id int64 39 79M | url stringlengths 31 227 | text stringlengths 6 334k | source stringlengths 1 150 ⌀ | categories listlengths 1 6 | token_count int64 3 71.8k | subcategories listlengths 0 30 |
|---|---|---|---|---|---|---|
321,895 | https://en.wikipedia.org/wiki/Cullen%20number | In mathematics, a Cullen number is a member of the integer sequence (where is a natural number). Cullen numbers were first studied by James Cullen in 1905. The numbers are special cases of Proth numbers.
Properties
In 1976 Christopher Hooley showed that the natural density of positive integers for which Cn is a prime is of the order o(x) for . In that sense, almost all Cullen numbers are composite. Hooley's proof was reworked by Hiromi Suyama to show that it works for any sequence of numbers n·2n + a + b where a and b are integers, and in particular also for Woodall numbers. The only known Cullen primes are those for n equal to:
1, 141, 4713, 5795, 6611, 18496, 32292, 32469, 59656, 90825, 262419, 361275, 481899, 1354828, 6328548, 6679881 .
Still, it is conjectured that there are infinitely many Cullen primes.
A Cullen number Cn is divisible by p = 2n − 1 if p is a prime number of the form 8k − 3; furthermore, it follows from Fermat's little theorem that if p is an odd prime, then p divides Cm(k) for each m(k) = (2k − k)
(p − 1) − k (for k > 0). It has also been shown that the prime number p divides C(p + 1)/2 when the Jacobi symbol (2 | p) is −1, and that p divides C(3p − 1)/2 when the Jacobi symbol (2 | p) is + 1.
It is unknown whether there exists a prime number p such that Cp is also prime.
Cp follows the recurrence relation
.
Generalizations
Sometimes, a generalized Cullen number base b is defined to be a number of the form n·bn + 1, where n + 2 > b; if a prime can be written in this form, it is then called a generalized Cullen prime. Woodall numbers are sometimes called Cullen numbers of the second kind.
As of October 2021, the largest known generalized Cullen prime is 2525532·732525532 + 1. It has 4,705,888 digits and was discovered by Tom Greer, a PrimeGrid participant.
According to Fermat's little theorem, if there is a prime p such that n is divisible by p − 1 and n + 1 is divisible by p (especially, when n = p − 1) and p does not divide b, then bn must be congruent to 1 mod p (since bn is a power of bp − 1 and bp − 1 is congruent to 1 mod p). Thus, n·bn + 1 is divisible by p, so it is not prime. For example, if some n congruent to 2 mod 6 (i.e. 2, 8, 14, 20, 26, 32, ...), n·bn + 1 is prime, then b must be divisible by 3 (except b = 1).
The least n such that n·bn + 1 is prime (with question marks if this term is currently unknown) are
1, 1, 2, 1, 1242, 1, 34, 5, 2, 1, 10, 1, ?, 3, 8, 1, 19650, 1, 6460, 3, 2, 1, 4330, 2, 2805222, 117, 2, 1, ?, 1, 82960, 5, 2, 25, 304, 1, 36, 3, 368, 1, 1806676, 1, 390, 53, 2, 1, ?, 3, ?, 9665, 62, 1, 1341174, 3, ?, 1072, 234, 1, 220, 1, 142, 1295, 8, 3, 16990, 1, 474, 129897, ?, 1, 13948, 1, ?, 3, 2, 1161, 12198, 1, 682156, 5, 350, 1, 1242, 26, 186, 3, 2, 1, 298, 14, 101670, 9, 2, 775, 202, 1, 1374, 63, 2, 1, ...
References
Further reading
.
.
.
.
External links
Chris Caldwell, The Top Twenty: Cullen primes at The Prime Pages.
The Prime Glossary: Cullen number at The Prime Pages.
Chris Caldwell, The Top Twenty: Generalized Cullen at The Prime Pages.
Cullen prime: definition and status (outdated), Cullen Prime Search is now hosted at PrimeGrid
Paul Leyland, (Generalized) Cullen and Woodall Numbers
Integer sequences
Unsolved problems in number theory
Classes of prime numbers | Cullen number | [
"Mathematics"
] | 1,026 | [
"Sequences and series",
"Unsolved problems in mathematics",
"Integer sequences",
"Mathematical structures",
"Recreational mathematics",
"Mathematical objects",
"Unsolved problems in number theory",
"Combinatorics",
"Mathematical problems",
"Numbers",
"Number theory"
] |
321,913 | https://en.wikipedia.org/wiki/Quasiperfect%20number | In mathematics, a quasiperfect number is a natural number n for which the sum of all its divisors (the sum-of-divisors function σ(n)) is equal to 2n + 1. Equivalently, n is the sum of its non-trivial divisors (that is, its divisors excluding 1 and n). No quasiperfect numbers have been found so far.
The quasiperfect numbers are the abundant numbers of minimal abundance (which is 1).
Theorems
If a quasiperfect number exists, it must be an odd square number greater than 1035 and have at least seven distinct prime factors.
Related
For a perfect number n the sum of all its divisors is equal to 2n.
For an almost perfect number n the sum of all its divisors is equal to 2n - 1.
Betrothed numbers relate to quasiperfect numbers like amicable numbers relate to perfect numbers.
Notes
References
Arithmetic dynamics
Divisor function
Integer sequences
Unsolved problems in mathematics | Quasiperfect number | [
"Mathematics"
] | 213 | [
"Sequences and series",
"Unsolved problems in mathematics",
"Integer sequences",
"Mathematical structures",
"Number theory stubs",
"Recreational mathematics",
"Mathematical objects",
"Arithmetic dynamics",
"Combinatorics",
"Mathematical problems",
"Numbers",
"Number theory",
"Dynamical syste... |
321,918 | https://en.wikipedia.org/wiki/Semiperfect%20number | In number theory, a semiperfect number or pseudoperfect number is a natural number n that is equal to the sum of all or some of its proper divisors. A semiperfect number that is equal to the sum of all its proper divisors is a perfect number.
The first few semiperfect numbers are: 6, 12, 18, 20, 24, 28, 30, 36, 40, ...
Properties
Every multiple of a semiperfect number is semiperfect. A semiperfect number that is not divisible by any smaller semiperfect number is called primitive.
Every number of the form 2mp for a natural number m and an odd prime number p such that p < 2m+1 is also semiperfect.
In particular, every number of the form 2m(2m+1 − 1) is semiperfect, and indeed perfect if 2m+1 − 1 is a Mersenne prime.
The smallest odd semiperfect number is 945 (see, e.g., Friedman 1993).
A semiperfect number is necessarily either perfect or abundant. An abundant number that is not semiperfect is called a weird number.
With the exception of 2, all primary pseudoperfect numbers are semiperfect.
Every practical number that is not a power of two is semiperfect.
The natural density of the set of semiperfect numbers exists.
Primitive semiperfect numbers
A primitive semiperfect number (also called a primitive pseudoperfect number, irreducible semiperfect number or irreducible pseudoperfect number) is a semiperfect number that has no semiperfect proper divisor.
The first few primitive semiperfect numbers are 6, 20, 28, 88, 104, 272, 304, 350, ...
There are infinitely many such numbers. All numbers of the form 2mp, with p a prime between 2m and 2m+1, are primitive semiperfect, but this is not the only form: for example, 770. There are infinitely many odd primitive semiperfect numbers, the smallest being 945, a result of Paul Erdős: there are also infinitely many primitive semiperfect numbers that are not harmonic divisor numbers.
Every semiperfect number is a multiple of a primitive semiperfect number.
See also
Hemiperfect number
Erdős–Nicolas number
Notes
References
Section B2.
External links
Integer sequences
Perfect numbers
de:Vollkommene Zahl#Pseudovollkommene Zahlen | Semiperfect number | [
"Mathematics"
] | 524 | [
"Sequences and series",
"Integer sequences",
"Mathematical structures",
"Perfect numbers",
"Recreational mathematics",
"Mathematical objects",
"Combinatorics",
"Numbers",
"Number theory"
] |
321,921 | https://en.wikipedia.org/wiki/Osborne%20Reynolds | Osborne Reynolds (23 August 1842 – 21 February 1912) was an Irish-born British innovator in the understanding of fluid dynamics. Separately, his studies of heat transfer between solids and fluids brought improvements in boiler and condenser design. He spent his entire career at what is now the University of Manchester.
Life
Osborne Reynolds was born in Belfast and moved with his parents soon afterward to Dedham, Essex. His father, Reverend Osborne Reynolds, was a Fellow of Queens' College, Cambridge who worked as a school headmaster and clergyman, but was also a very able mathematician with a keen interest in mechanics. The father took out a number of patents for improvements to agricultural equipment, and the son credits him with being his chief teacher as a boy. Reynolds showed an early aptitude and liking for the study of mechanics. In his late teens, for the year before entering university, he went to work as an apprentice at the workshop of Edward Hayes, a well known shipbuilder in Stony Stratford, where he obtained practical experience in the manufacture and fitting out of coastal steamers (and thus gained an early appreciation of the practical value of understanding fluid dynamics).
Osborne Reynolds attended Queens' College, Cambridge and graduated in 1867 as the seventh wrangler in mathematics. He had chosen to study mathematics at Cambridge because, in his own words in his 1868 application for the professorship, "From my earliest recollection I have had an irresistible liking for mechanics and the physical laws on which mechanics as a science is based.... my attention drawn to various mechanical phenomena, for the explanation of which I discovered that a knowledge of mathematics was essential."
For the year immediately following his graduation from Cambridge he again took up a post with a civil engineering firm, Lawson and Mansergh of London, as a practising civil engineer working with the London (Croydon) sewage transport system.
In 1868 he was appointed to the newly instituted Chair of Civil and Mechanical Engineering at Owens College in Manchester (now the University of Manchester), becoming in that year one of the first professors in UK university history to hold the title of "Professor of Engineering". This professorship had been newly created and financed by a group of manufacturing industrialists in the Manchester area, and they also had a leading role in selecting the 25–year–old Reynolds to fill the position.
Reynolds remained at Owens College for the rest of his career – in 1880 the college became a constituent college of the newly founded Victoria University.
Reynolds was elected a Fellow of the Royal Society in 1877 and awarded the Royal Medal in 1888. He retired in 1905 and died of influenza 21 February 1912 at Watchet in Somerset. He was buried at the Church of St Decuman, Watchet.
Fluid mechanics
Reynolds most famously studied the conditions in which the flow of fluid in pipes transitioned from laminar flow to turbulent flow.
In 1883 Reynolds demonstrated the transition to turbulent flow in a classic experiment in which he examined the behaviour of water flow under different flow rates using a small jet of dyed water introduced into the centre of flow in a larger pipe.
The larger pipe was glass so the behaviour of the layer of dyed flow could be observed, and at the end of this pipe there was a flow control valve used to vary the water velocity inside the tube. When the velocity was low, the dyed layer remained distinct through the entire length of the large tube. When the velocity was increased, the layer broke up at a given point and diffused throughout the fluid's cross-section. The point at which this happened was the transition point from laminar to turbulent flow.
From these experiments came the dimensionless Reynolds number for dynamic similarity—the ratio of inertial forces to viscous forces. Reynolds also proposed what is now known as Reynolds-averaging of turbulent flows, where quantities such as velocity are expressed as the sum of mean and fluctuating components. Such averaging allows for 'bulk' description of turbulent flow, for example using the Reynolds-averaged Navier–Stokes equations.
Reynolds' contributions to fluid mechanics were not lost on ship designers ("naval architects"). The ability to make a small scale model of a ship, and extract useful predictive data with respect to a full size ship, depends directly on the experimentalist applying Reynolds' turbulence principles to friction drag computations, along with a proper application of William Froude's theories of gravity wave energy and propagation. Reynolds himself had a number of papers concerning ship design published in Transactions of the Institution of Naval Architects.
Publications
His publications in fluid dynamics began in the early 1870s. His final theoretical model published in the mid-1890s is still the standard mathematical framework used today. Examples of titles from his more groundbreaking reports:
Other work
Reynolds published about seventy science and engineering research reports. When towards the end of his career these were republished as a collection they filled three volumes. For a catalogue and short summaries of them see the External links. Areas covered besides fluid dynamics included thermodynamics, kinetic theory of gases, condensation of steam, screw-propeller-type ship propulsion, turbine-type ship propulsion, hydraulic brakes, hydrodynamic lubrication, and laboratory apparatus for better measurement of Joule's mechanical equivalent of heat. For his work on lubrication, he was named by Duncan Dowson as one of the 23 "Men of Tribology".
One of the subjects that Reynolds studied in the 1880s was the properties of granular materials, including dilatant materials. In 1903 appeared his 250-page book The Sub-Mechanics of the Universe, in which he tried to generalise the mechanics of granular materials to be "capable of accounting for all the physical evidence, as we know it, in the Universe". His aim seems to have been to construct a theory of aether, which he considered to be in a liquid state. The ideas were extremely difficult to understand or evaluate, and in any case were overtaken by other developments in physics around the same time.
See also
References
Further reading
External links
Reynolds the Engineer
Reynolds the Scientist
1842 births
1912 deaths
Academics of the Victoria University of Manchester
Alumni of Queens' College, Cambridge
British civil engineers
British physicists
Fellows of Queens' College, Cambridge
Fellows of the Royal Society
Fluid dynamicists
Geotechnical engineers
Engineers from Belfast
People from Dedham, Essex
Royal Medal winners
Tribologists
Manchester Literary and Philosophical Society
Recipients of the Dalton Medal | Osborne Reynolds | [
"Chemistry",
"Materials_science"
] | 1,294 | [
"Tribology",
"Fluid dynamicists",
"Tribologists",
"Fluid dynamics"
] |
321,929 | https://en.wikipedia.org/wiki/Seven%20Sleepers | The Seven Sleepers (; ), also known in Christendom as Seven Sleepers of Ephesus, and in Islam as Aṣḥāb al-Kahf (اصحاب الکهف, aṣḥāb al-kahf, lit. Companions of the Cave), is a late antique Christian legend, and a Qur’anic Islamic story. The Christian legend speaks about a group of youths who hid inside a cave outside the city of Ephesus (modern-day Selçuk, Turkey) around AD 250 to escape Roman persecutions of Christians and emerged many years later. The Qur'anic version of the story appears in Sura 18 (18:9–26).
Origins and propagation
The story appeared in several Syriac sources before Gregory of Tours's lifetime (538–594). The earliest Syriac manuscript copy is in MS Saint-Petersburg No. 4, which dates to the fifth century.
The earliest known version of this story is found in the writings of the Syriac bishop Jacob of Serugh (–521), who relies on an earlier Greek source, now lost. Jacob of Serugh, an Edessan poet-theologian, wrote a homily in verse on the subject of the Seven Sleepers, which was published in the Acta Sanctorum. Another sixth-century version, in a Syrian manuscript in the British Museum (Cat. Syr. Mss, p. 1090), gives eight sleepers.
Whether the original account was written in Syriac or Greek was a matter of debate, but today a Greek original is generally accepted. The pilgrim account De situ terrae sanctae, written between 518 and 531, records the existence of a church dedicated to the sleepers in Ephesus.
An outline of this tale appears in the 6th-century writings of Gregory of Tours and in History of the Lombards of Paul the Deacon (720–799). The best-known Western version of the story appears in Jacobus de Voragine's Golden Legend (1259–1266). It also appears in BHO (Pueri septem), BHG (Pueri VII) and BHL Dormientes (Septem) Ephesi.
Accounts of the Christian legend are found in at least nine medieval languages and preserved in over 200 manuscripts, mainly dating to between the 9th and 13th centuries. These include 104 Latin manuscripts, 40 Greek, 33 Arabic, 17 Syriac, six Ethiopic, five Coptic, two Armenian, one Middle Irish, and one Old English. Byzantine writer Symeon the Metaphrast (died c. 1000) alluded to it. It was also translated into Sogdian. In the 13th century, the poet Chardri composed an Old French version. The ninth-century Irish calendar commemorates the Seven Sleepers on 7 August.
It was also translated into Persian, Kyrgyz, and Tatar.
Dissemination in the West: story and relics
The story rapidly attained a wide diffusion throughout Christendom. It was popularized in the West by Gregory of Tours, in his late 6th-century collection of miracles, De gloria martyrum (Glory of the Martyrs). Gregory claimed to have gotten the story from "a certain Syrian interpreter" (Syro quidam interpretante), but this could refer to either a Syriac- or Greek-speaker from the Levant. During the period of the Crusades, bones from the sepulchres near Ephesus, identified as relics of the Seven Sleepers, were transported to Marseille, France, in a large stone coffin, which remained a trophy of the Abbey of St Victor, Marseille.
The Seven Sleepers were included in the Golden Legend compilation, the most popular book of the later Middle Ages, which fixed a precise date for their resurrection, AD 478, in the reign of Theodosius.
Christian story
The story says that during the persecutions by the Roman emperor Decius, around AD 250, seven young men were accused of following Christianity. They were given some time to recant their faith, but they refused to bow to Roman idols. Instead they chose to give their worldly goods to the poor and retire to a mountain cave to pray, where they fell asleep. The Emperor, seeing that their attitude towards paganism had not improved, ordered the mouth of the cave to be sealed.
Decius died in 251, and many years passed during which Christianity went from being persecuted to being the state religion of the Roman Empire. At some later time—usually given as during the reign of Theodosius II (408–450)—in AD 447 when heated discussions were taking place between various schools of Christianity about the resurrection of the body in the day of judgement and life after death, a landowner decided to open up the sealed mouth of the cave, thinking to use it as a cattle pen. He opened it and found the sleepers inside. They awoke, imagining that they had slept but one day, and sent one of their number to Ephesus to buy food, with instructions to be careful.
Upon arriving in the city, this person was astounded to find buildings with crosses attached; the townspeople for their part were astounded to find a man trying to spend old coins from the reign of Decius. The bishop was summoned to interview the sleepers; they told him their miracle story, and died praising God.
The various lives of the Seven Sleepers in Greek and in other non-Latin languages are listed at BHO.
Account in the Quran
The polytheists (mushriks) of Mecca, after consulting with the people of the Book, tested Muhammad by asking him three questions, and
Surah Al-Kahf was sent down in answer to them. The mushriks inquired about the identity of the Sleepers of the Cave, the real story of Khidr, and about Dhu al-Qarnayn.
The story of the Companions of the Cave () is referred to in Quran 18:9-26. The precise number of the sleepers is not stated. The Quran furthermore points to the fact that people, shortly after the incident emerged, started to make "idle guesses" as to how many people were in the cave. To this the Quran asserts that: "My Sustainer knows best how many they were". Similarly, regarding the exact period of time the people stayed in the cave, the Quran, after asserting the guesswork of the people that "they remained in the cave for 300 years and nine added", resolves that "God knows best how long they remained [there]." According to the 25th verse of Al-Kahf, the Companions of the Cave have slept for 300 years in the solar calendar and slept 309 in the lunar calendar since the lunar calendar is 11 days shorter than the solar, which explains the inclusion of the additional nine years. The Quran says that the sleepers included a dog, which Islamic tradition names as Qitmir, who guarded the entrance of the cave (verse 18).
Number and names
Jewish and Christian versions
Early versions do not all agree on or even specify the number of sleepers. Some Jewish circles and the Christians of Najran believed in only three brothers; the East Syriac, five. Most Syriac accounts have eight, including a nameless watcher which God sets over the sleepers. A 6th-century Latin text titled "Pilgrimage of Theodosius" featured the sleepers as seven people in number, with a dog named Viricanus.
Bartłomiej Grysa lists at least seven different sets of names for the sleepers:
Maximian, Martinian, Dionisius, John, Constantine, Malchus, Serapion
Maximilian, Martinian, Dionisius, John, Constantine, Malkhus, Serapion, Anthony
Maximilian, Martinian, Dionisius, John, Constantine, Yamblikh (Iamblichus), Anthony
Makṯimilīnā (Maksimilīnā, Maḥsimilīnā), Marnūš (Marṭūs), Kafašṭaṭyūš (Ksōṭōnos), Yamlīḫā (Yamnīḫ), Mišlīnā, Saḏnūš, Dabranūš (Bīrōnos), Samōnos, Buṭōnos, Qālos (according to aṭ-Ṭabarī and ad-Damīrī)
Achillides, Probatus, Stephanus, Sambatus, Quiriacus, Diogenus, Diomedes (according to Gregory of Tours)
Ikilios, Fruqtis, Istifanos, Sebastos, Qiryaqos, Dionisios (according to Michael the Syrian)
Aršellītīs, Probatios, Sabbastios, Stafanos, Kīriakos, Diōmetios, Avhenios (according to the Coptic version)
Islamic view
In Islam no specific number is mentioned. Qur'an 18:22 discusses the disputes regarding their numbers. The verse says:
Some will say, "They were three, their dog was the fourth," while others will say, "They were five, their dog was the sixth," only guessing blindly. And others will say, "They were seven and their dog was the eighth." Say, O Prophet, "My Lord knows best their exact number. Only a few people know as well." So do not argue about them except with sure knowledge, nor consult any of those who debate about them.
Duration
Christian accounts
The number of years the sleepers slept also varies between accounts. The highest number, given by Gregory of Tours, was 373 years. Some accounts have 372. Jacobus de Voragine calculated it at 196 (from the year 252 until 448). Other calculations suggest 195.
Islamic accounts
The Qu'ran in regard to the duration of the sleep only mentions the conflicting numbers that people assigned, in Surah 18:25-26, which states, "They remained in the Cave for three hundred years; and others added nine more years. / Say: 'Allah knows best how long they remained in it, for only He knows all that is hidden in the heavens and the earth. How well He sees; how well He hears! The creatures have no other guardian than Him; He allows none to share His authority.'"
Caves of the Seven Sleepers
Several sites are attributed as the "Cave of the Seven Sleepers", but none could empirically convince to be the original site associated with the legend. As the earliest versions of the legend spread out from Ephesus, an early Christian catacomb in that area came to be associated with it, attracting scores of pilgrims. On the slopes of Mount Pion (Mount Coelian) near Ephesus (near modern Selçuk in Turkey), the grotto of the Seven Sleepers with ruins of the religious site built over it was excavated in 1926–1928. The excavation brought to light several hundred graves dated to the 5th and 6th centuries. Inscriptions dedicated to the Seven Sleepers were found on the walls and in the graves. This grotto is still shown to tourists.
Other possible sites of the cave of the Seven Sleepers are in Damascus, Syria and Afşin and Tarsus, Turkey. Afşin is near the antique Roman city of Arabissus, to which the East Roman Emperor Justinian paid a visit. The site was a Hittite temple, used as a Roman temple and later as a church in Roman and Byzantine times. The Emperor brought marble niches from Western Anatolia as gifts for it, which are preserved inside the Eshab-ı Kehf Kulliye mosque to this day. The Seljuks continued to use the place of worship as a church and a mosque. It was turned into a mosque over time, with the conversion of the local population to Islam.
There is a cave near Amman, Jordan, also known as the Cave of Seven Sleepers, which has eight smaller sealed tombs present inside and a ventilation duct coming out of the cave.
List of notable sites
Asia Minor
, Ephesus, Turkey
Eshab-ı Kehf Cave, Tarsus, Turkey
Grotto of the Seven Sleepers, İzmir, Turkey
Eshab-ı Kehf Kulliye, outside Afşin, Turkey
MENA region
Mar Musa, monastery in Syria
Mount Qasioun, Damascus, Syria
Cave of the Seven Sleepers, Al-Rajeb (Greater Amman), Jordan
Mosquée de Sept Dormants, Chenini, Tunisia
China
Tuyuq Khojam Mazar, Turpan, China
Gallery
Modern literature
Early modern
The account had become proverbial in 16th century Protestant culture. The poet John Donne could ask,
I wonder, by my troth, what thou and I
Did, till we loved? Were we not weaned till then?
But sucked on country pleasures, childishly?
Or snorted we in the Seven Sleepers' den?—John Donne, "The Good-Morrow".
In John Heywood's Play called the Four PP (1530s), the Pardoner, a Renaissance update of the protagonist in Chaucer's "The Pardoner's Tale", offers his companions the opportunity to kiss "a slipper / Of one of the Seven Sleepers", but the relic is presented as absurdly as the Pardoner's other offerings, which include "the great-toe of the Trinity" and "a buttock-bone of Pentecost."
Little is heard of the Seven Sleepers during the Enlightenment, but the account revived with the coming of Romanticism. The Golden Legend may have been the source for retellings of the Seven Sleepers in Thomas de Quincey's Confessions of an English Opium-Eater, in a poem by Goethe, Washington Irving's "Rip van Winkle", H. G. Wells's The Sleeper Awakes. It also might have an influence on the motif of the "King asleep in mountain". Mark Twain did a burlesque of the story of the Seven Sleepers in Chapter 13 of Volume 2 of The Innocents Abroad.
Contemporary
Edward Gibbon gives different accounts of the story in The History of the Decline and Fall of the Roman Empire.
The Serbian writer Danilo Kiš retells the story of the Seven Sleepers in a short story, "The Legend of the Sleepers", from his book The Encyclopedia of the Dead.
The Italian author Andrea Camilleri incorporates the story in his novel The Terracotta Dog in which the protagonist is led to a cave containing the titular watchdog (as described in the Qur'an and called "Kytmyr" in Sicilian folklore) and the saucer of silver coins with which one of the sleepers is to buy "pure food" from the bazaar in Ephesus (Qur'an 18.19). The Seven Sleepers are symbolically replaced by lovers Lisetta Moscato and Mario Cunich, who were killed in their nuptial bed by an assassin hired by Lisseta's incestuous father and later laid to rest in a cave in the Sicilian countryside.
In Susan Cooper's The Dark Is Rising series, Will Stanton awakens the Seven Sleepers in The Grey King, and in Silver on the Tree, they ride in the last battle against the Dark.
The Seven Sleepers series by Gilbert Morris takes a modern approach to the story in which seven teenagers must be awakened to fight evil in a post-nuclear-apocalypse world.
John Buchan refers to the Seven Sleepers in The Three Hostages in which Richard Hannay surmises that his wife Mary, who is a sound sleeper, is descended from one of the seven who has married one of the Foolish Virgins.
The Seven Sleepers are mentioned in the song "Les Invisibles" on the 1988 Blue Öyster Cult album Imaginos.
Several languages have idioms related to the Seven Sleepers, including:
Hungarian: hétalvó, literally a "seven-sleeper", or "one who sleeps for an entire week", is a colloquial reference to a person who oversleeps or who is typically drowsy.
Irish: "Na seacht gcodlatáin" refers to hibernating animals.
Norwegian: a late riser may be referred to as a syvsover ("seven sleeper")
Swedish: a late riser may be referred to as a sjusovare ("seven sleeper").
Welsh: a late riser may be referred to as a saith cysgadur ("seven sleeper") – as in the 1885 novel Rhys Lewis by Daniel Owen, where the protagonist is referred to as such in chapter 37, p. 294 (Hughes a'i Fab, Caerdydd, 1948).
Feast day
The most recent edition of the Roman Martyrology commemorates the Seven Sleepers of Ephesus under the date of 27 July. The Byzantine calendar commemorates them with feasts on 4 August and 22 October. Syriac Orthodox calendars gives various dates: 21 April, 2 August, 13 August, 23 October and 24 October.
See also
Epimenides
King asleep in mountain
The Men of Angelos
Rip Van Winkle
Seven Sleepers' Day
The Three Sleepers: characters in the C. S. Lewis children's novel The Voyage of the Dawn Treader
References
Further reading
External links
Quran–Authorized English Version The Cave- Sura 18 – Quran – Authorized English Version
"SS. Maximian, Malchus, Martinian, Dionysius, John, Serapion, and Constantine, Martyrs", Butler's Lives of the Saints
Text containing the Seven Sleepers' commemoration as part of the Office of Prime.
Sura al-Kahf at Wikisource
Photos of the excavated site of the Seven Sleepers cult.
Gregory of Tours, The Patient Impassioned Suffering of the Seven Sleepers of Ephesus translated by Michael Valerie
The Lives of the Seven Sleepers from The Golden Legend by Jacobus de Voragine, William Caxton Middle English translation.
The Seven Sleepers of Ephesus by Chardri, translated into English by Tony Devaney Morinelli: Medieval Sourcebook. fordham.edu
Medieval legends
Legendary Greek people
Saints from Roman Anatolia
Groups of Christian martyrs of the Roman era
Groups of Roman Catholic saints
Quranic narratives
Sleep in mythology and folklore
3rd-century Christian saints
Rip Van Winkle-type stories
Dogs in religion
Decian dynasty
Ancient Ephesians
Septets in religion
Christianity and Islam | Seven Sleepers | [
"Biology"
] | 3,791 | [
"Behavior",
"Sleep",
"Sleep in mythology and folklore"
] |
321,930 | https://en.wikipedia.org/wiki/Weird%20number | In number theory, a weird number is a natural number that is abundant but not semiperfect. In other words, the sum of the proper divisors (divisors including 1 but not itself) of the number is greater than the number, but no subset of those divisors sums to the number itself.
Examples
The smallest weird number is 70. Its proper divisors are 1, 2, 5, 7, 10, 14, and 35; these sum to 74, but no subset of these sums to 70. The number 12, for example, is abundant but not weird, because the proper divisors of 12 are 1, 2, 3, 4, and 6, which sum to 16; but 2 + 4 + 6 = 12.
The first few weird numbers are
70, 836, 4030, 5830, 7192, 7912, 9272, 10430, 10570, 10792, 10990, 11410, 11690, 12110, 12530, 12670, 13370, 13510, 13790, 13930, 14770, ... .
Properties
Infinitely many weird numbers exist. For example, 70p is weird for all primes p ≥ 149. In fact, the set of weird numbers has positive asymptotic density.
It is not known if any odd weird numbers exist. If so, they must be greater than 1021.
Sidney Kravitz has shown that for k a positive integer, Q a prime exceeding 2k, and
also prime and greater than 2k, then
is a weird number.
With this formula, he found the large weird number
Primitive weird numbers
A property of weird numbers is that if n is weird, and p is a prime greater than the sum of divisors σ(n), then pn is also weird. This leads to the definition of primitive weird numbers: weird numbers that are not a multiple of other weird numbers . Among the 1765 weird numbers less than one million, there are 24 primitive weird numbers. The construction of Kravitz yields primitive weird numbers, since all weird numbers of the form are primitive, but the existence of infinitely many k and Q which yield a prime R is not guaranteed. It is conjectured that there exist infinitely many primitive weird numbers, and Melfi has shown that the infinitude of primitive weird numbers is a consequence of Cramér's conjecture.
Primitive weird numbers with as many as 16 prime factors and 14712 digits have been found.
See also
Untouchable number
References
External links
Divisor function
Integer sequences | Weird number | [
"Mathematics"
] | 526 | [
"Sequences and series",
"Integer sequences",
"Mathematical structures",
"Recreational mathematics",
"Mathematical objects",
"Combinatorics",
"Numbers",
"Number theory"
] |
321,936 | https://en.wikipedia.org/wiki/Primeval%20number | In recreational number theory, a primeval number is a natural number n for which the number of prime numbers which can be obtained by permuting some or all of its digits (in base 10) is larger than the number of primes obtainable in the same way for any smaller natural number. Primeval numbers were first described by Mike Keith.
The first few primeval numbers are
1, 2, 13, 37, 107, 113, 137, 1013, 1037, 1079, 1237, 1367, 1379, 10079, 10123, 10136, 10139, 10237, 10279, 10367, 10379, 12379, 13679, ...
The number of primes that can be obtained from the primeval numbers is
0, 1, 3, 4, 5, 7, 11, 14, 19, 21, 26, 29, 31, 33, 35, 41, 53, 55, 60, 64, 89, 96, 106, ...
The largest number of primes that can be obtained from a primeval number with n digits is
1, 4, 11, 31, 106, 402, 1953, 10542, 64905, 362451, 2970505, ...
The smallest n-digit number to achieve this number of primes is
2, 37, 137, 1379, 13679, 123479, 1234679, 12345679, 102345679, 1123456789, 10123456789, ...
Primeval numbers can be composite. The first is 1037 = 17×61. A Primeval prime is a primeval number which is also a prime number:
2, 13, 37, 107, 113, 137, 1013, 1237, 1367, 10079, 10139, 12379, 13679, 100279, 100379, 123479, 1001237, 1002347, 1003679, 1012379, ...
The following table shows the first seven primeval numbers with the obtainable primes and the number of them.
Base 12
In base 12, the primeval numbers are: (using inverted two and three for ten and eleven, respectively)
1, 2, 13, 15, 57, 115, 117, 125, 135, 157, 1017, 1057, 1157, 1257, 125Ɛ, 157Ɛ, 167Ɛ, ...
The number of primes that can be obtained from the primeval numbers is: (written in base 10)
0, 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 20, 23, 27, 29, 33, 35, ...
Note that 13, 115 and 135 are composite: 13 = 3×5, 115 = 7×1Ɛ, and 135 = 5×31.
See also
Permutable prime
Truncatable prime
External links
Chris Caldwell, The Prime Glossary: Primeval number at The Prime Pages
Mike Keith, Integers Containing Many Embedded Primes
Base-dependent integer sequences
Prime numbers | Primeval number | [
"Mathematics"
] | 659 | [
"Prime numbers",
"Mathematical objects",
"Numbers",
"Number theory"
] |
321,962 | https://en.wikipedia.org/wiki/Woodall%20number | In number theory, a Woodall number (Wn) is any natural number of the form
for some natural number n. The first few Woodall numbers are:
1, 7, 23, 63, 159, 383, 895, … .
History
Woodall numbers were first studied by Allan J. C. Cunningham and H. J. Woodall in 1917, inspired by James Cullen's earlier study of the similarly defined Cullen numbers.
Woodall primes
Woodall numbers that are also prime numbers are called Woodall primes; the first few exponents n for which the corresponding Woodall numbers Wn are prime are 2, 3, 6, 30, 75, 81, 115, 123, 249, 362, 384, ... ; the Woodall primes themselves begin with 7, 23, 383, 32212254719, ... .
In 1976 Christopher Hooley showed that almost all Cullen numbers are composite. In October 1995, Wilfred Keller published a paper discussing several new Cullen primes and the efforts made to factorise other Cullen and Woodall numbers. Included in that paper is a personal communication to Keller from Hiromi Suyama, asserting that Hooley's method can be reformulated to show that it works for any sequence of numbers , where a and b are integers, and in particular, that almost all Woodall numbers are composite. It is an open problem whether there are infinitely many Woodall primes. , the largest known Woodall prime is 17016602 × 217016602 − 1. It has 5,122,515 digits and was found by Diego Bertolotti in March 2018 in the distributed computing project PrimeGrid.
Restrictions
Starting with W4 = 63 and W5 = 159, every sixth Woodall number is divisible by 3; thus, in order for Wn to be prime, the index n cannot be congruent to 4 or 5 (modulo 6). Also, for a positive integer m, the Woodall number W2m may be prime only if 2m + m is prime. As of January 2019, the only known primes that are both Woodall primes and Mersenne primes are W2 = M3 = 7, and W512 = M521.
Divisibility properties
Like Cullen numbers, Woodall numbers have many divisibility properties. For example, if p is a prime number, then p divides
W(p + 1) / 2 if the Jacobi symbol is +1 and
W(3p − 1) / 2 if the Jacobi symbol is −1.
Generalization
A generalized Woodall number base b is defined to be a number of the form n × bn − 1, where n + 2 > b; if a prime can be written in this form, it is then called a generalized Woodall prime.
The smallest value of n such that n × bn − 1 is prime for b = 1, 2, 3, ... are
3, 2, 1, 1, 8, 1, 2, 1, 10, 2, 2, 1, 2, 1, 2, 167, 2, 1, 12, 1, 2, 2, 29028, 1, 2, 3, 10, 2, 26850, 1, 8, 1, 42, 2, 6, 2, 24, 1, 2, 3, 2, 1, 2, 1, 2, 2, 140, 1, 2, 2, 22, 2, 8, 1, 2064, 2, 468, 6, 2, 1, 362, 1, 2, 2, 6, 3, 26, 1, 2, 3, 20, 1, 2, 1, 28, 2, 38, 5, 3024, 1, 2, 81, 858, 1, 2, 3, 2, 8, 60, 1, 2, 2, 10, 5, 2, 7, 182, 1, 17782, 3, ...
, the largest known generalized Woodall prime with base greater than 2 is 2740879 × 322740879 − 1.
See also
Mersenne prime - Prime numbers of the form 2n − 1.
References
Further reading
.
.
.
External links
Chris Caldwell, The Prime Glossary: Woodall number, and The Top Twenty: Woodall, and The Top Twenty: Generalized Woodall, at The Prime Pages.
Steven Harvey, List of Generalized Woodall primes.
Paul Leyland, Generalized Cullen and Woodall Numbers
Integer sequences
Unsolved problems in number theory
Classes of prime numbers | Woodall number | [
"Mathematics"
] | 950 | [
"Sequences and series",
"Unsolved problems in mathematics",
"Integer sequences",
"Mathematical structures",
"Recreational mathematics",
"Mathematical objects",
"Unsolved problems in number theory",
"Combinatorics",
"Mathematical problems",
"Numbers",
"Number theory"
] |
321,963 | https://en.wikipedia.org/wiki/Riesel%20number | In mathematics, a Riesel number is an odd natural number k for which is composite for all natural numbers n . In other words, when k is a Riesel number, all members of the following set are composite:
If the form is instead , then k is a Sierpiński number.
Riesel problem
In 1956, Hans Riesel showed that there are an infinite number of integers k such that is not prime for any integer n. He showed that the number 509203 has this property, as does 509203 plus any positive integer multiple of 11184810. The Riesel problem consists in determining the smallest Riesel number. Because no covering set has been found for any k less than 509203, it is conjectured to be the smallest Riesel number.
To check if there are k < 509203, the Riesel Sieve project (analogous to Seventeen or Bust for Sierpiński numbers) started with 101 candidates k. As of December 2022, 57 of these k had been eliminated by Riesel Sieve, PrimeGrid, or outside persons. The remaining 42 values of k that have yielded only composite numbers for all values of n so far tested are
23669, 31859, 38473, 46663, 67117, 74699, 81041, 107347, 121889, 129007, 143047, 161669, 206231, 215443, 226153, 234343, 245561, 250027, 315929, 319511, 324011, 325123, 327671, 336839, 342847, 344759, 362609, 363343, 364903, 365159, 368411, 371893, 384539, 386801, 397027, 409753, 444637, 470173, 474491, 477583, 485557, 494743.
The most recent elimination was in April 2023, when 97139 × 218397548 − 1 was found to be prime by Ryan Propper. This number is 5,538,219 digits long.
As of January 2023, PrimeGrid has searched the remaining candidates up to n = 14,900,000.
Known Riesel numbers
The sequence of currently known Riesel numbers begins with:
509203, 762701, 777149, 790841, 992077, 1106681, 1247173, 1254341, 1330207, 1330319, 1715053, 1730653, 1730681, 1744117, 1830187, 1976473, 2136283, 2251349, 2313487, 2344211, 2554843, 2924861, ...
Covering set
A number can be shown to be a Riesel number by exhibiting a covering set: a set of prime numbers that will divide any member of the sequence, so called because it is said to "cover" that sequence. The only proven Riesel numbers below one million have covering sets as follows:
has covering set {3, 5, 7, 13, 17, 241}
has covering set {3, 5, 7, 13, 17, 241}
has covering set {3, 5, 7, 13, 19, 37, 73}
has covering set {3, 5, 7, 13, 19, 37, 73}
has covering set {3, 5, 7, 13, 17, 241}.
The smallest n for which k · 2n − 1 is prime
Here is a sequence for k = 1, 2, .... It is defined as follows: is the smallest n ≥ 0 such that is prime, or −1 if no such prime exists.
2, 1, 0, 0, 2, 0, 1, 0, 1, 1, 2, 0, 3, 0, 1, 1, 2, 0, 1, 0, 1, 1, 4, 0, 3, 2, 1, 3, 4, 0, 1, 0, 2, 1, 2, 1, 1, 0, 3, 1, 2, 0, 7, 0, 1, 3, 4, 0, 1, 2, 1, 1, 2, 0, 1, 2, 1, 3, 12, 0, 3, 0, 2, 1, 4, 1, 5, 0, 1, 1, 2, 0, 7, 0, 1, ... . The first unknown n is for that k = 23669.
Related sequences are (not allowing n = 0), for odd ks, see or (not allowing n = 0).
Simultaneously Riesel and Sierpiński
A number both Riesel and Sierpiński is a Brier number. The five smallest known examples (and note that some might be smaller, i.e. that the sequence might not be comprehensive) are: 3316923598096294713661, 10439679896374780276373, 11615103277955704975673, 12607110588854501953787, 17855036657007596110949, ... ().
The dual Riesel problem
The dual Riesel numbers are defined as the odd natural numbers k such that |2n - k| is composite for all natural numbers n. There is a conjecture that the set of this numbers is the same as the set of Riesel numbers. For example, |2n - 509203| is composite for all natural numbers n, and 509203 is conjectured to be the smallest dual Riesel number.
The smallest n which 2n - k is prime are (for odd ks, and this sequence requires that 2n > k)
2, 3, 3, 39, 4, 4, 4, 5, 6, 5, 5, 6, 5, 5, 5, 7, 6, 6, 11, 7, 6, 29, 6, 6, 7, 6, 6, 7, 6, 6, 6, 8, 8, 7, 7, 10, 9, 7, 8, 9, 7, 8, 7, 7, 8, 7, 8, 10, 7, 7, 26, 9, 7, 8, 7, 7, 10, 7, 7, 8, 7, 7, 7, 47, 8, 14, 9, 11, 10, 9, 10, 8, 9, 8, 8, ...
The odd ks which k - 2n are all composite for all 2n < k (the de Polignac numbers) are
1, 127, 149, 251, 331, 337, 373, 509, 599, 701, 757, 809, 877, 905, 907, 959, 977, 997, 1019, 1087, 1199, 1207, 1211, 1243, 1259, 1271, 1477, ...
The unknown values of ks are (for which 2n > k)
1871, 2293, 25229, 31511, 36971, 47107, 48959, 50171, 56351, 63431, 69427, 75989, 81253, 83381, 84491, ...
Riesel number base b
One can generalize the Riesel problem to an integer base b ≥ 2. A Riesel number base b is a positive integer k such that gcd(k − 1, b − 1) = 1. (if gcd(k − 1, b − 1) > 1, then gcd(k − 1, b − 1) is a trivial factor of k×bn − 1 (Definition of trivial factors for the conjectures: Each and every n-value has the same factor)) For every integer b ≥ 2, there are infinitely many Riesel numbers base b.
Example 1: All numbers congruent to 84687 mod 10124569 and not congruent to 1 mod 5 are Riesel numbers base 6, because of the covering set {7, 13, 31, 37, 97}. Besides, these k are not trivial since gcd(k + 1, 6 − 1) = 1 for these k. (The Riesel base 6 conjecture is not proven, it has 3 remaining k, namely 1597, 9582 and 57492)
Example 2: 6 is a Riesel number to all bases b congruent to 34 mod 35, because if b is congruent to 34 mod 35, then 6×bn − 1 is divisible by 5 for all even n and divisible by 7 for all odd n. Besides, 6 is not a trivial k in these bases b since gcd(6 − 1, b − 1) = 1 for these bases b.
Example 3: All squares k congruent to 12 mod 13 and not congruent to 1 mod 11 are Riesel numbers base 12, since for all such k, k×12n − 1 has algebraic factors for all even n and divisible by 13 for all odd n. Besides, these k are not trivial since gcd(k + 1, 12 − 1) = 1 for these k. (The Riesel base 12 conjecture is proven)
Example 4: If k is between a multiple of 5 and a multiple of 11, then k×109n − 1 is divisible by either 5 or 11 for all positive integers n. The first few such k are 21, 34, 76, 89, 131, 144, ... However, all these k < 144 are also trivial k (i. e. gcd(k − 1, 109 − 1) is not 1). Thus, the smallest Riesel number base 109 is 144. (The Riesel base 109 conjecture is not proven, it has one remaining k, namely 84)
Example 5: If k is square, then k×49n − 1 has algebraic factors for all positive integers n. The first few positive squares are 1, 4, 9, 16, 25, 36, ... However, all these k < 36 are also trivial k (i. e. gcd(k − 1, 49 − 1) is not 1). Thus, the smallest Riesel number base 49 is 36. (The Riesel base 49 conjecture is proven)
We want to find and proof the smallest Riesel number base b for every integer b ≥ 2. It is a conjecture that if k is a Riesel number base b, then at least one of the three conditions holds:
All numbers of the form k×bn − 1 have a factor in some covering set. (For example, b = 22, k = 4461, then all numbers of the form k×bn − 1 have a factor in the covering set: {5, 23, 97})
k×bn − 1 has algebraic factors. (For example, b = 9, k = 4, then k×bn − 1 can be factored to (2×3n − 1) × (2×3n + 1))
For some n, numbers of the form k×bn − 1 have a factor in some covering set; and for all other n, k×bn − 1 has algebraic factors. (For example, b = 19, k = 144, then if n is odd, then k×bn − 1 is divisible by 5, if n is even, then k×bn − 1 can be factored to (12×19n/2 − 1) × (12×19n/2 + 1))
In the following list, we only consider those positive integers k such that gcd(k − 1, b − 1) = 1, and all integer n must be ≥ 1.
Note: k-values that are a multiple of b and where k−1 is not prime are included in the conjectures (and included in the remaining k with color if no primes are known for these k-values) but excluded from testing (Thus, never be the k of "largest 5 primes found"), since such k-values will have the same prime as k / b.
Conjectured smallest Riesel number base n are (start with n = 2)
509203, 63064644938, 9, 346802, 84687, 408034255082, 14, 4, 10176, 862, 25, 302, 4, 36370321851498, 9, 86, 246, 144, 8, 560, 4461, 476, 4, 36, 149, 8, 144, 4, 1369, 134718, 10, 16, 6, 287860, 4, 7772, 13, 4, 81, 8, 15137, 672, 4, 22564, 8177, 14, 3226, 36, 16, 64, 900, 5392, 4, 6852, 20, 144, 105788, 4, 121, 13484, 8, 187258666, 9, ...
See also
Sierpiński number
Woodall number
Experimental mathematics
BOINC
PrimeGrid
References
Sources
External links
PrimeGrid
The Riesel Problem: Definition and Status
The Prime Glossary: Riesel number
List of primes of the form: k*2^n-1, k<300
List of primes of the form: k*2^n-1, k<300, Project Riesel Prime Search
Riesel and Proth Prime Database
Analytic number theory
Unsolved problems in number theory
Prime numbers | Riesel number | [
"Mathematics"
] | 2,944 | [
"Unsolved problems in mathematics",
"Analytic number theory",
"Prime numbers",
"Mathematical objects",
"Unsolved problems in number theory",
"Mathematical problems",
"Numbers",
"Number theory"
] |
321,987 | https://en.wikipedia.org/wiki/Anunnaki | The Anunnaki (Sumerian: , also transcribed as Anunaki, Annunaki, Anunna, Ananaki and other variations) are a group of deities of the ancient Sumerians, Akkadians, Assyrians and Babylonians. In the earliest Sumerian writings about them, which come from the Post-Akkadian period, the Anunnaki are deities in the pantheon, descendants of An (the god of the heavens) and Ki (the goddess of earth), and their primary function was to decree the fates of humanity.
Etymology
The name Anunnaki is derived from An, the Sumerian god of the sky. The name is variously written "da-nuna", "da-nuna-ke4-ne", or "da-nun-na", meaning "princely offspring" or "offspring of An".
The Anunnaki were believed to be the offspring of An and the earth goddess Ki. Samuel Noah Kramer identifies Ki with the Sumerian mother goddess Ninhursag, stating that they were originally the same figure. The oldest of the Anunnaki was Enlil, the god of air and chief god of the Sumerian pantheon. The Sumerians believed that, until Enlil was born, heaven and earth were inseparable. Then, Enlil split heaven and earth in two and carried away the earth while his father An carried away the sky.
Worship and iconography
The Anunnaki are chiefly mentioned in literary texts and very little evidence to support the existence of any cult of them has yet been unearthed. This is likely because each member of the Anunnaki had his or her own individual cult, separate from the others. Similarly, no representations of the Anunnaki as a complete group have yet been discovered, although a few depictions of two or three individual members together have been identified. Deities in ancient Mesopotamia were almost exclusively anthropomorphic. They were thought to possess extraordinary powers and were often envisioned as being of tremendous physical size. The deities typically wore melam, an ambiguous substance which "covered them in terrifying splendor". Melam could also be worn by heroes, kings, giants, and even demons. The effect that seeing a deity's melam has on a human is described as ni, a word for the physical tingling of the flesh. Deities were almost always depicted wearing horned caps, consisting of up to seven superimposed pairs of ox-horns. They were also sometimes depicted wearing clothes with elaborate decorative gold and silver ornaments sewn into them.
The ancient Mesopotamians believed that their deities lived in Heaven, after an earlier history of visiting earth in the mythological texts, and that a god's statue was a physical embodiment of the god himself. As such, cult statues were given constant care and attention and a set of priests was assigned to tend to them. These priests would clothe the statues and place feasts before them so they could "eat". A deity's temple was believed to be that deity's literal place of residence. The gods had boats, full-sized barges which were normally stored inside their temples and were used to transport their cult statues along waterways during various religious festivals. The gods also had chariots, which were used for transporting their cult statues by land. Sometimes a deity's cult statue would be transported to the location of a battle so that the deity could watch the battle unfold. The major deities of the Mesopotamian pantheon, which included the Anunnaki, were believed to participate in the "assembly of the gods", through which the gods made all of their decisions. This assembly was seen as a divine counterpart to the semi-democratic legislative system that existed during the Third Dynasty of Ur ( 2112 BC – 2004 BC).
Mythology
Sumerian
The earliest known usages of the term Anunnaki come from inscriptions written during the reign of Gudea ( 2144–2124 BC) and the Third Dynasty of Ur. In the earliest texts, the term is applied to the most powerful and important deities in the Sumerian pantheon: the descendants of the sky-god An.This group of deities probably included the "seven gods who decree": An, Enlil, Enki, Ninhursag, Nanna, Utu, and Inanna.
Although certain deities are described as members of the Anunnaki, no complete list of the names of all the Anunnaki has survived and they are usually only referred to as a cohesive group in literary texts. Furthermore, Sumerian texts describe the Anunnaki inconsistently and do not agree on how many Anunnaki there were, or what their divine function was. Originally, the Anunnaki appear to have been heavenly deities with immense powers. In the poem Enki and the World Order, the Anunnaki "do homage" to Enki, sing hymns of praise in his honor, and "take up their dwellings" among the people of Sumer. The same composition twice states that the Anunnaki "decree the fates of mankind".
Virtually every major deity in the Sumerian pantheon was regarded as the patron of a specific city and was expected to protect that city's interests. The deity was believed to permanently reside within that city's temple. One text mentions as many as fifty Anunnaki associated with the city of Eridu. In Inanna's Descent into the Netherworld, there are only seven Anunnaki, who reside within the Underworld and serve as judges. Inanna stands trial before them for her attempt to take over the Underworld; they deem her guilty of hubris and condemn her to death.
Major deities in Sumerian mythology were associated with specific celestial bodies. Inanna was believed to be the planet Venus. Utu was believed to be the sun. Nanna was the moon. An was identified with all the stars of the equatorial sky, Enlil with those of the northern sky, and Enki with those of the southern sky. The path of Enlil's celestial orbit was a continuous, symmetrical circle around the north celestial pole, but those of An and Enki were believed to intersect at various points.
Akkadian, Babylonian and Assyrian
Akkadian texts of the second millennium BC follow similar portrayals of the Anunnaki from Inanna's Descent into the Netherworld, depicting them as chthonic Underworld deities. In an abbreviated Akkadian version of Inanna's Descent written in the early second millennium, Ereshkigal, the queen of the Underworld, comments that she "drink[s] water with the Anunnaki". Later in the same poem, Ereshkigal orders her servant Namtar to fetch the Anunnaki from Egalgina, to "decorate the threshold steps with coral", and to "seat them on golden thrones".
During the Old Babylonian Period ( 1830 BC – c. 1531 BC), a new set of deities known as the Igigi are introduced. The relationship between the Anunnaki and the Igigi is unclear. On some occasions, the categories appear to be used synonymously, but in other writings, such as The Poem of Erra, there is a clear distinction between the two. In the late Akkadian Atra-Hasis epic, the Igigi are the sixth generation of the gods who are forced to perform labor for the Anunnaki. After forty days, the Igigi rebel and the god Enki, one of the Anunnaki, creates humans to replace them.
From the Middle Babylonian Period ( 1592 – 1155 BC) onward, the name Anunnaki was applied generally to the deities of the underworld; whereas the name Igigi was applied to the heavenly deities. During this period, the underworld deities Damkina, Nergal, and Madānu are listed as the most powerful among the Anunnaki, alongside Marduk, the national god of ancient Babylon.
In the standard Akkadian Epic of Gilgamesh ( 1200 BC) Utnapishtim, the immortal survivor of the Great Flood, describes the Anunnaki as seven judges of the Underworld, who set the land aflame as the storm approaches. Later, when the flood comes, Ishtar (the East Semitic equivalent to Inanna) and the Anunnaki mourn over the destruction of humanity.
In the Babylonian Enûma Eliš, Marduk assigns the Anunnaki their positions. A late Babylonian version of the epic mentions 600 Anunnaki of the underworld, but only 300 Anunnaki of heaven, indicating the existence of a complex underworld cosmology. In gratitude, the Anunnaki, the "Great Gods", build Esagila, a "splendid" temple dedicated to Marduk, Ea, and Ellil. In the eighth-century BC Poem of Erra, the Anunnaki are described as the brothers of the god Nergal and are depicted as antagonistic towards humanity.
A badly damaged text from the Neo-Assyrian Period (911 – 612 BC) describes Marduk leading his army of Anunnaki into the sacred city of Nippur and causing a disturbance. The disturbance causes a flood, which forces the resident gods of Nippur to take shelter in the Eshumesha temple to Ninurta. Enlil is enraged at Marduk's transgression and orders the gods of Eshumesha to take Marduk and the other Anunnaki as prisoners. The Anunnaki are captured, but Marduk appoints his front-runner Mushteshirhablim to lead a revolt against the gods of Eshumesha and sends his messenger Neretagmil to alert Nabu, the god of literacy. When the Eshumesha gods hear Nabu speak, they come out of their temple to search for him. Marduk defeats the Eshumesha gods and takes 360 of them as prisoners of war, including Enlil himself. Enlil protests that the Eshumesha gods are innocent, so Marduk puts them on trial before the Anunnaki. The text ends with a warning from Damkianna (another name for Ninhursag) to the gods and to humanity, pleading them not to repeat the war between the Anunnaki and the gods of Eshumesha.
Hurrian and Hittite
In the mythologies of the Hurrians and Hittites (which flourished in the mid to late second millennium BC), the oldest generation of gods was believed to have been banished by the younger gods to the Underworld, where they were ruled by the goddess Lelwani. Hittite scribes identified these deities with the Anunnaki. In ancient Hurrian, the Anunnaki are referred to as karuileš šiuneš, which means "former ancient gods", or kattereš šiuneš, which means "gods of the earth". Hittite and Hurrian treaties were often sworn by the old gods in order to ensure that the oaths would be kept. In one myth, the gods are threatened by the stone giant Ullikummi, so Ea (the later name for Enki) commands the Former Gods to find the weapon that was used to separate the heavens from the earth. They find it and use it to cut off Ullikummi's feet.
Although the names of the Anunnaki in Hurrian and Hittite texts frequently vary, they are always eight in number. In one Hittite ritual, the names of the old gods are listed as: "Aduntarri the diviner, Zulki the dream interpretess, Irpitia Lord of the Earth, Narā, Namšarā, Minki, Amunki, and Āpi." The old gods had no identifiable cult in the Hurrio-Hittite religion; instead, the Hurrians and Hittites sought to communicate with the old gods through the ritual sacrifice of a piglet in a pit dug in the ground. The old gods were often invoked to perform ritual purifications.
The Hittite account of the old gods' banishment to the Underworld is closely related with the Greek poet Hesiod's narrative of the overthrow of the Titans by the Olympians in his Theogony. The Greek sky-god Ouranos (whose name means "Heaven") is the father of the Titans and is derived from the Hittite version of Anu. In Hesiod's account, Ouranos is castrated by his son Cronus, just as Anu was castrated by his son Kumarbi in the Hittite story.
Pseudoarchaeology and conspiracy theories
Over a series of published books (starting with Chariots of the Gods? in 1968), pseudoarchaeologist Erich von Däniken claimed that extraterrestrial "ancient astronauts" had visited a prehistoric Earth. Däniken explains the origins of religions as reactions to contact with an alien race, and offers interpretations of Sumerian texts and the Old Testament as evidence.
In his 1976 book The Twelfth Planet, author Zecharia Sitchin claimed that the Anunnaki were actually an advanced humanoid extraterrestrial species from the undiscovered planet Nibiru, who came to Earth around 500,000 years ago and constructed a base of operations in order to mine gold after discovering that the planet was rich in the precious metal. According to Sitchin, the Anunnaki hybridized their species and Homo erectus via in vitro fertilization in order to create humans as a slave species of miners. Sitchin claimed that the Anunnaki were forced to temporarily leave Earth's surface and orbit the planet when Antarctic glaciers melted, causing the Great Flood, which also destroyed the Anunnaki's bases on Earth. These had to be rebuilt, and the Anunnaki, needing more humans to help in this massive effort, taught mankind agriculture.
Ronald H. Fritze writes that, according to Sitchin, "the Annunaki built the pyramids and all the other monumental structures from around the ancient world that ancient astronaut theorists consider so impossible to build without highly advanced technologies." Sitchin expanded on this mythology in later works, including The Stairway to Heaven (1980) and The Wars of Gods and Men (1985). In The End of Days: Armageddon and the Prophecy of the Return (2007), Sitchin predicted that the Anunnaki would return to earth, possibly as soon as 2012, corresponding to the end of the Mesoamerican Long Count calendar. Sitchin's writings have been universally rejected by mainstream historians, who have labelled his books as pseudoarchaeology, asserting that Sitchin seems to deliberately misrepresent Sumerian texts by quoting them out of context, truncating quotations, and mistranslating Sumerian words to give them radically different meanings from their accepted definitions.
