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# Pressure measurement
## Units
The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N·m^−2^ or kg·m^−1^·s^−2^). This special name for the unit was added in 1971; before that, pressure in SI was expressed in units such as N·m^−2^. When indicated, the zero reference is stated in parentheses following the unit, for example 101 kPa (abs). The pound per square inch (psi) is still in widespread use in the US and Canada, for measuring, for instance, tire pressure. 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). Manometric measurement is the subject of pressure head calculations. The most common choices for a manometer\'s fluid 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. The abbreviation \"W.C.\" or the words \"water column\" are often printed on gauges and measurements that use water for the manometer. `{{see also|Mercury pressure gauge}}`{=mediawiki}
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. So measurements in \"millimetres of mercury\" or \"inches of mercury\" can be converted to SI units as long as attention is paid to the local factors of fluid density and gravity. Temperature fluctuations change the value of fluid density, while location can affect gravity.
Although no longer preferred, these **manometric units** are still encountered in many fields. Blood pressure is measured in millimetres of mercury (see torr) in most of the world, central venous pressure and lung pressures in centimeters of water are still common, as in settings for CPAP machines. Natural gas pipeline pressures are measured in inches of water, expressed as \"inches W.C.\"
Underwater divers use manometric units: the ambient pressure is measured in units of metres sea water (msw) which is defined as equal to one tenth of a bar. The unit used in the US is the foot sea water (fsw), based on standard gravity and a sea-water density of 64 lb/ft^3^. According to the US Navy Diving Manual, one fsw equals 0.30643 msw, `{{val|.030643|ul=bar}}`{=mediawiki}, or `{{val|0.44444|ul=psi}}`{=mediawiki}, though elsewhere it states that 33 fsw is `{{val|14.7|u=psi}}`{=mediawiki} (one atmosphere), which gives one fsw equal to about 0.445 psi. The msw and fsw are the conventional units for measurement of diver pressure exposure used in decompression tables and the unit of calibration for pneumofathometers and hyperbaric chamber pressure gauges. Both msw and fsw are measured relative to normal atmospheric pressure.
In vacuum systems, the units torr (millimeter of mercury), micron (micrometer of mercury), 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 hectopascal (hPa), kilopascal (kPa), millibar (mbar) or atmospheres (atm). In American and Canadian engineering, stress is often measured in kip. 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 dyn·cm^−2^. 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^2^ or grams-force/cm^2^ (sometimes as kg/cm^2^ 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 prohibited in SI; the unit of force in SI is the newton (N).
## Static and dynamic pressure {#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.
**Example:** A water tank has a pressure of 10 atm. The atmospheric pressure is 1 atm. What is the gauge pressure?
P_g = P_a - P_v\
= 10 atm - 1 atm\
= 9 atm
Therefore, the gauge pressure is 9 atm.
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# Pressure measurement
## Instruments
A **pressure sensor** is a device for pressure measurement of gases or liquids. Pressure sensors can alternatively be called **pressure transducers**, **pressure transmitters**, **pressure senders**, **pressure indicators**, **piezometers** and **manometers**, among other names.
Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer; it generates a signal as a function of the pressure imposed.
Pressure sensors can vary drastically in technology, design, performance, application suitability and cost. A conservative estimate would be that there may be over 50 technologies and at least 300 companies making pressure sensors worldwide. There is also a category of pressure sensors that are designed to measure in a dynamic mode for capturing very high speed changes in pressure. Example applications for this type of sensor would be in the measuring of combustion pressure in an engine cylinder or in a gas turbine. These sensors are commonly manufactured out of piezoelectric materials such as quartz.
Some pressure sensors are pressure switches, which turn on or off at a particular pressure. For example, a water pump can be controlled by a pressure switch so that it starts when water is released from the system, reducing the pressure in a reservoir.
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 Christiaan Huygens in 1661.
There are two basic categories of analog pressure sensors: force collector and other types.
Force collector types: These types of electronic pressure sensors generally use a force collector (such a diaphragm, piston, Bourdon tube, or bellows) to measure strain (or deflection) due to applied force over an area (pressure).
- ***Piezoresistive strain gauge***: Uses the piezoresistive effect of bonded or formed strain gauges to detect strain due to an applied pressure, electrical resistance increasing as pressure deforms the material. Common technology types are silicon (monocrystalline), polysilicon thin film, bonded metal foil, thick film, silicon-on-sapphire and sputtered thin film. Generally, the strain gauges are connected to form a Wheatstone bridge circuit to maximize the output of the sensor and to reduce sensitivity to errors. This is the most commonly employed sensing technology for general purpose pressure measurement.
- ***Capacitive***: Uses a diaphragm and pressure cavity to create a variable capacitor to detect strain due to applied pressure, capacitance decreasing as pressure deforms the diaphragm. Common technologies use metal, ceramic, and silicon diaphragms. Capacitive pressure sensors are being integrated into CMOS technology and it is being explored if thin 2D materials can be used as diaphragm material.
- ***Electromagnetic***: Measures the displacement of a diaphragm by means of changes in inductance (reluctance), linear variable differential transformer (LVDT), Hall effect, or by eddy current principle.
- ***Piezoelectric***: Uses the piezoelectric effect in certain materials such as quartz to measure the strain upon the sensing mechanism due to pressure. This technology is commonly employed for the measurement of highly dynamic pressures. As the basic principle is dynamic, no static pressures can be measured with piezoelectric sensors.
- ***Strain-Gauge***: Strain gauge based pressure sensors also use a pressure sensitive element where metal strain gauges are glued on or thin-film gauges are applied on by sputtering. This measuring element can either be a diaphragm or for metal foil gauges measuring bodies in can-type can also be used. The big advantages of this monolithic can-type design are an improved rigidity and the capability to measure highest pressures of up to 15,000 bar. The electrical connection is normally done via a Wheatstone bridge, which allows for a good amplification of the signal and precise and constant measuring results.
- ***Optical***: Techniques include the use of the physical change of an optical fiber to detect strain due to applied pressure. A common example of this type utilizes Fiber Bragg Gratings. This technology is employed in challenging applications where the measurement may be highly remote, under high temperature, or may benefit from technologies inherently immune to electromagnetic interference. Another analogous technique utilizes an elastic film constructed in layers that can change reflected wavelengths according to the applied pressure (strain).
- ***Potentiometric***: Uses the motion of a wiper along a resistive mechanism to detect the strain caused by applied pressure.
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- ***Force balancing***: Force-balanced fused quartz Bourdon tubes use a spiral Bourdon tube to exert force on a pivoting armature containing a mirror, the reflection of a beam of light from the mirror senses the angular displacement and current is applied to electromagnets on the armature to balance the force from the tube and bring the angular displacement to zero, the current that is applied to the coils is used as the measurement. Due to the extremely stable and repeatable mechanical and thermal properties of fused quartz and the force balancing which eliminates most non-linear effects these sensors can be accurate to around 1PPM of full scale. Due to the extremely fine fused quartz structures which are made by hand and require expert skill to construct these sensors are generally limited to scientific and calibration purposes. Non force-balancing sensors have lower accuracy and reading the angular displacement cannot be done with the same precision as a force-balancing measurement, although easier to construct due to the larger size these are no longer used.
Other types: These types of electronic pressure sensors use other properties (such as density) to infer pressure of a gas, or liquid.
- ***Resonant***: Uses the changes in resonant frequency in a sensing mechanism to measure stress, or changes in gas density, caused by applied pressure. This technology may be used in conjunction with a force collector, such as those in the category above. Alternatively, resonant technology may be employed by exposing the resonating element itself to the media, whereby the resonant frequency is dependent upon the density of the media. Sensors have been made out of vibrating wire, vibrating cylinders, quartz, and silicon MEMS. Generally, this technology is considered to provide very stable readings over time. The squeeze-film pressure sensor is a type of MEMS resonant pressure sensor that operates by a thin membrane that compresses a thin film of gas at high frequency. Since the compressibility and stiffness of the gas film are pressure dependent, the resonance frequency of the squeeze-film pressure sensor is used as a measure of the gas pressure.
- ***Thermal***: Uses the changes in thermal conductivity of a gas due to density changes to measure pressure. A common example of this type is the Pirani gauge.
- ***Ionization***: Measures the flow of charged gas particles (ions) which varies due to density changes to measure pressure. Common examples are the Hot and Cold Cathode gauges.
A pressure sensor, a resonant quartz crystal strain gauge with a Bourdon tube force collector, is the critical sensor of DART. DART detects tsunami waves from the bottom of the open ocean. It has a pressure resolution of approximately 1mm of water when measuring pressure at a depth of several kilometers.
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# Pressure measurement
## Instruments
### 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 spring (for example tire-pressure gauges of comparatively low accuracy) or a solid weight, in which case it is known as a deadweight tester and may be used for calibration of other gauges.
#### Liquid column (manometer) {#liquid_column_manometer}
Liquid-column gauges consist of a column of liquid in a tube whose ends are exposed to different pressures. The column will rise or fall until its weight (a force applied due to gravity) is in equilibrium with the pressure differential between the two ends of the tube (a force applied due to fluid pressure). 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 levels represents the applied pressure. The pressure exerted by a column of fluid of height *h* and density *ρ* is given by the hydrostatic pressure equation, *P* = *hgρ*. Therefore, the pressure difference between the applied pressure *P~a~* and the reference pressure *P*~0~ in a U-tube manometer can be found by solving `{{nowrap|''P<sub>a</sub>'' − ''P''<sub>0</sub> {{=}}`{=mediawiki} *hgρ*}}. In other words, the pressure on either end of the liquid (shown in blue in the figure) must be balanced (since the liquid is static), and so `{{nowrap|''P<sub>a</sub>'' {{=}}`{=mediawiki} *P*~0~ + *hgρ*}}.
In most liquid-column measurements, the result of the measurement is the height *h*, expressed typically in mm, cm, or inches. The *h* is also known as the pressure head. When expressed as a pressure head, pressure is specified in units of length and the measurement fluid must be specified. When accuracy is critical, the temperature of the measurement fluid must likewise be specified, because liquid density is a function of temperature. So, for example, pressure head might be written \"742.2 mm~Hg~\" or \"4.2 in~H~2~O~ at 59 °F\" for measurements taken with mercury or water as the manometric fluid respectively. The word \"gauge\" or \"vacuum\" may be added to such a measurement to distinguish between a pressure above or below the atmospheric pressure. Both mm of mercury and inches of water are common pressure heads, which can be converted to S.I. units of pressure using unit conversion and the above formulas.
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, except when measuring differential pressure of a fluid (for example, across an orifice plate or venturi), in which case the density ρ should be corrected by subtracting the density of the fluid being measured.
Although any fluid can be used, mercury is preferred for its high density (13.534 g/cm^3^) and low vapour pressure. Its convex meniscus is advantageous since this means there will be no pressure errors from wetting the glass, though under exceptionally clean circumstances, the mercury will stick to glass and the barometer may become stuck (the mercury can sustain a negative absolute pressure) even under a strong vacuum. For low pressure differences, light oil or water are commonly used (the latter giving rise to units of measurement such as inches water gauge and millimetres H~2~O). Liquid-column pressure gauges have a highly linear calibration. They have poor dynamic response because the fluid in the column may react slowly to a pressure change.
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 can isolate the liquids to prevent them from mixing, but this can be unnecessary, for example, when mercury is used as the manometer fluid to measure differential pressure of a fluid such as water. Simple hydrostatic gauges can measure pressures ranging from a few torrs (a few 100 Pa) to a few atmospheres (approximately `{{val|1,000,000|u=Pa}}`{=mediawiki}).
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 types of manometers are used
1. Simple manometer
2. Micromanometer
3. Differential manometer
4. Inverted differential manometer
#### McLeod gauge {#mcleod_gauge}
A McLeod gauge isolates a sample of gas and compresses it in a modified mercury manometer until the pressure is a few millimetres of mercury. The technique is very slow and unsuited to continual monitoring, but is capable of good accuracy. Unlike other manometer gauges, the McLeod gauge reading is dependent on the composition of the gas, since the interpretation relies on the sample compressing as an ideal gas. Due to the compression process, the McLeod gauge completely ignores partial pressures from non-ideal vapors that condense, such as pump oils, mercury, and even water if compressed enough.
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-dependent properties. These indirect measurements must be calibrated to SI units by a direct measurement, most commonly a McLeod gauge.
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# Pressure measurement
## Instruments
### Aneroid
**Aneroid** gauges are based on a metallic pressure-sensing element that 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 capacitance are often referred to as capacitance manometers.
#### Bourdon tube`{{Anchor|Bourdon gauge}}`{=mediawiki} {#bourdon_tube}
The Bourdon pressure gauge uses the principle that a flattened tube tends to straighten or regain its circular form in cross-section when pressurized. (A party horn illustrates this principle.) This change in cross-section may be hardly noticeable, involving moderate stresses within the elastic range of easily workable materials. The strain of the material of the tube is magnified by forming the tube into a C shape or even a helix, such that the entire tube tends to straighten out or uncoil elastically as it is pressurized. Eugène Bourdon patented his gauge in France in 1849, and it was widely adopted because of its superior simplicity, linearity, and accuracy; Bourdon is now part of the Baumer group and still manufacture Bourdon tube gauges in France. Edward Ashcroft purchased Bourdon\'s American patent rights in 1852 and became a major manufacturer of gauges. Also in 1849, Bernard Schaeffer in Magdeburg, Germany patented a successful diaphragm (see below) pressure gauge, which, together with the Bourdon gauge, revolutionized pressure measurement in industry. But in 1875 after Bourdon\'s patents expired, his company Schaeffer and Budenberg also manufactured Bourdon tube gauges.
In practice, a flattened thin-wall, closed-end tube is connected at the hollow end to a fixed pipe containing the fluid pressure to be measured. As the pressure increases, the closed end moves in an arc, and this motion is converted into the rotation of a (segment of a) gear by a connecting link that is usually adjustable. A small-diameter pinion gear is on the pointer shaft, so the motion is magnified further by the gear ratio. The positioning of the indicator card behind the pointer, the initial pointer shaft position, the linkage length and initial position, all provide means to calibrate the pointer to indicate the desired range of pressure for variations in the behavior of the Bourdon tube itself. Differential pressure can be measured by gauges containing two different Bourdon tubes, with connecting linkages (but is more usually measured via diaphragms or bellows and a balance system).
Bourdon tubes measures gauge pressure, relative to ambient atmospheric pressure, as opposed to absolute pressure; vacuum is sensed as a reverse motion. Some aneroid barometers use Bourdon tubes closed at both ends (but most use diaphragms or capsules, see below). When the measured pressure is rapidly pulsing, such as when the gauge is near a reciprocating pump, an orifice restriction in the connecting pipe is frequently used to avoid unnecessary wear on the gears and provide an average reading; when the whole gauge is subject to mechanical vibration, the case (including the pointer and dial) can be filled with an oil or glycerin. Typical high-quality modern gauges provide an accuracy of ±1% of span (Nominal diameter 100mm, Class 1 EN837-1), and a special high-accuracy gauge can be as accurate as 0.1% of full scale.
