Opera is a form of theatre in which music has a leading role and the parts are taken by singers, but is distinct from musical theater. Such a "work" is a collaboration between a composer and a librettist and incorporates a number of the performing arts, such as acting, scenery and sometimes dance or ballet; the performance is given in an opera house, accompanied by an orchestra or smaller musical ensemble, which since the early 19th century has been led by a conductor. Opera is a key part of the Western classical music tradition. Understood as an sung piece, in contrast to a play with songs, opera has come to include numerous genres, including some that include spoken dialogue such as musical theater, Singspiel and Opéra comique. In traditional number opera, singers employ two styles of singing: recitative, a speech-inflected style, self-contained arias; the 19th century saw the rise of the continuous music drama. Opera originated in Italy at the end of the 16th century and soon spread through the rest of Europe: Heinrich Schütz in Germany, Jean-Baptiste Lully in France, Henry Purcell in England all helped to establish their national traditions in the 17th century.

In the 18th century, Italian opera continued to dominate most of Europe, attracting foreign composers such as George Frideric Handel. Opera seria was the most prestigious form of Italian opera, until Christoph Willibald Gluck reacted against its artificiality with his "reform" operas in the 1760s; the most renowned figure of late 18th-century opera is Wolfgang Amadeus Mozart, who began with opera seria but is most famous for his Italian comic operas The Marriage of Figaro, Don Giovanni, Così fan tutte, as well as Die Entführung aus dem Serail, The Magic Flute, landmarks in the German tradition. The first third of the 19th century saw the high point of the bel canto style, with Gioachino Rossini, Gaetano Donizetti and Vincenzo Bellini all creating works that are still performed, it saw the advent of Grand Opera typified by the works of Auber and Meyerbeer. The mid-to-late 19th century was a golden age of opera and dominated by Giuseppe Verdi in Italy and Richard Wagner in Germany; the popularity of opera continued through the verismo era in Italy and contemporary French opera through to Giacomo Puccini and Richard Strauss in the early 20th century.

During the 19th century, parallel operatic traditions emerged in central and eastern Europe in Russia and Bohemia. The 20th century saw many experiments with modern styles, such as atonality and serialism and Minimalism. With the rise of recording technology, singers such as Enrico Caruso and Maria Callas became known to much wider audiences that went beyond the circle of opera fans. Since the invention of radio and television, operas were performed on these media. Beginning in 2006, a number of major opera houses began to present live high-definition video transmissions of their performances in cinemas all over the world. Since 2009, complete performances are live streamed; the words of an opera are known as the libretto. Some composers, notably Wagner, have written their own libretti. Traditional opera referred to as "number opera", consists of two modes of singing: recitative, the plot-driving passages sung in a style designed to imitate and emphasize the inflections of speech, aria in which the characters express their emotions in a more structured melodic style.

Vocal duets and other ensembles occur, choruses are used to comment on the action. In some forms of opera, such as singspiel, opéra comique and semi-opera, the recitative is replaced by spoken dialogue. Melodic or semi-melodic passages occurring in the midst of, or instead of, are referred to as arioso; the terminology of the various kinds of operatic voices is described in detail below. During both the Baroque and Classical periods, recitative could appear in two basic forms, each of, accompanied by a different instrumental ensemble: secco recitative, sung with a free rhythm dictated by the accent of the words, accompanied only by basso continuo, a harpsichord and a cello. Over the 18th century, arias were accompanied by the orchestra. By the 19th century, accompagnato had gained the upper hand, the orchestra played a much bigger role, Wagner revolutionized opera by abolishing all distinction between aria and recitative in his quest for what Wagner termed "endless melody". Subsequent composers have tended to follow Wagner's example, though some, such as Stravinsky in his The Rake's Progress have bucked the trend.

