"
] | 101 | [
"Molecules",
"Set index articles on molecular formulas",
"Isomerism",
"Molecular formulas",
"Matter"
] |
25,870,519 | https://en.wikipedia.org/wiki/Sample%20and%20Data%20Relationship%20Format | The Sample and Data Relationship Format (SDRF) is part of the MAGE-TAB standard for communicating the results
of microarray investigations, including all information required for MIAME compliance.
An SDRF file is a tab-delimited file describing the relationships between samples, arrays, data, and other objects used or produced in a microarray investigation.
For simple experimental designs, constructing the SDRF file is straightforward, and even complex loop designs can be expressed in this format.
References
External links
MAGE-TAB — FGED (formerly MGED) Society
Sample and Data Relationship Format — U. S. National Cancer Institute's wiki
Minimum Information Standards
Microarrays | Sample and Data Relationship Format | [
"Chemistry",
"Materials_science",
"Biology"
] | 138 | [
"Biochemistry methods",
"Genetics techniques",
"Bioinformatics stubs",
"Microtechnology",
"Microarrays",
"Biotechnology stubs",
"Biochemistry stubs",
"Bioinformatics",
"Molecular biology techniques"
] |
25,872,275 | https://en.wikipedia.org/wiki/Markstein%20number | In combustion engineering and explosion studies, the Markstein number (named after George H. Markstein who first proposed the notion in 1951) characterizes the effect of local heat release of a propagating flame on variations in the surface topology along the flame and the associated local flame front curvature. There are two dimensionless Markstein numbers: one is the curvature Markstein number and the other is the flow-strain Markstein number. They are defined as:
where is the curvature Markstein length, is the flow-strain Markstein length and is the characteristic laminar flame thickness. The larger the Markstein length, the greater the effect of curvature on localised burning velocity. George H. Markstein (1911—2011) showed that thermal diffusion stabilized the curved flame front and proposed a relation between the critical wavelength for stability of the flame front, called the Markstein length, and the thermal thickness of the flame. Phenomenological Markstein numbers with respect to the combustion products are obtained by means of the comparison between the measurements of the flame radii as a function of time and the results of the analytical integration of the linear relation between the flame speed and either flame stretch rate or flame curvature. The burning velocity is obtained at zero stretch, and the effect of the flame stretch acting upon it is expressed by a Markstein length. Because both flame curvature and aerodynamic strain contribute to the flame stretch rate, there is a Markstein number associated with each of these components.
Clavin–Williams formula
The Markstein number with respect to the unburnt gas mixture was derived by Paul Clavin and Forman A. Williams in 1982, using activation energy asymptotics. The formula was extended to include temperature dependences on the thermal conductivities by Paul Clavin and Pedro Luis Garcia Ybarra in 1983. The Clavin–Williams formula is given by
where
Here
The function , in most cases, is simply given by , where , in which case, we have
In the constant transport coefficient assumption, , in which case, we have
where is the dilogarithm function.
See also
G equation
Matalon–Matkowsky–Clavin–Joulin theory
Clavin–Garcia equation
References
Combustion
Dimensionless numbers of fluid mechanics
Fluid dynamics
Dimensionless numbers of chemistry | Markstein number | [
"Chemistry",
"Engineering"
] | 466 | [
"Chemical engineering",
"Combustion",
"Piping",
"Dimensionless numbers of chemistry",
"Fluid dynamics"
] |
25,873,579 | https://en.wikipedia.org/wiki/Matriname | A matrilineal surname or matriname is a family name inherited from one's mother, and maternal grandmother, and so on whose line of descent is called a mother-line, mitochondrial line, or matriline. A matriname passed on to subsequent issue is unchanged, as compared to a matronymic, which is derived from the first name of each new mother.
The term "matriname" was introduced by Prof. Bryan Sykes in his book The Seven Daughters of Eve, stating that "We would then all have three names: a first name, a surname and a new one, a matriname perhaps."
The mitochondrial DNA (mtDNA) is inherited by biological motherhood whereas the matriname can be equally given after adoption or surrogacy.
Single surname
The usual lack of matrinames to pass on in patrilineal cultures makes traditional genealogy more difficult in the maternal line than in the paternal line. After all, father-line surnames originated partly to identify individuals clearly and were adopted partly for administrative reasons, and these patrinames help in searching for facts and documentation from centuries ago. Patrinames are stable identity-surnames, surnames which identify an individual, whether now or in the past or future; matrinames similarly are identity-surnames for women.
