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Ruy Lopez

The Ruy Lopez, also called the Spanish Opening or Spanish Game, is a chess opening characterised by the moves:

 * 1. e4 e5
 * 2. Nf3 Nc6
 * 3. Bb5

The Ruy Lopez is named after 16th-century Spanish priest Ruy López de Segura. It is one of the most popular openings, with many variations. In the Encyclopaedia of Chess Openings (ECO), all codes from C60 to C99 are assigned to the Ruy Lopez.

History
The opening is named after the 16th-century Spanish priest Ruy López de Segura, who made a systematic study of this and other openings in the 150-page book on chess Libro del Axedrez, written in 1561. Lopez advocated 3.Bb5 as superior to 3.Bc4, and was of the opinion that Black should play 2...d6 (the Philidor Defence) to avoid it. Although it bears his name, this particular opening was included in the Göttingen manuscript, which dates from c.1490. A popular use of the Ruy Lopez opening did not develop, however, until the mid-19th century, when the Finnish and Russian theoretician Carl Jaenisch "rediscovered" its potential. The opening remains the most commonly used amongst the open games in master play; it has been adopted by almost all players during their careers, many of whom have played it with both colours. Due to the difficulty for Black in achieving equality, a common nickname for the opening is "The Spanish Torture".

Basics
At the most basic level, White's third move attacks the knight that defends the e5-pawn from the attack by the f3-knight. White's apparent threat to win Black's e-pawn with 4.Bxc6 dxc6 5.Nxe5 is illusory—Black can respond 5...Qd4, forking the knight and e4-pawn, winning back the  with a good position. White's 3.Bb5 is still a good move, however; it a piece, prepares castling, and sets up a potential pin against Black's king. Since White's third move carries no immediate threat, Black can respond in a wide variety of ways.

Traditionally, White's objective in playing the Ruy Lopez is to spoil Black's pawn structure; either way Black recaptures following the exchange on c6 will have negative features, although recapturing gains the. In modern practice, however, White does not always exchange bishop for knight on c6, preferring the retreat 4.Ba4 if chased by 3...a6.

The theory of the Ruy Lopez is the most extensively developed of all Open Games, with some lines having been analysed well beyond move thirty. At nearly every move there are many reasonable alternatives, and most have been deeply explored. It is convenient to divide the possibilities into two groups based on whether or not Black responds with 3...a6, the Morphy Defence, named after Paul Morphy, although he was not the originator of the line. The variations with Black moves other than 3...a6 are older and generally simpler, but the Morphy Defence lines are more commonly played.

Morphy Defence: 3...a6
The most commonly played third move for Black is the Morphy Defence, 3...a6, a move which forces White to decide whether to retreat or to exchange for Black's knight. The Morphy Defence thus "puts the question" to the white bishop, a traditional usage which Larry Evans attributed to Aron Nimzowitsch. The main point of 3...a6 is that after the common retreat 4.Ba4, Black will have the possibility of breaking a future pin on the by playing ...b5. White must take some care not to fall into the Noah's Ark Trap, in which Black traps White's on the b3-square with a ...a6, ...b5, and ...c4 pawn advance on the. Ercole del Rio, in his 1750 treatise Sopra il giuoco degli Scacchi, Osservazioni pratiche dell'anonimo Modenese (On the game of Chess, practical Observations by an anonymous Modenese), was the first author to mention 3...a6. The move became popular after it was played by Paul Morphy and it is named for him. An influential chess player at that time, Wilhelm Steinitz, did not approve of the move, however; in 1889, he wrote, "on principle this ought to be disadvantageous as it drives the bishop where it wants to go". Steinitz's opinion did not prevail, however; today, 3...a6 is played in over 65 percent of all games beginning with the Ruy Lopez.

Morphy Defence: alternatives to Closed Defence
After 3...a6, the most commonly played line is the Closed Defence, which goes 4.Ba4 Nf6 5.0-0 Be7, discussed in the two following sections. Alternatives to the Closed Defence described in this section are:
 * 4.Bxc6 (Exchange Variation)
 * 4.Ba4
 * 4...b5 5.Bb3 Na5 (Norwegian Defence)
 * 4...b5 5.Bb3 Bc5 (Graz Defence)
 * 4...b5 5.Bb3 Bb7 (Caro Variation)
 * 4...Bc5 (Classical Defence Deferred)
 * 4...Nge7 (Cozio Defence Deferred)
 * 4...g6 (Fianchetto Defence Deferred)
 * 4...f5 (Schliemann Defence Deferred)
 * 4...d6 (Modern Steinitz Defence)
 * 4...Nf6
 * 5.Nc3 (Ruy Lopez Four Knights Variation)
 * 5.Qe2 (Wormald Variation)
 * 5.d4 (Mackenzie Variation)
 * 5.d3 (Anderssen Variation)
 * 5.0-0
 * 5...d6 (Russian Defence)
 * 5...Bc5 (Møller Defence)
 * 5...b5 6.Bb3 Bb7 (Arkhangelsk Defence)
 * 5...b5 6.Bb3 Bc5 (Modern Arkhangelsk Defence)
 * 5...Nxe4 (Open Defence)

Exchange Variation: 4.Bxc6
In the Exchange Variation, 4.Bxc6, (ECO C68–C69) White damages Black's pawn structure, gaining a ready-made long-term plan of playing d4 ...exd4 Qxd4, followed by exchanging all the pieces and winning the pure pawn ending. Max Euwe gives the pure pawn ending in this position (with all pieces except kings removed) as a win for White. Black gains good compensation in the form of the bishop pair, however, and the variation is not considered White's most ambitious, though former world champions Emanuel Lasker and Bobby Fischer employed it with success.

After 4.Bxc6, Black almost always responds 4...dxc6. The similar move 4...bxc6 is rarely played due to the reply 5.d4 exd4 6.Qxd4 which gives White control of the centre. After 4...dxc6, the obvious 5.Nxe5 is weak, since 5...Qd4 6.Nf3 Qxe4+ 7.Qe2 Qxe2+ 8.Kxe2 leaves White with no compensation for Black's bishop pair.

In the late 19th and early 20th centuries, Emanuel Lasker had great success with 5.d4 exd4 6.Qxd4 Qxd4 7.Nxd4, most notably his famous win against José Raúl Capablanca in the St. Petersburg 1914 chess tournament.

Since then, better defences for Black have been developed, and this line is considered to slightly favour Black. Jon Jacobs wrote in the July 2005 Chess Life (p. 21): "A database search (limited to games longer than 20 moves, both players FIDE 2300+) reveals the position after 7.Nxd4 was reached 20 times from 1985–2002. White's results were abysmal: +0−7=13."

After 5.Nc3, Black usually plays 5...f6 to defend the e-pawn. A notable game is Adhiban–Nakamura from the 2013 FIDE World Cup.

The flexible 5.0-0 is sometimes called the Barendregt Variation, but it was Fischer who developed it into a serious weapon in the 1960s. Unlike 5.d4, it forces Black to defend the e-pawn, usually with 5...f6, 5...Bg4, 5...Qd6 (the sharpest line, preparing queenside castling), 5...Qf6, 5...Qe7, or 5...Bd6. Some other moves that have been played are 5...Ne7, 5...Be7, and 5...Be6. The idea behind these three moves is that if White plays 6.Nxe5, Black plays 6...Qd4, forking the knight and the e4-pawn. The move ...Qd4, regaining the pawn at e4, is usually impossible in these variations once White has castled, due to the open e-file.

Notable games are Fischer–Portisch, and Fischer–Gligorić, both played at the 17th Chess Olympiad in Havana 1966.

White may also delay the exchange for a move or two: 4.Ba4 Nf6 5.Bxc6 or 5.0-0 Be7 6.Bxc6 (the Delayed Exchange Deferred), for example; at first glance this seems a waste of time, but Black having played ...Nf6 rules out defending the pawn with ...f6, and the bishop already being on e7 means that ...Bd6 would be a loss of tempo.

Norwegian Defence: 4.Ba4 b5 5.Bb3 Na5
The Norwegian Variation (also called the Taimanov or Wing Variation) (ECO C70), 3...a6 4.Ba4 b5 5.Bb3 Na5 aims to eliminate the white bishop but is generally considered too time-consuming for Black. The usual continuation is 6.0-0 d6 7.d4 Nxb3, but the speculative sacrifice 6.Bxf7+ Kxf7 7.Nxe5+, which drives the black king out, has been played. With accurate play, however, Black can avoid any disadvantage while holding onto the extra piece.

In the 1950s, Mark Taimanov played it with some success, though it remained a sideline, as it has to this day. This defence has been known since the 1880s and was reintroduced in 1901 by Carl Schlechter. The Norwegian connection was first introduced by Svein Johannessen who played the line from 1957 and later strengthened when Simen Agdestein and some other Norwegian players adopted the variation. In 1995 Jonathan Tisdall published the article "Ruy Lopez. The Norwegian Variation" in New in Chess Yearbook 37.

Variations combining 3...a6 and ...Bc5
The Graz Defence, Classical Defence Deferred, and Møller Defence combine 3...a6 with the active move ...Bc5. For a century it was believed that it was safer for Black to place the bishop on e7, but it is much more active on c5. White can gain time by playing c3 and d4 as the black bishop will have to move, but this does not always seem to be as important as was once thought.

The Møller Defence, 3...a6 4.Ba4 Nf6 5.0-0 Bc5 was already an old line in 1903 when Jørgen Møller (1873–1944) analysed it in Tidskrift för Schack. Alexander Alekhine played this for Black in the early portion of his career; despite his advocacy, it never achieved great popularity, and even he eventually came to consider it dubious.

The Graz Defence, 3...a6 4.Ba4 b5 5.Bb3 Bc5, was analysed by Alois Fink (b. 1910) in Österreichische Schachzeitung in 1956 and in Wiener Schach Nachrichten in 1979, although it did not become popular until the 1990s.

Modern Steinitz Defence: 4.Ba4 d6
In the Modern Steinitz Defence (also called Neo-Steinitz Defence) (ECO C71–C76), Black interpolates 3...a6 4.Ba4 before playing 4...d6, which was frequently played by Alexander Alekhine, José Raúl Capablanca, and Paul Keres. The possibility of breaking the pin with a timely ...b5 gives Black more latitude than in the Old Steinitz Defence; in particular, in the Old Steinitz, White can practically force Black to give up the stronghold at e5, but in the Modern Steinitz, Black is able to maintain control of the. Most plausible White moves are playable here, including 5.c3, 5.c4, 5.Bxc6, 5.d4, and 5.0-0. The sharp Siesta Variation arises after 5.c3 f5, while a manoeuvring game results from the calmer 5.c3 Bd7 6.d4. The game is also sharp after 5.Bxc6+ bxc6 6.d4 (ECO C73) or 5.0-0 Bg4 6.h3 h5 (ECO C72). The older lines starting with 5.c4 and 5.d4 are not regarded as testing for Black, though the latter offers a tricky gambit. There are six ECO classifications for the Modern Steinitz. White's responses 5.d4, 5.Nc3, and 5.c4 are included in C71, while 5.0-0 is C72. The delayed exchange 5.Bxc6+ bxc6 6.d4 is C73. C74–C76 all begin with 5.c3. C74 covers 5...Nf6, but primarily focuses on 5...f5 6.exf5 Bxf5 with 7.d4 or 7.0-0. C75's main continuation is 5...Bd7 6.d4 Nge7, the Rubinstein Variation. C76 is characterised by the Black fianchetto 5...Bd7 6.d4 g6.