David Icke, the British conspiracy theorist who popularised the reptilian conspiracy theory, has claimed that the reptilian overlords of his theory are in fact the Anunnaki. Clearly influenced by Sitchin's writings, Icke adapts them "in favor of his own New Age and conspiratorial agenda". Icke's speculation on the Anunnaki incorporates far-right views on history, positing an Aryan master race descended by blood from the Anunnaki. It also incorporates dragons, Dracula, and draconian laws, these three elements apparently linked only by superficial linguistic similarity. He formulated his views on the Anunnaki in the 1990s and has written several books about his theory.
See also
Ancient Mesopotamian religion
Æsir
Deva (Hinduism)
Dingir
Elohim
Hutena
Eridu Genesis
Epic of Gilgamesh
Tuatha Dé Danann
Twelve Olympians
References
Citations
General and cited references
External links
Ancient Mesopotamian Gods and Goddesses: Anunna (Anunnaku, Anunnaki) (a group of gods)
Ancient astronaut speculation
Characters in the Enūma Eliš
Chthonic beings
Epic of Gilgamesh
Hittite deities
Hurrian deities
Mesopotamian deities
Sky and weather deities
Time and fate deities
Underworld deities | Anunnaki | [
"Physics"
] | 3,367 | [
"Weather",
"Sky and weather deities",
"Physical phenomena"
] |
322,003 | https://en.wikipedia.org/wiki/Perpetuity | In finance, a perpetuity is an annuity that has no end, or a stream of cash payments that continues forever. There are few actual perpetuities in existence. For example, the United Kingdom (UK) government issued them in the past; these were known as consols and were all finally redeemed in 2015.
Real estate and preferred stock are among some types of investments that affect the results of a perpetuity, and prices can be established using techniques for valuing a perpetuity. Perpetuities are but one of the time value of money methods for valuing financial assets.
Perpetuities can be structured as a perpetual bond and are a form of ordinary annuities. The concept is closely linked to terminal value and terminal growth rate in valuation.
Detailed description
A perpetuity is an annuity in which the periodic payments begin on a fixed date and continue indefinitely. It is sometimes referred to as a perpetual annuity. Fixed coupon payments on permanently invested (irredeemable) sums of money are prime examples of perpetuities. Scholarships paid perpetually from an endowment fit the definition of perpetuity.
The value of the perpetuity is finite because receipts that are anticipated far in the future have extremely low present value (present value of the future cash flows). Unlike a typical bond, because the principal is never repaid, there is no present value for the principal. Assuming that payments begin at the end of the current period, the price of a perpetuity is simply the coupon amount over the appropriate discount rate or yield; that is,
where PV = present value of the perpetuity, A = the amount of the periodic payment, and r = yield, discount rate or interest rate.
To give a numerical example, a 3% UK government war loan will trade at 50 pence per pound in a yield environment of 6%, while at 3% yield it is trading at par. That is, if the face value of the loan is £100 and the annual payment £3, the value of the loan is £50 when market interest rates are 6%, and £100 when they are 3%.
The duration, or the price-sensitivity to a small change in the interest rate r, of a perpetuity is given by the following formula:
This of course follows the fact that for bigger changes the new price must be calculated with the present-value formula given that for changes greater than a few basis-points the calculated duration is not reflective of the true-change in price.
Real-life examples
Valuing real estate with a capitalization rate or cap rate (the convention used in real estate finance) is a more current example. Using a cap rate, the value of a particular real estate asset is either the net income or the net cash flow of the property, divided by the cap rate. Effectively, the use of a cap rate to value a piece of real estate assumes that the current income from the property continues in perpetuity. Underlying this valuation is the assumption that rents will rise at the same rate as inflation. Although the property may be sold in future (or even the very near future), the assumption is that other investors will apply the same valuation approach to the property.
UK government perpetuities (called consols) were undated as well as irredeemable except by act of Parliament. As with war bonds, they paid fixed coupons (interest payments), and traded actively in the bond market until the government redeemed them in 2015. Very long dated bonds have financial characteristics that can appeal to some investors and in some circumstances: e.g. long-dated bonds have prices that change rapidly (either up or down) when yields change (fall or rise) in the financial markets.
The constant growth dividend discount model for the valuation of the common stock of a corporation is another example. This model assumes that the market price per share is equal to the discounted stream of all future dividends, which is assumed to be perpetual. If the discount rate for stocks (shares) with this level of systematic risk is 12.50%, then a constant perpetuity of dividend income per dollar is eight dollars. However, if the future dividends represent a perpetuity increasing at 5.00% per year, then the dividend discount model, in effect, subtracts 5.00% off the discount rate of 12.50% for 7.50% implying that the price per dollar of income is $13.33.
References
See also
Geometric progression
Perpetual bond
Mathematical finance
Annuities | Perpetuity | [
"Mathematics"
] | 938 | [
"Applied mathematics",
"Mathematical finance"
] |
322,008 | https://en.wikipedia.org/wiki/Almost%20perfect%20number | In mathematics, an almost perfect number (sometimes also called slightly defective or least deficient number) is a natural number n such that the sum of all divisors of n (the sum-of-divisors function σ(n)) is equal to 2n − 1, the sum of all proper divisors of n, s(n) = σ(n) − n, then being equal to n − 1. The only known almost perfect numbers are powers of 2 with non-negative exponents . Therefore the only known odd almost perfect number is 20 = 1, and the only known even almost perfect numbers are those of the form 2k for some positive integer k; however, it has not been shown that all almost perfect numbers are of this form. It is known that an odd almost perfect number greater than 1 would have at least six prime factors.
If m is an odd almost perfect number then is a Descartes number. Moreover if a and b are positive odd integers such that and such that and are both primes, then would be an odd weird number.
See also
Perfect number
Quasiperfect number
References
Further reading
External links
Arithmetic dynamics
Divisor function
Integer sequences | Almost perfect number | [
"Mathematics"
] | 245 | [
"Sequences and series",
"Integer sequences",
"Mathematical structures",
"Number theory stubs",
"Recreational mathematics",
"Mathematical objects",
"Arithmetic dynamics",
"Combinatorics",
"Numbers",
"Number theory",
"Dynamical systems"
] |
322,059 | https://en.wikipedia.org/wiki/Drumhead | A drumhead or drum skin is a membrane stretched over one or both of the open ends of a drum. The drumhead is struck with sticks, mallets, or hands, so that it vibrates and the sound resonates through the drum.
Additionally outside of percussion instruments, drumheads are also used on some string instruments, most notably the banjo.
History
Originally, drumheads were made from animal hide and were first used in early human history, long before records began. The term drumhead is first attested in English in 1580, in the writings of the soldier Thomas Churchyard, who mentioned how "Dice plaie began ... on the toppe of Drommes heddes".
In 1956, Chick Evans invented the plastic drumhead. Plastic drumheads made from polyester are cheaper, more durable, and less sensitive to weather than animal skin. In 1957, Remo Belli and Sam Muchnick together developed a polymer head (also known as Mylar) leading to the development of the Remo drumhead company.
Despite the benefits of plastic heads, drummers in historical reenactment groups such as fife and drum use animal skin heads for historical accuracy. Rawhide heads are also popular with musicians performing in the jazz, orchestral and early music genres due to their preference for period correct sounds and instruments. Real hide heads are used on most hand drums, including djembes, frame drums, bongos, and congas, and also some Banjos. In recent years, companies have begun manufacturing synthetic counterparts (most notably Fiberskin) for certain hand drums such as congas, and also banjos. There has also been a resurgence in the use of genuine rawhide heads by drum kit players, with companies such as AF cueros orquestales from Argentina, AK Drums, Buchler Trommelbau and Kentville Drums or the Austrian Drumhead Company offering goat, calf and kangaroo hide drumheads respectively.
Another common material used for drumheads is aramid fiber, such as kevlar. Kevlar heads are also used in marching percussion.
Mesh heads
Mesh heads - drum heads that are usually constructed from a weave of synthetic material - were traditionally used on electronic drums, as they provide a very similar playing feel to traditional heads. Over time, however, manufacturers began to produce mesh heads that are attachable to acoustic drums, in order to create a playing experience that has a very similar feel and sound to playing a traditional drumkit, but at a drastically reduced volume, making them suitable for either practicing in a place where noise is a concern, or even recording using drum triggers.
Tuning
A drum "hoop" or "rim" may be made of metal, wood, or other material and is used to hold a drumhead against a drum shell, either with bolts through metal "claws" attached directly to a hoop, or bolts through holes in a flanged rim. The bolts, called "tension rods", are screwed into threaded "lugs" attached to the drum shell, in order to tighten and tune the drumhead. A "drum key" is a four sided wrench used to screw the tension rods into the lugs.
Muffling
Drummers occasionally muffle their drums using special drumheads. Some drumheads come pre-muffled. Most muffling is done by external muffles.
See also
Vibrations of a drum head for an illustrated mathematical treatment
List of drum manufacturers
References
External links
Know-How Is The Difference In Drumheads Know-How Is The Difference In Drumheads - Anatomy of a Drumhead
Accessory Fetish A Complete List of Drum Head Manufacturers
Resonant Drum Head Explained
Drumming
Musical instrument parts and accessories | Drumhead | [
"Technology"
] | 745 | [
"Components",
"Musical instrument parts and accessories"
] |
322,170 | https://en.wikipedia.org/wiki/Hyperperfect%20number | In number theory, a -hyperperfect number is a natural number for which the equality holds, where is the divisor function (i.e., the sum of all positive divisors of ). A hyperperfect number is a -hyperperfect number for some integer . Hyperperfect numbers generalize perfect numbers, which are 1-hyperperfect.
The first few numbers in the sequence of -hyperperfect numbers are , with the corresponding values of being . The first few -hyperperfect numbers that are not perfect are .
List of hyperperfect numbers
The following table lists the first few -hyperperfect numbers for some values of , together with the sequence number in the On-Line Encyclopedia of Integer Sequences (OEIS) of the sequence of -hyperperfect numbers:
It can be shown that if is an odd integer and and are prime numbers, then is -hyperperfect; Judson S. McCranie has conjectured in 2000 that all -hyperperfect numbers for odd are of this form, but the hypothesis has not been proven so far. Furthermore, it can be proven that if are odd primes and is an integer such that then is -hyperperfect.
It is also possible to show that if and is prime, then for all such that is prime, is -hyperperfect. The following table lists known values of and corresponding values of for which is -hyperperfect:
Hyperdeficiency
The newly introduced mathematical concept of hyperdeficiency is related to the hyperperfect numbers.
Definition (Minoli 2010): For any integer and for integer , define the -hyperdeficiency (or simply the hyperdeficiency) for the number as
A number is said to be -hyperdeficient if
Note that for one gets which is the standard traditional definition of deficiency.
Lemma: A number is -hyperperfect (including ) if and only if the -hyperdeficiency of ,
Lemma: A number is -hyperperfect (including ) if and only if for some , for at least one .
References
Further reading
Articles
.
.
.
.
.
.
.
.
.
Books
Daniel Minoli, Voice over MPLS, McGraw-Hill, New York, NY, 2002, (p. 114-134)
External links
MathWorld: Hyperperfect number
A long list of hyperperfect numbers under Data
Divisor function
Integer sequences
Perfect numbers | Hyperperfect number | [
"Mathematics"
] | 497 | [
"Sequences and series",
"Integer sequences",
"Mathematical structures",
"Perfect numbers",
"Recreational mathematics",
"Mathematical objects",
"Combinatorics",
"Numbers",
"Number theory"
] |
322,355 | https://en.wikipedia.org/wiki/Deep%20time | Deep time is a term introduced and applied by John McPhee to the concept of geologic time in his book Basin and Range (1981), parts of which originally appeared in The New Yorker magazine.
The philosophical concept of geological time was developed in the 18th century by Scottish geologist James Hutton; his "system of the habitable Earth" was a deistic mechanism keeping the world eternally suitable for humans. The modern concept entails huge changes over the age of the Earth which has been determined to be, after a long and complex history of developments, around 4.55 billion years.
Concept
James Hutton based his view of deep time on a form of geochemistry that had developed in Scotland and Scandinavia from the 1750s onward. As mathematician John Playfair, one of Hutton's friends and colleagues in the Scottish Enlightenment, remarked upon seeing the strata of the angular unconformity at Siccar Point with Hutton and James Hall in June 1788, "the mind seemed to grow giddy by looking so far into the abyss of time".
Early geologists such as Nicolas Steno and Horace Bénédict de Saussure had developed ideas of geological strata forming from water through chemical processes, which Abraham Gottlob Werner developed into a theory known as Neptunism, envisaging the slow crystallisation of minerals in the ancient oceans of the Earth to form rock. Hutton's innovative 1785 theory, based on Plutonism, visualised an endless cyclical process of rocks forming under the sea, being uplifted and tilted, then eroded to form new strata under the sea. In 1788 the sight of Hutton's Unconformity at Siccar Point convinced Playfair and Hall of this extremely slow cycle, and in that same year Hutton memorably wrote "we find no vestige of a beginning, no prospect of an end".
Other scientists such as Georges Cuvier put forward ideas of past ages, and geologists such as Adam Sedgwick incorporated Werner's ideas into concepts of catastrophism; Sedgwick inspired his university student Charles Darwin to exclaim "What a capital hand is Sedgewick [sic] for drawing large cheques upon the Bank of Time!". In a competing theory, Charles Lyell in his Principles of Geology (1830–1833) developed Hutton's comprehension of endless deep time as a crucial scientific concept into uniformitarianism. As a young naturalist and geological theorist, Darwin studied the successive volumes of Lyell's book exhaustively during the Beagle survey voyage in the 1830s, before beginning to theorise about evolution.
Physicist Gregory Benford addresses the concept in Deep Time: How Humanity Communicates Across Millennia (1999), as does paleontologist and Nature editor Henry Gee in In Search of Deep Time: Beyond the Fossil Record to a New History of Life (2001) Stephen Jay Gould's Time's Arrow, Time's Cycle (1987) also deals in large part with the evolution of the concept.
In Time's Arrow, Time's Cycle, Gould cited one of the metaphors McPhee used in explaining the concept of deep time:
Consider the Earth's history as the old measure of the English yard, the distance from the King's nose to the tip of his outstretched hand. One stroke of a nail file on his middle finger erases human history.
Concepts similar to geologic time were recognized in the 11th century by the Persian geologist and polymath Avicenna, and by the Chinese naturalist and polymath Shen Kuo. The Roman Catholic theologian Thomas Berry explored spiritual implications of the concept of deep time. Berry proposes that a deep understanding of the history and functioning of the evolving universe is a necessary inspiration and guide for our own effective functioning as individuals and as a species. This view has greatly influenced the development of deep ecology and ecophilosophy. The experiential nature of the experience of deep time has also greatly influenced the work of Joanna Macy.
H. G. Wells and Julian Huxley regarded the difficulties of coping with the concept of deep time as exaggerated:
"The use of different scales is simply a matter of practice," they said in The Science of Life (1929). "We very soon get used to maps, though they are constructed on scales down to a hundred-millionth of natural size ... to grasp geological time all that is needed is to stick tight to some magnitude which shall be the unit on the new and magnified scale—a million years is probably the most convenient—to grasp its meaning once and for all by an effort of imagination, and then to think of all passage of geological time in terms of this unit."
See also
Notes and references
Sources
Web
Books
Rossi, Paolo (1984). The Dark Abyss of Time: The History of the Earth and the History of Nations from Hooke to Vico, tr. by Lydia Cochrane, Chicago: University of Chicago Press, pp. 338, .
Journals
External links
"The benefits of embracing 'deep time' in a year like 2020" (Vincent Ialenti)—BBC Future.
ChronoZoom is a timeline for Big History being developed for the International Big History Association by Microsoft Research and University of California, Berkeley
Deep Time in Evolution (TV series). Note: This PBS/WGBH website advises Flash Player and Shockwave Player installation.
Deep Time – A History of the Earth: Interactive Infographic
Deep Time Walk App – A new story of the living Earth: Interactive Walking Experience
"Embracing 'Deep Time' Thinking" (Vincent Ialenti) NPR Cosmos & Culture.
"Pondering 'Deep Time' Could Inspire New Ways to View Climate Change" (Vincent Ialenti) NPR Cosmos & Culture.
Evolution
Geochronology
Historical geology
History of Earth science
Time
1981 neologisms | Deep time | [
"Physics",
"Mathematics"
] | 1,181 | [
"Physical quantities",
"Time",
"Quantity",
"Spacetime",
"Wikipedia categories named after physical quantities"
] |
322,359 | https://en.wikipedia.org/wiki/Emily%20Greene%20Balch | Emily Greene Balch (January 8, 1867 – January 9, 1961) was an American economist, sociologist and pacifist. Balch combined an academic career at Wellesley College with a long-standing interest in social issues such as poverty, child labor, and immigration, as well as settlement work to uplift poor immigrants and reduce juvenile delinquency.
She moved into the peace movement at the start of World War I in 1914, and began collaborating with Jane Addams of Chicago. She became a central leader of the Women's International League for Peace and Freedom (WILPF) based in Switzerland, for which she won the Nobel Peace Prize in 1946.
Early life and education
Balch was born to a prominent Yankee family in Jamaica Plain, Massachusetts (later a neighborhood of Boston), the daughter of Francis V. and Ellen (née Noyes) Balch. Her father was a successful lawyer and one time secretary to United States Senator Charles Sumner. She graduated from Bryn Mawr College in 1889 after reading widely in the classics and languages and focusing on economics. She did graduate work in Paris and published her research as Public Assistance of the Poor in France (1893). She did settlement housework in Boston before deciding on an academic career.
She then studied at Harvard University, the University of Chicago, and the University of Berlin.
Career
Balch began teaching at Wellesley College in 1896. She focused on immigration, consumption, and the economic roles of women. In 1913, she was appointed to serve as Professor of Economics at Wellesley, following the resignation of political economist Katharine Coman, who had founded the Department. That same year, Balch was promoted from Associate Professor to Professor of Political Economy and of Political and Social Science.
Balch served on numerous state commissions, such as the first commission on minimum wages for women. She was a leader of the Women's Trade Union League, which supported women who belonged to labor unions. She published a major sociological study of Our Slavic Fellow Citizens in 1910.
She was a longtime pacifist, and was a participant in Henry Ford's International Committee on Mediation, the follow-up organization to the Neutral Conference for Continuous Mediation. When the United States entered the war, she became a political activist opposing conscription in espionage legislation, and supporting the civil liberties of conscientious objectors. She collaborated with Jane Addams in the Women's Peace Party and numerous other groups.
In a letter to the president of Wellesley, she wrote we should follow "the ways of Jesus." Her spiritual thoughts were that American economy was "far from being in harmony with the principles of Jesus which we profess." Wellesley College terminated her contract in 1919. Balch served as an editor of The Nation, a well-known magazine of political commentary.
Balch converted from Unitarianism to Quakerism in 1921. She stated, "Religion seems to me one of the most interesting things in life, one of the most puzzling, richest and thrilling fields of human thought and speculation... religious experience and thought need also a light a day and sunshine and a companionable sharing with others of which it seems to me there is generally too little... The Quaker worship at its best seems to me give opportunities for this sort of sharing without profanation."
Her major achievements were just beginning, as she became an American leader of the international peace movement. In 1919, Balch played a central role in the International Congress of Women. It changed its name to the Women's International League for Peace and Freedom and was based in Geneva.
She was hired by the League as its first international Secretary-Treasurer, administering the organization's activities. She helped set up summer schools on peace education and created new branches in over 50 countries. She cooperated with the newly established League of Nations regarding drug control, aviation, refugees, and disarmament. In World War II, she supported the Allied powers and did not criticize the war effort, but she did support the rights of conscientious objectors.
Nobel prize
John Randall, professor of philosophy at Columbia University, and his wife, Mercedes Randall, one of the leaders of the US section the Women's International League for Peace and Freedom, initiated a campaign to nominate Balch for the peace prize. The campaign was supported by five US organizations that established a committee called the "Committee to sponsor Emily Greene Balch for the Nobel Peace Prize". The organizations were the Women's International League for Peace and Freedom, the National Federation of Settlements, the Women's Trade Union League of America, the National Council of Women of the U.S.A., and the NAACP.
Balch won the 1946 Nobel Peace Prize for her work with the Women's International League for Peace and Freedom (WILPF). She donated her share of the prize money to the WILPF. Her acceptance speech highlighted the issues of nationalism and efforts for international peace.
Personal life
Balch never married. She died the day after her 94th birthday.
See also
List of female Nobel laureates
List of peace activists
Boston Women's Heritage Trail
References
Bibliography
Emily Greene Balch, Public Assistance of the Poor in France, Vol. 8, Nos. 4 & 5, Publications of the American Economic Association.
Emily Greene Balch, "A Study of Conditions of City Life: with Special Reference to Boston, A Bibliography", 1903, 13 pages
Our Slavic Fellow Citizens By Emily Greene Balch, 1910, 536 pages.
Women at the Hague: the International Congress of Women and its Results, By Jane Addams, Emily Greene Balch, and Alice Hamilton. 171 pages, New York: MacMillan, 1915.
Approaches to the Great Settlement By Emily Greene Balch & Pauline Knickerbocker Angell (1918), 351 pages
Further reading
Solomon, Barbara Miller. "Balch, Emily Greene," in Barbara Sicherman and Carol Hurd Green, eds. Notable American Women: The Modern Period, A Biographical Dictionary (1980) pp 41–45
External links
including the Nobel Lecture, April 7, 1948 Toward Human Unity or Beyond Nationalism
Tribute to Emily Greene Balch by John Dewey, pages 149–150 in Later Works of John Dewey volume 17. First published in Women's International League for Peace and Freedom, 1946 page 2.
1867 births
1961 deaths
American Christian pacifists
American magazine editors
American Nobel laureates
American Quakers
Bryn Mawr College alumni
Converts to Quakerism
American women economists
Economists from Massachusetts
Nobel Peace Prize laureates
Writers from Boston
Wellesley College faculty
Women Nobel laureates
American women sociologists
American sociologists
American anti–World War I activists
Women's International League for Peace and Freedom people
Women's Trade Union League people
American women magazine editors
People from Jamaica Plain
American women's rights activists
Quaker feminists
The Nation editors | Emily Greene Balch | [
"Technology"
] | 1,373 | [
"Women Nobel laureates",
"Women in science and technology"
] |
322,376 | https://en.wikipedia.org/wiki/Ecological%20succession | Ecological succession is the process of change in the species that make up an ecological community over time.
The process of succession occurs either after the initial colonization of a newly created habitat, or after a disturbance substantially alters a pre-existing habitat. Succession that begins in new habitats, uninfluenced by pre-existing communities, is called primary succession, whereas succession that follows disruption of a pre-existing community is called secondary succession. Primary succession may happen after a lava flow or the emergence of a new island from the ocean. Surtsey, a volcanic island off the southern coast of Iceland, is an important example of a place where primary succession has been observed. On the other hand, secondary succession happens after disturbance of a community, such as from a fire, severe windthrow, or logging.
Succession was among the first theories advanced in ecology. Ecological succession was first documented in the Indiana Dunes of Northwest Indiana and remains an important ecological topic of study. Over time, the understanding of succession has changed from a linear progression to a stable climax state, to a more complex, cyclical model that de-emphasizes the idea of organisms having fixed roles or relationships.
History
Precursors of the idea of ecological succession go back to the beginning of the 19th century. As early as 1742 French naturalist Buffon noted that poplars precede oaks and beeches in the natural evolution of a forest. Buffon was later forced by the theological committee at the University of Paris to recant many of his ideas because they contradicted the biblical narrative of Creation.
Swiss geologist Jean-André Deluc and the later French naturalist Adolphe Dureau de la Malle were the first to make use of the word succession concerning the vegetation development after forest clear-cutting. In 1859 Henry David Thoreau wrote an address called "The Succession of Forest Trees" in which he described succession in an oak-pine forest. "It has long been known to observers that squirrels bury nuts in the ground, but I am not aware that any one has thus accounted for the regular succession of forests." The Austrian botanist Anton Kerner published a study about the succession of plants in the Danube river basin in 1863.
Ragnar Hult's 1885 study on the stages of forest development in Blekinge noted that grassland becomes heath before the heath develops into forest. Birch dominated the early stages of forest development, then pine (on dry soil) and spruce (on wet soil). If the birch is replaced by oak it eventually develops to beechwood. Swamps proceed from moss to sedges to moor vegetation followed by birch and finally spruce.
H. C. Cowles
Between 1899 and 1910, Henry Chandler Cowles, at the University of Chicago, developed a more formal concept of succession. Inspired by studies of Danish dunes by Eugen Warming, Cowles studied vegetation development on sand dunes on the shores of Lake Michigan (the Indiana Dunes). He recognized that vegetation on dunes of different ages might be interpreted as different stages of a general trend of vegetation development on dunes (an approach to the study of vegetation change later termed space-for-time substitution, or chronosequence studies). He first published this work as a paper in the Botanical Gazette in 1899 ("The ecological relations of the vegetation of the sand dunes of Lake Michigan"). In this classic publication and subsequent papers, he formulated the idea of primary succession and the notion of a sere—a repeatable sequence of community changes specific to particular environmental circumstances.
Gleason and Clements
From about 1900 to 1960, however, understanding of succession was dominated by the theories of Frederic Clements, a contemporary of Cowles, who held that seres were highly predictable and deterministic and converged on a climatically determined stable climax community regardless of starting conditions. Clements explicitly analogized the successional development of ecological communities with ontogenetic development of individual organisms, and his model is often referred to as the pseudo-organismic theory of community ecology. Clements and his followers developed a complex taxonomy of communities and successional pathways.
Henry Gleason offered a contrasting framework as early as the 1920s. The Gleasonian model was more complex and much less deterministic than the Clementsian. It differs most fundamentally from the Clementsian view in suggesting a much greater role of chance factors and in denying the existence of coherent, sharply bounded community types. Gleason argued that species distributions responded individualistically to environmental factors, and communities were best regarded as artifacts of the juxtaposition of species distributions. Gleason's ideas, first published in 1926, were largely ignored until the late 1950s.
Two quotes illustrate the contrasting views of Clements and Gleason. Clements wrote in 1916:
while Gleason, in his 1926 paper, said:
Gleason's ideas were, in fact, more consistent with Cowles' original thinking about succession. About Clements' distinction between primary succession and secondary succession, Cowles wrote (1911):
Eugene Odum
In 1969, Eugene Odum published The Strategy of Ecosystem Development, a paper that was highly influential to conservation and environmental restoration. Odum argued that ecological succession was an orderly progression toward a climax state where “maximum biomass and symbiotic function between organisms are maintained per unit energy flow." Odum highlighted how succession was not merely a change in the species composition of an ecosystem, but also created change in more complex attributes of the ecosystem, such as structure and nutrient cycling.
Modern era
A more rigorous, data-driven testing of successional models and community theory generally began with the work of Robert Whittaker and John Curtis in the 1950s and 1960s. Succession theory has since become less monolithic and more complex. J. Connell and R. Slatyer attempted a codification of successional processes by mechanism. Among British and North American ecologists, the notion of a stable climax vegetation has been largely abandoned, and successional processes have come to be seen as much less deterministic, with important roles for historical contingency and for alternate pathways in the actual development of communities. Debates continue as to the general predictability of successional dynamics and the relative importance of equilibrial vs. non-equilibrial processes. Former Harvard professor Fakhri A. Bazzaz introduced the notion of scale into the discussion, as he considered that at local or small area scale the processes are stochastic and patchy, but taking bigger regional areas into consideration, certain tendencies can not be denied.
More recent definitions of succession highlight change as the central characteristic. New research techniques are greatly enhancing contemporary scientists' ability to study succession, which is now seen as neither entirely random nor entirely predictable.
Factors
Both consistent patterns and variability are observed in ecological succession. Theories of ecological succession identify different factors that help explain why plant communities change the way they do.
Diversity of possible trajectories
Ecological succession was formerly seen as an orderly progression through distinct stages, where several plant communities would replace each other in a fixed order and eventually reach a stable end point known as the climax. The climax community was sometimes referred to as the 'potential vegetation' of a site, and thought to be primarily determined by the local climate. This idea has been largely abandoned by modern ecologists in favor of nonequilibrium ideas of ecosystems dynamics. Most natural ecosystems experience disturbance at a rate that makes a "climax" community unattainable. Climate change often occurs at a rate and frequency sufficient to prevent arrival at a climax state.
The trajectory of successional change can be influenced by initial site conditions, by the type of disturbance that triggers succession, by the interactions of the species present, and by more random factors such as availability of colonists or seeds or weather conditions at the time of disturbance. Some aspects of succession are broadly predictable; others may proceed more unpredictably than in the classical view of ecological succession. Coupled with the stochastic nature of disturbance events and other long-term (e.g., climatic) changes, such dynamics make it doubtful whether the 'climax' concept ever applies or is particularly useful in considering actual vegetation.
Stochastic events
Succession is influenced partially by random chance, but it is debated how much random chance directs the trajectory of succession, as opposed to more deterministic factors. The timing of a disturbance such as a weather event may be random and unpredictable. Dispersal of propagules to a new site may also be random. However, community assembly is also determined by processes that select species non-randomly from the local species pool.
Dispersal limitation vs. environmental filtering
Succession is impacted both by the ability of seeds to disperse to new sites, and the suitability of site conditions for those seeds to grow and survive. Dispersal limitation means that even though favorable sites for a plant to live might exist, the plant's seeds may be unable to reach those sites. Environmental filtering, also called establishment limitation, implies that although seeds may be distributed to a site, those seeds may be unable to survive due to various characteristics of the site. The predicted impact of these two factors varies under different models of ecological succession.
Feedback loops
Ecological succession is driven by feedbacks between plants and their environment. As plants grow following a disturbance, they change their environment, for example by creating shade, attracting seed dispersers, contributing organic matter to the soil, changing the availability of soil nutrients, creating microhabitats, and buffering temperature and moisture fluctuations. This creates opportunities for different plants to grow, which causes directional change in the ecosystem. The development of some ecosystem attributes, such as soil properties and nutrient cycles, are both influenced by community properties, and, in turn, influence further successional development. This feed-back process may occur over centuries or millennia. Plants may facilitate the establishment of other plants by creating suitable conditions for them to grow, for example by providing shade or allowing for soil formation. Plants may also competitively exclude or otherwise prevent the growth of other plants.
Patterns
Though the idea of a fixed, predictable process of succession with a single well-defined climax is an overly simplified model, several predictions made by the classical model are accurate. Species diversity, overall plant biomass, plant lifespans, the importance of decomposer organisms, and overall stability all increase as a community approaches a climax state, while the rate at which soil nutrients are consumed, rate of biogeochemical cycling, and rate of net primary productivity all decrease as a community approaches a climax state.
Communities in early succession will be dominated by fast-growing, well-dispersed species (opportunist, fugitive, or r-selected life-histories). These are also called pioneer species. As succession proceeds, these species will tend to be replaced by more competitive (k-selected) species.
Some of these trends do not apply in all cases. For example, species diversity almost necessarily increases during early succession as new species arrive, but may decline in later succession as competition eliminates opportunistic species and leads to dominance by locally superior competitors. Net Primary Productivity, biomass, and trophic properties all show variable patterns over succession, depending on the particular system and site.
Disruptions
Two important perturbation factors today are human actions and climatic change. Additions to available species pools through range expansions and introductions can also continually reshape communities.
Types
Primary succession
Successional dynamics beginning with colonization of an area that has not been previously occupied by an ecological community are referred to as primary succession. This includes newly exposed rock or sand surfaces, lava flows, and newly exposed glacial tills. The stages of primary succession include pioneer microorganisms, plants (lichens and mosses), grassy stage, smaller shrubs, and trees. Animals begin to return when there is food there for them to eat. When it is a fully functioning ecosystem, it has reached the climax community stage.
Secondary succession
Secondary succession follows severe disturbance or removal of a preexisting community that has remnants of the previous ecosystem. Secondary succession is strongly influenced by pre-disturbance conditions such as soil development, seed banks, remaining organic matter, and residual living organisms. Because of residual fertility and preexisting organisms, community change in early stages of secondary succession can be relatively rapid.
Secondary succession is much more commonly observed and studied than primary succession. Particularly common types of secondary succession include responses to natural disturbances such as fire, flood, and severe winds, and to human-caused disturbances such as logging and agriculture. In secondary succession, the soils and organisms need to be left unharmed so there is a way for the new material to rebuild.
As an example, in a fragmented old field habitat created in eastern Kansas, woody plants "colonized more rapidly (per unit area) on large and nearby patches".
Secondary succession can quickly change a landscape. In the 1900s, Acadia National Park had a wildfire that destroyed much of the landscape. Originally evergreen trees grew in the landscape. After the fire, the area took at least a year to grow shrubs. Eventually, deciduous trees started to grow instead of evergreens.
Secondary succession has been occurring in Shenandoah National Park following the 1995 flood of the Moorman's and Rapidan rivers, which destroyed plant and animal life.
Seasonal and cyclic dynamics
Unlike secondary succession, these types of vegetation change are not dependent on disturbance but are periodic changes arising from fluctuating species interactions or recurring events. These models modify the climax concept towards one of dynamic states.
Causes of plant succession
Autogenic succession can be brought by changes in the soil caused by the organisms there. These changes include accumulation of organic matter in litter or humic layer, alteration of soil nutrients, or change in the pH of soil due to the plants growing there. The structure of the plants themselves can also alter the community. For example, when larger species like trees mature, they produce shade on to the developing forest floor that tends to exclude light-requiring species. Shade-tolerant species will invade the area.
Allogenic succession is caused by external environmental influences and not by the vegetation. For example, soil changes due to erosion, leaching or the deposition of silt and clays can alter the nutrient content and water relationships in the ecosystems. Animals also play an important role in allogenic changes as they are pollinators, seed dispersers and herbivores. They can also increase nutrient content of the soil in certain areas, or shift soil about (as termites, ants, and moles do) creating patches in the habitat. This may create regeneration sites that favor certain species.
Climatic factors may be very important, but on a much longer time-scale than any other. Changes in temperature and rainfall patterns will promote changes in communities. As the climate warmed at the end of each ice age, great successional changes took place. The tundra vegetation and bare glacial till deposits underwent succession to mixed deciduous forest. The greenhouse effect resulting in increase in temperature is likely to bring profound Allogenic changes in the next century. Geological and climatic catastrophes such as volcanic eruptions, earthquakes, avalanches, meteors, floods, fires, and high wind also bring allogenic changes.
Mechanisms
In 1916, Frederic Clements published a descriptive theory of succession and advanced it as a general ecological concept. His theory of succession had a powerful influence on ecological thought. Clements' concept is usually termed classical ecological theory.
According to Clements, succession is a process involving several phases:
Nudation: Succession begins with the development of a bare site, called Nudation (disturbance).
Migration: refers to arrival of propagules.
Ecesis: involves establishment and initial growth of vegetation.
Competition: as vegetation becomes well established, grows, and spreads, various species begin to compete for space, light and nutrients.
Reaction: during this phase autogenic changes such as the buildup of humus affect the habitat, and one plant community replaces another.
Stabilization: a supposedly stable climax community forms.
Seral communities
A seral community is an intermediate stage found in an ecosystem advancing towards its climax community. In many cases more than one seral stage evolves until climax conditions are attained. A prisere is a collection of seres making up the development of an area from non-vegetated surfaces to a climax community. Depending on the substratum and climate, different seres are found.
Changes in animal life
Succession theory was developed primarily by botanists. The study of succession applied to whole ecosystems initiated in the writings of Ramon Margalef, while Eugene Odum's publication of The Strategy of Ecosystem Development is considered its formal starting point.
Animal life also exhibits changes with changing communities. In the lichen stage, fauna is sparse. It comprises a few mites, ants, and spiders living in cracks and crevices. The fauna undergoes a qualitative increase during the herb grass stage. The animals found during this stage include nematodes, insect larvae, ants, spiders, mites, etc. The animal population increases and diversifies with the development of the forest climax community. The fauna consists of invertebrates like slugs, snails, worms, millipedes, centipedes, ants, bugs; and vertebrates such as squirrels, foxes, mice, moles, snakes, various birds, salamanders and frogs.
A review of succession research by Hodkinson et al. (2002) documented what was likely first noted by Darwin during his voyage on the H.M.S. Beagle:
These naturalists note that prior to the establishment of autotrophs, there is a foodweb formed by heterotrophs built on allochthonous inputs of dead organic matter (necromass). Work on volcanic systems such as Kasatochi Volcano in the Aleutians by Sikes and Slowik (2010) supports this idea.
Microsuccession
Succession of micro-organisms including fungi and bacteria occurring within a microhabitat is known as microsuccession or serule. In artificial bacterial meta-communities of motile strains on-chip it has been shown that ecological succession is based on a trade-off between colonization and competition abilities. To exploit locations or explore the landscape? Escherichia coli is a fugitive species, whereas Pseudomonas aeruginosa is a slower colonizer but superior competitor. Like in plants, microbial succession can occur in newly available habitats (primary succession) such as surfaces of plant leaves, recently exposed rock surfaces (i.e., glacial till) or animal infant guts, and also on disturbed communities (secondary succession) like those growing in recently dead trees, decaying fruits, or animal droppings. Microbial communities may also change due to products secreted by the bacteria present. Changes of pH in a habitat could provide ideal conditions for a new species to inhabit the area. In some cases the new species may outcompete the present ones for nutrients leading to the primary species demise. Changes can also occur by microbial succession with variations in water availability and temperature. Theories of macroecology have only recently been applied to microbiology and so much remains to be understood about this growing field. A recent study of microbial succession evaluated the balances between stochastic and deterministic processes in the bacterial colonization of a salt marsh chronosequence. The results of this study show that, much like in macro succession, early colonization (primary succession) is mostly influenced by stochasticity while secondary succession of these bacterial communities was more strongly influenced by deterministic factors.
Climax concept
According to classical ecological theory, succession stops when the sere has arrived at an equilibrium or steady state with the physical and biotic environment. Barring major disturbances, it will persist indefinitely. This end point of succession is called climax.
Climax community
The final or stable community in a sere is the climax community or climatic vegetation. It is self-perpetuating and in equilibrium with the physical habitat. There is no net annual accumulation of organic matter in a climax community. The annual production and use of energy is balanced in such a community.
Characteristics
The vegetation is tolerant of environmental conditions.
It has a wide diversity of species, a well-drained spatial structure, and complex food chains.
The climax ecosystem is balanced. There is equilibrium between gross primary production and total respiration, between energy used from sunlight and energy released by decomposition, between uptake of nutrients from the soil and the return of nutrient by litter fall to the soil.
Individuals in the climax stage are replaced by others of the same kind. Thus the species composition maintains equilibrium.
It is an index of the climate of the area. The life or growth forms indicate the climatic type.
Types of climax
Climatic Climax If there is only a single climax and the development of climax community is controlled by the climate of the region, it is termed as climatic climax. For example, development of Maple-beech climax community over moist soil. Climatic climax is theoretical and develops where physical conditions of the substrate are not so extreme as to modify the effects of the prevailing regional climate.
Edaphic Climax When there are more than one climax communities in the region, modified by local conditions of the substrate such as soil moisture, soil nutrients, topography, slope exposure, fire, and animal activity, it is called edaphic climax. Succession ends in an edaphic climax where topography, soil, water, fire, or other disturbances are such that a climatic climax cannot develop.
Catastrophic Climax Climax vegetation vulnerable to a catastrophic event such as a wildfire. For example, in California, chaparral vegetation is the final vegetation. The wildfire removes the mature vegetation and decomposers. A rapid development of herbaceous vegetation follows until the shrub dominance is re-established. This is known as catastrophic climax.
Disclimax When a stable community, which is not the climatic or edaphic climax for the given site, is maintained by man or his domestic animals, it is designated as Disclimax (disturbance climax) or anthropogenic subclimax (man-generated). For example, overgrazing by stock may produce a desert community of bushes and cacti where the local climate actually would allow grassland to maintain itself.
Subclimax The prolonged stage in succession just preceding the climatic climax is subclimax.
Preclimax and Postclimax In certain areas different climax communities develop under similar climatic conditions. If the community has life forms lower than those in the expected climatic climax, it is called preclimax; a community that has life forms higher than those in the expected climatic climax is postclimax. Preclimax strips develop in less moist and hotter areas, whereas Postclimax strands develop in more moist and cooler areas than that of surrounding climate.
Theories
There are three schools of interpretations explaining the climax concept:
Monoclimax or Climatic Climax Theory was advanced by Clements (1916) and recognizes only one climax whose characteristics are determined solely by climate (climatic climax). The processes of succession and modification of environment overcome the effects of differences in topography, parent material of the soil, and other factors. The whole area would be covered with uniform plant community. Communities other than the climax are related to it, and are recognized as subclimax, postclimax and disclimax.
Polyclimax Theory was advanced by Tansley (1935). It proposes that the climax vegetation of a region consists of more than one vegetation climaxes controlled by soil moisture, soil nutrients, topography, slope exposure, fire, and animal activity.
Climax Pattern Theory was proposed by Whittaker (1953). The climax pattern theory recognizes a variety of climaxes governed by responses of species populations to biotic and abiotic conditions. According to this theory the total environment of the ecosystem determines the composition, species structure, and balance of a climax community. The environment includes the species' responses to moisture, temperature, and nutrients, their biotic relationships, availability of flora and fauna to colonize the area, chance dispersal of seeds and animals, soils, climate, and disturbance such as fire and wind. The nature of climax vegetation will change as the environment changes. The climax community represents a pattern of populations that corresponds to and changes with the pattern of environment. The central and most widespread community is the climatic climax.
The theory of alternative stable states suggests there is not one end point but many which transition between each other over ecological time.
Succession by habitat type
Forest succession
Forests, being an ecological system, are subject to the species succession process. There are "opportunistic" or "pioneer" species that produce great quantities of seed that are disseminated by the wind, and therefore can colonize big empty extensions. They are capable of germinating and growing in direct sunlight. Once they have produced a closed canopy, the lack of direct sun radiation at the soil makes it difficult for their own seedlings to develop. It is then the opportunity for shade-tolerant species to become established under the protection of the pioneers. When the pioneers die, the shade-tolerant species replace them. These species are capable of growing beneath the canopy, and therefore, in the absence of disturbances, will stay. For this reason it is then said the stand has reached its climax. When a disturbance occurs, the opportunity for the pioneers opens up again, provided they are present or within a reasonable range.
An example of pioneer species, in forests of northeastern North America are Betula papyrifera (White birch) and Prunus serotina (Black cherry), that are particularly well-adapted to exploit large gaps in forest canopies, but are intolerant of shade and are eventually replaced by other shade-tolerant species in the absence of disturbances that create such gaps. In the tropics, well known pioneer forest species can be found among the genera Cecropia, Ochroma and Trema.
Things in nature are not black and white, and there are intermediate stages. It is therefore normal that between the two extremes of light and shade there is a gradient, and there are species that may act as pioneer or tolerant, depending on the circumstances. It is of paramount importance to know the tolerance of species in order to practice an effective silviculture.
Wetland succession
Since many types of wetland environments exist, succession may follow a wide array of trajectories and patterns in wetlands. Under the classical model, the process of secondary succession holds that a wetland progresses over time from an initial state of open water with few plants, to a forested climax state where decayed organic matter has built up over time, forming peat. However, many wetlands are maintained by regular disturbance or natural processes at an equilibrium state that does not resemble the predicted forested "climax." The idea that ponds and wetlands gradually fill in to become dry land has been criticized and called into question due to lack of evidence.
Wetland succession is a uniquely complex, non-linear process shaped by hydrology. Hydrological factors often work against linear processes that predict a succession to a "climax" state. The energy carried by moving water may create a continuous source of disturbance. For example, in coastal wetlands, the tides moving in and out continuously acts upon the ecological community. Fire may also maintain an equilibrium state in a wetland by burning off vegetation, thus interrupting the accumulation of peat.
Water entering and leaving the wetland follows patterns that are broadly cyclical but erratic. For example, seasonal flooding and drying may occur with yearly changes in precipitation, causing seasonal changes in the wetland community that maintain it at a stable state. However, unusually heavy rain or unusually severe drought may cause the wetland to enter a positive feedback loop where it begins to change in a linear direction. Since wetlands are sensitive to changes in the natural processes that maintain them, human activities, invasive species, and climate change could initiate long-term changes in wetland ecosystems.
Grassland succession
For a long time, grasslands were thought to be early stages of succession, dominated by weedy species and with little conservation value. However, comparing grasslands that form after recovery from long-term disruptions like agricultural tillage with ancient or "old-growth" grasslands has shown that grasslands are not inherently early-successional communities. Rather, grasslands undergo a centuries-long process of succession, and a grassland that is tilled up for agriculture or otherwise destroyed is estimated to take a minimum of 100 years, and potentially on average 1,400 years, to recover to its previous level of biodiversity. However, planting a high diversity of late-successional grassland species in a disturbed environment can accelerate the recovery of the soil's ability to sequester carbon, resulting in twice as much carbon storage as a naturally recovering grassland over the same period of time.
Many grassland ecosystems are maintained by disturbance, such as fire and grazing by large animals, or else the process of succession will change them to forest or shrubland. In fact, it is debated whether fire should be considered disturbance at all for the North American prairie ecosystems, since it maintains, rather than disrupts, an equilibrium state. Many late-successional grassland species have adaptations that allow them to store nutrients underground and re-sprout rapidly after "aboveground" disturbances like fire or grazing. Disturbance events that severely disrupt or destroy the soil, such as tilling, eliminate these late-successional species, reverting the grassland to an early successional stage dominated by pioneers, whereas fire and grazing benefit late-successional species. Both too much and too little disturbance can damage the biodiversity of disturbance-dependent ecosystems like grasslands.
In North American semi-arid grasslands, the introduction of livestock ranching and absence of fire was observed to cause a transition away from grasses to woody vegetation, particularly mesquite. However, the means by which ecological succession under frequent disturbance results in ecosystems of the sort seen in remnant prairies is poorly understood.
See also
Connell–Slatyer model of ecological succession
Cyclic succession
Ecological stability
Intermediate disturbance hypothesis
References
Further reading
External links
Science Aid: Succession Explanation of succession for high school students.
Biographical sketch of Henry Chandler Cowles.
Robbert Murphy sees a significantly ideological, rather than scientific, basis for the disfavour shown towards succession by the current ecological orthodoxy and seeks to reinstate succession by holistic and teleological argument.
Succession
Succession
Environmental terminology
Habitat | Ecological succession | [
"Physics",
"Biology"
] | 6,134 | [
"Ecology terminology",
"Physical phenomena",
"Ecological processes",
"Earth phenomena"
] |
322,533 | https://en.wikipedia.org/wiki/Project%20Orion%20%28nuclear%20propulsion%29 | Project Orion was a study conducted in the 1950s and 1960s by the United States Air Force, DARPA, and NASA into the viability of a nuclear pulse spaceship that would be directly propelled by a series of atomic explosions behind the craft. Early versions of the vehicle were proposed to take off from the ground; later versions were presented for use only in space. The design effort took place at General Atomics in San Diego, and supporters included Wernher von Braun, who issued a white paper advocating the idea. Non-nuclear tests were conducted with models, but the project was eventually abandoned for several reasons, including the 1963 Partial Test Ban Treaty, which banned nuclear explosions in space, amid concerns over nuclear fallout.
Physicist Stanislaw Ulam proposed the general idea of nuclear pulse propulsion in 1946, and preliminary calculations were made by Frederick Reines and Ulam in a Los Alamos memorandum dated 1947. In August 1955, Ulam co-authored a classified paper proposing the use of nuclear fission bombs, "ejected and detonated at a considerable distance", for propelling a vehicle in outer space. The project was led by Ted Taylor at General Atomics and physicist Freeman Dyson who, at Taylor's request, took a year away from the Institute for Advanced Study in Princeton to work on the project. In July 1958, DARPA agreed to sponsor Orion at an initial level of $1 million per year, at which point the project received its name and formally began. The agency granted a study of the concept to the General Dynamics Corporation, but decided to withdraw support in late 1959. The U.S. Air Force agreed to support Orion if a military use was found for the project, and the NASA Office of Manned Spaceflight also contributed funding. The concept investigated by the government used a blast shield and shock absorber to protect the crew and convert the detonations into a continuous propulsion force. The most successful model test, in November 1959, reached roughly 100 meters in altitude with six sequenced chemical explosions. NASA also produced a Mars mission profile for a 125 day round trip with eight astronauts, at a predicted development cost of $1.5 billion. Orion was canceled in 1964, after the United States signed the Partial Test Ban Treaty the prior year; the treaty greatly reduced political support for the project. NASA had also decided, in 1959, that the civilian space program would be non-nuclear in the near-term.
The Orion concept offered both high thrust and high specific impulse, or propellant efficiency: 2,000 pulse units (Isp) under the original design and an Isp of perhaps 4,000 to 6,000 seconds according to the Air Force plan, with a later 1968 fusion bomb proposal by Dyson potentially increasing this to more than 75,000 Isp, enabling velocities of 10,000 km/sec. A moderate-sized nuclear device was estimated, at the time, to produce about 5 or 10 billion horsepower. The extreme power of the nuclear explosions, relative to the vehicle's mass, would be managed by using external detonations, although an earlier version of the pulse concept did propose containing the blasts in an internal pressure structure, with one such design prepared by The Martin Company. As a qualitative power comparison, traditional chemical rockets, such as the Saturn V that took the Apollo program to the Moon, produce high thrust with low specific impulse, whereas electric ion engines produce a small amount of thrust very efficiently. Orion, by contrast, would have offered performance greater than the most advanced conventional or nuclear rocket engines then under consideration. Supporters of Project Orion felt that it had potential for cheap interplanetary travel.
From Project Longshot to Project Daedalus, Mini-Mag Orion, and other proposals which reach engineering analysis at the level of considering thermal power dissipation, the principle of external nuclear pulse propulsion to maximize survivable power has remained common among serious concepts for interstellar flight without external power beaming and for very high-performance interplanetary flight. Such later proposals have tended to modify the basic principle by envisioning equipment driving detonation of much smaller fission or fusion pellets, in contrast to Project Orion's larger nuclear pulse units (full nuclear bombs). In 1979 General Dynamics donated a 26 inch (56 cm) tall wooden model of the craft to the Smithsonian, which displays it at the Steven F. Udvar-Hazy Center near Dulles International Airport in Northern Virginia.
Basic principles
The Orion nuclear pulse drive combines a very high exhaust velocity, from 19 to 31 km/s (12 to 19 mi/s) in typical interplanetary designs, with meganewtons of thrust. Many spacecraft propulsion drives can achieve one of these or the other, but nuclear pulse rockets are the only proposed technology that could potentially meet the extreme power requirements to deliver both at once (see spacecraft propulsion for more speculative systems).
Specific impulse (Isp) measures how much thrust can be derived from a given mass of fuel, and is a standard figure of merit for rocketry. For any rocket propulsion, since the kinetic energy of exhaust goes up with velocity squared (kinetic energy = mv2), whereas the momentum and thrust go up with velocity linearly (momentum = mv), obtaining a particular level of thrust (as in a number of g acceleration) requires far more power each time that exhaust velocity and Isp are much increased in a design goal. (For instance, the most fundamental reason that electric propulsion systems of high Isp tend to be low thrust is due to their limits on available power. Their thrust is actually inversely proportional to Isp if power going into exhaust is constant or at its limit from heat dissipation needs or other engineering constraints.) The Orion concept detonates nuclear explosions externally at a rate of power release which is beyond what nuclear reactors could survive internally with known materials and design.
Since weight is no limitation, an Orion craft can be extremely robust. An uncrewed craft could tolerate very large accelerations, perhaps 100 g. A human-crewed Orion, however, must use some sort of damping system behind the pusher plate to smooth the near instantaneous acceleration to a level that humans can comfortably withstand – typically about 2 to 4 g.
The high performance depends on the high exhaust velocity, in order to maximize the rocket's force for a given mass of propellant. The velocity of the plasma debris is proportional to the square root of the change in the temperature (Tc) of the nuclear fireball. Since such fireballs typically achieve ten million degrees Celsius or more in less than a millisecond, they create very high velocities. However, a practical design must also limit the destructive radius of the fireball. The diameter of the nuclear fireball is proportional to the square root of the bomb's explosive yield.
The shape of the bomb's reaction mass is critical to efficiency. The original project designed bombs with a reaction mass made of tungsten. The bomb's geometry and materials focused the X-rays and plasma from the core of nuclear explosive to hit the reaction mass. In effect each bomb would be a nuclear shaped charge.
A bomb with a cylinder of reaction mass expands into a flat, disk-shaped wave of plasma when it explodes. A bomb with a disk-shaped reaction mass expands into a far more efficient cigar-shaped wave of plasma debris. The cigar shape focuses much of the plasma to impinge onto the pusher-plate. For greatest mission efficiency the rocket equation demands that the greatest fraction of the bomb's explosive force be directed at the spacecraft, rather than being spent isotropically.
The maximum effective specific impulse, Isp, of an Orion nuclear pulse drive generally is equal to:
where C0 is the collimation factor (what fraction of the explosion plasma debris will actually hit the impulse absorber plate when a pulse unit explodes), Ve is the nuclear pulse unit plasma debris velocity, and gn is the standard acceleration of gravity (9.81 m/s2; this factor is not necessary if Isp is measured in N·s/kg or m/s). A collimation factor of nearly 0.5 can be achieved by matching the diameter of the pusher plate to the diameter of the nuclear fireball created by the explosion of a nuclear pulse unit.
The smaller the bomb, the smaller each impulse will be, so the higher the rate of impulses and more than will be needed to achieve orbit. Smaller impulses also mean less g shock on the pusher plate and less need for damping to smooth out the acceleration.
The optimal Orion drive bomblet yield (for the human crewed 4,000 ton reference design) was calculated to be in the region of 0.15 kt, with approx 800 bombs needed to orbit and a bomb rate of approx 1 per second.
Sizes of vehicles
The following can be found in George Dyson's book. The figures for the comparison with Saturn V are taken from this section and converted from metric (kg) to US short tons (abbreviated "t" here).
In late 1958 to early 1959, it was realized that the smallest practical vehicle would be determined by the smallest achievable bomb yield. The use of 0.03 kt (sea-level yield) bombs would give vehicle mass of 880 tons. However, this was regarded as too small for anything other than an orbital test vehicle and the team soon focused on a 4,000 ton "base design".
At that time, the details of small bomb designs were shrouded in secrecy. Many Orion design reports had all details of bombs removed before release. Contrast the above details with the 1959 report by General Atomics, which explored the parameters of three different sizes of hypothetical Orion spacecraft:
The biggest design above is the "super" Orion design; at 8 million tons, it could easily be a city. In interviews, the designers contemplated the large ship as a possible interstellar ark. This extreme design could be built with materials and techniques that could be obtained in 1958 or were anticipated to be available shortly after.
Most of the three thousand tons of each of the "super" Orion's propulsion units would be inert material such as polyethylene, or boron salts, used to transmit the force of the propulsion units detonation to the Orion's pusher plate, and absorb neutrons to minimize fallout. One design proposed by Freeman Dyson for the "Super Orion" called for the pusher plate to be composed primarily of uranium or a transuranic element so that upon reaching a nearby star system the plate could be converted to nuclear fuel.
Theoretical applications
The Orion nuclear pulse rocket design has extremely high performance. Orion nuclear pulse rockets using nuclear fission type pulse units were originally intended for use on interplanetary space flights.
Missions that were designed for an Orion vehicle in the original project included single stage (i.e., directly from Earth's surface) to Mars and back, and a trip to one of the moons of Saturn.
Freeman Dyson performed the first analysis of what kinds of Orion missions were possible to reach Alpha Centauri, the nearest star system to the Sun. His 1968 paper "Interstellar Transport" (Physics Today) retained the concept of large nuclear explosions but Dyson moved away from the use of fission bombs and considered the use of one megaton deuterium fusion explosions instead. His conclusions were simple: the debris velocity of fusion explosions was probably in the 3000–30,000 km/s range and the reflecting geometry of Orion's hemispherical pusher plate would reduce that range to 750–15,000 km/s.
To estimate the upper and lower limits of what could be done using 1968 technology, Dyson considered two starship designs. The more conservative energy limited pusher plate design simply had to absorb all the thermal energy of each impinging explosion (4×1015 joules, half of which would be absorbed by the pusher plate) without melting. Dyson estimated that if the exposed surface consisted of copper with a thickness of 1 mm, then the diameter and mass of the hemispherical pusher plate would have to be 20 kilometers and 5 million tonnes, respectively. 100 seconds would be required to allow the copper to radiatively cool before the next explosion. It would then take on the order of 1000 years for the energy-limited heat sink Orion design to reach Alpha Centauri.
In order to improve on this performance while reducing size and cost, Dyson considered an alternative momentum limited pusher plate design where an ablation coating of the exposed surface is substituted to get rid of the excess heat. The limitation is then set by the capacity of shock absorbers to transfer momentum from the impulsively accelerated pusher plate to the smoothly accelerated vehicle. Dyson calculated that the properties of available materials limited the velocity transferred by each explosion to ~30 meters per second independent of the size and nature of the explosion. If the vehicle is to be accelerated at 1 Earth gravity (9.81 m/s2) with this velocity transfer, then the pulse rate is one explosion every three seconds. The dimensions and performance of Dyson's vehicles are given as:
Later studies indicate that the top cruise velocity that can theoretically be achieved are a few percent of the speed of light (0.08–0.1c). An atomic (fission) Orion can achieve perhaps 9–11% of the speed of light. A nuclear pulse drive starship powered by fusion-antimatter catalyzed nuclear pulse propulsion units would be similarly in the 10% range and pure Matter-antimatter annihilation rockets would be theoretically capable of obtaining a velocity between 50% and 80% of the speed of light. In each case saving fuel for slowing down halves the maximum speed. The concept of using a magnetic sail to decelerate the spacecraft as it approaches its destination has been discussed as an alternative to using propellant; this would allow the ship to travel near the maximum theoretical velocity.
At 0.1c, Orion thermonuclear starships would require a flight time of at least 44 years to reach Alpha Centauri, not counting time needed to reach that speed (about 36 days at constant acceleration of 1g or 9.8 m/s2). At 0.1c, an Orion starship would require 100 years to travel 10 light years. The astronomer Carl Sagan suggested that this would be an excellent use for stockpiles of nuclear weapons.
