Roof

China Product


Parts of a roof

There are two parts to a roof, its supporting structure and its outer skin, or uppermost weatherproof layer. In a minority of buildings, the outer layer is also a self-supporting structure.

The roof structure is generally supported upon walls, although some building styles, for example, geodesic and A-frame, blur the distinction between wall and roof. teak mat

Support bath mat non slip

Main article: Roof construction spa bath mat

The roof of a library, Sweden.

Tree-like supporting pillars of roof (Sagrada Famlia, Barcelona).

The supporting structure of a roof usually comprises beams that are long and of strong, fairly rigid material such as timber, and since the mid 19th century, cast iron or steel. In countries that use bamboo extensively, the flexibility of the material causes a distinctive curving line to the roof, characteristic of Oriental architecture.

Timber lends itself to a great variety of roof shapes. The timber structure can fulfil an aesthetic as well as practical function, when left exposed to view.

Stone lintels have been used to support roofs since prehistoric times, but cannot bridge large distances. The stone arch came into extensive use in the ancient Roman period and in variant forms could be used to span spaces up to 140 feet across. The stone arch or vault, with or without ribs, dominated the roof structures of major architectural works for about 2,000 years, only giving way to iron beams with the Industrial Revolution and the designing of such buildings as Paxton's Crystal Palace, completed 1851.

With continual improvements in steel girders, these became the major structural support for large roofs, and eventually for ordinary houses as well. Another form of girder is the reinforced concrete beam, in which metal rods are encased in concrete, giving it greater strength under tension.

Outer layer

This part of the roof shows great variation dependent upon availability of material. In simple vernacular architecture, roofing material is often vegetation, such as thatches, the most durable being sea grass with a life of perhaps 40 years. In many Asian countries bamboo is used both for the supporting structure and the outer layer where split bammboo stems are laid turned alternately and overlapped. In areas with an abundance of timber, wooden shingles are used, while in some countries the bark of certain trees can be peeled off in thick, heavy sheets and used for roofing.

The 20th century saw the manufacture of composition shingles which can last from a thin 20-year shingle to the thickest which are limited lifetime shingles, the cost depending on the thickness and durability of the shingle. When a layer of shingles wears out, they are usually stripped, along with the underlay and roofing nails, allowing a new layer to be installed. An alternative method is to install another layer directly over the worn layer. While this method is faster, it does not allow the roof sheathing to be inspected and water damage, often associated with worn shingles, to be repaired. Having multiple layers of old shingles under a new layer causes roofing nails to be located further from the sheathing, weakening their hold. The greatest concern with this method is that the weight of the extra material could exceed the dead load capacity of the roof structure and cause collapse.

Slate is an ideal, and durable material, while in the Swiss Alps roofs are made from huge slabs of stone, several inches thick. The slate roof is often considered the best type of roofing. A slate roof may last 75 to 150 years, and even longer. However, slate roofs are often expensive to install in the USA, for example, a slate roof may have the same cost as the rest of the house. Often, the first part of a slate roof to fail is the fixing nails; they corrode, allowing the slates to slip. In the UK, this condition is known as "nail sickness". Because of this problem, fixing nails made of stainless steel or copper are recommended, and even these must be protected from the weather.

Roofs made of cut turf (modern ones known as Green roofs, traditional ones as sod roofs) have good insulating properties and are increasingly encouraged as a way of "greening" the Earth. Adobe roofs are roofs of clay, mixed with binding material such as straw or animal hair, and plastered on lathes to form a flat or gently sloped roof, usually in areas of low rainfall.

In areas where clay is plentiful, roofs of baked tiles have been the major form of roof. The casting and firing of roof tiles is an industry that is often associated with brickworks. While the shape and colour of tiles was once regionally distinctive, now tiles of many shapes and colours are produced commercially, to suit the taste and pocketbook of the purchaser.

Sheet metal in the form of copper and lead has also been used for many hundreds of years. Both are expensive but durable, the vast copper roof of Chartres Cathedral, oxidised to a pale green colour, having been in place for hundreds of years. Lead, which is sometimes used for church roofs, was most commonly used as flashing in valleys and around chimneys on domestic roofs, particularly those of slate. Copper was used for the same purpose.

In the 19th century, iron, electroplated with zinc to improve its resistance to rust, became a light-weight, easily-transported, waterproofing material. While its insulating properties were poor, its low cost and easy application made it the most accessible commercial roofing, world wide. Since then, many types of metal roofing have been developed. Steel shingle or standing-seam roofs last about 50 years or more depending on both the method of installation and the moisture barrier (underlayment) used and are between the cost of shingle roofs and slate roofs. In the 20th century a large number of roofing materials were developed, including roofs based on bitumen (already used in previous centuries), on rubber and on a range of synthetics such as thermoplastic and on fibreglass.

Outer layer

Cameroon, a wattle and daub house, roofed with banana leaves.

Japan, rice straw thatch.

England, slate.

Hungary, terracotta tiles.

Namibia, metal roof.

Insulation

Some roofing materials, particularly those of natural fibrous material, such as thatch, have excellent insulating properties. For those that do not, extra insulation is often installed under the outer layer. In developed countries, the majority of dwellings have a ceiling installed under the structural member of the roof. The purpose is to insulate against heat and cold, noise, dirt and often from the droppings and lice of birds who frequently choose roofs as nesting places.

Other forms of insulation are felt or plastic sheeting, sometimes with a reflective surface, installed directly below the tiles or other material; synthetic foam batting laid above the ceiling and recycled paper products and other such materials that can be inserted or sprayed into roof cavities.

So called Cool roofs are becoming increasingly popular, and in some cases are mandated by local codes. Cool roofs are defined as roofs with both high reflectivity and high emissivity.

Drainage

The primary job of most roofs is to keep out water. The large area of a roof repels a lot of water, which must be directed in some suitable way, so that it does not cause damage or inconvenience.

Flat roof of adobe dwellings generally have a very slight slope. In a Middle Eastern country, where the roof may be used for recreation, it is often walled, and drainage holes must be provided to stop water from pooling and seeping through the porous roofing material.

Similar problems, although on a very much larger scale, confront the builders of modern commercial properties which often have flat roofs. Because of the very large nature of such roofs, it is essential that the outer skin is of a highly impermiable material. Most industrial and commercial structures have conventional roofs of low pitch.

In general, the pitch of the roof is proportional to the amount of precipitation. Houses in areas of low rainfall frequently have roofs of low pitch while those in areas of high rainfall and snow, have steep roofs. The longhouses of Papua New Guinea, for example, being roof-dominated architecture, the high roofs sweeping almost to the ground. The high steeply-pitched roofs of Germany and Holland are typical in regions of snowfall. In parts of the North America such as Buffalo USA or Montreal Canada, there is a required minimum slope of 6 inches in 12 inches, a pitch of 30 degrees.

There are regional building styles which contradict this trend, the stone roofs of the Alpine chalets being usually of gentler incline. These buildings tend to accumulate a large amount of snow on them, which is seen as a factor in their insulation. The pitch of the roof is in part determined by the roofing material available, a pitch of 3/12 or greater slope generally being covered with asphalt shingles, wood shake, corrugated steel, slate or tile.

The water repelled by the roof during a rainstorm is potentially damaging to the building that the roof protects. If it runs down the walls, it may seep into the mortar or through panels. If it lies around the foundations it may cause seepage to the interior, rising damp or dry rot. For this reason most buildings have a system in place to protect the walls of a building from most of the roof water. Overhanging eaves are commonly employed for this purpose. Most modern roofs and many old ones have systems of valleys, gutters, waterspouts, waterheads and drainpipes to remove the water from the vicinity of the building. In many parts of the world, roofwater is collected and stored for domestic use.

Areas prone to heavy snow benefit from a metal roof because their smooth surfaces shed the weight of snow more easily and resist the force of wind better than a wood shingle or a concrete tile roof.

See also: Trade hall roof collapse in Katowice, Poland and Bad Reichenhall ice rink roof collapse

Insulation, drainage and solar roofing

Snow on the roof of houses in Poland.

The flat roofs of the Middle East, Israel.

Steeply pitched, gabled roofs in Northern Europe.

The overhanging eaves of China.

Green roof with solar panels, Findhorn.

Solar roofs

Newer systems include solar shingles which generate electricity as well as cover the roof. There are also solar systems available that generate hot water or hot air and which can also act as a roof covering. More complex systems may carry out all of these functions: generate electricity, recover thermal energy, and also act as a roof covering.

Solar systems can be integrated with roofs by:

integration in the covering of pitched roofs, e.g. solar shingles.

mounting on an existing roof, e.g. solar panel on a tile roof.

integration in a flat roof membrane using heat welding, e.g. PVC.

mounting on a flat roof with a construction and additional weight to prevent uplift from wind.

Roof shapes

Arched Roof

Barrel-arched

Catenary

Conical

Cut Roof

Domical

Flat

Helm Roof - Rhenish helm - a pyramidal roof with gable ends -- Speyer Cathedral

Outshot

Pyramidal

Ridged

Pitched or gabled

Asian traditional style

Crow-stepped gable (also called corbie step) gable

Dutch gable a hybrid of hipped and gable

Shaped gable

Salt-box

Saddleback a gabled roof atop a tower

Hip roof includes a sketch of a Dutch gable (Australian terminology)

Half-hipped

Mansard with the pitch divided into a shallow slope above a steeper slope

Gambrel as a mansard, but on only two sides of the roof

Bell-cast as a mansard, but with the shallow slope below the steeper slope

pavilion

Skillion roof single-sloped, lean to, or shed roof

cat-slide

Lean-to

Saw-tooth

Roof shapes

Flat roof, Western Australia.

Mansard roof on a county jail, Mount Gilead, Ohio.

Temple roof Chang Mai, Thailand with a decorated gable end and ceramic tile covering.

Commercially available roofing materials

The weather proofing material is the topmost or outermost layer, exposed to the weather. Many materials have been used as weather proofing material:

Thatch is roofing made of plant material, in overlapping layers.

Wheat Straw, widely used in England, France and other parts of Europe.

Seagrass, used in coastal areas where there are esturies such as Scotland. Has a longer life than straw. Claimed to have a life in exccess of 60 years.

