Micrometre

The micrometre (International spelling as used by the International Bureau of Weights and Measures;[1] SI symbol: μm) or micrometer (American spelling), also commonly known by the previous name micron, is an SI derived unit of length equalling 1×10−6 metre (SI standard prefix "micro-" = 10−6); that is, one millionth of a metre (or one thousandth of a millimetre, 0.001 mm, or about 0.000039 inch).[1]

The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria,[1] and for grading wool by the diameter of the fibres.[2] The width of a single human hair ranges from approximately 10 to 200 μm. The longest human chromosome is approximately 10 μm in length.

Micrometre
Cfaser haarrp
A 6 μm diameter carbon filament above a 50 μm diameter human hair
General information
Unit systemmetric
Unit oflength
Symbolμm 
Conversions
1 μm in ...... is equal to ...
   SI units   1×10−6 m
   Natural units   6.1877×1028 P
1.8897×104 a0
   imperial/US units   3.2808×10−6 ft
 3.9370×10−5 in

Examples

Between 1 μm and 10 μm:

Between 10 μm and 100 μm

  • about 10–12 μm – thickness of plastic wrap (cling wrap)
  • 10 to 55 μm – width of wool fibre[5]
  • 17 to 181 μm – diameter of human hair[6]
  • 70 to 180 μm – thickness of paper

SI standardization

The term micron and the symbol μ were officially accepted for use in isolation to denote the micrometre in 1879, but officially revoked by the International System of Units (SI) in 1967.[7] This became necessary because the older usage was incompatible with the official adoption of the unit prefix micro-, denoted μ, during the creation of the SI in 1960.

In the SI, the systematic name micrometre became the official name of the unit, and μm became the official unit symbol.

Nevertheless, in practice, "micron" remains a widely used term in preference to "micrometre" in many English-speaking countries, both in academic science (including geology, biology, physics, and astronomy) and in applied science and industry (including machining, the semiconductor industry, and plastics manufacturing). Additionally, in American English, the use of "micron" helps differentiate the unit from the micrometer, a measuring device, because the unit's name in mainstream American spelling is a homograph of the device's name. In spoken English, they may be distinguished by pronunciation, as the name of the measuring device is invariably stressed on the second syllable, whereas the systematic pronunciation of the unit name, in accordance with the convention for pronouncing SI units in English, places the stress on the first syllable.

The plural of micron is normally "microns", though "micra" was occasionally used before 1950.[8][9][10]

Symbol

The official symbol for the SI prefix micro- is a Greek lowercase mu (μ).[11] In Unicode, there is also a micro sign with the code point U+00B5 (µ), distinct from the code point U+03BC (μ) of the Greek letter lowercase mu. According to the Unicode Consortium, the Greek letter character is preferred,[12] but implementations must recognize the micro sign as well. Most fonts use the same glyph for the two characters.

See also

Notes and references

  1. ^ a b c "micrometre". Encyclopædia Britannica Online. Retrieved 18 May 2014.
  2. ^ "Wool Fibre". "NSW Department of Education and Communities". Archived from the original (Word Document download) on 17 June 2016. Retrieved 18 May 2014.
  3. ^ Smith, D.J.; Gaffney, E.A.; Blake, J.R.; Kirkman-Brown, J.C. (25 February 2009). "Human sperm accumulation near surfaces: a simulation study" (PDF). Journal of Fluid Mechanics. Cambridge University Press. 621: 295. Bibcode:2009JFM...621..289S. doi:10.1017/S0022112008004953. Archived from the original (PDF) on 6 November 2013. Retrieved 20 May 2012.
  4. ^ Ramel, Gordon. "Spider Silk". Archived from the original on 4 December 2008. Retrieved 14 December 2008. A typical strand of garden spider silk has a diameter of about 0.003 mm ... Dragline silk (about .00032 inch (.008 mm) in Nephila)
  5. ^ "Fibreshape applications". IST - Innovative Sintering Technologies Ltd. Retrieved 4 December 2008. Histogram of Fiber Thickness [micrometer]
  6. ^ The diameter of human hair ranges from 17 to 181 μm. Ley, Brian (1999). Elert, Glenn (ed.). "Diameter of a human hair". The Physics Factbook. Retrieved 8 December 2018.
  7. ^ BIPM - Resolution 7 of the 13th CGPM 1967/68), "Abrogation of earlier decisions (micron, new candle.)"
  8. ^ Proceedings of the Royal Society of Queensland. Part I. XIX. H. Pole & Co. – via Google Books.
  9. ^ Bigalow, Edward Fuller; Agassiz Association (1905). The Observer. 7–8 – via Google Books.
  10. ^ 10 micra/10 microns (Start at 1885; before that, the word "micron", singular or plural, was rare)
  11. ^ "Prefixes of the International System of Units". International Bureau of Weights and Measures. Retrieved 9 May 2016.
  12. ^ Beeton, Barbara; Freytag, Asmus; Sargent, Murray III (30 May 2017). "Unicode® Technical Report #25". Unicode Technical Reports. Unicode Consortium. p. 11.

