History.

Origins.

The estate originally known as Hillerødsholm near Hillerød had traditionally belonged to the Gøyes, one of the noble families of Denmark. In the 1520s and 1530s, Mogens Gøye (c.1470–1544), Steward of the Realm, had been instrumental in introducing the Danish Reformation. He lived in a half-timbered building on the most northerly of three adjoining islets on the estate's lake. The property was known as Hillerødsholm (literally islet of Hillerød). After his daughter, Birgitte, married the courtier and naval hero Herluf Trolle in 1544, the couple became its proprietors. In the 1540s, Trolle replaced the old building with a larger manor house. In 1550, Frederick II who was king of Denmark and Norway from 1559 to 1588, concluded an exchange agreement with Herluf Trolle and his wife whereby Trolle received the manor of Skovkloster in the south of Zealand while the king acquired the Hillerødsholm Estate. As the old building with twin towers was too small for the king, in 1560 he arranged for extensions and additions under Trolle's supervision. At the king's request, Trolle remained on the premises until the work was completed. The king then renamed the estate Frederiksborg (literally Frederik's castle). Interested in deer hunting, he used the castle with the neighbouring Bath House as a royal hunting lodge, centred as it was in the fields and forests he owned in the north of Zealand. The additions included a gated wall to the south, separating the estate from the town. Still standing today is the quadrangular red-brick, tip-roofed house on Staldgade known as Herluf Trolle's Tower (c.1560). Adjoining this are two long, narrow red-brick stable buildings: the King's Stables to the west and the Hussars' Stables to the east. These in turn lead to a wall along the lake with two round towers completed in 1562 bearing the arms of Frederick II and his motto "Mein Hoffnung zu Gott allein" (My hope to God alone). On the central islet, the long pantry house with stepped gables (1575) can also be seen today. The most important building from Frederick II's times is the Bath House in the park northwest of the islets. Completed in 1581 in the Renaissance style with three protruding step-gabled wings, it served the king as a hunting lodge during the summer months.  Frederiksborg Castle was the first Danish castle to be built inland. All previous castles had been on the coast or close to ports as the sea had traditionally been the principal means of travel. It was also the first to be built for purely recreational purposes rather than for defence. Its location in Hillerød led to the development of vastly improved roads, initially reserved for the king. Kongevej (King's Way), linking Frederiksborg with Copenhagen, was completed in 1588. James VI of Scotland visited on 13 March 1590 after his marriage to Anne of Denmark. He gave money to the poor, to the keeper of the park who lent the couple horses, to a woman who kept pheasants and "spruce fowls", and 100 Danish dalers to the Captain of Frederiksborg for his officers and servants.

Renaissance castle.

Frederik's son Christian, who was born there became very attached to the castle as a child. Nevertheless, when reigning as Christian IV (1588–1648) he decided to have it completely rebuilt in the Flemish and Dutch Renaissance style (Northern Mannerism). The old building was demolished in 1599 and the Flemish architect Hans van Steenwinckel the Elder was charged with planning the new building. After his death in 1601, his sons Hans and Lorenz completed the assignment. The main four-storey building with its three wings was completed around 1610 but work continued on the Chapel until 1618. The entire complex was finished around 1620, becoming the largest Renaissance building in Scandinavia. The main Renaissance building built by Christian IV was thus completed in under ten years, an astonishing accomplishment at the time, although there were additions until the early 1620s.  In 1659 during the Second Northern War, the castle was captured by the Swedes who took most of its artworks as war reparations. During the Swedish occupation, the queen of Sweden, Hedvig Eleonora of Holstein-Gottorp, used the palace and hunted in the woods with the English envoy to Sweden.  After Christian IV's death in 1648, the castle was used mainly for ceremonial events. The Chapel was the scene of the coronations and anointments of all the Danish monarchs from 1671 to 1840 except for that of Christian VII.  In July 1720, the Treaty of Frederiksborg was signed in the castle, ending the Great Northern War between Sweden and Denmark-Norway which had started in 1700.

Fire and reconstruction.

In the 1850s, the castle was again used as a residence by King Frederick VII. While he was staying there on the night of 16 December 1859, he retired to a room on the third floor to examine his historic artefacts. But as it was a cold night, he asked for a fire to be lit in the room. Unfortunately, the chimney was under repair, causing a fire to break out. As the lake was frozen, the only water available came from the pantry and the kitchen. The fire spread quickly, ruining most of the building within a few hours although the Chapel, the Audience Chamber and the Privy Passage were not seriously damaged. The intricate internal decorations were also destroyed but over 300 paintings were saved and are now displayed in the castle's history museum. Reconstruction was funded by public subscription, with substantial contributions from the king and state, as well as from the prominent philanthropist J. C. Jacobsen of the Carlsberg Brewery. Jacobsen's funding provided for the establishment of the Museum of National History in the castle. It was formally established on 5 April 1878 and opened to the public in 1882. The restoration and reconstruction work began in 1860 on the basis of old plans from the archives as well as detailed paintings and drawings by Heinrich Hansen. When work was completed under the leadership of the historicist architect Ferdinand Meldahl in 1864, the castle once again took on its original appearance. Jacobsen also donated a copy of the Neptune Fountain (the original by Adrian de Vries having been taken to Sweden) which was placed in the outer courtyard in 1888.

Architecture.

In line with Flemish and Dutch Renaissance tradition, the quadrangular castle covering the entire area of the northern islet is built of red brick with stepped gables, towering spires and light sandstone decorations. The symmetry of the main structure is broken by the large bell tower on the Chapel Wing. All three wings are fundamentally independent buildings which have been joined together to form a complex. The usual concern with symmetry was overridden by the need to glorify Christian IV with sculptural decorations evoking astrology and mythology as can be seen in the gate house, the Terrace Wing and the Neptune Fountain. The window gables also display statues of historic emperors including Alexander the Great and Julius Caesar.  The King's Wing, the main wing of the Renaissance building, was completed in 1604, the Chapel Wing followed in 1606 and the Princess's Wing on the eastern side in 1608. All three were three storeys high but the Terrace Wing, completed in 1609, had only one storey. The side of the Terrace Wing next to the moat was decorated with mythological figures while open arcades overlooked the courtyard. The central portal bears the arms of King Christian and Queen Anne Catherine and its completion date, 1609.  The castle is noted for its towers and turrets. All the outer corners are decorated with towers. Two octagonal towers with lofty spires overlook the lake (Mønttårnet to the west and Jægerbakkettårnet to the east) and two round one-storey towers face the central islet. Stair turrets with copper-clad domes decorate the courtyard side of the King's Wing. The highest and most impressive tower stands above the Chapel. The chamfered corners of its multistorey spire are decorated with four obelisks.  The Audience House (Audienshuset) was completed in 1616. With its swinging gables and protruding bay windows in the Renaissance style, the elegant five-wing building on the middle islet over the moat from the Mønttårn tower on the main building. Its south-facing portal, Møntporten, decorated with figures including Venus and Mars surrounded by musicians, is considered to be one of Denmark's finest. In 1621, Christian IV decorated the King's Wing with the Great Gallery overlooking the courtyard. The statues of the gods, decorating the two storeys, were crafted by Hans van Steenwinckel the Younger in Amsterdam and brought to Denmark by ship.  The middle islet was further developed during the reign of Christian IV. The lord lieutenant's manor (Slotsherrens Hus) to the west was completed in 1611. The Chancellery to the east was erected in 1615 as a true copy of Berritsgård on the island of Lolland, one of the finest Renaissance buildings in Denmark. Both buildings were decorated with an octagonal turret and sweeping gables.  While most of the castle was destroyed by fire in 1859, the Chapel and its furnishings suffered only minor damage. The Chapel has also been used as the ceremonial chapel for the Order of the Elephant and the Order of the Dannebrog since 1693. It houses the Danish royal family's art collection, notably works on the life of Jesus by the Danish painter Carl Heinrich Bloch. The Chapel was also the site of the signing of the Treaty of Frederiksborg. Since the times of Christian IV, it has been used as a parish church. Today it is served by four priests and two organists.  The coats-of-arms of recipients of the Order of the Elephant and of the Dannebrog are displayed on the Chapel walls. They include those of international figures such as Nelson Mandela and outstanding Danes including Niels Bohr and Mærsk McKinney Møller.

Neptune fountain.

Designed by Adrien de Vries, the Neptune fountain is considered to be the castle's sculptural masterpiece. It was created from 1620 to 1622 to stand on the castle's forecourt symbolizing Denmark's position as a leading Nordic power in the early 17th century. The large bronze figures were cast in Prague where de Vries was employed as a sculptor by the imperial palace. Symbolizing the Danish king, the sea god Neptune is the central figure, while tritons piping their seashells decorate the outer basin. The current fountain is a copy of the original which was dismantled by the Swedish troops in 1659 and taken to Sweden for war reparations following the Treaty of Roskilde in 1658. The reassembled fountain now stands in the gardens of Drottningholm Palace outside Stockholm. The copy was made by Heinrich Hansen in 1888 with funding from J.C. Jacobsen.

The Museum of National History.

The Frederiksborg Museum was founded by a royal decree on 5 April 1878 and was opened to the public on 1 February 1882. The original collection was based on the paintings which had been saved from the castle fire but, with the help of the Jacobsen fund, it was soon extended to include other cultural artefacts including paintings and furniture. Over the next thirty years, the collection was considerably extended with paintings providing a national record of the most important figures in Danish history from the Middle Ages to the present day. Today the portrait collection is the largest in Denmark. In addition to its 70 rooms in the three storeys of the King's Wing and the Princess's Wing, the Chapel, the Rose Room and the Audience Room are included in the museum. The museum also hosts special exhibitions. Since 2010 it has also hosted a censored international portrait exhibition.

Valdemar Room.

The first and second storeys of the King's Wing present the history of Denmark from the 12th to the 17th century. The Valdemar Room contains a number of history paintings which were specially commissioned for the museum, including Carl Bloch's "" (1871), Otto Bache's "" (1882) showing the conspirators riding away from Finderup near Viborg after the murder of Erik Klipping, and Laurits Tuxens 1894 work depicting Valdemar the Great and Absalon destroying Svantevit's temple on the island of Rügen. The Valdemar Room also contains a copy of the oldest Danish flag from 1427. The original used to hang in Lübeck Cathedral where it was destroyed by bombing in 1942. The portrait collection also contains a number of truly historic works including Karel van Mander's paintings of Leonora Christina and Christian IV, and a number of works by Jacob Binck. The works in the east wing are mainly from the 18th and 19th centuries and include Constantin Hansen's historic painting of the "".

Chapel.