Shingles, Wood shingles longer than 16" are called shakes in North America. Shingles is the generic term for a roofing material that is in many overlapping sections, regardless of the nature of the material.

Redcedar. Life expectancy, up to 30 years. However, young growth redcedar has a short life expectancy. High cost. Should be allowed to breathe, usually installed on lath strip for this purpose. The lath may rest on a roof deck with underlayment or be fastened directly to the rafters.

Hardwood. Very durable roofing found in Colonial Australian architecture, its use now limited to restorations.

Slate. Higher cost with a life expectancy of 50 to 200 years depending on the thickness and type of slate used. Being a heavy material, the supporting structure must be rated to support the weight load.

Ceramic tile. High cost, life of 20-100 years.

Imbrex and tegula, style dating back to ancient Greece and Rome.

Metal shakes or shingles. Long life. High cost, suitable for roofs of 4/12 pitch or greater. Because of the flexibility of metal, they can be manufactured to lock together, giving durability and reducing assembly time.

Mechanically seamed metal. Long life. High cost, suitable for roofs of low pitch such as 0.5/12 to 3/12 pitch.

Concrete, usually reinforced with fibres of some sort. Not suitable in climates that experience many freeze/thaw cycles during a year which will cause this type of material to form cracks and fail.

Asphalt shingle, made of bitumen embedded in an organic or fiberglass mat, usually covered with colored, man-made ceramic grit. Cheaper and lighter than slate or tiles. Life expectancies vary from 20 to 50 years depending on the product. Sun is the enemy of asphalt shingles so longer life can be expected in cloudier locations or at higher latitudes.

Asbestos shingles. Lifespans vary. Fireproof. Rarely used anymore because of health concerns. Abatement costs can be high when the old roof needs to be replaced and is subject to additional state and local environmental regulation and oversight.

Membrane. membrane roofing is in large sheets, generally fused in some way at the joints to form a continuous surface.

Thermosetting plastic (e.g. EPDM rubber). Synthetic rubber sheets adhered together with contact adhesive or tape. Primary application is big box store with large open areas and little vertical protrusions.

Thermoplastic (e.g. PVC, TPO, CSPE). Plastic sheets welded together with hot air creating one continuous sheet membrane. Can be rewelded with the exception of CSPE. Lends itself well to both big box and small roof application because of its hot air weldability.

Modified bitumen heat welded, asphalt adhered or installed with adhesive. Asphalt is mixed with polymers such as APP or SBS, then applied to fiberglass and/or polyester mat, seams sealed by locally melting the asphalt with heat, hot mopping of asphalt, or adhesive. Lends itself well to all applications.

Built-Up Roof Multiple plies of asphalt saturated organic felt or coated fiberglass felts. Plies of felt are adhered with hot asphalt, coal tar pitch or adhesive.

Sprayed-in-Place Polyurethane Foam (SPUF) Foam sprayed in-place on the roof, then coated with a wide variety of coatings, or in some instances, covered with gravel.

Fabric.

Polyester.

PTFE, (synthetic fluoropolymer) embedded in fibreglass.

Metal roofing. Generally a relatively inexpensive building material.

Galvanised steel frequently manufactured with wavy corrugations to resist lateral flexing and fitted with exposed fasteners. Widely used for low cost and durability. Sheds are normally roofed with this material. Known as Gal iron or Corro, it was the most extensively used roofing material of 20th century Australia, now replaced in popularity by steel roofing coated with an alloy of zinc and aluminium, claimed to have up to four times the life of galvanized steel.

Standing-seam metal with concealed fasteners.

Mechanically seamed metal with concealed fasteners contains sealant in seams for use on very low sloped roofs.

Flat-seam metal with soldered seams.

Reed thatch on the island of Sylt

Wooden shingles

A church roof under repair with terracotta tiles

Imbrex and tegula tiles, with a newly tiled roof in the foreground

Bitumen, USA

Corrugated iron, Australia

Sheet metal roof

PVC roof

Gallery of significant roofs

Imbrex and tegula tiles on the dome of Florence Cathedral.

The marble dome of the Taj Mahal.

The hip roofs and dormers of Chateau Chenonceau.

The polychrome tiles of the Hospice of Beaune, France.

The copper roof of Speyer Cathedral, Germany. photo Wolfi.

The lead roof of King's College Chapel, England.

The glass roof of the Grand Palais, Paris.

The glazed ceramic tiles of the Sydney Opera House.

See also

Wikimedia Commons has media related to: Roofs

Bituminous waterproofing

Building construction

Building envelope

Green roof

Metal roof

Metal Roofing Alliance

Roof crush

Roof garden

Roofer

Roofing felt

Solar panel

Tensile architecture

Tented roof

Thin-shell structure

Tile

History

List of Greco-Roman roofs

References

^ Thatching specifications

^ Fleming, Honour, & Pevsner, A Dictionary of Architecture

^ Thatching Information

^ a b c Robert Roskind (2000). Building Your Own House. Ten Speed Press. p. 353. http://books.google.com/books?id=Q3QCV5wzmJoC. Retrieved 2009-03-14. 

^ Hometips Wooden shingle roofing, with good diagrams

^ a b Taunton Press Staff (1997). Roofing. Taunton Press. p. 11. http://books.google.com/books?id=VFTkJrl3WEEC&pg=PA11&dq=. Retrieved 2009-03-14. 

^ a b Steven Bolt (1996). Roofing the right way. McGraw-Hill Professional. p. 7. ISBN 0070066507. http://books.google.com/books?id=iDjyitMjGHkC&pg=PA8&dq=. Retrieved 2009-03-14. 

^ HomeTips: Metal shingle roofing

^ Asbestos and Your Health, Victorian Government

^ Asbestos Diseases Advisory Service

^ Ken Watson, Executive Director, National Association of Steel Framed Housing. Steel Framed Housing. p. 2. http://www.innovatek.co.nz/pdfs/Steel_Framed_Housing.pdf. Retrieved accessdate=2009-03-14. 

Further reading

Francis Ching; Building Construction Illustrated, Visual Dictionary of Architecture, Architecture: Form, Space, and Order.

External links

Roof innovations and patents

Categories: Roofs | Structural engineering | Structural system | Tensile architecture

Pressure measurement

China Product


Absolute, gauge and differential pressures - zero reference

Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other ad hoc reference. When distinguishing between these zero references, the following terms are used:

Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. commercial steam cleaner

Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted. upholstery steam cleaner

Differential pressure is the difference in pressure between two points. surface steam cleaner

The zero reference in use is usually implied by context, and these words are only added when clarification is needed. Tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute. Differential pressures are commonly used in industrial process systems. Differential pressure gauges have two inlet ports, each connected to one of the volumes whose pressure is to be monitored. In effect, such a gauge performs the mathematical operation of subtraction through mechanical means, obviating the need for an operator or control system to watch two separate gauges and determine the difference in readings. Moderate vacuum pressures are often ambiguous, as they may represent absolute pressure or gauge pressure without a negative sign. Thus a vacuum of 26 inHg gauge is equivalent to an absolute pressure of 30 inHg (typical atmospheric pressure) 26 inHg = 4 inHg.

Atmospheric pressure is typically about 100 kPa at sea level, but is variable with altitude and weather. If the absolute pressure of a fluid stays constant, the gauge pressure of the same fluid will vary as atmospheric pressure changes. For example, when a car drives up a mountain, the tire pressure goes up. Some standard values of atmospheric pressure such as 101.325 kPa or 100 kPa have been defined, and some instruments use one of these standard values as a constant zero reference instead of the actual variable ambient air pressure. This impairs the accuracy of these instruments, especially when used at high altitudes.

Use of the atmosphere as reference is usually signified by a (g) after the pressure unit e.g. 30 psi g, which means that the pressure measured is the total pressure minus atmospheric pressure. There are two types of gauge reference pressure: vented gauge (vg) and sealed gauge (sg).

A vented gauge pressure transmitter for example allows the outside air pressure to be exposed to the negative side of the pressure sensing diaphragm, via a vented cable or a hole on the side of the device, so that it always measures the pressure referred to ambient barometric pressure. Thus a vented gauge reference pressure sensor should always read zero pressure when the process pressure connection is held open to the air.

A sealed gauge reference is very similar except that atmospheric pressure is sealed on the negative side of the diaphragm. This is usually adopted on high pressure ranges such as hydraulics where atmospheric pressure changes will have a negligible effect on the accuracy of the reading, so venting is not necessary. This also allows some manufacturers to provide secondary pressure containment as an extra precaution for pressure equipment safety if the burst pressure of the primary pressure sensing diaphragm is exceeded.

There is another way of creating a sealed gauge reference and this is to seal a high vacuum on the reverse side of the sensing diaphragm. Then the output signal is offset so the pressure sensor reads close to zero when measuring atmospheric pressure.

A sealed gauge reference pressure transducer will never read exactly zero because atmospheric pressure is always changing and the reference in this case is fixed at 1 bar.

An absolute pressure measurement is one that is referred to absolute vacuum. The best example of an absolute referenced pressure is atmospheric or barometric pressure.

To produce an absolute pressure sensor the manufacturer will seal a high vacuum behind the sensing diaphragm. If the process pressure connection of an absolute pressure transmitter is open to the air, it will read the actual barometric pressure.

Units

Pressure Units

 

pascal

(Pa)

bar

(bar)

technical atmosphere

(at)

atmosphere

(atm)

torr

(Torr)

pound-force per

square inch

(psi)

1 Pa

1 N/m2

105

1.0197105

9.8692106

7.5006103

145.04106

1 bar

100,000

106 dyn/cm2

1.0197

0.98692

750.06

14.5037744

1 at

98,066.5

0.980665

1 kgf/cm2

0.96784

735.56

14.223

1 atm

101,325

1.01325

1.0332

1 atm

760

14.696

1 torr

133.322

1.3332103

1.3595103

1.3158103

1 Torr;  1 mmHg

19.337103

1 psi

6.894103

68.948103

70.307103

68.046103

51.715

1 lbf/in2

Example reading:  1 Pa = 1 N/m2  = 105 bar  = 10.197106 at  = 9.8692106 atm, etc.

