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1,522,626 | https://en.wikipedia.org/wiki/Wigner%E2%80%93Seitz%20cell | The Wigner–Seitz cell, named after Eugene Wigner and Frederick Seitz, is a primitive cell which has been constructed by applying Voronoi decomposition to a crystal lattice. It is used in the study of crystalline materials in crystallography.
The unique property of a crystal is that its atoms are arranged in a regular three-dimensional array called a lattice. All the properties attributed to crystalline materials stem from this highly ordered structure. Such a structure exhibits discrete translational symmetry. In order to model and study such a periodic system, one needs a mathematical "handle" to describe the symmetry and hence draw conclusions about the material properties consequent to this symmetry. The Wigner–Seitz cell is a means to achieve this.
A Wigner–Seitz cell is an example of a primitive cell, which is a unit cell containing exactly one lattice point. For any given lattice, there are an infinite number of possible primitive cells. However there is only one Wigner–Seitz cell for any given lattice. It is the locus of points in space that are closer to that lattice point than to any of the other lattice points.
A Wigner–Seitz cell, like any primitive cell, is a fundamental domain for the discrete translation symmetry of the lattice. The primitive cell of the reciprocal lattice in momentum space is called the Brillouin zone.
Overview
Background
The concept of Voronoi decomposition was investigated by Peter Gustav Lejeune Dirichlet, leading to the name Dirichlet domain. Further contributions were made from Evgraf Fedorov, (Fedorov parallelohedron), Georgy Voronoy (Voronoi polyhedron), and Paul Niggli (Wirkungsbereich).
The application to condensed matter physics was first proposed by Eugene Wigner and Frederick Seitz in a 1933 paper, where it was used to solve the Schrödinger equation for free electrons in elemental sodium. They approximated the shape of the Wigner–Seitz cell in sodium, which is a truncated octahedron, as a sphere of equal volume, and solved the Schrödinger equation exactly using periodic boundary conditions, which require at the surface of the sphere. A similar calculation which also accounted for the non-spherical nature of the Wigner–Seitz cell was performed later by John C. Slater.
There are only five topologically distinct polyhedra which tile three-dimensional space, . These are referred to as the parallelohedra. They are the subject of mathematical interest, such as in higher dimensions. These five parallelohedra can be used to classify the three dimensional lattices using the concept of a projective plane, as suggested by John Horton Conway and Neil Sloane. However, while a topological classification considers any affine transformation to lead to an identical class, a more specific classification leads to 24 distinct classes of voronoi polyhedra with parallel edges which tile space. For example, the rectangular cuboid, right square prism, and cube belong to the same topological class, but are distinguished by different ratios of their sides. This classification of the 24 types of voronoi polyhedra for Bravais lattices was first laid out by Boris Delaunay.
Definition
The Wigner–Seitz cell around a lattice point is defined as the locus of points in space that are closer to that lattice point than to any of the other lattice points.
It can be shown mathematically that a Wigner–Seitz cell is a primitive cell. This implies that the cell spans the entire direct space without leaving any gaps or holes, a property known as tessellation.
Constructing the cell
The general mathematical concept embodied in a Wigner–Seitz cell is more commonly called a Voronoi cell, and the partition of the plane into these cells for a given set of point sites is known as a Voronoi diagram.
The cell may be chosen by first picking a lattice point. After a point is chosen, lines are drawn to all nearby lattice points. At the midpoint of each line, another line is drawn normal to each of the first set of lines. The smallest area enclosed in this way is called the Wigner–Seitz primitive cell.
For a 3-dimensional lattice, the steps are analogous, but in step 2 instead of drawing perpendicular lines, perpendicular planes are drawn at the midpoint of the lines between the lattice points.
As in the case of all primitive cells, all area or space within the lattice can be filled by Wigner–Seitz cells and there will be no gaps.
Nearby lattice points are continually examined until the area or volume enclosed is the correct area or volume for a primitive cell. Alternatively, if the basis vectors of the lattice are reduced using lattice reduction only a set number of lattice points need to be used. In two-dimensions only the lattice points that make up the 4 unit cells that share a vertex with the origin need to be used. In three-dimensions only the lattice points that make up the 8 unit cells that share a vertex with the origin need to be used.
Composite lattices
For composite lattices, (crystals which have more than one vector in their basis) each single lattice point represents multiple atoms. We can break apart each Wigner–Seitz cell into subcells by further Voronoi decomposition according to the closest atom, instead of the closest lattice point. For example, the diamond crystal structure contains a two atom basis. In diamond, carbon atoms have tetrahedral sp3 bonding, but since tetrahedra do not tile space, the voronoi decomposition of the diamond crystal structure is actually the triakis truncated tetrahedral honeycomb. Another example is applying Voronoi decomposition to the atoms in the A15 phases, which forms the polyhedral approximation of the Weaire–Phelan structure.
Symmetry
The Wigner–Seitz cell always has the same point symmetry as the underlying Bravais lattice. For example, the cube, truncated octahedron, and rhombic dodecahedron have point symmetry Oh, since the respective Bravais lattices used to generate them all belong to the cubic lattice system, which has Oh point symmetry.
Brillouin zone
In practice, the Wigner–Seitz cell itself is actually rarely used as a description of direct space, where the conventional unit cells are usually used instead. However, the same decomposition is extremely important when applied to reciprocal space. The Wigner–Seitz cell in the reciprocal space is called the Brillouin zone, which is used in constructing band diagrams to determine whether a material will be a conductor, semiconductor or an insulator.
See also
Delaunay triangulation
Coordination geometry
Crystal field theory
Wigner crystal
References
Crystallography
Mineralogy | Wigner–Seitz cell | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 1,371 | [
"Crystallography",
"Condensed matter physics",
"Materials science"
] |
1,522,637 | https://en.wikipedia.org/wiki/Beta%20Scorpii | Beta Scorpii (β Scorpii, abbreviated Beta Sco, β Sco) is a multiple star system in the southern zodiac constellation of Scorpius. It bore the traditional proper name of Acrab , though the International Astronomical Union now regards that name as applying only to the β Scorpii Aa component.
Components
Observed through a small telescope, Beta Scorpii appears as a binary star with a separation between the two components of 13.5 arcseconds and a combined apparent magnitude of 2.50. This pair, designated β¹ Scorpii and β² Scorpii, form the top branches of a hierarchy of six orbiting components.
Hierarchy of orbits in the β Scorpii system
β¹ Scorpii, the brighter of the pair, consists of two sub-components, designated β Scorpii A and β Scorpii B, orbiting at an angular separation of 0.3 arcseconds with an orbital period of 610 years. β Scorpii A is itself a spectroscopic binary, with the two components designated β Scorpii Aa (also named Acrab) and β Scorpii Ab. They are separated by 1.42 milliarcseconds and have an orbital period of 6.82 days.
β² Scorpii also has two sub-components, designated β Scorpii C and β Scorpii E, orbiting at an angular separation of 0.1328 arcseconds with an orbital period of 39 years. β Scorpii E in turn is a spectroscopic binary with components designated β Scorpii Ea and β Scorpii Eb and having an orbital period of 10.7 days.
Component β Scorpii D is the unrelated seventh magnitude star HD 144273, 520" away. Some authors have also referred to component Ab as D.
A companion to component B, β Scorpii G, has been proposed to account for missing mass in the system, but no further evidence of its existence has been found. β Scorpii F refers to a theorised companion to component E.
Nomenclature
β Scorpii (Latinised to Beta Scorpii) is the star's Bayer designation; β¹ and β² Scorpii, those of its two components. The designations of the sub-components - β Scorpii A, Aa, Ab, B, C, E, Ea and Eb - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
Beta Scorpii bore the traditional names Acrab, Akrab or Elacrab, all deriving from the Arabic name () al-'Aqrab 'the Scorpion' for the whole constellation, as well as Graffias , Italian for "the claws", a name it shared with Xi Scorpii.
In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Acrab for the component β Scorpii Aa on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning Room, refers to an asterism consisting of both of β1 Scorpii and β2 Scorpii, π Scorpii, ρ Scorpii and δ Scorpii, . Consequently, the Chinese name for both of β1 Scorpii and β2 Scorpii is (), "the Fourth Star of Room".
Namesake
USS Graffias (AF-29) was once a United States navy ship named after the star.
Properties
The β Scorpii system is a kinematic member of the Upper Scorpius subgroup of the Scorpius–Centaurus association, a group of thousands of young stars with mean age 11 million years at distance 470 light years (145 parsecs). Analysis of β1 Scorpii as a single star derived an evolutionary age between 9 and 12 million years, but analysis of the β Scorpii system as a whole suggest an age closer to 6 million years.
The two components of β Scorpii A are the most massive members of the system, and respectively. The combined spectral type is B1 V. The individual spectral types cannot be clearly measured, but are estimated to be B0.5 and B1.5. Component Aa is evolving slightly away from the zero age main sequence and its luminosity class is estimated to be intermediate between subgiant (IV) and main sequence (V). Component Ab has a main sequence luminosity class, a temperature of 26,400 K, and a luminosity of .
Component B is over 20 times fainter than the combined component A stars and a clear spectral type has not been measured. Its mass is estimated to be approximately .
Component C has a stellar classification of B2 V and a mass of . It has an effective surface temperature of 24,000 K, a radius of and a bolometric luminosity of .
Component E is determined to have a temperature of 13,000 K, radius of , and luminosity of . It is chemically peculiar, with high abundances of manganese and strontium. It is possibly a mercury-manganese (HgMn) star, but abundances of other metals are unexpectedly low.
Beta Scorpii is 1.01 degree from the ecliptic and can be occulted by the Moon and, very rarely, by planets. On December 9, 1906, it was occulted by Venus. The last occultation by a planet took place on 13 May 1971, by Jupiter.
In culture
Beta Scorpii appears on the flag of Brazil, symbolising the state of Maranhão.
References
External links
Beta Scorpii by Jim Kaler
Scorpii, Beta
Spectroscopic binaries
6
B-type main-sequence stars
Scorpius
Acrab
Upper Scorpius
Scorpii, 08
5984 5
144217 8
078820 1
Durchmusterung objects
Mercury-manganese stars | Beta Scorpii | [
"Astronomy"
] | 1,333 | [
"Scorpius",
"Constellations"
] |
1,522,648 | https://en.wikipedia.org/wiki/Graffias | Graffias ("claws") is a traditional name for several stars in the constellations between Scorpius and Libra.
It can refer to:
β Sco; later transferred from ξ Sco.
ξ Sco (also 51 Lib); applied to Bayer's star list in his Uranometria.
Burritt's ξ of Libra; applied to Burritt's star map.
ζ Sco; applied to Becvar's star list, as Grafias.
See also
List of stars in Libra
List of stars in Scorpius
References
Libra (constellation)
Scorpius
Stars with proper names | Graffias | [
"Astronomy"
] | 136 | [
"Scorpius",
"Libra (constellation)",
"Constellations"
] |
1,522,658 | https://en.wikipedia.org/wiki/Nu%20Scorpii | Nu Scorpii (ν Scorpii, abbreviated Nu Sco, ν Sco) is a multiple star system in the constellation of Scorpius. It is most likely a septuple star system, consisting of two close groups (designated Nu Scorpii AB and CD) that are separated by 41 arcseconds. Based on parallax measurements, it is approximately 470 light-years from the Sun.
The component Nu Scorpii Aa is formally named Jabbah .
(Contrast the similar-sounding Dschubba, Delta Scorpii.)
Location
Nu Scorpii is the system that causes the reflection nebula cataloged as IC 4592 and known as the Blue Horsehead nebula. Reflection nebulae are actually made up of very fine dust that normally appears dark but can look quite blue when reflecting the light of energetic nearby stars.
Since it is near the ecliptic, Nu Scorpii can be occulted by the Moon and, very rarely, by planets. Mercury occulted it on 14 December 1821, but will not occult it again until 2 December 2031. The last occultation by Venus took place on 27 December 1852 and the next will take place on 30 December 2095. On 29 July 1808 there was an occultation by Neptune.
Nomenclature
ν Scorpii (Latinised to Nu Scorpii) is the system's Bayer designation. The designations of its two constituent groups as Nu Scorpii AB and CD; of the component Nu Scorpii Aa, and of other components similarly lettered, derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
Nu Scorpii bore the traditional name Jabbah, possibly from the Arabic Iklīl al Jabhah (إكليل الجبهة 'the crown of the forehead'). In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Jabbah for the component Nu Scorpii Aa on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.
In Chinese astronomy, Nu Scorpii is called 鍵閉, Pinyin: Jiànbì, meaning Door Bolt, because it is marking itself and standing alone in the Door Bolt asterism, Room mansion (see : Chinese constellations). 鍵閉 (Jiànbì), westernized into Keen Pi, but that name (meaning "the Two Parts of a Lock") was ascribed to the pair Lambda Scorpii (Shaula) and Upsilon Scorpii (Lesath) by R.H. Allen.
Multiplicity
Hierarchy of orbits in the ν Scorpii system
Nu Scorpii is a septuple star system. It is one of only two such known systems, the other being AR Cassiopeiae. Higher-multiplicity star systems are uncommon because they are less stable than their simpler counterparts, and often decay into smaller systems.
Nu Scorpii is split into two groups, Nu Scorpii AB and Nu Scorpii CD. Nu Scorpii CD is located 41 arcseconds away from Nu Scorpii A, and is also known as HR 6026.
Nu Scorpii A
Nu Scorpii A is the brightest member of the system. It has an apparent magnitude from 4.35, meaning that it can be seen with the naked eye. However, Nu Scorpii AB and CD cannot be resolved using the naked eye, but it can be resolved using a telescope.
Nu Scorpii A is itself a triple star system. The main component of Nu Scorpii A is known as Nu Scorpii Aab, and it is a single-lined spectroscopic binary. Its components cannot be resolved but the stars' movements cause periodic Doppler shifts in their spectra. "Single-lined" means that light from only one of the stars can be detected. The pair has an orbital period of 5.5521 days and an eccentricity of 0.11, and an estimated separation of about 1.057 milliarcseconds. The brighter component, Nu Scorpii Aa, has a spectral type of B3V implying a B-type main sequence star. The fainter component, Nu Scorpii Ab, is thought to have an apparent magnitude of 6.90.
Nu Scorpii Ac is the third component of the Nu Scorpii A subsystem. 63 milliarcseconds away, it has an apparent magnitude of 6.62.
Nu Scorpii B
Nu Scorpii B is part of the Nu Scorpii AB sub-system and orbits Nu Scorpii A. It has an apparent magnitude of 5.40, but its spectral type is unknown. Nu Scorpii A and B are separated by 1.305 arcseconds; this translates to an orbital period of over 452 years, so no orbital motion has been detected.
Nu Scorpii CD
Nu Scorpii CD is also a triple star system. The primary component of the system, Nu Scorpii C, is a late B-type giant with a spectral type of B9III. With an apparent magnitude of 6.90, it outshines its fainter companion, Nu Scorpii D, which only has an apparent magnitude of 7.39. The two are separated by about 2 arcseconds.
Nu Scorpii D, with an apparent magnitude of 7.39, is the faintest component of the Nu Scorpii system. It is one of a class of chemically peculiar stars known as Ap/Bp stars; in particular, it has strong silicon emission lines. It too is likely also another spectroscopic binary: Nu Scorpii Da is another B9III-type star, similar to Nu Scorpii C, but very little is known about Nu Scorpii Db.
References
External links
Scorpii, Nu
B-type main-sequence stars
B-type subgiants
7
Scorpius
Spectroscopic binaries
Jabbah
Scorpii, 14
079374
6026 7
145501 2
Durchmusterung objects | Nu Scorpii | [
"Astronomy"
] | 1,358 | [
"Scorpius",
"Constellations"
] |
1,522,674 | https://en.wikipedia.org/wiki/Beta%20Librae | Beta Librae (β Librae, abbreviated Beta Lib, β Lib), formally named Zubeneschamali , is (despite its 'beta' designation) the brightest star in the zodiac constellation of Libra. From parallax measurements, its distance can be estimated as from the Sun.
The apparent visual magnitude of this star is 2.6. According to Eratosthenes, Beta Librae was observed to be brighter than Antares. Ptolemy, 350 years later, said it was as bright as Antares. The discrepancy may be due to Antares becoming brighter, but this is not known for certain. It could simply be caused by Beta Librae being a variable star, showing a present-day variability of 0.03 of a magnitude.
Name
β Librae (Latinised to Beta Librae) is the star's Bayer designation.
It bore the traditional name Zubeneschamali (less common renderings, or corruptions, are Zuben Eschamali, Zuben el Chamali, Zubenesch, Zubenelg), derived from the Arabic الزُّبَانَى الشَمَالِي (al-zubānā al-šamāliyy) meaning "the northern claw". This name originated in a time when Libra was viewed as representing the "claws of the scorpion". There was also Kiffa Borealis, from the Arabic al-kiffah aš-šamāliyy "the northern pan (of the scales)" and the Latin equivalent Lanx Borealis. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Zubeneschamali for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, (), meaning Root, refers to an asterism consisting of β Librae, α2 Librae, ι Librae and γ Librae. Consequently, the Chinese name for β Librae itself is (), "the Fourth Star of Root".
Properties
Based upon the features of its spectrum, Beta Librae has a stellar classification of B8 V, making it a B-type main-sequence star. It is about 130 times more luminous than the Sun and has a surface temperature of , double that of the Sun. This high temperature produces light with a simple spectrum, making it ideal for examining the interstellar gas and dust between Earth and the star. Like many stars of its kind, it is spinning rapidly, over 100 times faster than the Sun with a projected rotational velocity of . The measured angular diameter of the primary star is 0.801 mas. At the estimated distance of this system, this yields a physical size of about 4.9 times the radius of the Sun.
This type of massive, hydrogen-fusing star often appears blue-white, and is usually stated to be white or bluish by modern observers, but earlier observers often described Beta Librae as the only greenish star visible to the naked eye. There seems to be no generally accepted explanation for why some observers see it as green. The small periodic variations in the magnitude of Beta Librae suggest the presence of a companion star which is not directly observable from Earth. However, it is categorized as a single star.
In around 200 million years, Beta Librae would have exhausted the supply of hydrogen in its core and become a giant star similar to Beta Herculis, which had a similar initial mass.
See also
List of stars in Libra
Alpha Librae (Zubenelgenubi)
References
External links
– Find more Arabic Star Names and their meanings.
Librae, Beta
B-type main-sequence stars
Libra (constellation)
Zubeneschamali
Librae, 27
074785
Suspected variables
5685
135742
Durchmusterung objects | Beta Librae | [
"Astronomy"
] | 828 | [
"Libra (constellation)",
"Constellations"
] |
1,522,677 | https://en.wikipedia.org/wiki/Cope%20rearrangement | The Cope rearrangement is an extensively studied organic reaction involving the [3,3]-sigmatropic rearrangement of 1,5-dienes. It was developed by Arthur C. Cope and Elizabeth Hardy. For example, 3-methyl-hexa-1,5-diene heated to 300 °C yields hepta-1,5-diene.
The Cope rearrangement causes the fluxional states of the molecules in the bullvalene family.
Mechanism
The Cope rearrangement is the prototypical example of a concerted sigmatropic rearrangement. It is classified as a [3,3]-sigmatropic rearrangement with the Woodward–Hoffmann symbol [π2s+σ2s+π2s] and is therefore thermally allowed. It is sometimes useful to think of it as going through a transition state energetically and structurally equivalent to a diradical, although the diradical is not usually a true intermediate (potential energy minimum). The chair transition state illustrated here is preferred in open-chain systems (as shown by the Doering-Roth experiments). However, conformationally constrained systems like cis-1,2-divinyl cyclopropanes can undergo the rearrangement in the boat conformation.
It is currently generally accepted that most Cope rearrangements follow an allowed concerted route through a Hückel aromatic transition state and that a diradical intermediate is not formed. However, the concerted reaction can often be asynchronous and electronically perturbed systems may have considerable diradical character at the transition state. A representative illustration of the transition state of the Cope rearrangement of the electronically neutral hexa-1,5-diene is presented below. Here one can see that the two π-bonds are breaking while two new π-bonds are forming, and simultaneously the σ-bond is breaking while a new σ-bond is forming. In contrast to the Claisen rearrangement, Cope rearrangements without strain release or electronic perturbation are often close to thermally neutral, and may therefore reach only partial conversion due to an insufficiently favorable equilibrium constant. In the case of hexa-1,5-diene, the rearrangement is degenerate (the product is identical to the starting material), so K = 1 by necessity.
In asymmetric dienes one often needs to consider the stereochemistry, which in the case of pericyclic reactions, such as the Cope rearrangement, can be predicted with the Woodward–Hoffmann rules and consideration of the preference for the chair transition state geometry.
Examples
The rearrangement is widely used in organic synthesis. It is symmetry-allowed when it is suprafacial on all components. The transition state of the molecule passes through a boat or chair like transition state. An example of the Cope rearrangement is the expansion of a cyclobutane ring to a cycloocta-1,5-diene ring:
In this case, the reaction must pass through the boat transition state to produce the two cis double bonds. A trans double bond in the ring would be too strained. The reaction occurs under thermal conditions. The driving force of the reaction is the loss of strain from the cyclobutane ring.
An organocatalytic Cope rearrangement was first reported in 2016. In this process, an aldehyde-substituted 1,5-diene is used, allowing "iminium catalysis" to be achieved using a hydrazide catalyst and moderate levels of enantioselectivity (up to 47% ee) to be achieved.
A number of enzymes catalyze the Cope rearrangement, although its occurrence is rare in nature.
Oxy-Cope rearrangement and related variants
In the oxy-Cope rearrangement, a hydroxyl group is added at C3 forming an enal or enone after keto-enol tautomerism of the intermediate enol.
In its original implementation, the oxy-Cope reaction required high temperatures. Subsequent work showed that the corresponding potassium alkoxides rearranged faster by 1010 to 1017. By virtue of this innovation, reaction proceed well at room temperature or even 0 °C. Typically potassium hydride and 18-crown-6 are employed to generate the dissociated potassium alkoxide:
The diastereomer of the starting material shown above with an equatorial vinyl group does not react, providing evidence of the concerted nature of this reaction. Nevertheless, the transition state of the reaction is believed to have a high degree of diradical character. Consequently, the anion-accelerated oxy-Cope reaction can proceed with high efficiency even in systems that do not permit efficient orbital overlap, as illustrated by a key step in the synthesis periplanone B:
The corresponding neutral oxy-Cope and siloxy-Cope rearrangements failed, giving only elimination products at 200 °C.
Another variation of the Cope rearrangement is the aza-Cope rearrangements.
See also
Claisen rearrangement, another widely studied [3,3] sigmatropic rearrangement
divinylcyclopropane-cycloheptadiene rearrangement
References
Rearrangement reactions
Name reactions | Cope rearrangement | [
"Chemistry"
] | 1,100 | [
"Name reactions",
"Rearrangement reactions",
"Organic reactions"
] |
1,522,682 | https://en.wikipedia.org/wiki/Gamma%20Virginis | Gamma Virginis (γ Virginis, abbreviated Gamma Vir, γ Vir), officially named Porrima , is a binary star system in the constellation of Virgo. It consists of two almost identical main sequence stars at a distance of about 38 light-years.
Name
γ Virginis (Latinised to Gamma Virginis) is the star's Bayer designation.
The traditional name Porrima derives from Ancient Rome: Porrima, also known as Antevorta, was one of the Camenae or goddesses of prophecy. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Porrima for this star.
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Laouiyet al Aoua, which was translated into Latin as Angulus Latratoris, meaning 'the angle of the barker'. This star, along with Beta Virginis (Zavijava), Eta Virginis (Zaniah), Delta Virginis (Minelauva) and Epsilon Virginis (Vindemiatrix), were Al ʽAwwāʼ, the Barker.
In Chinese, (), meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of Gamma Virginis, Eta Virginis, Delta Virginis, Epsilon Virginis and Alpha Comae Berenices. Consequently, the Chinese name for Gamma Virginis itself is (, .), representing (), meaning The First Eastern Minister. 東上相 (Dōngshǎngxiāng), westernized into Shang Seang by R. H. Allen and the meaning is "the High Minister of State".
Properties
Gamma Virginis is a binary star, consisting of two stars of nearly equal apparent magnitudes 3.65 and 3.56, and of spectral type F0V. With an orbital period of 168.93 years, it was an easy object for amateur astronomers until the beginning of the 1990s, but in 2011 the smaller apparent distance between the stars requires a larger telescope or special techniques such as speckle interferometry, adaptive optics or optical interferometry to resolve the individual components. The last time they were at periapsis was in 1836. The distance became wide enough in 2020 to view with a small telescope. The star system has a combined apparent magnitude of 2.9. The system is 39 light-years away from the Sun.
Gamma Virginis is 2.8 degrees north of the ecliptic, so it can be occulted by the Moon and (rarely) by planets. In June 2011 Saturn passed a quarter of a degree south of Porrima.
Based upon X-ray emissions—an indicator of the strength of the stellar magnetic field—this system has an estimated age of 1.14 billion years.
Changes of distance and position angle
This table shows the apparent distance between the two stars and their relative position angle: the first three columns show data predicted from an orbit calculated in 1937, the next two columns show in 2006, the next three columns show observations reported by the Hanwell Community Observatory.
References
Virginis, Gamma
Binary stars
Virginis, 029
Virgo (constellation)
F-type main-sequence stars
Porrima
061941
4825 6
110379 80
Durchmusterung objects
Am stars
0482 | Gamma Virginis | [
"Astronomy"
] | 725 | [
"Virgo (constellation)",
"Constellations"
] |
1,522,693 | https://en.wikipedia.org/wiki/Gamma%20Leonis | Gamma Leonis (γ Leonis, abbreviated Gamma Leo, γ Leo), also named Algieba , is a binary star system in the constellation of Leo, made up of two red giants. In 2009, a planetary companion around the primary was announced.
Nomenclature
γ Leonis (Latinised to Gamma Leonis) is the star's Bayer designation. The A and B components of the binary are often referred to as γ1 Leonis and γ2 Leonis, respectively.
It also bore the traditional name Algieba or Al Gieba, which originated from the Arabic الجبهة Al-Jabhah, meaning 'the forehead' (despite this meaning, the star actually appears in the mane of Leo). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Algieba for this star.
The star's traditional Latin name was Juba. It is known as 軒轅十二 (the Twelfth Star of Xuanyuan) in Chinese (Xuanyuan is the name of the Yellow Emperor).
Algieba, along with Zeta Leonis, Regulus, Mu Leonis, Epsilon Leonis and Eta Leonis, have collectively been called the Sickle, which is an asterism that marks the head of Leo.
Stellar system
The bright binary system in Leo with orange-red and yellow or greenish-yellow components is visible through a modest telescope under good atmospheric conditions. To the naked eye, the Algieba system shines at mid-second magnitude, but a telescope easily splits the pair. The double nature of Gamma Leonis was discovered by William Herschel in 1792.
The brighter component (named Gamma1 Leonis) has an apparent magnitude of +2.28 and is of spectral class K0III. This giant K star has a surface temperature of , 250 times the luminosity of the Sun, and 26 times the Sun's diameter. The companion (named Gamma2 Leonis) has an apparent magnitude of +3.51 and belongs to the spectral class G7III. This giant G star has a temperature of , is 63 times more luminous and 10 times larger than the Sun. Both are more likely red clump giants, evolved stars that have initiated helium ignition at their core. They are estimated to be 2 billion years old and have subsolar metallicites.
The orbital parameters of Gamma Leonis are still uncertain due to the very long orbit. The orbital period is thought to be between 400 and 700 years. Preliminary data show that the stars have an orbital period of 554 years, are visually separated by 3.1' in the sky and have a highly-eccentric (0.93) orbit. Nonetheless, these parameters are contradictory with the physical parameters, by the Kepler's third law, it would imply that the combined mass is of . Another data set show parameters that imply a combined mass of , even more contradictory with the observed combined mass ().
Variability
γ Leonis was a suspected variable star, with a visual magnitude range of 1.84 to 2.03. It is not known which of the two components is variable. The American Association of Variable Star Observers mention that it is a RS Canum Venaticorum variable with a smaller range of 1.98 to 2.02. In 1959, the star was mistakenly published as an eclipsing binary due to a typographical error when referring to .
The flare star AD Leonis lies just 5' from . It is unrelated to the pair, and much closer to Earth at a distance of .
Planetary system
On November 6, 2009, the discovery of a planetary companion around primary star γ1 Leonis (γ Leonis A) was announced. The radial velocity measurements suggest two additional periodicities of 8.5 and 1,340 days. The former is likely due to stellar pulsation, whereas the latter could be indicative of the presence of an additional planetary companion with 2.14 Jupiter masses, moderate eccentricity (e=0.13) and located at 2.6 AU away from the giant star. Nevertheless, the nature of such a signal is still unclear and further investigations are needed to confirm or rule out an additional substellar companion.
A new study revised the minimum mass for Gamma1 Leonis b to about (increased by 20%), based on a larger mass for the host star ( instead of ).
Notes
References
External links
Algieba at Jim Kaler's Stars
Astronomical Reference from Author David Darling
K-type giants
G-type giants
Binary stars
Suspected variables
Planetary systems with one confirmed planet
Leo (constellation)
Leonis, Gamma
4057
BD+20 2467
Leonis, 41
089484
050583
Algieba | Gamma Leonis | [
"Astronomy"
] | 1,004 | [
"Leo (constellation)",
"Constellations"
] |
1,522,699 | https://en.wikipedia.org/wiki/Gamma%20Arietis | Gamma Arietis (γ Arietis, abbreviated Gamma Ari, γ Ari) is a binary star (possibly trinary) in the northern constellation of Aries. Called "The First Star in Aries" as having been at one time the nearest visible star to the equinoctial point. The two components are designated γ1 Arietis or Gamma Arietis B and γ2 Arietis or Gamma Arietis A (formally named Mesarthim , the traditional name for the Gamma Arietis system). γ1 Arietis may itself be a spectroscopic binary with a low mass companion.
The combined apparent visual magnitude of the stars is 3.86, which is readily visible to the naked eye and makes this the fourth-brightest member of Aries. Based upon parallax measurements obtained during the Hipparcos mission, the distance to Gamma Arietis from the Sun is approximately .
Properties
The double star nature of this system was discovered by Robert Hooke in 1664. The two components have an angular separation of 7.606 arcseconds, which can be resolved with a small telescope. The orbital period of the pair is greater than 5000 years.
The brighter component, γ2 Arietis, is an α2 CVn type variable star, a type of star with a strong magnetic field and enhanced spectral lines of some metals, with high chromospheric activity causing brightness changes as the star rotates. Its brightness varies by 0.04 magnitudes with a period of 2.61 days. It is also an Ap star, a type of chemically peculiar star with enhanced lines of many metals. The spectral class has been given as A2IVpSiSrCr, noting the particular strength of lines of silicon, strontium, and chromium, although other lines such as europium, mercury, and manganese are also stronger than in a normal star. This spectral type suggests that the star is an A2-class subgiant. One study identified a low-mass companion to γ2 Arietis, a probable red dwarf in a close orbit.
The marginally fainter of the two visible stars, γ1 Arietis, is a Lambda Boötis (chemically peculiar) star with a stellar classification of A0Vnp and a magnitude of 4.64. Lambda Boötis stars are identified based on unusually low abundances of iron peak elements in their spectra. The spectral class has also been given as A0IV-V(n)kB8, indicating that calcium K lines in its spectrum are more typical of a B8 star. Older studies often classified it as B9 or B9.5 with a luminosity class of IV or V, indicating either a main sequence or subgiant.
Both of the visible stars have mass of about , luminosities of about , effective temperatures of about , and radii of about . Their age is about 34 million years.
Nomenclature
γ Arietis (Latinised to Gamma Arietis) is the system's Bayer designation; γ1 and γ2 Arietis those of its two components. The designation of the two components as Gamma Arietis A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
Gamma Arietis has been called "the First Star in Aries" as having been at one time the nearest visible star to the equinoctial point.
It bore the traditional name Mesarthim. Originally it had shared the name Sheratan with Beta Arietis. However, this got corrupted to "Sartai" in medieval manuscripts, which Bayer erroneously explained as being the Hebrew grammatical term "servants", and later scholars picked up on this term.
In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Mesarthim for the component γ2 Arietis on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, (), meaning Bond (asterism), refers to an asterism consisting of Gamma, Beta and Alpha Arietis. Consequently, the Chinese name for Gamma Arietis itself is (, ).
In Hindu astrology, Gamma Arietis and Beta Arietis (Sheratan) are Ashvins, the twin Rigvedic deities who act as doctors of the divine of the world.(Richard H Allen)
References
External links
HR 545
HR 546
The Constellations and Named Stars
Image Gamma Arietis
Image Gamma2 Arietis
011502
Binary stars
008832
Aries (constellation)
Arietis, Gamma
Alpha2 Canum Venaticorum variables
A-type main-sequence stars
Mesarthim
Arietis, 05
0545 6
A-type subgiants
Durchmusterung objects
Lambda Boötis stars | Gamma Arietis | [
"Astronomy"
] | 1,041 | [
"Aries (constellation)",
"Constellations"
] |
1,522,713 | https://en.wikipedia.org/wiki/Hexadecimal%20time | Hexadecimal time is the representation of the time of day as a hexadecimal number in the interval [0, 1).
The day is divided into 1016 (1610) hexadecimal hours, each hour into 10016 (25610) hexadecimal minutes, and each minute into 1016 (1610) hexadecimal seconds.
History
This time format was proposed by the Swedish-American engineer John W. Nystrom in 1863 as part of his tonal system.
In 1997, the American Mark Vincent Rogers of Intuitor proposed a similar system of hexadecimal time and implemented it in JavaScript as the Hexclock.
Implementation
A day is unity, or 1, and any fraction thereof can be shown with digits to the right of the hexadecimal separator. So the day begins at midnight with .0000 and one hexadecimal second after midnight is .0001. Noon is .8000 (one half), one hexadecimal second before was .7FFF and one hexadecimal second before next midnight will be .FFFF.
Intuitor-hextime may also be formatted with an underscore separating hexadecimal hours, minutes and seconds. For example:
Clock
Conversions
See also
Binary time
Decimal time
Metric time
References
Further reading
External links
Hexadecimal Time Applet - digital and analog
True Binary Time - local time as a binary number
Analog hexadecimal clock - Florence Mean Time
Time measurement systems
Hexadecimal numeral system
Clock designs | Hexadecimal time | [
"Physics"
] | 333 | [
"Spacetime",
"Time measurement systems",
"Physical quantities",
"Time"
] |
1,522,954 | https://en.wikipedia.org/wiki/Network%20performance | Network performance refers to measures of service quality of a network as seen by the customer.
There are many different ways to measure the performance of a network, as each network is different in nature and design. Performance can also be modeled and simulated instead of measured; one example of this is using state transition diagrams to model queuing performance or to use a Network Simulator.
Performance measures
The following measures are often considered important:
Bandwidth commonly measured in bits/second is the maximum rate that information can be transferred
Throughput is the actual rate that information is transferred
Latency the delay between the sender and the receiver decoding it, this is mainly a function of the signals travel time, and processing time at any nodes the information traverses
Jitter variation in packet delay at the receiver of the information
Error rate the number of corrupted bits expressed as a percentage or fraction of the total sent
Bandwidth
The available channel bandwidth and achievable signal-to-noise ratio determine the maximum possible throughput. It is not generally possible to send more data than dictated by the Shannon-Hartley Theorem.
Throughput
Throughput is the number of messages successfully delivered per unit time. Throughput is controlled by available bandwidth, as well as the available signal-to-noise ratio and hardware limitations. Throughput for the purpose of this article will be understood to be measured from the arrival of the first bit of data at the receiver, to decouple the concept of throughput from the concept of latency. For discussions of this type, the terms 'throughput' and 'bandwidth' are often used interchangeably.
The Time Window is the period over which the throughput is measured. The choice of an appropriate time window will often dominate calculations of throughput, and whether latency is taken into account or not will determine whether the latency affects the throughput or not.
Latency
The speed of light imposes a minimum propagation time on all electromagnetic signals. It is not possible to reduce the latency below
where s is the distance and cm is the speed of light in the medium (roughly 200,000 km/s for most fiber or electrical media, depending on their velocity factor). This approximately means an additional millisecond round-trip delay (RTT) per 100 km (or 62 miles) of distance between hosts.
Other delays also occur in intermediate nodes. In packet switched networks delays can occur due to queueing.
Jitter
Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of periodic signals. Jitter is a significant, and usually undesired, factor in the design of almost all communications links (e.g., USB, PCI-e, SATA, OC-48). In clock recovery applications it is called timing jitter.
Error rate
In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit synchronization errors.
The bit error rate or bit error ratio (BER) is the number of bit errors divided by the total number of transferred bits during a studied time interval. BER is a unitless performance measure, often expressed as a percentage.
The bit error probability pe is the expectation value of the BER. The BER can be considered as an approximate estimate of the bit error probability. This estimate is accurate for a long time interval and a high number of bit errors.
Interplay of factors
All of the factors above, coupled with user requirements and user perceptions, play a role in determining the perceived 'fastness' or utility, of a network connection. The relationship between throughput, latency, and user experience is most aptly understood in the context of a shared network medium, and as a scheduling problem.
Algorithms and protocols
For some systems, latency and throughput are coupled entities. In TCP/IP, latency can also directly affect throughput. In TCP connections, the large bandwidth-delay product of high latency connections, combined with relatively small TCP window sizes on many devices, effectively causes the throughput of a high latency connection to drop sharply with latency. This can be remedied with various techniques, such as increasing the TCP congestion window size, or more drastic solutions, such as packet coalescing, TCP acceleration, and forward error correction, all of which are commonly used for high latency satellite links.
TCP acceleration converts the TCP packets into a stream that is similar to UDP. Because of this, the TCP acceleration software must provide its own mechanisms to ensure the reliability of the link, taking the latency and bandwidth of the link into account, and both ends of the high latency link must support the method used.
In the Media Access Control (MAC) layer, performance issues such as throughput and end-to-end delay are also addressed.
Examples of latency or throughput dominated systems
Many systems can be characterized as dominated either by throughput limitations or by latency limitations in terms of end-user utility or experience. In some cases, hard limits such as the speed of light present unique problems to such systems and nothing can be done to correct this. Other systems allow for significant balancing and optimization for best user experience.
Satellite
A telecom satellite in geosynchronous orbit imposes a path length of at least 71000 km between transmitter and receiver. which means a minimum delay between message request and message receipt, or latency of 473 ms. This delay can be very noticeable and affects satellite phone service regardless of available throughput capacity.
Deep space communication
These long path length considerations are exacerbated when communicating with space probes and other long-range targets beyond Earth's atmosphere. The Deep Space Network implemented by NASA is one such system that must cope with these problems. Largely latency driven, the GAO has criticized the current architecture. Several different methods have been proposed to handle the intermittent connectivity and long delays between packets, such as delay-tolerant networking.
Even deeper space communication
At interstellar distances, the difficulties in designing radio systems that can achieve any throughput at all are massive. In these cases, maintaining communication is a bigger issue than how long that communication takes.
Offline data transport
Transportation is concerned almost entirely with throughput, which is why physical deliveries of backup tape archives are still largely done by vehicle.
See also
Bitrate
Measuring network throughput
Network traffic measurement
Response time
Notes
References
Fall, Kevin, "A Delay-Tolerant Network Architecture for Challenged Internets", Intel Corporation, February, 2003, Doc No: IRB-TR-03-003
Government Accountability Office (GAO) report 06-445, NASA'S DEEP SPACE NETWORK: Current Management Structure is Not Conducive to Effectively Matching Resources with Future Requirements, April 27, 2006
External links
NASA's Deep Space Network Website
"It's the Latency, Stupid"
Computing comparisons
Information theory | Network performance | [
"Mathematics",
"Technology",
"Engineering"
] | 1,443 | [
"Telecommunications engineering",
"Applied mathematics",
"Computing comparisons",
"Computer science",
"Information theory"
] |
1,522,987 | https://en.wikipedia.org/wiki/Gonochorism | In biology, gonochorism is a sexual system where there are two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric.
Gonochorism contrasts with simultaneous hermaphroditism but it may be hard to tell if a species is gonochoric or sequentially hermaphroditic e.g. parrotfish, Patella ferruginea. However, in gonochoric species individuals remain either male or female throughout their lives. Species that reproduce by thelytokous parthenogenesis and do not have males can still be classified as gonochoric.
Terminology
The term is derived from Greek gone 'generation' + chorizein 'to separate'. The term gonochorism originally came from German Gonochorismus.
Gonochorism is also referred to as unisexualism or gonochory.
Evolution
Gonochorism has evolved independently multiple times. It is very evolutionarily stable in animals. Its stability and advantages have received little attention. Gonochorism owes its origin to the evolution of anisogamy, but it is unclear if the evolution of anisogamy first led to hermaphroditism or gonochorism.
Gonochorism is thought to be the ancestral state in polychaetes, Hexacorallia, nematodes, and hermaphroditic fishes. Gonochorism is thought to be ancestral in hermaphroditic fishes because it is widespread in basal clades of fish and other vertebrate lineages.
Two papers from 2008 have suggested that transitions between hermaphroditism and gonochorism or vice versa have occurred in animals between 10 and 20 times. In a 2017 study involving 165 taxon groups, more evolutionary transitions from gonochorism to hermaphroditism were found than the reverse.
Use across species
Animals
The term gonochorism is most often used for animal species, an estimated 95% of which are gonochoric. It is very common in vertebrate species, 99% of which are gonochoric. Ninety-eight percent of fishes are gonochoric. Mammals (including humans) and birds are solely gonochoric. and Tardigrades are almost always gonochoric. Seventy-five percent of snails are gonochoric. Most arthropods including a majority of crustaceans are gonochoric.
In animals, sex is most often genetically determined, but may be determined by other mechanisms. For example, alligators use temperature-dependent sex determination during egg incubation.
Plants
The term gonochorism is not usually applied to plants. Vascular plants which have single-sex individuals are called dioecious, while bryophytes with single-sex individuals are dioicous. In flowering plants, individual flowers may be hermaphroditic (i.e., with both stamens and ovaries) or dioecious (unisexual), having either no stamens (i.e., no male parts) or no ovaries (i.e., no female parts). Among flowering plants with unisexual flowers, some also produce hermaphrodite flowers, and the three types may occur in different arrangements on the same or separate plants. Plant species can thus be hermaphrodite, monoecious, dioecious, trioecious, polygamomonoecious, polygamodioecious, andromonoecious, or gynomonoecious.
Examples of species with gonochoric or dioecious pollination include hollies and kiwifruit. In these plants the male plant that supplies the pollen is referred to as the pollenizer.
Other reproductive strategies
Gonochorism stands in contrast to other reproductive strategies such as asexual reproduction and hermaphroditism. Closely related taxa can have differing sexual strategies – for example, the genus Ophryotrocha contains species that are gonochoric and species that are hermaphrodites.
The sex of an individual may also change during its lifetimethis sequential hermaphroditism can, for example, be found in parrotfish and cockles.
See also
Diclinous
Monoclinous
Plant sexuality
Gynogenesis
References
Reproduction
Pollination
Sexual system | Gonochorism | [
"Biology"
] | 943 | [
"Behavior",
"Sex",
"Reproduction",
"Sexual system",
"Biological interactions"
] |
1,523,418 | https://en.wikipedia.org/wiki/Follow%20the%20Drinkin%27%20Gourd | Follow the Drinking Gourd is an African-American folk song first published in 1928. The "drinking gourd" is another name for the Big Dipper asterism. Folklore has it that enslaved people in the United States used it as a point of reference so they would not get lost during their journey of escape to the North and to freedom.
According to legend, the song was used by a conductor of the Underground Railroad, called Peg Leg Joe, to guide some fugitive slaves, and many of the lyrics are simply cartographic directions to advise the runaways on their escape route. While the song may possibly refer to some lost fragment of history, the origin and context remain a mystery.
A more recent source challenges the claim that the song helped free anyone from slavery, as no pre-1910 reference to it has ever been found.
History
Texas Folklore Society and H. B. Parks
Follow the Drinking Gourd was collected by H. B. Parks, an entomologist and amateur folklorist, in the 1910s. Parks reported that Peg Leg Joe, an operative of the Underground Railroad, had passed as a laborer and spread the song to different plantations, giving directions for slaves to escape. The song was published by the Texas Folklore Society in 1928. (The cover spells the title "Foller de Drinkin' Gou'd.")
Lee Hays
In 1947, Lee Hays, of the Almanac Singers and The Weavers, rearranged Follow the Drinkin' Gourd and published it in the People's Songs Bulletin. Familiar with African-American music and culture, Hays stated that he himself had heard parts of the song from an elderly black woman named Aunty Laura. Hays described the melody as coming from Aunty Laura, while the lyrics came from anthologies – probably the Parks version.
Randy Sparks/John Woodum
In 1955, singer Randy Sparks heard the song from an elderly street singer named John Woodum. These lyrics diverged greatly from the Parks and Hays versions and included no geographical information. Sparks later founded The New Christy Minstrels, with whom he recorded a version of the song based on Woodum's lyrics.
Song Lyrics
Follow the drinkin' gourd
Follow the drinkin' gourd
For the old man is comin' just to carry you to freedom
Follow the drinkin' gourd
When the sun comes back, and the first quail calls
Follow the drinkin' gourd
For the old man is waiting just to carry you to freedom
Follow the drinkin' gourd
Follow the drinkin' gourd
Follow the drinkin' gourd
For the old man is waiting to carry you to freedom
Follow the drinkin' gourd
Well the river bank makes a mighty good road
Dead trees will show you the way
Left foot, peg foot, travelin' on
Follow the drinkin' gourd
Follow the drinkin' gourd
Follow the drinkin' gourd
For the old man is waiting to carry you to freedom
Follow the drinkin' gourd
Well the river ends, between two hills
Follow the drinkin' gourd
There's another river on the other side
Follow the drinkin' gourd
Follow the drinkin' gourd
Follow the drinkin' gourd
For the old man is waiting to carry you to freedom
Follow the drinkin' gourd
Well, where the great big river meets the little river
Follow the drinkin' gourd
The old man is waiting to carry you to freedom
Follow the drinkin' gourd
Follow the drinkin' gourd
Follow the drinkin' gourd
For the old man is waiting to carry you to freedom
Follow the drinkin' gourd
For the old man is waiting just to carry you to freedom
If you follow the drinkin' gourd
Meaning
Two of the stars in the Big Dipper line up very closely with and point to Polaris. Polaris is a circumpolar star, and so it is always seen pretty close to the direction of true north. Hence, according to a popular myth, all slaves had to do was look for the Drinking Gourd and follow it to the North Star (Polaris) north to freedom. James Kelley has argued against the historicity of this interpretation in the Journal of Popular Culture.
See also
Songs of the Underground Railroad
Pete Seeger
Songlines
Notes
External links
Follow the Drinkin' Gourd MP3 featuring Roger McGuinn and Nedra Talley Ross (of The Ronettes) at the Folk Den
The New Christy Minstrels & Gene Clark-1963-Part lll (The Muddy Road to Freedom: Follow the Drinking Gourd) Live at Fordham University
Asterisms (astronomy)
Songs about American slavery
Songs about the Underground Railroad
African-American spiritual songs | Follow the Drinkin' Gourd | [
"Astronomy"
] | 983 | [
"Constellations",
"Sky regions",
"Asterisms (astronomy)"
] |
1,523,424 | https://en.wikipedia.org/wiki/The%20Family%20of%20Man | The Family of Man was an ambitious exhibition of 503 photographs from 68 countries curated by Edward Steichen, the director of the New York City Museum of Modern Art's (MoMA) department of photography. According to Steichen, the exhibition represented the "culmination of his career". The title was taken from a line in a Carl Sandburg poem.
The Family of Man was exhibited in 1955 from January 24 to May 8 at the New York MoMA, then toured the world for eight years to record-breaking audience numbers. Commenting on its appeal, Steichen said, "The people in the audience looked at the pictures, and the people in the pictures looked back at them. They recognized each other." The physical collection is archived and displayed at Clervaux Castle in Edward Steichen's home country of Luxembourg, where he was born in 1879 in Bivange. It was first exhibited there in 1994 after restoration of the prints.
In 2003, the Family of Man photographic collection was added to UNESCO's Memory of the World Register in recognition of its historical value.
Tours
United States
1955, 24 January – 8 May: Museum of Modern Art
1955, 22 June – 4 September: Minneapolis Institute of Art
1955, 7 October – 4 December: Dallas Museum of Art
1956, 24 January – 4 March: Cleveland Museum of Art
1956, 29 April – 20 May: Munson-Williams-Proctor Arts Institute
1956, 25 May – 15 July: Baltimore Museum of Art
1956, 4–25 June: Saint Louis Art Museum
1956, July: Corning Museum of Glass
1956, 9–30 July: GEH Dryden Gallery
1956, 3–30 October: Museum of Fine Arts, Boston
World tour
As part of the Museum of Modern Art's International Program, the exhibition The Family of Man toured the world, making stops in thirty-seven countries on six continents. More than 10 million people viewed the exhibit, which is in excess of the largest audience for any other photographic exhibition. The photographs in the exhibition focused on the commonalities that bind people and cultures around the world, the exhibition serving as an expression of humanism in the decade following World War II.
The recently-formed United States Information Agency was instrumental in touring the photographs throughout the world in five different versions for seven years, under the auspices of the Museum of Modern Art International Program. Notably, it was not shown in Franco's Spain, in Vietnam, nor in China.
First European tour
Copy 1 (503 photo panels, 50 text panels) was organized by Edward Steichen. Duplication, with minor changes, of the exhibition presented at MoMA, Jan 24-May 8, 1955 and subsequently circulated in the United States (1956–57). Commissioned by the USIA for circulation in Europe (circulated 1955-1962. Dispersed 1962). It was shown in:
Central America, India, Africa, Middle East
Copy 2, a duplicate of Copy 1 was commissioned by the USIA, circulated 1955–1963 and dispersed in 1963. It was shown in:
Second European tour
Copy 3, a duplicate of Copy 1 commissioned by the USIA. Circulated 1957–1965 and at Steichen's request, this version of the exhibition was presented to the Government of Luxembourg for permanent display at Common Market Headquarters, Luxembourg, 1965. Previously, it was shown in:
South America, Australia and South-East Asia
Copy 4, a duplicate of Copy 1. Commissioned by the U.S.I.A. Circulated 1957–62. Dispersed 1962. It was shown in:
Middle East
A revised version of the original shown at MoMA 1955. Circulated in the United States, 1957–59, then acquired by the USIA for circulation abroad (1957–58; dispersed 1958), and shown in Tel Aviv, Israel and Beirut, Lebanon
Soviet Union
Copy 5: Following a bilateral agreement between the USA and USSR, in 1959 the American National Exhibition was to be held in Moscow and the Soviets were to have had the use of New York City's Coliseum. This Moscow trade fair at Sokolniki Park was the scene of Soviet Premier Nikita Khrushchev and United States Vice President Richard Nixon's 'Kitchen Debate' over the relative merits of communism and capitalism.
The Family of Man was a late inclusion that had not been originally envisaged in MoMA's itinerary. With a grant to the Museum of $15,000 (less than half of what it requested) and funding from the plastics industry for the radical pre-fabricated translucent pavilion design to house it, a fifth copy of the show was salvaged from what was left of the Beirut and Scandinavia showings, augmented with new prints.
In Moscow, in the context of a trade show 'supermarket' meant to demonstrate lavish consumerism, and a multimedia display assembled by Charles Eames, the collection's overtones of peace and human brotherhood symbolized a lifting of the imminent threat of an atomic war for Soviet citizens in the midst of the Cold War. This meaning seemed to be grasped especially by Soviet students and intellectuals. Recognising the importance of the Moscow exhibition as "the high spot of the project," Steichen attended its opening and made copious photographs of the event.
Clervaux Castle, Luxembourg
The original prints from Copy 3 exhibited in the permanent collection at Clervaux Castle in Luxembourg have been restored twice, once in the 1990s and more comprehensively during a closure of the museum in the years 2010-2013.
An innovative exhibit
The physical installation and layout of the Family of Man exhibition were designed to enable the visitor to view it as if it were a photo-essay about human development and cycles of life, that affirmed a common human identity and destiny against the contemporary Cold War threats of nuclear war.
Architect Paul Rudolph designed a series of temporary walls set amongst the existing structural columns, which guided visitors past the images, which he described as "telling a story", encouraging them to pause at those that attracted their attention. His layout and display features were adapted as much as possible to the international venues, which varied considerably from the original space at MoMA.
Open spaces within the layout encouraged viewers' interaction; to choose their own path through the exhibition, and to gather to discuss it. The layout and placement of prints and their variation in size encouraged the bodily participation of the audience, who would have to bend down to examine a small print displayed below eye level and then to step back to view a mural image, and to negotiate both narrow and expansive spaces.
The prints range in size from to and were made, in the case of the contemporary images, by assistant Jack Jackson, from the negative supplied to Steichen by each photographer. Also included were copies of historical images, for example a Mathew Brady civil war documentation, and a Lewis Carroll portrait. Blown-up, often mural scale images, angled, floated or curved, some inset into other floor-to-ceiling prints, even displayed on the ceiling (a canted view of a silhouetted axeman and tree), on posts like finger-boards (in the final room), and the floor (for a Ring o' Roses series), were grouped together according to diverse themes. Repeated prints of Eugene Harris' portrait of a Peruvian flute-player formed a coda, or acted as 'Pied Piper' to the audience, in the opinion of some reviewers, and according to Steichen himself, expressed "a little bit of mischief, but much sweetness—that's the song of life." Lighting intensities varied throughout the series of ten rooms in order to set the mood.
The exhibition opened with an entrance archway papered with a blow-up of a crowd in London by Pat English framing Wyn Bullock's Chinese landscape of sunlight on water into which was inset an image of a truncated nude of a pregnant woman in an evocation of creation myths. Subjects then ranged in sequence from lovers, to childbirth, to household, and careers, then to death and, on a topical and portentous note, the hydrogen bomb (an image from LIFE magazine of the test detonation Mike, Operation Ivy, Enewetak Atoll, October 31, 1952) which was the only full-colour image; a room-filling backlit Eastman transparency, replaced for the travelling version of the show with a different view of the same explosion in black and white.
Finally, full cycle, visitors returned once more to children in a room in which the last picture was W. Eugene Smith's iconic 1946 A Walk to Paradise Garden. As the centrepiece of the exhibition a hanging sculptural installation of photographs including Vito Fiorenza's Sicilian family group and Carl Mydans' of a Japanese family (both from nations which were recent enemies of the Allies in WW2), another from Bechuanaland by Nat Farbman and a rural family of the United States by Nina Leen, encouraged circulation to view double-sided prints and invited reflection on the universal nature of the family beyond cultural differences.
Photos were chosen according to their capacity to communicate a story, or a feeling, that contributed to the overarching narrative. Each grouping of images builds upon the next, creating an intricate story of human life. The design of the exhibition built on trade displays and Steichen's 1945 Power In The Pacific exhibition which was designed by George Kidder Smith for MoMA, Steichen's commissioning of Herbert Bayer for the presentation of his curatorship of other exhibitions and his own long history of initiation of innovative exhibits dating back to his association with Gallery 291 early in the century. In 1963 Steichen elaborated on the special opportunities offered by the exhibition format;
In the cinema and television, the image is revealed at a pace set by the director. In the exhibition gallery, the visitor sets his own pace. He can go forward and then retreat or hurry along according to his own impulse and mood as these are stimulated by the exhibition. In the creation of such an exhibition, resources are brought into play that are not available elsewhere. The contrast in scale of images, the shifting of focal points, the intriguing perspective of long- and short- range visibility with the images to come being glimpsed beyond the images at hand —all these permit the spectator an active participation that no other form of visual communication can give.
Texts used in the exhibition and book
The enlarged prints by the multiple photographers were displayed without explanatory captions, and instead were intermingled with quotations by, among others, James Joyce, Thomas Paine, Lillian Smith, and William Shakespeare, chosen by photographer and social activist Dorothy Norman. Carl Sandburg, Steichen's brother-in-law, 1951 recipient of the Pulitzer Prize for Poetry and known for his biography of Abraham Lincoln, inspired the title of the exhibition with a line from his poem The Long Shadow of Lincoln: A Litany (1944);There is dust alive
With dreams of the Republic,
With dreams of the family of man
Flung wide on a shrinking globe;
It was Sandburg who added an accompanying poetic commentary also displayed as text panels throughout the exhibition and included in the publication, of which the following are samples;
Book
Jerry Mason (1913–1991) contemporaneously edited and published a complementary book of the exhibition through Maco Magazine Corporation, formed for the purpose in 1955 in partnership with Fred Sammis.It was the first time hard-cover and soft-cover editions were published simultaneously. The book, which has never been out of print, was designed by Leo Lionni (May 5, 1910 – October 11, 1999). Many of Lionni’s book covers, like that of The Family of Man, incorporate playful modernist collages of apparently cut or torn coloured paper, which he repeats, for example in his 1962 design for The American Character and for children’s books, an aesthetic also used in exhibitions from his parallel career as a fine artist. The publication was reproduced in a variety of formats (most popularly a soft-cover volume) in the 1950s, and reprinted in large format for its 40th anniversary, and in its various editions has sold more than four million copies. Most images from the exhibition were reproduced with an introduction by Carl Sandburg, whose prologue reads, in part:
The first cry of a baby in Chicago, or Zamboango, in Amsterdam or Rangoon, has the same pitch and key, each saying, "I am! I have come through! I belong! I am a member of the Family. Many the babies and grownup here from photographs made in sixty-eight nations round our planet Earth. You travel and see what the camera saw. The wonder of human mind, heart wit and instinct is here. You might catch yourself saying, 'I'm not a stranger here.'
However, an omission from the book, highly significant and contrary to Steichen's stated pacifist aim, was the image of a hydrogen bomb test explosion; audiences of the time were highly sensitive to the threat of universal nuclear annihilation. In place of the huge colour transparency to which a space was devoted in the MoMA exhibition, and the black-and-white mural print that toured countries other than Japan, only this quotation of Bertrand Russell's anti-nuclear warning, in white type on a black page, appears in the book;
[...] The best authorities are unanimous in saying that a war with hydrogen bombs is quite likely to put an end to the human race [...] There will be universal death — sudden for only a minority, but for the majority a slow torture of disease and disintegration.