The chapel, consecrated in 1617, is also part of the museum. It is the best preserved part of the Renaissance complex, having largely escaped damage in the 1859 fire. The chapel extends along the entire length of the west wing with a long nave and a two-storey gallery. The richly decorated six-vaulted stucco ceiling is borne by pillars rising from the galleries.  The pillars bear grisaille frescos of Biblical figures, painted in the 1690s. The galleries were decorated during the reign of Frederick III (1648–1670) as can be see from his arms.  The Chapel's most significant artifact is the organ, built by Esajas Compenius in 1610. It was installed by Compenius himself shortly before his death in Hillerød in 1617. The oldest organ in Denmark, it has 1,001 wooden pipes. Its original manually driven blower has been preserved. The instrument is richly decorated with ebony, ivory and silver.  The altarpiece and pulpit from the early 17th century are the work of the silversmith Jacob Mores from Hamburg. In the king's prayer chamber adjoining the Chapel, there is a small silver altar crafted by the goldsmith Matthäus Wallbaum from Augsburg in 1600.

Great Hall.

The Great Hall ("Riddersalen") is situated above the Chapel and also extends over the length of the west wing. It was destroyed by fire in 1859 but was almost fully restored thanks to architectural paintings made by Heinrich Hansen and F.C. Lund. The restoration work, completed in 1880, was carried out by Ferdinand Meldahl who made use of preserved segments of the ornate gilded ceiling. The large chandelier in the centre of the room is the work of Meldahl's pupil, Carl Brummer. The original tapestries depicting important events in the life of Christian IV were woven in Karel van Mander's workshop in Delft. The copies decorating the walls of the hall today were created from Mander's sketches.

The Rose.

The room on the ground floor in the King's Wing known as the Rose was originally a dining room for the king and his courtiers. It was also destroyed by the fire in 1859, but was reconstructed from old paintings. The two series of six vaults rest on free-standing pillars. It is thought Mehldahl managed to reuse parts of the window decorations including the monograms of Christian IV and Queen Catherine.

Audience Chamber.

Extending into the middle islet, the Audience Chamber also escaped damage from the fire in 1859. It was decorated by Christian V's master builder Lambert van Haven in the 1680s, combining the Renaissance style with Baroque. He had himself brought the paintings in adjoining Privy Passage ("Conseilgangen") back from Italy. His work was completed in 1688, making the Audience Chamber the oldest preserved Baroque room in Denmark. The sumptuous ceiling in the Privy Passage with flowering vines, creepers and rosettes is the work of the stucco artists Jan Wilckens van Verelt and Christian Nerger. The Audience Chamber itself was completed in 1689. The chandelier with a carved deer was crafted around 1625 by Hans Ocksen. The chair in the north-east corner allowed the king to be lifted up from the building's entrance. The central dome, designed by van Haven, bears the motto of Christian V, "Pietate et Justitia" (Piety and Justice) and is decorated with allegorical paintings of a Christian queen, a negro, a Turk, and an American Indian representing Europe, Africa, Asia and America. The paintings on the walls by the Christian V's court painter Jacob d'Agar depict the kings ancestors. They are surmounted by scenes from the king's glorious Scanian War (1675–1697) painted by Claus Møinchen and Christian Morholt, despite the fact that in the end, Denmark was defeated.

Castle parks.

In 1850, Frederick VII had a landscaped garden laid out to the north-west of the castle with winding paths, canals and artificial lakes. On Louise's Island, named after his third wife, a small wooden manor house was built in the Norwegian style, from which the king could go out fishing and enjoy uninterrupted breaks with his wife.  To the east of the castle, the Baroque Park with its waterfalls was originally created by the court gardener Johan Cornelius Krieger for Frederick IV in the early 1720s. Its carefully planned symmetrical features were designed to surround the parks centrepiece, a fountain from which water cascaded down the terraces to the lake below. Neatly laid out paths, shrubs and flowerbeds were arranged around the central fountain. The garden was maintained until the beginning of the 19th century when it was abandoned. The shrubs grew wild but the paths and terraces could still be seen. In 1993 it was decided to recreate the park in its original style. Now known as "Kaskaderne" (The Cascades), it was reopened in 1996 with a multitude of new shrubs and trees, making it Denmark's most notable Baroque garden. Crafted in miniature hedges, the monograms of Frederick IV, Christian VI, Frederick V and Margrethe II form part of the central layout.

Countess of Frederiksborg.

Alexandra Christina Manley was created Countess of Frederiksborg ("Grevinde af Frederiksborg") by Queen Margrethe II on April 16, 2005, eight days after her divorce from Prince Joachim. The title refers to her marriage to the prince which took place in the castle's chapel.

Cultural references.

Frederiksborg Castle features prominently in Theodor Fontane’s novel Irretrievable (German: Unwiederbringlich, 1892, also known as Beyond Recall and No Way Back).  It is also used as a location at 0:07:57 in the 1978 "Olsen-banden" film "The Olsen Gang Sees Red"..

Frederiksborg in art.

There are a number of notable paintings of Frederiksborg, including:  Court life at the castle and the 1859 fire are depicted in the 1892 novel "Irretrievable" by German realist Theodor Fontane.

Frederiksborg Castle () is a palatial complex in Hillerød, Denmark. It was built as a royal residence for King Christian IV of Denmark-Norway in the early 17th century, replacing an older castle acquired by Frederick II and becoming the largest Renaissance residence in Scandinavia. Situated on three islets in the "Slotssøen" (castle lake), it is adjoined by a large formal garden in the Baroque style.

腓特烈堡城堡,又称水晶宫,位于丹麦的希勒勒。腓特烈堡城堡始建于1560年,当时的腓特烈堡城堡是一块私人庄园,不过丹麦国王弗雷德里克二世为了讨好皇后苏菲,于是用一座森林寺院与庄园的主人海洛夫·特罗勒交换,弗雷德里克二世并在城堡的两翼加建了皇后长廊,连接教堂及宫殿。弗雷德里克二世死后,其儿子克利斯蒂安四世执政,花了二十年时间对城堡进行了改建,使城堡复修成荷兰风格的文艺复兴建筑。1721年,克利斯蒂安六世建造了一座新的行宫,名为和平宫,而腓特烈堡城堡则辟建为皇家博物馆。1878年,丹麦正式将腓特烈堡城堡改为国家历史博物馆。1882年,腓特烈堡城堡正式向公众开放。


Pre-zygotic isolation.

Pre-zygotic isolation mechanisms are the most economic in terms of the natural selection of a population, as resources are not wasted on the production of a descendant that is weak, non-viable or sterile. These mechanisms include physiological or systemic barriers to fertilization.

Temporal or habitat isolation.

Any of the factors that prevent potentially fertile individuals from meeting will reproductively isolate the members of distinct species. The types of barriers that can cause this isolation include: different habitats, physical barriers, and a difference in the time of sexual maturity or flowering.  An example of the ecological or habitat differences that impede the meeting of potential pairs occurs in two fish species of the family "Gasterosteidae" (sticklebacks). One species lives all year round in fresh water, mainly in small streams. The other species lives in the sea during winter, but in spring and summer individuals

Behavioral isolation.

The different mating rituals of animal species creates extremely powerful reproductive barriers, termed sexual or behavior isolation, that isolate apparently similar species in the majority of the groups of the animal kingdom. In dioecious species, males and females have to search for a partner, be in proximity to each other, carry out the complex mating rituals and finally copulate or release their gametes into the environment in order to breed.  Mating dances, the songs of males to attract females or the mutual grooming of pairs, are all examples of typical courtship behavior that allows both recognition and reproductive isolation. This is because each of the stages of courtship depend on the behavior of the partner. The male will only move onto

Mechanical isolation.

Mating pairs may not be able to couple successfully if their genitals are not compatible. The relationship between the reproductive isolation of species and the form of their genital organs was signaled for the first time in 1844 by the French entomologist Léon Dufour. Insects' rigid carapaces act in a manner analogous to a lock and key, as they will only allow mating between individuals with complementary structures, that is, males and females of the same species (termed "co-specifics").  Evolution

Gametic isolation.

The synchronous spawning of many species of coral in marine reefs means that inter-species hybridization can take place as the gametes of hundreds of individuals of tens of species are liberated into the same water at the same time. Approximately a third of all the possible crosses between species are compatible, in the sense that the gametes will fuse and lead to individual hybrids. This hybridization apparently plays a fundamental role in the evolution of coral species. However, the other two-thirds of possible crosses are incompatible. It has been observed that in sea urchins of the genus "Strongylocentrotus" the concentration of spermatocytes that allow 100% fertilization of the ovules of the same species is only able to fertilize 1.5% of the ovules of other species. This inability to produce hybrid offspring, despite the fact that the gametes are

Post-zygotic isolation.

A number of mechanisms which act after fertilization preventing successful inter-population crossing are discussed below.

Zygote mortality and non-viability of hybrids.

A type of incompatibility that is found as often in plants as in animals occurs when the egg or ovule is fertilized but the zygote does not develop, or it develops and the resulting individual has a reduced viability. This is the case for crosses between species of the frog genus, where widely differing results are observed depending upon the species involved. In some crosses there is no segmentation of the zygote (or it may be that the hybrid is extremely non-viable and changes occur from the first mitosis). In others, normal segmentation occurs in the blastula but gastrulation fails. Finally, in other crosses, the initial stages are normal but errors occur in the final phases of embryo

Hybrid sterility.

A hybrid may have normal viability but is typically deficient in terms of reproduction or is sterile. This is demonstrated by the mule and in many other well known hybrids. In all of these cases sterility is due to the interaction between the genes of the two species involved; to chromosomal imbalances due to the different number of chromosomes in the parent species; or to nucleus-cytoplasmic interactions such as in the case of "Culex" described above.  Hinnies and mules are hybrids resulting from a cross between a horse and a donkey or between a mare and a donkey, respectively. These animals are nearly always sterile due to the difference in the number of chromosomes between the two parent species. Both horses and donkeys belong to the genus "Equus", but "Equus caballus" has 64 chromosomes, while "Equus asinus" only has 62. A cross will produce

Multiple mechanisms.

In general, the barriers that separate species do not consist of just one mechanism. The twin species of "Drosophila", "D. pseudoobscura" and "D. persimilis", are isolated from each other by habitat ("persimilis" generally lives in colder regions at higher altitudes), by the timing of the mating season ("persimilis" is generally more active in the morning and "pseuoobscura" at night) and by behavior during mating (the females of both species prefer the males of their respective species). In this way, although the

Hybrid sex: Haldane's rule.

Haldane's rule states that when one of the two sexes is absent in interspecific hybrids between two specific species, then the sex that is not produced, is rare or is sterile is the heterozygous (or heterogametic) sex. In mammals, at least, there is growing evidence to suggest that this is due to high rates of mutation of the genes determining masculinity in the Y chromosome.  It has been suggested that Haldane's rule simply reflects the fact that the male sex

Genetics.

