History.

Throughout the 1980s and 1990s, the American hip hop music market was primarily dominated by artists from the East Coast and West Coast. Los Angeles and New York City were the two main cities where hip hop was receiving widespread attention. The West Coast was mainly represented by groups like N.W.A., Death Row Records, and the East Coast had people like The Notorious B.I.G. and groups like the Wu-Tang Clan. In the late 1980s, cities throughout the Southern United States began to catch on to the hip hop music movement. The Geto Boys, a hip hop group from Houston, were among the first hip hop artists from the Southern United States to gain widespread popularity. Southern hip hop's roots can be traced to the success of Geto Boys' "Grip It! On That Other Level" in 1989, the Rick Rubin produced "The Geto Boys" in 1990, and "We Can't Be Stopped" in 1991. After the Geto Boys rose to stardom, Houston became the center for Southern hip hop. Miami also played a major role in the rise of Southern hip hop during this time frame with successful acts like 2 Live Crew (originally formed in California but fully relocated to Miami around 1987) and other artists who relied heavily on the Miami bass sound. In the early 1990s, other rising rap groups such as P.K.O from San Antonio, Texas, UGK from Port Arthur, Texas, and 8Ball & MJG from Memphis, moved to Houston to further their musical careers.  By the mid-1990s, Atlanta had become a controlling city in southern hip hop music. LaFace Records had given Atlanta a reputation as "the Motown of the South" with acts like TLC, Usher, and Kriss Kross. Local production crews such as Organized Noize that represented hip hop groups such as OutKast and Goodie Mob played a huge part in helping the South become a center for hip hop music. OutKast became the first Southern artists to generate album sales like the powerhouse rappers on the East and West coasts.  A defining moment for Southern rap was at the 1995 Source Awards. The duo Outkast had just been awarded Best New Artist, and within the tension that was the East Coast–West Coast feud, member André came up on stage followed by boos and said, "But it's like this though, I'm tired of them closed minded folks, it's like we gotta demo tape but don't nobody want to hear it. But it's like this: the South got something to say, that's all I got to say." As stated by rapper T.I., "Outkast, period. Outkast. That's when it changed. That was the first time when people began to take Southern rap seriously."  The most successful Southern independent labels during the mid-to-late 90s came out of the cities of Memphis and New Orleans. Both scenes borrowed heavily from a production style first introduced by way of the obscure late-1980s New York rap group The Showboys, heavily sampling the beats from their song "Drag Rap (Trigger Man)." By the turn of the century these scenes found mainstream success through Cash Money Records and No Limit Records out of New Orleans and Hypnotize Minds out of Memphis, revolutionizing financial structures and strategies for independent Southern rap labels. According to hiphopdx, "Not only is the South on the radar, but now the region that was an underdog is the barometer for rap music and HipHop culture.” By the early to mid-2000s, artists from all over the South had begun to develop mainstream popularity with artists like T.I., Ludacris, Lil Jon, Young Jeezy from Atlanta, Trick Daddy and Rick Ross from Miami, Lil Wayne and Juvenile from New Orleans, and Three 6 Mafia from Memphis all becoming major label stars during this time. In 2004, OutKast won six Grammy awards for their album "Speakerboxxx/The Love Below", including Best Album, while in 2006 the members of Three 6 Mafia won the Academy Award for Best Original Song for "It's Hard Out Here For A Pimp" from "Hustle and Flow", a Hollywood film about a fictional Southern rap artist. In 2005, the Houston rap scene saw a revival in mainstream popularity, and many Houston rappers started to get nationwide and worldwide audiences such as Paul Wall, Mike Jones, Chamillionaire, Lil' Flip, Slim Thug, Z-Ro, Trae, and many members of the Screwed Up Click.  The height of Southern hip-hop was reached from 2002 through 2004. In 2002, Southern hip-hop artists accounted for 50 to 60 percent of the singles on hip-hop music charts. On the week of December 13, 2003, Southern urban artists, labels and producers accounted for six of the top 10 slots on the "Billboard" Hot 100: OutKast had two singles, Ludacris, Kelis (produced by The Neptunes), Beyoncé and Chingy (on Ludacris' Disturbing Tha Peace label). In addition to this, from October 2003 through December 2004, the number one position on the "Billboard" Hot 100 pop chart was held by a Southern urban artist for 58 out of 62 weeks. This was capped by the week of December 11, 2004 when seven out of the top ten songs on the chart were held by or featured Southern urban artists. In 2004, Vibe magazine reported that Southern artists accounted for 43.6% of the airplay on urban radio stations (compared to 29.7% for the Midwest, 24.1% for the East Coast and 2.5% for the West coast). Rich Boy from Mobile, Alabama was successful in 2007 with his debut album. Since the early 2010s, many contemporary hip hop artists have become mainstream.

Georgia.

In 2009, the "New York Times" called Atlanta "hip-hop's center of gravity", and the city is home to many famous hip-hop, R&B and neo soul musicians.  In the 1980s and early 1990s, Atlanta's hip hop scene was characterized by a local variant of Miami's electro-driven bass music, with stars like Kilo Ali, MC Shy-D, Raheem the Dream and DJ Smurf (later Mr. Collipark). MC Shy-D is credited with bringing authentic Bronx-style hip-hop to Atlanta (and Miami), such as 1988's "Shake it" produced by DJ Toomp; Jones was signed to controversial southern rap label Luke Records, run by Luther Campbell aka "Uncle Luke". Arrested Development won the Grammy in 1992 with "Tennessee", while "Mr. Wendal" and "People Everyday" and Kris Kross won with their hit song "Jump".  By the mid-1990s, the rise of OutKast, Goodie Mob and the production collective Organized Noize, let to the development of the Dirty South style of hip-hop and of Atlanta gaining a reputation for "soul-minded hip-hop eccentrics", contrasting with other regional styles. August 3,1995 Outkast received the award for best new artist in New York City at the Source Awards. At the time the primary hip hop heard nationally was from artists on the East and West Coasts, due at least in part to high profile disputes between rappers from each coast. It was groups such as Outkast who were determined to let the world know that the South had something to say.  From the late 1990s to early 2000s, producer Lil Jon was a driving force behind the party-oriented style known as crunk. Record producers L.A. Reid and Babyface founded LaFace Records in Atlanta in the late-1980s; the label eventually became the home to multi-platinum selling artists such as Toni Braxton, TLC, Ciara. It is also the home of So So Def Records, a label founded by Jermaine Dupri in the mid-1990s, that signed acts such as Da Brat, Jagged Edge, Xscape and Dem Franchise Boyz. The success of LaFace and SoSo Def led to Atlanta as an established scene for record labels such as LaFace parent company Arista Records to set up satellite offices.  In 2009, the "New York Times" noted that after 2000, Atlanta moved "from the margins to becoming hip-hop's center of gravity, part of a larger shift in hip-hop innovation to the South." This had a lot to due with the massive popularity of Waka Flocka Flame's 2009 debut mixtape. Producer Drumma Boy called Atlanta "the melting pot of the South". Producer Fatboi called the Roland TR-808 ("808") synthesizer "central" to Atlanta music's versatility, used for snap, crunk, trap, and pop rap styles. The same article named Drumma Boy, Fatboi, Shawty Redd, Lex Luger and Zaytoven the five "hottest producers driving the city".

Texas.

In the late 1980s, the Geto Boys were Houston's first rap group to gain mainstream popularity. Before the early 1990s, most Southern hip hop was upbeat and fast, like Miami bass and crunk. In Texas the music was generally slower. In the early 1990s DJ Screw created "chopped and screwed" music. Although people associated with Screw have indicated any time between 1987 and 1991, Screw said he started slowing music down in 1990. In Tulsa, Oklahoma, Dj Dinero And Dj Z-Nasty helped popularize Chopped And Screwed music in the Mid South. There is no debate, however, that DJ Screw invented the music style. He discovered that dramatically reducing the pitch of a record gave a mellow, heavy sound that emphasized lyrics to the point of almost storytelling. After experimenting with the sound for a while Screw started making full length "Screw Tapes".  Between 1991 and 1992, there was increased abuse of purple drank in East Texas. Purple drank has been considered to be a major influence in the making of and listening to chopped and screwed music due to its effect of slowing down perception. DJ Screw said that purple drank is not required to enjoy screwed and chopped music. Screw, a known user of purple drank, said he came up with chopped and screwed music when high on marijuana.  As the spread of Southern hip hop continued, its mainstream breakthrough occurred in 2000. Rap duo UGK made a high-profile guest appearance on Jay-Z's smash hit "Big Pimpin'" and also appeared on Three 6 Mafia's hit "Sippin' on Some Syrup." Both of these collaborations greatly increased their reputation and helped fuel anticipation for their next project.The Hip Hop world was ready for the next adventure but unfortunately the UGK rapper Pimp C died from a sudden heart attack after overdosing on purple drank on December 4, 2007 at the age of 33. A song that originally appeared on the compilation album "The Day Hell Broke Loose 2", Mike Jones' "Still Tippin'", which achieved mainstream success in 2004 leading to local Houston rap label Swishahouse signing a national distribution deal with Asylum Records. Jones released his major label debut, "Who Is Mike Jones?", on Swishahouse/Warner Bros. in April 2005; the album Who is Mike Jones? went certified platinum that June. Paul Wall's major label debut, "The Peoples Champ", on Swishahouse/Atlantic, was released in September 2005, eventually topping the "Billboard" 200. Before embarking on his rap career and while still at school, Wall was also working in the Swishahouse office.

Louisiana.

In the late 1990s "bounce" music was born in New Orleans. In 1992, Cash Money Records was founded, releasing bounce and gangster rap music.

Crunk.

The term "crunk" is used as a blanket term to denote any style of southern hip hop, it is mainly used to denote a musical style that was originated by Three Six Mafia in Memphis, Tennessee, in the mid-to-late 1990s. It was popularized by Atlanta rapper Lil Jon, and gained mainstream popularity in the period 2003–04. A typical crunk track uses a drum machine rhythm, heavy bassline, and shouting vocals, often in call and response manner.

Southern hip hop, also known as Southern rap, South Coast hip hop, or dirty south, is a blanket term for a regional genre of American hip hop music that emerged in the Southern United States and the Southeastern United States, especially in Atlanta, New Orleans, Houston, Memphis, and Miami—five cities which constitute the "Southern Network" in rap music.

