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conductors to protect them from corrosion or wear. For instance, in 1902, steel cables supporting the Manhattan Bridge were first covered in linseed oil then wrapped in duck tape before being laid in place. In the 1910s, certain boots and shoes used canvas duck fabric for the upper or for the insole, and duck tape was sometimes sewn in for reinforcement. In 1936, the US-based Insulated Power Cables Engineers Association specified a wrapping of duck tape as one of many methods used to protect rubber-insulated power cables. In 1942, Gimbel's department store offered venetian blinds that were held together with vertical strips of duck tape. All of these foregoing uses were for plain cotton or linen
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tape that came without a layer of applied adhesive.
Adhesive tapes of various sorts were in use by the 1910s, including rolls of cloth tape with adhesive coating one side. White adhesive tape made of cloth soaked in rubber and zinc oxide was used in hospitals to bind wounds, but other tapes such as friction tape or electrical tape could be substituted in an emergency. In 1930, the magazine "Popular Mechanics" described how to make adhesive tape at home using plain cloth tape soaked in a heated liquid mixture of rosin and rubber from inner tubes.
In 1923, Richard Gurley Drew working for 3M invented masking tape, a paper-based tape with a mildly sticky adhesive. In 1925 this became the Scotch
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brand masking tape. In 1930, Drew developed a transparent tape based on cellophane, called Scotch Tape. This tape was widely used beginning in the Great Depression to repair household items. Author Scott Berkun has written that duct tape is "arguably" a modification of this early success by 3M. However, neither of Drew's inventions was based on cloth tape.
The idea for what became duct tape came from Vesta Stoudt, an ordnance-factory worker and mother of two Navy sailors, who worried that problems with ammunition box seals would cost soldiers precious time in battle. She wrote to President Franklin D. Roosevelt in 1943 with the idea to seal the boxes with a fabric tape, which she had tested
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at her factory. The letter was forwarded to the War Production Board, who put Johnson & Johnson on the job. The Revolite division of Johnson & Johnson had made medical adhesive tapes from duck cloth from 1927 and a team headed by Revolite's Johnny Denoye and Johnson & Johnson's Bill Gross developed the new adhesive tape, designed to be ripped by hand, not cut with scissors.
Their new unnamed product was made of thin cotton duck coated in waterproof polyethylene (plastic) with a layer of rubber-based gray adhesive (branded as "Polycoat") bonded to one side. It was easy to apply and remove, and was soon adapted to repair military equipment quickly, including vehicles and weapons. This tape, colored
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in army-standard matte olive drab, was widely used by the soldiers.
After the war, the duck tape product was sold in hardware stores for household repairs. The Melvin A. Anderson Company of Cleveland, Ohio, acquired the rights to the tape in 1950. It was commonly used in construction to wrap air ducts. Following this application, the name "duct tape" came into use in the 1950s, along with tape products that were colored silvery gray like tin ductwork. Specialized heat- and cold-resistant tapes were developed for heating and air-conditioning ducts. By 1960 a St. Louis, Missouri, HVAC company, Albert Arno, Inc., trademarked the name "Ductape" for their "flame-resistant" duct tape, capable of
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holding together at .
In 1971, Jack Kahl bought the Anderson firm and renamed it Manco. In 1975, Kahl rebranded the duct tape made by his company. Because the previously used generic term "duck tape" had fallen out of use, he was able to trademark the brand "Duck Tape" and market his product complete with a yellow cartoon duck logo. Manco chose the "Duck" name as "a play on the fact that people often refer to duct tape as 'duck tape, and as a marketing differentiation to stand out against other sellers of duct tape. In 1979, the Duck Tape marketing plan involved sending out greeting cards with the duck branding, four times a year, to 32,000 hardware managers. This mass of communication combined
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with colorful, convenient packaging helped Duck Tape become popular. From a near-zero customer base Manco eventually controlled 40% of the duct tape market in the US. Acquired by Henkel in 1998, in 2009 Duck Tape was sold to Shurtape Technologies, which is owned by the Shuford family of North Carolina.
Duck is not Shurtape's only brand of duct tape; their high-end offering is called "T-Rex Tape." "Ultimate Duck", which had been Henkel's top of the line variety, is still sold in the United Kingdom. Ultimate Duck, T-Rex Tape, and the competing Gorilla Tape all advertise "three-layer technology".
After profiting from Scotch Tape in the 1930s, 3M produced military materiel during WWII, and by
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1946 had developed the first practical vinyl electrical tape. By 1977, the company was selling a heat-resistant duct tape for heating ducts. In the late 1990s, 3M was running a $300 million duct tape division, the US industry leader. In 2004, 3M invented a transparent duct tape.
# Manufacture.
Modern duct tape is made with any one of a variety of woven fabrics to provide strength. The threads or fill yarn of the fabric may be cotton, polyester, nylon, rayon or fiberglass. The fabric is a very thin gauze called "scrim" which is laminated to a backing of low-density polyethylene (LDPE). The color of the LDPE is provided by various pigments; the usual gray color comes from powdered aluminum mixed
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into the LDPE. There are two commonly produced tape widths: and . Other widths are also offered. The largest commercial rolls of duct tape were made in 2005 for Henkel, with width, a roll diameter of and weighing .
# Common uses.
Duct tape is commonly used in situations that require a strong, flexible, and very sticky tape. Some have a long-lasting adhesive and resistance to weathering.
A specialized version, gaffer tape, which does not leave a sticky residue when removed, is preferred by gaffers in the theatre, motion picture and television industries.
Duct tape, in its guise as "racer's tape", "race tape" or "100 mile an hour tape" has been used in motorsports for more than 40 years to
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repair fiberglass bodywork (among other uses). Racer's tape comes in a wide range of colors to help match it to common paint colors. In the UK, it is usually referred to as "tank tape" in motorsports use.
## Usage on ductwork.
The product now commonly called duct tape should not be confused with special tapes actually designed for sealing heating and ventilation (HVAC) ducts, though these tapes may also be called "duct tapes." To provide laboratory data about which sealants and tapes last, and which are likely to fail, research was conducted at Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division. Their major conclusion was that one should not use duct tape to
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seal ducts (they had defined duct tape as any fabric-based tape with rubber adhesive). The testing done shows that under challenging but realistic conditions, duct tapes become brittle and may fail quickly, at times becoming leaky or falling off completely.
Common duct tape carries no safety certifications such as UL or Proposition 65, which means the tape may burn violently, producing toxic smoke; it may cause ingestion and contact toxicity; it can have irregular mechanical strength; and its adhesive may have low life expectancy. Its use in ducts has been prohibited by the state of California and by building codes in many other places.
## Usage in spaceflight.
According to NASA Warning Systems
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engineer Jerry Woodfill, a 52-year NASA veteran, duct tape had been stowed on board every mission since early in the Gemini days.
NASA engineers and astronauts have used duct tape in the course of their work, including in some emergency situations. One such usage occurred in 1970 when Woodfill was working in Mission Control, when the square carbon dioxide filters from Apollo 13's failed command module had to be modified to fit round receptacles in the lunar module, which was being used as a lifeboat after an explosion en route to the moon. A workaround used duct tape and other items on board Apollo 13, with the ground crew relaying instructions to the flight crew. The lunar module's CO scrubbers
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started working again, saving the lives of the three astronauts on board.
Ed Smylie, who designed the scrubber modification in just two days, said later that he knew the problem was solvable when it was confirmed that duct tape was on the spacecraft: "I felt like we were home free," he said in 2005. "One thing a Southern boy will never say is, 'I don't think duct tape will fix it.'"