Schliemann Defence Deferred: 4.Ba4 f5
The Schliemann Defence Deferred, 3...a6 4.Ba4 f5, is rarely seen, with practically its only top-level appearances being in the 1974 Candidates Final, when Viktor Korchnoi adopted it to ultimately draw the game versus Anatoly Karpov, and by R Praggnanandhaa who won against Vidit Gujrathi in the 2024 Candidates Tournament. It is considered inferior to the regular Schliemann since White can answer effectively with 5.d4! exd4 6.e5.

Wormald Variation: 4.Ba4 Nf6 5.Qe2
5.Qe2 (ECO C77), first played in the 1840s, normally continues 5...b5 6.Bb3 Be7 7.c3 followed by 8.d4. Robert Wormald (1834–1876) wrote openings manuals and completed Staunton's last book, analyzing the line in Chess World, 1867. The line is also known as Paulsen–Alapin Attack, and Schlecter Variation.

Mackenzie Variation: 4.Ba4 Nf6 5.d4
The variation 5.d4 (ECO C77), named after George Henry Mackenzie who employed it on a regular basis, is an old line which, according to modern theory, does not promise White any advantage, though is adopted as an alternative to the main variation 5.0-0. The main line continues with 5...exd4 (5...Nxe4 6.0-0 transposes to the Open Defence) 6.0-0 (6.e5 Ne4 is harmless) Be7 (6...Nxe4 transposes to the Riga Variation of the Open Defence) which leads to the Centre Attack (ECO C84) of the Closed Defence.

Steinitz Defence Deferred: 4.Ba4 Nf6 5.0-0 d6
The Steinitz Defence Deferred (ECO C79) also called the Russian Defence. With the move order 3...a6 4.Ba4 Nf6 5.0-0 d6, Black waits until White castles before playing ...d6. This can enable Black to avoid some lines in the Steinitz Defence Deferred in which White castles queenside, although the position of the knight on f6 also precludes Black from supporting the centre with ...f7–f6. These nuances seem to have little importance today, as neither the Steinitz Defence Deferred nor the Russian Defence have been popular for many years.

Mikhail Chigorin played the Russian Defence in the 1890s, and later it was adopted by Akiba Rubinstein and Alekhine. The last significant use of the Russian Defence was in the 1950s, when it was played by some Russian masters. Today, however, it has purely practical value, as White has found numerous ways to an opening advantage by quickly opening lines in the center, where Black's developmental lag seems to be a significant factor.

Arkhangelsk Defence: 4.Ba4 Nf6 5.0-0 b5 6.Bb3 Bb7
The Arkhangelsk Defence (or Archangel Defence) (ECO C78) was popularized by Soviet players from the city of Arkhangelsk such as GM Vladimir Malaniuk. The variation begins 3...a6 4.Ba4 Nf6 5.0-0 b5 6.Bb3 Bb7. This line often leads to sharp positions in which Black wagers that the fianchettoed bishop's influence on the centre and kingside will offset Black's delay in castling. White has several options, including attempting to build an ideal pawn centre with c3 and d4, defending the e-pawn with Re1 or simply developing. The Arkhangelsk Defence is tactically justified by Black's ability to meet 7.Ng5 with 7...d5 8.exd5 Nd4! (not 8...Nxd5, when White gets the advantage with 9.Qh5 g6 10.Qf3).

Modern Arkhangelsk Defence: 4.Ba4 Nf6 5.0-0 b5 6.Bb3 Bc5
The Modern Arkhangelsk Defence (or Modern Archangel Defence) (ECO C78), sometimes called the Neo-Arkhangelsk or Neo-Archangel, is a refinement of the regular Arkhangelsk Defence by incorporating ideas similar to the Møller Defence. Black normally does not fianchetto the queen's bishop, which would transpose to regular Arkhangelsk setups, but plays ...Bg4 to increase the pressure against White's pawn centre. White's main continuation is 7.a4 after which Black responds with the typical move 7...Rb8 reaching the starting point of this highly complex variation. Another line is the more traditional 7.c3 d6 8.d4 and after 8...Bb6 Black's position is fine. 8...exd4 occurred in Löwenthal–Morphy, London 1859, which seems to be the first time this variation was ever played. Fabiano Caruana is one of the most notable players of this variation, employing it in the Candidates Tournament 2020.

Open Defence: 4.Ba4 Nf6 5.0-0 Nxe4
In the Open Defence, 3...a6 4.Ba4 Nf6 5.0-0 Nxe4, Black tries to make use of the time White will take to regain the pawn to gain a foothold in the centre, with play usually continuing 6.d4 b5 7.Bb3 d5 8.dxe5 Be6 (but not 7...exd4? 8.Re1 d5 9.Nc3!, Bobby Fischer–Petar Trifunović, Bled 1961 ).

Here 8.Nxe5, once adopted by Fischer, is much less often seen, and Black should equalise after the accurate 8...Nxe5 9.dxe5 c6, which avoids prematurely committing the light-squared bishop and solidly defends d5, often a problem in the Open.

The Riga Variation, 6...exd4, is considered inferior; the main line runs 7.Re1 d5 8.Nxd4 Bd6! 9.Nxc6 Bxh2+! 10.Kh1! (10.Kxh2 Qh4+ 11.Kg1 Qxf2+ draws by perpetual check.) Qh4 11.Rxe4+! dxe4 12.Qd8+! Qxd8 13.Nxd8+ Kxd8 14.Kxh2 Be6 (14...f5 15.Bg5) and now the endgame is considered to favour White after 15.Be3 or Nd2 (but not 15.Nc3 c5!, playing to trap the bishop). A famous example of this line is the game José Raúl Capablanca–Edward Lasker, New York 1915. White is objectively better here, but Black keeps some good practical chances owing to the sharp positions that occur.

White has a variety of options at move nine, including 9.c3, 9.Be3, 9.Qe2, and 9.Nbd2.

The classical line starts with 9.c3 when Black may choose 9...Be7 (the main line) or the aggressive 9...Bc5.

After 9.c3 Bc5 10.Nbd2 0-0 11.Bc2, Black must meet the attack on e4, with the following possibilities from which to choose: 11...f5, 11...Bf5, both of which aim to maintain the strongpoint on e4, or the forcing line 11...Nxf2, introduced by the English amateur Vernon Dilworth.

Today, 9.Be3 Be7 10.c3 is often used to transpose into the main line, 9.c3, while obviating the option of the Dilworth.

An old continuation is 11...f5, when after 12.Nb3 Bb6 13.Nfd4 Nxd4 14.Nxd4 Bxd4 White can gain some advantage with Bogoljubov's 15.Qxd4. Instead, the very sharp La Grande Variante continues 15.cxd4 f4 16.f3 Ng3 17.hxg3 fxg3 18.Qd3 Bf5 19.Qxf5 Rxf5 20.Bxf5 Qh4 21.Bh3 Qxd4+ 22.Kh1 Qxe5, with unclear consequences. Perhaps the most famous game in this variation is Smyslov–Reshevsky, 1945 USSR–USA Radio Match. An analysis of the line had just been published in a Russian chess magazine, and Smyslov was able to follow it to quickly obtain a winning position. Reshevsky had not seen the analysis and he struggled in vain to solve the position over the board with his chess clock running. The Dilworth Variation (or Attack), 11...Nxf2 12.Rxf2 f6 13.exf6 Bxf2+ 14.Kxf2 Qxf6 has scored well for Black, with many traps for the ill-prepared White player. The main line leads to unbalanced endgames which are difficult to play for both sides, though with a strong drawing tendency. Artur Yusupov is one of the few grandmasters who has adopted the Dilworth repeatedly.

In the Howell Attack (ECO C81), 9.Qe2, White aims for play against d5 after Rd1. The game usually continues 9...Be7 10.Rd1 followed by 10...Nc5 or 10...0-0. Paul Keres played this line against Max Euwe and Samuel Reshevsky at the World Chess Championship tournament 1948. This has been played at the top by World No.2 Fabiano Caruana among others, and he recommends this in his video series for Chessbase.

Karpov's move, 9.Nbd2, limits Black's options. In the 1978 Karpov–Korchnoi World Chess Championship match, following 9.Nbd2 Nc5 10.c3 d4 (10...Be7 is an old move that remains popular) Karpov introduced the surprising 11.Ng5, a move suggested by his trainer, Igor Zaitsev. If Black takes the knight with 11...Qxg5 White regains the material with 12.Qf3. This variation played a decisive role in a later World Championship match, Kasparov–Anand 1995, when Anand was unable to successfully defend as Black.

Closed Defence 4.Ba4 Nf6 5.0-0 Be7: alternatives to Main line
In the main line, White normally retreats the bishop with 4.Ba4, when the usual continuation is 4...Nf6 5.0-0 Be7. Black now threatens to win a pawn with 6...b5 followed by 7...Nxe4, so White must respond. Usually White defends the e-pawn with 6.Re1 which, in turn, threatens Black with the loss of a pawn after 7.Bxc6 and 8.Nxe5. Although it is possible to defend the pawn with 6...d6, Black most commonly averts this threat by driving away the white bishop with 6...b5 7.Bb3.

After 4...Nf6 5.0-0 Be7, the most frequently seen continuation is 6.Re1 b5 7.Bb3 d6 8.c3 0-0, discussed in the next section. Examined in this section are the alternatives to the main line:
 * 6.Bxc6 (Delayed Exchange Variation Deferred)
 * 6.d4 (Centre Attack)
 * 6.Nc3 (Morphy Attack)
 * 6.Qe2 (Worrall Attack)
 * 6.d3 (Modern Line)
 * 6.Re1 d6 (Averbakh Variation)
 * 6.Re1 b5 7.Bb3
 * 7...Bb7 (Trajković Variation)
 * 7...0-0 8.c3 d5 (Marshall Attack)

Delayed Exchange Variation Deferred: 6.Bxc6
The Delayed Exchange Variation Deferred (or Exchange Variation Doubly Deferred) (ECO C85), 6.Bxc6, loses a tempo compared to the Exchange Variation, though in compensation, the black knight on f6 and bishop on e7 are awkwardly placed. The knight on f6 prevents Black from supporting the e-pawn with ...f7–f6, and the bishop is somewhat passively posted on e7.

Centre Attack: 6.d4
The Centre Attack (or Centre Variation) (ECO C84), 6.d4, leads to sharp play. After 6...exd4 (6...Nxe4 and 6...b5 are viable alternatives) 7.Re1 b5 (7...0-0 8.e5 Ne8 is a playable alternative) White can play either 8.Bb3 or the sharp 8.e5. In case of the immediate 7.e5 Black takes advantage of the absence of the white rook from e1 and plays 7...Ne4 with the idea of 8...Nc5.