南部嘻哈(英语:Southern hip hop)或称南部说唱(Southern rap),是美国嘻哈乐的一个流派,兴起于20世纪80年代晚期包括新奥尔良、休斯敦、纳什维尔、亚特兰大、孟菲斯、夏洛特及迈阿密等美国南部城市的夜店之中。该音乐流派是对自80年代以来从纽约市到加州席卷全美的嘻哈风潮的回应,可视作是继东海岸嘻哈和西海岸嘻哈之后,美国第三大主流嘻哈流派。许多早期的南部嘻哈艺人在90年代由于无法签下唱片合约,选择通过独立发行音乐或混音带。


Description.

The skulls of ornithomimosaurs were small, with large eyes, above relatively long and slender necks. The most basal members of the taxon (such as "Pelecanimimus" and "Harpymimus") had a jaw with small teeth, while the later and more derived species had a toothless beak. The fore limbs ("arms") were long and slender and bore powerful claws. The hind limbs were long and powerful, with a long foot and short, strong toes terminating in hooflike claws. Ornithomimosaurs were probably among the fastest of all dinosaurs. Like other coelurosaurs, the ornithomimosaurian hide was feathered rather than scaly.

Palaeobiology.

Ornithomimosaurs probably acquired most of their calories from plants. Many ornithomimosaurs, including primitive species, have been found with numerous gastroliths in their stomachs, characteristic of herbivores. Henry Fairfield Osborn suggested that the long, sloth-like "arms" of ornithomimosaurs may have been used to pull down branches on which to feed, an idea supported by further study of their strange, hook-like hands. The sheer abundance of ornithomimids — they are the most common small dinosaurs in North America — is consistent with the idea that they were plant eaters, as herbivores usually outnumber carnivores in an ecosystem. However, they may have been omnivores that ate both plants and small animal prey.  Comparisons between the scleral rings of two ornithomimosaur genera ("Garudimimus" and "Ornithomimus") and modern birds and reptiles indicate that they may have been cathemeral, active throughout the day at short intervals.

Feathers.

Unambiguous evidence of feathers is known from "Ornithomimus"/"Dromiceiomimus", of which there are multiple specimens preserving feather traces. "Deinocheirus" and "Pelecanimimus" have been speculated to be feathered as well, the former due to the presence of a pygostyle, and the later due to possible impressions (otherwise taken to be collagen fibers).  There is a debate on whereas ornithomimids possessed the pennaceous feathers seen in Pennaraptora. Otherwise, a very ostrich-like plumage and feather range is seen in known in one specimen.

Classification.

Named by O.C. Marsh in 1890, the family Ornithomimidae was originally classified as a group of "megalosaurs" (a "wastebasket taxon" containing any medium to large sized theropod dinosaurs), but as more theropod diversity was uncovered, their true relationships to other theropods started to resolve, and they were moved to the Coelurosauria. Recognizing the distinctiveness of ornithomimids compared to other dinosaurs, Rinchen Barsbold placed ornithomimids within their own infraorder, Ornithomimosauria, in 1976. The contents of Ornithomimidae and Ornithomimosauria varied from author to author as cladistic definitions began to appear for the groups in the 1990s.  In the early 1990s, prominent paleontologists such as Thomas R. Holtz, Jr. proposed a close relationship between theropods with an "arctometatarsalian" foot; that is, bipedal dinosaurs in which the upper foot bones were 'pinched' together, an adaptation for running. Holtz (1994) defined the clade Arctometatarsalia as "the first theropod to develop the arctometatarsalian pes and all of its descendants." This group included the Troodontidae, Tyrannosauroidea, and Ornithomimosauria. Holtz (1996, 2000) later refined this definition to the branch-based ""Ornithomimus" and all theropods sharing a more recent common ancestor with "Ornithomimus" than with birds." Subsequently, the idea that all arctometatarsalian dinosaurs formed a natural group was abandoned by most paleontologists, including Holtz, as studies began to demonstrate that tyrannosaurids and troodontids were more closely related to other groups of coelurosaurs than they were to ornithomimosaurs. Since the strict definition of Arctometatarsalia was based on "Ornithomimus", it became redundant with the name Ornithomimosauria under broad definitions of that clade, and the name Arctometatarsalia was mostly abandoned.  The paleontologist Paul Sereno, in 2005, proposed the clade "Ornithomimiformes", defining them as all species closer to "Ornithomimus edmontonicus" than to "Passer domesticus". Because he had redefined Ornithomimosauria in a much narrower sense, a new term was made necessary within his preferred terminology to denote the clade containing the sistergroups Ornithomimosauria and Alvarezsauridae — previously the latter had been contained within the former. However, this concept only appeared on Sereno's Web site and has not yet been officially published as a valid name.  "Ornithomimiformes" was identical in content to Holtz's Arctometatarsalia, as it has a very similar definition. While "Ornithomimiformes" is the newer group, Sereno rejected the idea that Arctometatarsalia should take precedence, because the meaning of the former name has been changed very radically by Holtz.

Phylogeny.

Ornithomimosauria has variously been used for the branch-based group of all dinosaurs closer to "Ornithomimus" than to birds, and in more restrictive senses. The more exclusive sense began to grow in popularity when the possibility arose that alvarezsaurids might fall under Ornithomimosauria if an inclusive definition were adopted. Another clade, Ornithomimiformes, was defined by Sereno (2005) as ("Ornithomimus velox" > "Passer domesticus") and replaces the more inclusive use of Ornithomimosauria when alvarezsaurids or some other group are found to be closer relatives of ornithomimosaurs than maniraptorans, with Ornithomimosauria redefined to include dinosaurs closer to "Ornithomimus" than to alvarezsaurids. Gregory S. Paul has proposed that Ornithomimosauria might be a group of primitive, flightless birds, more advanced than Deinonychosauria and Oviraptorosauria.  The cladogram below follows an analysis by Yuong-Nam Lee, Rinchen Barsbold, Philip J. Currie, Yoshitsugu Kobayashi, Hang-Jae Lee, Pascal Godefroit, François Escuillié & Tsogtbaatar Chinzorig. The analysis was published in 2014, and includes many ornithomimosaurian taxa.  The cladogram below follows an analysis by Jin Liyong, Chen Jun and Pascal Godefroit (2012).  The cladogram presented here follows the one recovered by Turner, Clarke, Ericson and Norell, 2007. Clade names follow definitions provided by Sereno, 2005.

The Ornithomimosauria, ornithomimosaurs ("bird-mimic lizards") or ostrich dinosaurs are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia (now Asia, Europe and North America), as well as Africa and possibly Australia. The group first appeared in the Early Cretaceous and persisted until the Late Cretaceous. Primitive members of the group include "Nqwebasaurus", "Pelecanimimus", "Shenzhousaurus", "Hexing" and "Deinocheirus", the arms of which reached 2.4 m (8 feet) in length. More advanced species, members of the family Ornithomimidae, include "Gallimimus", "Struthiomimus", and "Ornithomimus". Some paleontologists, like Paul Sereno, consider the enigmatic alvarezsaurids to be close relatives of the ornithomimosaurs and place them together in the superfamily Ornithomimoidea (see classification below).

似鸟龙下目()意为「鸟类模仿者蜥蜴」,是一群兽脚亚目恐龙,外表类似现代的鸵鸟,例如似鸡龙。牠们是群快速、敏捷、杂食性或草食性恐龙,生存于白垩纪的劳亚大陆(现在的亚洲、欧洲、北美洲)。似鸟龙下目首次出现于早白垩纪,并存活到晚白垩纪。牠们似乎与较原始的虚骨龙类恐龙有亲缘关系,例如细颈龙与暴龙科。似鸟龙下目的原始物种包括:似鹈鹕龙、神州龙、似鸟身女妖龙,还有大型的恐手龙,恐手龙的手臂长度可达2.4米。更先进的种都属于似鸟龙科,包括:似鸡龙、古似鸟龙、似鹅龙、似鸵龙、以及似鸟龙。有些古生物学家,例如保罗·塞里诺(Paul Sereno),认为充满谜题的阿瓦拉慈龙科是似鸟龙下目的近亲,并将牠们分类于似鸟龙超科(Ornithomimoidea)。


Critical point of a single variable function.

A critical point of a function of a single real variable, "f"("x"), is a value "x" in the domain of "f" where it is not differentiable or its derivative is 0 ("f" ′("x") = 0). A critical value is the image under "f" of a critical point. These concepts may be visualized through the graph of "f": at a critical point, the graph has a horizontal tangent if you can assign one at all.  Notice how, for a differentiable function, "critical point" is the same as stationary point.  Although it is easily visualized on the graph (which is a curve), the notion of critical point of a function must not be confused with the notion of critical point, in some direction, of a curve (see below for a detailed definition). If "g"("x","y") is a differentiable function of two variables, then "g"("x","y") = 0 is the implicit equation of a curve. A critical point of such a curve, for the projection parallel to the "y"-axis (the map ("x", "y") → "x"), is a point of the curve where formula_2. This means that the tangent of the curve is parallel to the "y"-axis, and that, at this point, "g" does not define an implicit function from "x" to "y" (see implicit function theorem). If ("x", "y") is such a critical point, then "x" is the corresponding critical value. Such a critical point is also called a bifurcation point, as, generally, when "x" varies, there are two branches of the curve on a side of "x" and zero on the other side.  It follows from these definitions that a differentiable function "f"("x") has a critical point "x" with critical value "y", if and only if ("x", "y") is a critical point of its graph for the projection parallel to the "x"-axis, with the same critical value "y." If "f" is not differentiable at x due to the tangent becoming parallel to the y-axis, then x is again a critical point of "f", but now (x, y) is a critical point of its graph for the projection parallel to "y"-axis.  For example, the critical points of the unit circle of equation "x" + "y" - 1 = 0 are (0, 1) and (0, -1) for the projection parallel to the "x"-axis, and (1, 0) and (-1, 0) for the direction parallel to the "y"-axis. If one considers the upper half circle as the graph of the function formula_3, then "x" = 0 is a critical point with critical value 1 due to the derivative being equal to 0, and x=-1 and x=1 are critical points with critical value 0 due to the derivative being undefined.

Location of critical points.