External links

  • The dictionary definition of micrometre at Wiktionary
Beauty micrometer

The beauty micrometer, also known as the beauty calibrator, was a device designed in the early 1930s to help in the identification of the areas of a person's face which need to have their appearance reduced or enhanced by make-up. The inventors include famed beautician Max Factor Sr. A 2013 Wired article described the device as "a Clockwork Orange style device" that combines "phrenology, cosmetics and a withering pseudo-scientific analysis". A photograph of Factor, using the device on actress Marjorie Reynolds featured in a 1935 article in science magazine Modern Mechanix and, when republished by The Guardian in 2013, the caption described it as being "a contraption that looks like an instrument of torture".Placed on and around the head and face, the beauty micrometer uses flexible metal strips which align with a person's facial features. The screws holding the strips in place allow for 325 adjustments, enabling the operator to make fine measurements with a precision of one thousandth of an inch. The inventors stated that there are two key measurements that they looked for: the heights of the nose and forehead should be the same, and the eyes should be separated by the width of one eye. When an imperfection is identified, corrective make-up can be applied to enhance or subdue the feature. The company Max Factor claims that the device helped Max Factor, Sr. to better understand the female face.The beauty micrometer was completed in 1932 and was primarily intended for use in the movie industry. When an actor's face is shown in a very large scale their "flaws" are magnified and can become "glaring distortions", according to the Modern Mechanix article. This device was intended to remedy the perceived problem, and the inventors also envisioned it being used in beauty shops. However, it did not become popular and did not gain widespread usage. Only one beauty micrometer is believed to exist. It is featured in a display at the Hollywood Entertainment Museum and came up for auction in 2009, falling significantly short of the $10,000–$20,000 estimate.

Charcot–Bouchard aneurysm

Charcot–Bouchard aneurysms are aneurysms of the brain vasculature which occur in small blood vessels (less than 300 micrometre diameter). Charcot–Bouchard aneurysms are most often located in the lenticulostriate vessels of the basal ganglia and are associated with chronic hypertension. Charcot–Bouchard aneurysms are a common cause of cerebral hemorrhage.

Dark nebula

A dark nebula or absorption nebula is a type of interstellar cloud that is so dense that it obscures the light from objects behind it, such as background stars and emission or reflection nebulae. The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of larger molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called Bok globules. Like other interstellar dust or material, things it obscures are only visible using radio waves in radio astronomy or infrared in infrared astronomy.

Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, C18O (CO with oxygen as the 18O isotope), CS, NH3 (ammonia), H2CO (formaldehyde), c-C3H2 (cyclopropenylidene) and a molecular ion N2H+ (diazenylium), all of which are relatively transparent. These clouds are the spawning grounds of stars and planets, and understanding their development is essential to understanding star formation.The form of such dark clouds is very irregular: they have no clearly defined outer boundaries and sometimes take on convoluted serpentine shapes. The largest dark nebulae are visible to the naked eye, appearing as dark patches against the brighter background of the Milky Way like the Coalsack Nebula and the Great Rift. These naked-eye objects are sometimes known as dark cloud constellations and take on a variety of names.

In the inner outer molecular regions of dark nebulae, important events take place, such as the formation of stars and masers.