Force-balanced fused quartz Bourdon tube sensors work on the same principle but uses the reflection of a beam of light from a mirror to sense the angular displacement and current is applied to electromagnets to balance the force of the tube and bring the angular displacement back to zero, the current that is applied to the coils is used as the measurement. Due to the extremely stable and repeatable mechanical and thermal properties of quartz and the force balancing which eliminates nearly all physical movement these sensors can be accurate to around 1 PPM of full scale. Due to the extremely fine fused quartz structures which must be made by hand these sensors are generally limited to scientific and calibration purposes.
In the following illustrations of a compound gauge (vacuum and gauge pressure), the case and window has been removed to show only the dial, pointer and process connection. This particular gauge is a combination vacuum and pressure gauge used for automotive diagnosis:
- The left side of the face, used for measuring vacuum, is calibrated in inches of mercury on its outer scale and centimetres of mercury on its inner scale
- The right portion of the face is used to measure fuel pump pressure or turbo boost and is scaled in pounds per square inch on its outer scale and kg/cm^2^ on its inner scale.
Mechanical details include stationary and moving parts.
Stationary parts: `{{ordered list | list-style-type = upper-alpha
| 1 = 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.
| 2 = Chassis plate. The dial is attached to this. It contains bearing holes for the axles.
| 3 = Secondary chassis plate. It supports the outer ends of the axles.
| 4 = Posts to join and space the two chassis plates.
}}`{=mediawiki}
Moving parts:
1. Stationary end of Bourdon tube. This communicates with the inlet pipe through the receiver block.
2. Moving end of Bourdon tube. This end is sealed.
3. Pivot and pivot pin
4. Link joining pivot pin to lever (5) with pins to allow joint rotation
5. Lever, an extension of the sector gear (7)
6. Sector gear axle pin
7. Sector gear
8. 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.
9. Hair spring to preload the gear train to eliminate gear lash and hysteresis
#### Diaphragm (membrane) `{{anchor|Diaphragm|Membrane}}`{=mediawiki} {#diaphragm_membrane}
A second type of aneroid gauge uses 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. The useful range is above 10^−2^ Torr (roughly 1 Pa). For absolute measurements, welded pressure capsules with diaphragms on either side are often used. Membrane shapes include:
- Flat
- Corrugated
- Flattened tube
- Capsule
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# Pressure measurement
## Instruments
### Aneroid
#### 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**. (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.
#### Magnetic coupling {#magnetic_coupling}
These gauges use the attraction of two magnets to translate differential pressure into motion of a dial pointer. As differential pressure increases, a magnet attached to either a piston or rubber diaphragm moves. A rotary magnet that is attached to a pointer then moves in unison. To create different pressure ranges, the spring rate can be increased or decreased.
### Spinning-rotor gauge {#spinning_rotor_gauge}
The spinning-rotor gauge works by measuring how a rotating ball is slowed by the viscosity of the gas being measured. The ball is made of steel and is magnetically levitated inside a steel tube closed at one end and exposed to the gas to be measured at the other. The ball is brought up to speed (about 2500 or 3800 rad/s), and the deceleration rate is measured after switching off the drive, by electromagnetic transducers. The range of the instrument is 5^−5^ to 10^2^ Pa (10^3^ Pa with less accuracy). It is accurate and stable enough to be used as a secondary standard. During the last years this type of gauge became much more user friendly and easier to operate. In the past the instrument was famous for requiring some skill and knowledge to use correctly. For high accuracy measurements various corrections must be applied and the ball must be spun at a pressure well below the intended measurement pressure for five hours before using. It is most useful in calibration and research laboratories where high accuracy is required and qualified technicians are available. Insulation vacuum monitoring of cryogenic liquids is a well suited application for this system too. With the inexpensive and long term stable, weldable sensor, that can be separated from the more costly electronics, it is a perfect fit to all static vacuums.
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# Pressure measurement
## Electronic pressure instruments`{{anchor|Electronic}}`{=mediawiki} {#electronic_pressure_instruments}
Metal strain gauge
: The strain gauge is generally glued (foil strain gauge) or deposited (thin-film strain gauge) onto a membrane. Membrane deflection due to pressure causes a resistance change in the strain gauge which can be electronically measured.
Piezoresistive strain gauge
: Uses the piezoresistive effect of bonded or formed strain gauges to detect strain due to applied pressure.
Piezoresistive silicon pressure sensor
: The sensor is generally a temperature compensated, piezoresistive silicon pressure sensor chosen for its excellent performance and long-term stability. Integral temperature compensation is provided over a range of 0--50 °C using laser-trimmed resistors. An additional laser-trimmed resistor is included to normalize pressure sensitivity variations by programming the gain of an external differential amplifier. This provides good sensitivity and long-term stability. The two ports of the sensor, apply pressure to the same single transducer, please see pressure flow diagram below.
This is an over-simplified diagram, but you can see the fundamental design of the internal ports in the sensor. The important item here to note is the \"diaphragm\" as this is the sensor itself. Is it slightly convex in shape (highly exaggerated in the drawing); this is important as it affects the accuracy of the sensor in use.
The shape of the sensor is important because it is calibrated to work in the direction of air flow as shown by the RED arrows. This is normal operation for the pressure sensor, providing a positive reading on the display of the digital pressure meter. Applying pressure in the reverse direction can induce errors in the results as the movement of the air pressure is trying to force the diaphragm to move in the opposite direction. The errors induced by this are small, but can be significant, and therefore it is always preferable to ensure that the more positive pressure is always applied to the positive (+ve) port and the lower pressure is applied to the negative (-ve) port, for normal \'gauge pressure\' application. The same applies to measuring the difference between two vacuums, the larger vacuum should always be applied to the negative (-ve) port. The measurement of pressure via the Wheatstone Bridge looks something like this\....
The effective electrical model of the transducer, together with a basic signal conditioning circuit, is shown in the application schematic. The pressure sensor is a fully active Wheatstone bridge which has been temperature compensated and offset adjusted by means of thick film, laser trimmed resistors. The excitation to the bridge is applied via a constant current. The low-level bridge output is at +O and -O, and the amplified span is set by the gain programming resistor (r). The electrical design is microprocessor controlled, which allows for calibration, the additional functions for the user, such as Scale Selection, Data Hold, Zero and Filter functions, the Record function that stores/displays MAX/MIN.
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 principle.
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 to 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 {#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 thermometer (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^−3^ Torr to 10 Torr, but their calibration is sensitive to the chemical composition of the gases being measured.
#### Pirani (one wire) {#pirani_one_wire}
*Main article: Pirani gauge* 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.
#### Two-wire {#two_wire}
In two-wire gauges, one wire coil is used as a heater, and the other is used to measure temperature due to convection. **Thermocouple gauges** and **thermistor gauges** work in this manner using a thermocouple or thermistor, respectively, to measure the temperature of the heated wire.
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# Pressure measurement
## Electronic pressure instruments`{{anchor|Electronic}}`{=mediawiki} {#electronic_pressure_instruments}
### Ionization gauge {#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 generates 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. `{{block indent | em = 1.5 | text = '''Useful range''': 10<sup>−10</sup> - 10<sup>−3</sup> torr (roughly 10<sup>−8</sup> - 10<sup>−1</sup> Pa)}}`{=mediawiki}
Most ion gauges come in two types: hot cathode and cold cathode. 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 10^−3^ Torr to 10^−10^ Torr. The principle behind cold cathode version is the same, except that electrons are produced in the discharge of a high voltage. Cold cathode gauges are accurate from 10^−2^ Torr to 10^−9^ 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 {#hot_cathode}
A hot-cathode ionization gauge is composed mainly of three electrodes acting together as a triode, wherein the cathode is the filament. The three electrodes are a collector or plate, a filament, and a grid. The collector current is measured in picoamperes by an electrometer. The filament voltage to ground is usually at a potential of 30 volts, while the grid voltage at 180--210 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 10^−8^ Torr and the Bayard--Alpert to about 10^−10^ 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 and 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.
#### Cold cathode {#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 1`{{e|−12}}`{=mediawiki} Torr.
Likewise, 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 - in particular in Penning gauges, which use an axially symmetric magnetic field to create path lengths for electrons that 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 are, in general, 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 that eventually either short-circuit the electrodes of the gauge or impede the generation of a discharge path.
Physical phenomena Instrument Governing equation Limiting factors Practical pressure range Ideal accuracy Response time
-------------------- --------------------------------------------------------- ----------------------- --------------------------------------------------- ----------------------------------------------------------------------------- ------------------------------------------------------------------------------------------ ----------------------------
Mechanical Liquid column manometer $\Delta P = \rho g h$ atm. to 1 mbar
Mechanical Capsule dial gauge Friction 1000 to 1 mbar ±5% of full scale Slow
Mechanical Strain gauge 1000 to 1 mbar Fast
Mechanical Capacitance manometer Temperature fluctuations atm to 10^−6^ mbar ±1% of reading Slower when filter mounted
Mechanical McLeod Boyle\'s law 10 to 10^−3^ mbar ±10% of reading between 10^−4^ and 5⋅10^−2^ mbar
Transport Spinning rotor (drag) 10^−1^ to 10^−7^ mbar ±2.5% of reading between 10^−7^ and 10^−2^ mbar 2.5 to 13.5% between 10^−2^ and 1 mbar
Transport Pirani (Wheatstone bridge) Thermal conductivity 1000 to 10^−3^ mbar (const. temperature) 10 to 10^−3^ mbar (const. voltage) ±6% of reading between 10^−2^ and 10 mbar Fast
Transport Thermocouple (Seebeck effect) Thermal conductivity 5 to 10^−3^ mbar ±10% of reading between 10^−2^ and 1 mbar
Ionization Cold cathode (Penning) Ionization yield 10^−2^ to 10^−7^ mbar +100 to -50% of reading
Ionization Hot cathode (ionization induced by thermionic emission) Low current measurement; parasitic x-ray emission 10^−3^ to 10^−10^ mbar ±10% between 10^−7^ and 10^−4^ mbar ±20% at 10^−3^ and 10^−9^ mbar ±100% at 10^−10^ mbar
: Comparison of pressure measurement instruments
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# Pressure measurement
## Dynamic transients {#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
## Calibration and standards {#calibration_and_standards}
The American Society of Mechanical Engineers (ASME) has developed two separate and distinct standards on pressure measurement, B40.100 and PTC 19.2. B40.100 provides guidelines on Pressure Indicated Dial Type and Pressure Digital Indicating Gauges, Diaphragm Seals, Snubbers, and Pressure Limiter Valves. PTC 19.2 provides instructions and guidance for the accurate determination of pressure values in support of the ASME Performance Test Codes. The choice of method, instruments, required calculations, and corrections to be applied depends on the purpose of the measurement, the allowable uncertainty, and the characteristics of the equipment being tested.
The methods for pressure measurement and the protocols used for data transmission are also provided. Guidance is given for setting up the instrumentation and determining the uncertainty of the measurement. Information regarding the instrument type, design, applicable pressure range, accuracy, output, and relative cost is provided. Information is also provided on pressure-measuring devices that are used in field environments i.e., piston gauges, manometers, and low-absolute-pressure (vacuum) instruments.
These methods are designed to assist in the evaluation of measurement uncertainty based on current technology and engineering knowledge, taking into account published instrumentation specifications and measurement and application techniques. This Supplement provides guidance in the use of methods to establish the pressure-measurement uncertainty.
### European (CEN) Standard {#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.
### US ASME Standards {#us_asme_standards}
- B40.100-2013: Pressure gauges and Gauge attachments.
- PTC 19.2-2010 : The Performance test code for pressure measurement.
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# Pressure measurement
## Applications
There are many applications for pressure sensors:
- **Pressure sensing**
This is where the measurement of interest is pressure, expressed as a force per unit area. This is useful in weather instrumentation, aircraft, automobiles, and any other machinery that has pressure functionality implemented.
- **Altitude sensing**
This is useful in aircraft, rockets, satellites, weather balloons, and many other applications. All these applications make use of the relationship between changes in pressure relative to the altitude. This relationship is governed by the following equation: $h = (1-(P/P_\mathrm{ref})^{0.190284}) \times 145366.45\mathrm{ ft}$ This equation is calibrated for an altimeter, up to 36,090 feet (11,000 m). Outside that range, an error will be introduced which can be calculated differently for each different pressure sensor. These error calculations will factor in the error introduced by the change in temperature as we go up.
Barometric pressure sensors can have an altitude resolution of less than 1 meter, which is significantly better than GPS systems (about 20 meters altitude resolution). In navigation applications altimeters are used to distinguish between stacked road levels for car navigation and floor levels in buildings for pedestrian navigation.
- **Flow sensing**
This is the use of pressure sensors in conjunction with the venturi effect to measure flow. Differential pressure is measured between two segments of a venturi tube that have a different aperture. The pressure difference between the two segments is directly proportional to the flow rate through the venturi tube. A low pressure sensor is almost always required as the pressure difference is relatively small.
- **Level / depth sensing** `{{anchor|Level}}`{=mediawiki}
A pressure sensor may also be used to calculate the level of a fluid. This technique is commonly employed to measure the depth of a submerged body (such as a diver or submarine), or level of contents in a tank (such as in a water tower). For most practical purposes, fluid level is directly proportional to pressure. In the case of fresh water where the contents are under atmospheric pressure, 1psi = 27.7 inH~2~O / 1Pa = 9.81 mmH~2~O. The basic equation for such a measurement is $P = \rho gh$ where *P* = pressure, *ρ* = density of the fluid, *g* = standard gravity, *h* = height of fluid column above pressure sensor
- **Leak testing**
A pressure sensor may be used to sense the decay of pressure due to a system leak. This is commonly done by either comparison to a known leak using differential pressure, or by means of utilizing the pressure sensor to measure pressure change over time.
- **Groundwater measurement**
A **piezometer** is either a device used to measure liquid pressure in a system by measuring the height to which a column of the liquid rises against gravity, or a device which measures the pressure (more precisely, the piezometric head) of groundwater at a specific point. A piezometer is designed to measure static pressures, and thus differs from a pitot tube by not being pointed into the fluid flow. Observation wells give some information on the water level in a formation, but must be read manually. Electrical pressure transducers of several types can be read automatically, making data acquisition more convenient.
The first piezometers in geotechnical engineering were open wells or standpipes (sometimes called **Casagrande piezometers**) installed into an aquifer. A Casagrande piezometer will typically have a solid casing down to the depth of interest, and a slotted or screened casing within the zone where water pressure is being measured. The casing is sealed into the drillhole with clay, bentonite or concrete to prevent surface water from contaminating the groundwater supply. In an unconfined aquifer, the water level in the piezometer would not be exactly coincident with the water table, especially when the vertical component of flow velocity is significant. In a confined aquifer under artesian conditions, the water level in the piezometer indicates the pressure in the aquifer, but not necessarily the water table. Piezometer wells can be much smaller in diameter than production wells, and a 5 cm diameter standpipe is common.