The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (Nm2 or kgm1s2). This special name for the unit was added in 1971; before that, pressure in SI was expressed in units such as N/m. When indicated, the zero reference is stated in parenthesis following the unit, for example 101 kPa (abs). The pound per square inch (psi) is still in widespread use in the US and Canada, notably for cars. A letter is often appended to the psi unit to indicate the measurement's zero reference; psia for absolute, psig for gauge, psid for differential, although this practice is discouraged by the NIST .

Because pressure was once commonly measured by its ability to displace a column of liquid in a manometer, pressures are often expressed as a depth of a particular fluid (e.g. inches of water). The most common choices are mercury (Hg) and water; water is nontoxic and readily available, while mercury's density allows for a shorter column (and so a smaller manometer) to measure a given pressure.

Fluid density and local gravity can vary from one reading to another depending on local factors, so the height of a fluid column does not define pressure precisely. When 'millimetres of mercury' or 'inches of mercury' are quoted today, these units are not based on a physical column of mercury; rather, they have been given precise definitions that can be expressed in terms of SI units. The water-based units usually assume one of the older definitions of the kilogram as the weight of a litre of water.

Although no longer favoured by measurement experts, these manometric units are still encountered in many fields. Blood pressure is measured in millimetres of mercury in most of the world, and lung pressures in centimeters of water are still common. Natural gas pipeline pressures are measured in inches of water, expressed as '"WC' ('Water Column'). Scuba divers often use a manometric rule of thumb: the pressure exerted by ten metres depth of water is approximately equal to one atmosphere. In vacuum systems, the units torr, micrometre of mercury (micron), and inch of mercury (inHg) are most commonly used. Torr and micron usually indicates an absolute pressure, while inHg usually indicates a gauge pressure.

Atmospheric pressures are usually stated using kilopascal (kPa), or atmospheres (atm), except in American meteorology where the hectopascal (hPa) and millibar (mbar) are preferred. In American and Canadian engineering, stress is often measured in kip. Note that stress is not a true pressure since it is not scalar. In the cgs system the unit of pressure was the barye (ba), equal to 1 dyncm2. In the mts system, the unit of pressure was the pieze, equal to 1 sthene per square metre.

Many other hybrid units are used such as mmHg/cm or grams-force/cm (sometimes as kg/cm and g/mol2 without properly identifying the force units). Using the names kilogram, gram, kilogram-force, or gram-force (or their symbols) as a unit of force is forbidden in SI; the unit of force in SI is the newton (N).

Static and Dynamic pressure

Static pressure is uniform in all directions, so pressure measurements are independent of direction in an immovable (static) fluid. Flow, however, applies additional pressure on surfaces perpendicular to the flow direction, while having little impact on surfaces parallel to the flow direction. This directional component of pressure in a moving (dynamic) fluid is called dynamic pressure. An instrument facing the flow direction measures the sum of the static and dynamic pressures; this measurement is called the total pressure or stagnation pressure. Since dynamic pressure is referenced to static pressure, it is neither gauge nor absolute; it is a differential pressure.

While static gauge pressure is of primary importance to determining net loads on pipe walls, dynamic pressure is used to measure flow rates and airspeed. Dynamic pressure can be measured by taking the differential pressure between instruments parallel and perpendicular to the flow. Pitot-static tubes, for example perform this measurement on airplanes to determine airspeed. The presence of the measuring instrument inevitably acts to divert flow and create turbulence, so its shape is critical to accuracy and the calibration curves are often non-linear.

Applications

Altimeter

Barometer

MAP sensor

Pitot tube

Sphygmomanometer

Instruments

Many instruments have been invented to measure pressure, with different advantages and disadvantages. Pressure range, sensitivity, dynamic response and cost all vary by several orders of magnitude from one instrument design to the next. The oldest type is the liquid column (a vertical tube filled with mercury) manometer invented by Evangelista Torricelli in 1643. The U-Tube was invented by Christian Huygens in 1661.

Hydrostatic

Hydrostatic gauges (such as the mercury column manometer) compare pressure to the hydrostatic force per unit area at the base of a column of fluid. Hydrostatic gauge measurements are independent of the type of gas being measured, and can be designed to have a very linear calibration. They have poor dynamic response.

Piston

Piston-type gauges counterbalance the pressure of a fluid with a solid weight or a spring. Another name for piston gauge is deadweight tester. For example, dead-weight testers used for calibration or tire-pressure gauges.

Liquid column

The difference in fluid height in a liquid column manometer is proportional to the pressure difference.

Liquid column gauges consist of a vertical column of liquid in a tube whose ends are exposed to different pressures. The column will rise or fall until its weight is in equilibrium with the pressure differential between the two ends of the tube. A very simple version is a U-shaped tube half-full of liquid, one side of which is connected to the region of interest while the reference pressure (which might be the atmospheric pressure or a vacuum) is applied to the other. The difference in liquid level represents the applied pressure. The pressure exerted by a column of fluid of height h and density is given by the hydrostatic pressure equation, P = hg. Therefore the pressure difference between the applied pressure Pa and the reference pressure P0 in a U-tube manometer can be found by solving Pa P0 = hg. If the fluid being measured is significantly dense, hydrostatic corrections may have to be made for the height between the moving surface of the manometer working fluid and the location where the pressure measurement is desired.

Although any fluid can be used, mercury is preferred for its high density (13.534 g/cm3) and low vapour pressure. For low pressure differences well above the vapour pressure of water, water is commonly used (and "inches of water" is a common pressure unit). Liquid-column pressure gauges are independent of the type of gas being measured and have a highly linear calibration. They have poor dynamic response. When measuring vacuum, the working liquid may evaporate and contaminate the vacuum if its vapor pressure is too high. When measuring liquid pressure, a loop filled with gas or a light fluid must isolate the liquids to prevent them from mixing. Simple hydrostatic gauges can measure pressures ranging from a few Torr (a few 100 Pa) to a few atmospheres. (Approximately 1,000,000 Pa)

A single-limb liquid-column manometer has a larger reservoir instead of one side of the U-tube and has a scale beside the narrower column. The column may be inclined to further amplify the liquid movement. Based on the use and structure following type of manometers are used

Simple Manometer

Micromanometer

Differential manometer

Inverted differential manometer

A McLeod gauge, drained of mercury

McLeod gauge

A McLeod gauge isolates a sample of gas and compresses it in a modified mercury manometer until the pressure is a few mmHg. The gas must be well-behaved during its compression (it must not condense, for example). The technique is slow and unsuited to continual monitoring, but is capable of good accuracy.

Useful range: above 10-4 torr (roughly 10-2 Pa) as high as 106 Torr (0.1 mPa),

0.1 mPa is the lowest direct measurement of pressure that is possible with current technology. Other vacuum gauges can measure lower pressures, but only indirectly by measurement of other pressure-controlled properties. These indirect measurements must be calibrated to SI units via a direct measurement, most commonly a McLeod gauge.

Aneroid

Aneroid gauges are based on a metallic pressure sensing element which flexes elastically under the effect of a pressure difference across the element. "Aneroid" means "without fluid," and the term originally distinguished these gauges from the hydrostatic gauges described above. However, aneroid gauges can be used to measure the pressure of a liquid as well as a gas, and they are not the only type of gauge that can operate without fluid. For this reason, they are often called mechanical gauges in modern language. Aneroid gauges are not dependent on the type of gas being measured, unlike thermal and ionization gauges, and are less likely to contaminate the system than hydrostatic gauges. The pressure sensing element may be a Bourdon tube, a diaphragm, a capsule, or a set of bellows, which will change shape in response to the pressure of the region in question. The deflection of the pressure sensing element may be read by a linkage connected to a needle, or it may be read by a secondary transducer. The most common secondary transducers in modern vacuum gauges measure a change in capacitance due to the mechanical deflection. Gauges that rely on a change in capacitances are often referred to as Baratron gauges.

Bourdon

Membrane-type manometer

A Bourdon gauge uses a coiled tube, which, as it expands due to pressure increase causes a rotation of an arm connected to the tube. In 1849 the Bourdon tube pressure gauge was patented in France by Eugene Bourdon.

The pressure sensing element is a closed coiled tube connected to the chamber or pipe in which pressure is to be sensed. As the gauge pressure increases the tube will tend to uncoil, while a reduced gauge pressure will cause the tube to coil more tightly. This motion is transferred through a linkage to a gear train connected to an indicating needle. The needle is presented in front of a card face inscribed with the pressure indications associated with particular needle deflections. In a barometer, the Bourdon tube is sealed at both ends and the absolute pressure of the ambient atmosphere is sensed. Differential Bourdon gauges use two Bourdon tubes and a mechanical linkage that compares the readings.

In the following illustrations the transparent cover face of the pictured combination pressure and vacuum gauge has been removed and the mechanism removed from the case. This particular gauge is a combination vacuum and pressure gauge used for automotive diagnosis:

Indicator side with card and dial

Mechanical side with Bourdon tube

the left side of the face, used for measuring manifold vacuum, is calibrated in centimetres of mercury on its inner scale and inches of mercury on its outer scale.

the right portion of the face is used to measure fuel pump pressure and is calibrated in fractions of 1 kgf/cm on its inner scale and pounds per square inch on its outer scale.

Mechanical details

Mechanical details

Stationary parts:

A: Receiver block. This joins the inlet pipe to the fixed end of the Bourdon tube (1) and secures the chassis plate (B). The two holes receive screws that secure the case.

B: Chassis plate. The face card is attached to this. It contains bearing holes for the axles.

C: Secondary chassis plate. It supports the outer ends of the axles.

D: Posts to join and space the two chassis plates.

Moving Parts:

Stationary end of Bourdon tube. This communicates with the inlet pipe through the receiver block.

Moving end of Bourdon tube. This end is sealed.

Pivot and pivot pin.

Link joining pivot pin to lever (5) with pins to allow joint rotation.

Lever. This an extension of the sector gear (7).

Sector gear axle pin.

Sector gear.

Indicator needle axle. This has a spur gear that engages the sector gear (7) and extends through the face to drive the indicator needle. Due to the short distance between the lever arm link boss and the pivot pin and the difference between the effective radius of the sector gear and that of the spur gear, any motion of the Bourdon tube is greatly amplified. A small motion of the tube results in a large motion of the indicator needle.

Hair spring to preload the gear train to eliminate gear lash and hysteresis.

Diaphragm

A pile of pressure capsules with corrugated diaphragms in an aneroid barograph.