As part of the development of Project Orion, to garner funding from the military, a derived "space battleship" space-based nuclear-blast-hardened nuclear-missile weapons platform was mooted in the 1960s by the United States Air Force. It would comprise the USAF "Deep Space Bombardment Force".
Later developments
A concept similar to Orion was designed by the British Interplanetary Society (B.I.S.) in the years 1973–1974. Project Daedalus was to be a robotic interstellar probe to Barnard's Star that would travel at 12% of the speed of light. In 1989, a similar concept was studied by the U.S. Navy and NASA in Project Longshot. Both of these concepts require significant advances in fusion technology, and therefore cannot be built at present, unlike Orion.
From 1998 to the present, the nuclear engineering department at Pennsylvania State University has been developing two improved versions of project Orion known as Project ICAN and Project AIMStar using compact antimatter catalyzed nuclear pulse propulsion units, rather than the large inertial confinement fusion ignition systems proposed in Project Daedalus and Longshot.
Costs
The expense of the fissionable materials required was thought to be high, until the physicist Ted Taylor showed that with the right designs for explosives, the amount of fissionables used on launch was close to constant for every size of Orion from 2,000 tons to 8,000,000 tons. The larger bombs used more explosives to super-compress the fissionables, increasing efficiency. The extra debris from the explosives also serves as additional propulsion mass.
The bulk of costs for historical nuclear defense programs have been for delivery and support systems, rather than for production cost of the bombs directly (with warheads being 7% of the U.S. 1946–1996 expense total according to one study). After initial infrastructure development and investment, the marginal cost of additional nuclear bombs in mass production can be relatively low. In the 1980s, some U.S. thermonuclear warheads had $1.1 million estimated cost each ($630 million for 560). For the perhaps simpler fission pulse units to be used by one Orion design, a 1964 source estimated a cost of $40,000 or less each in mass production, which would be up to approximately $0.3 million each in modern-day dollars adjusted for inflation.
Project Daedalus later proposed fusion explosives (deuterium or tritium pellets) detonated by electron beam inertial confinement. This is the same principle behind inertial confinement fusion. Theoretically, it could be scaled down to far smaller explosions, and require small shock absorbers.
Vehicle architecture
From 1957 to 1964 this information was used to design a spacecraft propulsion system called Orion, in which nuclear explosives would be thrown behind a pusher-plate mounted on the bottom of a spacecraft and exploded. The shock wave and radiation from the detonation would impact against the underside of the pusher plate, giving it a powerful push. The pusher plate would be mounted on large two-stage shock absorbers that would smoothly transmit acceleration to the rest of the spacecraft.
During take-off, there were concerns of danger from fluidic shrapnel being reflected from the ground. One proposed solution was to use a flat plate of conventional explosives spread over the pusher plate, and detonate this to lift the ship from the ground before going nuclear. This would lift the ship far enough into the air that the first focused nuclear blast would not create debris capable of harming the ship.
A preliminary design for a nuclear pulse unit was produced. It proposed the use of a shaped-charge fusion-boosted fission explosive. The explosive was wrapped in a beryllium oxide channel filler, which was surrounded by a uranium radiation mirror. The mirror and channel filler were open ended, and in this open end a flat plate of tungsten propellant was placed. The whole unit was built into a can with a diameter no larger than and weighed just over so it could be handled by machinery scaled-up from a soft-drink vending machine; Coca-Cola was consulted on the design.
At 1 microsecond after ignition the gamma bomb plasma and neutrons would heat the channel filler and be somewhat contained by the uranium shell. At 2–3 microseconds the channel filler would transmit some of the energy to the propellant, which vaporized. The flat plate of propellant formed a cigar-shaped explosion aimed at the pusher plate.
The plasma would cool to as it traversed the distance to the pusher plate and then reheat to as, at about 300 microseconds, it hits the pusher plate and is recompressed. This temperature emits ultraviolet light, which is poorly transmitted through most plasmas. This helps keep the pusher plate cool. The cigar shaped distribution profile and low density of the plasma reduces the instantaneous shock to the pusher plate.
Because the momentum transferred by the plasma is greatest in the center, the pusher plate's thickness would decrease by approximately a factor of 6 from the center to the edge. This ensures the change in velocity is the same for the inner and outer parts of the plate.
At low altitudes where the surrounding air is dense, gamma scattering could potentially harm the crew without a radiation shield; a radiation refuge would also be necessary on long missions to survive solar flares. Radiation shielding effectiveness increases exponentially with shield thickness, see gamma ray for a discussion of shielding. On ships with a mass greater than the structural bulk of the ship, its stores along with the mass of the bombs and propellant, would provide more than adequate shielding for the crew. Stability was initially thought to be a problem due to inaccuracies in the placement of the bombs, but it was later shown that the effects would cancel out.
Numerous model flight tests, using conventional explosives, were conducted at Point Loma, San Diego in 1959. On November 14, 1959 the one-meter model, also known as "Hot Rod" and "putt-putt", first flew using RDX (chemical explosives) in a controlled flight for 23 seconds to a height of . Film of the tests has been transcribed to video and were featured on the BBC TV program "To Mars by A-Bomb" in 2003 with comments by Freeman Dyson and Arthur C. Clarke. The model landed by parachute undamaged and is in the collection of the Smithsonian National Air and Space Museum.
The first proposed shock absorber was a ring-shaped airbag. It was soon realized that, should an explosion fail, the pusher plate would tear away the airbag on the rebound. So a two-stage detuned spring and piston shock absorber design was developed. On the reference design the first stage mechanical absorber was tuned to 4.5 times the pulse frequency whilst the second stage gas piston was tuned to 0.5 times the pulse frequency. This permitted timing tolerances of 10 ms in each explosion.
The final design coped with bomb failure by overshooting and rebounding into a center position. Thus following a failure and on initial ground launch it would be necessary to start or restart the sequence with a lower yield device. In the 1950s methods of adjusting bomb yield were in their infancy and considerable thought was given to providing a means of swapping out a standard yield bomb for a smaller yield one in a 2 or 3 second time frame or to provide an alternative means of firing low yield bombs. Modern variable yield devices would allow a single standardized explosive to be tuned down (configured to a lower yield) automatically.
The bombs had to be launched behind the pusher plate with enough velocity to explode beyond it every 1.1 seconds. Numerous proposals were investigated, from multiple guns poking over the edge of the pusher plate to rocket propelled bombs launched from roller coaster tracks; however, the final reference design used a simple gas gun to shoot the devices through a hole in the center of the pusher plate.
Potential problems
Exposure to repeated nuclear blasts raises the problem of ablation (erosion) of the pusher plate. Calculations and experiments indicated that a steel pusher plate would ablate less than 1 mm, if unprotected. If sprayed with an oil it would not ablate at all (this was discovered by accident: a test plate had oily fingerprints on it and the fingerprints suffered no ablation). The absorption spectra of carbon and hydrogen minimize heating. The design temperature of the shockwave, , emits ultraviolet light. Most materials and elements are opaque to ultraviolet, especially at the pressures the plate experiences. This prevents the plate from melting or ablating.
One issue that remained unresolved at the conclusion of the project was whether or not the turbulence created by the combination of the propellant and ablated pusher plate would dramatically increase the total ablation of the pusher plate. According to Freeman Dyson, in the 1960s they would have had to actually perform a test with a real nuclear explosive to determine this; with modern simulation technology this could be determined fairly accurately without such empirical investigation.
Another potential problem with the pusher plate is that of spalling—shards of metal—potentially flying off the top of the plate. The shockwave from the impacting plasma on the bottom of the plate passes through the plate and reaches the top surface. At that point, spalling may occur, damaging the pusher plate. For that reason, alternative substances—plywood and fiberglass—were investigated for the surface layer of the pusher plate and thought to be acceptable.
If the conventional explosives in the nuclear bomb detonate but a nuclear explosion does not ignite, shrapnel could strike and potentially critically damage the pusher plate.
True engineering tests of the vehicle systems were thought to be impossible because several thousand nuclear explosions could not be performed in any one place. Experiments were designed to test pusher plates in nuclear fireballs and long-term tests of pusher plates could occur in space. The shock-absorber designs could be tested at full-scale on Earth using chemical explosives.
However, the main unsolved problem for a launch from the surface of the Earth was thought to be nuclear fallout. Freeman Dyson, group leader on the project, estimated back in the 1960s that with conventional nuclear weapons, each launch would statistically cause on average between 0.1 and 1 fatal cancers from the fallout. That estimate is based on no-threshold model assumptions, a method often used in estimates of statistical deaths from other industrial activities. Each few million dollars of efficiency indirectly gained or lost in the world economy may statistically average lives saved or lost, in terms of opportunity gains versus costs. Indirect effects could matter for whether the overall influence of an Orion-based space program on future human global mortality would be a net increase or a net decrease, including if change in launch costs and capabilities affected space exploration, space colonization, the odds of long-term human species survival, space-based solar power, or other hypotheticals.
Danger to human life was not a reason given for shelving the project. The reasons included lack of a mission requirement, the fact that no one in the U.S. government could think of any reason to put thousands of tons of payload into orbit, the decision to focus on rockets for the Moon mission, and ultimately the signing of the Partial Test Ban Treaty in 1963. The danger to electronic systems on the ground from an electromagnetic pulse was not considered to be significant from the sub-kiloton blasts proposed since solid-state integrated circuits were not in general use at the time.
From many smaller detonations combined, the fallout for the entire launch of a Orion is equal to the detonation of a typical 10 megaton (40 petajoule) nuclear weapon as an air burst, therefore most of its fallout would be the comparatively dilute delayed fallout. Assuming the use of nuclear explosives with a high portion of total yield from fission, it would produce a combined fallout total similar to the surface burst yield of the Mike shot of Operation Ivy, a 10.4 Megaton device detonated in 1952. The comparison is not quite perfect as, due to its surface burst location, Ivy Mike created a large amount of early fallout contamination. Historical above-ground nuclear weapon tests included 189 megatons of fission yield and caused average global radiation exposure per person peaking at in 1963, with a residual in modern times, superimposed upon other sources of exposure, primarily natural background radiation, which averages globally but varies greatly, such as in some high-altitude cities. Any comparison would be influenced by how population dosage is affected by detonation locations, with very remote sites preferred.
With special designs of the nuclear explosive, Ted Taylor estimated that fission product fallout could be reduced tenfold, or even to zero, if a pure fusion explosive could be constructed instead. A 100% pure fusion explosive has yet to be successfully developed, according to declassified US government documents, although relatively clean PNEs (Peaceful nuclear explosions) were tested for canal excavation by the Soviet Union in the 1970s with 98% fusion yield in the Taiga test's 15 kiloton devices, 0.3 kilotons fission, which excavated part of the proposed Pechora–Kama Canal.
The vehicle's propulsion system and its test program would violate the Partial Test Ban Treaty of 1963, as currently written, which prohibits all nuclear detonations except those conducted underground as an attempt to slow the arms race and to limit the amount of radiation in the atmosphere caused by nuclear detonations. There was an effort by the US government to put an exception into the 1963 treaty to allow for the use of nuclear propulsion for spaceflight but Soviet fears about military applications kept the exception out of the treaty. This limitation would affect only the US, Russia, and the United Kingdom. It would also violate the Comprehensive Nuclear-Test-Ban Treaty which has been signed by the United States and China as well as the de facto moratorium on nuclear testing that the declared nuclear powers have imposed since the 1990s.
The launch of such an Orion nuclear bomb rocket from the ground or low Earth orbit would generate an electromagnetic pulse that could cause significant damage to computers and satellites as well as flooding the van Allen belts with high-energy radiation. Since the EMP footprint would be a few hundred miles wide, this problem might be solved by launching from very remote areas. A few relatively small space-based electrodynamic tethers could be deployed to quickly eject the energetic particles from the capture angles of the Van Allen belts.
An Orion spacecraft could be boosted by non-nuclear means to a safer distance only activating its drive well away from Earth and its satellites. The Lofstrom launch loop, space elevator, or other alternative launch systems hypothetically provide excellent solutions; in the case of the space elevator, existing carbon nanotubes composites, with the possible exception of Colossal carbon tubes, do not yet have sufficient tensile strength. All chemical rocket designs are extremely inefficient and expensive when launching large mass into orbit but could be employed if the result were cost effective.
Notable personnel
Lew Allen, contract manager
Jerry Astl, explosives engineer
Jeremy Bernstein, physicist
Edward Creutz, physicist
Brian Dunne, Orion's chief scientist
Freeman Dyson, physicist
Harold Finger, physicist
Burt Freeman, physicist
Edward B. Giller, USAF liaison
Charles Clark Loomis, physicist
Harris Mayer, physicist
James Nance, project director
H. Pierre Noyes, physicist
Ronald F. Prater, USAF liaison
Don Prickett, USAF liaison
Kedar "Bud" Pyatt, mathematician
Morris Scharff, physicist
Ted Taylor, project director
Micheal Treshow, physicist
Stanisław Ulam, mathematician
Operation Plumbbob
A test that was similar to the test of a pusher plate occurred as an accidental side effect of a nuclear containment test called "Pascal-B" conducted on 27 August 1957. The test's experimental designer Dr. Robert Brownlee performed a highly approximate calculation that suggested that the low-yield nuclear explosive would accelerate the massive (900 kg) steel capping plate to six times escape velocity. The plate was never found but Dr. Brownlee believes that the plate never left the atmosphere; for example, it could have been vaporized by compression heating of the atmosphere due to its high speed. The calculated velocity was interesting enough that the crew trained a high-speed camera on the plate which, unfortunately, only appeared in one frame indicating a very high lower bound for the speed of the plate.
Notable appearances in fiction
The first appearance of the idea in print appears to be Robert A. Heinlein's 1940 short story, "Blowups Happen."
As discussed by Arthur C. Clarke in his recollections of the making of 2001: A Space Odyssey in The Lost Worlds of 2001, a nuclear-pulse version of the U.S. interplanetary spacecraft Discovery One was considered. However the Discovery in the movie did not use this idea, as Stanley Kubrick thought it might be considered parody after making Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb.
An Orion spaceship features prominently in the science fiction novel Footfall by Larry Niven and Jerry Pournelle. In the face of an alien siege/invasion of Earth, the humans must resort to drastic measures to get a fighting ship into orbit to face the alien fleet.
The opening premise of the show Ascension is that in 1963 President John F. Kennedy and the U.S. government, fearing the Cold War will escalate and lead to the destruction of Earth, launched the Ascension, an Orion-class spaceship, to colonize a planet orbiting Proxima Centauri, assuring the survival of the human race.
Author Stephen Baxter's science fiction novel Ark employs an Orion-class generation ship to escape ecological disaster on Earth.
Towards the conclusion of his Empire Games trilogy, Charles Stross includes a spacecraft modeled after Project Orion. The crafts' designers, constrained by a 1960s level of industrial capacity, intend it to be used to explore parallel worlds and to act as a nuclear deterrent, leapfrogging their foes more contemporary capabilities.
In the horror novel Torment by Jeremy Robinson (written under the pseudonym Jeremy Bishop), the main characters escape from a global nuclear war in a nuclear pulse propulsion craft. The craft is among 3 others; part of the "Orion Protocol", an escape mechanism for members of the federal government. The craft are housed in a subterranean chamber below The Ellipse.
In the science fiction novel "3 Body Problem" and its associated television shows, a probe is launched towards an approaching alien fleet using a variation of the Orion method.
See also
AIMStar
Antimatter-catalyzed nuclear pulse propulsion
Helios (propulsion system)
NERVA (Nuclear Engine for Rocket Vehicle Application)
Nuclear propulsion
Project Pluto
Project Prometheus
Project Valkyrie
Peaceful nuclear explosion
References
Further reading
"Nuclear Pulse Propulsion (Project Orion) Technical Summary Report" RTD-TDR-63-3006 (1963–1964); GA-4805 Vol. 1: Reference Vehicle Design Study, Vol. 2: Interaction Effects, Vol. 3: Pulse Systems, Vol. 4: Experimental Structural Response. (From the National Technical Information Service, U.S.A.)
"Nuclear Pulse Propulsion (Project Orion) Technical Summary Report" 1 July 1963 – 30 June 1964, WL-TDR-64-93; GA-5386 Vol. 1: Summary Report, Vol. 2: Theoretical and Experimental Physics, Vol. 3: Engine Design, Analysis and Development Techniques, Vol. 4: Engineering Experimental Tests. (From the National Technical Information Service, U.S.A.)
General Atomics, Nuclear Pulse Space Vehicle Study, Volume I – Summary, September 19, 1964
General Atomics, Nuclear Pulse Space Vehicle Study, Volume III – Conceptual Vehicle Designs And Operational Systems, September 19, 1964
General Atomics, Nuclear Pulse Space Vehicle Study, Volume IV – Mission Velocity Requirements And System Comparisons, February 28, 1966
General Atomics, Nuclear Pulse Space Vehicle Study, Volume IV – Mission Velocity Requirements And System Comparisons (Supplement), February 28, 1966
NASA, Nuclear Pulse Vehicle Study Condensed Summary Report (General Dynamics Corp), January 14, 1964
External links
The case for Orion
Freeman Dyson talking about Project Orion
Electromagnetic Pulse Shockwaves as a result of Nuclear Pulse Propulsion
George Dyson talking about Project Orion at TED
Orion
Hypothetical spacecraft
Single-stage-to-orbit
Space access
Orion
Freeman Dyson
Interstellar travel | Project Orion (nuclear propulsion) | [
"Astronomy",
"Technology",
"Engineering"
] | 7,121 | [
"Exploratory engineering",
"Astronomical hypotheses",
"Hypothetical spacecraft",
"Interstellar travel",
"nan"
] |
322,550 | https://en.wikipedia.org/wiki/Standard%20Performance%20Evaluation%20Corporation | The Standard Performance Evaluation Corporation (SPEC) is a non-profit consortium that establishes and maintains standardized benchmarks and performance evaluation tools for new generations of computing systems. SPEC was founded in 1988 and its membership comprises over 120 computer hardware and software vendors, educational institutions, research organizations, and government agencies internationally.
SPEC benchmarks and tools are widely used to evaluate the performance of computer systems; the test results are published on the SPEC website.
External links
Official List of SPEC Benchmarks
Computer performance
Evaluation of computers
Companies established in 1988
Companies based in Virginia
Standards organizations in the United States | Standard Performance Evaluation Corporation | [
"Technology"
] | 115 | [
"Computing stubs",
"Evaluation of computers",
"Computers",
"Computer performance"
] |
322,555 | https://en.wikipedia.org/wiki/Ectasia | Ectasia (), also called ectasis (), is dilation or distention of a tubular structure, either normal or pathophysiologic but usually the latter (except in atelectasis, where absence of ectasis is the problem).
Specific conditions
Bronchiectasis, chronic dilatation of the bronchi
Duct ectasia of breast, a dilated milk duct. Duct ectasia syndrome is a synonym for nonpuerperal (unrelated to pregnancy and breastfeeding) mastitis.
Dural ectasia, dilation of the dural sac surrounding the spinal cord, usually in the very low back.
Pyelectasis, dilation of a part of the kidney, most frequently seen in prenatal ultrasounds. It usually resolves on its own.
Rete tubular ectasia, dilation of tubular structures in the testicles. It is usually found in older men.
Corneal ectasia (secondary keratoconus), a bulging of the cornea.
Vascular ectasias
Most broadly, any abnormal dilatation of a blood vessel, including aneurysms
Annuloaortic ectasia, dilation of the aorta. It can be associated with Marfan syndrome.
Dolichoectasias, weakening of arteries, usually caused by high blood pressure.
Intracranial dolichoectasias, dilation of arteries inside the head.
Gastric antral vascular ectasia, dilation of small blood vessels in the last part of the stomach.
Telangiectasias are small dilated blood vessels found anywhere on the body, but commonly seen on the face around the nose, cheeks, and chin.
Venous ectasia, dilation of veins or venules, such as:
Chronic venous insufficiency, often in the leg
Jugular vein ectasia, in the jugular veins returning blood from the head
See also
References
Anatomy
Pathophysiology | Ectasia | [
"Biology"
] | 412 | [
"Anatomy"
] |
322,632 | https://en.wikipedia.org/wiki/Agency%20for%20Toxic%20Substances%20and%20Disease%20Registry | The Agency for Toxic Substances and Disease Registry (ATSDR) is a federal public health agency within the United States Department of Health and Human Services' Centers for Disease Control and Prevention. The agency focuses on minimizing human health risks associated with exposure to hazardous substances. It works closely with other federal, state, and local agencies; tribal governments; local communities; and healthcare providers. Its mission is to "Serve the public through responsive public health actions to promote healthy and safe environments and prevent harmful exposures." ATSDR was created as an advisory, nonregulatory agency by the Superfund legislation and was formally organized in 1985.
Although ATSDR is an independent operating agency within the Department of Health and Human Services, the Centers for Disease Control and Prevention (CDC) performs many of its administrative functions. The CDC director also serves as the ATSDR administrator, and ATSDR has a joint Office of the Director with the National Center for Environmental Health (NCEH). The ATSDR headquarters are located in Atlanta, Georgia, at the CDC Chamblee campus. In fiscal year 2010, ATSDR had an operating budget of $76.8 million and had roughly 300 full-time employees (not including contractors).
The ATSDR is formally and administratively overseen by the Director of the Centers for Disease Control and Prevention (CDC), currently Mandy Cohen since July 10, 2023 Direction is provided by ATSDR's Director, currently Patrick N. Breysse, who ranks below the Administrator, and ATSDR's Associate Director, currently Christopher M. Reh.
Overview
ATSDR is an agency within the US Department of Health and Human Services concerned with the effects of hazardous substances on human health. ATSDR is charged with assessing the presence and nature of health hazards at specific Superfund sites, as well as helping prevent or reduce further exposure and the illnesses that can result from such exposures. ATSDR is an oversight agency created to ensure that public health protection and environmental regulation work hand in hand.
ATSDR functions include public health assessments of National Priority List (NPL or Superfund) hazardous waste sites; petitioned health consultations or assessments concerning specific waste sites or industrial facilities that US citizens have requested further action upon; the conduct of health studies (including surveillance and registries) to determine the long-term impact of these facilities; response to emergency releases of hazardous substances, applied research in support of public health assessments, information development and dissemination, and education and training concerning hazardous substances. ATSDR also prepares toxicological profiles for hazardous substances found at National Priorities List sites, as well as at federal sites administered by the Department of Defense and Department of Energy.
Goals
ATSDR has seven goals:
Protect the public from environmental hazards and toxic exposures.
Promote healthy environments.
Advance the science of environmental public health.
Support environmental public health practice.
Educate communities, partners, and policy makers about environmental health risks and protective measures.
Promote environmental justice and reduce health disparities associated with environmental exposures.
Provide unique scientific and technical expertise to advance public health science and practice.
Authority
Unlike the Environmental Protection Agency (EPA), ATSDR is an advisory, nonregulatory agency. ATSDR conducts research on the health impacts of hazardous waste sites and provides information and recommendations to federal and state agencies, community members, and other interested parties. However, ATSDR is not involved in cleanup of those sites, nor can ATSDR provide or fund medical treatment for people who have been exposed to hazardous substances.
History
In response to the environmental disasters at Love Canal and Times Beach, Missouri, Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), commonly known as the Superfund legislation. CERCLA gave EPA primary responsibility for identifying, investigating, and cleaning up hazardous waste sites. CERCLA also authorized the establishment of ATSDR to assess the presence and nature of health hazards to communities living near Superfund sites, to help prevent or reduce harmful exposures, and to expand the knowledge base about the health effects that result from exposure to hazardous substances.
A 1982 lawsuit litigated by Chemical Manufacturers Association and the American Petroleum Institute forced the creation of ATSDR, which was created as an agency under the Department of Health and Human Services on April 19, 1983. James O. Mason served as the agency's first administrator. The Hazardous and Solid Waste Amendments of 1984 to the Resource Conservation and Recovery Act (RCRA) gave ATSDR additional authority related to hazardous waste storage facilities. ATSDR was charged with conducting public health assessments at these sites when requested by EPA, states, or individuals, as well as assisting EPA to determine which substances should be regulated and the levels at which chemicals may pose a threat to human health. ATSDR was formally organized as an agency on June 11, 1985. The Superfund Amendments and Reauthorization Act of 1986 (SARA) broadened ATSDR's responsibilities in the areas of public health assessments, establishment and maintenance of toxicological databases, information dissemination, and medical education.
In 2003, the position of assistant administrator was replaced with a director who is shared with NCEH.
Organization
Administration
CDC Director Mandy Cohen serves concurrently/ex officio as ATSDR administrator and CDC director, heading the Office of the Administrator. Patrick N. Breysse, PhD. serves as director of NCEH/ATSDR, heading the Office of the Director. The ATSDR administrator/CDC director, who provides overall leadership of the agency, is appointed by the president of the United States; the appointment does not require Senate approval. The ATSDR administrator appoints the NCEH/ATSDR director, who is responsible for managing the agency's programs and activities.
Organizational structure
Office of the Administrator (also CDC Director)
Office of the Director (also NCEH (National Center for Environmental Health) head)
Office of Communications
Office of Science
Office of Management and Analytics
Office of Policy, Partnerships, and Planning
Office of the Associate Director
Office of Innovation and Analytics (OIA)
Office of Community Health Hazard Assessment (OCHHA)
Office of Capacity Development and Applied Prevention Science (OCDAPS)
The Office of the Director (of ASTDR) is joint with that of NCEH; it also contains seven functional units, five offices, five program-specific divisions to support and implement six program areas:
Public Health Assessments
Toxicological Profiles
Emergency Response
Exposure and Disease Registries
Health Effects Research
Health Education
Regional offices
The Division of Community Health Investigations manages an office in Washington, D.C., as well as offices in each of the 10 EPA regions:
Boston (Region 1: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont)
New York and Edison, New Jersey (Region 2: New Jersey, New York, Puerto Rico, U.S. Virgin Islands)
Philadelphia (Region 3: Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, West Virginia)
Atlanta (Region 4: Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee)
Chicago (Region 5: Illinois, Indiana, Michigan, Minnesota, Ohio, Wisconsin)
Dallas (Region 6: Arkansas, Louisiana, New Mexico, Oklahoma, Texas)
Kansas City, Kansas (Region 7: Iowa, Kansas, Missouri, Nebraska)
Denver and Helena, Montana (Region 8: Colorado, Montana, North Dakota, South Dakota, Utah, Wyoming)
San Francisco (Region 9: American Samoa, Arizona, California, Guam, Hawaii, Nevada, Northern Mariana Islands, Trust Territories)
Seattle and Anchorage, Alaska (Region 10: Alaska, Idaho, Oregon, Washington)
The regional offices work cooperatively with EPA, state and local health departments, health professionals, community groups, and other partners to implement programs and initiatives.
Programs
Public health assessments and health consultations
One of ATSDR’s primary responsibilities is conducting public health assessments and health consultations. The agency conducts public health assessments for all current or proposed sites on the National Priorities List (commonly known as Superfund sites). The purpose of public health assessments is to examine whether hazardous substances at a site pose a human health hazard and to issue recommendations about limiting or stopping exposure to those substances. ATSDR also conducts health consultations, often in response to requests from EPA and state and local agencies. Health consultations examine specific health questions, such as the health effects of exposure to a specific chemical at a site. Health consultations are more limited in scope than public health assessments. ATSDR also conducts public health assessments and health consultations in response to petitions from members of the public. To conduct public health assessments and health consultations, ATSDR relies on its own scientists or establishes cooperative agreements with states, providing technical assistance to state health departments. ATSDR issued more than 200 public health assessments in 2009 and provides about 1,000 health consultations each year.
When investigating sites, ATSDR examines environmental data, health data, and information from community members about how the site affects their quality of life. ATSDR normally does not collect its own environmental data; rather, it usually relies on partner organizations, such as EPA, to conduct testing and gather data. This environmental data provides information on the amount of contamination and possible ways humans could be exposed to the hazardous substances at the site. The health data provides information on rates of illness, disease, and death in the local community. Since ATSDR is an advisory agency, the conclusions in its public health assessments and health consultations are often in the form of recommendations to state and national environmental and health agencies, such as EPA, that have regulatory authority. Other agencies and the general public rely on ATSDR to provide trusted information on the health effects of hazardous substances at contaminated sites.
Toxicology research
Another major responsibility of ATSDR is producing toxicological profiles for the most common substances that are found at Superfund sites. The toxicological profiles summarize important studies on the substances’ health effects. ATSDR also publishes ToxFAQs, ToxGuides, and public health statements, which summarize the health information in toxicological profiles for use by the general public and health professionals. The agency maintains a Toxic Substances Portal that compiles all of the agency’s toxicology information and allows users to search by chemical. ATSDR has published toxicological profiles for more than 250 hazardous substances.
ATSDR has a computational toxicology laboratory that conducts research and modeling on the effects of toxic substances on human health. The agency's toxicology work involves pharmacokinetic/pharmacodynamic modeling, quantitative structure–activity relationship methods, and benchmark dose modeling, as well as establishing minimal risk levels for human exposure to hazardous substances. One model developed by the toxicology laboratory showed that children were much more susceptible than adults to chemical exposure from inhalation and oral exposure. In the aftermath of chemical spills and emergencies, the laboratory also conducts research for state and local health departments on the health effects of the chemicals involved.
Health registries
ATSDR maintains registries of people who were exposed to certain toxic substances or have certain diseases. Participation in these registries is voluntary, and individual data and personal information is kept private. The information collected is used by epidemiologists and other researchers to examine long-term health outcomes or risk factors for illness. It can also help doctors diagnose those health conditions in other individuals and treat them earlier. The agency also uses registries to contact registered individuals with important health information.
Tremolite Asbestos Registry
The Tremolite Asbestos Registry contains people who lived in or worked in Libby, Montana, while vermiculite was mined there; these people were at risk for exposure to the tremolite asbestos that was naturally occurring in the vermiculite. ATSDR began addressing public health concerns in Libby in 1999 and created the registry in 2004. The purpose of the registry was to monitor the long-term health effects of people in Libby exposed to tremolite asbestos and to assist with communicating important health information to registrants. Researchers have used the registry to study how asbestos exposure affects human health. This research has yielded several important findings. Registry data was used to conduct the first study of the relationship between asbestos exposure and respiratory problems in children. Another study using registry data found a significant relationship between asbestos exposure and death from cardiovascular disease.
World Trade Center Health Registry
The World Trade Center Health Registry was established in 2002 by ATSDR and the New York City Department of Health and Mental Hygiene to track the long-term physical and mental health effects of the September 11 attacks. The registry contains more than 71,000 people who lived, worked, or went to school near the World Trade Center site, as well as emergency response personnel who were involved in rescue and recovery efforts. It is the largest post-disaster health registry in the United States. Researchers use the registry to study the health effects of the disaster and to develop public health recommendations for future disasters. A 2009 study based on registry data found that posttraumatic stress disorder and asthma were the two most commonly reported conditions among registry participants 5 to 6 years after the disaster. The study found that 19% of adult participants reported new posttraumatic stress symptoms, and 10% of adult participants reported developing new asthma.
ALS Registry
ATSDR is starting a new registry for people with amyotrophic lateral sclerosis (also known as ALS or Lou Gehrig's Disease). President George W. Bush signed the ALS Registry Act, which provided for establishment of the registry, on October 8, 2008. It is hoped that the registry will provide information on the prevalence of ALS and lead to a better understanding of factors that may be associated with the disease. The agency began registering people for the registry on October 20, 2010.
Surveillance
ATSDR conducts surveillance by maintaining projects to collect and analyze information on diseases and chemical exposures. Research using that information and data can then be used to prevent future and control injury, disease, and death.
Hazardous Substances Emergency Events Surveillance Program
One of the most notable surveillance projects was the Hazardous Substances Emergency Events Surveillance (HSEES) program, which lasted from 1990 to 2009. ATSDR partnered with 15 states to collect information for HSEES in order to track, report, and study chemical spills. The information in the HSEES system was used to plan for emergency events involving hazardous substances (including terrorist attacks). States also used the information to develop policies and programs to strengthen public health and reduce illnesses and deaths that can result from exposure to hazardous substances. For example, states used HSEES data to support legislation addressing the problem of hazardous chemicals at illegal methamphetamine labs. Other states used HSEES data to implement programs designed to minimize exposure to hazardous chemicals and mercury at schools. More than 50 published studies were conducted using HSEES data.
National Toxic Substance Incidents Program
As a successor to the HSEES program, ATSDR launched the National Toxic Substance Incidents Program (NTSIP) in 2009. One aspect of NTSIP is a national database of information related to chemical spills. NTSIP also has Assessment of Chemical Exposure teams to assist state and local health departments in the aftermath of toxic spills. These teams interview people who were exposed to the hazardous substances and collect samples to test the level of contamination in the environment and in people.
Emergency response
ATSDR represents the Department of Health and Human Services on the National Response Team and works with other agencies to provide technical assistance during emergencies involving hazardous substances, such as chemical spills. In July 2007, for example, ATSDR responded to the Verdigris River flood in Coffeyville, Kansas, after an oil refinery spilled crude oil into the floodwaters, contaminating many homes in the city. ATSDR worked with EPA and state and local authorities to provide health information to local residents and advised those agencies during the clean-up process. ATSDR also assists with responding to terrorism incidents, which have included the September 11 attacks and the 2001 anthrax attacks. ATSDR responded to 132 chemical emergency events in 2008.
In addition to working with communities and other agencies in the aftermath of chemical emergencies, ATSDR has developed the Managing Hazardous Materials Incidents series, which includes several tools to assist emergency medical services personnel and hospital emergency departments during chemical emergencies. This includes important information on emergency planning, emergency response, and rescuer protection. Another tool is the Medical Management Guidelines, which summarize important information on exposure to common chemicals and provide suggestions for safely treating and decontaminating patients.
Brownfield/land reuse initiative
ATSDR works closely with communities to evaluate the public health effects related to redevelopment of brownfields properties. These are sites that were formerly used for industrial purposes and may still be contaminated with hazardous substances. ATSDR has worked at more than 400 brownfield or land reuse sites to assess health effects of potential exposure to hazardous substances. The agency has created resources to provide guidance to communities when planning redevelopment projects, including tools to evaluate the potential threat of chemicals at development sites. In addition to evaluating the health effects of contamination at specific brownfield sites, ATSDR encourages communities to monitor community health. One of the agency's brownfields projects was the Menomonee Valley in Milwaukee, Wisconsin, where the agency evaluated potential health effects of contamination at the site and worked closely with developers and the city.
Community partnerships
A major focus of the work ATSDR does involves interacting with communities. ATSDR often establishes partnerships with state and local health departments to assist them with their public health duties. In 2008, ATSDR had cooperative agreements with 29 states and one tribal government, providing technical assistance to help those partners address local environmental health concerns. ATSDR also creates community assistance panels to solicit feedback and community health concerns from local residents when the agency works at sites to evaluate health effects resulting from exposure to toxic substances.
National Conversation on Public Health and Chemical Exposures
In June 2009, ATSDR and NCEH launched a joint project, the National Conversation on Public Health and Chemical Exposures. The goal of the National Conversation is to develop recommendations for ways ATSDR and other government agencies can improve their efforts to protect the public from harmful chemical exposures. To foster a productive dialogue, ATSDR encouraged broad public participation in the National Conversation and welcomed involvement from all interested stakeholders, including government agencies, public health professionals, environmental organizations, community leaders, business and industry representatives, tribal groups, and other interested citizens. The National Conversation is led by a 40-person Leadership Council that includes experts in various areas related to environmental public health. In addition, there are six work groups, which also have a diverse membership, to research and propose recommendations on certain key areas. To encourage involvement from community groups, interested citizens, and the general public, ATSDR developed a community toolkit to assist community leaders in holding discussions to solicit feedback and ideas for the National Conversation. ATSDR plans to release its final action agenda in early 2011.
Quality of work
ATSDR prides itself on using "the best science." And in 2003, BBC News described ATSDR as "widely regarded as the world's leading agency on public health and the environment."
However, ATSDR has also been the focus of scrutiny from Congress and other groups. Much of the criticism is due to the fact that the agency has been overtasked yet understaffed and underfunded for much of its history.
In August 1991, the General Accounting Office (now the Government Accountability Office) published a report that faulted the quality of ATSDR's original public health assessments and questioned their usefulness. It also placed part of the blame on the deadlines and requirements that Congress imposed with SARA: "SARA’s requirement that ATSDR quickly assess 951 Superfund sites came at a time when the agency was still relatively new and ... not staffed or organized for the job." The report also noted that after meeting the SARA deadline, ATSDR was able to increase the rigor of its public health assessments.
In May 1992, the Environmental Health Network and the National Toxics Campaign Fund published "Inconclusive by Design," a report which noted structural limitations to the work of CDC and ATSDR.
In April 2008, the United States House of Representatives Committee on Science and Technology Subcommittee on Investigations and Oversight held a hearing on formaldehyde exposures in trailers that the Federal Emergency Management Agency (FEMA) provided as temporary housing to people displaced by Hurricane Katrina. A report based on the hearing, issued by the subcommittee's Democratic majority staff in September 2008, noted shortcomings in the agency’s original health consultation that examined the health risks of formaldehyde in the FEMA trailers.
In March 2009, the Democratic majority staff of the Subcommittee on Investigations and Oversight issued another report on ATSDR, which called for leadership changes within the agency. The report stated: "Time and time again ATSDR appears to avoid clearly and directly confronting the most obvious toxic culprits that harm the health of local communities throughout the nation. Instead, they deny, delay, minimize, trivialize or ignore legitimate concerns and health considerations of local communities and well respected scientists and medical professionals."
In the March 12, 2009, congressional hearing, the subcommittee chairman, Congressman Brad Miller, characterized ATSDR as keen to "please industries and government agencies" and referred to ATSDR's reports as "jackleg assessments saying 'not to worry.'" In defense of ATSDR's work, director Howard Frumkin noted that ATSDR's staff has declined from 500 to about 300, and that often communities expect "definitive answers about the links between exposures and illnesses," but expectations can be unmet due to scientific uncertainty. However, Frumkin also acknowledged the possibility that some assessments did not use the best data or monitoring techniques.
Vieques, Puerto Rico
In 2003, ATSDR released public health assessments that evaluated the potential health effects of pollution left behind by the United States Navy in Vieques, Puerto Rico. The public health assessments noted that residents of the island were exposed to environmental contamination at such low levels that no harmful health effects were expected, and the agency concluded that there was "no apparent public health hazard." In 2009, however, ATSDR announced that it had identified gaps in environmental data and planned to take a "fresh look" at Vieques by reviewing studies on the island.
West Lake Landfill, Missouri
In 2015, ATSDR released a report, based on EPA data, declaring no health risk to communities near West Lake Landfill. The agency's assessment contradicted findings from scientific investigations initiated by the Missouri attorney general and affected residents, who started organizing in 2012 when an underground fire in the landfill raised awareness of radioactive material and high rates of childhood cancer. Republic Services, one of the parties responsible for the landfill, has cited the report to argue against the removal of toxic waste.
See also
Centers for Disease Control and Prevention
United States Department of Health and Human Services
National Priorities List
United States Navy in Vieques, Puerto Rico
List of Superfund sites in the United States
TOXMAP
References
External links
ATSDR website
Agency for Toxic Substances and Disease Registry in the Federal Register
World Trade Center Health Registry
National Priorities List
Why CDC Responded With 'Lack of Urgency' to Formaldehyde Warnings
1983 establishments in Georgia (U.S. state)
Biochemistry databases
Environment of the United States
Environmental agencies in the United States
Organizations based in Atlanta
Toxic effects of substances chiefly nonmedicinal as to source
Agencies of the United States Public Health Service | Agency for Toxic Substances and Disease Registry | [
"Chemistry",
"Biology",
"Environmental_science"
] | 4,818 | [
"Biochemistry",
"Biochemistry databases",
"Toxicology",
"Toxic effects of substances chiefly nonmedicinal as to source"
] |
322,678 | https://en.wikipedia.org/wiki/Cabinet%20%28file%20format%29 | Cabinet (or CAB) is an archive-file format for Microsoft Windows that supports lossless data compression and embedded digital certificates used for maintaining archive integrity. Cabinet files have .cab filename extensions and are recognized by their first four bytes (also called their magic number) MSCF. Cabinet files were known originally as Diamond files.
Design
A CAB archive can contain up to 65,535 folders (distinct from standard operating system directories), each of which can contain up to 65,535 files for a maximum of 4,294,836,225. Internally, each folder is treated as a single compressed block, which provides more efficient compression than individually compressing each file.
Every entry in a folder has to be a file. Due to this structure, it is not possible to store empty folders in CAB archives.
The following shows an example a CAB file structure, demonstrating the relationship between folders and files:
CAB file
First folder
Second folder
How paths should be handled is not specified in the CAB file format, leaving it to the software implementation:
Some affix file paths to filenames only, as if all files in a CAB archive are in a single folder. IExpress works this way, as does Microsoft Windows Explorer, which can open CAB archives as a folder.
Some can store the paths, and upon extraction, create folders as necessary. and (tools from Microsoft Cabinet SDK) as well as and (third-party open-source tools) work this way.
, only since version 6 (which is included from Windows Vista to above) can extract files to their paths. The previous versions don't do it.
The CAB file format may employ the following compression algorithms:
DEFLATE: invented by Phil Katz, the author of the ZIP file format (specifically, the MSZIP encapsulation)
Quantum compression: licensed from David Stafford, the author of the Quantum archiver (not available in all versions of makecab.exe/diamond.exe)
LZX: invented by Jonathan Forbes and Tomi Poutanen, given to Microsoft when Forbes joined the company
NULL: stored
A CAB archive can reserve empty spaces in the archive as well as for each file in the archive, for some application-specific uses like digital signatures or arbitrary data.
Implementations
Microsoft Windows supports creating CAB archive files using the makecab command-line utility. It supports extracting the contents of a CAB archive files using File Explorer, Setup API, and using the command-line commands expand.exe, extract.exe and extrac32.exe.
Other well-known software with CAB archive support includes WinZip, WinRAR or 7-Zip. The aforementioned cabextract is a common tool for Linux systems, but is only capable of extracting archives. The gcab tool however can both extract and create CAB archives. For a full list, see .
Uses
A variety of Microsoft installation technologies use the CAB format: these include Windows Installer, Windows Setup (from Windows 95 to Windows Server 2003), Setup API, Device Installer, Theme Pack and AdvPack (used by Internet Explorer to install ActiveX components). CAB files are also often associated with self-extracting programs like IExpress where the executable program extracts the associated CAB file. CAB files are also sometimes embedded into other files. For example, MSI and MSU files usually include one or more embedded CAB files.
Windows uses the cabinet format to archive its Component-Based Servicing (CBS) log, which is kept in the folder . A bug in the compression process can cause run-away generation of useless log files both in that folder and in , which can consume disk storage until completely filling the hard drive. Deletion of the files without following a specific procedure can cause the deleted files to be regenerated at an increased pace.
On Linux systems, CAB archives are used by fwupd to distribute firmware updates from hardware vendors that can be flashed on non-volatile memory.
Related formats
The .cab filename extension is also used by other installer programs (e.g. InstallShield) for their own proprietary archiving formats. InstallShield uses zlib for compression (see Deflate), but their headers are not the same as for Microsoft CAB files so they are incompatible and cannot be manipulated or edited with the programs that are made for standard cabinet format. Specialized third-party utilities, such as Unshield, can extract this specific proprietary format. This format has a different magic number of .
Windows CE software is distributed as CAB files where the first file inside, ending with extension ".000", details how it is installed.
Microsoft Installer .msi files sometimes contain CAB files, but are themselves in the Compound File Binary Format which has to be decoded first. Software like lessmsi can be used to unpack these files.
Microsoft Publisher has a "Pack and Go" feature that bundles a publisher document, together with all external links, into a CAB file with a .PUZ extension. These files are meant to be activated with a companion .EXE file which is distributed along with the .PUZ file. These files may be opened with any CAB file extraction program.
See also
List of archive formats
References
External links
Microsoft Cabinet SDK – updated versions of these resources are available in the Microsoft Windows SDK
Cabinet Software Development Kit (CAB SDK) – downloads of all Microsoft CAB SDK versions (free)
Archive formats
Windows administration | Cabinet (file format) | [
"Technology"
] | 1,120 | [
"Windows commands",
"Computing commands"
] |
322,701 | https://en.wikipedia.org/wiki/French%20Alternative%20Energies%20and%20Atomic%20Energy%20Commission | The French Alternative Energies and Atomic Energy Commission, or CEA (French: Commissariat à l'énergie atomique et aux énergies alternatives), is a French public government-funded research organisation in the areas of energy, defense and security, information technologies and health technologies. The CEA maintains a cross-disciplinary culture of engineers and researchers, building on the synergies between fundamental and technological research.
CEA is headed by a board headed by the general administrator (currently since 20 April 2018), advised by the high-commissioner for atomic energy (currently ). Its yearly budget amounts to €5.8 billion and its permanent staff is slightly over 21,000 persons.
History
CEA was created in 1945; since then, the successive high-commissioners have been Frédéric Joliot-Curie, Francis Perrin, , , Raoul Dautry, René Pellat, Bernard Bigot, Catherine Cesarsky, , and .
In December 2009, French President Nicolas Sarkozy declared that CEA should change its name from Commissariat à l’énergie atomique () to Commissariat à l’énergie atomique et aux énergies alternatives (); this change took effect on 10 March 2010, when the decision was published in the Journal officiel de la République française.
Research
It conducts fundamental and applied research into many areas, including the design of nuclear reactors, the manufacturing of integrated circuits, the use of radionucleides for curing illnesses, seismology and tsunami propagation, the safety of computerized systems, etc.
It has one of the top 100 supercomputers in the world, the Tera-100. TERA 100, first system designed and built in Europe to reach the petaflops in 2010, was ranked in 5th position in the worldwide TOP 500. CEA is now building TERA-1000 which is a key step in the implementation of their Exascale program for the computing needs that CEA would face by 2020.
In March 2016, Reuters published an article describing the "Top 25 Global Innovators – Government" and placed CEA as "number one" amongst "The World's Most Innovative Research Institutions."
Organisation
CEA is divided into four directorates, or divisions:
Energies division (DES)
The (DES) comprises four institutes:
Institut de recherche sur les systèmes nucléaires pour la production d’énergie bas carbone (IRESNE), in Cadarache
Institut des sciences et technologies pour une économie circulaire des énergies bas carbone (ISEC), in Marcoule
Institut des sciences appliquées et de la simulation pour les énergies bas carbone (ISAS), in CEA Saclay
Institut de technico-économie des systèmes énergétiques (ITESE or I-Tésé)
Technological research division (DRT)
The (DRT), known also as CEA Tech division, is divided between two CEA sites, at Saclay and Grenoble. CEA Tech focuses on technological research and development in the field of energy, IT (both hardware and software) and healthcare informatics. It plays an active role in transferring knowledge and research to industry.
The CEA Tech division is further divided into three research institutes:
The CEA-Leti lab works mainly on micro/nano technologies and specializes in microsystems, biotech, photonics and nanoelectronics. It is located mainly in Grenoble, France.
The CEA-List lab works mainly on systems and software-intensive technology and specializes in embedded systems, sensors and big data, and advanced manufacturing. It is located mainly in Paris-Saclay, France.
The lab works mainly on cutting edge technologies related to energy and nanomaterials. It specializes in building solar, carbon-free transports, biomass-hydrogen and nano materials-nanotechnologies.
The current director of DRT since january 2023 is Julie Galland.
Fundamental research division (DRF)
The (DRF) consists of 9 institutes:
Institut de biologie François Jacob (JACOB) in CEA Fontenay-aux-Roses
Institut des sciences du vivant Frédéric Joliot (JOLIOT) in CEA Saclay
Institut Rayonnement-Matière de Saclay (IRAMIS) in CEA Saclay
Institut de recherche sur les lois fondamentales de l'Univers (Irfu) in CEA Saclay
Laboratoire des sciences du climat et de l'environnement (LSCE) in CEA Saclay
Institut de recherche interdisciplinaire de Grenoble (IRIG) in
Institut de physique théorique (IPhT) in CEA Saclay
Institut de Recherche sur la Fusion par confinement Magnétique (IRFM) in Cadarache
Institut de Biosciences et de Biotechnologies d'Aix-Marseille (BIAM) in Cadarache
The current DRF director since 2 november 2019 is Elsa Cortijo.
Military applications division (DAM)
The (DAM) builds the nuclear weapons of the French military and designs the power plants for the nuclear submarines of the French Navy.
Facilities
Civilian research centres
CEA Saclay, Essonne (, headquarters since 2006) and the associated National Laboratory GANIL at Caen - Calvados
CEA Fontenay-aux-Roses, Fontenay-aux-Roses, Hauts-de-Seine
, Grenoble (Polygone Scientifique), Isère
, Cadarache, Bouches-du-Rhône
CEA Valrhô, Marcoule and Pierrelatte, Gard
Civilian emergency organizations
Groupe INTRA
Research centres for military applications
The sites of the DAM include:
, Bruyères-le-Châtel, Essonne
CEA Valduc, Côte-d'Or
INBS PN CADARACHE, in Cadarache
CEA Cesta, Gironde
CEA Gramat
CEA Le Ripault, Indre-et-Loire
Spin-off companies
CEA has spun off multiple companies, some being partial subsidiaries or where CEA has minority interest. Some such companies are listed below:
Orano
STMicroelectronics
Soitec
LYNRED (formerly Sofradir)
It owned Areva
Kalray
CEA in Academics
University of Paris-Saclay
CEA has played an active role in research, development and innovation in the four main areas of low-carbon energies (nuclear and renewable), technologies for information and health technologies, very large research infrastructures (TGIR), and defense and global security.
Moreover, two of the ten CEA centers across France have joined with the University of Paris-Saclay to develop high quality research and training. The centers which form a part of the University of Paris-Saclay include:
CEA Saclay Center, which conducts research mainly in areas related to climate and environment, materials science, nuclear energy, life sciences and technological research
CEA Fontenay-aux-Roses Center, which conducts research and innovation in areas related to imaging and biomedical technologies
(Since 2017, these two centers merged into CEA Paris-Saclay center, and are now referred to as sites in that center.)
The CEA researchers involved in the University of Paris-Saclay represent over 20% of the university's research potential, particularly in the field of physics and engineering. CEA maintains a strong presence in training to master and engineer level by administering INSTN, wherein various courses are taught by its researchers.
CEA has around 400 researchers who hold an accreditation to supervise research, making it a significant contributor to the research and doctoral programs of the University Paris-Saclay.
INSTN
The INSTN, Institut national des sciences et techniques nucléaires (National Institute for Nuclear Science and Technology) is a public higher education institution administered by the CEA (French Atomic Energy and Alternative Energies Commission) under the joint authority of the Ministry of National Education, Higher Education and Research, the Ministry of the Economy, Industry and the Digital Sector and the Ministry of the Environment, Energy and Marine Affairs.
Others
Atos, ENS Paris-Saclay and CEA launched an academic partnership in 2016.
See also
GANIL (laboratory shared between the CEA and the CNRS)
Groupe INTRA
Laser Mégajoule
Pascal Elleaume
References
Bibliography
Bertrand Goldschmidt, Le Complexe atomique : histoire politique de l’énergie nucléaire, Fayard, 1980
Gabrielle Hecht, Le rayonnement de la France : Énergie nucléaire et identité nationale après la Seconde Guerre mondiale, La Découverte, 2004
Marie-José Lovérini, L’Atome de la recherche à l’industrie : le Commissariat à l’énergie atomique, Gallimard, 1996
Jean-François Picard, Alain Beltran et Martine Bungener, Histoire de l’EDF : comment se sont prises les décisions de 1946 à nos jours, Dunod, 1985
Government agencies of France
Governmental nuclear organizations
Nuclear energy in France
Nuclear research institutes
Nuclear technology organizations of France
Paris-Saclay University
1945 establishments in France | French Alternative Energies and Atomic Energy Commission | [
"Engineering"
] | 1,913 | [
"Nuclear research institutes",
"Nuclear organizations",
"Governmental nuclear organizations"
] |
322,840 | https://en.wikipedia.org/wiki/Automatic%20direction%20finder | An automatic direction finder (ADF) is a marine or aircraft radio-navigation instrument that automatically and continuously displays the relative bearing from the ship or aircraft to a suitable radio station. ADF receivers are normally tuned to aviation or marine NDBs (Non-Directional Beacon) operating in the LW band between 190 – 535 kHz. Like RDF (Radio Direction Finder) units, most ADF receivers can also receive medium wave (AM) broadcast stations, though these are less reliable for navigational purposes.
The operator tunes the ADF receiver to the correct frequency and verifies the identity of the beacon by listening to the Morse code signal transmitted by the NDB. On marine ADF receivers, the motorized ferrite-bar antenna atop the unit (or remotely mounted on the masthead) would rotate and lock when reaching the null of the desired station. A centerline on the antenna unit moving atop a compass rose indicated in degrees the bearing of the station. On aviation ADFs, the unit automatically moves a compass-like pointer (RMI) to show the direction of the beacon. The pilot may use this pointer to home directly towards the beacon, or may also use the magnetic compass and calculate the direction from the beacon (the radial) at which their aircraft is located.
Unlike the RDF, the ADF operates without direct intervention, and continuously displays the direction of the tuned beacon. Initially, all ADF receivers, both marine and aircraft versions, contained a rotating loop or ferrite loopstick aerial driven by a motor which was controlled by the receiver. Like the RDF, a sense antenna verified the correct direction from its 180-degree opposite.
More modern aviation ADFs contain a small array of fixed aerials and use electronic sensors to deduce the direction using the strength and phase of the signals from each aerial. The electronic sensors listen for the trough that occurs when the antenna is at right angles to the signal, and provide the heading to the station using a direction indicator. In flight, the ADF's RMI or direction indicator will always point to the broadcast station regardless of aircraft heading. Dip error is introduced, however, when the aircraft is in a banked attitude, as the needle dips down in the direction of the turn. This is the result of the loop itself banking with the aircraft and therefore being at a different angle to the beacon. For ease of visualisation, it can be useful to consider a 90° banked turn, with the wings vertical. The bearing of the beacon as seen from the ADF aerial will now be unrelated to the direction of the aircraft to the beacon.
Dip error is sometimes wrongly confused with quadrantal error, which is the result of radio waves being bounced and reradiated by the airframe. Quadrantal error does not affect signals from straight ahead or behind, nor on the wingtips. The further from these cardinal points and the closer to the quadrantal points (i.e. 45°, 135°, 225° and 315° from the nose) the greater the effect, but quadrantal error is normally much less than dip error, which is always present when the aircraft is banked.
ADF receivers can be used to determine current position, track inbound and outbound flight path, and intercept a desired bearing. These procedures are also used to execute holding patterns and non-precision instrument approaches.
Typical service ranges of non-directional beacons (NDBs)
Non-directional beacons in North America are classified by power output: "low" power rating is less than 50 watts; "medium" from 50 W to 2,000 W; and "high" at more than 2,000 W.
ADF indicators
The ADF indicators are a kind of navigational display consisting of a dial and a needle that rotates around the dial and points to the beacon. This needle suggests the "to" bearing of the beacon, and to fly the "from" bearing, 180° needs to be added or subtracted from the reading.
There are two types of ADF indicators: the "fixed azimuth dial" type with 0° always represents the aircraft nose, and 180° always represents the aircraft tail; and the type with rotating dials that can be rotated to align the azimuth with the aircraft heading.
Stages
Station passage
As an aircraft nears an NDB station, the ADF becomes increasingly sensitive, small lateral deviations result in large deflections of the needle which sometimes shows erratic left/right oscillations. Ideally, as the aircraft overflies the beacon, the needle swings rapidly from directly ahead to directly behind. This indicates station passage and provides an accurate position fix for the navigator. Less accurate station passage, passing slightly to one side or another, is shown by slower (but still rapid) swinging of the needle. The time interval from the first indications of station proximity to positive station passage varies with altitude — a few moments at low levels to several minutes at high altitude.
Homing
The ADF may be used to home in on a station. Homing is flying the aircraft on the heading required to keep the needle pointing directly to the 0° (straight ahead) position. To home into a station, tune the station, identify the Morse code signal, then turn the aircraft to bring the ADF azimuth needle to the 0° position. Turn to keep the ADF heading indicator pointing directly ahead. Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind, and will have to fly further and for longer than the direct track.
Tracking
The ADF may also be used to track a desired course using an ADF and allowing for winds aloft, winds which may blow the aircraft off-course. Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind. As the flight progresses, the pilot monitors the direction to or from the NDB using the ADF, adjusts the correction as required. A direct track will yield the shortest distance and time to the ADF location.
Radio magnetic indicator (RMI)
A radio magnetic indicator (RMI) is an alternate ADF display providing more information than a standard ADF. While the ADF shows relative angle of the transmitter with respect to the aircraft, an RMI display incorporates a compass card, actuated by the aircraft's compass system, and permits the operator to read the magnetic bearing to or from the transmitting station, without resorting to arithmetic.
Most RMI's incorporate two direction needles. Often one needle (the thicker, double-barred needle) is connected to an ADF and the other (generally thin or single-barred) is connected to a VOR. Some models allow the operator to select which needle is connected to each navigation radio. There is great variation between models, and the operator must take care that their selection displays information from the appropriate ADF and VOR.
This instrument display can replace a magnetic compass display in the instrument panel, but not necessarily the gyroscopic Heading Indicator. The Heading Indicator can be combined with information from navigation radios (primarily VOR/ILS) in a similar way, to create the Horizontal Situation Indicator. The HSI, along with the VOR system, has largely replaced use of the RMI, however the HSI's much higher cost keeps the older combination of an RMI and an Omni Bearing Indicator attractive to cost-conscious pilots.
References
Avionics
American inventions
Radio navigation
Italian inventions
Aircraft instruments
Air navigation
Navigational aids | Automatic direction finder | [
"Technology",
"Engineering"
] | 1,541 | [
"Avionics",
"Aircraft instruments",
"Measuring instruments"
] |
322,913 | https://en.wikipedia.org/wiki/Native%20state | In biochemistry, the native state of a protein or nucleic acid is its properly folded and/or assembled form, which is operative and functional. The native state of a biomolecule may possess all four levels of biomolecular structure, with the secondary through quaternary structure being formed from weak interactions along the covalently-bonded backbone. This is in contrast to the denatured state, in which these weak interactions are disrupted, leading to the loss of these forms of structure and retaining only the biomolecule's primary structure.
