Chain reaction and Escalator over the Hill

A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events.

Chain reactions are one way in which systems which are in thermodynamic non-equilibrium can release energy or increase entropy in order to reach a state of higher entropy. For example, a system may not be able to reach a lower energy state by releasing energy into the environment, because it is hindered or prevented in some way from taking the path that will result in the energy release. If a reaction results in a small energy release making way for more energy releases in an expanding chain, then the system will typically collapse explosively until much or all of the stored energy has been released. Since chain reactions result in energy transformation into forms associated with larger amounts of entropy. In accordance with the laws of thermodynamics, the reactions cannot be reversed.

A macroscopic metaphor for chain reactions is thus a snowball causing a larger snowball until finally an avalanche results ("snowball effect"). This is a result of stored gravitational potential energy seeking a path of release over friction. Chemically, the equivalent to a snow avalanche is a spark causing a forest fire. In nuclear physics, a single stray neutron can result in an prompt critical event, which may be finally be energetic enough for a nuclear reactor meltdown or (in a bomb) a nuclear explosion.

Contents 1 Chemical chain reactions 1.1 Example 1.2 Further chemical examples 2 Nuclear chain reactions 3 Electron avalanche in gases 4 Avalanche breakdown in semiconductors 5 Chain reactions in economics 6 See also 7 References 8 External links

Chemical chain reactions

In 1913 the German chemist Max Bodenstein first put forth the idea of chemical chain reactions. If two molecules react, not only molecules of the final reaction products are formed, but also some unstable molecules, having the property of being able to further react with the parent molecules with a far larger probability than the initial reactants. In the new reaction, further unstable molecules are formed besides the stable products, and so on.

In 1923, Danish and Dutch scientists Christian Christiansen and Hendrik Anthony Kramers, in an analysis of formation of polymers, pointed out that such a chain reaction need not start with a molecule excited by light, but could also start with two molecules colliding violently in the traditional way classically previously proposed for initiation of chemical reactions, by van' t Hoff.

Christiansen and Kramers also noted that if, in one link of the reaction chain, two or more unstable molecules are produced, the reaction chain would branch and grow. The result is in fact an exponential growth, thus giving rise to explosive increases in reaction rates, and indeed to chemical explosions themselves. This was the first proposal for the mechanism of chemical explosions.

A quantitative chain chemical reaction theory was created by Soviet physicist Nikolay Semyonov in 1934. Semyonov shared the Nobel Prize in 1956 with Sir Cyril Norman Hinshelwood, who independently developed many of the same quantitative concepts.

The main steps of chain reaction occur via the following steps. Initiation (at this step an active particle, often a free radical, is produced). Propagation (may comprise several elementary steps, as, for instance, reaction elementary acts, where the active particle through reaction forms another active particle which continues the reaction chain by entering the next elementary step); particular cases are: * chain branching (the case of propagation step when more new active particles form in the step than enter it); * chain transfer (the case in which one active particle enters an elementary reaction with the inactive particle which as a result becomes another active particle along with forming of another inactive particle from the initial active one). Termination (elementary step in which active particle loses its activity without transferring the chain; e. g. recombination of the free radicals).

Some chain reactions have complex rate equations with fractional order or mixed order kinetics. Example

The reaction H2 + Br2 → 2 HBr proceeds by the following mechanism: Initiation Br2 → 2 Br• each Br atom is a free radical, indicated by the symbol « • » representing an unpaired electron. Propagation (here a cycle of two steps) Br• + H2 → HBr + H• H• + Br2 → HBr + Br• the sum of these two steps corresponds to the overall reaction H2 + Br2 → 2 HBr, with catalysis by Br• which participates in the first step. Retardation (inhibition) H• + HBr → H2 + Br• this step is specific to this example, and corresponds to the first propagation step in reverse. Termination 2 Br• → Br2 recombination of two radicals, corresponding in this example to initiation in reverse.