By the Gauss-Lucas theorem, all of a polynomial function's critical points in the complex plane are within the convex hull of the roots of the function. Thus for a polynomial function with only real roots, all critical points are real and are between the greatest and smallest roots.  Sendov's conjecture asserts that, if all of a function's roots lie in the unit disk in the complex plane, then there is at least one critical point within unit distance of any given root.

Critical points of an implicit curve.

Critical points play an important role in the study of plane curves defined by implicit equations, in particular for sketching them and determining their topology. The notion of critical point that is used in this section, may seem different from that of previous section. In fact it is the specialization to a simple case of the general notion of critical point given below.  Thus, we consider a curve defined by an implicit equation formula_4, where is a differentiable function of two variables, commonly a bivariate polynomial. The points of the curve are the points of the Euclidean plane whose Cartesian coordinates satisfy the equation. There are two standard projections formula_5 and formula_6, defined by formula_7 and formula_8 that map the curve onto the coordinate axes. They are called the "projection parallel to the y-axis" and the "projection parallel to the x-axis", respectively.  A point of is critical for formula_5, if the tangent to exists and is parallel to the "y"-axis. In that case, the images by formula_5 of the critical point and of the tangent are the same point of the "x"-axis, called the critical value. Thus a point is critical for formula_5 if its coordinates are solution of the system of equations:  This implies that this definition is a special case of the general definition of a critical point, which is given below.  The definition of a critical point for formula_6 is similar. If is the graph of a function formula_14, then is critical for formula_6 if and only if is a critical point of, and that the critical values are the same.  Some authors define the critical points of as the points that are critical for either formula_6 or formula_5, although they depend not only on, but also on the choice of the coordinate axes. It depends also on the authors if the singular points are considered as critical points. In fact the singular points are the points that satisfy  and are thus solutions of either system of equations characterizing the critical points. With this more general definition, the critical points for formula_5 are exactly the points where the implicit function theorem does not apply.

Use of the discriminant.

When the curve is algebraic, that is when it is defined by a bivariate polynomial, then the discriminant is a useful tool to compute the critical points.  Here we consider only the projection formula_5; Similar results apply to formula_6 by exchanging and.  Let formula_22 be the discriminant of viewed as a polynomial in with coefficients that are polynomials in. This discriminant is thus a polynomial in which has the critical values of formula_5 among its roots.  More precisely, a simple root of formula_22 is either a critical value of formula_5 such the corresponding critical point is a point which is not singular nor an inflection point, or the -coordinate of an asymptote which is parallel to the -axis and is tangent "at infinity" to an inflection point (inflexion asymptote).  A multiple root of the discriminant correspond either to several critical points or inflection asymptotes sharing the same critical value, or to a critical point which is also an inflection point, or to a singular point.

Several variables.

For a function of several real variables, a point "P" (that is a set of values for the input variables, which is viewed as a point in R) is critical if it is a point where the gradient is undefined or the gradient is zero. The critical values are the values of the function at the critical points.  A critical point may be either a local maximum, a local minimum or a saddle point. If the function is at least twice continuously differentiable the different cases may be distinguished by considering the eigenvalues of the Hessian matrix of second derivatives.  A critical point at which the Hessian matrix is nonsingular is said to be "nondegenerate", and the signs of the eigenvalues of the Hessian determine the local behavior of the function. In the case of a function of a single variable, the Hessian is simply the second derivative, viewed as a 1×1-matrix, which is nonsingular if and only if it is not zero. In this case, a non-degenerate critical point is a local maximum or a local minimum, depending on the sign of the second derivative, which is positive for a local minimum and negative for a local maximum. If the second derivative is null, the critical point is generally an inflection point, but may also be an undulation point, which may be a local minimum or a local maximum.  For a function of "n" variables, the number of negative eigenvalues of the Hessian matrix at a critical point is called the "index" of the critical point. A non-degenerate critical point is a local maximum if and only if the index is "n", or, equivalently, if the Hessian matrix is negative definite; it is a local minimum if the index is zero, or, equivalently, if the Hessian matrix is positive definite. For the other values of the index, a non-degenerate critical point is a saddle point, that is a point which is a maximum in some directions and a minimum in others.

Application to optimization.

By Fermat's theorem, all local maxima and minima of a continuous function occur at critical points. Therefore, to find the local maxima and minima of a differentiable function, it suffices, theoretically, to compute the zeros of the gradient and the eigenvalues of the Hessian matrix at these zeros. This does not work well in practice because it requires the solution of a nonlinear system of simultaneous equations, which is a difficult task. The usual numerical algorithms are much more efficient for finding local extrema, but cannot certify that all extrema have been found. In particular, in global optimization, these methods cannot certify that the output is really the global optimum.  When the function to minimize is a multivariate polynomial, the critical points and the critical values are solutions of a system of polynomial equations, and modern algorithms for solving such systems provide competitive certified methods for finding the global minimum.

Critical point of a differentiable map.

Given a differentiable map "f" from R into R, the critical points of "f" are the points of R, where the rank of the Jacobian matrix of "f" is not maximal. The image of a critical point under "f" is a called a critical value. A point in the complement of the set of critical values is called a regular value. Sard's theorem states that the set of critical values of a smooth map has measure zero. In particular, if "n" = 1, there is a finite number of critical values in each bounded interval.  Some authors give a slightly different definition: a critical point of "f" is a point of R where the rank of the Jacobian matrix of "f" is less than "n". With this convention, all points are critical when "m" < "n".  These definitions extend to differential maps between differentiable manifolds in the following way. Let formula_26 be a differential map between two manifolds and of respective dimensions "m" and "n". In the neighborhood of a point of and of, charts are diffeomorphisms formula_27 and formula_28 The point is critical for if formula_29 is critical for formula_30 This definition does not depend on the choice of the charts because the transitions maps being diffeomorphisms, their Jacobian matrices are invertible and multiplying by them does not modify the rank of the Jacobian matrix of formula_30 If "M" is a Hilbert manifold (not necessarily finite dimensional) and "f" is a real-valued function then we say that "p" is a critical point of "f" if "f" is "not" a submersion at "p".

Application to topology.

Critical points are fundamental for studying the topology of manifolds and real algebraic varieties. In particular, they are the basic tool for Morse theory and catastrophe theory.  The link between critical points and topology already appears at a lower level of abstraction. For example, let formula_32 be a sub-manifold of formula_33 and be a point outside formula_34 The square of the distance to of a point of formula_32 is a differential map such that each connected component of formula_32 contains at least a critical point, where the distance is minimal. It follows that the number of connected components of formula_32 is bounded above by the number of critical points.  In the case of real algebraic varieties, this observation associated with Bézout's theorem allows us to bound the number of connected components by a function of the degrees of the polynomials that define the variety.

Critical point is a wide term used in many branches of mathematics.

在数学上,一个可微的实函数或复函数formula_1的临界点是指在formula_1的定义域中导数为 0 的点 。有些作者会把临界点的定义包括一般实或复函数的定义域中导数为 0 的点和不可微的点。对于一个而言,临界点是在定义域中所有偏导数为 0 的点。一个函数的临界点的函数值称为临界值。


Methodology.

The use of qualitative methods, particularly ethnography, distinguishes media anthropology from other disciplinary approaches to mass media. Within media studies, media ethnographies have been of increasing interest since the 1980s. However, as Stephen Putnam Hughes remarks in a recent review, these studies often do not engage in rigorous ethnographic fieldwork, ignoring or misapplying such landmark anthropological techniques as participant observation or long-term fieldwork. Given such differences, anthropologists who take an interest in the media see themselves as forming a distinct subfield from ethnographic approaches to media studies and cultural studies.

Theory.

The anthropology of media is a fairly inter-disciplinary area, with a wide range of other influences. The theories used in the anthropology of media range from practice approaches, associated with theorists such as Pierre Bourdieu, as well as discussions of the appropriation and adaptation of new technologies and practices. Theoretical approaches have also been adopted from visual anthropology and from film theory, as well as from studies of ritual and performance studies (e.g. dance and theatre), studies of consumption, audience reception in media studies, new media and network theories, theories of globalisation, theories of international civil society, and discussions on participatory communications and governance in development studies.

Ethnographic contexts.

The types of ethnographic contexts explored in the anthropology of media range from contexts of media production (e.g., ethnographies of newsrooms in newspapers, journalists in the field, film production) to contexts of media reception, following audiences in their everyday responses to media such as newspaper cartoons (Khanduri 2014). Other types include cyber anthropology, a relatively new area of internet research, as well as ethnographies of other areas of research which happen to involve media, such as development work, social movements, human rights or health education. This is in addition to many classic ethnographic contexts, where media such as radio, the press, new media and television (Mankekar 1999, Abu-Lughod 2005) have started to make their presences felt since the early 1990s.

Anthropology of media (also anthropology of mass media, media anthropology) is an area of study within social or cultural anthropology that emphasizes ethnographic studies as a means of understanding producers, audiences, and other cultural and social aspects of mass media.

媒体人类学 (Anthropology of media,亦称大众媒体人类学anthropology of mass media)是社会人类学或文化人类学的一门研究领域,强调民族志做为一种理解大众媒体的生产者、阅听者及其他文化社会面向的研究方法。


Description.