Absent also from the book, and removed by week eleven of the initial MoMA exhibition, was the distressing photograph of the aftermath of a lynching, of a dead young African American man, tied to a tree with his bound arms tautly tethered with a rope that stretches out of frame.
For most purchasers, this was their first encounter with a book that gave priority to the photographic image over text.
In 2015, to mark the sixtieth anniversary of the inaugural exhibition, MoMA reissued the book as a hardcover edition, with the original jacket design from 1955 (albeit without the signature of designer Leo Lionni) and duotone printing from new copies of all of the photographs.
Photographers
Steichen's stated objective was to draw attention, visually, to the universality of human experience and the role of photography in its documentation. The exhibition brought together 503 photos from 68 countries, the work of 273 photographers (163, or 59.3% of whom were Americans) which, with 70 European photographers, means that the ensemble represents a primarily Western viewpoint. That forty were women photographers can in some part be attributed to Joan Miller's contribution to the selection, and to Dorothea Lange who assisted her friend Edward Steichen in recruiting photographers. She contacted her FSA and Life connections who in turn promoted the project to their colleagues. In 1953 she circulated a letter; "A Summons to Photographers All Over the World," calling on them to;
show Man to Man across the world. Here we hope to reveal by visual images Man's dreams and aspirations, his strength, his despair under evil. If photography can bring these things to life, this exhibition will be created in a spirit of passionate and devoted faith in Man. Nothing short of that will do.
The letter then listed topics that photographs might cover and these categories are reflected in the show's final arrangement. Lange's work features in the exhibition.
Steichen and his team drew heavily on Life archives for the photographs used in the final exhibition, seventy-five by Abigail Solomon-Godeau's count, more than 20% of the total (111 out of 503), while some were obtained from other magazines; Vogue was represented by nine, Fortune (7), Argosy (seven, all by Homer Page), Ladies Home Journal (4); Popular Photography (3), and others Seventeen, Glamour, Harper's Bazaar, Time, the British Picture Post and the French Du, by one. From picture agencies American, Soviet, European and international, which also supplied the above magazines, came about 13% of the content, with Magnum represented by 43 of the pictures, Rapho with thirteen, Black Star with ten, Pix with seven, Sovfoto, which had three and Brackman with four, with around half a dozen other agencies represented by one photo.
Steichen travelled internationally to collect images, through 11 European countries including France, Switzerland, Austria and Germany. In total, Steichen procured 300 images from European photographers, many from the humanist group, which were first shown in the Post-War European Photography exhibition at the Museum of Modern Art in 1953. Due to the incorporation of this body of work into the 1955 The Family of Man exhibition, Post-War European Photography is thought of as a preview to The Family of Man. The international tour of the definitive 1955 exhibition was sponsored by the now defunct United States Information Agency, whose aim was to counter Cold War propaganda by creating a better world image of American policies and values.
Though most photographers were represented by a single picture, some had several included; Robert Doisneau, Homer Page, Helen Levitt, Manuel Álvarez Bravo, Bill Brandt, Édouard Boubat, Harry Callahan (with two), Nat Farbman (five of Bechuanaland, and more from Life), Robert Frank (four), Bert Hardy and Robert Harrington (three). Steichen himself supplied five photos, while his assistant Wayne Miller had thirteen chosen; by far the greatest number.
The following lists notable participating photographers, excluding those with no professional or exhibiting history (see original 1955 MoMA checklist):
Ansel Adams (USA)
Max Alpert (USSR)
Erich Andres (Germany)
Emmy Andriesse (Netherlands)
Diane and Allan Arbus (U.S.A., Vogue)
Eve Arnold (USA)
Richard Avedon (USA)
Ruth-Marion Baruch (USA)
Hugh Bell (U.S.A.)
Wermund Bendtsen (Denmark)
Paul Berg (USA)
Lou Bernstein (USA)
John Bertolino(Italy/USA)
Eva Besnyö (Netherlands)
Werner Bischof (Switzerland)
Maria Bordy (Russia, UN)
Édouard Boubat (France)
Margaret Bourke-White (USA)
Mathew Brady (USA)
Bill Brandt (UK)
Brassai (France)
Lola Álvarez Bravo (Mexico)
Manuel Álvarez Bravo (Mexico)
Josef Breitenbach (Brackman Associates) (Germany, USA)
David Brooks (Canada)
Reva Brooks (Canada)
Ernst Brunner (Switzerland)
Esther Bubley (USA)
Wynn Bullock (USA)
Shirley Burden (USA)
Rudolf Busler (Germany)
Harry Callahan (USA)
Cornell Capa (USA)
Robert Capa
Robert Carrington
Lewis Carroll (UK)
Henri Cartier-Bresson (France)
Ted Castle (USA)
Marcos Chamúdez (Chile)
Al Chang (USA)
Ed Clark (USA)
Hermann Claasen (Germany)
Jerry Cooke (USA)
Roy DeCarava (USA)
Loomis Dean (USA)
Jack Delano (USA)
Nick De Morgoli
J. De Pietro
Robert Diament (USSR)
Robert Doisneau (France)
Nell Dorr (USA)
Nora Dumas (French)
David Douglas Duncan (USA)
Alfred Eisenstaedt (USA)
Elliott Erwitt (USA)
J. R. Eyerman (USA)
Sam Falk (USA)
Nat Farbman (USA)
Eleanor Fast
Louis Faurer (USA)
Ed Feingersh (USA)
Andreas Feininger (USA)
Vito Fiorenza (Italy)
Leopold Fischer (Austria)
John Florea (USA)
Robert Frank (USA)
Toni Frissell (USA)
Unosuke Gamou (Japan)
William Garnett (USA)
Herbert Gehr (Edmund Bert Gerard) (USA)
Guy Gillette (USA)
Burt Glinn (USA)
Fritz Goro (USA)
Allan Grant (USA)
Farrell Grehan (USA)
René Groebli (Switzerland)
Mildred Grossman (USA)
Karl W. Gullers (Sweden)
Ernst Haas (USA)
Peter W. Haberlin (Switzerland)
Hideo Haga (Japan)
Otto Hagel (USA)
Robert Halmi (Hungary)
Hiroshi Hamaya(Japan)
Hans Hammarskiöld (Sweden)
Hella Hammid (USA)
Bert Hardy (UK)
Eugene Harris (USA)
Caroline Hebbe-Hammarskiöld (Sweden)
Paul Himmel (USA)
Frank Horvat (Italy)
Willi Huttig (Germany)
Yasuhiro Ishimoto (Japan)
Izis (France)
Fenno Jacobs (USA)
Raymond Jacobs (USA)
Ronny Jaques (Canada)
Bob Jakobsen (USA)
Nico Jesse (Netherlands)
Constantin Joffé
Carter Jones (USA)
Henk Jonker (Netherlands)
Victor Jorgensen (USA)
Clemens Kalischer (USA)
Simpson Kalisher (USA)
Consuelo Kanaga (USA)
Dmitri Kessel (USA)
Keystone Press (Agency, USA)
Ihei Kimura (Japan)
Martha Kitchen (USA)
Nikolai Kolli (USSR)
Torkel Korling (USA)
Nikolai Kozlovsky (USSR)
Ewing Krainin (USA)
Herman Kreider (USA)
Walter B. Lane
Dorothea Lange (USA)
Harry Lapow (USA
Lisa Larsen (USA)
Alma Lavenson (USA)
Arthur Lavine (USA)
Russell Lee (USA)
Nina Leen (Russia/USA)
Laurence Le Guay (Australia)
Henri Leighton (USA)
Arthur Leipzig (USA)
Charles Leirens (Belgium)
Gita Lenz (USA)
Leon Levinstein (USA)
Helen Levitt (USA)
Margery Lewis (USA)
Sol Libsohn (USA)
David Linton
Herbert List (Germany)
Jacob Lofman (Poland/USA)
Hans Malmberg (Sweden)
G.H. Metcalf
Gjon Mili (Albania/USA)
Frank Miller (USA)
Joan Miller (USA)
Lee Miller (USA)
Wayne Miller (USA)
May Mirin (USA)
Lisette Model (Austria/USA)
Peter Moeschlin (Switzerland)
David Moore (Australia)
Barbara Morgan (USA)
Hedda Morrison (Germany)
Ralph Morse (USA)
Robert Mottar (USA)
Carl Mydans (USA)
David Myers (USA)
Fritz Neugass (Germany/USA)
Lennart Nilsson (Sweden)
Pål Nils Nilsson (Sweden)
Emil Obrovsky (Austria)
Yoichi Okamoto (USA)
Cas Oorthuys (Netherlands)
Ruth Orkin (USA)
Don Ornitz (USA)
Eiju Otaki
Homer Page (USA)
Marion Palfi (USA)
Gordon Parks (USA)
Rondal Partridge (USA)
Irving Penn (USA)
Carl Perutz (USA)
John Phillips (Algeria/USA)
Leonti Planskoy (Russia/UK)
Ray Platnick (USA)
Fred Plaut (Germany)
Rudolf Pollak (Germany)
Rapho Guilumette (Agency, France)
Gottfried Rainer (Austria)
Daniel J. Ransohoff (USA)
Bill Rauhauser (USA)
Satyajit Ray (India)
Anna Riwkin-Brick (Russia/Sweden)
George Rodger (Great Britain)
Willy Ronis (France)
Annelise Rosenberg
Hannes Rosenberg
August Sander (Germany)
Walter Sanders (USA)
Sanford H. Roth (USA)
Gotthard Schuh
Éric Schwab (France)
Bob Schwalberg (USA)
Kurt Severin (Germany/USA)
David Seymour (Poland)
Ben Shahn (Lithuania/USA)
Musya S. Sheeler (USA)
Li Shu (China)
George Silk (New Zealand/USA)
Bradley Smith (USA)
Ian Smith (UK)
W. Eugene Smith (USA)
Howard Sochurek (USA)
Peter Stackpole (USA)
Alfred Statler (USA)
Gitel Steed (USA)
Edward Steichen (Luxembourg/USA)
Richard Steinheimer (USA)
Ezra Stoller (USA)
Lou Stoumen (USA)
George Strock (USA)
Constance Stuart (South Africa)
Étienne Sved (Hungary)
Suzanne Szasz (USA)
Yoshisuke Terao
Gustavo Thorlichen (Argentina)
Charles Trieschmann (USA)
François Tuefferd (France)
Jakob Tuggener (Switzerland)
Allan Turoff
Doris Ulmann (USA)
Alexander Uzylan (U.S.S.R.)
Ed van der Elsken (Netherlands)
William Vandivert
Pierre Verger (France/Brazil)
Ike Vern (USA)
'Véro' (Werner Rosenberg) (France)
Roman Vishniac (Russia/USA)
Carmel Vitullo (USA)
Edward Wallowitch (USA)
Todd Webb (USA)
Sabine Weiss (Switzerland)
Edward Weston (USA)
Bob Willoughby (USA)
Garry Winogrand (USA)
Arthur Witman (USA)
Jasper Wood (USA)
Yosuke Yamahata (Japan)
Shizuo Yamamoto
Reception and criticism
Photography, said Steichen, "communicates equally to everybody throughout the world. It is the only universal language we have, the only one requiring no translation." When the exhibition opened most reviewers—and Eleanor Roosevelt who wrote in her column My Day, "I could not have enjoyed anything more .... "—loved the show. Some embraced the idea of this 'universal language', as with Don Langer's response in the New York Herald Tribune:" It can truly be said that with this show, photography has come of age as a medium of expression and as an art form," and even The New York Times art critic Aline B. Saarinen, in an article titled "The Camera versus the Artist" asked "Has photography replaced painting as the great visual art of our time?” Others lauded Steichen as a sort of author and the exhibition as a text or essay. Photographer Barbara Morgan, in Aperture, connected this concept with the show's universalising theme;
In comprehending the show the individual himself is also enlarged, for these photographs are not photographs only — they are also phantom images of our co-citizens; this woman into whose photographic eyes I now look is perhaps today weeding her family rice paddy, or boiling a fish in coconut milk. Can you look at the polygamist family group and imagine the different norms that make them live happily in their society which is so unlike — yet like — our own? Empathy with these hundreds of human beings truly expands our sense of values.
Expressing the contrary view, Cora Alsberg and George Wright, partners and freelance writers, co-wrote a response ‘One Family’s Opinion’ in the same Aperture issue devoted to the show, that;
Any really great photographer, like a great painter, creates his own visual universe...You can distinguish a Gene Smith from a Cartier Bresson without a signature. You can instantly recognize an Adams, a Weston, a Laughlin print, or that of any mature worker whose previous work you've seen...But mixed with others in a show, he surrenders this individuality-just as a writer might if he gave permission for single paragraphs to be quoted by an editor in any sequence and in any context. Hilton Kramer, then managing editor of the magazine Arts, asserted a negative view, one taken up by more recent critics, that The Family of Man was a; self-congratulatory means for obscuring the urgency of real problems under a blanket of ideology which takes for granted the essential goodness, innocence, and moral superiority of the international 'little man; 'the man in the street: the active, disembodied hero of a world-view which regards itself as superior to mere politics.
Roland Barthes too was quick to criticise the exhibition as being an example of his concept of myth - the dramatization of an ideological message. In his book Mythologies, published in France a year after the exhibition in Paris in 1956, Barthes declared it to be a product of "conventional humanism," a collection of photographs in which everyone lives and "dies in the same way everywhere." "Just showing pictures of people being born and dying tells us, literally, nothing."
Many other noteworthy reactions, both positive and negative, have been proffered in social/cultural studies and as part of artistic and historical texts. The earliest critics of the show were, ironically, photographers, who felt that Steichen had downplayed individual talent and discouraged the public from accepting photography as art. The show was the subject of an entire issue of Aperture; "The Controversial 'Family of Man.'" Walker Evans disdained its "human familyhood [and] bogus heartfeeling" Phoebe Lou Adams complained that "If Mr. Steichen's well-intentioned spell doesn't work, it can only be because he has been so intent on [Mankind's] physical similarities that...he has utterly forgotten that a family quarrel can be as fierce as any other kind."
Some critics complained that Steichen merely transposed the magazine photo-essay from page to museum wall; in 1955 Rollie McKenna likened the experience to a ride through a funhouse, while Russell Lynes in 1973 wrote that Family of Man "was a vast photo-essay, a literary formula basically, with much of the emotional and visual quality provided by sheer bigness of the blow-ups and its rather sententious message sharpened by juxtaposition of opposites — wheat fields and landscapes of boulders, peasants and patricians, a sort of 'look at all these nice folks in all these strange places who belong to this family.'" Jacob Deschin, photography critic for The New York Times, wrote, "the show is essentially a picture story to support a concept and an editorial achievement rather than an exhibition of photography."
From an optic of struggle, echoing Barthes, Susan Sontag in On Photography accused Steichen of sentimentalism and oversimplification: "... they wished, in the 1950s, to be consoled and distracted by a sentimental humanism. ... Steichen's choice of photographs assumes a human condition or a human nature shared by everybody." Directly quoting Barthes, without acknowledgement, she continues; "By purporting to show that individuals are born, work, laugh, and die everywhere in the same way, The Family of Man denies the determining weight of history - of genuine and historically embedded differences, injustices, and conflicts."
Allan Sekula in "The Traffic in Photographs" (1981) posits The Family of Man as a capitalist cultural tool levering world domination at the height of the Cold War; "My main point here is that The Family of Man, more than any other single photographic project, was a massive and ostentatious bureaucratic attempt to universalize photographic discourse," an exercise in hegemony which, "In the foreign showings of the exhibition, arranged by the United States Information Agency and co-sponsoring corporations like Coca-Cola, the discourse was explicitly that of American multinational capital and government–the new global management team–cloaked in the familiar and musty garb of patriarchy." Sekula revises and expands this notion in relation to his ideas about economic globalisation in an article in October entitled "Between the Net and the Deep Blue Sea: Rethinking the Traffic in Photographs".
Others attacked the show as an attempt to paper over problems of race and class, including Christopher Phillips, John Berger, and Abigail Solomon-Godeau, who in her 2004 essay, while describing herself as among "those who intellectually came of age as postmodernists, poststructuralists, feminists, Marxists, antihumanists, or, for that matter, atheists, this little essay of Barthes's efficiently demonstrated the problem — indeed the bad faith — of sentimental humanism", concedes that "as photography exhibitions go, it is perhaps the ultimate "bad object" for progressives or critical theorists", but "good to think with". Many of these critics, including Solomon-Godeau who openly admits it, had not viewed the exhibition but were working from the published catalogue which notably excludes the initially shown but soon removed picture of the lynched Robert McDaniels and the image of the atomic explosion as the apex at the end of the exhibition.
While The Family of Man was being exhibited there at its last venue in 1959 several pictures were torn down in Moscow by the Nigerian student Theophilus Neokonkwo. An Associated Press report of the time suggests that his actions were in a protest at colonialist attitudes to black races.
Conversely, other critics defended the exhibition, referring to the political and cultural environment in which it was staged. Among these were Fred Turner, Eric J. Sandeen, Blake Stimson and Walter L. Hixson. Most recently, a compilation of essays by contemporary critics supported by newly translated writings contemporary to the exhibition's appearances collected and edited by Gerd Hurm, Anke Reitz and Shamoon Zamir presents a revised reading of Steichen's motivations and audience reactions, and a reassessment of the validity of Roland Barthes' influential criticism in "La grande famille des hommes" in his Mythologies.
A number of photographers and artists refer to their experience of The Family of Man exhibition or publication as formative or influential on them and some, including Australian Graham McCarter, being motivated by it to take up photography. These include; Ans Westra, Marti Friedlander, Larry Seigel, John Cato, Paul Cox, Jan Yoors, Pentti Sammallahti, Robert McFarlane (photographer), John Blakemore, Robert Weingarten, and painter Francisco Toledo.
Tributes, sequels and critical revisions
In the years since The Family of Man, several exhibitions stemmed from projects directly inspired by Steichen's work and others were presented in opposition to it. Still others were alternative projects offering new thoughts on the themes and motifs presented in 1955. These serve to represent artists', photographers' and curators' responses to the exhibition beside those of the cultural critics, and to track the evolution of reactions as societies and their self-images change.
World Exhibition of Photography
Following The Family of Man by 10 years, the 1965 Weltausstellung der Fotografie (World Exhibition of Photography) was based on an idea by Karl Pawek and, supported by the German magazine he edited, Stern, toured the world. It presented 555 photographs by 264 authors from 30 countries, outweighing the numbers in Steichen's exhibition. In the preface to the catalogue entitled "Die humane Kamera" ('The human Camera'), Heinrich Boll wrote: "There are moments in which the meaning of a landscape and its breath become felt in a photograph. The portrayed person becomes familiar or a historical moment happens in front of the lens; a child in uniform, women who search the battlefield for their dead. They are moments in which crying is more than private as it becomes the crying of mankind. Secrets are not revealed, the secret about human existence becomes visible."
The exhibition, wrote Pawek, "would like to keep alive the spirit of Edward Steichen's wonderful ideas and of his memorable collection, The Family of Man". His exhibition posed the question 'Who is Man?' in 42 topics. It focused on issues that were sublimated in The Family of Man by the idea of universal brotherhood between men and women of different races and cultures. Racism, which in Steichen's show was represented by a lynching scene (replaced in the European showings by an enlargement of the famous picture of the Nuremberg trials), is confronted in the Weltausstellung der Fotografie section VIII "Das Missverständnis mit der Rasse" ('The Misunderstanding about Race') by the black man in the photograph by Gordon Parks who seems to view from his window two scenes of attacks on black people (photographed by Charles Moore). Another photograph by Henri Leighton shows two children walking together in public holding hands, one black, one white.
Though reference to the content of the older exhibition in the new is evident, the unifying idealism of The Family of Man is here replaced with a much more fragmented and sociological one. Sarah E. James points to its use of harsh juxtaposition to create a "stereoscopic vision" to entrain viewers reactions. The exhibition met with rejection by the press and functionaries in the photographic profession in Germany and Switzerland, and was described by Fritz Kempe, photographer, photo historian and board member of a prominent photo company, as "tasty fodder to stimulate the aggressive instincts of semi—intellectual young men.". Nevertheless, it went on to tour 261 art museums in 36 countries and was visited by 3,500,000 people.
2nd World Exhibition of Photography
In 1968, a second Weltausstellung der Photographie (2nd World Exhibition of Photography) was devoted to images of women with 522 photographs from 85 countries by 236 photographers, of whom barely 10% were female (compared to 21% for The Family of Man), though there is evidence of the effect of feminist consciousness in images of men in domestic environments cleaning, cooking and tending babies. In his introduction, Karl Pawek writes: "I had approached the first exhibition with my entire theological, philosophical and sociological equipment. 'What is Man?'; the question had to awaken ideological ideas. [...] I also operated from a philosophical point of view when presenting the[se] photos. As far as woman was concerned, the theme of the second exhibition, I knew nothing. There I was, without any philosophy about woman. Perhaps woman is not a philosophical theme. Perhaps there is only mankind, and woman is something unique and special? Thus I could only hold on to what was concrete in the pictures." The exhibition tour included the Institute of Contemporary Art (ICA), which at the time rarely showed photography, and her experience of installing it was in part the inspiration for Sue Davies to start The Photographers Gallery, London.
The Family of Children
UNESCO named 1977 The Year of Children and in response the book The Family of Children was dedicated to Steichen by editor Jerry Mason, and imitated the original catalogue in its layout, in the use of quotations and in the colours used on the cover. As for Steichen's show there was a call-out for imagery but 300,000 entries were received compared to the 4 million at the MoMA show, resulting in a selection of 377 photos by 218 participants from 70 countries.
The Family of Man 1955-1984
Independent curator Marvin Heiferman's The Family of Man 1955·1984 was a floor to ceiling collage of over 850 images and texts from magazines, newspapers and the art world shown in 1984 at PSI, The Institute for Art and Urban Resources Inc. (now MoMA PS1) Long Island City N.Y. Abigail Solomon-Godeau described it as a reexamination of the themes of the 1955 show and critique of Steichen's arrangement of them into a "spectacle";
...a grab bag of imagery and publicity ranging from baby food and sanitary napkin boxes to hard-core pornography, from detergent boxes to fashion photography, a cornucopia of consumer culture much of which, in one way or another, could be seen to engage the same themes purveyed in The Family of Man. In a certain sense, Heifferman's [sic] riposte to Steichen's show made the useful connection between the spectacle of the exhibition and the spectacle of the commodity, suggesting that both must be understood within the framing context of late capitalism.
Oppositions: We are the world, you are the third world
In 1990 the second Rotterdam Biennale lead exhibition was Oppositions: We are the world, you are the third world - Commitment and cultural identity in contemporary photography from Japan, Canada, Brazil, the Soviet Union and the Netherlands. The cover of the catalogue imitates the layout and colour of the original but replaces the famous image of the little flute player by Eugene Harris with six images, four photographs of young women from different cultural backgrounds and two excerpts from paintings. In the exhibit scenes of an endangered ecology and the threat to cultural identity in the global village predominate, but there are intimations that nature and love may prevail, despite everything artificial that surrounds it, notably so in family life.
New Relations. The Family of Man Revisited
In 1992 the American photographer and critic Larry Fink published a collection of photographs under the heading of New Relations. The Family of Man Revisited in the Photography Center Quarterly. His approach updated Steichen's vision by integrating aspects of human existence which Steichen had omitted both because of his wish for coherence and of his innermost convictions. Fink provides only the following commentary: "Rather than a fawn pretence to anthropological/sociologic analysis of the events depicted; rather than categorise and choose democratically for social relevance. I took the path of least resistance and most reward. I simply selected quality images with the belief that the path of strong visual energies would visit equal strong social presences". He concludes:
The show is a compendium of visual hints. It is not an answer or even a full question, but cognitive clues....
family, nation, tribe, community: SHIFT
In September/October 1996 the NGBK (Neue Gesellschaft fur Bildende kunst Berlin - New Society for the Visual Arts Berlin) in the context of Haus der Kulturen der Welt (House of World Cultures Berlin) conceived and organised the project family, nation, tribe, community: SHIFT with direct reference to the historical MoMA exhibition. In the catalogue, five authors; Ezra Stoller, Max Kozloff, Torsten Neuendorff, Bettina Allamoda and Jean Back analyse and comment on the historical model and twenty-two artists offer individual approaches around the following themes: Universalism/Separatism, Family/Anti-family, Individualisation, Common Strategies, Differences. The works are predominantly from artist photographers rather than photojournalists; Bettina Allamoda, Aziz + Cucher, Los Carpinteros, Alfredo Jaar, Mike Kelley, Edward and Nancy Reddin Kienholz, Lovett/Codagnone, Loring McAlpin, Christian Philipp Müller, Anna Petrie, Martha Rosler, Lisa Schmitz, Elaine Sturtevant, Mitra Tabizian and Andy Golding, Wolfgang Tillmans, Danny Tisdale, Lincoln Tobler, and David Wojnarowicz reflect major contemporary issues: identity, the information crisis, the illusion of leisure, and ethics. In his introduction to the exhibition, Frank Wagner writes that Steichen had offered a vision of an harmonious, neat and highly structured world which, in reality, was complex, often unintelligible and even contradictory, but by contrast, this Berlin exhibition highlights 'first' and 'third' world tensions and is eager to concentrate on a variety of attitudes.
The 90s: A Family of Man?
The following year Enrico Lunghi directed the exhibition The 90s: A Family of Man?: images of mankind in contemporary art, held 2 October–30 November 1997 in Luxembourg, Steichen's birthplace and by then the repository of the archive of a full version of his The Family of Man. Aside from their understanding of Steichen's efforts to present commonalities amongst the human race, curators Paul di Felice and Pierre Stiwer interpret Steichen's show as an effort to make content of Museum of Modern Art accessible to the public in an era when it was regarded as the elitist supporter of 'incomprehensible' abstract art. They point to their predecessor's success in having his show embraced by a record audience and emphasise that dissenting voices of criticism were heard only amongst 'intellectuals'. However, Steichen's success, they caution, was to manipulate the message of his selected imagery; "After all," they write, "wasn't he the artistic director of Vogue and Vanity Fair ... ?". They proclaim their desire to retain the exhibiting artists' 'autonomy' while not posing their work as the antithesis of Steichen's concept, but to respect, and echo, its arrangement while "raising questions"<it does not become clear, if the above words in simple '..' are actual quotations or just relativise the terms themselves.--> as indicated by the question mark in their quotation of the original title. The exhibition and catalogue 'quote' from Steichen, setting pages of the book of his exhibition with their quotations around groupings of images (in monochrome) beside the works of contemporary artists (predominantly in colour) collected in themes used in the original, though the correlation fails for some contemporary ideas, which digital imaging, installation and montage works effectively convey. The thirty-five artists include Christian Boltanski, Nan Goldin, Inez van Lamsweerde, Orlan and Wolfgang Tillmans.
The Family of Man 2
From 1999 to 2005, Leica Users Group members: Alastair Firkin, Satoshi Oka, Tim Spragens, Tom Smart and Stanislaw Stawowy organized The Family of Man 2 project to celebrate new millennium, 50 years of the Leica M system, and the Edward Steichen project anniversary. As with Steichen's project, the thousands of photos received were edited to 500, 100 annually during the project. It was exhibited online and an album with winning photos was privately published.
Reconsidering The Family of Man
The Photographic Society of America (PSA) drew on their archives to stage Reconsidering The Family of Man during April and May 2012. Not hung and mounted as an installation, Artspace at Untitled executive director<--Artspace at Burris' display? unintelligible. + Untitled (publication)--> Jon Burris' linear display was based on the concept of Steichen's original exhibit but concentrated on his sub-theme of the passage from birth to death. From the close to 5,000 photographs in the PSA collection, a selection of 50 original prints was made for their show. One work in common with the original exhibition was Ansel Adams' Mount Williamson from Manzanar which in The Family of Man was presented at mural scale, while the PSA used a vintage, 11" x 14" Adams print from their collection, displaying it while a first edition copy of The Family of Man publication opened to a double-page spread of Adams photograph.
The Family of the Invisibles
As part of the 2015-2016 France-Korea year, curators of the (Cnap) and the Fonds Régional d’Art Contemporain of Aquitaine (Frac Aquitaine), Pascal Beausse (Cnap), Claire Jacquet (Frac Aquitaine), and Magali Nachtergael, Assistant Professor at the Sorbonne, collaborated to produce the exhibition The Family of the Invisibles at the Seoul Museum of Art (SeMA) and the Ilwoo Space in Seoul, from 5 April to 29 May 2016. The show was devoted to invisible and minority figures, their demands for identity, and the possibility of reconfiguring a politics of representation to the ideal of giving a place to each member of the human community as represented in more than 200 emblematic photographs. The works from the 1930s to 2016, drawn from the Cnap and Frac Aquitaine collections were selected on the principle of Roland Barthes' deconstruction identified by the curators in his Mythologies and in Camera Lucida, the latter being treated as a visual manifesto for minorities. The exhibition was presented in the Seoul Museum of Art in four sections, culminating in provocative contemporary photography including the 2009 series of deceased migrants wrapped in cloth in Les Proscrits ('The Outcasts') by Mathieu Pernot, and Sophie Calle’s 1986 Les Aveugles in which she photographed those things that her blind subjects described as the most beautiful. The "Prologue" of the exhibition at the Ilwoo Space, provided a critical and historical counterpoint. Texts by Pascal Beausse, Jacqueline Guittard, Claire Jacquet and Magali Nachtergael, Suejin Shin (Ilwoo Foundation) and Kyung-hwan Yeo (SeMA) were presented in a catalogue.
The Family Of No Man: Re-visioning the world through non-male eyes
The Family Of No Man: Re-visioning the world through non-male eyes, held July 2–8, 2018 in Arles brought together responses to an open call by Cosmos Arles Books, a satellite space of the Rencontres d'Arles, by 494 female and inter-gender artists from all around the world, in a revisitation of Edward Steichen’s original. Works were displayed in interactive installations outdoors and indoors, and uploaded to an online platform as they were received.
Permanent installation, Chateau Clervaux, Luxembourg
The permanent installation of the exhibition today at Chateau Clervaux in Luxembourg follows the layout of the inaugural exhibition at MoMA in order to recreate the original viewing experience, though of necessity, it is adapted to the unique space of two floors of the restored Castle. Since the 2013 restoration it has incorporated a library (that includes some of the catalogues of the sequel exhibitions above) and contextualises The Family of Man with historical material and interpretation.
Cultural references to The Family of Man
Karl Dallas' song, The Family of Man, also recorded by the English band The Spinners and others, was written in 1955, after Dallas saw the exhibition.
In 1962, Instytut Mikołowski published Komentarze do fotografii. The Family of Man by Polish poet Witold Wirpsza (1918–1985), a commentary on individual photographs and selected displays from the exhibition.
References
Further reading
Berlier, Monique, ‘The Family of Man: Readings of an Exhibition’. In
Chapter 3 ‘Subtle Subterfuge: The Flawed Nobility of Edward Steichen's Family of Man.’ In
Gedney, W and Donaghy, D. ‘From The family of man (1955) to Robert Frank. William.’ In
Giocobbi, Giorgio, ‘Humanist Photography and The "Catholic" Family of Man.’ In
‘Photography as popular culture: The Family of Man.’ In
Gresh, Kristen. 2005. "The European Roots of 'The Family of Man' ". History of Photography 29, (4): 331-343.
Hurm, Gerd (ed.); Reitz, Anke (ed.); Zamir, Shamoon (ed.) (2018), The family of man revisited : photography in a global age, London I.B.Tauris,
Priem, K and Thyssen, G. ‘Puppets on a string in a theatre of display? Interactions of image, text, material, space and motion in The Family of Man’. In
Sandeen, Eric J. Picturing An Exhibition: The Family of Man and 1950s America. Albuquerque: University of New Mexico Press, 1995.
Sandeen, Eric J. ‘The Family of Man on the Road to Moscow.’ In
Steichen, Edward (2003) [1955]. The Family of Man. New York: The Museum of Modern Art.
Szarkowski, J. “The family of man”. In
‘The family of man: refurbishing humanism for a postmodern age’ (2004) In
Stimson, Blake (2006) The Pivot of the World: Photography and Its Nation. Cambridge, Massachusetts: MIT Press.
Turner, Fred (2012) 'The Family of Man and the Politics of Attention in Cold War America' in Public Culture 24:1 Duke University Press.
Hurm, Gerd / Reitz Anke / Zamir Shamoon (2018) ' The Family of Man Revisited. Photography in a Global Age '. London / New York : I.B. Tauris.
External links
Photographs documenting the complete original exhibition at MoMA
Official website of the Museum The Family of Man, Clervaux, Luxembourg
Official educational platform of the Museum The Family of Man
Official website of the Estate of Edward Steichen
Steichen Collection Musée National d'Histoire et d'Art, Luxembourg
The Bitter Years, Waasertuerm Gallery
Museum of Modern Art, Grace M. Mayer Papers
Steichen family papers the Beinecke Library Yale University
Smithsonian, National Air and Space Museum - American Expeditionary Force Photo Section (Steichen) Collection 1917-1919
Smithsonian, National Air and Space Museum - Edward J. Steichen World War II Navy Photographs Collection, 1941-1945
Carl Sandburg Home
University of Illinois Library, Carl Sandburg Papers
CarlSandburg.net: a Research Website for Sandburg Studies
1955 non-fiction books
Edward Steichen
Photographic collections
Photography exhibitions
Clervaux
Memory of the World Register
Museum of Modern Art (New York City) exhibitions
1955 in art
Cold War
Photojournalism
Documentary photography
Exhibition designers
History of photography
Culture of Luxembourg
Kinship and descent | The Family of Man | [
"Biology"
] | 11,031 | [
"Behavior",
"Human behavior",
"Kinship and descent"
] |
1,523,443 | https://en.wikipedia.org/wiki/Arthur%20Birch%20%28organic%20chemist%29 | Arthur John Birch, AC CMG FRS FAA (3 August 1915 – 8 December 1995) was an Australian organic chemist.
Birch developed the Birch reduction of aromatic rings (by treatment with lithium metal and ammonia) which is widely used in synthetic organic chemistry. The Birch Reduction enables the modification of steroids. In 1948 Birch published the first total synthesis of a male sex hormone (19-nortestosterone), as the first member of a new structural series. This series later comprised the first oral contraceptive pill, which was made by others. The Birch reduction also allows for the development of other steroid drugs and antibiotics – he also made the first simple synthesis of the ring A-B structure of cholesterol. Birch published over 440 scientific papers and reports.
Early life and education
Birch won a scholarship to attend the University of Sydney graduating with a BSc in 1937 and a MSc in 1938. He travelled to the University of Oxford to undertake his D.Phil., graduating in 1940.
Career
The hormone research he became involved with in 1940 was initiated by the RAF who then believed German fighter pilots were given cortical hormones He remained a research Fellow at Oxford until 1948 working under Sir Robert Robinson, when he became the Smithson Fellow at the University of Cambridge where he remained until 1952. At Cambridge he worked with Lord Todd.
He returned to Australia in 1952 to take up a Professorship in organic chemistry at the University of Sydney, he was made a fellow of the Australian Academy of Science in 1954. He held his position at the University of Sydney until 1955 when he took a similar position at Manchester University. He was made a Fellow of the Royal Society in 1958.
Birch returned to Australia again in 1967 to establish the Research School of Chemistry at the Australian National University in Canberra, becoming its founding dean. He remained involved with the school until 1980. He served as President of the Royal Australian Chemical Institute from 1977 to 1978, and also chaired the 1977 Independent Inquiry into CSIRO.
He served as President of the Australian Academy of Science from 1982 to 1986. Birch was made a Companion of the Order of Australia (AC) in 1987 for his contributions to science in Australia. He was awarded Honorary Fellowship of the Royal Australian Chemical Institute, in 1994. He was also a founding member of the Australian Science and Technology Council.
Before his death in 1995, the Research School of Chemistry building at ANU was named the "Birch Building" in his honour.
References
External links
Birch Reduction
1915 births
1995 deaths
Chemists at the University of Cambridge
Australian chemists
Companions of the Order of Australia
Fellows of the Australian Academy of Science
Fellows of the Royal Society
Foreign members of the USSR Academy of Sciences
Foreign members of the Russian Academy of Sciences
Organic chemists
Alumni of the University of Oxford
University of Sydney alumni
Academic staff of the University of Sydney
Presidents of the Australian Academy of Science | Arthur Birch (organic chemist) | [
"Chemistry"
] | 570 | [
"Organic chemists"
] |
1,523,861 | https://en.wikipedia.org/wiki/Carte%20de%20visite | The carte de visite (, English: 'visiting card', abbr. 'CdV', pl. cartes de visite) was a format of small photograph which was patented in Paris by photographer André Adolphe Eugène Disdéri in 1854, although first used by Louis Dodero in 1851.
Each photograph was the size of a formal visiting card about 4½ x 2½ inches (11.4 x 6.3 cm) and such photograph cards, in an early form of social media, were commonly traded among friends and visitors in the 1860s. Albums for the collection and display of cards became a common fixture in Victorian parlors. The popularity of the format and its rapid uptake worldwide were due to their relative cheapness, which made portrait photographs accessible to a broader demographic, and prior to the advent of mechanical reproduction of photographs, led to the publication and collection of portraits of prominent persons. It was the success of the carte de visite that led to photography's institutionalisation.
History
Format
The carte de visite was usually an albumen print from a collodion negative on thin paper glued onto a thicker paper card. The size of a carte de visite is × (approximately the size of a business card), mounted on a card sized × . The reverse was generally printed with the logo of the photographer or the photography studio from which it came, as both protection of copyright and advertising, and sometimes carried instructions for effective posing.
Camera
The daguerreotype for portrait photography had met with immediate and widespread popularity and quickly displaced the portrait miniature and its cheaper versions, the silhouette and the physionotrace. However its technologies were limited; a single copy was made in the camera could be reproduced only by copying the original onto another plate. The carte-de-visite provided a wet collodion negative from which could be made multiple prints, in a standardised format, with cheaper materials, thus permitting production on an industrial scale. Consequently it was even more affordable than the daguerreotype.
Special cameras were designed with multiple lenses for their efficient production. Disdéri's 1854 patent was a camera of taking eight separate negatives on a single plate in a special holder. Rather than one large collodion plate being used to produce one image of the posed subject, Disdéri's design initially exposed ten images on one plate, exposed either simultaneously or in sequence.
Each individual carte print was made at a fraction of the cost of producing one full-plate picture and ten were printed at once, saving time and thus efficiently serving the burgeoning consumer market for photography. Disdéri's patent was modified when making four images was found to be more practical, and in March 1860 optician Hyacinthe Hermagis patented a four-lens camera with a sliding back that became the standard. Désiré Monckhoven reported in 1859; We saw at M. Hermagis' a magnificent device, consisting of 4 identical double lenses mounted on a double frame camera built by M. Besson. This device, in a single operation, provides a plate on which 8 copies of the same image appear with perfect clarity. It seems that in the big cities, such as Paris, London, Berlin, St. Petersburg, these cartes de visite are widely used, so the device we saw at M. Hermagis' enjoys considerable success.
Enlargements
Cartes de visite were made using a contact print—by placing the negative in contact with the albumen paper under glass and exposing the sandwiched materials to a light source. No enlarger was required.
Nevertheless, the development of the solar camera enabled enlargements of cartes up to life-size, often hand-coloured and retouched so that they rivalled the painted portrait, and could be framed and displayed. Prominent London photographer the French-born Antoine Claudet lectured on the technology to the British Association in Oxford in June 1860, and in 1862 presented "On the means of following the small divisions of the scale regulating the distances and enlargement in the solar camera" at the British Association for the Advancement of Science in October. Earlier that year he exhibited a number of life-size portrait enlargements from carte de visite negatives at the 1862 World Fair, which were praised as 'magnificent' and 'without distortion'.
Popularity
France
The carte de visite was slow to gain widespread use until 1859, when Disdéri published Emperor Napoleon III's photos in this format. This made the format an overnight success; as Disdéri was to boast; "Everyone knows how I suddenly became popular by inventing the carte de visite which I had patented in 1854." He charged 20 francs for twelve photographs when previously a single print would cost 50 to 100 francs, so that portraits were suddenly available at a cost that the lower middle classes could afford. The new invention was so popular that "cardomania" spread quickly throughout Europe and then to the rest of the world.
Britain
In England John Jabez Edwin Mayall in Regent Street announced in August 1860 that he had; ...just received the Royal permission to publish a series of portraits which had been previously taken of the Royal family and of several other illustrious personages who have the honour of being intimate friends of her Majesty. These charming portraits are of miniature size; some of them are mounted on cards, and opposite to that of the Queen in the catalogue we find it described as a carte de visite. A complete series is placed upon a screen, in the centre of which are large portraits of his Royal Highness the Prince of Wales in military uniform, and his Royal Highness Prince Alfred in the dress of a midshipman in the Royal navy. Besides the single.figure portraits of the Royal family, there are several most delightful groups of them variously arranged [...] These portraits having been entirely divested of all appearance of Royal state, possess an air of novelty, and the illustrious personages being represented as if perfectly unconscious of the photographer's presence, and engaged in their ordinary occupations, seem to afford the public a legitimate peep into the privacy of the Royal apartments, and give a decided charm to this publication [...] purchasers may, while they have the satisfaction of displaying their loyalty, also have the pleasure of selecting those arrangements of the portraits to which they may give a preference. The whole series, including the personal friends of her Majesty, amounts to 32 portraits, and are very beautiful specimens of the photographic art.Mayall's publication of a carte-de-visite album of the Royal Family influenced the growing demand from the Victorian public for their own family photographic albums.
Germany
In Germany, Emperor Wilhelm I encouraged this pictorial culture by investing approximately 120 studios with the imprimatur of Hofphotograph (court photographer), based on the cartes that each had made of the kaiser, flatteringly posed with his gloved right fist planted powerfully on a table bearing his plumed helmet, and of his family. Millions of his photographs were collected in German family albums.
India
By the late 1850s the carte-de-visite had been taken up in India, particularly among the wealthy of Bombay. Hurrychind Chintamon was a successful early Indian photographers who made carte-de visite portraits of literary, political, and business figures, the most famous of which was of the Maharaja of Baroda, thousands of which were circulated.
China
While numbers of European photographers visited and practiced in the country, Lai Afong () was a successful Chinese-born photographer who, after working at the studio of Portuguese photographer José Joaquim Alves de Silvieria between 1865 and 1867, established Afong Studio in Hong Kong in the late Qing Dynasty from c.1870, and was photographer to Governor of Hong Kong Sir Arthur Kennedy KCB and Grand Duke Alexei Alexandrovich of Russia. Other Chinese photo studios producing cartes de visite in the 1890s include those of Kung Tai (公泰照相樓) and Sze Yuen Ming (上洋耀華照相) in Shanghai, and Pun Lun (繽綸) in Hong Kong.
Africa
Frederick York of Cape Town received the first carte-de-visite camera in South Africa as a present from H.R.H. Prince Alfred in February 1861.
United States
The carte de visite was introduced in New York, probably by Charles DeForest Fredricks, late in the summer of 1859 and proved immediately popular in the era of the Civil War. During the war years, photography studios across the country generated hundreds of thousands of carte-de-visite portraits in decorative pressed-paper and tooled-leather albums prized by the soldiers, and their families, thousands of which artefacts survive intact today. As The Times of London reported on August 30, 1862:America swarms with the members of the mighty tribe of cameristas, and the civil war has developed their business in the same way that it has given an impetus to the manufacturers of metallic air-tight coffins and embalmers of the dead. The young Volunteer rushes off at once to the studio when he puts on his uniform, and the soldier of a year's campaign sends home his likeness that the absent ones may see what changes have been produced in him by war's alarms. In every glade and by the roadsides of the camp may be seen all kinds of covered carts and portable sheds for the worker in metal acid and sun-ray. Washington has burst out into signboards of ambrotypists and collodionists, and the "professors" of New York, Boston, and Philadelphia send their representatives to pick up whatever is left, and to follow the camps as well as they can.Major studios producing cartes de visite included Brady & Company, Samuel Masury, J. Hall & Company, and N A. & R.A. Moore.
Americans, as with citizens of other countries, were also not only buying photographs of themselves, but also collecting photographs of celebrities.
South America
Portuguese-born Cristiano Júnior in Argentina, and German-born Alberto Henschel and Italian-born photographer Auguste Stahl in Brazil, made carte de visite pictures of “racial types” in the anthropometric genre—standardised poses of naked or semi-naked bodies—of slaves and freed people. As such they were not portraits since they lack any contextual information, or the name of the person; they illustrate contemporaneous biological theories of race being disseminated in Brazil, though not yet widely accepted. Stahl's were shown at the second National Exhibition in 1866. Such cartes de visites were circulated in Brazil between the 1860s and 1880s, as were caste-paintings in late 18th-century Spanish America, but Stahl's were exhibited only once as photographs. Even though praised for their “exceptionally high quality” by the painter Victor Meirelles they were excluded from the Brazilian representation at the London Exhibition of 1862, but at subsequent world's fairs they were present as engraved copies illustrating Swiss-American naturalist Louis Agassiz’ A Journey in Brazil (1868) circulated at the Vienna Universal Exhibition (1873) and the Philadelphia Centennial Exhibition (1876).From 1854 through the end of the century, the Peruvian photographic firm C. Clavijo produced carte de visite. This unique calling card depicts an unidentified woman as a tapada. The tapada was the most widespread “tipo de antano” or a sentimental, nostalgic stereotype of traditional stock characters from times gone by, a symbol of the lost colonial Lima. The tapada – meaning “covered” or “veiled” - refers to a type of traditional dress. The costume consisted of the manto (“shawl”) and saya (a close-fitting pleated skirt), both in conservative dark colors. The manto covered the head and was drawn to completely cover the face, leaving a triangular window exposing a single eye.
Australia
In Australia Manchester-born William Davies began his photographic career with Walter Woodbury (inventor of the Woodburytype) and established several studios in Melbourne from 1858. William Davies and Co at 98 Bourke St., being opposite the Theatre Royal, sold cartes de visite of famous actors, actresses and opera singers. The company also specialised in carte de visite portraits of Protestant clergymen posed as if writing their sermons. The Albury Banner and Wodonga Express of May 1863 finds it noteworthy that "a gentleman had occasion to advertise for a cook. Amongst other applications in answer to his advertisement was one from a "young lady" of the profession, enclosing her carte de visite and stating her salary."
As social media
Now regarded as an early manifestation of "social media", cartes-de-visite were an adjunct to letter-writing; unlike the fragile daguerreotypes which preceded them and which also were used predominantly for portraits, they could be posted in regular manufactured envelopes which had become available only ten years before.
For example, as Belknap notes, Charles Darwin exchanged in his correspondence a large number; 132 photographic portraits before 1882. Their value to him was demonstrated in his response to their gift of an album by Dutch naturalists containing 217 carte de visites; "...for the few remaining years of my life, whenever I want cheering, I will look at the portraits of my distinguish co-workers in the field of science, and remember their generous sympathy. When I die the album will be the most precious bequest to my children."
However, as a Saturday Review, of 1862 notes; "The demand for photographs is not limited to relations or friends. […] Anyone who has seen you, or has seen anybody that has seen you, or knows anyone that says he has seen a person who thought he had seen you, considers himself entitled to ask you for your photograph."
John Ruskin considered a photograph of him taken by William Downey as ʻvisible libelʼ, while Punch illustrator John Tenniel discovered John Watkins selling a portrait of himself that he found unflattering and tried to prevent further sales. Women in particular found themselves vulnerable to having their pictures purchased by 'cads' who would boast that she had gifted them the image and, given the moral standards of the day, discovered their reputations 'tarnished'.
Photographers were in effect publishers, distributing thousands of copies of their images. They would pay a well-known sitter in return for the right to publish their photograph; “the person photographed was offered a flat fee ranging from 25 to 1000 dollars, depending upon notoriety, or a royalty based upon the number of copies sold”. Those whose faces attracted sales, or who already had some incidental notoriety, earned further celebrity and might thus trade on it. However, copyright laws enacted contemporaneously in England protected photographers' rights over those of the subject. Andrew Wynter noted in 1862 that:
"The commercial value of the human face was never tested to such an extent as it is at the present moment in these handy photographs. No man, or woman either, knows but some accident may elevate them to the position of hero of the hour and send up the value their countenances to a degree they never dreamed of."
Demise
By the early 1870s, cartes de visite began to be supplanted by the cheaper tintypes franchised as the "American Gem," and by "cabinet cards" (the term established in Cabinet painting), which were also usually albumen prints, but larger, and mounted on cardboard backs measuring by . Nevertheless, while larger framed prints became available at photography studios, the two smaller formats were the main trade of professional portrait photographers even between 1888, when George Eastman introduced the mass produced and pre-loaded Kodak which industrialised the processing and printing of amateurs' photographs, and 1900, when the Brownie camera simplified the technology and so reduced the cost of the medium that snapshot photography became a mass phenomenon.
Gallery of cartes de visite
See also
Business card
Cabinet card
Postcard
Trading card
References
External links
Portraits of Scientists: Increase Lapham's Cartes-de-visite Collection Collected by pioneering Wisconsin antiquarian Increase A. Lapham between 1862–75, this album of carte-de-visite photographic portraits depicts many notable 19th-century scientists from America and Europe. Available on Wisconsin Historical Images, the Wisconsin Historical Society's online image database.
University of Washington Libraries Digital Collections – 19th Century Actors Photographs Cartes-de-visite studio portraits of entertainers, actors, singers, comedians and theater managers who were involved with or performed on the American stage in the mid-to-late 19th century.
William Emerson Strong Photograph Album – Duke University Libraries Digital Collections 200 cartes de visite depicting officers in the Confederate Army and Navy, officials in the Confederate government, famous Confederate wives, and other notable figures of the Confederacy. Also included are 64 photographs attributed to Mathew Brady.
Southern Cartes de Visite Collection, A.S. Williams III American Collection, Division of Special Collections, University of Alabama Libraries. Over 3300 digitized cartes de visite, the majority of them from southern studios.
The Carte de Visite file at the New-York Historical Society
Cartes de Visite of California photographers at Beinecke Library via flickr
Cartes-de-visite collection at the Smithsonian National Museum of American History
Ephemera
Photographic techniques dating from the 19th century
Portrait photography
Photography
French inventions
19th-century inventions
Popular culture
Social media | Carte de visite | [
"Technology"
] | 3,620 | [
"Computing and society",
"Social media"
] |
1,523,927 | https://en.wikipedia.org/wiki/Matrix%20representation | Matrix representation is a method used by a computer language to store column-vector matrices of more than one dimension in memory.
Fortran and C use different schemes for their native arrays. Fortran uses "Column Major" (AoS), in which all the elements for a given column are stored contiguously in memory. C uses "Row Major" (SoA), which stores all the elements for a given row contiguously in memory.
LAPACK defines various matrix representations in memory. There is also Sparse matrix representation and Morton-order matrix representation.
According to the documentation, in LAPACK the unitary matrix representation is optimized. Some languages such as Java store matrices using Iliffe vectors. These are particularly useful for storing irregular matrices. Matrices are of primary importance in linear algebra.
Basic mathematical operations
An m × n (read as m by n) order matrix is a set of numbers arranged in m rows and n columns. Matrices of the same order can be added by adding the corresponding elements. Two matrices can be multiplied, the condition being that the number of columns of the first matrix is equal to the number of rows of the second matrix. Hence, if an m × n matrix is multiplied with an n × r matrix, then the resultant matrix will be of the order m × r.
Operations like row operations or column operations can be performed on a matrix, using which we can obtain the inverse of a matrix. The inverse may be obtained by determining the adjoint as well. rows and columns are the different classes of matrices
In 3D graphics
The choice of representation for 4×4 matrices commonly used in 3D graphics affects the implementation of matrix/vector operations in systems with packed SIMD instructions:
Row major (SoA)
With row-major matrix order, it is easy to transform vectors using dot product operations, since the coefficients of each component are sequential in memory. Consequently, this layout may be desirable if a processor supports dot product operations natively. It is also possible to efficiently use a '3×4' affine transformation matrix without padding or awkward permutes.
Column major (AoS)
With column-major order, a "matrix × vector" multiply can be implemented with vectorized multiply-add operations, if the vector's components are broadcast to each SIMD lane. It is also easy to access the basis vectors represented by a transformation matrix as individual column vectors, as these are contiguous in memory.
See also
Row- and column-major order
Sparse matrix
Skyline matrix
Locality of reference
References
External links
a description of sparse matrices in R.
Matrices
Arrays | Matrix representation | [
"Mathematics"
] | 524 | [
"Matrices (mathematics)",
"Mathematical objects"
] |
1,524,006 | https://en.wikipedia.org/wiki/Shirt-sleeve%20environment | "Shirt-sleeve environment" is a term used in aircraft design to describe the interior of an aircraft in which no special clothing need be worn. Early aircraft had no internal pressurization, so the crews of those that reached the stratosphere had to be garbed to withstand the low temperature and pressure of the air outside. Respirator masks needed to cover the mouth and nose. Silk socks were worn to retain heat. Sometimes leather clothing, such as boots, were electrically heated. When jet fighter aircraft reached still higher altitudes, something similar to a space suit had to be worn, and pilots of the highest reconnaissance aircraft wore real space suits.
Commercial jet airliners fly in the stratosphere, but because they are pressurized, they could be said to have a shirt-sleeve environment. Crews of the US Apollo spacecraft always began the flight phases of launch, docking, and re-entry in space suits, although they could remove them for many hours. The Soviets tried to perfect this to save weight. This worked well, until an accidental depressurization on entry resulted in the deaths of an entire Soyuz crew. Protocols were changed shortly thereafter to require at least partial spacesuits. Early Soyuz spacecraft had no provision for space suits in the re-entry module, although the orbital module was intended for use as an airlock. Thus these operated in a shirt-sleeve environment except for spacewalks.
This term is also used in science fiction to describe an alien planet with an atmosphere breathable by humans without special equipment.
The Space Shuttle's Spacelab Habitable module was an area with expanded volume for astronauts to work in a shirt sleeve environment and had space for equipment racks and related support equipment for operations in Low Earth orbit.
One of the goals for MOLAB rover was to achieve a shirt-sleeve environment (compared to the Lunar Roving Vehicle which was open to space and required the use of space suits to operate). One of the considerations was the habitable volume that could be occupied.
References
Aerospace engineering
Safety engineering
Human habitats | Shirt-sleeve environment | [
"Engineering"
] | 414 | [
"Safety engineering",
"Systems engineering",
"Aerospace engineering"
] |
1,524,030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Cyclohexane conformations are any of several three-dimensional shapes adopted by cyclohexane. Because many compounds feature structurally similar six-membered rings, the structure and dynamics of cyclohexane are important prototypes of a wide range of compounds.
The internal angles of a regular, flat hexagon are 120°, while the preferred angle between successive bonds in a carbon chain is about 109.5°, the tetrahedral angle (the arc cosine of −). Therefore, the cyclohexane ring tends to assume non-planar (warped) conformations, which have all angles closer to 109.5° and therefore a lower strain energy than the flat hexagonal shape.
Consider the carbon atoms numbered from 1 to 6 around the ring. If we hold carbon atoms 1, 2, and 3 stationary, with the correct bond lengths and the tetrahedral angle between the two bonds, and then continue by adding carbon atoms 4, 5, and 6 with the correct bond length and the tetrahedral angle, we can vary the three dihedral angles for the sequences (2,3,4), (3,4,5), and (4,5,6). The next bond, from atom 6, is also oriented by a dihedral angle, so we have four degrees of freedom. But that last bond has to end at the position of atom 1, which imposes three conditions in three-dimensional space. If the bond angle in the chain (6,1,2) should also be the tetrahedral angle then we have four conditions. In principle this means that there are no degrees of freedom of conformation, assuming all the bond lengths are equal and all the angles between bonds are equal. It turns out that, with atoms 1, 2, and 3 fixed, there are two solutions called chair, depending on whether the dihedral angle for (1,2,3,4) is positive or negative, and these two solutions are the same under a rotation. But there is also a continuum of solutions, a topological circle where angle strain is zero, including the twist boat and the boat conformations. All the conformations on this continuum have a twofold axis of symmetry running through the ring, whereas the chair conformations do not (they have D symmetry, with a threefold axis running through the ring). It is because of the symmetry of the conformations on this continuum that it is possible to satisfy all four constraints with a range of dihedral angles at (1,2,3,4). On this continuum the energy varies because of Pitzer strain related to the dihedral angles. The twist boat has a lower energy than the boat. In order to go from the chair conformation to a twist-boat conformation or the other chair conformation, bond angles have to be changed, leading to a high-energy half-chair conformation. So the relative stabilities are: . All relative conformational energies are shown below. At room temperature the molecule can easily move among these conformations, but only chair and twist-boat can be isolated in pure form, because the others are not at local energy minima.
The boat and twist-boat conformations, as said, lie along a continuum of zero angle strain. If there are substituents that allow the different carbon atoms to be distinguished, then this continuum is like a circle with six boat conformations and six twist-boat conformations between them, three "right-handed" and three "left-handed". (Which should be called right-handed is unimportant.) But if the carbon atoms are indistinguishable, as in cyclohexane itself, then moving along the continuum takes the molecule from the boat form to a "right-handed" twist-boat, and then back to the same boat form (with a permutation of the carbon atoms), then to a "left-handed" twist-boat, and then back again to the achiral boat. The passage boat⊣twist-boat⊣boat⊣twist-boat⊣boat constitutes a pseudorotation.
Coplanar carbons
Another way to compare the stability within two molecules of cyclohexane in the same conformation is to evaluate the number of coplanar carbons in each molecule. Coplanar carbons are carbons that are all on the same plane. Increasing the number of coplanar carbons increases the number of eclipsing substituents trying to form a 120°, which is unattainable due to the overlapping hydrogens. This overlap increases the overall torsional strain and decreases the stability of the conformation. Cyclohexane diminishes the torsional strain from eclipsing substituents through adopting a conformation with a lower number of nonplanar carbons. For example, if a half-chair conformation contains four coplanar carbons and another half-chair conformation contains five coplanar carbons, the conformation with four coplanar carbons will be more stable.
Principal conformers
The different conformations are called "conformers", a blend of the words "conformation" and "isomer".
Chair conformation
The chair conformation is the most stable conformer. At , 99.99% of all molecules in a cyclohexane solution adopt this conformation.