This reaction has an initial rate of fractional order, and a complete rate equation with a two-term denominator (mixed-order kinetics). Further chemical examples In a chemical reaction, every step of the H2 + Cl2 chain reaction consumes one molecule of H2 or Cl2, one free radical H· or Cl· producing one HCl molecule and another free radical. In chain-growth polymerization, the propagation step corresponds to the elongation of the growing polymer chain. Polymerase chain reaction, a technique used in molecular biology to amplify (make many copies of) a piece of DNA by in vitro enzymatic replication using a DNA polymerase. Nuclear chain reactions Main article: Nuclear chain reaction

A nuclear chain reaction was proposed by Leó Szilárd in 1933, shortly after the neutron was discovered, yet more than five years before nuclear fission was first discovered. Szilárd knew of chemical chain reactions, and he had been reading about an energy-producing nuclear reaction involving high-energy protons bombarding lithium, demonstrated by John Cockcroft and Ernest Walton, in 1932. Now, Szilárd proposed to use neutrons theoretically-produced from certain nuclear reactions in lighter isotopes, to induce further reactions in light isotopes that produced more neutrons. This would in theory produce a chain reaction at the level of the nucleus. He did not envision nuclear fission as one of these neutron-producing reactions, since this reaction was not known at the time. Experiments he proposed using beryllium and indium failed.

Later, after nuclear fission was discovered in 1938, Szilárd immediately realized the possibility of using neutron-induced fission as the particular nuclear reaction necessary to create a chain-reaction, so long as fission also produced neutrons. In 1939, with Enrico Fermi, Szilárd proved this neutron-multiplying reaction in uranium. In this reaction, a neutron plus a fissionable atom causes a fission resulting in a larger number of neutrons than the single one that was consumed in the initial reaction. Thus was born the practical nuclear chain reaction by the mechanism of neutron-induced nuclear fission.

Specifically, if one or more of the produced neutrons themselves interact with other fissionable nuclei, and these also undergo fission, then there is a possibility that the macroscopic overall fission reaction will not stop, but continue throughout the reaction material. This is then a self-propagating and thus self-sustaining chain reaction. This is the principle for nuclear reactors and atomic bombs.

Demonstration of a self-sustaining nuclear chain reaction was accomplished by Enrico Fermi and others, in the successful operation of Chicago Pile-1, the first artificial nuclear reactor, in late 1942. Electron avalanche in gases

An electron avalanche happens between two unconnected electrodes in a gas when an electric field exceeds a certain threshold. Random thermal collisions of gas atoms may result in a few free electrons and positively-charged gas ions, in a process called impact ionization. Acceleration of these free electrons in a strong electric field causes them to gain energy, and when they impact other atoms, the energy causes release of new free electrons and ions (ionization), which fuels the same process. If this process happens faster than it is naturally quenched by ions recombining, the new ions multiply in successive cycles until the gas breaks down into a plasma and current flows freely in a discharge.

Electron avalanches are essential to the dielectric breakdown process within gases. The process can culminate in corona discharges, streamers, leaders, or in a spark or continuous electric arc that completely bridges the gap. The process may extends to huge sparks — streamers in lightning discharges propagate by formation of electron avalanches created in the high potential gradient ahead of the streamers' advancing tips. Once begun, avalanches are often intensified by the creation of photoelectrons as a result of ultraviolet radiation emitted by the excited medium's atoms in the aft-tip region. The extremely high temperature of the resulting plasma cracks the surrounding gas molecules and the free ions recombine to create new chemical compounds.