Morphy Attack: 6.Nc3
The Morphy Attack (ECO C84) named after Paul Morphy who introduced the idea in a 1859 blindfolded simul, is aggressive and may lead to a very small edge for White, but less than in 6.Re1 and 6.d3. Similar to those two moves, White's defence of his e-pawn compels Black to drive away White's bishop with 6...b5 (6...d6 is also possible, but less popular). After 7.Bb3, Black can play 7...0-0 or 7...d6. Note that Marshall attack-style ideas of 7...0-0 and playing ...d5 next, sacrificing a pawn, make little sense when White's knight on c3 both controls d5 and means White has a more developed queenside, one of the upsides of the Marshall usually being White's underdeveloped queenside. The main line of 7...d6, 8.Nd5 Na5 9.Nxe7 Qxe7 10.d3 0-0, with Black eventually relinquishing White of his bishop pair with ...Nxb3, shows a common attacking idea in the Morphy Attack; Nd5. In the main line, 8...Nxd5? is wrong because 9.Bxd5! leaves White with a strong bishop on the outpost square d5, exerting a troublesome pin on the undefended c6-knight. After 7...0-0, 8.d3 transposes to one of the main lines of 6.d3, with 6... b5 7.Bb3 0-0 8.Nc3. Paul Keres and Boris Spassky have both played the line a few times throughout their careers (both playing it against one another once), and Siegbert Tarrasch played it three times in his 1911 match against Schlechter (scoring 1 win, 1 draw, 1 loss in that order), but it remains the least popular option for White on move 6.

Worrall Attack: 6.Qe2
In the Worrall Attack (ECO C86), White replaces 6.Re1 with 6.Qe2. The idea is that the queen will support the e-pawn, leaving the rook free to move to d1 to support the advance of the d-pawn, although there is not always time for this. Play normally continues 6...b5 7.Bb3 followed by 7...0-0 8.c3 and 8...d5 or 8...d6.

Paul Keres played the line several times. More recently, Sergei Tiviakov has played it, as has Nigel Short, who essayed it twice in his 1992 match against Anatoly Karpov and won both games.

Modern Line: 6.d3
By playing 6.d3, often called the Martinez Variation, White steers clear of the Marshall Attack and any of the anti-Marshall lines. White threatens 7.Bxc6 winning the e5-pawn leaving Black a choice of either 6...d6 or 6...b5. After 6...d6 the e5-pawn is firmly defended and Black threatens to trade off White's Ruy Lopez bishop with 7...b5 and 8...Na5. White normally continues with 7.c3, and after 8...0-0 White can choose between 9.Nbd2 or 9 Re1. Black can also play 6...b5, and after 7.Bb3 d6 (7...0-0 is a viable alternative) White has to deal with the threat of 8...Na5 by playing 8.a3 (8.c3 or 8.a4 are perfectly playable as well), and after 8...0-0 (the immediate 8...Na5 is also feasible) 9.Nc3 we have reached a modern of the Ruy Lopez. This position was first reached in a high-level encounter between Viswanathan Anand and Michael Adams, Grenke Chess Classic 2013. 6.d3 has gained wide popularity among the top players and has almost supplanted the Ruy Lopez main line with 6.Re1.

This variation can transpose into 6.Re1 lines but with a potentially advantageous move order. For example, in the 8.a4 anti-Marshall variation which can ensue after 6.Re1, one of the mainlines is 8...Bb7 9.d3, which can also be reached by way of 6.d3 b5 7.Bb3 0-0 8.a4 Bb7 9.Re1. A perhaps more challenging response to the anti-Marshall is 8...b4, after which White may wish to ambitiously play 9.a5 (preventing ...Na5) d6 10.d3 Be6!, where White cannot avoid the trade of bishops (the main moves being either 11.Bxe6 or 11.Nbd2 Bxb3). If Black elects not to exchange, however, we may see 11.Nbd2 Rb8 12.Nc4 where White may retain some pull in the position. On the other hand, to be considered is 6.d3 b5 7.Bb3 0-0 8.a4 b4 9.a5 d6 10.Nbd2 Be6 11.Nc4!, where White has avoided the exchange and can transpose directly to the anti-Marshall line if desired by playing Re1 later. Play may also in some rare cases transpose to a traditional closed Spanish (with 7...d6) after something like 6.d3 d6 7.c3 0-0 8.Re1 b5 9.Bc2 Bb7 10.Nbd2 Re8 11.h3 Bf8 12.d4, reaching a reasonably well-trodden position in the Zaitsev system, though both players may deviate at many points in this line.

Also possible is to transpose to the Pilnik Variation, after 6...b5 7.Bb3 d6 8.c3 0-0, where 9.Re1 would transpose to the Pilnik, with the Marshall successfully avoided (which the Pilnik does not do). In general, if 6...b5 7.Bb3 d6 8.c3, positions could resemble a traditional closed Spanish such as the Zaitsev, Flohr, Smyslov, Karpov, Breyer, or Chigorin where White has played 10.d3 (or in the case of the Chigorin, 11.d3 with 10.Bc2 c5 included) instead of 10.d4 (in the case of the Chigorin, 11.d4) if White plays Re1 and h3. In every case, 10.d3 is far less popular than 10.d4 (again, 11.d4 for Chigorin), but is the only move besides d4 to ever be seriously considered. 10.d3 in those variations are often referred to as the 'quiet' variation of that variation (quiet Breyer, quiet Flohr, quiet Chigorin, etc). In the case of Flohr–Zaitsev-type setups, White may quickly push d3–d4 without h3 and lose a tempo compared to the traditional Zaitsev, but the move h3 is what would be lost, which is not so relevant with the bishop already committed to b7, so the only thing h3 provides is luft (an idea shared with the Pilnik).

Averbakh Variation: 6.Re1 d6
In the Averbakh Variation (C87), named for Yuri Averbakh, Black defends the threatened e-pawn with 6...d6 instead of driving away the white bishop with the more common 6...b5. This defence shares some similarities with the Modern Steinitz and Russian Defences as Black avoids the ...b5 advance that weakens the queenside. White can reply with either 7.Bxc6 bxc6 8.d4 or 7.c3 Bg4 (it is too late for Black to transpose into the more usual lines of the Closed Defence, because 7...b5 would allow 8.Bc2, saving White a tempo over the two-move sequence Bb3–c2 found in other variations). The pin temporarily prevents White from playing d2–d4. In response, White can either force d4 with 8.h3 Bh5 9.Bxc6 bxc6 10.d4, or postpone d4 for the time being and play 8.d3 followed by manoeuvering the queen knight to the kingside with Nbd2–f1–g3.

Trajković Variation: 6.Re1 b5 7.Bb3 Bb7
An alternative to 6...d6 is 6...b5 7.Bb3 Bb7. This is known as the Trajković Variation. Black may sacrifice a pawn with 8.c3 d5 9.exd5 Nxd5 10.Nxe5 Nxe5 11.Rxe5 Nf4.

7...0-0
After 6.Re1 b5 7.Bb3, Black often plays 7...0-0. White can circumvent the Marshall Attack after 8.c3 d5 and play any of the alternative moves 8.a4, 8.h3, 8.d4, and 8.d3, which are commonly referred to as "anti-Marshall" systems, as they try to deter Black from playing ...d5.

When White opts for 8.c3, Black, in addition to transposing to the main line with 8...d6, can play 8...d5, introducing the Marshall Attack.

Marshall Attack: 7...0-0 8.c3 d5
One of Black's more aggressive alternatives is the Marshall Attack: after 3...a6 4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5 7.Bb3 0-0 8.c3 Black plays the gambit 8...d5, sacrificing a pawn. The main line begins with 9.exd5 Nxd5 (9...e4?!, the Herman Steiner variation, is considered weaker) 10.Nxe5 Nxe5 11.Rxe5 c6 (Marshall's original moves, 11...Nf6, and 11...Bb7 are considered inferior, but have also yielded good results at top levels of play for Black. GM Joel Benjamin suggests that 11...Bb7 is inferior due to 12.Qf3 ). The resulting position is shown in the diagram. To the casual observer it might seem that Black has been careless and lost a pawn; however, the sacrifice has also stripped off White's kingside defenders, given Black a lead in development, and rendered White's 8.c3 irrelevant. Since Black's compensation is based on rather than  considerations, it is difficult or perhaps impossible to find a refutation. Black generally goes all-in with a massive kingside attack, which has been analysed to great depth (sometimes beyond move 30) with no definite conclusion as to the Marshall's soundness. The Marshall Attack is a very sharp opening system in which a great amount of theoretical knowledge is vital, and many White players, including Garry Kasparov, avoid it by playing one of the anti-Marshall systems, 8.d4, 8.a4 or 8.h3 instead of 8.c3.

This gambit became famous when Frank James Marshall used it as a against José Raúl Capablanca in 1918; nevertheless, Capablanca found a way through the complications and won. It is often said that Marshall had kept this gambit a secret for use against Capablanca since his defeat in their 1909 match. The most common counterclaim is that Marshall had used a similar approach in 1917 against Walter Frere. However, Edward Winter found no clear evidence of the date for Frere–Marshall; several games between 1910 and 1918 where Marshall passed up opportunities to use the Marshall Attack against Capablanca; and an 1893 game that used the same line as in Frere–Marshall.

Improvements to Black's play were found (Marshall played 11...Nf6!? originally, but later discovered 11...c6!) and the Marshall Attack was adopted by top players including Boris Spassky, John Nunn, and more recently Michael Adams. In the Classical World Chess Championship 2004, challenger Peter Leko used the Marshall to win an important game against World Champion Vladimir Kramnik.

Currently, Armenian grandmaster Levon Aronian is one of the main advocates for the Marshall Attack.

Main line: 4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5 7.Bb3 d6 8.c3 0-0
The main lines of the Closed Ruy Lopez continue 6.Re1 b5 7.Bb3 d6 8.c3 0-0. White can now play 9.d3 or 9.d4, but by far the most common move is 9.h3 which prepares d4 while preventing the awkward pin ...Bg4. This can be considered the main line of the opening as a whole, and thousands of top-level games have reached this position. White aims to play d4 followed by Nbd2–f1–g3, which would firmly support e4 with the bishops on open diagonals and both knights threatening Black's kingside. Black will try to counter this knight manoeuver by expanding on the queenside, taking action in the centre, or putting pressure on e4.

After 6.Re1 b5 7.Bb3 d6 8.c3 0-0, we have:
 * 9.d3 (Pilnik Variation)
 * 9.d4 (Yates Variation)
 * 9...Bg4 (Bogoljubow Variation)
 * 9...Bg4 10.a4 (Yates Variation, Short Attack)
 * 9.a3 (Suetin Variation)
 * 9.Bc2 (Lutikov Variation)
 * 9.h3
 * 9...Na5 (Chigorin Variation)
 * 9...Nb8 (Breyer Variation)
 * 9...Bb7 (Zaitsev Variation)
 * 9...Nd7 (Karpov Variation)
 * 9...Be6 (Kholmov Variation)
 * 9...h6 (Smyslov Variation)
 * 9...Qd7 (Smyslov Variation)
 * 9...a5 (Keres Variation)

Pilnik Variation: 9.d3
The Pilnik Variation, named for Hermann Pilnik, is also known as the Teichmann Variation from the game Teichmann–Schlechter, Karlsbad 1911. White plays 9.d3 intending to later advance to d4 under favourable circumstances. Although d2–d3–d4 appears to lose a tempo compared to d2–d4, White may be able to omit h3 regaining the tempo, especially if Black plays ...Bb7.