Piezometers in durable casings can be buried or pushed into the ground to measure the groundwater pressure at the point of installation. The pressure gauges (transducer) can be vibrating-wire, pneumatic, or strain-gauge in operation, converting pressure into an electrical signal. These piezometers are cabled to the surface where they can be read by data loggers or portable readout units, allowing faster or more frequent reading than is possible with open standpipe piezometers
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# Medieval dance
thumb\|upright=1.1\|Dance with musicians, Tacuinum sanitatis casanatense (Lombardy, Italy, late 14th century)
Sources for an understanding of dance in Europe in the Middle Ages are limited and fragmentary, being composed of some interesting depictions in paintings and illuminations, a few musical examples of what may be dances, and scattered allusions in literary texts. The first detailed descriptions of dancing only date from 1451 in Italy, which is after the start of the Renaissance in Western Europe.
## Carole
The most documented form of secular dance during the Middle Ages is the carol also called the \"carole\" or \"carola\" and known from the 12th and 13th centuries in Western Europe in rural and court settings. It consisted of a group of dancers holding hands usually in a circle, with the dancers singing in a leader and refrain style while dancing. No surviving lyrics or music for the carol have been identified. In northern France, other terms for this type of dance included \"ronde\" and its diminutives \"rondet\", \"rondel\", and \"rondelet\" from which the more modern music term \"rondeau\" derives. In the German-speaking areas, this same type of choral dance was known as \"reigen\".
Mullally in his book on the carole makes the case that the dance, at least in France, was done in a closed circle with the dancers, usually men and women interspersed, holding hands. He adduces evidence that the general progression of the dance was to the left (clockwise) and that the steps probably were very simple consisting of a step to the left with the left foot followed by a step on the right foot closing to the left foot.
### France
#### Chretien de Troyes {#chretien_de_troyes}
Some of the earliest mentions of the carol occur in the works of the French poet Chrétien de Troyes in his series of Arthurian romances. In the wedding scene in Erec and Enide (about 1170)
In The Knight of the Cart (probably late 1170s) at a meadow where there are knights and ladies, various games are played while:
In what is probably Chretien\'s last work, Perceval, the Story of the Grail, probably written 1181--1191, we find:
> Men and women danced rounds through every street and square
and later at a court setting:
> The queen \... had all her maidens join hands together to dance and begin the merry-making. In his honour they began their singing, dances, and rounds
### Italy
Dante (1265--1321) has a few minor references to dance in his works but a more substantive description of the round dance with song from Bologna comes from Giovanni del Virgilio (floruit 1319--1327).
Later in the 14th century Giovanni Boccaccio (1313--1375) shows us the \"carola\" in Florence in the *Decameron* (about 1350--1353) which has several passages describing men and women dancing to their own singing or accompanied by musicians. Boccaccio also uses two other terms for contemporary dances, *ridda* and *ballonchio*, both of which refer to round dances with singing.
Approximately contemporary with the *Decameron* are a series of frescos in Siena by Ambrogio Lorenzetti painted about 1338--40, one of which shows a group of women doing a \"bridge\" figure while accompanied by another woman playing the tambourine.
### England
In a life of Saint Dunstan composed about 1000, the author tells how Dunstan, going into a church, found maidens dancing in a ring and singing a hymn. According to the *Oxford English Dictionary* (1933) the term \"carol\" was first used in England for this type of circle dance accompanied by singing in manuscripts dating to as early as 1300. The word was used as both a noun and a verb and the usage of carol for a dance form persisted well into the 16th century. One of the earliest references is in Robert of Brunne\'s early 14th century *Handlyng Synne* (Handling Sin) where it occurs as a verb.
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# Medieval dance
## Other chain dances {#other_chain_dances}
Circle or line dances also existed in other parts of Europe outside England, France and Italy where the term carol was best known. These dances were of the same type with dancers hand-in-hand and a leader who sang the ballad.
### Scandinavia
In Denmark, old ballads mention a closed Ring dance which can open into a Chain dance. A fresco in Ørslev church in Zealand from about 1400 shows nine people, men and women, dancing in a line. The leader and some others in the chain carry bouquets of flowers. Dances could be for men and women, or for men alone, or women alone. In the case of women\'s dances, however, there may have been a man who acted as the leader. Two dances specifically named in the Danish ballads which appear to be line dances of this type are *The Beggar Dance*, and *The Lucky Dance* which may have been a dance for women. A modern version of these medieval chains is seen in the Faroese chain dance, the earliest account of which goes back only to the 17th century.
In Sweden too, medieval songs often mentioned dancing. A long chain was formed, with the leader singing the verses and setting the time while the other dancers joined in the chorus. These \"Long Dances\" have lasted into modern times in Sweden. A similar type of song dance may have existed in Norway in the Middle Ages as well, but no historical accounts have been found.
### Central Europe {#central_europe}
The same dance in Germany was called \"Reigen\" and may have originated from devotional dances at early Christian festivals. Dancing around the church or a fire was frequently denounced by church authorities which only underscores how popular it was. There are records of church and civic officials in various German towns forbidding dancing and singing from the 8th to the 10th centuries. Once again, in singing processions, the leader provided the verse and the other dancers supplied the chorus. The minnesinger Neidhart von Reuental, who lived in the first half of the 13th century wrote several songs for dancing, some of which use the term \"reigen\".
In southern Tyrol, at Runkelstein Castle, a series of frescos was executed in the last years of the 14th century. One of the frescos depicts Elisabeth of Poland, Queen of Hungary leading a chain dance.
Circle dances were also found in the area that is today the Czech Republic. Descriptions and illustrations of dancing can be found in church registers, chronicles and the 15th century writings of Bohuslav Hasištejnský z Lobkovic. Dancing was primarily done around trees on the village green but special houses for dancing appear from the 14th century. In Poland as well the earliest village dances were in circles or lines accompanied by the singing or clapping of the participants.
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# Medieval dance
## Other chain dances {#other_chain_dances}
### The Balkans {#the_balkans}
The present-day folk dances in the Balkans consist of dancers linked together in a hand or shoulder hold in an open or closed circle or a line. The basic round dance goes by many names in the various countries of the region: *choros*, *kolo*, *oro*, *horo* or *hora*. The modern couple dance so common in western and northern Europe has only made a few inroads into the Balkan dance repertory.
Chain dances of a similar type to these modern dance forms have been documented from the medieval Balkans. Tens of thousands of medieval tombstones called \"Stećci\" are found in Bosnia and Hercegovina and neighboring areas in Montenegro, Serbia and Croatia. They date from the end of the 12th century to the 16th century. Many of the stones bear inscription and figures, several of which have been interpreted as dancers in a ring or line dance. These mostly date to the 14th and 15th centuries. Usually men and women are portrayed dancing together holding hands at shoulder level but occasionally the groups consist of only one sex.
Further south in Macedonia, near the town of Zletovo, Lesnovo monastery, originally built in the 11th century, was renovated in the middle of the 14th century and a series of murals were painted. One of these shows a group of young men linking arms in a round dance. They are accompanied by two musicians, one playing the kanun while the other beats on a long drum.
There is also some documentary evidence from the Dalmatian coast area of what is now Croatia. An anonymous chronicle from 1344 exhorts the people of the city of Zadar to sing and dance circle dances for a festival while in the 14th and 15th centuries, authorities in Dubrovnik forbid circle dances and secular songs on the cathedral grounds. Another early reference comes from the area of present-day Bulgaria in a manuscript of a 14th-century sermon which calls chain dances \"devilish and damned.\"
At a later period there are the accounts of two western European travelers to Constantinople, the capital of the Ottoman Empire. Salomon Schweigger (1551--1622) was a German preacher who traveled in the entourage of Jochim von Sinzendorf, Ambassador to Constantinople for Rudolf II in 1577. He describes the events at a Greek wedding:
Another traveler, the German pharmacist Reinhold Lubenau, was in Constantinople in November 1588 and reports on a Greek wedding in these terms:
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# Medieval dance
## Estampie
If the story is true that troubadour Raimbaut de Vaqueiras (about 1150--1207) wrote the famous Provençal song *Kalenda Maya* to fit the tune of an estampie that he heard two jongleurs play, then the history of the estampie extends back to the 12th century. The only musical examples actually identified as \"estampie\" or \"istanpita\" occur in two 14th-century manuscripts. The same manuscripts also contain other pieces named \"danse real\" or other dance names. These are similar in musical structure to the estampies but consensus is divided as to whether these should be considered the same.
In addition to these instrumental music compositions, there are also mentions of the estampie in various literary sources from the 13th and 14th centuries. One of these as \"stampenie\" is found in Gottfried von Strassburg\'s *Tristan* from 1210 in a catalog of Tristan\'s accomplishments:
Later, in a description of Isolde:
A century and a half later in the poem *La Prison amoreuse* (1372--73) by French chronicler and poet Jean Froissart (c. 1337--1405), we find:
Opinion is divided as to whether the Estampie was actually a dance or simply early instrumental music. Sachs believes the strong rhythm of the music, a derivation of the name from a term meaning \"to stamp\" and the quotation from the Froissart poem above definitely label the estampie as a dance. However, others stress the complex music in some examples as being uncharacteristic of dance melodies and interpret Froissart\'s poem to mean that the dancing begins with the carol. There is also debate on the derivation of the word \"estampie\". In any case, no description of dance steps or figures for the estampie are known.
## Couple dances {#couple_dances}
upright=0.6\|thumb\|Heinrich von Stretlingen upright=0.6\|thumb\|Hiltbolt von Schwangau
According to German dance historian Aenne Goldschmidt, the oldest notice of a couple dance comes from the southern German Latin romance Ruodlieb probably composed in the early to mid-11th century. The dance is done at a wedding feast and is described in the translation by Edwin Zeydel as follows:
Another literary mention comes from a later period in Germany with a description of couple dancing in Wolfram von Eschenbach\'s epic poem *Parzival*, usually dated to the beginning of the 13th century. The scene occurs on manuscript page 639, the host is Gawain, the tables from the meal have been removed and musicians have been recruited:
Eschenbach also remarks that while many of the noblemen present were good fiddlers, they knew only the old style dances, not the many new dances from Thuringia.
The early 14th century Codex Manesse from Heidelberg has miniatures of many Minnesang poets of the period. The portrait of Heinrich von Stretelingen shows him engaged in a \"courtly pair dance\" while the miniature of Hiltbolt von Schwangau depicts him in a trio dance with two ladies, one in each hand, with a fiddler providing the music
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# Medieval music
**Medieval music** encompasses the sacred and secular music of Western Europe during the Middle Ages, from approximately the 6th to 15th centuries. It is the first and longest major era of Western classical music and is followed by the Renaissance music; the two eras comprise what musicologists generally term as early music, preceding the common practice period. Following the traditional division of the Middle Ages, medieval music can be divided into Early (500--1000), High (1000--1300), and Late (1300--1400) medieval music.
Medieval music includes liturgical music used for the church, other sacred music, and secular or non-religious music. Much medieval music is purely vocal music, such as Gregorian chant. Other music used only instruments or both voices and instruments (typically with the instruments accompanying the voices).
The medieval period saw the creation and adaptation of systems of music notation which enabled creators to document and transmit musical ideas more easily, although notation coexisted with and complemented oral tradition.
## Overview
### Genres
Medieval music was created for a number of different uses and contexts, resulting in different music genres. Liturgical as well as more general sacred contexts were important, but secular types emerged as well, including love songs and dances. During the earlier medieval period, liturgical music was monophonic chant; Gregorian chant became the dominant style. Polyphonic genres, in which multiple independent melodic lines are performed simultaneously, began to develop during the high medieval era, becoming prevalent by the later 13th and early 14th century. The development of polyphonic forms is often associated with the Ars antiqua style associated with Notre-Dame de Paris, but improvised polyphony around chant lines predated this.
Organum, for example, elaborated on a chant melody by creating one or more accompanying lines. The accompanying line could be as simple as a second line sung in parallel intervals to the original chant (often a perfect fifth or perfect fourth away from the main melody). The principles of this kind of organum date back at least to an anonymous 9th century tract, the *Musica enchiriadis*, which describes the tradition of duplicating a preexisting plainchant in parallel motion at the interval of an octave, a fifth or a fourth. Some of the earliest written examples are in a style known as Aquitanian polyphony, but the largest body of surviving organum comes from the Notre-Dame school. This loose collection of repertory is often called the *Magnus Liber Organi* (*Great Book of Organum*).
Related polyphonic genres included the motet and clausula genres, both also often built on an original segment of plainchant or as an elaboration on an organum passage. While most early motets were sacred and may have been liturgical (designed for use in a church service), by the end of the thirteenth century the genre had expanded to include secular topics, such as political satire and courtly love, and French as well as Latin texts. They also included from one to three upper voices, each with its own text.
In Italy, the secular genre of the Madrigal became popular. Similar to the polyphonic character of the motet, madrigals featured greater fluidity and motion in the leading melody. The madrigal form also gave rise to polyphonic canons (songs in which multiple singers sing the same melody, but starting at different times), especially in Italy where they were called *caccie.* These were three-part secular pieces, which featured the two higher voices in canon, with an underlying instrumental long-note accompaniment.
In the late middle ages, some purely instrumental music also began to be notated, though this remained rare. Dance music makes up most of the surviving instrumental music, and includes types such as the estampie, ductia, and nota.
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# Medieval music
## Overview
### Instruments
Many instruments used to perform medieval music still exist in the 21st century, but in different and typically more technologically developed forms. The flute was made of wood in the medieval era rather than silver or other metal, and could be made as a side-blown or end-blown instrument. While modern orchestral flutes are usually made of metal and have complex key mechanisms and airtight pads, medieval flutes had holes that the performer had to cover with the fingers (as with the recorder). The recorder was made of wood during the medieval era, and despite the fact that in the 21st century, it may be made of synthetic materials such as plastic, it has more or less retained its past form. The gemshorn is similar to the recorder as it has finger holes on its front, though it is actually a member of the ocarina family. One of the flute\'s predecessors, the pan flute, was popular in medieval times, and is possibly of Hellenic origin. This instrument\'s pipes were made of wood, and were graduated in length to produce different pitches.
Medieval music used many plucked string instruments like the lute, a fretted instrument with a pear-shaped hollow body which is the predecessor to the modern guitar. Other plucked stringed instruments included the mandore, gittern, citole and psaltery. The dulcimers, similar in structure to the psaltery and zither, were originally plucked, but musicians began to strike the dulcimer with hammers in the 14th century after the arrival of new metal technology that made metal strings possible.
The bowed lyra of the Byzantine Empire was the first recorded European bowed string instrument. Like the modern violin, a performer produced sound by moving a bow with tensioned hair over tensioned strings. The Persian geographer Ibn Khurradadhbih of the 9th century (`{{died in|911}}`{=mediawiki}) cited the Byzantine lyra, in his lexicographical discussion of instruments as a bowed instrument equivalent to the Arab rabāb and typical instrument of the Byzantines along with the *urghun* (organ),`{{Failed verification|date=September 2017}}`{=mediawiki} *shilyani* (probably a type of harp or lyre) and the *salandj* (probably a bagpipe). The hurdy-gurdy was (and still is) a mechanical violin using a rosined wooden wheel attached to a crank to \"bow\" its strings. Instruments without sound boxes like the jew\'s harp were also popular. Early versions of the pipe organ, fiddle (or vielle), and a precursor to the modern trombone (called the sackbut) were used.