A second type of aneroid gauge uses the deflection of a flexible membrane that separates regions of different pressure. The amount of deflection is repeatable for known pressures so the pressure can be determined by using calibration. The deformation of a thin diaphragm is dependent on the difference in pressure between its two faces. The reference face can be open to atmosphere to measure gauge pressure, open to a second port to measure differential pressure, or can be sealed against a vacuum or other fixed reference pressure to measure absolute pressure. The deformation can be measured using mechanical, optical or capacitive techniques. Ceramic and metallic diaphragms are used.

Useful range: above 10-2 Torr (roughly 1 Pa)

For absolute measurements, welded pressure capsules with diaphragms on either side are often used.

Shape:

Flat

corrugated

flattened tube

capsule

Bellows

In gauges intended to sense small pressures or pressure differences, or require that an absolute pressure be measured, the gear train and needle may be driven by an enclosed and sealed bellows chamber, called an aneroid, which means "without liquid". (Early barometers used a column of liquid such as water or the liquid metal mercury suspended by a vacuum.) This bellows configuration is used in aneroid barometers (barometers with an indicating needle and dial card), altimeters, altitude recording barographs, and the altitude telemetry instruments used in weather balloon radiosondes. These devices use the sealed chamber as a reference pressure and are driven by the external pressure. Other sensitive aircraft instruments such as air speed indicators and rate of climb indicators (variometers) have connections both to the internal part of the aneroid chamber and to an external enclosing chamber.

Electronic pressure sensors

Main article: Pressure sensor

Piezoresistive Strain Gage

Uses the piezoresistive effect of bonded or formed strain gauges to detect strain due to applied pressure.

Capacitive

Uses a diaphragm and pressure cavity to create a variable capacitor to detect strain due to applied pressure.

Magnetic

Measures the displacement of a diaphragm by means of changes in inductance (reluctance), LVDT, Hall Effect, or by eddy current principal.

Piezoelectric

Uses the piezoelectric effect in certain materials such as quartz to measure the strain upon the sensing mechanism due to pressure.

Optical

Uses the physical change of an optical fiber to detect strain due applied pressure.

Potentiometric

Uses the motion of a wiper along a resistive mechanism to detect the strain caused by applied pressure.

Resonant

Uses the changes in resonant frequency in a sensing mechanism to measure stress, or changes in gas density, caused by applied pressure.

Thermal conductivity

Generally, as a real gas increases in density -which may indicate an increase in pressure- its ability to conduct heat increases. In this type of gauge, a wire filament is heated by running current through it. A thermocouple or Resistance Temperature Detector (RTD) can then be used to measure the temperature of the filament. This temperature is dependent on the rate at which the filament loses heat to the surrounding gas, and therefore on the thermal conductivity. A common variant is the Pirani gauge which uses a single platinum filament as both the heated element and RTD. These gauges are accurate from 10 Torr to 103 Torr, but they are sensitive to the chemical composition of the gases being measured.

Two wire

One wire coil is used as a heater, and the other is used to measure nearby temperature due to convection.

Pirani (one wire)

A Pirani gauge consists of a metal wire open to the pressure being measured. The wire is heated by a current flowing through it and cooled by the gas surrounding it. If the gas pressure is reduced, the cooling effect will decrease, hence the equilibrium temperature of the wire will increase. The resistance of the wire is a function of its temperature: by measuring the voltage across the wire and the current flowing through it, the resistance (and so the gas pressure) can be determined. This type of gauge was invented by Marcello Pirani.

Thermocouple gauges and thermistor gauges work in a similar manner, except a thermocouple or thermistor is used to measure the temperature of the wire.

Useful range: 10-3 - 10 Torr (roughly 10-1 - 1000 Pa)

Ionization gauge

Ionization gauges are the most sensitive gauges for very low pressures (also referred to as hard or high vacuum). They sense pressure indirectly by measuring the electrical ions produced when the gas is bombarded with electrons. Fewer ions will be produced by lower density gases. The calibration of an ion gauge is unstable and dependent on the nature of the gases being measured, which is not always known. They can be calibrated against a McLeod gauge which is much more stable and independent of gas chemistry.

Thermionic emission generate electrons, which collide with gas atoms and generate positive ions. The ions are attracted to a suitably biased electrode known as the collector. The current in the collector is proportional to the rate of ionization, which is a function of the pressure in the system. Hence, measuring the collector current gives the gas pressure. There are several sub-types of ionization gauge.

Useful range: 10-10 - 10-3 torr (roughly 10-8 - 10-1 Pa)

Most ion gauges come in two types: hot cathode and cold cathode, a third type exists which is more sensitive and expensive known as a spinning rotor gauge, but is not discussed here. In the hot cathode version an electrically heated filament produces an electron beam. The electrons travel through the gauge and ionize gas molecules around them. The resulting ions are collected at a negative electrode. The current depends on the number of ions, which depends on the pressure in the gauge. Hot cathode gauges are accurate from 103 Torr to 1010 Torr. The principle behind cold cathode version is the same, except that electrons are produced in a discharge created by a high voltage electrical discharge. Cold Cathode gauges are accurate from 102 Torr to 109 Torr. Ionization gauge calibration is very sensitive to construction geometry, chemical composition of gases being measured, corrosion and surface deposits. Their calibration can be invalidated by activation at atmospheric pressure or low vacuum. The composition of gases at high vacuums will usually be unpredictable, so a mass spectrometer must be used in conjunction with the ionization gauge for accurate measurement.

Hot cathode

Bayard-Alpert hot cathode ionization gauge

A hot cathode ionization gauge is mainly composed of three electrodes all acting as a triode, where the cathode is the filament. The three electrodes are a collector or plate, a filament, and a grid. The collector current is measured in picoamps by an electrometer. The filament voltage to ground is usually at a potential of 30 volts while the grid voltage at 180210 volts DC, unless there is an optional electron bombardment feature, by heating the grid which may have a high potential of approximately 565 volts. The most common ion gauge is the hot cathode Bayard-Alpert gauge, with a small ion collector inside the grid. A glass envelope with an opening to the vacuum can surround the electrodes, but usually the Nude Gauge is inserted in the vacuum chamber directly, the pins being fed through a ceramic plate in the wall of the chamber. Hot cathode gauges can be damaged or lose their calibration if they are exposed to atmospheric pressure or even low vacuum while hot. The measurements of a hot cathode ionization gauge are always logarithmic.

Electrons emitted from the filament move several times in back and forth movements around the grid before finally entering the grid. During these movements, some electrons collide with a gaseous molecule to form a pair of an ion and an electron (Electron ionization). The number of these ions is proportional to the gaseous molecule density multiplied by the electron current emitted from the filament, and these ions pour into the collector to form an ion current. Since the gaseous molecule density is proportional to the pressure, the pressure is estimated by measuring the ion current.

The low pressure sensitivity of hot cathode gauges is limited by the photoelectric effect. Electrons hitting the grid produce x-rays that produce photoelectric noise in the ion collector. This limits the range of older hot cathode gauges to 108 Torr and the Bayard-Alpert to about 1010 Torr. Additional wires at cathode potential in the line of sight between the ion collector and the grid prevent this effect. In the extraction type the ions are not attracted by a wire, but by an open cone. As the ions cannot decide which part of the cone to hit, they pass through the hole and form an ion beam. This ion beam can be passed on to a

Faraday cup

Microchannel plate detector with Faraday cup

Quadrupole mass analyzer with Faraday cup

Quadrupole mass analyzer with Microchannel plate detector Faraday cup

ion lens and acceleration voltage and directed at a target to form a sputter gun. In this case a valve lets gas into the grid-cage.

See also: Electron ionization

Cold cathode

There are two subtypes of cold cathode ionization gauges: the Penning gauge (invented by Frans Michel Penning), and the Inverted magnetron, also called a Redhead gauge. The major difference between the two is the position of the anode with respect to the cathode. Neither has a filament, and each may require a DC potential of about 4 kV for operation. Inverted magnetrons can measure down to 1x1012 Torr.

Such gauges cannot operate if the ions generated by the cathode recombine before reaching the anodes. If the mean-free path of the gas within the gauge is smaller than the gauge's dimensions, then the electrode current will essentially vanish. A practical upper-bound to the detectable pressure is, for a Penning gauge, of the order of 103 Torr.

Similarly, cold cathode gauges may be reluctant to start at very low pressures, in that the near-absence of a gas makes it difficult to establish an electrode current - particularly in Penning gauges which use an axially symmetric magnetic field to create path lengths for ions which are of the order of metres. In ambient air suitable ion-pairs are ubiquitously formed by cosmic radiation; in a Penning gauge design features are used to ease the set-up of a discharge path. For example, the electrode of a Penning gauge is usually finely tapered to facilitate the field emission of electrons.

Maintenance cycles of cold cathode gauges is generally measured in years, depending on the gas type and pressure that they are operated in. Using a cold cathode gauge in gases with substantial organic components, such as pump oil fractions, can result in the growth of delicate carbon films and shards within the gauge which eventually either short-circuit the electrodes of the gauge, or impede the generation of a discharge path.

Calibration

Pressure gauges are either direct- or indirect-reading. Hydrostatic and elastic gauges measure pressure are directly influenced by force exerted on the surface by incident particle flux, and are called direct reading gauges. Thermal and ionization gauges read pressure indirectly by measuring a gas property that changes in a predictable manner with gas density. Indirect measurements are susceptible to more errors than direct measurements.

Dead weight tester

McLeod

mass spec + ionization

Dynamic transients

When fluid flows are not in equilibrium, local pressures may be higher or lower than the average pressure in a medium. These disturbances propagate from their source as longitudinal pressure variations along the path of propagation. This is also called sound. Sound pressure is the instantaneous local pressure deviation from the average pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water. The effective sound pressure is the root mean square of the instantaneous sound pressure over a given interval of time. Sound pressures are normally small and are often expressed in units of microbar.

frequency response of pressure sensors

resonance

History

Further information: Timeline of temperature and pressure measurement technology

European (CEN) Standard

EN 472 : Pressure gauge - Vocabulary.

EN 837-1 : Pressure gauges. Bourdon tube pressure gauges. Dimensions, metrology, requirements and testing.

EN 837-2 : Pressure gauges. Selection and installation recommendations for pressure gauges.