The Pilnik has seen a small resurgence in recent years, but that is mainly by transposition through 6.d3, which avoids the Marshall Attack. The line starting with 6.d3 leading to the Pilnik is 6. d3 b5 7.Bb3 d6 8.c3 0-0 9. Re1

Yates Variation and Bogoljubow Variation: 9.d4
White usually plays 9.h3 instead of 9.d4 (the Yates Variation) because after 9.d4 Bg4 (the Bogoljubow Variation), the pin of the white king knight is troublesome. The variation takes its name from the game Capablanca–Bogoljubow, London 1922.

Chigorin Variation: 9.h3 Na5
The Chigorin Variation was refined by Mikhail Chigorin around the turn of the 20th century and became the primary Black defence to the Ruy Lopez for more than fifty years. With 9...Na5 Black chases the white bishop from the a2–g8 diagonal and frees the c-pawn for queenside expansion. After 10.Bc2 c5 11.d4 the classical Black follow up is 11...Qc7, reinforcing e5 and placing the queen on the c-file which may later become open after ...cxd4. Other Black moves in this position are 11...Bb7 and 11...Nd7; the latter was adopted by Keres a few times in the 1960s. The Chigorin Variation has declined in popularity because Black must spend some time bringing his offside knight on a5 back into the game.

The Chigorin is divided into four ECO classifications. In C96, Black or White deviate after 10.Bc2, and do not reach the classical main line position 10...c5 11.d4 Qc7. In C97, White proceeds from the diagram with 12.a4, 12.d5, 12.b4, or the main line 12.Nbd2 when Black responds with ...Be6, ...Rd8, ...Re8, ...Bb7 or ...Bd7. The C98 classification covers 12.Nbd2 Nc6, while C99 covers 12.Nbd2 cxd4 13.cxd4.

Breyer Variation: 9.h3 Nb8
The Breyer Variation was recommended by Gyula Breyer as early as 1911, but there are no known game records in which Breyer employed this line. The Breyer Variation did not become popular until the 1960s when it was adopted by Boris Spassky and others. In particular, Spassky's back to back wins over Mikhail Tal at Tbilisi in 1965 did much to enhance its reputation, and Spassky has a career-plus score with the Breyer. The variation was the choice of many top level players as White has had trouble proving an advantage against it. Nowadays, however, this variation is considered too passive, and players prefer to play the Berlin or the Petroff as they seem to equalise more easily.

With 9...Nb8 Black frees the c-pawn and intends to route the knight to d7 where it supports e5. If White fortifies the centre with 10.d3 the opening is classified ECO code C94. The more common continuation, 10.d4, is ECO C95. The main line continues 10.d4 Nbd7 11.Nbd2 Bb7 12.Bc2 Re8 13.Nf1 Bf8. Black is threatening to win the e4-pawn via ...exd4 uncovering an attack on the pawn, so White plays 14.Ng3. Black generally plays 14...g6 to stop White's knight from going to f5. White then usually tries to attack the Black queenside via 15.a4. Black seeks in the centre via 15...c5. White can attack either the kingside or the queenside. This forces resolution of the centre via 16.d5. Black can exploit the weak squares on the queenside via 16...c4. White will try to attack on the kingside via 17.Bg5, moving forces to the kingside. Black will kick the bishop with 17...h6. The logical retreat is 18.Be3, which is met by 18...Nc5. White plays 19.Qd2, forcing 19...h5. The point of this manoeuver was to weaken Black's kingside.

Zaitsev Variation: 9.h3 Bb7
The Zaitsev Variation (also called the Flohr–Zaitsev Variation) was advocated by Igor Zaitsev, who was one of Karpov's trainers for many years. A Karpov favourite, the Zaitsev remains one of the most important variations of the Ruy Lopez. With 9...Bb7 Black prepares to put more pressure on e4 after 10.d4 Re8 11.Nbd2 Bf8, when play can become very sharp and tactical. One drawback of this line if Black is playing for a win is that White can force Black to choose a different defence or allow a draw by repetition of position with 11.Ng5 Rf8 12.Nf3. Today the theory in the Zaitsev variations extends beyond the middlegame, and it is rarely seen at the top levels because of the need to remember a lot of theory.

Karpov Variation: 9.h3 Nd7
Karpov tried 9...Nd7 several times in the 1990 World Championship match, but Kasparov achieved a significant advantage against it in the 18th game. It is solid but slightly passive. Confusingly 9...Nd7 is also called the Chigorin Variation so there are two variations of the Ruy Lopez with that name, but 9...Na5 is the move more commonly associated with Chigorin. This defence is also known as the Keres Variation, after Paul Keres.

Kholmov Variation: 9.h3 Be6
The Kholmov Variation, 9...Be6, was popular in the 1980s but is now played less often at the master level. The main line runs 10.d4 Bxb3 11.axb3 (11.Qxb3 is another option) exd4 12.cxd4 d5 13.e5 Ne4 14.Nc3 f5 15.exf6 Bxf6 16.Nxe4 dxe4 17.Rxe4 Qd5 18.Rg4, when it has been shown that White's extra pawn is more valuable than Black's more active and harmonised pieces.

Smyslov Variation: 9.h3 h6
The Smyslov Variation (ECO C93) is a plan similar to that of the Zaitsev Variation. With 9...h6 Black prepares to play 10...Re8 and 11...Bf8 without fear of 10.Ng5. The loss of a tempo with 9...h6 gives White enough time to complete the Nbd2–f1–g3 manoeuver, and the pawn move can also weaken Black's kingside. The Zaitsev can be considered to be an improved Smyslov in which Black tries to save a tempo by omitting ...h6.

Kasparov played the Smyslov Variation in a loss to the Deep Blue chess computer in Game 2 of their 1997 Man vs. Machine match.

Svetozar Gligorić has been the most prolific C93 player.

Smyslov Variation: 9.h3 Qd7
9...Qd7 is another variation by Smyslov.

Black defences other than 3...a6
Of the variations in this section, the Berlin and Schliemann Defences are the most popular today, followed by the Classical Defence. and other less-common third moves for Black.
 * 3...Nge7 (Cozio Defence)
 * 3...g6 (Smyslov or Fianchetto Defence)
 * 3...Nd4 (Bird's Defence)
 * 3...d6 (Steinitz Defence)
 * 3...f5!? (Schliemann Defence)
 * 3...Bc5 (Classical or Cordel Defence)
 * 3...Nf6 (Berlin Defence)

Cozio Defence: 3...Nge7
The Cozio Defence (part of ECO C60), 3...Nge7, is distinctly old-fashioned and the least popular of the defences at Black's third move. Although Bent Larsen used it occasionally with success, it remains one of the least explored variations of the Ruy Lopez.

Smyslov Defence: 3...g6
The Smyslov Defence, Fianchetto Defence, Barnes Defence, or Pillsbury Defence (part of ECO C60), 3...g6, is a quiet positional system played occasionally by Vasily Smyslov and Boris Spassky, becoming popular in the 1980s when it was shown that 4.c3 a6! gives Black a good game.

It was later discovered that 4.d4 exd4 5.Bg5 gives White the advantage, and as such the variation is rarely played today. An interesting gambit line 4.d4 exd4 5.c3 has also been recommended by Alexander Khalifman, although some of the resulting positions have yet to be extensively tested.

Bird's Defence: 3...Nd4
Bird's Defence (ECO C61), 3...Nd4, is an uncommon variation in modern praxis. With careful play White is held to gain an advantage. The best moves are 4.Nxd4 exd4 5.0-0 Bc5 6.d3 c6 7.Ba4 Ne7.

This defence was published in 1843 in Paul Rudolf von Bilguer's Handbuch des Schachspiels and explored by Henry Bird in the late 19th century. Bird played it as Black at least 25 times, scoring +9−13=3 (nine wins, thirteen losses, three draws). Bird's Defence was later used a few times in tournament play by Siegbert Tarrasch, Boris Spassky, and Alexander Khalifman. Although it is still sometimes seen as a surprise weapon, no strong master since Bird has adopted it regularly. The world champion Magnus Carlsen played it as Black in the 2014 Chess Olympiad against Ivan Šarić and lost.

Steinitz Defence: 3...d6
The Steinitz Defence (also called the Old Steinitz Defence) (ECO C62), 3...d6, is solid but passive and cramped. Although the favourite of the first world champion Wilhelm Steinitz, and often played by world champions and expert defensive players Emanuel Lasker, José Capablanca, and occasionally by Vasily Smyslov, it largely fell into disuse after World War I, as its inherent passivity spurred a search for more active means of defending the Spanish.

White's most direct approach is 4.d4 immediately challenging Black's pawn on e5, while 4.c3 and 4.0-0 remain viable alternatives. Following 4.d4, Black proceeds with 4...Bd7 which breaks the pin but also defends against White's threat of winning a pawn with 5.Bxc6 and 6.dxe5. Next White plays 5.Nc3 protecting e4 and renewing the threat of winning a pawn to which Black responds with 5...Nf6. After 6.0-0 Be7 7.Re1 Black is forced to concede the centre with 7...exd4, since 7...0-0? leads to the Tarrasch Trap.

The Modern Steinitz Defence (3...a6 4.Ba4 d6) offers Black a freer position and is more popular.

Schliemann Defence: 3...f5
The Schliemann Defence or Schliemann–Jaenisch Gambit (ECO C63), 3...f5, is a sharp line in which Black plays for a kingside attack, frequently sacrificing one or two pawns. This variation was originated by Carl Jaenisch in 1847 and is sometimes named after him. Although later named for German lawyer Adolf Karl Wilhelm Schliemann (1817–1872), the line Schliemann actually played in the 1860s was a gambit variation of the Cordel Defence (3...Bc5 4.c3 f5). The most common responses for White to 3...f5!? are 4.d3 or 4.Nc3, with play after 4.Nc3 fxe4 5.Nxe4 going 5...d5, with great complications to follow, or 5...Nf6, which generally leads to quieter play. This line is considered to be a good practical weapon, but is positionally risky, especially against a strong and prepared opponent. In the 1970s Jozef Boey played it in the ICCF correspondence chess world championship final and wrote a book about it. It is not a true gambit since after 4.exf5 4...e4 forces the knight to retreat, after which 5...Qg5 will regain the pawn as it forks the pawns on f5 and g2 (as well as preventing Qh5+). Teimour Radjabov is currently the only top player who regularly employs this line, with mixed results.

Classical Defence: 3...Bc5
The Classical Defence or Cordel Defence (ECO C64), 3...Bc5, is possibly the oldest defence to the Ruy Lopez, and has been played occasionally by former world champion Boris Spassky and Boris Gulko. White's most common reply is 4.c3, when Black may choose to play 4...f5, the Cordel Gambit, leading to sharp play, after which 5.d4 is considered the strongest reply. More solid for Black is 4...Nf6, when 5.0-0 0-0 6.d4 Bb6 leads to the Benelux Variation. White's principal alternative to 4.c3 is 4.0-0, when Black can transpose to the Classical Berlin with 4...Nf6 or play 4...Nd4, which is not so bad for Black.

An alternative for White is the fork trick 4.Nxe5. Few games have been played with this line, but there is no clear refutation for Black. The name derives from White's play if Black captures the knight: 4...Nxe5 5.d4.