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# Medieval music
## Overview
### Notation
During the medieval period the foundation was laid for the notational and theoretical practices that would shape Western music into the norms that developed during the common practice era. The most obvious of these is the development of a comprehensive music notational system; however the theoretical advances, particularly in regard to rhythm and polyphony, are equally important to the development of Western music.
The earliest medieval music did not have any kind of notational system. The tunes were primarily monophonic (a single melody without accompaniment) and transmitted by oral tradition. As Rome tried to centralize the various liturgies and establish the Roman rite as the primary church tradition the need to transmit these chant melodies across vast distances effectively was equally glaring. So long as music could only be taught to people \"by ear,\" it limited the ability of the church to get different regions to sing the same melodies, since each new person would have to spend time with a person who already knew a song and learn it \"by ear.\" The first step to fix this problem came with the introduction of various signs written above the chant texts to indicate direction of pitch movement, called *neumes*.
The origin of *neumes* is unclear and subject to some debate; however, most scholars agree that their closest ancestors are the classic Greek and Roman grammatical signs that indicated important points of declamation by recording the rise and fall of the voice. The two basic signs of the classical grammarians were the *acutus*, /, indicating a raising of the voice, and the *gravis*, \\, indicating a lowering of the voice. A singer reading a chant text with neume markings would be able to get a general sense of whether the melody line went up in pitch, stayed the same, or went down in pitch. Since trained singers knew the chant repertoire well, written neume markings above the text served as a reminder of the melody but did not specify the actual intervals. However, a singer reading a chant text with neume markings would not be able to sight read a song which he or she had never heard sung before; these pieces would not be possible to interpret accurately today without later versions in more precise notation systems.
These neumes eventually evolved into the basic symbols for *neumatic* notation, the *virga* (or \"rod\") which indicates a higher note and still looked like the *acutus* from which it came; and the *punctum* (or \"dot\") which indicates a lower note and, as the name suggests, reduced the *gravis* symbol to a point. Thus the *acutus* and the *gravis* could be combined to represent graphical vocal inflections on the syllable. This kind of notation seems to have developed no earlier than the eighth century, but by the ninth it was firmly established as the primary method of musical notation. The basic notation of the *virga* and the *punctum* remained the symbols for individual notes, but other *neumes* soon developed which showed several notes joined. These new *neumes*---called ligatures---are essentially combinations of the two original signs.
The first music notation was the use of dots over the lyrics to a chant, with some dots being higher or lower, giving the reader a general sense of the direction of the melody. However, this form of notation only served as a memory aid for a singer who already knew the melody. This basic *neumatic* notation could only specify the number of notes and whether they moved up or down. There was no way to indicate exact pitch, any rhythm, or even the starting note. These limitations are further indication that the *neumes* were developed as tools to support the practice of oral tradition, rather than to supplant it. However, even though it started as a mere memory aid, the worth of having more specific notation soon became evident.
The next development in musical notation was \"heighted *neumes*\", in which *neumes* were carefully placed at different heights in relation to each other. This allowed the *neumes* to give a rough indication of the size of a given interval as well as the direction. This quickly led to one or two lines, each representing a particular note, being placed on the music with all of the *neumes* relating to the earlier ones. At first, these lines had no particular meaning and instead had a letter placed at the beginning indicating which note was represented. However, the lines indicating middle C and the F a fifth below slowly became most common. Having been at first merely scratched on the parchment, the lines now were drawn in two different colored inks: usually red for F, and yellow or green for C. This was the beginning of the musical staff. The completion of the four-line staff is usually credited to Guido d\'Arezzo (c. 1000--1050), one of the most important musical theorists of the Middle Ages. While older sources attribute the development of the staff to Guido, some modern scholars suggest that he acted more as a codifier of a system that was already being developed. Either way, this new notation allowed a singer to learn pieces completely unknown to him in a much shorter amount of time. However, even though chant notation had progressed in many ways, one fundamental problem remained: rhythm. The *neumatic* notational system, even in its fully developed state, did not clearly define any kind of rhythm for the singing of notes.
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# Medieval music
## Music theory {#music_theory}
The music theory of the medieval period saw several advances over previous practice both in regard to tonal material, texture, and rhythm.
### Rhythm
Concerning rhythm, this period had several dramatic changes in both its conception and notation. During the early medieval period there was no method to notate rhythm, and thus the rhythmical practice of this early music is subject to debate among scholars. The first kind of written rhythmic system developed during the 13th century and was based on a series of modes. This rhythmic plan was codified by the music theorist Johannes de Garlandia, author of the *De Mensurabili Musica* (c. 1250), the treatise which defined and most completely elucidated these rhythmic modes. In his treatise Johannes de Garlandia describes six *species* of mode, or six different ways in which longs and breves can be arranged. Each mode establishes a rhythmic pattern in beats (or *tempora*) within a common unit of three *tempora* (a *perfectio*) that is repeated again and again. Furthermore, notation without text is based on chains of *ligature*s (the characteristic notations by which groups of notes are bound to one another).
The rhythmic mode can generally be determined by the patterns of ligatures used. Once a rhythmic mode had been assigned to a melodic line, there was generally little deviation from that mode, although rhythmic adjustments could be indicated by changes in the expected pattern of ligatures, even to the extent of changing to another rhythmic mode. The next step forward concerning rhythm came from the German theorist Franco of Cologne. In his treatise *Ars cantus mensurabilis* (\"The Art of Mensurable Music\"), written around 1280, he describes a system of notation in which differently shaped notes have entirely different rhythmic values. This is a striking change from the earlier system of de Garlandia. Whereas before the length of the individual note could only be gathered from the mode itself, this new inverted relationship made the mode dependent upon---and determined by---the individual notes or *figurae* that have incontrovertible durational values, an innovation which had a massive impact on the subsequent history of European music. Most of the surviving notated music of the 13th century uses the rhythmic modes as defined by Garlandia. The step in the evolution of rhythm came after the turn of the 13th century with the development of the *Ars Nova* style.
The theorist who is most well recognized in regard to this new style is Philippe de Vitry, famous for writing the *Ars Nova* (\"New Art\") treatise around 1320. This treatise on music gave its name to the style of this entire era. In some ways the modern system of rhythmic notation began with Vitry, who completely broke free from the older idea of the rhythmic modes. The notational predecessors of modern time meters also originate in the *Ars Nova*. This new style was clearly built upon the work of Franco of Cologne. In Franco\'s system, the relationship between a breve and a semibreves (that is, half breves) was equivalent to that between a breve and a long: and, since for him *modus* was always perfect (grouped in threes), the *tempus* or beat was also inherently perfect and therefore contained three semibreves. Sometimes the context of the mode would require a group of only two semibreves, however, these two semibreves would always be one of normal length and one of double length, thereby taking the same space of time, and thus preserving the perfect subdivision of the *tempus*. This ternary division held for all note values. In contrast, the *Ars Nova* period introduced two important changes: the first was an even smaller subdivision of notes (semibreves, could now be divided into *minim*), and the second was the development of \"mensuration.\"
Mensurations could be combined in various manners to produce metrical groupings. These groupings of mensurations are the precursors of simple and compound meter. By the time of *Ars Nova*, the perfect division of the *tempus* was not the only option as duple divisions became more accepted. For Vitry the breve could be divided, for an entire composition, or section of one, into groups of two or three smaller semibreves. This way, the *tempus* (the term that came to denote the division of the breve) could be either \"perfect\" (*tempus perfectum*), with ternary subdivision, or \"imperfect\" (*tempus imperfectum*), with binary subdivision. In a similar fashion, the semibreve\'s division (termed *prolation*) could be divided into three *minima* (*prolatio perfectus* or major prolation) or two *minima* (*prolatio imperfectus* or minor prolation) and, at the higher level, the longs division (called *modus*) could be three or two breves (*modus perfectus* or perfect mode, or *modus imperfectus* or imperfect mode respectively). Vitry took this a step further by indicating the proper division of a given piece at the beginning through the use of a \"mensuration sign\", equivalent to our modern \"time signature\".
*Tempus perfectum* was indicated by a circle, while *tempus imperfectum* was denoted by a half-circle (the current symbol `{{music|common-time}}`{=mediawiki}, used as an alternative for the `{{music|time|4|4}}`{=mediawiki} time signature, is actually a holdover of this symbol, not a letter *C* as an abbreviation for \"common time\", as popularly believed). While many of these innovations are ascribed to Vitry, and somewhat present in the *Ars Nova* treatise, it was a contemporary---and personal acquaintance---of de Vitry, named Johannes de Muris (or Jehan des Mars) who offered the most comprehensive and systematic treatment of the new mensural innovations of the *Ars Nova* (for a brief explanation of the mensural notation in general, see the article Renaissance music). Many scholars, citing a lack of positive attributory evidence, now consider \"Vitry\'s\" treatise to be anonymous, but this does not diminish its importance for the history of rhythmic notation. However, this makes the first definitely identifiable scholar to accept and explain the mensural system to be de Muris, who can be said to have done for it what Garlandia did for the rhythmic modes.
For the duration of the medieval period, most music would be composed primarily in perfect tempus, with special effects created by sections of imperfect tempus; there is a great current controversy among musicologists as to whether such sections were performed with a breve of equal length or whether it changed, and if so, at what proportion. This *Ars Nova* style remained the primary rhythmical system until the highly syncopated works of the *Ars subtilior* at the end of the 14th century, characterized by extremes of notational and rhythmic complexity. This sub-genera pushed the rhythmic freedom provided by *Ars Nova* to its limits, with some compositions having different voices written in different mensurations simultaneously. The rhythmic complexity that was realized in this music is comparable to that in the 20th century.
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# Medieval music
## Music theory {#music_theory}
### Polyphony
Of equal importance to the overall history of western music theory were the textural changes that came with the advent of polyphony. This practice shaped western music into the harmonically dominated music that we know today. The first accounts of this textural development were found in two anonymous yet widely circulated treatises on music, the *Musica* and the *Scolica enchiriadis*. These texts are dated to sometime within the last half of the ninth century. The treatises describe a technique that seemed already to be well established in practice. This early polyphony is based on three simple and three compound intervals. The first group comprises fourths, fifths, and octaves; while the second group has octave-plus-fourths, octave-plus-fifths, and double octaves. This new practice is given the name *organum* by the author of the treatises. *Organum* can further be classified depending on the time period in which it was written. The early *organum* as described in the *enchiriadis* can be termed \"strict *organum*\" Strict *organum* can, in turn, be subdivided into two types: *diapente* (organum at the interval of a fifth) and *diatesseron* (organum at the interval of a fourth). However, both of these kinds of strict *organum* had problems with the musical rules of the time. If either of them paralleled an original chant for too long (depending on the mode) a tritone would result.
This problem was somewhat overcome with the use of a second type of *organum*. This second style of *organum* was called \"free *organum*\". Its distinguishing factor is that the parts did not have to move only in parallel motion, but could also move in oblique, or contrary motion. This made it much easier to avoid the dreaded tritone. The final style of *organum* that developed was known as \"melismatic *organum*\", which was a rather dramatic departure from the rest of the polyphonic music up to this point. This new style was not note against note, but was rather one sustained line accompanied by a florid melismatic line. This final kind of *organum* was also incorporated by the most famous polyphonic composer of this time---Léonin. He united this style with measured discant passages, which used the rhythmic modes to create the pinnacle of *organum* composition. This final stage of *organum* is sometimes referred to as Notre Dame school of polyphony, since that was where Léonin (and his student Pérotin) were stationed. Furthermore, this kind of polyphony influenced all subsequent styles, with the later polyphonic genera of motets starting as a trope of existing Notre Dame *organums*.
Another important element of medieval music theory was the system by which pitches were arranged and understood. During the Middle Ages, this systematic arrangement of a series of whole steps and half steps, what we now call a scale, was known as a mode. The modal system worked like the scales of today, insomuch that it provided the rules and material for melodic writing. The eight church modes are: *Dorian*, *Hypodorian*, *Phrygian*, *Hypophrygian*, *Lydian*, *Hypolydian*, *Mixolydian*, and *Hypomixolydian*. Much of the information concerning these modes, as well as the practical application of them, was codified in the 11th century by the theorist Johannes Afflighemensis. In his work he describes three defining elements to each mode: the final (or *finalis)*, the reciting tone (*tenor* or *confinalis*), and the range (or *ambitus*). The *finalis* is the tone that serves as the focal point for the mode and, as the name suggests, is almost always used as the final tone. The reciting tone is the tone that serves as the primary focal point in the melody (particularly internally). It is generally also the tone most often repeated in the piece, and finally the range delimits the upper and lower tones for a given mode. The eight modes can be further divided into four categories based on their final (*finalis*).
Medieval theorists called these pairs *maneriae* and labeled them according to the Greek ordinal numbers. Those modes that have d, e, f, and g as their final are put into the groups *protus*, *deuterus*, *tritus*, and *tetrardus* respectively. These can then be divided further based on whether the mode is \"authentic\" or \"plagal.\" These distinctions deal with the range of the mode in relation to the final. The authentic modes have a range that is about an octave (one tone above or below is allowed) and start on the final, whereas the plagal modes, while still covering about an octave, start a perfect fourth below the authentic. Another interesting aspect of the modal system is the use of \"Musica ficta\" which allows pitches to be altered (changing B`{{music|natural}}`{=mediawiki} to B`{{music|flat}}`{=mediawiki} for example) in certain contexts regardless of the mode. These changes have several uses, but one that seems particularly common is to avoid melodic difficulties caused by the tritone.
These ecclesiastical modes, although they have Greek names, have little relationship to the modes as set out by Greek theorists. Rather, most of the terminology seems to be a misappropriation on the part of the medieval theorists Although the church modes have no relation to the ancient Greek modes, the overabundance of Greek terminology does point to an interesting possible origin in the liturgical melodies of the Byzantine tradition. This system is called *octoechos* and is also divided into eight categories, called *echoi*.
For specific medieval music theorists, see also: Isidore of Seville, Aurelian of Réôme, Odo of Cluny, Guido of Arezzo, Hermannus Contractus, Johannes Cotto (Johannes Afflighemensis), Johannes de Muris, Franco of Cologne, Johannes de Garlandia (Johannes Gallicus), Anonymous IV, Marchetto da Padova (Marchettus of Padua), Jacques of Liège, Johannes de Grocheo, Petrus de Cruce (Pierre de la Croix), and Philippe de Vitry.
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# Medieval music
## Early medieval music (500--1000) {#early_medieval_music_5001000}
### Early chant traditions {#early_chant_traditions}
thumb\|upright=0.5\|Hildegard of Bingen, one of the best-known composers of sacred monophony Chant (or plainsong) is a monophonic sacred (single, unaccompanied melody) form which represents the earliest known music of the Christian church. Chant developed separately in several European centres. Although the most important were Rome, Hispania, Gaul, Milan, and Ireland, there were others as well. These styles were all developed to support the regional liturgies used when celebrating the Mass there. Each area developed its own chant and rules for celebration. In Spain and Portugal, Mozarabic chant was used and shows the influence of North African music. The Mozarabic liturgy even survived through Muslim rule, though this was an isolated strand and this music was later suppressed in an attempt to enforce conformity on the entire liturgy. In Milan, Ambrosian chant, named after St. Ambrose, was the standard, while Beneventan chant developed around Benevento, another Italian liturgical center. Gallican chant was used in Gaul, and Celtic chant in Ireland and Great Britain.