In the 1979 Convention on the Elimination of Discrimination Against Women (CEDAW) the UN holds the view, in item (g) of its Article 16, that women and men, and specifically wife and husband, have the same rights to choose a "family name" as well as a "profession" and an "occupation". These three rights are a small part of the document's long list of rights related to gender equality meant to ensure women have equal opportunities to men. However, the United States has signed but not yet ratified this UN Convention.
Sykes argues choosing a "family name", or surname, should mean combining a matriname with a patriname, to avoid discriminating against either women or men.
Some cultures have no surnames at all. If a culture has these then to not discriminate it combines both, as mentioned above; that is, the matriname and the patriname are both given in each child's birth record.
Note that one's resulting birth surname is one's legal surname, unless one changes the latter.
In several purely patrilineal cultures, including most of Europe, women traditionally change to their husband's patriname at marriage: see married and maiden names and name change.
Double surname
Some cultures use both paternal and maternal surname, such as Spanish naming customs, Portuguese names, and the naming customs of Hispanic America. The patrilineal surname—patriname—taken from the mother in these patrilineal cultures does not qualify as a matriname. Instead, this Hispanic practice uses the maternal patriname.
Double surnames were discussed in The Seven Daughters of Eve. Double surnames were also used by one English family, along with the matriname "Phythian".
In this case the mother has the birth double surname "Phythian-Adams", and the father has birth double surname "??-Monkhouse". They both choose to retain their birth double surnames unchanged throughout their lives. They agree to denominate all of their daughters and sons with the birth double surname "Phythian-Monkhouse": The mother passes on her matriname (and mtDNA), and symmetrically, the father passes on his patriname. All of their sons have the Y-DNA of and, accordingly, the patriname "Monkhouse" of their patriline, while all of the daughters have both the mtDNA of and, accordingly, the matriname "Phythian" of their matriline. (Note that most societies give all children of a family the same surname, as in this example.) Each person has only one identity-surname, which in this example is either "Phythian" or "Monkhouse". The identity-surname of each is stable throughout life and always half of whatever double surname(s) he or she assumes throughout life, including at birth and marriage(s).
The parents in this example share this one family name, "Phythian-Monkhouse".
One's own identity-surname (here, the matriname "Phythian" or the patriname "Monkhouse") are always available as one's own usage name, such as in one's profession/vocation.
In summary, gender-symmetric single surnames are simpler and briefer, but if used alone, give different surnames for members of the different genders in a nuclear family. In the double system, all of the children in a nuclear family have the same double surname. Also, the system generally records on all legal documents the matriname and patriname, with both identity-surnames later aiding each gender in genealogy and other searches of historical records.
See also
Double surname
Extinction of surnames
Family name
Gender equality
List of matrilineal or matrilocal societies
List of people who adopted matrilineal surnames
Lucy Stone League, on the topic of identity-surnames
Maiden and married names
Matrilineality
Patrilineality
Patronymic surname
Women's rights
Notes
References
External links
(on the topic of identity-surnames)
Gender equality
Kinship and descent
Matriarchy
Surname | Matriname | [
"Biology"
] | 1,132 | [
"Behavior",
"Human behavior",
"Kinship and descent"
] |
3,854,878 | https://en.wikipedia.org/wiki/Microlensing%20Observations%20in%20Astrophysics | Microlensing Observations in Astrophysics (MOA) is a collaborative project between researchers in New Zealand and Japan, led by Professor Yasushi Muraki of Nagoya University. They use microlensing to observe dark matter, extra-solar planets, and stellar atmospheres from the Southern Hemisphere. The group concentrates especially on the detection and observation of gravitational microlensing events of high magnification, of order 100 or more, as these provide the greatest sensitivity to extrasolar planets. They work with other groups in Australia, the United States and elsewhere. Observations are conducted at New Zealand's Mt. John University Observatory using a reflector telescope built for the project.
In September 2020, astronomers using microlensing techniques reported the detection, for the first time, of an earth-mass rogue planet unbounded by any star, and free floating in the Milky Way galaxy. In January 2022 in collaboration with Optical Gravitational Lensing Experiment (OGLE) they reported in a preprint the first rogue BH while there have been others candidates this is the most solid detection so far as their technique allowed to measure not only the amplification of light but also its deflection by the BH from the microlensing data.