Endomicroscopy

Endomicroscopy is a technique for obtaining histology-like images from inside the human body in real-time, a process known as ‘optical biopsy’. It generally refers to fluorescence confocal microscopy, although multi-photon microscopy and optical coherence tomography have also been adapted for endoscopic use. Commercially available clinical and pre-clinical endomicroscopes can achieve a resolution on the order of a micrometre, have a field-of-view of several hundred µm, and are compatible with fluorophores which are excitable using 488 nm laser light. The main clinical applications are currently in imaging of the tumour margins of the brain and gastro-intestinal tract, particularly for the diagnosis and characterisation of Barrett’s Esophagus, pancreatic cysts and colorectal lesions. A number of pre-clinical and transnational applications have been developed for endomicroscopy as it enables researchers to perform live animal imaging. Major pre-clinical applications are in gastro-intestinal tract, toumous margin detection, uterine complications, ischaemia, live imaging of cartilage and tendon, organoid imaging etc.

Goldschläger

Goldschläger is a Swiss cinnamon schnapps (43.5% alcohol by volume or 87 proof; originally it was 53.5% alcohol or 107 proof), a liqueur with very thin, yet visible flakes of gold floating in it. The actual amount of gold has been measured at approximately 13 mg in a one litre bottle. As of January 2018 this amounts to €0.46 EUR or lower on the international gold market.Goldschläger was produced in Switzerland until the 1990s, when the brand was acquired by Diageo, which continued production in Italy. Since 2008 it is a brand of Global Brands and was produced in Switzerland again. Bloomberg reported in November 2018 that Diageo agreed to sell Goldschläger as part of a 19-brand portfolio of spirits brands to the U.S. distiller Sazerac Co. The German word Goldschläger ("gold beater") designates the profession of gold leaf makers, who beat bars of gold into micrometre-thin sheets.

Layer (electronics)

A layer is the deposition of molecules on a substrate or base (glass, ceramic, semiconductor, or plastic/bioplastic) .

High temperature substrates includes stainless steel and polyimide film (expensive) and PET (cheap).

A depth of less than one micrometre is generally called a thin film while a depth greater than one micrometre is called a coating.

A web is a flexible substrate.

Mesoscopic physics

Disambiguation: This page refers to the sub-discipline of condensed matter physics, not the branch of mesoscale meteorology concerned with the study of weather systems smaller than synoptic scale systems.Mesoscopic physics is a subdiscipline of condensed matter physics that deals with materials of an intermediate length. The scale of these materials can be described as being between the nanoscale size of a quantity of atoms (such as a molecule) and of materials measuring micrometres. The lower limit can also be defined as being the size of individual atoms. At the micrometre level are bulk materials. Both mesoscopic and macroscopic objects contain a large number of atoms. Whereas average properties derived from its constituent materials describe macroscopic objects, as they usually obey the laws of classical mechanics, a mesoscopic object, by contrast, is affected by fluctuations around the average, and is subject to quantum mechanics.In other words, a macroscopic device, when scaled down to a meso-size, starts revealing quantum mechanical properties. For example, at the macroscopic level the conductance of a wire increases continuously with its diameter. However, at the mesoscopic level, the wire's conductance is quantized: the increases occur in discrete, or individual, whole steps. During research, mesoscopic devices are constructed, measured and observed experimentally and theoretically in order to advance understanding of the physics of insulators, semiconductors, metals and superconductors. The applied science of mesoscopic physics deals with the potential of building nanodevices.

Mesoscopic physics also addresses fundamental practical problems which occur when a macroscopic object is miniaturized, as with the miniaturization of transistors in semiconductor electronics. The physical properties of materials change as their size approaches the nanoscale, where the percentage of atoms at the surface of the material becomes significant. For bulk materials larger than one micrometre, the percentage of atoms at the surface is insignificant in relation to the number of atoms in the entire material. The subdiscipline has dealt primarily with artificial structures of metal or semiconducting material which have been fabricated by the techniques employed for producing microelectronic circuits.There is no rigid definition for mesoscopic physics but the systems studied are normally in the range of 100 nm (the size of a typical virus) to 1 000 nm (the size of a typical bacterium): 100 nanometers is the approximate upper limit for a nanoparticle. Thus, mesoscopic physics has a close connection to the fields of nanofabrication and nanotechnology. Devices used in nanotechnology are examples of mesoscopic systems. Three categories of new phenomena in such systems are interference effects, quantum confinement effects and charging effects.