Pre-copulatory mechanisms in animals.

The genetics of ethological isolation barriers will be discussed first. Pre-copulatory isolation occurs when the genes necessary for the sexual reproduction of one species differ from the equivalent genes of another species, such that if a male of species A and a female of species B are placed together they are unable to copulate. Study of the genetics involved in this reproductive barrier tries to identify the genes that govern distinct sexual behaviors in the two species. The males of "Drosophila melanogaster" and those of "D. simulans" conduct an elaborate courtship with their respective females, which are different for each species, but the differences between the species are more quantitative than qualitative. In fact the "simulans" males are able to hybridize with the "melanogaster" females. Although there are

Post-copulation or fertilization mechanisms in animals.

Reproductive isolation between species appears, in certain cases, a long time after fertilization and the formation of the zygote, as happens – for example – in the twin species "Drosophila pavani" and "D. gaucha". The hybrids between both species are not sterile, in the sense that they produce viable gametes, ovules and spermatozoa. However, they cannot produce offspring as the sperm of the hybrid male do not survive in the semen receptors of the females, be they hybrids or from the parent lines. In the same way, the sperm of the males of the two parent species do not survive in the reproductive tract of the hybrid female. This type of post-copulatory isolation appears as the most efficient system for maintaining reproductive isolation in many species.  The development of a zygote into an adult is a complex and delicate process of interactions between genes and the environment that must be carried out precisely, and if there is any alteration in the usual process, caused by the absence of a necessary gene or the presence of a different one, it can arrest the normal development causing the non-viability of the hybrid or its sterility. It should be borne in mind that half of the chromosomes and genes

In plants.

A large variety of mechanisms have been demonstrated to reinforce reproductive isolation between closely related plant species that either historically lived or currently live in sympatry. This phenomenon is driven by strong selection against hybrids, typically resulting from instances in which hybrids suffer reduced fitness. Such negative fitness consequences have been proposed to be the result of negative epistasis in hybrid genomes and can also result from the effects of hybrid sterility. In such cases, selection gives rise to population-specific isolating mechanisms to prevent either fertilization by interspecific gametes or the development of hybrid embryos.  Because many sexually reproducing species of

Examples of pre-fertilization mechanisms.

A well-documented example of a pre-fertilization isolating mechanism comes from study of Louisiana iris species. These iris species were fertilized with interspecific and conspecific pollen loads and it was demonstrated by measure of hybrid progeny success that differences in pollen-tube growth between interspecific and conspecific pollen led to a lower fertilization rate by interspecific pollen. This

Examples of post-fertilization mechanisms.

Crosses between diploid and tetraploid species of Paspalum provide evidence of a post-fertilization mechanism preventing hybrid formation when pollen from tetraploid species was used to fertilize a female of a diploid species. There

Effects of hybrid necrosis.

Plant hybrids often suffer from an autoimmune syndrome known as hybrid necrosis. In the hybrids, specific gene products contributed by one of the parents may be

Chromosomal rearrangements in yeast.

In brewers' yeast "Saccharomyces cerevisiae", chromosomal rearrangements are a major mechanism to reproductively isolate different strains. Hou et al. showed that reproductive isolation acts postzygotically and could be

Incompatibility caused by microorganisms.

In addition to the genetic causes of reproductive isolation between species there is another factor that can cause post zygotic isolation: the presence of microorganisms in the cytoplasm of certain species. The presence of these organisms in a species and their absence in another causes the non-viability of the corresponding hybrid. For example, in the semi-species of the group "D. paulistorum" the hybrid females are fertile but the males are sterile, this is due to the presence of a "Wolbachia" in the cytoplasm which alters spermatogenesis leading to sterility. It is interesting that incompatibility or isolation can also arise at an intraspecific level. Populations of "D. simulans" have been studied that show hybrid sterility according to the direction

Selection.

In 1950 K. F. Koopman reported results from experiments designed to examine the hypothesis that selection can increase reproductive isolation between populations. He used "D. pseudoobscura" and "D. persimilis" in these experiments. When the flies of these species are kept at 16 °C approximately a third of the matings are interspecific. In the experiment equal numbers of males and females of both species were placed in containers suitable for their survival and reproduction. The progeny of each generation were examined in order to determine if there were any interspecific hybrids. These hybrids were then eliminated. An equal number of males and females of the resulting progeny were then chosen to act as progenitors of the next generation. As the hybrids were destroyed in each generation the flies that solely mated with members of their own species produced more surviving descendants than the flies that mated solely with individuals of the other species. In the adjacent table it can be seen that for each generation the number of hybrids continuously decreased up to the tenth generation when hardly any interspecific hybrids were produced. It is evident that selection against the hybrids was very effective in increasing reproductive isolation between these species. From the third generation, the proportions of the hybrids were less than 5%.

Notes.

a. The DNA of the mitochondria and chloroplasts is inherited from the maternal line, i.e. all the progeny derived from a particular cross possess the same cytoplasm (and genetic factors located in it) as the female progenitor. This is because the zygote possesses the same cytoplasm as the ovule, although its nucleus comes equally from the father and the mother.

The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring are sterile. These barriers maintain the integrity of a species by reducing gene flow between related species.

生殖隔离,又称生殖屏障,在生物学上通常指由于生殖方面的原因,即使地缘关系相近,但物种不同的类群之间不能互相交配,或不易交配成功的隔离机制。一般来讲生殖隔离用以定义物种,不具有生殖隔离的两个个体则以最多以亚种加以区分,生殖隔离的演化即是物种形成。


Name.

For a while during the rule of Antiochus IV Epiphanes (175 - 164 BCE) the city was named "Callirrhoe" or "Antiochia on the Callirhoe" (). During Byzantine rule it was named "Justinopolis". Prior to Turkish rule, it was often best known by the name given it by the Seleucids,, "Édessa".  "Şanlı" means "great, glorious, dignified" in Turkish, and Urfa was officially renamed "Şanlıurfa" ("Urfa the Glorious") by the Turkish Grand National Assembly in 1984, in recognition of the local resistance in the Turkish War of Independence. The title was achieved following repeated requests by the city's members of parliament, desirous to earn a title similar to those of neighbouring cities "Gazi" (veteran) Antep and "Kahraman" (Heroic) Maraş.

History.

The history of Urfa is recorded from the 4th century BC, but may date back at least to 9000 BC, when there is ample evidence for the surrounding sites at Duru, Harran and Nevali Cori. Within the further area of the city are three Neolithic sites known: Göbekli Tepe, Gürcütepe and the city itself, where the life-sized limestone "Urfa Man" statue was found during an excavation in Balıklıgöl and is now on display at the Şanlıurfa Archaeology and Mosaic Museum. The city was one of several in the upper Euphrates-Tigris basin, the fertile crescent where agriculture began.  According to Jewish and Muslim sources, Urfa is Ur Kasdim, the hometown of Abraham, the grandfather of Jacob whom God named Israel. This identification was disputed by Leonard Woolley, the excavator of the Sumerian city of Ur in 1927 and scholars remain divided on the issue. Urfa is also one of several cities that have traditions associated with Job.  For the Armenians, Urfa is considered a holy place since it is believed that the Armenian alphabet was invented there.  Urfa was conquered repeatedly throughout history, and has been dominated by many civilizations, including the Ebla, Akkadians, Sumerians, Babylonians, Hittites, Hurri-Mitannis, Assyrians, Medes, Persians, Ancient Macedonians (under Alexander the Great), Seleucids, Armenians, Arameans, the Neo-Assyrian Osrhoenes, Romans, Sassanids, Byzantines, and Arabs

City of Edessa.

Although the site of Urfa has been inhabited since prehistoric times, the modern city was founded in 304 B.C by Seleucus I Nicator and named after the ancient capital of Macedonia. In the late 2nd century, as the Seleucid dynasty disintegrated, it became the capital of the Arab Nabataean Abgar dynasty, which was successively a Parthian, Armenian, and Roman client state and eventually a Roman province. Its location on the eastern frontier of the Empire meant it was frequently conquered during periods when the Byzantine central government was weak, and for centuries, it was alternately conquered by Arab, Byzantine, Armenian, Turkish rulers. In 1098, the Crusader Baldwin of Boulogne induced the final Armenian ruler to adopt him and then seized power, establishing the first Crusader State known as the County of Edessa and imposing Latin Christianity on the Greek Orthodox and Armenian Apostolic majority of the population.

Age of Islam.

Islam first arrived in Urfa around 638 AD, when the region surrendered to the Rashidun army without resisting, and became a significant presence under the Ayyubids (see: Saladin Ayubbi), Seljuks. In 1144, the Crusader state fell to the Turkish Abassid general Zengui, who had most of the Christian inhabitants slaughtered together with the Latin archbishop (see Siege of Edessa) and the subsequent Second Crusade failed to recapture the city. Subsequently, Urfa was ruled by Zengids, Ayyubids, Sultanate of Rum, Ilkhanids, Memluks, Akkoyunlu and Safavids before Ottoman conquest in 1516.  Under the Ottomans Urfa was initially made centre of Raqqa Eyalet, laterly part Urfa (Sanjak) of the Aleppo Vilayet. The area became a centre of trade in cotton, leather, and jewellery. There was a small but ancient Jewish community in Urfa, with a population of about 1,000 by the 19th century. Most of the Jews emigrated in 1896, fleeing the Hamidian massacres, and settling mainly in Aleppo, Tiberias and Jerusalem. There were three Christian communities: Syriac, Armenian, and Latin. According to Lord Kinross, 8,000 Armenians were massacred in Urfa in 1895. The last Neo-Aramaic Christians left in 1924 and went to Aleppo (where they settled in a place that was later called "Hay al-Suryan" "The Syriac Quarter").

First World War and after.

During the First World War, Urfa was a site of the Armenian and Assyrian Genocides, beginning in August 1915. By the end of the war, the entire Christian population had been killed, had fled, or was in hiding.  The British occupation of the city of Urfa started de facto on 7 March 1919 and officially de jure as of 24 March 1919, and lasted until 30 October 1919. French forces took over the next day and lasted until 11 April 1920, when they were defeated by local resistance forces before the formal declaration of the Republic of Turkey on 23 April 1920).  The French retreat from the city of Urfa was conducted under an agreement reached between the occupying forces and the representatives of the local forces, commanded by Captain Ali Saip Bey assigned from Ankara. The withdrawal was meant to take place peacefully, but was disrupted by an ambush on the French units by irregular Kuva-yi Milliye Şebeke Pass on the way to Syria, leading to 296 casualties among the French.  Modern Urfa presents stark contrasts between its old and new quarters.

Politics.

It is a stronghold of the governing Justice and Development Party. However, in the 2009 local elections, the city elected an independent, Ahmet Eşref Fakibaba, as mayor.