The reigning Carolingian dynasty wanted to standardize the Mass and chant across its Frankish Empire. At this time, Rome was the religious centre of western Europe, and northern Gaul and Rhineland (most notably the city of Aachen) was the political centre. The standardization effort consisted mainly of combining the two -- Roman and Gallican -- regional liturgies. Charlemagne (742--814) sent trained singers throughout the Empire to teach this new form of chant. This body of chant became known as Gregorian Chant, named after Pope Gregory I. Gregorian chant was said to be collected and codified during his papacy or even composed by himself, inspired by the Holy Spirit in the form of a dove. However, that is only a popular legend that was spread by the Carolingians who wanted to legitimize their liturgy unification efforts. Gregorian chant certainly didn\'t exist at that time. It is possible, nevertheless, that Gregory\'s papacy really may have contributed to collecting and codifying the Roman chant of the time which then, in the 9th and 10th centuries, formed -- alongside the Gallican chant -- one of the two roots of the Gregorian chant. By the 12th and 13th centuries, Gregorian chant had superseded all the other Western chant traditions, with the exception of the Ambrosian chant in Milan and the Mozarabic chant in a few specially designated Spanish chapels. Hildegard von Bingen (1098--1179) was one of the earliest known female composers. She wrote many monophonic works for the Catholic Church, almost all of them for female voices.
### Early polyphony: organum {#early_polyphony_organum}
Around the end of the 9th century, singers in monasteries such as St. Gall in Switzerland began experimenting with adding another part to the chant, generally a voice in parallel motion, singing mostly in perfect fourths or fifths above the original tune (see interval). This development is called organum and represents the beginnings of counterpoint and, ultimately, harmony. Over the next several centuries, organum developed in several ways.
The most significant of these developments was the creation of \"florid organum\" around 1100, sometimes known as the school of St. Martial (named after a monastery in south-central France, which contains the best-preserved manuscript of this repertory). In \"florid organum\" the original tune would be sung in long notes while an accompanying voice would sing many notes to each one of the original, often in a highly elaborate fashion, all the while emphasizing the perfect consonances (fourths, fifths and octaves), as in the earlier organa. Later developments of organum occurred in England, where the interval of the third was particularly favoured, and where organa were likely improvised against an existing chant melody, and at Notre Dame in Paris, which was to be the centre of musical creative activity throughout the thirteenth century.
Much of the music from the early medieval period is anonymous. Some of the names may have been poets and lyric writers, and the tunes for which they wrote words may have been composed by others. Attribution of monophonic music of the medieval period is not always reliable. Surviving manuscripts from this period include the Musica Enchiriadis, Codex Calixtinus of Santiago de Compostela, the Magnus Liber, and the Winchester Troper. For information about specific composers or poets writing during the early medieval period, see Pope Gregory I, St. Godric, Hildegard of Bingen, Hucbald, Notker Balbulus, Odo of Arezzo, Odo of Cluny, and Tutilo.
### Liturgical drama {#liturgical_drama}
Another musical tradition of Europe originating during the early Middle Ages was the liturgical drama.
Liturgical drama developed possibly in the 10th century from the tropes---poetic embellishments of the liturgical texts. One of the tropes, the so-called Quem Quaeritis, belonging to the liturgy of Easter morning, developed into a short play around the year 950. The oldest surviving written source is the Winchester Troper. Around the year 1000 it was sung widely in Northern Europe.`{{Failed verification|date=May 2020|reason=Contrary to claiming the Winchester Troper was sung in Northern Europe, the source says "The tropes – new phrases added into Gregorian chants – show the adoption in England of a way of singing widely practised in northern Europe by the 11th century."}}`{=mediawiki}
Shortly,`{{Clarify|date=September 2018}}`{=mediawiki} a similar Christmas play was developed, musically and textually following the Easter one, and other plays followed.
There is a controversy among musicologists as to the instrumental accompaniment of such plays, given that the stage directions, very elaborate and precise in other respects, do not request any participation of instruments. These dramas were performed by monks, nuns and priests. In contrast to secular plays, which were spoken, the liturgical drama was always sung. Many have been preserved sufficiently to allow modern reconstruction and performance (for example the *Play of Daniel*, which has been recently recorded at least ten times).
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## High medieval music (1000--1300) {#high_medieval_music_10001300}
### Goliards
The Goliards were itinerant poet-musicians of Europe from the tenth to the middle of the thirteenth century. Most were scholars or ecclesiastics, and they wrote and sang in Latin. Although many of the poems have survived, very little of the music has. They were possibly influential---even decisively so---on the troubadour-trouvère tradition which was to follow. Most of their poetry is secular and, while some of the songs celebrate religious ideals, others are frankly profane, dealing with drunkenness, debauchery and lechery. One of the most important extant sources of Goliards chansons is the Carmina Burana.
### *Ars antiqua* {#ars_antiqua}
The flowering of the Notre Dame school of polyphony from around 1150 to 1250 corresponded to the equally impressive achievements in Gothic architecture: indeed the centre of activity was at the cathedral of Notre Dame itself. Sometimes the music of this period is called the Parisian school, or Parisian organum, and represents the beginning of what is conventionally known as *Ars antiqua*. This was the period in which rhythmic notation first appeared in western music, mainly a context-based method of rhythmic notation known as the rhythmic modes.
This was also the period in which concepts of formal structure developed which were attentive to proportion, texture, and architectural effect. Composers of the period alternated florid and discant organum (more note-against-note, as opposed to the succession of many-note melismas against long-held notes found in the florid type), and created several new musical forms: clausulae, which were melismatic sections of organa extracted and fitted with new words and further musical elaboration; conductus, which were songs for one or more voices to be sung rhythmically, most likely in a procession of some sort; and tropes, which were additions of new words and sometimes new music to sections of older chant. All of these genres save one were based upon chant; that is, one of the voices, (usually three, though sometimes four) nearly always the lowest (the tenor at this point) sang a chant melody, though with freely composed note-lengths, over which the other voices sang organum. The exception to this method was the conductus, a two-voice composition that was freely composed in its entirety.
The motet, one of the most important musical forms of the high Middle Ages and Renaissance, developed initially during the Notre Dame period out of the clausula, especially the form using multiple voices as elaborated by Pérotin, who paved the way for this particularly by replacing many of his predecessor (as canon of the cathedral) Léonin\'s lengthy florid clausulae with substitutes in a discant style. Gradually, there came to be entire books of these substitutes, available to be fitted in and out of the various chants. Since, in fact, there were more than can possibly have been used in context, it is probable that the clausulae came to be performed independently, either in other parts of the mass, or in private devotions. The clausula, thus practised, became the motet when troped with non-liturgical words, and this further developed into a form of great elaboration, sophistication and subtlety in the fourteenth century, the period of *Ars nova*. Surviving manuscripts from this era include the Montpellier Codex, Bamberg Codex, and Las Huelgas Codex.
Composers of this time include Léonin, Pérotin, W. de Wycombe, Adam de St. Victor, and Petrus de Cruce (Pierre de la Croix). Petrus is credited with the innovation of writing more than three semibreves to fit the length of a breve. Coming before the innovation of imperfect tempus, this practice inaugurated the era of what are now called \"Petronian\" motets. These late 13th-century works are in three to four parts and have multiple texts sung simultaneously. Originally, the tenor line (from the Latin *tenere*, \"to hold\") held a preexisting liturgical chant line in the original Latin, while the text of the one, two, or even three voices above, called the *voces organales*, provided commentary on the liturgical subject either in Latin or in the vernacular French. The rhythmic values of the *voces organales* decreased as the parts multiplied, with the *duplum* (the part above the tenor) having smaller rhythmic values than the tenor, the *triplum* (the line above the *duplum*) having smaller rhythmic values than the *duplum*, and so on. As time went by, the texts of the *voces organales* became increasingly secular in nature and had less and less overt connection to the liturgical text in the tenor line.
The increasing rhythmic complexity seen in Petronian motets would be a fundamental characteristic of the 14th century, though music in France, Italy, and England would take quite different paths during that time.
### Cantigas de Santa Maria {#cantigas_de_santa_maria}
*Main article: Cantigas de Santa Maria* The ***Cantigas de Santa Maria*** (\"Canticles of St. Mary\") are 420 poems with musical notation, written in Galician-Portuguese during the reign of Alfonso X *The Wise* (1221--1284). The manuscript was probably compiled from 1270 to 1280, and is highly decorated, with an illumination every 10 poems. The illuminations often depict musicians making the manuscript a particularly important source of medieval music iconography. Though the *Cantigas* are often attributed to Alfonso, it remains unclear as to whether he was a composer himself, or perhaps a compiler; Alfonso is known to regularly invited musicians and poets to court whom were undoubtedly involved in the *Cantigas* production.
It is one of the largest collections of monophonic (solo) songs from the Middle Ages and is characterized by the mention of the Virgin Mary in every song, while every tenth song is a hymn. The manuscripts have survived in four codices: two at El Escorial, one at Madrid\'s National Library, and one in Florence, Italy. Some have colored miniatures showing pairs of musicians playing a wide variety of instruments.
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## High medieval music (1000--1300) {#high_medieval_music_10001300}
### Troubadours and trouvères {#troubadours_and_trouvères}
The music of the troubadours and trouvères was a vernacular tradition of monophonic secular song, probably accompanied by instruments, sung by professional, occasionally itinerant, musicians who were as skilled as poets as they were singers and instrumentalists. The language of the troubadours was Occitan (also known as the langue d\'oc, or Provençal); the language of the trouvères was Old French (also known as langue d\'oïl). The period of the troubadours corresponded to the flowering of cultural life in Provence which lasted through the twelfth century and into the first decade of the thirteenth. Typical subjects of troubadour song were war, chivalry and courtly love---the love of an idealized woman from afar. The period of the troubadours wound down after the Albigensian Crusade, the fierce campaign by Pope Innocent III to eliminate the Cathar heresy (and northern barons\' desire to appropriate the wealth of the south). Surviving troubadours went either to Portugal, Spain, northern Italy or northern France (where the trouvère tradition lived on), where their skills and techniques contributed to the later developments of secular musical culture in those places.
The trouvères and troubadours shared similar musical styles, but the trouvères were generally noblemen. The music of the trouvères was similar to that of the troubadours, but was able to survive into the thirteenth century unaffected by the Albigensian Crusade. Most of the more than two thousand surviving trouvère songs include music, and show a sophistication as great as that of the poetry it accompanies.
### Minnesänger and Meistersinger {#minnesänger_and_meistersinger}
right\|thumb\|upright=0.5\|Portrait of Walther von der Vogelweide The Minnesänger tradition was the Germanic counterpart to the activity of the troubadours and trouvères to the west. Unfortunately, few sources survive from the time; the sources of Minnesang are mostly from two or three centuries after the peak of the movement, leading to some controversy over the accuracy of these sources. Among the Minnesängers with surviving music are Wolfram von Eschenbach, Walther von der Vogelweide, and Niedhart von Reuenthal.
A Meistersinger (German for \"master singer\") was a member of a German guild for lyric poetry, composition and unaccompanied art song of the 14th, 15th and 16th centuries. The Meistersingers were drawn from middle class males for the most part. Konrad von Würzburg, Reinmar von Zweter, and Heinrich Frauenlob. Frauenlob allegedly established the earliest Meistersinger school at Mainz, early in the 14th century. The schools originated first in the upper Rhine district, then spread elsewhere.
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## High medieval music (1000--1300) {#high_medieval_music_10001300}
### Trovadorismo
In the Middle Ages, Galician-Portuguese was the language used in nearly all of Iberia for lyric poetry. From this language derive both modern Galician and Portuguese. The Galician-Portuguese school, which was influenced to some extent (mainly in certain formal aspects) by the Occitan troubadours, is first documented at the end of the twelfth century and lasted until the middle of the fourteenth.
The earliest extant composition in this school is usually agreed to be *Ora faz ost\' o senhor de Navarra* by the Portuguese João Soares de Paiva, usually dated just before or after 1200. The troubadours of the movement, not to be confused with the Occitan troubadours (who frequented courts in nearby León and Castile), wrote almost entirely *cantigas*. Beginning probably around the middle of the thirteenth century, these songs, known also as *cantares* or *trovas*, began to be compiled in collections known as *cancioneiros* (songbooks). Three such anthologies are known: the Cancioneiro da Ajuda, the Cancioneiro Colocci-Brancuti (or Cancioneiro da Biblioteca Nacional de Lisboa), and the Cancioneiro da Vaticana. In addition to these there is the priceless collection of over 400 Galician-Portuguese *cantigas* in the Cantigas de Santa Maria, which tradition attributes to Alfonso X.
The Galician-Portuguese *cantigas* can be divided into three basic genres: male-voiced love poetry, called *cantigas de amor* (or *cantigas d\'amor*, in Galician-Portuguese spelling) female-voiced love poetry, called *cantigas de amigo* (or *cantigas d\'amigo*); and poetry of insult and mockery called *cantigas de escárnio e maldizer* (or *cantigas d\'escarnho e de mal dizer*). All three are lyric genres in the technical sense that they were strophic songs with either musical accompaniment or introduction on a stringed instrument. But all three genres also have dramatic elements, leading early scholars to characterize them as lyric-dramatic.
The origins of the cantigas d\'amor are usually traced to Provençal and Old French lyric poetry, but formally and rhetorically they are quite different. The *cantigas d\'amigo* are probably rooted in a native song tradition, though this view has been contested. The *cantigas d\'escarnho e maldizer* may also (according to Lang) have deep local roots. The latter two genres (totalling around 900 texts) make the Galician-Portuguese lyric unique in the entire panorama of medieval Romance poetry.