The C–C ring of the chair conformation has the same shape as the 6-membered rings in the diamond cubic lattice. This can be modeled as follows. Consider a carbon atom to be a point with four half-bonds sticking out towards the vertices of a tetrahedron. Place it on a flat surface with one half-bond pointing straight up. Looking from directly above, the other three half-bonds will appear to point outwards towards the vertices of an equilateral triangle, so the bonds will appear to have an angle of 120° between them. Arrange six such atoms above the surface so that these 120° angles form a regular hexagon. Reflecting three of the atoms to be below the surface yields the desired geometry.
All carbon centers are equivalent. They alternate between two parallel planes, one containing C1, C3 and C5, and the other containing C2, C4, and C6. The chair conformation is left unchanged after a rotation of 120° about the symmetry axis perpendicular to these planes, as well as after a rotation of 60° followed by a reflection in the midpoint plane, resulting in a symmetry group of D3d. While all C–C bonds are tilted relative to the plane, diametrically opposite bonds (such as C1–C2 and C4–C5) are parallel to each other.
Six of the twelve C–H bonds are axial, pointing upwards or downwards almost parallel to the symmetry axis. The other six C–H bonds are equatorial, oriented radially outwards with an upwards or downwards tilt. Each carbon center has one axial C–H bond (pointed alternately upwards or downwards) and one equatorial C–H bond (tilted alternately downwards or upwards), enabling each X–C–C–Y unit to adopt a staggered conformation with minimal torsional strain. In this model, the dihedral angles for series of four carbon atoms going around the ring alternate between exactly +60° (gauche+) and −60° (gauche−).
The chair conformation cannot be deformed without changing bond angles or lengths. It can be represented as two linked chains, C1–C2–C3–C4 and C1–C6–C5–C4, each mirroring the other, with opposite dihedral angles. The C1–C4 distance depends on the absolute value of this dihedral angle, so in a rigid model, changing one angle requires changing the other angle. If both dihedral angles change while remaining opposites of each other, it is not possible to maintain the correct C–C–C bond angles at C1 and C4.
The chair geometry is often preserved when the hydrogen atoms are replaced by halogens or other simple groups. However, when these hydrogens are substituted for a larger group, additional strain may occur due to diaxial interactions between pairs of substituents occupying the same-orientation axial position, which are typically repulsive due to steric crowding.
Boat and twist-boat conformations
The boat conformations have higher energy than the chair conformations. The interaction between the two flagpole hydrogens, in particular, generates steric strain. Torsional strain also exists between the C2–C3 and C5–C6 bonds (carbon number 1 is one of the two on a mirror plane), which are eclipsed — that is, these two bonds are parallel one to the other across a mirror plane. Because of this strain, the boat configuration is unstable (i.e. is not a local energy minimum).
The molecular symmetry is C2v.
The boat conformations spontaneously distorts to twist-boat conformations. Here the symmetry is D2, a purely rotational point group with three twofold axes. This conformation can be derived from the boat conformation by applying a slight twist to the molecule so as to remove eclipsing of two pairs of methylene groups. The twist-boat conformation is chiral, existing in right-handed and left-handed versions.
The concentration of the twist-boat conformation at room temperature is less than 0.1%, but at it can reach 30%. Rapid cooling of a sample of cyclohexane from to will freeze in a large concentration of twist-boat conformation, which will then slowly convert to the chair conformation upon heating.
Dynamics
Chair to chair
The interconversion of chair conformers is called ring flipping or chair-flipping. Carbon–hydrogen bonds that are axial in one configuration become equatorial in the other, and vice versa. At room temperature the two chair conformations rapidly equilibrate. The proton NMR spectrum of cyclohexane is a singlet at room temperature, with no separation into separate signals for axial and equatorial hydrogens.
In one chair form, the dihedral angle of the chain of carbon atoms (1,2,3,4) is positive whereas that of the chain (1,6,5,4) is negative, but in the other chair form, the situation is the opposite. So both these chains have to undergo a reversal of dihedral angle. When one of these two four-atom chains flattens to a dihedral angle of zero, we have the half-chair conformation, at a maximum energy along the conversion path. When the dihedral angle of this chain then becomes equal (in sign as well as magnitude) to that of the other four-atom chain, the molecule has reached the continuum of conformations, including the twist boat and the boat, where the bond angles and lengths can all be at their normal values and the energy is therefore relatively low. After that, the other four-carbon chain has to switch the sign of its dihedral angle in order to attain the target chair form, so again the molecule has to pass through the half-chair as the dihedral angle of this chain goes through zero. Switching the signs of the two chains sequentially in this way minimizes the maximum energy state along the way (at the half-chair state) — having the dihedral angles of both four-atom chains switch sign simultaneously would mean going through a conformation of even higher energy due to angle strain at carbons 1 and 4.
The detailed mechanism of the chair-to-chair interconversion has been the subject of much study and debate. The half-chair state (D, in figure below) is the key transition state in the interconversion between the chair and twist-boat conformations. The half-chair has C2 symmetry. The interconversion between the two chair conformations involves the following sequence: chair → half-chair → twist-boat → half-chair′ → chair′.
Twist-boat to twist-boat
The boat conformation (C, below) is a transition state, allowing the interconversion between two different twist-boat conformations. While the boat conformation is not necessary for interconversion between the two chair conformations of cyclohexane, it is often included in the reaction coordinate diagram used to describe this interconversion because its energy is considerably lower than that of the half-chair, so any molecule with enough energy to go from twist-boat to chair also has enough energy to go from twist-boat to boat. Thus, there are multiple pathways by which a molecule of cyclohexane in the twist-boat conformation can achieve the chair conformation again.
Substituted derivatives
In cyclohexane, the two chair conformations have the same energy. The situation becomes more complex with substituted derivatives.
Monosubstituted cyclohexanes
A monosubstituted cyclohexane is one in which there is one non-hydrogen substituent in the cyclohexane ring. The most energetically favorable conformation for a monosubstituted cyclohexane is the chair conformation with the non-hydrogen substituent in the equatorial position because it prevents high steric strain from 1,3 diaxial interactions. In methylcyclohexane the two chair conformers are not isoenergetic. The methyl group prefers the equatorial orientation. The preference of a substituent towards the equatorial conformation is measured in terms of its A value, which is the Gibbs free energy difference between the two chair conformations. A positive A value indicates preference towards the equatorial position. The magnitude of the A values ranges from nearly zero for very small substituents such as deuterium, to about 5 kcal/mol (21 kJ/mol) for very bulky substituents such as the tert-butyl group. Thus, the magnitude of the A value will also correspond to the preference for the equatorial position. Though an equatorial substituent has no 1,3 diaxial interaction that causes steric strain, it has a Gauche interaction in which an equatorial substituent repels the electron density from a neighboring equatorial substituent.
Disubstituted cyclohexanes
For 1,2- and 1,4-disubstituted cyclohexanes, a cis configuration leads to one axial and one equatorial group. Such species undergo rapid, degenerate chair flipping. For 1,2- and 1,4-disubstituted cyclohexane, a trans configuration, the diaxial conformation is effectively prevented by its high steric strain. For 1,3-disubstituted cyclohexanes, the cis form is diequatorial and the flipped conformation suffers additional steric interaction between the two axial groups. trans-1,3-Disubstituted cyclohexanes are like cis-1,2- and cis-1,4- and can flip between the two equivalent axial/equatorial forms.
Cis-1,4-Di-tert-butylcyclohexane has an axial tert-butyl group in the chair conformation and conversion to the twist-boat conformation places both groups in more favorable equatorial positions. As a result, the twist-boat conformation is more stable by at as measured by NMR spectroscopy.
Also, for a disubstituted cyclohexane, as well as more highly substituted molecules, the aforementioned A values are additive for each substituent. For example, if calculating the A value of a dimethylcyclohexane, any methyl group in the axial position contributes 1.70 kcal/mol- this number is specific to methyl groups and is different for each possible substituent. Therefore, the overall A value for the molecule is 1.70 kcal/mol per methyl group in the axial position.
1,3 diaxial interactions and gauche interactions
1,3 Diaxial interactions occur when the non-hydrogen substituent on a cyclohexane occupies the axial position. This axial substituent is in the eclipsed position with the axial substituents on the 3-carbons relative to itself (there will be two such carbons and thus two 1,3 diaxial interactions). This eclipsed position increases the steric strain on the cyclohexane conformation and the confirmation will shift towards a more energetically favorable equilibrium.
Gauche interactions occur when a non-hydrogen substituent on a cyclohexane occupies the equatorial position. The equatorial substituent is in a staggered position with the 2-carbons relative to itself (there will be two such carbons and thus two 1,2 gauche interactions). This creates a dihedral angle of ~60°. This staggered position is generally preferred to the eclipsed positioning.
Effects of substituent size on stability
Once again, the conformation and position of groups (ie. substituents) larger than a singular hydrogen are critical to the overall stability of the molecule. The larger the group, the less likely to prefer the axial position on its respective carbon. Maintaining said position with a larger size costs more energy from the molecule as a whole because of steric repulsion between the large groups' nonbonded electron pairs and the electrons of the smaller groups (ie. hydrogens). Such steric repulsions are absent for equatorial groups. The cyclohexane model thus assesses steric size of functional groups on the basis of gauche interactions. The gauche interaction will increase in energy as the size of the substituent involved increases. For example, a t-butyl substituent would sustain a higher energy gauche interaction as compared to a methyl group, and therefore, contribute more to the instability of the molecule as a whole.
In comparison, a staggered conformation is thus preferred; the larger groups would maintain the equatorial position and lower the energy of the entire molecule. This preference for the equatorial position among bulkier groups lowers the energy barriers between different conformations of the ring. When the molecule is activated, there will be a loss in entropy due to the stability of the larger substituents. Therefore, the preference of the equatorial positions by large molecules (such as a methyl group) inhibits the reactivity of the molecule and thus makes the molecule more stable as a whole.
Effects on conformational equilibrium
Conformational equilibrium is the tendency to favor the conformation where cyclohexane is the most stable. This equilibrium depends on the interactions between the molecules in the compound and the solvent. Polarity and nonpolarity are the main factors in determining how well a solvent interacts with a compound. Cyclohexane is considered nonpolar, meaning that there is no electronegative difference between its bonds and its overall structure is symmetrical. Due to this, when cyclohexane is immersed in a polar solvent, it will have less solvent distribution, which signifies a poor interaction between the solvent and solute. This produces a limited catalytic effect. Moreover, when cyclohexane comes into contact with a nonpolar solvent, the solvent distribution is much greater, showing a strong interaction between the solvent and solute. This strong interaction yields a heighten catalytic effect.
Heterocyclic analogs
Heterocyclic analogs of cyclohexane are pervasive in sugars, piperidines, dioxanes, etc. They exist generally follow the trends seen for cyclohexane, i.e. the chair conformer being most stable. The axial–equatorial equilibria (A values) are however strongly affected by the replacement of a methylene by O or NH. Illustrative are the conformations of the glucosides. 1,2,4,5-Tetrathiane ((SCH2)3) lacks the unfavorable 1,3-diaxial interactions of cyclohexane. Consequently its twist-boat conformation is populated; in the corresponding tetramethyl structure, 3,3,6,6-tetramethyl-1,2,4,5-tetrathiane, the twist-boat conformation dominates.
Historical background
In 1890, , a 28-year-old assistant in Berlin, published instructions for folding a piece of paper to represent two forms of cyclohexane he called symmetrical and asymmetrical (what we would now call chair and boat). He clearly understood that these forms had two positions for the hydrogen atoms (again, to use modern terminology, axial and equatorial), that two chairs would probably interconvert, and even how certain substituents might favor one of the chair forms (). Because he expressed all this in mathematical language, few chemists of the time understood his arguments. He had several attempts at publishing these ideas, but none succeeded in capturing the imagination of chemists. His death in 1893 at the age of 31 meant his ideas sank into obscurity. It was only in 1918 that , based on the molecular structure of diamond that had recently been solved using the then very new technique of X-ray crystallography, was able to successfully argue that Sachse's chair was the pivotal motif. Derek Barton and Odd Hassel shared the 1969 Nobel Prize in Chemistry for work on the conformations of cyclohexane and various other molecules.
Practical applications
Cyclohexane is the most stable of the cycloalkanes, due to the stability of adapting to its chair conformer. This conformer stability allows cyclohexane to be used as a standard in lab analyses. More specifically, cyclohexane is used as a standard for pharmaceutical reference in solvent analysis of pharmaceutical compounds and raw materials. This specific standard signifies that cyclohexane is used in quality analysis of food and beverages, pharmaceutical release testing, and pharmaceutical method development; these various methods test for purity, biosafety, and bioavailability of products. The stability of the chair conformer of cyclohexane gives the cycloalkane a versatile and important application when regarding the safety and properties of pharmaceuticals.
References
Further reading
Colin A. Russell, 1975, "The Origins of Conformational Analysis," in Van 't Hoff–Le Bel Centennial, O. B. Ramsay, Ed. (ACS Symposium Series 12), Washington, D.C.: American Chemical Society, pp. 159–178.
William Reusch, 2010, "Ring Conformations" and "Substituted Cyclohexane Compounds," in Virtual Textbook of Organic Chemistry, East Lansing, MI, USA:Michigan State University, see and , accessed 20 June 2015.
External links
Java applets of all conformations from the University of Nijmegen
Stereochemistry
Cyclohexanes
de:Konformation#Konformationen bei cyclischen Molekülen
it:Cicloesano#Conformazione | Cyclohexane conformation | [
"Physics",
"Chemistry"
] | 4,788 | [
"Spacetime",
"Stereochemistry",
"Space",
"nan"
] |
1,524,234 | https://en.wikipedia.org/wiki/Project%20Manhigh | Project Manhigh was a pre-Space Age military project that took men in balloons to the middle layers of the stratosphere, funded as an aero-medical research program, though seen by its designers as a stepping stone to space. It was conducted by the United States Air Force between 1955 and 1958.
History
The project started in December 1955 to study the effects of cosmic rays on humans. Three balloon flights to the stratosphere were made during the program:
Manhigh I to , by Captain Joseph W. Kittinger on June 2, 1957. The balloon was launched from South St. Paul Airport and the flight was cut short due to one of the capsule's valves being installed backwards which vented the oxygen supply outside, but not before reaching a record altitude of 96,784 feet.
Manhigh II to , by Major David G. Simons on August 19–20, 1957, launched from Portsmouth Mine in Crosby, Minnesota, for a 32-hour flight that included a set of 25 experiments and observations, and earned Simons a Life magazine cover spot. With the pilot and the scientific payload, the Manhigh II gondola had a total mass of . At maximum altitude, the balloon expanded to a diameter of with a volume of over .
Manhigh III to , by Lieutenant Clifton M. McClure on October 8, 1958
Candidates for the Manhigh project were put through a series of physical and psychological tests that became the standard for qualifying astronauts for the Project Mercury, America's first manned orbital space program.
Similar projects in which men in a gondola reached near-space altitudes were performed by Swiss physicist Auguste Piccard and Paul Kipfer, reaching in 1931, USSR-1 piloted by Georgy Prokofiev reaching in 1933, and Osoaviakhim-1 reaching in 1934 as well as Explorer II reaching in 1935.
See also
John Stapp
Project Excelsior, follow-on flights in 1959 and 1960
Project Adam, a contemporary plan using Manhigh hardware by the United States Army
Flight altitude record
References
Further reading
External links
Details of Manhigh I, Manhigh II flight, and Manhigh III at stratocat.com.ar
Space Men (American Experience episode)
Ballooning
Space research
Human subject research in the United States
Military projects of the United States | Project Manhigh | [
"Engineering"
] | 478 | [
"Military projects of the United States",
"Military projects"
] |
1,524,402 | https://en.wikipedia.org/wiki/Chgrp | The (from change group) command may be used by unprivileged users on various operating systems to change the group associated with a file system object (such as a computer file, directory, or link) to one of which they are a member. A file system object has 3 sets of access permissions, one set for the owner, one set for the group and one set for others. Changing the group of an object could be used to change which users can write to a file.
History
The command was originally developed as part of the Unix operating system by AT&T Bell Laboratories.
It is also available in the Plan 9 and Inferno operating systems and in most Unix-like systems.
The command has also been ported to the IBM i operating system.
The version of chgrp bundled in GNU coreutils was written by David MacKenzie.
Syntax
chgrp [options] group FSO
The group parameter specifies the new group with which the files or directories should be associated. It may either be a symbolic name or an identifier.
The FSO specifies one or more file system objects, which may be the result of a glob expression like .
Frequently implemented options
recurse through subdirectories.
verbosely output names of objects changed. Most useful when is a list.
force or forge ahead with other objects even if an error is encountered.
Example
$ ls -l *.conf
-rw-rw-r-- 1 gbeeker wheel 3545 Nov 04 2011 prog.conf
-rw-rw-r-- 1 gbeeker wheel 3545 Nov 04 2011 prox.conf
$ chgrp staff *.conf
$ ls -l *.conf
-rw-rw-r-- 1 gbeeker staff 3545 Nov 04 2011 prog.conf
-rw-rw-r-- 1 gbeeker staff 3545 Nov 04 2011 prox.conf
The above command changes the group associated with file prog.conf from to (provided the executing user is a member of that group). This could be used to allow members of staff to modify the configuration for programs and .
See also
chmod
chown
Group identifier (Unix)
List of Unix commands
id (Unix)
References
External links
Operating system security
Standard Unix programs
Unix SUS2008 utilities
Plan 9 commands
Inferno (operating system) commands
IBM i Qshell commands
de:Unix-Kommandos#Benutzer- und Rechteverwaltung | Chgrp | [
"Technology"
] | 525 | [
"IBM i Qshell commands",
"Standard Unix programs",
"Computing commands",
"Plan 9 commands",
"Inferno (operating system) commands"
] |
1,524,517 | https://en.wikipedia.org/wiki/Chinese%20astronomy | Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categorized in the twenty-eight mansions have been found on oracle bones unearthed at Anyang, dating back to the mid-Shang dynasty. The core of the "mansion" (宿 xiù) system also took shape around this period, by the time of King Wu Ding (1250–1192 BCE).
Detailed records of astronomical observations began during the Warring States period (fourth century BCE). They flourished during the Han period (202 BCE – 220 CE) and subsequent dynasties with the publication of star catalogues. Chinese astronomy was equatorial, centered on close observation of circumpolar stars, and was based on different principles from those in traditional Western astronomy, where heliacal risings and settings of zodiac constellations formed the basic ecliptic framework. Joseph Needham has described the ancient Chinese as the most persistent and accurate observers of celestial phenomena anywhere in the world before the Islamic astronomers.
Some elements of Indian astronomy reached China with the expansion of Buddhism after the Eastern Han dynasty (25–220 CE), but most incorporation of Indian astronomical thought occurred during the Tang dynasty (618–907 CE), when numerous Indian astronomers took up residence in the Chinese capital Chang'an, and Chinese scholars, such as the Tantric Buddhist monk and mathematician Yi Xing, mastered the Indian system. Islamic astronomers collaborated closely with their Chinese colleagues during the Yuan dynasty, and, after a period of relative decline during the Ming dynasty, astronomy was revitalized under the stimulus of Western cosmology and technology after the Jesuits established their missions. The telescope was introduced from Europe in the seventeenth century. In 1669, the Peking observatory was completely redesigned and refitted under the direction of Ferdinand Verbiest. Today, China continues to be active in the field of astronomy, with many observatories and its own space program.
Early history
Purpose of astronomical observations in the past
One of the main functions of astronomy was for the purpose of timekeeping. The Chinese used a lunisolar calendar, but as the cycles of the Sun and the Moon are different, leap months had to be inserted regularly.
The Chinese calendar was considered to be a symbol of a dynasty. As dynasties would rise and fall, astronomers and astrologers of each period would often prepare a new calendar, making observations for that purpose.
Astrological divination was also an important part of astronomy. Astronomers took note of "guest stars", usually supernovas or comets, which appear among the fixed stars. The supernova which created the Crab Nebula, now known as SN 1054, is an example of an astronomical event observed by Ancient Chinese astronomers. Ancient astronomical records of phenomena like comets and supernovae are sometimes used in modern astronomical studies.
Cosmology
The Chinese developed multiple cosmological models before Western influences changed the field:
Gai Tian ("canopy heaven") – The sky is a hemisphere, the Earth is a disc at the bottom, surrounded by water, which rotates around the North Pole once a day. The Sun traces a circle in the hemisphere, the size of which varies with the seasons. As described in the Zhoubi Suanjing.
Hun Tian ("the entire sky") – Similar to Gai Tian, but the sky is a full sphere. The seasons are explained by the North Pole shifting rather than remaining directly overhead.
Shuen Ye, Xuan Ye, or Suan Ye – The heavens are infinite in extent, the celestial bodies are floating about on their own at rare intervals, and "the speed of the luminaries depends on their individual natures, which shows they are not attached to anything." Very few pieces of information are known about this school of thought.
Constellations
The divisions of the sky began with the Northern Dipper and the 28 mansions. In 1977, a lacquer box was excavated from the Tomb of Marquis Yi of Zeng, in Suixian, Hubei Province. Names of the 28 lunar mansions were found on the cover of the box, proving that the use of this classification system was made before 433 BCE.
As lunar mansions have such an ancient origin, the meanings of most of their names have become obscure. Contributing to later confusion, the name of each lunar mansion consists of only one Chinese word, the meaning of which could vary at different times in history. The meanings of the names are still under discussion.
Besides the 28 lunar mansions, most constellations are based on the works of Shi Shen-fu and Gan De, who were astrologists during the period of the Warring States (481–221 BCE) in China. In his Shiji, the Western Han era historian Sima Qian (145–86 BCE) provided a star catalogue that includes 90 constellations. The Eastern Han era polymath scientist and inventor Zhang Heng (78–139 CE) published a star catalogue in 120 CE that features 124 recorded constellations.
In the late period of the Ming dynasty, the agricultural scientist and mathematician Xu Guangqi (1562–1633 CE) introduced 23 additional constellations near to the Celestial South Pole, which are based on star catalogues from the Western world introduced by his colleague, the Italian Jesuit Matteo Ricci.
Star catalogues and maps
Star catalogues
In the fourth century BCE, the two Chinese astronomers responsible for the earliest information going into the star catalogues were Shi Shen and Gan De of the Warring States period.
These books appeared to have lasted until the sixth century, but were lost after that. A number of books share similar names, often quoted and named after them. These texts should not be confused with the original catalogues written by them. Notable works that helped preserve the contents include:
Wu Xian (巫咸) has been one of the astronomers under debate. He is often represented as one of the "Three Schools Astronomical tradition", along with Gan and Shi. The Chinese classic text Star Manual of Master Wu Xian (巫咸星經) and its authorship is still in dispute, because it mentioned names of twelve countries that did not exist in the Shang dynasty, the era in which it was supposed to have been written. Moreover, it was customary in the past for the Chinese to forge works of notable scholars, as this could lead to a possible explanation for the inconsistencies found. Wu Xian is generally mentioned as the astronomer who lived many years before Gan and Shi.
The Han dynasty astronomer and inventor Zhang Heng (78–139 CE) not only catalogued some 2500 different stars, but also recognized more than 100 different constellations. Zhang Heng also published his work Ling Xian, a summary of different astronomical theories in China at the time. In the subsequent period of the Three Kingdoms (220–280 CE), Chen Zhuo (陳卓) combined the work of his predecessors, forming another star catalogue. This time, 283 constellations and 1464 stars were listed. The astronomer Guo Shoujin of the Yuan dynasty (1279–1368 CE) created a new catalogue, which was believed to contain thousands of stars. Unfortunately, many of the documents of that period were destroyed, including that of Shoujin. Imperial Astronomical Instruments (儀象考成) was published in 1757 and contains 3083 stars exactly.
Star maps
The Chinese drew many maps of stars in the past centuries. It is debatable as to which counts as the oldest star maps, since pottery and old artifacts can also be considered star maps. One of the oldest existent star maps in printed form is from Su Song's (1020–1101 CE) celestial atlas of 1092 CE, which was included in the horological treatise on his clocktower. The most famous one is perhaps the Dunhuang map found in Dunhuang, Gansu. Uncovered by the British archaeologist Marc Aurel Stein in 1907, the star map was brought to the British Museum in London. The map was drawn on paper and represents the complete sky, with more than 1,350 stars. Although ancient Babylonians and Greeks also observed the sky and catalogued stars, no such complete record of the stars may exist or survive. Hence, this is the oldest chart of the skies at present.
According to recent studies, the map may date the manuscript to as early as the seventh century CE (Tang dynasty). Scholars believe the star map dates from 705 to 710 CE, which is the reign of Emperor Zhongzong of Tang. There are some texts (Monthly Ordinances, 月令) describing the movement of the sun along the sky each month, which was not based on the observation at that time.
Solar and lunar eclipses
Chinese astronomers recorded 1,600 observations of solar and lunar eclipses from 750 BCE. The ancient Chinese astronomer Shi Shen (fl. fourth century BCE) was aware of the relation of the Moon in a solar eclipse, as he provided instructions in his writing to predict them by using the relative positions of the Moon and the Sun. The radiating-influence theory, where the Moon's light was nothing but a reflection of the Sun's, was supported by the mathematician and music theorist Jing Fang (78–37 BCE), yet opposed by the Chinese philosopher Wang Chong (27–97 CE), who made clear in his writing that this theory was nothing new. Jing Fang wrote:
The ancient Greeks had known this as well, since Parmenides and Aristotle supported the theory of the Moon shining because of reflected light. The Chinese astronomer and inventor Zhang Heng (78–139 CE) wrote of both solar eclipse and lunar eclipse in the publication of Ling Xian (靈憲), 120 CE:
The sun is like fire and the moon like water. The fire gives out light and the water reflects it. Thus, the moon's brightness is produced from the radiance of the sun, and the moon's darkness (pho) is due to (the light of) the sun being obstructed (pi). The side which faces the sun is fully lit, and the side which is away from it is dark. The planets (as well as the moon) have the nature of water and reflect light. The light pouring forth from the sun (tang jih chih chhung kuang) does not always reach the moon, owing to the obstruction (pi) of the earth itself—this is called 'an-hsü', a lunar eclipse. When (a similar effect) happens with a planet (we call it) an occultation (hsing wei); when the moon passes across (kuo) (the sun's path) then there is a solar eclipse (shih).
The later Song dynasty scientist Shen Kuo (1031–1095 CE) used the models of lunar eclipse and solar eclipse in order to prove that the celestial bodies were round, not flat. This was an extension of the reasoning of Jing Fang and other theorists as early as the Han dynasty. In his Dream Pool Essays of 1088 CE, Shen related a conversation he had with the director of the Astronomical Observatory, who had asked Shen if the shapes of the Sun and the Moon were round like balls or flat like fans. Shen Kuo explained his reasoning for the former:
If they were like balls they would surely obstruct each other when they met. I replied that these celestial bodies were certainly like balls. How do we know this? By the waxing and waning of the moon. The moon itself gives forth no light, but is like a ball of silver; the light is the light of the sun (reflected). When the brightness is first seen, the sun (-light passes almost) alongside, so the side only is illuminated and looks like a crescent. When the sun gradually gets further away, the light shines slanting, and the moon is full, round like a bullet. If half of a sphere is covered with (white) powder and looked at from the side, the covered part will look like a crescent; if looked at from the front, it will appear round. Thus we know that the celestial bodies are spherical.
When he asked Shen Kuo why eclipses occurred only on an occasional basis while in conjunction and opposition once a month, Shen Kuo wrote:
I answered that the ecliptic and the moon's path are like two rings, lying one over the other, but distant by a small amount. (If this obliquity did not exist), the sun would be eclipsed whenever the two bodies were in conjunction, and the moon would be eclipsed whenever they were exactly in opposition. But (in fact) though they may occupy the same degree, the two paths are not (always) near (each other), and so naturally, the bodies do not (intrude) upon one another.
Equipment and innovation
Armillary sphere (渾儀)
The earliest development of the armillary sphere in China goes back to the 1st century BCE, as they were equipped with a primitive single-ring armillary instrument. This would have allowed them to measure the north polar distance (去極度, the Chinese form of declination) and measurement that gave the position in a hsiu (入宿度, the Chinese form of right ascension).
During the Western Han dynasty (202 BCE–9 CE), additional developments made by the astronomers Luoxia Hong (落下閎), Xianyu Wangren (鮮于妄人) , and Geng Shouchang (耿壽昌) advanced the use of the armillary in its early stage of evolution. In 52 BCE, it was the astronomer Geng Shou-chang who introduced the fixed equatorial ring to the armillary sphere. In the subsequent Eastern Han dynasty (23–220 CE) period, the astronomers Fu An and Jia Kui added the elliptical ring by 84 CE. With the famous statesman, astronomer, and inventor Zhang Heng (78–139 CE), the sphere was totally completed in 125 CE, with horizon and meridian rings. It is of great importance to note that the world's first hydraulic (i.e., water-powered) armillary sphere was created by Zhang Heng, who operated his by use of an inflow clepsydra clock (see Zhang's article for more detail).
Abridged armilla (簡儀)
Designed by famous astronomer Guo Shoujing in 1276 CE, it solved most problems found in armillary spheres at that time.
The primary structure of abridged armilla contains two large rings that are perpendicular to each other, of which one is parallel with the equatorial plane and is accordingly called "equatorial ring", and the other is a double ring that is perpendicular to the center of the equatorial ring, revolving around a metallic shaft, and is called "right ascension double ring".
The double ring holds within itself a sighting tube with crosshairs. When observing, astronomers would aim at the star with the sighting tube, whereupon the star's position could be deciphered by observing the dials of the equatorial ring and the right ascension double ring.
A foreign missionary melted the instrument in 1715 CE. The surviving one was built in 1437 CE and was taken to what is now Germany. It was then stored in a French Embassy in 1900, during the Eight-Nation Alliance. Under the pressure of international public discontent, Germany returned the instrument to China. In 1933, it was placed in Purple Mountain Observatory, which prevented it from being destroyed in the Japanese invasion of China. In the 1980s, it had become seriously eroded and rusted down and was nearly destroyed. In order to restore the device, the Nanjing government spent 11 months to repair it.
Celestial globe (渾象) before the Qing dynasty
Besides star maps, the Chinese also made celestial globes, which show stars' positions like a star map and can present the sky at a specific time. Because of its Chinese name, it is often confused with the armillary sphere, which is just one word different in Chinese (渾象 vs. 渾儀).
According to records, the first celestial globe was made by Geng Shou-chang (耿壽昌) between 70 BCE and 50 BCE. In the Ming dynasty, the celestial globe at that time was a huge globe, showing the 28 mansions, celestial equator, and ecliptic. None of them have survived.
Celestial globe (天體儀) in the Qing dynasty
Celestial globes were named 天體儀 ("Miriam celestial bodies") in the Qing dynasty. The one in Beijing Ancient Observatory was made by Belgian missionary Ferdinand Verbiest (南懷仁) in 1673 CE. Unlike other Chinese celestial globes, it employs 360 degrees rather than the 365.24 degrees (which is a standard in ancient China). It is also the first Chinese globe that shows constellations near to the Celestial South Pole.
The water-powered armillary sphere and celestial globe tower (水運儀象台)
The inventor of the hydraulic-powered armillary sphere was Zhang Heng (78–139 CE) of the Han dynasty. Zhang was well-known for his brilliant applications of mechanical gears, as this was one of his most impressive inventions (alongside his seismograph to detect the cardinal direction of earthquakes that struck hundreds of miles away).
Started by Su Song (蘇頌) and his colleagues in 1086 CE and finished in 1092 CE, his large astronomical clock tower featured an armillary sphere (渾儀), a celestial globe (渾象), and a mechanical chronograph. It was operated by an escapement mechanism and the earliest known chain drive. However, 35 years later, the invading Jurchen army dismantled the tower in 1127 CE upon taking the capital of Kaifeng. The armillary sphere part was brought to Beijing, yet the tower was never successfully reinstated, not even by Su Song's son.
Fortunately, two versions of Su Song's treatise, written on his clock tower, have survived the ages, so that studying his astronomical clock tower is made possible through medieval texts.
True north and planetary motion
The polymath Chinese scientist Shen Kuo (1031–1095 CE) was not only the first in history to describe the magnetic-needle compass, but also made a more accurate measurement of the distance between the pole star and true north that could be used for navigation. Shen achieved this by making nightly astronomical observations, along with his colleague Wei Pu, using Shen's improved design of a wider sighting tube that could be fixed to observe the pole star indefinitely. Along with the pole star, Shen Kuo and Wei Pu also established a project of nightly astronomical observation over a period of five successive years, an intensive work that would even rival the later work of Tycho Brahe in Europe. Shen Kuo and Wei Pu charted the exact coordinates of the planets on a star map for this project and created theories of planetary motion, including retrograde motion.
Foreign influences
Indian astronomy
Buddhism first reached China during the Eastern Han dynasty, and translation of Indian works on astronomy came to China by the Three Kingdoms era (220–265 CE). However, the most detailed incorporation of Indian astronomy occurred only during the Tang dynasty (618–907), when a number of Chinese scholars—such as Yi Xing—were versed in both types of astronomy. A system of Indian astronomy was recorded in China as Jiuzhi-li (718 CE), the author of which was an Indian by the name of Qutan Xida.
The astronomical table of sines by the Indian astronomer and mathematician Aryabhata was translated into the Chinese astronomical and mathematical book Treatise on Astrology of the Kaiyuan Era (Kaiyuan Zhanjing), compiled in 718 CE, during the Tang dynasty. The Kaiyuan Zhanjing was compiled by Gautama Siddha, an astronomer and astrologer born in Chang'an, and whose family was originally from India. He was also notable for his translation of the Navagraha calendar into Chinese.
The Chinese translations of the following works are mentioned in the Sui Shu, or Official History of the Sui dynasty (seventh century):
Po-lo-men Thien Wen Ching (Brahminical Astronomical Classic) in 21 books.
Po-lo-men Chieh-Chhieh Hsien-jen Thien Wen Shuo (Astronomical Theories of Brahman;a Chieh-Chhieh Hsienjen) in 30 books.
Po-lo-men Thien Ching (Brahminical Heavenly Theory) in one book.
Mo-teng-Chia Ching Huang-thu (Map of Heaven and Earth in the Matangi Sutra) in one book.
Po-lo-men Suan Ching (Brahminical Arithmetical Classic) in three books.
Po-lo-men Suan Fa (Brahminical Arithmetical Rules) in one book.
Po-lo-men Ying Yang Suan Ching (Brahminical Method of Calculating Time)
Although these translations are lost, they were also mentioned in other
sources.
Islamic astronomy in East Asia
Islamic influence on Chinese astronomy was first recorded during the Song dynasty, when a Hui Muslim astronomer named Ma Yize introduced the concept of 7 days in a week and made other contributions.
Islamic astronomers were brought to China in order to work on calendar-making and astronomy during the Mongol Empire and the succeeding Yuan dynasty. The Chinese scholar Yelü Chucai accompanied Genghis Khan to Persia in 1210 and studied their calendar for use in the Mongol Empire. Kublai Khan brought Iranians to Beijing to construct an observatory and an institution for astronomical studies.
Several Chinese astronomers worked at the Maragheh observatory, founded by Nasir al-Din al-Tusi in 1259 under the patronage of Hulagu Khan in Persia. One of these Chinese astronomers was Fu Mengchi, or Fu Mezhai.
In 1267, the Persian astronomer Jamal ad-Din, who previously worked at Maragha observatory, presented Kublai Khan with seven Persian astronomical instruments, including a terrestrial globe and an armillary sphere, as well as an astronomical almanac, which was later known in China as the Wannian Li ("Ten Thousand Year Calendar" or "Eternal Calendar"). He was known as "Zhama Luding" in China, where, in 1271, he was appointed by the Khan as the first director of the Islamic observatory in Beijing, known as the Islamic Astronomical Bureau, which operated alongside the Chinese Astronomical Bureau for four centuries. Islamic astronomy gained a good reputation in China for its theory of planetary latitudes, which did not exist in Chinese astronomy at the time, and for its accurate prediction of eclipses.
Some of the astronomical instruments constructed by the famous Chinese astronomer Guo Shoujing shortly afterwards resemble the style of instrumentation built at Maragheh. In particular, the "simplified instrument" (jianyi) and the large gnomon at the Gaocheng Astronomical Observatory show traces of Islamic influence. While formulating the Shoushili calendar in 1281, Shoujing's work in spherical trigonometry may have also been partially influenced by Islamic mathematics, which was largely accepted at Kublai's court. These possible influences include a pseudo-geometrical method for converting between equatorial and ecliptic coordinates, the systematic use of decimals in the underlying parameters, and the application of cubic interpolation in the calculation of the irregularity in the planetary motions.
Emperor Taizu (r. 1368–1398) of the Ming dynasty (1328–1398), in the first year of his reign (1368), conscripted Han and non-Han astrology specialists from the astronomical institutions in Beijing of the former Mongolian Yuan to Nanjing to become officials of the newly established national observatory.
That year, the Ming government summoned, for the first time, the astronomical officials to come south from the upper capital of Yuan. There were fourteen of them. In order to enhance accuracy in methods of observation and computation, Emperor Taizu reinforced the adoption of parallel calendar systems, the Han and the Hui. In the following years, the Ming Court appointed several Hui astrologers to hold high positions in the Imperial Observatory. They wrote many books on Islamic astronomy and also manufactured astronomical equipment based on the Islamic system.
The translation of two important works into Chinese was completed in 1383: Zij (1366) and al-Madkhal fi Sina'at Ahkam al-Nujum, Introduction to Astrology (1004).
In 1384, a Chinese astrolabe was made for observing stars based on the instructions for making multi-purposed Islamic equipment. In 1385, the apparatus was installed on a hill in northern Nanjing.
Around 1384, during the Ming dynasty, Emperor Zhu Yuanzhang ordered the Chinese translation and compilation of Islamic astronomical tables, a task that was carried out by the scholars Mashayihei, a Muslim astronomer, and Wu Bozong, a Chinese scholar-official. These tables came to be known as the Huihui Lifa (Muslim System of Calendrical Astronomy), which was published in China a number of times until the early 18th century, though the Qing dynasty had officially abandoned the tradition of Chinese-Islamic astronomy in 1659. The Muslim astronomer Yang Guangxian was known for his attacks on the Jesuit's astronomical sciences.
Jesuit activity in China
Early-modern European science was introduced into China by Jesuit priest astronomers as part of their missionary efforts, in the late sixteenth century and early seventeenth century.
The telescope was introduced to China in the early seventeenth century. The telescope was first mentioned in Chinese writing by Manuel Dias the Younger (Yang Manuo), who wrote his Tian Wen Lüe in 1615. In 1626, Johann Adam Schall von Bell (Tang Ruowang) published the Chinese treatise on the telescope known as the Yuan Jing Shuo (The Far-Seeing Optic Glass). The Chongzhen Emperor (1627–1644) of the Ming dynasty acquired the telescope of Johannes Terrentius (or Johann Schreck; Deng Yu-han) in 1634, ten years before the collapse of the Ming dynasty. However, the impact on Chinese astronomy was limited.
The Jesuit China missions of the sixteenth and seventeenth centuries brought Western astronomy, then undergoing its own revolution, to China and—via João Rodrigues's gifts to Jeong Duwon—to Joseon Korea. After the Galileo affair early in the seventeenth century, the Roman Catholic Jesuit order was required to adhere to geocentrism and ignore the heliocentric teachings of Copernicus and his followers, even though they were becoming standard in European astronomy. Thus, the Jesuits initially shared an Earth-centered and largely pre-Copernican astronomy with their Chinese hosts (i.e., the Ptolemaic-Aristotelian views from Hellenistic times). The Jesuits (such as Giacomo Rho) later introduced Tycho's geoheliocentric model as the standard cosmological model. The Chinese often were fundamentally opposed to this as well, since the Chinese had long believed (from the ancient doctrine of Xuan Ye) that the celestial bodies floated in a void of infinite space. This contradicted the Aristotelian view of solid concentric crystalline spheres, where there was not a void, but a mass of air between the heavenly bodies.
Of course, the views of Copernicus, Galileo, and Tycho Brahe would eventually triumph in European science, and these ideas slowly leaked into China despite Jesuit efforts to curb them in the beginning. In 1627, the Polish Jesuit Michael Boym (Bu Mige) introduced Johannes Kepler's Copernican Rudolphine Tables, with much enthusiasm, to the Ming court at Beijing. In Adam Schall von Bell's Chinese-written treatise of Western astronomy in 1640, the names of Copernicus (Ge-Bai-Ni), Galileo (Jia-li-lüe), and Tycho Brahe (Di-gu) were formally introduced to China. There were also Jesuits in China who were in favor of the Copernican theory, such as Nicholas Smogulecki and Wenceslaus Kirwitzer. However, Copernican views were not widespread or wholly accepted in China during this time.
Ferdinand Augustin Hallerstein (Liu Songling) created the first spherical astrolabe as the Head of the Imperial Astronomical Bureau from 1739 until 1774. The former Beijing Astronomical observatory, now a museum, still hosts the armillary sphere with rotating rings, which was made under Hallerstein's leadership, and is considered the most prominent astronomical instrument.
While in Edo Japan, the Dutch aided the Japanese with the first modern observatory of Japan in 1725, headed by Nakane Genkei, whose observatory of astronomers wholly accepted the Copernican view. In contrast, the Copernican view was not accepted in mainstream China until the early nineteenth century, with the Protestant missionaries such as Joseph Edkins, Alex Wylie, and John Fryer.
Astronomy during Ming China
The Ming dynasty in China lasted from 1368 until 1644 and experienced a decrease in astronomical expansion. The occupation of astronomer during these times relied less on discovery and more on the use of astronomy. Astronomers worked in the two Astronomical Bureaus, both of which underwent many changes throughout the years since their formation. The path into the occupation was hereditary; because of the rigidity and high level of intelligence needed for this occupation, children of astronomers were banned from pursuing other professions.
Astronomical Bureaus
When transitioning into the Ming dynasty, the two largest institutions of astronomy were the Traditional Chinese Astronomical Bureau (also named T’ai-shih-chien), which had been established in the third century BC, and the Muslim Astronomical Bureau (also named Hui-hui ssu-t’ien-chien), which had been previously established by the Mongols. Both sectors worked together, until the Muslim Bureau was absorbed in 1370 by the Traditional Chinese Bureau. When the merge occurred, the overall name of the new bureau became Ch’in-t’ien-chien. To accommodate the influx of new workers, the ranking system within the occupation also transitioned. There became one Director, supported by two Deputy Directors, followed by a Registrar with four seasonal Chiefs. Then came eight Chief Astronomers, five Chief Diviners, two Chiefs of the Clepsydras, and three Observers. Following that was two Calendar Officials, eight Observers of Sunrise, and six Professors of the Clepsydra.
Responsibilities of the Bureau
Some of the roles astronomers played in Ming China were to make calendars, report abnormalities to the emperor, and preside over ceremonies. As calendar makers and people who understand the heavens, the Bureau also decided what days were auspicious and good for different events such as military parades, marriage, construction, and more. The astronomers also used astronomy to predict invasions or dangerous moments within the empire. However, records indicate that the majority of work the Astronomical Bureaus did was simply recording the movements of the stars and planets.
In regards to the specific jobs each position does, the Chief Officials of the Five Agencies would fix the calendar and the time of the seasons, along with the Calendar Officials and Astronomers. However, the Chief Astronomer observes the positions of the sun, moon, and planets to make notes regarding what might be an abnormality. The Chief Diviner specializes in analyzing the astronomical abnormalities. The Chief Clepsydra Officer looks after the CLepsydra, along with the Clepsydra professor, who then tell the Sunrise Announcer when sunrise and sunset would occur.
Colleagues
The Astronomical Bureaus worked closely with The Ministry of Rites. The bureau submitted monthly ordinances, planetary and celestial locations, and seasonal accounts within the calendar to the Ministry. The Ministry also helped train children of astronomers for their future jobs and helped select outsiders in certain cases, but not specifying from where they draw these candidates. The Bureaus were also in close contact with the Emperor, and he often read the reports sent by the Bureau to the Ministry.
Training
Because becoming an astronomer was a hereditary profession, and those that are employed by the Bureau are not transferable to other occupations, students were trained very young by the Ministry of Rites. However, when there was a shortage of workers in the Bureau, the Ministry of Rites would scout suitable students and train them on a trial basis. Calendrical recordings greatly attracted Confucian scholars, which widened interest into this subject, and thus, into astronomy and divination. Confucian students' deep need for knowledge and practicality made these tasks appeal to academics. Astronomy was attractive because it blended the physical world with larger implications. However, astronomy was considered part of the "small dao", a title used to attempt to discourage Confucian scholars from studying subjects that, while interesting at first, could eventually bog them down.
Payment
Within the Bureau, payment was decided upon by rank. As established in the year 1392, the top rank of Director was paid sixteen piculs of rice per month. The Deputy Directors and Chiefs of the Five Agencies were allotted ten piculs per month, the Astronomers received seven piculs, while both the Registrars and Chief Diviners had six-and-a-half piculs. The Chiefs of the Clepsydras received six piculs, and the Calendar Officers and Observers both had five-and-a-half piculs. The lowest payment level went to the Observers of the Sunrise and the Professors of the Clepsydras, at five piculs per month.
Instruments Used by the Occupation
Memorial
The memorial was used by astronomers as a record keeper of anomalies, as the heavens are demonstrative of the effect of the ruler's actions. Originally, authors signed each contribution individually but that was eventually replaced by the official seal of the astronomical bureau.
Imperial Observatory
The imperial observatory was a platform where the observations were made. It was first located just south of Nanjing, but later moved to Jiming Mountain city. However, in 1402 there was another platform created in the capital of Beijing.
Armillary Sphere (Ming China)
The armillary sphere has three sets of rings that represent the celestial sphere. The first group contains fixed meridian, horizon, and equatorial rings. The second group contains ecliptic, solstitial, and equinoctial rings that turn as a unit. The inner group contains one meridian ring that moves around the celestial pole. These allow the astronomer to set a celestial object within their sights and judge distance.
The Simplified Instrument
The simplified instrument serves a very similar purpose to the armillary sphere but has fewer parts. With only two sets of coordinates, this instrument has a larger range and vision than the armillary spheres.
Yuan Gnomon
The Yuan Gnomon is a shadow casting instrument used to measure the position of the sun. However, it does not appear to be very accurate. A crucial aspect of this mechanism was that it was oriented along the north–south meridian line, which allowed it to show the local noon. While not included in the 1392 list of official instruments, in 1437 Huangfu Zhonghe included it, likely due less to its practicality and more to the ingenuity behind it.
Clepsydra
The clepsydra, or water clock, was the most prevalent of time-keeping devices for astronomers. The clepsydra was also used as the official state time-keeping device. The Astronomical Bureau used a three-chamber-intake clepsydra, although there is no record of a water clock at Nanjing. It was not until the Bureau moved to Beijing that an official water hall was observed.
Outside Perspective
Because of the ideological importance of astronomy regarding politics, and the lack of precision by the instruments, many people believed the observations were false. Other recorded corruption, such as accepting bribery, stealing, and not being punctual, were also experienced. This led to a strict policy of punishment if the astronomers were found to be corrupt. Punishments included such actions as dismissal, deprivation of salary, or even beatings.
Famous Chinese astronomers
Gan De (4th century BCE)
Shi Shen (4th century BCE)
Zhang Heng (78 – 139 CE)
Yu Xi (307 – 345 CE)
Shen Kuo (1031 – 1095 CE)
Su Song (1020 – 1101 CE)
Guo Shoujing (1231 – 1316 CE)
Xu Guangqi (1562 – 1633 CE)
Wang Xishan 王錫闡 (1628 – 1682)
Observatory
Beijing Ancient Observatory
Astro Observatory
See also
Book of Silk
Chinese astrology
Chinese constellations
Chu Silk Manuscript
Flat Earth in China
History of astronomy
Timeline of Chinese astronomy
Traditional Chinese star names
References
Citations
Sources
Ho Peng Yoke. “The Astronomical Bureau in Ming China” Journal of Asian History, vol. 3, no. 2, 1969, pp. 137–157. .
Deane, Thatcher E. “Instruments and Observation at the Imperial Astronomical Bureau during the Ming Dynasty.” Osiris, vol. 9, 1994, pp. 126–140. .
Yung Sik Kim, “Confucian Scholars and Specialized Scientific and Technical Knowledge in Traditional China, 1000–1700: A Preliminary Overview,” East Asian Science, Technology, and Society: an International Journal Volume 4.2 (April): 207–228.
Further reading
Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures, edited by Helaine Selin. Dordrecht: Kluwer, 1997. S.v. "Astronomy in China" by Ho Peng Yoke.
Sun Xiaochun, "Crossing the Boundaries Between Heaven and Man: Astronomy in Ancient China" in Astronomy Across Cultures: The History of Non-Western Astronomy, edited by H. Selin, pp. 423–454. Dordrecht: Kluwer, 2000.
Chan Ki-hung: Chinese Ancient Star Map, Leisure and Cultural Services Department, 2002,
Gems of the ancient Chinese astronomy relics,
External links
The Mathematics of the Chinese Calendary by Helmar Aslaksen
Boundaries Crossing: Western Astronomy in Confucian China, 1600–1800 by Pingyi Chu
Homepage of the National Astronomical Observatories, Chinese Academy of Sciences
Chinese astronomy at the University of Maine
Virtual exhibition about Joseph-Nicolas Delisle and oriental astronomy on the digital library of Paris Observatory
History of astronomy | Chinese astronomy | [
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"History of astronomy"
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1,524,607 | https://en.wikipedia.org/wiki/Fourth%20Cambridge%20Survey | The Fourth Cambridge Survey (4C) is an astronomical catalogue of celestial radio sources as measured at 178 MHz using the 4C Array. It was published in two parts, in 1965 (for declinations +20 to +40) and 1967 (declinations -7 to + 20 and +40 to +80), by the Radio Astronomy Group of the University of Cambridge. References to entries in this catalogue use the prefix 4C followed by the declination in degrees, followed by a period, and then followed by the source number on that declination strip, e.g. 4C-06.23.
The 4C Array, which used the technique of aperture synthesis, could reliably position sources with flux densities of around 2 Jy, to within about 0.35 arcmin in Right ascension and 2.5 arcmin in declination.
References
4 | Fourth Cambridge Survey | [
"Astronomy"
] | 182 | [
"Astronomical catalogue stubs",
"Astronomy stubs"
] |
1,524,612 | https://en.wikipedia.org/wiki/Fifth%20Cambridge%20Survey%20of%20Radio%20Sources | The 5C Survey of Radio Sources (5C) is an astronomical catalogue of celestial radio sources as measured at 408 MHz and 1407 MHz. It was published in a number of parts between 1975 and 1995 by the Radio Astronomy Group of the University of Cambridge. The One-Mile Telescope used to produce this catalogue had an angular resolution of 80 arcseconds and 23 arcseconds at 408 MHz and 1407 MHz respectively, and catalogued radio sources as faint as 2 milli-Janskys, considerably fainter than any previously catalogued radio source.
References to entries in this catalogue use the prefix 5C followed by the catalogue part, a "." and then the entry number, with no space perforce; i.e., 5C12.311 for the 311th entry in part 12 of the 5C catalogue.
External links
The 5C catalogue is publicly available:
Publication describing the catalogue
Data access to the 5C Survey
5 | Fifth Cambridge Survey of Radio Sources | [
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] | 197 | [
"Astronomical catalogue stubs",
"Astronomy stubs"
] |
1,524,626 | https://en.wikipedia.org/wiki/Ninth%20Cambridge%20survey%20at%2015GHz | The 9C survey at 15 GHz (9C) is an astronomical catalogue generated from the radio observations of the Ninth Cambridge survey at 15 GHz. It was published in 2003 by the Cavendish Astrophysics Group of the University of Cambridge. The catalogue was originally made in order to locate radio sources which were interfering with observations using the Very Small Array, but the catalogue has also proved useful for other astronomical programs.
Sources are labelled 9CJHHMM+DDMM where HHMM+DDMM are the coordinates in the J2000 system, e.g. 9CJ1510+4138.
References
External links
Article describing the 9C survey at 15GHz.
Online data access to the 9C survey at 15GHz.
9 | Ninth Cambridge survey at 15GHz | [
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] | 151 | [
"Astronomical catalogue stubs",
"Astronomy stubs"
] |
1,524,630 | https://en.wikipedia.org/wiki/Alternatives%20to%20the%20Standard%20Higgs%20Model | Alternative models to the Standard Higgs Model are models which are considered by many particle physicists to solve some of the Higgs boson's existing problems. Two of the most currently researched models are quantum triviality, and Higgs hierarchy problem.
Overview
In particle physics, elementary particles and forces give rise to the world around us. Physicists explain the behaviors of these particles and how they interact using the Standard Model—a widely accepted framework believed to explain most of the world we see around us. Initially, when these models were being developed and tested, it seemed that the mathematics behind those models, which were satisfactory in areas already tested, would also forbid elementary particles from having any mass, which showed clearly that these initial models were incomplete. In 1964 three groups of physicists almost simultaneously released papers describing how masses could be given to these particles, using approaches known as symmetry breaking. This approach allowed the particles to obtain a mass, without breaking other parts of particle physics theory that were already believed reasonably correct. This idea became known as the Higgs mechanism, and later experiments confirmed that such a mechanism does exist—but they could not show exactly how it happens.
The simplest theory for how this effect takes place in nature, and the theory that became incorporated into the Standard Model, was that if one or more of a particular kind of "field" (known as a Higgs field) happened to permeate space, and if it could interact with elementary particles in a particular way, then this would give rise to a Higgs mechanism in nature. In the basic Standard Model there is one field and one related Higgs boson; in some extensions to the Standard Model there are multiple fields and multiple Higgs bosons.
In the years since the Higgs field and boson were proposed as a way to explain the origins of symmetry breaking, several alternatives have been proposed that suggest how a symmetry breaking mechanism could occur without requiring a Higgs field to exist. Models which do not include a Higgs field or a Higgs boson are known as Higgsless models. In these models, strongly interacting dynamics rather than an additional (Higgs) field produce the non-zero vacuum expectation value that breaks electroweak symmetry.
List of alternative models
A partial list of proposed alternatives to a Higgs field as a source for symmetry breaking includes:
Technicolor models break electroweak symmetry through new gauge interactions, which were originally modeled on quantum chromodynamics.
Extra-dimensional Higgsless models use the fifth component of the gauge fields to play the role of the Higgs fields. It is possible to produce electroweak symmetry breaking by imposing certain boundary conditions on the extra dimensional fields, increasing the unitarity breakdown scale up to the energy scale of the extra dimension. Through the AdS/QCD correspondence this model can be related to technicolor models and to "UnHiggs" models in which the Higgs field is of unparticle nature.
Models of composite W and Z vector bosons.
Top quark condensate.
"Unitary Weyl gauge". By adding a suitable gravitational term to the standard model action in curved spacetime, the theory develops a local conformal (Weyl) invariance. The conformal gauge is fixed by choosing a reference mass scale based on the gravitational coupling constant. This approach generates the masses for the vector bosons and matter fields similar to the Higgs mechanism without traditional spontaneous symmetry breaking.
Asymptotically safe weak interactions based on some nonlinear sigma models.
Preon and models inspired by preons such as Ribbon model of Standard Model particles by Sundance Bilson-Thompson, based in braid theory and compatible with loop quantum gravity and similar theories. This model not only explains mass but leads to an interpretation of electric charge as a topological quantity (twists carried on the individual ribbons) and colour charge as modes of twisting.
Symmetry breaking driven by non-equilibrium dynamics of quantum fields above the electroweak scale.
Unparticle physics and the unhiggs. These are models that posit that the Higgs sector and Higgs boson are scaling invariant, also known as unparticle physics.
In theory of superfluid vacuum masses of elementary particles can arise as a result of interaction with the physical vacuum, similarly to the gap generation mechanism in superconductors.
UV-completion by classicalization, in which the unitarization of the WW scattering happens by creation of classical configurations.
See also
Composite Higgs models
References
External links
Higgsless model on arxiv.org
Physics beyond the Standard Model
Electroweak theory
Mass | Alternatives to the Standard Higgs Model | [
"Physics",
"Mathematics"
] | 933 | [
"Scalar physical quantities",
"Physical phenomena",
"Physical quantities",
"Quantity",
"Mass",
"Unsolved problems in physics",
"Electroweak theory",
"Size",
"Fundamental interactions",
"Particle physics",
"Wikipedia categories named after physical quantities",
"Physics beyond the Standard Mode... |
1,524,698 | https://en.wikipedia.org/wiki/Timeline%20of%20Chinese%20astronomy | This is a timeline of Chinese records and investigations in astronomy.
2137 BC - October 22, the Chinese book, the Book of Documents, records the earliest known solar eclipse.
c. 2000 BC - Chinese determine that Jupiter needs 12 years to complete one revolution of its orbit.
c. 1400 BC - Chinese record the regularity of solar and lunar eclipses and the earliest known Solar prominence and two novas ().
c. 1200 BC - Chinese divide the sky into twenty eight regions (Chinese constellations) for recognition of the stars.
c. 1100 BC - Chinese first determine the spring equinox.
776 BC - Chinese make the earliest reliable record of a solar eclipse.
613 BC - In July, a Comet, possibly Comet Halley, is recorded in the Spring and Autumn Annals ().
532 BC - A nova was recorded in the Records of the Grand Historian and Zuo Zhuan ().
364 BC - Earliest recorded observation of sunspots made by Gan De.
28 BC - May 10, Chinese imperial history book, the Book of Han, makes earliest known dated record of sunspots; systematic Chinese observations of sunspots continue thereafter.
185 - The earliest recorded supernova of RCW 86
687 - Chinese make earliest known record of meteor shower.
1054 - July 4, Chinese astronomers noted the appearance of a guest star, the supernova which produced the Crab Nebula, Messier's M1.
1088 - In his Dream Pool Essays, the polymath Chinese scientist Shen Kuo (1031–1095) wrote of his findings for the improved meridian measurement between the pole star and true north, which was an invaluable concept for aiding navigation by use of the magnetic compass. Shen Kuo also argued for spherical celestial bodies by using evidence of lunar eclipses and solar eclipses, which promoted the spherical Earth theory and went against the flat Earth theory.