Microelectronics

Microelectronics is a subfield of electronics. As the name suggests, microelectronics relates to the study and manufacture (or microfabrication) of very small electronic designs and components. Usually, but not always, this means micrometre-scale or smaller. These devices are typically made from semiconductor materials. Many components of normal electronic design are available in a microelectronic equivalent. These include transistors, capacitors, inductors, resistors, diodes and (naturally) insulators and conductors can all be found in microelectronic devices. Unique wiring techniques such as wire bonding are also often used in microelectronics because of the unusually small size of the components, leads and pads. This technique requires specialized equipment and is expensive.

Digital integrated circuits (ICs) consist mostly of transistors. Analog circuits commonly contain resistors and capacitors as well. Inductors are used in some high frequency analog circuits, but tend to occupy larger chip area due to their lower reactance at low frequencies. Gyrators can replace them in many applications.

As techniques have improved, the scale of microelectronic components has continued to decrease. At smaller scales, the relative impact of intrinsic circuit properties such as interconnections may become more significant. These are called parasitic effects, and the goal of the microelectronics design engineer is to find ways to compensate for or to minimize these effects, while delivering smaller, faster, and cheaper devices.

Today, microelectronics design is largely aided by Electronic Design Automation software.

Microscopic scale

The microscopic scale (from Greek: μικρός, mikrós, "small" and σκοπέω, skopéō "look") is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiring a lens or microscope to see them clearly. In physics, the microscopic scale is sometimes regarded as the scale between the macroscopic scale and the quantum scale. Microscopic units and measurements are used to classify and describe very small objects. One common microscopic length scale unit is the micrometre (also called a micron) (symbol: μm), which is one millionth of a metre.

Microtechnology

Microtechnology is technology with features near one micrometre (one millionth of a metre, or 10−6 metre, or 1μm).

Around 1970, scientists learned that by arraying large numbers of microscopic transistors on a single chip, microelectronic circuits could be built that dramatically improved performance, functionality, and reliability, all while reducing cost and increasing volume. This development led to the Information Revolution.

More recently, scientists have learned that not only electrical devices, but also mechanical devices, may be miniaturized and batch-fabricated, promising the same benefits to the mechanical world as integrated circuit technology has given to the electrical world. While electronics now provide the ‘brains’ for today’s advanced systems and products, micro-mechanical devices can provide the sensors and actuators — the eyes and ears, hands and feet — which interface to the outside world.

Today, micromechanical devices are the key components in a wide range of products such as automobile airbags, ink-jet printers, blood pressure monitors, and projection display systems. It seems clear that in the not-too-distant future these devices will be as pervasive as electronics.

Nanostructure

A nanostructure is a structure of intermediate size between microscopic and molecular structures. Nanostructural detail is microstructure at nanoscale.

In describing nanostructures, it is necessary to differentiate between the number of dimensions in the volume of an object which are on the nanoscale. Nanotextured surfaces have one dimension on the nanoscale, i.e., only the thickness of the surface of an object is between 0.1 and 100 nm. Nanotubes have two dimensions on the nanoscale, i.e., the diameter of the tube is between 0.1 and 100 nm; its length can be far more. Finally, spherical nanoparticles have three dimensions on the nanoscale, i.e., the particle is between 0.1 and 100 nm in each spatial dimension. The terms nanoparticles and ultrafine particles (UFP) are often used synonymously although UFP can reach into the micrometre range. The term nanostructure is often used when referring to magnetic technology.

Nanoscale structure in biology is often called ultrastructure.

Properties of nanoscale objects and ensembles of these objects are widely studied in physics.

Orders of magnitude (area)

This page is a progressive and labelled list of the SI area orders of magnitude, with certain examples appended to some list objects.

Picometre

The picometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: pm) or picometer (American spelling) is a unit of length in the metric system, equal to 1×10−12 m, or one trillionth (1/1000000000000) of a metre, which is the SI base unit of length.