#### Troubadours with surviving melodies {#troubadours_with_surviving_melodies}
- Aimeric de Belenoi
- Aimeric de Peguilhan
- Airas Nunes
- Albertet de Sestaro
- Arnaut Daniel
- Arnaut de Maruoill
- Beatritz de Dia
- Berenguier de Palazol
- Bernart de Ventadorn
- Bertran de Born
- Blacasset
- Cadenet
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- Daude de Pradas
- Denis of Portugal
- Folquet de Marselha
- Gaucelm Faidit
- Gui d\'Ussel
- Guilhem Ademar
- Guilhem Augier Novella
- Guilhem Magret
- Guilhem de Saint Leidier
- Guiraut de Bornelh
- Guiraut d\'Espanha
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- Guiraut Riquier
- Jaufre Rudel
- João Soares de Paiva
- João Zorro
- Jordan Bonel
- Marcabru
- Martín Codax
- Monge de Montaudon
- Peire d\'Alvernhe
- Peire Cardenal
- Peire Raimon de Tolosa
- Peire Vidal
- Peirol
- Perdigon
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- Pistoleta
- Pons d\'Ortaffa
- Pons de Capduoill
- Raimbaut d\'Aurenga
- Raimbaut de Vaqueiras
- Raimon Jordan
- Raimon de Miraval
- Rigaut de Berbezilh
- Uc Brunet
- Uc de Saint Circ
- William IX of Aquitaine
### Timeline of Composers of the high and late medieval era {#timeline_of_composers_of_the_high_and_late_medieval_era}
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# Medieval music
## Late medieval music (1300--1400) {#late_medieval_music_13001400}
### France: *Ars nova* {#france_ars_nova}
The beginning of the *Ars nova* is one of the few clear chronological divisions in medieval music, since it corresponds to the publication of the *Roman de Fauvel*, a huge compilation of poetry and music, in 1310 and 1314. The *Roman de Fauvel* is a satire on abuses in the medieval church, and is filled with medieval motets, lais, rondeaux and other new secular forms. While most of the music is anonymous, it contains several pieces by Philippe de Vitry, one of the first composers of the isorhythmic motet, a development which distinguishes the fourteenth century. The isorhythmic motet was perfected by Guillaume de Machaut, the finest composer of the time.
During the *Ars nova* era, secular music acquired a polyphonic sophistication formerly found only in sacred music, a development not surprising considering the secular character of the early Renaissance (while this music is typically considered \"medieval\", the social forces that produced it were responsible for the beginning of the literary and artistic Renaissance in Italy---the distinction between Middle Ages and Renaissance is a blurry one, especially considering arts as different as music and painting). The term \"*Ars nova*\" (new art, or new technique) was coined by Philippe de Vitry in his treatise of that name (probably written in 1322), in order to distinguish the practice from the music of the immediately preceding age.
The dominant secular genre of the Ars Nova was the *chanson*, as it would continue to be in France for another two centuries. These chansons were composed in musical forms corresponding to the poetry they set, which were in the so-called *formes fixes* of *rondeau*, *ballade*, and *virelai*. These forms significantly affected the development of musical structure in ways that are felt even today; for example, the *ouvert-clos* rhyme-scheme shared by all three demanded a musical realization which contributed directly to the modern notion of antecedent and consequent phrases. It was in this period, too, in which began the long tradition of setting the mass ordinary. This tradition started around mid-century with isolated or paired settings of Kyries, Glorias, etc., but Machaut composed what is thought to be the first complete mass conceived as one composition. The sound world of Ars Nova music is very much one of linear primacy and rhythmic complexity. \"Resting\" intervals are the fifth and octave, with thirds and sixths considered dissonances. Leaps of more than a sixth in individual voices are not uncommon, leading to speculation of instrumental participation at least in secular performance. Surviving French manuscripts include the Ivrea Codex and the Apt Codex.
For information about specific French composers writing in late medieval era, see Jehan de Lescurel, Philippe de Vitry, Guillaume de Machaut, Borlet, Solage, and François Andrieu.
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# Medieval music
## Late medieval music (1300--1400) {#late_medieval_music_13001400}
### Italy: *Trecento* {#italy_trecento}
Most of the music of *Ars nova* was French in origin; however, the term is often loosely applied to all of the music of the fourteenth century, especially to include the secular music in Italy. There this period was often referred to as *Trecento*. Italian music has always been known for its lyrical or melodic character, and this goes back to the 14th century in many respects. Italian secular music of this time (what little surviving liturgical music there is, is similar to the French except for somewhat different notation) featured what has been called the *cantalina* style, with a florid top voice supported by two (or even one; a fair amount of Italian Trecento music is for only two voices) that are more regular and slower moving. This type of texture remained a feature of Italian music in the popular 15th and 16th century secular genres as well, and was an important influence on the eventual development of the trio texture that revolutionized music in the 17th.
There were three main forms for secular works in the Trecento. One was the madrigal, not the same as that of 150--250 years later, but with a verse/refrain-like form. Three-line stanzas, each with different words, alternated with a two-line *ritornello*, with the same text at each appearance. Perhaps we can see the seeds of the subsequent late-Renaissance and Baroque ritornello in this device; it too returns again and again, recognizable each time, in contrast with its surrounding disparate sections. Another form, the *caccia* (\"chase,\") was written for two voices in a canon at the unison. Sometimes, this form also featured a ritornello, which was occasionally also in a canonic style. Usually, the name of this genre provided a double meaning, since the texts of *caccia* were primarily about hunts and related outdoor activities, or at least action-filled scenes; second meaning was that a voice *caccia* (follows, run after) the preceding one. The third main form was the *ballata*, which was roughly equivalent to the French *virelai*.
Surviving Italian manuscripts include the Squarcialupi Codex and the Rossi Codex. For information about specific Italian composers writing in the late medieval era, see Francesco Landini, Gherardello da Firenze, Andrea da Firenze, Lorenzo da Firenze, Giovanni da Firenze (aka Giovanni da Cascia), Bartolino da Padova, Jacopo da Bologna, Donato da Cascia, Lorenzo Masini, Niccolò da Perugia, and Maestro Piero.
### Germany: *Geisslerlieder* {#germany_geisslerlieder}
The Geisslerlieder were the songs of wandering bands of flagellants, who sought to appease the wrath of an angry God by penitential music accompanied by mortification of their bodies. There were two separate periods of activity of Geisslerlied: one around the middle of the thirteenth century, from which, unfortunately, no music survives (although numerous lyrics do); and another from 1349, for which both words and music survive intact due to the attention of a single priest who wrote about the movement and recorded its music. This second period corresponds to the spread of the Black Death in Europe, and documents one of the most terrible events in European history. Both periods of Geisslerlied activity were mainly in Germany.
### *Ars subtilior* {#ars_subtilior}
As often seen at the end of any musical era, the end of the medieval era is marked by a highly manneristic style known as *Ars subtilior*. In some ways, this was an attempt to meld the French and Italian styles. This music was highly stylized, with a rhythmic complexity that was not matched until the 20th century. In fact, not only was the rhythmic complexity of this repertoire largely unmatched for five and a half centuries, with extreme syncopations, mensural trickery, and even examples of *augenmusik* (such as a chanson by Baude Cordier written out in manuscript in the shape of a heart), but also its melodic material was quite complex as well, particularly in its interaction with the rhythmic structures. Already discussed under Ars Nova has been the practice of isorhythm, which continued to develop through late-century and in fact did not achieve its highest degree of sophistication until early in the 15th century. Instead of using isorhythmic techniques in one or two voices, or trading them among voices, some works came to feature a pervading isorhythmic texture which rivals the integral serialism of the 20th century in its systematic ordering of rhythmic and tonal elements. The term \"mannerism\" was applied by later scholars, as it often is, in response to an impression of sophistication being practised for its own sake, a malady which some authors have felt infected the *Ars subtilior*.
One of the most important extant sources of Ars Subtilior chansons is the Chantilly Codex. For information about specific composers writing music in *Ars subtilior* style, see Anthonello de Caserta, Philippus de Caserta (aka Philipoctus de Caserta), Johannes Ciconia, Matteo da Perugia, Lorenzo da Firenze, Grimace, Jacob Senleches, and Baude Cordier.
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# Medieval music
## Late medieval music (1300--1400) {#late_medieval_music_13001400}
### Transitioning to the Renaissance {#transitioning_to_the_renaissance}
Demarcating the end of the medieval era and the beginning of the Renaissance era, with regard to the composition of music, is difficult. While the music of the fourteenth century is fairly obviously medieval in conception, the music of the early fifteenth century is often conceived as belonging to a transitional period, not only retaining some of the ideals of the end of the Middle Ages (such as a type of polyphonic writing in which the parts differ widely from each other in character, as each has its specific textural function), but also showing some of the characteristic traits of the Renaissance (such as the increasingly international style developing through the diffusion of Franco-Flemish musicians throughout Europe, and in terms of texture an increasing equality of parts). Music historians do not agree on when the Renaissance era began, but most historians agree that England was still a medieval society in the early fifteenth century (see periodization issues of the Middle Ages). While there is no consensus, 1400 is a useful marker, because it was around that time that the Renaissance came into full swing in Italy.
The increasing reliance on the interval of the third as a consonance is one of the most pronounced features of transition into the Renaissance. Polyphony, in use since the 12th century, became increasingly elaborate with highly independent voices throughout the 14th century. With John Dunstaple and other English composers, partly through the local technique of faburden (an improvisatory process in which a chant melody and a written part predominantly in parallel sixths above it are ornamented by one sung in perfect fourths below the latter, and which later took hold on the continent as \"fauxbordon\"), the interval of the third emerges as an important musical development; because of this *Contenance Angloise* (\"English countenance\"), English composers\' music is often regarded as the first to sound less truly bizarre to 2000s-era audiences who are not trained in music history.
English stylistic tendencies in this regard had come to fruition and began to influence continental composers as early as the 1420s, as can be seen in works of the young Dufay, among others. While the Hundred Years\' War continued, English nobles, armies, their chapels and retinues, and therefore some of their composers, travelled in France and performed their music there; it must also of course be remembered that the English controlled portions of northern France at this time. English manuscripts include the Worcester Fragments, the Old St. Andrews Music Book, the Old Hall Manuscript, and Egerton Manuscript. For information about specific composers who are considered transitional between the medieval and the Renaissance, see Zacara da Teramo, Paolo da Firenze, Giovanni Mazzuoli, Antonio da Cividale, Antonius Romanus, Bartolomeo da Bologna, Roy Henry, Arnold de Lantins, Leonel Power, and John Dunstaple.
An early composer from the Franco-Flemish School of the Renaissance was Johannes Ockeghem (1410/1425 --1497). He was the most famous member of the Franco-Flemish School in the last half of the 15th century, and is often considered`{{Weasel inline|date=May 2017}}`{=mediawiki} the most influential composer between Dufay and Josquin des Prez. Ockeghem probably studied with Gilles Binchois, and at least was closely associated with him at the Burgundian court. Antoine Busnois wrote a motet in honor of Ockeghem. Ockeghem is a direct link from the Burgundian style to the next generation of Netherlanders, such as Obrecht and Josquin. A strong influence on Josquin des Prez and the subsequent generation of Netherlanders, Ockeghem was famous throughout Europe Charles VII for his expressive music, although he was equally renowned for his technical prowess.
## Influence
The musical style of Pérotin influenced 20th-century composers such as John Luther Adams and minimalist composer Steve Reich.
Bardcore, which involves remixing famous pop songs to have a medieval instrumentation, became a popular meme in 2020
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# Mesa (programming language)
**Mesa** is a programming language developed in the mid 1970s at the Xerox Palo Alto Research Center in Palo Alto, California, United States. The language name was a pun based upon the programming language catchphrases of the time, because Mesa is a \"high level\" programming language.
Mesa is an ALGOL-like language with strong support for modular programming. Every library module has at least two source files: a *definitions* file specifying the library\'s interface plus one or more *program* files specifying the implementation of the procedures in the interface. To use a library, a program or higher-level library must \"import\" the definitions. The Mesa compiler type-checks all uses of imported entities; this combination of separate compilation with type-checking was unusual at the time.
Mesa introduced several other innovations in language design and implementation, notably in the handling of software exceptions, thread synchronization, and incremental compilation.
Mesa was developed on the Xerox Alto, one of the first personal computers with a graphical user interface, however, most of the Alto\'s system software was written in BCPL. Mesa was the system programming language of the later Xerox Star workstations, and for the GlobalView desktop environment. Xerox PARC later developed Cedar, which was a superset of Mesa.
Mesa and Cedar had a major influence on the design of other important languages, such as Modula-2 and Java, and was an important vehicle for the development and dissemination of the fundamentals of GUIs, networked environments, and the other advances Xerox contributed to the field of computer science.
## History
Mesa was originally designed in the Computer Systems Laboratory (CSL), a branch of the Xerox Palo Alto Research Center, for the Alto, an experimental micro-coded workstation. Initially, its spread was confined to PARC and a few universities to which Xerox had donated some Altos.
Mesa was later adopted as the systems programming language for Xerox\'s commercial workstations such as the Xerox 8010 (Xerox Star, Dandelion) and Xerox 6085 (Daybreak), in particular for the Pilot operating system.
A secondary development environment, called the Xerox Development Environment (XDE) allowed developers to debug both the operating system Pilot as well as ViewPoint GUI applications using a world swap mechanism. This allowed the entire \"state\" of the world to be swapped out, and allowed low-level system crashes which paralyzed the whole system to be debugged. This technique did not scale very well to large application images (several megabytes), and so the Pilot/Mesa world in later releases moved away from the world swap view when the micro-coded machines were phased out in favor of SPARC workstations and Intel PCs running a Mesa PrincOps emulator for the basic hardware instruction set.
Mesa was compiled into a stack-machine language, purportedly with the highest code density ever achieved (roughly 4 bytes per high-level language statement). This was touted in a 1981 paper where implementors from the Xerox Systems Development Department (then, the development arm of PARC), tuned up the instruction set and published a paper on the resultant code density.
Mesa was taught via the Mesa Programming Course that took people through the wide range of technology Xerox had available at the time and ended with the programmer writing a \"hack\", a workable program designed to be useful. An actual example of such a hack is the BWSMagnifier, which was written in 1988 and allowed people to magnify sections of the workstation screen as defined by a resizable window and a changeable magnification factor. Trained Mesa programmers from Xerox were well versed in the fundamental of GUIs, networking, exceptions, and multi-threaded programming, almost a decade before they became standard tools of the trade.
Within Xerox, Mesa was eventually superseded by the Cedar programming language. Many Mesa programmers and developers left Xerox in 1985; some of them went to DEC Systems Research Center where they used their experience with Mesa in the design of Modula-2+, and later of Modula-3.
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# Mesa (programming language)
## Main features {#main_features}
### Semantics
Mesa was a strongly typed programming language with type-checking across module boundaries, but with enough flexibility in its type system that heap allocators could be written in Mesa.
Due to its strict separation between interface and implementation, Mesa allows true incremental compilation and encourages architecture- and platform-independent programming. They also simplified source-level debugging, including remote debugging via the Ethernet.
Mesa had rich exception handling facilities, with four types of exceptions. It had support for thread synchronization via monitors. Mesa was the first language to implement monitor BROADCAST, a concept introduced by the Pilot operating system.
### Syntax
Mesa has an \"imperative\" and \"algebraic\" syntax, based on ALGOL and Pascal rather than on BCPL or C; for instance, compound commands are indicated by the `{{Mono|BEGIN}}`{=mediawiki} and `{{Mono|END}}`{=mediawiki} keywords rather than braces. In Mesa, all keywords are written in uppercase.
Due to PARC\'s using the 1963 variant of ASCII rather than the more common 1967 variant, the Alto\'s character set included a left-pointing arrow (←) rather than an underscore. The result of this is that Alto programmers (including those using Mesa, Smalltalk etc.) conventionally used camelCase for compound identifiers, a practice which was incorporated in PARC\'s standard programming style. On the other hand, the availability of the left-pointing arrow allowed them to use it for the assignment operator, as it originally had been in ALGOL.