Berlin Defence: 3...Nf6
The Berlin Defence, 3...Nf6, has long had a reputation for solidity and drawishness and is commonly referred to as "the Berlin Wall". The Berlin Defence was played in the late 19th century and early 20th century by Emanuel Lasker and others, who typically answered 4.0-0 with 4...d6 in the style of the Steinitz Defence. This approach ultimately fell out of favour, as had the old form of the Steinitz, due to its passivity, and the entire variation became rare. Arthur Bisguier played the Berlin for decades, but always chose the variation 4.0-0 Nxe4. Ever since Vladimir Kramnik successfully used the line as a against Garry Kasparov in their 2000 World Chess Championship match, the Berlin has experienced a remarkable renaissance: even players with a dynamic style such as Alexei Shirov, Veselin Topalov, Hikaru Nakamura, and Kasparov himself have tried it, and Magnus Carlsen and Viswanathan Anand both used it (Carlsen extensively so) during the 2013 World Chess Championship and 2014 World Chess Championship.

Since Black's third move does not threaten to win the e-pawn—if Black captures it, White will win back the pawn on e5 —White usually castles. After 4.0-0, Black can play either the solid 4...Nxe4 (the Berlin Main Variation) or the more combative 4...Bc5 (the Berlin Classical Variation). After 4...Nxe4 5.d4 Nd6 (5...Be7 is the Rio de Janeiro Variation) 6.Bxc6 dxc6 7.dxe5 Nf5 8.Qxd8+ Kxd8 (l'Hermet Variation), White is considered to have a small advantage from a somewhat better pawn structure and Black's awkwardly placed king. Black, by way of compensation, possesses the and has no positional weaknesses, so it is difficult for White to exploit the structural superiority without opening the game for Black's bishops; all four of the games in the Kasparov–Kramnik match in which this line was employed ended in draws. An alternative for Black, though seldom seen since the 1890s, is 6...bxc6 7.dxe5 Nb7, although White keeps an advantage despite Black's two bishops, as it is difficult for Black to gain active counterplay. Despite its drawish tendency, however, the Berlin endgame remains the sternest test of the entire variation beginning with 3...Nf6, and a lot of theory has evolved here. Today's consensus is that Black will hold with accurate play in the Berlin endgame, so players have moved on to the lines with 4.0-0 Nxe4 5.Re1, the modern main line, considered to be White's best try for an opening advantage, and advocated by Fabiano Caruana in his Chessbase Series on the Ruy Lopez opening.

White's move 4.Nc3 transposes to the Four Knights Game, Spanish Variation.

An important alternative is 4.d3, dubbed the Anti-Berlin, which avoids the notorious Berlin endgame. Wilhelm Steinitz scored many spectacular successes with it during his reign as World Champion. The main replies for Black are 4...d6 and 4...Bc5, the latter being more popular. White's most important continuations after 4...Bc5 are 5.0-0, 5.Bxc6, and 5.c3. An uncommon reply to 4.d3 is 4...Ne7, which tries to set up the Mortimer Trap.

Another alternative is playing 4.Bxc6 immediately. The main replies for Black are 4...dxc6 and 4...bxc6, the latter of which is playable in the Berlin Defense, unlike the Exchange Variation in the Morphy Defense. This may transpose into the Anti-Berlin above if White continues with 5.d3, or in the case of 4...bxc6, to the main line with 5.0-0 Nxe4 or 5.d4 Nxe4, but White has other continuations to 4...bxc6, such as 5.Nc3, and Black has other replies to both 5.0-0 and 5.d4.

The Berlin is assigned ECO codes C65–C67. Code C65 covers alternatives to 4.0-0, including 4.d3 as well as 4.0-0 Bc5. Code C66 covers 4.0-0 d6, while C67 is 4.0-0 Nxe4.

Other
Less-common third moves for Black:
 * 3...Bb4 (Alapin Defence)
 * 3...Qf6 (Gunderam Variation)
 * 3...f6 (Nuremberg Defence)
 * 3...Qe7 (Vinogradov Variation)
 * 3...Na5 (Pollock's Defence)
 * 3...g5 (Brentano Defence)
 * 3...b6? (Rotary Defence or Albany Defence)
 * 3...d5? (Sawyer's Gambit or Spanish Countergambit)
 * 3...Be7 (Lucena Defence)
 * 3...a5 (Bulgarian Variation)

title: Ruy Lopez


text:
National Health Planning and Resources Development Act

The National Health Planning and Resources Development Act, or Public Law 93-641 is a piece of 1974 American Congressional legislation. Many Certificate of Need programs trace their origin to the act which offered incentives for states to implement these programs.

Details of the Act
In this Act, three distinct existing programs were consolidated:
 * Hill-Burton
 * Regional Medical Program
 * Comprehensive Health Planning Act

Congress realized that the provision of federal funds for the construction of new health care facilities was contributing to increasing health care costs by generating duplication of facilities.

The intent of Congress in passing this Act was to create throughout the United States, a strengthened and improved federal-, state- and area-wide system of health planning and resources development that would help provide solutions to several identified problems.

The perceived problems the Act was intended to address were as follows:
 * lack of equal access to quality health care at reasonable cost
 * infusion of federal funds into the health care system was contributing to inflationary health care costs while failing to produce an adequate supply or distribution of health resources
 * the lack of a comprehensive, rational approach by the public and private sectors to creation of uniformly effective methods of delivering health care
 * misdistribution of health care facilities and manpower
 * increasing and uncontrolled inflation of health care costs, particularly the costs associated with hospital stays
 * inadequate incentives for the use of alternative levels of health care and the substitution of ambulatory and intermediate care for inpatient hospital care
 * the lack of basic knowledge regarding proper personal health care and methods for effective use of available health services in large segments of the population

This legislation was also intended to encourage health care providers to play an active role in developing health policy.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Talk:Name your own price

Redirect
I wasn't sure whether to redirect this page to a new article "Name-Your-Own-Price" or not. Any suggestions? The acronym is rather arcane.

Alextorrenegra (talk) 18:44, 24 May 2009 (UTC) The "name your own price" feature is not a reverse action. As the name of the patent describes it, it is a "Method and apparatus for a cryptographically assisted commercial network system designed to facilitate buyer-driven conditional purchase offers". The key phrase is "buyer-driven conditional purchase offers". The word "auction" is not used in the patent anywhere, neither on the website of Priceline. The patent No is 5,794,207.

title: Talk:Name your own price


text:
Sequoia National Park

Sequoia National Park is an American national park in the southern Sierra Nevada east of Visalia, California. The park was established on September 25, 1890, and today protects 404,064 acre of forested mountainous terrain. Encompassing a vertical relief of nearly 13000 ft, the park contains the highest point in the contiguous United States, Mount Whitney, at 14505 ft above sea level. The park is south of, and contiguous with, Kings Canyon National Park; both parks are administered by the National Park Service together as Sequoia and Kings Canyon National Parks. UNESCO designated the areas as Sequoia-Kings Canyon Biosphere Reserve in 1976.

The park is notable for its giant sequoia trees, including the General Sherman tree, the largest tree on Earth by volume. The General Sherman tree grows in the Giant Forest, which contains five of the ten largest trees in the world. The Giant Forest is connected by the Generals Highway to Kings Canyon National Park's General Grant Grove, home of the General Grant tree among other giant sequoias. The park's giant sequoia forests are part of 202430 acre of old-growth forests shared by Sequoia and Kings Canyon National Parks. The parks preserve a landscape that was first cultivated by the Monache tribe, the southern Sierra Nevada before Euro-American settlement.

Front country
Many park visitors enter Sequoia National Park through its southern entrance near the town of Three Rivers at Ash Mountain at 1700 ft elevation. The lower elevations around Ash Mountain contain the only National Park Service-protected California Foothills ecosystem, consisting of blue oak woodlands, foothills chaparral, grasslands, yucca plants, and steep, mild river valleys. Seasonal weather results in a changing landscape throughout the foothills with hot summer yielding an arid landscape while spring and winter rains result in blossoming wildflowers and lush greens. The region is also home to abundant wildlife: bobcats, foxes, ground squirrels, rattlesnakes, and mule deer are commonly seen in this area, and more rarely, reclusive mountain lions and the Pacific fisher are seen as well. The last California grizzly was killed in this park in 1922 (at Horse Corral Meadow). The California Black Oak is a key transition species between the chaparral and higher elevation conifer forest.

At higher elevations in the front country, between 5500 and 9000 ft in elevation, the landscape becomes montane forest-dominated coniferous belt. Found here are Ponderosa, Jeffrey, sugar, and lodgepole pine trees, as well as abundant white and red fir. Found here too are the giant sequoia trees, the most massive living single-stem trees on earth. Between the trees, spring and summer snowmelts sometimes fan out to form lush, though delicate, meadows. In this region, visitors often see mule deer, Douglas squirrels, and American black bears, which sometimes break into unattended cars to eat food left by careless visitors. There are plans to reintroduce the bighorn sheep to this park.

Back country
The vast majority of the park is roadless wilderness; no road crosses the Sierra Nevada within the park's boundaries. 84 percent of Sequoia and Kings Canyon National Parks is designated wilderness and is accessible only by foot or by horseback. The majority was designated Sequoia-Kings Canyon Wilderness in 1984 and the southwest portion was protected as John Krebs Wilderness in 2009.

History
The area which now is Sequoia National Park shows evidence of Native American settlement as early as AD 1000. The area was first home to "Monachee" (Western Mono) Native Americans, who resided mainly in the Kaweah River drainage in the Foothills region of what is now the park, though evidence of seasonal habitation exists as high as the Giant Forest. Members of this tribe were permanent residents of the park, with a population estimate of around 2,000. In the summertime the Tubatulabal Native Americans used the eastern part of the area (the Kern River drainage) as their summer hunting grounds. During this time, the Western Mono tribe would travel over the high mountain passes to trade with tribes to the East. To this day, pictographs can be found at several sites within the park, notably at Hospital Rock and Potwisha, as well as bedrock mortars used to process acorns, a staple food for the Monachee people.

The first European settler to homestead in the area was Hale Tharp, who famously built a home out of a hollowed-out fallen giant sequoia log in the Giant Forest next to Log Meadow. Tharp arrived in 1858 to the region and encountered several groups of Native Americans, the largest being around 600 with several other smaller groups found at higher elevations. After becoming friendly with the Western Mono tribe, Tharp was shown the Giant Forest Sequoia Grove. After his settlement, more settlers came around 1860. Shortly thereafter - between 1860 and 1863, epidemics of smallpox, measles, and scarlet fever killed the majority of the Native Americans living in the area. After this, the rest of the Native Americans left with the largest campsite (Hospital Rock) abandoned by 1865. During their time in the area, the Monachee used periodic fire burning to aid in hunting and agriculture. This technique played an important role in the ecology of the region and allowed for a "natural" vegetation cover development. After they left, Tharp and other settlers allowed sheep and cattle to graze the meadow, while at the same time maintaining a respect for the grandeur of the forest and led early battles against logging in the area. From time to time, Tharp received visits from John Muir, who would stay at Tharp's log cabin. Tharp's Log can still be visited today in its original location in the Giant Forest.

Tharp's attempts to conserve the giant sequoias were at first met with only limited success. In the 1880s, white settlers seeking to create a utopian society founded the Kaweah Colony, which sought economic success in trading Sequoia timber. Giant Sequoia trees, unlike their coast redwood relatives, were later discovered to splinter easily and therefore were ill-suited to timber harvesting, though thousands of trees were felled before logging operations finally ceased. Benjamin Harrison ultimately signed legislation that established the Sequoia National Park on 25 September 1890, ending logging in the area.