EN 837-3 : Pressure gauges. Diaphragm and capsule pressure gauges. Dimensions, metrology, requirements and testing..

See also

Force gauge

Piezometer

Vacuum engineering

External links

Home Made Manometer

Manometer

References

^ NIST

^ [Was: "fluidengineering.co.nr/Manometer.htm". At 1/2010 that took me to bad link. Types of fluid Manometers]

^ Techniques of high vacuum

^ Beckwith, Thomas G.; Roy D. Marangoni and John H. Lienhard V (1993). "Measurement of Low Pressures". Mechanical Measurements (Fifth ed.). Reading, MA: Addison-Wesley. pp. 591595. ISBN 0-201-56947-7. 

^ Product brochure from Schoonover, Inc

^ VG Scienta

^ Robert M. Besanon, ed (1990). "Vacuum Techniques" (3rd edition ed.). Van Nostrand Reinhold, New York. pp. 12781284. ISBN 0-442-00522-9. 

Wikimedia Commons has media related to: Pressure gauge

Categories: Underwater diving | Vacuum | Pressure gauges | Measuring instruments

Shrimp

China Product


Taxonomy

A number of more or less unrelated crustaceans share the word "shrimp" in their common name. Examples are the mantis shrimp and the opossum or mysid shrimp, both of which belong to the same class (Malacostraca) as the true shrimp, but constitute two different orders within it, the Stomatopoda and the Mysidacea. Triops longicaudatus and Triops cancriformis are also popular animals in freshwater aquaria, and are often called shrimp, although they belong instead to the Notostraca, a quite unrelated group.

Biological definition dunlopillo mattress

Shrimp (Caridea) typically have two pairs of claws, and the second segment of the abdomen overlaps those on either side. The abdomen shows a pronouned caridean bend. natural crib mattress

Prawns (Dendrobanchiata), such as this Penaeus species, typically have three pairs of claws, and even sized segments on the abdomen. There is no pronounced bend in the abdomen inflatable air mattress

The class Malacostraca contains about half of the crustaceans. The members of this class have a primitive body plan that can be described as shrimp-like, consisting of a 5-8-7 body plan. They have a small carapace that encloses the head and the thorax, and have a muscular abdomen for swimming. They also have a thin exoskeleton to maintain a light weight. These general characters are common in all members of the class.

The class can be further divided into the decapods, which are even still divided into the dendrobranchiates (prawns) and the carideans (shrimp and snapping shrimp) .

The prawns have sequentially overlapping body segments (segment one covers the segment two, segment two covers segment three, etc), chlelate (claw like) first three leg pairs, and have a very basic larval body type.

The shrimps also have overlapping segments, however, in a different pattern (segment two overlaps segments one and three), only the first two leg pairs are chelate, and they have a more complex larval form.

Biologists distinguish the true shrimp from the true prawn because of the differences in their gill structures. The gill structure is lamellar in shrimp but branching in prawns. The easiest practical way to separate true shrimps from true prawns is to examine the second abdominal segment. The second segment of a shrimp overlaps both the first and the third segment, while the second segment of a prawn overlaps only the third segment .

Commercial and culinary definition

While in biological terms shrimps and prawns belong to different suborders of Decapoda, they are very similar in appearance. In commercial farming and fisheries, the terms shrimp and prawn are often used interchangeably. However, recent aquaculture literature increasingly uses the term "prawn" only for the freshwater forms of palaemonids and "shrimp" for the marine penaeids .

In the United Kingdom, the word rawn is more common on menus than hrimp; while the opposite is the case in North America. The term rawn is also loosely used to describe any large shrimp, especially those that come 15 (or fewer) to the pound (such as ing prawns, yet sometimes known as umbo shrimp). Australia and some other Commonwealth nations follow this British usage to an even greater extent, using the word rawn almost exclusively. When Australian comedian Paul Hogan used the phrase, 'll slip an extra shrimp on the barbie for you in an American television advertisement , it was intended to make what he was saying easier for his American audience to understand, and was thus a deliberate distortion of what an Australian would typically say.

In Britain very small crustaceans with a brownish shell are called shrimp, and are used to make potted shrimp. They are also used in dishes where they are not the primary ingredient.

Consumption

A fresh catch of brown shrimp, Crangon crangon

As with other seafood, shrimp is high in calcium, iodine and protein but low in food energy. A shrimp-based meal is also a significant source of cholesterol, from 122 mg to 251 mg per 100 g of shrimp, depending on the method of preparation  Shrimp consumption, however, is considered healthy for the circulatory system because the lack of significant levels of saturated fat in shrimp means that the high cholesterol content in shrimp actually improves the ratio of LDL to HDL cholesterol and lowers triglycerides .

Shrimp and other shellfish are among the most common food allergens . They are not kosher and thus are forbidden in Jewish cuisine. However, according to some Madh'hab, shrimp are halal, and therefore are permissible in Islamic cuisine.

Commercial fishing

Main article: Shrimp fishery

Double-rigged shrimp trawler hauling in the nets

Common commercial methods for catching shrimp and prawns include otter trawls, cast nets, seines, shrimp baiting and dip netting. Trawling involves the use of a system of nets. In some parts of the Pacific Northwest, fishing with baited traps is also common.

The following table shows the yearly weight of shrimp and prawns captured globally in millions of tonnes .

Production

1999

2000

2001

2002

2003

2004

2005

Million tonnes

3.03

3.09

2.96

2.97

3.55

3.54

3.42

The highest rates of incidental catch of non-target species is associated with shrimp trawling. In 1997, the FAO documented the estimated bycatch and discard levels from shrimp fisheries around the world. They found discard rates as high as 20 pounds for every pound of shrimp, with a world average of 5.7 pounds for every pound of shrimp .

Trawl nets in general, and shrimp trawls in particular, have been identified as sources of mortality for species of finfish and cetaceans . Bycatch is often discarded dead or dying by the time it is returned to the sea, and may alter the ecological balance in discarded regions . Worldwide, shrimp trawl fisheries generate about 2% of the world catch of fish in weight, but result in more than one third of the global bycatch total.

Farming

Tanks in a shrimp hatchery

Main articles: Shrimp farm and Freshwater prawn farm

A shrimp farm is an aquaculture business for the cultivation of marine shrimp or prawnsa for human consumption. Commercial shrimp farming began in the 1970s, and production grew steeply, particularly to match the market demands of the U.S., Japan and Western Europe. The total global production of farmed shrimp reached more than 1.6 million tonnes in 2003, representing a value of nearly 9,000 million U.S. dollars. About 75% of farmed shrimp are produced in Asia, in particular in China and Thailand. The other 25% are produced mainly in Latin America, where Brazil is the largest producer. The largest exporting nation is Thailand.

Marketing

Main article: Shrimp marketing

Shrimp are marketed and commercialized with several issues in mind. Most shrimp are sold frozen and marketed based on their categorization of presentation, grading, colour, and uniformity .

Preparation

Wikibooks Cookbook has a recipe/module on

shrimp

A steamed tail-on shrimp

Preparing shrimp for consumption usually involves removing the head, shell, tail, and "sand vein".

To deshell a shrimp, the tail is held while gently removing the shell around the body. The tail can be detached completely at this point, or left attached for presentation purposes.

Removing the "vein" (a euphemism for the digestive tract) can be referred to as "deveining", though in fact shrimp do not have any real veins; they have an open circulatory system. The "vein" can be removed by making a shallow cut lengthwise down the outer curve of the shrimp's body, allowing the dark ribbon-like digestive tract to be removed with a pointed utensil. Alternatively, if the tail has been detached, the vein can be pinched at the tail end and pulled out completely with the fingers. The shrimp is then rinsed under cold running water.

Shrimp and prawns are versatile ingredients, and are often used as an accompaniment to fried rice. Common methods of preparation include baking, boiling, and frying.

Recipes using shrimp form part of the cuisine of many cultures. Strictly speaking, dishes containing scampi should be made from the Norway lobster, a shrimp-like crustacean more closely related to the lobster than shrimp, but in some places it is quite common for large shrimp to be used instead.

Wet shrimp is commonly used as a flavouring and as a soup base in Asian cuisines (such as Thai tom yum goong) while fried shrimp is popular in North America. In Europe, shrimp is very popular, forming a necessary ingredient in Spanish paella de marisco, Italian cacciucco, Portuguese caldeirada and many other seafood dishes. Shrimp curry is very popular in South Asia and Southeast Asia. Shrimp are also found in Latin and Caribbean dishes such as enchiladas and coconut shrimp. Other recipes include jambalaya, okonomiyaki, poon choi and bagoong. It is consumed as salad, frying, pilav and shrimp casserole at western and southern coasts of Turkey.

Life cycle

Most shrimp mature and breed only in a marine habitat, although there are a small number of freshwater species. The females lay 50,000 to 1 million eggs, which hatch after some 24 hours into tiny nauplii. These nauplii feed on yolk reserves within their body and then undergo a metamorphosis into zoeae. This second larval stage feeds in the wild on algae and after a few days metamorphoses again into the third stage to become myses. At this stage the myses already begin to appear like tiny versions of fully-developed adults and feed on algae and zooplankton. After another three to four days they metamorphose a final time into postlarvae: young shrimp having all the characteristics of adults. The whole process takes about 12 days from hatching. In the wild, the marine postlarvae then migrate into estuaries, which are rich in nutrients and low in salinity. There they grow and eventually migrate back into open waters when they mature. Most adult shrimp are benthic animals living primarily on the sea floor.

Common shrimp species include pink, brown, white and snapping shrimp. Depending on the species and location, they grow from about 1.2 to 30 centimetres (0.47 to 11.8 in) long, and live between one and 6.5 years .

Fossil record

The fossil record of shrimp is sparse, with only 57 exclusively fossil species known . The earliest of these cannot be assigned to any family, but date from the Lower Jurassic and Cretaceous .

Home aquaria

Lysmata debelius, a popular aquarium shrimp

Several types of shrimp are kept in home aquaria. Some are purely ornamental, while others are useful in controlling algae and removing debris . Freshwater shrimp commonly available for aquaria include the Japanese marsh shrimp (Caridina multidentata, also called "Amano shrimp," as their use in aquaria was pioneered by Takashi Amano), cherry shrimp (Neocaridina heteropoda), and ghost or glass shrimp (Palaemonetes spp.). Popular saltwater shrimp include the cleaner shrimp Lysmata amboinensis, the fire shrimp (Lysmata debelius) and the harlequin shrimp (Hymenocera picta).