The tyrannosaurids were all large animals, with all species capable of weighing at least 1 metric ton. A single specimen of "Alioramus" of an individual estimated at between long has been discovered, although it is considered by some experts to be a juvenile. "Albertosaurus", "Gorgosaurus" and "Daspletosaurus" all measured between long, while "Tarbosaurus" reached lengths of from snout to tail. The massive "Tyrannosaurus" reached in one of the largest specimens, FMNH PR2081.  Tyrannosaurid skull anatomy is well understood as complete skulls are known for all genera but "Alioramus", which is known only from partial skull remains. "Tyrannosaurus", "Tarbosaurus", and "Daspletosaurus" had skulls that exceeded in length. Adult tyrannosaurids had tall, massive skulls, with many bones fused and reinforced for strength. At the same time, hollow chambers within many skull bones and large openings (fenestrae) between those bones helped to reduce skull weight. Many features of tyrannosaurid skulls were also found in their immediate ancestors, including tall premaxillae and fused nasal bones.  Tyrannosaurid skulls had many unique characteristics, including fused parietal bones with a prominent sagittal crest, which ran longitudinally along the sagittal suture and separated the two supratemporal fenestrae on the skull roof. Behind these fenestrae, tyrannosaurids had a characteristically tall nuchal crest, which also arose from the parietals but ran along a transverse plane rather than longitudinally. The nuchal crest was especially well-developed in "Tyrannosaurus", "Tarbosaurus" and "Alioramus". "Albertosaurus", "Daspletosaurus" and "Gorgosaurus" had tall crests in front of the eyes on the lacrimal bones, while "Tarbosaurus" and "Tyrannosaurus" had extremely thickened postorbital bones forming crescent-shaped crests behind the eyes. "Alioramus" had a row of six bony crests on top of its snout, arising from the nasal bones; lower crests have been reported on some specimens of "Daspletosaurus" and "Tarbosaurus", as well as the more basal tyrannosauroid "Appalachiosaurus".  The snout and other parts of the skull also sported numerous foramina. According to a 2017 study, the description of "D. horneri", scaly integument, as well as tactile sensitivity, was correlated with the multiple rows of neurovascular foramina seen in crocodylians and tyrannosaurids. The skull was perched at the end of a thick, "S"-shaped neck, and a long, heavy tail acted as a counterweight to balance out the head and torso, with the center of mass over the hips. Tyrannosaurids are known for their proportionately very small two-fingered forelimbs, although remnants of a vestigial third digit are sometimes found. "Tarbosaurus" had the shortest forelimbs compared to its body size, while "Daspletosaurus" had the longest.  Tyrannosaurids walked exclusively on their hindlimbs, so their leg bones were massive. In contrast to the forelimbs, the hindlimbs were longer compared to body size than almost any other theropods. Juveniles and even some smaller adults, like more basal tyrannosauroids, had longer tibiae than femora, a characteristic of fast-running dinosaurs like ornithomimids. Larger adults had leg proportions characteristic of slower-moving animals, but not to the extent seen in other large theropods like abelisaurids or carnosaurs. The third metatarsals of tyrannosaurids were pinched between the second and fourth metatarsals, forming a structure known as the arctometatarsus.  It is unclear when the arctometatarsus first evolved; it was not present in the earliest tyrannosauroids like "Dilong", but was found in the later "Appalachiosaurus". This structure also characterized troodontids, ornithomimids and caenagnathids, but its absence in the earliest tyrannosauroids indicates that it was acquired by convergent evolution.

History of discovery.

The first remains of tyrannosaurids were uncovered during expeditions led by the Geological Survey of Canada, which located numerous scattered teeth. These distinctive dinosaur teeth were given the name "Deinodon" ("terrible tooth") by Joseph Leidy in 1856. The first good specimens of a tyrannosaurid were found in the Horseshoe Canyon Formation of Alberta, and consisted of nearly complete skulls with partial skeletons. These remains were first studied by Edward Drinker Cope in 1876, who considered them a species of the eastern tyrannosauroid "Dryptosaurus". In 1905, Henry Fairfield Osborn recognized that the Alberta remains differed considerably from "Dryptosaurus", and coined a new name for them: "Albertosaurus sarcophagus" ("flesh-eating Alberta lizard"). Cope described more tyrannosaur material in 1892, in the form of isolated vertebrae, and gave this animal the name "Manospondylus gigas". This discovery was mostly overlooked for over a century, and caused controversy in the early 2000s when it was discovered that this material actually belonged to, and had name priority over, "Tyrannosaurus rex".  In his 1905 paper naming "Albertosaurus", Osborn described two additional tyrannosaur specimens that had been collected from in Montana and Wyoming during a 1902 expedition of the American Museum of

Distribution.

While earlier tyrannosauroids are found on all three northern continents, tyrannosaurid fossils are known only from North America and Asia. Sometimes fragmentary remains uncovered in the Southern Hemisphere have been reported as "Southern Hemisphere tyrannosaurids," although these seem to have been misidentified abelisaurid fossils. The exact time and place of origin of the family remain unknown due to the poor fossil record in the middle part of the Cretaceous on both continents, although the earliest confirmed tyrannosaurids lived in the early Campanian stage in western North America.  Tyrannosaurid remains have never been recovered from eastern North America, while more basal tyrannosauroids, like "Dryptosaurus" and "Appalachiosaurus", persisted there until the end of the Cretaceous, indicating that tyrannosaurids must have evolved in or dispersed into western North America after the continent was divided in half by the Western Interior Seaway in the middle of the Cretaceous. Tyrannosaurid fossils have been found in Alaska, which may have provided a route for dispersal between North America and Asia. "Alioramus" and "Tarbosaurus" are found to be related in one cladistic analysis, forming a unique Asian branch of the family. This was later disproven with the discovery of "Qianzhousaurus" and the description of the tyrannosaur family

Physiology.

Growth.

Paleontologist Gregory Erickson and colleagues have studied the growth and life history of tyrannosaurids. Analysis of bone histology can determine the age of a specimen when it died. Growth rates can be examined when the age of various individuals are plotted against their size on a graph. Erickson has shown that after a long time as juveniles, tyrannosaurs underwent tremendous growth spurts for about four years midway through their lives. After the rapid growth phase ended with sexual maturity, growth slowed down considerably in adult animals. A tyrannosaurid growth curve is S-shaped, with the maximum growth rate of individuals around 14 years of age.  The smallest known "Tyrannosaurus rex" individual (LACM 28471, the "Jordan theropod") is estimated to have weighed only at only 2 years old, while the largest, such as FMNH PR2081 ("Sue"), most likely weighed about, estimated to have been 28 years old, an age which may have been close to the maximum for the species. "T. rex" juveniles remained under until approximately 14 years of age, when body size began to increase dramatically. During this rapid growth phase, a

Life history.

The end of the rapid growth phase suggests the onset of sexual maturity in "Albertosaurus", although growth continued at a slower rate throughout the animals' lives. Sexual maturation while still actively growing appears to be a shared trait among small and large dinosaurs as well as in large mammals, such as humans and elephants. This pattern of relatively early sexual maturation differs strikingly from the pattern in birds, which delay their sexual maturity until after they have finished growing.  By tabulating the number of specimens of each age group, Erickson and his colleagues were able to draw conclusions about life history in tyranosauridae populations. Their analysis showed that while juveniles were rare in the fossil record, subadults in the rapid growth phase and adults were far more common. Over half of the known "T. rex" specimens appear to have died within six years of reaching sexual maturity, a pattern

Locomotion.

Locomotion abilities are best studied for "Tyrannosaurus", and there are two main issues concerning this: how well it could turn; and what its maximum straight-line speed was likely to have been. "Tyrannosaurus" may have been slow to turn, possibly taking one to two seconds to turn only 45° – an amount that humans, being vertically oriented and tail-less, can spin in a fraction of a second. The cause of the difficulty is rotational inertia, since much of "Tyrannosaurus"s mass was some distance from its center of gravity, like

Integument.

An ongoing debate in the paleontological community surrounds the extent and nature of tyrannosaurid integumentary covering. Long filamentous structures have been preserved along with skeletal remains of numerous coelurosaurs from the Early Cretaceous Yixian Formation and other nearby geological formations from Liaoning, China. These filaments have usually been interpreted as "protofeathers," homologous with the branched feathers found in birds and some non-avian theropods, although other hypotheses have been proposed. A skeleton of "Dilong" was described in 2004 that included the first example of "protofeathers" in a tyrannosauroid. Similarly to down feathers of modern birds, the "protofeathers" found in "Dilong" were branched

Vision.

The eye-sockets of "Tyrannosaurus" are positioned so that the eyes would point forward, giving them binocular vision slightly better than that of modern hawks. While predatory theropods in general had binocular vision directly in front of their skull, tyrannosaurs had a significantly larger area of overlap. Jack Horner also pointed out that the tyrannosaur lineage had a history of steadily improving binocular vision. It is hard to see how natural selection would have favored this long-term trend if tyrannosaurs

Facial sensory system.

Based on comparisons of bone texture of "Daspletosaurus" with extant crocodilians, a detailed study in 2017 by Thomas D. Carr "et al." found that tyrannosaurs had large, flat scales on their snouts. At the center of these scales

Bony crests.

Bony crests are found on the skulls of many theropods, including many tyrannosaurids. "Alioramus", a possible tyrannosaurid from Mongolia, bears a single row of five prominent bony bumps on the nasal bones; a similar row of much lower bumps is present on the skull of

Thermoregulation.

"Tyrannosaurus", like most dinosaurs, was long thought to have an ectothermic ("cold-blooded") reptilian metabolism but was challenged by scientists like Robert T. Bakker and John Ostrom in the early years of the "Dinosaur Renaissance", beginning in the late 1960s. "Tyrannosaurus rex" itself was claimed to have been endothermic ("warm-blooded"), implying a very active lifestyle. Since then, several paleontologists have sought to determine the ability of "Tyrannosaurus" to regulate its body temperature. Histological evidence of high growth rates in young "T. rex", comparable to those of mammals and birds, may support the hypothesis of a high metabolism. Growth curves indicate that, as in mammals and

Paleoecology.

Coexistence of "Daspletosaurus" and "Gorgosaurus".

In the Dinosaur Park Formation, "Gorgosaurus" lived alongside a rarer species of the tyrannosaurine "Daspletosaurus". This is one of the few examples of two tyrannosaur genera coexisting. Similarly-sized predators in modern predator guilds are separated into different ecological niches by anatomical, behavioral or geographical differences that limit competition. Niche differentiation between the Dinosaur Park tyrannosaurids is not well understood. In 1970, Dale Russell hypothesized that the more common "Gorgosaurus" actively hunted fleet-footed hadrosaurs, while the rarer and more troublesome ceratopsians and ankylosaurians (horned and heavily armoured dinosaurs) were left to the more heavily built "Daspletosaurus". However, a specimen of "Daspletosaurus" (OTM 200)

Social behavior.

There is limited evidence of social behavior among the tyrannosaurids. For example, the "Sue" "T.-rex" specimen apparently died from a massive bite to the head, which could only have been inflicted by another tyrannosaur. Researchers reported that a subadult and a juvenile skeleton were found in the same quarry as the "Sue" specimen, which has been used to support the hypothesis that tyrannosaurs may have lived in social groups of some kind. While there is no evidence of gregarious behavior in "Gorgosaurus", there is evidence of some pack behavior for "Albertosaurus" and "Daspletosaurus".  A young specimen of the Dinosaur Park "Daspletosaurus" species (TMP 94.143.1) shows bite marks on the face that were inflicted by another

Feeding.