Biochemistry
Proteins
While all protein molecules begin as simple unbranched chains of amino acids, once completed they assume highly specific three-dimensional shapes. That ultimate shape, known as tertiary structure, is the folded shape that possesses a minimum of free energy. It is a protein's tertiary, folded structure that makes it capable of performing its biological function. In fact, shape changes in proteins are the primary cause of several neurodegenerative diseases, including those caused by prions and amyloid (i.e. mad cow disease, kuru, Creutzfeldt–Jakob disease).
Many enzymes and other non-structural proteins have more than one native state, and they operate or undergo regulation by transitioning between these states. However, "native state" is used almost exclusively in the singular, typically to distinguish properly folded proteins from denatured or unfolded ones. In other contexts, the folded shape of a protein is most often referred to as its native "conformation" or "structure."
Folded and unfolded proteins are often easily distinguished by virtue of their water solubilities, as many proteins become insoluble on denaturation. Proteins in the native state will have defined secondary structure, which can be detected spectroscopically, by circular dichroism and by nuclear magnetic resonance (NMR).
The native state of a protein can be distinguished from a molten globule, by among other things, distances measured by NMR. Amino acids widely separated in a protein's sequence may touch or lie very close to one another within a stably folded protein. In a molten globule, on the other hand, their time-averaged distances are liable to be greater.
Learning how native state proteins can be manufactured is important, as attempts to create proteins from scratch have resulted in molten globules and not true native state products. Therefore, an understanding of the native state is crucial in protein engineering.
Nucleic acids
Nucleic acids attain their native state through base pairing and, to a lesser extent, other interactions such as coaxial stacking. Biological DNA usually exists as long linear double helices bound to proteins in chromatin, and biological RNA such as tRNA often form complex native configurations approaching the complexity of folded proteins. Additionally, artificial nucleic acid structures used in DNA nanotechnology are designed to have specific native configurations in which multiple nucleic acid strands are assembled into a single complex.
In some cases native state of biological DNA performs their functions without being controlled by any other regulatory units.
References
Protein structure | Native state | [
"Chemistry"
] | 634 | [
"Protein structure",
"Structural biology"
] |
322,915 | https://en.wikipedia.org/wiki/Italian%20Renaissance | The Italian Renaissance ( ) was a period in Italian history between the 14th and 16th centuries. The period is known for the initial development of the broader Renaissance culture that spread across Western Europe and marked the transition from the Middle Ages to modernity. Proponents of a "long Renaissance" argue that it started around the year 1300 and lasted until about 1600. In some fields, a Proto-Renaissance, beginning around 1250, is typically accepted. The French word renaissance (corresponding to rinascimento in Italian) means "rebirth", and defines the period as one of cultural revival and renewed interest in classical antiquity after the centuries during what Renaissance humanists labelled as the "Dark Ages". The Italian Renaissance historian Giorgio Vasari used the term rinascita ("rebirth") in his Lives of the Most Excellent Painters, Sculptors, and Architects in 1550, but the concept became widespread only in the 19th century, after the work of scholars such as Jules Michelet and Jacob Burckhardt.
The Renaissance began in Tuscany in Central Italy and centred in the city of Florence. The Florentine Republic, one of the several city-states of the peninsula, rose to economic and political prominence by providing credit for European monarchs and by laying down the groundwork for developments in capitalism and in banking. Renaissance culture later spread to Venice, the heart of a Mediterranean empire and in control of the trade routes with the east since its participation in the Crusades and following the journeys of Marco Polo between 1271 and 1295. Thus Italy renewed contact with the remains of ancient Greek culture, which provided humanist scholars with new texts. Finally the Renaissance had a significant effect on the Papal States and on Rome, largely rebuilt by humanist and Renaissance popes, such as Julius II and Leo X, who frequently became involved in Italian politics, in arbitrating disputes between competing colonial powers and in opposing the Protestant Reformation, which started .
The Italian Renaissance has a reputation for its achievements in painting, architecture, sculpture, literature, music, philosophy, science, technology, and exploration. Italy became the recognized European leader in all these areas by the late 15th century, during the era of the Peace of Lodi (1454–1494) agreed between Italian states. The Italian Renaissance peaked in the mid-16th century as domestic disputes and foreign invasions plunged the region into the turmoil of the Italian Wars (1494–1559). However, the ideas and ideals of the Italian Renaissance spread into the rest of Europe, setting off the Northern Renaissance from the late 15th century. Italian explorers from the maritime republics served under the auspices of European monarchs, ushering in the Age of Discovery. The most famous voyage was that of Christopher Columbus (who sailed for Spain) and laid the foundation for European dominance of the Americas. Other explorers include Giovanni da Verrazzano (for France), Amerigo Vespucci (for Spain), and John Cabot (for England). Italian scientists such as Falloppio, Tartaglia, Galileo and Torricelli played key roles in the Scientific Revolution, and foreigners such as Copernicus and Vesalius worked in Italian universities. Historiographers have proposed various events and dates of the 17th century, such as the conclusion of the European wars of religion in 1648, as marking the end of the Renaissance.
Accounts of proto-Renaissance literature usually begin with the three great Italian writers of the 14th century: Dante Alighieri (Divine Comedy), Petrarch (Canzoniere), and Boccaccio (Decameron). Famous vernacular poets of the Renaissance include the epic authors Luigi Pulci (Morgante), Matteo Maria Boiardo (Orlando Innamorato), Ludovico Ariosto (Orlando Furioso), and Torquato Tasso (Jerusalem Delivered). 15th-century writers such as the poet Poliziano and the Platonist philosopher Marsilio Ficino made extensive translations from both Latin and Greek. In the early 16th century, Baldassare Castiglione laid out his vision of the ideal gentleman and lady in The Book of the Courtier, while Niccolò Machiavelli rejected the ideal with an eye on la verità effettuale della cosa ('the effectual truth of things') in The Prince, composed, in humanistic style, chiefly of parallel ancient and modern examples of virtù. Historians of the period include Machiavelli himself, his friend and critic Francesco Guicciardini and Giovanni Botero (The Reason of State). The Aldine Press, founded in 1494 by the printer Aldo Manuzio, active in Venice, developed Italic type and pocket editions that one could carry in one's pocket; it became the first to publish printed editions of books in Ancient Greek. Venice also became the birthplace of the commedia dell'arte.
Italian Renaissance art exercised a dominant influence on subsequent European painting and sculpture for centuries afterwards, with artists such as Leonardo da Vinci, Michelangelo, Raphael, Donatello, Giotto, Masaccio, Fra Angelico, Piero della Francesca, Domenico Ghirlandaio, Perugino, Botticelli, and Titian. Italian Renaissance architecture had a similar Europe-wide impact, as practised by Brunelleschi, Leon Battista Alberti, Andrea Palladio, and Bramante. Their works include the Florence Cathedral, St. Peter's Basilica in Rome, and the Tempio Malatestiano in Rimini, as well as several private residences. The musical era of the Italian Renaissance featured composers such as Giovanni Pierluigi da Palestrina, the Roman School and later the Venetian School, and the birth of opera through figures like Claudio Monteverdi in Florence. In philosophy, thinkers such as Galileo, Machiavelli, Giordano Bruno and Pico della Mirandola emphasized naturalism and humanism, thus rejecting dogma and scholasticism.
Origins and background
Northern and Central Italy in the Late Middle Ages
By the Late Middle Ages (), Latium, the former heartland of the Roman Empire, and southern Italy were generally poorer than the North. Rome was a city of ancient ruins, and the Papal States were loosely administered, and vulnerable to external interference, particularly by France, and later Spain. The Papacy was affronted when the Avignon Papacy was created in southern France as a consequence of pressure from King Philip the Fair of France. In the south, Sicily had for some time been under foreign domination, by the Arabs and then the Normans. Sicily had prospered for 150 years during the Emirate of Sicily and later for two centuries during the Norman Kingdom and the Hohenstaufen Kingdom, but had declined by the Late Middle Ages.
In contrast, Northern and Central Italy had become far more prosperous, and it has been calculated that the region was among the richest in Europe. The Crusades had built trade links to the Levant, and the Fourth Crusade had done much to destroy the Byzantine Empire as a commercial rival to the Venetians and the Genoese. The main trade routes from the east passed through the Byzantine Empire or the Arab lands and onward to the ports of Genoa, Pisa, and Venice. Luxury goods bought in the Levant, such as spices, dyes, and silks were imported to Italy and then resold throughout Europe. Moreover, the inland city-states profited from the rich agricultural land of the Po Valley. From France, Germany, and the Low Countries, through the medium of the Champagne fairs, land and river trade routes brought goods such as wool, wheat, and precious metals into the region. The extensive trade that stretched from Egypt to the Baltic generated substantial surpluses that allowed significant investment in mining and agriculture. By the 14th century, the city of Venice had become an emporium for lands as far as Cyprus; it boasted a naval fleet of over 5000 ships thanks to its arsenal, a vast complex of shipyards that was the first European facility to mass-produce commercial and military vessels. Genoa also had become a maritime power. Thus, while northern Italy was not richer in resources than many other parts of Europe, the level of development, stimulated by trade, allowed it to prosper. In particular, Florence became one of the wealthiest of the cities of Northern Italy, mainly due to its woollen textile production, developed under the supervision of its dominant trade guild, the Arte della Lana. Wool was imported from Northern Europe (and in the 16th century from Spain) and together with dyes from the east were used to make high-quality textiles.
The Italian trade routes that covered the Mediterranean and beyond were also major conduits of culture and knowledge. The recovery of lost Greek classics brought to Italy by refugee Byzantine scholars who migrated during and following the Ottoman conquest of the Byzantine Empire in the 15th century were important in sparking the new linguistic studies of the Renaissance, in newly created academies in Florence and Venice. Humanist scholars searched monastic libraries for ancient manuscripts and recovered Tacitus and other Latin authors. The rediscovery of Vitruvius meant that the architectural principles of Antiquity could be observed once more, and Renaissance artists were encouraged, in the atmosphere of humanist optimism, to excel in the achievements of the Ancients, like Apelles, of whom they read.
Religious background
After the fall of the Western Roman Empire in the fifth century AD, the Catholic Church filled the subsequent vacuum. In the Middle Ages, the Church was considered to be conveying the will of God, and it regulated the standard of behaviour in life. A lack of literacy required most people to rely on the priest's explanation of the Bible and laws.
In the eleventh century, the Church persecuted many groups including pagans, Jews, and lepers in order to eliminate irregularities in society and strengthen its power. In response to the laity's challenge to Church authority, bishops played an important role, as they gradually lost control of secular authority, and to regain the power of discourse, they adopted extreme control methods, such as persecuting infidels.
The Church also collected wealth from believers in the Middle Ages, such as through the sale of indulgences. It also did not pay taxes, making the Church's wealth even more than some kings.
Thirteenth century
In the 13th century, much of Europe experienced strong economic growth. The trade routes of the Italian states linked with those of established Mediterranean ports and eventually the Hanseatic League of the Baltic and northern regions of Europe to create a network economy in Europe for the first time since the 4th century. The city-states of Italy expanded greatly during this period and grew in power to become de facto fully independent of the Holy Roman Empire; apart from the Kingdom of Naples, outside powers kept their armies out of Italy. During this period, the modern commercial infrastructure developed, with double-entry book-keeping, joint stock companies, an international banking system, a systematized foreign exchange market, insurance, and government debt. Florence became the centre of this financial industry and the gold florin became the main currency of international trade.
The new mercantile governing class, who gained their position through financial skill, adapted to their purposes the feudal aristocratic model that had dominated Europe in the Middle Ages. A feature of the High Middle Ages in Northern Italy was the rise of the urban communes which had broken from the control by bishops and local counts. In much of the region, the landed nobility was poorer than the urban patriarchs in the High Medieval money economy whose inflationary rise left land-holding aristocrats impoverished. The increase in trade during the early Renaissance enhanced these characteristics. The decline of feudalism and the rise of cities influenced each other; for example, the demand for luxury goods led to an increase in trade, which led to greater numbers of tradesmen becoming wealthy, who, in turn, demanded more luxury goods. This atmosphere of assumed luxury of the time created a need for the creation of visual symbols of wealth, an important way to show a family's affluence and taste.
This change also gave the merchants almost complete control of the governments of the Italian city-states, again enhancing trade. One of the most important effects of this political control was security. Those who grew extremely wealthy in a feudal state ran the constant risk of running afoul of the monarchy and having their lands confiscated, as famously occurred to Jacques Cœur in France. The northern states also kept many medieval laws that severely hampered commerce, such as those against usury, and prohibitions on trading with non-Christians. In the city-states of Italy, these laws were repealed or rewritten.
Fourteenth-century collapse
The 14th century saw a series of catastrophes that caused the European economy to go into recession. The Medieval Warm Period was ending as the transition to the Little Ice Age began. This climate change saw agricultural output decline significantly, leading to repeated famines, exacerbated by the rapid population growth of the earlier era. The Hundred Years' War between England and France disrupted trade throughout northwest Europe, most notably when, in 1345, King Edward III of England repudiated his debts, contributing to the collapse of the two largest Florentine banks, those of the Bardi and Peruzzi. In the east, war was also disrupting trade routes, as the Ottoman Empire began to expand throughout the region. Most devastating, though, was the Black Death that decimated the populations of the densely populated cities of Northern Italy and returned at intervals thereafter. Florence, for instance, which had a pre-plague population of 45,000 decreased over the next 47 years by 25–50%. Widespread disorder followed, including a revolt of Florentine textile workers, the ciompi, in 1378.
It was during this period of instability that authors such as Dante and Petrarch lived, and the first stirrings of Renaissance art were to be seen, notably in the realism of Giotto. Paradoxically, some of these disasters would help establish the Renaissance. The Black Death wiped out a third of Europe's population. The resulting labour shortage increased wages and the reduced population was therefore much wealthier, better fed, and, significantly, had more surplus money to spend on luxury goods. As incidences of the plague began to decline in the early 15th century, Europe's devastated population once again began to grow. The new demand for products and services also helped create a growing class of bankers, merchants, and skilled artisans. The horrors of the Black Death and the seeming inability of the Church to provide relief would contribute to a decline of church influence. Additionally, the collapse of the Bardi and Peruzzi banks would open the way for the Medici to rise to prominence in Florence. Roberto Sabatino Lopez argues that the economic collapse was a crucial cause of the Renaissance. According to this view, in a more prosperous era, businessmen would have quickly reinvested their earnings in order to make more money in a climate favourable to investment. However, in the leaner years of the 14th century, the wealthy found few promising investment opportunities for their earnings and instead chose to spend more on culture and art.
Unlike Roman texts, which had been preserved and studied in Western Europe since late antiquity, the study of ancient Greek texts was very limited in medieval Italy. Ancient Greek works on science, maths and philosophy had been studied since the High Middle Ages in Western Europe and in the Islamic Golden Age (normally in translation), but Greek literary, oratorical and historical works (such as Homer, the Greek dramatists, Demosthenes and Thucydides) were not studied in either the Latin or medieval Muslim worlds; in the Middle Ages these sorts of texts were only studied by Byzantine scholars. Some argue that the Timurid Renaissance in Samarkand was linked with the Ottoman Empire, whose conquests led to the migration of Greek scholars to Italy. One of the greatest achievements of Italian Renaissance scholars was to bring this entire class of Greek cultural works back into Western Europe for the first time since late antiquity.
Another popular explanation for the Italian Renaissance is the thesis, first advanced by historian Hans Baron, that states that the primary impetus of the early Renaissance was the long-running series of wars between Florence and Milan. By the late 14th century, Milan had become a centralized monarchy under the control of the Visconti family. Giangaleazzo Visconti, who ruled the city from 1378 to 1402, was renowned both for his cruelty and for his abilities, and set about building an empire in Northern Italy. He launched a long series of wars, with Milan steadily conquering neighbouring states and defeating the various coalitions led by Florence that sought in vain to halt the advance. This culminated in the 1402 siege of Florence when it looked as though the city was doomed to fall, before Giangaleazzo suddenly died and his empire collapsed.
Baron's thesis suggests that during these long wars, the leading figures of Florence rallied the people by presenting the war as one between the free republic and a despotic monarchy, between the ideals of the Greek and Roman Republics and those of the Roman Empire and Medieval kingdoms. For Baron, the most important figure in crafting this ideology was Leonardo Bruni. This time of crisis in Florence was the period when the most influential figures of the early Renaissance were coming of age, such as Ghiberti, Donatello, Masolino, and Brunelleschi. Inculcated with this republican ideology they later went on to advocate republican ideas that were to have an enormous impact on the Renaissance.
Development
International relationships
Northern Italy and upper Central Italy were divided into a number of warring city-states, the most powerful being Milan, Florence, Pisa, Siena, Genoa, Ferrara, Mantua, Verona and Venice. High Medieval Northern Italy was further divided by the long-running battle for supremacy between the forces of the Papacy and of the Holy Roman Empire: each city aligned itself with one faction or the other, yet was divided internally between the two warring parties, Guelfs and Ghibellines. Warfare between the states was common, and invasion from outside Italy was confined to intermittent sorties of Holy Roman Emperors. Renaissance politics developed from this background. Since the 13th century, as armies became primarily composed of mercenaries, prosperous city-states could field considerable forces, despite their low populations. In the course of the 15th century, the most powerful city-states annexed their smaller neighbours. Florence took Pisa in 1406, Venice captured Padua and Verona, while the Duchy of Milan annexed a number of nearby areas including Pavia and Parma.
The first part of the Renaissance saw almost constant warfare on land and sea as the city-states vied for preeminence. On land, these wars were primarily fought by armies of mercenaries known as condottieri, bands of soldiers drawn from around Europe, but especially Germany and Switzerland, led largely by Italian captains. The mercenaries were not willing to risk their lives unduly, and war became one largely of sieges and manoeuvring, occasioning few pitched battles. It was also in the interest of mercenaries on both sides to prolong any conflict, to continue their employment. Mercenaries were also a constant threat to their employers; if not paid, they often turned on their patron. If it became obvious that a state was entirely dependent on mercenaries, the temptation was great for the mercenaries to take over the running of it themselves—this occurred on a number of occasions. Neutrality was maintained with France, which found itself surrounded by enemies when Spain disputed Charles VIII's claim to the Kingdom of Naples. Peace with France ended when Charles VIII invaded Italy to take Naples.
At sea, Italian city-states sent many fleets out to do battle. The main contenders were Pisa, Genoa, and Venice, but after a long conflict, the Genoese succeeded in reducing Pisa. Venice proved to be a more powerful adversary, and with the decline of Genoese power during the 15th century Venice became pre-eminent on the seas. In response to threats from the landward side, from the early 15th century Venice developed an increased interest in controlling the terrafirma as the Venetian Renaissance opened.
On land, decades of fighting saw Florence, Milan, and Venice emerge as the dominant players, and these three powers finally set aside their differences and agreed to the Peace of Lodi in 1454, which saw relative calm brought to the region for the first time in centuries. This peace would hold for the next forty years, and Venice's unquestioned hegemony over the sea also led to unprecedented peace for much of the rest of the 15th century. At the beginning of the 15th century, adventurers and traders such as Niccolò Da Conti (1395–1469) travelled as far as Southeast Asia and back, bringing fresh knowledge on the state of the world, presaging further European voyages of exploration in the years to come.
Florence under the Medici
Until the late 14th century, prior to the Medici, Florence's leading family were the House of Albizzi. In 1293 the Ordinances of Justice were enacted which effectively became the constitution of the Republic of Florence throughout the Italian Renaissance. The city's numerous luxurious palazzi were becoming surrounded by townhouses, built by the ever prospering merchant class. In 1298, one of the leading banking families of Europe, the Bonsignoris, were bankrupted and so the city of Siena lost her status as the banking centre of Europe to Florence.
The main challengers of the Albizzi family were the Medicis, first under Giovanni de' Medici, and later under his son Cosimo de' Medici. The Medici controlled the Medici bank—then Europe's largest bank—and an array of other enterprises in Florence and elsewhere. In 1433, the Albizzi managed to have Cosimo exiled. The next year, however, saw a pro-Medici Signoria elected and Cosimo returned. The Medici became the town's leading family, a position they would hold for the next three centuries. Florence organized the trade routes for commodities between England and the Netherlands, France, and Italy. By the middle of the century, the city had become the banking capital of Europe and thereby obtained vast riches. In 1439, Byzantine Emperor John VIII Palaiologos attended a council in Florence in an attempt to unify the Eastern and Western Churches. This brought books and, especially after the fall of the Byzantine Empire in 1453, an influx of scholars to the city. Ancient Greece began to be studied with renewed interest, especially the Neoplatonic school of thought, which was the subject of an academy established by the Medici.
Florence remained a republic until 1532 (see Duchy of Florence), traditionally marking the end of the High Renaissance in Florence, but the instruments of republican government were firmly under the control of the Medici and their allies, save during the intervals after 1494 and 1527. Cosimo and Lorenzo de' Medici rarely held official posts but were the unquestioned leaders. Cosimo was highly popular among the citizenry, mainly for bringing an era of stability and prosperity to the town. One of his most important accomplishments was negotiating the Peace of Lodi with Francesco Sforza ending the decades of war with Milan and bringing stability to much of Northern Italy. Cosimo was also an important patron of the arts, directly and indirectly, by the influential example he set.
Cosimo was succeeded by his sickly son Piero de' Medici, who died after five years in charge of the city. In 1469 the reins of power passed to Cosimo's 21-year-old grandson Lorenzo, who would become known as "Lorenzo the Magnificent." Lorenzo was the first of the family to be educated from an early age in the humanist tradition and is best known as one of the Renaissance's most important patrons of the arts. Lorenzo reformed Florence's ruling council from 100 members to 70, formalizing the Medici rule. The republican institutions continued, but they lost all power. Lorenzo was less successful than his illustrious forebears in business, and the Medici commercial empire was slowly eroded. Lorenzo continued the alliance with Milan, but relations with the papacy soured, and in 1478, Papal agents allied with the Pazzi family in an attempt to assassinate Lorenzo. Although the Pazzi conspiracy failed, Lorenzo's young brother, Giuliano, was killed at Easter Sunday mass in the city's cathedral. The failed assassination led to a war with the Papacy and was used as justification to further centralize power in Lorenzo's hands.
Spread
Renaissance ideals first spread from Florence to the neighbouring states of Tuscany such as Siena and Lucca. The Tuscan culture soon became the model for all the states of Northern Italy, and the Tuscan dialect came to predominate throughout the region, especially in literature. In 1447 Francesco Sforza came to power in Milan and rapidly transformed that still medieval city into a major centre of art and learning that drew Leone Battista Alberti. Venice, one of the wealthiest cities due to its control of the Adriatic Sea, also became a centre for Renaissance culture, especially Venetian Renaissance architecture. Smaller courts brought Renaissance patronage to lesser cities, which developed their characteristic arts: Ferrara, Mantua under the Gonzaga, and Urbino under Federico da Montefeltro. In Naples, the Renaissance was ushered in under the patronage of Alfonso I, who conquered Naples in 1443 and encouraged artists like Francesco Laurana and Antonello da Messina and writers like the poet Jacopo Sannazaro and the humanist scholar Angelo Poliziano.
In 1417 the Papacy returned to Rome, but that once-imperial city remained poor and largely in ruins through the first years of the Renaissance. The great transformation began under Pope Nicholas V, who became pontiff in 1447. He launched a dramatic rebuilding effort that would eventually see much of the city renewed. The humanist scholar Aeneas Silvius Piccolomini became Pope Pius II in 1458. As the papacy fell under the control of wealthy families, such as the Medici and the Borgias, the spirit of Renaissance art and philosophy came to dominate the Vatican. Pope Sixtus IV continued Nicholas' work, most famously ordering the construction of the Sistine Chapel. The popes also became increasingly secular rulers as the Papal States were forged into a centralized power by a series of "warrior popes".
The nature of the Renaissance also changed in the late 15th century. The Renaissance ideal was fully adopted by the ruling classes and the aristocracy. In the early Renaissance artists were seen as craftsmen with little prestige or recognition. By the later Renaissance, the top figures wielded great influence and could charge great fees. A flourishing trade in Renaissance art developed. While in the early Renaissance many of the leading artists were of lower- or middle-class origins, increasingly they became aristocrats.
Wider population
As a cultural movement, the Italian Renaissance affected only a small part of the population. Italy was the most urbanized region of Europe, but three-quarters of the people were still rural peasants. For this section of the population, life remained essentially unchanged from the Middle Ages. Classic feudalism had never been prominent in Northern Italy, and most peasants worked on private farms or as sharecroppers. Some scholars see a trend towards refeudalization in the later Renaissance as the urban elites turned themselves into landed aristocrats.
The situation differed in the cities. These were dominated by a commercial elite; as exclusive as the aristocracy of any Medieval kingdom. This group became the main patrons of and audience for Renaissance culture. Below them, there was a large class of artisans and guild members who lived comfortable lives and had significant power in the republican governments. This was in sharp contrast to the rest of Europe where artisans were firmly in the lower class. Literate and educated, this group participated in the Renaissance culture. The largest section of the urban population was the urban poor of semi-skilled workers and the unemployed. Like the peasants, the Renaissance had little effect on them. Historians debate how easy it was to move between these groups during the Italian Renaissance. Examples of individuals who rose from humble beginnings can be instanced, but Burke notes two major studies in this area that have found that the data do not clearly demonstrate an increase in social mobility. Most historians feel that early in the Renaissance social mobility was quite high, but that it faded over the course of the 15th century. Inequality in society was very high. An upper-class figure would control hundreds of times more income than a servant or labourer. Some historians see this unequal distribution of wealth as important to the Renaissance, as art patronage relies on the very wealthy.
The Renaissance was not a period of great social or economic change, only of cultural and ideological development. It only touched a small fraction of the population, and in modern times this has led many historians, such as any that follow historical materialism, to reduce the importance of the Renaissance in human history. These historians tend to think in terms of "Early Modern Europe" instead. Roger Osborne argues that "The Renaissance is a difficult concept for historians because the history of Europe quite suddenly turns into a history of Italian painting, sculpture and architecture."
The waning of the Renaissance in Italy
The end of the Italian Renaissance is as imprecisely marked as its starting point. For many, the rise to power in Florence of the austere monk Girolamo Savonarola in 1494–1498 marks the end of the city's flourishing; for others, the triumphant return of the Medici family to power in 1512 marks the beginning of the late phase in the Renaissance arts called Mannerism. Other accounts trace the end of the Italian Renaissance to the French invasions of the early 16th century and the subsequent conflict between France and Spanish rulers for control of Italian territory. Savonarola rode to power on a widespread backlash over the secularism and indulgence of the Renaissance. His brief rule saw many works of art destroyed in the "Bonfire of the Vanities" in the centre of Florence. With the Medici returned to power, now as Grand Dukes of Tuscany, the counter-movement in the church continued. In 1542 the Sacred Congregation of the Inquisition was formed and a few years later the Index Librorum Prohibitorum banned a wide array of Renaissance works of literature, which marks the end of the illuminated manuscript together with Giulio Clovio, who is considered the greatest illuminator of the Italian High Renaissance, and arguably the last very notable artist in the long tradition of the illuminated manuscript, before some modern revivals.
Under the suppression of the Catholic Church and the ravages of war, humanism became "akin to heresy".
Equally important was the end of stability with a series of foreign invasions of Italy known as the Italian Wars that would continue for several decades. These began with the 1494 invasion by France that wreaked widespread devastation on Northern Italy and ended the independence of many of the city-states. Most damaging was the 6 May 1527, Spanish and German troops' sacking Rome that for two decades all but ended the role of the Papacy as the largest patron of Renaissance art and architecture.
While the Italian Renaissance was fading, the Northern Renaissance adopted many of its ideals and transformed its styles. A number of Italy's greatest artists chose to emigrate. The most notable example was Leonardo da Vinci, who left for France in 1516, but teams of lesser artists invited to transform the Château de Fontainebleau created the School of Fontainebleau that infused the style of the Italian Renaissance in France. From Fontainebleau, the new styles, transformed by Mannerism, brought the Renaissance to the Low Countries and thence throughout Northern Europe.
This spread north was also representative of a larger trend. No longer was the Mediterranean Europe's most important trade route. In 1498, Vasco da Gama reached India, and from that date the primary route of goods from the Orient was through the Atlantic ports of Lisbon, Seville, Nantes, Bristol, and London.
Culture
Literature and poetry
The thirteenth-century Italian literary revolution helped set the stage for the Renaissance. Before the Renaissance, the Italian language was not the literary language in Italy. It was only in the 13th century that Italian authors began writing in their native language rather than Latin, French, or Provençal. The 1250s saw a major change in Italian poetry as the Dolce Stil Novo (Sweet New Style, which emphasized Platonic rather than courtly love) came into its own, pioneered by poets like Guittone d'Arezzo and Guido Guinizelli. Especially in poetry, major changes in Italian literature had been taking place decades before the Renaissance truly began.
With the printing of books initiated in Venice by Aldus Manutius, an increasing number of works began to be published in the Italian language in addition to the flood of Latin and Greek texts that constituted the mainstream of the Italian Renaissance. The source for these works expanded beyond works of theology and towards the pre-Christian eras of Imperial Rome and Ancient Greece. This is not to say that no religious works were published in this period: Dante Alighieri's The Divine Comedy reflects a distinctly medieval world view. Christianity remained a major influence for artists and authors, with the classics coming into their own as a second primary influence.
In the early Italian Renaissance, much of the focus was on translating and studying classic works from Latin and Greek. Renaissance authors were not content to rest on the laurels of ancient authors, however. Many authors attempted to integrate the methods and styles of the ancient Greeks into their own works. Among the most emulated Romans are Cicero, Horace, Sallust, and Virgil. Among the Greeks, Aristotle, Homer, and Plato were now being read in the original for the first time since the 4th century, though Greek compositions were few.
The literature and poetry of the Renaissance were largely influenced by the developing science and philosophy. The humanist Francesco Petrarch, a key figure in the renewed sense of scholarship, was also an accomplished poet, publishing several important works of poetry. He wrote poetry in Latin, notably the Punic War epic Africa, but is today remembered for his works in the Italian vernacular, especially the Canzoniere, a collection of love sonnets dedicated to his unrequited love Laura. He was the foremost writer of Petrarchan sonnets, and translations of his work into English by Thomas Wyatt established the sonnet form in that country, where it was employed by William Shakespeare and countless other poets.
Petrarch's disciple, Giovanni Boccaccio, became a major author in his own right. His major work was the Decameron, a collection of 100 stories told by ten storytellers who have fled to the outskirts of Florence to escape the black plague over ten nights. The Decameron in particular and Boccaccio's work, in general, were a major source of inspiration and plots for many English authors in the Renaissance, including Geoffrey Chaucer and William Shakespeare.
Aside from Christianity, classical antiquity, and scholarship, a fourth influence on Renaissance literature was politics. The political philosopher Niccolò Machiavelli's most famous works are Discourses on Livy, Florentine Histories and finally The Prince, which has become so well known in modern societies that the word Machiavellian has come to refer to the cunning and ruthless actions advocated by the book. Along with many other Renaissance works, The Prince remains a relevant and influential work of literature today.
Many Italian Renaissance humanists also praised and affirmed the beauty of the body in poetry and literature. In Baldassare Rasinus's panegyric for Francesco Sforza, Rasinus considered that beautiful people usually have virtue. In northern Italy, humanists had discussions about the connection between physical beauty and inner virtues. In Renaissance Italy, virtue and beauty were often linked together to praise men.
Philosophy
One role of Petrarch is as the founder of a new method of scholarship, Renaissance humanism.
Petrarch encouraged the study of the Latin classics and carried his copy of Homer about, at a loss to find someone to teach him to read Greek. An essential step in the classic humanist education being propounded by scholars like Pico della Mirandola was the hunting down of lost or forgotten manuscripts that were known only by reputation. These endeavours were greatly aided by the wealth of Italian patricians, merchant-princes and despots, who would spend substantial sums building libraries. Discovering the past had become fashionable and it was a passionate affair pervading the upper reaches of society. I go, said Cyriac of Ancona, I go to awake the dead. As the Greek works were acquired, manuscripts found, libraries and museums formed, the age of the printing press was dawning. The works of Antiquity were translated from Greek and Latin into the contemporary modern languages throughout Europe, finding a receptive middle-class audience, which might be, like Shakespeare, "with little Latin and less Greek".
While concern for philosophy, art, and literature all increased greatly in the Renaissance, the period is usually seen as one of scientific backwardness. The reverence for classical sources further enshrined the Aristotelian and Ptolemaic views of the universe. Humanism stressed that nature came to be viewed as an animate spiritual creation that was not governed by laws or mathematics. At the same time, philosophy lost much of its rigour as the rules of logic and deduction were seen as secondary to intuition and emotion.
Science and technology
During the Renaissance, great advances occurred in geography, astronomy, chemistry, physics, mathematics, manufacturing, anatomy and engineering. The collection of ancient scientific texts began in earnest at the start of the 15th century and continued up to the Fall of Constantinople in 1453, and the invention of printing democratized learning and allowed a faster propagation of new ideas. Although humanists often favoured human-centred subjects like politics and history over study of natural philosophy or applied mathematics, many others went beyond these interests and had a positive influence on mathematics and science by rediscovering lost or obscure texts and by emphasizing the study of original languages and the correct reading of texts.
Italian universities such as Padua, Bologna and Pisa were scientific centres of renown and with many northern European students, the science of the Renaissance spread to Northern Europe and flourished there as well. Figures such as Copernicus, Francis Bacon, Descartes, and Galileo made contributions to scientific thought and experimentation, paving the way for the scientific revolution that later flourished in Northern Europe. Bodies were also stolen from gallows and examined by many like Andreas Vesalius, a professor of anatomy. This allowed him to create more accurate skeleton models by making more than 200 corrections to the works of Galen who dissected animals.
Mathematics
Major developments in mathematics include the spread of algebra throughout Europe, especially Italy. Luca Pacioli published a book on mathematics at the end of the fifteenth century, in which he first published positive and negative signs. Basic mathematical symbols were introduced by Simon Stevin in the 16th and early 17th centuries. Symbolic algebra was established by the French mathematician François Viete in the 16th century. He published "Introduction to Analytical Methods" in 1591, systematically sorting out algebra, and for the first time consciously using letters to represent unknown and known numbers. In his other book "On the Recognition and Correction of Equations", Viete improved the solution of the third-degree and fourth-degree equations, and also established the relationship between the roots and coefficients of quadratic and cubic equations, which is called "Viete's formulas" now. Trigonometry also achieved greater development during the Renaissance. The German mathematician Regiomontanus's "On Triangles of All Kinds" was Europe's first trigonometric work independent of astronomy. The book systematically elaborated plane triangles and spherical triangles, as well as a very precise table of trigonometric functions.
Painting and sculpture
In painting, the Late Medieval painter Giotto di Bondone, or Giotto, helped shape the artistic concepts that later defined much of the Renaissance art. The key ideas that he explored – classicism, the illusion of three-dimensional space and a realistic emotional context – inspired other artists such as Masaccio, Michelangelo and Leonardo da Vinci. He was not the only Medieval artist to develop these ideas, however; the artists Pietro Cavallini and Cimabue both influenced Giotto's use of statuesque figures and expressive storylines.
The frescos of Florentine artist Masaccio are generally considered to be among the earliest examples of Italian Renaissance art. Masaccio incorporated the ideas of Giotto, Donatello and Brunelleschi into his paintings, creating mathematically precise scenes that give the impression of three-dimensional space. The Holy Trinity fresco in the Florentine church of Santa Maria Novella, for example, looks as if it is receding at a dramatic angle into the dark background, while single-source lighting and foreshortening appear to push the figure of Christ into the viewer's space.
While mathematical precision and classical idealism fascinated painters in Rome and Florence, many Northern artists in the regions of Venice, Milan and Parma preferred highly illusionistic scenes of the natural world. The period also saw the first secular (non-religious) themes. There has been much debate as to the degree of secularism in the Renaissance, which had been emphasized by early 20th-century writers like Jacob Burckhardt based on, among other things, the presence of a relatively small number of mythological paintings. Those of Botticelli, notably The Birth of Venus and Primavera, are now among the best known, although he was deeply religious (becoming a follower of Savonarola) and the great majority of his output was of traditional religious paintings or portraits.
In sculpture, the Florentine artist Donato di Niccolò di Betto Bardi, or Donatello, was among the earliest sculptors to translate classical references into marble and bronze. His second sculpture of David was the first free-standing bronze nude created in Europe since the Roman Empire.
The period known as the High Renaissance of painting was the culmination of the varied means of expression and various advances in painting technique, such as linear perspective, the realistic depiction of both physical and psychological features, and the manipulation of light and darkness, including tone contrast, sfumato (softening the transition between colours) and chiaroscuro (contrast between light and dark), in a single unifying style which expressed total compositional order, balance and harmony. In particular, the individual parts of the painting had a complex but balanced and well-knit relationship to the whole. The most famous painters from this phase are Leonardo da Vinci, Raphael, and Michelangelo and their images, including Leonardo's The Last Supper and Mona Lisa, Raphael's The School of Athens and Michelangelo's Sistine Chapel Ceiling are the masterpieces of the period and among the most widely known works of art in the world.
High Renaissance painting evolved into Mannerism, especially in Florence. Mannerist artists, who consciously rebelled against the principles of High Renaissance, tend to represent elongated figures in illogical spaces. Modern scholarship has recognized the capacity of Mannerist art to convey strong (often religious) emotion where the High Renaissance failed to do so. Some of the main artists of this period are Pontormo, Bronzino, Rosso Fiorentino, Parmigianino and Raphael's pupil Giulio Romano.
Architecture
In Florence, the Renaissance style was introduced with a revolutionary but incomplete monument by Leone Battista Alberti. Some of the earliest buildings showing Renaissance characteristics are Filippo Brunelleschi's church of San Lorenzo and the Pazzi Chapel. The interior of Santo Spirito expresses a new sense of light, clarity and spaciousness, which is typical of the early Italian Renaissance. Its architecture reflects the philosophy of Renaissance humanism, the enlightenment and clarity of mind as opposed to the darkness and spirituality of the Middle Ages. The revival of classical antiquity can best be illustrated by the Palazzo Rucellai. Here the pilasters follow the superposition of classical orders, with Doric capitals on the ground floor, Ionic capitals on the piano nobile and Corinthian capitals on the uppermost floor. Soon, Renaissance architects favoured grand, large domes over tall and imposing spires, doing away with the Gothic style of the predating ages.
In Mantua, Alberti ushered in the new antique style, though his culminating work, Sant'Andrea, was not begun until 1472, after the architect's death.
The High Renaissance, as we call the style today, was introduced to Rome with Donato Bramante's Tempietto at San Pietro in Montorio (1502) and his original centrally planned St. Peter's Basilica (1506), which was the most notable architectural commission of the era, influenced by almost all notable Renaissance artists, including Michelangelo and Giacomo della Porta. The beginning of the late Renaissance in 1550 was marked by the development of a new column order by Andrea Palladio. Giant order columns that were two or more stories tall decorated the facades.
During the Italian Renaissance, mathematics was developed and spread widely. As a result, some Renaissance architects used mathematical knowledge like calculation in their drawings, such as Baldassarre Peruzzi.
Music
In Italy, during the 14th century, there was an explosion of musical activity that corresponded in scope and level of innovation to the activity in the other arts. Although musicologists typically group the music of the Trecento (music of the 14th century) with the late medieval period, it included features which align with the early Renaissance in important ways: an increasing emphasis on secular sources, styles and forms; a spreading of culture away from ecclesiastical institutions to the nobility, and even to the common people; and quick development of entirely new techniques. The principal forms were the Trecento madrigal, the caccia, and the ballata. Overall, the musical style of the period is sometimes labelled as the "Italian ars nova." From the early 15th century to the middle of the 16th century, the centre of innovation in religious music was in the Low Countries, and a flood of talented composers came to Italy from this region. Many of them sang in either the papal choir in Rome or the choirs at the numerous chapels of the aristocracy, in Rome, Venice, Florence, Milan, Ferrara and elsewhere; and they brought their polyphonic style with them, influencing many native Italian composers during their stay.
The predominant forms of sacred music during the period were the mass and the motet. By far the most famous composer of church music in 16th-century Italy was Palestrina, the most prominent member of the Roman School, whose style of smooth, emotionally cool polyphony was to become the defining sound of the late 16th century, at least for generations of 19th- and 20th-century musicologists. Other Italian composers of the late 16th century focused on composing the main secular form of the era, the madrigal; for almost a hundred years these secular songs for multiple singers were distributed all over Europe. Composers of madrigals included Jacques Arcadelt, at the beginning of the age, Cipriano de Rore, in the middle of the century, and Luca Marenzio, Philippe de Monte, Carlo Gesualdo, and Claudio Monteverdi at the end of the era. Italy was also a centre of innovation in instrumental music. By the early 16th century keyboard improvisation came to be greatly valued, and numerous composers of virtuoso keyboard music appeared. Many familiar instruments were invented and perfected in late Renaissance Italy, such as the violin, the earliest forms of which came into use in the 1550s.
By the late 16th century, Italy was the musical centre of Europe. Almost all of the innovations which were to define the transition to the Baroque period originated in northern Italy in the last few decades of the century. In Venice, the polychoral productions of the Venetian School, and associated instrumental music, moved north into Germany; in Florence, the Florentine Camerata developed monody, the important precursor to opera, which itself first appeared around 1600; and the avant-garde, manneristic style of the Ferrara school, which migrated to Naples and elsewhere through the music of Carlo Gesualdo, was to be the final statement of the polyphonic vocal music of the Renaissance.
Historiography
Any unified theory of a renaissance, or cultural overhaul, during the European early modern period, is overwhelmed by a massive volume of differing historiographical approaches. Historians like Jacob Burckhardt (1818–1897) have often romanticized the enlightened vision that Italian Renaissance writers have promulgated concerning their own narrative of denouncing the fruitlessness of the Middle Ages. By promoting the Renaissance as the definitive end to the "stagnant" Middle Ages, the Renaissance has acquired the powerful and enduring association with progress and prosperity for which Burckhardt's The Civilization of the Renaissance in Italy is most responsible. Modern scholars have objected to this prevailing narrative, citing the medieval period's own vibrancy and key continuities that link, rather than divide, the Middle Ages and the Renaissance.
Elizabeth Lehfeldt (2005) points to the Black Death as a turning point in Europe that set in motion several movements that were gaining massive traction in the years before, and has accounted for many subsequent events and trends in Western civilization, such as the Reformation. Rather than see this as a distinct cutoff between eras of history, the rejuvenated approach to studying the Renaissance aims to look at this as a catalyst that accelerated trends in art and science that were already well developed. For example, Danse Macabre, the artistic movement using death as the focal point, is often credited as a Renaissance trend, yet Lehfeldt argues that the emergence of Gothic art during medieval times was morphed into Danse Macabre after the Black Death swept over Europe.
Recent historians who take a more revisionist perspective, such as Charles Haskins (1860–1933), identify the hubris and nationalism of Italian politicians, thinkers, and writers as the cause of the distortion of the attitude towards the early modern period. In The Renaissance of the Twelfth Century (1927), Haskins asserts that it is human nature to draw stark divides in history to better understand the past. However, it is essential to understand history as continuous and constantly building off of the past. Haskins was one of the leading scholars in this school of thought, and it was his (along with several others) belief that the building blocks for the Italian Renaissance were all laid during the Middle Ages, calling on the rise of towns and bureaucratic states in the late 11th century as proof of the significance of this "pre-renaissance." The flow of history that he describes paints the Renaissance as a continuation of the Middle Ages that may not have been as positive of a change as popularly imagined. Many historians after Burckhardt have argued that the regression of the Latin language, economic recession, and social inequality during the Renaissance have been intentionally glossed over by previous historians in order to promote the mysticism of the era.
Burckhardt famously described the Middle Ages as a period that was "seen clad in strange hues", promoting the idea that this era was inherently dark, confusing, and unprogressive. The term middle ages was first referred to by humanists such as Petrarch and Biondo, during the late 15th century, describing it as a period connecting an important beginning and an important end, and as a placeholder for the history that exists between both sides of the period. This period was eventually referred to as the "dark" ages in the 19th century by English historians, which has further tainted the narrative of medieval times in favour of promoting a positive feeling of individualism and humanism that spurred from the Renaissance.
See also
Italian Renaissance garden
Italian Renaissance interior design
Renaissance illumination
Notes
References
Baker, Nicholas Scott. The Fruit of Liberty: Political Culture in the Florentine Renaissance, 1480–1550. Harvard University Press, 2013.
Baron, Hans. The Crisis of the Early Italian Renaissance: Civic Humanism and Republican Liberty in an Age of Classicism and Tyranny. Princeton: Princeton University Press, 1966.
Burckhardt, Jacob. The Civilization of the Renaissance in Italy. 1878 (online).
Burke, Peter. The Italian Renaissance: Culture and Society in Italy. Princeton: Princeton University Press, 1999.
Capra, Fritjof (2008). The Science of Leonardo. Inside the Mind of the Great Genius of the Renaissance. Doubleday, .
Ceriani Sebregondi, Giulia. On Architectural Practice and Arithmetic Abilities in Renaissance Italy. Architectural Histories, vol. 3, no. 1, 2015 (online).
Cronin, Vincent:
The Florentine Renaissance. 1967, .
The Flowering of the Renaissance. 1969, .
The Renaissance. 1992, .
Hagopian, Viola L. "Italy", in Stanley Sadie (ed.). The New Grove Dictionary of Music and Musicians. London: Macmillan Publishers Ltd., 1980.
Hay, Denys. The Italian Renaissance in Its Historical Background. Cambridge: Cambridge University Press, 1977.
Jensen, De Lamar. Renaissance Europe. 1992.
Jurdjevic, Mark. "Hedgehogs and Foxes: The Present and Future of Italian Renaissance Intellectual History", in Past & Present 195 (2007), pp. 241–268.
Lopez, Robert Sabatino. The Three Ages of the Italian Renaissance. Charlottesville: University Press of Virginia, 1970.
Petrocchi, Alessandra & Joshua Brown. Languages and Cross-Cultural Exchanges in Renaissance Italy. Turnhout: Brepols, 2023.
Pullan, Brian S. History of Early Renaissance Italy. London: Lane, 1973.
Raffini, Christine. Marsilio Ficino, Pietro Bembo, Baldassare Castiglione: Philosophical, Aesthetic, and Political Approaches in Renaissance Platonism. Renaissance and Baroque Studies and Texts 21, Peter Lang Publishing, 1998, .
Ruggiero, Guido. The Renaissance in Italy: A Social and Cultural History of the Rinascimento. Cambridge University Press, 2015 (online review).
External links
The High Renaissance in Florence – video
Victoria and Albert Museum: Renaissance House
The Prince by Niccolò Machiavelli. .
14th-century establishments in Italy
17th-century disestablishments in Italy
Renaissance
Renaissance
Italian Renaissance
Italian Renaissanceworks
Renaissance art
Renaissance architecture
Italy
Italy
Italian Renaissance | Italian Renaissance | [
"Engineering"
] | 11,095 | [
"Environmental design",
"Architectural history",
"Design history",
"Design",
"Architecture"
] |
322,931 | https://en.wikipedia.org/wiki/Random%20coil | In polymer chemistry, a random coil is a conformation of polymers where the monomer subunits are oriented randomly while still being bonded to adjacent units. It is not one specific shape, but a statistical distribution of shapes for all the chains in a population of macromolecules. The conformation's name is derived from the idea that, in the absence of specific, stabilizing interactions, a polymer backbone will "sample" all possible conformations randomly. Many unbranched, linear homopolymers — in solution, or above their melting temperatures — assume (approximate) random coils.
Random walk model: The Gaussian chain
There are an enormous number of different ways in which a chain can be curled around in a relatively compact shape, like an unraveling ball of twine with much open space, and comparatively few ways it can be more or less stretched out. So, if each conformation has an equal probability or statistical weight, chains are much more likely to be ball-like than they are to be extended — a purely entropic effect. In an ensemble of chains, most of them will, therefore, be loosely balled up. This is the kind of shape any one of them will have most of the time.
Consider a linear polymer to be a freely-jointed chain with N subunits, each of length , that occupy zero volume, so that no part of the chain excludes another from any location. One can regard the segments of each such chain in an ensemble as performing a random walk (or "random flight") in three dimensions, limited only by the constraint that each segment must be joined to its neighbors. This is the ideal chain mathematical model. It is clear that the maximum, fully extended length L of the chain is . If we assume that each possible chain conformation has an equal statistical weight, it can be shown that the probability P(r) of a polymer chain in the population to have distance r between the ends will obey a characteristic distribution described by the formula
where is the mean of .
The average (root mean square) end-to-end distance for the chain, , turns out to be times the square root of N — in other words, the average distance scales with N 0.5.
Real polymers
A real polymer is not freely-jointed. A -C-C- single bond has a fixed tetrahedral angle of 109.5 degrees. The value of L is well-defined for, say, a fully extended polyethylene or nylon, but it is less than N x l because of the zig-zag backbone. There is, however, free rotation about many chain bonds. The model above can be enhanced. A longer, "effective" unit length can be defined such that the chain can be regarded as freely-jointed, along with a smaller N, such that the constraint L = N x l is still obeyed. It, too, gives a Gaussian distribution. However, specific cases can also be precisely calculated. The average end-to-end distance for freely-rotating (not freely-jointed) polymethylene (polyethylene with each -C-C- considered as a subunit) is l times the square root of 2N, an increase by a factor of about 1.4. Unlike the zero volume assumed in a random walk calculation, all real polymers' segments occupy space because of the van der Waals radii of their atoms, including bulky substituent groups that interfere with bond rotations. This can also be taken into account in calculations. All such effects increase the mean end-to-end distance.
Because their polymerization is stochastically driven, chain lengths in any real population of synthetic polymers will obey a statistical distribution. In that case, we should take N to be an average value. Also, many polymers have random branching.
Even with corrections for local constraints, the random walk model ignores steric interference between chains, and between distal parts of the same chain. A chain often cannot move from a given conformation to a closely related one by a small displacement because one part of it would have to pass through another part, or through a neighbor. We may still hope that the ideal-chain, random-coil model will be at least a qualitative indication of the shapes and dimensions of real polymers in solution, and in the amorphous state, as long as there are only weak physicochemical interactions between the monomers. This model, and the Flory-Huggins Solution Theory, for which Paul Flory received the Nobel Prize in Chemistry in 1974, ostensibly apply only to ideal, dilute solutions. But there is reason to believe (e.g., neutron diffraction studies) that excluded volume effects may cancel out, so that, under certain conditions, chain dimensions in amorphous polymers have approximately the ideal, calculated size
When separate chains interact cooperatively, as in forming crystalline regions in solid thermoplastics, a different mathematical approach must be used.
Stiffer polymers such as helical polypeptides, Kevlar, and double-stranded DNA can be treated by the worm-like chain model.
Even copolymers with monomers of unequal length will distribute in random coils if the subunits lack any specific interactions. The parts of branched polymers may also assume random coils.
Below their melting temperatures, most thermoplastic polymers (polyethylene, nylon, etc.) have amorphous regions in which the chains approximate random coils, alternating with regions that are crystalline. The amorphous regions contribute elasticity and the crystalline regions contribute strength and rigidity.
More complex polymers such as proteins, with various interacting chemical groups attached to their backbones, self-assemble into well-defined structures. But segments of proteins, and polypeptides that lack secondary structure, are often assumed to exhibit a random-coil conformation in which the only fixed relationship is the joining of adjacent amino acid residues by a peptide bond. This is not actually the case, since the ensemble will be energy weighted due to interactions between amino acid side-chains, with lower-energy conformations being present more frequently. In addition, even arbitrary sequences of amino acids tend to exhibit some hydrogen bonding and secondary structure. For this reason, the term "statistical coil" is occasionally preferred. The conformational entropy of the random-coil stabilizes the unfolded protein state and represents main free energy contribution that opposes to protein folding.
Spectroscopy
A random-coil conformation can be detected using spectroscopic techniques. The arrangement of the planar amide bonds results in a distinctive signal in circular dichroism. The chemical shift of amino acids in a random-coil conformation is well known in nuclear magnetic resonance (NMR). Deviations from these signatures often indicates the presence of some secondary structure, rather than complete random coil. Furthermore, there are signals in multidimensional NMR experiments that indicate that stable, non-local amino acid interactions are absent for polypeptides in a random-coil conformation. Likewise, in the images produced by crystallography experiments, segments of random coil result simply in a reduction in "electron density" or contrast. A randomly coiled state for any polypeptide chain can be attained by denaturing the system. However, there is evidence that proteins are never truly random coils, even when denatured (Shortle & Ackerman).
See also
Protein folding
Native state
Molten globule
Probability theory
References
External links
polymer statistical mechanics
A topological problem in polymer physics: configurational and mechanical properties of a random walk enclosing a constant are
D. Shortle and M. Ackerman, Persistence of native-like topology in a denatured protein in 8 M urea, Science 293 (2001), pp. 487–489
Sample chapter "Conformations, Solutions, and Molecular Weight" from "Polymer Science & Technology" courtesy of Prentice Hall Professional publications
Polymer physics
Physical chemistry | Random coil | [
"Physics",
"Chemistry",
"Materials_science"
] | 1,642 | [
"Polymer physics",
"Applied and interdisciplinary physics",
"Polymer chemistry",
"nan",
"Physical chemistry"
] |
323,114 | https://en.wikipedia.org/wiki/Acesulfame%20potassium | Acesulfame potassium (, or ), also known as acesulfame K or Ace K, is a synthetic calorie-free sugar substitute (artificial sweetener) often marketed under the trade names Sunett and Sweet One. In the European Union, it is known under the E number (additive code) E950. It was discovered accidentally in 1967 by German chemist Karl Clauss at Hoechst AG (now Nutrinova). Acesulfame potassium is the potassium salt of 6-methyl-1,2,3-oxathiazine-4(3H)-one 2,2-dioxide. It is a white crystalline powder with molecular formula and a molecular weight of 201.24 g/mol.
Properties
Acesulfame K is 200 times sweeter than sucrose (common sugar), as sweet as aspartame, about two-thirds as sweet as saccharin, and one-third as sweet as sucralose. Like saccharin, it has a slightly bitter aftertaste, especially at high concentrations. Kraft Foods patented the use of sodium ferulate to mask acesulfame's aftertaste. Acesulfame K is often blended with other sweeteners (usually sucralose or aspartame). These blends are reputed to give a more sucrose-like taste whereby each sweetener masks the other's aftertaste, or exhibits a synergistic effect by which the blend is sweeter than its components. Acesulfame potassium has a smaller particle size than sucrose, allowing for its mixtures with other sweeteners to be more uniform.
Unlike aspartame, acesulfame K is stable under heat, even under moderately acidic or basic conditions, allowing it to be used as a food additive in baking, or in products that require a long shelf life. Although acesulfame potassium has a stable shelf life, it can eventually degrade to acetoacetamide, which is toxic in high doses. In carbonated drinks, it is almost always used in conjunction with another sweetener, such as aspartame or sucralose. It is also used as a sweetener in protein shakes and pharmaceutical products, especially chewable and liquid medications, where it can make the active ingredients more palatable. The acceptable daily intake of acesulfame potassium is listed as 15 mg/kg/day.
Acesulfame potassium is widely used in the human diet and excreted by the kidneys. It thus has been used by researchers as a marker to estimate to what degree swimming pools are contaminated by urine.
Other names for acesulfame K are potassium acesulfamate, potassium salt of 6-methyl-1,2,3-oxothiazin-4(3H)-one-2,3-dioxide, and potassium 6-methyl-1,2,3-oxathiazine-4(3H)-one-3-ate-2,2-dioxide.
Effect on body weight
Acesulfame potassium provides a sweet taste with no caloric value. There is no high-quality evidence that using acesulfame potassium as a sweetener affects body weight or body mass index (BMI).
Discovery
Acesulfame potassium was developed after the accidental discovery of a similar compound (5,6-dimethyl-1,2,3-oxathiazin-4(3H)-one 2,2-dioxide) in 1967 by Karl Clauss and Harald Jensen at Hoechst AG. After accidentally dipping his fingers into the chemicals with which he was working, Clauss licked them to pick up a piece of paper. Clauss is the inventor listed on a United States patent issued in 1975 to the assignee Hoechst Aktiengesellschaft for one process of manufacturing acesulfame potassium. Subsequent research showed a number of compounds with the same basic ring structure had different levels of sweetness. 6-methyl-1,2,3-oxathiazine-4(3H)-one 2,2-dioxide had particularly favourable taste characteristics and was relatively easy to synthesize, so it was singled out for further research, and received its generic name (acesulfame-K) from the World Health Organization in 1978. Acesulfame potassium first received approval for table top use in the United States in 1988.
Safety
The United States Food and Drug Administration (FDA) approved its general use as a safe food additive in 1988, and maintains that safety assessment, as of 2023. In a 2000 scientific review, the European Food Safety Authority determined that acesulfame K is safe in typical consumption amounts, and does not increase the risk of diseases.
References
External links
Joint FAO/WHO Expert Committee on Food Additives evaluation monograph of Acesulfame Potassium
FDA approval of Acesulfame Potassium
FDA approval of Acesulfame Potassium as a General Purpose Sweetener in Food
Elmhurst College, Illinois Virtual ChemBook Acesulfame K
Discovery News Sweeteners Linger in Groundwater
Excipients
Food additives
Oxathiazines
Potassium compounds
Sulfamates
Sugar substitutes
E-number additives | Acesulfame potassium | [
"Chemistry"
] | 1,055 | [
"Sulfamates",
"Functional groups"
] |
323,137 | https://en.wikipedia.org/wiki/Geometric%20phase | In classical and quantum mechanics, geometric phase is a phase difference acquired over the course of a cycle, when a system is subjected to cyclic adiabatic processes, which results from the geometrical properties of the parameter space of the Hamiltonian. The phenomenon was independently discovered by S. Pancharatnam (1956), in classical optics and by H. C. Longuet-Higgins (1958) in molecular physics; it was generalized by Michael Berry in (1984).