Cuisine.

As the city of Urfa is deeply rooted in history, so its unique cuisine is an amalgamation of the cuisines of the many civilizations that have ruled in Urfa. Dishes carry names in Kurdish, Arabic, Armenian, Syriac, and Turkish, and are often prepared in a spicy manner. It is widely believed that Urfa is the birthplace of many dishes, including Raw Kibbé (Çiğ Köfte), that according to the legend, was crafted by the Prophet Abraham from ingredients he had at hand. The walnut-stuffed Turkish dessert crepe (called "şıllık") is a regional specialty.  Many vegetables are used in the Urfa cuisine, such as the "'Ecır," the "Kenger," and the "İsot", the legendary local red capsicum that is a smaller and darker cultivar of the Aleppo pepper that takes a purplish black hue when dried and cured.  Unlike most of the Turkish cities that use different versions of regular butter in their regional cuisine, Urfa is, together with Antep, Mardin and Siirt a big user of clarified butter, made exclusively from sheep's milk, called locally "Urfayağı" (""Urfabutter"").

Transport.

Şanlıurfa GAP Airport is located about 34 km (21 mi) northeast of the city and has direct flights to Istanbul, Ankara and Izmir.  The first 7.7km section, connecting the city centre with the museum quarter, of a planned 4-route, 78km network of trolleybus lines opened on 16 October 2018. An initial fleet of 10 bi-articulated trolleybuses, together with all fixed equipment, has been supplied by manufacturer Bozankaya.

Climate.

Urfa has a hot summer Mediterranean climate (Köppen climate classification "Csa"). Urfa is very hot during the summer months. Temperatures in the height of summer usually reach 39 °C (102 °F). Rainfall is almost non-existent during the summer months. Winters are cool and wet. Frost is common and there is sporadic snowfall. Spring and autumn are mild and also wet.

Urfa, officially known as Şanlıurfa (; ; ; ; and known in ancient times as Edessa, is a city with a population of over 2 million residents in south-eastern Turkey, and the capital of Şanlıurfa Province. Urfa is a multiethnic city with a Turkish, Kurdish and Arab population. Urfa is situated on a plain about eighty kilometres east of the Euphrates River. Its climate features extremely hot, dry summers and cool, moist winters.

尚勒乌尔法(;),当地人一般简称作乌尔法(;;),古时称为埃德萨, 是土耳其的城市,也是尚勒乌尔法省的首府,位于该国东南部,海拔高度518米,受半干旱气候影响,每年平均降雨量442毫米,2010年人口498,111。当地人口混杂,土耳其人、库尔德人及阿拉伯人均有在当地定居。乌尔法位于幼发拉底河以东80公里的一个平地,夏季非常热和干,而冬天清凉潮湿。


Accidents.

1960 loss of coolant.

On 13 October 1960, while operating in the Barents Sea, "K-8" suffered a ruptured steam generator tube, causing a loss-of-coolant accident. While the crew jury-rigged a system to supply emergency cooling water to the reactor, preventing a reactor core meltdown, large amounts of radioactive gas leaked out which contaminated the entire vessel. The gas radiation levels could not be determined because instrumentation could not measure such large scales. Three of the crew suffered visible radiation injuries, and many crewmen were exposed to doses of up to 1.8–2 Sv (180–200 rem).

1970 Bay of Biscay fire.

During the large-scale "Ocean-70" naval exercise, K-8 suffered fires in two compartments simultaneously on 8 April 1970. Due to short circuits that took place in III and VII compartments simultaneously at a depth of, a fire spread through the air-conditioning system. Both nuclear reactors were shut down.  The captain ordered his entire crew to abandon ship but was countermanded once a towing vessel arrived. Fifty-two crewmen, including the commander, Captain 2nd Rank Vsevolod Borisovich Bessonov, re-boarded the surfaced submarine that was to be towed. This was the first loss of a Soviet nuclear-powered submarine, which sank in rough seas as it was being towed in the Bay of Biscay of the North Atlantic Ocean. Eight mariners had already died due to certain compartments being locked to prevent further flooding as well as the spread of the fire as soon as it was detected. All hands on board died due to CO poisoning and the flooding of the surfaced submarine during 80 hours of damage control in stormy conditions. Seventy-three crewmen survived. "K-8" sank with four nuclear torpedoes out of total 24 on board to a depth of approximately northwest of Spain.

K-8 was a of the Soviet Northern Fleet that sank in the Bay of Biscay with her nuclear weapons on board on April 12, 1970. A fire on April 8 had disabled the submarine and it was being towed in rough seas. Fifty-two crewmen were killed attempting the salvage of the boat when it sank.

信号情报(SIGINT)是一个总称,包括通信情报(COMINT)、电子情报(ELINT)以及量度与特征情报(MASINT)系统。美国国防部的定义为: 卫星拍摄或者航空摄影等手段获得的图像情报(IMINT),包括可见光、红外成像、紫外成像、合成孔径雷达(SAR)或活动目标指示器(MTI)成像等,一般不算作信号情报。


Other cultivar groups of "Brassica oleracea".

Other cultivar groups of "Brassica oleracea" include cabbage (Capitata Group), cauliflower and Romanesco broccoli (Botrytis Group), kale and collard (Acephala Group), kohlrabi (Gongylodes Group), Brussels sprouts (Gemmifera Group), and kai-lan (Alboglabra Group). Broccolini or "Tenderstem broccoli" is a cross between broccoli and Chinese broccoli.

Varieties.

There are three commonly grown types of broccoli. The most familiar is Calabrese broccoli, often referred to simply as "broccoli", named after Calabria in Italy. It has large (10 to 20 cm) green heads and thick stalks. It is a cool-season annual crop. Sprouting broccoli (white or purple) has a larger number of heads with many thin stalks. Purple cauliflower is a type of broccoli grown in Europe and North America. It has a head shaped like cauliflower, but consisting of tiny flower buds. It sometimes, but not always, has a purple cast to the tips of the flower buds.  Other popular cultivars include Belstar, Blue Wind, Coronado Crown, Destiny, DiCicco, Green Goliath, Green Magic, Purple Sprouting, Romanesco, Sun King and Waltham 29.  Beneforté is a variety of broccoli containing 2–3 times more glucoraphanin and produced by crossing broccoli with a wild Brassica variety, "Brassica oleracea" var "villosa".

Production.

In 2017, global production of broccoli (combined for production reports with cauliflowers) was 26.0 million tonnes, with China and India together accounting for 73% of the world total. Secondary producers, each having about one million tonnes or less annually, were the United States, Spain, Mexico and Italy.  In the United States, broccoli is grown year-round in California – which produces 92% of the crop nationally – with 95% of the total crop produced for fresh sales.

Cultivation.

The majority of broccoli cultivars are cool-weather crops that do poorly in hot summer weather. Broccoli grows best when exposed to an average daily temperature between. When the cluster of flowers, also referred to as a "head" of broccoli, appear in the center of the plant, the cluster is generally green. Garden pruners or shears are used to cut the head about an inch from the tip. Broccoli should be harvested before the flowers on the head bloom bright yellow.<ref

Broccoli is an edible green plant in the cabbage family (family Brassicaceae, genus "Brassica") whose large flowering head and stalk is eaten as a vegetable. The word "broccoli" comes from the Italian plural of "", which means "the flowering crest of a cabbage", and is the diminutive form of "brocco", meaning "small nail" or "sprout".

-{zh-cn:西兰花; zh-tw:青花菜; zh-hk:西兰花;}-(学名:,英语:Broccoli),又称-{zh-cn:青花菜; zh-tw:西兰花; zh-hk:青花菜;}-、绿花菜、绿花椰菜、百加利(一些海外的中国餐馆所用音译),是一种蔬菜。西兰花源于意大利,和花椰菜、结球甘蓝、翠绿花椰菜同为甘蓝的变种。因产自西方,与同属甘蓝变种的芥蓝味道极其相似,而又像其花朵得名西兰花,也因像青绿色菜花而得名绿菜花。


History.

Flavius Victor was born at an unknown date, to Magnus Maximus, the Magister militum per Gallias (Master of the Soldiers in Gaul), and future usurper of the Western Roman Empire. Maximus was declared emperor in July 383AD while in Britain, in opposition to Gratian. Maximus held control over both Gaul and Spain, and was recognized by Theodosius I, the Eastern Roman Emperor, as the true Western Roman Emperor.  Victor was elevated to "augustus" of the Western Roman Empire either 383/384 or mid-387, making him co-emperor with his father Magnus Maximus. It is considered highly likely that Maximus had the intent of establishing a dynasty, as the number of coins minted that bore Victor's image was greater even than the number bearing Maximus'.  Magnus Maximus invaded Italy in late 387, in order to depose Valentinian II, the brother of Gratian. He gained control of Italy, although he failed to capture Valentinian, who fled to Thessalonica in the Eastern Roman Empire. Once there, Valentinian sent multiple appeals to Theodosius, although for several months they were ignored. Theodosius I then agreed to restore Valentinian II to the throne, although the reasoning for this is disputed. Rufinus says that Valentinian agreed to convert to Orthodoxy, whereas Eunapius says that Valentinian offered his sister, Galla, in marriage to Theodosius, whose wife had recently died, in exchange for assistance in regaining the throne. News that Theodosius was marching to invade the Western Roman Empire arrived in late spring 388, leading Maximus to rush to put together a defence force. His army was defeated twice in Pannonia, at Siscia and Poetovio, before retreating to Italy, where they were crushed in battle on 28 August 388, near Aquilea. During this battle, Maximus himself was captured, and quickly beheaded. Victor, who was still in Gaul, was executed in Trier by the Frankish general Arbogast in the same month.

Victor (Flavius Victor Augustus; Unknown – August 388AD) was a Western Roman Emperor from either 383/384 or 387 to August 388. He was the son of the Magister militum per Gallias Magnus Maximus, who later became an usurper of the Western Roman Empire, in opposition to Gratian. Maximus rose up in 383, and was recognized as the legitimate emperor in the west by Theodosius I. Victor was elevated to "augustus" of the Western Roman Empire in either 383/384 or mid-387, making him co-emperor with his father. Maximus invaded Italy, in 387, to depose Valentinian II, the brother and successor of the late Gratian. Because of Maximus' invasion, Theodosius invaded the Western Roman Empire in 388. Theodosius defeated Maximus in two battles in Pannonia, before crushing his army at Aquilea, and capturing Maximus. Maximus was executed on 28 August 388. His death was followed quickly by Victor's, who was executed where he had stayed in Trier by the Frankish General Arbogast.