Tyrannosaur tooth marks are the most commonly preserved feeding traces of carnivorous dinosaurs. They have been reported from ceratopsians, hadrosaurs and other tyrannosaurs. Tyrannosaurid bones with tooth marks represent about 2% of known fossils with preserved tooth marks. Tyrannosaurid teeth were used as holdfasts for pulling meat off a body, rather than knife-like cutting functions. Tooth wear patterns hint that complex head shaking behaviors may have been involved in tyrannosaur feeding.  Speculation on the pack-hunting habits of "Albertosaurus" were made by a few researchers

Classification.

The name Deinodontidae was coined by Edward Drinker Cope in 1866 for this family, and continued to be used in place of the newer name Tyrannosauridae through the 1960s. The type genus of the Deinodontidae is "Deinodon", which was named after isolated teeth from Montana. However, in a 1970 review of North American tyrannosaurs, Dale Russell concluded that "Deinodon" was not a valid taxon, and used the name Tyrannosauridae in place of Deinodontidae, stating that this was in accordance with ICZN rules. Therefore, Tyrannosauridae is preferred by modern experts.  "Tyrannosaurus" was named by Henry Fairfield Osborn in 1905, along with the family Tyrannosauridae. The name is derived from the Ancient Greek words "τυραννος" (') ('tyrant') and "σαυρος" (') ('lizard'). The very common suffix "-idae" is normally appended to zoological family names and is derived from the Greek suffix "-ιδαι" "-", which indicates a plural noun.

Taxonomy.

Tyrannosauridae is a family in rank-based Linnaean taxonomy, within the superfamily Tyrannosauroidea and the suborder Theropoda.  Tyrannosauridae is uncontroversially divided into two subfamilies. Albertosaurinae comprises the North American genera "Albertosaurus" and "Gorgosaurus", while Tyrannosaurinae includes "Daspletosaurus", "Teratophoneus", "Bistahieversor", "Tarbosaurus", "Nanuqsaurus", "Zhuchengtyrannus", and "Tyrannosaurus" itself. Some authors include the species "Gorgosaurus libratus" in the genus "Albertosaurus" and "Tarbosaurus bataar" in the genus "Tyrannosaurus", while others prefer to retain "Gorgosaurus" and "Tarbosaurus" as separate genera. Albertosaurines are characterized by more slender builds, lower skulls, and proportionately longer tibiae than tyrannosaurines. In tyrannosaurines, the sagittal crest on the parietals continues forward onto the frontals. In 2014,

Phylogeny.

With the advent of phylogenetic taxonomy in vertebrate paleontology, Tyrannosauridae has been given several explicit definitions. The original was produced by Paul Sereno in 1998, and included all tyrannosauroids closer to Tyrannosaurus than to either "Alectrosaurus", "Aublysodon" or "Nanotyrannus". However, "Nanotyrannus" is often considered to be a juvenile "Tyrannosaurus rex", while "Aublysodon" is usually regarded as a "nomen dubium" unsuitable for use in the definition of a clade. Definitions since then have been based on more well-established genera.  In 2001, Thomas R. Holtz, Jr. published a cladistic analysis of the tyrannosauridae. He concluded that there were two subfamilies: the more primitive Aublysodontinae, characterized by unserrated premaxillary teeth; and the Tyrannosaurinae. The Aublysodontinae included "Aublysodon", the "Kirtland "Aublysodon"", and "Alectrosaurus". Holtz also found that "Siamotyrannus" exhibited some of the synapomorphies of the tyrannosauridae, but lay "outside the <nowiki>[</nowiki>family<nowiki>]</nowiki> proper."  Later in the same paper, he proposed that Tyrannosauridae be defined as "all descendants of the most recent common ancestor of "Tyrannosaurus" and "Aublysodon"". He also criticized definitions previously proposed by other workers, like one proposed by Paul Sereno, that the Tyrannosauridae was "all taxa closer to "Tyrannosaurus" than to "Alectrosaurus", "Aublysodon", and "Nanotyrannus"". Holtz observed that since "Nanotyrannus" was probably a misidentified "T. rex" juvenile, Sereno's proposed definition would have the family Tyrannosauridae as a subtaxon of the genus "Tyrannosaurus". Further, his proposed definition of the subfamily Tyrannosaurinae would also be limited to "Tyrannosaurus".  A 2003 attempt by Christopher Brochu included "Albertosaurus", "Alectrosaurus",

Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous "Tyrannosaurus". The exact number of genera is controversial, with some experts recognizing as few as three. All of these animals lived near the end of the Cretaceous Period and their fossils have been found only in North America and Asia.

暴龙科(学名:,意指「暴君蜥蜴」)是兽脚亚目虚骨龙类暴龙超科的一科,包含艾伯塔龙亚科与暴龙亚科,共计十五个属。暴龙科生活于白垩纪晚期。化石可见于北美以及东亚,各地物种不尽相同。


Life.

The future al-Mu'tamid was a son of Caliph al-Mutawakkil (r. 847–861) and a Kufan slave girl called Fityan. His full name was Ahmad ibn Abi Jaʿfar, and was also known by the patronymic Abu'l-Abbas and from his mother as Ibn Fityan. After al-Muhtadi was deposed by the Turkish commanders Bayakbak and Yarjukh, he was selected by the military as his successor and proclaimed Caliph with the regnal name "al-Muʿtamid ʿAlā ’llāh" on 16 or 19 June 870. On 21 June, al-Muhtadi was executed.

Reign and relationship with al-Muwaffaq.

The accession of al-Mu'tamid brought an end to the turmoils of the "Anarchy at Samarra", which had begun with the murder of al-Mutawakkil in 861. Caliphal authority in the provinces collapsed during that period, with the result that the central government lost effective control over most of the Caliphate outside the metropolitan region of Iraq. In the west, Egypt had fallen under the control of the ambitious Turkish soldier Ahmad ibn Tulun, who also had designs on Syria, while Khurasan and most of the Islamic East had been taken over by the Saffarids under Ya'qub ibn al-Layth, who replaced the Abbasids' loyal client state, the Tahirids. Most of the Arabian peninsula was likewise lost to local potentates, while in Tabaristan a radical Zaydi Shi'a dynasty took power. Even in Iraq, a rebellion of the Zanj slaves had begun and soon threatened Baghdad itself, while further south the Qarmatians were a nascent threat. In addition, al-Mu'tamid's position was undermined from within, as during the coups of the previous years real power had come to lie with the elite Turkish troops, and with al-Mu'tamid's brother Abu Ahmad Talha, who, as the Caliphate's main military commander, served as the chief intermediary between the caliphal government and the Turks. When Caliph al-Mu'tazz died in 869, there was even popular agitation in Baghdad in favour of his elevation to Caliph.  In contrast to his brother, al-Mu'tamid appears to have lacked any experience of, and involvement in, politics, as well as a power base he could rely on. At the time al-Muhtadi was killed by the Turks, Abu Ahmad was at Mecca. Immediately he hastened north to Samarra, where he and Musa ibn Bugha effectively sidelined al-Mu'tamid, and assumed control of the government. Al-Mu'tamid was thus quickly reduced to a figurehead ruler, which remained the case for the remainder of his reign. Within a short time, Abu Ahmad was conferred an extensive governorate covering most of the lands still under caliphal authority: western Arabia, southern Iraq with Baghdad, and Fars. To denote his authority, he assumed an honorific name in the style of the caliphs, "al-Muwaffaq bi-Allah". As one of the few vestiges of actual power, al-Mu'tamid retained the right to appoint his own viziers, originally choosing the experienced Ubayd Allah ibn Yahya ibn Khaqan, who had already served al-Mutawakkil. During his tenure, the Caliph retained some freedom of action, but after his death in 877, he was replaced by al-Muwaffaq's secretary, Sulayman ibn Wahb. Ibn Wahb was soon disgraced and replaced as vizier by Isma'il ibn Bulbul. Real power however lay again with al-Muwaffaq's new secretary, Sa'id ibn Makhlad, until his own disgrace and downfall in 885, after which Ibn Bulbul became the sole vizier to both al-Mu'tamid and al-Muwaffaq.  On 20 July 875, al-Mu'tamid formally arranged for the governance of the state and his succession: his underage son Ja'far was given the honorific name "al-Mufawwad ila-llah", was named heir-apparent and assigned the western half of the Caliphate—Ifriqiya, Egypt, Syria, the Jazira and Mosul, Armenia, Mihrajanqadhaq and Hulwan— while al-Muwaffaq received the eastern provinces and was named second heir, except for the event that the Caliph died while al-Mufawwad was still a minor. In practice, al-Mufawwad never exercised any real authority, and al-Muwaffaq continued to exercise control over the western provinces as well through his trusted lieutenant Musa ibn Bugha, who was named al-Mufawwad's deputy. Al-Muwaffaq's power was strengthened by the military threats the Caliphate faced on all fronts, since he commanded the loyalty of the army. In April 876, al-Muwaffaq and Musa ibn Bugha defeated Ya'qub ibn al-Layth's attempt to capture Baghdad at the Battle of Dayr al-'Aqul and saved the Caliphate from collapse. The repulse of the Saffarids then allowed the Abbasids to concentrate their resources in suppressing the Zanj Revolt in the south. The Zanj rebels had managed to capture much of lower Iraq, and inflicted several defeats on the Abbasid troops. In 879, al-Muwaffaq's son Abu'l-Abbas, the future Caliph al-Mu'tadid (r. 892–902), was given the command against the Zanj, and in the next year, al-Muwaffaq himself joined the campaign. In a succession of engagements in the marshes of southern Iraq, the Abbasid forces drove back the Zanj towards their capital, Mukhtara, which fell in August 883.

Ibn Tulun and al-Mu'tamid's attempted flight to Egypt.