Duct tape, referred to as ""...good old-fashioned American gray tape..."" was used by the Apollo 17 astronauts on the moon to improvise a repair to a damaged fender on the lunar rover, preventing possible damage from the spray of lunar dust as they drove.
## Military usage.
In the US submarine fleet, an adhesive
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cloth tape is called "EB Green," as the duct tape used by Electric Boat was green. It is also called "duck tape", "riggers' tape", "hurricane tape", or "100-mph tape"—a name that comes from the use of a specific variety of duct tape that was supposed to withstand up to winds. The tape is so named because it was used during the Vietnam War to repair or balance helicopter rotor blades.
# Alternative uses.
Duct tape's widespread popularity and multitude of uses has earned it a strong place in popular culture, and has inspired a vast number of creative and imaginative applications.
Duct tape occlusion therapy (DTOT) is a method intended to treat warts by covering them with duct tape for an extended
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period. The evidence for its effectiveness is poor; thus it is not recommended as routine treatment. However, other studies suggest the duct tape treatment is more effective than existing medical options. Duct tape is often used in shoe repair due to its resiliency.
Duct tape has been used to temporarily fix Apple's iPhone 4 dropped call issue, as an alternative to Apple's own rubber case.
## In popular culture.
The Duct Tape Guys (Jim Berg and Tim Nyberg) have written seven books about duct tape, . Their bestselling books have sold over 1.5 million copies and feature real and unusual uses of duct tape. In 1994 they coined the phrase "it ain't broke, it just lacks duct tape". Added to that
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phrase in 1995 with the publication of their book about lubricant WD-40 book was, "Two rules get you through life: If it's stuck and it's not supposed to be, WD-40 it. If it's not stuck and it's supposed to be, duct tape it". Their website features thousands of duct tape uses from people around the world ranging from fashions to auto repair. The combination of WD-40 and duct tape is sometimes referred to as "the redneck repair kit".
The Canadian sitcom "The Red Green Show" title character often used duct tape (which he dubbed "the handyman's secret weapon") as both a shortcut to proper fastening as well as for unconventional uses. The series sometimes showcased fan duct tape creations. The
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series had a feature film based on it entitled "Duct Tape Forever" and several VHS/DVD compilations of the show's use of the tape have been released. Since 2000, series star Steve Smith (as "Red Green") has been the "Ambassador of Scotch Duct Tape" for 3M.
The Discovery Channel series "MythBusters" featured duct tape in a number of myths that involve non-traditional uses. Confirmed myths include suspending a car for a period of time, building a functional cannon, a two-person sailboat, a two-person canoe (with duct tape paddles), a two-person raft, Roman sandals, a chess set, a leak proof water canister, rope, a hammock that can support the weight of an adult male, holding a car in place, a
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bridge that spanned the width of a dry dock, and a full-scale functional trebuchet with duct tape as the only binder. In the episode "Duct Tape Plane", the MythBusters repaired (and eventually replaced) the skin of a lightweight airplane with duct tape and flew it a few meters above a runway.
Garrison Keillor's radio show "A Prairie Home Companion" includes comedic fictional commercials sponsored by the "American Duct Tape Council".
# Duct tape alert.
The "duct tape alert" refers to the recommendations made by the U.S. Department of Homeland Security on February 10, 2003, that Americans should prepare for a biological, chemical, or radiological terrorist attack by assembling a "disaster supply
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kit", including duct tape and plastic (presumably to attempt to seal one's home against nuclear, chemical, and biological contaminants), among other items.
The recommendations came on the heels of an increase in the Department's official threat level to "orange", or "high risk", citing "recent intelligence reports".
According to press reports, the recommendations caused a surge in demand for duct tape.
The media sensation surrounding duct tape was fodder for comedians and satirists. Some referred to it as "duct and cover", a reference to duck and cover.
# See also.
- Speed tape
- List of adhesive tapes
# Specifications.
- ASTM International ASTM D5486 Standard Specification for Pressure-Sensitive
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Tape for Packaging, Box Closure, and Sealing, Type IV woven cloth backing
- ASTM D580 Standard Specification for Greige Woven Glass Tapes and Webbings
- ASTM D4514-12 Standard Specification for Friction Tape
- ASTM D2754-10 Standard Specification for High-Temperature Glass Cloth Pressure-Sensitive Electrical Insulating Tape
- MODUK DEF STAN 81-25, EN-Tape Pressure-Sensitive Adhesive (Water Resistant Fabric)
- McDonnell-Douglas DMS1968E
- Lockheed LCP-86-1226-A
- Boeing D 6-8099
- Ford specification ESB-M3G71-B
- etc.
## Books.
- "Pressure-Sensitive Adhesives and Applications", Istvan Benedek, 2004,
- "Pressure Sensitive Adhesive Tapes", J. Johnston, PSTC, 2003,
- "Pressure Sensitive
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M D4514-12 Standard Specification for Friction Tape
- ASTM D2754-10 Standard Specification for High-Temperature Glass Cloth Pressure-Sensitive Electrical Insulating Tape
- MODUK DEF STAN 81-25, EN-Tape Pressure-Sensitive Adhesive (Water Resistant Fabric)
- McDonnell-Douglas DMS1968E
- Lockheed LCP-86-1226-A
- Boeing D 6-8099
- Ford specification ESB-M3G71-B
- etc.
## Books.
- "Pressure-Sensitive Adhesives and Applications", Istvan Benedek, 2004,
- "Pressure Sensitive Adhesive Tapes", J. Johnston, PSTC, 2003,
- "Pressure Sensitive Formulation", I. Benedek, VSP, 2000,
# External links.
- Duct Sealant Longevity
- "Duct Tape and Cover" A spoof on the original "Duck and Cover" video
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Radiation pressure
Radiation pressure is the pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength which is absorbed, reflected, or otherwise emitted (e.g. black-body radiation) by matter on any scale (from macroscopic objects to dust particles to gas molecules).
The forces generated by radiation pressure are generally too small to be noticed under everyday circumstances; however, they are important in some physical processes. This particularly includes objects in outer space where it is usually the main force acting on objects besides gravity, and
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where the net effect of a tiny force may have a large cumulative effect over long periods of time. For example, had the effects of the sun's radiation pressure on the spacecraft of the Viking program been ignored, the spacecraft would have missed Mars orbit by about . Radiation pressure from starlight is crucial in a number of astrophysical processes as well. The significance of radiation pressure increases rapidly at extremely high temperatures, and can sometimes dwarf the usual gas pressure, for instance in stellar interiors and thermonuclear weapons.
Radiation pressure can equally well be accounted for by considering the momentum of a classical electromagnetic field or in terms of the momenta
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of photons, particles of light. The interaction of electromagnetic waves or photons with matter may involve an exchange of momentum. Due to the law of conservation of momentum, any change in the total momentum of the waves or photons must involve an equal and opposite change in the momentum of the matter it interacted with (Newton's third law of motion), as is illustrated in the accompanying figure for the case of light being perfectly reflected by a surface. This transfer of momentum is the general explanation for what we term radiation pressure.
# Discovery.
Johannes Kepler put forward the concept of radiation pressure back in 1619 to explain the observation that a tail of a comet always
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points away from the Sun.
The assertion that light, as electromagnetic radiation, has the property of momentum and thus exerts a pressure upon any surface it is exposed to was published by James Clerk Maxwell in 1862, and proven experimentally by Russian physicist Pyotr Lebedev in 1900 and by Ernest Fox Nichols and Gordon Ferrie Hull in 1901. The pressure is very feeble, but can be detected by allowing the radiation to fall upon a delicately poised vane of reflective metal in a Nichols radiometer (this should not be confused with the Crookes radiometer, whose characteristic motion is "not" caused by radiation pressure but by impacting gas molecules).