弗拉菲乌斯·维克多(,?-388年-8月),于383/384年或387年中至388年8月间短暂在任罗马皇帝(西部皇帝)。维克多的生年不详,其父马格努斯·马格西穆斯于383年7月反叛并击败了时任西部皇帝格拉提安,之后获东部皇帝狄奥多西一世承认为格拉提安的继任者。383/384年或387年中,维克多受封为奥古斯都,成为皇帝。387年,马格西穆斯入侵意大利,企图消灭格拉提安之弟瓦伦提尼安二世的势力;惟狄奥多西一世于388年挥军攻打西部罗马,马格西穆斯于潘诺尼亚两次与之交战皆被击败,之后在阿奎莱亚被狄奥多西一世擒获,当年8月28日被处决。同月,维克多亦于特里尔遭到法兰克人将领阿波加斯特处决。


Geography.

Elephantine is from north to south, and is across at its widest point. The layout of this and other nearby islands in Aswan can be seen from west bank hillsides along the Nile. The island is located just downstream of the First Cataract, at the southern border of Upper Egypt with Lower Nubia. This region above is referred to as Upper Egypt because it is further up the Nile.  The island may have received its name after its shape, which in aerial views is similar to that of an elephant tusk, or from the rounded rocks along the banks resembling elephants.

Ancient Egypt.

Known to the Ancient Egyptians as "Elephant" (Middle Egyptian: → Medio-Late Egyptian: → Coptic: (Ⲉ)<unk>ⲏ<unk> ), the island of Elephantine stood at the border between Egypt and Nubia. It was an excellent defensive site for a city and its location made it a natural cargo transfer point for river trade. This border is near the Tropic of Cancer, the most northerly latitude at which the sun can appear directly overhead at noon and from which it appears to reverse direction or "turn back" at the solstices.  Elephantine was a fort that stood just before the First Cataract of the Nile. During the Second Intermediate Period (1650–1550 BC), the fort marked the southern border of Egypt.  According to ancient Egyptian religion, Elephantine was the dwelling place of Khnum, the ram-headed god of the cataracts, who guarded and controlled the waters of the Nile from caves beneath the island. He was worshipped here as part of a late triad of Egyptian deities. This "Elephantine Triad" included Satis and Anuket. Satis was worshipped from very early times as a war goddess and protector of this strategic region of Egypt. When seen as a fertility goddess, she personified the bountiful annual flooding of the Nile, which was identified as her daughter, Anuket. The cult of Satis originated in the ancient city of Aswan. Later, when the triad was formed, Khnum became identified as her consort and, thereby, was thought of as the father of Anuket. His role in myths changed later and another deity was assigned his duties with the river. At that time his role as a potter enabled him to be assigned a duty in the creation of human bodies.

Archaeological sites.

Ongoing excavations by the German Archaeological Institute at the town have uncovered many findings, on display in the Aswan Museum located on the island, including a mummified ram of Khnum. Artifacts dating back to prehistoric Egypt have been found on Elephantine. A rare calendar, known as the "Elephantine Calendar of Things", which dates to the reign of Thutmose III during the Eighteenth Dynasty, was found in fragments on the island.  In ancient times the island was also an important stone quarry, providing granite for monuments and buildings all over Egypt.

Temples.

Prior to 1822, there were temples to Thutmose III and Amenhotep III on the island. At that time they were destroyed during the campaign of Muhammad Ali, who had taken power in Egypt, to conquer Sudan. Both temples were relatively intact prior to the deliberate demolition.  The first temple was the Temple of Satet, it was founded around 3000 BC and enlarged and renovated over the next 3,000 years. There are records of an Egyptian temple to Khnum on the island as early as the Third Dynasty. This temple was completely rebuilt in the Late Period, during the Thirtieth Dynasty of Egypt, just before the foreign rule that followed in the Graeco-Roman Period. The Greeks formed the Ptolemaic dynasty during their three-hundred-year rule over Egypt (305–30 BC) and maintained the ancient religious customs and traditions, while often associating the Egyptian deities with their own.  Most of the present day southern tip of the island is taken up by the ruins of the Temple of Khnum. These, the oldest ruins still standing on the island, are composed of a granite step pyramid from the Third Dynasty and a small temple built for the local Sixth Dynasty nomarch, Heqaib. In the Middle Kingdom, many officials, such as the local governors Sarenput I or Heqaib III, dedicated statues and shrines into the temple.

Nilometers.

A nilometer was a structure for measuring the Nile River's clarity and the water level during the annual flood season. There are two nilometers at Elephantine Island. The more famous is a corridor nilometer associated with the Temple of Satis, with a stone staircase that descends the corridor. It is one of the oldest nilometers in Egypt, last reconstructed in Roman times and still in use as late as the nineteenth century AD. Ninety steps that lead down to the river are marked with Arabic, Roman, and hieroglyphic numerals. Visible at the water's edge are inscriptions carved deeply into the rock during the Seventeenth Dynasty.  The other Nilometer is a rectangular basin located at the island's southern tip, near the Temple of Khnum and opposite the Old Cataract Hotel. It is probably the older of the two. One of the nilometers, though it is not certain which, is mentioned by the Greek historian Strabo.  Many sources claim that the fabled "Well of Eratosthenes", famous in connection with Eratosthenes' presumed calculation of the Earth's circumference, was located on the island. Strabo mentions a well that was used to observe that Aswan lies on the Tropic of Cancer, but the reference is to a well at Aswan, not at Elephantine. Neither nilometer at Elephantine is suitable for the purpose, while the well at Aswan is apparently lost.

Jewish presence.

The Elephantine papyri are caches of legal documents and letters written in Aramaic, which document a Jewish community, perhaps made up of mercenaries, dating to sometime in the 5th century BC. They maintained their own temple (also see House of Yahweh), in which sacrifices were offered, evincing polytheistic beliefs, which functioned alongside that of Khnum. The temple was destroyed in 410 BC at the instigation of the priests of Khnum.  The temple may have been built in reaction to Manasseh's reinstitution of pagan worship or simply to serve the needs of the Jewish community.

Other features.

The Aswan Museum is located at the southern end of the island. Ongoing excavations by the German Archaeological Institute at the island's ancient town site have uncovered many findings that are now on display in the museum, including a mummified ram of Khnum. A sizable population of Nubians live in three villages in the island's middle section. A large luxury hotel is at the island's northern end.  The Aswan Botanical Garden is adjacent to the west on el Nabatat Island.

Elephantine ( ; ; ; "Elephantíne"; "(Ə)iêw") is an island on the Nile, forming part of the city of Aswan in Upper Egypt. There are archaeological sites on the island.

象岛(),音译为斐莱岛等,埃及阿斯旺附近尼罗河中一岛屿,南北长1.2公里,东西宽0.4公里,著名景点。


Location.

Most modern island arcs are near the continental margins (majorly in the northern and western margins of the Pacific Ocean). However, no direct evidence from within the arcs shows that they have always existed at their present position with respect to the continents, although evidence from some continental margins suggests that some arcs may have migrated toward the continents during the late Mesozoic or early Cenozoic.  The movement of the island arcs towards the continent could be possible if, at some point, the ancient Benioff zones dipped toward the present ocean rather than toward the continent, as in most arcs today. This will have resulted in the loss of ocean floor between the arc and the continent, and consequently, in the migration of the arc during spreading episodes.  The fracture zones in which some active island arcs terminate may be interpreted in terms of plate tectonics as resulting from movement along transform faults, which are plate margins where the crust is neither being consumed nor generated. Thus the present location of these inactive island chains is due to the present pattern of lithospheric plates. However, their volcanic history, which indicates that they are fragments of older island arcs, is not necessarily related to the present plate pattern and may be due to differences in position of plate margins in the past.

Tectonic formation.

Understanding the source of heat that causes the melting of the mantle was a contentious problem. Researchers believed that the heat was produced through friction at the top of the slab. However, this is unlikely because the viscosity of the asthenosphere decreases with increasing temperature, and at the temperatures required for partial fusion, the asthenosphere would have such a low viscosity that shear melting could not occur.  It is now believed that water acts as the primary agent that drives partial melting beneath arcs. It has been shown that the amount of water present in the down-going slab is related to the melting temperature of the mantle. The greater the amount of water present, the more the melting temperature of the mantle is reduced. This water is released during the transformation of minerals as pressure increases, with the mineral carrying the most water being serpentinite.  These metamorphic mineral reactions cause the dehydration of the upper part of the slab as the hydrated slab sinks. Heat is also transferred to it from the surrounding asthenosphere. As heat is transferred to the slab, temperature gradients are established such that the asthenosphere in the vicinity of the slab becomes cooler and more viscous than surrounding areas, particularly near the upper part of the slab. This more viscous asthenosphere is then dragged down with the slab causing less viscous mantle to flow in behind it. It is the interaction of this down-welling mantle with aqueous fluids rising from the sinking slab that is thought to produce partial melting of the mantle as it crosses its wet solidus. In addition, some melts may result from the up-welling of hot mantle material within the mantle wedge. If hot material rises quickly enough so that little heat is lost, the reduction in pressure may cause pressure release or decompression partial melting.  On the subducting side of the island arc is a deep and narrow oceanic trench, which is the trace at the Earth's surface of the boundary between the down-going and overriding plates. This trench is created by the downward gravitational pull of the relatively dense subducting plate on the leading edge of the plate. Multiple earthquakes occur along this subduction boundary with the seismic hypocenters located at increasing depth under the island arc: these quakes define the Benioff zone.  Island arcs can be formed in intra-oceanic settings, or from the fragments of continental crust that have migrated away from an adjacent continental land mass or at subduction-related volcanoes active at the margins of continents.

Features.

Below are some of the generalized features present in most island arcs.  Fore-arc: This region comprises the trench, the accretionary prism, and the fore-arc basin. A bump from the trench in the oceanward side of the system is present (Barbados in the Lesser Antilles is an example). The fore-arc basin forms between the fore-arc ridge and the island arc; it is a region of undisturbed flat-bedded sedimentation.  Trenches: These are the deepest features of ocean basins; the deepest being the Mariana trench (~36,000 feet). They are formed by flexing of the oceanic lithosphere, developing on the ocean side of island arcs.  Back-arc basin: They are also referred to as marginal seas and are formed in the inner, concave side of island arcs bounded by back-arc ridges. They develop in response to tensional tectonics due to rifting of an existing island arc.  Benioff zone or Wadatti-Benioff zone: This is a plane that dips under the overriding plate where intense volcanic activity occurs, which is defined by the location of seismic events below the arc. Earthquakes occur from near surface to ~660 km depth. The dip of Benioff zones ranges from 30° to near vertical.  An ocean basin may be formed between the continental margin and the island arcs on the concave side of the arc. These basins have a crust which is either oceanic or intermediate between the normal oceanic crust and that typical of continents; heat flow in the basins is higher than in normal continental or oceanic areas.  Some arcs, such as the Aleutians, pass laterally into the continental shelf on the concave side of the arc, while most of the arcs are separated from the continental crust.  Movement between two lithospheric plates explains the major features of active island arcs. The island arc and small ocean basin are situated on the overlying plate which meets the descending plate containing normal oceanic crust along the Benioff zone. The sharp bending of the oceanic plate downward produces a trench.