Etymology

The term shrimp originated around the 14th century with the Middle English shrimpe, akin to the Middle Low German schrempen, and meaning to contract or wrinkle; and the Old Norse skorpna, meaning to shrivel up .

See also

List of shrimp and prawn species

List of freshwater aquarium shrimp

The Shrimp Girl by William Hogarth

Shrimp baiting

References

^ a b Sammy De Grave, N. Dean Pentcheff, Shane T. Ahyong et al. (2009). "A classification of living and fossil genera of decapod crustaceans" (PDF). Raffles Bulletin of Zoology Suppl. 21: 1109. http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf. 

^ "Biology of Shrimps". Museum Victoria Australia. http://museumvictoria.com.au/crust/caribiol.html#svp. Retrieved Janaury 9, 2010. 

^ Charles Raabe & Linda Raabe (2008). "The Caridean shrimp: Shrimp Anatomy - Illustrations and Glossary". http://www.chucksaddiction.com/Caridean.html. 

^ "Shrimp Aquaculture and the Environment - An Environment Impact Assessment Report, chapter 2; IAA report". Indian Aquaculture Authority. 2001. http://aquaculture.tn.nic.in/pdf/farming.pdf. 

^ Bill Baker & Peggy Bendel. "Come and Say Gay!". Travel Marketing Decisions (Association of Travel Marketing Executives) (Summer 2005). http://www.atme.org/pubs/archives/77_1898_11926.cfm. Retrieved December 21, 2007. 

^ "Cholesterol Content in Seafoods". http://www.dietaryfiberfood.com/cholesterol-shrimp.php. Retrieved January 7, 2007. 

^ Elizabeth R. De Oliveira e Silva, Cynthia E. Seidman, Jason J. Tian, Lisa C. Hudgins, Frank M. Sacks & Jan L. Breslow (l996). "Effects of shrimp consumption on plasma lipoproteins". American Journal of Clinical Nutrition 64: 712717. http://www.ajcn.org/cgi/reprint/64/5/712.pdf. 

^ "Common Food Allergens". Food Allergy & Anaphylaxis Network. http://www.foodallergy.org/allergens/index.html. Retrieved June 24, 2007. 

^ State of the World Fisheries and Aquaculture 2006. FAO. 2007. ISBN 978-92-5-105568-7. http://www.fao.org/docrep/009/A0699e/A0699e00.htm. 

^ Ivor Clucas (1997). Discards and bycatch in shrimp trawl fisheries. Fisheries Circular No. 928 FIIU/C928. Food and Agriculture Organization. http://www.fao.org/docrep/W6602E/w6602E09.htm. 

^ "Final Habitat Plan for the South Atlantic Region". South Atlantic Fisheries Management Council. 1998. http://www.safmc.net/Default.aspx?tabid=80. 

^ Lance E. Morgan & Ratana Chuenpagdee (2003). Shifting Gears. Addressing the Collateral Impacts of Fishing Methods in U.S. Waters. Pew science series on conservation and the environment. Island Press. ISBN 1-55963-659-9. http://www.mcbi.org/publications/pub_pdfs/ShiftingGears.pdf. 

^ "ScienceDirect - Aquaculture : Comparative economics of shrimp farming in Asia". www.sciencedirect.com. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T4D-3T8P28T-F&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=48a8882e385af72d0dbdbacde67a9ebe. Retrieved March 27, 2008. 

^ "A bouillabaisse of fascinating facts about fish". NOAA: National Marine Fisheries Service. http://www.nefsc.noaa.gov/faq/. Retrieved October 22, 2009. 

^ Fenner A. Chace, Jr. & Raymond B. Manning (1972). "Two New Caridean Shrimps, One Representing a New Family, from Marine Pools on Ascension Island (Crustacea: Decapoda: Natantia)". Smithsonian Contributions to Zoology 131: 18 pp. http://si-pddr.si.edu/dspace/bitstream/10088/5471/2/SCtZ-0131-Lo_res.pdf. 

^ Joe Anderson. "Freshwater Shrimp in the Aquarium". The Krib. http://www.thekrib.com/Fish/Shrimp/. Retrieved July 19, 2006. 

^ "Shrimp". Merriam-Webster Online Dictionary. 2008. http://www.merriam-webster.com/dictionary/shrimp. Retrieved October 13, 2008. 

External links

Wikimedia Commons has media related to: Caridea

Wikispecies has information related to: Caridea

About shrimp, for kids and teens at the Open Directory Project

Shrimp biology at the Open Directory Project

Shrimp recipes at the Open Directory Project

v  d  e

Principal commercial fishery species groups

Wild

Large pelagic fish

Mackerel  Salmon  Shark  Swordfish  Tuna (yellowfin, bigeye, bluefin, albacore and skipjack)

Forage fish

Anchovy  Capelin  Herring  Hilsa  Menhaden  Sardines  Shad

Demersal fish

Catfish  Cod (Atlantic, Pacific)  Flatfish (flounder, halibut, plaice, sole and turbot)  Haddock  Mullet  Orange roughy  Pollock  Smelt-whitings  Toothfish

Freshwater fish

Carp  Sturgeon  Tilapia  Trout

Other wild fish

Eel  Whitebait  more...

Crustaceans

Crab  Krill  Lobster  Shrimp  more...

Molluscs

Abalone  Mussels  Octopus  Oysters  Scallops  Squid  more...

Echinoderms

Sea cucumbers  Sea urchin  more...

Farmed

Carp (bighead, common, crucian, grass, silver)  Catfish  Freshwater prawns  Mussels  Oysters  Salmon (Atlantic, salmon trout, coho, chinook)  Tilapia  Shrimp

Commercial fishing  World fish production  Fishing topics  Fisheries glossary

Categories: Caridea | Edible crustaceans | Commercial crustaceans | Seafood

Nanoparticle

China Product


Background

Although nanoparticles are generally considered an invention of modern science, they actually have a very long history. Nanoparticles were used by artisans as far back as the 9th century in Mesopotamia for generating a glittering effect on the surface of pots.

Even these days, pottery from the Middle Ages and Renaissance often retain a distinct gold or copper colored metallic glitter. This so called luster is caused by a metallic film that was applied to the transparent surface of a glazing. The luster can still be visible if the film has resisted atmospheric oxidation and other weathering. bridal corset

The luster originated within the film itself, which contained silver and copper nanoparticles dispersed homogeneously in the glassy matrix of the ceramic glaze. These nanoparticles were created by the artisans by adding copper and silver salts and oxides together with vinegar, ochre and clay, on the surface of previously-glazed pottery. The object was then placed into a kiln and heated to about 600 C in a reducing atmosphere. cheap corsets

In the heat the glaze would soften, causing the copper and silver ions to migrate into the outer layers of the glaze. There the reducing atmosphere reduced the ions back to metals, which then came together forming the nanoparticles that give the colour and optical effects. slimming undergarments

Luster technique showed that ancient craftsmen had a rather sophisticated empirical knowledge of materials. The technique originated in the islamic world. As Muslims were not allowed to use gold in artistic representations, they had to find a way to create a similar effect without using real gold. The solution they found was using luster.

Michael Faraday provided the first description, in scientific terms, of the optical properties of nanometer-scale metals in his classic 1857 paper. In a subsequent paper, the author (Turner) points out that: "It is well known that when thin leaves of gold or silver are mounted upon glass and heated to a temperature which is well below a red heat (~500 C), a remarkable change of properties takes place, whereby the continuity of the metallic film is destroyed. The result is that white light is now freely transmitted, reflection is correspondingly diminished, while the electrical resistivity is enormously increased."

Uniformity

Colloidal crystal composed of amorphous hydrated colloidal silica (particle diameter 600 nm)

The chemical processing and synthesis of high performance technological components for the private, industrial and military sectors requires the use of high purity ceramics, polymers, glass-ceramics and material composites. In condensed bodies formed from fine powders, the irregular particle sizes and shapes in a typical powder often lead to non-uniform packing morphologies that result in packing density variations in the powder compact.

Uncontrolled agglomeration of powders due to attractive van der Waals forces can also give rise to in microstructural inhomogeneities. Differential stresses that develop as a result of non-uniform drying shrinkage are directly related to the rate at which the solvent can be removed, and thus highly dependent upon the distribution of porosity. Such stresses have been associated with a plastic-to-brittle transition in consolidated bodies, and can yield to crack propagation in the unfired body if not relieved.

In addition, any fluctuations in packing density in the compact as it is prepared for the kiln are often amplified during the sintering process, yielding inhomogeneous densification. Some pores and other structural defects associated with density variations have been shown to play a detrimental role in the sintering process by growing and thus limiting end-point densities. Differential stresses arising from inhomogeneous densification have also been shown to result in the propagation of internal cracks, thus becoming the strength-controlling flaws.

It would therefore appear desirable to process a material in such a way that it is physically uniform with regard to the distribution of components and porosity, rather than using particle size distributions which will maximize the green density. The containment of a uniformly dispersed assembly of strongly interacting particles in suspension requires total control over interparticle forces. Monodisperse nanoparticles and colloids provide this potential.

Monodisperse powders of colloidal silica, for example, may therefore be stabilized sufficiently to ensure a high degree of order in the colloidal crystal or polycrystalline colloidal solid which results from aggregation. The degree of order appears to be limited by the time and space allowed for longer-range correlations to be established. Such defective polycrystalline colloidal structures would appear to be the basic elements of submicrometer colloidal materials science, and, therefore, provide the first step in developing a more rigorous understanding of the mechanisms involved in microstructural evolution in high performance materials and components.

Properties

Silicon nanopowder

Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures. A bulk material should have constant physical properties regardless of its size, but at the nano-scale size-dependent properties are often observed. Thus, the properties of materials change as their size approaches the nanoscale and as the percentage of atoms at the surface of a material becomes significant. For bulk materials larger than one micrometer (or micron), the percentage of atoms at the surface is insignificant in relation to the number of atoms in the bulk of the material. The interesting and sometimes unexpected properties of nanoparticles are therefore largely due to the large surface area of the material, which dominates the contributions made by the small bulk of the material.