# Theory.
Radiation pressure can be viewed
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as a consequence of the conservation of momentum given the momentum attributed to electromagnetic radiation. That momentum can be equally well calculated on the basis of electromagnetic theory or from the combined momenta of a stream of photons, giving identical results as is shown below.
## Radiation pressure from momentum of an electromagnetic wave.
According to Maxwell's theory of electromagnetism, an electromagnetic wave carries momentum, which will be transferred to an opaque surface it strikes.
The energy flux (irradiance) of a plane wave is calculated using the Poynting vector formula_1, whose magnitude we denote by S. S divided by the speed of light is the density of the linear momentum
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per unit area (pressure) of the electromagnetic field. So, dimensionally, the Poynting vector is S=(power/area)=(rate of doing work/area)=(ΔF/Δt)Δx/area, which is the speed of light, c=Δx/Δt, times pressure, ΔF/area. That pressure is experienced as radiation pressure on the surface:
where formula_3 is pressure (usually in Pascals), formula_4 is the incident irradiance (usually in W/m) and formula_5 is the speed of light in vacuum.
If the surface is planar at an angle α to the incident wave, the intensity across the surface will be geometrically reduced by the cosine of that angle and the component of the radiation force against the surface will also be reduced by the cosine of α, resulting
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in a pressure:
The momentum from the incident wave is in the same direction of that wave. But only the component of that momentum normal to the surface contributes to the pressure on the surface, as given above. The component of that force tangent to the surface is not called pressure.
## Radiation pressure from reflection.
The above treatment for an incident wave accounts for the radiation pressure experienced by a black (totally absorbing) body. If the wave is specularly reflected, then the recoil due to the reflected wave will further contribute to the radiation pressure. In the case of a perfect reflector, this pressure will be identical to the pressure caused by the incident wave:
thus
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"doubling" the net radiation pressure on the surface:
For a partially reflective surface, the second term must be multiplied by the reflectivity (also known as reflection coefficient of intensity), so that the increase is less than double. For a diffusely reflective surface, the details of the reflection and geometry must be taken into account, again resulting in an increased net radiation pressure of less than double.
## Radiation pressure by emission.
Just as a wave reflected from a body contributes to the net radiation pressure experienced, a body that emits radiation of its own (rather than reflected) obtains a radiation pressure again given by the irradiance of that emission "in the
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direction normal to the surface" "I":
The emission can be from black-body radiation or any other radiative mechanism. Since all materials emit black-body radiation (unless they are totally reflective or at absolute zero), this source for radiation pressure is ubiquitous but usually very tiny. However, because black-body radiation increases rapidly with temperature (according to the fourth power of temperature as given by the Stefan–Boltzmann law), radiation pressure due to the temperature of a very hot object (or due to incoming black-body radiation from similarly hot surroundings) can become very significant. This becomes important in stellar interiors which are at millions of degrees.
##
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Radiation pressure in terms of photons.
Electromagnetic radiation can be viewed in terms of particles rather than waves; these particles are known as photons. Photons do not have a rest-mass; however, photons are never at rest (they move at the speed of light) and acquire a momentum nonetheless which is given by:
where "p" is momentum, "h" is Planck's constant, λ is wavelength, and "c" is speed of light in vacuum. And "E" is the energy of a single photon given by:
The radiation pressure again can be seen as the transfer of each photon's momentum to the opaque surface, plus the momentum due to a (possible) recoil photon for a (partially) reflecting surface. Since an incident wave of irradiance
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"I" over an area "A" has a power of "IA", this implies a flux of "I/E" photons per second per unit area striking the surface. Combining this with the above expression for the momentum of a single photon, results in the same relationships between irradiance and radiation pressure described above using classical electromagnetics. And again, reflected or otherwise emitted photons will contribute to the net radiation pressure identically.
## Compression in a uniform radiation field.
In general, the pressure of electromagnetic waves can be obtained from the vanishing of the trace of the electromagnetic stress tensor: Since this trace equals 3"P" – "u", we get
where "u" is the radiation density
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per unit volume.
This can also be shown in the specific case of the pressure exerted on surfaces of a body in thermal equilibrium with its surroundings, at a temperature "T": The body will be surrounded by a uniform radiation field described by the Planck black-body radiation law, and will experience a compressive pressure due to that impinging radiation, its reflection, and its own black body emission. From that it can be shown that the resulting pressure is equal to one third of the total radiant energy per unit volume in the surrounding space.
By using Stefan–Boltzmann law, this can be expressed as
where formula_14 is the Stefan–Boltzmann constant.
# Solar radiation pressure.
Solar radiation
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pressure is due to the sun's radiation at closer distances, thus especially within the Solar System. While it acts on all objects, its net effect is generally greater on smaller bodies since they have a larger ratio of surface area to mass. All spacecraft experience such a pressure except when they are behind the shadow of a larger orbiting body.
Solar radiation pressure on objects near the earth may be calculated using the sun's irradiance at 1 AU, known as the solar constant or "G", whose value is set at 1361 W/m as of 2011.
All stars have a spectral energy distribution that depends on their surface temperature. The distribution is approximately that of black-body radiation. This distribution
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must be taken into account when calculating the radiation pressure or identifying reflector materials for optimizing a solar sail for instance.
## Pressures of absorption and reflection.
Solar radiation pressure at the earth's distance from the sun, may be calculated by dividing the solar constant "G" (above) by the speed of light c. For an absorbing sheet facing the sun, this is simply:
This result is in the S.I. unit Pascals, equivalent to N/m (newtons per square meter). For a sheet at an angle α to the sun, the effective area "A" of a sheet is reduced by a geometrical factor resulting in a force "in the direction of the sunlight" of:
To find the component of this force normal to the surface,
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another cosine factor must be applied resulting in a pressure "P" on the surface of:
Note, however, that in order to account for the net effect of solar radiation on a spacecraft for instance, one would need to consider the "total" force (in the direction away from the sun) given by the preceding equation, rather than just the component normal to the surface that we identify as "pressure".
The solar constant is defined for the sun's radiation at the distance to the earth, also known as one astronomical unit (AU). Consequently, at a distance of "R" astronomical units ("R" thus being dimensionless), applying the inverse-square law, we would find:
Finally, considering not an absorbing but a
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perfectly reflecting surface, the pressure is "doubled" due to the reflected wave, resulting in:
Note that unlike the case of an absorbing material, the resulting force on a reflecting body is given exactly by this pressure acting normal to the surface, with the tangential forces from the incident and reflecting waves canceling each other. In practice, materials are neither totally reflecting nor totally absorbing, so the resulting force will be a weighted average of the forces calculated using these formulae.
## Radiation pressure perturbations.
Solar radiation pressure is a source of orbital perturbations. It significantly affects the orbits and trajectories of small bodies including all
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spacecraft.
Solar radiation pressure affects bodies throughout much of the Solar System. Small bodies are more affected than large ones because of their lower mass relative to their surface area. Spacecraft are affected along with natural bodies (comets, asteroids, dust grains, gas molecules).
The radiation pressure results in forces and torques on the bodies that can change their translational and rotational motions. Translational changes affect the orbits of the bodies. Rotational rates may increase or decrease. Loosely aggregated bodies may break apart under high rotation rates. Dust grains can either leave the Solar System or spiral into the Sun.
A whole body is typically composed of
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numerous surfaces that have different orientations on the body. The facets may be flat or curved. They will have different areas. They may have optical properties differing from other aspects.