See also
History of astronomy
References
Chinese astronomy
zh:中国天文学史 | Timeline of Chinese astronomy | [
"Astronomy"
] | 406 | [
"Astronomy timelines",
"Astronomy stubs",
"Astronomy in China",
"History of astronomy"
] |
1,524,753 | https://en.wikipedia.org/wiki/Eighth%20Cambridge%20Survey | The 8C Survey (8C) or Rees 38 MHz survey is an astronomical catalogue of celestial radio sources as measured at 38 MHz. It was published in 1990 by the Radio Astronomy Group of the University of Cambridge. Sources are labelled 8C HHMM+DDd where HHMM is the Right Ascension in hours and minutes, and DDd is the Declination in degrees and tenths of a degree, e.g. 8C 0014+861 for a source at Right Ascension 00 14 and 86.1 degrees Declination in 1950 coordinates.
External links
The Rees 38-MHz survey
8 | Eighth Cambridge Survey | [
"Astronomy"
] | 126 | [
"Astronomical catalogue stubs",
"Astronomy stubs"
] |
1,524,768 | https://en.wikipedia.org/wiki/List%20of%20text%20editors | The following is a list of notable text editors.
Graphical and text user interface
The following editors can either be used with a graphical user interface or a text user interface.
Graphical user interface
Text user interface
System default
Others
vi clones
Sources:
No user interface (editor libraries/toolkits)
ASCII and ANSI art
Editors that are specifically designed for the creation of ASCII and ANSI text art.
ACiDDraw – designed for editing ASCII text art. Supports ANSI color (ANSI X3.64)
TheDraw – ANSI/ASCII text editor for DOS and PCBoard file format support
ASCII font editors
FIGlet – for creating ASCII art text
TheDraw – DOS ANSI/ASCII text editor with built-in editor and manager of ASCII fonts
Historical
Visual and full-screen editors
Line editors
See also
Comparison of text editors
Editor war
Line editor
List of HTML editors
List of word processors
Outliner, a specialized type of word processor
Source code editor
Notes
Text editors | List of text editors | [
"Technology"
] | 212 | [
"Computing-related lists",
"Lists of software"
] |
1,524,792 | https://en.wikipedia.org/wiki/ATP%20hydrolysis | ATP hydrolysis is the catabolic reaction process by which chemical energy that has been stored in the high-energy phosphoanhydride bonds in adenosine triphosphate (ATP) is released after splitting these bonds, for example in muscles, by producing work in the form of mechanical energy. The product is adenosine diphosphate (ADP) and an inorganic phosphate (Pi). ADP can be further hydrolyzed to give energy, adenosine monophosphate (AMP), and another inorganic phosphate (Pi). ATP hydrolysis is the final link between the energy derived from food or sunlight and useful work such as muscle contraction, the establishment of electrochemical gradients across membranes, and biosynthetic processes necessary to maintain life.
Anhydridic bonds are often labelled as "high-energy bonds". P-O bonds are in fact fairly strong (~30 kJ/mol stronger than C-N bonds) and themselves not particularly easy to break. As noted below, energy is released by the hydrolysis of ATP. However, when the P-O bonds are broken, input of energy is required. It is the formation of new bonds and lower-energy inorganic phosphate with a release of a larger amount of energy that lowers the total energy of the system and makes it more stable.
Hydrolysis of the phosphate groups in ATP is especially exergonic, because the resulting inorganic phosphate molecular ion is greatly stabilized by multiple resonance structures, making the products (ADP and Pi) lower in energy than the reactant (ATP). The high negative charge density associated with the three adjacent phosphate units of ATP also destabilizes the molecule, making it higher in energy. Hydrolysis relieves some of these electrostatic repulsions, liberating useful energy in the process by causing conformational changes in enzyme structure.
In humans, approximately 60 percent of the energy released from the hydrolysis of ATP produces metabolic heat rather than fuel the actual reactions taking place.
Due to the acid-base properties of ATP, ADP, and inorganic phosphate, the hydrolysis of ATP has the effect of lowering the pH of the reaction medium. Under certain conditions, high levels of ATP hydrolysis can contribute to lactic acidosis.
Amount of energy produced
Hydrolysis of the terminal phosphoanhydridic bond is a highly exergonic process. The amount of released energy depends on the conditions in a particular cell. Specifically, the energy released is dependent on concentrations of ATP, ADP and Pi. As the concentrations of these molecules deviate from values at equilibrium, the value of Gibbs free energy change (ΔG) will be increasingly different. In standard conditions (ATP, ADP and Pi concentrations are equal to 1M, water concentration is equal to 55 M) the value of ΔG is between -28 and -34 kJ/mol.
The range of the ΔG value exists because this reaction is dependent on the concentration of Mg2+ cations, which stabilize the ATP molecule. The cellular environment also contributes to differences in the ΔG value since ATP hydrolysis is dependent not only on the studied cell, but also on the surrounding tissue and even the compartment within the cell. Variability in the ΔG values is therefore to be expected.
The relationship between the standard Gibbs free energy change ΔrGo and chemical equilibrium is revealing. This relationship is defined by the equation ΔrGo = -RT ln(K), where K is the equilibrium constant, which is equal to the reaction quotient Q in equilibrium. The standard value of ΔG for this reaction is, as mentioned, between -28 and -34 kJ/mol; however, experimentally determined concentrations of the involved molecules reveal that the reaction is not at equilibrium. Given this fact, a comparison between the equilibrium constant, K, and the reaction quotient, Q, provides insight. K takes into consideration reactions taking place in standard conditions, but in the cellular environment the concentrations of the involved molecules (namely, ATP, ADP, and Pi) are far from the standard 1 M. In fact, the concentrations are more appropriately measured in mM, which is smaller than M by three orders of magnitude. Using these nonstandard concentrations, the calculated value of Q is much less than one. By relating Q to ΔG using the equation ΔG = ΔrGo + RT ln(Q), where ΔrGo is the standard change in Gibbs free energy for the hydrolysis of ATP, it is found that the magnitude of ΔG is much greater than the standard value. The nonstandard conditions of the cell actually result in a more favorable reaction.
In one particular study, to determine ΔG in vivo in humans, the concentration of ATP, ADP, and Pi was measured using nuclear magnetic resonance. In human muscle cells at rest, the concentration of ATP was found to be around 4 mM and the concentration of ADP was around 9 μM. Inputing these values into the above equations yields ΔG = -64 kJ/mol. After ischemia, when the muscle is recovering from exercise, the concentration of ATP is as low as 1 mM and the concentration of ADP is around 7 μM. Therefore, the absolute ΔG would be as high as -69 kJ/mol.
By comparing the standard value of ΔG and the experimental value of ΔG, one can see that the energy released from the hydrolysis of ATP, as measured in humans, is almost twice as much as the energy produced under standard conditions.
See also
Dephosphorylation
References
Further reading
Cellular respiration
Exercise physiology | ATP hydrolysis | [
"Chemistry",
"Biology"
] | 1,155 | [
"Biochemistry",
"Cellular respiration",
"Metabolism"
] |
1,524,850 | https://en.wikipedia.org/wiki/Complex%20text%20layout | Complex text layout (CTL) or complex text rendering is the typesetting of writing systems in which the shape or positioning of a grapheme depends on its relation to other graphemes. The term is used in the field of software internationalization, where each grapheme is a character.
Scripts which require CTL for proper display may be known as complex scripts. Examples include the Arabic alphabet and scripts of the Brahmic family, such as Devanagari, Khmer script or the Thai alphabet. Many scripts do not require CTL. For instance, the Latin alphabet or Chinese characters can be typeset by simply displaying each character one after another in straight rows or columns. However, even these scripts have alternate forms or optional features (such as cursive writing) which require CTL to produce on computers.
Characteristics requiring CTL
The main characteristics of CTL complexity are:
Bi-directional text, where characters may be written from either right-to-left or left-to-right direction.
Context-sensitive shaping and ligatures, where a character may change its shape, dependent on its location and/or the surrounding characters. For example, a character in Arabic script can have as many as four different shape-forms, depending on context.
Ordering, where the displayed order of the characters is not the same as the logical order. For example, in Devanagari, which is written from left to right, the grapheme for "short i" appears to the left of ("before") the consonant that it follows: in ki, the -i should render on the left, its bow reaching until above the k- to the right.
Not all occurrences of these characteristics require CTL. For example, the Greek alphabet has context-sensitive shaping of the letter sigma, which appears as ς at the end of a word and σ elsewhere. However, these two forms are normally stored as different characters; for instance, Unicode has both and , and does not treat them as equivalent. For collation and comparison purposes, software should consider the string "δῖος Ἀχιλλεύς" equivalent to "δῖοσ Ἀχιλλεύσ", but for typesetting purposes they are distinct and CTL is not required to choose the correct form.
Implementations
Most text-rendering software that is capable of CTL will include information about specific scripts, and so will be able to render them correctly without font files needing to supply instructions on how to lay out characters. Such software is usually provided in a library; examples include:
Core Text for macOS
Uniscribe (with Universal Shaping Engine) and DirectWrite for Microsoft Windows
HarfBuzz, a cross-platform library
Pango, a cross-platform library which nowadays incorporates HarfBuzz
However, such software is unable to properly render any script for which it lacks instructions, which can include many minority scripts. The alternative approach is to include the rendering instructions in the font file itself. Rendering software still needs to be capable of reading and following the instructions, but this is relatively simple.
Examples of this latter approach include Apple Advanced Typography (AAT) and Graphite. Both of these names encompass both the instruction format and the software supporting it; AAT is included on Apple operating systems, while Graphite is available for Microsoft Windows and Linux-based systems.
The OpenType format is primarily intended for systems using the first approach (layout knowledge in the renderer, not the font), but it has a few features that assist with CTL, such as contextual ligatures. AAT and Graphite instructions can be embedded in OpenType font files.
See also
Typography
Unicode
Writing systems which require complex text layout:
Arabic alphabet
Most of the Brahmic family of scripts
N'Ko script
Tengwar (diacritics and numbers)
References
External links
Examples of complex rendering — SIL international's examples of complex writing systems around the world
Complex Text Layout — The Open Group's Desktop Technologies
Supporting Indic Scripts in Mozilla — also other CTL scripts
Project SILA — Graphite and Mozilla integration project
CTL Architecture in Solaris — Solaris Globalization Whitepapers
Complex Scripts — Microsoft Global Development and Computing Portal
Theppitak's Homepage — information about Thai language processing
HarfBuzz's page at Freedesktop.org
D-Type Unicode Text Module — Portable software library for complex text
BidiRenderer — An application that illustrates the shaping and layout of complex text in bidirectional paragraphs using FriBidi, FreeType, and HarfBuzz
Tehreer-Android — A library that gives full control over text related technologies such as bidirectional algorithm, open type shaping, text typesetting and text rendering
Tehreer-Cocoa — Standalone font/text engine for iOS
Typesetting
Indic computing
Natural language and computing | Complex text layout | [
"Technology"
] | 1,000 | [
"Natural language and computing"
] |
1,524,877 | https://en.wikipedia.org/wiki/Comparison%20of%20text%20editors | This article provides basic comparisons for notable text editors. More feature details for text editors are available from the Category of text editor features and from the individual products' articles. This article may not be up-to-date or necessarily all-inclusive.
Feature comparisons are made between stable versions of software, not the upcoming versions or beta releases – and are exclusive of any add-ons, extensions or external programs (unless specified in footnotes).
Overview
Operating system support
This section lists the operating systems that different editors can run on. Some editors run on additional operating systems that are not listed.
Cross-platform
Natural language (localization)
Document interface
Notes
Multiple instances: multiple instances of the program can be opened simultaneously for editing multiple files. Applies both for single document interface (SDI) and multiple document interface (MDI) programs. Also applies for program that has a user interface that looks like multiple instances of the same program (such as some versions of Microsoft Word).
Single document window splitting: window can be split to simultaneously view different areas of a file.
MDI: Overlappable windows: each opened document gets its own fully movable window inside the editor environment.
MDI: Tabbed document interface: multiple documents can be viewed as tabs in a single window.
MDI: Window splitting: splitting application window to show multiple documents (non-overlapping windows).
Basic features
Programming features
Notes
Syntax highlighting: Displays text in different colors and fonts according to the category of terms.
Function list: Lists all functions from current file in a window or sidebar and allows user to jump directly to the definition of that function for example by double-clicking on the function name in the list. More or less realtime (does not require creating a symbol database, see below).
Symbol database: Database of functions, variable and type definitions, macro definitions etc. in all the files belonging to the software being developed. The database can be created by the editor itself or by an external program such as ctags. The database can be used to instantly locate the definition even if it is in another file.
Bracket matching: Find matching parenthesis or bracket, taking into account nesting.
Auto indentation: May refer to just simple indenting to the same level as the line above, or intelligent indenting that is language specific, e.g., ensuring a given indent style.
Compiler integration: Allows running compilers/linkers/debuggers from within editor, capturing the compiler output and stepping through errors, automatically moving cursor to corresponding location in the source file.
Extra features
Large file support:
In general, most text editors do not support large text files. Some restrict themselves to available in-core RAM while others use sophisticated virtual memory management techniques and paging algorithms.
Search in files:
Perform search (and possibly replace) in multiple files on disk, for example on a sub-directory and recursively all the directories below it.
Similar to grep.
Key bindings
Support for custom key bindings.
Notes, bugs
Vim: custom maps of Ctrl-1 .. Ctrl-9, Ctrl-0 cannot be set, nor is Control-Shift-<char> distinguished from Ctrl-<char>.
Notepad++: custom shortcuts of Shift-<char> cannot be set, they need an added modifier such as Ctrl or Alt. i.e. SCI_LINESCROLLUP cannot be bound to "Shift-I"as the "Add"button is greyed out.
Emacs and Pico: pico uses most of Emacs's motion and deletion commands: ^F ^B ^P ^N ^D etc.
Protocol support
Support for editing files over a network or the Internet.
Unicode and other character encodings
To support specified character encoding, the editor must be able to load, save, view and edit text in the specific encoding and not destroy any characters. For UTF-8 and UTF-16, this requires internal 16-bit character support.
Partial support is indicated if: 1) the editor can only convert the character encoding to internal (8-bit) format for editing.
2) If some encodings are supported only in some platforms.
3) If the editor can only display specific character set (such as OEM) by loading corresponding font, but does not support keyboard entry for that character set.
Right-to-left and bidirectional text
Support for Right-To-Left (RTL) texts is necessary for editing some languages like Arabic, Persian, Hebrew, and Yiddish and the mixture of left to right (LTR) and RTL known as bi-directional (BiDi) support.
Depending on the algorithm used in the programs it might only render the bidirectional text correctly but may not be able to edit them. (e.g. Notepad++ 5.1.3 shows bidirectional texts correctly but cannot edit it and user should change the text direction to RTL to be able to edit RTL texts correctly.)
Newline support
See also
Editor war
Comparison of
word processors
integrated development environments
HTML editors
TeX editors
hex editors
notetaking software
wiki software
Lists of
text editors
wiki software
personal information managers
outliners for
desktops
mobile devices
web-based
Notes
References
Text editors
Software comparisons | Comparison of text editors | [
"Technology"
] | 1,089 | [
"Software comparisons",
"Computing comparisons"
] |
1,524,935 | https://en.wikipedia.org/wiki/K-65%20residues | K-65 residues are the very radioactive mill residues resulting from the uniquely concentrated uranium ore discovered before WW II in Katanga province (Shinkolobwe mine) of the Democratic Republic of the Congo (formerly Belgian Congo).
According to Zoellner, "Remnants from typical uranium from the southwestern United States give a radioactive signature of about forty picocuries per gram, about ten times the amount of picocuries per liter of air that is considered safe for humans to breathe. The Shinkolobwe remnants, by contrast, emit a stunning 520,000 picocuries per gram." The Linde Air Products Company and Electro Metallurgical plant near Niagara Falls built the ring-and-plug in Little Boy. Linde Air used the Lake Ontario Ordnance Works site at the end of the war to dispose of its atomic waste, cuttings from the African uranium, some 200 dump trucks' worth. The eventual location of all this waste is called the "Interim Waste Containment Structure" of the Niagara Falls Storage Site of the U.S. Army Corps of Engineers.
This ore, dubbed "K-65", had a record 65% uranium content. It also held very high concentrations of thorium and radium (and their decay products, including radon gas) which are retained in the tailings (residues). The very high concentrations of these extremely toxic, long-lived radionuclides present in these wastes prompted the National Academy of Sciences' National Research Council to categorize them as indistinguishable in hazard from High-Level Waste in its 1995 report, "Safety of the High-Level Uranium Ore Residues at the Niagara Falls Storage Site, Lewiston, New York" .
The K-65 ores were refined as a key part of the Manhattan Project during World War II at the Linde Ceramics Plant at Tonawanda, NY, and at the Mallinckrodt Chemical Works in St. Louis, MO; these ores were the primary raw material source of ~80% of the uranium used in the Hiroshima bomb. The Mallinckrodt "K-65 residues" were later moved to the Feed Materials Production Center, a Cold War era uranium refinery at Fernald, OH (outside of Cincinnati) which commenced operations in 1951. The refining of "K-65" ore was continued at Fernald. The Linde "K-65 residues" were transported to a storage silo built at the federally appropriated Lake Ontario Ordnance Works site outside of Lewiston, NY, a short distance from Niagara Falls, NY.
References
Nuclear materials
Uranium | K-65 residues | [
"Physics"
] | 533 | [
"Materials",
"Nuclear materials",
"Matter"
] |
1,524,963 | https://en.wikipedia.org/wiki/Froebel%20gifts | The Froebel gifts () are educational play materials for young children, originally designed by Friedrich Fröbel for the first kindergarten at Bad Blankenburg. Playing with Froebel gifts, singing, dancing, and growing plants were each important aspects of this child-centered approach to education. The series was later extended from the original six to at least ten sets of gifts.
Description
The Sunday Papers () published by Fröbel between 1838 and 1840 explained the meaning and described the use of each of his six initial "play gifts" (): "The active and creative, living and life producing being of each person, reveals itself in the creative instinct of the child. All human education is bound up in the quiet and conscientious nurture of this instinct of activity; and in the ability of the child, true to this instinct, to be active."
Between May 1837 and 1850, the Froebel gifts were made in Bad Blankenburg in the principality of Schwarzburg Rudolstadt, by master carpenter Löhn, assisted by artisans and women of the village. In 1850, production was moved to the Erzgebirge region of the Kingdom of Saxony in a factory established for this purpose by S F Fischer.
Fröbel also developed a series of activities ("occupations") such as sewing, weaving, and modeling with clay, for children to extend their experiences through play. Ottilie de Liagre in a letter to Fröbel in 1844 observed that playing with the Froebel gifts empowers children to be lively and free, but people can degrade it into a mechanical routine.
Each of the first five gifts was assigned a number by Fröbel in the Sunday Papers, which indicated the sequence in which each gift was to be given to the child.
Gift 1 (infant)
The first gift is a soft ball or yarn ball in solid color, which is the right size for the hand of a small child. When attached to a matching string, the ball can be moved by a mother in various ways as she sings to the child. Although Fröbel sold single balls, they are now usually supplied in sets of six balls consisting of the primary colors: red, yellow, and blue; as well as the secondary colors: purple, green, and orange. These soft balls can be squashed in the hand, and they revert to their original shapes.
The first gift was intended by Fröbel to be given to very young children. His intention was that, through holding, dropping, rolling, swinging, hiding, and revealing the balls, the child may acquire knowledge of objects and spatial relationships, movement, speed and time, color and contrast, and weights and gravity.
Gift 2 (1–2 years)
The second gift originally consisted of two wooden objects, a sphere and a cube. Fröbel called this gift "the child's delight", since he observed the joy of each child discovering the differences between the sphere and cube.
The child is already familiar with the shape of the wooden sphere, which is the same as the ball of the first gift. The wooden sphere always looks the same when viewed from any direction. Like the child, the wooden sphere is always on the move. When rolled on a hard surface, the wooden sphere produces sounds. In contrast, the wooden cube is the surprise of the second gift. It remains where it is placed, and from each direction presents a different appearance.
The second gift was developed to enable a child to explore and enjoy the differences between shapes. By attaching a string or inserting a rod in a hole drilled through these wooden geometric shapes, they can be spun by a child. Although the sphere always appears the same, the spinning cube reveals many shapes when spun in different ways. This led Fröbel to later include a wooden cylinder in the second gift, which may also be spun in many different ways.
Gift 3 (2–3 years)
The familiar shape of the cube is now divided into eight identical beechwood cubes, about one inch along each edge, which is a convenient size for the hand of a small child. A child delights in pulling apart this gift, rearranging the eight cubes in many ways, and then reassembling them in the form of a cube. This is the first building gift.
Gift 4 (2–3 years)
This second building gift at first appears the same as in Gift 3. But a surprise awaits the child when the pieces are pulled apart. Each of these eight identical beechwood blocks is a rectangular plank, twice as long and half the width of the cubes of the previous gift. Many new possibilities for play and construction arise due to these differences.
Gift 5 (3–4 years)
This building gift consists of more cubes, some of which are divided in halves or quarters.
Gift 6 (4–5 years)
A set of more complex wooden blocks that includes cubes, planks, and triangular prisms.
Influence
Froebel's gifts were adapted by Caroline Pratt for the school, which she founded in 1913 in the Greenwich Village district of New York City. This school embodied a child-centered approach to education. Children worked together to reconstruct their experiences through play. Based on the ideas of Friedrich Fröbel, the curriculum was drawn from the environment of the child; observations about the neighborhood inspired each child to reflect on their world directly so that they could make sense of their experiences.
Joachim Liebschner commented in his book, A Child's Work: Freedom and Guidance in Froebel's Educational Theory and Practice "Realising how the Gifts were eventually misused by Kindergarten teachers who followed after Fröbel, it is important to consider what Fröbel expected the gifts to achieve. He envisaged that the Gifts will teach the child to use his (or her) environment as an educational aid; secondly, that they will give the child an indication of the connection between human life and life in nature; and finally, that they will create a bond between the adult and the child who play with them".
Fröbel's building forms and movement games were forerunners of abstract art as well as a source of inspiration to the Bauhaus movement. Many modernist architects were exposed as children to Fröbel's ideas about geometry, including Frank Lloyd Wright, Le Corbusier, and Buckminster Fuller. Wright was given a set of the Froebel blocks at about age nine, and in his autobiography he cited them indirectly in explaining that he learned the geometry of architecture in kindergarten play: Wright later wrote, "The virtue of all this lay in the awakening of the child-mind to rhythmic structures in Nature… I soon became susceptible to constructive pattern evolving in everything I saw."
Current availability
Froebel gifts continue to be used in early childhood education in Korea and Japan, where they are made from local timber.
Reproduction sets can be ordered via the Internet.
See also
Alphabet blocks (ABC blocks)
Montessori sensorial materials
Unit block
Waldorf doll
References
External links
Play is the work of children
Friedrich Froebel website
Froebel Web
Froebel USA
Online links to Froebel educational resources
Link to paper by Quinn which includes detailed descriptions and color photographs
Early childhood education materials
Construction toys
Educational toys
Wooden toys
Mathematical manipulatives | Froebel gifts | [
"Mathematics"
] | 1,488 | [
"Recreational mathematics",
"Mathematical manipulatives"
] |
1,525,528 | https://en.wikipedia.org/wiki/SGR%201806%E2%88%9220 | SGR 1806−20 is a magnetar, a type of neutron star with a very powerful magnetic field, that was discovered in 1979 and identified as a soft gamma repeater. SGR 1806−20 is located about 13 kiloparsecs (42,000 light-years) from Earth on the far side of the Milky Way in the constellation of Sagittarius. It has a diameter of no more than and rotates on its axis every 7.5 seconds ( rotation speed at the equator on the surface). , SGR 1806-20 is the most highly magnetized object ever observed, with a magnetic field of over 1015 gauss (G) (1011 tesla) intensity (compared to the Sun's 1–5 G and Earth's 0.25–0.65 G).
Explosion
Forty-two thousand years after a starquake occurred on the surface of SGR 1806-20, the radiation from the resultant explosion reached Earth on December 27, 2004 (GRB 041227). In terms of gamma rays, the burst had an absolute magnitude of around −29. It was the brightest event known to have been sighted on this planet from an origin outside the Solar System until GRB 080319B. The magnetar released more energy in one-tenth of a second (1.0 J) than the Sun releases in 150,000 years (4 W × 4.8 s = 1.85 J). Such a burst is thought to be the largest explosion observed in this galaxy by humans since the SN 1604, a supernova observed by Johannes Kepler in 1604. The gamma rays struck Earth's ionosphere and created more ionization, which briefly expanded the ionosphere. The quake was equivalent to a magnitude 32 on the Richter scale.
A similar blast within 3 parsecs (10 light years) of Earth would severely affect the atmosphere, by destroying the ozone layer and causing mass extinction, and be similar in effect to a 12-kiloton nuclear blast at . The nearest known magnetar to Earth is 1E 1048.1-5937, located 9,000 light-years away in the constellation Carina.
Location
SGR 1806−20 lies at the core of radio nebula G10.0-0.3 and is a member of an open cluster named after it, itself a component of W31, one of the largest H II regions in the Milky Way. Cluster 1806-20 is made up of some highly unusual stars, including at least two carbon-rich Wolf–Rayet stars (WC9d and WCL), two blue hypergiants, and LBV 1806-20, one of the brightest/most massive stars in the galaxy.
Planetary system
A 2024 paper posited that periodic gamma-ray and x-ray bursts from the pulsar are caused by a planet orbiting SGR 1806-20. This SGR 1806-20 b would be some kind of rocky world with a mass between 10-18 Earth masses with an orbital period of 398 days and a semi-major axis of 1.18 astronomical units. SGR 1806-20 b is notable for its eccentricity of 0.994, which would make it the most eccentric exoplanet known.
See also
LBV 1806−20 – luminous blue variable
Notes
References
External links
Anniversary of a Cosmic Blast (Phil Plait Dec. 27, 2012)
An exceptionally bright flare from SGR 1806-20 and the origins of short-duration big gamma-ray bursts, 2005-04-28 (Nature)
Huge 'star-quake' rocks Milky Way, 2005-02-18, (BBC News Online)
Brightest galactic flash ever detected hits Earth 2005-02-18 (space.com)
2005-02-20 (The Age) Registration required.
Huge quake cracks star 2005-09-27 (space.com)
NASA Sees Hidden Structure Of Neutron Star In Starquake (SpaceDaily) April 26, 2006
Soft gamma repeaters
Sagittarius (constellation)
Astronomical objects discovered in 1979
Magnetars
Hypothetical planetary systems | SGR 1806−20 | [
"Astronomy"
] | 836 | [
"Magnetars",
"Magnetism in astronomy",
"Sagittarius (constellation)",
"Constellations"
] |
1,525,551 | https://en.wikipedia.org/wiki/List%20of%20astronomical%20interferometers%20at%20visible%20and%20infrared%20wavelengths | Here is a list of currently existing astronomical optical interferometers (i.e. operating from visible to mid-infrared wavelengths), and some parameters describing their performance.
Current performance of ground-based interferometers
Columns 2-5 determine the range of targets that can be observed and the range of science which can be done. Higher limiting magnitude means that the array can observe fainter sources. The limiting magnitude is determined by the atmospheric seeing, the diameters of the telescopes and the light lost in the system. A larger range of baselines means that a wider variety of science can be done and on a wider range of sources.
Columns 6-10 indicate the approximate quality and total amount of science data the array is expected to obtain. This is per year, to account for the average number of cloud-free nights on which each array is operated.
New interferometers and improvements to existing interferometers
See also
Lists of telescopes
Photometric system has a key for waveband letters.
References
Further reading
Lists of telescopes
I | List of astronomical interferometers at visible and infrared wavelengths | [
"Astronomy"
] | 211 | [
"Astronomy-related lists",
"Lists of telescopes",
"Outer space",
"Outer space lists"
] |
1,525,710 | https://en.wikipedia.org/wiki/Assimilation%20%28biology%29 | Assimilation is the process of absorption of vitamins, minerals, and other chemicals from food as part of the nutrition of an organism. In humans, this is always done with a chemical breakdown (enzymes and acids) and physical breakdown (oral mastication and stomach churning). Chemical alteration of substances in the bloodstream by the liver or cellular secretions. Although a few similar compounds can be absorbed in digestion bio assimilation, the bioavailability of many compounds is dictated by this second process since both the liver and cellular secretions can be very specific in their metabolic action (see chirality). This second process is where the absorbed food reaches the cells via the liver.
Most foods are composed of largely indigestible components depending on the enzymes and effectiveness of an animal's digestive tract. The most well-known of these indigestible compounds is cellulose; the basic chemical polymer in the makeup of plant cell walls. Most animals, however, do not produce cellulase; the enzyme needed to digest cellulose. However, some animals and species have developed symbiotic relationships with cellulase-producing bacteria (see termites and metamonads.) This allows termites to use the energy-dense cellulose carbohydrate. Other such enzymes are known to significantly improve bio-assimilation of nutrients. Because of the use of bacterial derivatives, enzymatic dietary supplements now contain such enzymes as amylase, glucoamylase, protease, invertase, peptidase, lipase, lactase, phytase, and cellulase.
Examples of biological assimilation
Photosynthesis, a process whereby carbon dioxide and water are transformed into a number of organic molecules in plant cells.
Nitrogen fixation from the soil into organic molecules by symbiotic bacteria which live in the roots of certain plants, such as Leguminosae.
Magnesium supplements orotate, oxide, sulfate, citrate, and glycerate are all structurally similar. However, oxide and sulfate are not water-soluble and do not enter the bloodstream, while orotate and glycerate have normal exiguous liver conversion. Chlorophyll sources or magnesium citrate are highly bioassimilable.
The absorption of nutrients into the body after digestion in the intestine and its transformation in biological tissues and fluids.
See also
Anabolism
Biochemistry
Nutrition
Respiration
Transportation
Excretion
References
Biological processes
Metabolism | Assimilation (biology) | [
"Chemistry",
"Biology"
] | 507 | [
"Biochemistry",
"Metabolism",
"nan",
"Cellular processes"
] |
1,525,765 | https://en.wikipedia.org/wiki/Cluster%20%28physics%29 | In physics, the term clusters denotes small, polyatomic particles. As a rule of thumb, any particle made of between 3×100 and 3×107 atoms is considered a cluster.
The term can also refer to the organization of protons and neutrons within an atomic nucleus, e.g. the alpha particle (also known as "α-cluster"), consisting of two protons and two neutrons (as in a helium nucleus).
Overview
Although first reports of cluster species date back to the 1940s, cluster science emerged as a separate direction of research in the 1980s, One purpose of the research was to study the gradual development of collective phenomena which characterize a bulk solid. For example, these are the color of a body, its electrical conductivity, its ability to absorb or reflect light, and magnetic phenomena such as ferro-, ferri-, or antiferromagnetism. These are typical collective phenomena which only develop in an aggregate of a large number of atoms.
It was found that collective phenomena break down for very small cluster sizes. It turned out, for example, that small clusters of a ferromagnetic material are super-paramagnetic rather than ferromagnetic. Paramagnetism is not a collective phenomenon, which means that the ferromagnetism of the macrostate was not conserved by going into the nanostate. The question then was asked for example, "How many atoms do we need in order to obtain the collective metallic or magnetic properties of a solid?" Soon after the first cluster sources had been developed in 1980, an ever larger community of cluster scientists was involved in such studies.
This development led to the discovery of fullerenes in 1986 and carbon nanotubes a few years later.
In science, a lot is known about properties of the gas phase; however, comparatively little is known about the condensed phases (the liquid phase and solid phase.) The study of clusters attempts to bridge this gap of knowledge by clustering atoms together and studying their characteristics. If enough atoms were clustered together, eventually one would obtain a liquid or solid.
The study of atomic and molecular clusters also benefits the developing field of nanotechnology. If new materials are to be made out of nanoscale particles, such as nanocatalysts and quantum computers, the properties of the nanoscale particles (the clusters) must first be understood.
See also
Cluster chemistry
Nanoparticle
Nanocluster
References
External links
Scientific community portal for clusters, fullerenes, nanotubes, nanostructures, and similar small systems.
Nanomaterials | Cluster (physics) | [
"Materials_science"
] | 533 | [
"Nanotechnology",
"Materials science stubs",
"Nanotechnology stubs",
"Nanomaterials"
] |
1,525,933 | https://en.wikipedia.org/wiki/Rodrigues%27%20rotation%20formula | In the theory of three-dimensional rotation, Rodrigues' rotation formula, named after Olinde Rodrigues, is an efficient algorithm for rotating a vector in space, given an axis and angle of rotation. By extension, this can be used to transform all three basis vectors to compute a rotation matrix in , the group of all rotation matrices, from an axis–angle representation. In terms of Lie theory, the Rodrigues' formula provides an algorithm to compute the exponential map from the Lie algebra to its Lie group .
This formula is variously credited to Leonhard Euler, Olinde Rodrigues, or a combination of the two. A detailed historical analysis in 1989 concluded that the formula should be attributed to Euler, and recommended calling it "Euler's finite rotation formula." This proposal has received notable support, but some others have viewed the formula as just one of many variations of the Euler–Rodrigues formula, thereby crediting both.
Statement
If is a vector in and is a unit vector describing an axis of rotation about which rotates by an angle according to the right hand rule, the Rodrigues formula for the rotated vector is
The intuition of the above formula is that the first term scales the vector down, while the second skews it (via vector addition) toward the new rotational position. The third term re-adds the height (relative to ) that was lost by the first term.
An alternative statement is to write the axis vector as a cross product of any two nonzero vectors and which define the plane of rotation, and the sense of the angle is measured away from and towards . Letting denote the angle between these vectors, the two angles and are not necessarily equal, but they are measured in the same sense. Then the unit axis vector can be written
This form may be more useful when two vectors defining a plane are involved. An example in physics is the Thomas precession which includes the rotation given by Rodrigues' formula, in terms of two non-collinear boost velocities, and the axis of rotation is perpendicular to their plane.
Derivation
Let be a unit vector defining a rotation axis, and let be any vector to rotate about by angle (right hand rule, anticlockwise in the figure), producing the rotated vector .
Using the dot and cross products, the vector can be decomposed into components parallel and perpendicular to the axis ,
where the component parallel to is called the vector projection of on ,
,
and the component perpendicular to is called the vector rejection of from :
,
where the last equality follows from the vector triple product formula: . Finally, the vector is a copy of rotated 90° around . Thus the three vectors form a right-handed orthogonal basis of , with the last two vectors of equal length.
Under the rotation, the component parallel to the axis will not change magnitude nor direction:
while the perpendicular component will retain its magnitude but rotate its direction in the perpendicular plane spanned by and , according to
in analogy with the planar polar coordinates in the Cartesian basis , :
Now the full rotated vector is:
Substituting or in the last expression gives respectively:
Matrix notation
The linear transformation on defined by the cross product is given in coordinates by representing and as column matrices:
That is, the matrix of this linear transformation (with respect to standard coordinates) is the cross-product matrix:
That is to say,
The last formula in the previous section can therefore be written as:
Collecting terms allows the compact expression
where
is the rotation matrix through an angle counterclockwise about the axis , and the identity matrix. This matrix is an element of the rotation group of , and is an element of the Lie algebra generating that Lie group (note that is skew-symmetric, which characterizes ).
In terms of the matrix exponential,
To see that the last identity holds, one notes that
characteristic of a one-parameter subgroup, i.e. exponential, and that the formulas match for infinitesimal .
For an alternative derivation based on this exponential relationship, see exponential map from to . For the inverse mapping, see log map from to .
The above result can be written in index notation as follows. The elements of the matrix for an active rotation by an angle about an axis are given by
Here, i, j, and k label the Cartesian components (x, y, z) or (1, 2, 3), and are the Kronecker and Levi-Civita symbols, and there is an implicit sum on repeated indices.
The Hodge dual of the rotation is just which enables the extraction of both the axis of rotation and the sine of the angle of the rotation from the rotation matrix itself, with the usual ambiguity,
where . The above simple expression results from the fact that the Hodge duals of and are zero, and .
See also
Axis angle
Rotation (mathematics)
SO(3) and SO(4)
Euler–Rodrigues formula
References
Leonhard Euler, "Problema algebraicum ob affectiones prorsus singulares memorabile", Commentatio 407 Indicis Enestoemiani, Novi Comm. Acad. Sci. Petropolitanae 15 (1770), 75–106.
Olinde Rodrigues, "Des lois géométriques qui régissent les déplacements d'un système solide dans l'espace, et de la variation des coordonnées provenant de ces déplacements considérés indépendants des causes qui peuvent les produire", Journal de Mathématiques Pures et Appliquées 5 (1840), 380–440. online.
Richard M. Friedberg (2022) "Rodrigues, Olinde: "Des lois géométriques qui régissent les déplacements d'un systéme solide...", translation and commentary". arXiv:2211.07787.
Don Koks, (2006) Explorations in Mathematical Physics, Springer Science+Business Media, LLC. . Ch.4, pps 147 et seq. A Roundabout Route to Geometric Algebra
External links
Johan E. Mebius, Derivation of the Euler-Rodrigues formula for three-dimensional rotations from the general formula for four-dimensional rotations., arXiv General Mathematics 2007.
For another descriptive example see: http://chrishecker.com/Rigid_Body_Dynamics#Physics_Articles, Chris Hecker, physics section, part 4. "The Third Dimension" – on page 3, section ``Axis and Angle'', http://chrishecker.com/images/b/bb/Gdmphys4.pdf
Rotation in three dimensions
Euclidean geometry
Orientation (geometry)
fr:Rotation vectorielle#Cas général | Rodrigues' rotation formula | [
"Physics",
"Mathematics"
] | 1,392 | [
"Topology",
"Space",
"Geometry",
"Spacetime",
"Orientation (geometry)"
] |
1,526,274 | https://en.wikipedia.org/wiki/Roadgeek | A roadgeek (from road + geek) is a person involved in "roadgeeking" or "road enthusiasm", an enthusiasm for roads, fond of road trips as a hobby. One may also be called a road enthusiast, road buff, roadfan or Roads Scholar, the latter a play on "Rhodes Scholar".
Interest
Roadgeeks view their interest as an appreciation of engineering and planning feats:
Roadgeeks are not necessarily interested in motor vehicles; there may also be an interest in cartography and map design. Enthusiasts may focus on a single activity related to roads, such as driving the full length of a highway (known as 'clinching') or researching the history, planning and quirks of a particular road or national highway system. Sometimes, road geeks are called "highway historians" for the knowledge and interests.
Even the numbering system can be a subject of deep interest, as Joe Moran describes in his book "On Roads: A Hidden History":
Online
In 2002, the St. Louis Post-Dispatch reported that road enthusiasm was an Internet phenomenon. There is a Usenet newsgroup, misc.transport.road, where participants discuss all facets of roads and road trips from "construction projects to quirks and inconsistencies in signage". Those who await each annual Rand McNally road atlas release found a community of others online who were also interested in roads as a hobby. These communities of people could share photos, swap their thoughts on the highways in their areas and "debate the finer points of interchange design".
Web based forums are popular; one of the largest is AARoads Forum.
SABRE
Started in 1999, the Society for All British and Irish Road Enthusiasts (SABRE), originally known as "Study and Appreciation of the British Roads Experience", is one of the larger and most prominent communities of road enthusiasts online. The organization hosts a large collection of articles and histories of particular roads and terminology, online photo galleries, discussion forums, and an application to overlay and compare historical roadmaps. Although SABRE is primarily an online group, members organize group tours to visit sites of interest.
Taiwan websites
In 2006, a board called "Road" () in the PTT Bulletin Board System, which is a Taiwanese forum, was established. Because some Taiwanese road enthusiasts didn't know how to use a terminal or BBS reader to access it, the web forum Taiwan Highway Club (; literally, "Highway State") was started in 2008. It contains subforums where users discuss road policies and post highway news and images.
Relationship with governments
In Taiwan, the Ministry of Transportation and Communications' Directorate General of Highways () has held occasional Road Fan Conferences () since 2011 where roadfans and highway transportation-related organizations made suggestions to the government.
References
Further reading
External links
AARoads Glossary
Hobbies
Transport culture
Greek
Transportation engineering
Highways | Roadgeek | [
"Physics",
"Engineering"
] | 586 | [
"Transport culture",
"Industrial engineering",
"Physical systems",
"Transport",
"Transportation engineering",
"Civil engineering"
] |
1,526,448 | https://en.wikipedia.org/wiki/Enclosed%20cremation%20cemetery | Enclosed cremation cemetery is a term used by archaeologists to describe a type of cemetery found in north western Europe during the late Neolithic and early Bronze Age. They are similar to urnfield burial grounds in that they consist of a concentration of pits containing cremated remains which have usually also been placed into pottery vessels. However they are also surrounded by a circular or oval bank and outer ditch which gives them their name. The most famous example is Stonehenge which functioned as such a cemetery during its early use when it was a simple earthwork enclosure. Its status has been questioned as its not clear that that was its only use at the time. They are interpreted as being variations on the ritual and funerary practice of enclosing significant sites of activity during the period, also exhibited by henges and stone circles.
References
Archaeology in Europe
Cemeteries
Cremation | Enclosed cremation cemetery | [
"Chemistry"
] | 173 | [
"Cremation",
"Incineration"
] |
1,526,681 | https://en.wikipedia.org/wiki/Barricade | Barricade (from the French barrique - 'barrel') is any object or structure that creates a barrier or obstacle to control, block passage or force the flow of traffic in the desired direction. Adopted as a military term, a barricade denotes any improvised field fortification, such as on city streets during urban warfare.
Barricades also include temporary traffic barricades designed with the goal of dissuading passage into a protected or hazardous area or large slabs of cement whose goal is to prevent forcible passage by a vehicle. Stripes on barricades and panel devices slope downward in the direction traffic must travel.
There are also pedestrian barricades - sometimes called bike rack barricades for their resemblance to a now obsolete form of bicycle stand, or police barriers. They originated in France approximately 50 years ago and are now used around the world. They were first used in the U.S. 40 years ago by Friedrichs Mfg for New Orleans's Mardi Gras parades.
Anti-vehicle barriers and blast barriers are sturdy barricades that can respectively counter vehicle and bomb attacks.
In history
The origins of the barricade are often erroneously traced back to the "First Day of the Barricades", a confrontation that occurred in Paris on 12 May 1588 in which the supporters of the Duke of Guise and the ultra-Catholic Holy League successfully challenged the authority of King Henri III. In actuality, although barricades came to widespread public awareness in that uprising (and in the equally momentous "Second Day of the Barricades" on 27 August 1648), none of several conflicting claims concerning who may have "invented" the barricade stand up to close scrutiny for the simple reason that Blaise de Monluc had already documented insurgents' use of the technique at least as early as 1569 in religiously based conflicts in southwestern France.
Although barricade construction began in France in the sixteenth century and remained an exclusively French practice for two centuries, the nineteenth century remained the classic era of the barricade. Contrary to a number of historical sources, barricades were present in various incidents of the great French Revolution of 1789, but they never played a central role in those events. They were, however, a highly visible and consequential element in many of the insurrections that occurred in France throughout the 1800s, including in the revolutions of 1830 ("the July Days") and 1848 (in both February and June.) Other Parisian events included the June Rebellion of 1832, which was smaller in scale, but rendered famous by Victor Hugo's account in Les Misérables, the combat that ended the Paris Commune in May 1871, and the more symbolic structures created in May 1968.
The barricade began its diffusion outside France in the 1780s and played a significant role in the Belgian Revolution of 1830, but it was only in the course of the upheaval of 1848 that it became truly international in scope. Its spread across the Continent was aided by the circulation of students, political refugees, and itinerant workers through the French capital, where many gained first-hand experience of one or another Parisian insurrection. The barricade had, by the middle of the nineteenth century, become the preeminent symbol of a revolutionary tradition that would ultimately spread worldwide. Barricade references appear in many colloquial expressions and are used, often metaphorically, in poems and songs celebrating radical social movements.
Crowd control
Barricades are used for crowd control applications at public events or during exceptionally busy shopping times. Different types of barricade are designed to fit the environment and use cases the organizer decides on.
Bridge Feet Typically used for outdoor use, where the ground is not perfectly flat. The bridge design of the feet allows for better stability.
Flat FeetUsed on surfaces such as streets, sidewalks, and tarmacs, these barricades are designed for use on flat surfaces.
Heavy Duty Feet Similar to flat feet, but larger in size and made of heavy duty steel, allowing for more durability and support.
Barricade Gates These gates swing open like a doorway, allowing for passage of people of goods through a run of barricades.
Expanding Barricades Designed for indoor use and for use on sites where construction or work is occurring. Easy to move and store these barricades serve as a temporary barricade.
Gallery
See also
The Barricades
Bulwark
Border barrier
Rampart
Ley Anti Barricadas
Jersey barrier
A las Barricadas ('To the Barricades')
References
Traffic signs
Types of wall
Fortifications by type | Barricade | [
"Engineering"
] | 934 | [
"Structural engineering",
"Types of wall"
] |
1,526,737 | https://en.wikipedia.org/wiki/Interstate%20Highway%20standards | Standards for Interstate Highways in the United States are defined by the American Association of State Highway and Transportation Officials (AASHTO) in the publication A Policy on Design Standards: Interstate System. For a certain highway to be considered an Interstate Highway, it must meet these construction requirements or obtain a waiver from the Federal Highway Administration.
Standards
Standardization helps keep road design consistent, such that drivers can learn the consistent features and drive accordingly. Standardization can therefore decrease accidents and increase driver safety.
These standards are, :
Controlled access: All access onto and off the highway is to be controlled with interchanges and grade separations, including all railroad crossings. Interchanges are to provide access to and from both directions of the highway and both directions of the crossroad. Interchanges should be spaced at least apart in urban areas and apart in rural areas; collector/distributor roads or other roadway configurations that reduce weaving can be used in urban areas to shorten this distance.
In urban areas, there should be no driveways or other access points to adjacent properties along the crossroad for at least from entrance and exit ramps, in both directions, and for at least in rural areas.
In urban and suburban areas, consideration should be given to accommodating bicycles and pedestrians along crossroads.
Minimum design speed: A minimum design speed of is to be used, except in mountainous and urban areas, where the minimum is .
The sight distance, curvature and superelevation of the highway should follow the current edition of AASHTO's A Policy on Geometric Design of Highways and Streets for the chosen design speed.
Maximum grade: The maximum permissible vertical angle, or grade, along the highway is determined from terrain and design speed, with up to 6% generally allowed in mountainous areas, 5% in rolling terrain, and 4% on level terrain. An additional 1% is allowed in urban areas.
Minimum number of lanes: There are to be at least two lanes in each direction, unless more are necessary for an acceptable level of service, according to the current edition of AASHTO's A Policy on Geometric Design of Highways and Streets. Climbing lanes and emergency escape ramps should be provided where appropriate.
Minimum lane width: The minimum lane width is , identical to most US and state highways.
Shoulder width: The minimum width of the left paved shoulder is , and of the right paved shoulder . With three or more lanes in each direction, both shoulders are to be at least wide. In mountainous terrain, a left shoulder of and a right shoulder of are acceptable, except where there are at least four lanes in each direction, in which case both shoulders are to be at least wide. In places with higher truck traffic, over 250 directional design hour volume, wider shoulders should be considered.
Pavement sloping: On straight sections of the highway, the roadway is to have a cross slope of at least 1.5%, and preferably 2% to ensure proper drainage, with up to 2.5% in areas of heavy rainfall. The cross slope of both the left and right shoulders should be between 2% and 6%, but not less than the main lanes.
Median width: The median should have a width of least , and preferably , in rural areas, and , plus a barrier, in urban or mountainous areas.
Recovery areas: There should be no fixed objects in the clear zone, the width of which should be determined by the design speed in accordance with the current edition of AASHTO's Roadside Design Guide. When this is not possible, breakaway supports or barriers guarding the objects should be used. Special care should be taken in depressed highways, where piers and walls should be placed at least beyond the outer edge of either shoulder. Slopes in the clear zone should be at most 1:4, and should typically be 1:6.
Curbs: No curb is to be placed nearer to the roadway than the outside edge of the paved shoulder. Any curb is to have a sloping, and not a vertical face, and be no more than in height. Special care should be taken when curbs are combined with barriers.
Vertical clearance: The minimum vertical clearance under overhead structures, such as bridges, is , including both paved shoulders and an allowance for extra layers of pavement. Through urban areas, at least one routing is to have clearances, but others may have a lesser clearance of . Sign supports and pedestrian overpasses must be at least above the road, except on urban routes with lesser clearance, where they should be at least higher than other objects. The cross bracing of truss bridges has a special additional clearance requirement of .
Bridges: Bridges less than long should carry the full width of the roadway, including the paved shoulders. Longer bridges can reduce the width of both shoulders to .
Existing bridges can remain part of the Interstate system if they have at least lanes with shoulder on the left and a shoulder on the right, except that longer bridges can have shoulders on both sides. For all bridges, the railing should be upgraded if necessary.
Tunnel clearance: Tunnels should not differ significantly from bridges, but because of the high costs of tunnels, the width of both shoulders may be reduced to . An exit walkway wide is also required, which should either be elevated or separated from the roadway with a barrier. In addition, access for emergency responders needs to be accommodated. The minimum vertical clearance is the same as it is under bridges.
Markings: All road markings should be retroreflective.
Exceptions
Interstate standards have changed over the years, which has resulted in many older roads not conforming to current standards and an increase of roads not being built to these standards because to do so would be too costly or environmentally unsound.
Some roads were grandfathered into the system. Most of these were toll roads that were built before the Interstate system came into existence or were under construction at the time President Dwight D. Eisenhower signed the Federal-Aid Highway Act of 1956. One example is the Pennsylvania Turnpike, which originally had a very narrow median that later required the installation of a steel guardrail and later a Jersey barrier due to heavy traffic loads. The Kansas Turnpike had a depressed median ( narrower than the Interstate minimum) along its entire length from its opening in 1956 through the mid-1980s when Jersey barriers were installed.
Interstate 35E through Saint Paul, Minnesota is an example of a freeway that was not grandfathered into the system but is nonetheless an exception to standards. Initially designed in the 1960s, but not opened until 1990, the freeway has a speed limit of , and does not allow vehicles weighing over gross vehicle weight (GVW). This is due to political opposition from surrounding homeowners in local neighborhoods, which greatly delayed and modified the project. Interstate 670, a spur of Interstate 70, also fails to reach the 50 mile per hour minimum and instead passes through Downtown Kansas City, Missouri at 45 miles per hour.
Interstate 75 on the Mackinac Bridge between St. Ignace and Mackinaw City, Michigan, is undivided. The bridge was designed before the start of the Interstate Highway System, and it was grandfathered into the system.
Interstate 93 through Franconia Notch, New Hampshire is also a notable exception, being a super two parkway with a speed limit of .
All of the unsigned Interstates in Alaska and Puerto Rico are exempt from Interstate Highway standards and are instead, per Title 23, Chapter 1, Section 103 of the U.S. Code, "designed in accordance with such geometric and construction standards as are adequate for current and probable future traffic demands and the needs of the locality of the highway".
References
External links
Public Safety Standards, United States (Federal Government) – Offers free downloads of documents, including AASHTO's "A Policy on Design Standards", that have been incorporated by reference into the US Code of Federal Regulations and can therefore be freely copied as edicts of government.
AASHTO Bookstore – A Policy on Design Standards – Interstate System ()
Standards
Standards of the United States
Construction standards | Interstate Highway standards | [
"Engineering"
] | 1,608 | [
"Construction",
"Construction standards"
] |
1,526,810 | https://en.wikipedia.org/wiki/Dynamic%20stereochemistry | In chemistry, dynamic stereochemistry studies the effect of stereochemistry on the reaction rate of a chemical reaction. Stereochemistry is involved in:
stereospecific reactions
stereoselective or asymmetric reactions
racemisation processes
References
Carey, Francis A.; Sundberg, Richard J.; (1984). Advanced Organic Chemistry Part A Structure and Mechanisms (2nd ed.). New York N.Y.: Plenum Press .
Stereochemistry
Chemical kinetics | Dynamic stereochemistry | [
"Physics",
"Chemistry"
] | 100 | [
"Chemical reaction engineering",
"Stereochemistry",
"Space",
"Stereochemistry stubs",
"nan",
"Spacetime",
"Chemical kinetics"
] |
1,526,836 | https://en.wikipedia.org/wiki/Plasmogamy | Plasmogamy is a stage in the sexual reproduction of fungi, in which the protoplasm of two parent cells (usually from the mycelia) fuse without the fusion of nuclei, effectively bringing two haploid nuclei close together in the same cell. This state is followed by karyogamy, where the two nuclei fuse and then undergo meiosis to produce spores.
The dikaryotic state that comes after plasmogamy will often persist for many generations before the fungi undergoes karyogamy. In lower fungi however, plasmogamy is usually immediately followed by karyogamy. A comparative genomic study indicated the presence of the machinery for plasmogamy, karyogamy and meiosis in the Amoebozoa.
References
Mycology | Plasmogamy | [
"Biology"
] | 166 | [
"Mycology"
] |
1,526,867 | https://en.wikipedia.org/wiki/Stereospecificity | In chemistry, stereospecificity is the property of a reaction mechanism that leads to different stereoisomeric reaction products from different stereoisomeric reactants, or which operates on only one (or a subset) of the stereoisomers.
In contrast, stereoselectivity is the property of a reactant mixture where a non-stereospecific mechanism allows for the formation of multiple products, but where one (or a subset) of the products is favored by factors, such as steric access, that are independent of the mechanism.
A stereospecific mechanism specifies the stereochemical outcome of a given reactant, whereas a stereoselective reaction selects products from those made available by the same, non-specific mechanism acting on a given reactant. Given a single, stereoisomerically pure starting material, a stereospecific mechanism will give 100% of a particular stereoisomer (or no reaction), although loss of stereochemical integrity can easily occur through competing mechanisms with different stereochemical outcomes. A stereoselective process will normally give multiple products even if only one mechanism is operating on an isomerically pure starting material.
The term stereospecific reaction is ambiguous, since the term reaction itself can mean a single-mechanism transformation (such as the Diels–Alder reaction), which could be stereospecific, or the outcome of a reactant mixture that may proceed through multiple competing mechanisms, specific and non-specific. In the latter sense, the term stereospecific reaction is commonly misused to mean highly stereoselective reaction.
Chiral synthesis is built on a combination of stereospecific transformations (for the interconversion of existing stereocenters) and stereoselective ones (for the creation of new stereocenters), where also the optical activity of a chemical compound is preserved.
The quality of stereospecificity is focused on the reactants and their stereochemistry; it is concerned with the products too, but only as they provide evidence of a difference in behavior between reactants. Of stereoisomeric reactants, each behaves in its own specific way. Stereospecificity towards enantiomers is called enantiospecificity.
Examples
Nucleophilic substitution at sp3 centres can proceed by the stereospecific SN2 mechanism, causing only inversion, or by the non-specific SN1 mechanism, the outcome of which can show a modest selectivity for inversion, depending on the reactants and the reaction conditions to which the mechanism does not refer. The choice of mechanism adopted by a particular reactant combination depends on other factors (steric access to the reaction centre in the substrate, nucleophile, solvent, temperature).
For example, tertiary centres react almost exclusively by the SN1 mechanism whereas primary centres (except neopentyl centres) react almost exclusively by the SN2 mechanism. When a nucleophilic substitution results in incomplete inversion, it is because of a competition between the two mechanisms, as often occurs at secondary centres, or because of double inversion (as when iodide is the nucleophile).
The addition of singlet carbenes to alkenes is stereospecific in that the geometry of the alkene is preserved in the product. For example, dibromocarbene and cis-2-butene yield cis-2,3-dimethyl-1,1-dibromocyclopropane, whereas the trans isomer exclusively yields the trans cyclopropane.
This addition remains stereospecific even if the starting alkene is not isomerically pure, as the products' stereochemistry will match the reactants'.
The disrotatory ring closing reaction of conjugated trienes is stereospecific in that isomeric reactants will give isomeric products. For example, trans,cis,trans-2,4,6-octatriene gives cis-dimethylcyclohexadiene, whereas the trans,cis,cis reactant isomer gives the trans product and the trans,trans,trans reactant isomer does not react in this manner.
See also
Dynamic stereochemistry
References
Stereochemistry | Stereospecificity | [
"Physics",
"Chemistry"
] | 880 | [
"Spacetime",
"Stereochemistry",
"Space",
"nan"
] |
1,526,870 | https://en.wikipedia.org/wiki/Heterokaryon | A heterokaryon is a multinucleate cell that contains genetically different nuclei. Heterokaryotic and heterokaryosis are derived terms. This is a special type of syncytium. This can occur naturally, such as in the mycelium of fungi during sexual reproduction, or artificially as formed by the experimental fusion of two genetically different cells, as e.g., in hybridoma technology.
Etymology
Heterokaryon is from neo-classic Greek hetero, meaning different, and karyon, meaning kernel or in this case nucleus.
The term was coined in 1965, independently by B. Ephrussi and M. Weiss, by H. Harris and J. F. Watkins, and by Y. Okada and F. Murayama.
Occurrence
Heterokaryons are found in the life cycle of yeasts, for example Saccharomyces cerevisiae, a genetic model organism. The heterokaryon stage is produced from the fusion of two haploid cells. This transient heterokaryon can produce further haploid buds, or cell nuclei can fuse and produce a diploid cell, which can then undergo mitosis.
Ciliate protozoans
The term was first used for ciliate protozoans such as Tetrahymena. This has two types of cell nuclei, a large, somatic macronucleus and a small, germline micronucleus. Both exist in a single cell at the same time and carry out different functions with distinct cytological and biochemical properties.
True fungi
Many fungi (notably the arbuscular mycorrhizal fungi) exhibit heterokaryosis. The haploid nuclei within a mycelium may differ from one another not merely by accumulating mutations, but by the non-sexual fusion of genetically distinct fungal hyphae, although a self / non-self recognition system exists in Fungi and usually prevents fusions with non-self.
Heterokaryosis is also common upon mating, as in Dikarya (Ascomycota and Basidiomycota). Mating requires the encounter of two haploid nuclei of compatible mating types. These nuclei do not immediately fuse, and remain haploid in a n+n state until the very onset of meiosis: this phenomenon is called delayed karyogamy. Heterokaryosis can lead to individuals that have different nuclei in different parts of their mycelium, although in ascomycetes, particularly in "Neurospora", nuclei have been shown to flow and mix throughout the mycelium. In heterokaryons, the notion of individual itself becomes vague since the rule of “one genome = one individual” does not apply any more. Genetic heterogeneity within an individual is indeed usually considered to be detrimental, as selfish variants may be selected for and disrupt the integrity of the individual level.