An excellent example of this is the absorption of solar radiation in photovoltaic cells, which is much higher in materials composed of nanoparticles than it is in thin films of continuous sheets of material. In this case, the smaller the particles, the greater the solar absorption.

Other size-dependent property changes include quantum confinement in semiconductor particles, surface plasmon resonance in some metal particles and superparamagnetism in magnetic materials. Ironically, the changes in physical properties are not always desirable. Ferroelectric materials smaller than 10 nm can switch their magnetisation direction using room temperature thermal energy, thus making them unsuitable for memory storage.

Suspensions of nanoparticles are possible since the interaction of the particle surface with the solvent is strong enough to overcome density differences, which otherwise usually result in a material either sinking or floating in a liquid. Nanoparticles also often possess unexpected optical properties as they are small enough to confine their electrons and produce quantum effects. For example gold nanoparticles appear deep red to black in solution.

Nanoparticles have a very high surface area to volume ratio, which provides a tremendous driving force for diffusion, especially at elevated temperatures. Sintering can take place at lower temperatures, over shorter time scales than for larger particles. This theoretically does not affect the density of the final product, though flow difficulties and the tendency of nanoparticles to agglomerate complicates matters. The large surface area to volume ratio also reduces the incipient melting temperature of nanoparticles.

Moreover nanoparticles have been found to impart some extra properties to various day to day products. For example the presence of titanium dioxide nanoparticles imparts what we call the self-cleaning effect, and the size being nanorange, the particles can not be observed. Zinc oxide particles have been found to have superior UV blocking properties compared to its bulk substitute. This is one of the reasons why it is often used in the preparation of sunscreen lotions.

Clay nanoparticles when incorporated into polymer matrices increase reinforcement, leading to stronger plastics, verifiable by a higher glass transition temperature and other mechanical property tests. These nanoparticles are hard, and impart their properties to the polymer (plastic). Nanoparticles have also been attached to textile fibers in order to create smart and functional clothing.

Metal, dielectric, and semiconductor nanoparticles have been formed, as well as hybrid structures (e.g., core-shell nanoparticles). Nanoparticles made of semiconducting material may also be labeled quantum dots if they are small enough (typically sub 10 nm) that quantization of electronic energy levels occurs. Such nanoscale particles are used in biomedical applications as drug carriers or imaging agents.

Semi-solid and soft nanoparticles have been manufactured. A prototype nanoparticle of semi-solid nature is the liposome. Various types of liposome nanoparticles are currently used clinically as delivery systems for anticancer drugs and vaccines.

Synthesis

There are several methods for creating nanoparticles, including both attrition and pyrolysis. In attrition, macro or micro scale particles are ground in a ball mill, a planetary ball mill, or other size reducing mechanism. The resulting particles are air classified to recover nanoparticles. In pyrolysis, a vaporous precursor (liquid or gas) is forced through an orifice at high pressure and burned. The resulting solid (a version of soot) is air classified to recover oxide particles from by-product gases. Pyrolysis often results in aggregates and agglomerates rather than singleton primary particles.

A thermal plasma can also deliver the energy necessary to cause evaporation of small micrometer size particles. The thermal plasma temperatures are in the order of 10,000 K, so that solid powder easily evaporates. Nanoparticles are formed upon cooling while exiting the plasma region. The main types of the thermal plasma torches used to produce nanoparticles are dc plasma jet, dc arc plasma and radio frequency (RF) induction plasmas. In the arc plasma reactors, the energy necessary for evaporation and reaction is provided by an electric arc which is formed between the anode and the cathode. For example, silica sand can be vaporized with an arc plasma at atmospheric pressure. The resulting mixture of plasma gas and silica vapour can be rapidly cooled by quenching with oxygen, thus ensuring the quality of the fumed silica produced. In RF induction plasma torches, energy coupling to the plasma is accomplished through the electromagnetic field generated by the induction coil. The plasma gas does not come in contact with electrodes, thus eliminating possible sources of contamination and allowing the operation of such plasma torches with a wide range of gases including inert, reducing, oxidizing and other corrosive atmospheres.

The working frequency is typically between 200 kHz and 40 MHz. Laboratory units run at power levels in the order of 30-50 kW while the large scale industrial units have been tested at power levels up to 1 MW. As the residence time of the injected feed droplets in the plasma is very short it is important that the droplet sizes are small enough in order to obtain complete evaporation. The RF plasma method has been used to synthesize different nanoparticle materials, for example synthesis of various ceramic nanoparticles such as oxides, carbours/carbides and nitrides of Ti and Si (see Induction plasma technology).

Inert-gas condensation is frequently used to make nanoparticles from metals with low melting points. The metal is vaporized in a vacuum chamber and then supercooled with an inert gas stream. The supercooled metal vapor condenses in to nanometer-sized particles, which can be entrained in the inert gas stream and deposited on a substrate or studied in situ.

Sol-gel

The sol-gel process is a wet-chemical technique (also known as chemical solution deposition) widely used recently in the fields of materials science and ceramic engineering. Such methods are used primarily for the fabrication of materials (typically a metal oxide) starting from a chemical solution (sol, short for solution) which acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers.

Typical precursors are metal alkoxides and metal chlorides, which undergo hydrolysis and polycondensation reactions to form either a network "elastic solid" or a colloidal suspension (or dispersion) a system composed of discrete (often amorphous) submicrometer particles dispersed to various degrees in a host fluid. Formation of a metal oxide involves connecting the metal centers with oxo (M-O-M) or hydroxo (M-OH-M) bridges, therefore generating metal-oxo or metal-hydroxo polymers in solution. Thus, the sol evolves towards the formation of a gel-like diphasic system containing both a liquid phase and solid phase whose morphologies range from discrete particles to continuous polymer networks.

In the case of the colloid, the volume fraction of particles (or particle density) may be so low that a significant amount of fluid may need to be removed initially for the gel-like properties to be recognized. This can be accomplished in any number of ways. The most simple method is to allow time for sedimentation to occur, and then pour off the remaining liquid. Centrifugation can also be used to accelerate the process of phase separation.

Removal of the remaining liquid (solvent) phase requires a drying process, which is typically accompanied by a significant amount of shrinkage and densification. The rate at which the solvent can be removed is ultimately determined by the distribution of porosity in the gel. The ultimate microstructure of the final component will clearly be strongly influenced by changes implemented during this phase of processing. Afterwards, a thermal treatment, or firing process, is often necessary in order to favor further polycondensation and enhance mechanical properties and structural stability via final sintering, densification and grain growth. One of the distinct advantages of using this methodology as opposed to the more traditional processing techniques is that densification is often achieved at a much lower temperature.

The precursor sol can be either deposited on a substrate to form a film (e.g. by dip-coating or spin-coating), cast into a suitable container with the desired shape (e.g. to obtain a monolithic ceramics, glasses, fibers, membranes, aerogels), or used to synthesize powders (e.g. microspheres, nanospheres). The sol-gel approach is a cheap and low-temperature technique that allows for the fine control of the product chemical composition. Even small quantities of dopants, such as organic dyes and rare earth metals, can be introduced in the sol and end up in unifromly dispersed in the final product. It can be used in ceramics processing and manufacturing as an investment casting material, or as a means of producing very thin films of metal oxides for various purposes. Sol-gel derived materials have diverse applications in optics, electronics, energy, space, (bio)sensors, medicine (e.g. controlled drug release) and separation (e.g. chromatography) technology.

The interest in sol-gel processing can be traced back in the mid-1880s with the observation that the hydrolysis of tetraethyl orthosilicate (TEOS) under acidic conditions led to the formation of SiO2 in the form of fibers and monoliths. Sol-gel research grew to be so important that in the 1990s more than 35,000 papers were published worldwide on the process.

Colloids

Nanostars of vanadium(IV) oxide

The term colloid is used primarily to describe a broad range of solid-liquid (and/or liquid-liquid) mixtures, all of which contain distinct solid (and/or liquid) particles which are dispersed to various degrees in a liquid medium. The term is specific to the size of the individual particles, which are larger than atomic dimensions but small enough to exhibit Brownian motion. If the particles are large enough, then their dynamic behavior in any given period of time in suspension would be governed by forces of gravity and sedimentation. But if they are small enough to be colloids, then their irregular motion in suspension can be attributed to the collective bombardment of a myriad of thermally agitated molecules in the liquid suspending medium, as described originally by Albert Einstein in his dissertation. Einstein proved the existence of water molecules by concluding that this erratic particle behavior could adequately be described using the theory of Brownian motion, with sedimentation being a possible long-term result. This critical size range (or particle diameter) typically ranges from nanometers (109 m) to micrometers (106 m).

Morphology

Scientists have taken to naming their particles after the real world shapes that they might represent. Nanospheres, nanoreefs , nanoboxes and more have appeared in the literature. These morphologies sometimes arise spontaneously as an effect of a templating or directing agent present in the synthesis such as miscellar emulsions or anodized alumina pores, or from the innate crystallographic growth patterns of the materials themselves. Some of these morphologies may serve a purpose, such as long carbon nanotubes being used to bridge an electrical junction, or just a scientific curiosity like the stars shown at right.

Generally speaking, amorphous particles will adopt a spherical shape (due to their microstructural isotropy)-- whereas anisotropic microcrystlaline whiskers will adopt the geometrical form corresponding to their particular crystal habit. At the small end of the size range, nanoparticles are often referred to as clusters. Spheres, rods, fibers, and cups are just a few of the shapes that have been grown. The study of fine particles is called micromeritics.

Characterization

TEM image of magnetic Fe3O4 nanoparticle

Nanoparticle characterization is necessary to establish understanding and control of nanoparticle synthesis and applications. Characterization is done by using a variety of different techniques, mainly drawn from materials science. Common techniques are electron microscopy (TEM,SEM), atomic force microscopy (AFM), dynamic light scattering (DLS), x-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF),ultraviolet-visible spectroscopy, dual polarisation interferometry and nuclear magnetic resonance (NMR).

Whilst the theory has been known for over a century (see Robert Brown), the technology for Nanoparticle tracking analysis (NTA) allows direct tracking of the Brownian motion and this method therefore allows the sizing of individual nanoparticles in solution.