It is also known as the Pancharatnam–Berry phase, Pancharatnam phase, or Berry phase.
It can be seen in the conical intersection of potential energy surfaces and in the Aharonov–Bohm effect. Geometric phase around the conical intersection involving the ground electronic state of the C6H3F3+ molecular ion is discussed on pages 385–386 of the textbook by Bunker and Jensen. In the case of the Aharonov–Bohm effect, the adiabatic parameter is the magnetic field enclosed by two interference paths, and it is cyclic in the sense that these two paths form a loop. In the case of the conical intersection, the adiabatic parameters are the molecular coordinates. Apart from quantum mechanics, it arises in a variety of other wave systems, such as classical optics. As a rule of thumb, it can occur whenever there are at least two parameters characterizing a wave in the vicinity of some sort of singularity or hole in the topology; two parameters are required because either the set of nonsingular states will not be simply connected, or there will be nonzero holonomy.
Waves are characterized by amplitude and phase, and may vary as a function of those parameters. The geometric phase occurs when both parameters are changed simultaneously but very slowly (adiabatically), and eventually brought back to the initial configuration. In quantum mechanics, this could involve rotations but also translations of particles, which are apparently undone at the end. One might expect that the waves in the system return to the initial state, as characterized by the amplitudes and phases (and accounting for the passage of time). However, if the parameter excursions correspond to a loop instead of a self-retracing back-and-forth variation, then it is possible that the initial and final states differ in their phases. This phase difference is the geometric phase, and its occurrence typically indicates that the system's parameter dependence is singular (its state is undefined) for some combination of parameters.
To measure the geometric phase in a wave system, an interference experiment is required. The Foucault pendulum is an example from classical mechanics that is sometimes used to illustrate the geometric phase. This mechanics analogue of the geometric phase is known as the Hannay angle.
Berry phase in quantum mechanics
In a quantum system at the n-th eigenstate, an adiabatic evolution of the Hamiltonian sees the system remain in the n-th eigenstate of the Hamiltonian, while also obtaining a phase factor. The phase obtained has a contribution from the state's time evolution and another from the variation of the eigenstate with the changing Hamiltonian. The second term corresponds to the Berry phase, and for non-cyclical variations of the Hamiltonian it can be made to vanish by a different choice of the phase associated with the eigenstates of the Hamiltonian at each point in the evolution.
However, if the variation is cyclical, the Berry phase cannot be cancelled; it is invariant and becomes an observable property of the system. By reviewing the proof of the adiabatic theorem given by Max Born and Vladimir Fock, in Zeitschrift für Physik 51, 165 (1928), we could characterize the whole change of the adiabatic process into a phase term. Under the adiabatic approximation, the coefficient of the n-th eigenstate under adiabatic process is given by
where is the Berry's phase with respect to parameter t. Changing the variable t into generalized parameters, we could rewrite the Berry's phase into
where parametrizes the cyclic adiabatic process. Note that the normalization of implies that the integrand is imaginary, so that is real. It follows a closed path in the appropriate parameter space. Geometric phase along the closed path can also be calculated by integrating the Berry curvature over surface enclosed by .
Examples of geometric phases
Foucault pendulum
One of the easiest examples is the Foucault pendulum. An easy explanation in terms of geometric phases is given by Wilczek and Shapere:
To put it in different words, there are no inertial forces that could make the pendulum precess, so the precession (relative to the direction of motion of the path along which the pendulum is carried) is entirely due to the turning of this path. Thus the orientation of the pendulum undergoes parallel transport. For the original Foucault pendulum, the path is a circle of latitude, and by the Gauss–Bonnet theorem, the phase shift is given by the enclosed solid angle.
Derivation
In a near-inertial frame moving in tandem with the Earth, but not sharing the rotation of the Earth about its own axis, the suspension point of the pendulum traces out a circular path during one sidereal day.
At the latitude of Paris, 48 degrees 51 minutes north, a full precession cycle takes just under 32 hours, so after one sidereal day, when the Earth is back in the same orientation as one sidereal day before, the oscillation plane has turned by just over 270 degrees. If the plane of swing was north–south at the outset, it is east–west one sidereal day later.
This also implies that there has been exchange of momentum; the Earth and the pendulum bob have exchanged momentum. The Earth is so much more massive than the pendulum bob that the Earth's change of momentum is unnoticeable. Nonetheless, since the pendulum bob's plane of swing has shifted, the conservation laws imply that an exchange must have occurred.
Rather than tracking the change of momentum, the precession of the oscillation plane can efficiently be described as a case of parallel transport. For that, it can be demonstrated, by composing the infinitesimal rotations, that the precession rate is proportional to the projection of the angular velocity of Earth onto the normal direction to Earth, which implies that the trace of the plane of oscillation will undergo parallel transport. After 24 hours, the difference between initial and final orientations of the trace in the Earth frame is , which corresponds to the value given by the Gauss–Bonnet theorem. is also called the holonomy or geometric phase of the pendulum. When analyzing earthbound motions, the Earth frame is not an inertial frame, but rotates about the local vertical at an effective rate of radians per day. A simple method employing parallel transport within cones tangent to the Earth's surface can be used to describe the rotation angle of the swing plane of Foucault's pendulum.
From the perspective of an Earth-bound coordinate system (the measuring circle and spectator are Earth-bounded, also if terrain reaction to Coriolis force is not perceived by spectator when he moves), using a rectangular coordinate system with its axis pointing east and its axis pointing north, the precession of the pendulum is due to the Coriolis force (other fictitious forces as gravity and centrifugal force have not direct precession component, Euler's force is low because Earth's rotation speed is nearly constant). Consider a planar pendulum with constant natural frequency in the small angle approximation. There are two forces acting on the pendulum bob: the restoring force provided by gravity and the wire, and the Coriolis force (the centrifugal force, opposed to the gravitational restoring force, can be neglected). The Coriolis force at latitude is horizontal in the small angle approximation and is given by
where is the rotational frequency of Earth, is the component of the Coriolis force in the direction, and is the component of the Coriolis force in the direction.
The restoring force, in the small-angle approximation and neglecting centrifugal force, is given by
Using Newton's laws of motion, this leads to the system of equations
Switching to complex coordinates , the equations read
To first order in , this equation has the solution
If time is measured in days, then and the pendulum rotates by an angle of during one day.
Polarized light in an optical fiber
A second example is linearly polarized light entering a single-mode optical fiber. Suppose the fiber traces out some path in space, and the light exits the fiber in the same direction as it entered. Then compare the initial and final polarizations. In semiclassical approximation the fiber functions as a waveguide, and the momentum of the light is at all times tangent to the fiber. The polarization can be thought of as an orientation perpendicular to the momentum. As the fiber traces out its path, the momentum vector of the light traces out a path on the sphere in momentum space. The path is closed, since initial and final directions of the light coincide, and the polarization is a vector tangent to the sphere. Going to momentum space is equivalent to taking the Gauss map. There are no forces that could make the polarization turn, just the constraint to remain tangent to the sphere. Thus the polarization undergoes parallel transport, and the phase shift is given by the enclosed solid angle (times the spin, which in case of light is 1).
Stochastic pump effect
A stochastic pump is a classical stochastic system that responds with nonzero, on average, currents to periodic changes of parameters.
The stochastic pump effect can be interpreted in terms of a geometric phase in evolution of the moment generating function of stochastic currents.
Spin
The geometric phase can be evaluated exactly for a spin- particle in a magnetic field.
Geometric phase defined on attractors
While Berry's formulation was originally defined for linear Hamiltonian systems, it was soon realized by Ning and Haken that similar geometric phase can be defined for entirely different systems such as nonlinear dissipative systems that possess certain cyclic attractors. They showed that such cyclic attractors exist in a class of nonlinear dissipative systems with certain symmetries. There are several important aspects of this generalization of Berry's phase: 1) Instead of the parameter space for the original Berry phase, this Ning-Haken generalization is defined in phase space; 2) Instead of the adiabatic evolution in quantum mechanical system, the evolution of the system in phase space needs not to be adiabatic. There is no restriction on the time scale of the temporal evolution; 3) Instead of a Hermitian system or non-hermitian system with linear damping, systems can be generally nonlinear and non-hermitian.
Exposure in molecular adiabatic potential surface intersections
There are several ways to compute the geometric phase in molecules within the Born–Oppenheimer framework. One way is through the "non-adiabatic coupling matrix" defined by
where is the adiabatic electronic wave function, depending on the nuclear parameters . The nonadiabatic coupling can be used to define a loop integral, analogous to a Wilson loop (1974) in field theory, developed independently for molecular framework by M. Baer (1975, 1980, 2000). Given a closed loop , parameterized by where is a parameter, and . The D-matrix is given by
(here is a path-ordering symbol). It can be shown that once is large enough (i.e. a sufficient number of electronic states is considered), this matrix is diagonal, with the diagonal elements equal to where are the geometric phases associated with the loop for the -th adiabatic electronic state.
For time-reversal symmetrical electronic Hamiltonians the geometric phase reflects the number of conical intersections encircled by the loop. More accurately,
where is the number of conical intersections involving the adiabatic state encircled by the loop
An alternative to the D-matrix approach would be a direct calculation of the Pancharatnam phase. This is especially useful if one is interested only in the geometric phases of a single adiabatic state. In this approach, one takes a number of points along the loop with and then using only the j-th adiabatic states computes the Pancharatnam product of overlaps:
In the limit one has (see Ryb & Baer 2004 for explanation and some applications)
Geometric phase and quantization of cyclotron motion
An electron subjected to magnetic field moves on a circular (cyclotron) orbit. Classically, any cyclotron radius is acceptable. Quantum-mechanically, only discrete energy levels (Landau levels) are allowed, and since is related to electron's energy, this corresponds to quantized values of . The energy quantization condition obtained by solving Schrödinger's equation reads, for example, for free electrons (in vacuum) or for electrons in graphene, where . Although the derivation of these results is not difficult, there is an alternative way of deriving them, which offers in some respect better physical insight into the Landau level quantization. This alternative way is based on the semiclassical Bohr–Sommerfeld quantization condition
which includes the geometric phase picked up by the electron while it executes its (real-space) motion along the closed loop of the cyclotron orbit. For free electrons, while for electrons in graphene. It turns out that the geometric phase is directly linked to of free electrons and of electrons in graphene.
See also
Riemann curvature tensor – for the connection to mathematics
Berry connection and curvature
Chern class
Optical rotation
Winding number
Notes
For simplicity, we consider electrons confined to a plane, such as 2DEG and magnetic field perpendicular to the plane.
is the cyclotron frequency (for free electrons) and is the Fermi velocity (of electrons in graphene).
Footnotes
Sources
(See chapter 13 for a mathematical treatment)
Connections to other physical phenomena (such as the Jahn–Teller effect) are discussed here: Berry's geometric phase: a review
Paper by Prof. Galvez at Colgate University, describing Geometric Phase in Optics: Applications of Geometric Phase in Optics
Surya Ganguli, Fibre Bundles and Gauge Theories in Classical Physics: A Unified Description of Falling Cats, Magnetic Monopoles and Berry's Phase
Robert Batterman, Falling Cats, Parallel Parking, and Polarized Light
M. Baer, Electronic non-adiabatic transitions: Derivation of the general adiabatic-diabatic transformation matrix, Mol. Phys. 40, 1011 (1980);
M. Baer, Existence of diabetic potentials and the quantization of the nonadiabatic matrix, J. Phys. Chem. A 104, 3181–3184 (2000).
Further reading
Michael V. Berry, The geometric phase, Scientific American 259 (6) (1988), 26–34.
External links
Classical mechanics
Quantum phases | Geometric phase | [
"Physics",
"Chemistry",
"Materials_science"
] | 3,102 | [
"Quantum phases",
"Phases of matter",
"Classical mechanics",
"Quantum mechanics",
"Mechanics",
"Condensed matter physics",
"Matter"
] |
323,141 | https://en.wikipedia.org/wiki/Epigrams%20on%20Programming | "Epigrams on Programming" is an article by Alan Perlis published in 1982, for ACM's SIGPLAN journal. The epigrams are a series of short, programming-language-neutral, humorous statements about computers and programming, which are widely quoted.
It first appeared in SIGPLAN Notices 17(9), September 1982.
In epigram #54, Perlis coined the term "Turing tarpit", which he defined as a programming language where "everything is possible but nothing of interest is easy."
References
External links
List of quotes (Yale)
Full article text -- (including so-called "meta epigrams", numbers 122-130)
Magazine articles
Association for Computing Machinery | Epigrams on Programming | [
"Technology"
] | 152 | [
"Computing stubs",
"Computer science",
"Computer science stubs"
] |
323,158 | https://en.wikipedia.org/wiki/Public%20works | Public works are a broad category of infrastructure projects, financed and procured by a government body for recreational, employment, and health and safety uses in the greater community. They include public buildings (municipal buildings, schools, and hospitals), transport infrastructure (roads, railroads, bridges, pipelines, canals, ports, and airports), public spaces (public squares, parks, and beaches), public services (water supply and treatment, sewage treatment, electrical grid, and dams), environmental protection (drinking water protection, soil erosion reduction,
wildlife habitat preservation,
preservation and restoration of forests and wetlands) and other, usually long-term, physical assets and facilities. Though often interchangeable with public infrastructure and public capital, public works does not necessarily carry an economic component, thereby being a broader term. Construction may be undertaken either by directly employed labour or by a private operator.
Public works has been encouraged since antiquity. The Roman emperor Nero encouraged the construction of various infrastructure projects during widespread deflation.
Overview
Public works is a multi-dimensional concept in economics and politics, touching on multiple arenas including: recreation (parks, beaches, trails), aesthetics (trees, green space), economy (goods and people movement, energy), law (police and courts), and neighborhood (community centers, social services buildings). It represents any constructed object that augments a nation's physical infrastructure.
Municipal infrastructure, urban infrastructure, and rural development usually represent the same concept but imply either large cities or developing nations' concerns respectively. The terms public infrastructure or critical infrastructure are at times used interchangeably. However, critical infrastructure includes public works (dams, waste water systems, bridges, etc.) as well as facilities like hospitals, banks, and telecommunications systems and views them from a national security viewpoint and the impact on the community that the loss of such facilities would entail.
Furthermore, the term public works has recently been expanded to include digital public infrastructure projects. For example, in the United States, the first nationwide digital public works project is an effort to create an open source software platform for e-voting (created and managed by the Open Source Digital Voting Foundation).
Reflecting increased concern with sustainability, urban ecology and quality of life, efforts to move towards sustainable municipal infrastructure are common in developed nations, especially in the European Union and Canada (where the FCM InfraGuide provides an officially mandated best practice exchange to move municipalities in that direction).
Public works programmes
A public employment programme or public works programme is the provision of employment by the creation of predominantly public goods at a prescribed wage for those unable to find alternative employment. This functions as a form of social safety net. Public works programmes are activities which entail the payment of a wage (in cash or in kind) by the state, or by an Agent (or cash-for work/CFW). One particular form of public works, that of offering a short-term period of employment, has come to dominate practice, particularly in regions such as Sub-Saharan Africa. Applied in the short term, this is appropriate as a response to transient shocks and acute labour market crises.
Investing in public works projects in order to stimulate the general economy has been a popular policy measure since the economic crisis of the 1930s. Spearheaded by U.S. Secretary of Labor Frances Perkins, the first female Cabinet member in the United States, the New Deal resulted in the creation of programs such as the Civilian Conservation Corps, Public Works Administration, and the Works Progress Administration, among others, all of which created public goods through labor and infrastructure investments.
More recent examples are the 2008–2009 Chinese economic stimulus program, India's National Infrastructure Pipeline of 2020, the 2008 European Union stimulus plan, and the American Recovery and Reinvestment Act of 2009.
Utility of investment
While it is argued that capital investment in public works can be used to reduce unemployment, opponents of internal improvement programs argue that such projects should be undertaken by the private sector, not the public sector, because public works projects are often inefficient and costly to taxpayers. Further, some argue that public works, when used excessively by a government, are characteristic of socialism and other public or collectivist forms of government because of their 'tax and spend' policies to achieve long-term economic improvement. However, in the private sector, entrepreneurs bear their own losses and so private-sector firms are generally unwilling to undertake projects that could result in losses or would not develop a revenue stream. Governments will invest in public works because of the overall benefit to society when there is a lack of private sector benefit (a project that does generate revenue) or the risk is too great for a private company to accept on its own.
According to research conducted at the Aalborg University, 86% of public works projects end up with cost overruns. Some findings of the research were the following:
Technically difficult projects were not more likely to exceed the budget than less difficult projects.
Projects in which more people were directly and indirectly affected by the project turned out to be more susceptible to cost overruns.
Project managers generally did not learn from similar projects attempted in the past.
Generally, contracts awarded by public tenders include a provision for unexpected expenses (cost overruns), which typically amount to 10% of the value of the contract. This money is spent during the course of the project only if the construction managers judge that it is necessary, and the expenditure must typically be justified in writing.
See also
Contingencies fund
Department of transportation
E-procurement
Infrastructure
Internal improvements
Madaket Ditch, one of the first public works projects in America
Make-work job
Public good, an economic discussion
Utility district
Individual programs
Egyptian Public Works
New Deal
Opera Publica
Public Works Administration
External links
American Public Works Association - Professional society
References
Civil engineering
Fiscal policy
Infrastructure
Public economics
Public works ministries
Domestic policy | Public works | [
"Engineering"
] | 1,174 | [
"Construction",
"Civil engineering",
"Infrastructure"
] |
323,169 | https://en.wikipedia.org/wiki/Alois%20Brunner | Alois Brunner (8 April 1912 – December 2001 or 2010) was an Austrian officer who held the rank of (captain) during World War II. Brunner played a significant role in the implementation of the Holocaust through rounding up and deporting Jews in occupied Austria, Greece, France, and Slovakia. He was known as Final Solution architect Adolf Eichmann's right-hand man.
Brunner was responsible for sending over 100,000 European Jews from Austria, Greece, France and Slovakia to ghettos and concentration camps in eastern Europe. At the start of the war, he oversaw the deportation of 47,000 Austrian Jews to camps. In Greece, 43,000 Jews were deported in two months while he was stationed in Thessaloniki. He then became commander of the Drancy internment camp outside Paris from June 1943 to August 1944, during which nearly 24,000 men, women and children were sent to the gas chambers. His last assignment involved the destruction of the Jewish community of Slovakia.
After some narrow escapes from the Allies in the immediate aftermath of World War II, Brunner managed to elude capture and fled West Germany in 1954, first for Egypt, then Syria, where he remained until his death. He was the object of many manhunts, investigations, and assassination attempts over the years by different groups, including the Simon Wiesenthal Center, the Klarsfelds and Mossad. In 1954 he was convicted in absentia in France for crimes against humanity and sentenced to death, later commuted to life imprisonment in 2001 (France had abolished the death penalty in 1981). In Syria, he lost an eye and then the fingers of his left hand as a result of letter bombs sent to him in 1961 and 1980, reportedly by Israeli intelligence.
Starting in the 1990s and continuing for two decades, Brunner was one of the most-wanted Nazi war criminals. In November 2014, the Simon Wiesenthal Center reported that Brunner had died in Syria in 2010, and that he was buried somewhere in Damascus. However, recent information based on new evidence uncovered during a 2017 investigation point to December 2001 as the time of his death in Damascus, Syria. The German intelligence agency Verfassungsschutz claims he died in 2010. Brunner's exact date and place of death remain unknown.
Early life
Alois Brunner was born on 8 April 1912 in the town of Vas, Austria-Hungary (now Rohrbrunn, Burgenland, Austria), the son of Joseph Brunner and Ann Kruise. He joined the Nazi Party at the age of sixteen and the Sturmabteilung (SA) a year later. In 1933, Brunner moved to Germany where he joined the Nazi paramilitary group Austrian Legion. After the annexation of Austria in 1938 he volunteered with the SS and was assigned to the staff of the Central Office for Jewish Emigration in Vienna becoming its director in 1939. Following the German occupation of the Czech lands on 15 March 1939 he was sent to the Protectorate of Bohemia and Moravia to accelerate the emigration of Czech Jews. Brunner became known as Adolf Eichmann's right-hand man.
Second World War
After the war started, Brunner worked closely with Eichmann on the Nisko Plan, a failed attempt to set up a Jewish reservation in Poland, Brunner managed by October 1939 to organise the deportation of more than 1,500 Viennese Jews to Nisko, Poland. Over time Brunner supervised the deportation of 56,000 Austrian Jews. In October 1942, he was transferred to Berlin to implement his method there.
Brunner held the rank of SS-Hauptsturmführer (captain) when he organized deportations to Nazi concentration camps from Vichy France and Slovakia. He was commander of a train of Jews deported from Vienna to Riga in February 1942. En route, Brunner shot and killed Jewish financier Siegmund Bosel, who, although ill, had been hauled out of a Vienna hospital and placed on the train. According to historian Gertrude Schneider, who as a young girl was deported to Riga on the same train, but survived the Holocaust:
Before being named commander of Drancy internment camp near Paris in June 1943, Brunner deported 43,000 Jews from Vienna and 46,000 from Salonika. He was personally sent by Eichmann in 1944 to Slovakia to oversee the deportation of Jews. In the last days of the Third Reich, he managed to deport another 13,500 from Slovakia to Theresienstadt, Sachsenhausen, Bergen-Belsen, and Stutthof of whom a few survived; the remainder, including all the children, were sent to Auschwitz, where none are known to have survived. According to some accounts, Brunner was responsible for the deportation of 129,000 people to death camps.
While serving as the commandant at Drancy, Brunner was remembered for his exceptional brutality. He personally conducted interrogations of new prisoners, and survivors of the camp have claimed that his office was covered in bloodstains and bullet holes. He instituted torture even for slight offences. As he was personally responsible to Eichmann, he circumvented the typical chain of command that included Helmut Knochen, the Chief of the SS in Paris, and Heinz Rothke, the Jewish Affairs expert of the German police. He introduced a rigid system of categorization to control the inmates using information about their race and ethnicity derived from the interrogations. He deliberately misled prisoners about the living standards of their destinations at the extermination camps in the General Government, including Auschwitz-Birkenau. Brunner also led round-ups of Jews in the Italian Military Administration of France when the Germans assumed control in 1943 following the Armistice of Cassibile, ended all legal exemptions preventing Jews from being deported by Vichy France, and extended the deportations to Jews of French nationality. He continued deportations and arrests even as the Allies and the Free French Forces advanced towards Paris.
While the Wehrmacht was already retreating from France, Brunner had 1,327 Jewish children arrested and deported in Paris between July 20 and 24, 1944. Brunner left Paris on August 17 in 1944, a week before the liberation of Paris, on the last train from the Drancy transit camp with fifty-one deported people, including Georges André Kohn (Bullenhuser Damm), and other German military personnel. His intention was to use the deportees as potential hostages.
Brunner had 23,500 Jews of all ages deported from France to the concentration camps. From 30 September 1944 to 31 March 1945 he smashed the Jewish underground movement in Slovakia and headed the Sereď concentration camp, from where he had approximately 11,500 people deported to Auschwitz, Sachsenhausen, Bergen-Belsen, and Terezín for extermination.
Postwar flight and escape to Syria
In a 1985 interview with the West German magazine Bunte, Brunner described how he escaped capture by the Allies immediately after World War II. The identity of Brunner was apparently mixed up with that of another SS member with the same surname, Anton Brunner, who was executed for war crimes. Alois, like Josef Mengele, did not have the SS blood type tattoo, which prevented his identity from detection in an Allied prison camp. Anton Brunner, who had worked in Vienna deporting Jews, was confused after the war with Alois due to the shared surname, including by historians such as Gerald Reitlinger.
Claiming he had "received official documents under a false name from American authorities", Brunner claimed he had found work as a driver for the United States Army in the period after the war.
It has been alleged that Brunner found a working relationship after World War II with the Gehlen Organization.
He fled West Germany only in 1954, on a fake Red Cross passport, first to Rome, then Egypt, where he worked as a weapons dealer, and then to Syria, where he took the pseudonym of Dr Georg Fischer. In Syria, he was hired as a government adviser. The exact nature of his work is unknown. Syria had long refused entry to French investigators as well as to Nazi hunter Serge Klarsfeld, who spent nearly 15 years bringing the case to court in France. Simon Wiesenthal tried unsuccessfully to trace Brunner's whereabouts. However, East Germany, led by Erich Honecker, negotiated with Syria in the late 1980s to have Brunner extradited and arrested in Berlin. The government of Syria under Hafez al-Assad was close to extraditing Brunner to East Germany, but the fall of the Berlin Wall in November 1989 severed contacts and halted the extradition plan. During his long residence in Syria, Brunner was reportedly granted asylum, a generous salary and protection by the ruling Ba'ath Party in exchange for his advice on effective torture and interrogation techniques used by the Germans in World War II.
In the Bunte interview, Brunner was quoted as saying he regrets nothing and that all of the Jews deserved their fate. In a 1987 telephone interview with Chuck Ashman, published in the Chicago Sun Times, Brunner was reported to have said: "All of [the Jews] deserved to die because they were the Devil's agents and human garbage. I have no regrets and would do it again." (While the attribution of this quotation to Brunner was never directly disputed, Ashman was a controversial figure among his peers as journalists, and had previously been convicted of check fraud.) In an interview with Austrian neo-Nazi Gerd Honsik, Brunner denied claims of gas chambers.
Until the early 1990s, he lived in an apartment building on 7 Rue Haddad in Damascus, meeting with foreigners and occasionally being photographed. In the 1990s, the French Embassy received reports that Brunner was meeting regularly and having tea with former East German nationals. According to The Guardian, he was last seen alive by reliable witnesses in 1992.
In December 1999, unconfirmed reports surfaced that Brunner had died in 1996 and been buried in a Damascus cemetery. However, he was reportedly sighted at the Meridian Hotel in Damascus by German journalists that same year, where he was said to be living under police protection. The last reported sighting of him was at the Meridian Hotel in late 2001 by German journalists.
In 2011, Der Spiegel reported that the German intelligence service Bundesnachrichtendienst had destroyed its file on Brunner in the 1990s, and that remarks in remaining files contain conflicting statements as to whether Brunner had worked for the BND at some point.
Assassination attempts
In 1961 and 1980, letter bombs were sent to Brunner while he was a resident in Syria. As a result of the letter bomb he received in 1961, he lost an eye, and in 1980, he lost the fingers on his left hand when the parcel blew up in his hands. A 2018 article in Newsweek by journalist Ronen Bergman disclosed that the 1961 bomb was sent by Military Intelligence Unit 188, a branch of the Israel Defense Forces, and was the first target of a new method of letter bomb that was developed for deployment against ex-Nazi scientists working for Gamal Abdel Nasser in developing missiles targeting Israel. The article, excerpted from Bergman's book Rise and Kill First, says that Brunner was located by Israeli spy Eli Cohen.
According to information released by the Israeli intelligence agency Mossad in 2017, it was behind the 1980 letter bomb attack. After intelligence gathering revealed that Brunner had previously bought herbs from an Austrian mail order firm, Mossad agents broke into its office to steal brochures and envelopes with the company logo. After a suitable explosive device was created in Israel, the agents then returned to the town in Austria where the office was located in order to post the letter bomb, however the slot in the mailbox was too small for it to fit. This necessitated in the agents having to repackage the device into a smaller envelope with less explosives, which resulted in Brunner only being injured rather than being killed outright in the blast it created.
Convictions in absentia
Germany and other countries unsuccessfully requested his extradition. He was twice sentenced to death in absentia in the 1950s; one of those convictions was in France in 1954. In August 1987, an Interpol "red notice" was issued for him. In 1995, German state prosecutors in Cologne and Frankfurt posted a $330,000 reward for information leading to his arrest.
On 2 March 2001, he was found guilty in absentia by a French court for crimes against humanity, including the arrest and deportation of 345 orphans from the Paris region (which had not been judged in the earlier trials) and was sentenced to life imprisonment. According to Serge Klarsfeld, the trial was largely symbolic—an effort to honour the memories of victims. Klarsfeld's own father, arrested in 1943, was reportedly one of Brunner's victims.
Later attempts to locate
In 2004, the television series Unsolved History, in an episode titled "Hunting Nazis", used facial recognition software to compare Alois Brunner's official SS photograph with a recent photo of "Georg Fischer" from Damascus, and came up with a match of 8.1 points out of 10, which they claimed was, despite the elapse of over 50 years in aging, equivalent to a match with 95% certainty.
In 2005, Brazilian police were reportedly investigating whether a suspect living in the country under an assumed name was actually Alois Brunner. Deputy Commander Asher Ben-Artzi, the head of Israel's Interpol and Foreign Liaison Section, passed on a Brazilian request for Brunner's fingerprints to Nazi hunter Efraim Zuroff, head of the Simon Wiesenthal Center in Jerusalem, but Zuroff could not find any.
In July 2007, the Austrian Justice Ministry declared that they would pay €50,000 for information leading to his arrest and extradition to Austria.
In March 2009, the Simon Wiesenthal Center acknowledged the "slim" possibility of Brunner still being alive. In 2011, some media reports included him on a list of "World's Most Wanted" criminals.
In 2013, the Simon Wiesenthal Center described Brunner as "the most important unpunished Nazi war criminal who may still be alive". Brunner was last seen in 2001 in Syria, whose government had long rebuffed international efforts to locate or apprehend him, but was presumed dead .
In April 2014, Brunner was removed from the Simon Wiesenthal Center's list of most-wanted Nazi war criminals.
Death
On 30 November 2014, the Simon Wiesenthal Center reported receiving credible information that Brunner had died in Syria in 2010. He would have been 97 or 98 years old. Partly due to the ongoing Syrian Civil War, the exact date and place of death were unknown.
According to the director of the Wiesenthal Center, Efraim Zuroff, the information came from a "reliable" former German secret service agent who had served in the Middle East. The information was also reported in the press. The new evidence revealed that Brunner was buried in an unknown location in Damascus around 2010, unrepentant of his crimes to the end. Zuroff said that, owing to the civil war in Syria, the exact location of Brunner's grave was unknowable.
In 2017, the French quarterly review published an investigation about Brunner's last years in Syria by journalists Hédi Aouidj and Mathieu Palain. Three former security guards in charge of the protection of Brunner recounted how the Assad family used him to train intelligence services staff, then afterwards kept him under house arrest in a Damascus basement throughout the 1990s until his death in December 2001. One of the former guards said that Brunner, who went by the name of Abu Hussein, "suffered and cried a lot in his final years", "couldn't even wash" and ate only "an egg or a potato" a day. According to the report at the time of his death, Brunner's body was washed according to Islamic rites. Brunner was buried in secret, at night in the Al-Affif cemetery in Damascus. Serge Klarsfeld called the report "highly credible". In March 2021, the district court in Vienna-Döbling officially declared him dead.
References
Notes
Sources
1912 births
2001 deaths
Antisemitism in Austria
Antisemitism in Syria
Austrian amputees
Austrian blind people
Austrian expatriates in Syria
Austrian Legion personnel
Austrian neo-Nazis
Austrian people convicted of crimes against humanity
Austrian people of Hungarian descent
Drancy internment camp
Fugitives wanted by France
Fugitives wanted by Germany
Fugitives wanted on crimes against humanity charges
Fugitives wanted on war crimes charges
Gestapo personnel
Holocaust perpetrators in Austria
Holocaust perpetrators in France
Holocaust perpetrators in Greece
Holocaust perpetrators in Slovakia
Hungarian-German people
Nazi concentration camp commandants
Nazi fugitives
Nazi Party officials
People from Jennersdorf District
SS-Hauptsturmführer
The Holocaust in Thessaloniki
Explosion survivors
Nazis sentenced to death in absentia by France | Alois Brunner | [
"Chemistry"
] | 3,537 | [
"Explosion survivors",
"Explosions"
] |
323,176 | https://en.wikipedia.org/wiki/Primacord | Primacord is a brand of detonating cord used in blasting. It was developed in 1936 by the Ensign-Bickford Company. Ensign-Bickford sold their registered trademark for Primacord to Dyno Nobel in 2003. which manufactures it in their Graham, Kentucky factory. The name is also used as a genericized trademark for any detonating cord.
Description
Primacord consists of a continuous core of PETN, RDX or other high explosive, bound by textile yarns and finished with plastic and wax as waterproofing agents. It is produced in eight strengths:
Primaline is a related product differing principally in having a plastic jacket instead of textile. Primaline is also available in higher loadings, up to 85 g/m (400 gr/ft):
Operation
Primacord is initiated with a blasting cap or by a donor line of detonating cord or other high explosive. It detonates along its entire length at a velocity of approximately per second. It is used to create explosive effects and to build reliable explosive charges. It is used in conjunction with other high explosive materials to form charges, including linear charges, capable of near instantaneous results.
See also
Cordtex
References
Detonators
Explosives | Primacord | [
"Chemistry"
] | 253 | [
"Explosives",
"Explosions"
] |
323,207 | https://en.wikipedia.org/wiki/George%20Constantinescu | George "Gogu" Constantinescu (; last name also Constantinesco; 4 October 1881 – 11 December 1965) was a Romanian scientist, engineer, and inventor. During his career, he registered over 130 inventions. Constantinescu was the creator of the theory of sonics, a new branch of continuum mechanics, in which he described the transmission of mechanical energy through vibrations.
Biography
Early years
Born in Craiova in "the Doctor's House" near the Mihai Bravu Gardens, Constantinescu was influenced by his father George, born in 1844 (a professor of mathematics and engineering science, specialized in mathematics at the Sorbonne University). Gogu Constantinescu settled in the United Kingdom in 1912. He was an honorary member of the Romanian Academy.
Family
He married Alexandra (Sandra) Cocorescu in Richmond, London, in December 1914. The couple moved to Wembley and, after their son Ian was born, they moved to Weybridge. The marriage broke down in the 1920s and ended in divorce. He then married Eva Litton and the couple moved to Oxen House, beside Lake Coniston. Eva had two children, Richard and Michael, by a previous marriage.
Inventions and designs
Synchronization gear
His hydraulic machine gun synchronization gear allowed airplane-mounted guns to shoot between the spinning blades of the propeller. The Constantinesco synchronization gear (or "CC" gear) was first used operationally on the D.H.4s of No. 55 squadron R.F.C. from March 1917, during World War I, and rapidly became standard equipment, replacing a variety of mechanical gears. It continued to be used by the Royal Air Force until World War II – the Gloster Gladiator being the last British fighter to be equipped with "CC" gear.
Sonics
In 1918, he published the book A treatise on transmission of power by vibrations in which he described his theory of sonics. The theory is applicable to various systems of power transmission but has mostly been applied to hydraulic systems. Sonics differs from hydrostatics, being based on waves, rather than pressure, in the liquid. Constantinescu argued that, contrary to popular belief, liquids are compressible. Transmission of power by waves in a liquid (e.g. water or oil) required a generator to produce the waves and a motor to use the waves to do work, either by percussion (as in rock drills) or by conversion to rotary motion.
Internal combustion engines
He had several patents for improvements to carburetors, for example US1206512. He also devised a hydraulic system (patent GB133719) for operating both the valves and the fuel injectors for diesel engines.
Torque converter
He invented a mechanical torque converter actuated by a pendulum. This was applied to the Constantinesco, a French-manufactured car. It was also tried on rail vehicles. A 250 hp petrol engined locomotive with a Constantinescu torque converter was exhibited at the 1924 Wembley Exhibition. The system was not
adopted on British railways but it was applied to some railcars on the Romanian State Railways.
Other
Other inventions included a "railway motor wagon". The latter ran on normal flanged steel wheels but the drive used a road vehicle powertrain with rubber tyres pressed against the rails. This is similar to the system used on many modern road-rail vehicles. He also designed the Grand Mosque of Constanța (a project completed by the architect Victor Ştefănescu, then known as the Carol I Mosque).
Recent developments
Research on a sonic asynchronous motor for vehicle applications (based on Constantinescu's work) has been done at the Transilvania University of Brașov. The date of the paper is believed to be 5 October 2010.
Death
He died at Oxen House, beside Coniston Water on 11/12 December 1965, and is buried in the churchyard at Lowick, Cumbria.
Recognition
The Dimitrie Leonida Technical Museum in Bucharest has exhibits relating to George Constantinescu.
References
External links
Biography
Patents of G. Constantinescu
George (Gogu) Constantinescu (ro)
Autoturism Homepage
YouTube showing operation of Constantinesco-Colley synchronising gear for WW1 aircraft
1881 births
1965 deaths
Aerodynamicists
Burials in Cumbria
Carol I National College alumni
Romanian emigrants to the United Kingdom
Fluid mechanics
People from Craiova
Romanian aerospace engineers
20th-century Romanian engineers
Romanian inventors
Romanian scientists
Titular members of the Romanian Academy | George Constantinescu | [
"Engineering"
] | 908 | [
"Civil engineering",
"Fluid mechanics"
] |
323,221 | https://en.wikipedia.org/wiki/Sun%20dog | A sun dog (or sundog) or mock sun, also called a parhelion (plural parhelia) in atmospheric science, is an atmospheric optical phenomenon that consists of a bright spot to one or both sides of the Sun. Two sun dogs often flank the Sun within a 22° halo.
The sun dog is a member of the family of halos caused by the refraction of sunlight by ice crystals in the atmosphere. Sun dogs typically appear as a pair of subtly colored patches of light, around 22° to the left and right of the Sun, and at the same altitude above the horizon as the Sun. They can be seen anywhere in the world during any season, but are not always obvious or bright. Sun dogs are best seen and most conspicuous when the Sun is near the horizon.
Formation and characteristics
Sun dogs are commonly caused by the refraction and scattering of light from horizontally oriented plate-shaped hexagonal ice crystals either suspended in high and cold cirrus or cirrostratus clouds, or drifting in freezing moist air at low levels as diamond dust. The crystals act as prisms, bending the light rays passing through them with a minimum deflection of 22°. As the crystals gently float downwards with their large hexagonal faces almost horizontal, sunlight is refracted horizontally, and sun dogs are seen to the left and right of the Sun. Larger plates wobble more, and thus produce taller sun dogs.
Sun dogs are red-colored at the side nearest the Sun; farther out the colors grade through oranges to blue. The colors overlap considerably and are muted, never pure or saturated. The colors of the sun dog finally merge into the white of the parhelic circle (if the latter is visible).
The same plate-shaped ice crystals that cause sun dogs are also responsible for the colorful circumzenithal arc, meaning that these two types of halo tend to co-occur. The latter is often missed by viewers, since it is located more or less directly overhead. Another halo variety often seen together with sun dogs is the 22° halo, which forms a ring at roughly the same angular distance from the sun as the sun dogs, thus appearing to interconnect them. As the Sun rises higher, the rays passing through the plate crystals are increasingly skewed from the horizontal plane, causing their angle of deviation to increase and the sun dogs to move farther from the 22° halo, while staying at the same elevation.
It is possible to predict the forms of sun dogs as would be seen on other planets and moons. Mars might have sun dogs formed by both water-ice and CO2-ice. On the giant planets—Jupiter, Saturn, Uranus, and Neptune—other crystals form clouds of ammonia, methane, and other substances that can produce halos with four or more sun dogs.
A related phenomenon, the Crown flash is also known as a "leaping Sundog".
Terminology
A somewhat common misconception among the general public is to refer to any member of the ice halo family as a "sun dog" (especially the 22° halo, being one of the most common varieties). However, sun dogs represent just one of many different types of halos. For referring to the atmospheric phenomenon in general, the term (ice crystal) halo(s) is more appropriate.
Etymology
The exact etymology of sun dog largely remains a mystery. The Oxford English Dictionary says it is "of obscure origin".
In Abram Palmer's 1882 book Folk-etymology: A Dictionary of Verbal Corruptions Or Words Perverted in Form Or Meaning, by False Derivation Or Mistaken Analogy, sun-dogs are defined:
(Dog in English as a verb can mean "hunt, track, or follow", so Dog the true [sun] has meant track the true [sun] since the 1510s.)
Alternatively, Jonas Persson suggested that out of Norse mythology and archaic names — (sun dog), (sun dog), (sun wolf) — in the Scandinavian languages, constellations of two wolves hunting the Sun and the Moon, one after and one before, may be a possible origin for the term.
Parhelion (plural parhelia) comes from (, 'beside the sun'; from (, 'beside') and (, 'sun')).
In the Anglo-Cornish dialect of Cornwall, United Kingdom, sun dogs are known as weather dogs (described as "a short segment of a rainbow seen on the horizon, foreshowing foul weather"). It is also known as a lagas in the sky which comes from the Cornish language term for the sun dog meaning 'weather's eye' (, 'eye' and , 'weather/wind'). This is in turn related to the Anglo-Cornish term cock's eye for a halo round the Sun or the Moon, also a portent of bad weather.
History
Antiquity
Aristotle (Meteorology III.2, 372a14) notes that "two mock suns rose with the sun and followed it all through the day until sunset." He says that "mock suns" are always to the side, never above or below, most commonly at sunrise or sunset, more rarely in the middle of the day.
The poet Aratus (Phaenomena, lines 880–891) mentions parhelia as part of his catalogue of Weather Signs; according to him, they can indicate rain, wind, or an approaching storm.
Artemidorus in his Oneirocritica ('On the Interpretation of Dreams') included the mock suns amongst a list of celestial deities.
A passage in Cicero's On the Republic (54–51 BC) is one of many Roman authors who refer to sun dogs and similar phenomena:
Seneca makes an incidental reference to sun dogs in the first book of his Naturales Quaestiones.
The 2nd-century Roman writer and philosopher Apuleius in his Apologia says "What is the cause of the prismatic colours of the rainbow, or of the appearance in heaven of two rival images of the sun, with sundry other phenomena treated in a monumental volume by Archimedes of Syracuse."
Fulcher of Chartres, writing in Jerusalem in the early twelfth century, notes in his Historia Hierosolymitana (1127) that on February 23, 1106
Wars of the Roses
The prelude to the Battle of Mortimer's Cross in Herefordshire, England in 1461 is supposed to have involved the appearance of a halo display with three "suns". The Yorkist commander, later Edward IV of England, convinced his initially frightened troops that it represented the three sons of the Duke of York, and Edward's troops won a decisive victory. The event was dramatized by William Shakespeare in King Henry VI, Part 3, and by Sharon Kay Penman in The Sunne In Splendour.
Early modern era
Another early clear description of sun dogs is by Jacob Hutter, who wrote in his Brotherly Faithfulness: Epistles from a Time of Persecution:
The observation most likely occurred in Auspitz (Hustopeče), Moravia on 31 October 1533. The original was written in German and is from a letter originally sent in November 1533 from Auspitz in Moravia to the Adige Valley in South Tyrol. The Kuntz Maurer and Michel Schuster mentioned in the letter left Hutter on the Thursday after the feast day of Simon and Jude, which is 28 October. The Thursday after was 30 October. It is likely that the "two rainbows with their backs turned toward each other, almost touching" involved two further halo phenomena, possibly a circumzenithal arc (prone to co-occur with sun dogs) together with a partial 46° halo or supralateral arc.
While mostly known and often quoted for being the oldest color depiction of the city of Stockholm, Vädersolstavlan (Swedish; "The Sundog Painting", literally "The Weather Sun Painting") is arguably also one of the oldest known depictions of a halo display, including a pair of sun dogs. For two hours in the morning of 20 April 1535, the skies over the city were filled with white circles and arcs crossing the sky, while additional suns (i.e., sun dogs) appeared around the sun. The phenomenon quickly resulted in rumours of an omen of God's forthcoming revenge on King Gustav Vasa (1496–1560) for having introduced Protestantism during the 1520s and for being heavy-handed with his enemies allied with the Danish king.
Hoping to end speculations, the Chancellor Olaus Petri (1493–1552), a Lutheran scholar, ordered a painting to be produced documenting the event. When confronted with the painting, the King, however, interpreted it as a conspiracy — the real sun, of course, being himself —threatened by competing fake suns, one being Olaus Petri and the other the clergyman and scholar Laurentius Andreae (1470–1552). Both were thus accused of treachery, but eventually escaped capital punishment. The original painting is lost, but a copy from the 1630s survives and can still be seen in the church Storkyrkan in central Stockholm.
A series of complex parhelia displays in Rome in 1629, and again in 1630, were described by Christoph Scheiner in his book Parhelia, one of the earliest works on the subject. It had a profound effect, causing René Descartes to interrupt his metaphysical studies and led to his work of natural philosophy called The World.
On 20 February 1661 the people of Gdańsk witnessed a complex halo display, described by Georg Fehlau in a pamphlet, the Sevenfold Sun Miracle, and again the following year by Johannes Hevelius in his book, Mercurius in Sole visus Gedani.
On 18 June 1790 Johann Tobias Lowitz, in Saint Petersburg, Russia, observed a complex display of haloes and parhelia which included his Lowitz arcs.
Late modern era to current day
In 1843, winter in the British Colony of Newfoundland was referred to as the 'Winter of Three Suns' and was unusually cold with 15 days of temperatures between 3–10 degrees below zero.
"Part of the time we marched in the teeth of a biting storm of snow, and at every hour of the day the sun could be discerned sulking behind soft grey mists in company with rivals, known in the language of the plains as 'Sun-dogs', whose parahelic splendors warned the traveler of the approach of the ever-to-be-dreaded 'blizzard'."
On 14 February 2020, the people of Inner Mongolia Autonomous Region witnessed a different complex halo display called the Five-fold sun miracle, in which all five sun halos were linked to each other by rays, forming a circle among them.
See also
Anthelion
Circumhorizontal arc
Corona (optical phenomenon)
Crown flash
Liljequist parhelion
Moon dog
References
Further reading
External links
Sundogs – Parhelia, Explanations and Images
Starry Night Photography – Sun Dog, Sun Halo, Moon Halo
Photo slideshow
4 point Sun dog with complete 360 degree ring in Shubarkurduk, Kazachstan
Rare sun halo appears
SDO Sundog Mystery – A phenomenon that occurred during the launch of the Solar Dynamics Observatory
Atmospheric optical phenomena
Sun | Sun dog | [
"Physics"
] | 2,331 | [
"Optical phenomena",
"Physical phenomena",
"Atmospheric optical phenomena",
"Earth phenomena"
] |
323,260 | https://en.wikipedia.org/wiki/Explosive%20booster | An explosive booster is a sensitive explosive charge that acts as a bridge between a (relatively weak) conventional detonator and a low-sensitivity (but typically high-energy) explosive such as TNT. By itself, the initiating detonator would not deliver sufficient energy to set off the low-sensitivity charge. However, it detonates the primary charge (the booster), which then delivers an explosive shockwave that is sufficient to detonate the secondary, main, high-energy charge.
Unlike C4 plastic explosive, not all explosives can be detonated simply by inserting a detonator and firing it.
An initiator such as a shock tube, cannon fuse, or even a conventional detonator does not deliver sufficient shock to detonate charges comprising TNT, Composition B, ANFO and many other high explosives. Therefore, some form of "booster" is required to amplify the energy released by the detonator so that the main charge will detonate.
At first, picric acid was used as a booster to detonate TNT, though it was superseded due to the inherent danger of picrate formation. Tetryl replaced picric acid because it is more stable, and was once a very popular chemical for booster charges, particularly during World War II. However, since then, tetryl has largely been replaced by other compositions, e.g. a small cylinder or pellet of phlegmatized RDX (e.g. CH-6 or Composition A-5) or PETN (slightly larger than the actual detonator) into which the detonator itself is inserted.
Note: booby traps and improvised explosive devices frequently use plastic explosive as the booster charge, for example, some C4 or Semtex stuffed into the empty fuze pocket of a 120mm mortar shell. This is because any standard detonator will initiate plastic explosive as is.
When encountered in connection with artillery shells or air dropped bombs, a booster charge is sometimes referred to as the "gaine", from . See detonators.
At a purely technical level, a sufficiently large detonator would initiate high explosives without the need for a booster charge. However, there are very good reasons why this method is never used. Firstly, there is a major safety issue, i.e. detonators are (like all primary explosives) much more sensitive to shock, heat, and friction than an explosive booster. Therefore, minimising the amount of primary explosive that users must store or carry greatly reduces the likelihood of serious accidents. An additional economic reason for using explosive booster charges is that chemical compounds used in detonators (e.g. lead styphnate) are comparatively expensive to produce and encapsulate when compared to the manufacturing costs of explosive boosters.
A common form for boosters is to cast the explosive material into a cylindrical shell made of cardboard or plastic; these are accordingly known as cast boosters.
Gallery
Explosives | Explosive booster | [
"Chemistry"
] | 602 | [
"Explosives",
"Explosions"
] |
14,438,036 | https://en.wikipedia.org/wiki/ADS%2016402 | ADS 16402 is a binary star system, composed of two sun-like stars located approximately 525 light-years away in the constellation Lacerta. It was first identified as a binary star by John Herschel in 1831. The two stars are separated by 11.26 arcseconds which leads to a projected separation of roughly 1500 astronomical units at the distance of ADS 16402. The star system is estimated to be 1.9 ± 0.6 billion years old. The secondary star ADS 16402 B is also designated HAT-P-1.
Planetary system
On September 14, 2006 the HATNet Project announced their first extrasolar planet discovery HAT-P-1b, a hot jupiter type gas giant in orbit around the secondary star ADS 16402B. Following the designation scheme used by the HATNet Project, the secondary star is known as HAT-P-1, and the planet itself designated HAT-P-1b.
See also
HATNet Project or HAT
References
External links
Binary stars
G-type main-sequence stars
Lacerta
Planetary transit variables
Planetary systems with one confirmed planet
F-type main-sequence stars
2 | ADS 16402 | [
"Astronomy"
] | 225 | [
"Lacerta",
"Constellations"
] |
14,438,348 | https://en.wikipedia.org/wiki/Cannabinoid%20receptor%201 | Cannabinoid receptor 1 (CB1), is a G protein-coupled cannabinoid receptor that in humans is encoded by the CNR1 gene. And discovered, by determination and characterization in 1988, and cloned in 1990 for the first time. The human CB1 receptor is expressed in the peripheral nervous system and central nervous system. It is activated by endogenous cannabinoids called endocannabinoids, a group of retrograde neurotransmitters that include lipids, such as anandamide and 2-arachidonoylglycerol; plant phytocannabinoids, such as docosatetraenoylethanolamide found in wild daga, the compound tetrahydrocannabinol which is an active constituent of the psychoactive drug cannabis; and synthetic analogs of tetrahydrocannabinol. CB1 is antagonized by the phytocannabinoid tetrahydrocannabivarin at low doses and at higher doses, it activate the CB1 receptor as an agonist, but with less potency than tetrahydrocannabinol.
The primary endogenous agonist of the human CB1 receptor is anandamide.
Structure
The CB1 receptor shares the structure characteristic of all G-protein-coupled receptors, possessing seven transmembrane domains connected by three extracellular and three intracellular loops, an extracellular N-terminal tail, and an intracellular C-terminal tail. The receptor may exist as a homodimer or form heterodimers or other GPCR oligomers with different classes of G-protein-coupled receptors. Observed heterodimers include A2A–CB1, CB1–D2, OX1–CB1, μOR–CB1, while many more may only be stable enough to exist in vivo. The CB1 receptor possesses an allosteric modulatory binding site.
The CB1 receptor is encoded by the gene CNR1, located on human chromosome 6. Two transcript variants encoding different isoforms have been described for this gene. CNR1 orthologs have been identified in most mammals.
The CNR1 gene has a structure consisting of a single coding-exon and multiple alternative 5' untranslated exons. The CB1 receptor is created by transcription of the last exon on the CNR1 gene.
Mechanism
The CB1 receptor is a pre-synaptic heteroreceptor that modulates neurotransmitter release when activated in a dose-dependent, stereoselective and pertussis toxin-sensitive manner. The CB1 receptor is activated by cannabinoids, generated naturally inside the body (endocannabinoids) or exogenously, normally through cannabis or a related synthetic compound.
Research suggests that the majority of CB1 receptors are coupled through Gi/o proteins. Upon activation, CB1 receptor exhibits its effects mainly through activation of Gi, which decreases intracellular cAMP concentration by inhibiting its production enzyme, adenylate cyclase, and increases mitogen-activated protein kinase (MAP kinase) concentration. Alternatively, in some rare cases CB1 receptor activation may be coupled to Gs proteins, which stimulate adenylate cyclase. cAMP is known to serve as a second messenger coupled to a variety of ion channels, including the positively influenced inwardly rectifying potassium channels (=Kir or IRK), and calcium channels, which are activated by cAMP-dependent interaction with such molecules as protein kinase A (PKA), protein kinase C (PKC), Raf-1, ERK, JNK, p38, c-fos, c-jun, and others.
In terms of function, the inhibition of intracellular cAMP expression shortens the duration of pre-synaptic action potentials by prolonging the rectifying potassium A-type currents, which is normally inactivated upon phosphorylation by PKA. This inhibition grows more pronounced when considered with the effect of activated CB1 receptors to limit calcium entry into the cell, which does not occur through cAMP but by a direct G-protein-mediated inhibition. As presynaptic calcium entry is a requirement for vesicle release, this function will decrease the transmitter that enters the synapse upon release. The relative contribution of each of these two inhibitory mechanisms depends on the variance of ion channel expression by cell type.
The CB1 receptor can also be allosterically modulated by synthetic ligands in a positive and negative manner. In vivo exposure to tetrahydrocannabinol impairs long-term potentiation and leads to a reduction of phosphorylated CREB.
The signaling properties of activated CB1 are furthermore modified by the presence of SGIP1, that hinders receptor internalization and decreases ERK1/2 signalling while augmenting the interaction with GRK3, β-arrestin-2.
In summary, CB1 receptor activity has been found to be coupled to certain ion channels, in the following manner:
Positively to inwardly rectifying and A-type outward potassium channels.
Negatively to D-type outward potassium channels
Negatively to N-type and P/Q-type calcium channels.
Expression
CB1 receptors are localized throughout the central and peripheral nervous systems, particularly on axon terminals in the cerebellum, hippocampus, basal ganglia, frontal cortex, amygdala, hypothalamus, and midbrain. The CB1 receptor is primarily expressed in the presynaptic terminals of GABAergic (amygdala and cerebellum), glutamatergic (cortex, hippocampus and amygdala), dopaminergic, GABAergic interneurons, cholinergic neurons, noradrenergic, and serotonergic neurons. Acting as a neuromodulator, the CB1 receptor inhibits the release of both excitatory and inhibitory neurotransmitters including acetylcholine, glutamate, GABA, noradrenaline, 5-HT, dopamine, D-aspartate, and cholecystokinin. Repeated administration of receptor agonists may result in receptor internalization and/or a reduction in receptor protein signaling.
The inverse agonist MK-9470 makes it possible to produce in vivo images of the distribution of CB1 receptors in the human brain with positron emission tomography.
Brain
The CB1 receptor is recognized as the most abundant metabotropic receptor in the brain. CB1 receptors are found moderately to highly expressed within the cerebral cortex (cingulate gyrus, prefrontal cortex, and hippocampus), periaqueductal gray, hypothalamus, amygdala, cerebellum, and basal ganglia (globus pallidus, substantia nigra). Varying levels of CB1 can also be detected in the olfactory bulb, cortical regions (neocortex, pyriform cortex), parts of basal ganglia, thalamic, hypothalamic, and brainstem nuclei, as well as in subcortical regions (e.g., the septal region), and cerebellar cortex.
CB1 receptors are expressed most densely in the central nervous system and are largely responsible for mediating the effects of cannabinoid binding in the brain. Endocannabinoids released by a depolarized neuron bind to CB1 receptors on pre-synaptic glutamatergic and GABAergic neurons, resulting in a respective decrease in either glutamate or GABA release. Limiting glutamate release causes reduced excitation, while limiting GABA release suppresses inhibition, a common form of short-term plasticity in which the depolarization of a single neuron induces a reduction in GABA-mediated inhibition, in effect exciting the postsynaptic cell.
Brainstem
High expression of CB1 is found in brainstem medullary nuclei, including the nucleus of the solitary tract and area postrema. CB1 receptor is relatively low in medullary respiratory brainstem control centers.
Hippocampal formation
CB1 mRNA transcripts are abundant in GABAergic interneurons of the hippocampus, indirectly reflecting the expression of these receptors and elucidating the established effect of cannabinoids on memory. These receptors are densely located in cornu ammonis pyramidal cells, which are known to release glutamate. Cannabinoids suppress the induction of LTP and LTD in the hippocampus by inhibiting these glutamatergic neurons. By reducing the concentration of glutamate released below the threshold necessary to depolarize the postsynaptic NMDA receptor, a receptor known to be directly related to the induction of LTP and LTD, cannabinoids are a crucial factor in the selectivity of memory.
These receptors are highly expressed by GABAergic interneurons as well as glutamatergic principal neurons. However, a higher density is found within GABAergic cells. This means that, although synaptic strength/frequency, and thus potential to induce LTP, is lowered, net hippocampal activity is raised. In addition, CB1 receptors in the hippocampus indirectly inhibit the release of acetylcholine. This serves as the modulatory axis opposing GABA, decreasing neurotransmitter release. Cannabinoids also likely play an important role in the development of memory through their neonatal promotion of myelin formation, and thus the individual segregation of axons.
Basal ganglia
CB1 receptors are expressed throughout the basal ganglia and have well-established effects on movement in rodents. As in the hippocampus, these receptors inhibit the release of glutamate or GABA transmitter, resulting in decreased excitation or reduced inhibition based on the cell they are expressed in. Consistent with the variable expression of both excitatory glutamate and inhibitory GABA interneurons in both the basal ganglia's direct and indirect motor loops, synthetic cannabinoids are known to influence this system in a dose-dependent triphasic pattern. Decreased locomotor activity is seen at both higher and lower concentrations of applied cannabinoids, whereas an enhancement of movement may occur upon moderate dosages. However, these dose-dependent effects have been studied predominately in rodents, and the physiological basis for this triphasic pattern warrants future research in humans. Effects may vary based on the site of cannabinoid application, input from higher cortical centers, and whether drug application is unilateral or bilateral.