Another consequence of the Giant Forest becoming Sequoia National Park was the shift in park employment. Prior to the incorporation by the National Park Service, the park was managed by US army troops of the 24th Regiment of Infantry and the 9th Regiment of Cavalry, better known as the Buffalo Soldiers. These segregated troops, founded in 1866, were African-American men from the South, an invaluable demographic to the military with the lowest rates of desertion. The Buffalo Soldiers completed park infrastructure projects as well as park management duties, helping to shape the role of the modern-day park ranger. The Buffalo Soldiers rose to this position due to a lack of funding for the park which led to an inability to hire civilians. The third African American West Point graduate, Captain Charles Young led the cavalries of Buffalo Soldiers in the Sequoia and General Grant Parks. Young landed this post as a result of the segregation rampant throughout the Army: as a black man, he was not permitted to head any combat units. He did demonstrate his leadership capability through his initiatives in the National Park delegating park infrastructure projects, hosting tourists and politicians, and setting a standard of a strong work ethic into his men. Young was also a prominent figure regarding the early conservation of Sequoia National Park. He greenlighted the dedication of trees in honor of prominent figures as a means of promoting their preservation. One such example is the Redwood dedicated to the escaped slave and activist, Booker T Washington. Young also argued to the Secretary of the Interior that the lack of enforcement of forest protection laws allowed the detrimental practices of logging and the popular tourist hobby of carving names into the redwoods to continue.

An expansions occurred in 1978, when grassroots efforts, spearheaded by the Sierra Club, fought off attempts by the Walt Disney Company to purchase a high-alpine former mining site south of the park for use as a ski resort. This site known as Mineral King was annexed to the park. Its name dates back to early 1873 when the miners in the area formed the Mineral King Mining District. Mineral King is the highest-elevation developed site within the park and a popular destination for backpackers.

The national park was partially closed in September 2020 due to the SQF Complex Fire, and fully closed in mid-September through mid-December 2021 due to the KNP Complex Fire.

Climate
According to the Köppen climate classification system, Sequoia National Park encompasses five climate types listed here from highest to lowest elevation; Tundra (ET), Mediterranean-influenced Subarctic climate (Dsc), Mediterranean-influenced warm-summer Humid continental climate (Dsb), Warm-summer Mediterranean climate (Csb), and Hot-summer Mediterranean climate (Csa). Precipitation also decreases with elevation. According to the United States Department of Agriculture, the Plant Hardiness zone at Giant Forest Visitor Center (6444 ft) is 8a with an average annual extreme minimum temperature of 12.0 F.

Geology
Sequoia National Park contains a significant portion of the Sierra Nevada. The park's mountainous landscape includes the tallest mountain in the contiguous United States, Mount Whitney, which rises to 14505 ft above sea level. The Great Western Divide parallels the Sierran crest and is visible at various places in the park, for example, Mineral King, Moro Rock, and the Giant Forest. Peaks in the Great Western Divide rise to more than 12000 ft. Deep canyons lie between the mountains, including Tokopah Valley above Lodgepole, Deep Canyon on the Marble Fork of the Kaweah River, and Kern Canyon in the park's backcountry, which is more than 5000 ft deep for 30 mi.

Most of the mountains and canyons in the Sierra Nevada are composed of granitic rocks. These rocks, such as granite, diorite and monzonite, formed when molten rock cooled far beneath the surface of the earth. The molten rock was the result of a geologic process known as subduction. Powerful forces in the earth forced the landmass under the waters of the Pacific Ocean beneath and below an advancing North American Continent. Super-hot water driven from the subducting ocean floor migrated upward and melted rock as it proceeded. This process took place during the Cretaceous Period, 100 million years ago. Granitic rocks have a speckled salt-and-pepper appearance because they contain various minerals including quartz, feldspars and micas. Valhalla, or the Angel Wings, are prominent granitic cliffs that rise above the headwaters of the Middle Fork of the Kaweah River.

The Sierra Nevada is a young mountain range, probably not more than 10 million years old. Forces in the earth, probably associated with the development of the Great Basin, forced the mountains to rise. During the last 10 million years, at least four ice ages have coated the mountains in a thick mantle of ice. Glaciers form and develop during long periods of cool and wet weather. Glaciers move very slowly through the mountains, carving deep valleys and craggy peaks. The extensive history of glaciation within the range and the erosion-resistant nature of the granitic rocks that make up most of the Sierra Nevada have together created a landscape of hanging valleys, waterfalls, craggy peaks, alpine lakes (such as Tulainyo Lake) and glacial canyons.

Park caves, like most caves in the Sierra Nevada of California, are mostly solutional caves dissolved from marble. Marble rock is essentially limestone that was metamorphosed by the heat and pressure of the formation and uplift of the Sierra Nevada Batholith. The batholith's rapid uplift over the past 10 million years led to a rapid erosion of the metamorphic rocks in the higher elevations, exposing the granite beneath; therefore, most Sierra Nevada caves are found in the middle and lower elevations (below 7000 ft), though some caves are found in the park at elevations as high as 10000 ft such as the White Chief cave and Cirque Cave in Mineral King. These caves are carved out of the rock by the abundant seasonal streams in the park. Most of the larger park caves have, or have had, sinking streams running through them.

The park contains more than 270 known caves, including Lilburn Cave which is California's longest cave with nearly 17 mi of surveyed passages. The only commercial cave open to park visitors is Crystal Cave, the park's second-longest cave at over 3.4 mi. Crystal Cave was discovered on April 28, 1918, by Alex Medley and Cassius Webster. The cave is a constant 48 F, and is only accessible by guided tour.

Caves are discovered every year in the park with the most recently discovered major cave being Ursa Minor in August 2006.

Flora and fauna
Sequoia National Park encompasses many classifications of ecological zones, with the highest zone consisting of alpine tundra vegetation, then followed by California conifer forests, with chaparral at the lower elevations of the park.

In the early 2000s, lumber company, Sierra Pacific Industries, began creating a living gene bank of trees using seeds harvested from the park.

Animals that inhabit this park are coyote, badger, black bear, bighorn sheep, deer, fox, cougar, eleven species of woodpecker, various species of turtle, three species of owl, opossum, various species of snake, wolverine, beaver, various species of frog, and muskrat.

Park attractions
In addition to hiking, camping, fishing, and backpacking, the following attractions are highlights with many park visitors:

 * Sherman Tree Trail An 0.8-mile roundtrip paved trail that descends from the parking lot to the base of the General Sherman tree and meanders through a grove of giant sequoia trees.
 * Tunnel Log is a fallen giant sequoia tree in Sequoia National Park. The tree, which measured 275 ft tall and 21 ft in diameter, fell across a park road in 1937 due to natural causes. The following year, a crew cut an 8 ft tall, 17 ft wide tunnel through the trunk, making the road passable again.
 * Tokopah Falls The trail to Tokopah Falls starts just beyond the Marble Fork Bridge in Lodgepole Campground. It is an easy 1.7 mile (one way) walk along the Marble Fork of the Kaweah River to the impressive granite cliffs and waterfall of Tokopah Canyon. Tokopah Falls is 1,200 ft high, and is most impressive in early summer.
 * Crescent Meadow is a small, sequoia-rimmed meadow in the Giant Forest region of Sequoia National Park. This sierran montane meadow marks the western terminus of the High Sierra Trail, which stretches from the meadow across the Great Western Divide to Mount Whitney. Pioneer Hale Tharp homesteaded in this and nearby Log Meadow. Conservationist John Muir visited this meadow many times and called it the "Gem of the Sierra". The meadow lies at the end of a three-mile paved road which leaves the Generals Highway near the Giant Forest Museum.
 * Moro Rock is a granite dome located in the center of the park, at the head of Moro Creek, between Giant Forest and Crescent Meadow. A 351-step stairway, built in the 1930s by the Civilian Conservation Corps, is cut into and poured onto the rock, so that visitors can hike to the top. The stairway is listed on the National Register of Historic Places. The view from the rock encompasses much of the Park, including the Great Western Divide. It has an elevation of 6725 ft.
 * Campgrounds in the park include three in the foothills area: Potwisha (42 sites), Buckeye Flat (28 sites), and South Fork (10 sites). Four campgrounds are at higher, conifer-dominated elevations, ranging from 6650 to 7500 ft: Atwell Mill (21 sites), Cold Springs (40 sites), Lodgepole (214 sites), and Dorst Creek (204 sites).
 * Giant Forest Museum offers information about giant sequoias and human history in the forest. The historic museum was built in 1928 by architect Gilbert Stanley Underwood.

In popular culture
macOS Sequoia was named after Sequoia National Park.

title: Sequoia National Park


text:
Free Art License

The Free Art License (FAL) (Licence Art Libre, LAL) is a copyleft license that grants the right to freely copy, distribute, and transform creative works except for computer hardware and software, including for commercial use.

History
The license was written in July 2000, with contributions from the mailing list copyleft_attitude@april.org and, in particular, with French lawyers Mélanie Clément-Fontaine and David Geraud, and French artists Isabelle Vodjdani and Antoine Moreau. It followed meetings held by Copyleft Attitude Antoine Moreau, with the artists gathered around the magazine Allotopie: Francis Deck, Antonio Gallego, Roberto Martinez, and Emma Gall. They took place at "Accès Local" in January 2000 and "Public" in March 2000, two places of contemporary art in Paris.

In 2005, Moreau wrote a memoir edited by Liliane Terrier entitled in Le copyleft appliqué à la création artistique. Le collectif Copyleft Attitude et la Licence Art Libre (Copyleft applied to artistic creation. The Copyleft Attitude collective and the Free Art License).

In 2007, version 1.3 of the Free Art License was amended to provide greater legal certainty and optimum compatibility with other copyleft licenses.

Application
The license was inspired by FLOSS licenses and issues related but not exclusive to digital arts: "It was born out of the observation of the world of free software and the Internet, but its applicability is not limited to digital support."Version 1.1 was adopted by art organizations like Constant (Brussels) and was translated into English by artist and technologist Antoine Schmitt. The Open Definition website of the Open Knowledge Foundation lists FAL 1.2 and 1.3 as one of the licenses conformant with the principles outlined in the Open Definition.

Compatibility
The Free Art License 1.3 has been declared compatible with CC BY-SA 4.0, but incompatible with the GNU GPL. It is recommended by the Free Software Foundation in the following terms: "We don't take the position that artistic or entertainment works must be free, but if you want to make one free, we recommend the Free Art License."

Compatibility with CC BY-SA 4.0
The Free Art License 1.3 is equivalent to the Creative Commons Attribution-Share Alike (CC BY-SA) 4.0 license.

On October 21, 2014, after public discussions, the Copyleft Attitude collective announced that the Free Art License is now legally compatible with the Creative Commons Attribution-Share Alike 4.0 International (CC BY-SA 4.0) license. The Creative Commons organization warmly welcomed this decision as it had defended this compatibility since the beginning.

title: Free Art License


text:
Talk:George, Washington

Untitled
Removed this: ( It is the only city in the United States, named for a President.) Lincoln, Nebraska is a counterexample that pops readily to mind.