Volcanic rocks in the island arc.

There are generally three volcanic series from which the types of volcanic rock that occur in island arcs are formed:  This volcanic series is related to the age of the subduction zone and the depth. The tholeiitic magma series is well represented above young subduction zones formed by magma from relative shallow depth. The calc-alkaline and alkaline series are seen in mature subduction zones, and are related to magma of greater depths. Andesite and basaltic andesite are the most abundant volcanic rock in island arc which is indicative of the calc-alkaline magmas. Some Island arcs have distributed volcanic series as can be seen in the Japanese island arc system where the volcanic rocks change from tholeiite—calc-alkaline—alkaline with increasing distance from the trench.  Several processes are involved in arc magmatism which gives rise to the great spectrum of rock composition encountered. These processes are, but not limited to, magma mixing, fractionation, variations in the depth and degree of partial melting and assimilation. Therefore, the three volcanic series results in a wide range of rock composition and do not correspond to absolute magma types or source regions.

Examples of ancient island arcs.

Remains of former island arcs have been identified at some locations. The table below mention a selection of these.

Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries (such as the Ring of Fire). Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction zone. They are the principal way by which continental growth is achieved.

岛弧(英语:Island arc)是位于大陆附近,向海洋凸出成圆弧状的列岛。它们常排列成花彩状,故可合称为花彩列岛。岛弧的形成是海洋板块沉入另一个邻近海洋板块时,岩浆喷出形成与板块平行的火山群岛或山脉。岛弧主要分布在太平洋边缘,是全球火山与地震最活跃的地带之一。


Geography.

The East China Sea is a part of the Pacific Ocean and covers an area of roughly. It is bounded on the east by Kyūshū and the Ryukyu Islands of Japan, on the south by the South China Sea, and on the west by the Asian continent. It connects with the Sea of Japan through the Korea Strait; it opens in the north to the Yellow Sea.  Countries with borders on the sea (clockwise from north) include: South Korea, Japan, Taiwan and the People's Republic of China.

Extent.

The International Hydrographic Organization defines the limits of the "Eastern China Sea (Tung Hai)" as follows:

Rivers.

The Yangtze River (Chang Jiang) is the largest river flowing into the East China Sea.

Islands and reefs.

There is a cluster of submerged reefs in the northern East China Sea. These include:

Nomenclature.

The sea is called the East Sea in Chinese (; "Dōng Hǎi"), and is one of the Four Seas of Chinese literature. There are three other seas, one for each of the four cardinal directions.  Until World War II, the sea was referred to as ("Higashi Shina Kai"; "East Shina Sea") in Japanese. In 2004, official documents of the Japanese Foreign Ministry and other departments switched to the name (pronounced the same), which has become the standard usage in Japan.  Common usage in Indonesia refers to the sea as "Laut Cina Timur" (East China Sea). This name was used officially by the Indonesian government until 2014, when Indonesia switched usage from the word Cina to Tiongkok instead; since then, the name "Laut Tiongkok Timur" become standard usage in Indonesia. Despite this, many Indonesian media outlets and publications continue to use the former sea name.

History.

Whaling.

American whaleships cruised for right whales in the sea between 1849 and 1892.

EEZ disputes.

There are disputes between the People's Republic of China (PRC), Japan, and South Korea over the extent of their respective exclusive economic zones (EEZ).  The dispute between the PRC and Japan concerns the different application of the 1982 United Nations Convention on the Law of the Sea (UNCLOS), which both nations have ratified. China and Japan both claim 200 nautical miles EEZ rights, but the East China Sea width is only 360 nautical miles. China proposed the application of UNCLOS, considering the natural prolongation of its continental shelf, advocating that the EEZ extends as far as the Okinawa Trough. Its Ministry of Foreign Affairs has stated that "the natural prolongation of the continental shelf of China in the East China Sea extends to the Okinawa Trough and beyond 200 nautical miles from the baselines from which the breadth of the territorial sea of China is measured," which is applicable to the relevant UNCLOS provisions that support China's right to the natural shelf. In 2012, China presented a submission under the UNCLOS concerning the outer limits of the continental shelf to the UN. However, Japan claims about 40,000 square kilometers part of this territory as its own EEZ because it is within 200 nautical miles (370 km) from its coast, and thus proposed the Median line division of the EEZ.  Rounds of disputes about island ownership in the East China Sea have triggered both official and civilian protests between China and Japan. The dispute between PRC and South Korea concerns Socotra Rock, a submerged reef on which South Korea has constructed the Ieodo Ocean Research Station. While neither country claims the rock as territory, the PRC has objected to Korean activities there as a breach of its EEZ rights.

Navy of the People's Republic of China (PRC).

In their sphere of naval operations along their littoral (in the East and South China Seas), China today possesses more naval vessels than those of the US Navy. US Presidents Barack Obama and Donald Trump have given priority to US naval operations, under the US Indo-Pacific Command, to expand its sphere of influence in the Pacific Ocean, to counter China's growing strength, and to be ready for any unforeseen challenges in the future.

East China Sea in astronomy.

Possibly, East China Sea ("Donghai" in Chinese) is represented with the star Eta Serpentis in asterism "Left Wall", Heavenly Market enclosure (see Chinese constellation).

The East China Sea is a marginal sea of the Western Pacific Ocean, located directly east of East China (hence the name), covering an area of roughly. Its northern extension between mainland China and the Korean Peninsula is the Yellow Sea, separated by an imaginary line between the eastern tip of Qidong, Jiangsu at the Yangtze River estuary and the southwestern tip of South Korea's Jeju Island.

东海,是指长江出海口以南、欧亚大陆以东的大片海域,为太平洋西部的陆缘海之一。南接台湾海峡,北临黄海以长江口北侧与韩国济州岛的连线为界,东临太平洋,以日本九州和琉球群岛为界。东海的面积是70余万平方公里,平均水深在1千余米,最深处接近日本冲绳本岛西侧的中琉界沟(),为2,700米。盐度为31-32‰,东部为34‰。海水温度平均9.2°C。冬季南部水温在20°C以上。整个海区介于北纬23°00′～33°10′,东经117°11′～ 131°00′之间。


History.

Guard dogs and watchdogs are one of the closest common human friends. The history of human beings and guard dogs dates back to the first day of the first generation of these animals.  The use of dogs as guardians is well known since ancient times. The Romans used to put mosaics ("Cave canem" mosaics) at the entrance of the houses to warn visitors and intruders of the presence of dangerous dogs at the property.  One of the 1st dog types used as guardians were the primitive mastiff-type landraces of the group known as Livestock guardian dogs with the function of protecting livestock against large predators such as wolves, bears and leopards. Orthrus is a famous example of a livestock guardian dog from the Greek mythology knowned for guarding Geryon's red cattle.  Some ancient guard dogs in more urban areas, such as the extinct bandogges, were chained during the day and released at night to protect properties, camps and villages.  Many landlords will not allow intimidating looking guard dog breeds and big game hunting breeds to live on their properties.

Barking.

Both guard dogs and watchdogs bark loudly to alert their owners of an intruder's presence and to scare away the intruder. The watchdog's function ends here; a guard dog is then capable of attacking and/or restraining the intruder.  Livestock guardian dogs are often large enough (100-200 lbs.) and strong enough to attack and drive away livestock predators. Some smaller breeds (such as Keeshonds and Tibetan Terriers) are excellent watchdogs, but not guard dogs, because they bark loudly to alert their masters of intruders, but are physically small and not given to assertive behavior. Guard dogs will bark to alert their master and to warn off an approaching animal or human threat prior to their interception of the trespasser. They are different from the smaller watchdogs in that they do not continue barking; they take action. Specifically, livestock guardian dogs such as the Kangal use loud alarm barks as a first line of defense against presumed threats; if these do not deter a perceived foe (either human or animal predators), other displays such as bluffing and charging are employed. For livestock guardians, proactive forms of defense such as bites are only used if all other forms of deterrence fail.  The following breeds are the best at watchdog barking:  If the risk is from human intruders, a suitable dog can be simply trained to be aggressive towards unrecognized humans and then tethered or enclosed unsupervised in an area that the owner wishes to protect when he is not around (such as at night); the stereotypical "junkyard dog" is a common example of this. If the purpose of the dog is to protect against human intruders after nightfall, a large, dark-colored dog in a dark house (lights off) would give the dog an advantage over the burglar.  It is claimed that female dogs tend to make better personal guardians than males, due to maternal instincts, but males are considered better for guarding property because of their greater territorial instinct. That may be true in general, but all dogs are individuals. Guarding against wolves, large male dogs would, in general, do better against large male wolves.  Despite the natural tendency for the guard function the training is essential to any dog.

Breeds.

Many currently prominent guard dogs started as general purpose farm dogs, but gradually developed into guard breeds. Some dog breeds such as the Dobermann and the Brazilian Dogo were carefully developed from the beginning for guard duty.  Many guard dog breeds have a greater amount of molossoid or mastiff DNA. This is confirmed by a DNA study done on over 270 purebred dogs. It suggests that 13 ancient breeds broke off early on, after which a group of mastiff-type dogs were developed. Despite this, the guard dogs are not restricted to mastiffs. Other dogs, like some shepherd dogs, spitz dogs, cattle dogs and some catch dogs are also great guard dogs as well as being useful as multifunctional dogs, acting as attack dogs, personal protection dogs, police dogs, sport dogs such as schutzhund dogs, etc.  Guard dog breeds tend to be territorial, averse to strangers, dominant, and protective and loyal with family. The Fila brasileiro for example has a reputation for being very intolerant of strangers and guests to the home and property. Other fierce guard dogs include breeds and landraces of the Ovtcharka type and other farm guard dogs such as the Boerboel.  Some breeds who make excellent guards are more commonly having breed specific legislation passed against them, banning them from some communities and whole countries.

Legality.

The laws regarding ownership and usage of guard dogs vary from country to country.In England the main legislation relating to the use of guard dogs on commercial premises are contained within the 1975 Guard Dogs Act, The act specifies the requirements of kennels and the need to display Guard Dog Warning Signs at the entrance to sites.

A guard dog or watchdog (not to be confused with an attack dog) is a dog used to guard property against, and watch for, unwanted or unexpected human or animal intruders.

看门狗(watchdog)或护卫犬(guard dog)是用来守卫或保安的狗,护卫犬会看守住家或是其他重要地点,避免未预期人员或动物的接近。


Name.