Cerebellum and neocortex
The role of the CB1 receptor in the regulation of motor movements is complicated by the additional expression of this receptor in the cerebellum and neocortex, two regions associated with the coordination and initiation of movement. Research suggests that anandamide is synthesized by Purkinje cells and acts on presynaptic receptors to inhibit glutamate release from granule cells or GABA release from the terminals of basket cells. In the neocortex, these receptors are concentrated on local interneurons in cerebral layers II-III and V-VI. Compared to rat brains, humans express more CB1 receptors in the cerebral cortex and amygdala and less in the cerebellum, which may help explain why motor function seems to be more compromised in rats than humans upon cannabinoid application.
Spine
Many of the documented analgesic effects of cannabinoids are based on the interaction of these compounds with CB1 receptors on spinal cord interneurons in the superficial levels of the dorsal horn, known for its role in nociceptive processing. In particular, the CB1 is heavily expressed in layers 1 and 2 of the spinal cord dorsal horn and in lamina 10 by the central canal. Dorsal root ganglion also express these receptors, which target a variety of peripheral terminals involved in nociception. Signals on this track are also transmitted to the periaqueductal gray (PAG) of the midbrain. Endogenous cannabinoids are believed to exhibit an analgesic effect on these receptors by limiting both GABA and glutamate of PAG cells that relate to nociceptive input processing, a hypothesis consistent with the finding that anandamide release in the PAG is increased in response to pain-triggering stimuli.
Other
CB1 is expressed on several types of cells in pituitary gland, thyroid gland, and possibly in the adrenal gland. CB1 is also expressed in several cells relating to metabolism, such as fat cells, muscle cells, liver cells (and also in the endothelial cells, Kupffer cells and stellate cells of the liver), and in the digestive tract. It is also expressed in the lungs and the kidney.
CB1 is present on Leydig cells and human sperms. In females, it is present in the ovaries, oviducts myometrium, decidua, and placenta. It has also been implicated in the proper development of the embryo.
CB1 is also expressed in the retina. In the retina, they are expressed in the photoreceptors, inner plexiform, outer plexiform, bipolar cells, ganglion cells, and retinal pigment epithelium cells. In the visual system, cannabinoids agonist induce a dose dependent modulation of calcium, chloride and potassium channels. This alters vertical transmission between photoreceptor, bipolar and ganglion cells. Altering vertical transmission in turn results in the way vision is perceived.
Physiological and pathological conditions
The activation of CB1 in the human body generally inhibits neurotransmitter release, controls pain, regulates metabolism, and monitors the cardiovascular system. CB1 receptors are implicated in a number of physiological processes related to the central nervous system (CNS) including brain development, learning and memory, motor behavior, regulation of appetite, body temperature, pain perception, and inflammation.
The localization of CB1 receptors is expressed in several neuronal types, including GABAergic, glutamatergic, and serotonergic neurons. CB1 receptors localized in GABAergic neurons can modulate food intake, learning and memory processes, drug addiction, and related behaviors. CB1 receptors localized in glutamatergic neurons are capable of mediating olfactory processes, neuroprotection, social behaviors, anxiety, and fear memories. The localization of CB1 receptors in serotonergic neurons can regulate emotional responses.
Clinically, CB1 is a direct drug target for addiction, pain, epilepsy, and obesity. CB1 receptor function is involved with several psychiatric, neurological, neurodevelopmental, and neurodegenerative disorders including Huntington's disease (HD), multiple sclerosis (MS), and Alzheimer's disease (AD). Major loss of CB1 receptors is reported in patients with HD. However, stimulation of the CB1 receptor has potential to reduce the progression of HD. Improvements from use of CB agonist in MS are associated with the activation of CB1 and CB2 receptors, leading to dual anti-inflammatory and neuroprotective effects throughout the CNS. Similarly, activation of CB1 and CB2 receptors could provide neuroprotective effects against amyloid-β (Aβ) toxicity in AD. In several brain regions, including the dorsolateral prefrontal cortex (DLPFC) and hippocampus, dysregulation of the CB1 receptor is implicated in the development of schizophrenia. Abnormal functioning of the CB1 receptor compromises intricate neural systems that are responsible for controlling cognition and memory, which contributes to the pathology. PET imaging modalities implicate that alterations of CB1 levels in certain brain systems are strongly associated with schizophrenia symptoms. Neurobehavioral disorders, such as attention deficit hyperactivity disorder (ADHD), are associated with genetic variants of CNR1 in rat models of ADHD.
Use of antagonists
Selective CB1 agonists may be used to isolate the effects of the receptor from the CB2 receptor, as most cannabinoids and endocannabinoids bind to both receptor types.
CB1 selective antagonists such as rimonabant are used for weight reduction and smoking cessation. A substantial number of antagonists of the CB1 receptor have been discovered and characterized. TM38837 has been developed as a CB1 receptor antagonist that is restricted to targeting only peripheral CB1 receptors.
Ligands
Agonists
Minocycline
Dronabinol
Selective
Epigallocatechin
Epicatechin
Kavain
Yangonin
Oleamide
Unspecified efficacy
N-Arachidonoyl dopamine
Cannabinol
HU-210
11-Hydroxy-THC
Levonantradol
Partial
Endogenous
2-Arachidonyl glyceryl ether
Phyto
Tetrahydrocannabinol
Hexahydrocannabinol
Full
Endogenous
2-Arachidonoylglycerol
Synthetic
JWH-073
AM-2201
CP 55,940
JWH-018
WIN 55,212-2
Allosteric agonist
GAT228
Antagonists
Cannabigerol
Ibipinabant
Otenabant
Tetrahydrocannabivarin
Virodhamine (Endogenous CB1 antagonist and CB2 agonist)
Inverse agonists
Rimonabant
Taranabant
Zevaquenabant
Monlunabant
INV-202
Allosteric modulators
Lipoxin A4 – endogenous, PAM
ZCZ-011 – PAM
Pregnenolone – endogenous, NAM
Cannabidiol – NAM
Fenofibrate – NAM
GAT100 – NAM
PSNCBAM-1 – NAM
RVD-Hpα – NAM
Binding affinities
Evolution
The CNR1 gene is used in animals as a nuclear DNA phylogenetic marker. This intronless gene has first been used to explore the phylogeny of the major groups of mammals, and contributed to reveal that placental orders are distributed into five major clades: Xenarthra, Afrotheria, Laurasiatheria, Euarchonta, and Glires. CNR1 has also proven useful at lower taxonomic levels, such as rodents, and for the identification of dermopterans as the closest primate relatives.
Paralogues
Source:
CNR2
S1PR1
LPAR1
S1PR3
S1PR5
S1PR2
GPR6
GPR12
S1PR4
LPAR3
LPAR2
GPR3
MC3R
MC5R
MC2R
MC1R
MC4R
GPR119
See also
Discovery and development of Cannabinoid Receptor 1 Antagonists
Cannabinoid receptor
Cannabinoid receptor type 2 (CB2)
References
External links
Cannabinoid receptor 1 (CNR1) Human Protein Atlas
G protein-coupled receptors | Cannabinoid receptor 1 | [
"Chemistry"
] | 4,005 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,438,412 | https://en.wikipedia.org/wiki/Cannabinoid%20receptor%202 | The cannabinoid receptor 2 (CB2), is a G protein-coupled receptor from the cannabinoid receptor family that in humans is encoded by the CNR2 gene. It is closely related to the cannabinoid receptor 1 (CB1), which is largely responsible for the efficacy of endocannabinoid-mediated presynaptic-inhibition, the psychoactive properties of tetrahydrocannabinol (THC), the active agent in cannabis, and other phytocannabinoids (plant cannabinoids). The principal endogenous ligand for the CB2 receptor is 2-Arachidonoylglycerol (2-AG).
CB2 was cloned in 1993 by a research group from Cambridge looking for a second cannabinoid receptor that could explain the pharmacological properties of tetrahydrocannabinol. The receptor was identified among cDNAs based on its similarity in amino-acid sequence to the cannabinoid receptor 1 (CB1) receptor, discovered in 1990. The discovery of this receptor helped provide a molecular explanation for the established effects of cannabinoids on the immune system.
Structure
The CB2 receptor is encoded by the CNR2 gene. Approximately 360 amino acids comprise the human CB2 receptor, making it somewhat shorter than the 473-amino-acid-long CB1 receptor.
As is commonly seen in G protein-coupled receptors, the CB2 receptor has seven transmembrane spanning domains, a glycosylated N-terminus, and an intracellular C-terminus. The C-terminus of CB2 receptors appears to play a critical role in the regulation of ligand-induced receptor desensitization and downregulation following repeated agonist application, perhaps causing the receptor to become less responsive to particular ligands.
The human CB1 and the CB2 receptors possess approximately 44% amino acid similarity. When only the transmembrane regions of the receptors are considered, however, the amino acid similarity between the two receptor subtypes is approximately 68%. The amino acid sequence of the CB2 receptor is less highly conserved across human and rodent species as compared to the amino acid sequence of the CB1 receptor. Based on computer modeling, ligand interactions with CB2 receptor residues S3.31 and F5.46 appears to determine differences between CB1 and CB2 receptor selectivity. In CB2 receptors, lipophilic groups interact with the F5.46 residue, allowing them to form a hydrogen bond with the S3.31 residue. These interactions induce a conformational change in the receptor structure, which triggers the activation of various intracellular signaling pathways. Further research is needed to determine the exact molecular mechanisms of signaling pathway activation.
Mechanism
Like the CB1 receptors, CB2 receptors inhibit the activity of adenylyl cyclase through their Gi/Goα subunits. CB2 can also couple to stimulatory Gαs subunits leading to an increase of intracellular cAMP, as has been shown for human leukocytes. Through their Gβγ subunits, CB2 receptors are also known to be coupled to the MAPK-ERK pathway, a complex and highly conserved signal transduction pathway, which regulates a number of cellular processes in mature and developing tissues. Activation of the MAPK-ERK pathway by CB2 receptor agonists acting through the Gβγ subunit ultimately results in changes in cell migration.
Five recognized cannabinoids are produced endogenously: arachidonoylethanolamine (anandamide), 2-arachidonoyl glycerol (2-AG), 2-arachidonyl glyceryl ether (noladin ether), virodhamine, as well as N-arachidonoyl-dopamine (NADA). Many of these ligands appear to exhibit properties of functional selectivity at the CB2 receptor: 2-AG activates the MAPK-ERK pathway, while noladin inhibits adenylyl cyclase.
Expression
Dispute
Originally it was thought that the CB2 receptor was only expressed in peripheral tissue while the CB1 receptor is the endogenous receptor on neurons. Recent work with immunohistochemical staining has shown expression within neurons. Subsequently, it was shown that CB2 knock out mice produced the same immunohistochemical staining, indicating the presence of the CB2 receptor where none was expressed. This has created a long history of debate as to whether the CB2 receptor is expressed in the CNS. A new mouse model was described in 2014 that expresses a fluorescent protein whenever CB2 is expressed within a cell. This has the potential to resolve questions about the expression of CB2 receptors in various tissues.
Immune system
Initial investigation of CB2 receptor expression patterns focused on the presence of CB2 receptors in the peripheral tissues of the immune system, and found the CB2 receptor mRNA in the spleen, tonsils, and thymus gland. CB2 expression in human peripheral blood mononuclear cells at protein level has been confirmed by whole cell radioligand binding. Northern blot analysis further indicates the expression of the CNR2 gene in immune tissues, where they are primarily responsible for mediating cytokine release. These receptors were localized on immune cells such as monocytes, macrophages, B-cells, and T-cells.
Brain
Further investigation into the expression patterns of the CB2 receptors revealed that CB2 receptor gene transcripts are also expressed in the brain, though not as densely as the CB1 receptor and located on different cells. Unlike the CB1 receptor, in the brain, CB2 receptors are found primarily on microglia. The CB2 receptor is expressed in some neurons within the central nervous system (e.g.; the brainstem), but the expression is very low. CB2s are expressed on some rat retinal cell types. Functional CB2 receptors are expressed in neurons of the ventral tegmental area and the hippocampus, arguing for a widespread expression and functional relevance in the CNS and in particular in neuronal signal transmission.
Gastrointestinal system
CB2 receptors are also found throughout the gastrointestinal system, where they modulate intestinal inflammatory response. Thus, CB2 receptor is a potential therapeutic target for inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. The role of endocannabinoids, as such, play an important role in inhibiting unnecessary immune action upon the natural gut flora. Dysfunction of this system, perhaps from excess FAAH activity, could result in IBD. CB2 activation may also have a role in the treatment of irritable bowel syndrome. Cannabinoid receptor agonists reduce gut motility in IBS patients.
Peripheral nervous system
Application of CB2-specific antagonists has found that these receptors are also involved in mediating analgesic effects in the peripheral nervous system. However, these receptors are not expressed by nociceptive sensory neurons, and at present are believed to exist on an undetermined, non-neuronal cell. Possible candidates include mast cells, known to facilitate the inflammatory response. Cannabinoid mediated inhibition of these responses may cause a decrease in the perception of noxious-stimuli.
Function
Immune system
Primary research on the functioning of the CB2 receptor has focused on the receptor's effects on the immunological activity of leukocytes. To be specific, this receptor has been implicated in a variety of modulatory functions, including immune suppression, induction of apoptosis, and induction of cell migration. Through their inhibition of adenylyl cyclase via their Gi/Goα subunits, CB2 receptor agonists cause a reduction in the intracellular levels of cyclic adenosine monophosphate (cAMP). CB2 also signals via Gαs and increases intracellular cAMP in human leukocytes, leading to induction of interleukins 6 and 10. Although the exact role of the cAMP cascade in the regulation of immune responses is currently under debate, laboratories have previously demonstrated that inhibition of adenylyl cyclase by CB2 receptor agonists results in a reduction in the binding of transcription factor CREB (cAMP response element-binding protein) to DNA. This reduction causes changes in the expression of critical immunoregulatory genes and ultimately suppression of immune function.
Later studies examining the effect of synthetic cannabinoid agonist JWH-015 on CB2 receptors revealed that changes in cAMP levels result in the phosphorylation of leukocyte receptor tyrosine kinase at Tyr-505, leading to an inhibition of T cell receptor signaling. Thus, CB2 agonists may also be useful for treatment of inflammation and pain, and are currently being investigated, in particular for forms of pain that do not respond well to conventional treatments, such as neuropathic pain. Consistent with these findings are studies that demonstrate increased CB2 receptor expression in the spinal cord, dorsal root ganglion, and activated microglia in the rodent neuropathic pain model, as well as on human hepatocellular carcinoma tumor samples.
CB2 receptors have also been implicated in the regulation of homing and retention of marginal zone B cells. A study using knock-out mice found that CB2 receptor is essential for the maintenance of both MZ B cells and their precursor T2-MZP, though not their development. Both B cells and their precursors lacking this receptor were found in reduced numbers, explained by the secondary finding that 2-AG signaling was demonstrated to induce proper B cell migration to the MZ. Without the receptor, there was an undesirable spike in the blood concentration of MZ B lineage cells and a significant reduction in the production of IgM. While the mechanism behind this process is not fully understood, the researchers suggested that this process may be due to the activation-dependent decrease in cAMP concentration, leading to reduced transcription of genes regulated by CREB, indirectly increasing TCR signaling and IL-2 production. Together, these findings demonstrate that the endocannabinoid system may be exploited to enhance immunity to certain pathogens and autoimmune diseases.
Clinical applications
CB2 receptors may have possible therapeutic roles in the treatment of neurodegenerative disorders such as Alzheimer's disease. Specifically, the CB2 agonist JWH-015 was shown to induce macrophages to remove native beta-amyloid protein from frozen human tissues. In patients with Alzheimer's disease, beta-amyloid proteins form aggregates known as senile plaques, which disrupt neural functioning.
Changes in endocannabinoid levels and/or CB2 receptor expressions have been reported in almost all diseases affecting humans, ranging from cardiovascular, gastrointestinal, liver, kidney, neurodegenerative, psychiatric, bone, skin, autoimmune, lung disorders to pain and cancer. The prevalence of this trend suggests that modulating CB2 receptor activity by either selective CB2 receptor agonists or inverse agonists/antagonists depending on the disease and its progression holds unique therapeutic potential for these pathologies
Modulation of cocaine reward
Researchers investigated the effects of CB2 agonists on cocaine self-administration in mice. Systemic administration of JWH-133 reduced the number of self-infusions of cocaine in mice, as well as reducing locomotor activity and the break point (maximum amount of level presses to obtain cocaine). Local injection of JWH-133 into the nucleus accumbens was found to produce the same effects as systemic administration. Systemic administration of JWH-133 also reduced basal and cocaine-induced elevations of extracellular dopamine in the nucleus accumbens. These findings were mimicked by another, structurally different CB2 agonist, GW-405,833, and were reversed by the administration of a CB2 antagonist, AM-630.
Ligands
Many selective ligands for the CB2 receptor are now available.
Agonists
Minocycline
Partial agonists
GW-405,833
Unspecified efficacy agonists
AM-1241
HU-308
JWH-015
JWH-133
L-759,633
L-759,656
Herbal
Echinacea purpurea
Inverse agonists
AM-630
BML-190
JTE-907
SR-144,528
APD371
Binding affinities
Evolution
Paralogues
Source:
CNR1
GPR12
GPR6
S1PR1
S1PR4
S1PR3
S1PR5
S1PR2
LPAR1
GPR3
LPAR3
LPAR2
MC4R
MC5R
GPR119
MC1R
MC3R
MC2R
References
External links
Cannabinoid Receptor 2 (CNR2) Human Protein Atlas
G protein-coupled receptors | Cannabinoid receptor 2 | [
"Chemistry"
] | 2,664 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,044 | https://en.wikipedia.org/wiki/Krak%C3%B3w%20School%20of%20Mathematics%20and%20Astrology | The Kraków School of Mathematics and Astrology () was an influential mid-to-late-15th-century group of mathematicians and astrologers at the University of Kraków (later Jagiellonian University).
Notable members
Jan of Głogów (1445–1507), author of widely recognized mathematical and astrological tracts
Marcin Biem (1470–1540), contributor to the Gregorian calendar
Marcin Bylica of Olkusz (1433–93), later court astrologer to King Matthias Corvinus of Hungary
Albert Brudzewski (1446–1495), teacher to notable scholars active at European universities
Marcin Król of Żurawica (1422–1460)
Nicolaus Copernicus (1473–1543), student at Kraków in 1491–95
See also
Kraków School of Mathematics
Polish School of Mathematics
References
History of education in Poland
Education in Kraków
History of mathematics
Jagiellonian University
Polish mathematics
Astrological organizations | Kraków School of Mathematics and Astrology | [
"Astronomy"
] | 204 | [
"Astronomy stubs",
"Astronomy organizations",
"Astronomy organization stubs"
] |
14,439,211 | https://en.wikipedia.org/wiki/GPR160 | Probable G-protein coupled receptor 160 is a protein that in humans is encoded by the GPR160 gene. It has been identified as the receptor for Cocaine- and amphetamine-regulated transcript, also known as CART.
References
Further reading
G protein-coupled receptors | GPR160 | [
"Chemistry"
] | 56 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,230 | https://en.wikipedia.org/wiki/GPR82 | Probable G-protein coupled receptor 82 is a protein that in humans is encoded by the GPR82 gene.
G protein-coupled receptors (GPCRs, or GPRs) contain 7 transmembrane domains and transduce extracellular signals through heterotrimeric G proteins.[supplied by OMIM]
References
Further reading
G protein-coupled receptors | GPR82 | [
"Chemistry"
] | 75 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,246 | https://en.wikipedia.org/wiki/Hydroxycarboxylic%20acid%20receptor%201 | Hydroxycarboxylic acid receptor 1 (HCA1), formerly known as G protein-coupled receptor 81 (GPR81), is a protein that in humans is encoded by the HCAR1 gene. HCA1, like the other hydroxycarboxylic acid receptors HCA2 and HCA3, is a G protein-coupled receptor (GPCR). The primary endogenous agonist of HCA1 is lactic acid (and its conjugate base, lactate). More recently, 3,5-dihydroxybenzoic acid has been reported to activate HCA1.
Lactate was initially found to activate HCA1 on fat cells and thereby to inhibit these cells lipolysis i.e., break-down of their fats into free fatty acids and glycerol. Subsequent studies have found that in addition to fat cells, HCA1 is expressed on cells in the brain, skeletal muscle, lymphoid tissue, uterus, kidney, liver, and pancreas as well as on immune cells such as macrophages and antigen-presenting cells. In the brain, HCA1 acts to dampen neuron excitation and may also function to promote neurogenesis (the production of neurons from neural stem cells) and angiogenesis (the formation of new blood vessels from pre-existing blood vessels). The functions of HCA1 in non-fat and non-neural tissues have not been fully defined but in many cases appear to involve promoting the survival of cells, including various types of cancer cells.
References
Further reading
G protein-coupled receptors | Hydroxycarboxylic acid receptor 1 | [
"Chemistry"
] | 331 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,274 | https://en.wikipedia.org/wiki/Petri%20Net%20Markup%20Language | Petri Net Markup Language (PNML) is an interchange format aimed at enabling Petri net tools to exchange Petri net models. PNML is an XML-based syntax for high-level Petri nets, which is being designed as a standard interchange format for Petri net tools.
It will end up being the second part of the ISO standard ISO/IEC 15909.
PNML grammar is publicly available on its reference site.
The first part of this international standard, provides the mathematical definitions for high-level Petri nets.
These definitions are called the semantic model.
It also provides the graphical form definition, known as High-level Petri Net Graph (HLPNG), and its mapping to the semantic model.
the first part is an international standard.
References
External links
pnml.org - PNML reference site
XML-based standards
Petri nets | Petri Net Markup Language | [
"Technology"
] | 182 | [
"Computer standards",
"XML-based standards"
] |
14,439,377 | https://en.wikipedia.org/wiki/OXGR1 | OXGR1, i.e., 2-oxoglutarate receptor 1 (also known as GPR99, cysteinyl leukotriene receptor E, i.e., CysLTE, and cysteinyl leukotriene receptor 3, i.e., CysLT3) is a G protein-coupled receptor located on the surface membranes of certain cells. It functions by binding one of its ligands and thereby becoming active in triggering pre-programmed responses in its parent cells. OXGR1 has been shown to be activated by α-ketoglutarate, itaconate, and three cysteinyl-containing leukotrienes (abbreviated as CysLTs), leukotriene E4 (i.e., LTE4), LTC4, and LTD4. α-Ketoglutarate and itaconate are the dianionic forms of α-ketoglutaric acid and itaconic acid, respectively. α-Ketoglutaric and itaconic acids are short-chain dicarboxylic acids that have two carboxyl groups (notated as -) both of which are bound to hydrogen (i.e., ). However, at the basic pH levels (i.e., pH>7) in virtually all animal tissues, α-ketoglutaric acid and itaconic acid exit almost exclusively as α-ketoglutarate and itaconate, i.e., with their carboxy residues being negatively charged (notated as -), because they are not bound to (see Conjugate acid-base theory). It is α-ketoglutarate and itaconate, not α-ketoglutaric or itaconic acids, which activate OXGR1.
History
In 2001, a human gene projected to code for a G protein-coupled receptor (i.e., a receptor that stimulates cells by activating G proteins) was identified. Its protein product was classified as an orphan receptor, i.e., a receptor whose activating ligand and function are unknown. The projected amino acid sequence of the protein encoded by this gene bore similarities to the purinergic receptor, P2Y1, and therefore might, like P2Y1, be a receptor for purines. This study named the new receptor and its gene GPR80 and GPR80, respectively. Shortly thereafter, a second study found this same gene, indicated that it coded for a G protein-coupled receptor, had an amino acid sequence similar to two purinergic receptors, P2Y1 and GPR91, and determined that a large series of purine nucleotides, other nucleotides, and derivatives of these compounds did not activate this receptor. The study named this receptor GPR99. A third study published in 2004 reported an orphan G protein-coupled receptor with an amino acid sequence similar to the P2Y receptor family of nucleotides was activated by two purines, adenosine and adenosine monophosphate. The study nominated this receptor to be a purinergic receptor and named it the P2Y15 receptor. However, a review in 2004 of these three studies by members of the International Union of Pharmacology Subcommittee for P2Y Receptor Nomenclature and Classification decided that GPR80/GPR99 is not a receptor for adenosine, adenosine monophosphate, or any other nucleotide. A fourth study, also published in 2004, found that GPR80/GPR99 -bearing cells responded to α-ketoglutarate. In 2013, IUPHAR accepted this report and the names OXGR1 and OXGR1 for the α-ketoglutarate responsive receptor and its gene, respectively. In 2013, a fifth study found that LTE4, LTC4, and LTD4 activated OXGR1. Finally, a 2023 study provided evidence that itaconate also activated OXGR1.
OXGR1 gene
The human OXGR1 gene is located on chromosome 13 at position 13q32.2; that is, it resides at position 32.2 (i.e., region 3, band 2, sub-band 2) on the "q" arm (i.e., long arm) of chromosome 13. OXGR1 codes for a G protein coupled-receptor that is primarily linked to and activates heterotrimeric G proteins containing the Gq alpha subunit. When bound to one of its ligands, OXGR1 activates Gq alpha subunit-regulated cellular pathways (see Functions of the Gq alpha pathways) that stimulate the cellular responses that these pathways are programmed to elicit.
OXGR1 activating and inhibiting ligands
Activating ligands
OXGR1 is the receptor for α-ketoglutarate, LTE4, LTC4, LTD4, and itaconate. These ligands have the following relative potencies in stimulating responses in cultures of cells expressing human OXGR1:
LTE4 >> LTC4 = LTD4 > α-ketoglutarate = itaconate
LTE4 is able to stimulate responses in at least some of its target cells at concentrations as low as a few picomoles/liter whereas LTC4, LTD4, α-ketoglutarate, and itaconate require far higher levels to do so.
The relative potencies that LTC4, LTD4, and LTE4 have in activating their target receptors, i.e., cysteinyl leukotriene receptor 1 (CysLTR1), cysteinyl leukotriene receptor 2 (CysLTR2), and OXGR1 are:
CysLTR1: LTD4 > LTC4 >> LTE4
CysLTR2: LTC4 = LTD4 >> LTE4
OXGR1: LTE4 > LTC4 > LTD4
These relationships suggest that CysTR1 and CysLTR2 are physiological receptors for LTD4 and LTC4 but due to its relative weakness in stimulating these two receptors, perhaps not or to a far lesser extent for LTE4. Indeed, the LTE4 concentrations needed to activate CysTR1 and CysLTR2 may be higher than those that normally occur in vivo (see Functions of OXGR1 in mediating the actions of LTE4, LTD4, and LTC4). These potency relationships suggest that the LTE4's actions are mediated primarily by OXGR1. The following findings support this suggestion. First, pretreatment of guinea pig trachea and human bronchial smooth muscle with LTE4 but not with LTC4 or LTD4 enhanced their smooth muscle contraction responses to histamine. This suggests LTE4's target receptor differs from the receptors targeted by LTC4 and LTD4. Second, LTE4 was as potent as LTC4 and LTD4 in eliciting vascular leakage when injected into the skin of guinea pigs and humans; the inhalation of LTE4 by asthmatic individuals caused the accumulation of eosinophils and basophils in their bronchial mucosa whereas the inhalation of LTD4 did not have this effect; and mice engineered to lack CysLTR1 and CysLTR2 receptors exhibited edema responses to the intradermal injection of LTC4, LTD4, and LTE4 but LTE4 was 64-fold more potent in triggering this response in these mice than in wild type mice. Since LTE4 should have been far less active than LTC4 or LTD4 in triggering vascular leakage, the recruitment of the cited cells into the lung, and causing vascular edema responses in mice lacking CysLT1 and CysLT2 receptors, these findings imply that the latter two receptors are not the primary receptors mediating LTF4' actions. And third, mice engineered to lack all three CysLTR1, CysLTR2, and OXGR1 receptors did not exhibit dermal edema responses to the injection of LTC4, LTD4, or LTE4 thereby indicating that at least one of these receptors was responsible for each of their actions. Overall, these findings suggest that LTE4 commonly acts through a different receptor than LTC4 and LTD4 and that this receptor is OXGR1. Indeed, studies have defined OXGR1 as the high affinity receptor for LTF4. Nonetheless, several studies have reported that cultures of certain types of inflammatory cells, e.g., the human LAD2 (but not LUVA) mast cell lines, T helper cell lymphocytes that have differentiated into Th2 cells, and mouse ILC2 lymphocytes (also termed type 2 innate lymphoid cells) The levels of LTE4 used in some of these studies may not develop in animals or humans. In all events, dysfunctions caused by deleting the OXGR1 gene in cells, tissues or animals and dysfunctions in humans that are associated with a lack of a viable OXGR1 gene implicate the lack of OXGR1 protein in the development of these dysfunctions.
Inhibiting ligand
OXGR1 is inhibited by Montelukast, a well-known and clinically useful receptor antagonist, i.e., inhibitor, of CysLTR1 but not CysTR2 activation. (Inhibitors of CysLTR2 have not been identified.) In consequence, Montelukast blocks the binding and thereby the actions of LTE4, LTC4, and LTD4 that are mediated by OXGR1. It is presumed to act similarly to block the actions of α-ketoglutarate and itaconate on OXGR1. It is not yet known if other CysLTR1 inhibitors can mimic Montelukast in blocking OXGR1's responses to α-ketoglutarate and itaconate. Montelukast is used to treat various disorders including asthma, exercise-induced bronchoconstriction, allergic rhinitis, primary dysmenorrhea (i.e. menstrual cramps not associated with known causes, see causes of dysmenorrhea), and urticaria (see Functions of CysLTR1). While it is likely that its inhibition of CysLTR1 accounts for its effects in these diseases, the ability of these leukotrienes, particularly LTE4, to stimulate OXGR1 allows that Montelukast's effects on these conditions may be due at least in part to its ability to block OXGR1.
Expression
Based on their content of the OXGR1 protein or mRNA that directs its synthesis, OXGR1 is expressed in human: a) kidney, placenta, and fetal brain; b) cells that promote allergic and other hypersensitivity reactions, i.e., eosinophils and mast cells; c) tissues involved in allergic and other hypersensitivity reactions such as the lung trachea, salivary glands, and nasal mucosa; and d) fibroblasts, i.e., cells that synthesize the extracellular matrix and collagen (when pathologically activated, these cells produce tissue fibrosis). In mice, Oxgr1 mRNA is highly expressed in kidneys, testes, smooth muscle tissues, nasal epithelial cells, and lung epithelial cells.
Functions
Associated with OXGR1 gene defects or deficiencies
The following studies have defined OXGR1 functions based on the presence of disorders in mice or humans that do not have a viable OXGR1 protein. It is not been determined which of OXGR1's ligands, if any, are responsible for stimulating OXGR1 to prevent these disorders.
Otitis media
Mice lacking OXGPR1 protein due the knockout of their OXGR1 gene developed (82% penetrance) otitis media (i.e., inflammation in their middle ears), mucus effusions in their middle ears, and hearing losses all which had many characteristics of human otitis media. The study did not find evidence that these mice had a middle ear bacterial infection. (Infection with Streptococcus pneumoniae, Moraxella catarrhalis, or other bacteria is one of the most common causes of otitis media.) While the underlying mechanism for the development of this otitis has not been well-defined, the study suggests that OXER1 functions to prevent middle ear inflammations and Oxgr1 gene knockout mice may be a good model to study and relate to human ear pathophysiology.
Goblet cells
Mice lacking OXGR1 protein due the knockout of their OXGR1 gene had significantly fewer numbers of mucin-containing goblet cells in their nasal mucosa than control mice. Cysltr1 gene knockout mice and Cysltr2 gene knockout mice had normal numbers of these nasal goblet cells. This finding implicates OXGR1 in functioning to maintain higher numbers of airway goblet cells.
Kidney stones and nephrocalcinosis
Majmunda et al. identified 6 individuals from different families with members that had histories of developing calcium-containing kidney stones (also termed nephrolithiasis) and/or nephrocalcinosis (i.e., the deposition of calcium-containing material in multiple sites throughout the kidney). Each of these 6 individuals had dominant variants in their OXGR1 gene. These variant genes appeared (based on their OXGR1 gene's DNA structure as defined by exome sequencing) to be unable to form an active OXGR1 protein. The study proposed that the OXGR1 gene is a candidate for functioning to suppress the development of calcium-containing nephrolithiasis and nephrocalcinosis in humans.
Associated with α-ketoglutarate-regulated functions
Studies in rodents have found that the ability of α-ketoglutarate to regulate various functions is dependent on its activation of OXGR1 (see OXGR1 receptor-dependent bioactions of α-ketoglutarate). These functions include: promoting normal kidney functions such as the absorption of key urinary ions and maintenance of acid base balance; regulating the development of glucose tolerance as defined by glucose tolerance tests; suppressing the development of diet-induced obesity; and suppressing the muscle atrophy response to excessive exercise.
Associated with LTE4-induced functions
A study showed that LTE4, LTC4, and LTD4 produce similar levels of vascular leakage and localized tissue swelling when injected into the skin of guinea pigs or humans. Studies that examined the effects of using various doses of these LTs after injection into the earlobes of mice found that, in comparison to control mice, OXGR1 gene knockout mice showed virtually no response to injection of a low dose of LTE4, a greatly reduced response to injection of an intermediate dose of LTE4, and a somewhat delayed but otherwise similar response to a high dose of LTE4 (these doses were 0.008, 0.0625, and 0.5 nmols, respectively). The study concluded that lower levels of LTE4 act primarily through OXGR1 to cause vascular permeability and, since it is the major cysteinyl leukotriene that accumulates in inflamed tissues, suggested that OXGR1 may be a therapeutic target for treating inflammatory disorders. Another study found that the application of an extract of Alternaria alternata (a genus of fungi that infects plants and causes allergic diseases, infections, and toxic reactions in animals and humans) into the noses of mice caused their nasal epithelial cells to release mucin and their nasal submucosa to swell. (The nasal as well as lung epithelial cells of these mice expressed OXGR1). OXGR1 gene knockout mice did not show these responses to the fungal toxin. The study also showed that a) Cysltr1 and Cysltr2 double gene knockout mice had full mucin release response to the toxin and b) Cstlr2 gene knockout mice had full submucosal swelling responses to the toxin but Csltr1 gene knockout mice did not show submucosal swelling responses to the toxin. The study concluded that LTE4's activation of OXGR1 controls key airway epithelial cell functions in mice and suggested that the inhibition of LTE4-induced OXGR1 activation may prove useful for treating asthma and other allergic and inflammatory disorders. A subsequent study examined the effects of LTE4-OXGR1 on a certain type of tuft cell. When located in intestinal mucosa, these tuft cells are termed tuft cells but when located in the nasal respiratory mucosa they are termed solitary chemosensory cells and when located in the trachea they are termed brush cells. Control mice that inhaled the mold Alternaria alternata, the American house dust mite Dermatophagoides farinae, or LTF4 developed increases in the number of their tracheal brush cells, release of the inflammation-promoting cytokine, interleukin 25, and lung inflammation whereas OXGR1 gene knockout mice did not show these responses. These findings indicate that the activation of OXGR1 regulates airway: brush cell numbers, interleukin 25 release, and inflammation.
Associated with itaconate-regulated functions
A study reported in 2023 was the first and to date (2024) only study indicating that itaconate's actions are mediated by activating OXGR1. This study showed that itaconate stimulated the nasal secretion of mucus when applied to the noses of mice, reduced the number of Pseudomonas aeruginosa bacteria in their lung tissue and bronchoalveolar lavage fluid (i.e., airway washing) in mice injected intranasally with these bacteria, and stimulated cultured mouse respiratory epithelium cells to raise their cytosolic Ca2+ levels (an indicator of cell activation). Itaconate was unable to induce these responses in OXGR1 gene knockout mice or in the respiratory epithelial cells isolated from the OXGR1 gene knockout mice. The study concluded that the activation of OXGR1 by itaconate contributes to regulating the pulmonary innate immune response to Pseudomonas aeruginosa and might also do so in other bacterial infections.
References
Further reading
G protein-coupled receptors | OXGR1 | [
"Chemistry"
] | 3,872 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,392 | https://en.wikipedia.org/wiki/GPR78 | Probable G-protein coupled receptor 78 is a protein that in humans is encoded by the GPR78 gene.
G protein-coupled receptors (GPCRs, or GPRs) contain 7 transmembrane domains and transduce extracellular signals through heterotrimeric G proteins.[supplied by OMIM]
References
Further reading
G protein-coupled receptors | GPR78 | [
"Chemistry"
] | 75 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,429 | https://en.wikipedia.org/wiki/C5AR2 | Complement component 5a receptor 2 is a protein of the complement system that in humans is encoded by the C5AR2 gene. It is highly expressed in the blood and spleen, predominantly by myeloid cells.
Function
The anaphylatoxins C3a and C5a are fragments of C3 and C5 generated via proteolytic cleavage by C3 convertases and C5 convertases during the complement cascade. They are pro-inflammatory mediators which bind to the anaphylatoxin receptors, C3aR, C5aR1 and C5aR2. The anaphylatoxin receptors are a family of three proteins which beloing to the G protein-coupled receptor superfamily. C3aR and C5aR1 bind C3a and C5a, respectively, which mediate a broad range of effects in host defense, including chemoattraction, vasodilation and immune cell activation. C5aR2 binds C5a, but lacks GPCR activity, and its function is less well understood.
C5aR2 was initially thought be a decoy receptor, acting as a sink for C5a to negatively regulate C5aR1 function. However, more recent research has uncovered independent roles for C5aR2, including modulation of the innate immune response in myeloid cells, translocation of C5a to drive transendothelial migration of neutrophils, β-arrestin recruitment and modulation of ERK signalling and modulation of lipid metabolism in obesity through C3a-desArg binding. C5aR2 has been implicated in a broad range of inflammatory and infectious diseases.
References
G protein-coupled receptors | C5AR2 | [
"Chemistry"
] | 350 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,450 | https://en.wikipedia.org/wiki/P2RY10 | Putative P2Y purinoceptor 10 is a protein that, in humans, is encoded by the P2RY10 gene.
Function
The protein encoded by this gene belongs to the family of G-protein coupled receptors that is preferentially activated by adenosine and uridine nucleotides. Two alternatively spliced transcript variants encoding the same protein isoform have been found for this gene.
See also
P2Y receptor
References
Further reading
G protein-coupled receptors | P2RY10 | [
"Chemistry"
] | 101 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,463 | https://en.wikipedia.org/wiki/GPR171 | Probable G-protein coupled receptor 171 is a protein that in humans is encoded by the GPR171 gene.
References
Further reading
G protein-coupled receptors | GPR171 | [
"Chemistry"
] | 33 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,487 | https://en.wikipedia.org/wiki/GPR132 | G protein coupled receptor 132, also termed G2A, is classified as a member of the proton sensing G protein coupled receptor (GPR) subfamily. Like other members of this subfamily, i.e. GPR4, GPR68 (OGR1), and GPR65 (TDAG8), G2A is a G protein coupled receptor that resides in the cell surface membrane, senses changes in extracellular pH, and can alter cellular function as a consequence of these changes. Subsequently, G2A was suggested to be a receptor for lysophosphatidylcholine (LPC). However, the roles of G2A as a pH-sensor or LPC receptor are disputed. Rather, current studies suggest that it is a receptor for certain metabolites of the polyunsaturated fatty acid, linoleic acid.
The G2A gene
G2A in humans is encoded by the GPR132 gene. The G2A gene is located on chromosome 14q32.3 codes for two alternative splice variants, the original one, G2A-a, and G2A-b, that consist of 380 and 371 amino acids, respectively; the two receptor variants, when expressed in Chinese hamster ovary cells, gave very similar results when analyzed for functionality. G2A-a and G2A-b mRNA are expressed at similar levels in blood leukocytes ( macrophages, dendritic cells, neutrophils [PMN], mast cells, T lymphocytes and B lymphocytes at the highest levels followed by lower levels in spleen, lung and heart tissues; both variants are expressed at similar levels, and are almost equally induced by DNA synthesis inhibitors (hydroxyurea and cytosine arabinoside) or a differentiation inducer (all-trans retinoic acid) in HL-60 human leukemic cells.
The mouse G2A receptor, encoded by Gpr132, has 67% amino acid identity to human G2A but does not sense pH and does not respond to certain presumptive ligands (i.e. linoleic acid metabolites) that activate the human G2A.
G2A deficiency in mice
Targeted disruption of G2A in mice causes the development of a late onset (> 1 year) slowly progressive wasting and autoimmune disease characterized by lymphoid organ enlargement, lymphocytic infiltration into various tissues, glomerular immune complex deposition, and anti-nuclear autoantibodies. Mice transplanted with bone marrow cells containing the BCR-ABL leukemia-inducing fusion gene but deficient in G2A exhibit expanded populations of leukemic cells compared to recipients of BCR-ABL-containing, G2A-sufficient bone marrow cells. BCR-ABL is the oncogene of the Philadelphia chromosome that causes human Chronic myelogenous leukemia and is sometimes found associated with human acute lymphocytic leukemia and acute myelocytic leukemia; furthermore, the forced expression of BCR-ABL in cultured rodent cells induces the expression of G2A and the overexpression of G2A inhibits the malignant growth to these cells. Thus, the G2A deficiency studies suggest that G2A functions in mice to suppress certain immune dysfunctions and BCR-ABL-related leukemic cell growth.
G2A function
pH sensor
G2A was initially defined as one of the gene products whose production was stimulated in mouse pre-B lymphocytes (see Immunoglobulin heavy chain) by transfecting the cells with the human oncogene (i.e., cancer causing) BCR-ABL or by treating the cells with DNA damaging agents; its expression in these cells blocked their progression through the cell cycle specifically at the G2-M DNA damage checkpoint. These studies allow that G2A limits the potentially malignant growth of certain cells in mice and possible could do so in humans. In addition, Gene knockout studies in mice find G2A to be necessary for suppressing an autoimmune syndrome (see G2A deficiency in mice). These results allow that G2A may function in blocking certain aspects of autoimmunity, particularly those involving the proliferation and tissue trafficking of lymphocytes. Early studies first classified G2A as a proton-sensing receptor and suggested that G2A contributed to the regulation of proliferation in certain cells and the regulation of lymphocytes' contributions to certain immune functions by being activated by changes in extracellular pH. Tissues suffering malignant cell growth, autoimmune reactions, poor blood flow ischemia, inflammation and allergy reactions, and tissue injury develop extracellular acidification due to the stimulation of anaerobic glycolysis; The proton-sensing function of G2A could be involved in combating or, in certain cases promoting these conditions. An example implicating G2A's pH sensitivity in physiological responses involves pain perception. In rats, G2A, similar to other pH sensing GPCRs, is located in dorsal root ganglia neurons, small diameter neurons responsible for nociception, and other nerve tissues responsible for sensing pain; it is suggested that G2A in these nerve tissues detects the acid changes that occur in the extracellular media of injured tissues and signal for the perception of pain
However, the activity of the human G2A receptor and its mouse homolog are significantly less sensitive to pH fluctuations than other pH sensing GPCRs; indeed, in studies of thymocytes and splenocytes taken from mice deficient in either the G2A or another pH-sensing GPCR, TDAG8, TDAG8 was found critical while G2A was found dispensable for sensing pH changes. Thus, the cited functions of G2A presumed due to its pH sensing ability could reflect other means for this receptor's activation.
Receptor for lyso-phospholipids
A report working with human neutrophils proposed that G2A was a receptor for a phospholipid, lysophosphatidylcholine (LPC), and a Sphingomyelin, sphingosylphosphorylcholine. However, these studies did not give evidence that these lyso-phospholipids actually bound to G2A; some 4 years later this report was withdrawn. Nonetheless, many of LPC's activities do depend on G2A; more recent data suggest that rather than acting directly as a ligand that binds to G2A, LPC alters G2A's distribution within the cell by increasing its movement from the cell interior to the cell surface and/or by preventing its movement away from the cell surface to the cell interior. That is, in neutrophils and other cell types which have internal stores of G2A in membrane-bound secretory vesicles, G2A-containing vesicles continuously merge with and move back out of a cell's surface membrane. Lyso-phospholipids may act as a)) detergents to increase a cell's permeability thereby allowing entry of small extracellular molecules such as ionic calcium which trigger the movement of the intracellular vesicles to the surface membrane or b) agents that intercalate or wedge into the cell's surface membrane to promote this vesicle movement or slow this vesicle movement out of the membrane . Such effects increase the expression of G2A at the cell surface membrane which, if G2A has a sub-stimulatory level of activity when normally express but stimulatory when it is overexpressed at the surface membrane, may lead to G2A-dependent cellular responses. With respect to this view, small decreases in extracellular pH reduce the internalization of G2A thereby increasing its surface membrane expression.
LPCs that contain the unsaturated fatty acids hexadecanoic acid or octadecanoic acid bound to their sn-1 act to permeablize, while LPC with the monounsaturated fatty acid, oleic acid at sn-1 act to perturb target cell surface membranes. While not involving G2A receptor binding, some actions of LPCs are G2A-dependent. For example, LPCs increase the bactericidal activity of rodent neutrophils, enhance hydrogen peroxide production in rodent neutrophils triggered by the ingestion of bacteria, stimulate the chemotaxis of human monocytes, and protect mice from the lethal effects of experimentally induced bacterial sepsis endotoxin. G2A may similarly be responsible for the activities of other phospholipids which, like LPC have not been shown to bind to G2A but still require G2A for certain of their activities viz., lysophosphatidylserine and lysophosphatidylethanolamine; these two lyso-phospholipids stimulate calcium signaling pathways in human neutrophils by a G2A dependent mechanism. Furthermore, activated neutrophils greatly increase their surface membrane content of lysophosphatidylserine. In a mouse model, mouse neutrophils with increased levels of lysophosphatidylserine on their surface membrane due to cell activation or artificial addition showed an increase in there engulfment by mouse macrophages in vitro that was dependent on the expression of G2A in the macrophages and an increased rate of clearance in mice by a mechanism that was dependent on the expression of G2A by the mice. Lysophosphotidylserine-laden neutrophils stimulated the G2A-dependent production the proinflammatory mediator, prostaglandin E2, by macrophages in the in vitro studies and inhibited the production of pro-inflammatory mediators, interleukin-6 and keratinocyte chemoattractant, for in vivo studies. G2A is also involved in blood-borne lysophosphatidylcholine (LPC) mediated amplification of microbial TLR ligands induced inflammatory responses from human cells. Taken together, these studies suggest that G2A, activated by certain phospholipids contributes not only to the development but also the resolution of certain inflammation and innate immune responses in mice and may also do so in humans.
Receptor for fatty acid metabolites
The linoleic acid metabolites, 9(S)-hydroxyoctadecadienoic acid (HODE), 9(R)-HODE, and 13(R)-HODE, and the arachidonic acid metabolites 5(S)-hydroxyicosatetraenoic acid (HETE), 12(S)-HETE, 15(S)-HETE, and racemic 5-HETE, 12-HETE, 15-HETE, 8-HETE, 9-HETE, and 11-HETE stimulate Chinese hamster ovary cells made to express G2A; these effects, unlike those of phospholipids, appear to involve and require the binding of the metabolites to G2A as evidenced by the ability of the most potent of these metabolites, 9-HODE to stimulate G2A-dependent functions in membranes isolated from these cells. 9-HODE induces cultured normal human epidermal keratinocytes to stop growing by inhibiting their cell cycle at the G1 stage; it also stimulates these cells to secrete three cytokines that stimulate keratinocyte growth vis., interleukin-6, interleukin-8, and GM-CSF. These activities are G2A-dependent. It is suggested that 9-HODE acts in human skin to block the proliferation of damaged cells while concurrently, by triggering the secretion of the cited cytokines, stimulating the proliferation of undamaged skin cells; these actions may thereby serve to rejuvenate skin damaged for example by UV light.
See also
Proton-sensing G protein-coupled receptors
References
Further reading
G protein-coupled receptors | GPR132 | [
"Chemistry"
] | 2,594 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,684 | https://en.wikipedia.org/wiki/Relaxin/insulin-like%20family%20peptide%20receptor%203 | Relaxin/insulin-like family peptide receptor 3, also known as RXFP3, is a human G-protein coupled receptor.
See also
Relaxin receptor
References
Further reading
External links
G protein-coupled receptors | Relaxin/insulin-like family peptide receptor 3 | [
"Chemistry"
] | 45 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,765 | https://en.wikipedia.org/wiki/S1PR5 | Sphingosine-1-phosphate receptor 5 also known as S1PR5 is a human gene which encodes a G protein-coupled receptor which binds the lipid signaling molecule sphingosine 1-phosphate (S1P). Hence this receptor is also known as S1P5.
Agonists
A-971432
Sphingosine 1-phosphate receptor agonists: a patent review (2010-2012)
Evolution
Paralogues for S1PR5 Gene
S1PR1
S1PR3
S1PR2
S1PR4
LPAR1
LPAR2
GPR3
LPAR3
GPR12
CNR1
GPR6
CNR2
MC4R
MC3R
MC5R
GPR119
MC1R
MC2R
See also
Lysophospholipid receptor
References
Further reading
External links
G protein-coupled receptors | S1PR5 | [
"Chemistry"
] | 181 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,807 | https://en.wikipedia.org/wiki/P2RY13 | P2Y purinoceptor 13 is a protein that in humans is encoded by the P2RY13 gene.
The product of this gene, P2Y13, belongs to the family of G-protein coupled receptors. This family has several receptor subtypes with different pharmacological selectivity, which overlaps in some cases, for various adenosine and uridine nucleotides. This receptor is activated by ADP. Two transcript variants encoding the same protein have been identified for this gene.
See also
P2Y receptor
References
Further reading
External links
G protein-coupled receptors | P2RY13 | [
"Chemistry"
] | 125 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,828 | https://en.wikipedia.org/wiki/GPR84 | Probable G-protein coupled receptor 84 is a protein that in humans is encoded by the GPR84 gene.
Discovery
GPR84 (EX33) was described practically in the same time by two groups. One was the group of Timo Wittenberger in the Zentrum fur Molekulare Neurobiologie, Hamburg, Germany (Wittenberg T. et al.) and the other was the group of Gabor Jarai in Novartis Horsham Research Centre, Horsham, United Kingdom. In their papers they described the sequence and expression profile of five new members of GPC receptor family. One among them was GPR84 which represents a unique GPCR sub-family so far.
Gene
Hgpr84 locates to chromosome 12q13.13, and its coding sequence is not interrupted by introns.
Protein
The human and the murine GPR84 ORFs both encode proteins of 396 amino acid residues length with 85% identity and are therefore considered as orthologs. The hgpr84 was found by Northern blot analysis as a transcript of about 1.5 kb in brain, heart, muscle, colon, thymus, spleen, kidney, liver, intestine, placenta, lung, and leukocytes. In addition, a 1.2 kb transcript in heart and a strong band at 1.3 kb in muscle were detected. A Northern blot from different brain regions revealed strongest expression of the 1.5 kb transcript in the medulla and the spinal cord. Somewhat less transcript was found in the substantia nigra, thalamus, and the corpus callosum. The 1.5 kb band was also visible in other brain regions, but at very low levels. EST clones corresponding to hgpr84 were from B cells (leukemia), neuroendocrine lung as well as in microglial cells and adipocytes. A more detailed description of expression profile can be found in www.genecards.org. The resting expression of GPR84 is usually low but it is highly inducible in inflammation. Its expression on neutrophils can be increased with LPS stimulation and reduced with GM-CSF stimulation. The LPS-induced upregulation of GPR84 was not sensitive to dexamathasone pretreatment. There was also a GPR84 downregulation in dentritic cell derived from FcRgamma chain KO mice. In microglial cells, the GPR84 induction with interleukin-1 (IL-1) and tumor necrosis factor α (TNFα) was also demonstrated. 24 h treatment with IL-1β also induced 5.8 times increase in GPR84 expression on PBMC from healthy individuals. . Transcriptional dynamics of human umbilical cord blood T helper cells cultured in absence and presence of cytokines promoting Th1 or Th2 differentiation was studies. It turned out that GPR84 belongs to the Th1 specific subset genes. While another publication suggests that GPR84 is rather a CCL1 related Th2 type gene.
GPR84 was also upregulated on both macrophages and neutrophyl granulocytes after LPS stimulation. Not only LPS challenge but Staphylococcus enterotoxin B was sufficient to cause a 50 times increase in GPR84 expression on isolated human leukocytes stimulated with compared to the expression of naive leukocytes. A viral infection following Japanese encephalitis virus infection also increased GPR84 expression by 2–4.5% in the mice brain.
Ablating lysosomal acid lipase (Lal-/-) in mice led to aberrant expansion of myeloid-derived suppressive cells (MDSCs) (>40% in the blood, and >70% in the bone marrow) that arise from dysregulated production of myeloid progenitor cells in the bone marrow. Ly6G + MDSCs in Lal-/- mice show strong immunosuppression on T cells, which contributes to impaired T cell proliferation and function in vivo. GPR84 was 9.1 fold upregulated in the MDSCs of Lal-/- mice. GPR84 is normally expressed at low levels in myeloid cells and can be induced in vitro by stimulating macrophage or microglial cells with LPS, TNFα, or PMA. Elevated expression of GPR84 was also observed during the demyelination phase of the reversible Cuprizone-Induced Demyelinating Disease mouse model. Finally, it has also shown that GPR84 expression is increased in both the normal appearing white matter and plaque in brains from human Multiple Sclerosis patients. Expression of GPR84 increases in mouse whole brain samples from experimental autoimmune encephalomyelitis before the onset of clinical disease. In cultured microglia in response to simulated blast overpressure the expression of GPR84 was increased 2.9 fold. In ageing TgSwe mice were subjected to traumatic brain injury GPR84 was upregulated by 6.3 fold. GPR84 expression was increased by 49.9 times in M1 type macrophages isolated from aortic atherosclerotic lesions of LDLR-/- mice were fed a western diet. GPR84 is important in regulating the expression of cytokines: CD4+ T cells from GPR84-/- mice show increase IL-4 secretion in the presence of anti-CD3 and anti-CD28 antibodies; GPR84 potentiates LPS-induced IL12p40 secretion in RAW264.7 cells.
Recent work by Nagasaki et al. explored 3T3-L1 adipocytes cocultured with RAW264.7 cells to examine this potential interaction. RAW264.7 coculture increases GPR84 expression in 3T3-L1 adipocytes, and incubation with capric acid can inhibit TNFα-induced adiponectin release. Adiponectin regulates many metabolic processes associated with glucose and fatty acids, including insulin sensitivity and lipid breakdown. Furthermore, a high-fat diet can increase GPR84 expression. The authors suggest that GPR84 may explain the relationship between diabetes and obesity. As adipocytes release fatty acids in the presence of macrophages, the loop of increased GPR84 expression and its stimulation prevent the release of regulating hormones. The work on GPR84 is still very early and needs to be expanded in the context of pathophysiology and immune regulation. Some people presume the role of GPR84 in food intake too. GPR84 is expressed in the gastric corpus mucosa and this receptor can be an important luminal sensors of food intake and are most likely expressed on entero-endocrine cells, where it stimulates the release of peptide hormones including incretins glucagon-like peptide (GLP) 1 and 2.
Ligands
The ligands for GPR84 suggest also a relationship between inflammation and fatty acid sensing or regulation. Medium-chain free fatty acid (FFA) with carbon chain lengths of C9 to C14. Capric acid (C10:0), undecanoic acid (C11:0) and lauric acid (C12:0) are the most potent described endogeneous agonists of GPR84. Not activated by short-chain and long-chain saturated and unsaturated FFAs induced in monocytes/macrophages by LPS. In addition, the activation of GPR84 in monocytes/macrophages amplifies LPS stimulated IL-12 p40 production in a concentration dependent manner. IL-12 plays an important role in promoting cell mediated immunity to eradicate pathogens by inducing and maintaining T helper 1 responses and inhibiting T helper 2 responses. Medium chain FFAs inhibited forskolin-induced cAMP production and stimulated [35S]GTPgammaS binding in a GPR84-dependent manner. The EC50 values for medium-chain FFAs capric acid, undecanoic acid, and lauric acid at GPR84 (4, 8, and 9 mM, respectively, in the cAMP assay). These results suggest that GPR84 activation by medium-chain FFAs is coupled to a pertussis toxin-sensitive Gi/o pathway. Besides medium-chain FFAs diindolylmethane was also described as GPR84 agonist. However, the target selectivity of this molecule is also questionable because diindolylmethane is an aryl hydrocarbon receptor modulator, too. The patent literature mentions that besides medium chain FFAs other substances as 2,5-Dihydroxy-3-undecyl(1,4)benzoquinon, Icosa-5,8,11,14-tetraynoic acid and 5S,6R-Dihydroxy-icosa-7,9,11,14-tetraenoic acid (5S,6RdiHETE) are also ligands of GPR84. These two latest molecules say against the statement that long chain FFAs are not ligands of GPR84. Based on these results it is probable that besides medium chain FFAs some long chain FFAs can also be endogeneous ligands of GPR84. Further work is needed to confirm this hypothesis.
Classification of GPR84
Based on its binding and activation by medium-chain fatty acids, GPR84 has been recognized as a possible member of the free fatty acid receptor family. However, GPR84 has not yet been given a FFAR designation possibly because capric acid, the most potent medium-chain fatty acid in activating GPR44, requires high concentrations (e.g., in the micromolar range) to do so. This consideration supports the need to search for other naturally-occurring agents that are more potent than caproic acid in activating this receptor. In the meantime, GPR84 continues to be defined as an orphan receptor, i.e., a receptor whose naturally occurring activator(s) is unclear.
Major mediator in pathologic fibrotic pathways
GPR84 has been proposed to be a major mediator in pathologic fibrotic pathways.
Drugs under investigation
The molecule GLPG1205 was under investigation by the Belgian firm Galapagos NV. Its clinical effect against inflammatory disorders like inflammatory bowel disease was being investigated in 2015 in a Phase 2 Proof-of-Concept study in ulcerative colitis patients. The results published in January 2016 showed good pharmacokinetics, safety and tolerability. However, the target efficacy was not met. The development of GLPG1205 for ulcerative colitis was therefore stopped.
The molecule PBI-4050 which inhibits GPR84 signaling is under investigation by the Canadian biotechnology firm Prometic. As of August 2018, it remains a promising drug targeting multiple type of fibrosis entering phase 3 clinical trials.