Probably someone meant something like "It's the only city that when read with its state's name afterward sounds like the name of a president" but I'm not sure of what value that particular fact might be... -- Someone else 02:15, 10 Aug 2003 (UTC)

I am amazed at the level of random vandalism on this page. For a teeny little agricultural town of 500 people in the middle of the Columbia Basin sagebrush, it sure gets a lot of attention. Hats off to you, Mr. Brown! Nothingofwater (talk) 00:03, 10 January 2009 (UTC)

 * I don't find it amazing at all. I find it perfectly "normal" (not acceptable, mind you, but normal) that people would choose to vandalize a page for a town with a unique name. -- 70.57.75.185 (talk) 21:37, 3 August 2012 (UTC)

Cross-Link with Cristóbal, Colón
Just wondering why user SDY cross-linked this Columbia Gorge city's page with that of another city on the Panama-canal on 7 June. Maybe they are "sister-cities"? Should we make clearer what the connection is? Bookerj (talk) 14:41, 20 September 2012 (UTC)

Well, Cristobal Colon is the spanish name of Christopher Columbus, and Cristobal is also a city in the province of colon. Same pun on another same, basically.87.122.43.36 (talk) 15:58, 18 February 2013 (UTC)

External links modified
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 * The link to the city Web site is wrong. I'm not going to fix it, because I don't edit Wikipedia anymore. SimpsonDG (talk) 14:09, 29 June 2017 (UTC)

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Racial Makeup is Screwy
"The racial makeup of the city was 38.1% White, 1.4% Native American, 59.9% from other races, and 0.6% from two or more races. Hispanic or Latino of any race were 75.0% of the population."

75.0% Hispanic or Latino when 38.1% White? Misplaced decimal point?

154.5.158.238 (talk) 04:45, 27 December 2017 (UTC)

 * The data from the 2010 census on which that statement was based is here. The statement accurately reflects the source data.  Race and Hispanic/Latino ethnicity are not the same metric, and one cannot expect to add the percentages of each to arrive at 100%.  General Ization  Talk  05:22, 27 December 2017 (UTC)
 * Neither Hispanic nor Latino are a "race". They are considered an "ethnicity". There are both black and white Latinos, for example, which is why the wording says "Hispanic or Latino of any race". That said, it's a screwy way to say that. A little confusing. I'll try a simple rewrite. 76.178.169.118 (talk) 21:08, 23 March 2023 (UTC)

title: Talk:George, Washington


text:
Polyethylene terephthalate

Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins.

In 2016, annual production of PET was 56 million tons. The biggest application is in fibres (in excess of 60%), with bottle production accounting for about 30% of global demand. In the context of textile applications, PET is referred to by its common name, polyester, whereas the acronym PET is generally used in relation to packaging. Polyester makes up about 18% of world polymer production and is the fourth-most-produced polymer after polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC).

PET consists of repeating (C10H8O4) units. PET is commonly recycled, and has the digit 1 (♳) as its resin identification code (RIC). The National Association for PET Container Resources (NAPCOR) defines PET as: "Polyethylene terephthalate items referenced are derived from terephthalic acid (or dimethyl terephthalate) and mono ethylene glycol, wherein the sum of terephthalic acid (or dimethyl terephthalate) and mono ethylene glycol reacted constitutes at least 90 percent of the mass of monomer reacted to form the polymer, and must exhibit a melting peak temperature between 225 °C and 255 °C, as identified during the second thermal scan in procedure 10.1 in ASTM D3418, when heating the sample at a rate of 10 °C/minute."

Depending on its processing and thermal history, polyethylene terephthalate may exist both as an amorphous (transparent) and as a semi-crystalline polymer. The semicrystalline material might appear transparent (particle size less than 500 nm) or opaque and white (particle size up to a few micrometers) depending on its crystal structure and particle size.

One process for making PET uses bis(2-hydroxyethyl) terephthalate, which can be synthesized by the esterification reaction between terephthalic acid and ethylene glycol with water as a byproduct (this is also known as a condensation reaction), or by transesterification reaction between ethylene glycol and dimethyl terephthalate (DMT) with methanol as a byproduct. Polymerization is through a polycondensation reaction of the monomers (done immediately after esterification/transesterification) with water as the byproduct.

Textiles
Polyester fibres are widely used in the textile industry. The invention of the polyester fibre is attributed to J. R. Whinfield. It was first commercialized in the 1940s by ICI, under the brand 'Terylene'. Subsequently E. I. DuPont launched the brand 'Dacron'. As of 2022, there are many brands around the world, mostly Asian.

Polyester fibres are used in fashion apparel often blended with cotton, as heat insulation layers in thermal wear, sportswear and workwear and automotive upholstery.

Rigid packaging
Plastic bottles made from PET are widely used for soft drinks, both still and sparkling. For beverages that are degraded by oxygen, such as beer, a multilayer structure is used. PET sandwiches an additional polyvinyl alcohol (PVOH) or polyamide (PA) layer to further reduce its oxygen permeability.

Non-oriented PET sheet can be thermoformed to make packaging trays and blister packs. Crystallizable PET withstands freezing and oven baking temperatures. Both amorphous PET and BoPET are transparent to the naked eye. Color-conferring dyes can easily be formulated into PET sheet.

PET is permeable to oxygen and carbon dioxide and this imposes shelf life limitations of contents packaged in PET.

In the early 2000s, the global PET packaging market grew at a compound annual growth rate of 9% to €17 billion in 2006.

Flexible packaging
Biaxially oriented PET (BOPET) film (often known by one of its trade names, "Mylar") can be aluminized by evaporating a thin film of metal onto it to reduce its permeability, and to make it reflective and opaque (MPET). These properties are useful in many applications, including flexible food packaging and thermal insulation (such as space blankets).

Photovoltaic modules
BOPET is used in the backsheet of photovoltaic modules. Most backsheets consist of a layer of BOPET laminated to a fluoropolymer or a layer of UV stabilized BOPET.

PET is also used as a substrate in thin film solar cells.

Thermoplastic resins
PET can be compounded with glass fibre and crystallization accelerators, to make thermoplastic resins. These can be injection moulded into parts such as housings, covers, electrical appliance components and elements of the ignition system.

Nanodiamonds
PET is stoichiometrically a mixture of carbon and H2O, and therefore has been used in an experiment involving laser-driven shock compression which created nanodiamonds and superionic water. This could be a possible way of producing nanodiamonds commercially.

Other applications

 * A waterproofing barrier in undersea cables.
 * As a film base.
 * As a fibre, spliced into bell rope tops to help prevent wear on the ropes as they pass through the ceiling.
 * Since late 2014 as liner material in type IV composite high pressure gas cylinders. PET works as a much better barrier to oxygen than earlier used (LD)PE.
 * As a 3D printing filament, as well as in the 3D printing plastic PETG (polyethylene terephthalate glycol). In 3D printing PETG has become a popular material - used for high-end applications like surgical fracture tables to automotive and aeronautical sectors, among other industrial applications. The surface properties can be modified to make PETG self-cleaning for applications like the fabrication of traffic signs for the manufacture of light-emitting diode LED spotlights.
 * As one of three layers for the creation of glitter; acting as a plastic core coated with aluminum and topped with plastic to create a light reflecting surface, although as of 2021 many glitter manufacturing companies have begun to phase out the use of PET after calls from organizers of festivals to create bio-friendly glitter alternatives.
 * Film for tape applications, such as the carrier for magnetic tape or backing for pressure-sensitive adhesive tapes. Digitalization has caused the virtual disappeance of the magnetic audio and videotape application.
 * Water-resistant paper.

History
PET was patented in 1941 by John Rex Whinfield, James Tennant Dickson and their employer the Calico Printers' Association of Manchester, England. E. I. DuPont de Nemours in Delaware, United States, first used the trademark Mylar in June 1951 and received registration of it in 1952. It is still the best-known name used for polyester film. The current owner of the trademark is DuPont Teijin Films.

In the Soviet Union, PET was first manufactured in the laboratories of the Institute of High-Molecular Compounds of the USSR Academy of Sciences in 1949, and its name "Lavsan" is an acronym thereof (лаборатории Института высокомолекулярных соединений Академии наук СССР).

The PET bottle was invented in 1973 by Nathaniel Wyeth and patented by DuPont.

Physical properties
PET in its most stable state is a colorless, semi-crystalline resin. However it is intrinsically slow to crystallize compared to other semicrystalline polymers. Depending on processing conditions it can be formed into either non-crystalline (amorphous) or crystalline articles. Its amenability to drawing in manufacturing makes PET useful in fibre and film applications. Like most aromatic polymers, it has better barrier properties than aliphatic polymers. It is strong and impact-resistant. PET is hygroscopic and absorbs water.

About 60% crystallization is the upper limit for commercial products, with the exception of polyester fibers. Transparent products can be produced by rapidly cooling molten polymer below the glass transition temperature (Tg) to form a non-crystalline amorphous solid. Like glass, amorphous PET forms when its molecules are not given enough time to arrange themselves in an orderly, crystalline fashion as the melt is cooled. While at room temperature the molecules are frozen in place, if enough heat energy is put back into them afterward by heating the material above Tg, they can begin to move again, allowing crystals to nucleate and grow. This procedure is known as solid-state crystallization. Amorphous PET also crystallizes and becomes opaque when exposed to solvents, such as chloroform or toluene.

A more crystalline product can be produced by allowing the molten polymer to cool slowly. Rather than forming one large single crystal, this material has a number of spherulites (crystallized areas) each containing many small crystallites (grains). Light tends to scatter as it crosses the boundaries between crystallites and the amorphous regions between them, causing the resulting solid to be translucent. Orientation also renders polymers more transparent. This is why BOPET film and bottles are both crystalline, to a degree, and transparent.

Flavor absorption
PET has an affinity for hydrophobic flavors, and drinks sometimes need to be formulated with a higher flavor dosage, compared to those going into glass, to offset the flavor taken up by the container. While heavy gauge PET bottles returned for re-use, as in some EU countries, the propensity of PET to absorb flavors makes it necessary to conduct a "sniffer test" on returned bottles to avoid cross-contamination of flavors.

Intrinsic viscosity
Different applications of PET require different degrees of polymerization, which can be obtained by modifying the process conditions. The molecular weight of PET is measured by solution viscosity. The preferred method to measure this viscosity is the intrinsic viscosity (IV) of the polymer. Intrinsic viscosity is a dimensionless measurement found by extrapolating the relative viscosity (measured in (dℓ/g)) to zero concentration. Shown below are the IV ranges for common applications:

Copolymers
PET is often copolymerized with other diols or diacids to optimize the properties for particular applications. For example, cyclohexanedimethanol (CHDM) can be added to the polymer backbone in place of ethylene glycol. Since this building block is much larger (six additional carbon atoms) than the ethylene glycol unit it replaces, it does not fit in with the neighboring chains the way an ethylene glycol unit would. This interferes with crystallization and lowers the polymer's melting temperature. In general, such PET is known as PETG or PET-G (polyethylene terephthalate glycol-modified). It is a clear amorphous thermoplastic that can be injection-molded, sheet-extruded or extruded as filament for 3D printing. PETG can be colored during processing. Another common modifier is isophthalic acid, replacing some of the 1,4-(para-) linked terephthalate units. The 1,2-(ortho-) or 1,3-(meta-) linkage produces an angle in the chain, which also disturbs crystallinity.