At any particular time, some facets will be exposed to the Sun and some will be in shadow. Each surface exposed to the Sun will be reflecting, absorbing, and emitting radiation. Facets in shadow will be emitting radiation. The summation of pressures across all of the facets will define the net force and torque on the body. These can be calculated using the equations in the preceding sections.
The Yarkovsky effect affects the translation of a small body. It results from a face leaving solar exposure being
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at a higher temperature than a face approaching solar exposure. The radiation emitted from the warmer face will be more intense than that of the opposite face, resulting in a net force on the body that will affect its motion.
The YORP effect is a collection of effects expanding upon the earlier concept of the Yarkovsky effect, but of a similar nature. It affects the spin properties of bodies.
The Poynting–Robertson effect applies to grain-size particles. From the perspective of a grain of dust circling the Sun, the Sun's radiation appears to be coming from a slightly forward direction (aberration of light). Therefore, the absorption of this radiation leads to a force with a component against
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the direction of movement. (The angle of aberration is tiny since the radiation is moving at the speed of light while the dust grain is moving many orders of magnitude slower than that.) The result is a gradual spiral of dust grains into the Sun. Over long periods of time, this effect cleans out much of the dust in the Solar System.
While rather small in comparison to other forces, the radiation pressure force is inexorable. Over long periods of time, the net effect of the force is substantial. Such feeble pressures can produce marked effects upon minute particles like gas ions and electrons, and are essential in the theory of electron emission from the Sun, of cometary material, and so on.
Because
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the ratio of surface area to volume (and thus mass) increases with decreasing particle size, dusty (micrometre-size) particles are susceptible to radiation pressure even in the outer solar system. For example, the evolution of the outer rings of Saturn is significantly influenced by radiation pressure.
As a consequence of light pressure, Einstein in 1909 predicted the existence of "radiation friction" which would oppose the movement of matter. He wrote, "radiation will exert pressure on both sides of the plate. The forces of pressure exerted on the two sides are equal if the plate is at rest. However, if it is in motion, more radiation will be reflected on the surface that is ahead during the
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motion (front surface) than on the back surface. The backward acting force of pressure exerted on the front surface is thus larger than the force of pressure acting on the back. Hence, as the resultant of the two forces, there remains a force that counteracts the motion of the plate and that increases with the velocity of the plate. We will call this resultant 'radiation friction' in brief."
## Solar sails.
Solar sailing, an experimental method of spacecraft propulsion, uses radiation pressure from the Sun as a motive force. The idea of interplanetary travel by light was mentioned by Jules Verne in "From the Earth to the Moon".
A sail reflects about 90% of the incident radiation. The 10%
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that is absorbed is radiated away from both surfaces, with the proportion emitted from the unlit surface depending on the thermal conductivity of the sail. A sail has curvature, surface irregularities, and other minor factors that affect its performance.
The Japan Aerospace Exploration Agency (JAXA) has successfully unfurled a solar sail in space which has already succeeded in propelling its payload with the IKAROS project.
# Cosmic effects of radiation pressure.
Radiation pressure has had a major effect on the development of the cosmos, from the birth of the universe to ongoing formation of stars and shaping of clouds of dust and gasses on a wide range of scales.
## The early universe.
The
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photon epoch is a phase when the energy of the universe was dominated by photons, between 10 seconds and 380,000 years after the Big Bang.
## Galaxy formation and evolution.
The process of galaxy formation and evolution began early in the history of the cosmos. Observations of the early universe strongly suggest that objects grew from bottom-up (i.e., smaller objects merging to form larger ones). As stars are thereby formed and become sources of electromagnetic radiation, radiation pressure from the stars becomes a factor in the dynamics of remaining circumstellar material.
## Clouds of dust and gases.
The gravitational compression of clouds of dust and gases is strongly influenced by radiation
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pressure, especially when the condensations lead to star births. The larger young stars forming within the compressed clouds emit intense levels of radiation that shift the clouds, causing either dispersion or condensations in nearby regions, which influences birth rates in those nearby regions.
## Clusters of stars.
Stars predominantly form in regions of large clouds of dust and gases, giving rise to star clusters. Radiation pressure from the member stars eventually disperses the clouds, which can have a profound effect on the evolution of the cluster.
Many open clusters are inherently unstable, with a small enough mass that the escape velocity of the system is lower than the average velocity
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of the constituent stars. These clusters will rapidly disperse within a few million years. In many cases, the stripping away of the gas from which the cluster formed by the radiation pressure of the hot young stars reduces the cluster mass enough to allow rapid dispersal.
## Star formation.
Star formation is the process by which dense regions within molecular clouds in interstellar space collapse to form stars. As a branch of astronomy, star formation includes the study of the interstellar medium and giant molecular clouds (GMC) as precursors to the star formation process, and the study of protostars and young stellar objects as its immediate products. Star formation theory, as well as accounting
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for the formation of a single star, must also account for the statistics of binary stars and the initial mass function.
## Stellar planetary systems.
Planetary systems are generally believed to form as part of the same process that results in star formation. A protoplanetary disk forms by gravitational collapse of a molecular cloud, called a solar nebula, and then evolves into a planetary system by collisions and gravitational capture. Radiation pressure can clear a region in the immediate vicinity of the star. As the formation process continues, radiation pressure continues to play a role in affecting the distribution of matter. In particular, dust and grains can spiral into the star or escape
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the stellar system under the action of radiation pressure.
## Stellar interiors.
In stellar interiors the temperatures are very high. Stellar models predict a temperature of 15 MK in the center of the Sun, and at the cores of supergiant stars the temperature may exceed 1 GK. As the radiation pressure scales as the fourth power of the temperature, it becomes important at these high temperatures. In the Sun, radiation pressure is still quite small when compared to the gas pressure. In the heaviest non-degenerate stars, radiation pressure is the dominant pressure component.
## Comets.
Solar radiation pressure strongly affects comet tails. Solar heating causes gases to be released from the comet
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nucleus, which also carry away dust grains. Radiation pressure and solar wind then drive the dust and gases away from the Sun's direction. The gases form a generally straight tail, while slower moving dust particles create a broader, curving tail.
# Laser applications of radiation pressure.
## Optical tweezers.
Lasers can be used as a source of monochromatic light with wavelength formula_20. With a set of lenses, one can focus the laser beam to a point that is formula_20 in diameter (or formula_22).
The radiation pressure of a 30 mW laser of 1064 nm can therefore be computed as follows:
formula_23
formula_24
formula_25
This is used in optical tweezers.
## Other examples.
Laser cooling
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is applied to cooling materials very close to absolute zero. Atoms traveling towards a laser light source perceive a doppler effect tuned to the absorption frequency of the target element. The radiation pressure on the atom slows movement in a particular direction until the Doppler effect moves out of the frequency range of the element, causing an overall cooling effect.
Large lasers operating in space have been suggested as a means of propelling sail craft in beam-powered propulsion.
The reflection of a laser pulse from the surface of an elastic solid gives rise to various types of elastic waves that propagate inside the solid. The weakest waves are generally those that are generated by the
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radiation pressure acting during the reflection of the light. Recently, such light-pressure-induced elastic waves were observed inside an ultrahigh-reflectivity dielectric mirror. These waves are the most basic fingerprint of a light-solid matter interaction on the macroscopic scale.