When the Mesa designers wanted to implement an exception facility, they hired a recent M.Sc. graduate`{{who|date=October 2021}}`{=mediawiki} from Colorado who had written his thesis on exception handling facilities in algorithmic languages. This led to the richest exception facility for its time, with primitives `{{Mono|SIGNAL}}`{=mediawiki}, `{{Mono|ERROR}}`{=mediawiki}, `{{Mono|ABORT}}`{=mediawiki}, `{{Mono|RETRY}}`{=mediawiki}, `{{Mono|CATCH}}`{=mediawiki}, and `{{Mono|CONTINUE}}`{=mediawiki}. As the language did not have type-safe checks to verify full coverage for signal handling, uncaught exceptions were a common cause of bugs in released software.
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# Mesa (programming language)
## Cedar
Mesa was the precursor to the programming language Cedar. Cedar\'s main additions were garbage collection, dynamic types, better string support through ropes, a limited form of type parameterization, and special syntax for identifying the type-safe parts of multi-module software packages, to ensure deterministic execution and prevent memory leaks.
## Descendants
- The United States Department of Defense approached Xerox to use Mesa for its \"IronMan\" programming language (see Steelman language requirements), but Xerox declined due to conflicting goals. Xerox PARC employees argued that Mesa was a proprietary advantage that made Xerox software engineers more productive than engineers at other companies. The Department of Defense instead eventually chose and developed the Ada programming language from the candidates.
- The original Star Desktop evolved into the ViewPoint Desktop and later became GlobalView which was ported to various Unix platforms, such as SunOS Unix and AIX. A Mesa to C compiler was written and the resulting code compiled for the target platform. This was a workable solution but made it nearly impossible to develop on the Unix machines since the power of the Mesa compiler and associated tool chain was lost using this approach. There was some commercial success on Sun SPARC workstations in the publishing world, but this approach resulted in isolating the product to narrow market opportunities.
- In 1976, during a sabbatical at Xerox PARC, Niklaus Wirth became acquainted with Mesa, which had a major influence in the design of his Modula-2 language.
- Java explicitly refers to Mesa as a predecessor
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# Magical organization
A **magical organization** or **magical order** is an organization or secret society created for the practice of initiation into ceremonial or other forms of occult magic or to further the knowledge of magic among its members. Magical organizations can include Hermetic orders, esoteric societies, arcane colleges, and other groups which may use different terminology and similar though diverse practices.
## 18th century {#th_century}
The Order of the Golden and Rosy Cross (*Orden des Gold- und Rosenkreutz*) was a German Rosicrucian organization founded in the 1750s by Freemason and alchemist Hermann Fictuld. Candidates were expected to be Master Masons in good standing. Alchemy was to be a central study for members.
The Order of Knight-Masons Elect Priests of the Universe (*Ordre des Chevaliers Maçons Élus Coëns de l'Univers*) or simply Élus Coëns (Hebrew for \"Elect Priests\"), was a theurgical organization founded by Martinez de Pasqually in 1767. It spread in France in the latter part of the 18th century and is the first branch of the Martinist tradition.
## 19th century {#th_century_1}
Societas Rosicruciana in Anglia (Rosicrucian Society of England), or SRIA, is a Rosicrucian esoteric Christian order formed by Robert Wentworth Little in 1865. Members are confirmed from the ranks of subscribing Master Masons of a Grand Lodge in amity with United Grand Lodge of England. The structure and grades of this order were derived from the 18th-century Order of the Golden and Rosy Cross. It later became the grade system used in the Hermetic Order of the Golden Dawn.
The Hermetic Brotherhood of Luxor was an initiatic occult organization that first became public in late 1894, although according to an official document of the order it began its work in 1870. The Order\'s teachings drew heavily from the magico-sexual theories of Paschal Beverly Randolph, who influenced later groups such as Ordo Templi Orientis, although it is not clear whether or not Randolph himself was actually a member of the Order.
The Hermetic Order of the Golden Dawn has been credited with a vast revival of occult literature and practices and was founded in 1887 or 1888 by William Wynn Westcott, Samuel Liddell MacGregor Mathers and William Robert Woodman. The teachings of the Order include ceremonial magic, Enochian magic, Christian mysticism, Qabalah, Hermeticism, the paganism of ancient Egypt, theurgy, and alchemy.
The Brotherhood of Myriam (Fratellanza di Myriam) is an Italian esoteric organization founded by Giuliano Kremmerz in 1899, blending Hermeticism with therapeutic practices and mystical traditions, rooted in Western esotericism. Its philosophy emphasizes spiritual healing, the study of ancient texts, and magical science.
Ordo Templi Orientis (O.T.O.) was founded by Carl Kellner in 1895, and is said to have been \"reorganized and reconstituted\" from the Hermetic Brotherhood of Light.
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# Magical organization
## 20th century {#th_century_2}
Alpha et Omega was a continuation of the Hermetic Order of the Golden Dawn. Following a rebellion of adepts in London and an ensuing public scandal which brought the name of the Order into disrepute, Mathers renamed the branch of the Golden Dawn remaining loyal to his leadership to \"Alpha et Omega\" sometime between 1903 and 1913. Another faction, led by Robert Felkin, became the Stella Matutina.
A∴A∴ was created in 1907 by Aleister Crowley and George Cecil Jones. It teaches magick and Thelema, which is a religion shared by several occult organizations. The main text of Thelema is *The Book of the Law*.
Ordo Templi Orientis was reworked by Aleister Crowley after he took control of the Order in the early 1920s. Ecclesia Gnostica Catholica functions as the ecclesiastical arm of Ordo Templi Orientis.
Builders of the Adytum (or B.O.T.A.) was created in 1922 by Paul Foster Case and was extended by Dr. Ann Davies. It teaches Hermetic Qabalah, astrology and occult tarot.
Also in 1922, after a falling-out with Moina Mathers and with Moina\'s consent, Dion Fortune left the Alpha et Omega to form an offshoot organization. This indirectly brought new members to the Alpha et Omega. In 1924, Fortune\'s group became known as the Fraternity of the Inner Light.
Fraternitas Saturni (\'Brotherhood of Saturn\') is a German magical order, founded in 1926 by Eugen Grosche (also known as Gregor A. Gregorius) and four others. It is one of the oldest continuously running magical groups in Germany. The lodge is, as Gregorius states, \"concerned with the study of esotericism, mysticism, and magic in the cosmic sense\".
The UR Group was an Italian esotericist association, founded around 1927 by intellectuals including Julius Evola, Arturo Reghini and Giovanni Colazza for the study of Traditionalism and Magic.
In 1954, Kenneth Grant began the work of founding the New Isis Lodge, which became operational in 1955. This became the Typhonian Ordo Templi Orientis (TOTO), which was eventually renamed to Typhonian Order.
The Church of Satan, a religious organization dedicated to Satanism as codified in *The Satanic Bible*, was established in 1966, by Anton LaVey, who was the Church\'s High Priest until his death in 1997. Church members may also participate in a system of magic which LaVey defined as greater and lesser magic. In 1975, Michael Aquino broke off from the Church of Satan and founded the Temple of Set.
The satanic and neo-nazi Order of Nine Angles (O9A or ONA) was founded in the United Kingdom during the 1970s. Hope not Hate have lobbied to have O9A designated a terrorist organization.
In 1973 John Gibbs-Bailey and John Yeowell founded the *Committee for the Restoration of the Odinic Rite* or *Odinist Committee* in England. Yeowell had been a member of the British Union of Fascists in his youth and bodyguard to leader Oswald Mosley. In 1980 the organization changed its name to Odinic Rite. It is a white supremicist organization.
In 1976, James Lees founded the magical order O∴A∴A∴ in order to assist others in the pursuit of their own spiritual paths. The work of this order is based in English Qaballa.
In 1977, The Hermetic Order of the Golden Dawn, Inc. was founded by Chic Cicero in Columbus, Georgia. This Order is notable for having the only working Golden Dawn temple in the United States at the end of the 1970s, making it the oldest continuously operating Golden Dawn offshoot in the U.S.
The Sangreal Sodality is a spiritual brotherhood founded by British writer William G. Gray and Jacobus G. Swart in 1980.
During the last two decades of the 20th century, several organizations practicing chaos magic were founded. These include Illuminates of Thanateros, and Thee Temple ov Psychick Youth. These groups rely on the use of sigils. Their main texts include *Liber Null* (1978) and *Psychonaut* (1982), now published as a single book.
On the Vernal Equinox of 1990, Christopher Hyatt and David Cherubim founded the Thelemic Order of the Golden Dawn in Los Angeles.
## 21st century {#st_century}
The Open Source Order of the Golden Dawn (OSOGD) was an esoteric community of magical practitioners, many of whom came from pagan backgrounds, founded by Sam Webster in 2002 and based on the principles of the open-source software movement. It was an initiatory teaching Order that drew upon the knowledge, experience, practices and spirit of the system of magical training and attainment developed by the original Hermetic Order of the Golden Dawn. The OSOGD ceased operating in September 2019.
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# Magical organization
## Schools
The Grey School of Wizardry is an online school with a focus on secular esoteric education. Founded in 2004 by former headmaster Oberon Zell-Ravenheart, it operates primarily online and as a non-profit educational institution in California.
Arcanorium College is an online school of magic founded by chaos magician Peter J. Carroll
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# Central moment
In probability theory and statistics, a **central moment** is a moment of a probability distribution of a random variable about the random variable\'s mean; that is, it is the expected value of a specified integer power of the deviation of the random variable from the mean. The various moments form one set of values by which the properties of a probability distribution can be usefully characterized. Central moments are used in preference to ordinary moments, computed in terms of deviations from the mean instead of from zero, because the higher-order central moments relate only to the spread and shape of the distribution, rather than also to its location.
Sets of central moments can be defined for both univariate and multivariate distributions.
## Univariate moments {#univariate_moments}
The `{{mvar|n}}`{=mediawiki}-th moment about the mean (or `{{mvar|n}}`{=mediawiki}-th **central moment**) of a real-valued random variable `{{mvar|X}}`{=mediawiki} is the quantity `{{math|1=''μ''<sub>''n''</sub> := E[(''X'' − E[''X''])<sup>''n''</sup>]}}`{=mediawiki}, where E is the expectation operator. For a continuous univariate probability distribution with probability density function `{{math|''f''(''x'')}}`{=mediawiki}, the `{{mvar|n}}`{=mediawiki}-th moment about the mean `{{mvar|μ}}`{=mediawiki} is $\mu_n = \operatorname{E} \left[ {\left( X - \operatorname{E}[X] \right)}^n \right] = \int_{-\infty}^{+\infty} (x - \mu)^n f(x)\,\mathrm{d} x.$
For random variables that have no mean, such as the Cauchy distribution, central moments are not defined.
The first few central moments have intuitive interpretations:
- The \"zeroth\" central moment `{{math|''μ''<sub>0</sub>}}`{=mediawiki} is 1.
- The first central moment `{{math|''μ''<sub>1</sub>}}`{=mediawiki} is 0 (not to be confused with the first raw moment or the expected value `{{mvar|μ}}`{=mediawiki}).
- The second central moment `{{math|''μ''<sub>2</sub>}}`{=mediawiki} is called the variance, and is usually denoted `{{math|''σ''<sup>2</sup>}}`{=mediawiki}, where `{{mvar|σ}}`{=mediawiki} represents the standard deviation.
- The third and fourth central moments are used to define the standardized moments which are used to define skewness and kurtosis, respectively.
### Properties
For all `{{mvar|n}}`{=mediawiki}, the `{{mvar|n}}`{=mediawiki}-th central moment is homogeneous of degree `{{mvar|n}}`{=mediawiki}:
$\mu_n(cX) = c^n \mu_n(X).\,$
*Only* for `{{mvar|n}}`{=mediawiki} such that n equals 1, 2, or 3 do we have an additivity property for random variables `{{mvar|X}}`{=mediawiki} and `{{mvar|Y}}`{=mediawiki} that are independent:
$\mu_n(X+Y) = \mu_n(X)+\mu_n(Y)\,$ provided *n* ∈ `{{math|{1, 2, 3}<nowiki/>}}`{=mediawiki}.
A related functional that shares the translation-invariance and homogeneity properties with the `{{mvar|n}}`{=mediawiki}-th central moment, but continues to have this additivity property even when `{{math|''n'' ≥ 4}}`{=mediawiki} is the `{{mvar|n}}`{=mediawiki}-th cumulant `{{math|''κ''<sub>''n''</sub>(''X'')}}`{=mediawiki}. For `{{math|1=''n'' = 1}}`{=mediawiki}, the `{{mvar|n}}`{=mediawiki}-th cumulant is just the expected value; for `{{mvar|n}}`{=mediawiki} = either 2 or 3, the `{{mvar|n}}`{=mediawiki}-th cumulant is just the `{{mvar|n}}`{=mediawiki}-th central moment; for `{{math|''n'' ≥ 4}}`{=mediawiki}, the `{{mvar|n}}`{=mediawiki}-th cumulant is an `{{mvar|n}}`{=mediawiki}-th-degree monic polynomial in the first `{{mvar|n}}`{=mediawiki} moments (about zero), and is also a (simpler) `{{mvar|n}}`{=mediawiki}-th-degree polynomial in the first `{{mvar|n}}`{=mediawiki} central moments.
### Relation to moments about the origin {#relation_to_moments_about_the_origin}
Sometimes it is convenient to convert moments about the origin to moments about the mean. The general equation for converting the `{{mvar|n}}`{=mediawiki}-th-order moment about the origin to the moment about the mean is
$\mu_n = \operatorname{E}\left[\left(X - \operatorname{E}[X]\right)^n\right]
= \sum_{j=0}^n \binom{n}{j} {\left(-1\right)}^{n-j} \mu'_j \mu^{n-j},$
where `{{mvar|μ}}`{=mediawiki} is the mean of the distribution, and the moment about the origin is given by
$\mu'_m = \int_{-\infty}^{+\infty} x^m f(x)\,dx = \operatorname{E}[X^m] = \sum_{j=0}^m \binom{m}{j} \mu_j \mu^{m-j}.$
For the cases `{{math|1=''n'' = 2, 3, 4}}`{=mediawiki} --- which are of most interest because of the relations to variance, skewness, and kurtosis, respectively --- this formula becomes (noting that $\mu = \mu'_1$ and $\mu'_0=1$):
$\mu_2 = \mu'_2 - \mu^2\,$ which is commonly referred to as $\operatorname{Var}(X) = \operatorname{E}[X^2] - \left(\operatorname{E}[X]\right)^2$
$\begin{align}
\mu_3 &= \mu'_3 - 3 \mu \mu'_2 +2 \mu^3 \\
\mu_4 &= \mu'_4 - 4 \mu \mu'_3 + 6 \mu^2 \mu'_2 - 3 \mu^4.
\end{align}$
\... and so on, following Pascal\'s triangle, i.e.