The picometre is one thousandth of a nanometre, one millionth of a micrometre (also known as a micron), and used to be called micromicron, stigma, or bicron. The symbol µµ was once used for it. It is also one hundredth of an Ångström, an internationally recognised (but non-SI) unit of length.

Q-type asteroid

Q-type asteroids are relatively uncommon inner-belt asteroids with a strong, broad 1 micrometre olivine and pyroxene feature, and a spectral slope that indicates the presence of metal. There are absorption features shortwards and longwards of 0.7 µm, and the spectrum is generally intermediate between the V and S-type.

Q-type asteroids are spectrally more similar to ordinary chondrite meteorites (types H, L, LL) than any other asteroid type. This has led scientists to speculate that they are abundant, but only about 20 of this type has been characterized. Examples of Q-type asteroids are: 1862 Apollo, 2102 Tantalus, 3753 Cruithne, 6489 Golevka, and 9969 Braille.

Sempron

Sempron has been the marketing name used by AMD for several different budget desktop CPUs, using several different technologies and CPU socket formats. The Sempron replaced the AMD Duron processor and competes against Intel's Celeron series of processors. AMD coined the name from the Latin semper, which means "always", to suggest the Sempron is suitable for "daily use, practical, and part of everyday life".

Solar Mesosphere Explorer

The Solar Mesosphere Explorer (also known as Explorer 64) was a United States unmanned spacecraft to investigate the processes that create and destroy ozone in Earth's upper atmosphere. The mesosphere is a layer of the atmosphere extending from the top of the stratosphere to an altitude of about 80 kilometers (50 mi). The spacecraft carried five instruments to measure ozone, water vapor and incoming solar radiation.

Launched on October 6, 1981, on a Delta rocket from Vandenberg Air Force Base, in California, the satellite returned data until April 4, 1989. The spacecraft reentered Earth's atmosphere on March 5, 1991.

Managed for NASA by the Jet Propulsion Laboratory, the Solar Mesosphere Explorer was built by Ball Space Systems and operated by the Laboratory for Atmospheric and Space Physics of the University of Colorado where one hundred undergraduate and graduate students were involved.

Mass: 437 kilograms (963 pounds)

Power: Solar panels which charged NiCad batteries

Configuration: Cylinder 1.25 meter (4.1 ft) diameter by 1.7 meter (5.6 ft) high

Science instruments: Ultraviolet ozone spectrometer, 1.27 micrometre spectrometer, nitrogen dioxide spectrometer, four-channel infrared radiometer, solar ultraviolet monitor, solar proton alarm detector

Thin-film memory

Thin-film memory is a high-speed variation of core memory developed by Sperry Rand in a government-funded research project.

Instead of threading individual ferrite cores on wires, thin-film memory consisted of 4 micrometre thick dots of permalloy, an iron-nickel alloy, deposited on small glass plates by vacuum evaporation techniques and a mask. The drive and sense lines were then added using printed circuit wiring over the alloy dots. This provided very fast access times in the range of 670 nanoseconds, but was very expensive to produce.

In 1962, the UNIVAC 1107, intended for the civilian marketplace, used thin-film memory only for its 128-word general register stack. Military computers, where cost was less of a concern, used larger amounts of thin-film memory. Thin film was also used in a number of high-speed computer projects, including the high-end of the IBM System/360 line, but general advances in core tended to keep pace.

Torr

The torr (symbol: Torr) is a unit of pressure based on an absolute scale, now defined as exactly 1/760 of a standard atmosphere (101325 Pa). Thus one torr is exactly 101325/760 pascals (≈ 133.32 Pa).

Historically, one torr was intended to be the same as one "millimeter of mercury". However, subsequent redefinitions of the two units made them slightly different (by less than 0.000015%). The torr is not part of the International System of Units (SI), but it is often combined with the metric prefix milli to name one millitorr (mTorr) or 0.001 Torr.

The unit was named after Evangelista Torricelli, an Italian physicist and mathematician who discovered the principle of the barometer in 1644.

WR 102ka

WR 102ka, also known as the Peony star, is a Wolf–Rayet star that is one of several candidates for the most luminous-known star in the Milky Way.

Metric units of length

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