Slime molds
Heterokaryosis is most common in fungi, but also occurs in slime molds. This happens because the nuclei in the 'plasmodium' form are the products of many pairwise fusions between amoeboid haploid individuals. When genetically divergent nuclei come together in the plasmodium form, cheaters have been shown to emerge. However, genetic homogeneity among fusing amoeboid serves to maintain the multicellular plasmodium.
Artificial heterokaryon
A medical example is a heterokaryon composed of nuclei from Hurler syndrome and Hunter syndrome. Both of these diseases result in problems in mucopolysaccharide metabolism. However, a heterokaryon of nuclei from both of these diseases exhibits normal mucopolysaccharide metabolism, proving that the two syndromes affect different proteins and so can correct each other in the heterokaryon.
See also
Dikaryon
Heterokairy
References
External links
MedicineNet.com
Eukaryotic cells
Mycology
Cell biology | Heterokaryon | [
"Biology"
] | 828 | [
"Cell biology",
"Mycology"
] |
1,526,874 | https://en.wikipedia.org/wiki/Stereoselectivity | In chemistry, stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non-stereospecific creation of a new stereocenter or during a non-stereospecific transformation of a pre-existing one. The selectivity arises from differences in steric and electronic effects in the mechanistic pathways leading to the different products. Stereoselectivity can vary in degree but it can never be total since the activation energy difference between the two pathways is finite: both products are at least possible and merely differ in amount. However, in favorable cases, the minor stereoisomer may not be detectable by the analytic methods used.
An enantioselective reaction is one in which one enantiomer is formed in preference to the other, in a reaction that creates an optically active product from an achiral starting material, using either a chiral catalyst, an enzyme or a chiral reagent. The degree of selectivity is measured by the enantiomeric excess. An important variant is kinetic resolution, in which a pre-existing chiral center undergoes reaction with a chiral catalyst, an enzyme or a chiral reagent such that one enantiomer reacts faster than the other and leaves behind the less reactive enantiomer, or in which a pre-existing chiral center influences the reactivity of a reaction center elsewhere in the same molecule.
A diastereoselective reaction is one in which one diastereomer is formed in preference to another (or in which a subset of all possible diastereomers dominates the product mixture), establishing a preferred relative stereochemistry. In this case, either two or more chiral centers are formed at once such that one relative stereochemistry is favored, or a pre-existing chiral center (which needs not be optically pure) biases the stereochemical outcome during the creation of another. The degree of relative selectivity is measured by the diastereomeric excess.
Stereoconvergence can be considered an opposite of stereospecificity, when the reaction of two different stereoisomers yield a single product stereoisomer.
The quality of stereoselectivity is concerned solely with the products, and their stereochemistry. Of a number of possible stereoisomeric products, the reaction selects one or two to be formed.
Stereomutation is a general term for the conversion of one stereoisomer into another. For example, racemization (as in SN1 reactions), epimerization (as in interconversion of D-glucose and D-mannose in Lobry de Bruyn–Van Ekenstein transformation), or asymmetric transformation (conversion of a racemate into a pure enantiomer or into a mixture in which one enantiomer is present in excess, or of a diastereoisomeric mixture into a single diastereoisomer or into a mixture in which one diastereoisomer predominates).
Examples
An example of modest stereoselectivity is the dehydrohalogenation of 2-iodobutane which yields 60% trans-2-butene and 20% cis-2-butene. Since alkene geometric isomers are also classified as diastereomers, this reaction would also be called diastereoselective.
Cram's rule predicts the major diastereomer resulting from the diastereoselective nucleophilic addition to a carbonyl group next to a chiral center. The chiral center need not be optically pure, as the relative stereochemistry will be the same for both enantiomers. In the example below the (S)-aldehyde reacts with a thiazole to form the (S,S) diastereomer but only a small amount of the (S,R) diastereomer:
The Sharpless epoxidation is an example of an enantioselective process, in which an achiral allylic alcohol substrate is transformed into an optically active epoxyalcohol. In the case of chiral allylic alcohols, kinetic resolution results. Another example is Sharpless asymmetric dihydroxylation. In the example below the achiral alkene yields only one of the possible 4 stereoisomers.
With a stereogenic center next to the carbocation the substitution can be stereoselective in inter- and intramolecular reactions. In the reaction depicted below the nucleophile (furan) can approach the carbocation formed from the least shielded side away from the bulky t-butyl group resulting in high facial diastereoselectivity:
Stereoselective biosynthesis
Pinoresinol biosynthesis involved a protein called a dirigent protein. The first dirigent protein was discovered in Forsythia intermedia. This protein has been found to direct the stereoselective biosynthesis of (+)-pinoresinol from coniferyl alcohol monomers. Recently, a second, enantiocomplementary dirigent protein was identified in Arabidopsis thaliana, which directs enantioselective synthesis of (−)-pinoresinol.
See also
Dynamic stereochemistry
Torquoselectivity
Regioselectivity
Chemoselectivity
Notes and references
Stereochemistry | Stereoselectivity | [
"Physics",
"Chemistry"
] | 1,131 | [
"Spacetime",
"Stereochemistry",
"Space",
"nan"
] |
1,527,098 | https://en.wikipedia.org/wiki/Clairaut%27s%20theorem%20%28gravity%29 | Clairaut's theorem characterizes the surface gravity on a viscous rotating ellipsoid in hydrostatic equilibrium under the action of its gravitational field and centrifugal force. It was published in 1743 by Alexis Claude Clairaut in a treatise which synthesized physical and geodetic evidence that the Earth is an oblate rotational ellipsoid. It was initially used to relate the gravity at any point on the Earth's surface to the position of that point, allowing the ellipticity of the Earth to be calculated from measurements of gravity at different latitudes. Today it has been largely supplanted by the Somigliana equation.
History
Although it had been known since antiquity that the Earth was spherical, by the 17th century evidence was accumulating that it was not a perfect sphere. In 1672 Jean Richer found the first evidence that gravity was not constant over the Earth (as it would be if the Earth were a sphere); he took a pendulum clock to Cayenne, French Guiana and found that it lost minutes per day compared to its rate at Paris. This indicated the acceleration of gravity was less at Cayenne than at Paris. Pendulum gravimeters began to be taken on voyages to remote parts of the world, and it was slowly discovered that gravity increases smoothly with increasing latitude, gravitational acceleration being about 0.5% greater at the poles than at the equator.
British physicist Isaac Newton explained this in his Principia Mathematica (1687) in which he outlined his theory and calculations on the shape of the Earth. Newton theorized correctly that the Earth was not precisely a sphere but had an oblate ellipsoidal shape, slightly flattened at the poles due to the centrifugal force of its rotation. Using geometric calculations, he gave a concrete argument as to the hypothetical ellipsoid shape of the Earth.
The goal of Principia was not to provide exact answers for natural phenomena, but to theorize potential solutions to these unresolved factors in science. Newton pushed for scientists to look further into the unexplained variables. Two prominent researchers that he inspired were Alexis Clairaut and Pierre Louis Maupertuis. They both sought to prove the validity of Newton's theory on the shape of the Earth. In order to do so, they went on an expedition to Lapland in an attempt to accurately measure a meridian arc. From such measurements they could calculate the eccentricity of the Earth, its degree of departure from a perfect sphere.
Clairaut confirmed that Newton's theory that the Earth was ellipsoidal was correct, but that his calculations were in error, and he wrote a letter to the Royal Society of London with his findings. The society published an article in Philosophical Transactions the following year, 1737. In it Clairaut pointed out (Section XVIII) that Newton's Proposition XX of Book 3 does not apply to the real earth. It stated that the weight of an object at some point in the earth depended only on the proportion of its distance from the centre of the earth to the distance from the centre to the surface at or above the object, so that the total weight of a column of water at the centre of the earth would be the same no matter in which direction the column went up to the surface. Newton had in fact said that this was on the assumption that the matter inside the earth was of a uniform density (in Proposition XIX). Newton realized that the density was probably not uniform, and proposed this as an explanation for why gravity measurements found a greater difference between polar regions and equatorial regions than what his theory predicted. However, he also thought this would mean the equator was further from the centre than what his theory predicted, and Clairaut points out that the opposite is true. Clairaut points out at the beginning of his article that Newton did not explain why he thought the earth was ellipsoid rather than like some other oval, but that Clairaut, and James Stirling almost simultaneously, had shown why the earth should be an ellipsoid in 1736.
Clairaut's article did not provide a valid equation to back up his argument as well. This created much controversy in the scientific community.
It was not until Clairaut wrote Théorie de la figure de la terre in 1743 that a proper answer was provided. In it, he promulgated what is more formally known today as Clairaut's theorem.
Formula
Clairaut's theorem says that the acceleration due to gravity g (including the effect of centrifugal force) on the surface of a spheroid in hydrostatic equilibrium (being a fluid or having been a fluid in the past, or having a surface near sea level) at latitude is:
where is the value of the acceleration of gravity at the equator, m the ratio of the centrifugal force to gravity at the equator, and f the flattening of a meridian section of the earth, defined as:
(where a = semimajor axis, b = semiminor axis). The contribution of centrifugal force is approximately whereas the gravitational attraction itself varies approximately as This formula holds when the surface is perpendicular to the direction of gravity (including centrifugal force), even if (as usually) the density is not constant (in which case the gravitational attraction can be calculated at any point from the shape alone, without reference to ). For the earth, and while so is greater at the poles than on the equator.
Clairaut derived the formula under the assumption that the body was composed of concentric coaxial spheroidal layers of constant density.
This work was subsequently pursued by Laplace, who assumed surfaces of equal density which were nearly spherical.
The English mathematician George Stokes showed in 1849 that the theorem applied to any law of density so long as the external surface is a spheroid of equilibrium. A history of more recent developments and more detailed equations for g can be found in Khan.
The above expression for g has been supplanted by the Somigliana equation (after Carlo Somigliana).
Geodesy
The spheroidal shape of the Earth is the result of the interplay between gravity and centrifugal force caused by the Earth's rotation about its axis. In his Principia, Newton proposed the equilibrium shape of a homogeneous rotating Earth was a rotational ellipsoid with a flattening f given by 1/230. As a result, gravity increases from the equator to the poles. By applying Clairaut's theorem, Laplace found from 15 gravity values that f = 1/330. A modern estimate is 1/298.25642. See Figure of the Earth for more detail.
For a detailed account of the construction of the reference Earth model of geodesy, see Chatfield.
References
Eponymous theorems of physics
Geodesy
Navigation
Surveying
Gravimetry | Clairaut's theorem (gravity) | [
"Physics",
"Mathematics",
"Engineering"
] | 1,417 | [
"Equations of physics",
"Applied mathematics",
"Eponymous theorems of physics",
"Surveying",
"Civil engineering",
"Geodesy",
"Physics theorems"
] |
1,527,151 | https://en.wikipedia.org/wiki/Speeds%20and%20feeds | The phrase speeds and feeds or feeds and speeds refers to two separate parameters in machine tool practice, cutting speed and feed rate. They are often considered as a pair because of their combined effect on the cutting process. Each, however, can also be considered and analyzed in its own right.
Cutting speed (also called surface speed or simply speed) is the speed difference (relative velocity) between the cutting tool and the surface of the workpiece it is operating on. It is expressed in units of distance across the workpiece surface per unit of time, typically surface feet per minute (sfm) or meters per minute (m/min). Feed rate (also often styled as a solid compound, feedrate, or called simply feed) is the relative velocity at which the cutter is advanced along the workpiece; its vector is perpendicular to the vector of cutting speed. Feed rate units depend on the motion of the tool and workpiece; when the workpiece rotates (e.g., in turning and boring), the units are almost always distance per spindle revolution (inches per revolution [in/rev or ipr] or millimeters per revolution [mm/rev]). When the workpiece does not rotate (e.g., in milling), the units are typically distance per time (inches per minute [in/min or ipm] or millimeters per minute [mm/min]), although distance per revolution or per cutter tooth are also sometimes used.
If variables such as cutter geometry and the rigidity of the machine tool and its tooling setup could be ideally maximized (and reduced to negligible constants), then only a lack of power (that is, kilowatts or horsepower) available to the spindle would prevent the use of the maximum possible speeds and feeds for any given workpiece material and cutter material. Of course, in reality those other variables are dynamic and not negligible, but there is still a correlation between power available and feeds and speeds employed. In practice, lack of rigidity is usually the limiting constraint.
Outside of the context of machine tooling, "speeds and feeds" can be used colloquially to refer to the technical details of a product or process.
Cutting speed
Cutting speed may be defined as the rate at the workpiece surface, irrespective of the machining operation used. A cutting speed for mild steel of 100 ft/min is the same whether it is the speed of the cutter passing over the workpiece, such as in a turning operation, or the speed of the cutter moving past a workpiece, such as in a milling operation. The cutting conditions will affect the value of this surface speed for mild steel.
Schematically, speed at the workpiece surface can be thought of as the tangential speed at the tool-cutter interface, that is, how fast the material moves past the cutting edge of the tool, although "which surface to focus on" is a topic with several valid answers. In drilling and milling, the outside diameter of the tool is the widely agreed surface. In turning and boring, the surface can be defined on either side of the depth of cut, that is, either the starting surface or the ending surface, with neither definition being "wrong" as long as the people involved understand the difference. An experienced machinist summed this up succinctly as "the diameter I am turning from" versus "the diameter I am turning to." He uses the "from", not the "to", and explains why, while acknowledging that some others do not. The logic of focusing on the largest diameter involved (OD of drill or end mill, starting diameter of turned workpiece) is that this is where the highest tangential speed is, with the most heat generation, which is the main driver of tool wear.
There will be an optimum cutting speed for each material and set of machining conditions, and the spindle speed (RPM) can be calculated from this speed. Factors affecting the calculation of cutting speed are:
The material being machined (steel, brass, tool steel, plastic, wood) (see table below)
The material the cutter is made from (High-Carbon Steel, high-speed steel (HSS), Carbide, Ceramics, and Diamond tools)
The economical life of the cutter (the cost to regrind or purchase new, compared to the quantity of parts produced)
Cutting speeds are calculated on the assumption that optimum cutting conditions exist. These include:
Metal removal rate (finishing cuts that remove a small amount of material may be run at increased speeds)
Full and constant flow of cutting fluid (adequate cooling and chip flushing)
Rigidity of the machine and tooling setup (reduction in vibration or chatter)
Continuity of cut (as compared to an interrupted cut, such as machining square section material in a lathe)
Condition of material (mill scale, hard spots due to white cast iron forming in castings)
The cutting speed is given as a set of constants that are available from the material manufacturer or supplier. The most common materials are available in reference books or charts, but will always be subject to adjustment depending on the cutting conditions. The following table gives the cutting speeds for a selection of common materials under one set of conditions. The conditions are a tool life of 1 hour, dry cutting (no coolant), and at medium feeds, so they may appear to be incorrect depending on circumstances. These cutting speeds may change if, for instance, adequate coolant is available or an improved grade of HSS is used (such as one that includes [cobalt]).
Machinability rating
The machinability rating of a material attempts to quantify the machinability of various materials. It is expressed as a percentage or a normalized value. The American Iron and Steel Institute (AISI) determined machinability ratings for a wide variety of materials by running turning tests at 180 surface feet per minute (sfpm). It then arbitrarily assigned 160 Brinell B1112 steel a machinability rating of 100%. The machinability rating is determined by measuring the weighed averages of the normal cutting speed, surface finish, and tool life for each material. Note that a material with a machinability rating less than 100% would be more difficult to machine than B1112 and material and a value more than 100% would be easier.
Machinability ratings can be used in conjunction with the Taylor tool life equation, in order to determine cutting speeds or tool life. It is known that B1112 has a tool life of 60 minutes at a cutting speed of 100 sfpm. If a material has a machinability rating of 70%, it can be determined, with the above knowns, that in order to maintain the same tool life (60 minutes), the cutting speed must be 70 sfpm (assuming the same tooling is used).
When calculating for copper alloys, the machine rating is arrived at by assuming the 100 rating of 600 SFM. For example, phosphorus bronze (grades A–D) has a machinability rating of 20. This means that phosphor bronze runs at 20% the speed of 600 SFM or 120 SFM. However, 165 SFM is generally accepted as the basic 100% rating for "grading steels".
Formula
Cutting Speed (V)= [πDN]/1000 m/min
Where
D=Diameter of Workpiece in meter or millimeter
N=Spindle Speed in rpm
Spindle speed
The spindle speed is the rotational frequency of the spindle of the machine, measured in revolutions per minute (RPM). The preferred speed is determined by working backward from the desired surface speed (sfm or m/min) and incorporating the diameter (of workpiece or cutter).
The spindle may hold the:
Material (as in a Lathe chuck)
Drill bit in a drill
Milling cutter in a milling machine
Router bit in a wood router
Shaper cutter or knife in a wood shaper or spindle moulder
Grinding wheel on a grinding machine.
Excessive spindle speed will cause premature tool wear, breakages, and can cause tool chatter, all of which can lead to potentially dangerous conditions. Using the correct spindle speed for the material and tools will greatly enhance tool life and the quality of the surface finish.
For a given machining operation, the cutting speed will remain constant for most situations; therefore the spindle speed will also remain constant. However, facing, forming, parting off, and recess operations on a lathe or screw machine involve the machining of a constantly changing diameter. Ideally, this means changing the spindle speed as the cut advances across the face of the workpiece, producing constant surface speed (CSS). Mechanical arrangements to effect CSS have existed for centuries, but they were never applied commonly to machine tool control. In the pre-CNC era, the ideal of CSS was ignored for most work. For unusual work that demanded it, special pains were taken to achieve it. The introduction of CNC-controlled lathes has provided a practical, everyday solution via automated CSS Machining Process Monitoring and Control. By means of the machine's software and variable speed electric motors, the lathe can increase the RPM of the spindle as the cutter gets closer to the center of the part.
Grinding wheels are designed to be run at a maximum safe speed, the spindle speed of the grinding machine may be variable but this should only be changed with due attention to the safe working speed of the wheel. As a wheel wears it will decrease in diameter, and its effective cutting speed will be reduced. Some grinders have the provision to increase the spindle speed, which corrects for this loss of cutting ability; however, increasing the speed beyond the wheels rating will destroy the wheel and create a serious hazard to life and limb.
Generally speaking, spindle speeds and feed rates are less critical in woodworking than metalworking. Most woodworking machines including power saws such as circular saws and band saws, jointers, Thickness planers rotate at a fixed RPM. In those machines, cutting speed is regulated through the feed rate. The required feed rate can be extremely variable depending on the power of the motor, the hardness of the wood or other material being machined, and the sharpness of the cutting tool.
In woodworking, the ideal feed rate is one that is slow enough not to bog down the motor, yet fast enough to avoid burning the material. Certain woods, such as black cherry and maple are more prone to burning than others. The right feed rate is usually obtained by "feel" if the material is hand fed, or by trial and error if a power feeder is used. In thicknessers (planers), the wood is usually fed automatically through rubber or corrugated steel rollers. Some of these machines allow varying the feed rate, usually by changing pulleys. A slower feed rate usually results in a finer surface as more cuts are made for any length of wood.
Spindle speed becomes important in the operation of routers, spindle moulders or shapers, and drills. Older and smaller routers often rotate at a fixed spindle speed, usually between 20,000 and 25,000 rpm. While these speeds are fine for small router bits, using larger bits, say more than or 25 millimeters in diameter, can be dangerous and can lead to chatter. Larger routers now have variable speeds and larger bits require slower speed. Drilling wood generally uses higher spindle speeds than metal, and the speed is not as critical. However, larger diameter drill bits do require slower speeds to avoid burning.
Cutting feeds and speeds, and the spindle speeds that are derived from them, are the ideal cutting conditions for a tool. If the conditions are less than ideal then adjustments are made to the spindle's speed, this adjustment is usually a reduction in RPM to the closest available speed, or one that is deemed (through knowledge and experience) to be correct.
Some materials, such as machinable wax, can be cut at a wide variety of spindle speeds, while others, such as stainless steel require much more careful control as the cutting speed is critical, to avoid overheating both the cutter and workpiece. Stainless steel is one material that hardens very easily under cold working, therefore insufficient feed rate or incorrect spindle speed can lead to less than ideal cutting conditions as the work piece will quickly harden and resist the tool's cutting action. The liberal application of cutting fluid can improve these cutting conditions; however, the correct selection of speeds is the critical factor.
Spindle speed calculations
Most metalworking books have nomograms or tables of spindle speeds and feed rates for different cutters and workpiece materials; similar tables are also likely available from the manufacturer of the cutter used.
The spindle speeds may be calculated for all machining operations once the SFM or MPM is known. In most cases, we are dealing with a cylindrical object such as a milling cutter or a workpiece turning in a lathe so we need to determine the speed at the periphery of this round object. This speed at the periphery (of a point on the circumference, moving past a stationary point) will depend on the rotational speed (RPM) and diameter of the object.
One analogy would be a skateboard rider and a bicycle rider travelling side by side along the road. For a given surface speed (the speed of this pair along the road) the rotational speed (RPM) of their wheels (large for the skater and small for the bicycle rider) will be different. This rotational speed (RPM) is what we are calculating, given a fixed surface speed (speed along the road) and known values for their wheel sizes (cutter or workpiece).
The following formulae may be used to estimate this value.
Approximation
The exact RPM is not always needed, a close approximation will work. For instance, a machinist may want to take the value of to be 3 if performing calculations by hand.
e.g. for a cutting speed of 100 ft/min (a plain HSS steel cutter on mild steel) and diameter of 10 inches (the cutter or the work piece)
and, for an example using metric values, where the cutting speed is 30 m/min and a diameter of 10 mm (0.01 m),
Accuracy
However, for more accurate calculations, and at the expense of simplicity, this formula can be used:
and using the same example
and using the same example as above
where:
RPM is the rotational speed of the cutter or workpiece.
Speed is the recommended cutting speed of the material in meters/minute or feet/min
Diameter in millimeters or inches.
Feed rate
Feed rate is the velocity at which the cutter is fed, that is, advanced against the workpiece. It is expressed in units of distance per revolution for turning and boring (typically inches per revolution [ipr] or millimeters per revolution). It can be expressed thus for milling also, but it is often expressed in units of distance per time for milling (typically inches per minute [ipm] or millimeters per minute), with considerations of how many teeth (or flutes) the cutter has then determined what that means for each tooth.
Feed rate is dependent on the:
Type of tool (a small drill or a large drill, high speed or carbide, a boxtool or recess, a thin form tool or wide form tool, a slide knurl or a turret straddle knurl).
Surface finish desired.
Power available at the spindle (to prevent stalling of the cutter or workpiece).
Rigidity of the machine and tooling setup (ability to withstand vibration or chatter).
Strength of the workpiece (high feed rates will collapse thin wall tubing)
Characteristics of the material being cut, chip flow depends on material type and feed rate. The ideal chip shape is small and breaks free early, carrying heat away from the tool and work.
Threads per inch (TPI) for taps, die heads and threading tools.
Cut Width. Any time the width of cut is less than half the diameter, a geometric phenomenon called Chip Thinning reduces the actual chipload. Feedrates need to be increased to offset the effects of chip thinning, both for productivity and to avoid rubbing which reduces tool life.
When deciding what feed rate to use for a certain cutting operation, the calculation is fairly straightforward for single-point cutting tools, because all of the cutting work is done at one point (done by "one tooth", as it were). With a milling machine or jointer, where multi-tipped/multi-fluted cutting tools are involved, then the desired feed rate becomes dependent on the number of teeth on the cutter, as well as the desired amount of material per tooth to cut (expressed as chip load). The greater the number of cutting edges, the higher the feed rate permissible: for a cutting edge to work efficiently it must remove sufficient material to cut rather than rub; it also must do its fair share of work.
The ratio of the spindle speed and the feed rate controls how aggressive the cut is, and the nature of the swarf formed.
Formula to determine feed rate
This formula can be used to figure out the feed rate that the cutter travels into or around the work. This would apply to cutters on a milling machine, drill press and a number of other machine tools. This is not to be used on the lathe for turning operations, as the feed rate on a lathe is given as feed per revolution.
Where:
FR = the calculated feed rate in inches per minute or mm per minute.
RPM = is the calculated speed for the cutter.
T = Number of teeth on the cutter.
CL = The chip load or feed per tooth. This is the size of chip that each tooth of the cutter takes.
Depth of cut
Cutting speed and feed rate come together with depth of cut to determine the material removal rate, which is the volume of workpiece material (metal, wood, plastic, etc.) that can be removed per time unit.
Interrelationship of theory and practice
Speed-and-feed selection is analogous to other examples of applied science, such as meteorology or pharmacology, in that the theoretical modeling is necessary and useful but can never fully predict the reality of specific cases because of the massively multivariate environment. Just as weather forecasts or drug dosages can be modeled with fair accuracy, but never with complete certainty, machinists can predict with charts and formulas the approximate speed and feed values that will work best on a particular job, but cannot know the exact optimal values until running the job. In CNC machining, usually the programmer programs speeds and feedrates that are as maximally tuned as calculations and general guidelines can supply. The operator then fine-tunes the values while running the machine, based on sights, sounds, smells, temperatures, tolerance holding, and tool tip lifespan. Under proper management, the revised values are captured for future use, so that when a program is run again later, this work need not be duplicated.
As with meteorology and pharmacology, however, the interrelationship of theory and practice has been developing over decades as the theory part of the balance becomes more advanced thanks to information technology. For example, an effort called the Machine Tool Genome Project is working toward providing the computer modeling (simulation) needed to predict optimal speed-and-feed combinations for particular setups in any internet-connected shop with less local experimentation and testing. Instead of the only option being the measuring and testing of the behavior of its own equipment, it will benefit from others' experience and simulation; in a sense, rather than 'reinventing a wheel', it will be able to 'make better use of existing wheels already developed by others in remote locations'.
Academic research examples
Speeds and feeds have been studied scientifically since at least the 1890s. The work is typically done in engineering laboratories, with the funding coming from three basic roots: corporations, governments (including their militaries), and universities. All three types of institution have invested large amounts of money in the cause, often in collaborative partnerships. Examples of such work are highlighted below.
In the 1890s through 1910s, Frederick Winslow Taylor performed turning experiments that became famous (and seminal). He developed Taylor's Equation for Tool Life Expectancy.
Scientific study by Holz and De Leeuw of the Cincinnati Milling Machine Company did for milling cutters what F. W. Taylor had done for single-point cutters.
"Following World War II, many new alloys were developed. New standards were needed to increase [U.S.] American productivity. Metcut Research Associates, with technical support from the Air Force Materials Laboratory and the Army Science and Technology Laboratory, published the first Machining Data Handbook in 1966. The recommended speeds and feeds provided in this book were the result of extensive testing to determine optimum tool life under controlled conditions for every material of the day, operation and hardness."
A study on the effect of the variation of cutting parameters in the surface integrity in turning of an AISI 304 stainless steel revealed that the feed rate has the greatest impairing effect on the quality of the surface, and that besides the achievement of the desired roughness profile, it is necessary to analyze the effect of speed and feed on the creation of micropits and microdefects on the machined surface. Moreover, they found that the conventional empirical relation that relates feed rate to roughness value does not fit adequately for low cutting speeds.
References
Bibliography
Further reading
External links
Free Advanced Machinist Calculator for Speeds, Feeds and more
Basic Speeds and Feeds Calculator
Illustrated Speed and feed calculator
Cuttingspeed Software Calculator
CNC Online Feeds and Speeds Calculator
Chip Thinning Tutorial
Metalworking terminology
Woodworking
Feeds | Speeds and feeds | [
"Physics"
] | 4,481 | [
"Physical phenomena",
"Physical quantities",
"Motion (physics)",
"Vector physical quantities",
"Velocity",
"Wikipedia categories named after physical quantities"
] |
1,527,289 | https://en.wikipedia.org/wiki/Eszopiclone | Eszopiclone, sold under the brand name Lunesta among others, is a medication used in the treatment of insomnia. Evidence supports slight to moderate benefit up to six months. It is taken by mouth.
Common side effects include headache, dry mouth, nausea, and dizziness. Severe side effects may include suicidal thoughts, hallucinations, and angioedema. Rapid decreasing of the dose may result in withdrawal. Eszopiclone is classified as a nonbenzodiazepine or Z-drug and a sedative and hypnotic of the cyclopyrrolone group. It is the S-stereoisomer of zopiclone. It works by interacting with the GABA receptors.
Approved for medical use in the United States in 2004, eszopiclone is available as a generic medication. In 2020, it was the 232nd most commonly prescribed medication in the United States, with more than 1million prescriptions. Eszopiclone is not sold in the European Union; as of 2009, the European Medicines Agency (EMA) ruled that it was too similar to zopiclone to be considered a new active substance.
Medical uses
A 2018 Cochrane review found that it produced moderate improvement in sleep onset and maintenance. The authors suggest that where preferred non-pharmacological treatment strategies have been exhausted, eszopiclone provides an efficient treatment for insomnia. In 2014, the US Food and Drug Administration asked that the starting dose be lowered from 2 milligrams to 1 milligram after it was observed in a study that even eight hours after taking the drug at night, some people were not able to cope with their next-day activities like driving and other activities that require full alertness.
Eszopiclone is slightly effective in the treatment of insomnia where difficulty in falling asleep is the primary complaint. The benefit over placebo was found to be of questionable clinical significance. Although the drug effect and the placebo response were rather small and of questionable clinical importance, the two together produce a reasonably large clinical response.
Elderly
Sedative hypnotic drugs including eszopiclone are more commonly prescribed to the elderly than to younger patients despite benefits of medication being generally unimpressive.
In 2015, the American Geriatrics Society reviewed the safety information about eszopiclone and similar drugs and concluded that the "nonbenzodiazepine, benzodiazepine receptor agonist hypnotics (eszopiclone, zaleplon, zolpidem) are to be avoided without consideration of duration of use because of their association with harms balanced with their minimal efficacy in treating insomnia."
The review made this determination both because of the relatively large dangers to elderly individuals from zolpidem and other "z-drugs" together with the fact the drugs have "minimal efficacy in treating insomnia." This was a change from the 2012 AGS recommendation, which suggested limiting use to 90 days or less. The review stated: "the 90‐day‐use caveat [was] removed from nonbenzodiazepine, benzodiazepine receptor agonist hypnotics, resulting in an unambiguous 'avoid' statement (without caveats) because of the increase in the evidence of harm in this area since the 2012 update."
An extensive review of the medical literature regarding the management of insomnia and the elderly found that there is considerable evidence of the effectiveness and durability of non-drug treatments for insomnia in adults of all ages and that these interventions are underutilized. Compared with the benzodiazepines, the nonbenzodiazepine sedative-hypnotics, including eszopiclone appeared to offer few, if any, significant clinical advantages in efficacy or tolerability in elderly persons. It was found that newer agents with novel mechanisms of action and improved safety profiles, such as the melatonin receptor agonists, hold promise for the management of chronic insomnia in elderly people. Long-term use of sedative-hypnotics for insomnia lacks an evidence base and has traditionally been discouraged for reasons that include concerns about such potential adverse drug effects as cognitive impairment (anterograde amnesia), daytime sedation, motor incoordination, and increased risk of motor vehicle accidents and falls. In addition, the effectiveness and safety of long-term use of these agents remain to be determined. It was concluded that more research is needed to evaluate the long-term effects of treatment and the most appropriate management strategy for elderly persons with chronic insomnia.
A 2009 meta-analysis found a higher rate of infections.
Adverse effects
Sleeping pills, including eszopiclone, have been associated with an increased risk of death.
Hypersensitivity to eszopiclone is a contraindication to its use. The presence of liver impairment, lactation and activities requiring mental alertness (e.g., driving) may be considered when determining frequency and dosage.
unpleasant taste
headache
peripheral edema
chest pain
abnormal thinking
behavior changes
depression
hallucinations
sleep driving and sleepwalking
dry mouth
rash
altered sleep patterns
impaired coordination
dizziness
daytime drowsiness
itching
painful or frequent urination
back pain
aggressive behavior
confusion
agitation
suicidal thoughts
depersonalization
amnesia
A 2009 meta-analysis found a 44% higher rate of mild infections, such as pharyngitis or sinusitis, in people taking eszopiclone or other hypnotic drugs compared to those taking a placebo.
Dependence
In the United States, eszopiclone is a schedule IV controlled substance under the Controlled Substances Act. Use of eszopiclone may lead to physical and psychological dependence. The risk of non-medical use and dependence increases with the dose and duration of usage and concomitant use of other psychoactive substances. The risk is also greater in patients with a history of alcohol use disorder or other substance use disorder or history of psychiatric disorders. Tolerance may develop after repeated use of benzodiazepines and benzodiazepine-like drugs for a few weeks.
A study funded and carried out by Sepracor, the manufacturer of eszopiclone, found no signs of tolerance or dependence in a group of patients followed for up to six months.
Non-medical use
A study of non-medical use potential of eszopiclone found that in persons with a known history of non-medical benzodiazepine use, eszopiclone at doses of 6 and 12 mg produced effects similar to those of diazepam 20 mg. The study found that at these doses which are two or more times greater than the maximum recommended doses, a dose-related increase in reports of amnesia, sedation, sleepiness, and hallucinations was observed for both eszopiclone (Lunesta) as well as for diazepam (Valium).
Overdose
Overdoses of eszopiclone up to 90 times the recommended dose have been reported in which the patient fully recovered. Fatalities have been reported only in cases in which eszopiclone was combined with other drugs or alcohol. Overdose may be successfully treated with flumazenil, a GABAA receptor antagonist used also for benzodiazepine overdose.
Poison control centers reported that between 2005 and 2006 there were 525 total eszopiclone overdoses recorded in the state of Texas, the majority of which were intentional suicide attempts.
If consumed within the last hour, eszopiclone overdose can be treated with the administration of activated charcoal or via gastric lavage.
Interactions
There is an increased risk of central nervous system depression when eszopiclone is taken together with other CNS depressant agents, including antipsychotics, sedative hypnotics (like barbiturates or benzodiazepines), antihistamines, opioids, phenothiazines, and some antidepressants. There is also increased risk of central nervous system depression with other medications that inhibit the metabolic activities of the CYP3A4 enzyme system of the liver. Substances that inhibit this enzyme system include nelfinavir, ritonavir, ketoconazole, itraconazole, clarithromycin and grapefruit juice. Alcohol also has an additive effect when used concurrently with eszopiclone. Eszopiclone is most effective if it is not taken after a heavy meal with high fat content.
Pharmacology
Eszopiclone acts on benzodiazepine binding site situated on GABAA neurons as a positive allosteric modulator.
Eszopiclone is rapidly absorbed after oral administration, with serum levels peaking between .45 and 1.3 hours. The elimination half-life of eszopiclone is approximately 6 hours and it is extensively metabolized by oxidation and demethylation. Approximately 52% to 59% of a dose is weakly bound to plasma protein. Cytochrome P450 (CYP) isozymes CYP3A4 and CYP2E1 are involved in the biotransformation of eszopiclone; thus, drugs that induce or inhibit these CYP isozymes may affect the metabolism of eszopiclone. Less than 10% of the orally administered dose is excreted in the urine as racemic zopiclone. In terms of benzodiazepine receptor binding and relevant potency, 3 mg of eszopiclone is equivalent to 10 mg of diazepam.
History
In a controversial 2009 article in the New England Journal of Medicine, "Lost in Transmission — FDA Drug Information That Never Reaches Clinicians", it was reported that the largest of three Lunesta trials found that compared to placebo Lunesta "was superior to placebo" while it only shortened initial time falling asleep by 15 minutes on average. "Clinicians who are interested in the drug’s efficacy cannot find efficacy information in the label: it states only that Lunesta is superior to placebo. The FDA’s medical review provides efficacy data, albeit not until page 306 of the 403-page document. In the longest, largest phase 3 trial, patients in the Lunesta group reported falling asleep an average of 15 minutes faster and sleeping an average of 37 minutes longer than those in the placebo group. However, on average, Lunesta patients still met criteria for insomnia and reported no clinically meaningful improvement in next-day alertness or functioning."
Availability in Europe
On September 11, 2007, Sepracor signed a marketing deal with British pharmaceutical company GlaxoSmithKline for the rights to sell eszopiclone (under the name Lunivia rather than Lunesta) in Europe. Sepracor was expected to receive approximately $155 million if the deal went through. In 2008 Sepracor submitted an application to the EMA (the European Union's equivalent to the U.S. FDA) for authorization to market the drug in the EU, and initially received a favorable response. However, Sepracor withdrew its authorization application in 2009 after the EMA stated it would not be granting eszopiclone 'new active substance' status, as it was essentially pharmacologically and therapeutically too similar to zopiclone to be considered a new patentable product. Since the patent on zopiclone has expired, this ruling would have allowed rival companies to also legally produce cheaper generic versions of eszopiclone for the European market. , Sepracor has not resubmitted its authorization application and eszopiclone is not available in Europe. The deal with GSK fell through, and GSK instead launched a $3.3 billion deal to market Actelion's almorexant sleeping tablet, which entered phase 3 medical trials before development was abandoned due to side effects.
References
Wikipedia medicine articles ready to translate
Carbamates
Cyclopyrrolones
Enantiopure drugs
Nonbenzodiazepines
Chloropyridines
Pyrrolopyrazines
GABAA receptor positive allosteric modulators
4-Methylpiperazin-1-yl compounds
Lactams
Sedatives
Insomnia | Eszopiclone | [
"Chemistry"
] | 2,498 | [
"Stereochemistry",
"Enantiopure drugs"
] |
2,997,527 | https://en.wikipedia.org/wiki/Watchman%20route%20problem | The Watchman Problem is an optimization problem in computational geometry where the objective is to compute the shortest route a watchman should take to guard an entire area with obstacles given only a map of the area. The challenge is to make sure the watchman peeks behind every corner and to determine the best order in which corners should be visited in. The problem may be solved in polynomial time when the area to be guarded is a simple polygon. The problem is NP-hard for polygons with holes, but may be approximated in polynomial time by a solution whose length is within a polylogarithmic factor of optimal.
See also
Art gallery problem, which similarly involves viewing all points of a given area, but with multiple stationary watchmen
References
Geometric algorithms | Watchman route problem | [
"Mathematics"
] | 154 | [
"Geometry",
"Geometry stubs"
] |
2,997,610 | https://en.wikipedia.org/wiki/Bauer%E2%80%93Fike%20theorem | In mathematics, the Bauer–Fike theorem is a standard result in the perturbation theory of the eigenvalue of a complex-valued diagonalizable matrix. In its substance, it states an absolute upper bound for the deviation of one perturbed matrix eigenvalue from a properly chosen eigenvalue of the exact matrix. Informally speaking, what it says is that the sensitivity of the eigenvalues is estimated by the condition number of the matrix of eigenvectors.
The theorem was proved by Friedrich L. Bauer and C. T. Fike in 1960.
The setup
In what follows we assume that:
is a diagonalizable matrix;
is the non-singular eigenvector matrix such that , where is a diagonal matrix.
If is invertible, its condition number in -norm is denoted by and defined by:
The Bauer–Fike Theorem
Bauer–Fike Theorem. Let be an eigenvalue of . Then there exists such that:
Proof. We can suppose , otherwise take and the result is trivially true since . Since is an eigenvalue of , we have and so
However our assumption, , implies that: and therefore we can write:
This reveals to be an eigenvalue of
Since all -norms are consistent matrix norms we have where is an eigenvalue of . In this instance this gives us:
But is a diagonal matrix, the -norm of which is easily computed:
whence:
An Alternate Formulation
The theorem can also be reformulated to better suit numerical methods. In fact, dealing with real eigensystem problems, one often has an exact matrix , but knows only an approximate eigenvalue-eigenvector couple, and needs to bound the error. The following version comes in help.
Bauer–Fike Theorem (Alternate Formulation). Let be an approximate eigenvalue-eigenvector couple, and . Then there exists such that:
Proof. We can suppose , otherwise take and the result is trivially true since . So exists, so we can write:
since is diagonalizable; taking the -norm of both sides, we obtain:
However
is a diagonal matrix and its -norm is easily computed:
whence:
A Relative Bound
Both formulations of Bauer–Fike theorem yield an absolute bound. The following corollary is useful whenever a relative bound is needed:
Corollary. Suppose is invertible and that is an eigenvalue of . Then there exists such that:
Note. can be formally viewed as the relative variation of , just as is the relative variation of .
Proof. Since is an eigenvalue of and , by multiplying by from left we have:
If we set:
then we have:
which means that is an eigenvalue of , with as an eigenvector. Now, the eigenvalues of are , while it has the same eigenvector matrix as . Applying the Bauer–Fike theorem to with eigenvalue , gives us:
The Case of Normal Matrices
If is normal, is a unitary matrix, therefore:
so that . The Bauer–Fike theorem then becomes:
Or in alternate formulation:
which obviously remains true if is a Hermitian matrix. In this case, however, a much stronger result holds, known as the Weyl's theorem on eigenvalues. In the hermitian case one can also restate the Bauer–Fike theorem in the form that the map that maps a matrix to its spectrum is a non-expansive function with respect to the Hausdorff distance on the set of compact subsets of .
References
Spectral theory
Theorems in analysis
Articles containing proofs | Bauer–Fike theorem | [
"Mathematics"
] | 756 | [
"Theorems in mathematical analysis",
"Mathematical analysis",
"Mathematical problems",
"Articles containing proofs",
"Mathematical theorems"
] |
2,997,698 | https://en.wikipedia.org/wiki/Logical%20Methods%20in%20Computer%20Science | Logical Methods in Computer Science (LMCS) is a peer-reviewed open access scientific journal covering theoretical computer science and applied logic. It opened to submissions on September 1, 2004. The editor-in-chief is Stefan Milius (Friedrich-Alexander Universität Erlangen-Nürnberg).
History
The journal was initially published by the International Federation
for Computational Logic, and then by a dedicated non-profit. It moved to the . platform in 2017. The first editor-in-chief was Dana Scott. In its first year, the journal received 75 submissions.
Abstracting and indexing
The journal is abstracted and indexed in Current Contents/Engineering, Computing & Technology, Mathematical Reviews, Science Citation Index Expanded, Scopus, and Zentralblatt MATH. According to the Journal Citation Reports, the journal has a 2016 impact factor of 0.661.
References
External links
Academic journals established in 2005
Computer science journals
Open access journals
Logic journals
Logic in computer science
Formal methods publications
Quarterly journals
English-language journals | Logical Methods in Computer Science | [
"Mathematics"
] | 208 | [
"Mathematical logic",
"Logic in computer science"
] |
2,997,807 | https://en.wikipedia.org/wiki/Grass%20mountain | A grass mountain () in topography is a mountain covered with low vegetation, typically in the Alps and often steep-sided. The nature of such cover, which often grows particularly well on sedimentary rock, will reflect local conditions.
Distribution
The following mountain ranges of the Eastern Alps in Europe are often referred to as grass mountains (Grasberge):
the Allgäu Alps in Bavaria, Germany and Tyrol in Austria,
the Kitzbühel Alps in the Austrian states of Salzburg and Tyrol, and
the Dienten Mountains in Salzburg.
Other areas where grass mountains occur include: the gorges of the Himalayas, Scotland, Poland's Tatra Mountains, and Lofoten.
Individual examples
Geißstein (2,366 m), Kitzbühel Alps.
Höfats (2,259 m), Allgäu Alps
Schneck (2,268 m), Allgäu Alps
Latschur (2,236 m), Gailtal Alps
Ascent techniques
Negotiating the steep grass-covered sides of grass mountains requires a special type of climbing known as grass climbing (Grasklettern).
References
Biogeomorphology
Mountain geomorphology | Grass mountain | [
"Biology"
] | 240 | [
"Biogeomorphology"
] |
2,997,965 | https://en.wikipedia.org/wiki/Sewer%20alligator | The sewer alligator is an urban legend centered around alligators that live in sewers outside alligators' native range. Some cities in which sewer alligators have supposedly been found are New York City and Paris. Accounts of fully grown sewer alligators are unproven, but small alligators are sometimes rescued from sewers. Stories date back to the late 1920s and early 1930s; in most instances they are part of contemporary legend.
The New York Times reports the city rescues 100 alligators per year, some directly from homes where they are kept as illegal pets (which can be legally ordered online in other states and are legal to mail when small), and some from outside (where they can attract considerable attention) though mostly above-ground. Though escapees and former pets may survive for a short time in New York sewers, longer-term survival is not possible due to the low temperatures and the bacteria in human feces. Sewer maintenance crews insist there is no underground population of alligators in sewers.
Legend
The legend of alligators inhabiting the sewer system of New York City is a widely circulated urban myth. It suggests that alligators navigate the city's sewers, preying on rats and other refuse, and posing a threat to sewer workers, who are said to carry firearms for protection. According to the lore, these alligators are often described as large and vicious, with some attributing a lack of pigmentation to their purported status as "albinos." The urban myth has permeated popular culture, featuring in various forms of media including books, television shows, and movies. It has also inspired hoaxes and artistic projects, and is commemorated in the city with a quasi-holiday known as Alligator in the Sewer Day, celebrated on February 9.
Following reports of sewer alligators in the 1930s, the story built up over the decades and became more of a contemporary legend. It is questionable how accurate the original stories are, and some have even suggested they are fictions created by Teddy May, who was the Commissioner of Sewers at the time. Interviews with him were the basis of the first published accounts of sewer alligators. In their honor, February 9 is Alligators in the Sewers Day in Manhattan.
A similar story from 1851 involves feral pigs in the sewers of Hampstead, London.
Louisiana or Florida to New York City
As late as the middle of the 20th century, souvenir shops in Florida sold live baby alligators (in small fish tanks) as novelty souvenirs. Tourists from New York City would buy a baby alligator and try to raise it as a pet. When the alligator grew too large for comfort, the family would proceed to flush the reptile down the toilet.
The most common story is that the alligators survive and reside within the sewer and reproduce, feeding on rats and garbage, growing to huge sizes and striking fear into sewer workers. In Robert Daley's book The World Beneath the City (1959) he comments that one night a sewer worker in New York City was shocked to find a large albino alligator swimming toward him. Weeks of hunting followed.
The Journal of American Folklore has this to say on the subject:
An additional reference to the sewer alligator exists in Thomas Pynchon's first novel, V. It fictionalizes the account, stating Macy's was selling them for a time for 50 cents. Eventually the children became bored with the pets, setting them loose in the streets as well as flushing them into the sewers. Rather than poison, shotguns were used as the remedy. Benny Profane, one of the main characters in the book, continues to hunt them as a full-time job until the population is reduced.
A 1973 children's book, The Great Escape: Or, The Sewer Story by Peter Lippman anthropomorphizes these alligators and has them dress up in disguise as humans and charter an airplane to fly them home to the Florida swamps.
Versions including albinos and mutants
Some versions go further to suggest that, after the alligator was disposed of at such a young age, it would live the majority of its life in an environment not exposed to sunlight, and thus it would apparently in time lose its eyesight and the pigment in its hide and that the reptile would grow to be blind and completely albino (pure white in color with red or pink eyes). Another reason why an albino alligator would retreat to an underground sewer is its vulnerability to the sun in the wild; as there is no dark pigment in the creature's skin, it has no protection from the sun, which makes it very hard for it to survive in the wild.
Some people even spoke of mutant alligators living in the sewers which have been exposed to many different types of toxic chemical waste which altered them, making them deformed and sometimes even larger and with strange colouring. A gigantic mutant alligator based on these myths appears in the 1980 film Alligator.
Contemporary accounts
One 1927 account describes an experience of a Pittsburgh Bureau of Highways and Sewers employee who was assigned the task of clearing out a section of sewer pipe on Royal Street in the Northside Section of the city. The account reads, "[He] removed the manhole cover and began to clear an obstruction when he realized that a set of 'evil looking eyes' was staring at him." He then removed a alligator and took it home with him. There are other numerous recent media accounts of alligators occupying storm drains and sewer pipes, all from states in the southern US.
In Paris, France, a Nile crocodile was captured by firefighters in the sewers below the Pont Neuf bridge on March 7, 1984. The crocodile, named Eleonore (or Eleanore), lived at the Aquarium in Vannes and died in May 2022.
A baby alligator was caught in August 2010 by the NYPD in the sewers in Queens. However, it is unlikely that a fully grown adult would survive for long in New York, due to the cold winter temperatures.
Alligators have been sighted in the drains and sewers of Florida as recently as 2017, due to many of these waste outlets' backing out onto the swamps. During storm surges and in the colder winter months, alligators sometimes shelter in convenient drains and hunt for rats to supplement their diet.
See also
Sewer Gators (film)
Killer Croc
Leatherhead (Teenage Mutant Ninja Turtles)
References
Notes
Sources
Tales From the Urban Crypt: Legendary whoppers about Gotham run the ghastly and ghostly gamut Urbanlegends.com. Retrieved April 26, 2010
External links
Gatorhole.com
Urbanlegends.About.com
SewerGator.com
Gator Guide Lake Eufaula
IMDB page for 'Alligator'
News. Alligator found in sewer in Florida. Oct. 2005
Man Falls in with Alligator – St. Petersburg Times, June 16, 2000
Gator Aid – Houston Press, May 25, 2006
Alligator Stomp – Houston Press, January 27, 2005
See Ya Later, Alligator – Bluffton Today, May 8, 2006
No. 3: Reggie – DailyBreeze.com, December 28, 2005
Alligators and humans
Culture of New York City
American urban legends
Legendary reptiles
American legendary creatures
Subterranea (geography)
Alligator | Sewer alligator | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 1,474 | [
"Sewerage",
"Environmental engineering",
"Water pollution"
] |
2,997,967 | https://en.wikipedia.org/wiki/Chai%20%28symbol%29 | Chai or Hai ( "living" ) is a symbol that figures prominently in modern Jewish culture; the Hebrew letters of the word are often used as a visual symbol.
History
According to The Jewish Daily Forward, its use as an amulet originates in 18th century Eastern Europe. Chai as a symbol goes back to medieval Spain. Letters as symbols in Jewish culture go back to the earliest Jewish roots, the Talmud states that the world was created from Hebrew letters which form verses of the Torah. In medieval Kabbalah, Chai is the lowest (closest to the physical plane) emanation of God.
According to 16th century Greek rabbi Shlomo Hacohen Soloniki, in his commentary on the Zohar, Chai as a symbol has its linkage in the Kabbalah texts to God's attribute of 'Ratzon', or motivation, will, muse. A related number of Ratzon is 60, which is the minimum level of the Divine will.
Two common Jewish names used since Talmudic times, are based on this symbol, Chaya feminine, Chayim masculine.
Linguistics
The word is made up of two letters of the Hebrew alphabet – Chet () and Yod (), forming the word "chai", meaning "alive", or "living". The most common spelling in Latin script is "Chai", but the word is occasionally also spelled "Hai". The usual modern pronunciation of this word is , while a transcription of the Biblical and Mishnaic pronunciation would have likely been (with a pharyngeal consonant).
In Hebrew, the related word chaya () means "living thing" or "animal", and is derived from the Hebrew word chai (), meaning "alive".
Numerology
There have been various mystical numerological reflections about the fact that, according to the system of gematria, the Hebrew letters of chai (חַי) add up to 18 (see Lamedvavniks etc.). For this reason, 18 is a spiritually meaningful number in Judaism. Many Jews give gifts of money in multiples of 18 (see below).
In Jewish culture
Jews often give gifts and donations in multiples of 18, which is called "giving chai," meaning "giving life." Mailings from Jewish charities usually suggest the amounts to give in multiples of chai (18, 36, 54 dollars, etc.) rather than multiples of 10 or 25.
The Chai symbol (חַי) is worn by some Jews as a medallion around the neck, similarly to other Jewish symbols, such as the Star of David and the Hamsa.
It appears in the slogan "!" (, "The people of Israel live!").
It is heard in a BBC recording from April 20, 1945 of Jewish survivors of the Bergen-Belsen concentration camp five days after their liberation. This was the first Sabbath ceremony openly conducted on German soil since the beginning of the war. With people still dying around them, the survivors sang what would become the Israeli national anthem, "Hatikvah". At the end of "Hatikvah", British Army Chaplain Leslie Hardman shouts out, Am Yisrael Chai! ("The people of Israel is alive!")
In the Eurovision Song Contest 1983, which was held in Germany four decades after Shoah, Israel was represented with the song "Chai", performed by Ofra Haza, which includes the line Am Yisra'el chai.
Several Jewish radio stations have the word in their names, including Kol Chai (Israel), Radio Jai (Argentina), and ChaiFM (South Africa).
The Jewish toast (on alcoholic beverages such as wine) is L'Chaim, 'to life'.
Chai jewelry
Elvis Presley wore a chai necklace while performing toward the end of his life. Baseball star Rod Carew wore a chai necklace during his playing days; his first wife and daughters were Jewish, even though Carew himself never formally converted to Judaism. Canadian rapper Drake, himself Jewish, wore a chai necklace on the cover of Vibe magazine in 2010.
See also
Culture of Israel
Hamsa
Hayyi Rabbi
Jewish ceremonial art
Al-Ḥayy
References
Symbols
Jewish symbols
he:חי | Chai (symbol) | [
"Mathematics"
] | 881 | [
"Symbols"
] |
2,998,007 | https://en.wikipedia.org/wiki/Architecture%20Analysis%20%26%20Design%20Language | The Architecture Analysis & Design Language (AADL) is an architecture description language standardized by SAE. AADL was first developed in the field of avionics, and was known formerly as the Avionics Architecture Description Language. It was funded in part by the Army.
The Architecture Analysis & Design Language is derived from MetaH, an architecture description language made by the Advanced Technology Center of Honeywell. AADL is used to model the software and hardware architecture of an embedded, real-time system. Due to its emphasis on the embedded domain, AADL contains constructs for modeling both software and hardware components (with the hardware components named "execution platform" components within the standard). This architecture model can then be used either as a design documentation, for analyses (such as schedulability and flow control) or for code generation (of the software portion), like UML.
AADL ecosystem
AADL is defined by a core language with a single notation for both system and software aspects. Having a single model eases the analysis tools by having only one single representation of the system. The language specifies system-specific characteristics using properties.
The language can be extended with the following methods:
user-defined properties: users can extend the set of applicable properties and add their own to specify their own requirements
language annexes: the core language is enhanced by annex languages that enrich the architecture description. So far, the following annexes have been defined:
Behavior annex: add components behavior with state machines
Error-model annex: specifies fault and propagation concerns
ARINC653 annex: defines modelling patterns for avionics systems
Data-Model annex: describes the modelling of specific data constraints with AADL
AADL tools
AADL is supported by a wide range of tools:
MASIW - is an open source Eclipse-based IDE for development and analysis of AADL models. It is developed by ISP RAS
OSATE is an open source tool that includes a modeling platform, a graphical viewer and a constraint query languages. More information is available at the OSATE website.
Ocarina, an AADL toolchain for generating code from models
TASTE toolchain, supported by the European Space Agency
A complete list of the tool set can be found on the AADL public wiki
Related projects
AADL has been used for the following research projects:
AVSI/SAVI: an initiative that leverages AADL (among other languages) to perform virtual integration of aerospace and defense systems
META: a DARPA project for improving software engineering methods
PARSEC: a French initiative to validate and implement avionics systems from architecture models
TASTE: a platform for designing safety-critical systems from models
A complete list of the past and current projects/initiatives can not be found on the AADL public wiki because it has been retired. No replacement has been provided as of Dec 2020.
References
External links
AADL.info
AADL public wiki
AADL tools
AADL at Axlog
AADL at Ecole Nationale Supérieure des Télécommunications de Paris (ENST)
AADL performance analysis with Cheddar, Univ. of Brest (real time scheduling and queueing system analysis)
Industrial project support using Stood for AADL
AADL In Practice, a book dedicated to the use of the languages and its related modeling tools
Systems architecture
Architecture description language
Software modeling language
Modeling languages | Architecture Analysis & Design Language | [
"Engineering"
] | 677 | [
"Systems engineering",
"Design",
"Systems architecture"
] |
2,998,286 | https://en.wikipedia.org/wiki/Fourier%20number | In the study of heat conduction, the Fourier number, is the ratio of time, , to a characteristic time scale for heat diffusion, . This dimensionless group is named in honor of J.B.J. Fourier, who formulated the modern understanding of heat conduction. The time scale for diffusion characterizes the time needed for heat to diffuse over a distance, . For a medium with thermal diffusivity, , this time scale is , so that the Fourier number is . The Fourier number is often denoted as or .
The Fourier number can also be used in the study of mass diffusion, in which the thermal diffusivity is replaced by the mass diffusivity.
The Fourier number is used in analysis of time-dependent transport phenomena, generally in conjunction with the Biot number if convection is present. The Fourier number arises naturally in nondimensionalization of the heat equation.
Definition
The general definition of the Fourier number, , is:
For heat diffusion with a characteristic length scale in a medium of thermal diffusivity , the diffusion time scale is , so that
where:
is the thermal diffusivity (m2/s)
is the time (s)
is the characteristic length through which conduction occurs (m)
Interpretation of the Fourier number
Consider transient heat conduction in a slab of thickness that is initially at a uniform temperature, . One side of the slab is heated to higher temperature, , at time . The other side is adiabatic. The time needed for the other side of the object to show significant temperature change is the diffusion time, .
When , not enough time has passed for the other side to change temperature. In this case, significant temperature change only occurs close to the heated side, and most of the slab remains at temperature .
When , significant temperature change occurs all the way through the thickness . None of the slab remains at temperature .
When , enough time has passed for the slab to approach steady state. The entire slab approaches temperature .
Derivation and usage
The Fourier number can be derived by nondimensionalizing the time-dependent diffusion equation. As an example, consider a rod of length that is being heated from an initial temperature by imposing a heat source of temperature at time and position (with along the axis of the rod). The heat equation in one spatial dimension, , can be applied
where is the temperature for and . The differential equation can be scaled into a dimensionless form. A dimensionless temperature may be defined as , and the equation may be divided through by :
The resulting dimensionless time variable is the Fourier number, . The characteristic time scale for diffusion, , comes directly from this scaling of the heat equation.
The Fourier number is frequently used as the nondimensional time in studying transient heat conduction in solids. A second parameter, the Biot number arises in nondimensionalization when convective boundary conditions are applied to the heat equation. Together, the Fourier number and the Biot number determine the temperature response of a solid subjected to convective heating or cooling.