Safety

See also: Nanotoxicology , Fine particles, and Regulation of nanotechnology

Nanoparticles present possible dangers, both medically and environmentally. Most of these are due to the high surface to volume ratio, which can make the particles very reactive or catalytic. They are also able to pass through cell membranes in organisms, and their interactions with biological systems are relatively unknown. However, free nanoparticles in the environment quickly tend to agglomerate and thus leave the nano-regime, and nature itself presents many nanoparticles to which organisms on earth may have evolved immunity (such as salt particulates from ocean aerosols, terpenes from plants, or dust from volcanic eruptions)[citation needed]. A fuller analysis is provided in the article on nanotechnology.

According to the San Francisco Chronicle, "Animal studies have shown that some nanoparticles can penetrate cells and tissues, move through the body and brain and cause biochemical damage they also have shown to cause a risk factor in men for testicular cancer. But whether cosmetics and sunscreens containing nanomaterials pose health risks remains largely unknown, pending completion of long-range studies recently begun by the FDA and other agencies." Diesel nanoparticles have been found to damage the cardiovascular system in a mouse model.

See also

Ceramic engineering

Coating

Colloid

Colloid-facilitated transport

Colloidal crystal

Eigencolloid

Gallium selenide

Indium selenide

Liposome

Magnetic immunoassay

Magnetic nanoparticles

Micromeritics

Nanobiotechnology

Nanocrystalline silicon

Nanogeoscience

Nanomaterials

Nanoparticle Tracking Analysis

Nanotechnology

Photonic crystal

Plasmon

Quantum dot

Silicon

Silver Nano

Sol-gel

Transparent materials

v  d  e

Nanotechnology (portal)

Overview

History   Implications   Applications   Regulation   Organizations   Popular culture   List of topics

Nanomaterials

Fullerene   Carbon nanotubes   Nanoparticles

Nanomedicine

Nanotoxicology   Nanosensor

Molecular self-assembly

Self-assembled monolayer   Supramolecular assembly   DNA nanotechnology

Nanoelectronics

Molecular electronics   Nanolithography

Scanning probe microscopy

Atomic force microscope   Scanning tunneling microscope

Molecular nanotechnology

Molecular assembler   Nanorobotics   Mechanosynthesis

References

^ Cristina Buzea, Ivan Pacheco, and Kevin Robbie (2007). "Nanomaterials and Nanoparticles: Sources and Toxicity". Biointerphases 2: MR17R71. http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=BJIOBN00000200000400MR17000001&idtype=cvips&gifs=Yes. 

^ ASTM E 2456 - 06 Standard Terminology Relating to Nanotechnology

^ Fahlman, B. D. (2007). Materials Chemistry. Springer. pp. 282283. ISBN 1402061196. http://books.google.com/books?id=lByCslty2oUC&pg=PT287. 

^ Faraday, Michael (1857). "Experimental relations of gold (and other metals) to light". Phil. Trans. Roy. Soc. London 147: 145181. doi:10.1098/rstl.1857.0011. 

^ Beilby, G.T. (1903). "The Effects of Heat and of Solvents on Thin Films of Metal". Proc. Roy. Soc. A 72: 226. http://www.jstor.org/pss/116470. 

^ Turner, T. (1908). "Transparent Silver and Other Metallic Films". Proc. Roy. Soc. Lond. A 81 (548): 301. http://www.jstor.org/pss/93060. 

^ Edited by George Y. Onoda, Jr., and Larry L. Hench (1979). Onoda, G.Y., Jr. and Hench, L.L. Eds. ed. Ceramic Processing Before Firing. New York: Wiley & Sons. ISBN 0471654108. 

^ Aksay, I.A., Lange, F.F., Davis, B.I. (1983). "Uniformity of Al2O3-ZrO2 Composites by Colloidal Filtration". J. Am. Ceram. Soc. 66: C-190. doi:10.1111/j.1151-2916.1983.tb10550.x. 

^ Franks, G.V. and Lange, F.F. (1996). "Plastic-to-Brittle Transition of Saturated, Alumina Powder Compacts". J. Am. Ceram. Soc. 79: 3161. doi:10.1111/j.1151-2916.1996.tb08091.x. 

^ Evans, A.G. and Davidge, R.W. (1969). "The strength and fracture of fully dense polycrystalline magnesium oxide". Phil. Mag. 20 (164): 373. doi:10.1080/14786436908228708. 

^ J Mat. Sci. 5: 314. 1970. 

^ Lange, F.F. and Metcalf, M. (1983). "Processing-Related Fracture Origins: II, Agglomerate Motion and Cracklike Internal Surfaces Caused by Differential Sintering". J. Am. Ceram. Soc. 66: 398. doi:10.1111/j.1151-2916.1983.tb10069.x. 

^ Evans, A.G. (1987). "Considerations of Inhomogeneity Effects in Sintering". J. Am. Ceram. Soc. 65: 497. doi:10.1111/j.1151-2916.1982.tb10340.x. 

^ Whitesides, G.M., et al. (1991). "Molecular Self-Assembly and Nanochemistry: A Chemical Strategy for the Synthesis of Nanostructures". Science 254: 1312. doi:10.1126/science.1962191. 

^ Dubbs D. M, Aksay I.A. (2000). "Self-Assembled Ceramics". Ann. Rev. Phys. Chem. 51: 601. doi:10.1146/annurev.physchem.51.1.601. 

^ Buffat, Ph.; Burrel, J.-P. (1976). "Size effect on the melting temperature of gold particles". Physical Review A 13 (6): 22872298. doi:10.1103/PhysRevA.13.2287. 

^ "The Textiles Nanotechnology Laboratory". http://nanotextiles.human.cornell.edu/. 

^ Brinker, C.J.; G.W. Scherer (1990). Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing. Academic Press. ISBN 0121349705. 

^ L.L.Hench, J.K.West; West, Jon K. (1990). "The Sol-Gel Process". Chem. Rev. 90: 3372. doi:10.1021/cr00099a003. 

^ Klein, L. (1994). Sol-Gel Optics: Processing and Applications. Springer Verlag. ISBN 0792394240. http://books.google.com/books?id=wH11Y4UuJNQC&printsec=frontcover. 

^ Dislich, H., Glass. Tech. Berlin., Vol.44, p.1 (1971); Dislich, Helmut (1971). "New Routes to Multicomponent Oxide Glasses". Angewandte Chemie International Edition in English 10: 363. doi:10.1002/anie.197103631. 

^ Matijevic, Egon. (1986). "Monodispersed colloids: art and science". Langmuir 2: 12. doi:10.1021/la00067a002. 

^ Brinker, C. J.; Mukherjee, S. P. (1981). "Conversion of monolithic gels to glasses in a multicomponent silicate glass system". Journal of Materials Science 16: 1980. doi:10.1007/BF00540646. 

^ Sakka, S; Kamiya, K (1980). "Glasses from metal alcoholates". Journal of Non-Crystalline Solids 42: 403. doi:10.1016/0022-3093(80)90040-X. 

^ Yoldas, B. E. (1979). "Monolithic glass formation by chemical polymerization". Journal of Materials Science 14: 1843. doi:10.1007/BF00551023. 

^ Prochazka, S.; Klug, F. J. (1983). "Infrared-Transparent Mullite Ceramic". Journal of the American Ceramic Society 66: 874. doi:10.1111/j.1151-2916.1983.tb11004.x. 

^ Ikesue, Akio; Kinoshita, Toshiyuki; Kamata, Kiichiro; Yoshida, Kunio (1995). "Fabrication and Optical Properties of High-Performance Polycrystalline Nd:YAG Ceramics for Solid-State Lasers". Journal of the American Ceramic Society 78: 1033. doi:10.1111/j.1151-2916.1995.tb08433.x. 

^ Ikesue, A (2002). "Polycrystalline Nd:YAG ceramics lasers". Optical Materials 19: 183. doi:10.1016/S0925-3467(01)00217-8. 

^ Pais, A. (2005). Subtle is the Lord: The Science and the Life of Albert Einstein. Oxford University Press. ISBN 0192806726. http://books.google.com/books?id=U2mO4nUunuwC&printsec=frontcover. 

^ Agam, M. A.; Guo, Q (2007). "Electron Beam Modification of Polymer Nanospheres". Journal of Nanoscience and Nanotechnology 7 (10): 3615. doi:10.1166/jnn.2007.814. PMID 18330181. 

^ Choy J.H., Jang E.S., Won J.H., Chung J.H., Jang D.J., and Kim Y.W. (2004). "Hydrothermal route to ZnO nanocoral reefs and nanofibers". Appl. Phys. Lett. 84: 287. doi:10.1063/1.1639514. 

^ Sun, Y; Xia, Y (2002). "Shape-controlled synthesis of gold and silver nanoparticles.". Science 298 (5601): 21769. doi:10.1126/science.1077229. PMID 12481134. 

^ Murphy, Cj (2002). "Materials science. Nanocubes and nanoboxes.". Science 298 (5601): 213941. doi:10.1126/science.1080007. PMID 12481122. 

^ Mnyusiwalla, Anisa; Daar, Abdallah S; Singer, Peter A (2003). "Mind the gap : science and ethics in nanotechnology". Nanotechnology 14: R9. doi:10.1088/0957-4484/14/3/201. 

^ Ying, Jackie (2001). Nanostructured Materials. New York: Academic Press. ISBN 0127444513. http://books.google.com/books?id=_pbtbJwkj5YC&printsec=frontcover. 

^ Nanotechnologies: 6. What are potential harmful effects of nanoparticles?

^ Keay Davidson. "FDA urged to limit nanoparticle use in cosmetics and sunscreens". San Francisco Chronicle. http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/05/17/MNGFHIT1161.DTL. Retrieved 2007-04-20. 

^ Study Pollution Particles Lead to Higher Heart Attack Risk (Update1)

External links

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Nanotechnology

Nanohedron.com images of nanoparticles

International Liposome Society

Textiles Nanotechnology Laboratory at Cornell University

Assessing health risks of nanoparticles summary by GreenFacts of the European Commission SCENIHR assessment

Nano Structured Material

Nanoparticles Used In Solar Energy Conversion (ScienceDaily).

Application of nanoparticles in biology and medicine

Applications of Nanoparticles

Journal of Nanoparticle Research

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Lectures on All Phases of Nanoparticle Science and Technology

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