References
Further reading
G protein-coupled receptors | GPR84 | [
"Chemistry"
] | 2,377 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,837 | https://en.wikipedia.org/wiki/AUSTAL2000 | Austal2000 is an atmospheric dispersion model for simulating the dispersion of air pollutants in the ambient atmosphere. It was developed by Ingenieurbüro Janicke in Dunum, Germany under contract to the Federal Ministry for Environment, Nature Conservation and Nuclear Safety.
Although not named in the TA Luft, it is the reference dispersion model accepted as being in compliance with the requirements of Annex 3 of the TA Luft and the pertinent VDI Guidelines.
Description
It simulates the dispersion of air pollutants by utilizing a random walk process (Lagrangian simulation model) and it has capabilities for building effects, complex terrain, pollutant plume depletion by wet or dry deposition, and first order chemical reactions. It is available for download on the Internet free of cost.
Austal2000G is a similar model for simulating the dispersion of odours and it was also developed by Ingenieurbüro Janicke. The development of Austal 2000G was financed by three German states: Niedersachsen, Nordrhein-Westfalen and Baden-Württemberg.
See also
List of atmospheric dispersion models
UK Dispersion Modelling Bureau
UK Atmospheric Dispersion Modelling Liaison Committee
Further reading
www.crcpress.com
www.air-dispersion.com
References
Atmospheric dispersion modeling | AUSTAL2000 | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 285 | [
"Atmospheric dispersion modeling",
"Environmental modelling",
"Environmental engineering"
] |
14,439,860 | https://en.wikipedia.org/wiki/GPR87 | Probable G-protein coupled receptor 87 is a protein that in humans is encoded by the GPR87 gene.
G protein-coupled receptors play a role in cell communication. They are characterized by an extracellular N terminus, 7 transmembrane regions, and an intracellular C terminus.[supplied by OMIM]
References
Further reading
G protein-coupled receptors | GPR87 | [
"Chemistry"
] | 75 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,889 | https://en.wikipedia.org/wiki/GPR173 | Probable G-protein coupled receptor 173 is a protein that in humans is encoded by the GPR173 gene.
See also
SREB
References
Further reading
G protein-coupled receptors | GPR173 | [
"Chemistry"
] | 37 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,920 | https://en.wikipedia.org/wiki/LGR4 | Leucine-rich repeat-containing G-protein coupled receptor 4 is a protein that in humans is encoded by the LGR4 gene. LGR4 is known to have a role in the development of the male reproductive tract, eyelids, hair and bone.
Mutations in this gene have been associated to osteoporosis (doi:10.1038/nature12124).
References
Further reading
G protein-coupled receptors | LGR4 | [
"Chemistry"
] | 90 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,956 | https://en.wikipedia.org/wiki/Leukotriene%20B4%20receptor%202 | {{DISPLAYTITLE:Leukotriene B4 receptor 2}}
Leukotriene B4 receptor 2, also known as BLT2, BLT2 receptor, and BLTR2, is an Integral membrane protein that is encoded by the LTB4R2 gene in humans and the Ltbr2 gene in mice.
Discovered several years after the leukotriene B4 receptor 1 (BLT1), BLT2 receptor binds leukotriene B4 (LTB4) with far lower affinity than the BLT1 receptor does and therefore has been termed the low affinity LTB4 receptor. Sometime after its initial discovery, the BLT2 receptor was shown to bind and become activated by several other arachidonic acid metabolites, one of which, 12-hydroxyheptadecatrienoic acid (12-HHT), has 10- to 100-fold higher affinity for it than does LTB4; 12-HHT fails to bind or activate BLT1 receptors. While BLT2 receptors have some actions similar to BLT1 receptors, they have other actions which clearly oppose those of BLT1 in regulating inflammation and allergic responses; BLT2 receptors also have actions that extend beyond those of BLT1 receptors. Laboratory, animal, and other pre-clinical studies suggest that BLT2 receptors may be involved not only in inflammation and allergy but also in human cancer.
Function
BLT2 is a cell surface receptor that functions by recognizing, binding, and mediating responses to a particular set of messenger molecules or ligands. These messenger ligands are any one of a range of structurally different arachidonic acid metabolites made and released by nearby cells to act as paracrine signals for coordinating responses between cells or autocrine signals for modulating their parent cells' responses.
Genes
Several years after their identification of a leukotriene B4 (LTB4) receptor termed BLT1 or BLTR1 and encoded by the LTB4R1 gene, Shimizu and colleagues identified a second LTB4 receptor, BLT2 or BLTR2, encoded by the LTB4R2 gene. LTBR1 and LTBR2 encode for proteins with 45% amino acid identity that belong to the G protein-coupled receptor superfamily. The two genes form a cluster on human and mouse chromosome 14; in humans but not mice, this cluster has a very unusual configuration in that LTBR2's open reading frame overlaps the promoter and 5' untranslated region of LTBR1. The significance of this overlap is not known. Monkeys, rats, and dogs have also been shown to express LTB4R2 orthologs.
Two BLT2-like receptors, Blt2a and Blt2b, with 49% amino acid identity to each other and 34% and 29%, respectively, amino acid identities to human BLT2 have been cloned from zebrafish embryos. The latter citation presents a phylogenic tree on the amino acid relatedness of these two receptors as well as those from humans, monkeys, dogs, rats and mice to each other.
Mechanism of action
BLT2 receptors, similar to BLT1 receptors, are G protein-coupled receptors that, when ligand-bound, activate G proteins that contain either the Gi alpha subunit and are therefore inhibited by pertussis toxin or the Gq alpha subunit and therefore not inhibited by pertussis toxin. (Pertussis toxin sensitivity is an imported test for G protein receptor linkages.) BLT2 receptors stimulate cells to transiently elevated cytosolic calcium ion concentrations, thereby activating calcium-activated intracellular signaling molecules; it also stimulates cells to activate extracellular signal-regulated kinases (ERKs), protein kinase B (also known as Akt), c-Jun N-terminal kinases (JNKs), Janus kinase (JAK)-STAT protein (i.e. signal transducer and activator of transcription), NADPH oxidase (NOX), and NF-κB pathways. One prominent cell-activating pathway involves BLT2 receptor activation of NOX2 or NOX1 with the subsequent production of reactive oxygen species which in turn activate the transcription inducing function of NF-κB.
Tissue distribution
The human BLT2 receptor is expressed in a wide range of tissues including spleen, blood leukocytes, liver, ovary, pancreas, heart, prostate gland, testes, small intestine, kidney, lung, colon, thymus, muscle, and placenta; this contrasts with the BLT1 receptor which appears to have a more limited expression pattern including mainly circulating blood leukocytes and lymphocytes. The mouse Blt2 receptor also shows a more limited distribution pattern than the human BLT2 receptor, showing appreciable expression in the small intestine and skin, and low expression in the colon and spleen.
Ligands
While initially defined as a low affinity receptor for the 5-lipoxygenase product of arachidonic acid metabolism, LTB4, BLT2 binds and is activated by not only LTB4 but also the cycloxygenase–thromboxane synthase enzyme pathway of arachidonic acid metabolism, 12-hydroxyheptadecatrienoic acid (12-HHT) as well as by three products of the 12-lipoxygenase pathway of arachidonic acid metabolism, 12(S)-HETE, 12(S)-HpETE, and 12(R)-HETE (see 12-Hydroxyeicosatetraenoic acid), by a member of the 15-lipoxygenase pathway of arachidonic acid metabolism, 15(S)-HETE (see 15-Hydroxyicosatetraenoic acid), and by another member of the LTB4 family of arachidonic acid metabolites, 20-hydroxy-LTB4; the relative BLT2 receptor-binding affinities of these 7 metabolites are ~1000, 100, 10, 10, 3, 3, and 1, respectively. Thus, the most recently discovered ligand, 12-HHT, which does not bind to BLT1 receptors, shows by far the highest affinity of all of the tested ligands for BLT2 receptors. Among these 7 ligand, in contrast, BLT1 binds and is activated by only LTB4 and 20-hydroxy-LTB4.
The two BLT4-like receptors in zebrafish, Blt2a and Blt2b, when transfected into Chinese hamster ovary cells, mediate rises in cytosolic calcium responses to both 12-HHT and LTB4 with 12-HHT being about 500- to 1000-fold stronger that LTB4 in doing so; 12-HHT is inactive in this assay in Chinese hamster ovary cells made to express the zebrafish LTB4 receptor-1 (Blt1). Thus, BLT1 receptor exhibits exquisite specificity, binding 5(S),12(R)-dihydroxy-6Z,8E,10E,14Z-eicosatetraenoic acid (i.e. LTB4) but not LTB4's 12(S) or 6Z isomers whereas the BLT2 receptor exhibits a binding pattern that includes S and R stereoisomers, arachidonic acid metabolites composed of 17 and 20 carbons, and metabolites with a hydroxyl residue at the 5, 12, or 15 position. BLT2's binding pattern can only be considered as promiscuous. This promiscuous binding pattern complicates determination of which arachidonic acid metabolite and which metabolite-forming oxygenase (i.e. cyclooxygenase or lipoxygenase) is responsible for any given BLT2-dependent response. These determinations are often critical to defining the full mechanisms involved in, as well as the means for inhibiting or promoting, the functions of BLT2.
Based on the rather large structural differences in the known BLT2 receptor ligands, there may be other as yet undefined ligands that bind to and activate this receptor. For example, the formyl peptide receptor 2 (FPL2 receptor) was initially suggested to be a second receptor with ~70% amino acid identity to formyl peptide receptor 1 (FPL1 receptor). Both receptor types bind and are activated by a series of formylated oligopeptide chemotactic factors but FLP2 receptor appears to be a promiscuous receptor in that it also binds to and is activated by lipoxins and resolvins as well as various polypeptides and proteins. The FLP2 receptor appears to be engaged primarily in dampening and resolving inflammation responses, actions which appear to be diametrically opposite to the pro-inflammatory actions of FLP1 receptors.
Btr2 knockout mice
The expression of Blt2 receptors in mice appears limited to fewer tissues than the BLT2 receptor in humans; Blt1 is robustly expressed only in mouse small intestine and skin. LTB4R2 knockout mouse studies, therefore, may reveal a more limited role for the BLT2 receptor than that in humans.
BLT2 receptor knockout mice exhibit attenuated ovalbumen-induced allergic airway eosinophilia and interleukin 13 (IL-13) content in their bronchoalveolar lavage fluid compared with wild type mice and CD4-positive T cells isolated from the knockout mice showed a reduction IL-13 production but there was no change in the bronchospasm response to ovalbumin in these mice. The BLT2 receptor and metabolic producing this were not identified. These results indicate that the Blt2 receptor functions to promote the eosinophilic-base inflammation which accompanies and may contribute to allergic lung disease; this effect may be do in part to its ability to reduce production of the pro-allergic cytokine, IL-13; the receptor does not appear to be responsible for allergen-induced bronchospasm. BLT2 receptor could play a similar role in human allergic diseases such as asthma.
In response to the oral administration of the inflammation-inducer dextran sodium sulfate, Blt2 receptor knockout mice, compared to wild type or Blt1 receptor knockout mice, exhibited: a) more severe colitis inflammation and body weight loss; b) increased mRNA expression for the pro-inflammatory cytokines interferon-γ, IL1B, and Interleukin 6, two pro-inflammatory chemokines viz., chemokine ligand 9 (also termed chemokine ligand 10) and chemokine 19 (CCL19), and metalloproteinases-3, -10, and -13 in inflamed colon tissues; c) enhanced accumulation of interferon-producing macrophages in affected colon tissues; d) increased phosphorylation of signal transducer and activator of transcription 3 (i.e. STAT3) in the crypts of affected colon tissue; and e) reduced colon mucosa integrity and barrier function as deduced from the effects of in vitro studies on the impact of BLT2 receptor expression on leakage of FITC-dextran in Madin-Darby canine kidney II cells. These results suggest that Blt2 receptors normally function to suppress colon inflammation in mice; based on its mass content in affected colon tissues, 12-HHT appears at least partly responsible for maintaining this function by stimulating Blt2 receptors. A similar role for the 12-HHT-BLT2 axis could occur in humans and be relevant to diseases such as ulcerative colitis and Crohn's disease.
LTB4R1 gene knockout provides complete protection from the joint inflammation occurring in a mouse model of rheumatoid arthritis (collagen-induced arthritis); double knockout of LTB4R1 and LTB4R2 genes did not alter the complete protection afforded by LTB4R1 knockout. Further evidence for the role of BLT2 in arthritis was seen in a model of serum transfer arthritis where loss of BLT2 led to weakened inflammation and damage to joints.
Thus, the knockout studies available to date assign BLT2 receptors a protective role in dampening certain allergic and inflammatory responses; this role contrasts with the assignment of BLT1 receptors as contributing to both these types of responses. More study is needed to determine if BLT2 receptors protect against other allergic and inflammatory responses and if they function similarly in humans.
Bltr2 transgenic mice
The overexpression of BLT2 receptors in Bltr2 transgenic mice enhances the ability of subcutaneously injected LTB4 and 12-HETE to stimulate new blood vessel formation in skin. Studies indicate that the actions of both ligands were mediated by Blt2 receptors and, that Vascular endothelial growth factor (VEGF) stimulated BLT2 expression and 12-HETE production in Human umbilical vein endothelial cells (HUVEC), and that BLT2 receptor or 12-lipoxygenase knockdown inhibited VEGF-induced angiogenesis in in vitro assays. These results suggest that BLT2 receptors play critical roles in the development of VEGF-induced neovascularization and are of particular interest to the roles of BLT2 receptors in the growth and spread of cancers and in inflammation (see below).
Activities and clinical significance
Allergic airways disease
Mouse bone marrow mast cells and human eosinophils exhibit in vitro chemotaxis responses to 12-HHT. Since both cell types are implicated in allergic reactions, this suggests that BLT2 receptors could contribute to allergic responses in mice and humans. However, in a mouse model of ovalbumin-induced allergic airway disease: a) 12-HHT and its companion cyclooxygenase metabolites, Prostaglandin E2 and Prostaglandin D2, but not 12 other lipoxygenase or cyclooxygenase metabolites showed a statistically significantly increase in bronchoalveolar lavage fluid levels after intratracheal ovalbumin challenge; b) only 12-HHT, among the monitored BLT2 receptor-activating ligands (i.e. LTB4, the 12(S) stereoisomer of 12-HETE, and 15(S)-HETE) rose to a level capable of activating BLT2 receptors; and c) BLT2 knockout mice exhibited a greatly enhanced response to ovalbumin challenge. This study also found that the expression of BLT2 receptors was significantly reduced in CD4+ T cells (which are known to mediate allergy-reactions) taken from asthmatic compared to non-asthmatic human controls. Thus, BLT2 receptors suppress allergic airways disease in mice and may function similarly in humans. These studies also allow that BLT2 receptors play suppressive functions in other allergic diseases.
Inflammation
The high affinity BLT2 receptor agonist, 12-HHT, stimulates in vitro chemotactic responses in human neutrophils, suggesting that this receptor, similar to BLT1 receptors, contributes to inflammation by recruiting circulating blood neutrophils to disturbed tissue sites. Other studies, however, indicate that the role of BLT2 receptors in inflammation is directed toward other cell types than neutrophils and differs very much from that of BLT1 receptors. Immortalized human skin keratinocyte HaCaT cells respond to ultraviolet B (UVB) radiation by generating toxic reactive oxygen species which in turn trigger the cells to become apoptotic and eventually die. This response is BLT2 receptor-dependent since a) topical treatment of mouse skin with a BLT2 receptor antagonist, LY255283, protects against UVB radiation-induced apoptosis; b) BLT2-overexpressing transgenic mice exhibit more extensive skin apoptosis in response to UVB irradiation that wild type mice; and c) 12-HHT inhibits HaCaT cells from synthesizing the pro-inflammation mediator, interleukin-6 (IL-6), in response to UVB radiation. Furthermore, BLT2 receptor knock-out mice mount of more severe intestinal inflammation response to dextran sodium sulfate than either wild type or BLT1 receptor knockout mice (see Knockout studies). Thus, BLT2 receptors appear responsible for suppressing UVB-induced skin inflammation and, in contrast to BLT1 receptors, oppose the development and thereby dampen the severity of experimental colitis in mice.
Cancer
The Ras subfamily of small GTPases function as Signal transduction proteins by transmitting the presence of extracellular stimuli into inducing the expression of genes which regulate cellular survival, proliferation, differentiation, adherence to extracellular matrix, and motility as well as factors that are released to promote new blood vessel formation (i.e. Neovascularization) and to alter the extracellular matrix; the three members of this subfamily, KRAS, NRAS (i.e. Neuroblastoma RAS viral oncogene homolog), and HRAS, develop point mutations to become oncogenes that drive the growth and spread of some 20% of all human cancers. The highest levels of Ras mutations are found in adenocarcinoma of the pancreas (90%), colon (50%), and lung (30%) Bos, 1989).
Ras oncogenes can stimulate arachidonic acid metabolism: a) HRAS, in a rat intestinal epithelial cell line, and KRAS, in a rat lung epithelial cell line, up-regulate COX2 expression and prostaglandin synthesis; b) HRAS induces 12-lipoxygenase in the human epidermoid carcinoma A431 cells; and c) HRAS stimulates the expression of 5-lipoxygenase, 5-lipoxygenase-activating protein, LTB4, and BLT2 receptors Rat2 and a rat fibroblast cell lines thereby increasing the tumor-forming ability the latter cell line in athymic mice. These studies suggest that the metabolites of cyclooxygenase, 5-lipoxygenase, and 12-lipoxygenase, i.e. 12-HHT, LTB4, and 12-HTE, respectively, may act through BLT2 receptors to contribute to the growth and spread of cancers initiated and/or oncogenic Ras and possibly other oncogenes. This is supported by findings that BLT2 is abnormally expressed in many human cancers that concurrently overexpress these arachidonic acid metabolizing pathways viz., follicular thyroid adenoma, renal cell carcinoma, urinary bladder transitional cell carcinoma, esophagus squamous cell carcinoma, colon adenocarcinoma, the serous cystadenocarcinoma type of ovarian cancer, and uterine cervical carcinoma. Other studies have implicated BLT2 in these and other types of cancer as follows.
Prostate cancer
12-HHT stimulates the PC3 human prostate cancer cell line to activate several pro-growth and/or pro-survival signaling pathways including protein kinase B, phosphoinositide 3-kinase, protein kinase C, proto-oncogene tyrosine-protein kinase Src, and (by inducing the proteolytic cleavage and release of a ligand for the epidermal growth factor receptor [EGFR] receptor from HB-EGF), EGFR. When detached from surfaces, cultured non-malignant PWR-1E and PC3 prostate cancer cells die by engaging suicidal apoptosis pathways, a reaction termed anoikis. This is accompanied by increased expression of BLT2 receptors, activation of NADPH oxidase (NOX), increases in NOX-mediated production of reactive oxygen species (ROS), and ROS-induced activation of the pro-survival transcription factor, NF-κB. Ectopic expression and stimulation of BLT2 receptors by 12(S)-HETE or a synthetic BLT2 receptor agonist, CAY-10583, inhibits whereas Gene knockdown by mRNA interference or pharmacological inhibition by LY255283 enhances these cells' anoikis response to surface detachment. Unlike PC-3 cells, LNCaP and CWR22rv-1 human prostate cancer cell lines require exogenous androgen for their survival; this mimics the androgen dependency exhibited by most human prostate cancers in their early, untreated stages. Both cell lines overexpress BLT2 receptors compared to the PWR-1E non-malignant human prostate cell line. Treatment with the BLT2 receptor antagonist, Ly255283, caused both cell lines to become apoptotic; furthermore, BLT2 receptor knockdown using interference mRNA caused LNCaP but not PWR-1E cell apoptosis. The effect appears due to the loss of BLT2-induced NOX4 generation, consequential reactive oxygen species-induced NF-κB-activation, and NF-κB-stimulated expression of androgen receptors. 12-HETE also increases the survival of PC-3 cells by helping to maintain high levels of phosphorylated Rb retinoblastoma protein, an effect which reduces the ability of retinoblastoma protein to inhibit the synthesis of DNA and thereby cell division. Finally, 12-lipoxygenase is overexpressed and the mass of 12-HETE is far higher in human prostate cancer than nearby normal prostate tissue; These findings suggest that BLT2 receptors operate to promote the survival, growth, and spread of human prostate cancer It remains unclear which if any of its 12-HHT, LTB4, and/or 12-HETE ligands mediate BLT2 receptor activation in the human disease.
Urinary bladder cancer
LTB4 and 12(S)-HETE stimulate the invasiveness in an in vitro Matrigel invasion assay of highly malignant human 253 J-BV urinary bladder cancer cell; their activity in this assay is completely inhibited by a pharmacological inhibition or siRNA knockdown of BLT2 receptors. The expression of 5-lipoxygenase, 5-lipoxygenase-activating protein, 12-lipoxygenase (enzymes synthesizing LTB4 and 12(S)-HETE, respectively) as wells as LTB4 and 12(S)-HETE were substantially elevated in these cells. Pretreatment of these cells with an inhibitor of BLT2 receptors, reduced their tumor forming ability after injection into mice; intraperitoneal injections of LY255283 into the mice also decreased the metastasis-forming ability of the cells after injection in the urinary bladder. Finally, BLT2 receptor protein was over expressed by the malignant tissues of human urinary bladder cancer and this expression was positively associated with the severity of this cancer. The action of BLT2 receptors, similar to their actions on prostate cancer cells, appeared to involve the receptors activation of the NOX, reactive species of oxygen, NK-κB pathway. These results suggest that BLT2 receptors contribute to the aggressiveness and progression of human urinary bladder cancer.
Breast cancer
Compared to non-malignant IMR-90 and immortalized but non-malignant MCF-10A human breast cancer cell lines, MCF-7, ZR-75-1, T47-D, MDA-MB-231, MDA-MB-468, MDA-MB-453, and SK-BR-3 human breast cancer cell lines (see list of breast cancer cell lines) overexpress BLT2 mRNA and protein but show relatively little expression of BLT1 mRNA; treatment of the malignant but not non-malignant cells with a BLT2 antagonist, LY255283, but not a BLT1 antagonist, U75302, blocked proliferation of the cells in culture. LY255283 concurrently caused apoptosis in estrogen receptor negative MDA-MB-468 and MDA-MB-453 but not estrogen receptor positive MCF-7 and T47-D malignant cells. Since LY255283 also inhibits the BLT1 receptor, the apoptosis-inhibiting action of BLT2 receptors was also demonstrated by showing that siRNA-induced transient gene knockdown of BLT2 receptors caused apoptosis in the MDA-MB-468 cell line. BLT2 receptors link to the activation of the NADPH oxidase, NOX1 (a synthesizer of the superoxide anion which is a reactive oxygen species that, when inappropriately overproduced, causes cell death and tissue injury); the attendant increased production of reactive oxygen species and activation of NF-κB appeared responsible for these BLT-2 receptor dependent effects. Lipopolysaccharide (i.e. endotoxin) stimulates MDA-MB-231 and MDA-MB-435 cells to increase their invasiveness as determined with in vitro Matrigel Invasion Chamber assays; this effect appears due to its ability to induce the overexpression of BLT2 receptors, the enzymes which produce LTB4 and 12(S)-HETEs, and the key metabolites of these enzymes, LTB4 and 12(S)-HETE; furthermore, the latter the binding of the latter metabolites to cells overexpressed BLT2 receptors leads to the activation of NF-κB. These results indicate that the 12-HETE/BLT2 interaction reduces the survival of cultured human breast cells by stimulating the production of reactive oxygen species and the activation of NF-κB.
Epithelial–mesenchymal transition, a process whereby epithelial cells assume a mesenchymal phenotype, is proposed to occur in a subset of cells in various cancer tissues to promote their movement from a tumor site into blood and lymphatic vessels and thereby form distant metastases. Human breast cancer often expresses and appears promoted by Ras proteins (see carcinogenesis and the Ras subfamily). The forced expression of oncogenic Ras in cultured human MCF-10A breast cancer cells markedly up-regulates BLT2 receptors and this up-regulation appears essential for the epithelial–mesenchymal transition-promoting ability of transforming growth factor beta in these cells; BLT2 receptors in these cells appear to stimulate the production of reactive oxygen species and activation of NF-κB and may thereby contribute to the metastatic ability of breast cancer.
Since BLT2 receptors are significantly elevated in human breast cancer tissue compared to non-cancerous breast tissue, the cited studies, when taken together, indicate that BLT2 receptors promote the malignant growth, invasiveness, metastasis and possibly anti-cancer drug resistance of not only cultured human breast cancer cells but also of human breast cancer.
Ovarian cancer
Compared to CAOV-3 human ovarian cancer cells, SKOV-3 and CAOV-3 human ovarian cancer cells over express BLT4 receptors, LTB4 and 12-HETE metabolizing enzymes, two key metabolites of these enzymes, LTB4 and 12-HETE, and activated STAT3 also are far more invasive in animal models. Inhibition of BLT2 receptors by LY255283 but not of BLT1 receptors by U75302 and suppression of BLT2 receptors by siRNA treatment reduced the expression of NOX4 (i.e. NADPH oxidase 4, the reactive oxygen species made by this enzyme, activated STAT3, the invasion-promoting enzyme, MMP 2, and the in vitro invasiveness (Matrigel invasion assay) of SKOV-3 and CAOV-3 cells. LY255283 also inhibited the peritoneum metastasis of intra-peritoneal injected SKOV-3 cells in athymic mice. These studies indicate that the stimulation of BLT4 receptors by LTB4 and/or 12-HETE operate through a NOX4-reactive oxygen species-STAT-3-MMP2 pathway to promote the metastasis of SKOV-3 and CAOV-3 cancer cells in mice and may act similarly to promote metastases in human ovarian cancer.
Pancreatic cancer
BLT2 receptor protein and mRNA was found to be markedly elevated in human advanced pancreatic intraepithelial neoplasias in their primary pancreas sites as well as in lymph node metastasis sites; mRNA for BLT1 was also elevated in these tissues but to a ~5-fold greater extent. Both receptors' mRNA were also expressed in a wide range of human pancreas cancer cell lines with BLT1 receptor mRNA ~2-fold greater than that for BLT2. The stable over expression of BLT2 in AsPC-1, Colo357, and PANC-1 human pancreas cancer cell lines increased these cells' in vitro growth rates; specific BLT2 agonists also stimulated Colo367 and Panc-1 cell growth. BLT2 receptors mediated the in vitro migration of Panc-1 cells. These results allow that BLT2 receptors may contribute to the malignant growth and metastasis of human pancreas cancer.
Colon cancer
The proliferation of Caco-2 human epithelial colorectal adenocarcinoma cells in culture was stimulated by 12-HETE and inhibited by a somewhat selective inhibitor of 12-lipoxygenase, baicalein; the stimulatory effect of 12-HETE appeared due to its interaction with BLT2 receptors based on the effects of pharmacological inhibitors.
Esophageal cancer
Esophagus squamous cell carcinoma overexpresses BLT2 receptors.
Other activities
The BLT2 receptor mediates the itch scratching behavior induced by intradermal injection of 12-HETE in mice.
Antagonist
LY255283 has been presented as a "selective" BLT2 receptor antagonist. However, this compound is also a BLT1 receptor agonists and therefore cannot be used to discriminate between these two receptor types. In all of the studies using LY255283 quoted above, other methods, such as siRNA knockdown, were used in conjunction with LY255283 to identify BLT2-dependency. Currently, there are no reports on selective BLT2 receptor antagonists.
See also
Eicosanoid receptor
12-Hydroxyheptadecatrienoic acid
12-Hydroxyeicosatetraenoic acid
15-Hydroxyicosatetraenoic acid
References
Further reading
External links
G protein-coupled receptors | Leukotriene B4 receptor 2 | [
"Chemistry"
] | 6,568 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,439,978 | https://en.wikipedia.org/wiki/SUCNR1 | Succinate receptor 1 (SUCNR1), previously named G protein-coupled receptor 91 (GPR91), is a receptor that is activated by succinate, i.e., the anionic form of the dicarboxylic acid, succinic acid. Succinate and succinic acid readily convert into each other by gaining (succinate) or losing (succinic acid) protons, i.e., H+ (see Ions). Succinate is by far the predominant form of this interconversion in living organisms. Succinate is one of the intermediate metabolites in the citric acid cycle (also termed the TCA cycle or tricarboxylic acid cycle). This cycle is a metabolic pathway that operates in the mitochondria of virtually all eucaryotic cells. It consists of a series of biochemical reactions that serve the vital function of releasing the energy stored in nutrient carbohydrates, fats, and proteins. Recent studies have found that some of the metabolites in this cycle are able to regulate various physiological and pathological functions in a wide range of cell types. The succinyl CoA in this cycle may release its bound succinate; succinate is one of these mitochondrial-formed bioactive metabolites.
SUCNR1 is a G protein-coupled receptor (GPR). GPRs are cell surface receptors that bind any one of a specific set of ligands which they recognize and thereby are activated to elicit certain types of responses in their parent cells. The human SUCNR1 protein is encoded (i.e. its synthesis is directed) by the SUCNR1 gene. This gene is located at band position 25.1 on the long (i.e., "q") arm of human chromosome 3 (gene location notated as 3q25.1). Most studies have reported that the SUCNR1 protein consists of 330 amino acids although a few studies have detected a 334 amino acid product of this gene.
Cells exposed to a potentially tissue-damaging condition (e.g., severe inflammation, low energy levels due to excessive physical activity, or ischemia, i.e., shortage of the oxygen needed for cellular metabolism) develop rising levels of succinate in their mitochondrial matrix. The excess mitochondrial succinate flows into the cells' cytoplasm, adjacent extracellular matrix, and circulatory system. In addition, the succinate in food as well as that released by certain microorganisms and helminths (i.e., parasitic worms) in the gastrointestinal tract are absorbed into the walls of the small and large intestines. The succinate released by cells works as a signaling molecule to stimulate diverse functions in cells near or, after entering the circulation, far from the cells of origin while the intestinal succinate may stimulate cells in the intestines' walls. The stimulating actions of succinate often involve the activation of the SUCNR1 on cells. However, succinate can also alter cell functions by succinylating (i.e., covalently binding as a succinyl group to) lysine amino acid residues in various proteins, by stabilizing the transcription factor HIF1A, by stimulating the production of reactive oxygen species, or by altering the expression of various genes (see Biological functions of succinate). Consequently, studies implicating SUCNR1 in the actions of succinate should show that its actions are suppressed by reducing the expression of SUCNR1, by blocking succinate's binding to SUCNR1. or by inhibiting the activity of SUCNR1.
The research conducted to date on the function of SUCNR1 has been mostly preclinical studies in animals. These studies have shown that the activation of SUCNR1 by succinate produces a wide range of beneficial or detrimental effects on: the breakdown of fat tissue triglycerides; obesity; fatty acid levels in the liver; certain fatty acid liver diseases; blood glucose levels; diabetes; and certain heart, kidney, eye, vascular, and inflammatory diseases; and certain cancers. Consequently, the use of methods that stimulate or inhibit SUCNR1 to treat these diseases runs the risk of producing very undesirable side effects. Studies are needed to better define the beneficial versus detrimental effects of these treatments in mice and carry the studies to humans in order to determine if blocking or promoting SUCNR1's actions can be used as a safe treatment strategy.
Cells and tissues expressing SUCNR1
SUCNR1 is expressed by human: a) hepatic stellate cells (i.e., pericytes found in the perisinusoidal space of the liver); b) neutrophils, macrophages, blood monocytes, monocyte-derived dendritic cells, CD34+ progenitor cells (i.e., bone marrow hematopoietic stem cells used therapeutically to restore hematopoiesis), blood platelets, megakaryocytes (i.e., platelet-producing cells), erythroblasts (i.e., red blood cell precursors), and the erythroleukemia cell line, TF-1; c) adipocytes (i.e., fat cells); d) endothelial cells in the veins and arteries of the placenta and umbilical cord; e) human umbilical vein endothelial cells; f) epithelial cells, fibroblasts, and certain cells in the lamina propria of the small and large intestines; g) mast cells; h) HK-2 cells (a kidney proximal tubule epithelial non-cancerous cell line); i) A549 lung, PC3 prostate, and HT-29 colin cancer cell lines; j) a subset (10%) of nasal solitary chemosensory cells; and k) cells in the retina, particularly retinal pigment epithelium cells.
SUCNR1 activators and inhibitors
Succinate appears to be the primary agent that fully activates human SUCNR1. None of 800 tested compounds and 200 tested carboxylic acids fully activated SUCNR1 except for a) oxaloacetate, malate, α-ketoglutarate (α-ketoglutarate also activates the OXGR1 GPR receptor), and methylmalonate but were 5- to 10-fold less potent than succinate in doing so and b) two compounds/chemicals, cis-epoxysuccinic acid and cis-1,2-cyclopropanedicarboxylic acid, which were respectively similar to and 10- to 20-fold more potent than succinate in activating SUCNR1. Agents that have been found to inhibit SUCNCR1 activation include NF-56-EJ40, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide, and three compounds identified as 2c, 4c, and 5g. 4'-O-methylbavachadone, an active ingredient of the Chinese herbal remedy fructus psoraleae, has been reported to inhibit the binding of succinate to SUCNR1.
Functions regulated by SUCNR1
Lipolysis and obesity
Succinate inhibited the isolated fat tissues of mice from the isoproterenol-induce metabolic hydrolysis of their triglycerides into free fatty acids and glycerol, i.e., it inhibited stimulus-induced lipolysis. However, succinate did not effectively inhibit isoproterenol-stimulated lipolysis in mouse fat tissues that lacked SUCNR1 due to the knockout of their Sucnr1 genes. This anti-lipolysis action was therefore due at least in part to succinate's activation of SUCNR1. In related studies, Sucnr1 gene knockout mice fed a high-fat diet for 20 weeks had significantly higher body fat content than wild type mice (i.e., mice expressing normal levels of SUCNR1) fed this diet. These differences did not occur or were minimal in mice fed a standard diet. Furthermore, the total body weights of Sucnr1 gene knockout mice on the high-fat diet for 4–12 weeks was higher than wild type mice on this diet but by 16 weeks was similar to wild type mice on the standard diet. Thus, SUCNR1 inhibited one feature of high-fat diet-induced obesity, the accumulation of excessive body fat, but had only short-term effects on another of its features, the development of excessive total body weight. Further studies in animal models and human fat tissues are needed in order to understand more fully SUCNR1's role in and relevancy to human lipolysis and obesity.
Glucose metabolism and diabetes
In addition to evidencing increased levels of lipolysis (see preceding section), Sucnr1 gene knockout mice had increased plasma glucose levels, impaired glucose tolerance (i.e., abnormally slow decreases in blood glucose levels in response to a glucose challenge), and increased rates of resting metabolic activity. Some of these symptoms are features of human prediabetes. A study of 1152 type 2 diabetic versus 1152 heathy individuals conducted in China reported that three single-nucleotide polymorphisms (i.e., SNPs) in their SUCNR1 genes (viz., rs73168929, rs1557213 and rs17151584) were significantly more common in the diabetic individuals. (A SNP is a variation in a specifically identified nucleotide of a gene; the variation may alter the production, structure, and/or function of the protein directed to be made by the gene and is often identified as being associated with, and a potential cause of, a specific disease(s).). Gestational diabetes is a persistent increase in blood sugar levels first recognized during a woman's pregnancy and reversing after this pregnancy but over the following 3–6 years associated with a high risk of developing type 2 diabetes. A study of gestational diabetes patients reported that their placental tissues had significantly higher levels of succinate and SUCNR1 than the placentas of non-diabetic women. The study also reported that human umbilical vein endothelial cells (HUVECs) cultured in media with high levels of glucose (i.e., 20 mmol/l) expressed significantly higher levels of SUCNR1 than cells cultured in lower glucose levels (5.5 mmol/l); that succinate stimulated cultured HUVECs to proliferate, migrate, and heal wounds in assays of these functions; and that HUVECs that had their Sucnr1 gene knocked down showed significantly reduce proliferation and migration responses to succinate. Overall, these findings suggest that: a) SUCNR1 modulates glucose metabolism, glucose levels, and insulin resistance to cause a prediabetes-like condition in mice; b) certain SNP variants in the SUCNR1 gene are associated with and may contribute to the development of type 2 diabetes in humans; c) high levels of glucose stimulate HUVECs to increase their levels of SUCNR1; d) succinate-induced activation of the SUCNR1 on HUVECs stimulates their proliferation and motility; e) increases in placental succinate and SUCRN1 levels are closely associated with gestational diabetes; and f) SUCNR1 in the human placenta may be a target for treating excessive placental endothelial cell proliferation.
Liver diseases
Metabolic dysfunction–associated steatotic liver disease (i.e., MASLD), previously termed nonalcoholic fatty liver disease (i.e., NAFLD), is the excessive accumulation of fat in the liver resulting from metabolic disorders such as diabetes, the metabolic syndrome, obesity, and hyperlipidemia but not from excessive alcohol consumption. Nonalcoholic steatohepatitis (i.e., NASH), now termed steatotic liver disease (i.e., SLD), is a stage of MASLD that has higher levels of liver inflammation and may progress to advanced fibrosis, cirrhosis, liver failure, and liver cancer. Studies in mouse models of MASLD progressing to hepatic fibrosis have reported that: a) the levels of succinate (as well as 3-hydroxybutyrate and malate) were higher in the livers of mice on a high-fat diet than mice on a normal diet; b) the levels of SUCNR1 in the liver's hepatic stellate cells were far greater in mice on the high-fat diet than in mice on a normal diet; c) contrasting results were reported in studies finding that Sucnr1 gene knockdown mice fed a MASLD-inducing methionine- and choline-deficient diet had lower levels of steatosis (i.e., fat accumulation) and fibrosis in their livers than wild type mice but other studies finding that Sucnr1 gene knockdown mice feeding on a high-fat, choline deficient MASLD-inducing diet developed higher levels of steatosis and inflammation along with lower levels of fibrosis and glycogen in their livers than wild type mice (These different results may reflect differences in the diet compositions, durations, and/or stages of diseases examined.); d) succinate stimulated increases in the expression of SUCNR1 in cultured hepatic satellite cells that were isolated from the livers of rats or humans; e) analyses of the MASLD livers from patients showed that their livers' fibrosis levels increased with their livers' SUCNR1 levels. and f) the circulating blood levels of succinate were higher in 86 patients with higher fatty liver indexes than in 5 healthy individuals (this index is a composite score based on an individual's waist circumferences, basal metabolic rate, blood triglyceride level, and blood gamma-glutamyl transferase level). Further detailed studies are needed to clarify the role(s) of SUCNR1 in the progression of MASLD to more severe liver disease in mice and humans. The studies do suggest that the fatty liver index may be a useful non-invasive indicator of MASLD in humans.
Heart diseases
Mice treated with intravenous succinate for 5 consecutive days developed ventricular hypertrophy as defined by increases in the size of their cardiac muscle cells. These increases did not occur in SUCNR1 gene knockout mice. Furthermore, 8 patients diagnosed with acute myocardial infarction and/or chronic coronary artery disease had readily detectable serum blood levels of succinate whereas 6 healthy individuals had undetectable serum levels of succinate. These studies suggest that the succinate-induced activation of SUCNR1 plays a key role in pathological cardiomyocyte hypertrophy in mice and support studies to determine if it does so in humans.
Elderly individuals, even if otherwise healthy, can develop cardiac fibrosis severe enough to promote the development of a form of heart failure termed heart failure with preserved ejection fraction, i.e., HFpEF. HFpEF is characterized by diastolic dysfunction (i.e., poor relaxation of the heart's left ventricle) with normal systolic contraction.
Kidney diseases
SUCNR1 is expressed by various cell types in the kidneys of mice including cells in the epithelium of renal tubules, endothelial cells in the glomerulus, and macula densa (i.e., tightly packed cell areas in the ascending limb of the loop of Henle). Studies have shown that, compared to male mice who drank normal water, male mice who drank water containing 4% sodium succinate for 12 weeks developed greatly increased serum, urine, and kidney succinate levels; reduced amounts of urine output without changes in water intake; and pathological changes in their kidneys, e.g., detachment of their proximal tubule brush border epithelial cells, dilation of and urinary cast formation in their renal tubules, vacuolar degeneration (i.e., formation of non-livid vacuoles in the cytoplasm) of their renal tubular cells, and increases in the number of kidney cells dying due to apoptosis. Succinate also caused apoptosis in cultured human kidney-2 cells but its apoptosis-inducing action was greatly reduced in human kidney-2 cells that had their Sucnr1 gene knocked down. These findings, while requiring further studies including some on female mice, suggest that succinate injures kidney tissues in female mice and cultured human kidney-2 cells. This injury involves SUCNR1 activation in cultured human kidney cells.
Age-related macular degeneration
Age-related macular degeneration (AMD) is a disease of the macula (i.e., pigmented area in the center of the retina) that causes progressively increasing loses in central vision with peripheral vision remaining relatively intact (see central versus peripheral vision). By definition, the diagnosis of AMD is restricted to persons older than 55 years. AMD is divided into two forms, dry AMD characterized by the development of numerous large drusen (i.e., lipid-rich deposits that lie beneath the retinal pigment epithelium) and wet AMD characterized by the excessive growth of blood vessels (i.e. neovascularization) beneath the macula and the leakage from these vessels of blood and fluid into the central retina. Typically, AMD begins as dry AMD but at varying times thereafter may be followed by neovascularizations in and around the maucla, i.e., by its progression to wet AMD. Studies in mice showed that the expression of SUCNR1 in the retinal pigment epithelium decreased progressively with age and that Sucnr1 gene knockout mice had signs of premature sub-retinal damage similar to that in dry AMD, e.g., the accumulation of oxidized low-density lipoproteins, abnormal thickening of Bruch's membrane, and increased subretinal microglia. These findings suggest that deficiencies in SUCNR1 are a possible contributing factor to the pathogenesis of dry AMD in mice. A study of 5 patients with wet AMD showed that they had significantly higher levels of succinate in their eyes' aqueous humor than 5 patients who did not have AMD. The high levels of succinate in wet AMD may have acted to promote the development of the neovasculariztions (see Neovascularization section) which underlie the progression of dry to wet AMD. Finally, a gene analysis of 925 individuals with advanced dry AMD and 1199 AMD-free individuals revealed that there was an increased risk of developing advanced dry AMD in individuals that had single-nucleotide polymorphism variants (i.e., rs13315275) in their SUCNR1 gene. Overall, these studies suggest that SUCNR1 acts to prevent or slow the development of dry AMD in mice and humans but may promote the progression of dry to wet AMD in humans. Further studies comparing the aqueous humor succinate levels in individuals with wet AMD to non-AMD and adding studies comparing aqueous humor succinate levels of wet to dry AMD are needed to further test the hypothesis that succinate promotes the progression of dry to wet AMD.
Neovascularization
Retinopathy of prematurity
Retinopathy of prematurity (ROP) is a major cause of visual impairment and blindness in prematurely born infants who received oxygen therapy to combat their presumed low levels of retinal oxygen. Animal studies suggest that low levels of retinal oxygen increase the eye's production of succinate; the high levels of succinate activate retinal SUCNR1 which in turn stimulates neovascularization. In ROP, this retinal neovascularization is excessive, enters the aqueous humor by penetrating through the vitreous membrane that separates the aqueous humor from the retina, and causes traction on the retina, bleeding, and visual impairments including blindness. SUCNR1 is expressed by retinal pigment epithelium cells in humans and ganglion cells in rats. In a model of hypoxia-induced retinopathy of prematurity, rat pups who received oxygen therapy developed under-vascularized retinas. Succinate treatment of these rats promoted neovascularization in their under-vascularized retinas but was significantly less effective in doing so in Susnr1 gene knockdown rats. Thus, succinate-induced activation of SUCNR1 appears to be a signaling pathway that in ROP stimulates the excessive formation new blood vessels and thereby leads to visual defects. Inhibiting the activation of SUCNR1 may prove to be useful for treating infants with excessive retinal neovascularization due to ROP.
Diabetic retinopathy
Diabetic retinopathy is due at least in part to low levels of oxygen in the retina. In a model of streptozotocin-induced diabetic retinopathy, rats developed high blood glucose levels, increased levels of succinate in their retinas, retinal neovascularization, increased permeability of their retinal blood vessels, and thickening of their capillary basement membranes. These effects were significantly reduced in streptozotocin-treated mice who had the levels of SUCNRI in their eyes knocked down by the intraocular injection of lenticular virus containing shRNA directed against their Sucnr1 gene (see Delivery of shRNA). A study of rat pups that used oxygen-deprivation as a model of diabetic retinopathy likewise found that the intraocular injection of shRNA directed against the Sucnrn1 gene suppressed their development of diabetic retinopathy. Studies in humans on the role of the succinate-SUCNR1 axis in diabetic retinopathy could lead to the identification of new therapeutic strategies, i.e., the inhibition of SUCNR1 activation, to treat this disorder.
Vascular occlusions
In a model of muscle ischemia due to reduced blood flow, mice had their right hindlimb femoral artery ligated and partially resected. Following this procedure, their right quadriceps leg muscle was injected daily for 15 days with succinate or the buffered solution that carried the succinate. Compared to buffer-treated mice, succinate-treated mice had significantly higher levels of SUCNR1 in the muscles of their afflicted leg, better blood flow to the afflicted leg, and better recovery of function in their afflicted leg. Thus, succinate injections promoted the neovascularization and thereby recovery of function in the ischemia-damaged limbs of mice. In a cerebral cortex hypoxia-ischemia Rice-Vannucci model of permanent unilateral common carotid artery occlusion, 7 day old mouse pups were exposed to 8% oxygen (normal air level of oxygen is ~21%) for 90 minutes. Wild type and Sucnr1 gene-knockout mice showed a 3-fold increase in the succinate levels of the penumbra (i.e., area surrounding) the ischemic brain tissue 90 minutes after exposure to the 8% oxygen; these succinate levels returned to baseline values within the next 60 minutes. One day after exposure to 8% oxygen, wild type mice showed decreased followed in two days by increased microvascular densities in the penumbral regions whereas Sucnr1 gene knockout mice showed the decrease one day after but not the subsequent increase in penumbral vascularization. Finally, injections of succinate into the mice's cerebral ventricle reduced the size of the infarct (i.e., dead tissue) by more than 50% as determined 3 days after their exposure to low oxygen levels; the infarct size was not reduced in Sucnr1 gene knockout mice. These finding indicate that the succinate-SUCNR1 axis promotes neovascularization and thereby reduces the infarct size after vascular cerebral artery occlusion in mouse pups and suggest the therapeutic possibility that stimulating SUCNR1 may reduce the severity of vascular occlusion diseases such as strokes in humans.
Cancer
Epithelial–mesenchymal transition (EMT) is the transformation of stationary epithelial cells into mobile mesenchymal cells. Cells undergo EMT mainly when they need to be mobile such as during their embryonic development or stressful conditions such as wound healing and the need to repair a damaged tissue. However, recent studies indicate that the cells in localized epithelial cancers can similarly transform into mesenchymal-like cells and thereby attain the ability to migrate, invade adjacent tissues, and metastasize. This pro-malignant transformation may be due at least in some cases to the activation of SUCNR1 by succinate. A) Cultured Lewis lung carcinoma epithelioid mouse cells and four human epithelioid cancer cell lines, A549 lung, PC3 prostate, MCF-7 breast, and HT-29 colon cells, secreted high amounts of succinate into their culture media whereas cultures of non-malignant macrophages isolated from the peritoneal cavity of mice did not secrete detectable amounts of succinate and cultured human gastric epithelial non-malignant cells secreted relatively small amounts of succinate into their culture media. B) Succinate stimulated the migration and tissue-invasiveness of cultured Lewis lung carcinoma, A549, PD3, MCF-7, and HT-29 cells in assays of cell motility and invasiveness. C) A549 cells treated with a short hairpin RNA that knocked down their levels of SUCNR1 had significantly reduced migration responses to succinate. D) A549 cells treated with succinate showed increases in SNAI1, a transcription factor that promotes EMT. E) Metformin (which is an inhibitor of EMT) abolished the migration responses of A549 cells to succinate. F) Succinate stimulated the migration of Lewis lung carcinoma, A549, PC3, and HT-29 cells but did not do so when these cells were pretreated with an antibody that binds to and thereby blocks succinate from binding to SUCNR1. G) Mice injected subcutaneously with Lewis lung carcinoma cells had significantly higher levels of serum succinate 16 days after this injection compared to their pre-injection serum succinate levels. H) Serum succinate levels were significantly elevated in patients with lung cancer, squamous cell carcinomas of the head and neck, and the Cowden syndrome (a syndrome associated with extremely high rates of developing benign and malignant tumors). And, I) serum succinate levels are also elevated in patients with hereditary paragangliomas in the relatively uncommon cases of this disease that are caused by inactivating mutations in one of the four genes that encode for the four proteins that make up the succinate dehydrogenase heterotetrmer, i.e., the SDHD, SDHA, SDHC, and SDHB genes (inactivation of any one of these genes causes paraganglioma cells to produce excessive amounts of succinate). (Serum succinate levels are not elevated in all cancers, e.g., breast cancer patients do not show significant elevations of serum succinate; note also that MFC-7 cells do not express SUCNR1.) These studies suggest: that succinate stimulates SUCNR1 in A549 cells to transition from an epithelial to a mesenchymal phenotype and thereby increase their ability to migrate, invade tissues, and possibly metastasize; that A549, PC3, and HT-29 cells appear to also show SUCNR1-dependent EMT transformations by a SUCNR1-dependent mechanism; that paragangliomas caused by hereditary inactivating mutations in one of the four succinate dehydrogenase genes and possibly other types of cancers that overexpress succinate may be due at least in part to the activation of SUCNR1; and that high serum levels of succinate may indicate the presence of human cancers and thereby be useful markers to define the effectiveness of treating them.
Inflammation
Inflammatory bowel diseases
Studies have implicated the succinate-SUCNR1 axis in the development of inflammatory bowel diseases, i.e., Crohn's disease, ulcerative colitis, infectious cholitis, and various other causes of inflammation in the small and/or large intestines. Studies in mice reported that the only cells expressing SUCNR1 in the small intestine and colon epithelium are tuft cells and that the colon has far fewer tuft cells than the small intestine. Mice drinking water containing 100 mM succinate for 7 days developed intestinal features of type 2 inflammation similar to those evoked by intestinal parasitic worm infections, i.e., their small intestines showed increased numbers of tuft cells and increased numbers and sizes of goblet cells. Mice drinking plain water and Sucnr1 gene knockout mice drinking the succinate-containing water did not show these changes. A second study also found that succinate-containing drinking water caused an intestinal type 2 inflammation response. The study also showed that gastrointestinal infection with a Trichomoniasis parasite was sufficient to induce a type 2 inflammatory response in wild type but not in Sucnr1 gene knockout mice. However, the same experiment examining the response to the gastrointestinal roundworm, Nippostrongylus brasiliensis, found that it caused similar type 2 inflammatory responses in Sucnr1 gene knockout mice and wild type mice. In a model of 2,4,6-trinitrobenzenesulfonic acid (i.e., TNBS)-induced inflammatory bowel disease, the administration of TNBS into the rectums of mice caused within 2 days losses in body weight, shortening of colon lengths, colon histological damage (e.g., inflammatory infiltrates and disruptions of the colon's epithelial architecture), and increased colon tissue levels of SUCNR1. Most of these findings were significantly reduced in SUCNR1 gene knockout mice. These studies indicate that high levels of intestinal succinate activate SUCNR1 to produce inflammatory bowel disease-like changes in the small intestines of mice, that intestinal infections with some but not all pathogens produce SUCNR1-dependent inflammatory bowel disease, and that the TNBS model of chemical-induced colitis is also caused by succinate's activation of SUCNR1. Other studies have reported that: a) patients with Crohn's disease have higher blood plasma levels of succinate than healthy individuals; b) Crohn's disease patients with active disease have higher blood serum levels of SUCNR1 than Crohn's disease patients with inactive disease; c) Crohn's disease patients have higher levels of succinate within the small intestine and higher SUCNR1 levels in their small intestine's walls than individuals without Crohn's disease; d) Crohn's disease patients have higher levels of succinate in the fibroblasts (fibroblasts make extracellular fibrous tissue) isolated from their small intestines than the fibroblasts isolated from the small intestines of patients without inflammatory bowel disease; e) the primary fibroblasts isolated from the intestinal tissue of Crohn's disease patients had higher levels of SUCNR1 than the fibroblasts isolated from the intestines of patients without inflammatory bowel disease; f) succinate stimulated increases in the levels of SUCNR1, two markers of fibrosis (COL1a1, α-SMA), the pro-fibrotic factor TGFβ and the pro-inflammatory cytokine IL1β in primary fibroblasts isolated from patients without inflammatory disease but was far less effective in doing so when these cells had their SUCNR1 levels knocked down; and g) SUCNR1 was significantly increased in the colon tissues of patients with ulcerative colitis compared to patients without inflammatory bowel disease. These findings suggest that succinate-induced activation of SUCNR1 may promote the development of Crohn's disease and support studies to determine if succinate and SUCNR1 are similarly involved in the development of ulcerative colitis.
Autoimmune arthritis
In a murine model of autoimmune arthritis, mice were sensitized to bovine serum albumin (i.e., BSA) by injecting methylated BSA (mBSA) into two sites in the dermis of their backs 14 and 21 days after their right knee was injected with mBSA and their left knee was injected with the solution used to carry mBSA. The mBSA-injected left knees of mice became two-fold larger in size (indicating an increase in inflammation) and had three-fold higher levels of succinate in their synovial (i.e., joint) fluids) than their left knees. Further analyses suggested that the SUCNR1-expressing macrophages in these joints were activated by the rising levels of succinate to elicit inflammation and thereby joint swelling. A second study using this mBSA model found that mBSA-treated mouse knee joints developed hyperalgesia and high numbers of inflammation-inducing neutrophils whereas the mBSA-treated joints of SUCNR1 gene knockout mice did not develop hyperalgesia and had significantly fewer neutrophils. Rheumatoid arthritis is an autoimmune arthritis characterized by symmetric arthritis typically involving the small joints of the hands and feet but also commonly involving arthritis in larger joints and inflammation in a wide range of other tissues such as the lung, gastrointestinal tract, heart (e.g., dysfunction of the heart's microvasculature), and oral cavity. Patients with rheumatoid arthritis have high levels of succinate in the synovial fluid of their inflamed joins and increased numbers of SUCNR1-expressing dendritic cells in the synovial membranes of these joints as well as some lymph nodes. These findings suggest that the succinate-induced activation of SUCNR1 contributes to the development of at least one from of arthritis in mice and may play a similar role in human rheumatoid arthritis. The studies also support further studies to determine if activated SUCNR1 promotes human rheumatoid arthritis.
References
G protein-coupled receptors | SUCNR1 | [
"Chemistry"
] | 7,499 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,036 | https://en.wikipedia.org/wiki/LPAR5 | Lysophosphatidic acid receptor 5 also known as LPA5 is a protein that in humans is encoded by the LPAR5 gene. LPA5 is a G protein-coupled receptor that binds the lipid signaling molecule lysophosphatidic acid (LPA).
See also
Lysophospholipid receptor
References
Further reading
G protein-coupled receptors | LPAR5 | [
"Chemistry"
] | 81 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,076 | https://en.wikipedia.org/wiki/VN1R1 | Vomeronasal type-1 receptor 1 is a protein that in humans is encoded by the VN1R1 gene.
Function
Pheromones are chemical signals that elicit specific behavioral responses and physiologic alterations in recipients of the same species. The protein encoded by this gene is similar to pheromone receptors and is primarily localized to the olfactory mucosa. An alternate splice variant of this gene is thought to exist, but its full length nature has not been determined.
Ligands
Decanal
Hedione
Iso E Super
References
Further reading
G protein-coupled receptors | VN1R1 | [
"Chemistry"
] | 123 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,090 | https://en.wikipedia.org/wiki/GPR126 | G protein-coupled receptor 126 also known as VIGR and DREG is a protein encoded by the ADGRG6 gene. GPR126 is a member of the adhesion GPCR family.
Adhesion GPCRs are characterized by an extended extracellular region often possessing N-terminal protein modules that is linked to a TM7 region via a domain known as the GPCR-Autoproteolysis INducing (GAIN) domain.
GPR126 is all widely expressed on stromal cells. The N-terminal fragment of GPR126 contains C1r-C1s, Uegf and Bmp1 (CUB), and PTX-like modules.
Ligand
GPR126 was shown to bind collagen IV and laminin-211 promoting cyclic adenosine monophosphate (cAMP) to mediate myelination.
Signaling
Upon lipopolysaccharide (LPS) or thrombin stimulation, expression of GPR126 is induced by MAP kinases in endothelial cells. During angiogenesis, GPR126 promotes protein kinase A (PKA)–cAMP-activated signaling in endothelial cells. Forced GPR126 expression in COS-7 cells enhances cAMP levels by coupling to heterotrimeric Gαs/i proteins.
Function
GPR126 has been identified in genomic regions associated with adult height, more specially trunk height, pulmonary function and adolescent idiopathic scoliosis. In the vertebrate nervous system, many axons are surrounded by a myelin sheath to conduct action potentials rapidly and efficiently. Applying a genetic screen in zebrafish mutants, Talbot’s group demonstrated that GPR126 affects the development of myelinated axons. GPR126 drives the differentiation of Schwann cells through inducing cAMP levels, which causes Oct6 transcriptional activities to promote myelin gene activity. Mutation of gpr126 in zebrafish affects peripheral myelination. Monk’s group demonstrated domain-specific functions of GPR126 during Schwann cells development: the NTF is necessary and sufficient for axon sorting, while the CTF promotes wrapping through cAMP induction to regulate early and late stages of Schwann cells development.
Outside of neurons, GPR126 function is required for heart and inner ear development. GPR126 stimulates VEGF signaling and angiogenesis by modulating VEGF receptor 2 (VEGFR2) expression through STAT5 and GATA2 in endothelial cells.
Disease
Mouse models have shown GPR126 deletion to affect cartilage biology and spinal column development, supporting findings that variants of GPR126 have been associated with adolescent idiopathic scoliosis, and Mutations have been shown to be responsible for severe arthrogryposis multiplex congenita
References
External links
Adhesion GPCR consortium
G protein-coupled receptors | GPR126 | [
"Chemistry"
] | 600 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,094 | https://en.wikipedia.org/wiki/Ion%20trapping | In cell biology, ion trapping is the build-up of a higher concentration of a chemical across a cell membrane due to the pKa value of the chemical and difference of pH across the cell membrane. This results in basic chemicals accumulating in acidic bodily fluids such as the cytosol, and acidic chemicals accumulating in basic fluids.