MOA telescope mirror images
Planets discovered
The following planets have been announced by this survey, some in conjunction with other surveys.
See also
Optical Gravitational Lensing Experiment or OGLE, a similar microlensing survey
List of extrasolar planets
References
External links
MOA website
MicroFUN - Microlensing Follow-Up Network
Astronomical surveys
Experiments for dark matter search
Gravitational lensing
Exoplanet search projects | Microlensing Observations in Astrophysics | [
"Physics",
"Astronomy"
] | 332 | [
"Dark matter",
"Exoplanet search projects",
"Astronomical surveys",
"Unsolved problems in physics",
"Works about astronomy",
"Experiments for dark matter search",
"Astronomy projects",
"Astronomical objects"
] |
3,855,724 | https://en.wikipedia.org/wiki/No-slip%20condition | In fluid dynamics, the no-slip condition is a boundary condition which enforces that at a solid boundary, a viscous fluid attains zero bulk velocity. This boundary condition was first proposed by Osborne Reynolds, who observed this behaviour while performing his influential pipe flow experiments. The form of this boundary condition is an example of a Dirichlet boundary condition.
In the majority of fluid flows relevant to fluids engineering, the no-slip condition is generally utilised at solid boundaries. This condition often fails for systems which exhibit non-Newtonian behaviour. Fluids which this condition fails includes common food-stuffs which contain a high fat content, such as mayonnaise or melted cheese.
Physical justification
The no-slip condition is an empirical assumption that has been useful in modelling many macroscopic experiments. It was one of three alternatives that were the subject of contention in the 19th century, with the other two being the stagnant-layer (a thin layer of stationary fluid on which the rest of the fluid flows) and the partial slip (a finite relative velocity between solid and fluid) boundary conditions. However, by the start of the 20th century it became generally accepted that slip, if it did exist, was too small to be measured. The stagnant layer was deemed too thin, and the partial slip was considered to have negligible effect on the macroscopic scale.
While not derived from first principles, two possible mechanisms have been offered to explain the no-slip behaviour, with one or the other being dominant under different conditions. The first contends that the surface roughness is responsible for bringing the fluid to rest through viscous dissipation past the surface irregularities. The second is related to the attraction of fluid molecules to the surface. Particles close to a surface do not move along with a flow when adhesion is stronger than cohesion. At the fluid-solid interface, the force of attraction between the fluid particles and solid particles (adhesive forces) is greater than that between the fluid particles (cohesive forces). This force imbalance causes the fluid velocity to be zero adjacent to the solid surface, with the velocity approaching that of the stream as distance from the surface increases.
When a fluid is at rest, its molecules move constantly with a random velocity. When the fluid begins to flow, an average flow velocity, sometimes called the bulk velocity, is added to the random motion. At the boundary between the fluid and a solid surface, the attraction between the fluid molecules and the surface atoms is strong enough to slow the bulk velocity to zero. Consequently, the bulk velocity of the fluid decreases from its value away from the wall to zero at the wall.
Slip behaviour
As the no-slip condition was an empirical observation, there are physical scenarios in which it fails. For sufficiently rarefied flows, including flows of high altitude atmospheric gases and for microscale flows, the no-slip condition is inaccurate. For such examples, this change is driven by an increasing Knudsen number, which implies increasing rarefaction, and gradual failure of the continuum approximation. The first-order expression, which is often used to model fluid slip, is expressed as (also known as the Navier slip boundary condition)
where is the coordinate normal to the wall, is the mean free path and is some constant known as the slip coefficient, which is approximately of order 1. Alternatively, one may introduce as the slip length. Some highly hydrophobic surfaces, such as carbon nanotubes with added radicals, have also been observed to have a nonzero but nanoscale slip length.
While the no-slip condition is used almost universally in modeling of viscous flows, it is sometimes neglected in favor of the 'no-penetration condition' (where the fluid velocity normal to the wall is set to the wall velocity in this direction, but the fluid velocity parallel to the wall is unrestricted) in elementary analyses of inviscid flow, where the effect of boundary layers is neglected.