The name "Pamphylia" comes from the Greek Παμφυλία, itself from ("pamphylos"), literally "of mingled tribes or races", a compound of πᾶν ("pan"), neuter of πᾶς ("pas") "all" + φυλή ("phylē"), "race, tribe". Herodotus derived its etymology from a Dorian tribe, the Pamphyloi (Πάμφυλοι), who were said to have colonized the region. The tribe, in turn, was said to be named after Pamphylos (Greek: Πάμφυλος), son of Aigimios.

Origins of the Pamphylians.

The Pamphylians were a mixture of aboriginal inhabitants, immigrant Cilicians () and Greeks who migrated there from Arcadia and the Peloponnese in the 12th century BC. The significance of the Greek contribution to the origin of the Pamphylians can be attested alike by tradition and archaeology and Pamphylia can be considered a Greek country from the early Iron Age until the early Middle Ages.  There can be little doubt that the Pamphylians and Pisidians were the same people, though the former had received colonies from Greece and other lands, and from this cause, combined with the greater fertility of their territory, had become more civilized than their neighbours in the interior. But the distinction between the two seems to have been established at an early period. Herodotus, who does not mention the Pisidians, enumerates the Pamphylians among the nations of Asia Minor, while Ephorus mentions them both, correctly including the one among the nations on the coast, the other among those of the interior.  A number of scholars have distinguished in the Pamphylian dialect important isoglosses with both Arcadian and Cypriot (Arcadocypriot Greek) which allow them to be studied together with the group of dialects sometimes referred to as Achaean since it was settled not only by Achaean tribes but also colonists from other Greek-speaking regions, Dorians and Aeolians. The legend related by Herodotus and Strabo, which ascribed the origin of the Pamphylians to a colony led into their country by Amphilochus and Calchas after the Trojan War, is merely a characteristic myth.

History.

A treaty between the Hittite Great King Tudḫaliya IV and his vassal, the king of Tarḫuntašša, defined the latter's western border at the city "Parha" and the "Kastaraya River". The river is assumed to be the classical Kestros (Turkish Aksu Çayı); Parha, the future Perge. West of Parha were the "Lukka Lands". The Pamphylian language was likely a late Luwic dialect, related to Carian, Lycian, Lydian and/or Milyan.  When the region returns to history its population is "Pamphylian", that is Greek-speaking. On Cyrus's defeat of Croesus, Pamphylia passed to the Persian Empire. Darius included it in his first tax-district alongside Lycia, Magnesia, Ionia, Aeolia, Mysia, and Caria. At some point between 468 and 465 BC, the Athenians under Cimon fought the Persians at the Eurymedon, and won; thus adding Pamphylia to their "Delian League" empire. Toward the end of the Peloponnesian War, the Athenians were weakened enough that the Persians were able to retake it.  Upon Alexander the Great's defeat of Darius III, Pamphylia passed back to Greek rule, now Macedonians. After the defeat of Antiochus III in 190 BC they were included among the provinces annexed by the Romans to the dominions of Eumenes of Pergamum; but somewhat later they joined with the Pisidians and Cilicians in piratical ravages, and Side became the chief centre and slave mart of these freebooters. Pamphylia was for a short time included in the dominions of Amyntas, king of Galatia, but after his death lapsed into a district of a Roman province.  As of 1911, the district was largely peopled with recently settled Ottoman Muslims from Greece, Crete, and the Balkans, as a result of the long-term consequences of the Congress of Berlin and the collapse of the Ottoman Empire.

Pamphylia (, "Pamphylía", "Pamfylía" ) was a former region in the south of Asia Minor, between Lycia and Cilicia, extending from the Mediterranean to Mount Taurus (modern-day Antalya province, Turkey). It was bounded on the north by Pisidia and was therefore a country of small extent, having a coast-line of only about 120 km (75 miles) with a breadth of about 50 km (30 miles). Under the Roman administration the term Pamphylia was extended so as to include Pisidia and the whole tract up to the frontiers of Phrygia and Lycaonia, and in this wider sense it is employed by Ptolemy.

-{zh-hans:潘菲利亚;zh-hant:潘菲利亚}-(希腊语:Παμφυλία,台湾、香港及和合本圣经一般译作-{zh-hant:旁非利亚;zh-hans:旁非利亚}-)古代安纳托利亚南部的一个地区,位于今土耳其安塔利亚省境内,首府位于佩尔格。


Geography.

Lake Albert is located in the center of the African continent, on the border between Uganda and the Democratic Republic of the Congo. It is the northernmost of the chain of lakes in the Albertine Rift, the western branch of the East African Rift.  It is about 160 km (100 mi) long and 30 km (19 mi) wide, with a maximum depth of 51 m (168 ft), and a surface elevation of 619 m (2,030 ft) above sea level.  Lake Albert is part of the complicated system of the upper Nile. Its main sources are the White Nile, ultimately coming from Lake Victoria to the southeast, and the Semliki River, which issues from Lake Edward to the southwest. The water of the Victoria Nile is much less saline than that of Lake Albert. The lake’s outlet, at its northernmost tip, is the Albert Nile section of the White Nile. The river later becomes known as the Mountain Nile when its course enters South Sudan.  At the southern end of the lake, where the Semliki comes in, there are swamps. The Rwenzori Mountains are to the south of the lake and to the northwest, the Blue Mountains. The few settlements along the shore include Butiaba and Pakwach.

Water characteristics.

Unlike the very deep Lake Malawi, Lake Tanganyika and Lake Kivu, Lake Albert's water temperature is relatively stable throughout, typically around, and even its deeper sections contain oxygen.  The water has a pH of around or just below 9 and an electric conductivity of around 720–780 μS/cm. These are both very high for a freshwater lake but nevertheless lower than Lake Edward.

Animals.

Lake Albert is home to many aquatic and semi-aquatic animals like hippopotamuses, Uganda kob antelopes, Nile crocodiles, Nile monitors, African softshell turtles, Central African mud turtles, Williams' mud turtles, various semi-aquatic snakes and various frogs. Water birds are numerous and include pelicans, herons and the rare shoebill.

Fish and fishing.

There are 55 fish species in Lake Albert. Except for Nile crocodiles, the largest predators in the lake are the Nile perch (native, unlike in other Rift Valley lakes where introduced and invasive), elongate tigerfish, African tigerfish, marbled lungfish, cornish jack, "Bagrus docmak", African sharptooth catfish and vundu catfish. Others that support important fisheries are Nile tilapia, Niger barb, Albert lates, electric catfish and giraffe catfish that are caught by standard fishing methods, and the small "Brycinus nurse" and "Engraulicypris bredoi" that mainly are caught by light fishing. As much as 30% of the fish production in Uganda is from Lake Albert.  Lake Albert has fewer endemics than the other African Great Lakes. Although the Albert Nile–the section of the Nile that leaves Lake Albert—has several rapids in the Nimule region, these have not effectively isolated the lake from the main Nile sections. In contrast, Lake Edward (and ultimately Lake George) is effectively isolated from Lake Albert by the rapids on the Semliki River, while Lake Kyoga (and ultimately Lake Victoria) is effectively isolated from Lake Albert by the Murchison Falls on the Victoria Nile. As a consequence, most of Lake Albert's fish are widespread riverine species also found in the main Nile sections. There are few haplochromine cichlids; a group that is very diverse in other Rift Valley lakes. Of the six haplochromines in Lake Albert, four are endemic ("Haplochromis albertianus", "H. avium", "H. bullatus" and "H. mahagiensis") and two are also found in the Nile ("H. loati" and "Pseudocrenilabrus multicolor"). In comparison, most of the more than 60 haplochromines in Lake Edward–George and most of the roughly 600 haplochromines in Lake Victoria–Kyoga are endemic. The only other endemic fish species in Lake Albert are the small cyprinid "Engraulicypris bredoi" and the endangered Albert lates.

History.

Lake Albert was previously known as “Mwitanzige” (locusts killer) by the Banyoro and Batooro, as well as other peoples who have been populated the region for centuries before the colonial age. This was because of the ancient belief that locusts (locally called "enzige") perished in the lake as they tried to cross it. In 1864, the explorers Samuel Baker and Sass Flóra found the lake and renamed it after the recently deceased Prince Albert, consort of Queen Victoria. In the 20th century, Zairian President Mobutu Sese Seko temporarily named the lake after himself.  European colonialists operated shipping on the lake. The British planned shipping on Lake Albert as part of a network of railway, river steamer and lake steamer services linking British interests in Egypt, east Africa and southern Africa. The John I. Thornycroft & Company shipyard at Woolston, Hampshire built the cargo and passenger ship for this purpose in 1930. She was named after the British Army officer Robert Thorne Coryndon, who was governor of Uganda 1918-22. Winston Churchill described the ship as ""the best library afloat"" and Ernest Hemingway called her ""magnificence on water"". She either was scuttled in 1962 or sank in 1964. She remains unsalvaged and partly submerged in the lake at Butyaba landing site. These can still be seen to date.  Heritage Oil and Tullow Oil have announced major oil finds in the Lake Albert basin, with estimates that the multi-billion barrel field will prove to be the largest onshore field found in sub-saharan Africa for more than twenty years.  In March 2014, a boat carrying Congolese refugees capsized in Lake Albert, killing more than 250 people.  On 26 December 2016, a boat carrying 45 members and fans of a local village football team capsized in Lake Albert killing at least 30 people.  The Kibiro settlement on Lake Albert has cultural and archeological significance.

Lake Albert, also Mwitanzige and formerly Lake Mobutu Sese Seko, is a lake located in Uganda and the Democratic Republic of the Congo. It is Africa's seventh largest lake, as well as the second biggest of Uganda's Great Lakes.

阿尔伯特湖(Lake Albert;Lac Albert)是位于非洲中部乌干达和刚果民主共和国边界的淡水湖,它是大湖地区的非洲大湖之一。它是非洲的第七大湖,和世界的第二十七大湖。


Spectrum and channel allocation.

For Europe, Africa and Asia the MW band consists of 120 channels with centre frequencies from 531 to 1602 KHz spaced every 9 kHz. The total official spectrum including the modulated audio ranges from 526.5 kHz to 1606.5 kHz. Australia uses an expanded band up allocated up to 1701 kHz. North America uses 118 channels from 530 to 1700 kHz using 10 kHz spaced channels. The range above 1610 kHz is primarily only used by low power stations. It is the preferred range for services with automated traffic, weather and tourist information. Frequency coordination avoids the use of adjacent channels in one area.

Sound quality.