# See also.
- Absorption (electromagnetic radiation)
- Photon
- Poynting vector
- Poynting–Robertson effect
- Solar constant
- Solar sail
- Sunlight
- Wave–particle duality
- Yarkovsky effect
- Yarkovsky–O'Keefe–Radzievskii–Paddack effect
# Further reading.
- Demir, Dilek,"A table-top demonstration of radiation pressure",2011, Diplomathesis, E-Theses univie (http://othes.univie.ac.at/16381/)
- R. Shankar,
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light. Recently, such light-pressure-induced elastic waves were observed inside an ultrahigh-reflectivity dielectric mirror. These waves are the most basic fingerprint of a light-solid matter interaction on the macroscopic scale.
# See also.
- Absorption (electromagnetic radiation)
- Photon
- Poynting vector
- Poynting–Robertson effect
- Solar constant
- Solar sail
- Sunlight
- Wave–particle duality
- Yarkovsky effect
- Yarkovsky–O'Keefe–Radzievskii–Paddack effect
# Further reading.
- Demir, Dilek,"A table-top demonstration of radiation pressure",2011, Diplomathesis, E-Theses univie (http://othes.univie.ac.at/16381/)
- R. Shankar, "Principles of Quantum Mechanics", 2nd edition.
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Silicon dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as synthetic product. Notable examples include fused quartz, fumed silica, silica gel, and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries.
Inhaling finely divided crystalline silica is toxic and can lead to severe inflammation
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of the lung tissue, silicosis, bronchitis, lung cancer, and systemic autoimmune diseases, such as lupus and rheumatoid arthritis.
Inhalation of amorphous silicon dioxide, in high doses, leads to non-permanent short-term inflammation, where all effects heal.
# Structure.
In the majority of silicates, the silicon atom shows tetrahedral coordination, with four oxygen atoms surrounding a central Si atom. The most common example is seen in the quartz polymorphs.
It is a 3 dimensional network solid in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms.
For example, in the unit cell of α-quartz, the central tetrahedron shares all four of its corner O atoms,
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the two face-centered tetrahedra share two of their corner O atoms, and the four edge-centered tetrahedra share just one of their O atoms with other SiO tetrahedra. This leaves a net average of 12 out of 24 total vertices for that portion of the seven SiO tetrahedra that are considered to be a part of the unit cell for silica (see 3-D Unit Cell).
SiO has a number of distinct crystalline forms (polymorphs) in addition to amorphous forms. With the exception of stishovite and fibrous silica, all of the crystalline forms involve tetrahedral SiO units linked together by shared vertices in different arrangements. Silicon–oxygen bond lengths vary between the different crystal forms; for example in
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α-quartz the bond length is 161 pm, whereas in α-tridymite it is in the range 154–171 pm. The Si-O-Si angle also varies between a low value of 140° in α-tridymite, up to 180° in β-tridymite. In α-quartz, the Si-O-Si angle is 144°.
Fibrous silica has a structure similar to that of SiS with chains of edge-sharing SiO tetrahedra. Stishovite, the higher-pressure form, in contrast, has a rutile-like structure where silicon is 6-coordinate. The density of stishovite is 4.287 g/cm, which compares to α-quartz, the densest of the low-pressure forms, which has a density of 2.648 g/cm. The difference in density can be ascribed to the increase in coordination as the six shortest Si-O bond lengths in stishovite
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(four Si-O bond lengths of 176 pm and two others of 181 pm) are greater than the Si-O bond length (161 pm) in α-quartz.
The change in the coordination increases the ionicity of the Si-O bond. More importantly, any deviations from these standard parameters constitute microstructural differences or variations, which represent an approach to an amorphous, vitreous, or glassy solid.
The only stable form under normal conditions is alpha quartz, in which crystalline silicon dioxide is usually encountered. In nature, impurities in crystalline α-quartz can give rise to colors (see list). The high-temperature minerals, cristobalite and tridymite, have both lower densities and indices of refraction
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than quartz. Since the composition is identical, the reason for the discrepancies must be in the increased spacing in the high-temperature minerals. As is common with many substances, the higher the temperature, the farther apart the atoms are, due to the increased vibration energy.
The transformation from α-quartz to beta-quartz takes place abruptly at 573 °C. Since the transformation is accompanied by a significant change in volume, it can easily induce fracturing of ceramics or rocks passing through this temperature limit.
The high-pressure minerals, seifertite, stishovite, and coesite, though, have higher densities and indices of refraction than quartz. This is probably due to the intense
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compression of the atoms occurring during their formation, resulting in more condensed structure.
Faujasite silica is another form of crystalline silica. It is obtained by dealumination of a low-sodium, ultra-stable Y zeolite with combined acid and thermal treatment. The resulting product contains over 99% silica, and has high crystallinity and surface area (over 800 m/g). Faujasite-silica has very high thermal and acid stability. For example, it maintains a high degree of long-range molecular order or crystallinity even after boiling in concentrated hydrochloric acid.
Molten silica exhibits several peculiar physical characteristics that are similar to those observed in liquid water: negative
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temperature expansion, density maximum at temperatures ~5000 °C, and a heat capacity minimum. Its density decreases from 2.08 g/cm at 1950 °C to 2.03 g/cm at 2200 °C.
Molecular SiO with a linear structure is produced when molecular silicon monoxide, SiO, is condensed in an argon matrix cooled with helium along with oxygen atoms generated by microwave discharge.
Dimeric silicon dioxide, (SiO) has been prepared by reacting O with matrix isolated dimeric silicon monoxide, (SiO). In dimeric silicon dioxide there are two oxygen atoms bridging between the silicon atoms with an Si-O-Si angle of 94° and bond length of 164.6 pm and the terminal Si-O bond length is 150.2 pm. The Si-O bond length is
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148.3 pm, which compares with the length of 161 pm in α-quartz. The bond energy is estimated at 621.7 kJ/mol.
# Natural occurrence.
## Geology.
Silica with the chemical formula is most commonly found in nature as quartz, which comprises more than 10% by mass of the earth's crust. Quartz is the only polymorph of silica stable at the Earth's surface. Metastable occurrences of the high-pressure forms coesite and stishovite have been found around impact structures and associated with eclogites formed during ultra-high-pressure metamorphism. The high-temperature forms of tridymite and cristobalite are known from silica-rich volcanic rocks. In many parts of the world, silica is the major constituent
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of sand.
## Biology.
Even though it is poorly soluble, silica occurs in many plants. Plant materials with high silica phytolith content appear to be of importance to grazing animals, from chewing insects to ungulates. Silica accelerates tooth wear, and high levels of silica in plants frequently eaten by herbivores may have developed as a defense mechanism against predation.
Silica is also the primary component of rice husk ash, which is used, for example, in filtration and cement manufacturing.
For well over a billion years, silicification in and by cells has been common in the biological world. In the modern world it occurs in bacteria, single-celled organisms, plants, and animals (invertebrates
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and vertebrates).
Prominent examples include:
- Tests or frustules (i.e. shells) of diatoms, Radiolaria and testate amoebae.
- Silica phytoliths in the cells of many plants, including Equisetaceae, practically all grasses, and a wide range of dicotyledons.
- The spicules forming the skeleton of many sponges.
Crystalline minerals formed in the physiological environment often show exceptional physical properties (e.g., strength, hardness, fracture toughness) and tend to form hierarchical structures that exhibit microstructural order over a range of scales. The minerals are crystallized from an environment that is undersaturated with respect to silicon, and under conditions of neutral pH and
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low temperature (0–40 °C).
Formation of the mineral may occur either within the cell wall of an organism (such as with phytoliths), or outside the cell wall, as typically happens with tests. Specific biochemical reactions exist for mineral deposition. Such reactions include those that involve lipids, proteins, and carbohydrates.