The no-slip condition poses a problem in viscous flow theory at contact lines: places where an interface between two fluids meets a solid boundary. Here, the no-slip boundary condition implies that the position of the contact line does not move, which is not observed in reality. Analysis of a moving contact line with the no slip condition results in infinite stresses that can't be integrated over. The rate of movement of the contact line is believed to be dependent on the angle the contact line makes with the solid boundary, but the mechanism behind this is not yet fully understood.
See also
Boundary layer
Wind gradient
Shear stress
Shell balance
References
External links
No-Slip Condition at ScienceWorld
How a fluid behaves near a surface
chimney flow plot movie
Fluid dynamics
Boundary conditions | No-slip condition | [
"Chemistry",
"Engineering"
] | 953 | [
"Piping",
"Chemical engineering",
"Fluid dynamics"
] |
3,859,232 | https://en.wikipedia.org/wiki/Isaiah%20Shavitt | Isaiah Shavitt was a Polish-born Israeli and American theoretical chemist.
He was born Isaiah Kruk on July 29, 1925, in Kutno, Poland but his family moved to what would become Israel in 1929. After undergraduate degrees in chemistry (1950) and chemical engineering (1951) from the Technion in Haifa, he started a Ph.D. in experimental physical chemistry, but shortly after traveled to Cambridge University on a British Council Scholarship and completed his Ph.D. (1957) under the aegis of pioneering computational chemist S. Francis Boys.
Following postdoctoral work with Joseph O. Hirschfelder, a stint as a temporary assistant professor at Brandeis University, and further postdoctoral research with Martin Karplus, he became a professor at his alma mater in 1962. In 1967 he moved to a senior research position at Battelle Memorial Institute in Columbus, Ohio, United States. In 1968 he also became a part-time faculty member at the department of chemistry at Ohio State University and moved there full-time in 1981. In 1994 he retired from this position and continued part-time as an emeritus professor. Until his death he was also an adjunct professor in the department of chemistry at the University of Illinois at Urbana-Champaign, US.
Shavitt's landmark achievements include being responsible for two of the first applications of the then newly available computer to chemistry; developing the Gaussian transform method for calculating multicenter integrals of Slater-type orbitals; coining the concept of contracted Gaussian-type orbitals; the GUGA (Graphical Unitary Group Approach) to fast configuration interaction calculations; and major contributions to coupled cluster theory.
He is one of the founding authors of the COLUMBUS suite of ab initio computational chemistry programs.
An International Conference, entitled Molecular Quantum Mechanics: Methods and Applications" was held in memory of S. Francis Boys and in honor of Isaiah Shavitt in September, 1995 at St Catharine's College, Cambridge, and the proceedings published as a special issue of the Journal of Physical Chemistry.
He was a member of the International Academy of Quantum Molecular Science.
Shavitt died at the age of 87 on Dec. 8, 2012 at Carle Foundation Hospital, Urbana.
References
See also
I.Shavitt in methods of computational Physics vol.2 Academic(1963)
Publications
The Gaussian Function (1963)
The Method of Configuration Interaction (1977)
The Graphical Unitary Group Approach (1981)
Supercomputers and Chemistry (1981)
The Unitary Group (1983)
The Treatment of Electron Correlations (1984)
Unitary Group Approach (1988)
I. Shavitt and R. J. Bartlett, "Many-Body Methods in Chemistry and Physics" (Cambridge University Press, 2009), https://www.amazon.com/Many-Body-Methods-Chemistry-Physics-Coupled-Cluster/dp/052181832X/
External links
A biography by Uzi Kaldor and Russell M. Pitzer.
His International Academy of Quantum Molecular Science web page
1925 births
2012 deaths
Members of the International Academy of Quantum Molecular Science
American chemists
Theoretical chemists
Ohio State University faculty
Polish emigrants to Mandatory Palestine
People from Kutno
Technion – Israel Institute of Technology alumni
Alumni of the University of Cambridge
Academic staff of Technion – Israel Institute of Technology
University of Illinois Urbana-Champaign faculty
Israeli expatriates in the United Kingdom
Israeli emigrants to the United States
Fellows of the American Physical Society | Isaiah Shavitt | [
"Chemistry"
] | 703 | [
"Quantum chemistry",
"Theoretical chemistry",
"Theoretical chemists",
"Physical chemists"
] |
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