The process can also be used to detect radiation that initiates the process, as the passage of a single particles can amplified to large discharges. This is the mechanism of a Geiger counter and also the visualization possible with a spark chamber and other wire chambers. Avalanche breakdown in semiconductors

An avalanche breakdown process can happen in semiconductors, which in some ways conduct electricity analogously to a mildly-ionized gas. Semiconductors rely on free electrons knocked out of the crystal by thermal vibration for conduction. Thus, unlike metals, semiconductors become better conductors the higher the temperature. This sets up conditions for the same type of positive feedback—heat from current flow causes temperature to rise, which increases charge carriers, lowering resistance, and causing more current to flow. This can continue to the point of complete breakdown of normal resistance at a semiconductor junction, and failure of the device (this may be temporary or permanent depending on whether there is physical damage to the crystal). Certain devices, such as

Escalator over the Hill and Chain reaction

Contents 1 History 2 Reception 3 Track listing 4 Personnel 5 Awards 6 References 7 External links

History

Escalator Over the Hill is more than two hours long and was recorded over three years (1968 to 1971). It was originally released as a triple LP box which also contained a booklet with lyrics, photos and profiles of the musicians. Side six of the original LPs ended in a locked groove, the final track "...And It's Again" continuing infinitely on manual record players. (For the CD reissue, the hum is allowed to play for almost 20 minutes before slowly fading out.)

In 1997, a live version of Escalator Over the Hill, re-orchestrated by Jeff Friedman, was performed for the first time in Cologne, Germany. In 1998, "Escalator" toured Europe. Another live performance took place in May 2006 in Essen, Germany.

The musicians involved in the original recording play in various combinations, covering a wide range of musical genres, from Kurt Weill's theater music, to free jazz, rock and Indian music. Writer Stuart Broomer considers this to be a summing up "much of the creative energy that was loose between 1968 and 1972".

Viva acts as narrator. Jack Bruce also appears on bass and vocals (due to the album's long production, he also appeared on Frank Zappa's album Apostrophe, playing bass on the title track). Among the vocalists is a young (and still relatively unknown) Linda Ronstadt, in addition to Jeanne Lee, Paul Jones, Carla Bley, Don Preston, Sheila Jordan, and Bley's and Mantler's then-4-year-old daughter Karen Mantler.

In 2006, Paul Haines' daughter, Canadian musician Emily Haines, adapted the Escalator Over the Hill cover art for her own first widely distributed album under her own name, Knives Don't Have Your Back. Reception