It is unclear in what ways silica is important in the nutrition of animals. This field of research is challenging because silica is ubiquitous and in most circumstances dissolves in trace quantities only. All the same it certainly does occur in the living body, leaving us with the problem that it is hard to create proper silica-free controls for purposes of research.
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This makes it difficult to be sure when the silica present has had operative beneficial effects, and when its presence is coincidental, or even harmful. The current consensus is that it certainly seems important in the growth, strength, and management of many connective tissues. This is true not only for hard connective tissues such as bone and tooth but possibly in the biochemistry of the subcellular enzyme-containing structures as well.
# Uses.
## Structural use.
An estimated 95% of silicon dioxide (sand) produced is consumed in the construction industry, e.g. for the production of concrete (Portland cement concrete).
Silica, in the form of sand is used as the main ingredient in sand casting
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for the manufacture of metallic components in engineering and other applications. The high melting point of silica enables it to be used in such applications.
Crystalline silica is used in hydraulic fracturing of formations which contain tight oil and shale gas.
## Precursor to glass and silicon.
Silica is the primary ingredient in the production of most glass. The glass transition temperature of pure SiO is about 1475 K. When molten silicon dioxide SiO is rapidly cooled, it does not crystallize, but solidifies as a glass.
The structural geometry of silicon and oxygen in glass is similar to that in quartz and most other crystalline forms of silicon and oxygen with silicon surrounded by regular
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tetrahedra of oxygen centers. The difference between the glass and crystalline forms arises from the connectivity of the tetrahedral units: Although there is no long range periodicity in the glassy network ordering remains at length scales well beyond the SiO bond length. One example of this ordering is the preference to form rings of 6-tetrahedra.
## Fumed silica.
Fumed silica also known as pyrogenic silica is a very fine particulate or colloidal form of silicon dioxide. It is prepared by burning SiCl in an oxygen-rich hydrogen flame to produce a "smoke" of SiO.
The majority of optical fibers for telecommunication are also made from silica. It is a primary raw material for many ceramics
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such as earthenware, stoneware, and porcelain.
Silicon dioxide is used to produce elemental silicon. The process involves carbothermic reduction in an electric arc furnace:
## Food and pharmaceutical applications.
Silica is a common additive in food production, where it is used primarily as a flow agent in powdered foods, or to adsorb water in hygroscopic applications. It is used as an anti-caking agent in powdered foods such as spices and non-dairy coffee creamer. It is the primary component of diatomaceous earth. Colloidal silica is also used as a wine, beer, and juice fining agent. It has the E number reference E551.
In pharmaceutical products, silica aids powder flow when tablets are
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formed.
## Personal care.
In cosmetics, it is useful for its light-diffusing properties and natural absorbency.
Hydrated silica is used in toothpaste as a hard abrasive to remove tooth plaque.
## Other.
Hydrophobic silica is used as a defoamer component.
In its capacity as a refractory, it is useful in fiber form as a high-temperature thermal protection fabric.
Silica is used in the extraction of DNA and RNA due to its ability to bind to the nucleic acids under the presence of chaotropes.
A silica-based aerogel was used in the Stardust spacecraft to collect extraterrestrial particles.
Pure silica (silicon dioxide), when cooled as fused quartz into a glass with no true melting point,
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can be used as a glass fiber for fiberglass.
# Production.
Silicon dioxide is mostly obtained by mining, including sand mining and purification of quartz.
Quartz is suitable for many purposes, while chemical processing is required to make a purer or otherwise more suitable (e.g. more reactive or fine-grained) product.
## Silica fume.
Silica fume is obtained as byproduct from hot processes like ferrosilicon production. It is less pure than fumed silica and should not be confused with that product. The production process, particle characteristics and fields of application of fumed silica are all different from those of silica fume.
## Precipitated silica.
Precipitated silica or amorphous
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silica is produced by the acidification of solutions of sodium silicate. The gelatinous precipitate or silica gel, is first washed and then dehydrated to produce colorless microporous silica. The idealized equation involving a trisilicate and sulfuric acid is:
Approximately one billion kilograms/year (1999) of silica were produced in this manner, mainly for use for polymer composites – tires and shoe soles.
## On microchips.
Thin films of silica grow spontaneously on silicon wafers via thermal oxidation, producing a very shallow layer of about 1 nm or 10 Å of so-called native oxide.
Higher temperatures and alternative environments are used to grow well-controlled layers of silicon dioxide
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on silicon, for example at temperatures between 600 and 1200 °C, using so-called dry or wet oxidation with O
or HO, respectively.
The native oxide layer is beneficial in microelectronics, where it acts as electric insulator with high chemical stability. It can protect the silicon, store charge, block current, and even act as a controlled pathway to limit current flow.
## Laboratory or special methods.
### From organosilicon compounds.
Many routes to silicon dioxide start with an organosilicon compound, e.g., HMDSO, TEOS. Synthesis of silica is illustrated below using tetraethyl orthosilicate (TEOS). Simply heating TEOS at 680–730 °C results in the oxide:
Similarly TEOS combusts around
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400 °C:
TEOS undergoes hydrolysis via the so-called sol-gel process. The course of the reaction and nature of the product are affected by catalysts, but the idealized equation is:
### Other methods.
Being highly stable, silicon dioxide arises from many methods. Conceptually simple, but of little practical value, combustion of silane gives silicon dioxide. This reaction is analogous to the combustion of methane:
However the chemical vapor deposition of silicon dioxide onto crystal surface from silane had been used using nitrogen as a carrier gas at 200–500 °C.
# Chemical reactions.
Silica is converted to silicon by reduction with carbon.
Fluorine reacts with silicon dioxide to form SiF
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and O whereas the other halogen gases (Cl, Br, I) are essentially unreactive.
Silicon dioxide is attacked by hydrofluoric acid (HF) to produce hexafluorosilicic acid:
HF is used to remove or pattern silicon dioxide in the semiconductor industry.
Under normal conditions, silicon does not react with most acids but is dissolved by hydrofluoric acid.
Silicon is attacked by bases such as aqueous sodium hydroxide to give silicates.
Silicon dioxide acts as a Lux–Flood acid, being able to react with bases under certain conditions. As it does not contain any hydrogen, it cannot act as a Brønsted–Lowry acid. While not soluble in water, some strong bases will react with glass and have to be stored
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in plastic bottles as a result.
Silicon dioxide dissolves in hot concentrated alkali or fused hydroxide, as described in this idealized equation:
Silicon dioxide will neutralise basic metal oxides (e.g. sodium oxide, potassium oxide, lead(II) oxide, zinc oxide, or mixtures of oxides, forming silicates and glasses as the Si-O-Si bonds in silica are broken successively). As an example the reaction of sodium oxide and SiO can produce sodium orthosilicate, sodium silicate, and glasses, dependent on the proportions of reactants:
Examples of such glasses have commercial significance, e.g. soda-lime glass, borosilicate glass, lead glass. In these glasses, silica is termed the network former or lattice
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former. The reaction is also used in blast furnaces to remove sand impurities in the ore by neutralisation with calcium oxide, forming calcium silicate slag.
Silicon dioxide reacts in heated reflux under dinitrogen with ethylene glycol and an alkali metal base to produce highly reactive, pentacoordinate silicates which provide access to a wide variety of new silicon compounds. The silicates are essentially insoluble in all polar solvent except methanol.
Silicon dioxide reacts with elemental silicon at high temperatures to produce SiO:
## Water solubility.
The solubility of silicon dioxide in water strongly depends on its crystalline form and is three-four times higher for silica than quartz;
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as a function of temperature, it peaks around 340 °C. This property is used to grow single crystals of quartz in a hydrothermal process where natural quartz is dissolved in superheated water in a pressure vessel that is cooler at the top. Crystals of 0.5–1 kg can be grown over a period of 1–2 months. These crystals are a source of very pure quartz for use in electronic applications.