Application to mass transfer
An analogous Fourier number can be derived by nondimensionalization of Fick's second law of diffusion. The result is a Fourier number for mass transport, defined as:
where:
is the Fourier number for mass transport
is the mass diffusivity (m2/s)
is the time (s)
is the length scale of interest (m)
The mass-transfer Fourier number can be applied to the study of certain time-dependent mass diffusion problems.
See also
Biot number
Convection
Heat conduction
Heat equation
Molecular diffusion
Dimensionless numbers in fluid mechanics
References
Dimensionless numbers of thermodynamics | Fourier number | [
"Physics",
"Chemistry"
] | 743 | [
"Thermodynamic properties",
"Physical quantities",
"Dimensionless numbers of thermodynamics"
] |
2,998,304 | https://en.wikipedia.org/wiki/Feather%20cloak | Feather cloaks have been used by several cultures. It constituted noble and royal attire in and other Polynesian regions. It is a mythical bird-skin object that imparts power of flight upon the Gods in mythology and legend, including the account. In medieval Ireland, the chief poet (filí or ollam) was entitled to wear a feather cloak.
The feather robe or cloak (Chinese: yuyi; Japanese: hagoromo; ) was considered the clothing of the Immortals (xian; ), and features in swan maiden tale types where a tennyo ( "heavenly woman") robbed of her clothing or "feather robe" and becomes bound to live on mortal earth. However, the so-called "feather robe" of the Chinese and Japanese celestial woman came to be regarded as silk clothing or scarves around the shoulder in subsequent literature and iconography.
Hawaii
Elaborate feather cloaks called were created by early Hawaiians, and usually reserved for the use of high chiefs and aliʻi (royalty).
The scarlet honeycreeper (Vestiaria coccinea) was the main source of red feathers. Yellow feathers were collected in small amounts each time from the mostly black ʻōʻō (Moho spp.) or the mamo (Drepanis pacifica).
Another strictly regal item was the , a symbolic "staff of state" or standard, consisting of pole with plumage attached to the top of it. The Princess Nāhiʻenaʻena in her portrait (cf. fig. right) is depicted holding a while wearing a feather cloak. She would typically wear a feather cloak with a feather coronet and she would match these with a pair of ('skirts') which ordinarily would be barkcloth skirt, however, she also had a magnificent yellow feather skirt made for her, which featured in her funerary services.
Other famous examples include:
Kamehameha's feather cloak - made entirely of the golden-yellow feather of the mamo, inherited by Kamehameha I. King Kalākaua displayed this artefact to emphasize his own legitimate authority.
Kiwalao's feather cloak - King Kīwalaʻō's cloak, captured by half-brother Kamehameha I who slew him in 1782. It symbolized leadership and was worn by chieftains during times of war.
Liloa's kāʻei - sash of King Līloa of the island of Hawaii
Hawaiian mythology
A mythical enemy-incinerating kapa (barkcloth) cape, retold as a feather skirt in one telling, occurs in Hawaiian mythology. In the tradition regarding the hero ʻAukelenuiaʻīkū, the hero's grandmother Moʻoinanea who is matriarch of the divine lizards (, or simply moʻo) gives him her severed tail, which transforms into a cape (or , i.e. tapa) that turns enemies into ashes, and sends him off on a quest to woo his destined wife, Nāmaka. Nāmaka (who is predicted to attack him when he visits) will be immune to the cape's powers. She is also a granddaughter or descendant of the lizard, and has been given the lizard's battle pāʻū (skirt) and kāhili (feathered staff), also conferred with power to destroy enemy into ashes. In one retelling, Moʻoinanea (Ka-moʻo-inanea) gives her grandson ʻAukele her "feather skirt" and kāhili which "by shaking.. can reduce his enemies to ashes".
A commentator has argued that the feather garment of Nāhiʻenaʻena was regarded as imbued with the apotropaic "powers of a woman's genitals", reminiscent of the mythic pāʻū which Hiʻiaka was given by Pele.
Māori
It has been noted there is a pan-Polynesian culture of valuing the use of feathers in garments, especially of red colour, and there had even existed ancient trade in feathers. While various featherwork apparel were widespread across Polynesia, feather capes were limited to Hawaiʻi and New Zealand.
The Māori feather cloak or kahu huruhuru are known for their rectangular-shaped examples. The most prized were the red feathers which in Māori culture signified chiefly rank, and were taken from the kaka parrot to make the kahu kura which literally means 'red cape'.
The feather garment continues to be utilized as symbolic of rank or respect.
Brazil
The feather cloak or cape was traditional to the coastal Tupi people, notably the Tupinambá. The cape was called (var. ) in Tupi–Guarani, so called from the red plumage of guará (Eudocimus ruber, scarlet ibis) and not only did it have a hood at the top, but it was meant to cover the body to simulate becoming a bird, and even included a buttocks piece called enduaps. These feather capes were worn by Tupian shamans or (var. ) during rituals, and clearly held religious or sacred meaning. The cape was also worn in battle, but it has been clarified that the warrior as well as his victim were deliberately dressed as birds as executioners and the offering in ritual sacrifices.
Germanic
A bird- (pl. ) or feather cloak that enable the wearers to take the form of, or become, birds are widespread in Germanic mythology and legend. The goddess Freyja was known for her "feathered or falcon cloak" (, ), which could be borrowed by others to use, and the Þjazi may have had something similar, referred to as an (eagle-shape or coat).
The term has the dual meaning of "skin" or "shape", and in this context, has been translated variously as "feather-skin", "feather-fell", "feather-cloak", "feather coat", "feather-dress", "coat of feathers", or form, shape or guise.
The topic is often discussed in the broader sense of "ability to fly", inclusive of Óðinn's ability to transform into bird shape, and Wayland's flying contraption. This wider categorization is necissitated due to ambiguity: in the case of Óðinn (and Suttungr) resorting to the arnarhamr ("eagle cloak"), it is unclear whether this should be construed literally to mean the use of a garment, or be taken metaphorically as shape-shifting (e.g. "changed into eagle-shape"), perhaps by use of magic. Also, Völundr's "wing" is not a "feather cloak" per se, but only likened to it (cf. ).
Gods and jötnar
In Norse mythology, goddesses Freyja (as aforementioned) and Frigg each own a feather cloak that imparts the ability of flight.
Freyja is not attested as using the cloak herself, however she lent her ("feather cloak") to Loki so he could fly to Jötunheimr after Þórr's hammer went missing in Þrymskviða, and to rescue Iðunn from the Þjazi in Skáldskaparmál who had abducted the goddess while in an ("eagle shape"). The latter episode is also attested in the poem Haustlöng, where Freyja's garment is referred to as "hawk's flying-fur", or "hawk's flight-skin" and the employs a "cloak/shape of eagle".
Loki also uses Frigg's feather cloak to journey to Geirröðargarða ("Geirröðr's courts"{{Refn|Skaldskaparmál 18, "..Þórr fór til Geirröðargarða", "how Thor went to Geirrod's courts" ().}} in Jötunheimr), referred to here as a ("falcon-feathered cloak").
Óðinn is described as being able to change his shape into that of animals, as attested in the Ynglinga saga. discusses the transformation of gods "donning a feather coat", and in the attached footnoted (, p. 206) with an association with Oðinn's ability to transform into creatures in the Ynglinga saga. Furthermore, in the story of the Mead of Poetry from Skáldskaparmál, although Óðinn changes attire into an "eagle skin" (), this is interpreted as assuming an "eagle-form" or "shape", especially by later scholars; meanwhile, scholar Ruggerini argues Óðinn can use shape-shifting magic without the need of such skin, in contrast to the jötunn Suttung, who must put on his "eagle skin" () in order to pursue him.
Völsunga saga
In the Völsunga saga, the wife of King Rerir is unable to conceive a child and so the couple prays to Oðinn and Frigg for help. Hearing this, Frigg then sends one of her maids (Hljóð, possibly a valkyrja) wearing a (crow-cloak) to give the royal couple a magic apple which when eaten, made the queen pregnant with her son Völsung.
Swan maidens
There were also the three swan-maidens, also described as valkyrjur, and owned sets of "swan's garments" or "swan cloaks" (; sing.:), and these gave the wearer the form of a swan. And the maidens were wedded to Wayland the Smith and his brothers, according to the prose prologue to Völundarkviða ("Lay of Wayland").
This bears similarity to the account of the eight with in Helreið Brynhildar.
Wayland
The master smith Wayland () uses some sort of device to fly away and escape from King Niðhad after he is hamstrung, as described in the Eddic lay Völundarkviða. The lay has Völundr saying he has regained his "webbed feet" which soldiers had taken away from him, and with it he is able to soar into air. This is explained as a circumlocution for him recovering a magical artifact (perhaps a ring), which allows him to transform into a swan or such waterfowl with webbed feet. An alternate interpretation is that the text here should not be construed as "feet" but "wings" ("feather coat or artificial wings"), which gave him ability to fly away.
The second "wing" scenario coincides with the version of the story given in Þiðreks saga, where Völundr's brother Egill shot birds and collected plumage for him, providing him with the raw material for crafting a set of wings, and this latter story is also corroborated on depictions on the panels of the 8th-century whale-bone Franks Casket.
In the Þiðreks saga Wayland (here )'s device is referred to as "wings" or rather a single "wing" (, a term borrowed from the German ) but is described as resembling a , supposedly flayed from a griffin, or vulture, or an ostrich. Some modern commentators suggest that the Low German source originally just meant "wings", but the Norse translators took license to interpret it as being just like a "feather cloak". In the saga version, Velent not only requested his brother Egill to obtain the plumage material (as aforementioned) but also asks Egill to wear the wings first to perform a test flight. Afterwards Velent himself escapes with the wings, and instructs Egil to shoot him, but aiming for his blood sack prop to fake his death.
Metaphorical sense
As already noted, hamr could mean either a physical "skin" or the abstract "shape", and though on first blush, Freyja seems to have a (literally) a "feather cloak" she could lend to others, Larrington for instance glosses the feather cloak not as a 'skin' but an 'attribute' of the goddess which gives her ability to fly. Vincent Samson explains the hamr as the physical aspect taken on by a mobile (or transmigrating) soul when undergoing animal transformation, noting that François-Xavier Dillmann defines hamr as "external form of the soul".
Germanic translations of Celtic material
The Breton lai of Bisclavret was translated in the Old Norse Strengleikar, the notion of "shape of animal" was rendered as hamr. Another instance of such figure of speech usage occurs in the Old Norse telling of the British king's flying contraption, cf. below:
Bladud's wings
The legendary king Bladud of the Celtic Britons fashioned himself a pair of wings () to fly with, according to the original account in Geoffrey of Monmouth's Historia Regum Britanniae. This winged contraption is rendered as a "" in the Old Norse translation Breta sögur, here meant strictly as a flying suit, not a means of transformation into bird.
Bladud's wings are also rendered into Middle English as "", cognate with , in Layamon's Brut version of Geoffrey's History.
Other
There are bird-people depicted on the Oseberg tapestry fragments, which may be some personage or deity wearing winged cloaks, but it is difficult to identify the figures or even ascertain gender.
Celtic
King Bladud of Britain created artificial wings to enable flight according to Galfridian sources, conceived of as "feather skin" in Old Norse and Middle English versions (as already discussed above in ).
Poet's cloak
In Ireland, the elite class of poets known as the filid wore a feathered cloak, the , according to Sanas Cormaic ("Cormac's glossary"). Although the term may merely refer to a "precious" sort of toga, as Cormac glosses in Latin, it can also signify 'covering ' 'of birds', and goes on to describe the composition of this garment in minute detail.
Cormac's glossary goes on to describe the thus: "for it is of skins (, dat. ) of birds white and many-coloured that the poets' toga is made from their girdle downwards, and of [male] mallards' necks and of their crests from the girdle upwards to their neck".
Although John O'Donovan recognized an attestation to the cloak in the Lebor na Cert ("Book of Rights"), where verses by Benén mac Sescnéin are quoted, this may be an artefact of interpretive translation. In O'Donovan's rendition, the verse reads that the rights of the Kings of Cashel rested with the chief poet of Ireland, together with his bird cloak (), where the term taeidhean (normalized as taiden) is construed to be synonymous with tugen. However, is glossed as "Band, troop, company" and in a modern translation Myles Dillon renders the same line ("") as "The answer will always be found at the assemblies" with no mention of the bird cloak.
The tuigen is also described in the Immacallam in dá Thuarad ("The Colloquy of the two Sages"). According to the narrative, in Ulster, Néde son of Adna gains the ollam’s position ("ollaveship") of his father, supplanting the newly appointed Ferchertne, then goes on to sit on the ollam’s chair and wears the ollam’s robe (), which were of three colors, i.e., a band of bright bird's feathers in the middle, speckling of findruine (electrum) metal on the bottom, and "golden colour on the upper half". The tuigen is also mentioned in passing when Ferchertne speaks poetically and identifies his usurper as the young Néde, undeceived by the fake beard of grass.
The tuigen is also referred to (albeit allegorically) in the 17th elegy written for Eochaidh Ó hÉoghusa.
In the Old Norwegian work Konungs skuggsjá ("King's Mirror"), one can read a description of lunatics called "gelts" sprouting feathers, in the chapter dealing with Irish marvels (XI):
Regarding the above description of the "Gelts" sprouting feathers, it refers to the Irish word meaning a "lunatic" induced into madness by fear from battle such as described in "King's Mirror" above. The word geilt also occurs as a nickname for "Suibne Geilt" or "Mad Sweeney" who transforms into a feathered form according to the medieval narrative Buile Shuibhne.
This concept is adapted to the Greco-Roman mythology; Mercury, god of medicine, wears a "bird covering" or "feather mantle" rather than talaria (usually conceived of as feathered slippers) in medieval Irish versions of classical literature, such as the Aeneid.
China
Stories concerning the guhuoniao ( lit. "wench bird";) describes the heavenly maiden who by wearing a "feathered garment" can transform into a bird and attempts to snatch away human children, being childless herself. This story is considered to fall somewhat under the purview of the swan-maiden type. It is arguably the oldest example, a version being found in the and a slight variant in the Soushenji both dating to the 4th century.
In the Chinese Daoist concept of gods and immortals (, shenxian), these immortals wear feather garments or yuyi (). The xian also included human-born Daoists who purportedly attained immortality. These immortals have their antecedents in the myth of "feather-humans" or "winged men" (yuren, ). These "winged spirits" occur in ancient art, such as Han dynasty cast bronzes, and an example (cf. fig. right) appear to be clothed and possess a pair of wings. Early literary attestations are rather scant, though the Chu Ci () anthology may be cited (poetic work entitled Yuan You) as mentioning the yuren.
These yuren were originally supernatural divinities and strictly non-human, but later conflated or strongly associated with the xian (仙/僊) immortals, which Daoist adepts could aspire to become.
The Book of Han records that the Emperor Wu of Han allowed the fangshi sorcerer Luan Da to wear a feathered garment in his presence, interpreted to be the granting of the privilege to publicly appeal the sorcerer's attainment of the winged immortal's power or status.; A later commentator of the early Tang dynasty, Yan Shigu clarifies that the winged garment yuyi was made from bird feathers, and signifies the gods and immortals taking flight.
In the early Tang (or rather Wu Zhou) dynasty, the Empress Wu Zetian commanded her favorite paramour Daoist Zhang Changzong to be dressed up in a mock-up of famed Dao master . Part of the costume set he wore included a "bird-feathered coat". The coat was referred to as a ji cui (), that is to say, made from the gathered feathers of the kingfisher (feizui, ).
Shift to silk garment
Regarding the High Tang period Emperor Xuanzong, legend has it that he composed or arranged the ("Melody of the Rainbow Skirts, Feathered Coats"). According to the fabulous account (preserved in Taiping Guangji), the Emperor was conveyed to the immortal realm (Lunar Palace) by a xian named . The "rainbow skirts" and "feathered coats" in the tune's title have been surmised by commentators to refer to the clothing described as worn by the dancing immortal women in this account, namely the "white loose-fitting silk dress". Hence it is supposed that in the popular image of those times, the celestial "feather coats" were being regarded as silken, more specifically "white glossed silk" garments.
In modern times, a number of folktales have been collected from all over China that are classed as the swan-maiden type, which are renditions of the Weaver Maiden and the Cowherd legend. These consequently may not strictly have a "feather garment" as the implement in the flying motif. In the tale type, the Weaver Maiden is usually forcibly taken back to her celestial home, and the earthly Cowherd follows after, using various items, including heavenly costumes and girdles, but also oxen or oxhide in many cases. Although flight using oxhide seems counterintuitive, Wu Xiadon () has devised the theory that the Weaver Girl's primordial form was the silkworm (), and the ancient silk-woman or silk-horse myth, where a girl wrapped in the skin of her favorite horse metamorphoses into a silkworm. But even disregarding this theory, the Weaver Girl in China is considered (less a divinity of plant fiber weaving) and more a divinity of silk and sericulture, a being who descended from heaven and taught mankind how to raise silkworms. Namely, the notion that the celestial Weaver Girl raised silkworms in heaven, spun the thread into silk, and wore the woven silk garment is a widely accepted piece of lore.
Crane cloak
Cloth or clothing with the down of the crane woven in were called hechang () or [he]changyi (, lit. "crane down clothing"), and existed as actual pieces of clothing by the Tang Dynasty. It was standard uniform for courtly guards during Tang and Song, but both men and women civilians wore them also. A Taoist priest (daoshi) or adept (fangshi) wore these as well. It is also mentioned in the famous novel Dream of the Red Chamber that the ladies Lin Daiyu] and Xue Baochai wore such "crane cloak".
Japan
In Japan, there are also swan maiden type legends about a tennyo ( "heavenly woman") coming to the earthly world and having her garment, or hagoromo () stolen, translated as "feather cloak", or "feather robe", etc. The oldest attestation is set at in Ōmi Province (now Shiga Prefecture) and was recorded in a fragmentary quote from the lost Fudoki of that province ().
There is also the well-known folktale of the , where the crane-wife weaves fine cloth out of her own feathers, which might bear some relationship with the heavenly feather cloak.
The miniature boy deity Sukunabikona is described as wearing a garment made of wren's feathers in the Nihon shoki.
The Nara Period (8th century) refers to a byōbu or a folding "screen with figures of ladies standing; design worked out with birds ' feathers". That is to say, almost looks like a monochrome line-painting or piece, but had feathers of the copper pheasant pasted on them. In particular, the 2nd panel of 6 depicts a woman with a peculiar costume said to be a "feather garment", with "petal-shaped lobes overlapping like scales, extending from top to bottom". This is said to indicate the Japanese court's awareness of the trend in Tang Dynasty China of wearing garments using bird feathers. Art historian goes as far as to say this was an homage or allusion to the Chinese Daoist tradition that divinity and immortals wore yingyi made of bird's feathers.
The ancient swan maiden type myth does not only occur in the where the heavenly woman is forcibly married to a man. In different tale found in the , the heavenly woman is forcibly adopted by an old childless couple. Although only the former text explicitly mentions "feather robe", and the Tango version only says it was the heavenly woman's which was hidden away, it is surmised that the feather garment was meant there as well.
In The Tale of the Bamboo Cutter (written down in the Heian Period?), Princess Kaguya mounts a flying cart and ascends to the "Moon Palace", while the angelic tennin who arrived to escort her also brought for her the hagoromo feather garment as well as the medicine of immortality and agelessness. Due to the flying car, the feather garment here is supposedly not a direct means for her to be able to fly, and it is guessed to be an article of clothing shee needs in order for ther to transform or revert back into a genuine celestial being. It is pointed out that many scholars assume the tennin here to be the dictionary definition Buddhist entities, but the concept of immortality is incongruent with the Buddhist core tenet of transience and rebirth, so the tennin must really be regarded as the borrowing of divinities and immortals (xian; ) of Taoism.
As silken attire or scarf
The ancient legend about the Princess classed as a hagoromo densetsu ("tradition of the robe of feathers"), fails to clarify on how she was able to flew away as tennnyo in the older version. But the legend has a later Heian Period version where she put on a hire, i.e., a scarf ( or ) and took flight.
In other words, the so-called "feather robe" hagoromo came to be commonly depicted as what can only be described as the sheer silk scarf, called "" in olden times,
Later in the Muromachi Period, in performances of the Noh play Hagoromo, the dancing actor portraying the heavenly female tennyo wears a supposed hagoromo feather garment. The prop costume is apparently made from whitish thin silk (or sometimes, thicker colorful silk). Though the theatrical convention serves merely as a hint to what the original hagoromo garment was like,, but since sheer silk has been prized since the ancient Han or earlier, and even unearthed in Japanese Yayoi period sites, the hagoromo legend costume may well share origins with the tennnyo images found in Buddhist temples, etc. according to scholar Junrō Nunome, professedly speaking out of his textile expertise, being a non-folklorist.
However, the caveat is that while a dictionary consultation of tennyo (lit. "heavenly woman") typically explains it as a Buddhist female entity, the proper context is that of so-called "heavenly" beings actually refer to deities and immortals (, shenxian) of Taoism who dwell in the xian realm. And this caveat applies even to the case of the Bamboo Cutter's daughter Kaguya, who ascends to the "Moon Palace". As for the Nara Period work of art using real bird feathers, it has been theorized (by Kosugi) that it alludes to the feather garments of the shenxian, as aforementioned.
But even in the context of the shenxian garments, later literature dating to the golden age of Tang ascribe the Daoist heavenly immortals wearing spun and softened silk, as in the legendary tale surrounding the "" (q.v., above).
Explanatory notes
References
Bibliography
Primary
and "", p. xxii, 'valshamr'.
The chapter numbering follows the 1848 Copenhagen edition, which is the one usually cited (p. xxiii).
Secondary
(Hawaiian material)
(Brazilian material)
(European material)
(East Asian material)
Ozaki, Nobuo (1986) "Taketori no okina; jō 竹取の翁-上-」, Gakuen'' 学苑 (563), pp. 2–12 (original journal publication)
Tei, Kagei /
Polynesian clothing
Textile arts of Hawaii
History of Oceanian clothing
Featherwork
Mythological clothing
Magic items | Feather cloak | [
"Physics"
] | 5,846 | [
"Magic items",
"Physical objects",
"Matter"
] |
2,998,388 | https://en.wikipedia.org/wiki/K%26N%20Engineering | K&N Engineering, Inc. (also known simply as K&N) is a manufacturer of air filters, cold air intake systems, oil filters, performance parts, and other related products. K&N manufactures over 12,000 parts for various makes and models of cars, trucks, SUVs, motorcycles, ATVs, industrial applications and more. Founded in the United States in 1969, K&N is headquartered in Riverside, California, in a complex of 10 buildings comprising nearly 400,000 square feet. K&N also operates facilities in England, The Netherlands, and China.
History
K&N was founded by Ken Johnson and Norm McDonald in 1969. The name K&N came from the first letters in the founders' first names. Ken Johnson and Norm McDonald sold motorcycles and motorcycle parts and supported a K&N factory race team. Air filters soon became the primary focus of the company. In 1992, K&N introduced bolt-on cold air intake kits. K&N also released a line of oil filters with a stamped hex to accept a standard wrench off filter removal. In 2019, K&N released a line of washable home A/C filters, and began offering motor oil and wiper blades in 2021.
Racing
K&N has maintained very active involvement in racing and motorsports throughout its history, including the NASCAR Pro Series East and West, the King of the West 410 Sprint Car Series, the NHRA, and Formula Drift.
Technology
K&N's claims for their air filters have been the subject of some controversy, with some 3rd-party tests finding that K&N's oiled cotton gauze filters are less efficient and let more dirt into the engine than original-equipment paper filters, and that they become increasingly restrictive as they are coated with particulates. However, air filters in general become more airflow-restrictive as they collect contaminants, but efficiency typically increases for the majority of a filter’s service life. Other 3rd-party testing noted that a K&N oiled filter increased horsepower over its OEM counterpart.
Potential issues have been reported with oiled air filters on modern engines that use MAF sensors, which may stop working correctly when fouled by oil from an oiled-gauze air filter. However, there are several other common causes of damaged MAF sensors, including brake cleaner contamination, extremely dirty/contaminated filters, and loose battery terminals resulting in voltage spikes. K&N has published test results asserting that its oiled filters do not cause MAF sensor failures.
References
External links
Filter manufacturers
Automotive motorsports and performance companies
Manufacturing companies based in California
Companies based in Riverside, California
Manufacturing companies established in 1969
1969 establishments in California
American brands | K&N Engineering | [
"Chemistry"
] | 550 | [
"Filter manufacturers",
"Filters"
] |
2,998,760 | https://en.wikipedia.org/wiki/Facilitated%20variation | The theory of facilitated variation demonstrates how seemingly complex biological systems can arise through a limited number of regulatory genetic changes, through the differential re-use of pre-existing developmental components. The theory was presented in 2005 by Marc W. Kirschner (a professor and chair at the Department of Systems Biology, Harvard Medical School) and John C. Gerhart (a professor at the Graduate School, University of California, Berkeley).
The theory of facilitated variation addresses the nature and function of phenotypic variation in evolution. Recent advances in cellular and evolutionary developmental biology shed light on a number of mechanisms for generating novelty. Most anatomical and physiological traits that have evolved since the Cambrian are, according to Kirschner and Gerhart, the result of regulatory changes in the usage of various conserved core components that function in development and physiology. Novel traits arise as novel packages of modular core components, which requires modest genetic change in regulatory elements. The modularity and adaptability of developmental systems reduces the number of regulatory changes needed to generate adaptive phenotypic variation, increases the probability that genetic mutation will be viable, and allows organisms to respond flexibly to novel environments. In this manner, the conserved core processes facilitate the generation of adaptive phenotypic variation, which natural selection subsequently propagates.
Description of the theory
The theory of facilitated variation consists of several elements. Organisms are built from a set of highly conserved modules called "core processes" that function in development and physiology, and have remained largely unchanged for millions (in some instances billions) of years. Genetic mutation leads to regulatory changes in the package of core components (i.e. new combinations, amounts, and functional states of those components) exhibited by an organism. Finally, the altered combinations, amounts, and states of the conserved components function to develop and operate a new trait on which natural selection acts. Because of their modular organization, adaptability (e.g. arising through exploratory processes) and compartmentation, developmental systems tend to produce facilitated (i.e. functional and adaptive) phenotypic variation when challenged by genetic mutation or novel environmental conditions.
Conserved core components
Animals are built from a tool kit of components (e.g. like lego bricks). Most of the core components are conserved across diverse phyla of the animal kingdom. Examples of core components are:
DNA replication,
DNA transcription to RNA,
translation of RNA to protein,
formation of microfilament and microtubule cytoskeletons,
cell–cell signaling pathways,
cell adhesion processes,
anteroposterior axis formation
Additional core processes, such as appendage and limb formation in arthropods and tetrapods, respectively, are combinations of different conserved core processes linked in new regulatory configurations, and conserved in their entirety.
Weak regulatory linkage
Different core processes become linked, through differential regulation, in different combinations, and operate in different amounts, states, times, and places, to generate new anatomical and physiological traits. These regulatory linkages can be made and changed easily, a phenomenon that Kirschner and Gerhart call “weak regulatory linkage”. Regulatory signals can switch on and off the core components to elicit complex responses. Although the signal seems to control the response, typically the responding core process can produce the output by itself but inhibits itself from doing so. All the signal does is interfere with this self-inhibition. Regulatory change is easily effected because conserved core processes have switch-like behavior and alternative outputs already built into them, which means that regulation does not need to coevolve with the functional output.
Exploratory processes
Some conserved core processes, called "exploratory processes", have the ability to generate many different phenotypical outcomes or states. Examples include:
the formation of microtubule structures,
the development of the nervous system (i.e. connecting of axons and target organs),
synapse elimination,
muscle patterning,
the production of blood vessels,
vertebrate immune system,
animal learning
Exploratory processes first generate a very large amount of physiological variation, often at random, and then select or stabilize the most useful ones, with the rest disappearing or dying back. Hence, exploratory processes resemble a Darwinian process operating during development.
For example, as the vascular system develops, blood vessels expand to regions with insufficient oxygen supply. There is no predetermined genetically specified map for the distribution of blood vessels in the body, but the vascular system responds to signals from hypoxic tissues, whilst unrequired vessels in well-oxygenated tissues die back. Exploratory processes are powerful because they provide organisms with a tremendous scope for adaptation.
Compartmentation
Ancient regulatory processes (evolved in pre-Cambrian animals) allow the re-use of core processes in different combinations, amounts, and states in some regions of the body, or certain times in development, while decreasing their chances of generating disruptive or maladaptive pleiotropic effects elsewhere in the organism. Spatial compartmentation of transcriptional regulation and cell–cell signaling are examples. The vertebrate embryo is organized spatially into perhaps 200 compartments, each uniquely defined by its expression of one or a few key genes encoding transcription factors or signaling molecules. An example of compartmentation is found in the developing spine: all vertebrae contain bone-forming cells, but those in the chest form ribs, whereas those in the neck do not, because they arose in different compartments (expressing different Hox genes). Other forms of regulatory compartmentation include different cell types, developmental stages, and sexes.
Example: evolution of the wing
Gerhart and Kirschner give the example of the evolution of a bird or bat wing from a tetrapod forelimb. They explain how, if bones undergo regulatory change in length and thickness as a result of genetic mutation, the muscles, nerves and vasculature will accommodate to those changes without themselves requiring independent regulatory change. Studies of limb development show that muscle, nerve, and vascular founder cells originate in the embryonic trunk and migrate into the developing limb bud, which initially contains only bone and dermis precursors. Muscle precursors are adaptable; they receive signals from developing dermis and bone and take positions relative to them, wherever they are. Then, as noted previously, axons in large numbers extend into the bud from the nerve cord; some fortuitously contact muscle targets and are stabilized, and the rest shrink back. Finally, vascular progenitors enter. Wherever limb cells are hypoxic, they secrete signals that trigger nearby blood vessels to grow into their vicinity. Because of the adaptability conferred by exploratory processes, the co-evolution of bones, muscles, nerves and blood vessels is not required. Selection does not have to coordinate multiple independently varying parts. This not only means that viable phenotypes can easily be generated with little genetic change, but also that genetic mutations are less likely to be lethal, that large phenotypic changes can be favored by selection, and that phenotypic variation is functional and adaptive (i.e. ‘facilitated’).
Computational analyses
The theory of facilitated variation is supported by computational analyses of the evolution of regulatory networks. These studies confirm that phenotypic variability can be directed towards phenotypes with high fitness even when mutations are randomly distributed, and even when challenged with novel environmental conditions. Parter et al. demonstrate how key elements of facilitated variation theory, such as weak regulatory linkage, modularity, and reduced pleiotropy of mutations, evolve spontaneously under realistic conditions.
Facilitated variation and evolution
In the classical Darwinian view, a large number of successive mutations, each selected for its usefulness to the survival of the organism, is required to produce novel structures such as wings, limbs, or the brain. Alternatively, facilitated variation asserts that the physiological adaptability of core processes and properties such as weak linkage and exploratory processes enable proteins, cells, and body structures to interact in numerous ways that can lead to the creation of novelty with a limited number of genes, and a limited number of mutations.
Therefore, the role of mutations is often to change how, where, and when the genes are expressed during the development of the embryo and adult. The burden of creativity in evolution does not rest on selection alone. Through its ancient repertoire of core processes, the current phenotype of the animal determines the kind, amount, and viability of phenotypic variation the animal can produce in response to regulatory change. In emphasizing the adaptability of organisms, and their ability to produce functional phenotypes even in the face of mutation or environmental change, Kirschner and Gerhart’s theory builds upon earlier ideas by James Baldwin (the Baldwin effect), Ivan Schmalhausen, Conrad Waddington (genetic assimilation and accommodation), and Mary Jane West-Eberhard (‘genes are followers not leaders’). More recently, the theory of facilitated variation has been embraced by advocates of an extended evolutionary synthesis, and emphasized for its role in generating non-random phenotypic variation (‘developmental bias’). However, some evolutionary biologists remain skeptical as to whether facilitated variation adds a great deal to evolutionary theory.
Refutation of Intelligent Design
Creationists and advocates of Intelligent Design have argued that complex traits cannot evolve through successive small modifications to pre-existing functional systems. The theory of facilitated variation challenges this idea of irreducible complexity by explaining how random mutation can cause substantial and adaptive changes within a species. It explains how the individual organism can change from a passive target of natural selection, to an active player in the 3-billion-year history of evolution. Kirschner and Gerhart's theory thereby provides a scientific rebuttal to modern critics of evolution who champion Intelligent Design.
See also
Evolvability
Constructive development (biology)
Extended evolutionary synthesis
References
Evolutionary biology
Extended evolutionary synthesis | Facilitated variation | [
"Biology"
] | 2,014 | [
"Evolutionary biology"
] |
2,998,794 | https://en.wikipedia.org/wiki/Direct%20numerical%20control | Direct numerical control (DNC), also known as distributed numerical control (also DNC), is a common manufacturing term for networking CNC machine tools. On some CNC machine controllers, the available memory is too small to contain the machining program (for example machining complex surfaces), so in this case the program is stored in a separate computer and sent directly to the machine, one block at a time. If the computer is connected to a number of machines it can distribute programs to different machines as required. Usually, the manufacturer of the control provides suitable DNC software. However, if this provision is not possible, some software companies provide DNC applications that fulfill the purpose. DNC networking or DNC communication is always required when CAM programs are to run on some CNC machine control.
DNC TITAN, MICRO DNC, DNC USB
Wireless DNC is also used in place of hard-wired versions. Controls of this type are very widely used in industries with significant sheet metal fabrication, such as the automotive, appliance, and aerospace industries.
MICRO DNC 2
Currently there are some devices designed to support DNC function for CNC machines, see popular DNC devices on the market here: https://dncdevice.com
History
1950s-1970s
Programs had to be walked to NC controls, generally on paper tape. NC controls had paper tape readers precisely for this purpose. Many companies were still punching programs on paper tape well into the 1980s, more than twenty-five years after its elimination in the computer industry.
1980s
The focus in the 1980s was mainly on reliably transferring NC programs between a host computer and the control. The Host computers would frequently be Sun Microsystems, HP, Prime, DEC or IBM type computers running a variety of CAD/CAM software. DNC companies offered machine tool links using rugged proprietary terminals and networks. For example, DLog offered an x86 based terminal, and NCPC had one based on the 6809. The host software would be responsible for tracking and authorising NC program modifications. Depending on program size, for the first time operators had the opportunity to modify programs at the DNC terminal. No time was lost due to broken tapes, and if the software was correctly used, an operator running incorrect or out of date programs became a thing of the past.
Older controls frequently had no port capable of receiving programs such as an RS-232 or RS-422 connector. In these cases, a device known as a Behind The Reader or BTR card was used. The connection between the control's tape reader and the internal processor was interrupted by a microprocessor based device which emulated the paper tape reader's signals, but which had a serial port connected to the DNC system. As far as the control was concerned, it was receiving from the paper tape unit as it always had; in fact it was the BTR or Reader Emulation card which was transmitting. A switch was frequently added to permit the paper tape reader to be used as a backup.
1990s to present
The PC explosion in the late 1980s and early 1990s signalled the end of the road for proprietary DNC terminals. With some exceptions, CNC manufacturers began migrating to PC-based controls running DOS, Windows or OS/2 which could be linked in to existing networks using standard protocols. Customers began migrating away from expensive minicomputer and workstation based CAD/CAM toward more cost-effective PC-based solutions. Users began to demand more from their DNC systems than secure upload/download and editing. PC-based systems which could accomplish these tasks based on standard networks began to be available at minimal or no cost. In some cases, users no longer needed a DNC "expert" to implement shop floor networking, and could do it themselves. However, the task can still be a challenge based on the CNC Control wiring requirements, parameters and NC program format.
To remain competitive, therefore, DNC companies moved their offerings upmarket into DNC Networking, Shop Floor Control or SFC, Manufacturing Execution Systems or MES. These terms encompass concepts such as real-time Machine Monitoring, Graphics, Tool Management, Traveler Management and Scheduling. Instead of merely acting as a repository for programs, DNC systems aim to give operators at the machine an integrated view of all the information (both textual and graphical) they require in order to carry out a manufacturing operation, and give management timely information as to the progress of each step. DNC systems are frequently directly integrated with corporate CAD/CAM, ERP and Computer-aided Process Planning CAPP systems.
Special protocols
A challenge when interfacing into machine tools is that in some cases special protocols are used. Two well-known examples are Mazak's Mazatrol and Heidenhain's LSV2 protocol. Many DNC systems offer support for these protocols. Another protocol is DNC2 which is found on Fanuc controls. DNC2 allows advanced interchange of data with the control, such as tooling offsets, tool life information and machine status as well as automated transfer without operator intervention.
Machine monitoring
One of the issues involved in machine monitoring is whether or not it can be accomplished automatically in a practical way. In the 1980s monitoring was typically done by having a menu on the DNC terminal where the operator had to manually indicate what was being done by selecting from a menu, which has obvious drawbacks. There have been advances in passive monitoring systems where the machine condition can be determined by hardware attached in such a way as not to interfere with machine operations (and potentially void warranties). Many modern controls allow external applications to query their status using a special protocol. MTConnect is one prominent attempt to augment the existing world of proprietary systems with an open-source, industry-standard protocol using XML schemas. The end goal being to achieve higher levels of manufacturing business intelligence and workflow automation.
Alternatives
Smaller facilities will typically use a portable PC or laptop to avoid the expense of a fully networked DNC system. In the past Facit Walk Disk and a similar device from Mazak were very popular.
Footnotes
Computer-aided engineering
Industrial automation
Embedded systems
Machine tools | Direct numerical control | [
"Technology",
"Engineering"
] | 1,257 | [
"Computer engineering",
"Machine tools",
"Embedded systems",
"Industrial engineering",
"Computer systems",
"Computer-aided engineering",
"Construction",
"Computer science",
"Automation",
"Industrial automation",
"Industrial machinery"
] |
2,998,990 | https://en.wikipedia.org/wiki/Captain%20Underpants%20and%20the%20Perilous%20Plot%20of%20Professor%20Poopypants | Captain Underpants and the Perilous Plot of Professor Poopypants is the fourth book in the Captain Underpants series written by Dav Pilkey. The book is about a mad scientist named Professor Pippy P. Poopypants becoming a new science teacher at Jerome Horwitz Elementary. However, all the students laugh at his name.
Plot
A scientist from the fictional country of New Swissland named Professor Pippy P. Poopypants goes to the United States to demonstrate how his Shrinky-Pig and Goosy-Grow inventions can help the world, but everyone laughs at Poopypants' name instead of taking him seriously.
Meanwhile, Jerome Horwitz Elementary School is going to a restaurant-arcade called The Piqua Pizza Palace, but when George and Harold rearrange the lunch sign, Mr. Krupp demands they clean the teachers' lounge, making them lose their chance of going to the Piqua Pizza Palace with everyone else. However, the boys get their revenge by modifying things around in the teachers' lounge and after the field trip, the teachers get largely covered in glue and foam pellets. They chase the boys around the school and after seeing the teachers looking like abominable snowmen, Mr. Fyde resigns, thinking he's going insane. This forces Mr. Krupp to put an ad in the putting looking for a replacement, when Professor Poopypants sees it, he applies for the job thinking children to be kind and sweet-hearted, but only gets them interested by building a robot that makes gerbils jog along with them. Some time later, Ms. Ribble reads the Pied Piper of Hamelin, which inspires George and Harold to make a comic about the Professor trying to take over the world, which destroys the last of Professor Poopypants' sanity.
He makes the gerbil machine as large as a tall building, then shrinks the school and holds them hostage to turn their names sillier, with a system of 3 alphabetical name charts based on the first/last letter of each part of a first and last name. George and Harold (now "Fluffy" and "Cheeseball" respectively) get Captain Underpants (now "Buttercup Chickenfanny", but refuses to take the order to change names) to steal Professor Poopypants' enlarging machine, but he and the machine are shrunk in the process. The two of them try to enlarge the school back to normal size, but get flicked off the school. Harold makes a paper airplane that George enlarges and after many dangers, Underpants rescues them. George enlarges Underpants to the gerbil's size, then he defeats Professor Poopypants and everyone's names revert. The boys use the machines to bring the school and Captain Underpants back to normal size. Captain Underpants is soaked with water, turning him back into Mr. Krupp. Professor Poopypants is hauled off and from George and Harold, he changes his name to his grandfather's, Tippy Tinkletrousers, that which makes the prisoners and police officers ridicule him even more, much to his anger.
Sequel
The book following this was "Captain Underpants and the Wrath of the Wicked Wedgie Woman," released in 2001.
Reception
The book was removed from an elementary school in Page, North Dakota due to parental complaints.
See also
Dav Pilkey
Captain Underpants
Captain Underpants: The First Epic Movie, the Captain Underpants movie, with a plot similar to the book
References
2000 American novels
Captain Underpants novels
Fiction about size change
Scholastic Corporation books | Captain Underpants and the Perilous Plot of Professor Poopypants | [
"Physics",
"Mathematics"
] | 756 | [
"Fiction about size change",
"Quantity",
"Physical quantities",
"Size"
] |
2,999,180 | https://en.wikipedia.org/wiki/Psychology%2C%20philosophy%20and%20physiology | Psychology, philosophy and physiology (PPP) was a degree program at the University of Oxford. It was Oxford's
first psychology degree, beginning in 1947, but admitted its last students in October 2010. It has been, in part, replaced by psychology, philosophy, and linguistics (PPL, in which students usually study two of three subjects).
PPP covered the study of thought and behaviour from the differing points of view of psychology, physiology and philosophy. Psychology includes social interaction, learning, child development, mental illness and information processing. Physiology considers the organization of the brain and body of mammals and humans, from the molecular level to the organism as a whole. Philosophy is concerned with ethics, knowledge, the mind, etc.
External links
Academic courses at the University of Oxford
Philosophy education
Physiology
Psychology education | Psychology, philosophy and physiology | [
"Biology"
] | 163 | [
"Physiology"
] |
2,999,200 | https://en.wikipedia.org/wiki/Bush%20robot | A bush robot is a hypothetical machine whose body branches in a fractal way into trillions of nanoscale fingers, to achieve very high dexterity and reconfigurability. The concept was described by Hans Moravec in a final report for NASA in 1999, who projected that development of the necessary technology will take half a century.
Bush robots are also referenced as very recent technology in the Transhuman Space and Eclipse Phase roleplaying games. They are also featured in some novels, such as Rocheworld by physicist Robert L. Forward, Iron Sunrise and Singularity Sky by Charles Stross, Matter by Iain M. Banks, The Turing Option by Harry Harrison and artificial intelligence expert Marvin Minsky, The Return of Bruce Wayne #6 by Grant Morrison and Lee Garbett, The Big Chill by Alan Moore and Carlos D'Anda (as the last form of life in the universe) and The Adventures of Lando Calrissian by L. Neil Smith. Bush robots also play an important role in Ken Macleod's The Cassini Division, part of his science-fiction series The Fall Revolution.
The utility robots in the movie Interstellar (film) were fractal designs similar to a Moravec bush, but with only five levels of bifurcation.
See also
Utility fog
Further reading
Chapter 4 in particular.
References
- | Bush robot | [
"Physics",
"Technology"
] | 275 | [
"Physical systems",
"Machines",
"Robots"
] |
2,999,211 | https://en.wikipedia.org/wiki/Cometabolism | Cometabolism is defined as the simultaneous degradation of two compounds, in which the degradation of the second compound (the secondary substrate) depends on the presence of the first compound (the primary substrate). This is in contrast to simultaneous catabolism, where each substrate is catabolized concomitantly by different enzymes. Cometabolism occurs when an enzyme produced by an organism to catalyze the degradation of its growth-substrate to derive energy and carbon from it is also capable of degrading additional compounds. The fortuitous degradation of these additional compounds does not support the growth of the bacteria, and some of these compounds can even be toxic in certain concentrations to the bacteria.
The first report of this phenomenon was the degradation of ethane by the species Pseudomonas methanica. These bacteria degrade their growth-substrate methane with the enzyme methane monooxygenase (MMO). MMO was discovered to be capable of degrading ethane and propane, although the bacteria were unable to use these compounds as energy and carbon sources to grow.
Another example is Mycobacterium vaccae, which uses an alkane monooxygenase enzyme to oxidize propane. Accidentally, this enzyme also oxidizes, at no additional cost for M. vaccae, cyclohexane into cyclohexanol. Thus, cyclohexane is co-metabolized in the presence of propane. This allows for the commensal growth of Pseudomonas on cyclohexane. The latter can metabolize cyclohexanol, but not cyclohexane.
Cometabolism in Bioremediation
Some of the molecules that are cometabolically degraded by bacteria are xenobiotic, persistent compounds, such as PCE, TCE, and MTBE, that have harmful effects on several types of environments. Co-metabolism is thus used as an approach to biologically degrade hazardous solvents.
Cometabolism can be used for the biodegradation of methyl-tert-butyl ether (MTBE): an aquatic environment pollutant. Some Pseudomonas members were found to be able to fully degrade MTBE cometabolically with the enzymes they produce to oxidize n-alkanes (e.g. methane, propane).
Additionally, a promising method of bioremediation of chlorinated solvents involves cometabolism of the contaminants by aerobic microorganisms in groundwater and soils. Several aerobic microorganisms have been demonstrated to be capable of doing this, including n-alkane, aromatic compound (e.g. toluene, phenol) and ammonium oxidizers. One example is Pseudomonas stutzeri OX1, which can degrade a hazardous, and water-soluble compound tetrachloroethylene (PCE). PCE, one of the major underground water contaminants, was regarded as being undegradable under aerobic conditions and only degraded via reductive dehalogenation to be used as a growth-substrate by organisms. Reductive dehalogenation often results in the partial dechlorination of the PCE, giving rise to toxic compounds such as TCE, DCE, and vinyl chloride. Pseudomonas st. OX1 can degrade PCE under aerobic conditions by using toluene-o-xylene monooxygenase (ToMO), an enzyme they produce to derive energy and carbon from toluene and several other aromatic compounds. This biological process could be utilized to remove PCE from aerobic polluted sites.
However, the difficulties and high costs of maintaining the growth-substrates of the organisms capable of cometabolising these hazardous compounds and providing them an aerobic environment have led to the limited field-scale application of cometabolism for pollutant solvent degradation. Recently, this method of remediation has been proposed to be improved by the substitution of the synthetic aromatic growth-substrates (e.g. toluene) of these bacteria with cheap, non-toxic plant secondary metabolites.
References
Biomechanics | Cometabolism | [
"Physics"
] | 879 | [
"Biomechanics",
"Mechanics"
] |
2,999,213 | https://en.wikipedia.org/wiki/Antonia%20Fortress | The Antonia Fortress (Aramaic: קצטרא דאנטוניה) was a citadel built by Herod the Great and named for Herod's patron Mark Antony, as a fortress whose chief function was to protect the Second Temple. It was built in Jerusalem at the eastern end of the Second Wall, at the north-western corner of the Temple Mount, and was connected to the Temple by porticoes.
History
Herod (r. 37 – c. 4 BCE) built the fortress to protect the Temple. He named it for his patron Mark Antony (83–30 BCE).
The fortress housed some part of the Roman garrison of Jerusalem. The Romans also stored the high priest's vestments within the fortress.
The fortress was one of the last strongholds of the Jews in the Siege of Jerusalem (70 CE), when the Second Temple was destroyed.
Construction date controversy
The construction date is controversial because the name suggests that Herod built Antonia before the defeat of Mark Antony by Octavian in 31–30 BCE and Mark Antony's suicide in 30 BCE. Herod is famous for being an apt diplomat and pragmatist, who always aligned himself with the winning side and the "man in charge" of Rome. It is somewhat difficult to bring this date in accordance with the presumed date for the construction of the Herodian Temple.
Christian tradition
Traditionally, Christians have believed for centuries that the vicinity of the Antonia Fortress was the site of Pontius Pilate' praetorium, where Jesus was tried for high treason. This was based on the assumption that an area of Roman flagstones discovered beneath the Church of the Condemnation and the Convent of the Sisters of Zion was 'the pavement' which describes as the location of Jesus' trial.
Antonia pavement: archaeological counter-arguments
Pierre Benoit, former professor of New Testament studies at the École Biblique, reexamined the results of all previous surveys of the north-western escarpment of the Haram, of the archaeological studies of the sites owned by the Catholics in the area (Convent of the Sisters of Zion, Flagellation Monastery and St Anne Convent of the White Fathers), as well as the digs north of the Struthion Pool area, and published in 1971 his conclusions: Archaeological investigation indicates that about a century after the presumed time of Jesus' death, this area was rebuilt as the eastern of two forums belonging to the new city initiated by Hadrian in around 130 CE, the Aelia Capitolina, and it is conceivable that following the destruction of the Antonia Fortress during the siege of 70 CE, its pavement tiles were reused at Hadrian's forum. However, he also considers the possibility that the pavement is from Hadrian's time altogether. The eastern forum of the Aelia Capitolina was built over the Struthion Pool, which was mentioned by first-century historian Josephus as being adjacent to the fortress (Josephus, Jewish War 5:11:4).
Praetorium at royal palace, not at Antonia
There are textual and archaeological arguments against the trial of Jesus being carried out at the Antonia Fortress. Like Philo, Josephus testifies that the Roman governors stayed in Herod's Palace while they were in Jerusalem, and carried out their trials on the pavement immediately outside it (Josephus, Jewish Wars, 2:14:8). Josephus indicates that Herod's Palace is on the Western Hill (Jewish Wars, 5:2) and in 2001 some of its vestiges were rediscovered under a corner of the Tower of David. Archaeologists therefore conclude that in the first century, the praetorium—the residence of the praefectus (governor)—was in the former royal palace on the Western Hill, rather than at the Antonia Fortress, on the opposite side of the city. However, as the tradition retained its power in associating the fortress with Jesus' trial, the place where it once stood serves as the starting point of the Via Dolorosa commemorating the crucifixion of Jesus.
Two arguments for Antonia as the place of judgement
1. During the greatest pilgrimage feast, when hundreds of thousands came to the Temple, Pilate naturally had to be with his garrison next to the Temple mount as a potential focus of the uprising, and certainly the favorite place of religious and national zealots who wished independence from Rome.
2. According to Luke's Gospel (), Pilate found out that Christ was from Galilee, "and when he knew that he was of Herod's jurisdiction, he sent him unto Herod, who himself also was at Jerusalem in these days" (23:7). Herod Antipas, who came for the holiday from Galilee to Jerusalem, disappointed and angry because of Jesus’ silence, "sent him back to Pilate" (23:11), who then "called together the chief priests and the rulers and the people" (23:13). It seems that Pilate was not in Herod's castle. If the trial had taken place in Herod's castle, he could have simply asked Herod to come to the courtroom, as he summoned the chief priests and the leaders.
Description
Although modern reconstructions often depict the fortress as having a tower at each of four corners, Josephus repeatedly refers to it as "the tower Antonia", and states that it had been built by John Hyrcanus and later by King Herod, and used for a vestry, in which were reposited the vestments of the high priest. Josephus states:
The general appearance of the whole was that of a tower with other towers at each of the four corners; three of these turrets were fifty cubits high, while that at the south-east angle rose to seventy cubits and so commanded a view of the whole area of the temple.
Some archaeologists are also of the opinion that the fortress consisted only of a single tower, located at the south-east corner of the site. For example, Pierre Benoit writes that there is absolutely no archaeological support for there having been four towers.
Josephus attests to the importance of the Antonia: "For if the Temple lay as a fortress over the city, Antonia dominated the Temple & the occupants of that post were the guards of all three." Josephus placed the Antonia at the northwest corner of the colonnades surrounding the Temple. Modern depictions often show the Antonia as being located along the north side of the Temple enclosure.
Other theories
Some researchers and academics, including Marilyn Sams (M.A. in American Literature, Brigham Young University) and Dr. Robert Cornuke (Ph.D. in Bible and Theology, Louisiana Baptist University), have expanded on research by Dr. Ernest L. Martin (1932–2002, meteorologist, college professor, amateur archeologist), who offered evidence that the compound on what is commonly called the Temple Mount did not house the Jerusalem Temple, but is instead the remnants of a more massive Antonia Fortress, and that the rock inside the Dome of the Rock is not the Foundation Stone, but was inside the Praetorium of Pontius Pilate where Jesus was judged.
Jerome Murphy-O'Connor, however, argued that this theory "cannot be sustained", as it cannot be reconciled with Josephus' description, and it "does not account for the archaeological remains in the western section of the north wall". Josephus and archaeology don't leave much space for doubt in regard to the fact that the Temple Mount was indeed the site of the Herodian Temple, nor for the location of the Antonia near its north-western corner.
Both Josephus and archaeology concur that the Roman military camp after the 70 CE destruction was centered on the three towers next to Herod's royal palace on the Western Hill, and not on the Temple Mount, whose protective walls had been thrown down by the Romans, with the resulting debris visible until today along the Western Wall near Robinson's Arch. Roman military camps had rounded corners and four gates, one in each wall – the Herodian compound had angular corners and nine gates. Permanent camps were much larger, 50 acres on average; the Haram esplanade only contains 36 acres. There is no Roman camp explanation for the Hebrew inscription marking the Trumpeting Place. The Temple compound was surrounded by porticos (roofed colonnades following the inner walls of the compound), while military camps never were. Augustus trusted Herod and would not have built a controlling fortress towering over his capital and Temple, but no emperor would have gone so far as to entrust a legion to a client king.
Remains of a 4-metre thick wall and Herodian-style ashlars are still observable inside the Mamluk buildings in the north-west corner of the Haram and the adjacent area along its northern wall. Together they suggest the dimensions of the Antonia: 112 by 40 metres on the outside, signifying a 3300 square metre floor area, absolutely enough for a small garrison, but certainly not for the entire legion suggested by Martin.
Antonia did stand on a rocky outcrop, as written by Josephus, but here, as elsewhere in his writings, he did exaggerate its elevation above the surrounding ground. This still meant that the fortress dominated the Temple courts and porticos, the latter by over ten metres, matching Josephus' words: "the tower of Antonia lay at the angle where the two porticos, the western and the northern, of the first court of the Temple met" (JW 5:238), and "[a]t the point where the Antonia impinged on the porticos of the temple there were stairs leading down to both of them by which the guards descended" (JW 5:243; cf. ). The position and dimensions of those porticos can still be in part discerned, thanks to three surviving roof beam sockets carved out of the living rock of the rocky outcrop which once held the Antonia, north-west of the esplanade. Josephus' statement that all the porticos surrounding the Temple complex measured six stadia "including the Antonia" (JW 5:192) is off by a large margin (six stadia represent about 1.11 km, whereas the sides of the Haram esplanade today measure together about 1.55 km), but it clearly suggests that the fortress was contiguous with the Temple complex with no need for a "double causeway" to connect the two by spanning a distance of one stade (c. 150 m), as claimed by Martin.
See also
Bezetha
Church of Ecce Homo
Hasmonean Baris
Herodian architecture
References
Footnotes
Citations
External links
19 BC
Buildings and structures completed in the 1st century BC
Establishments in the Herodian kingdom
Jews and Judaism in the Roman Empire
Ancient sites in Jerusalem
Archaeological sites in Israel
Architectural history
Former buildings and structures in Israel
Forts in Israel
Herod the Great
Ancient history of Jerusalem
Temple Mount
1st-century BC fortifications
Pontius Pilate | Antonia Fortress | [
"Engineering"
] | 2,251 | [
"Architectural history",
"Architecture"
] |
2,999,407 | https://en.wikipedia.org/wiki/Light%20fixture | A light fixture (US English), light fitting (UK English), or luminaire is an electrical lighting device containing one or more light sources, such as lamps, and all the accessory components required for its operation to provide illumination to the environment. All light fixtures have a fixture body and one or more lamps. The lamps may be in sockets for easy replacement—or, in the case of some LED fixtures, hard-wired in place.
Fixtures may also have a switch to control the light, either attached to the lamp body or attached to the power cable. Permanent light fixtures, such as dining room chandeliers, may have no switch on the fixture itself, but rely on a wall switch.
Fixtures require an electrical connection to a power source, typically AC mains power, but some run on battery power for camping or emergency lights. Permanent lighting fixtures are directly wired. Movable lamps have a plug and cord that plugs into a wall socket.
Light fixtures may also have other features, such as reflectors for directing the light, an aperture (with or without a lens), an outer shell or housing for lamp alignment and protection, an electrical ballast or power supply, and a shade to diffuse the light or direct it towards a workspace (e.g., a desk lamp). A wide variety of special light fixtures are created for use in the automotive lighting industry, aerospace, marine and medicine sectors.
Portable light fixtures are often called lamps, as in table lamp or desk lamp. In technical terminology, the lamp is the light source, which, in casual terminology, is called the light bulb. Both the International Electrotechnical Commission (IEC) and the Illuminating Engineering Society (IES) recommend the term luminaire for technical use.
History
Fixture manufacturing began soon after production of the incandescent light bulb. When practical uses of fluorescent lighting were realized after 1924, the three leading companies to produce various fixtures were Lightolier, Artcraft Fluorescent Lighting Corporation, and Globe Lighting in the United States.
Fixture types
Light fixtures are classified by how the fixture is installed, the light function or lamp type.
Free-standing or portable
Table lamp fixtures, standard lamp fixtures, and office task light luminaires.
Balanced-arm lamp is a spot light with an adjustable arm such as anglepoise, RAMUN or Luxo L1.
Gooseneck (fixture)
Nightlight
Floor Lamp
Torch lamp or torchières are floor lamps with an upward-facing shade. They provide general lighting to the rest of the room.
Gooseneck lamp
Bouillotte lamp: see Bouillotte
Fixed
Ceiling Dome – the light source(s) are hidden behind a translucent dome typically made of glass, with some combination of frosting and surface texturing to diffuse the light. These can be flush-mount fixtures mounted into the ceiling, or semi-flush fixtures separated by a small distance (usually about 3–12").
Open ceiling dome – the translucent dome is suspended a short distance below the ceiling by a mechanism that is hidden with the exception of a screw-knob or other device appearing on the outer dome face, and pulling this knob releases the dome.
Enclosed ceiling dome – the translucent dome mates with a ring that is mounted flush with the ceiling.
Recessed light – the protective housing is concealed behind a ceiling or wall, leaving only the fixture itself exposed. The ceiling-mounted version is often called a downlight.