At the same time, al-Muwaffaq also had to contend with the ambitions of Ahmad ibn Tulun in the western provinces. Ibn Tulun and the Abbasid regent fell out in 875/6, on the occasion of a large remittance of revenue from Egypt to the central government. Counting on the rivalry between the Caliph and his over-mighty brother to maintain his own position, Ibn Tulun forwarded a larger share of the taxes to al-Mu'tamid instead of al-Muwaffaq: 2.2 million gold dinars went to the Caliph and only 1.2 million dinars to his brother. Al-Muwaffaq, who in his fight against the Zanj considered himself entitled to the major share of the provincial revenues, was angered by this, and by the implied machinations between Ibn Tulun and his brother. Al-Muwaffaq nominated Musa ibn Bugha as governor of Egypt and sent him with troops to Syria, but a lack of funds led to the expedition's failure before even reaching Egypt. In a public gesture of support for al-Mu'tamid and opposition to al-Muwaffaq, Ibn Tulun assumed the title of "Servant of the Commander of the Faithful" ("mawlā amīr al-muʾminīn") in 878. With the support of al-Mu'tamid, in 877/8 Ibn Tulun managed to be assigned responsibility for the entirety of Syria and the Cilician frontier zone (Thughur) with the Byzantine Empire.  In 881, Ibn Tulun added his own name to coins issued by the mints under his control, along with those of the Caliph and heir apparent, al-Mufawwad. In the autumn of 882, the Tulunid general Lu'lu' defected to the Abbasids, and the cities of the Thughur rejected Tulunid rule, forcing Ibn Tulun to go once again in person to Syria. Al-Mu'tamid used the moment to escape from his confinement in Samarra, and with a small entourage made for Tulunid domains. Messengers from the Caliph reached Ibn Tulun at Damascus, and the ruler of Egypt halted and awaited the Caliph's arrival with great anticipation: not only would the sole source of political legitimacy in the Muslim world reside under his control, but he would also be able to pose as the "rescuer" of the Caliph from his overreaching brother. In the event, however, Sa'id ibn Makhlad managed to alert the governor of Mosul, Ishaq ibn Kundaj, who overtook and defeated al-Mu'tamid and his escort at al-Haditha on the Euphrates. Al-Mu'tamid was brought back to Samarra (February 883), where he was placed under virtual house arrest in the Jawsak Palace. In May/June, he was even moved south to Wasit, where al-Muwaffaq could keep an eye on him in person. Only in March 884 was the powerless Caliph allowed to return to Samarra. In the meantime, he was obliged to denounce Ibn Tulun, and appoint—nominally at least—Ishaq ibn Kundaj as governor of Syria and Egypt.

Rise of al-Mu'tadid and death.

In 889, al-Muwaffaq fell out with his son, Abu'l-Abbas, for reasons that are unclear, and had him imprisoned. Al-Muwaffaq spent the next two years on campaign in the Jibal. By the time he returned to Baghdad in May 891, al-Muwaffaq was already nearing death. The garrison commander of Baghdad, and the vizier Isma'il ibn Bulbul, hatched a plot to keep Abu'l-Abbas imprisoned and allow power to pass to al-Mu'tamid. Therefore, they invited the Caliph and his son to come the city, which they did. In the event, however, the attempt to sideline Abu'l-Abbas failed, due to his popularity with the soldiers and the common people: the soldiers set him free, and when al-Muwaffaq died on 2 June, Abu'l-Abbas immediately assumed his father's position. Abu'l-Abbas assumed the title of "al-Mu'tadid bi-llah" and took his father's position in the line of succession after the Caliph and al-Mufawwad. The powerless al-Mufawwad was pushed aside on 30 April 892, and when al-Mu'tamid died on 14 October 892, "apparently as a result of a surfeit of drink and food" (Hugh N. Kennedy), al-Mu'tadid took power as caliph.

Abu’l-ʿAbbās Aḥmad ibn Jaʿfar (; – 14 October 892), better known by his regnal name al-Muʿtamid ʿalā ’llāh (, "Dependent on God"), was the Caliph of the Abbasid Caliphate from 870 to 892. His reign marks the end of the "Anarchy at Samarra" and the start of the Abbasid restoration, but he was a largely a ruler in name only. Power was held by his brother al-Muwaffaq, who held the loyalty of the military. Al-Mu'tamid's authority was circumscribed further after a failed attempt to flee to the domains controlled by Ahmad ibn Tulun in late 882, and he was placed under house arrest by his brother. In 891, when al-Muwaffaq died, loyalists attempted to restore power to the Caliph, but were quickly overcome by al-Muwaffaq's son al-Mu'tadid, who assumed his father's powers. When al-Mu'tamid died in 892, al-Mu'tadid succeeded him as caliph.

穆阿台米德(842年-892年-10月15日),伊斯兰教第三十三代哈里发,阿拔斯王朝第十五代哈里发(公元870年-892年在位)。842年出生,父亲是阿拔斯王朝第十代哈里发穆塔瓦基勒,869年7月9日继承堂兄弟穆赫塔迪,成为哈里发。892年10月15日去世,侄子穆阿台迪德即位。


Taxonomy.

The Barbary macaque was named by Carl Linnaeus in 1758, along with numerous other species named in that same year. The scientific name is "Macaca sylvanus". Phylogenetic and molecular analysis with other primates has been done. Studies concerning interspecific DNA variation within the genus "Macaca" show that the Barbary macaque is most related to the Asian macaques. Scientists have also studied the Y-chromosome; however, this has proven unfruitful. One study indicates that the Barbary macaque has origins in Morocco and Algeria. The results of a phylogenetic analysis show that "M. sylvanus" chromosomes resemble "M. mulatta" with the exception of chromosomes 1, 4, 9, and 16.

Physical description.

The monkey is yellowish-brown to grey with a lighter underside. The Barbary macaque has a mean body length of 556.8 mm (21.9 in) in females and 634.3 mm (25.0 in) in males, and mean body weight is reported to be 9.9 ± 10.3 kg (21.8 lbs) in females and 14.5 ± 17.5 kg (32.0 lbs) in males. Its face is dark pink and its tail is vestigial, measuring anywhere from 4 to 22mm. Males often have a more prominent tail. The front limbs of this monkey are longer than its hind limbs. Females are smaller than males.

Distribution and habitat.

The Barbary macaque lives mainly in the Atlas and Rif Mountain ranges of Morocco and Algeria. It is the only macaque species that is distributed outside Asia. It can live in a variety of habitats, such as cedar, fir, and oak forests, or grasslands, scrub, rocky ridges full of vegetation. Most Barbary macaques inhabit cedar forests currently in the Atlas Mountains, however, this could reflect the present habitat availability rather than a specific preference for this habitat.

Behaviour and ecology.

The Barbary macaque is gregarious, forming mixed groups of several females and males. Troops can have 10 to 100 individuals and are matriarchal, with their hierarchy determined by lineage to the lead female. Unlike other macaques, the males participate in rearing the young. Males may spend a considerable amount of time playing with and grooming infants. In this way, a strong social bond is formed between males and juveniles, both the male's own offspring and those of others in the troop. This may be a result of selectivity on the part of the females, who may prefer highly parental males.  The mating season runs from November through March. The gestation period is 147 to 192 days, and females usually have only one offspring per pregnancy. Females rear twins in rare instances. Offspring reach maturity at three to four years of age, and may live for 20 years or more.  Grooming other Barbary macaques leads to lower stress levels for the individuals that do the grooming. While stress levels do not appear to be reduced in animals that are groomed, grooming more individuals leads to even lower stress levels; this is a benefit that might outweigh the costs to the groomer, which include less time to participate in other activities such as foraging. The mechanism for reducing stress may be explained by the social relationships (and support) that are formed by grooming.  Male Barbary macaques interfere in conflicts and form coalitions with other males, usually with related males rather than with unrelated males. These relationships suggest that males do so in order to indirectly increase their own fitness. Furthermore, males form coalitions with closely related kin more often than they do with distantly related kin. These coalitions are not permanent and may change frequently as male ranking within the group changes. Although males are more likely to form coalitions with males who have helped them in the past, this is not as important as relatedness in determining coalitions. Males avoid conflicting with higher ranking males and will more frequently form coalitions with the higher ranking male in a conflict. Close grouping of males occur when infant Barbary macaques are present. Interactions between males are commonly initiated when a male presents an infant macaque to an adult male who is not caring for an infant, or when an unattached male approaches males who are caring for infants. This behaviour leads to a type of social buffering, which reduces the number of antagonistic interactions among males in a group.  An open mouth display by the Barbary macaque is used most commonly by juvenile macaques as a sign of playfulness.

Alarm calls.

The main purpose of calls in Barbary macaques is to alert other group members to possible dangers such as predators. Barbary macaques can discriminate calls by individuals in their own group from those by individuals in other groups of conspecific macaques. Neither genetic variation nor habitat differences are likely causes of acoustic variation in the calls of different social groups. Instead, minor variations in acoustic structure among groups similar to the vocal accommodation seen in humans are the likely cause. However, acoustic characteristics such as pitch and loudness are varied based on the vocalizations of individuals they associate with, and social situations play a role in the acoustic structure of calls.  Barbary macaque females have the ability to recognize their own offspring's calls through a variety of acoustic parameters. Because of this, infant calls do not have to differ dramatically for mothers to be able to recognize their own infant's call. Mothers demonstrate different behaviours on hearing the calls of other infant macaques as opposed to the calls of their own offspring. More parameters for vocalizations lead to more reliable identification of calls in both infants and in adult macaques so it is not surprising that the same acoustic characteristics that are heard in infant calls are also heard in adult calls.

Mating.

Although Barbary macaques are sexually active at all points during a female's reproductive cycle, male Barbary macaques determine a female's most fertile period by sexual swellings on the female. Mating is most common during a female's most fertile period. The swelling size of the female reaches a maximum around the time of ovulation, suggesting that size helps a male predict when he should mate. This is further supported by the fact that male ejaculation peaks at the same time that female sexual swelling peaks. There is not a sufficient change in female sexual behaviour around the time of ovulation in order to demonstrate to the male that the female is fertile. The swellings, therefore, appear necessary for predicting fertility.  Barbary macaque females differ from other non-human primates in that they often mate with a majority of the males in their social group. While females are active in choosing sexual associations, the mating behaviour of macaque social groups is not entirely determined by female choice. These multiple matings by females decreases the certainty of paternity of male Barbary macaques and may lead them to care for all infants within the group. In order for a male to ensure his reproductive success, he must maximize his time spent around the females in the group during their fertile periods. Injuries to male macaques peaks during the fertile period, which points to male-male competition as an important determinant of male reproductive success. Not allowing a female to mate with other males, however, would be costly to the male since doing so would not allow him to mate with more females.