# Health effects.
Silica ingested orally is essentially nontoxic, with an of 5000 mg/kg (5 g/kg). A 2008 study following subjects for 15 years found that higher levels of silica in water appeared to decrease the risk of dementia. An increase of 10 mg/day of silica in drinking water was associated with a decreased
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risk of dementia of 11%.
Inhaling finely divided crystalline silica dust can lead to silicosis, bronchitis, or lung cancer, as the dust becomes lodged in the lungs and continuously irritates the tissue, reducing lung capacities. When fine silica particles are inhaled in large enough quantities (such as through occupational exposure), it increases the risk of systemic autoimmune diseases such as lupus and rheumatoid arthritis compared to expected rates in the general population.
## Occupational hazard.
Silica is an occupational hazard for people who do sandblasting, or work with products that contain powdered crystalline silica. Amorphous silica, such as fumed silica, may cause irreversible
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lung damage in some cases, but is not associated with development of silicosis. Children, asthmatics of any age, those with allergies, and the elderly (all of whom have reduced lung capacity) can be affected in less time.
Crystalline silica is an occupational hazard for those working with stone countertops, because the process of cutting and installing the countertops creates large amounts of airborne silica. Crystalline silica used in hydraulic fracturing presents a health hazard to workers.
## Pathophysiology.
In the body, crystalline silica particles do not dissolve over clinically relevant periods. Silica crystals inside the lungs can activate the NLRP3 inflammasome inside macrophages
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and dendritic cells and thereby result in production of interleukin, a highly pro-inflammatory cytokine in the immune system.
## Regulation.
Regulations restricting silica exposure 'with respect to the silicosis hazard' specify that they are concerned only with silica, which is both crystalline and dust-forming.
In 2013, the U.S. Occupational Safety and Health Administration reduced the exposure limit to 50 µg/m of air. Prior to 2013, it had allowed 100 µg/m and in construction workers even 250 µg/m.
In 2013, OSHA also required "green completion" of fracked wells to reduce exposure to crystalline silica besides restricting the limit of exposure.
# Crystalline forms.
SiO, more so than
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almost any material, exists in many crystalline forms. These forms are called polymorphs.
# See also.
- Mesoporous silica
- Silicon carbide
# External links.
- Tridymite,
- Quartz,
- Cristobalite,
- amorphous, NIOSH Pocket Guide to Chemical Hazards
- crystalline, as respirable dust, NIOSH Pocket Guide to Chemical Hazards
- Formation of silicon oxide layers in the semiconductor industry. LPCVD and PECVD method in comparison. Stress prevention.
- Quartz SiO piezoelectric properties
- Silica (SiO) and Water
- Epidemiological evidence on the carcinogenicity of silica: factors in scientific judgement by C. Soutar and others. Institute of Occupational Medicine Research Report TM/97/09
-
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ket Guide to Chemical Hazards
- Formation of silicon oxide layers in the semiconductor industry. LPCVD and PECVD method in comparison. Stress prevention.
- Quartz SiO piezoelectric properties
- Silica (SiO) and Water
- Epidemiological evidence on the carcinogenicity of silica: factors in scientific judgement by C. Soutar and others. Institute of Occupational Medicine Research Report TM/97/09
- Scientific opinion on the health effects of airborne silica by A Pilkington and others. Institute of Occupational Medicine Research Report TM/95/08
- The toxic effects of silica by A Seaton and others. Institute of Occupational Medicine Research Report TM/87/13
- Structure of precipitated silica
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Hammer throw
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Hammer throw
The hammer throw is one of the four throwing events in regular track and field competitions, along with the discus throw, shot put and javelin. The "hammer" used in this sport is not like any of the tools also called by that name. It consists of a metal ball attached by a steel wire to a grip. The size of the ball varies between men's and women's competitions (see Competition section below for details).
# History.
With roots dating back to the 15th century, the contemporary version of the hammer throw is one of the oldest of Olympic Games competitions, first included at the 1900 games in Paris, France (the second Olympiad of the modern era). Its history since the late 1960s and
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legacy prior to inclusion in the Olympics have been dominated by European and Eastern European influence, which has affected interest in the event in other parts of the world.
The hammer evolved from its early informal origins to become part of the Scottish Highland games in the late 18th century, where the original version of the event is still contested today.
While the men's hammer throw has been part of the Olympics since 1900, the International Association of Athletics Federations did not start ratifying women's marks until 1995. Women's hammer throw was first included in the Olympics at the 2000 summer games in Sydney, Australia, after having been included in the World Championships
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a year earlier.
# Competition.
The men's hammer weighs and measures in length, and the women's hammer weighs and in length. Like the other throwing events, the competition is decided by who can throw the implement the farthest.
Although commonly thought of as a strength event, technical advancements in the last 30 years have evolved hammer throw competition to a point where more focus is on speed in order to gain maximum distance.
The throwing motion involves about two swings from stationary position, then three, four or very rarely five rotations of the body in circular motion using a complicated heel-toe movement of the foot. The ball moves in a circular path, gradually increasing in velocity
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with each turn with the high point of the hammer ball toward the target sector and the low point at the back of the circle. The thrower releases the ball from the front of the circle.
The world record for the women's hammer is held by Anita Włodarczyk, who threw during the Kamila Skolimowska Memorial on 28 August 2016.
# All-time top 25 hammer throwers.
## Men.
- Updated August 2015
### Notes.
Below is a list of all other throws superior to 86.50 metres:
- Yuriy Sedykh 86.66 m (1986). Sedykh also threw 86.68 m and 86.62 m ancillary marks during world record competition.
### Non-legal marks.
- Ivan Tsikhan of Belarus also threw 86.73 on 3 July 2005 in Brest, but this performance was
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annulled due to drugs disqualification.
## Women.
- Correct as of July 2019.
### Notes.
Below is a list of throws equal or superior to 78.00 m:
- Anita Włodarczyk also threw 82.87 m (2017), 82.29 m (2016), 81.77 m (2016), 81.74 (2016), 81.63 m (2017), 81.27 m (2016), 81.08 m (2015), 80.85 m (2015), 80.79 m (2017), 80.73 m (2017), 80.69 m (2017), 80.42 m (2017), 80.40 m (2016), 80.31 m (2016), 80.26 m (2016), 79.80 m (2017), 79.73 m (2017), 79.72 m (2017), 79.68 m (2016, 2017), 79.67 m (2016), 79.63 m (2017), 79.62 m (2016), 79.61 m (2016), 79.59 m (2018), 79.58 m (2016), 79.48 m (2016), 79.45 m (2016), 79.39 m (2016), 79.27 m (2017), 79.23 m (2017), 79.07 m (2017), 79.06 m (2017), 78.94
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m (2018), 78.76 m (2014), 78.74 m (2018), 78.69 m (2016), 78.59 m (2017), 78.55 m (2018), 78.54 m (2016), 78.52 m (2017), 78.46 m (2013), 78.35 m (2017), 78.30 m (2010), 78.28 m (2015), 78.24 m (2015), 78.22 m (2013), 78.17 m (2014), 78.16 m (2015), 78.14 m (2016), 78.10 (2016), 78.00 m (2017).
- Tatyana Lysenko also threw 78.51 m (2012) and 78.15 m (2013)
- Betty Heidler also threw 78.07 m (2012) and 78.00 m (2014).