The 9 / 10 kHz channel stepping on MW requires limiting the audio bandwidth to 4.5 / 5 kHz because the audio spectrum is transmitted twice on each side band. This is adequate for talk and news but not for good quality music. However, many stations use audio bandwidths up 10 kHz, which is not Hi-Fi but sufficient for casual listening. In the UK, most stations use a bandwidth of 6.3 kHz. With AM, it largely depends on the frequency filters of each receiver how the audio is reproduced. This is a major disadvantage compared to FM and digital modes where the demodulated audio is more objective. Extended audio bandwidths cause interference on adjacent channels.

Propagation characteristics.

Wavelengths in this band are long enough that radio waves are not blocked by buildings and hills and can propagate beyond the horizon following the curvature of the Earth; this is called the groundwave. Practical groundwave reception of strong transmitters typically extends to 200–300 miles, with greater distances over terrain with higher ground conductivity, and greatest distances over salt water. The groundwave reaches further on lower medium wave frequencies.  Medium waves can also reflect off charged particle layers in the ionosphere and return to Earth at much greater distances; this is called the skywave. At night, especially in winter months and at times of low solar activity, the lower ionospheric D layer virtually disappears. When this happens, MW radio waves can easily be received many hundreds or even thousands of miles away as the signal will be reflected by the higher F layer. This can allow very long-distance broadcasting, but can also interfere with distant local stations. Due to the limited number of available channels in the MW broadcast band, the same frequencies are re-allocated to different broadcasting stations several hundred miles apart. On nights of good skywave propagation, the skywave signals of a distant station may interfere with the signals of local stations on the same frequency. In North America, the North American Regional Broadcasting Agreement (NARBA) sets aside certain channels for nighttime use over extended service areas via skywave by a few specially licensed AM broadcasting stations. These channels are called clear channels, and they are required to broadcast at higher powers of 10 to 50 kW.

Use in the Americas.

Initially, broadcasting in the United States was restricted to two wavelengths: "entertainment" was broadcast at 360 meters (833 kHz), with stations required to switch to 485 meters (619 kHz) when broadcasting weather forecasts, crop price reports and other government reports. This arrangement had numerous practical difficulties. Early transmitters were technically crude and virtually impossible to set accurately on their intended frequency and if (as frequently happened) two (or more) stations in the same part of the country broadcast simultaneously the resultant interference meant that usually neither could be heard clearly. The Commerce Department rarely intervened in such cases but left it up to stations to enter into voluntary timesharing agreements amongst themselves. The addition of a third "entertainment" wavelength, 400 meters, did little to solve this overcrowding.  In 1923, the Commerce Department realized that as more and more stations were applying for commercial licenses, it was not practical to have every station broadcast on the same three wavelengths. On 15 May 1923, Commerce Secretary Herbert Hoover announced a new bandplan which set aside 81 frequencies, in 10 kHz steps, from 550 kHz to 1350 kHz (extended to 1500, then 1600 and ultimately 1700 kHz in later years). Each station would be assigned one frequency (albeit usually shared with stations in other parts of the country and/or abroad), no longer having to broadcast weather and government reports on a different frequency than entertainment. Class A and B stations were segregated into sub-bands.  In the US and Canada the maximum transmitter power is restricted to 50 kilowatts, while in Europe there are medium wave stations with transmitter power up to 2 megawatts daytime.  Most United States AM radio stations are required by the Federal Communications Commission (FCC) to shut down, reduce power, or employ a directional antenna array at night in order to avoid interference with each other due to night-time only long-distance skywave propagation (sometimes loosely called ‘skip’). Those stations which shut down completely at night are often known as "daytimers". Similar regulations are in force for Canadian stations, administered by Industry Canada; however, daytimers no longer exist in Canada, the last station having signed off in 2013, after migrating to the FM band.

Use in Europe.

Many countries have switched off most of their MW transmitters due to cost-cutting and low usage of MW by the listeners. Among those are Germany, France, Russia, Poland, Sweden, the Benelux, Austria, Switzerland, and most of the Balkans.  Large networks of transmitters are remaining in the UK, Spain, Romania and Italy. In the Netherlands and Scandinavia, some new idealistically driven stations have launched low power services on the former high power frequencies. This also applies to the ex-offshore pioneer Radio Caroline that now has a licence to use 648 kHz, which was used by the BBC World Service over decades. As the MW band is thinning out, many local stations from the remaining countries as well as from North Africa and the Middle East can now be received all over Europe, but often only weak with much interference.  In Europe, each country is allocated a number of frequencies on which high power (up to 2 MW) can be used; the maximum power is also subject to international agreement by the International Telecommunication Union (ITU).  In most cases there are two power limits: a lower one for omnidirectional and a higher one for directional radiation with minima in certain directions. The power limit can also be depending on daytime and it is possible that a station may not operate at nighttime, because it would then produce too much interference. Other countries may only operate low-powered transmitters on the same frequency, again subject to agreement. International medium wave broadcasting in Europe has decreased markedly with the end of the Cold War and the increased availability of satellite and Internet TV and radio, although the cross-border reception of neighbouring countries' broadcasts by expatriates and other interested listeners still takes place.  In the late 20th century, overcrowding on the Medium wave band was a serious problem in parts of Europe contributing to the early adoption of VHF FM broadcasting by many stations (particularly in Germany). Due to the high demand for frequencies in Europe, many countries set up single frequency networks; in Britain, BBC Radio Five Live broadcasts from various transmitters on either 693 or 909 kHz. These transmitters are carefully synchronized to minimize interference from more distant transmitters on the same frequency.

Use in Asia.

In Asia and the Middle East, many high powered transmitters remain in operation. China operates many single-frequency networks.

Stereo and digital transmissions.

Stereo transmission is possible and is or was offered by some stations in the U.S., Canada, Mexico, the Dominican Republic, Paraguay, Australia, The Philippines, Japan, South Korea, South Africa, Italy and France. However, there have been multiple standards for AM stereo. C-QUAM is the official standard in the United States as well as other countries, but receivers that implement the technology are no longer readily available to consumers. Used receivers with AM Stereo can be found. Names such as "FM/AM Stereo" or "AM & FM Stereo" can be misleading and usually do not signify that the radio will decode C-QUAM AM stereo, whereas a set labelled "FM Stereo/AM Stereo" or "AMAX Stereo" will support AM stereo.  In September 2002, the United States Federal Communications Commission approved the proprietary iBiquity in-band on-channel (IBOC) HD Radio system of digital audio broadcasting, which is meant to improve the audio quality of signals. The Digital Radio Mondiale (DRM) system standardised by ETSI supports stereo and is the ITU approved system for use outside North America and U.S. territories. Some HD Radio receivers also support C-QUAM AM stereo, although this feature is usually not advertised by the manufacturer.

Antennas.

For broadcasting, mast radiators are the most common type of antenna used, consisting of a steel lattice guyed mast in which the mast structure itself is used as the antenna. Stations broadcasting with low power can use masts with heights of a quarter-wavelength (about 310 millivolts per meter using one kilowatt at one kilometre) to 5/8 wavelength (225 electrical degrees; about 440 millivolts per meter using one kilowatt at one kilometre), while high power stations mostly use half-wavelength to 5/9 wavelength. The usage of masts taller than 5/9 wavelength (200 electrical degrees; about 410 millivolts per meter using one kilowatt at one kilometre) with high power gives a poor vertical radiation pattern, and 195 electrical degrees (about 400 millivolts per meter using one kilowatt at one kilometre) is generally considered ideal in these cases. Usually mast antennas are series-excited (base driven); the feedline is attached to the mast at the base. The base of the antenna is at high electrical potential and must be supported on a ceramic insulator to isolate it from the ground. Shunt-excited masts, in which the base of the mast is at a node of the standing wave at ground potential and so does not need to be insulated from the ground, have fallen into disuse, except in cases of exceptionally high power, 1 MW or more, where series excitation might be impractical. If grounded masts or towers are required, cage or long-wire aerials are used. Another possibility consists of feeding the mast or the tower by cables running from the tuning unit to the guys or crossbars at a certain height.  Directional aerials consist of multiple masts, which need not to be of the same height. It is also possible to realize directional aerials for mediumwave with cage aerials where some parts of the cage are fed with a certain phase difference.  For medium-wave (AM) broadcasting, quarter-wave masts are between and high, depending on the frequency. Because such tall masts can be costly and uneconomic, other types of antennas are often used, which employ capacitive top-loading (electrical lengthening) to achieve equivalent signal strength with vertical masts shorter than a quarter wavelength. A "top hat" of radial wires is occasionally added to the top of mast radiators, to allow the mast to be made shorter. For local broadcast stations and amateur stations of under 5 kW, T- and L-antennas are often used, which consist of one or more horizontal wires suspended between two masts, attached to a vertical radiator wire. A popular choice for lower-powered stations is the umbrella antenna, which needs only one mast one-tenth wavelength or less in height. This antenna uses a single mast insulated from ground and fed at the lower end against ground. At the top of the mast, radial top-load wires are connected (usually about six) which slope downwards at an angle of 40–45 degrees as far as about one-third of the total height, where they are terminated in insulators and thence outwards to ground anchors. Thus the umbrella antenna uses the guy wires as the top-load part of the antenna. In all these antennas the smaller radiation resistance of the short radiator is increased by the capacitance added by the wires attached to the top of the antenna.  In some rare cases dipole antennas are used, which are slung between two masts or towers. Such antennas are intended to radiate a skywave. The medium-wave transmitter at Berlin-Britz for transmitting RIAS used a cross dipole mounted on five 30.5-metre-high guyed masts to transmit the skywave to the ionosphere at nighttime.

Receiving antennas.

Because at these frequencies atmospheric noise is far above the receiver signal to noise ratio, inefficient antennas much smaller than a wavelength can be used for receiving. For reception at frequencies below 1.6 MHz, which includes long and medium waves, loop antennas are popular because of their ability to reject locally generated noise. By far the most common antenna for broadcast reception is the ferrite-rod antenna, also known as a loopstick antenna. The high permeability ferrite core allows it to be compact enough to be enclosed inside the radio's case and still have adequate sensitivity.

Medium wave (MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with limited sound quality. During daytime, only local stations can be received. Propagation in the night allows strong signals within a range of about 2000 km. This can cause massive interference because on most channels, about 20 to 50 transmitters operate simultaneously worldwide. In addition to that, amplitude modulation (AM) is prone to interference by all sorts of electronic devices, especially power supplies and computers. Strong transmitters cover larger areas than on the FM broadcast band but require more energy. Digital modes are possible but have not reached the momentum yet.

中波(英语:Medium wave,MW),是无线电的一个波长范围,其对应的频率范围称为中频。一般来说中波的波长范围为100米至1000米,中频则为0.3MHz到3MHz,其中用于广播通信的通常是550-1605kHz波段。电离层也能反射中波波段的电磁波,不过晚间时效果才比较显著,利用中波电磁波在电离层传播时的交叉调制效应还可对电离层进行研究。