The changing role of the orchestra in opera is described in more detail below. The Italian word opera means "work", both in the sense of the labour done and the result produced; the Italian word derives from the Latin opera, a singular noun meaning "work" and the plural of the noun opus. According to the Oxford English Dictionary, the Italian word was first used in the sense "composition in which poetry and music are combined" in 1639. Dafne by Jacopo Peri was the earliest composition considered opera, it was written

Shayla Worley

Shayla Worley is an American artistic gymnast. She was a member of the gold-medal-winning American team at the 2007 World Artistic Gymnastics Championships, she trained for most of her athletic career at Orlando Metro Gymnastics, where she was coached by Jeff Wood and Christi Barineau. From 2009 to 2013, she competed at the University of Georgia, the 10-time NCAA champion in gymnastics. Worley competed at Level 9 in 2001, placing first in the all-around competition at the Florida State Championships, her final meet of the season was the Level 9 Eastern Championships, the highest meet to which a Level 9 gymnast can advance, where she placed second all-around. She finished off the Junior Olympic levels by placing second all-around at the 2002 Level 10 Florida State Championships. In 2002, Worley became a junior national elite, now referred to as pre-elite, she won the all-around title at the American Challenge and placed well at the U. S. Challenge, she advanced to junior international elite in 2003.

At the U. S. Classic, she placed high enough to qualify to the U. S. National Championships, where she finished fourth all-around; this earned her a spot on the United States national team. In 2004, Worley helped the U. S. win a dual meet against Japan, at the American Classic, she finished fourth all-around and again qualified to the U. S. National Championships. A few weeks she finished fourth all-around at the Pacific Alliance Championships, she competed at the U. S. Classic, where she placed second all-around. In the fall, she won the all-around at the U. S. vs. Japan meet and was named to the Junior Pan American Games team, but could not compete because of a back injury. Worley's final year as a junior was 2005, she started off her season at the International Tri Meet. She went on a European tour that included meets against lower-ranked Great Britain and Switzerland. S. won both. Her next competition was the U. S. Classic. A potential winner, she finished fourth all-around after falling on floor. At the national championships one month a fall on bars kept her down in the standings on Day 1.

She battled back and tallied the highest all-around score on Day 2, finishing third overall behind Natasha Kelley. In her final meet of the season, the Massilia Cup, Worley only competed on bars, where she finished second. Worley turned senior in 2006, her first senior outing was the American Cup, where she finished second all-around behind Nastia Liukin. Next, she competed at the Pacific Alliance Championships, where she helped the U. S. finished second on bars, making her the highest-placed American. A hamstring injury prevented Worley from taking part in further competition in 2006; as a national team member who had scored well in the first half of the year, she had hopes of being named to the U. S. team for the World Championships in Aarhus, but her injury kept her from competing. Worley was ready in time for the 2007 American Cup, but a fall on her uneven bars dismount meant she narrowly missed qualifying for finals, she was selected to compete in the Britain vs. U. S. dual match in Northern Ireland, on St. Patrick's Day.

She made no major errors this time, in the absence of the world's top two bars competitors, Britain's Beth Tweddle and American teammate Liukin, she took the bars title and finished second all-around. At the U. S. Classic, she only competed on bars and beam, she placed second on beam, but one of her grips ripped in the middle of her bar routine, causing her to place out of the top three. At the Visa Championships, she was the runner-up to Shawn Johnson and was second on uneven bars, she was selected to represent the U. S. at the World Championships in Stuttgart, Germany. At the World Championships, the U. S. team finished first overall in team qualifying, about four points ahead of the second-place team, China. Worley qualified eighth for the all-around competition, but Liukin and Johnson placed ahead of her, because of rules permitting only two competitors per country, she was excluded from the final, she was excluded from the balance beam final because of the two-athlete-per-country rule. During the team finals, she competed on scoring 15.575 and 14.675, respectively.

The scores contributed to the U. S. total of 184.400. In 2008, Worley finished third on vault and bars, she traveled to Boston, for the Visa National Championships, but had to pull out after aggravating a herniated disc in training the month before. She petitioned to compete in the Olympic Trials, where she placed 14th all-around without competing on floor exercise, she was invited to the final training camp in Texas, but was not chosen as an Olympic team member because of a broken leg. Soon after, she retired from elite gymnastics. Worley attended William R. Boone High School in Orlando. Outside of gymnastics, she has competed in speech oration contests. At the end of 2008, after retiring from elite gymnastics, Worley committed to NCAA-level gymnastics with the University of Georgia Gymdogs after having her UCLA scholarship revoked for racist comments, she double majored in advertising. Worley is involved with the Cards for Hospitalized Kids foundation. Official site Worley on Twitter Shayla Worley at the International Gymnastics Federation Shayla Worley at USA Gymnastics