"Cans" with a variety of lamps – this term is jargon for inexpensive downlighting products that are recessed into the ceiling, or sometimes for uplights placed on the floor. The name comes from the shape of the housing. The term "pot lights" is often used in Canada and parts of the US.
Cove light – indirect lighting recessed into the ceiling in a long box against a wall.
Troffer – recessed fluorescent light fixtures, usually rectangular in shape to fit into a drop ceiling grid.
Surface-mounted light – the finished housing is exposed, not flush with the surface.
Pendant light – suspended from the ceiling with a chain or pipe.
Sconce – provide up or down lights; can be used to illuminate artwork, architectural details; commonly used in hallways or as an alternative to overhead lighting.
Track lighting fixture – individual fixtures ("track heads") can be positioned anywhere along the track, which provides electric power.
Under-cabinet light – mounted below kitchen wall cabinets.
Display Case or Showcase light – shows merchandise on display within an enclosed case such as jewelry, grocery stores, and chain stores.
Ceiling fan – may sometimes have a light, often referred to as a light kit mounted to it. Ceiling fans with built-in lights may eliminate the need for separate overhead light fixtures in a room, and light kits can also replace any ceiling-mounted light fixtures that were displaced by the installation of the ceiling fan.
Emergency lighting or exit sign – connected to a battery backup or to an electric circuit that has emergency power if the mains power fails.
High- and low-bay lighting – typically used for general lighting for industrial buildings and often big-box stores.
Strip lights or Industrial lighting – often long lines of fluorescent lamps used in a warehouse or factory.
Outdoor lighting and landscape lighting – used to illuminate walkways, parking lots, roadways, building exteriors and architectural details, gardens, and parks. Outdoor light fixtures can also include forms similar to indoor lighting, such as pendants, flush or close-to-ceiling light fixtures, wall-mounted lanterns and dome lights.
High-mast, usually pole – or stanchion-mounted – for landscape, roadways, and parking lots.
Bollard – a type of architectural outdoor lighting that is a short, upright ground-mounted unit typically used to provide cutoff type illumination for egress lighting, to light walkways, steps, or other pathways.
Solar lamp
Street light
Yard light
Special-purpose lights
Accent light – any directional light that highlights an object or attracts attention to a particular area.
Background light – for use in video production.
Blacklight
Christmas lights – also called fairy lights or twinkle lights and are often used at Christmas and other holidays for decoration.
Dock light - provides light for boating safety. Typically affixed atop pilings or directly upon the dock floor itself.
Emergency light – provides minimal light to a building during a power outage.
Exit sign
Flood light
Safelight (for use in a darkroom)
Safety lamp (for use in coal mines)
Searchlight (for military and advertising use)
Security lighting
Step light
Strobe light
Task light
Traffic light
Theatrical
Stage lighting instrument
Intelligent lighting
Followspot
Wallwasher
Lamp types
Arc lamps
Xenon arc lamp, Yablochkov candle
Fluorescent
Fluorescent lamp, compact fluorescent lamp (CFL), Induction lamp, blacklight.
Fuel lamps
Betty lamp, butter lamp, carbide lamp, gas lighting, kerosene lamp, oil lamp, rush light, torch, candle, Limelight, gas mantle
Safety lamps: Davy lamp and Geordie lamp
Gas-discharge lamp and high-intensity discharge lamp (HID)
Mercury-vapor lamp, Metal-halide (HMI, HQI, CDM), Sodium vapor or "high-pressure sodium"
Neon sign
Incandescent lamp
A-lamp, Parabolic aluminized reflector lamp (PAR), reflector lamp (R), bulged reflector lamp (BR) (refer to lamp shapes)
Obsolete types: limelight, carbon button lamp, Mazda (light bulb), Nernst glower
Novelty: Lava lamp
Special purpose: heat lamp, Globar, gas mantle
Halogen – special class of incandescent lamps
Nuclear: self-powered lighting
Plasma lamp
LED (solid-state lighting)
Light-fixture controls
There are various types of devices used to manage the amount of light used:
3-way 2-circuit switch
Dimmer (this allows the user to make a light brighter or dimmer, typically using a rotary dial)
Light switch (often part of the light socket or power cord on portable fixtures)
Lighting control system
Motion detector
Timer
Touch
X10 systems
See also
Architectural lighting design
Coefficient of utilization
Flashlight
History of street lighting in the United States
Lantern
Lampshade
Lightbulb socket
Lighting designer for the theater
Luminous efficacy
Timeline of lighting technology
Light pollution
References
External links
Look at the Chart and Pick Out the Reflector You Need, Popular Science, February 1919, page 75, Google Books
Electrical systems | Light fixture | [
"Physics"
] | 1,714 | [
"Physical systems",
"Electrical systems"
] |
2,999,725 | https://en.wikipedia.org/wiki/Kinetic%20bombardment | A kinetic bombardment or a kinetic orbital strike is the hypothetical act of attacking a planetary surface with an inert kinetic projectile from orbit (orbital bombardment), where the destructive power comes from the kinetic energy of the projectile impacting at very high speeds. The concept originated during the Cold War.
Typical depictions of the tactic are of a satellite containing a magazine of tungsten rods and a directional thrust system. When a strike is ordered, the launch vehicle brakes one of the rods out of its orbit and into a suborbital trajectory that intersects the target. The rods would typically be shaped to minimize air resistance and thus maximize velocity upon impact.
The kinetic bombardment has the advantage of being able to deliver projectiles from a very high angle at a very high speed, making them extremely difficult to defend against. In addition, projectiles would not require explosive warheads, and—in the simplest designs—would consist entirely of solid metal rods, giving rise to the common nickname "rods from God". Disadvantages include the technical difficulties of ensuring accuracy and the high costs of positioning ammunition in orbit.
Real life concepts and theories
Predecessors and early concepts
During the Korean and Vietnam Wars, there was limited use of the Lazy Dog bomb, a kinetic projectile shaped like a conventional bomb but only about long and in diameter. A piece of sheet metal was folded to make the fins and welded to the rear of the projectile. These were dumped from aircraft onto enemy troops and had the same effect as a machine gun fired vertically. Similar flechette projectiles have been used since World War I.
In the 1980s, another kinetic swarm system was conceptualized as a potential part of the Strategic Defense Initiative, there codenamed Brilliant Pebbles.
Project Thor was an idea for a weapons system that launches telephone pole-sized kinetic projectiles made from tungsten from Earth's orbit to damage targets on the ground. Jerry Pournelle created the concept while working in operations research at Boeing in the 1950s before becoming a science-fiction writer.
2003 United States Air Force proposal
A system described in the 2003 United States Air Force report called Hypervelocity Rod Bundles was that of , tungsten rods that are satellite-controlled and have global strike capability, with impact speeds of Mach 10.
The bomb would naturally contain large kinetic energy because it moves at orbital velocities, around in orbit and at impact. As the rod reenters Earth's atmosphere, it would lose most of its velocity, but the remaining energy would cause considerable damage. Some systems are quoted as having the yield of a small tactical nuclear bomb. These designs are envisioned as a bunker buster. As the name suggests, the 'bunker buster' is powerful enough to destroy a nuclear bunker. With 6–8 satellites on a given orbit, a target could be hit within 12–15 minutes from any given time, less than half the time taken by an ICBM and without the launch warning. Such a system could also be equipped with sensors to detect incoming anti-ballistic missile-type threats and relatively light protective measures to use against them (e.g. hit-to-kill missiles or megawatt-class chemical laser). The time between deorbit and impact would only be a few minutes, and depending on the orbits and positions in the orbits, the system would have a worldwide range. There would be no need to deploy missiles, aircraft, or other vehicles.
In the case of the system mentioned in the 2003 Air Force report above, a tungsten cylinder impacting at has kinetic energy equivalent to approximately . The mass of such a cylinder is itself greater than , so the practical applications of such a system are limited to those situations where its other characteristics provide a clear and decisive advantage—a conventional bomb/warhead of similar weight to the tungsten rod, delivered by conventional means, provides similar destructive capability and is far more practical and cost-effective.
The highly elongated shape and high mass of the projectiles are intended to enhance sectional density (and therefore minimize kinetic energy loss due to air friction) and maximize penetration of hard or buried targets. The larger device is expected to be quite effective at penetrating deeply buried bunkers and other command and control targets.
The weapon would be very hard to defend against. It has a very high closing velocity and a small radar cross-section. The launch is difficult to detect. Any infrared launch signature occurs in orbit, at no fixed position. The infrared launch signature also has a much smaller magnitude compared to a ballistic missile launch. The system would also have to cope with atmospheric heating from re-entry, which could melt non-tungsten components of the weapon.
The phrase "rods from God" is used to describe the same concept. An Air Force report called them "hypervelocity rod bundles".
In science fiction
In the 1970s and 1980s, this idea was refined in science fiction novels such as Footfall by Larry Niven and Jerry Pournelle (the same Pournelle that first proposed the idea for military use in a non-fiction context), in which aliens use a Thor-type system. During the 1980s and 1990s, references to such weapons became a staple of science fiction roleplaying games such as Traveller, Shadowrun, and Heavy Gear (the first of these games naming such weapons ortillery, a portmanteau of orbital artillery), as well as visual media including Babylon 5's "mass drivers", the film The Last Starfighter, and the film Starship Troopers, itself an adaptation of the Heinlein novel of the same name. A smaller "crowbar" variant is mentioned in David's Sling by Marc Stiegler (Baen, 1988). Set in the Cold War, the story is based on the use of (relatively inexpensive) information-based "intelligent" systems to overcome an enemy's numerical advantage. The orbital kinetic bombardment system is used first to destroy the Soviet tank armies that have invaded Europe and then to take out Soviet ICBM silos prior to a nuclear strike.
Halo features the Magnetic Accelerator Cannon (MAC), or Mass Accelerator Cannon, as the primary weapon system employed by the United Nations Space Command (UNSC) on its warships and orbital defense platforms. Essentially large coilguns, MACs are capable of firing a variety of ammunition types varying on the model and bore, ranging from hyper-dense kinetic kill slugs to sub-caliber rounds to semi-autonomous drone missiles. Most predominantly featured in Halo Wars and Halo Wars 2, the MAC is an ability that allows the player to utilize the UNSC Spirit of Fire's point-defense MAC for pinpoint orbital bombardment, allowing the player to heavily damage or destroy enemy units. However, there are variants of the MAC platforms mounted to various ships and stations, with the most powerful being able to fire a 3,000-ton projectile at anywhere between 0.4% and 25% the speed of light.
See also
Concrete bomb
Kinetic energy penetrator
Cobalt bomb
Prompt Global Strike
Railgun
Boeing X-37
Brilliant Pebbles
Flechette
Fractional Orbital Bombardment System
References
Further reading
External links
Space weapons
Rocketry
Doomsday scenarios
Weapons of mass destruction
Collision
Proposed weapons | Kinetic bombardment | [
"Physics",
"Engineering"
] | 1,446 | [
"Rocketry",
"Collision",
"Mechanics",
"Aerospace engineering"
] |
2,999,783 | https://en.wikipedia.org/wiki/Gut-associated%20lymphoid%20tissue | Gut-associated lymphoid tissue (GALT) is a component of the mucosa-associated lymphoid tissue (MALT) which works in the immune system to protect the body from invasion in the gut.
Owing to its physiological function in food absorption, the mucosal surface is thin and acts as a permeable barrier to the interior of the body. Equally, its fragility and permeability creates vulnerability to infection and, in fact, the vast majority of the infectious agents invading the human body use this route. The functional importance of GALT in body's defense relies on its large population of plasma cells, which are antibody producers, whose number exceeds the number of plasma cells in spleen, lymph nodes and bone marrow combined. GALT makes up about 70% of the immune system by weight; compromised GALT may significantly affect the strength of the immune system as a whole.
Structure
The gut-associated lymphoid tissue lies throughout the intestine, covering an area of approximately 260–300 m2. In order to increase the surface area for absorption, the intestinal mucosa is made up of finger-like projections (villi), covered by a monolayer of epithelial cells, which separates the GALT from the lumen intestine and its contents. These epithelial cells are covered by a layer of glycocalyx on their luminal surface so as to protect cells from the acid pH.
New epithelial cells derived from stem cells are constantly produced on the bottom of the intestinal glands, regenerating the epithelium (epithelial cell turnover time is less than one week). Although in these crypts conventional enterocytes are the dominant type of cells, Paneth cells can also be found. These are located at the bottom of the crypts and release a number of antibacterial substances, among them lysozyme, and are thought to be involved in the control of infections.
Underneath them, there is an underlying layer of loose connective tissue called lamina propria. There is also lymphatic circulation through the tissue connected to the mesenteric lymph nodes.
Both GALT and mesenteric lymph nodes are sites where the immune response is started due to the presence of immune cells through the epithelial cells and the lamina propria.
The GALT also includes the Peyer's patches of the small intestine, isolated lymphoid follicles present throughout the intestine, and the appendix in humans.
The following examples comprise lymphoid tissues that act as interfaces between immune system and incoming antigens either as food antigens or as pathogenic or commensal microbiota's antigens:
Waldeyer's tonsillar ring
Small lymphoid aggregates in the esophagus
Lymphoid tissue accumulating with age in the stomach
Peyer's patches in the small intestine
Diffusely distributed lymphoid cells and plasma cells in the lamina propria of the gut
Intraepithelial lymphocytes (IELs) interspersed into epithelial layer of mucosal surfaces
Lymphoid aggregates in the appendix and large intestine
Mesenteric lymph nodes draining lymph coming from the gut tissue
GALT can be also divided into two categories considering the structure, from which the function arise. There can be found 1.) organised GALT made up from folicules – such as Peyer's patches, mesenteric lymph nodes and even more organised appendix. Its main function is to induce immune reaction. 2.) diffuse GALT with single T and B cells, macrophages, eosinophiles, basophiles and mast cells, preferentially found in lamina propria. This part of GALT is made up from mature effector cells ready to perform their actions.
The GALT has been described in the adult eastern grey kangaroo (Macropus giganteus), tammar wallaby (Notamacropus eugenii), stripe-faced dunnart (Sminthopsis macroura), and red-tailed phascogale (Phascogale calura). The adult northern brown bandicoot (Isoodon macrourus) has been described to have both organised and diffuse GALT.
The development of the GALT has also been described in several marsupial species, including tammar wallabies, stripe-faced dunnarts (Sminthopsis macroura), and red-tailed phascogales
Peyer's patches
The Peyer's patch is an aggregate of lymphoid cells projected to the lumen of the gut which acts as a very important site for the initiation of the immune response. It forms a subepithelial dome where large number of B cell follicles with its germinal centers, T cell areas between them in a smaller number and dendritic cells are found. In this area, the subepithelial dome is separated from the intestinal lumen by a layer of follicle-associated epithelium. This contains conventional intestinal epithelial cells and a small number of specialized epithelial cells called microfold cells (M cells) in between. Unlike enterocytes, these M cells present a folded luminal surface instead of the microvilli, do not secrete digestive enzymes or mucus and lack a thick surface of glycocalix, so it can be in contact with microbiota and antigens presented in the content of gut.
Function
Under normal circumstances, immune system of the whole organism needs intestinal source of antigens to train and regulate development of various immune cells. Without having such stimulation, many properties of immune systems do not develop, as it is shown on the case of germ-free animals. Because immune cells are in constant touch with bacterial and food antigens, the primary response is set up as tolerogenic. The complex interaction between these intestinal microbiota, the intestinal epithelial layer, and the local mucosal immune system is essential for maintaining gut health and systemic immunity because the nutrition level of a person’s diet contributes to the gut microbiota (a multispecies microbial community of bacteria, fungi, and viruses, all in a particular niche) that is in synergy with the host. Still there must be a robust defence in a case that pathogens cross either the border line of epithelium or produce harmful substances like bacterial toxins. Such a walking on the edge of a knife is ensured by diverse types of immune cells:
B-lymphocytes
Plasma B cells residing at lamina propria produce high levels of specific secretory IgA (sIgA) antibodies. These IgA are secreted into the lumen of the gut through the epithelial layer by transcytosis. Firstly epithelial cell binds a dimer of IgA via polymeric Ig receptor at the basolateral side and transports it in a vesicle into the luminal space. Then the receptor is proteolytically cleaved and the dimer of IgA is released with a portion of the receptor called the secretory component. The secretory component protects secreted antibodies against the digestive milieu in the gut.
A high level of secretory IgA results from the interaction of B cells and intestinal antigen presenting dendritic cell (DC) in cooperation with follicular T helper cell (Tfh) in the germinal centers (GCs) of Peyer's patches. There are two main ways of IgA production 1) T-cell dependent resulting in sIgAs with high affinity and specificity and 2) T-cell independent generation of sIgA, which utilizes dendritic cells and their production of BAFF and APRIL cytokines. T-cell independently produced sIgAs have lower affinity and coat mainly commensals. General functions of secretory IgAs are to coat any of the intestinal bacteria (commensal or pathogenic ones) to impair their motility and to prevent them from getting in prolonged and direct contact with the intestinal epithelium and the host intestinal immune system. This is called immune exclusion. Secreted IgAs bind to bacterial toxins and neutralize them as well.
T-lymphocytes
Naïve CD4+T cells differentiate into Treg or various helper T cell subsets (Th1, Th2, Th17 or Tfh). In the gut-associated lymphoid tissue, the process of differentiation occurs via presentation of antigens derived from gut microbiota by antigen presenting cells such as dendritic cells or M cells in Peyer's patches. Typical process of an oral tolerance towards ingested food antigens can be described as continuous luminal sampling of antigens by DCs and their subsequent migration followed by priming of naïve T cells in mesenteric lymph nodes to become immunosuppressive T cells (Treg). Antigens received in this way ensure tolerance against them. Commensal microbiota activates immune response as well - in a way that protects host intestinal tissue from damaging it by immune cell reactions. The outcome of T cell populations in healthy individuals differs from the spectrum of T cells resulting from acute infection or chronic inflammation. Inappropriate stimulation (typically by segmented filamentous bacteria - SFB) of chronic Th1 or Th17 cell response plays a crucial role in pathological damage to the host.
Several novel gut-associated lymphoid cells have been described. They are of different origins and follow different maturation processes but share the same GALT role – to rapidly respond to pathogens and secrete effector cytokines. Such multi-layered protection systems highlights the susceptibility of mucosal sites to invading agents. The mucosal route is the most frequent way for entering of pathogenic infections into the host. Robust engagement of a variety of lymphoid cells patrolling the epithelial layer also reflects evolutionary pressure and arms race between immune systems and pathogens escaping its control.
Intraepithelial lymphocytes (IELs)
Long-lived and residential intraepithelial lymphocytes (IELs) are one of the largest populations of T-lymphocytes in the body. In contrast to other peripheral lymphocytes, IEL do not circulate in the blood stream or lymphatic system but reside in the epithelial layer in intestine. Such location in very special per itself – IELs patrol the condition within a single layer of cells and have dendritic look. They provide the first line of defense in case of pathogen crossing the epithelial barrier. IELs encompass surprising diversity of origins and divide into two main categories – conventional and nonconventional. It is based on molecular surface properties and the place where they acquire their final effector cytotoxic program.
Conventional IELs bear classical TCR receptor made up from α and β subunit together with CD4 or CD8 co-receptors. They represent a relative minority of the total intestinal IELs compared with unconventional IELs. They are derived from naïve T cells that encounter antigens in the periphery (typically antigens displayed by DC in the Peyer's patches). After this activation, conventional IELs express gut-tropic molecules allowing them to home in intestinal tissue after trafficking through lymph stream and subsequent blood stream. Conventional intraepithelial cells are thus tissue-resident effector memory T cells, capable of rapid respond with cytolytic activity and release of cytokines such as INFγ and TNF.
Unconventional IELs present majority of IEL cells in intestinal epithelial layer and acquire their effector program after exiting thymus as naïve cells and encountering antigens in GALT. After such stimulation, unconventional IELs (mainly γδ T cells) reside in the intestinal epithelium. γδ T cells express TCR receptor made of γ and δ subunit and do not recognize antigen peptides presented in the MHC-bound form. The process of their activation is still largely unknown. Main property of γδ T cells is formation of long-lived memory populations in barrier tissues such as intestinal epithelium or in the skin. They perform immune memory in particular tissue even after clearance of pathogen or retreat of inflammation.
Innate lymphoid cells (ILCs)
Innate lymphoid cells (ILCs) are the most recently discovered family of innate immune cells and term “innate” means they do not need antigen receptor gene rearrangement. Due to the development of novel method, such as single cell RNA sequencing, subtypes of innate lymphoid cells are described. Based on their transcriptional profile set by main transcription factors ILCs are divided into five distinct subsets: NK cells, ILC1s, ILC2s, ILC3s, and LTi cells. ILCs are prevalent at mucosal surfaces, playing a key role in mucosal immunity and homeostasis due to their ability of rapid secretion of immunoregulatory cytokines and thus communicating with other immune cells.
Innate immunity
Beside adaptive specific immunity, an innate immunity plays a significant role in GALT because it provides more rapid response. Recognition of microbial non-self signature occurs by pattern recognition receptors (PRR) that can be found on dendritic cells, macrophages, monocytes, neutrophils and epithelial cells. PRRs bind to conserved microbial pattern like cell walls components (LPS, teichoic acid, flagellin, peptidoglycan) or viral or bacterial nucleic acid. PRRs are localized extracellularly as membrane-bound receptors (Toll-like receptors) or intracellularly (NOD-like and RIG-like receptors). Varied palette of pattern recognition receptors is activated by various signals named PAMP (pathogen associated molecular patterns) or by signals connected to tissue damage named DAMP (damage associated molecular patterns).
Macrophages
Majority of antigen presenting cells (APCs) in intestine is derived from macrophages, which have very quick turnover. Macrophages are prevalent in lamina propria and submucosal deeper layers like muscularis layer. Macrophages can use their trans-epithelial dendrites (long cytoplasmic extensions) and directly contact epithelial layer and sample luminal bacteria. Under healthy conditions macrophages engulf commensal bacteria and surrounding cellular debris, secrete IL-10, drive maturation of Treg and contribute to tissue homeostasis. Because of low expression of innate response receptors and co-stimulatory surface molecules, intestinal macrophages do not initiate inflammation. But upon infection or inflammation, the profile of macrophages changes and they start to secrete large amounts of TNF-α and become proinflammatory effector cells.
Dendritic cells
DCs present less than 10% of lamina propria APC and typically do not reside in lower layers. Inherent production of retinoic acid and TGF-β (typical for gut-associated DCs) induces expression of gut-homing molecules and favor IgA switch during maturation of B cells in folicules. DCs also direct Treg and conventional IELs to receive their final phenotype of mature effector cells in intestine.
Other animals
The adaptive immunity, mediated by antibodies and T cells, is only found in vertebrates. Whereas all of them have a gut-associated lymphoid tissue and the vast majority have a version of spleen and thymus, not all vertebrates show bone marrow, lymph nodes or germinal centers, what means that not all vertebrates can generate lymphocytes in bone marrow. This different distribution of the adaptive organs in the different groups of vertebrates suggests GALT as the very first part of the adaptive immune system in vertebrates. It has been suggested that from this existing GALT, and due to the pressure put by commensal bacteria in gut that coevolved with vertebrates, later specializations as thymus, spleen or lymph nodes appeared as part of the adaptive immune system.
Additional images
References
External links
- "Digestive System: Alimentary Canal: colon, taenia coli"
- "Digestive System: Alimentary Canal: esophageal/stomach junction"
Immune system
Lymphatic system
Lymphatic tissue | Gut-associated lymphoid tissue | [
"Biology"
] | 3,447 | [
"Immune system",
"Organ systems"
] |
2,999,842 | https://en.wikipedia.org/wiki/Truel | Truel and triel are neologisms for a duel between three opponents, in which players can fire at one another in an attempt to eliminate them while surviving themselves.
Game theory overview
A variety of forms of truels have been studied in game theory. Features that determine the nature of a truel include
the probability of each player hitting their chosen targets (often not assumed to be the same for each player)
whether the players shoot simultaneously or sequentially, and, if sequentially, whether the shooting order is predetermined, or determined at random from among the survivors;
the number of bullets each player has (in particular, whether this is finite or infinite);
whether or not intentionally missing is allowed.
whether or not self-targeting or random selection of targets is allowed.
There is usually a general assumption that each player in the truel wants to be the only survivor, and will behave logically in a manner that maximizes the probability of this. (If each player only wishes to survive and does not mind if the others also survive, then the rational strategy for all three players can be to miss every time.)
In the widely studied form, the three have different probabilities of hitting their target.
If a single bullet is used, the probabilities of hitting the target are equal and deliberate missing is allowed, the best strategy for the first shooter is to deliberately miss. Since he is now disarmed, the next shooter will have no reason to shoot the first one and so will shoot at the third shooter. While the second shooter might miss deliberately, there would then be the risk that the third one would shoot him. If the first shooter does not deliberately miss, he will presumably be shot by whichever shooter remained.
If an unlimited number of bullets are used, then deliberate missing may be the best strategy for a duelist with lower accuracy than both opponents.
If both have better than 50% success rate, he should continue to miss until one of his opponents kills the other.
Then he will get the first shot at the remaining opponent.
But if the "middle" opponent is weak, it can be better to team up with him until the strongest is eliminated.
The details depend on the firing order. For example, if the order is P, Q, R, with respective probabilities
and it is R's turn, R should waste his shot if:
but not do so if:
In between, R should waste his shot if:
History
Frederick Marryat describes a three-way duel in his novel Mr. Midshipman Easy, published in 1836. This duel is more of a circular affair, with the first participant aiming only for the second, the second participant aiming only for the third, and the third participant aiming only at the first.
A later mention of three-person "duels" is A. P. Herbert's play Fat King Melon (1927). An extensive bibliography has been compiled by D. Marc Kilgour. The word "truel" was introduced in Martin Shubik's 1964 book Game Theory and Related Approaches to Social Behavior, page 43, and independently in Richard Epstein's 1967 book Theory of Gambling and Statistical Logic, page 343.
In popular culture
In one of the most famous spaghetti westerns, The Good, the Bad and the Ugly, the final showdown is played out to be a climactic truel among the three main characters: Blondie ("The Good"), Angel Eyes ("The Bad"), and Tuco ("The Ugly"). The standoff remains a signature piece for director Sergio Leone and one of the best-known scenes in film history.
The climactic ending to the 1987 film City on Fire features a truel which is interrupted by the arrival of police. The 1992 film Reservoir Dogs has a very similar confrontation among the characters Mr. White, Nice Guy Eddie, and Joe Cabot, in which only one survives.
The truel is also parodied at the climax of the film The Good, the Bad, the Weird.
A truel with swords is fought among Jack Sparrow, Will Turner, and James Norrington in the 2006 film Pirates of the Caribbean: Dead Man's Chest; all three characters survive.
The short film Truel explores the idea of a three-way duel.
In the novel and movie A Dog's Will, a truel is one of João Grilo's plans.
In an episode of the hit show The Office, Michael convinces everyone to play a board game similar to Clue. The episode ends with Michael, Andy, Dwight and Pam in a finger truel.
The film Tekken Blood Vengeance also features a truel during the climax where Jin Kazama, Kazuya Mishima and Heihachi Mishima fought each other in a three-way duel.
See also
Mexican standoff
References
Dueling
Logic puzzles
Non-cooperative games | Truel | [
"Mathematics"
] | 995 | [
"Game theory",
"Non-cooperative games"
] |
3,000,609 | https://en.wikipedia.org/wiki/Certance | Certance, LLC, was a privately held company engaged in design and manufacture of computer tape drives.
Based in Costa Mesa, California, Certance designed and manufactured drives using a variety of tape formats, including Travan, DDS, and Linear Tape-Open computer tape drives. Certance was one of the three original technology partners, (Certance, IBM, and Hewlett-Packard), that created the Linear Tape-Open technology.
In 2005, Certance was acquired by Quantum Corporation.
History
The company began as the removable storage systems division of Seagate Technology. The division was formed in 1996 from storage companies Archive Corporation, Irwin Magnetic Systems, Cipher Data Products, and Maynard Electronics. In a restructuring involving Seagate Technology and Veritas Software, the division was spun off in 2000 into the independent company Seagate Removable Storage Systems. The company was the worldwide unit volume shipment leader in 2001, 2002, and 2003.
The company name was changed to "Certance" in 2003. In 2004, Quantum Corporation announced plans to acquire Certance. The acquisition was completed in 2005, whereupon Certance ceased to exist as an independent company.
References
Computer storage companies
Companies based in Costa Mesa, California
Defunct computer hardware companies
1996 establishments in California
2005 establishments in California
2005 mergers and acquisitions
Computer companies established in 1996
Computer companies disestablished in 2005
Defunct computer companies of the United States
Tape-based computer storage | Certance | [
"Technology"
] | 294 | [
"Computing stubs",
"Computer company stubs"
] |
3,000,756 | https://en.wikipedia.org/wiki/Proportional-fair%20scheduling | Proportional-fair scheduling is a compromise-based scheduling algorithm. It is based upon maintaining a balance between two competing interests: Trying to maximize the total throughput of the network (wired or not) while at the same time allowing all users at least a minimal level of service. This is done by assigning each data flow a data rate or a scheduling priority (depending on the implementation) that is inversely proportional to its anticipated resource consumption.
Weighted fair queuing
Proportionally fair scheduling can be achieved by means of weighted fair queuing (WFQ), by setting the scheduling weights for data flow to , where the cost is the amount of consumed resources per data bit. For instance:
In CDMA spread spectrum cellular networks, the cost may be the required energy per bit in the transmit power control (the increased interference level).
In wireless communication with link adaptation, the cost may be the required time to transmit a certain number of bits using the modulation and error coding scheme that this required. An example of this is EVDO networks, where reported SNR is used as the primary costing factor.
In wireless networks with fast Dynamic Channel Allocation, the cost may be the number of nearby base station sites that can not use the same frequency channel simultaneously, in view to avoid co-channel interference.
User prioritization
Another way to schedule data transfer that leads to similar results is through the use of prioritization coefficients. Here we schedule the channel for the station that has the maximum of the priority function:
denotes the data rate potentially achievable for the station in the present time slot.
is the historical average data rate of this station.
and tune the "fairness" of the scheduler.
By adjusting and in the formula above, we are able to adjust the balance between serving the best mobiles (the ones in the best channel conditions) more often and serving the costly mobiles often enough that they have an acceptable level of performance.
In the extreme case ( and ) the scheduler acts in a "packet" round-robin fashion and serves all mobiles one after the other (but not equally often in time), with no regard for resource consumption, and such that each user gets the same amount of data. The ( and ) scheduler could be called "maximum fairness scheduler" (to be used to provide equal throughout to voice users for example). If and then the scheduler will always serve the mobile with the best channel conditions. This will maximize the throughput of the channel while stations with low are not served at all. The ( and ) scheduler could be called "max rate" scheduler. Using and will yield the proportional fair scheduling algorithm used in 3G networks. The ( and ) scheduler could be implemented by providing the same amount of time & spectrum for each user, irrespective of the desired packet size, channel quality and data rate (MCS) used. The proportional fair ( and ) scheduler could be called "equal effort scheduler" or "time/spectrum Round Robin scheduler".
This technique can be further parametrized by using a "memory constant" that determines the period of time over which the station data rate used in calculating the priority function is averaged. A larger constant generally improves throughput at the expense of reduced short-term fairness.
See also
Scheduling (computing) - an introduction to the general topic of scheduling.
Round-robin scheduling - a different scheduling algorithm.
Proportional-fair rule - a more general rule for selecting among different alternatives, based on the same principle of balancing efficiency and fairness.
References
Further reading
Radio resource management
Wireless
Mobile telecommunications
Network scheduling algorithms
Fair division protocols | Proportional-fair scheduling | [
"Technology",
"Engineering"
] | 736 | [
"Wireless",
"Mobile telecommunications",
"Telecommunications engineering"
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3,000,842 | https://en.wikipedia.org/wiki/Unique%20games%20conjecture | In computational complexity theory, the unique games conjecture (often referred to as UGC) is a conjecture made by Subhash Khot in 2002. The conjecture postulates that the problem of determining the approximate value of a certain type of game, known as a unique game, has NP-hard computational complexity. It has broad applications in the theory of hardness of approximation. If the unique games conjecture is true and P ≠ NP, then for many important problems it is not only impossible to get an exact solution in polynomial time (as postulated by the P versus NP problem), but also impossible to get a good polynomial-time approximation. The problems for which such an inapproximability result would hold include constraint satisfaction problems, which crop up in a wide variety of disciplines.
The conjecture is unusual in that the academic world seems about evenly divided on whether it is true or not.
Formulations
The unique games conjecture can be stated in a number of equivalent ways.
Unique label cover
The following formulation of the unique games conjecture is often used in hardness of approximation. The conjecture postulates the NP-hardness of the following promise problem known as label cover with unique constraints. For each edge, the colors on the two vertices are restricted to some particular ordered pairs. Unique constraints means that for each edge none of the ordered pairs have the same color for the same node.
This means that an instance of label cover with unique constraints over an alphabet of size k can be represented as a directed graph together with a collection of permutations πe: [k] → [k], one for each edge e of the graph. An assignment to a label cover instance gives to each vertex of G a value in the set [k] = {1, 2, ... k}, often called “colours.”
Such instances are strongly constrained in the sense that the colour of a vertex uniquely defines the colours of its neighbours, and hence for its entire connected component. Thus, if the input instance admits a valid assignment, then such an assignment can be found efficiently by iterating over all colours of a single node. In particular, the problem of deciding if a given instance admits a satisfying assignment can be solved in polynomial time.
The value of a unique label cover instance is the fraction of constraints that can be satisfied by any assignment. For satisfiable instances, this value is 1 and is easy to find. On the other hand, it seems to be very difficult to determine the value of an unsatisfiable game, even approximately. The unique games conjecture formalises this difficulty.
More formally, the (c, s)-gap label-cover problem with unique constraints is the following promise problem (Lyes, Lno):
Lyes = {G: Some assignment satisfies at least a c-fraction of constraints in G}
Lno = {G: Every assignment satisfies at most an s-fraction of constraints in G}
where G is an instance of the label cover problem with unique constraints.
The unique games conjecture states that for every sufficiently small pair of constants ε, δ > 0, there exists a constant k such that the (1 − δ, ε)-gap label-cover problem with unique constraints over alphabet of size k is NP-hard.
Maximizing Linear Equations Modulo k
Consider the following system of linear equations over the integers modulo k:
When each equation involves exactly two variables, this is an instance of the label cover problem with unique constraints; such instances are known as instances of the Max2Lin(k) problem. It is not immediately obvious that the inapproximability of Max2Lin(k) is equivalent to the UGC, but this is in fact the case, by a reduction. Namely, the UGC is equivalent to: for every sufficiently small pair of constants ε, δ > 0, there exists a constant k such that the (1 − δ, ε)-gap Max2Lin(k) problem is NP-hard.
Connection with computational topology
It has been argued that the UGC is essentially a question of computational topology, involving local-global principles (the latter are also evident in the proof of the 2-2 Games Conjecture, see below).
Linial observed that unique label cover is an instance of the Maximum Section of a Covering Graph problem (covering graphs is the terminology from topology; in the context of unique games these are often referred to as graph lifts). To date, all known problems whose inapproximability is equivalent to the UGC are instances of this problem, including Unique Label Cover and Max2Lin(k). When the latter two problems are viewed as instances of Max Section of a Covering Graph, the reduction between them preserves the structure of the graph covering spaces, so not only the problems, but the reduction between them has a natural topological interpretation. Grochow and Tucker-Foltz exhibited a third computational topology problem whose inapproximability is equivalent to the UGC: 1-Cohomology Localization on Triangulations of 2-Manifolds.
Two-prover proof systems
A unique game is a special case of a two-prover one-round (2P1R) game. A two-prover one-round game has two players (also known as provers) and a referee. The referee sends each player a question drawn from a known probability distribution, and the players each have to send an answer. The answers come from a set of fixed size. The game is specified by a predicate that depends on the questions sent to the players and the answers provided by them.
The players may decide on a strategy beforehand, although they cannot communicate with each other during the game. The players win if the predicate is satisfied by their questions and their answers.
A two-prover one-round game is called a unique game if for every question and every answer by the first player, there is exactly one answer by the second player that results in a win for the players, and vice versa. The value of a game is the maximum winning probability for the players over all strategies.
The unique games conjecture states that for every sufficiently small pair of constants ε, δ > 0, there exists a constant k such that the following promise problem (Lyes, Lno) is NP-hard:
Lyes = {G: the value of G is at least 1 − δ}
Lno = {G: the value of G is at most ε}
where G is a unique game whose answers come from a set of size k.
Probabilistically checkable proofs
Alternatively, the unique games conjecture postulates the existence of a certain type of probabilistically checkable proof for problems in NP.
A unique game can be viewed as a special kind of nonadaptive probabilistically checkable proof with query complexity 2, where for each pair of possible queries of the verifier and each possible answer to the first query, there is exactly one possible answer to the second query that makes the verifier accept, and vice versa.
The unique games conjecture states that for every sufficiently small pair of constants there is a constant such that every problem in NP has a probabilistically checkable proof over an alphabet of size with completeness , soundness , and randomness complexity which is a unique game.
Relevance
The unique games conjecture was introduced by Subhash Khot in 2002 in order to make progress on certain questions in the theory of hardness of approximation.
The truth of the unique games conjecture would imply the optimality of many known approximation algorithms (assuming P ≠ NP). For example, the approximation ratio achieved by the algorithm of Goemans and Williamson for approximating the maximum cut in a graph is optimal to within any additive constant assuming the unique games conjecture and P ≠ NP.
A list of results that the unique games conjecture is known to imply is shown in the adjacent table together with the corresponding best results for the weaker assumption P ≠ NP. A constant of or means that the result holds for every constant (with respect to the problem size) strictly greater than or less than , respectively.
Discussion and alternatives
Currently, there is no consensus regarding the truth of the unique games conjecture. Certain stronger forms of the conjecture have been disproved.
A different form of the conjecture postulates that distinguishing the case when the value of a unique game is at least from the case when the value is at most is impossible for polynomial-time algorithms (but perhaps not NP-hard). This form of the conjecture would still be useful for applications in hardness of approximation.
The constant in the above formulations of the conjecture is necessary unless P = NP. If the uniqueness requirement is removed the corresponding statement is known to be true by the parallel repetition theorem, even
Results
Marek Karpinski and Warren Schudy have constructed linear time approximation schemes for dense instances of unique games problem.
In 2008, Prasad Raghavendra has shown that if the unique games conjecture is true, then for every constraint satisfaction problem the best approximation ratio is given by a certain simple semidefinite programming instance, which is in particular polynomial.
In 2010, Prasad Raghavendra and David Steurer defined the gap-small-set expansion problem, and conjectured that it is NP-hard. The resulting small set expansion hypothesis implies the unique games conjecture. It has also been used to prove strong hardness of approximation results for finding complete bipartite subgraphs.
In 2010, Sanjeev Arora, Boaz Barak and David Steurer found a subexponential time approximation algorithm for the unique games problem. A key ingredient in their result was the spectral algorithm of Alexandra Kolla (see also the earlier manuscript of A. Kolla and Madhur Tulsiani). The latter also re-proved that unique games on expander graphs could be solved in polynomial time, and was one of (if not the) first graph algorithms to take advantage of the full spectrum of a graph rather than just its first two eigenvalues.
In 2012, it was shown that distinguishing instances with value at most from instances with value at least is NP-hard.
In 2018, after a series of papers, a weaker version of the conjecture, called the 2-2 games conjecture, was proven. In a certain sense, this proves "a half" of the original conjecture. This also improves the best known gap for unique label cover: it is NP-hard to distinguish instances with value at most from instances with value at least .
References
Further reading
.
2002 in computing
Approximation algorithms
Computational complexity theory
Computational hardness assumptions
Unsolved problems in computer science
Conjectures | Unique games conjecture | [
"Mathematics"
] | 2,167 | [
"Unsolved problems in mathematics",
"Unsolved problems in computer science",
"Approximation algorithms",
"Conjectures",
"Mathematical relations",
"Mathematical problems",
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3,000,968 | https://en.wikipedia.org/wiki/Solvatochromism | In chemistry, solvatochromism is the phenomenon observed when the colour of a solution is different when the solute is dissolved in different solvents.
The solvatochromic effect is the way the spectrum of a substance (the solute) varies when the substance is dissolved in a variety of solvents. In this context, the dielectric constant and hydrogen bonding capacity are the most important properties of the solvent. With various solvents there is a different effect on the electronic ground state and excited state of the solute, so that the size of energy gap between them changes as the solvent changes. This is reflected in the absorption or emission spectrum of the solute as differences in the position, intensity, and shape of the spectroscopic bands. When the spectroscopic band occurs in the visible part of the electromagnetic spectrum, solvatochromism is observed as a change of colour. This is illustrated by Reichardt's dye, as shown in the image.
Negative solvatochromism corresponds to a hypsochromic shift (or blue shift) with increasing solvent polarity. An examples of negative solvatochromism is provided by 4-(4-hydroxystyryl)-N-methylpyridinium iodide, which is red in 1-propanol, orange in methanol, and yellow in water.
Positive solvatochromism corresponds to a bathochromic shift (or red shift) with increasing solvent polarity. An example of positive solvatochromism is provided by 4,4'-bis(dimethylamino)fuchsone, which is orange in toluene, red in acetone.
The main value of the concept of solvatochromism is the context it provides to predict colors of solutions. Solvatochromism can in principle be used in sensors and in molecular electronics for construction of molecular switches. Solvatochromic dyes are used to measure solvent parameters, which can be used to explain solubility phenomena and predict suitable solvents for particular uses.
Solvatochromism of the photoluminescence/fluorescence of carbon nanotubes has been identified and used for optical sensor applications. In one such application, the wavelength of the fluorescence of peptide-coated carbon nanotubes was found to change when exposed to explosives, facilitating detection. However, more recently the small chromophore solvatochromism hypothesis has been challenged for carbon nanotubes in light of older and newer data showing electrochromic behavior. These and other observations regarding non-linear processes on the semiconducting nanotube suggest colloidal models will require new interpretations that are in line with classic semiconductor optical processes, including electrochemical processes, rather than small molecule physical descriptions. Conflicting hypotheses may be due to the fact the nanotube is only a single atom thick material interface unlike other "bulk" nanomaterials.
References
Further reading
External links
Negative solvatochromism experiment
Positive solvatochromism experiment
Chromism
Absorption spectroscopy | Solvatochromism | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 630 | [
"Spectrum (physical sciences)",
"Chromism",
"Materials science",
"Absorption spectroscopy",
"Smart materials",
"Spectroscopy"
] |
3,000,978 | https://en.wikipedia.org/wiki/Ionochromism | Ionochromism, similar to chromic methods such as photochromism, thermochromism and other chromism phenomena, is the reversible process of changing the color of a material by absorption or emission spectra of molecules using ions. Electrochromism is similar to ionochromism as it involves the use of electrons in order to change the color of materials. Both electrochromic and ionochromic materials undergo a change in color by the flow of charged particles, where electrochromic materials only involve an anionic species or negatively charged species such as electrons. An example of an ionochromic dye is a complexometric indicator. A complexometric indicator involves the presence of metal ions in order to facilitate color change and is often used in complexometric titration.
Overview
Ionochromism is the process of reacting an ionochromic material with a charged species, or a positively or negatively charged ion. Materials that have ionochromic properties exhibit reversible color change, where the absence of a stimulus such as an ionic species can result in the compound changing to its original color.
Various ionic color changing mechanisms that are used in chromic processes can be used in ionochromism, including:
Halochromism
Acidochromism
Metallochromism
Molecules with Ionochromic Properties
Ionochromic materials exist in a wide range of molecules, including organic molecules, pH-sensitive dyes and indicators, and other color-changing compounds with chromophores. Some of these molecules include phthalides, fluorans, and leucotriarylmethanes.
Ionochromic materials
Applications
Carbonless copy paper
Analytical chemistry
Lithographic process for printing plates
Direct thermal printing
References
Chromism
Complexometric indicators | Ionochromism | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 368 | [
"Spectrum (physical sciences)",
"Chromism",
"Materials science",
"Complexometric indicators",
"Smart materials",
"Spectroscopy"
] |
3,000,988 | https://en.wikipedia.org/wiki/Halochromism | A halochromic material is a material which changes colour when pH changes occur. The term ‘chromic’ is defined for materials that can change colour reversibly with the presence of an external factor. In this case, the factor is pH. One class of compounds with this property are pH indicators.
Halochromic substances are suited for use in environments where pH changes occur frequently, or places where changes in pH are extreme. Halochromic substances detect alterations in the acidity of substances, like detection of corrosion in metals.
Halochromic substances may be used as indicators to determine the pH of solutions of unknown pH. The colour obtained is compared with the colour obtained when the indicator is mixed with solutions of known pH. The pH of the unknown solution can then be estimated. Obvious disadvantages of this method include its dependency on the colour sensitivity of the human eye, and that unknown solutions that are already coloured cannot be used.
The colour change of halochromic substances occur when the chemical binds to existing hydrogen and hydroxide ions in solution. Such bonds result in changes in the conjugated systems of the molecule, or the range of electron flow. This alters the wavelength of light absorbed, which in turn results in a visible change of colour. Halochromic substances do not display a full range of colour for a full range of pH because, after certain acidities, the conjugated system will not change. The various shades result from different concentrations of halochromic molecules with different conjugated systems.
References
Chromism | Halochromism | [
"Physics",
"Chemistry",
"Materials_science",
"Astronomy",
"Engineering"
] | 318 | [
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"Spectrum (physical sciences)",
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"Materials science",
"Smart materials",
"Molecular physics stubs",
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] |
3,000,994 | https://en.wikipedia.org/wiki/Tribochromism | Tribochromism refers to a change in colour of a material caused by mechanical friction, similar to piezochromism, the change in colour of a material caused by pressure. It is a property of some materials and is often associated with thermochromism. Tribochromism and piezochromism are often grouped together under the term mechanochromism.
Tribochromatic materials may be used in sensors when friction has to be detected. These materials generally change colour under mechanical stress conditions; the colour gradually fades once the stress is removed.
See also
Triboluminescence – An optical phenomenon in which light is generated when material is subject to mechanical stress
Chromism
References | Tribochromism | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 146 | [
"Spectrum (physical sciences)",
"Chromism",
"Materials science",
"Smart materials",
"Spectroscopy"
] |
3,001,016 | https://en.wikipedia.org/wiki/Mehmaan%20khana | A mehmaan khana (Hindustani مہمان خانہ, मेहमान ख़ाना, ) is a drawing room where guests are entertained in many houses in North India, Bangladesh and Pakistan. Alternative names include hujra and baithak. These rooms were a typical feature of many Mughal era havelis palaces and mansions in the region. Many houses in the rural areas of Bangladesh, Pakistan and India still have mehmaan khanas for guests. In Bangladesh, it is more commonly known as baithak ghar or bangla ghar ().
Etymology
The term mehmān khānā is direct derivation from Persian and means "guest house" or "room". In Iran and adjoining areas, the term can refer to hotels. The term (also spelled memonkhona in Latin script) is also used to describe a guest room in other parts of Central Asia. The term baithak (بیٹهک, बैठक or বৈঠক) literally means sitting room in Hindustani and Bengali. Hujra is derived from Arabic and means room or cell. In non-Pashtun Muslim households or North India and Pakistan, the term hujra (حجره, हुजरा or হুজরা) can also refer to a dedicated prayer room. In Bangladesh, hujra usually refers to the sitting room of the imam in a mosque.
Hujra
The term hujra is especially prevalent in the predominantly Pashtun areas of Pakistan. Pashtun hujras are used mainly to entertain male guests in a household, although sometimes community hujras are also maintained by tribal units. In individual houses, the size and trappings of a hujra are sometimes indicative of family status.
As old as perhaps the Jirga itself is, Hujra is a community club situated in each village, each Khail (street) and some times owned by a well off family but shared by the whole community. Other than a place to accommodate collective ceremonies, male members of the community who hang out and associate like a larger family regularly attend hujra(s). Members of a Hujra are mostly close relatives but other people from neighborhood are also welcomed. Elderly people spend their day to enjoy hubble-bubble and chat over the tea, younger men in their spare time listen to the stories of elders and raise issues while the children keep playing around, waiting for a call from one of the elders to take a message or bring fresh tea. A guest house for male guests, Hujra also serves as a place to initiate Jirgas. Issues are put on the table, brainstormed and a consensus is developed before the issue can be put to the wider community. Hujra is considered to be a secular place but closely associated with Hujra is the role of mosque in the neighborhood. Although there are few similarities between a mosque and a Hujra, the role of mosque has gained more importance recently due to many national and regional settings tilted towards Islamization. Additionally, the role of Hujra is diminishing from community life because of the economic trends, and a faster pace of life which allows little leisure time with people to spare for community based activities. Decay in the institution of Hujra is definitely affecting the efficacy of Jirga, but this study tends not necessarily to argue for reinvigoration of Hujra; rather our focus will remain to find strengths and challenges for Jirga from where it is today and move forward.
Mehmaan Khana
To the east side of the Taj Mahal is a guest house or mehmankhana resembling the mosque Naqqar Khana, which gives symmetry to the facade.
References
Rooms
Culture of India
Culture of Bengal
Culture of Bangladesh
Culture of Pakistan
Architecture in Bangladesh
Architecture in Pakistan
Architecture in India | Mehmaan khana | [
"Engineering"
] | 780 | [
"Rooms",
"Architecture"
] |
3,001,241 | https://en.wikipedia.org/wiki/PCP%20theorem | In computational complexity theory, the PCP theorem (also known as the PCP characterization theorem) states that every decision problem in the NP complexity class has probabilistically checkable proofs (proofs that can be checked by a randomized algorithm) of constant query complexity and logarithmic randomness complexity (uses a logarithmic number of random bits).
The PCP theorem says that for some universal constant K, for every n, any mathematical proof for a statement of length n can be rewritten as a different proof of length poly(n) that is formally verifiable with 99% accuracy by a randomized algorithm that inspects only K letters of that proof.
The PCP theorem is the cornerstone of the theory of computational hardness of approximation, which investigates the inherent difficulty in designing efficient approximation algorithms for various optimization problems. It has been described by Ingo Wegener as "the most important result in complexity theory since Cook's theorem" and by Oded Goldreich as "a culmination of a sequence of impressive works […] rich in innovative ideas".
Formal statement
The PCP theorem states that
NP = PCP[O(log n), O(1)],
where PCP[r(n), q(n)] is the class of problems for which a probabilistically checkable proof of a solution can be given, such that the proof can be checked in polynomial time using r(n) bits of randomness and by reading q(n) bits of the proof, correct proofs are always accepted, and incorrect proofs are rejected with probability at least 1/2. n is the length in bits of the description of a problem instance. Note further that the verification algorithm is non-adaptive: the choice of bits of the proof to check depend only on the random bits and the description of the problem instance, not the actual bits of the proof.
PCP and hardness of approximation
An alternative formulation of the PCP theorem states that the maximum fraction of satisfiable constraints of a constraint satisfaction problem is NP-hard to approximate within some constant factor.
Formally, for some constants q and α < 1, the following promise problem (Lyes, Lno) is an NP-hard decision problem:
Lyes = {Φ: all constraints in Φ are simultaneously satisfiable}
Lno = {Φ: every assignment satisfies fewer than an α fraction of Φ's constraints},
where Φ is a constraint satisfaction problem (CSP) over a Boolean alphabet with at most q variables per constraint.
The connection to the class PCP mentioned above can be seen by noticing that checking a constant number of bits q in a proof can be seen as evaluating a constraint in q Boolean variables on those bits of the proof. Since the verification algorithm uses O(log n) bits of randomness, it can be represented as a CSP as described above with poly(n) constraints. The other characterisation of the PCP theorem then guarantees the promise condition with α = 1/2: if the NP problem's answer is yes, then every constraint (which corresponds to a particular value for the random bits) has a satisfying assignment (an acceptable proof); otherwise, any proof should be rejected with probability at least 1/2, which means any assignment must satisfy fewer than 1/2 of the constraints (which means it will be accepted with probability lower than 1/2). Therefore, an algorithm for the promise problem would be able to solve the underlying NP problem, and hence the promise problem must be NP hard.
As a consequence of this theorem, it can be shown that the solutions to many natural optimization problems including maximum boolean formula satisfiability, maximum independent set in graphs, and the shortest vector problem for lattices cannot be approximated efficiently unless P = NP. This can be done by reducing the problem of approximating a solution to such problems to a promise problem of the above form. These results are sometimes also called PCP theorems because they can be viewed as probabilistically checkable proofs for NP with some additional structure.
Proof
A proof of a weaker result, is given in one of the lectures of Dexter Kozen.
History
The PCP theorem is the culmination of a long line of work on interactive proofs and probabilistically checkable proofs. The first theorem relating standard proofs and probabilistically checkable proofs is the statement that NEXP ⊆ PCP[poly(n), poly(n)], proved by .
Origin of the initials
The notation PCPc(n), s(n)[r(n), q(n)] is explained at probabilistically checkable proof. The notation is that of a function that returns a certain complexity class. See the explanation mentioned above.
The name of this theorem (the "PCP theorem") probably comes either from "PCP" meaning "probabilistically checkable proof", or from the notation mentioned above (or both).
First theorem [in 1990]
Subsequently, the methods used in this work were extended by Babai, Lance Fortnow, Levin, and Szegedy in 1991 ,
Feige, Goldwasser, Lund, Safra, and Szegedy (1991), and Arora and Safra in 1992 to yield a proof of the PCP theorem by Arora, Lund, Motwani, Sudan, and Szegedy in 1998 .
The 2001 Gödel Prize was awarded to Sanjeev Arora, Uriel Feige, Shafi Goldwasser, Carsten Lund, László Lovász, Rajeev Motwani, Shmuel Safra, Madhu Sudan, and Mario Szegedy for work on the PCP theorem and its connection to hardness of approximation.
In 2005 Irit Dinur discovered a significantly simpler proof of the PCP theorem, using expander graphs. She received the 2019 Gödel Prize for this.
Quantum analog
In 2012, Thomas Vidick and Tsuyoshi Ito published a result that showed a "strong limitation on the ability of entangled provers to collude in a multiplayer game". This could be a step toward proving the quantum analogue of the PCP theorem, since when the result was reported in the media, professor Dorit Aharonov called it "the quantum analogue of an earlier paper on multiprover interactive proofs" that "basically led to the PCP theorem".
In 2018, Thomas Vidick and Anand Natarajan proved a games variant of quantum PCP theorem under randomized reduction. It states that , where is a complexity class of multi-prover quantum interactive proofs systems with f(n)-bit classical communications, and the completeness is c and the soundness is s. They also showed that the Hamiltonian version of a quantum PCP conjecture, namely a local Hamiltonian problem with constant promise gap is QMA-hard, implies the games quantum PCP theorem.
NLTS conjecture was a fundamental unresolved obstacle and precursor to a quantum analog of PCP. The NLTS conjecture was proven in 2022 by Anurag Anshu, Nikolas Breuckmann, and Chinmay Nirkhe.
Notes
References
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.
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Randomized algorithms
Theorems in computational complexity theory
Quantum information theory | PCP theorem | [
"Mathematics"
] | 1,512 | [
"Theorems in computational complexity theory",
"Theorems in discrete mathematics"
] |
3,001,409 | https://en.wikipedia.org/wiki/Rubidium%20hydride | Rubidium hydride is the hydride of rubidium. With the formula RbH, it is classified as an alkali metal hydride. It is a white solid and is insoluble in most solvents. It is synthesized by treating rubidium metal with hydrogen. Rubidium hydride is a powerful superbase and reacts violently with water.
References
Rubidium compounds
Metal hydrides
Superbases
Rock salt crystal structure | Rubidium hydride | [
"Chemistry"
] | 93 | [
"Superbases",
"Inorganic compounds",
"Reducing agents",
"Inorganic compound stubs",
"Metal hydrides",
"Bases (chemistry)"
] |
3,001,461 | https://en.wikipedia.org/wiki/Embryonal%20carcinoma | Embryonal carcinoma is a relatively uncommon type of nonseminomatous germ cell tumour that occurs in the ovaries and testes.
Signs and symptoms
The presenting features may be a palpable testicular mass or asymmetric testicular enlargement in some cases. The tumour may present as signs and symptoms relating to the presence of widespread metastases, without any palpable lump in the testis. The clinical features associated with metastasising embryonal carcinoma may include low back pain, dyspnoea, cough, haemoptysis, haematemesis and neurologic abnormalities.
Males with pure embryonal carcinoma tend to have a normal amount of the protein alpha-fetoprotein in the fluid component of their blood. The finding of elevated amounts of alpha-fetoprotein is more suggestive of a mixed germ cell tumour, with the alpha-fetoprotein being released by the yolk sac tumour component.
Diagnosis
The gross examination usually shows a two to three centimetre pale grey, poorly defined tumour with associated haemorrhage and necrosis.
The microscopic features include: indistinct cell borders, mitoses, a variable architecture (tubulopapillary, glandular, solid, embryoid bodies – ball of cells surrounded by empty space on three sides), nuclear overlap, and necrosis.
Solid (55%), glandular (17%), and papillary (11%) are the most common primary patterns (predominant architectural pattern occupying at least 50%). Other less common primary patterns included nested (3%), micropapillary (2%), anastomosing glandular (1%), sieve-like glandular (<1%), pseudopapillary (<1%), and blastocyst-like (<1%).
Testicular embryonal carcinoma occurs mostly (84%) as a component of a mixed germ cell tumor, but 16% are pure. Occasionally, embryonal carcinoma develops predominantly in the context of polyembryoma-like (6%) and diffuse embryoma-like ("necklace" pattern) (3%) proliferations.
Ovarian
In the ovary, embryonal carcinoma is quite rare, amounting to approximately three percent of ovarian germ cell tumours. The median age at diagnosis is 15 years. Symptoms and signs are varied, and may include sexual precocity and abnormal (increased, reduced or absent) uterine bleeding.
There may be elevations in serum human chorionic gonadotropin (hCG) and alpha fetoprotein (AFP) levels but it would be in association with other tumors, (e.g. yolk sac tumor) because they themselves do not produce the serum markers. At surgery, there is extension of the tumour beyond the ovary in forty percent of cases. They are generally large, unilateral tumours, with a median diameter of 17 centimetres. Long-term survival has improved following the advent of chemotherapy. The gross and histologic features of this tumour are similar to that seen in the testis.