Jonathon Cott's Rolling Stone aticle stated "Like an electric transformer, Escalator Over the Hill synthesizes and draws on an enormous range of musical materials - raga, jazz, rock, ring modulated piano sounds, all brought together through Carla Bley's extraordinary formal sense and ability to unify individual but diverse musical sections by means of the editing of the record medium... The opera is an international musical encounter of the first order." Track listing Side one "Hotel Overture"– 13:11 Side two "This Is Here..." – 6:02 "Like Animals" – 1:21 "Escalator Over the Hill" – 4:57 "Stay Awake" – 1:31 "Ginger and David" – 1:39 "Song to Anything That Moves" – 2:22 Side three "Eoth Theme" – 0:35 "Businessmen" – 5:38 "Ginger and David Theme" – 0:57 "Why" – 2:19 "It's Not What You Do" – 0:17 "Detective Writer Daughter" – 3:16 "Doctor Why" – 1:28 "Slow Dance (Transductory Music)" – 1:50 "Smalltown Agonist" – 5:24 Side four "End of Head" – 0:38 "Over Her Head" – 2:38 "Little Pony Soldier" – 4:36 "Oh Say Can You Do?" – 1:11 "Holiday in Risk" – 3:10 "Holiday in Risk Theme" – 0:52 Side five "A.I.R. (All India Radio)" – 3:58 "Rawalpindi Blues" – 12:44 Side six "End of Rawalpindi" – 9:40 "End of Animals" – 1:26 "... And It's Again" – 9:55 "... And It's Again" would later be expanded to a length of 27:17 for CD release, with 17:23 minutes of the humming sound found on the inner groove of the LP. Personnel Principal Cast Jack, Parrot: Jack Bruce Leader, Mutant, Voice, Desert Women: Carla Bley Sand Shepherd: Don Cherry Ginger: Linda Ronstadt Ginger II: Jeanne Lee David: Paul Jones Doctor, Lion: Don Preston Viva: Viva Cecil Clark: Tod Papageorge His Friends: Charlie Haden, Steve Ferguson Calliope Bill: Bill Leonard Roomer: Bob Stewart Ancient Roomer: Karen Mantler Loudspeaker: Roswell Rudd Used Woman: Sheila Jordan Operasinger: Rosalind Hupp Nurse: Jane Blackstone Yodelling Ventriloquist: Howard Johnson Therapist: Timothy Marquand Dad: Perry Robinson Phantoms, Multiple Public Members, Hotelpeople, Women, Men, Flies, Bullfrogs, Mindsweepers, Speakers, Blindman: Jane Blackstone, Carla Bley, Jonathan Cott, Sharon Freeman, Steve Gebhardt, Tyrus Gerlach, Eileen Hale, Rosalind Hupp, Jack Jeffers, Howard Johnson, Sheila Jordan, Michael Mantler, Timothy Marquand, Nancy Newton, Tod Papageorge, Don Preston, Bill Roughen, Phyllis Schneider, Bob Stewart, Pat Stewart, Viva Musicians (alphabetical) Gato Barbieri - tenor saxophone Souren Baronian - clarinet Karl Berger - vibraphone Carla Bley - organ, celeste, chimes, calliope, piano Sam Brown - guitar Jack Bruce - bass, vocal John Buckingham - tuba Sam Burtis - trombone Bob Carlisle - French horn Don Cherry - trumpet Roger Dawson - congas, xylophone Sharon Freeman - French horn Charlie Haden - bass Peggy Imig - clarinet Jack Jeffers - bass trombone Leroy Jenkins - violin Howard Johnson - tuba Sheila Jordan - vocal Jimmy Knepper - trombone Jeanne Lee - vocal Jimmy Lyons - alto saxophone Michael Mantler - prepared piano, trumpet, valve trombone Ron McClure - bass John McLaughlin - guitar Bill Morimando - orchestra bells, celeste Paul Motian - drums, dumbec Nancy Newton - viola Don Preston - Moog synthesizer Enrico Rava - trumpet Perry Robinson - clarinet Linda Ronstadt - vocal Roswell Rudd - trombone Calo Scott - cello Michael Snow - trumpet Chris Woods - baritone saxophone Richard Youngstein - bass Musicians (chronotransductional) Orchestra (& Hotel Lobby Band) Carla Bley (piano) Jimmy Lyons (alto saxophone) Gato Barbieri (tenor saxophone) Chris Woods (baritone saxophone) Michael Mantler, Enrico Rava (trumpet) Roswell Rudd, Sam Burtis, Jimmy Knepper (trombone) Jack Jeffers (bass trombone) Bob Carlisle, Sharon Freeman (French horn) John Buckingham (tuba) Nancy Newton (viola) Karl Berger (vibraphone) Charlie Haden (bass) Paul Motian (drums) Roger Dawson (congas) Bill Morimando (orchestra bells, celeste). Jack's Traveling Band Carla Bley (organ) John McLaughlin (guitar) Jack Bruce (bass) Paul Motian (drums) Desert Band Carla Bley (organ) Don Cherry (trumpet) Souren Baronia (clarinet) Leroy Jenkins (violin) Calo Scott (cello) Sam Brown (guitar) Ron McClure (bass) Paul Motian (dumbec) Original Hotel Amateur Band Carla Bley (piano) Michael Snow (trumpet) Michael Mantler (valve trombone) Howard Johnson (tuba) Perry Robinson, Peggy Imig (clarinet) Nancy Newton (viola) Richard Youngstein (bass) Paul Motian (drums) Phantom Music Carla Bley (organ, celeste, chimes, calliope) Michael Mantler (prepared piano) Don Preston (Moog synthesizer) Awards Jazz Album of the Year 1972 by a Melody Maker Readers Poll French Grand Prix du Disque in 1973
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