High-density solids pump

High-density solids pumps are hydrostatically operating machines which displace the medium being pumped and thus create a flow. High-density solids are mixtures of solid constituents; each have their own typical physical and chemical characteristics such as specific weight, solids content, maximum particle size as well as how they behave, for example thixotropically, abrasively or adhesively. Typical examples of high-density solids are concrete and slurries. Within industrial plants many substances with a high proportion of solids - such as mechanically dewatered sewage sludges, filter cakes, bituminous coal sludges and process sludges - have to be transported over long distances to landfills or incineration plants. In principle such long distances can be bridged with mechanical conveying equipment or high-density solids pumps. Types of mechanical conveyors include belts and scrapers, they are suitable for nearly all types of high-density solids. High-density solids pumps move slurries within an enclosed pipeline.

However, not every sludge or slurry is pumpable, depending on: Ratio: The mixture of solid and liquid components must be such that it results in a plastically deformable mass. Saturation: The volume of pore space in the sludges must be filled with sufficient quantity of liquid matter for particle to be able to rest on particle via a plastically viscous liquid and for the interstices to be filled. Gas component: By injection of gasses, sludges which do not have a gas component can be brought to a pumpable consistency. Depending on how the displacement principle is implemented, a distinction can be drawn between rotary and reciprocating pumps; the rotary circulation pumps includes eccentric screw pumps, centrifugal pumps, squeezed tube pumps. Reciprocating pumps include plunger and piston pumps; the high-density solids pumps which can be used in the widest range of situations are piston pumps. They can be realized as two-cylinder pumps. In the latter case, power is transferred to the material via delivery pistons working in push-pull-mode.

While one delivery piston sucks material from the feed hopper into the cylinder, the second piston pushes the material in the other delivery cylinder and into the delivery line. The most characteristic element of the transfer tube pump is the so-called "S" transfer tube installed inside the feed hopper; the job of the transfer tube is to control the flow of high-density solids - in other words, the pump cylinder, pushing the material is connected to the delivery line by such tube. At the end of each piston stroke the S-shaped tube, connected to the delivery line is swung over to the other delivery cylinder with the aid of two switch cylinders. A hydraulic circuit is used for synchronizing the position of the transfer tube and the movements of the two delivery pistons; the S tube should swing over and not suffer undue wear. This is effected with two large-sized plunger cylinders and a so-called spectacle plate including seal rings. In cross section the S-tube is circular with a diameter; this keeps the risk of clogging down.

The sealing faces of the spectacle plate and of the seal ring lie parallel with the swivelling movement of the S-tube, so that they cannot be damaged when foreign bodies are cut through or get stuck. This pump does not need check valves. Piston pumps with S-tube are suitable for concrete and mortar, for sludges with a solids content of up to 50% by weight and a fluctuating particle size distribution but for conveying fly ash, coal or minerals in a suspension; the large cross section of the holes in the spectacle plate means that with a delivery cylinder diameter of e.g. 200 mm it is possible to pump high-density solids with a mean grain size of as much as 80 mm. The maximum diameter of individual foreign bodies may be as high as 60% of the diameter of the delivery line - in this example this would be 120 mm; the steel housing of the seat valve pump contains four hydraulically controlled seat valves, two suction and two delivery valves for the two hydraulic cylinders. The suction and discharge valves are synchronized with the hydraulics of the delivery pistons - this ensures that the contents of the delivery cylinder is equal at all times to the volume being pumped.

Once the "sucking" piston reaches its end position, the corresponding suction or delivery valve is closed or opened. If there is overpressure in the delivery line, the suction valve will close first; this prevents the pumped medium from being pushed out of the pressure line back into the hopper. This pump does not need check valves. Seat valve pumps are suitable for an even pumping of media with a solids content of up to 50% and for the high-pressure pumping of paste-like industrial media such as sludges. Since valves are used in this two-cylinder pump it is suitable for grain sizes up to 8mm at most. Which type of valve is selected will depend on the high-density solids to be conveyed. For materials containing grains with a solids content up to 50% a sharp-edged metal valve seat is required. With low-viscosity, rather watery fine sludges the choice would be a large-area elastomeric valve seal. In one hydraulic control variant the valve is opened passively by the thrust of the medium. In this case the discharge valve has a non-return function which prevents flowback from the pressure line.

At the same time the high-densitiy solids are precompacted to close to the line pressure before the discharge valve opens. This means that pipe knocking resulting from pressure pulsations can be avoided