Parenting.

Unlike other macaques where most parental care comes from the mother, Barbary macaques from all age and sex groups participate in alloparental care of infants. Male care of infants has been of particular interest to research because high levels of care from males is uncommon in groups where paternity is highly uncertain. Males even act as true alloparents of infant macaques by carrying them and caring for them for hours at a time as opposed to just demonstrating more casual interactions with the infants. Female social status plays a role in female alloparental interactions with infants. Higher ranking females have more interactions whereas younger, lower ranking females have less access to infants.

Diet.

The diet of the Barbary macaque consists of a mixture of plants and insect prey. It consumes a large variety of gymnosperms and angiosperms. Almost every part of the plant is eaten, including flowers, fruits, seeds, seedlings, leaves, buds, bark, gum, stems, roots, bulbs, and corns. Common prey caught and consumed by Barbary macaques are snails, earthworms, scorpions, spiders, centipedes, millipedes, grasshoppers, termites, water striders, scale insects, beetles, butterflies, moths, ants, and even tadpoles.  Barbary macaques can cause major damage to the trees in their prime habitat, the Atlas cedar forests in Morocco. Since deforestation in Morocco has become a major environmental problem in recent years, research has been conducted to determine the cause of the bark stripping behaviour demonstrated by these macaques. Cedar trees are also vital to this population of Barbary macaques as an area with cedars can support a much higher density of macaques than one without them. A lack of a water source and exclusion of monkeys from water sources are major causes of cedar bark stripping behaviour in Barbary macaques. Density of macaques, however, is less correlated with the behaviour than the other causes considered.

Predators.

Their main predators are leopards, eagles, and domestic dogs. The approach of eagles and domestic dogs is known to elicit an alarm call response.

Threats.

Wild populations of Barbary macaques have suffered a major decline in recent years to the point of being declared an endangered species on the IUCN Red List in 2009. Three-quarters of the world population is located in the Middle Atlas Mountains.  This species is also poached for live specimens as pets in the illegal pet trade, and for clandestine collectors. Spain is the main entry point in Europe. Today, no accurate data exist on the location and number of individuals out of their habitat. An unknown number of individuals are included in zoological collections, at other institutions, in private hands, in storage, or waiting to be relocated to appropriate destinations.  The habitat of the Barbary macaque is under threat from increased logging activity. Local farmers view the monkeys as pests, and engage in extermination of the species. Once common throughout northern Africa and southern Europe, only an estimated 12,000 to 21,000 Barbary macaques are left in Morocco and Algeria. Once, their distribution was much more extensive, reaching Tunisia and Libya. Their range is no longer continuous, with only isolated areas of range remaining. During the Pleistocene, this species inhabited the Mediterranean coasts and Europe, reaching Italy, Hungary, Spain, Portugal and France, and as far north as Germany and the British Isles. The species decreased with the arrival of the Ice Age, becoming extinct in the Iberian Peninsula 30,000 years ago.  The Barbary macaque is threatened by habitat loss, overgrazing and illegal capture. In Morocco, tourists interact with Barbary macaques in many regions. Information collected in the interviews with inhabitants in the High Atlas of Morocco indicated that the capture of macaques occurs in these regions. Conflict between local people and wild macaques is one of the greatest challenges to Barbary macaque conservation in Morocco. The main threats to the survival of Barbary macaques in this region have been found to be habitat destruction and the impact of livestock grazing, but there are also increasing problems of conflict with inhabitants due to crop raiding and the illegal capture of macaques. One study has found that the human–macaque conflict is mainly due to crop raiding. In the High Atlas of Morocco, macaques attract a large number of tourists every year, and they are favourable for their potential benefits to tourism. In addition, macaques have some ecological roles, for example they are the predators of several destructive insects and pests of plants and participate in seed dispersal in many plant species.  In the Central High Atlas, the Barbary macaque occurs in relatively small and fragmented areas restricted to the main valleys at altitudes of 700–2,400 m. In a 2013 study, researchers reported that they found Barbary macaques in relatively small and fragmented habitats in 10 sites, and that the species no longer occurred in four localities. This could be attributed to habitat degradation, hunting activities, the impact of livestock grazing, and disturbance by people. As deforestation for agriculture and overgrazing continues, the remaining forest becomes increasingly fragmented. Consequently, the Barbary macaque is now restricted to small, fragmented relict habitats.

Human use and tourism.

Many of the mistaken ideas about human anatomy contained in the writings of Galen are apparently due to his use of these animals, the only anthropoid available to him, in dissections. Strong cultural taboos of his time prevented his performing any actual dissections of human cadavers, even in his role as physician and teacher of physicians.  Macaques in Morocco are frequently used as photo props, despite their protected status. Tourists are encouraged to take photos with the animals for a fee. Macaques are also sold as pets in Morocco and Algeria and exported to Europe to be used as pets and fighting monkeys, both in physical marketplaces and online.  Tourists interact with wild monkeys across the globe and in some situations tourists may be encouraged to feed, photograph and touch the monkeys. Although tourism has the potential to bring money in towards conservation goals and provides an incentive for the protection of natural habitats, close proximity and interactions with tourists can also have significant psychological impacts on the Barbary macaque. Fecal samples and stress-indicating behaviours, such as belly scratching, indicate that the presence of tourists has a negative impact on the macaques. Human activities such as taking photographs cause the animals stress, possibly because the people come too close to the animals and make prolonged eye contact (a sign of aggression in many primates). Macaques that live in areas close to human contact have more parasites and lower overall health than those that live in wilder environments, at least in part due to the unhealthy diets they receive as a result of feeding from humans.  Several groups of Barbary macaques can be found in tourist sites, where they are affected by the presence of visitors providing food to them. Researchers comparing two such groups in the central High Atlas mountains in 2008 found that the tourist group of Barbary macaques spent significantly more time engaged in resting and aggressive behaviour, and foraged and moved significantly less than the wild group. The tourist group spent significantly less time per day feeding on herbs, seeds and acorns than the wild group. Human food accounted for 26% of the daily feeding records for the tourist group, and 1% for the wild-feeding group. Scientists who collected data on the seasonal activity budget and diet composition of the endangered Barbary macaque group inhabiting a tourist site in Morocco found that activity budgets and diet of the study group varied markedly among seasons and habitats. The percentage of daily time spent in foraging and moving was lowest in spring, and the daily time spent in resting was highest in spring and summer. The time budget devoted to aggressive display was highest in spring than the other three seasons. There is an increase in the daily feeding time spent eating flowers and fruits in summer, seeds, acorns, roots and barks in winter and autumn, herbs in spring and summer, and a clear increase in consumption of the human food in spring. The tourist and the wild groups did not differ in the proportion of daily records devoted to terrestrial feeding, but the tourist group spent a significantly lower percentage of daily records in terrestrial foraging, moving and resting, while performing more terrestrial aggressive displays more than the wild group. There was no significant difference between the two groups in the proportion of terrestrial feeding records spent eating fruits; but the tourist group had lower daily percentages of terrestrial feeding on leaves, seeds and acorns, roots and barks, and herbs, while it spent higher daily percentages of terrestrial feeding on human food.  There is evidence that Barbary macaques were traded or perhaps given as diplomatic gifts as long ago as the Iron Age. Their remains have been found in such sites as Emain Macha in Ireland, dating to no later than 95 BC; an Iron Age hillfort, the Titelberg in Luxembourg; and two Roman sites in Britain.

Gibraltar population.

The last wild population in Europe is that of Gibraltar, which, unlike that of North Africa, is thriving. Currently, there are around 230 individuals living on the Rock of Gibraltar, and they form groups of up to 75 and will occasionally enter the town.

Alexander of Greece.

King Alexander of Greece (1893-1920) was famously killed from the results of an attack by a Barbary macaque. On 2 October 1920, Alexander, strolling through his gardens while walking his dog, was attacked by a macaque following a fight between his dog and another monkey. He was bit on the leg and torso, before servants chased the animals away. The wounds became infected and Alexander, not wanting the event to be publicised, was not properly treated. He died of sepsis on 25 October.

Pleistocene fossils.

Fossils of "Macaca sylvanus" have been found much further north and east into mainland Europe, dating to the Middle and Late Pleistocene. Some earlier fossils may be this species or the earlier Florentine macaque "Macaca florentina", or transitional between the two. Examples identified as "M.sylvanus" have been found in France, Germany, Israel, Italy, Romania, Spain and the United Kingdom. All the specimens date from interglacial and temperate phases and are considered a good indicator of warm climate.

The Barbary macaque ("Macaca sylvanus"), also known as Barbary ape or magot, is a species of macaque unique for its distribution outside Asia. Found in the Atlas Mountains of Algeria and Morocco along with a small population of uncertain origin in Gibraltar, the Barbary macaque is one of the best-known Old World monkey species. The Barbary macaque is of particular interest because males play an atypical role in rearing young. Because of uncertain paternity, males are integral to raising all infants. Generally, Barbary macaques of all ages and sexes contribute in alloparental care of young.

巴巴利猕猴(学名:'),又称为叟猴、地中海猕猴或直布罗陀猿,是一种尾部退化的猕猴。该物种分布在阿特拉斯山脉的阿尔及利亚和摩洛哥,在直布罗陀有少量分布,可能为引进物种。是欧洲惟一的非人灵长类动物。大约300年前来自北非的摩洛哥和阿尔及利亚。巴巴利猕猴为旧世界猴 。虽然物种常常被称为“巴巴利猿”,但是巴巴利猕猴是真正的猴,而不是猿。


History.

Its lyrics and title were based on Văn Cao's previous works, "Thăng Long". Part of the lyrics were also different during its early stages, as it went through numerous changes starting in the early 1940s.

Lyric changes and completion.