Mechanism
Many cells have other mechanisms to pump a molecule inside or outside the cell against the concentration gradient, but these processes are active ones, meaning that they require enzymes and consume cellular energy. In contrast, ion trapping does not require any enzyme or energy. It is similar to osmosis in that they both involve the semipermeable nature of the cell membrane.
Cells have a more acidic pH inside the cell than outside (gastric mucosal cells being an exception). Therefore, basic drugs (like bupivacaine, pyrimethamine) are more charged inside the cell than outside. The cell membrane is permeable to non-ionized (fat-soluble) molecules; ionized (water-soluble) molecules cannot cross it easily. Once a non-charged molecule of a basic chemical crosses the cell membrane to enter the cell, it becomes charged due to gaining a hydrogen ion because of the lower pH inside the cell, and thus becomes unable to cross back. Because transmembrane equilibrium must be maintained, another unionized molecule must diffuse into the cell to repeat the process. Thus its concentration inside the cell increases many times that of the outside. The non-charged molecules of the drug remain in equal concentration on either side of the cell membrane.
The charge of a molecule depends upon the pH of its solution. In an acidic medium, basic drugs are more charged and acidic drugs are less charged. The converse is true in a basic medium. For example, Naproxen is a non-steroidal anti-inflammatory drug that is a weak acid (its pKa value is 5.0). The gastric juice has a pH of 2.0. It is a three-fold difference (due to log scale) between its pH and its pKa; therefore there is a 1000× difference between the charged and uncharged concentrations. So, in this case, for every one molecule of charged Naproxen, there are 1000 molecules of uncharged Naproxen at a pH of 2. This is why weak acids are better absorbed from the stomach and weak bases from intestine where the pH is alkaline. When pH of a solution is equal to pKa of dissolved drug, then 50% of the drug is ionized, another 50% is unionized. This is described by the Henderson-Hasselbalch equation.
Pharmacokinetics
Ion trapping is the reason why basic (alkaline) drugs are secreted into the stomach (for example morphine), where pH is acidic, and acidic drugs are excreted in urine where the conditions are alkaline. Similarly, ingesting sodium bicarbonate with amphetamine, a weak base, causes better absorption of amphetamine (in stomach) and its lesser excretion (in urine), thus prolonging its actions. Ion trapping can cause partial failure of certain anti-cancer chemotherapies.
Ion trapping is also important outside of pharmacology. For example, it causes weakly acidic hormones to accumulate in the cytosol of cells. This is important in keeping the external concentration of the hormone low in the extracellular environment where many hormones are sensed. Examples of plant hormones that are subjected to ion trapping are abscisic acid, gibberellic acid and retinoic acid. Examples of animal hormones subjected to ion trapping include Prostacyclin and Leukotrienes.
See also
Osmosis
Biophysics
Forced diuresis
Henderson-Hasselbalch equation
References
Pharmacokinetics | Ion trapping | [
"Chemistry"
] | 797 | [
"Pharmacology",
"Pharmacokinetics"
] |
14,440,108 | https://en.wikipedia.org/wiki/GPR158 | Probable G-protein coupled receptor 158 (GPR158), also known as the metabotropic glycine receptor (mGlyR), is a protein that in humans is encoded by the GPR158 gene.
Function
This protein is an orphan class C GPCR. It is highly expressed in the brain, where it binds to RGS7, an inhibitor of Gi/o-coupled GPCR signaling, localizing it to the plasma membrane.
It is expressed at lower levels in other organs and shows an unusual subcellular localization pattern, being found at both the plasma membrane and in the nucleus.
Clinical significance
Role in mood regulation
GPR158 in the medial prefrontal cortex (mPFC) has been shown to regulate stress-induced depression in a mouse model of depression and has been found to be upregulated in post-mortem tissue samples from humans with major depressive disorder (MDD).
Role in prostate cancer
The GPR158 gene is an androgen-regulated gene that stimulates cell proliferation in prostate cancer cell lines, and it is linked to neuroendocrine differentiation.
References
G protein-coupled receptors | GPR158 | [
"Chemistry"
] | 239 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,189 | https://en.wikipedia.org/wiki/Relaxin/insulin-like%20family%20peptide%20receptor%201 | Relaxin/insulin-like family peptide receptor 1, also known as RXFP1, is a human G protein coupled receptor that is one of the relaxin receptors. It is a rhodopsin-like GPCR which is unusual in this class as it contains a large extracellular binding and signalling domain. Some reports suggest that RXFP1 forms homodimers, however the most recent evidence indicates that relaxin binds a non-homodimer of RXFP1.
See also
Relaxin family peptide hormones
Insulin/IGF/Relaxin family
Relaxin
Relaxin-3
References
Further reading
External links
G protein-coupled receptors | Relaxin/insulin-like family peptide receptor 1 | [
"Chemistry"
] | 133 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,221 | https://en.wikipedia.org/wiki/Neuropeptide%20FF%20receptor%201 | Neuropeptide FF receptor 1, also known as NPFF1 is a human protein, encoded by the NPFFR1 gene.
See also
Neuropeptide FF receptor
References
Further reading
External links
G protein-coupled receptors | Neuropeptide FF receptor 1 | [
"Chemistry"
] | 50 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,263 | https://en.wikipedia.org/wiki/Horst%20H.%20Berger | Horst H. Berger (born March 30, 1933) is a German electrical engineer noted for his contributions to semiconductor technologies for integrated circuits.
Berger was born in Liegnitz (Legnica), Lower Silesia, and received the Vordiplom. from the Technische Hochschule of Dresden, then worked at the IBM Laboratories in Böblingen. Afterwards he became a researcher and teacher at Technische Universität Berlin.
Together with Siegfried K. Wiedmann, Berger received the 1977 IEEE Morris N. Liebmann Memorial Award "for the invention and exploration of the Merged Transistor Logic, MTL".
Selected works
H. H. Berger and S. K. Wiedmann, "Merged-Transistor Logic (MTL) – A Low-Cost Bipolar Logic Concept", IEEE Journal of Solid-State Circuits, vol. SC-7, No. 5, Oct. 1972, pp. 340–346.
References
Fruchtbare Quelle: Horst Berger wurde 70 (German)
Contributors, IEEE Journal of Solid-State Circuits, Volume 7, Issue 5, pages 435–440. October 1972.
1933 births
Living people
People from Legnica
German electrical engineers
IBM employees
People from the Province of Lower Silesia
Academic staff of Technische Universität Berlin
Computer hardware engineers
Semiconductor technology | Horst H. Berger | [
"Materials_science",
"Technology",
"Engineering"
] | 274 | [
"Computer engineering",
"Microtechnology",
"Computer engineering stubs",
"Computing stubs",
"Semiconductor technology"
] |
14,440,276 | https://en.wikipedia.org/wiki/GPR135 | Probable G-protein coupled receptor 135 is a protein that in humans is encoded by the GPR135 gene.
References
Further reading
G protein-coupled receptors | GPR135 | [
"Chemistry"
] | 33 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,470 | https://en.wikipedia.org/wiki/GPR157 | Probable G-protein coupled receptor 157 is a protein that in humans is encoded by the GPR157 gene.
References
Further reading
G protein-coupled receptors | GPR157 | [
"Chemistry"
] | 33 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,503 | https://en.wikipedia.org/wiki/Indirect%20agonist | In pharmacology, an indirect agonist or indirect-acting agonist is a substance that enhances the release or action of an endogenous neurotransmitter but has no specific agonist activity at the neurotransmitter receptor itself. Indirect agonists work through varying mechanisms to achieve their effects, including transporter blockade, induction of transmitter release, and inhibition of transmitter breakdown.
Mechanisms of indirect agonism
Reuptake inhibition
Cocaine is a monoamine transporter blocker and, thus, an indirect agonist of dopamine receptors. Cocaine binds the dopamine transporter (DAT), blocking the protein's ability to uptake dopamine from the synaptic cleft and also blocking DAT from terminating dopamine signaling. Blockage of DAT increases the extracellular concentration of dopamine, therefore increasing the amount of dopamine receptor binding and signaling.
Dipyridamole inhibits reuptake of adenosine, resulting in greater extracellular concentrations of adenosine. Dipyridamole also inhibits the enzyme adenosine deaminase, the enzyme that catalyzes the breakdown of adenosine.
Evoking transmitter release
Fenfluramine is an indirect agonist of serotonin receptors. Fenfluramine binds to the serotonin transporter, blocking serotonin reuptake. However, fenfluramine also acts to induce non-exocytotic serotonin release; in a mechanism similar to that of methamphetamine in dopamine neurons, fenfluramine binds to VMAT2, disrupting the compartmentalization of serotonin into vesicles and increasing the concentration of cytoplasmic serotonin available for drug-induced release.
References
Biomolecules
Proteins
Neurotransmitters
Medical terminology
Pharmacodynamics
Physiology | Indirect agonist | [
"Chemistry",
"Biology"
] | 388 | [
"Pharmacology",
"Biomolecules by chemical classification",
"Natural products",
"Physiology",
"Pharmacodynamics",
"Neurotransmitters",
"Organic compounds",
"Biomolecules",
"Structural biology",
"Biochemistry",
"Proteins",
"Neurochemistry",
"Molecular biology"
] |
14,440,793 | https://en.wikipedia.org/wiki/Magnetic%20resonance%20spectroscopic%20imaging | Magnetic resonance spectroscopic imaging (MRSI) is a noninvasive imaging method that provides spectroscopic information in addition to the image that is generated by MRI alone.
Whereas traditional magnetic resonance imaging (MRI) generates a black-and-white image in which brightness is determined primarily by the T1 or T2 relaxation times of the tissue being imaged, the spectroscopic information obtained in an MRSI study can be used to infer further information about cellular activity (metabolic information). For example, in the context of oncology, an MRI scan may reveal the shape and size of a tumor, while an MRSI study provides additional information about the metabolic activity occurring in the tumor. MRSI can be performed on a standard MRI scanner, and the patient experience is the same for MRSI as for MRI. MRSI has broad applications in medicine, including oncology and general physiological studies.
When hydrogen is the target element, MRSI is also called 1H-nuclear magnetic resonance spectroscopic imaging and proton magnetic resonance spectroscopic imaging. MRSI can also be performed with phosphorus, or hyperpolarized carbon-13.
References
Magnetic resonance spectroscopic imaging entry in the public domain NCI Dictionary of Cancer Terms
External links
Magnetic resonance imaging | Magnetic resonance spectroscopic imaging | [
"Physics",
"Chemistry",
"Astronomy"
] | 256 | [
"Spectroscopy stubs",
"Nuclear magnetic resonance",
"Spectrum (physical sciences)",
"Magnetic resonance imaging",
"Astronomy stubs",
"Nuclear chemistry stubs",
"Nuclear magnetic resonance stubs",
"Molecular physics stubs",
"Spectroscopy",
"Physical chemistry stubs"
] |
14,440,807 | https://en.wikipedia.org/wiki/GPR63 | Probable G-protein coupled receptor 63 is a protein that in humans is encoded by the GPR63 gene.
G protein-coupled receptors (GPCRs, or GPRs) contain 7 transmembrane domains and transduce extracellular signals through heterotrimeric G proteins.[supplied by OMIM]
References
Further reading
G protein-coupled receptors | GPR63 | [
"Chemistry"
] | 75 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,888 | https://en.wikipedia.org/wiki/GPR101 | Probable G-protein coupled receptor 101 is a protein that is encoded by the GPR101 gene in humans.
G protein-coupled receptors (GPCRs, or GPRs) contain 7 transmembrane domains and transduce extracellular signals through heterotrimeric G proteins.
Clinical significance
A duplication event in GPR101 is implicated in cases of gigantism and acromegaly.
References
Further reading
G protein-coupled receptors | GPR101 | [
"Chemistry"
] | 94 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,931 | https://en.wikipedia.org/wiki/Mammotome | Mammotome is a Cincinnati, Ohio–based company who pioneered a vacuum-assisted breast biopsy (VAC) device that uses image guidance such as x-ray, ultrasound and/or MRI to perform breast biopsies. A biopsy using a Mammotome® device can be done on an outpatient basis with a local anesthetic. The Mammotome brand is sold in over 45 countries.
Indications
A stereotaxic macro-biopsy is often indicated after suspicious elements are seen on a mammography (mass, micro-calcifications or focal abnormal changes in the tissues). It is always used to analyse those elements but can sometimes also remove it completely. It is often used when:
The mammography shows a suspicious solid mass.
The mammography shows a suspicious "islet" of micro-calcifications.
The breast tissue seems deformed.
A new mass or micro-calcification islet is spotted in a zone previously targeted by surgery.
Risks associated with the procedure
Side effects:
Common: bruising, mild discomfort during the procedure, mild bleeding and tenderness at the biopsy site.
Rare: significant bleeding or pain during biopsy, significant tenderness and bleeding at the biopsy site.
Complications:
Rare: Post-biopsy breast infection. Allergic reaction to the local anaesthetic.
Complications from biopsies can delay subsequent breast surgery.
The procedure may, rarely, fail due to inaccurate sampling of the lesion; results may underestimate the severity of the lesion although these risks do not differ from other biopsy or surgical procedures. Occasionally, even after a successful biopsy, the diagnosis may remain uncertain and require a surgical biopsy, especially when atypical or precancerous cells are found on core biopsy.
Limitations of the procedure
Lesions accompanied by diffuse calcium deposits scattered throughout the breast or located near the chest wall are difficult to target or evaluate by stereotactic biopsy. If the mammogram shows only a vague change in tissue density but no definite mass or nodule, the x-ray-guided method may not be successful.
External links
Mammotome entry in the public domain NCI Dictionary of Cancer Terms
References
Medical equipment
Breast cancer
Biopsy | Mammotome | [
"Biology"
] | 462 | [
"Medical equipment",
"Medical technology"
] |
14,440,968 | https://en.wikipedia.org/wiki/Pyroglutamylated%20RFamide%20peptide%20receptor | Pyroglutamylated RFamide peptide receptor also known as orexigenic neuropeptide QRFP receptor or G-protein coupled receptor 103 (GPR103) is a protein that in humans is encoded by the QRFPR gene.
Function
G protein-coupled receptors (GPCRs, or GPRs) contain 7 transmembrane domains and transduce extracellular signals through heterotrimeric G proteins.
A 26-amino acid RF-amide peptide, P518 functions as a high-affinity ligand of GPR103. Both GPR103 and P518 precursor mRNA exhibited highest expression in brain. The 43-amino acid QRFP peptide, a longer form of the P518 peptide is necessary to exhibit full agonistic activity with GPR103. Intravenous administration QRFP caused release of aldosterone, suggesting that QRFP and GPR103 regulate adrenal function.
References
Further reading
External links
G protein-coupled receptors | Pyroglutamylated RFamide peptide receptor | [
"Chemistry"
] | 212 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,440,975 | https://en.wikipedia.org/wiki/Mediastinoscope | A mediastinoscope is a thin, tube-like instrument used to examine the tissues and lymph nodes in the area between the lungs (mediastinum) in a procedure known as mediastinoscopy. These tissues include the heart and its large blood vessels, trachea, esophagus, and bronchi. The mediastinoscope has a light and a lens for viewing and may also have a tool to remove tissue. It is inserted into the chest through a cut above the breastbone.
External links
Mediastinoscope entry in the public domain NCI Dictionary of Cancer Terms
Medical equipment | Mediastinoscope | [
"Biology"
] | 128 | [
"Medical equipment",
"Medical technology"
] |
14,440,977 | https://en.wikipedia.org/wiki/GPR123 | Probable G-protein coupled receptor 123 is a protein that in humans is encoded by the GPR123 gene. It is a member of the adhesion-GPCR family of receptors. Family members are normally characterized by an extended extracellular region with a variable number of protein domains coupled to a TM7 domain via a domain known as the GPCR-Autoproteolysis INducing (GAIN) domain.
References
Further reading
G protein-coupled receptors | GPR123 | [
"Chemistry"
] | 93 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,013 | https://en.wikipedia.org/wiki/GPR174 | Probable G-protein coupled receptor 174 is a protein that in humans is encoded by the GPR174 gene. The receptor has been reported to bind to lysophosphatidylserine.
References
Further reading
G protein-coupled receptors | GPR174 | [
"Chemistry"
] | 51 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,061 | https://en.wikipedia.org/wiki/GPR128 | G protein-coupled receptor 128 is a protein encoded by the ADGRG7 gene. GPR128 is a member of the adhesion GPCR family.
Adhesion GPCRs are characterized by an extended extracellular region often possessing N-terminal protein modules that is linked to a TM7 region via a domain known as the GPCR-Autoproteolysis INducing (GAIN) domain.
Tissue distribution
GPR128 is specifically expressed in human liver as well as in mouse bone marrow and intestinal tissues.
Function
Ni et al. showed that Gpr128 deletion in mice causes reduced body weight and induced intestinal contraction frequency.
Clinical significance
A 111-kb copy number gain with breakpoints within the TRK-fused gene (a target of translocations in lymphoma and thyroid tumors) and GPR128 has been identified in the genome of patients with atypical myeloproliferative neoplasms. Notably, the fused gene was also detected in few healthy individuals.
References
External links
Adhesion GPCR consortium
G protein-coupled receptors | GPR128 | [
"Chemistry"
] | 224 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,078 | https://en.wikipedia.org/wiki/GNRHR2 | Putative gonadotropin-releasing hormone II receptor is a protein that in humans is encoded by the GNRHR2 gene.
Function
The receptor for gonadotropin-releasing hormone 2 (GnRH2) is encoded by the GnRH2 receptor (GnRHR2) gene. In non-hominoid primates and non-mammalian vertebrates, GnRHR2 encodes a seven-transmembrane G protein-coupled receptor. However, in humans, the N-terminus of the predicted protein contains a frameshift and premature stop codon. In humans, GnRHR2 transcription occurs but whether the gene produces a functional C-terminal multi-transmembrane protein is currently unresolved. Alternative splice variants have been reported. An untranscribed pseudogene of GnRHR2 is also on chromosome 14.
See also
Gonadotropin-releasing hormone receptor
References
Further reading
External links
G protein-coupled receptors | GNRHR2 | [
"Chemistry"
] | 207 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,082 | https://en.wikipedia.org/wiki/GPR146 | G-protein coupled receptor 146 is a protein that in humans is encoded by the GPR146 gene. The receptor has been shown to bind cholesin/C17orf50, a gut-derived hormone that is secreted from the intestine in response to dietary cholesterol absorption. In response to cholesin binding, GPR146 signaling inhibit cholesterol synthesis. Consistent with this interaction, murine genetic disruption of GPR146 lowers serum cholesterol and reduces atherosclerotic aortic lesions.
GPR146 has also been identified as a possible receptor for C-peptide.
References
Further reading
G protein-coupled receptors | GPR146 | [
"Chemistry"
] | 139 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,107 | https://en.wikipedia.org/wiki/MRGPRD | Mas-related G-protein coupled receptor member D is a protein that in humans is encoded by the MRGPRD gene.
See also
MAS1 oncogene
References
Further reading
G protein-coupled receptors | MRGPRD | [
"Chemistry"
] | 43 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,122 | https://en.wikipedia.org/wiki/MRGPRE | Mas-related G-protein coupled receptor member E is a protein that in humans is encoded by the MRGPRE gene.
See also
MAS1 oncogene
References
Further reading
G protein-coupled receptors | MRGPRE | [
"Chemistry"
] | 43 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,133 | https://en.wikipedia.org/wiki/MRGPRX2 | Mas-related G-protein coupled receptor member X2 is a protein that in humans is encoded by the MRGPRX2 gene. It is most abundant on cutaneous mast cells, sensory neurons, and keratinocytes.
Activation of MRGPRX2 on mast cells leads to IgE-independent type 1 hypersensitivity-like symptoms, also known as pseudoallergic reactions, although more rapid and brief. Medications identified to cause MRGPRX2 activation including neuromuscular blocking agents (NMBA) (except for succinylcholine), antibiotics like DNA gyrase inhibitor fluoroquinolones or cell wall synthesis inhibitor vancomycin (which caused Red Man syndrome), icatibant, leuprolide, and morphine.
See also
MAS1 oncogene
Pseudoallergy
References
Further reading
G protein-coupled receptors | MRGPRX2 | [
"Chemistry"
] | 183 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,190 | https://en.wikipedia.org/wiki/GPR62 | Probable G-protein coupled receptor 62 is a protein that in humans is encoded by the GPR62 gene.
G protein–coupled receptors (GPCRs, or GPRs) contain 7 transmembrane domains and transduce extracellular signals through heterotrimeric G proteins.[supplied by OMIM]
References
Further reading
G protein-coupled receptors | GPR62 | [
"Chemistry"
] | 75 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,441,688 | https://en.wikipedia.org/wiki/UW%20Hybrid%20Vehicle%20Team | The Wisconsin Hybrid Vehicle Team consists mainly of undergraduate students from the University of Wisconsin–Madison who work together to build a hybrid electric vehicle.
The Team
Many of the members have little to no previous automotive experience. New team members are taught alongside veteran student members. This passing of knowledge ensures a legacy that is carried on to younger generations.
The team is subdivided into five major groups to handle necessary tasks. The Mechanical and Drivetrain groups work to design and implement new components, renovate old parts, and perform general vehicle maintenance.
The Control and Electrical Groups are responsible for maintaining all of the vehicle computer and electrical components; this includes developing a complex control strategy and programing the electronic control unit, rewiring the vehicle to accommodate the hybrid systems, and maintaining the battery pack as well as other electrically sensitive components.
The Outreach group is responsible for publishing newsletters, maintaining the website, obtaining positive relationships with local businesses and the community, and involving the team in community events.
Each group is led by a veteran team member who meets to coordinate projects and make decisions for the vehicle's progress. Each leader is responsible to teach each of the group's attendants safely.
Past Competitions
Current Competition
The EcoCar Challenge is a three-year competition sponsored by the U.S. DOE, GM, and Argonne National Labs for 2008-2010. Seventeen universities from the US and Canada were selected to participate.
In the first year, teams concentrated on designing, modeling, and simulating their teams proposed vehicle architecture. Additionally, teams worked to create a functional HIL (hardware-in-the-loop) to demonstrate their capability to manage a vehicle's ECU. The first year's competition was completed in June 2009 in Toronto, OH Canada.
In the first year of the competition, the UWHVT developed an architecture that was a powersplit hybrid design. Technical papers were created at intervals throughout the year dictating decisions and results of simulations. It consists of a prototype traction motor, the 150 kW Continental AG Sapphire drive. A Weber MPE 750 engine (operating on E85) and the Delphi DU174 motor (found in the EV1) complete the genset. A clutch implemented in between the DU174 and the Weber allow for efficient all electric drive, while a clutch implemented in between the DU174 and the rear differential allows the Weber engine to be directly coupled to the road at highway speeds. Lastly, the battery pack located in the spare rear wheel compartment will be a Johnson Controls Saft 41Ah lithium-ion pack.
The UWHVT expects to receive its stock Saturn Vue in August 2009 and proceed building the vehicle in year 2. Competition for year two of the challenge will be in Yuma, AZ at GM's new proving ground.
References
External links
UW Madison Hybrid Vehicle Team Homepage
Cameras in the UW Vehicle Teams Garage
Argonne National Laboratories
Olympian Motors
Department of Energy
General Motors Corporation
Automotive technologies
Green vehicles
Hybrid vehicles
Individual cars
Electric vehicle organizations | UW Hybrid Vehicle Team | [
"Engineering"
] | 609 | [
"Electrical engineering organizations",
"Electric vehicle organizations"
] |
14,442,271 | https://en.wikipedia.org/wiki/Tobramycin/dexamethasone | Tobramycin/dexamethasone, sold under the brand name Tobradex, is a fixed-dose combination medication in the form of eye drops and eye ointment, marketed by Alcon. The active ingredients are tobramycin (an antibiotic) and dexamethasone (a corticosteroid). It is prescribed for the treatment of pink eye in combination with bacterial infections.
Contraindications
It is contraindicated with herpetic and other viral eye infections. Other contraindications include fungal and mycobacterial infections because tobramycin is inactive against those, and the corticoid acts as an immunosuppressive agent, preventing the body's immune system from dealing with the infection. The drops are also contraindicated in patients with corneal lesions.
Side effects
Similarly to other corticosteroid eye drops, side effects include hypersensitivity and, especially after long-term use, secondary eye infections, cataract (clouding of the eye lens) and increased intraocular pressure, leading to glaucoma. Consequently, the drug should not be applied longer than 24 days without further medical evaluation.
Interactions
Anticholinergic eye drops potentiate the risk of increased intraocular pressure. Systemic aminoglycoside antibiotics increase toxicity for ears, nerves and kidney.
Brand names
Tobrason is a brand name in Jordan.
References
External links
Antibiotics
Glucocorticoids
Combination drugs
Drugs developed by Novartis | Tobramycin/dexamethasone | [
"Biology"
] | 314 | [
"Antibiotics",
"Biocides",
"Biotechnology products"
] |
14,442,399 | https://en.wikipedia.org/wiki/Antlia%20Cluster | The Antlia Cluster (or Abell S0636) is a cluster of galaxies located in the Hydra–Centaurus Supercluster. The Antlia Cluster is the third-nearest to the Local Group after the Virgo Cluster and Fornax Cluster. Antlia's distance from Earth is to and can be viewed from Earth in the constellation Antlia. The Antlia Cluster should not be confused with the Antlia Dwarf galaxy.
Antlia is classified as a rare Bautz–Morgan type III cluster, meaning it has no central dominant (cD) brightest cluster galaxy. However, the cluster is dominated by two massive elliptical galaxies, NGC 3268 and NGC 3258, and contains a total of about 234 galaxies. The cluster is very dense compared to other clusters such as Virgo and Fornax, thus containing early-type galaxies and a larger portion of dwarf ellipticals. The cluster is split into two galaxy groups, the Northern subgroup gravitating around NGC 3268, and the Southern subgroup centered on NGC 3258.
The cluster has an overall redshift of z = 0.0087, implying that the cluster is, like most objects in the Universe, receding from the Local Group. Using the now-obsolete scientific satellite ASCA, X-ray observations show that the cluster is almost isothermal, with a mean temperature of kT ~ 2.0 keV.
List of named objects in the Antlia Cluster
See also
Coma Cluster
Eridanus Cluster
List of galaxy groups and clusters
Norma Cluster
References
Further reading
Burnham Jr., Robert (1978) Burham's Celestial Handbook Revised Edition Vol. 1 of 3. Dover Publications. New York
External links
Galaxy clusters
S0636
Abell richness class 0
Hydra-Centaurus Supercluster | Antlia Cluster | [
"Astronomy"
] | 365 | [
"Galaxy clusters",
"Astronomical objects"
] |
14,443,159 | https://en.wikipedia.org/wiki/Eleidin | Eleidin is clear intracellular protein which is present in the stratum lucidum of the skin.
Eleidin is a transformation product of the amino acid complex keratohyalin, the lifeless matter deposited in the form of minute granules within the protoplasm of living cells. Eleidin is then converted to keratin in the stratum corneum.
Eleidin can be found in the vermilion border of the lip. The lip is thinly keratinized and has a high concentration of eleidin. The red appearance of the vermillion border is due to several factors, one of which is the transparent nature of eleidin showing the color of the red blood cells beneath.
References
Human proteins | Eleidin | [
"Chemistry"
] | 157 | [
"Biochemistry stubs",
"Protein stubs"
] |
14,444,088 | https://en.wikipedia.org/wiki/Positronium%20hydride | Positronium hydride, or hydrogen positride is an exotic molecule consisting of a hydrogen atom bound to an exotic atom of positronium (that is a combination of an electron and a positron). Its formula is PsH. It was predicted to exist in 1951 by A. Ore, and subsequently studied theoretically, but was not observed until 1990. R. Pareja, R. Gonzalez from Madrid trapped positronium in hydrogen-laden magnesia crystals. The trap was prepared by Yok Chen from the Oak Ridge National Laboratory. In this experiment the positrons were thermalized so that they were not traveling at high speed, and they then reacted with H− ions in the crystal. In 1992 it was created in an experiment done by David M. Schrader and F.M. Jacobsen and others at the Aarhus University in Denmark. The researchers made the positronium hydride molecules by firing intense bursts of positrons into methane, which has the highest density of hydrogen atoms. Upon slowing down, the positrons were captured by ordinary electrons to form positronium atoms which then reacted with hydrogen atoms from the methane.
Decay
PsH is constructed from one proton, two electrons, and one positron. The binding energy is . The lifetime of the molecule is 0.65 nanoseconds. The lifetime of positronium deuteride is indistinguishable from the normal hydride.
The decay of positronium is easily observed by detecting the two 511 keV gamma ray photons emitted in the decay. The energy of the photons from positronium should differ slightly by the binding energy of the molecule. However, this has not yet been detected.
Properties
The structure of PsH is as a diatomic molecule, with a chemical bond between the two positively charged centres. The electrons are more concentrated around the proton.
Predicting the properties of PsH is a four body Coulomb problem. Calculated using the stochastic variational method, the size of the molecule is larger than dihydrogen, which has a bond length of 0.7413 Å. In PsH the positron and proton are separated on average by 3.66 a0 (1.94 Å). The positronium in the molecule is swollen compared to the positronium atom, increasing to 3.48 a0 compared to 3 a0. Average distance of the electrons from the proton is larger than the dihydrogen molecule, at 2.31 a0 with the maximum density at 2.8 au.
Formation
Due to its short lifetime, establishing the chemistry of positronium hydride poses difficulties. Theoretical calculations can predict outcomes. One method of formation is through alkali metal hydrides reacting with positrons. Molecules with dipole moments greater than 1.625 debye are predicted to attract and hold positrons in a bound state. Crawford's model predicts this positron capture. In the case of lithium hydride, sodium hydride and potassium hydride molecules, this adduct decomposes and positronium hydride and the alkali positive ion form.
M+H− + e+ → PsH + M+
Similar compounds
PsH is a simple exotic compound. Other compounds of positronium are possible by the reactions e+ + AB → PsA + B+. Other substances that contain positronium are di-positronium and the ion Ps− with two electrons. Molecules of Ps with normal matter include halides and cyanide.
Positronium antihydride (Ps) contains antihydrogen instead of hydrogen. It can be made as the anti-hydride ion (+) reacts with positronium (Ps)
+ + Ps → Ps + e+
The GBAR experiment uses the similar reaction + Ps → + + e− which cannot produce positronium antihydride, as there is too much energy left over for positronium antihydride to be stable.
References
Extra reading
Antimatter
Molecular physics
Quantum electrodynamics
Exotic atoms
Substances discovered in the 1990s | Positronium hydride | [
"Physics",
"Chemistry"
] | 871 | [
"Antimatter",
"Molecular physics",
"Exotic atoms",
"Subatomic particles",
" molecular",
"nan",
"Nuclear physics",
"Atomic",
"Atoms",
"Matter",
" and optical physics"
] |
14,444,896 | https://en.wikipedia.org/wiki/OGLE-TR-182 |
OGLE-TR-182 is a dim magnitude 17 star far off in the constellation Carina at a distance of approximately 12,700 light years.
Planetary system
This star is home to the transiting extrasolar planet OGLE-TR-182b discovered in October 2007.
See also
List of extrasolar planets
Optical Gravitational Lensing Experiment OGLE
References
External links
G-type main-sequence stars
Planetary transit variables
Carina (constellation)
Planetary systems with one confirmed planet | OGLE-TR-182 | [
"Astronomy"
] | 95 | [
"Carina (constellation)",
"Constellations"
] |
14,444,947 | https://en.wikipedia.org/wiki/Lupus-TR-3b | Lupus-TR-3b is an extrasolar planet orbiting the star Lupus-TR-3 (a K-type main sequence star approximately 8,950 light-years away in the constellation Lupus). The planet was discovered in 2007 by personnel from the Center for Astrophysics Harvard & Smithsonian observing at the Siding Spring Observatory in Australia, by the transit method.
The planet has four-fifths the mass of Jupiter, nine-tenths the radius, and has density of 1.4 g/cm3. This planet is a typical “Hot Jupiter” as it orbits at 0.0464 AU distance from the star, taking 3.9 days to orbit. It is currently the faintest ground-based detection of a transiting planet.
See also
Harvard-Smithsonian Center for Astrophysics
References
External links
Lupus (constellation)
Transiting exoplanets
Hot Jupiters
Exoplanets discovered in 2007
Giant planets | Lupus-TR-3b | [
"Astronomy"
] | 190 | [
"Constellations",
"Lupus (constellation)"
] |
14,444,985 | https://en.wikipedia.org/wiki/HD%2037605 | HD 37605 is a star in the equatorial constellation of Orion. It is orange in hue but is too faint to be visible to the naked eye, having an apparent visual magnitude of 8.67. Parallax measurements yield a distance estimate of 152 light years from the Sun. It has a high proper motion and is drifting closer with a radial velocity of −22 km/s.
This object is a K-type main-sequence star with a stellar classification of K0 V. It is an inactive, metal-rich star. Age estimates range from 1.8 up to 7 billion years old, and it is spinning with a projected rotational velocity of 4.5 km/s. The star has 98% of the mass of the Sun and 89% of the Sun's radius. It is radiating 60% of the luminosity of the Sun from its photosphere at an effective temperature of 5,380 K.
Planets
There are two giant planets known in orbit. Planet b was discovered in 2004 and planet c was discovered eight years later. The planets do not transit relative to Earth; b's maximum inclination is 88.1%.
In a simulation, HD 37605 b's orbit "sweeps clean" most test particles within 0.5 AU; leaving only asteroids "in low-eccentricity orbits near the known planet’s apastron distance, near the 1:2 mean-motion resonance" with oscillating eccentricity up to 0.06, and also at 1:3 with oscillating eccentricity up to 0.4. Also, observation has ruled out planets heavier than 0.7 Jupiter mass with a period of one year or less; which still allows for planets at 0.8 AU or more.
References
External links
K-type main-sequence stars
Planetary systems with two confirmed planets
Orion (constellation)
Durchmusterung objects
037605
026664 | HD 37605 | [
"Astronomy"
] | 392 | [
"Constellations",
"Orion (constellation)"
] |
14,445,033 | https://en.wikipedia.org/wiki/HD%2092788 | HD 92788 is a star in the equatorial constellation of Sextans. It has a yellow hue but is too dim to be visible to the naked eye, having an apparent visual magnitude of 7.31. The star is located at a distance of 113 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −4.5 km/s. Two planets have been found in orbit around the star.
This is a G-type main-sequence star with a stellar classification of G6V. It is estimated to be around eight billion years old and is spinning with a rotation period of 31.7 days. The star has a similar mass to the Sun and is slightly larger in radius, with a high metallicity. It is radiating 1.25 times the luminosity of the Sun from its photosphere at an effective temperature of 5,722 K.
Planetary system
An extrasolar planet was discovered orbiting this star in 2001 by means of the radial velocity method. Designated component 'b', it is a Super-Jupiter or possibly a low-mass brown dwarf with an orbital period of . The star rotates at an inclination of 8 degrees relative to Earth. It is probable that this planet shares that inclination.
A low-mass brown dwarf companion was announced in 2019. Designated component 'c', it orbiting with a period of around and a semimajor axis of .
See also
List of extrasolar planets
References
External links
G-type main-sequence stars
Planetary systems with two confirmed planets
Sextans
BD–01 2431
092788
052409
J10424853-0211011 | HD 92788 | [
"Astronomy"
] | 343 | [
"Sextans",
"Constellations"
] |
14,445,101 | https://en.wikipedia.org/wiki/HD%20104985 | HD 104985, formally named Tonatiuh (), is a solitary star with a exoplanetary companion in the northern constellation of Camelopardalis. The companion is designated HD 104985 b and named Meztli (). This star has an apparent visual magnitude of 5.78 and thus is dimly visible to the naked eye under favorable seeing conditions. It is located at a distance of approximately 329 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −20 km/s.
The stellar classification of this star is G8.5IIIb, indicating this is an evolved giant star that has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. It is located in the red clump region of the HR diagram, suggesting it is on the horizontal branch and generating energy through core helium fusion. The star is approximately 4.4 billion years old with 1.2 times the mass of the Sun and has expanded to 10.6 times the Sun's radius. It is radiating 51 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,730 K.
In 2003, radial velocity measurements made by the Okayama Planet Search Program led to the announcement of an exoplanetary companion. It is orbiting at a distance of with a period of 199.5 days with an eccentricity (ovalness) of 0.09. Since the inclination of the exoplanet's orbital plane is unknown, only a lower bound on its mass can be determined. It has at least 8.3 times the mass of Jupiter.
Naming
HD 104985 is the star's entry in the Henry Draper Catalogue. Following its discovery in 2003 the planet was designated HD 104985 b. In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning names were Tonatiuh for this star and Meztli for its planet.
The winning names were those submitted by the Sociedad Astronomica Urania of Morelos, Mexico. 'Tonatiuh' was the Aztec god of the Sun; 'Meztli' was the Aztec goddess of the Moon.
In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. In its first bulletin of July 2016, the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.
See also
List of extrasolar planets
References
G-type giants
Horizontal-branch stars
Planetary systems with one confirmed planet
Camelopardalis
Durchmusterung objects
104985
058952
4609
Tonatiuh | HD 104985 | [
"Astronomy"
] | 636 | [
"Camelopardalis",
"Constellations"
] |
14,445,187 | https://en.wikipedia.org/wiki/HD%20106252 | HD 106252 is a star with a brown dwarf companion in the constellation Virgo. An apparent visual magnitude of 7.41 means this star is too faint to be visible to the naked eye. It is located at a distance of 210 light years from the Sun based on parallax measurements, and is receding with a radial velocity of 15 km/s.
The stellar classification of HD 106252 is G0V, matching an ordinary G-type main-sequence star. It has 5% more mass than the Sun and 10% greater in girth. This star is about three billion years old with a low level of magnetic activity and is spinning with a projected rotational velocity of 2 km/s. It is radiating 1.3 times the luminosity of the Sun from its photosphere at an effective temperature of 5,890 K.
In 2001, a massive sub-stellar companion was announced orbiting the star by the European Southern Observatory. The discovery was confirmed by a different team using the Lick Telescope. Astrometric observations from Hipparcos in 2011 suggested that its true mass is likely around , in the brown dwarf range. More accurate astrometry from Gaia in 2021 revealed a smaller true mass of .
References
External links
G-type main-sequence stars
Planetary systems with one confirmed planet
Virgo (constellation)
Durchmusterung objects
106252
059610 | HD 106252 | [
"Astronomy"
] | 283 | [
"Virgo (constellation)",
"Constellations"
] |
14,445,477 | https://en.wikipedia.org/wiki/Hydrocarbon%20economy | Hydrocarbon economy is a term referencing the global hydrocarbon industry and its relationship to world markets. Energy used mostly comes from three hydrocarbons: petroleum, coal, and natural gas. Hydrocarbon economy is often used when talking about possible alternatives like the hydrogen economy.
History of Hydrocarbon Economies
The history of hydrocarbon economies intertwines with the industrial revolution and the discovery of oil. Key historical moments include the rise of the petroleum industry in the late 19th century, the geopolitics of oil in the 20th century, and the emergence of OPEC. The control and access to oil have been pivotal in world events, including wars and economic crises.
Origins and Early Development
The origins and early development of hydrocarbon economies have significantly shaped global politics, economics, and technological advancements, emphasizing the crucial role of hydrocarbons in both economic and political spheres, as well as the strategic importance of oil in international and national contexts.
The inception of the modern petroleum industry can be traced back to the late 19th century with Edwin Drake's pioneering drilling of the first commercial oil well in Titusville, Pennsylvania in 1859. This event marked the beginning of the oil boom in the United States and laid the foundation for future developments in the industry. Further solidifying the U.S.'s stature in the global oil market was the discovery of the Spindletop gusher in Texas in 1901, which catalyzed a significant increase in oil exploration and production.
During the First and Second World Wars, oil played an indispensable role, being essential for powering military vehicles and ships. The strategic value of oil resources became increasingly apparent, influencing military strategies and outcomes in both conflicts. The formation of the Organization of Petroleum Exporting Countries (OPEC) in 1960 marked a pivotal shift in the control of oil resources, transferring significant influence from Western oil companies to the oil-producing nations and thus altering the global oil landscape.
The oil crises of the 1970s were turning points in the history of hydrocarbon economies. The 1973 oil crisis, triggered by an embargo by Arab oil producers, led to a drastic spike in oil prices and posed considerable economic challenges for oil-importing nations. This was followed by the 1979 energy crisis, caused by the Iranian Revolution, which again resulted in a major increase in oil prices and global economic difficulties.
The Gulf War in 1990-1991, instigated by Iraq's invasion of Kuwait, was largely driven by oil-related interests. This conflict had significant implications for the oil market, particularly concerning the security of oil supplies from the Persian Gulf. In the 21st century, the rise of hydraulic fracturing, or fracking, especially in the United States, has led to a substantial increase in oil and natural gas production. This development has reshaped global energy markets and has been instrumental in reducing the U.S.'s reliance on imported oil.
Hydrocarbon Price Volatility
Hydrocarbon price volatility, particularly in the context of hydrocarbon economies, is a complex phenomenon impacted by a confluence of geopolitical, economic, and market factors. The period between 2010 and 2014, where hydrocarbon prices hovered around USD 100 per barrel, followed by a dramatic decline in 2016 to about USD 30 per barrel, exemplifies this volatility.
This fluctuation in hydrocarbon prices can be attributed to several interconnected factors. During this period, there was a notable oversupply in the global oil market. This was largely driven by increased production, especially with the United States ramping up its shale oil output, leading to a surplus. Concurrently, the Organization of the Petroleum Exporting Countries (OPEC), which has a history of adjusting production to influence prices, decided to maintain high production levels. This strategy, diverging from OPEC's usual approach of production cuts to stabilize prices, contributed further to the oversupply.
Global economic conditions also played a significant role. For example, a slowdown in economic growth in major economies, such as China, led to reduced demand for oil. When combined with an oversupplied market, these factors contributed to the significant drop in oil prices.
The impact of such volatility is particularly pronounced in economies heavily reliant on hydrocarbon revenues. Sharp decreases in oil prices can lead to reduced national incomes, impacting government budgets and economic stability. This unpredictability underscores the risks associated with dependency on hydrocarbons, whose prices are subject to global economic forces and political dynamics.
Consequently, there has been an increasing emphasis on the need for these hydrocarbon-dependent countries to diversify their economies. Economic diversification is seen as a way to mitigate the risks associated with hydrocarbon price volatility. By developing other sectors such as technology, manufacturing, or tourism, countries can create a more balanced and resilient economic structure. This diversification is crucial not only for stabilizing national incomes but also for ensuring long-term economic sustainability in the face of fluctuating global oil prices.
Hydrocarbon Resources
Hydrocarbon resources (HCR), particularly coal, oil, and natural gas, play a crucial role in the global economy. Significant technological transformations in the oil and coal industries are taking place due to the "greening" of global economies. This shift is expected to alter the role of hydrocarbons, possibly leading to their partial substitution with alternative energy technologies.
Challenges in the oil industry include the lack of international regulation, depletion of easy-to-recover reserves, low oil recovery rates, insufficient investments in innovative technologies, and the absence of universally accepted indicators for sustainable development. In contrast, the gas sector, especially the production of liquefied natural gas (LNG), is experiencing robust growth. Natural gas is often regarded for its cost-effectiveness and comparatively lower carbon dioxide emissions during electricity generation, particularly when juxtaposed with coal. Reflecting this, the Liquefied Natural Gas (LNG) industry has witnessed a doubling of its capacities every decade since 1998, with projections indicating a continuing trend of rising demand and supply, though the potential for an oversupply exists. In this landscape, Russia has emerged as a notable player in the LNG market, strategically targeting regions such as Europe, Asia, and the Arctic. The "Nord Stream 2" and "Turkish Stream" projects, along with Russia's LNG production, are seen as complementary rather than competitive, creating favorable conditions for Russia's gas in the European market. Russia's extensive program aims to increase LNG production capacity, positioning it as a key player in the global LNG industry. The Arctic, despite its challenges, is considered a potential source for ensuring the stability of gas monetization schemes, contributing to market growth and facilitating the development of the Northern Sea Route.
Applications and Usage
Hydrocarbons are pivotal in various sectors. In transportation, they fuel vehicles, ships, and planes. In the industrial sector, they are used as raw materials for plastics, chemicals, and pharmaceuticals. In the energy sector, they are critical for electricity generation and heating.
In hydrocarbon economies, the transportation sector is heavily reliant on hydrocarbons, mainly petroleum products like gasoline and diesel. These fuels power a vast array of vehicles – cars, buses, trucks, ships, and airplanes – making them indispensable for facilitating global trade and personal mobility. The dominance of hydrocarbons in transportation is not only due to their energy density and efficiency but also due to the extensive infrastructure developed around their extraction, refining, and distribution. This sector's dependence on hydrocarbons significantly contributes to the economic strength and development of hydrocarbon-based economies.
Hydrocarbons play a critical role in the industrial sector, serving as essential raw materials for a wide range of products. Key among these are plastics, which find use in an array of applications from packaging to high-tech devices. The pharmaceutical industry also heavily relies on hydrocarbons for the production of various medicines and medical equipment. Furthermore, hydrocarbons are fundamental in the manufacture of a variety of chemicals, impacting numerous industries. The industrial utilization of hydrocarbons is indicative of their economic importance, driving innovation and supporting a multitude of manufacturing processes in hydrocarbon economies.
In the energy sector, hydrocarbons are a primary source of electricity generation globally. While coal, a type of hydrocarbon, has historically dominated power generation, natural gas is increasingly favored due to its cleaner-burning properties. Beyond electricity, hydrocarbons are critical for heating purposes, whether in industrial processes or residential settings. The efficiency and availability of hydrocarbons make them a preferred choice for energy production, underpinning the energy security and economic stability of hydrocarbon-dependent economies. The sector’s reliance on hydrocarbons underscores their vital role in maintaining energy supplies and supporting economic activities.
Production and Reserves
The discussion of production and reserves underpins the entire economic structure of hydrocarbon economies. Worldwide, major oil and natural gas reserves are unevenly distributed, with significant concentrations in certain regions, notably the Middle East, North America, Russia, and parts of Africa.
The Middle East, known for its vast oil reserves, remains a focal point in global oil markets. Countries like Saudi Arabia, Iraq, and Iran possess some of the largest proven oil reserves in the world, making the region pivotal in terms of global supply. The economic and political dynamics of these countries are deeply intertwined with their oil production capabilities and policies.
In North America, particularly the United States and Canada, the oil and gas industry has undergone significant transformation with the advent of new extraction technologies. The development and implementation of hydraulic fracturing, or fracking, has unlocked vast reserves of shale oil and gas, reshaping the production landscape in the region. This technological advancement has not only boosted domestic oil and gas production but also altered the global energy market by reducing North America's dependence on imported oil.
Russia, another major player in the global hydrocarbon market, has extensive oil and natural gas reserves, particularly in Siberia and the Arctic. The country's economy is heavily reliant on the export of these resources, making its production strategies and capabilities crucial both domestically and internationally.
Parts of Africa, including Nigeria, Angola, and Libya, are significant oil producers as well. The exploration and production activities in these countries contribute substantially to their national incomes, although they often grapple with challenges such as political instability and infrastructure constraints.
Advancements in extraction technologies, notably offshore drilling, have also played a key role in expanding production capabilities. Offshore drilling has opened up new reserves in deep-sea locations, previously inaccessible or uneconomical to explore. This technology has enabled countries with offshore reserves to tap into these resources, contributing to the diversification of global oil and gas supply sources.
The production and reserves of oil and natural gas are fundamental aspects of hydrocarbon economies, influencing not only the economic health of producing countries but also global energy dynamics. The distribution of these reserves and the adoption of advanced extraction technologies like fracking and offshore drilling continue to reshape the landscape of global hydrocarbon production.
Impact of Hydrocarbon Economy
The hydrocarbon industry also plays a crucial role in job creation and economic development. For example, in the United States, each land rig employs on average twenty-two people directly, and each drilling job leads to the creation of three additional jobs in the economy. T
his multiplier effect signifies the vast economic impact of the hydrocarbon sector. In 2012, the industry supported 2.1 million jobs and contributed almost $284 billion to the American gross domestic product. The industry's impact extends through the midstream and downstream sectors. Pipeline construction alone employed over 135,000 people in 2015, highlighting the extensive workforce involved in transporting crude oil and natural gas. Downstream activities, including refining and distribution, contributed to over 68,000 jobs.The industry's impact is not limited to jobs and revenue. The industry not only provides employment but also contributes significantly to tax revenues and fees in states like Colorado. Millions of dollars in tax and land lease revenues from oil and gas activities flow into local communities, enhancing education, improving roads, and supporting infrastructure development.
Transportation and Infrastructure
Hydrocarbon economies are heavily reliant on an extensive and complex infrastructure that encompasses the entire chain from extraction to distribution. Pipelines play a critical role in this network, serving as the arteries that transport oil and natural gas from production sites to refineries and storage facilities. They are the most efficient means for overland transportation of these resources, especially over long distances, forming an interconnected web that spans continents.
In addition to pipelines, the transportation of oil and gas across oceans relies heavily on tankers and strategic shipping routes. These tankers, varying in size from small vessels to ultra-large crude carriers, navigate through key maritime chokepoints like the Strait of Hormuz, the Suez Canal, and the Panama Canal. The Strait of Hormuz, for example, is particularly notable for its strategic importance, as a significant proportion of the world's oil trade passes through this narrow passage.
Refineries are another crucial component, where the crude oil undergoes processing to be converted into various usable products such as gasoline, diesel, and jet fuel. These facilities are often strategically located near major consumption areas or ports to optimize the distribution of refined products.
Lastly, storage facilities are integral to the hydrocarbon infrastructure, providing the capability to stockpile resources. This is vital for managing the supply to meet fluctuating demands and ensuring availability during periods of supply disruption. These facilities vary in form, including large tank farms and underground storage, and are positioned strategically to maintain a balance between supply, demand, and logistical requirements.
This comprehensive infrastructure is not only a logistical necessity for hydrocarbon economies but also represents a significant strategic asset. Control over key elements of this infrastructure, such as pipelines and shipping routes, holds considerable geopolitical significance. Disruptions in this network, whether due to political conflict, technical failures, or natural disasters, can have profound impacts on global energy supply and market stability. The intricate network of transportation and infrastructure thus forms the backbone of the global hydrocarbon economy, connecting production centers with markets worldwide and ensuring the steady flow of energy resources.
Economic Aspects
The economic impact of hydrocarbon economies is immense, profoundly influencing global markets and geopolitical dynamics. The prices of oil and gas, key commodities in these economies, are crucial determinants in the global market. Their fluctuations can have a ripple effect, impacting inflation rates, economic growth, and the overall health of both consumer and producer nations. High oil prices generally lead to increased costs for a wide array of products and services, affecting consumers and businesses globally. On the other hand, low oil prices, while beneficial for consumers, can pose significant challenges for countries that heavily rely on hydrocarbon exports for their fiscal revenues. These countries often face budget deficits and economic instability when prices plummet.
Moreover, hydrocarbon resources play a central role in shaping geopolitical relationships. Countries with rich hydrocarbon reserves often hold substantial geopolitical influence, which is evident in international alliances and conflicts centered around energy security. This dynamic is particularly noticeable in organizations like OPEC, where member states collaborate to manage oil supply and influence global prices. The decisions and policies of such organizations can have wide-reaching effects, extending beyond the energy sector to influence global politics and economics.
Countries heavily dependent on hydrocarbon exports encounter unique economic challenges. The concentration on the lucrative hydrocarbon sector often leads to a lack of diversification in their economies, making them vulnerable to external market shocks. This situation is commonly referred to as the “resource curse” or “Dutch disease,” where the prosperity brought by natural resource wealth paradoxically undermines the development of a diversified economic base. Additionally, these economies face the challenge of transitioning to more sustainable energy sources in response to global climate change concerns. As the world gradually shifts towards renewable energy, hydrocarbon-dependent countries are tasked with diversifying their economic structures and investing in new sectors to ensure long-term economic stability and growth.
In summary, hydrocarbon economies wield significant influence over global economic and political landscapes. The intricate relationship between hydrocarbon prices, global markets, and geopolitical dynamics, coupled with the inherent challenges faced by hydrocarbon-dependent nations, underscores the complex and pivotal role these economies play in the broader global context.
Environmental Impact and Climate Change
This section would address the environmental challenges of hydrocarbon economies, focusing on pollution, greenhouse gas emissions, and their contribution to global warming. It would also discuss the societal impacts and global initiatives for environmental protection.
Hydrocarbon Resources and Climate Change
Climate change, a global concern, is partly attributed to the significant increase in technogenic greenhouse gas emissions, particularly CO2. According to the International Energy Agency (IEA), the peak CO2 emissions in 2019, reaching 33 Gt, are largely a result of HCR use. Studies also highlight indirect losses associated with HCR, including land use for power plants and potential geopolitical conflicts. Despite debates on the primary drivers of climate change, the undeniable link between HCR and CO2 emissions underscores the need for a careful examination of the environmental impact and the development of strategies to improve the industry's environmental safety.
Hydrocarbon Resources and Alternative Energy Technologies
As the world navigates a transition to alternative energy technologies, hydrocarbon resources (HCR) play a central role in the discourse. The nuclear energy sector, contributing 4.5% to the global energy balance, faces challenges such as accidents and concerns about nuclear weapons development. Meanwhile, renewable energy sources (RES) present promise but encounter issues like non-uniform geographical distribution and technology immaturity. Hydrogen technologies, seen as a potential solution, face hurdles due to the high cost of production and the absence of market mechanisms. The text emphasizes the need for a balanced approach, urging consideration of the environmental and economic aspects while acknowledging the indispensable role HCR continue to play in the global energy landscape.
Challenges and Future Outlook
The future of hydrocarbon economies faces several challenges, including resource depletion, environmental concerns, and the shift to sustainable energy sources. This section would speculate on potential developments and the changing landscape of global energy.
Innovation in Hydrocarbon Economy
Innovation and technology are essential for transforming hydrocarbon-based economies. The growing rate of innovation and its transformative has a huge impact on various sectors. An innovative hydrocarbon economy focuses on resource optimization, extraction efficiency, environmental stewardship, and fostering collaboration and partnerships for knowledge exchange and technological advancements.
Shift from Resource Dependency to Knowledge Dependency
The transformation from resource-dependent to knowledge-dependent countries has become imperative for hydrocarbon economies. Nations such as Norway, Brazil, and the United Arab Emirates are already pioneering this shift. The 2020 International Monetary Fund (IMF) Report reinforces the idea that a nation's economic standing is intrinsically tied to the development and utilization of its knowledge domain. This shift is not merely a trend but a strategic response to reduce dependence on natural resources.
References
External links
Energy economics
Economics catchphrases
Economy by field | Hydrocarbon economy | [
"Environmental_science"
] | 3,869 | [
"Energy economics",
"Environmental social science"
] |
14,445,558 | https://en.wikipedia.org/wiki/SigmaStat | SigmaStat is a statistical software package, which was originally developed by Jandel Scientific Software in the 1980s. As of October 1996, Systat Software is now based in San Jose, California. SigmaStat can compare effects among groups, conduct survival analysis, analyze rates and proportions, perform regression and correlation analysis and calculate power and sample size. The program uses a wizard based interface which asks the user questions about the project and its data. After a test is run, the user receives a detailed report that interprets the results.
If installed with SigmaPlot, SigmaStat integrated with SigmaPlot and SigmaPlot gained advanced statistical analysis capabilities from version 11. SigmaStat is available both as a separate product or is available integrated with SigmaPlot.
On February 1, 2016 SigmaStat version 4 was relaunched as a separate Advisory Statistics Software by Systat Software Inc.
Version history
Version 1.0 : 1994
Version 2.0 : 1997
Version 3.0 : 2003
Version 3.1 : 2005
Version 3.5 : 2007 (integrated with SigmaPlot 10)
Version 4.0 : 2008 (integrated with SigmaPlot 11)
Version 4.00 : Relaunched as SigmaStat version 4.00 on February 1, 2016.
External links
Systat Webpage
SigmaPlot Webpage
Systat Software Webpage
Statistical software
Windows-only proprietary software | SigmaStat | [
"Mathematics"
] | 280 | [
"Statistical software",
"Mathematical software"
] |
14,445,573 | https://en.wikipedia.org/wiki/Extrachromosomal%20array | An extrachromosomal array is a method for mosaic analysis in genetics. It is a cosmid, and contains two functioning (wild-type) closely linked genes: a gene of interest and a mosaic marker. Such an array is injected into germ line cells, which already contain mutant (specifically, loss of function) alleles of all three genes in their chromosomal DNA. The cosmid, which is not packed correctly during mitosis, is occasionally present in only one daughter cell following cell division. The daughter cell containing the array expresses the gene of interest; the cell lacking the array does not.
The mosaic marker is a gene which exhibits a visible phenotype change between the functioning and non-functioning alleles. For example, ncl-1, located in chromosomal DNA, exhibits a larger nucleolus than the wild-type allele, which is in the array. Thus, cells which exhibit larger nucleoli have usually not retained the extrachromosomal array.
The gene of interest is the target of the mosaic analysis. Cells lacking the extrachromosomal array also lack the functional gene of interest. Cells which develop normally without the array do not require the gene of interest for normal function. Cells which do not develop normally are said to require the gene. In this way, those cell lineages which require a specific gene can be identified.
Extrachromosomal arrays replace an earlier technique involving a duplicated piece of chromosome called a free duplication. The latter technique required that the gene of interest and the mosaic marker be closely linked on the duplication; the former allows free choice of mosaic marker and target gene.
References
Miller LM, Waring DA, Kim SK (1996). Mosaic analysis using a ncl-1 (+) extrachromosomal array reveals that lin-31 acts in the Pn.p cells during Caenorhabditis elegans vulval development. Genetics 143 (3): 1181-1191.
Genetics | Extrachromosomal array | [
"Biology"
] | 410 | [
"Genetics"
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.