Such copolymers are advantageous for certain molding applications, such as thermoforming, which is used for example to make tray or blister packaging from co-PET film, or amorphous PET sheet (A-PET/PETA) or PETG sheet. On the other hand, crystallization is important in other applications where mechanical and dimensional stability are important, such as seat belts. For PET bottles, the use of small amounts of isophthalic acid, CHDM, diethylene glycol (DEG) or other comonomers can be useful: if only small amounts of comonomers are used, crystallization is slowed but not prevented entirely. As a result, bottles are obtainable via stretch blow molding ("SBM"), which are both clear and crystalline enough to be an adequate barrier to aromas and even gases, such as carbon dioxide in carbonated beverages.

Production
Polyethylene terephthalate is produced largely from purified terephthalic acid (PTA), as well as to a lesser extent from (mono-)ethylene glycol (MEG) and dimethyl terephthalate (DMT). As of 2022, ethylene glycol is made from ethene found in natural gas, while terephthalic acid comes from p-xylene made from crude oil. Typically an antimony or titanium compound is used as a catalyst, a phosphite is added as a stabilizer and a bluing agent such as cobalt salt is added to mask any yellowing.

Dimethyl terephthalate process
In the dimethyl terephthalate (DMT) process, DMT and excess ethylene glycol (MEG) are transesterified in the melt at 150–200 °C with a basic catalyst. Methanol (CH3OH) is removed by distillation to drive the reaction forward. Excess MEG is distilled off at higher temperature with the aid of vacuum. The second transesterification step proceeds at 270–280 °C, with continuous distillation of MEG as well.

The reactions can be summarized as follows:
 * First step
 * C6H4(CO2CH3)2 + 2 HOCH2CH2OH → C6H4(CO2CH2CH2OH)2 + 2 CH3OH

 * Second step
 * n C6H4(CO2CH2CH2OH)2 → [(CO)C6H4(CO2CH2CH2O)]n + n HOCH2CH2OH

Terephthalic acid process
In the terephthalic acid process, MEG and PTA are esterified directly at moderate pressure (2.7–5.5 bar) and high temperature (220–260 °C). Water is eliminated in the reaction, and it is also continuously removed by distillation:

 * n C6H4(CO2H)2 + n HOCH2CH2OH → [(CO)C6H4(CO2CH2CH2O)]n + 2n H2O

Bio-PET
Bio-PET is the bio-based counterpart of PET. Essentially in Bio-PET, the MEG is manufactured from ethylene derived from sugar cane ethanol. A better process based on oxidation of ethanol has been proposed, and it is also technically possible to make PTA from readily available bio-based furfural.

Bottle processing equipment

There are two basic molding methods for PET bottles, one-step and two-step. In two-step molding, two separate machines are used. The first machine injection molds the preform, which resembles a test tube, with the bottle-cap threads already molded into place. The body of the tube is significantly thicker, as it will be inflated into its final shape in the second step using stretch blow molding.

In the second step, the preforms are heated rapidly and then inflated against a two-part mold to form them into the final shape of the bottle. Preforms (uninflated bottles) are now also used as robust and unique containers themselves; besides novelty candy, some Red Cross chapters distribute them as part of the Vial of Life program to homeowners to store medical history for emergency responders. The two-step process lends itself to third party production remote from the user site. The preforms can be transported and stored by the thousand in a much smaller space than would finished containers, for the second stage to be carried out on the user site on a 'just in time' basis. In one-step machines, the entire process from raw material to finished container is conducted within one machine, making it especially suitable for molding non-standard shapes (custom molding), including jars, flat oval, flask shapes, etc. Its greatest merit is the reduction in space, product handling and energy, and far higher visual quality than can be achieved by the two-step system.

Degradation
PET is subject to degradation during processing. If the moisture level is too high, hydrolysis will reduce the molecular weight by chain scission, resulting in brittleness. If the residence time and/or melt temperature (temperature at melting) are too high, then thermal degradation or thermooxidative degradation will occur resulting in discoloration and reduced molecular weight, as well as the formation of acetaldehyde, and the formation "gel" or "fish-eye" formations through cross-linking. Mitigation measures include copolymerisation with other monomers like CHDM or isophthalic acid, which lower the melting point and thus the melt temperature of the resin, as well as the addition of polymer stabilisers such as phosphites.

Acetaldehyde
Acetaldehyde, which can form by degradation of PET after mishandling of the material, is a colorless, volatile substance with a fruity smell. Although it forms naturally in some fruit, it can cause an off-taste in bottled water. As well as high temperatures (PET decomposes above 300 °C or 570 °F) and long barrel residence times, high pressures and high extruder speeds (which cause shear raising the temperature), can also contribute to the production of acetaldehyde. Photo-oxidation can also cause the gradual formation acetaldehyde over the object's lifespan. This proceeds via a Type II Norrish reaction.

When acetaldehyde is produced, some of it remains dissolved in the walls of a container and then diffuses into the product stored inside, altering the taste and aroma. This is not such a problem for non-consumables (such as shampoo), for fruit juices (which already contain acetaldehyde), or for strong-tasting drinks like soft drinks. For bottled water, however, low acetaldehyde content is quite important, because if nothing masks the aroma, even extremely low concentrations (10–20 parts per billion in the water) of acetaldehyde can produce an off-taste.

Safety and environmental concerns
Commentary published in Environmental Health Perspectives in April 2010 suggested that PET might yield endocrine disruptors under conditions of common use and recommended research on this topic. Proposed mechanisms include leaching of phthalates as well as leaching of antimony. An article published in Journal of Environmental Monitoring in April 2012 concludes that antimony concentration in deionized water stored in PET bottles stays within EU's acceptable limit even if stored briefly at temperatures up to 60 °C (140 °F), while bottled contents (water or soft drinks) may occasionally exceed the EU limit after less than a year of storage at room temperature.

Antimony
Antimony (Sb) is a metalloid element that is used as a catalyst in the form of compounds such as antimony trioxide (Sb2O3) or antimony triacetate in the production of PET. After manufacturing, a detectable amount of antimony can be found on the surface of the product. This residue can be removed with washing. Antimony also remains in the material itself and can, thus, migrate out into food and drinks. Exposing PET to boiling or microwaving can increase the levels of antimony significantly, possibly above US EPA maximum contamination levels. The drinking water limit assessed by WHO is 20 parts per billion (WHO, 2003), and the drinking water limit in the United States is 6 parts per billion. Although antimony trioxide is of low toxicity when taken orally, its presence is still of concern. The Swiss Federal Office of Public Health investigated the amount of antimony migration, comparing waters bottled in PET and glass: The antimony concentrations of the water in PET bottles were higher, but still well below the allowed maximum concentration. The Swiss Federal Office of Public Health concluded that small amounts of antimony migrate from the PET into bottled water, but that the health risk of the resulting low concentrations is negligible (1% of the "tolerable daily intake" determined by the WHO). A later (2006) but more widely publicized study found similar amounts of antimony in water in PET bottles. The WHO has published a risk assessment for antimony in drinking water.

Fruit juice concentrates (for which no guidelines are established), however, that were produced and bottled in PET in the UK were found to contain up to 44.7 μg/L of antimony, well above the EU limits for tap water of 5 μg/L.

Shed microfibres
Clothing sheds microfibres in use, during washing and machine drying. Plastic litter slowly forms small particles. Microplastics which are present on the bottom of the river or seabed can be ingested by small marine life, thus entering the food chain. As PET has a higher density than water, a significant amount of PET microparticles may be precipitated in sewage treatment plants. PET microfibers generated by apparel wear, washing or machine drying can become airborne, and be dispersed into fields, where they are ingested by livestock or plants and end up in the human food supply. SAPEA have declared that such particles 'do not pose a widespread risk'. PET is known to degrade when exposed to sunlight and oxygen. As of 2016, scarce information exists regarding the life-time of the synthetic polymers in the environment.

Polyester recycling

While most thermoplastics can, in principle, be recycled, PET bottle recycling is more practical than many other plastic applications because of the high value of the resin and the almost exclusive use of PET for widely used water and carbonated soft drink bottling. PET bottles lend themselves well to recycling (see below). In many countries PET bottles are recycled to a substantial degree, for example about 75% in Switzerland. The term rPET is commonly used to describe the recycled material, though it is also referred to as R-PET or post-consumer PET (POSTC-PET).

The prime uses for recycled PET are polyester fiber, strapping, and non-food containers. Because of the recyclability of PET and the relative abundance of post-consumer waste in the form of bottles, PET is also rapidly gaining market share as a carpet fiber. PET, like many plastics, is also an excellent candidate for thermal disposal (incineration), as it is composed of carbon, hydrogen, and oxygen, with only trace amounts of catalyst elements (but no sulfur). In general, PET can either be chemically recycled into its original raw materials (PTA, DMT, and EG), destroying the polymer structure completely; mechanically recycled into a different form, without destroying the polymer; or recycled in a process that includes transesterification and the addition of other glycols, polyols, or glycerol to form a new polyol. The polyol from the third method can be used in polyurethane (PU foam) production,   or epoxy-based products, including paints.

In 2023 a process was announced for using PET as the basis for supercapacitor production. PET, being stoichiometrically carbon and H2O, can be turned into a form of carbon containing sheets and nanospheres, with a very high surface area. The process involves holding a mixture of PET, water, nitric acid, and ethanol at a high temperature and pressure for eight hours, followed by centrifugation and drying.

Significant investments were announced in 2021 and 2022 for chemical recycling of PET by glycolysis, methanolysis, and enzymatic recycling to recover monomers. Initially these will also use bottles as feedstock but it is expected that fibres will also be recycled this way in future.

PET is also a desirable fuel for waste-to-energy plants, as it has a high calorific value which helps to reduce the use of primary resources for energy generation.

Biodegradation
At least one species of bacterium in the genus Nocardia can degrade PET with an esterase enzyme. Esterases are enzymes able to cleave the ester bond between two oxygens that links subunits of PET. The initial degradation of PET can also be achieved esterases expressed by Bacillus, as well as Nocardia. Japanese scientists have isolated another bacterium, Ideonella sakaiensis, that possesses two enzymes which can break down the PET into smaller pieces digestible by the bacteria. A colony of I. sakaiensis can disintegrate a plastic film in about six weeks. French researchers report developing an improved PET hydrolase that can depolymerize (break apart) at least 90 percent of PET in 10 hours, breaking it down into individual monomers. Also, an enzyme based on a natural PET-ase was designed with the help of a machine learning algorithm to be able to tolerate pH and temperature changes by the University of Texas at Austin. The PET-ase was found to able to degrade various products and could break them down as fast as 24 hours.

title: Polyethylene terephthalate


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Comparison of free software for audio

This comparison of free software for audio lists notable free and open source software for use by sound engineers, audio producers, and those involved in sound recording and reproduction.

Distributions and other platforms
Various projects have formed to integrate the existing free software audio packages.

Programming languages
Many computer music programming languages are implemented in free software. See also the comparison of audio synthesis environments.

Radio broadcasting
See also streaming below.

Recording and editing
The following packages are digital audio editors.

Streaming
These programs are for use with streaming audio.

Trackers
These music sequencer programs allow users to arrange notes (pitch-shifted sound samples) on a timeline: see tracker (music software).

title: Comparison of free software for audio