"Tiến Quân Ca" went through many changes shortly after it was composed. For instance, the first sentence "Đoàn quân Việt Nam đi" was originally "Đoàn quân Việt Minh đi." The sixth part of the lyrics was also originally "Thề phanh thây uống máu quân thù", expressing the brutality of French colonial and pre-famine actions. After many suggestions, Văn Cao changed it to "Đường vinh quang xây xác quân thù". The last sentence "Tiến lên! Cùng tiến lên! Chí trai là nơi đây ước nguyền!" it was changed to "Núi sông Việt Nam ta vững bền", but when it was published it was changed to "Nước non Việt Nam ta vững bền!", which Văn Cao commented, "With a song that requires solemn, 'nước non' seemed too weak while being sung with 'núi sông' would be more reasonable."  After completion of work, Văn Cao met and let Vũ Quý try the song. Vũ Quý was very happy at his work, and "Tiến Quân Ca" was published in papers on November 1944 with lithographs by Văn Cao.  On August 17, 1945, the song was sung for the first time at a rally of civil servants in Hanoi by a Ph.D under the flag of the Việt Minh, and "robbed the loudspeakers". Văn Cao quoted, "That quiet man was an attraction to thousands of people listening that day".  The poet and musician Nguyễn Đình Thi was touched after hearing Văn Cao sing the song and asked each person to write another song for "The Viet Minh Frontline". He posted his own "Diệt Phát Xít", meaning "Killing Fascists". Văn Cao wrote "Chiến Sĩ Việt Nam", meaning "Vietnam Soldiers". Both songs are still popular and sung to the public today.

As a national anthem.

On August 17, 1945, Hồ Chí Minh approved Tiến Quân Ca to be officially recognized as the anthem of the Democratic Republic of Vietnam.  On September 2, 1945, marching was officially performed on the day of the Proclamation of Independence at Ba Đình Square by the Liberation Army band commanded by. At the day before the performance, musicians Dinh Ngoc Lien, Nguyen Huu Hieu, and Văn Cao discussed for changing the two words in "Tiến Quân Ca" in order to shorten the song by shortening the length of the first E pitches in the word "đoàn" and the F in the middle of the word "xác" to make the song more "snappy".  In 1946, the 1st National Assembly officially recognized "Tiến Quân Ca" as the national anthem. In the first Constitution of the Democratic Republic of Vietnam in Article 3, it states directly about the national anthem. In 1955, the 5th session of the first National Assembly decided to invite authors to participate in another editing of the song. Văn Cao had regrets after this because the "heroic spirit" of the song had been lost after being edited.  After 1975, the government of South Vietnam fell, and on July 2, 1976, the Provisional Revolutionary Government of the Republic of South Vietnam (in most common situation, the phrase "Viet Cong" actually refers to it) and the Democratic Republic of Vietnam agreed to be reunified into the new Socialist Republic of Vietnam. "Tiến Quân Ca" was chosen as the national anthem. In 1981, a contest was opened for a new national anthem but after more a year, it was and has never been mentioned again nor are there any official statement about the results. Thus, "Tiến Quân Ca" remains today as the national anthem of Vietnam.  On July 8, 2016, Painter Văn Thao, the eldest son of Văn Cao confirmed that he and his family were going to donate the song to their country and people as his father's last wish. A letter, signed by all the legal inheritors in the family, stated that the family would donate the song for free use.  On July 15, 2016, The National Assembly Office held a ceremony in Hanoi to receive the national anthem, donated by Văn Cao's family members.

Copyrighted anthem.

Shortly after the "donation", the Vietnam Center for Protection of Music Copyright stated that the national anthem would be under copyright protection regardless of the offer to "gift it" by Văn Cao's family. It states that only certain situations like ceremonies and school could be anthem will "from now on be subject to royalty". Veteran composers objected to the idea, saying that "people should be allowed to sing this song without worrying about royalty". However, Văn Cao said that his family "never reached consensus on 'gifting' the song, so they authorized the center to collect royalties on his father's songs".

Tiến Quân Ca, known in English as the "Army Marching Song", "Song of Marching Army" or "Song of Advancing Soldiers", is the National Anthem of Socialist Republic of Vietnam (SRV), both written and composed by Văn Cao in 1944. The "Army Marching Song" was adopted as the national anthem of Democratic Republic of Vietnam (DRV) in 1945, and was adopted as the national anthem of the new unified Socialist Republic of Vietnam in 1976, following the reunification of both North Vietnam and South Vietnam at the end of the Vietnam War. Though it has two verses, the first one is mainly sung.

《进军歌》()是越南社会主义共和国的国歌,由阮文高作曲及填词,1945年8月革命前产生于越北解放区。1946年召开的北越第一届国会第二次会议正式确定《进军歌》为国歌。1955年第一届国会第五次会议根据政府建议对《进军歌》的歌词作了一些小修改。1976年7月2日,统一的越南国会通过决议,确定《进军歌》为全国统一后的越南社会主义共和国国歌。


Function.

In the secondary market, securities are sold by and transferred from one investor or speculator to another. It is therefore important that the secondary market be highly liquid (originally, the only way to create this liquidity was for investors and speculators to meet at a fixed place regularly; this is how stock exchanges originated, see History of the Stock Exchange). As a general rule, the greater the number of investors that participate in a given marketplace, and the greater the centralization of that marketplace, the more liquid the market.  Fundamentally, secondary markets mesh the investor's preference for liquidity ("i.e.", the investor's desire not to tie up his or her money for a long period of time, in case the investor needs it to deal with unforeseen circumstances) with the capital user's preference to be able to use the capital for an extended period of time.  Accurate share price allocates scarce capital more efficiently when new projects are financed through a new primary market offering, but accuracy may also matter in the secondary market because: 1) price accuracy can reduce the agency costs of management, and make hostile takeover a less risky proposition and thus move capital into the hands of better managers; and 2) accurate share price aids the efficient allocation of debt finance whether debt offerings or institutional borrowing.

Related usage.

The term may refer to markets in things of value other than securities. For example, the ability to buy and sell intellectual property such as patents, or rights to musical compositions, is considered a secondary market because it allows the owner to freely resell property entitlements issued by the government. Similarly, secondary markets can be said to exist in some real estate contexts as well ("e.g.", ownership shares of time-share vacation homes are bought and sold outside of the official exchange set up by the timeshare issuers). These have very similar functions as secondary stock and bond markets in allowing for speculation, providing liquidity, and financing through securitization. It facilitates liquidity and marketability of the long-term instrument. It also provides instant valuation of securities caused by changes in the environment.

Private secondary markets.

Private equity secondary market refers to the buying and selling of pre-existing investor commitments to private equity funds. Sellers of private equity investments sell not only the investments in the fund, but also their remaining unfunded commitments to the funds.  Due to the increased compliance and reporting obligations enacted in the Sarbanes-Oxley Act of 2002, private secondary markets began to emerge, such as SecondMarket and SecondaryLink. These markets are generally only available to institutional or accredited investors, and allow trading of unregistered and private company securities.

The secondary market, also called the aftermarket and follow on public offering is the financial market in which previously issued financial instruments such as stock, bonds, options, and futures are bought and sold. Another frequent usage of "secondary market" is to refer to loans which are sold by a mortgage bank to investors such as Fannie Mae and Freddie Mac.

二级市场又称次级市场,是买卖已经上市公司股票的资本市场。新股发行不属于二级市场。二级市场是任何旧金融商品的交易市场,可为金融商品的最初投资者提供资金的流动性。这里金融商品可以是股票、债券、按揭、人寿保险等。各种资产的二级市场可能有所不同,从贷款到股票,从零散到集中,从非流动到非常流动。主要证券交易所是流动性二级市场最明显的例子 - 在这种情况下,是公开交易公司的股票。


Example: voltage-controlled current sink.

Figure 1 shows a voltage-controlled current sink. The sink is intended to draw the same current "i" regardless of the applied voltage "V" at the output. The value of current drawn is to be set by the input voltage "v". Here the sink is to be analyzed by idealizing the op amp as a nullor.  Using properties of the input nullator portion of the nullor, the input voltage across the op amp input terminals is zero. Consequently, the voltage across reference resistor "R" is the applied voltage "v", making the current in "R" simply "v"/"R". Again using the nullator properties, the input current to the nullor is zero. Consequently, Kirchhoff's current law at the emitter provides an emitter current of "v"/"R". Using properties of the norator output portion of the nullor, the nullor provides whatever current is demanded of it, regardless of the voltage at its output. In this case, it provides the transistor base current "i". Thus, Kirchhoff's current law applied to the transistor as a whole provides the output current drawn through resistor "R" as  where the base current of the bipolar transistor "i" is normally negligible provided the transistor remains in active mode. That is, based upon the idealization of a nullor, the output current is controlled by the user-applied input voltage "v" and the designer's choice for the reference resistor "R".  The purpose of the transistor in the circuit is to reduce the portion of the current in "R" supplied by the op-amp. Without the transistor, the current through "R" would be "i" = ("V" − "v")/"R", which interferes with the design goal of independence of "i" from "V". Another practical advantage of the transistor is that the op amp must deliver only the small transistor base current, which is unlikely to tax the op amp's current delivery capability. Of course, only real op amps are current-limited, not nullors.  The remaining variation of the current with the voltage "V" is due to the Early effect, which causes the β of the transistor to change with its collector-to-base voltage "V" according to the relation β = β(1 + "V"/"V"), where "V" is the so-called Early voltage. Analysis based upon a nullor leads to the output resistance of this current sink as "R" = "r"(β + 1) + "R", where "r" is the small-signal transistor output resistance given by "r" = ("V" + "V")/"i". See current mirror for the analysis.  Use of the nullor idealization allows design of the circuitry around the op-amp. The practical problem remains of designing an op-amp that behaves like a nullor.

A nullor is a theoretical two-port network consisting of a nullator at its input and a norator at its output. Nullors represent an ideal amplifier, having infinite current, voltage, transconductance and transimpedance gain. Its transmission parameters are all zero, that is, its input–output behavior is summarized with the matrix equation In negative-feedback circuits, the circuit surrounding the nullor determines the nullor output in such a way as to force the nullor input to zero.

零任偶(nullor)是一种理想的二端口网络,输入端为零极子,输出端为任意子,零任偶类似一个理想的放大器,其电压增益、电流增益、跨导增益和跨阻抗(transimpedance)增益都是无限大。其传输参数都为0,也就是说,其输入-输出关系可以用以下的矩阵方程序表示。 在负回授电路中,零任偶输出端附近的电路会调整其电压及电流,迫使零任偶输入端的电压及电流为零。例如理想的运算放大器就可以用零任偶来建模。一般教科书中分析有理想运算放大器的回授电路,就是利用零任偶的数学条件来分析运算放大器的周边电路。