Testicular
In the testis pure embryonal carcinoma is also uncommon, and accounts for approximately ten percent of testicular germ cell tumours. However, it is present as a component of almost ninety percent of mixed nonseminomatous germ cell tumours. The average age at diagnosis is 31 years, and typically presents as a testicular lump which may be painful. One-fifth to two-thirds of patients with tumours composed predominantly of embryonal carcinoma have metastases at diagnosis.
Differential diagnosis
An important key to distinguish it from other tumors, such as seminoma (vacuolated), teratocarcinoma (three differentiated germ layers), yolk sac tumor (Schiller–Duval bodies), and the Sertoli–Leydig cell tumor (strings of glands), is that the embryonal carcinoma cells are "trying" to evolve into their next stage of development. So in the testicle, they are often observed as blue cells attempting to form primitive tubules.
References
External links
Embryonal carcinoma at NIH Genetic and Rare Diseases Information Center
Embryonal Carcinoma: What to Know About This Rare Testicular Cancer at Healthgrades.com
Male genital neoplasia
Gynaecological neoplasia
Germ cell neoplasia
Histopathology | Embryonal carcinoma | [
"Chemistry"
] | 955 | [
"Histopathology",
"Microscopy"
] |
3,001,690 | https://en.wikipedia.org/wiki/JDBC%20driver | A JDBC driver is a software component enabling a Java application to interact with a database. JDBC drivers are analogous to ODBC drivers, ADO.NET data providers, and OLE DB providers.
To connect with individual databases, JDBC (the Java Database Connectivity API) requires drivers for each database. The JDBC driver gives out the connection to the database and implements the protocol for transferring the query and result between client and database.
JDBC technology drivers fit into one of four categories.
JDBC-ODBC bridge
Native-API driver
Network-Protocol driver (Middleware driver)
Database-Protocol driver (Pure Java driver) or thin driver.
Type 1 driver – JDBC-ODBC bridge
The JDBC type 1 driver, also known as the JDBC-ODBC bridge, is a dbase driver implementation that employs the ODBC driver to connect to the database. The driver converts JDBC method calls into ODBC function calls.
The driver is platform-dependent as it makes use of ODBC which in turn depends on native libraries of the underlying operating system the JVM is running upon. Also, use of this driver leads to other installation dependencies; for example, ODBC must be installed on the computer having the driver and the database must support an ODBC driver. The use of this driver is discouraged if the alternative of a pure-Java driver is available. The other implication is that any application using a type 1 driver is non-portable given the binding between the driver and platform. This technology isn't suitable for a high-transaction environment. Type 1 drivers also don't support the complete Java command set and are limited by the functionality of the ODBC driver.
Sun (now Oracle) provided a JDBC-ODBC Bridge driver: sun.jdbc.odbc.JdbcOdbcDriver. This driver is native code and not Java, and is closed source. Sun's/Oracle's JDBC-ODBC Bridge was removed in Java 8 (other vendors' are available).
If a driver has been written so that loading it causes an instance to be created and also calls DriverManager.registerDriver with that instance as the parameter, then it is in the DriverManager's list of drivers and available for creating a connection.
It may sometimes be the case that more than one JDBC driver is capable of connecting to a given URL. For example, when connecting to a given remote database, it might be possible to use a JDBC-ODBC bridge driver, a JDBC-to-generic-network-protocol driver, or a driver supplied by the database vendor. In such cases, the order in which the drivers are tested is significant because the DriverManager will use the first driver it finds that can successfully connect to the given URL.
First the DriverManager tries to use each driver in the order it was registered. (The drivers listed in jdbc.drivers are always registered first.) It will skip any drivers that are untrusted code unless they have been loaded from the same source as the code that is trying to open the connection.
It tests the drivers by calling the method Driver.connect on each one in turn, passing them the URL that the user originally passed to the method DriverManager.getConnection. The first driver that recognizes the URL makes the connection.
Advantages
Almost any database for which an ODBC driver is installed can be accessed, and data can be retrieved.
Disadvantages
Performance overhead since the calls have to go through the JDBC (java database connectivity) bridge to the ODBC (open database connectivity) driver, then to the native database connectivity interface (thus may be slower than other types of drivers).
The ODBC driver needs to be installed on the client machine.
Not suitable for applets, because the ODBC driver needs to be installed on the client.
Specific ODBC drivers are not always available on all platforms; hence, portability of this driver is limited.
No support from JDK 1.8 (Java 8).
Type 2 driver – Native-API driver
The JDBC type 2 driver, also known as the Native-API driver, is a database driver implementation that uses the client-side libraries of the database. The driver converts JDBC method calls into native calls of the database API. For example: Oracle OCI driver is a type 2 driver.
Advantages
As there is no implementation of JDBC-ODBC bridge, it may be considerably faster than a Type 1 driver.
Disadvantages
The vendor client library needs to be installed on the client machine.
Not all databases have a client-side library.
This driver is platform dependent.
This driver supports all Java applications except applets.
Type 3 driver – Network-Protocol driver (middleware driver)
The JDBC type 3 driver, also known as the Pure Java driver for database middleware, is a database driver implementation which makes use of a middle tier between the calling program and the database. The middle-tier (application server) converts JDBC calls directly or indirectly into a vendor-specific database protocol.
This differs from the type 4 driver in that the protocol conversion logic resides not at the client, but in the middle-tier. Like type 4 drivers, the type 3 driver is written entirely in Java.
The same client-side JDBC driver may be used for multiple databases. It depends on the number of databases the middleware has been configured to support. The type 3 driver is platform-independent as the platform-related differences are taken care of by the middleware. Also, making use of the middleware provides additional advantages of security and firewall access.
Functions
Sends JDBC API calls to a middle-tier net server that translates the calls into the DBMS-specific network protocol. The translated calls are then sent to a particular DBMS.
Follows a three-tier communication approach.
Can interface to multiple databases – Not vendor specific.
The JDBC Client driver written in java, communicates with a middleware-net-server using a database independent protocol, and then this net server translates this request into database commands for that database.
Thus the client driver to middleware communication is database independent.
Advantages
Since the communication between client and the middleware server is database independent, there is no need for the database vendor library on the client. The client need not be changed for a new database.
The middleware server (which can be a full-fledged J2EE Application server) can provide typical middleware services like caching (of connections, query results, etc.), load balancing, logging, and auditing.
A single driver can handle any database, provided the middleware supports it.
E.g.: IDA Server
Disadvantages
Requires database-specific coding to be done in the middle tier.
The middleware layer added may result in additional latency, but is typically overcome by using better middleware services.
Type 4 driver – Database-Protocol driver/Thin Driver (Pure Java driver)
The JDBC type 4 driver, also known as the Direct to Database Pure Java Driver, is a database driver implementation that converts JDBC calls directly into a vendor-specific database protocol.
Written completely in Java, type 4 drivers are thus platform independent. They install inside the Java virtual machine of the client. This provides better performance than the type 1 and type 2 drivers as it does not have the overhead of conversion of calls into ODBC or database API calls. Unlike the type 3 drivers, it does not need associated software to work.
As the database protocol is vendor specific, the JDBC client requires separate drivers, usually vendor supplied, to connect to different types of databases.
Advantages
Completely implemented in Java to achieve platform independence.
These drivers don't translate the requests into an intermediary format (such as ODBC).
The client application connects directly to the database server. No translation or middleware layers are used, improving performance.
The JVM can manage all aspects of the application-to-database connection; this can facilitate debugging.
Disadvantages
Drivers are database specific, as different database vendors use widely different (and usually proprietary) network protocols.
See also
ADO.NET
OLE DB
Open Database Connectivity (ODBC)
XQJ (XQuery API for Java)
References
Java platform
Data access technologies | JDBC driver | [
"Technology"
] | 1,707 | [
"Computing platforms",
"Java platform"
] |
3,001,700 | https://en.wikipedia.org/wiki/Crash%20reporter | A crash reporter is usually a system software whose function is to identify reporting crash details and to alert when there are crashes, in production or on development / testing environments. Crash reports often include data such as stack traces, type of crash, trends and version of software. These reports help software developers- Web, SAAS, mobile apps and more, to diagnose and fix the underlying problem causing the crashes. Crash reports may contain sensitive information such as passwords, email addresses, and contact information, and so have become objects of interest for researchers in the field of computer security.
Implementing crash reporting tools as part of the development cycle has become a standard, and crash reporting tools have become a commodity, many of them are offered for free, like Crashlytics.
Many giant industry players, that are part of the software development eco-system have entered the game. Companies such as Twitter, Google and others are putting a lot of efforts on encouraging software developers to use their APIs, knowing this will increase their revenues down the road (through advertisements and other mechanisms). As they realize that they must offer elegant solutions for as many as possible development issues, otherwise their competitors will take actions, they keep adding advanced features. Crash reporting tools make an important development functionality that giant companies include in their portfolio of solutions.
Many crash reporting tools are specialized in mobile app. Many of them are SDKs.
macOS
In macOS there is a standard crash reporter in . Crash Reporter.app sends the Unix crash logs to Apple for their engineers to look at. The top text field of the window has the crash log, while the bottom field is for user comments. Users may also copy and paste the log in their email client to send to the application vendor for them to use. Crash Reporter.app has 3 main modes: display nothing on crash, display "Application has crashed" dialog box or display Crash Report window.
Windows
Microsoft Windows includes a crash reporting service called Windows Error Reporting that prompts users to send crash reports to Microsoft for online analysis. The information goes to a central database run by Microsoft. It consists of diagnostic information that helps the company or development team responsible for the crash to debug and resolve the issue if they choose to do so. Crash reports for third party software are available to third party developers who have been granted access by Microsoft.
The system considers all parts of the debug and release process, such that targeted bug fixes can be applied through Windows Update. In other words, only people experiencing a particular type of crash can be offered the bug fix, thus limiting exposure to an issue.
According to Der Spiegel, the Microsoft crash reporter has been exploited by NSA's Tailored Access Operations (TAO) unit to hack into the computers of Mexico's Secretariat of Public Security. According to the same source, Microsoft crash reports are automatically harvested in NSA's XKeyscore database, in order to facilitate such operations.
CrashRpt
Another error reporting library for Windows is CrashRpt. CrashRpt library is a light-weight open source error handling framework for applications created in Microsoft Visual C++ and running under Windows. The library is distributed under New BSD License.
CrashRpt intercepts unhandled exceptions, creates a crash minidump file, builds a crash descriptor in XML format, presents an interface to allow user to review the crash report, and finally it compresses and sends the crash report to the software support team.
CrashRpt also provides a server-side command line tool for crash report analysis named crprober. The tool is able to read all received crash reports from a directory and generate a summary file in text format for each crash report. It also groups similar crash reports making it easier to determine the most popular problems. The crprober tool does not provide any graphical interface, so it is rather cryptic and difficult to use.
There is also an open-source server software named CrashFix Server that can store, organize and analyze crash reports sent by CrashRpt library. It can group similar crash reports, has a built-in bug tracker and can generate statistical reports. CrashFix server provides a web-based user interface making it possible for several project members to collaborate (upload debugging symbols, browse crash reports and associate bugs with crash reports).
Linux
ABRT
ABRT (Automated Bug Reporting Tool) is an error reporting tool made for Fedora and Red Hat Enterprise Linux. The developers do not currently have plans for porting it to other Linux distributions. ABRT intercepts core dumps or tracebacks from applications and (after user-confirmation) sends bug reports to various bug-tracking systems, such as Fedora Bugzilla .
Ubuntu Error tracker
Ubuntu hosts a public error tracker at errors.ubuntu.com which collects hundreds of thousands of error reports daily from millions of machines. If a program crashes on Ubuntu, a crash handler (such as Apport) will notify the user and offer to report the crash. If the user chooses to report the crash, the details (possibly including a core dump) will be uploaded to an Ubuntu server (daisy.ubuntu.com) for analysis. A core dump is automatically processed to create a stack trace and crash signature. The crash signature is used to classify subsequent crash reports caused by the same error.
GNOME
Bug Buddy is the crash reporting tool used by the GNOME platform. When an application using the GNOME libraries crashes, Bug Buddy generates a stack trace using gdb and invites the user to submit the report to the GNOME bugzilla. The user can add comments and view the details of the crash report.
KDE
The crash reporting tool used by KDE is called Dr. Konqi. When an application using the KDE libraries crashes, Dr. Konqi generates a backtrace using gdb and invites the user to submit the report to the KDE bugzilla. The user can add comments and view the details of the crash report.
Mozilla
Talkback
Talkback (also known as the Quality Feedback Agent) was the crash reporter used by Mozilla software up to version 1.8.1 to report crashes of its products to a centralized server for aggregation or case-by-case analysis. Talkback is proprietary software licensed to the Mozilla Corporation by SupportSoft. If a Mozilla product (e.g. Mozilla Firefox, Mozilla Thunderbird) were to crash with Talkback enabled, the Talkback agent would appear, prompting the user to provide optional information regarding the crash. Talkback does not replace the native OS crash reporter which, if enabled, will appear along with the Talkback agent.
Talkback has been replaced by Breakpad in Firefox since version 3.
Breakpad
Breakpad (previously called Airbag) is an open-source replacement for Talkback. Developed by Google and Mozilla, it is used in current Mozilla products such as Firefox and Thunderbird. Its significance is being the first open source multi-platform crash reporting system.
Since 2007, Breakpad is included in Firefox on Windows and Mac OS X, and Linux. Breakpad is typically paired with Socorro which receives and classifies crashes from users.
Breakpad itself is only part of a crash reporting system, as it includes no reporting mechanism.
Crashpad
Crashpad is an open-source crash reporter used by Google in Chromium. It was developed as a replacement for Breakpad due to an update in macOS 10.10 which removed API's used by Breakpad. Crashpad currently consists of a crash-reporting client and some related tools for macOS and Windows, and is considered substantially complete for those platforms. Crashpad became the crash reporter client for Chromium on macOS as of March 2015, and on Windows as of November 2015.
Mobile OSs
Android and iOS operating systems also have built in crash reporting functionality.
References
External links
How to create useful crash reports using KDE
KernelOops Linux kernel bug count site
ABRT - Automated Bug-Reporting Tool
A review of mobile crash reporting tools
Operating system technology
Software anomalies | Crash reporter | [
"Technology"
] | 1,670 | [
"Computer errors",
"Technological failures",
"Software anomalies"
] |
3,001,849 | https://en.wikipedia.org/wiki/Energy%20Community | The Energy Community, commonly referred to as the Energy Community for South East Europe (ECSEE), is an international organization consisting of the European Union (EU) and a number of non-EU countries. It aims to extend the EU internal energy market to wider Southeast Europe. The members commit to implement relevant EU energy acquis communautaire, to develop an adequate regulatory framework and to liberalize their energy markets in line with the acquis under the founding Treaty.
Aim
The Energy Community aims at establishing a Pan-European energy market by extending the energy acquis of the European Union to the territories of Southeast and Eastern Europe. The Energy Community legal framework covers legislation in the fields of energy, environment, and competition of the EU legislation.
After entry into force, the treaty acquis has been extended on several occasions. It now also includes legislation in relation to security of supply, energy efficiency, oil, renewable energy, statistics, infrastructure and climate.
In line with the update at the EU level, the Energy Community transposes and implements the EU's Third Energy Package since September 2011. The 2021 Ministerial Council adopted five key legislative acts stemming from the EU's Clean energy for all Europeans package. Renewables, energy efficiency and greenhouse gas reduction targets for 2030 will be adopted at the next Ministerial Council in 2022, following the finalization of a study by the European Commission.
Parties, participants and observers
Parties
Parties to the Energy Community Treaty are the European Union and nine Contracting Parties (date of ratification):
After having obtained the observer status, Moldova and Ukraine formally expressed their interest in full membership. Mandated by the Ministerial Council, the European Commission had the first round of formal negotiations with Moldova and Ukraine in late 2008. After three negotiation rounds, the technical negotiations were concluded in 2009. The Ministerial Council, however, made the membership conditional on legislative amendments. In concrete terms, it requested both countries to revise their gas laws and to align them with the EU's Gas Directive 2003/55/EC. Whilst Moldova became a full-fledged member as of 1 May 2010, Ukraine officially acceded to the Energy Community on 1 February 2011.
Georgia applied for full membership in 2014 and joined the organization as a fully-fledged member on 1 July 2017.
Observers
Any other neighbouring third country can obtain an observer status upon approval of a reasoned request by the Ministerial Council. A separate Procedural Act regulates the rights and obligations of the observers to the Treaty. The observers to the treaty are:
Participants
Pursuant to the treaty, any EU member state may obtain the status of a participant. In doing so, the EU member state has the right to attend the Ministerial Council, the Permanent High Level Group, the Regulatory Board and the fora and participate in the discussions in these bodies. This privilege is used by 19 EU member states, namely
Following their accession to the European Union, three of the original treaty signatories, Bulgaria, Croatia and Romania, have matured from a Contracting Party to a Participant.
Institutions
The main institutions established by the treaty are:
Ministerial Council
Permanent High Level Group
Energy Community Regulatory Board (ECRB)
Fora
Secretariat
Ministerial Council
The Ministerial Council is the principal decision-making institution of the Energy Community. It takes the key policy decisions and adopts the Energy Community's rules and procedures. The Ministerial Council is composed of one representative from each Contracting Party, usually the Minister responsible for energy, and of two representatives from the European Union, the European Commissioner for Energy and a high-level representative of the Presidency of the European Union.
Following a decision in December 2009, the Ministerial Council meets once a year. Moreover, the Presidency of the council is held in turn by each contracting party for a term of 12 months. For the period of 1 January to 31 December 2021, Serbia holds the presidency in office and chairs the key institutional meetings.
Permanent High Level Group
The Permanent High Level Group brings together senior officials from each Contracting Party and two representatives of the European Commission. It ensures the continuity of and follow-up to the political meetings by the ministers and decides, in certain cases, on implementing measures.
Energy Community Regulatory Board
The Regulatory Board is composed of high level representatives from the national energy regulatory agencies of the Energy Community Contracting Parties, Observers and Participants. It advises the Energy Community Ministerial Council and Permanent High Level Group (PHLG) on details of statutory, technical and regulatory rules and makes recommendations in the case of cross-border disputes between regulators. The Board can take regulatory measures when empowered by the Energy Community Ministerial Council.
The Board is currently chaired by its President (2020-2023), Mr Marko Bislimoski, President of the Energy and Water Services Regulatory Commission of the Republic of North Macedonia. The European Union, represented by the European Commission, acts as vice-president and is assisted by the Agency for the Cooperation of Energy Regulators (ACER). The Regulatory Board meets in Athens. Its work is supported by the Energy Community Secretariat.
Fora
The fora have the task to advise the Energy Community. Chaired by the European Commission, a forum brings together all interested stakeholders from the industry, regulators, industry associations and consumers. Their conclusions, agreed by consensus, are addressed to the Permanent High Level Group.
The establishment of the fora reflects the process leading to the creation of the Energy Community. The Athens Electricity Forum, previously known as South East Europe Energy Regulation Forum, met for the first time in 2002. The terms governing the Gas Forum were established in 2006. It was decided that the Gas Forum shall convene in Slovenia. The first Social Forum took place in November 2008. At its December 2008 meeting, the Ministerial Council decided to adopt oil stock legislation and to establish the Oil Forum. The first Oil Forum convened in 2009 in Belgrade. Recently, also a Vienna Law Forum, Just Transition Forum and Dispute Resolution Forum have been established.
Secretariat
The day-to-day activities of the Energy Community are administered by the Secretariat. The Secretariat assists the Contracting Parties in their implementation of the acquis. The Secretariat supports the Contracting Parties in the drafting of legislation and conducts expert missions when requested by the national authorities. The Secretariat organizes annually over 60 events, including institutional meetings and expert workshops.
Each year the Secretariat submits an Annual Implementation Report to the Ministerial Council of the Energy Community, which assesses the compliance of each Contracting Party with respect to its obligations under the treaty. If a Contracting Party fails to comply with its treaty obligations, the Secretariat may open an infringement procedure.
Since 1 December 2021, the director of the Secretariat is Mr Artur Lorkowski. Mr Lorkowski is the third Energy Community director, following Mr Janez Kopač (2012-2021) and Mr Slavtcho Neykov (2007-2012). The director of the Secretariat is responsible for ensuring that the Energy Community budget – to which all Parties contribute – is correctly spent and accounted for. The director also selects and appoints the staff on the basis of the approved establishment plan of the Energy Community. As of December 2021, the Secretariat has 34 staff members holding 18 nationalities.
The Secretariat has its seat in Vienna, Austria.
Role of the European Union
Represented by the European Commission, the European Union holds the permanent Vice-Presidency of the Energy Community. The European Commission assists the Presidency in the chairing of the Permanent High Level Group and the Ministerial Council and the preparation of agendas of all institutional meetings. At the annual Ministerial Council meeting, the European Commission is represented by the Commissioner for Energy. The European Union is the largest contributor to the Energy Community budget. Its contribution is nearly 95 per cent.
History
The roots of the Energy Community Treaty go back to the South-East Europe Regional Energy Market for electricity and natural gas formed originally in the framework of the Stability Pact for South Eastern Europe through the Athens Memorandum. To this end, the establishment of the Energy Community represents a very important political step in a key economic sector before the accession of the SEE countries to the EU. The institutional setting of the Energy Community shows great parallels to the structures of the European Union. It was in the negotiations for this treaty that the Commission "reproduced" the institutions that were created by the founding fathers of the European Communities and reproduced its own institutions outside its borders. On the occasion of the signing of the Treaty, the European Commission stated that the Energy Community Treaty is consciously modelled on the European Steel and Coal Community that was the genesis for the European Union.
Athens Memorandum
The 'Athens Memorandum' refers to the memorandum of understanding of 2002 and its revision of 2003, signed in Athens. It was proposed by the European Union and it outlined the principles and the institutional necessities for regional electricity market development in South East Europe. Following intense discussions, an agreement was reached at the first South East Europe Electricity Regulation Forum in June 2002. The signing of the memorandum took place in November 2002 by Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Greece, FYR of Macedonia, Romania, Serbia and Montenegro, and Turkey.
The 2003 revision added natural gas to the scope of work. Under the Athens Memorandum a South-East Europe Regional Energy Market was envisioned to form part of the EU's internal energy market. The Athens Memorandum also set up a number of institutions, which collectively are known as the 'Athens Process'. In 2004, the Athens Forum meeting decided to name the process 'Energy Community'. at the same time the location of future institutions was agreed.
Energy Community Treaty
In May 2004, the European Union opened negotiations with the countries of the south-eastern European region to conclude a legal agreement. The negotiations took place between the European Community on one side, and Albania, Bosnia and Herzegovina, Bulgaria, Croatia, FYR of Macedonia, Republic of Montenegro, Serbia, Romania, Turkey and UNMIK on behalf of Kosovo on the other side. The treaty establishing the Energy Community was signed in Athens, Greece, on 25 October 2005. Signature of the treaty was approved by the European Parliament on 29 May 2006. The treaty subsequently entered into force on 1 July 2006.
According to Article 97, the Treaty is concluded for a period of 10 years from the date of entry into force. In October 2013, the Energy Community Ministerial Council unilaterally decided to extend the duration of the treaty by ten years, to 2026.
On this occasion, the Ministerial Council also established a High Level Reflection Group, which was mandated to assess the adequacy of the institutional set up and working methods of the Energy Community in achieving the objectives of the Treaty. The Reflection Group published on 11 June 2014 its final report “An Energy Community for the Future”, outlining recommendations on how the Energy Community could be improved. A roadmap has been adopted as to how these proposals should be taken forward.
Critics
The treaty has been criticized by the European Public Service Union as it lacks a social dimension. The Energy Community acquis makes an explicit reference to public service obligations and customer protection. Whilst the Treaty may lack a legally binding acquis on social dialogue, the Contracting Parties have a legally binding obligation to foster social dimension within the process. In October 2007, the Parties signed the Memorandum of Understanding on Social Issues in the context of Energy Community. The Memorandum recognizes that economic development and social progress are mutually linked and should go hand in hand. It also spells out the importance and the necessity to involve social partners in the reform process. Ukraine and Moldova signed the Declaration of Memorandum of Understanding on Social Issues in October 2011.
Environmental organizations from south-eastern Europe criticized the process in December 2008 as they believed that the ECSEE contains insufficient safeguard mechanisms to ensure that the well-intentioned promotion of energy efficiency and renewable energy is not drowned out by the promotion of large and often environmentally harmful coal and hydropower plants. The Energy Community Ministerial Council decided to establish a task force in energy efficiency in 2007. It was renamed in 2013 to Energy Efficiency Coordination Group (EECG), providing a broad platform for cooperation between representatives of ministries and agencies in charge for energy and energy efficiency from Contracting Parties, Observer Countries and Participants. Since 2009 the Energy Community implements the core EU energy efficiency acquis. In the area of renewable energy the discussion to adopt the EU renewable energy directive started already in 2008. The Ministerial Council established a renewable energy task force in 2009 and adopted the Directive 2009/28/EC with binding renewable energy targets for 2020 in October 2012. In October 2015, the ministers decided to re-establish the renewable energy task force. The Energy Community Task Force on Environment has been operational since Spring 2011.
See also
Energy policy of the European Union
INOGATE
Energy Charter Treaty
Agency for the Cooperation of Energy Regulators
European Network of Transmission System Operators for Electricity (ENTSO-E)
European Network of Transmission System Operators for Gas (ENTSO-G)
References
External links
energy-community.org Energy Community official website
Treaty establishing the Energy Community
EU EU4Energy Initiative
Energy in the European Union
Energy policy
European integration
Intergovernmental organizations established by treaty
Organizations established in 2006
Organisations based in Vienna
Pan-European energy organisations | Energy Community | [
"Environmental_science"
] | 2,632 | [
"Environmental social science",
"Energy policy"
] |
3,001,891 | https://en.wikipedia.org/wiki/Toxicophore | A toxicophore is a chemical structure or a portion of a structure (e.g., a functional group) that is related to the toxic properties of a chemical. Toxicophores can act directly (e.g., dioxins) or can require metabolic activation (e.g., tobacco-specific nitrosamines).
Most toxic substances exert their toxicity through some interaction (e.g., covalent bonding, oxidation) with cellular macromolecules like proteins or DNA. This interaction leads to changes in the normal cellular biochemistry and physiology and downstream toxic effects.
Occasionally, the toxicophore requires bioactivation, mediated by enzymes, to produce a more reactive metabolite that is more toxic. For example, tobacco-specific nitrosamines are activated by cytochrome P450 enzymes to form a more reactive substance that can covalently bind to DNA, causing mutations that, if not repaired, can lead to cancer. Generally, different chemical compounds that contain the same toxicophore elicit similar toxic effects at the same site of toxicity.
Medicinal chemists and structural biologists study toxicophores in order to predict (and hopefully avoid) potentially toxic compounds early in the drug development process. Toxicophores can also be identified in lead compounds and removed or replaced later in the process with less toxic moieties. Both techniques, in silico (predictive) and a posteriori (experimental), are active areas of chemoinformatics research and development, within the field known as Computational Toxicology. For example, in the United States, the EPA's National Center for Computational Toxicology sponsors several toxicity databases based on predictive modeling as well as high-throughput screening experimental methods.
References
Toxicology | Toxicophore | [
"Environmental_science"
] | 364 | [
"Toxicology",
"Toxicology stubs"
] |
3,001,955 | https://en.wikipedia.org/wiki/Terephthaloyl%20chloride | Terephthaloyl chloride (TCL, 1,4-benzenedicarbonyl chloride) is the acyl chloride of terephthalic acid. It is a white solid at room temperature. It is one of two precursors used to make Kevlar, the other being p-phenylenediamine. TCL is used as a key component in performance polymers and aramid fibers, where it imparts flame resistance, chemical resistance, temperature stability, light weight, and very high strength. TCL is also an effective water scavenger, used to stabilize isocyanates and urethane prepolymers.
Preparation
Terephthalic acid dichloride is produced commercially by the reaction of 1,4-bis(trichloromethyl)benzene with terephthalic acid:
C6H4(CCl3)2 + C6H4(CO2H)2 → 2 C6H4(COCl)2 + 2 HCl
It can also be obtained by chlorination of dimethyl terephthalate.
Use
TCL is used for making various copolymers and aramid polymers such as Heracron, Twaron and Kevlar:
References
External links
Aramid
Acyl chlorides
Benzene derivatives
Monomers | Terephthaloyl chloride | [
"Chemistry",
"Materials_science"
] | 280 | [
"Monomers",
"Polymer chemistry"
] |
3,002,110 | https://en.wikipedia.org/wiki/Language%20binding | In programming and software design, a binding is an application programming interface (API) that provides glue code specifically made to allow a programming language to use a foreign library or operating system service (one that is not native to that language).
Characteristics
Binding generally refers to a mapping of one thing to another. In the context of software libraries, bindings are wrapper libraries that bridge two programming languages, so that a library written for one language can be used in another language. Many software libraries are written in system programming languages such as C or C++. To use such libraries from another language, usually of higher-level, such as Java, Common Lisp, Scheme, Python, or Lua, a binding to the library must be created in that language, possibly requiring recompiling the language's code, depending on the amount of modification needed. However, most languages offer a foreign function interface, such as Python's and OCaml's ctypes, and Embeddable Common Lisp's cffi and uffi.
For example, Python bindings are used when an extant C library, written for some purpose, is to be used from Python. Another example is libsvn which is written in C to provide an API to access the Subversion software repository. To access Subversion from within Java code, libsvnjavahl can be used, which depends on libsvn being installed and acts as a bridge between the language Java and libsvn, thus providing an API that invokes functions from libsvn to do the work.
Major motives to create library bindings include software reuse, to reduce reimplementing a library in several languages, and the difficulty of implementing some algorithms efficiently in some high-level languages.
Runtime environment
Object models
Common Object Request Broker Architecture (CORBA) – cross-platform-language model
Component Object Model (COM) – Microsoft Windows only cross-language model
Distributed Component Object Model (DCOM) – extension enabling COM to work over networks
Cross Platform Component Object Model (XPCOM) – Mozilla applications cross-platform model
Common Language Infrastructure – .NET Framework cross-platform-language model
Freedesktop.org D-Bus – open cross-platform-language model
Virtual machines
Comparison of application virtual machines
Porting
Portable object – cross-platform-language object model definition
See also
Application programming interface (API)
Application binary interface (ABI)
Calling convention
Embedded SQL
Name mangling
Simplified Wrapper and Interface Generator (SWIG) – interface binding generator from many languages to many languages, open-source
Wrapper function
References
External links
JTC1/SC22/WG11 - Binding Techniques, an ISO standard for language bindings
What is a language binding?
Compilers
Computer libraries | Language binding | [
"Technology"
] | 563 | [
"IT infrastructure",
"Computer libraries"
] |
3,002,252 | https://en.wikipedia.org/wiki/ASTRON | ASTRON is the Netherlands Institute for Radio Astronomy. Its main office is in Dwingeloo in the Dwingelderveld National Park in the province of Drenthe. ASTRON is part of the institutes organization of the Dutch Research Council (NWO).
Goals
ASTRON's main mission is to make discoveries in radio astronomy happen, via the development of new and innovative technologies, the operation of world-class radio astronomy facilities, and the pursuit of fundamental astronomical research. Engineers and astronomers at ASTRON have an outstanding international reputation for novel technology development, and fundamental research in galactic and extra-galactic astronomy. Its main funding comes from NWO.
ASTRON's programme has three principal elements:
The operation of front line observing facilities, including especially the Westerbork Synthesis Radio Telescope and LOFAR,
The pursuit of fundamental astronomical research using ASTRON facilities, together with a broad range of other telescopes around the world and space-borne instruments (e.g. Spitzer, HST etc.)
A strong technology development programme, encompassing both innovative instrumentation for existing telescopes and the new technologies needed for future facilities.
In addition, ASTRON is active in the international science policy arena and is one of the leaders in the international SKA project. The Square Kilometre Array will be the world's largest and most sensitive radio telescope with a total collecting area of approximately one square kilometre. The SKA will be built in Southern Africa and in Australia. It is a global enterprise bringing together 11 countries from the 5 continents.
Observing facilities
Radio telescopes
ASTRON operates the Westerbork Synthesis Radio Telescope (WSRT), one of the largest radio telescopes in the world. The WSRT and the International LOFAR Telescope (ILT) are dedicated to explore the universe at radio frequencies ranging from to .
In addition to its use as a stand-alone radio telescope, the Westerbork array participates in the European Very Long Baseline Interferometry Network (EVN) of radio telescopes.
ASTRON is the host institute for the Joint Institute for VLBI in Europe (JIVE). Its primary task is to operate the EVN MkIV VLBI Data Processor (correlator). JIVE also provides a high-level of support to astronomers and the Telescope Network. ASTRON also hosts the NOVA Optical/ Infrared instrumentation group.
Technology development
Discovery in astronomy goes hand in hand with innovation in technology. ASTRON pursues a proactive programme of technical development, aimed both at providing innovative instrumentation for use on current observing facilities, and at laying the groundwork for future generations of telescopes and signal processing instrumentation.
To these ends, the ASTRON facility in Dwingeloo maintains a well equipped R&D division specializing in the design, prototyping and qualification of:
Low noise, ambient and cryogenic radio receiver systems (0.2–345 GHz)
Very high speed digital electronics
Antennas, especially in the array environment
Advanced instrumentation for use at optical and infrared wavelengths
Algorithm and software engineering for instrument control and for imaging
External links
ASTRON
Astronomy institutes and departments
Organisations based in Drenthe
Research institutes in the Netherlands
Westerveld | ASTRON | [
"Astronomy"
] | 637 | [
"Astronomy organizations",
"Astronomy institutes and departments"
] |
3,002,380 | https://en.wikipedia.org/wiki/Crankpin | A crankpin or crank pin, also known as a rod bearing journal, is a mechanical device in an engine which connects the crankshaft to the connecting rod for each cylinder. It has a cylindrical surface, to allow the crankpin to rotate relative to the "big end" of the connecting rod.
The most common configuration is for a crankpin to serve one cylinder. However, many V engines have each crankpin shared by each pair of cylinders.
Design
The crankpin connects to the larger end of the connecting rod for each cylinder. This end of the connecting rod is called the "big end", as opposed to the "small end" or "little end" (which connects to the wrist/gudgeon pin in the piston).
The bearing which allows the crankpin to rotate around its shaft is called the "rod bearing". In automotive engines, the most common type of rod bearing is the plain bearing, however bushings or roller bearings are also used in some engines.
Configurations
In a single-cylinder engine, straight engine or flat engine, each crankpin normally serves just one cylinder. This results for a relatively simple design which is the cheapest to produce. Some V-twin engines use a single cylinder per crankpin.
Most V engines have each pair of cylinders sharing a crankpin. This usually requires an offset between the cylinders in each bank, resulting in a simple connecting rod design. If a cylinder offset is not used, then the connecting rods must be articulated or forked at the big end. Forked connecting rods are mainly used in V-twin motorcycle engines, but in the past were found on a number of automobile and aero engines, such as the Rolls-Royce Merlin aero engine of the WWII era. Articulated connecting rods consist of a "master" rod attached to the crank pin, with a "slave" rod connected to the big end of the master rod. This design was used in older or exotic V engines.
Radial engines use a more complicated version of articulated connecting rods, where a single "master" connecting rod attached to the single crankpin (one for each row in multi-row designs), and smaller bearings for each of the corresponding cylinders machined into the big end of the master rod.
Cylindrical crank pins were fitted onto the driving wheels of steam locomotives. They were connected to the driving rods that transmitted power from the cylinder to the wheel. The crank pin was usually made of high-quality steel because it had to withstand high forces.
The crank pin of a locomotive corresponds to the offset of a crankshaft in other crank drives. The distance from the centre of the crank pin to the centre of the wheel is also called offset and is exactly half the stroke of the pistons.
See also
Crank (mechanism)
Slider-crank linkage
References
Crankshafts
Engine technology | Crankpin | [
"Technology"
] | 567 | [
"Engine technology",
"Engines"
] |
3,002,477 | https://en.wikipedia.org/wiki/Cant%20%28architecture%29 | A cant in architecture is an angled (oblique-angled) line or surface that cuts off a corner.
Something with a cant is canted.
Canted façades are a typical of, but not exclusive to, Baroque architecture. The angle breaking the façade is less than a right angle, thus enabling a canted façade to be viewed as, and remain, one composition. Bay windows frequently have canted sides.
A cant is sometimes synonymous with chamfer and bevel.
References
Architectural elements
Building engineering | Cant (architecture) | [
"Technology",
"Engineering"
] | 105 | [
"Building engineering",
"Architectural elements",
"Civil engineering",
"Components",
"Architecture"
] |
3,002,478 | https://en.wikipedia.org/wiki/Horn%20%28Chinese%20constellation%29 | The Horn mansion (角宿, pinyin: Jiǎo Xiù) is one of the Twenty-eight mansions of the Chinese constellations. It is one of the eastern mansions of the Azure Dragon.
Asterisms
References
Chinese constellations | Horn (Chinese constellation) | [
"Astronomy"
] | 49 | [
"Chinese constellations",
"Constellations"
] |
3,002,490 | https://en.wikipedia.org/wiki/Quinbolone | Quinbolone (, ), sold under the brand names Anabolicum and Anabolvis, is an androgen and anabolic steroid (AAS) which was previously marketed in Italy. It was developed by Parke-Davis as a viable orally administered AAS with little or no liver toxicity.
Pharmacology
Most orally administered anabolic steroids function by having an alkylated 17α-carbon atom, which prevents first-pass metabolism by the liver. This approach however results in the AAS having hepatotoxicity. Quinbolone is not 17α-alkylated; instead it has increased oral bioavailability due to its cyclopentenyl ether group. After ingestion, the inactive quinbolone is transformed into boldenone.
Quinbolone itself has very few androgenic effects, and most of what it does have are a result of its conversion to boldenone and its metabolites. Because of high doses necessary for androgenic effects, cost and inconvenience meant that quinbolone never proved to be commercially successful, and its clinical applications were fulfilled by alternative, more effective, AAS. Its illicit usage in bodybuilding and athletics likewise proved limited, though drug tests are still used to detect its metabolites as it remains a banned substance for most competitive sports.
Quinbolone, via boldenone, can be transformed into estrogens, and hence may have some estrogenic activity.
Side effects
Chemistry
Quinbolone, also known as δ1-testosterone 17β-cyclopent-1-enyl enol ether or as androsta-1,4-dien-17β-ol-3-one 17β-(1-cyclopent-1-ene) enol ether, is a synthetic androstane steroid and a derivative of testosterone. It is the C17β cyclopentyl enol ether of boldenone (δ1-testosterone). A related AAS is boldenone undecylenate (δ1-testosterone 17β-undec-10-enoate).
Synthesis
Quinbolone can be prepared from testosterone. Dehydrogenation using DDQ forms boldenone. Reaction with 1,1-dimethoxycyclopentane followed by heating to eliminate methanol gives quinbolone.
History
Quinbolone was described as early as 1962. It was marketed in Italy by Parke-Davis.
References
Abandoned drugs
Androgen ethers
Anabolic–androgenic steroids
Androstanes
Cyclopentyl ethers
Dienes
Ketones
Prodrugs
Synthetic estrogens
World Anti-Doping Agency prohibited substances | Quinbolone | [
"Chemistry"
] | 574 | [
"Ketones",
"Functional groups",
"Drug safety",
"Prodrugs",
"Chemicals in medicine",
"Abandoned drugs"
] |
3,002,491 | https://en.wikipedia.org/wiki/Aluminium%20oxide%20%28data%20page%29 | This page provides supplementary chemical data on aluminium oxide.
Material Safety Data Sheet
SIRI
Science Stuff
Structure and properties
Thermodynamic properties
Spectral data
References
Chemical data pages
Chemical data pages cleanup | Aluminium oxide (data page) | [
"Chemistry"
] | 39 | [
"Chemical data pages",
"nan"
] |
3,002,552 | https://en.wikipedia.org/wiki/Torelli%20theorem | In mathematics, the Torelli theorem, named after Ruggiero Torelli, is a classical result of algebraic geometry over the complex number field, stating that a non-singular projective algebraic curve (compact Riemann surface) C is determined by its Jacobian variety J(C), when the latter is given in the form of a principally polarized abelian variety. In other words, the complex torus J(C), with certain 'markings', is enough to recover C. The same statement holds over any algebraically closed field. From more precise information on the constructed isomorphism of the curves it follows that if the canonically principally polarized Jacobian varieties of curves of genus are k-isomorphic for k any perfect field, so are the curves.
This result has had many important extensions. It can be recast to read that a certain natural morphism, the period mapping, from the moduli space of curves of a fixed genus, to a moduli space of abelian varieties, is injective (on geometric points). Generalizations are in two directions. Firstly, to geometric questions about that morphism, for example the local Torelli theorem. Secondly, to other period mappings. A case that has been investigated deeply is for K3 surfaces (by Viktor S. Kulikov, Ilya Pyatetskii-Shapiro, Igor Shafarevich and Fedor Bogomolov) and hyperkähler manifolds (by Misha Verbitsky, Eyal Markman and Daniel Huybrechts).
Notes
References
Algebraic curves
Abelian varieties
Moduli theory
Theorems in complex geometry
Theorems in algebraic geometry | Torelli theorem | [
"Mathematics"
] | 339 | [
"Theorems in algebraic geometry",
"Theorems in complex geometry",
"Theorems in geometry"
] |
3,002,595 | https://en.wikipedia.org/wiki/Max%20Planck%20Institute%20for%20Chemistry | The Max Planck Institute for Chemistry (Otto Hahn Institute; ) is a non-university research institute under the auspices of the Max Planck Society (German: Max-Planck-Gesellschaft) in Mainz, Germany. It was created as the Kaiser Wilhelm Institute for Chemistry in 1911 in Berlin.
In 2016 research at the Max Planck Institute for Chemistry in Mainz aims at an integral understanding of chemical processes in the Earth system, particularly in the atmosphere and biosphere. Investigations address a wide range of interactions between air, water, soil, life and climate in the course of Earth history up to today's human-driven epoch, the Anthropocene. The institute consists of five scientific departments (Atmospheric Chemistry, Climate Geochemistry, Biogeochemistry, Multiphase Chemistry, and Particle Chemistry) and additional research groups. The departments are independently led by their directors.
Research
The institute consists of five scientific departments and additional research groups.
Atmospheric Chemistry Department: The Atmospheric Chemistry Department which is led by Prof. Dr. Jos Lelieveld focuses on the study of ozone and other atmospheric photo-oxidants, their chemical reactions and global cycles. The researchers use kinetic and photochemical laboratory investigations, in situ and remote sensing measurements. The Atmospheric Chemistry department also develops numerical models to describe meteorological and chemical processes in the atmosphere, to simulate the complex atmospheric interactions and to test the theory through measurement campaigns (ground-based or by ship, aircraft, satellite). Research groups:
Reactive Processes (John Crowley)
Optical Spectroscopy (Horst Fischer)
Radical Measurements (Hartwig Harder)
Organic Reactive Species (Jonathan Williams)
Numerical modeling (Andrea Pozzer)
Biogeochemistry Department: The Department Biogeochemistry of Prof. Dr. Meinrat O. Andreae concentrates on the exchange and interactions of trace gases and aerosols between biosphere and atmosphere with a special focus on Amazon region. They use laboratory investigations, field measurements and numerical models to study this processes. Research topics are: exchange of chemically and climatically important trace gases between the soil/vegetation system and the atmosphere, formation of aerosol particles and their effects on climate, impact of vegetation fires on ecology and atmospheric pollution, and the changing global cycles of trace elements.
Department of Climate Geochemistry: Prof. (ETHZ) Dr. Gerald H. Haug and his team explore the climate -ocean-atmosphere system on annual up to geological timescales. Of particular interest is the Cenozoic (the past 65 million years). They investigate the changes in internal feedback processes, e.g. interactions between ocean and atmosphere, oceanic heat transport or its nutrient status. Moreover, the scientists study the biogeochemical processes in the polar oceans and their role in regulating atmospheric concentration between ice ages and warmer periods. Therefore, they examine geological archives such as sediments from the open ocean and speleothems. The department operates the Research sail yacht S/Y Eugen Seibold. Research groups:
Isotope Biogeochemistry (Stephen Galer)
Paleoclimate Research (Klaus P. Jochum)
Organic Isotope Geochemistry (Alfredo Martínez-García)
Geosientific databases (Bärbel Sarbas)
Micropaleontology (Ralf Schiebel)
Inorganic Gas Isotope Geochemistry (Hubert Vonhof)
Multiphase Chemistry Department: The department of Prof. Dr. Ulrich Pöschl deals with multiphase processes at the molecular level and its impact on the macroscopic and global scale. Concerning the Earth System and climate research, they focus on biological and organic aerosols, aerosol-cloud interactions and atmospheric surface exchange processes whereas in the field of life and health sciences, the researchers study the change of protein macromolecules air pollution and how this affects allergic reactions and diseases. Research groups:
Biomolecular Analyses & Interactions (J. Fröhlich)
Organic Pollutants & Exposure (G. Lammel)
Inflammatory Processes (K. Lucas)
Aerosol analysis & Microscopy (C. Pöhlker)
Multiscale Interactions & Integration (U. Pöschl)
Aerosol, Cloud & Surface Interactions (H. Su)
Microbial Communities & Processes (B. Weber)
Multiphase Chemical Kinetics and Reaction Mechanisms (T. Berkemeier)
Particle Chemistry Department: The department is led by Prof. Dr. Stephan Borrmann. Here they study the physical properties and chemical composition of atmospheric aerosol and cloud particles using laboratory experiments (e.g. in a vertical wind tunnel), measurements on ground and hill stations and on mobile measurement facilities (airplanes). Furthermore, extraterrestrial particles are being analyzed using isotopic measurements, such as presolar grains from meteorites and comets. Research groups:
Instrumental Aerosol Analytics (Frank Drewnick)
NAMIP - Nano- and Microparticle Research (Peter Hoppe)
Aerosol and Cloud Chemistry (Johannes Schneider)
Atmospheric Hydrometeors (Miklós Szakáll and Karoline Diehl)
Aerosol and Cloud Physics (Stefan Borrmann, Ralf Weigel and Jacob Fugal)
AEROTROP (Christiane Voigt)
Further research groups: In December 2016 there were four additional research groups at the institute: The Minerva group led by Dr. Yafang Cheng. They deal with the interaction of aerosols and regional air quality. Dr. Mikhail Eremets studies mater at high pressures. Prof. Dr. Thomas Wagner and his Satellite Research Group of analyzes satellite data in order to draw conclusions about tropospheric and stratospheric trace gases. The group "Terrestrial Paleoclimates" which is led by Dr. Kathryn Fitzsimmons, uses loess in Eurasia as climate archives for information of past climates.
In 2010 the Geochemistry department (which was led by Prof. Albrecht W. Hofmann) was closed and the scientific working groups were integrated into the Biogeochemistry department. This department conducted research on large-scale geological processes, such as the formation of continental and oceanic crusts, the chemical differentiation of the Earth's mantle and the circulation of present-day and former oceans. The scientists used mass spectrometric measurements of isotopic abundances to determine the absolute age of rocks. They also used isotopic abundances and trace element contents to determine the origin of volcanic lava from the Earth's mantle or crust and studies the long-term processes used by the Earth's mantle to recycle old crust.
History
The institute was founded as Kaiser Wilhelm Institute for Chemistry in Berlin Dahlem in 1911. The founding director was Ernst Beckmann (1853-1923), who also directed the Department of Inorganic and Physical Chemistry. The Department of Organic Chemistry was led by Richard Willstatter (1872-1942), who won the Nobel Prize for Chemistry in 1915 for his work on plant pigments. The teamwork of Otto Hahn (1879-1968), Lise Meitner (1878-1968) and Fritz Straßmann (1902-1980) led to the discovery of nuclear fission in December 1938. Otto Hahn was director of the institute from 1928 to 1946. He received the Nobel Prize for Chemistry in 1944.
During the war, in 1944, the Institute building was severely damaged as a result of air raids, including a raid on 15 February targeted to disrupt work on the German nuclear weapons program. Everything that hadn't been destroyed was then stored in a closed textile factory in Tailfingen, Württemberg (present-day Albstadt), where the institute continued the work it had started in Berlin for a time.
After World War II the institute moved to the campus of Johannes Gutenberg University of Mainz in 1949. In 1948 the Kaiser Wilhelm Society was restructured and renamed becoming the Max Planck Society, the institute was also renamed as the Max Planck Institute for Chemistry (1949). In order to adapt to changing scientific requirements, the institute's research activities changed several times over the years. When classic chemistry was practiced in the early years, it later focussed on Radiochemistry, Cosmochemistry, Nuclear Physics, and mass spectrometry. These days the Max Planck Institute for Chemistry focusses on an integral scientific understanding of chemical processes in the Earth System from molecular to global scales.
Nobel laureates of the institute
Richard Willstätter, director from 1912 until 1916. In 1915, he received the Nobel Prize for Chemistry for his research into plant dyes, primarily chlorophyll. He discovered, among other things, that the structure of green dye exhibits significant similarity to the structure of the red blood pigment hemoglobin.
Otto Hahn, director of the department for radioactive research from 1912 until 1948, from 1928 until 1946 managing director of the institute. The joint research by Otto Hahn, Lise Meitner and Fritz Straßmann into transuranic elements led to the discovery of nuclear fission in 1938. In 1945, Otto Hahn received the Nobel Prize for this.
Paul J. Crutzen, director of the Atmospheric Chemistry Department from 1980 until 2000, Nobel Prize for Chemistry 1995 for investigations on the formation and destruction of ozone in the atmosphere.
Staff
At the beginning of 2014 about 300 people were employed at the institute, including 77 scientists, 122 junior scientists and 11 trainees (mechanical workshop and electronics).
Max Planck Graduate School (MPGS)
The Max Planck Graduate School (MPGS) at MPI for Chemistry offers a PhD program in atmospheric chemistry and physics, environmental physics and geophysics. The program should enable the PhD students to widen their knowledge and skills beyond the research topic of the doctoral project by visiting different lectures, workshops, soft skill courses, an annual PhD Symposium and summer schools. It was established by the Max Planck Society in January 2003. The Graduate School is in close cooperation with the University of Mainz (Institute for Physics of the Atmosphere), the University of Heidelberg (Institute for Environmental Physics), University of Frankfurt (Institute for Atmospheric and Environmental Sciences).
Directors of the institute
Kaiser Wilhelm Institute for Chemistry
1912 Ernst Beckmann
1912 - 1916 Richard Willstätter
1912 - 1948 Otto Hahn
1916 - 1926 Alfred Stock
Max Planck Institute for Chemistry
1949 - 1953 Fritz Straßmann
1941 - 1965 Josef Mattauch
1953 - 1958 Friedrich A. Paneth
1959 - 1978 Heinrich Hintenberger
1959 - 1978 Hermann Wäffler
1967 - 1996 Heinrich Wänke
1968 - 1979 Christian Junge
1978 - 1995 Friedrich Begemann
1980 - 2000 Paul J. Crutzen
1980 - 2007 Albrecht W. Hofmann
1987 Meinrat O. Andreae
1996 Günter W. Lugmair
2000 Johannes Lelieveld
2001 Stephan Borrmann
2014 Ulrich Pöschl
2015 Gerald Haug (managing director since 2018)
Collaborative projects
The Earth System Research Partnership (ESRP) pools research excellence across disciplines to understand how the Earth functions as a complex system and to improve the predictability of the effects of human actions. It encompasses the Max-Planck-Institutes for Biogeochemistry in Jena, MPI for Chemistry in Mainz and MPI for Meteorology in Hamburg. Over the last century, marked changes in climate, air quality, biodiversity, and water availability occurred. More and potentially more rapid changes are predicted. To find solutions to the challenges these changes pose, the ESRP studies the complex interactions and feedbacks of land, ocean, atmosphere, biosphere and humans in the field, the lab and through models.
ATTO: "ATTO" stands for Amazonian Tall Tower Observatory. The German-Brazilian joint project was launched in 2009 and is coordinated by the Max Planck Institute for Chemistry. The tower aims at delivering groundbreaking findings which will be the basis for improved climate models. With a height of 300 meters the tower will extend the ground-level boundary layer, and will provide information taken from approximately 100 squarekilometers from the world's largest forest area. ATTO is the counterpart of the 2006 completed ZOTTO tower that stands in Siberia and the Max Planck Institute of Chemistry is also involved. ATTO will integrated into an existing structure of smaller Brazilian measuring towers. The cost for the construction of ATTO including the first five years of running costs is estimated to be 8.4 million €. which will be financed by Germany and Brazil in equal parts.
HALO: HALO - The High Altitude and LOng Range Research Aircraft is a Research Aircraft for atmospheric research and earth observation of the German Science Community. HALO is funded by the Federal Ministry of Education and Research, the Helmholtz-Gemeinschaft and the Max-Planck-Gesellschaft.
IBBI: Interdisciplinary Biomass Burning Initiative (IBBI)
CARIBIC: Global Atmospheric Composition and Climate Change Research EUROPE's SOLUTION FOR GLOBAL ATMOSPHERE MONITORING. CARIBIC is an innovative scientific project to study and monitor important chemical and physical processes in the Earth's atmosphere. Detailed and extensive measurements are made during long-distance flights. Since October 2015 the CARIBIC project has moved to the Karlsruhe Institute of Technology and the Institute of Meteorology and Climate Research - Atmospheric Trace Gases and Remote Sensing.
Databases
The institute provides four databases which give information about 1) reference materials of geological and environmental interest (GeoReM), 2) volcanic rocks and mantle xenoliths (GEOROC), 3) UV/VIS absorption cross sections, and 4) Henry's law constants.
References
External links
Homepage of the Max Planck Institute for Chemistry
Homepage of the Max Planck Society
Chemistry
Chemical research institutes
1911 establishments in Germany | Max Planck Institute for Chemistry | [
"Chemistry"
] | 2,737 | [
"Chemical research institutes"
] |
3,002,629 | https://en.wikipedia.org/wiki/Antimony%20trioxide%20%28data%20page%29 | This page provides supplementary chemical data on antimony trioxide.
Also known as Sb2O3. It has a melting point of 656 °C, and a boiling point of 1550 °C. It is a Cubic Crystal Structure with a
density of 5.2G/Cm3
Material Safety Data Sheet
MSDS from SIRI
Structure and properties
Thermodynamic properties
Spectral data
References
Chemical data pages
Chemical data pages cleanup | Antimony trioxide (data page) | [
"Chemistry"
] | 85 | [
"Chemical data pages",
"nan"
] |
3,002,779 | https://en.wikipedia.org/wiki/Arsine%20%28data%20page%29 | This page provides supplementary chemical data on arsine.
Material Safety Data Sheet
SIRI
Soxal
Structure and properties
Thermodynamic properties
Spectral data
References
Chemical data pages
Chemical data pages cleanup | Arsine (data page) | [
"Chemistry"
] | 39 | [
"Chemical data pages",
"nan"
] |
3,002,867 | https://en.wikipedia.org/wiki/Illicium%20anisatum | Illicium anisatum, with common names Japanese star anise, Aniseed tree, and sacred Anise tree, known in Japanese as , is an evergreen shrub or small tree closely related to the Chinese star anise (Illicium verum). Since it is highly toxic, the fruit is not edible; instead, the dried and powdered leaves are burned as incense in Japan. Its branches and evergreen leaves are considered highly sacred by Japanese Buddhists due to insects' aversion to them and their ability to remain fresh after pruning.
The sacred anise tree is native to parts of east Asia including Japan, South Korea and Taiwan. It normally grows between with leaves that are simple, arranged alternately and oval in shape and about in length. Its cream or white colored flowers have numerous petals and are clustered around the leaf axils. Its fruit is a dry follicle similar to the Chinese star anise, but toxic, smaller and with a weaker odour, reputed to be more similar to the aroma of cardamom than to that of anise.
Due to its poisonous nature, its seeds have been used as a fish poison as well as a natural agricultural pesticide and to repel animals from digging the grounds of Japanese graveyards. Its seeds have also been used medicinally to treat toothache and dermatitis topically, since it is unsuitable for internal use.
Toxicity and accidental use in food products
Japanese star anise contains anisatin, shikimin, and shikimitoxin, which cause severe inflammation of the kidneys, urinary tract, and digestive organs. Other compounds present in toxic species of Illicium are safrole and eugenol, which are not present in the edible Chinese star anise and are used to identify its toxicity. Shikimic acid, a substance also present in Japanese star anise, is so-called after the plant's Japanese name.
Due to its morphological similarities, it is impossible to distinguish Chinese and Japanese star anise in dried or processed form by their appearance only, and can only be unequivocally determined by using botanical microscopy. This process must be done before the plants have been made into tea and dried out.
Cases of product recalls have been reported when products containing star anise were found to be contaminated by Japanese anise. Cases of consumers admitted to hospital with neurological symptoms after ingesting excessive doses of star anise or smaller doses of products contaminated with Japanese anise have also occurred: In Europe, Chinese star anise tea is often used as a stress-relief tea. Cases of illness have been reported in France, Spain, and Switzerland after people were reported consuming Chinese star anise tea contaminated with Japanese star anise. This contamination hospitalized many people with epilepsy, hallucinations, and nausea all as a result of the toxin anisatin, found in the Japanese star anise. In 2001, there was a large outbreak of toxicity in the Netherlands due to accidental contamination of a tea blend containing more than 6 different tea plants with the Japanese star anise.
Essential oil components
The essential oil of air-dried I. anisatum seeds obtained by hydrodistillation was analysed by GC–MS. Fifty-two components were identified in the essential oil, the main component being eucalyptol (21.8%).
Etymology
Illicium is derived from Latin and means 'seductive'. The name is in reference to the plant's fragrance.
Anisatum means 'anise-scented'.
In literature
The sixteenth-century Chinese anthology Strange Stories from a Chinese Studio (聊 齋 誌 異) includes a mythical story titled "The Shuimang Herb" whose titular plant is inspired by Illicium anisatum.
See also
Illicium floridanum
Illicium verum
References
anisatum
Incense material
Plants described in 1759
Taxa named by Carl Linnaeus | Illicium anisatum | [
"Physics"
] | 796 | [
"Incense material",
"Materials",
"Matter"
] |
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