### Non-legal marks.
The following athletes had their performances (over 77.00 m) annulled due to doping offences:
- Aksana Miankova (Belarus) 78.69 m and 78.19 m (both 2012)
- Gulfiya Agafonova (Russia) 77.36 m (2007)
# See also.
- List of hammer throwers
# External links.
-
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4 m (2016), 78.10 (2016), 78.00 m (2017).
- Tatyana Lysenko also threw 78.51 m (2012) and 78.15 m (2013)
- Betty Heidler also threw 78.07 m (2012) and 78.00 m (2014).
### Non-legal marks.
The following athletes had their performances (over 77.00 m) annulled due to doping offences:
- Aksana Miankova (Belarus) 78.69 m and 78.19 m (both 2012)
- Gulfiya Agafonova (Russia) 77.36 m (2007)
# See also.
- List of hammer throwers
# External links.
- IAAF list of hammer-throw records in XML
- HammerThrow.eu (Results, Top-Lists, Records, Videos, ...)
- HammerThrow.org (Information about the event, coaching tips and resources, ...)
- Statistics
- Hammer Throw Records
- Hammer Throw History
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Saint Jerome (disambiguation)
Saint Jerome is a Christian church father, best known for translating the Bible into Latin.
Saint Jerome may also refer to:
# People.
- Jerome of Pavia (fl. 778–787), Bishop of Pavia
- Saint Jerome Emiliani (1486–1537), Italian humanitarian, founder of the Somaschi Fathers
- Saint Jerome Hermosilla, one of the Vietnamese Martyrs
# Places.
- Saint-Jérôme, Quebec, a suburb of Montreal, Canada
- Saint-Jérôme (electoral district)
- Roman Catholic Diocese of Saint-Jérôme
- Saint-Jérôme line, a commuter railway line
- Saint-Jérôme (AMT), a bus and train station
- St. Jerome Church (disambiguation), several churches
# Arts.
- Francesco "St Jerome", a c. 1595
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Jérôme (AMT), a bus and train station
- St. Jerome Church (disambiguation), several churches
# Arts.
- Francesco "St Jerome", a c. 1595 oil painting on copper attributed to the circle of Palma the Younger
- "Saint Jerome in His Study" (after van Eyck), a 1442 painting
- "Saint Jerome Writing", a 1605–1606 oil painting by Italian painter Caravaggio
- "Saint Jerome Writing" (Caravaggio, Valletta), a 1607 or 1608 oil painting
- "Saint Jerome", a song by Jason Schwartzman's solo-musical project Coconut Records for his 2009 album "Davy"
# See also.
- San Geronimo (disambiguation)
- San Jerónimo (disambiguation)
# See also.
- Boyeux-Saint-Jérôme, a commune in the Ain department, France
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Laurence Olivier
Laurence Kerr Olivier, Baron Olivier, (; 22 May 1907 – 11 July 1989) was an English actor and director who, along with his contemporaries Ralph Richardson, Peggy Ashcroft and John Gielgud, dominated the British stage of the mid-20th century. He also worked in films throughout his career, playing more than fifty cinema roles. Late in his career, he had considerable success in television roles.
His family had no theatrical connections, but Olivier's father, a clergyman, decided that his son should become an actor. After attending a drama school in London, Olivier learned his craft in a succession of acting jobs during the late 1920s. In 1930 he had his first important West End
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success in Noël Coward's "Private Lives", and he appeared in his first film. In 1935 he played in a celebrated production of "Romeo and Juliet" alongside Gielgud and Ashcroft, and by the end of the decade he was an established star. In the 1940s, together with Richardson and John Burrell, Olivier was the co-director of the Old Vic, building it into a highly respected company. There his most celebrated roles included Shakespeare's Richard III and Sophocles's Oedipus. In the 1950s Olivier was an independent actor-manager, but his stage career was in the doldrums until he joined the "avant garde" English Stage Company in 1957 to play the title role in "The Entertainer", a part he later played on
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film. From 1963 to 1973 he was the founding director of Britain's National Theatre, running a resident company that fostered many future stars. His own parts there included the title role in "Othello" (1965) and Shylock in "The Merchant of Venice" (1970).
Among Olivier's films are "Wuthering Heights" (1939), "Rebecca" (1940), and a trilogy of Shakespeare films as actor-director: "Henry V" (1944), "Hamlet" (1948), and "Richard III" (1955). His later films included "The Shoes of the Fisherman" (1968), "Sleuth" (1972), "Marathon Man" (1976), and "The Boys from Brazil" (1978). His television appearances included an adaptation of "The Moon and Sixpence" (1960), "Long Day's Journey into Night" (1973),
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"Love Among the Ruins" (1975), "Cat on a Hot Tin Roof" (1976), "Brideshead Revisited" (1981) and "King Lear" (1983).
Olivier's honours included a knighthood (1947), a life peerage (1970) and the Order of Merit (1981). For his on-screen work he received four Academy Awards, two British Academy Film Awards, five Emmy Awards and three Golden Globe Awards. The National Theatre's largest auditorium is named in his honour, and he is commemorated in the Laurence Olivier Awards, given annually by the Society of London Theatre. He was married three times, to the actresses Jill Esmond from 1930 to 1940, Vivien Leigh from 1940 to 1960, and Joan Plowright from 1961 until his death.
# Life and career.
##
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Family background and early life (1907–1924).
Olivier was born in Dorking, Surrey, the youngest of the three children of the Reverend Gerard Kerr Olivier (1869–1939) and his wife Agnes Louise, "née" Crookenden (1871–1920). Their elder children were Sybille (1901–1989) and Gerard Dacres "Dickie" (1904–1958). His great-great-grandfather was of French Huguenot descent, and Olivier came from a long line of Protestant clergymen. Gerard Olivier had begun a career as a schoolmaster, but in his thirties he discovered a strong religious vocation and was ordained as a priest of the Church of England. He practised extremely high church, ritualist Anglicanism and liked to be addressed as "Father Olivier".
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This made him unacceptable to most Anglican congregations, and the only church posts he was offered were temporary, usually deputising for regular incumbents in their absence. This meant a nomadic existence, and for Laurence's first few years, he never lived in one place long enough to make friends.
In 1912, when Olivier was five, his father secured a permanent appointment as assistant rector at St Saviour's, Pimlico. He held the post for six years, and a stable family life was at last possible. Olivier was devoted to his mother, but not to his father, whom he found a cold and remote parent. Nevertheless, he learned a great deal of the art of performing from him. As a young man Gerard Olivier
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had considered a stage career and was a dramatic and effective preacher. Olivier wrote that his father knew "when to drop the voice, when to bellow about the perils of hellfire, when to slip in a gag, when suddenly to wax sentimental ... The quick changes of mood and manner absorbed me, and I have never forgotten them."
In 1916, after attending a series of preparatory schools, Olivier passed the singing examination for admission to the choir school of All Saints, Margaret Street, in central London. His elder brother was already a pupil, and Olivier gradually settled in, though he felt himself to be something of an outsider. The church's style of worship was (and remains) Anglo-Catholic, with
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emphasis on ritual, vestments and incense. The theatricality of the services appealed to Olivier, and the vicar encouraged the students to develop a taste for secular as well as religious drama. In a school production of "Julius Caesar" in 1917, the ten-year-old Olivier's performance as Brutus impressed an audience that included Lady Tree, the young Sybil Thorndike, and Ellen Terry, who wrote in her diary, "The small boy who played Brutus is already a great actor." He later won praise in other schoolboy productions, as Maria in "Twelfth Night" (1918) and Katherine in "The Taming of the Shrew" (1922).
From All Saints, Olivier went on to St Edward's School, Oxford, from 1920 to 1924. He made
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