$\mu_5 = \mu'_5 - 5 \mu \mu'_4 + 10 \mu^2 \mu'_3 - 10 \mu^3 \mu'_2 + 4 \mu^5.\,$
because `{{nowrap|<math> 5\mu^4\mu'_1 - \mu^5 \mu'_0 = 5\mu^4\mu - \mu^5 = 5 \mu^5 - \mu^5 = 4 \mu^5</math>.}}`{=mediawiki}
The following sum is a stochastic variable having a ***compound distribution***
$W = \sum_{i=1}^M Y_i,$
where the $Y_i$ are mutually independent random variables sharing the same common distribution and $M$ a random integer variable independent of the $Y_k$ with its own distribution. The moments of $W$ are obtained as
$\operatorname{E}[W^n]= \sum_{i=0}^n\operatorname{E}\left[\binom{M}{i}\right] \sum_{j=0}^i \binom{i}{j} {\left(-1\right)}^{i-j} \operatorname{E} \left[ \left(\sum_{k=1}^j Y_k\right)^n \right],$
where $\operatorname{E} \left[ {\left(\sum_{k=1}^j Y_k\right)}^n\right]$ is defined as zero for $j = 0$.
### Symmetric distributions {#symmetric_distributions}
In distributions that are symmetric about their means (unaffected by being reflected about the mean), all odd central moments equal zero whenever they exist, because in the formula for the `{{mvar|n}}`{=mediawiki}-th moment, each term involving a value of `{{mvar|X}}`{=mediawiki} less than the mean by a certain amount exactly cancels out the term involving a value of `{{mvar|X}}`{=mediawiki} greater than the mean by the same amount.
## Multivariate moments {#multivariate_moments}
For a continuous bivariate probability distribution with probability density function `{{math|''f''(''x'',''y'')}}`{=mediawiki} the `{{math|(''j'',''k'')}}`{=mediawiki} moment about the mean `{{math|1=''μ'' = (''μ''<sub>''X''</sub>, ''μ''<sub>''Y''</sub>)}}`{=mediawiki} is $\begin{align}
\mu_{j,k} &= \operatorname{E} \left[ {\left( X - \operatorname{E}[X] \right)}^j {\left( Y - \operatorname{E}[Y] \right)}^k \right] \\[2pt]
&= \int_{-\infty}^{+\infty} \int_{-\infty}^{+\infty} {\left(x - \mu_X\right)}^j {\left(y - \mu_Y\right)}^k f(x,y) \, dx \, dy.
\end{align}$
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# Central moment
## Central moment of complex random variables {#central_moment_of_complex_random_variables}
The `{{mvar|n}}`{=mediawiki}-th central moment for a complex random variable `{{mvar|X}}`{=mediawiki} is defined as `{{Equation box 1
|indent = :
|equation = <math>\alpha_n = \operatorname{E} \left[ {\left( X - \operatorname{E}[X] \right)}^n \right],</math>
|cellpadding= 6
|border
|border colour = #0073CF
|background colour=#F5FFFA}}`{=mediawiki} The absolute `{{mvar|n}}`{=mediawiki}-th central moment of `{{mvar|X}}`{=mediawiki} is defined as `{{Equation box 1
|indent = :
|equation = <math>\beta_n = \operatorname{E} \left[ {\left|\left( X - \operatorname{E}[X] \right)\right|}^n \right].</math>
|cellpadding= 6
|border
|border colour = #0073CF
|background colour=#F5FFFA}}`{=mediawiki}
The 2nd-order central moment `{{math|''β''<sub>2</sub>}}`{=mediawiki} is called the *variance* of `{{mvar|X}}`{=mediawiki} whereas the 2nd-order central moment `{{math|''α''<sub>2</sub>}}`{=mediawiki} is the *pseudo-variance* of `{{mvar|X}}`{=mediawiki}
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# Mehmed I
**Mehmed I** (*I. Mehmed*; c. 1386/7 -- 26 May 1421), also known as **Mehmed Çelebi** (*چلبی محمد*, \"the noble-born\") or ***Kirişçi*** (*Kyritzis*, \"lord\'s son\"), was the sultan of the Ottoman Empire from 1413 to 1421. Son of Sultan Bayezid I and his concubine Devlet Hatun, he fought with his brothers over control of the Ottoman realm in the Ottoman Interregnum (1402--1413). Starting from the province of Rûm he managed to bring first Anatolia and then the European territories (Rumelia) under his control, reuniting the Ottoman state by 1413, and ruling it until his death in 1421. Called \"The Restorer,\" he reestablished central authority in Anatolia, and he expanded the Ottoman presence in Europe by the conquest of Wallachia in 1415. Venice destroyed his fleet off Gallipoli in 1416 as the Ottomans lost a naval war.
## Early life {#early_life}
Mehmed was born in 1386 or 1387 as the fourth son of Sultan Bayezid I (`{{reign|1389|1402}}`{=mediawiki}) and one of his consorts, the slave girl Devlet Hatun. Following Ottoman custom, when he reached adolescence in 1399, he was sent to gain experience as provincial governor over the Rûm Eyalet (central northern Anatolia), recently conquered from its Eretnid rulers.
On 20 July 1402, his father Bayezid was defeated in the Battle of Ankara by the Turko-Mongol conqueror and ruler Timur. The brothers (with the exception of Mustafa, who was captured and taken along with Bayezid to Samarkand) were rescued from the battlefield, Mehmed being saved by Bayezid Pasha, who took him to his hometown of Amasya. Mehmed later made Bayezid Pasha his grand vizier (1413--1421).
The early Ottoman Empire had no regulated succession, and according to Turkish tradition, every son could succeed his father. Of Mehmed\'s brothers, the eldest, Ertuğrul, had died in 1400, while the next in line, Mustafa, was a prisoner of Timur. Leaving aside the underage siblings, this left four princes---Mehmed, Süleyman, İsa, and Musa, to contend over control of the remaining Ottoman territories in the civil war known as the \"Ottoman Interregnum\". In modern historiography, these princes are usually called by the title *Çelebi\]\]*, but in contemporary sources, the title is reserved for Mehmed and Musa. The Byzantine sources translated the title as *Kyritzes* (*Κυριτζής*), which was in turn adopted into Turkish as *kirişçi*, sometimes misinterpreted as *güreşçi*, \'the wrestler\'.
During the early interregnum, Mehmed Çelebi behaved as Timur\'s vassal. Beside the other princes, Mehmed minted coin which Timur\'s name appeared as *Demur Han Gürgân* (*تيمور خان كركان*), alongside his own as *Mehmed bin Bayezid Han* (*محمد بن بايزيد خان*). This was probably an attempt on Mehmed\'s part to justify to Timur his conquest of Bursa after the Battle of Ulubad. After Mehmed established himself in *Rum*, Timur had already begun preparations for his return to Central Asia, and took no further steps to interfere with the *status quo* in Anatolia.
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# Mehmed I
## Reign
After winning the Interregnum, Mehmed crowned himself sultan in the Thracian city of Edirne that lay in the European part of the empire (the area dividing the Anatolian and European sides of the empire, Constantinople and the surrounding region, was still held by the Byzantine Empire), becoming Mehmed I. He consolidated his power, made Edirne the most important of the dual capitals, and conquered parts of Albania, the Jandarid emirate, and the Armenian Kingdom of Cilicia from the Mamluks. Taking his many achievements into consideration, Mehmed is widely known as the \"second founder\" of the Ottoman Sultanate.
Soon after Mehmed began his reign, his brother Mustafa Çelebi, who had originally been captured along with their father Bayezid I during the Battle of Ankara and held captive in Samarkand, hiding in Anatolia during the Interregnum, reemerged and asked Mehmed to partition the empire with him. Mehmed refused and met Mustafa\'s forces in battle, easily defeating them. Mustafa escaped to the Byzantine city of Thessaloniki, but after an agreement with Mehmed, the Byzantine emperor Manuel II Palaiologos exiled Mustafa to the island of Lemnos.
However, Mehmed still faced some problems, first being the problem of his nephew Orhan, who Mehmed perceived as a threat to his rule, much like his late brothers had been. There was allegedly a plot involving him by Manuel II Palaiologos, who tried to use Orhan against Sultan Mehmed; however, the sultan found out about the plot and had Orhan blinded for betrayal, according to a common Byzantine practice.
Furthermore, as a result of the Battle of Ankara and other civil wars, the population of the empire had become unstable and traumatized. A very powerful social and religious movement arose in the empire and became disruptive. The movement was led by Sheikh Bedreddin (1359--1420), a famous Muslim Sufi and charismatic theologian. He was an eminent Ulema, born of a Greek mother and a Muslim father in Simavna (Kyprinos) southwest of Edirne (formerly Adrianople). Mehmed\'s brother Musa had made Bedreddin his \"qadi of the army,\" or the supreme judge. Bedreddin created a populist religious movement in the Ottoman Sultanate, \"subversive conclusions promoting the suppression of social differences between rich and poor as well as the barriers between different forms of monotheism.\" Successfully developing a popular social revolution and syncretism of the various religions and sects of the empire, Bedreddin\'s movement began in the European side of the empire and underwent further expansion in western Anatolia.
In 1416, Sheikh Bedreddin started his rebellion against the throne. After a four-year struggle, he was finally captured by Mehmed\'s grand vizier Bayezid Pasha and hanged in the city of Serres, a city in modern-day Greece, in 1420.
## Death
The reign of Mehmed I as sultan of the re-united empire lasted only eight years before his death, but he had also been the most powerful brother contending for the throne and *de facto* ruler of most of the empire for nearly the whole preceding period of 11 years of the Ottoman Interregnum that passed between his father\'s captivity at Ankara and his own final victory over his brother Musa Çelebi at the Battle of Çamurlu.
Before his death, to secure passing the throne safely to his son Murad II, Mehmed blinded his nephew Orhan Çelebi (son of Süleyman), and decided to send his two sons Yusuf and Mahmud to be held as a hostage by Emperor Manuel II, hoping to ensure the continuing custody of his brother Mustafa.
He was buried in Bursa, in a mausoleum erected by himself near the celebrated mosque which he built there, and which, because of its decorations of green glazed tiles, is called the Green Mosque. Mehmed I also completed another mosque in Bursa, which his grandfather Murad I had commenced but which had been neglected during the reign of Bayezid. Mehmed founded in the vicinity of his own Green Mosque and mausoleum two other characteristic institutions, one a school and one a refectory for the poor, both of which he endowed with royal munificence.
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# Mehmed I
## Family
### Consorts
Mehmed I had three known consorts:
- Emine Hatun. Daughter of Nasireddin Mehmed Bey, fifth ruler of Dulkadirids. She married Mehmed in 1403 and according to tradition she was the mother of Murad II. Her niece Sittişah Hatun would later marry Mehmed II.
- Şahzade Hatun. Daughter of Dividdar Ahmed Pasha, third ruler of Kutluşah of Canik. According to some historians, she was the real mother of Murad II.
- Kumru Hatun. Slave concubine.
### Sons
Mehmed I had at least five sons:
- Murad II (1404--1451) - with Emine Hatun. Sultan of the Ottoman Empire.
- Mustafa Çelebi, known as *Küçük Mustafa* (1408--1423). He disputed the throne with Murad II, by whom he was defeated and executed.
- Mahmud Çelebi (1413 - August 1429. Buried in the mausoleum\'s Mehmed I, Bursa)
- Yusuf Çelebi (1414 - August 1429. Buried in the mausoleum\'s Mehmed I, Bursa)
- Ahmed Çelebi. Died in infancy.
### Daughters
Mehmed I had at least eight daughters:
- Selçuk Hatun (c. 1407 - 25 October 1485, buried in Mehmed I Mausoleum, Bursa) - with Kumru Hatun. She married Taceddin Ibrahim II Bey, ruler of Isfendiyarids (1392 -- 30 May 1443), son of İsfendiyar Bey. They had three sons and three daughters, all died in infancy except a daughter, Hatice Hanzade Hatun. After widowed, she married Anadolu Beylerbeyi Karaca. They had a daughter, who died young.
- Ilaldi Sultan Hatun (? - 1444). In 1425 she married Ibrahim II Bey, ruler of Karamanids (died 16 July 1464), son of Mehmed II Bey (son of Nefise Hatun, a Murad I\'s daughter), and had six sons, amongs them Piri Ahmed Bey, Kasim Bey, Kaya Bey (who married his cousin Hafsa Hatun, daughter of Murad II) and Alaeddin Bey; but the marriage was unhappy and her husband hated her and their sons because their Ottoman blood.
- Hatice Hatun (1408--1442). She married to Karaca Pasha (died on 10 November 1444).
- Hafsa Hatun (? - 1445, buried in Mehmed I Mausoleum, Bursa). She married Mahmud Bey (died in January 1444), son of Çandarlı Halil Pasha. By him she had six sons and a daughter.
- Incu Hatun. In 1427 she married to Isa Bey (died in 1437), son of Mehmed II Bey.
- Ayşe Sultan Hatun (1412--1469, buried in Mehmed I Mausoleum, Bursa). In 1427 she married to Alaeddin Ali Bey, ruler of Karamanids, son of Mehmed II Bey.
- Şahzade Sitti Hatun (1413-- ?, buried in Mehmed I Mausoleum, Bursa). In 1427 she married Sinan Pasha (died in 1442).
- Fatma Sultan Hatun. She married Kıvameddin Kazim Bey, son of Isfendyar Bey and brother of Selçuk\'s husband Ibrahim II Bey
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# Multitier architecture
In software engineering, **multitier architecture** (often referred to as ***n*-tier architecture**) is a client--server architecture in which presentation, application processing and data management functions are physically separated. The most widespread use of multitier architecture is the **three-tier architecture** (for example, Cisco\'s Hierarchical internetworking model).
*N*-tier application architecture provides a model by which developers can create flexible and reusable applications. By segregating an application into tiers, developers acquire the option of modifying or adding a specific tier, instead of reworking the entire application. N-tier architecture is a good fit for small and simple applications because of its simplicity and low-cost. Also, it can be a good starting point when architectural requirements are not clear yet. A three-tier architecture is typically composed of a *presentation* tier, a *logic* tier, and a *data* tier.
While the concepts of layer and tier are often used interchangeably, one fairly common point of view is that there is indeed a difference. This view holds that a *layer* is a logical structuring mechanism for the conceptual elements that make up the software solution, while a *tier* is a physical structuring mechanism for the hardware elements that make up the system infrastructure. For example, a three-layer solution could easily be deployed on a single tier, such in the case of an extreme database-centric architecture called **RDBMS-only architecture** or in a personal workstation.
## Layers
The \"Layers\" architectural pattern has been described in various publications.
### Common layers {#common_layers}
In a logical multilayer architecture for an information system with an object-oriented design, the following four are the most common:
- **Presentation layer** (a.k.a. UI layer, view layer, presentation tier in multitier architecture)
- **Application layer** (a.k.a. service layer or GRASP Controller Layer )
- **Business layer** (a.k.a. business logic layer (BLL), domain logic layer)
- **Data access layer** (a.k.a. persistence layer, logging, networking, and other services which are required to support a particular business layer)
If the application architecture has no explicit distinction between the business layer and the presentation layer (i.e., the presentation layer is considered part of the business layer), then a traditional client-server (two-tier) model has been implemented.
The more usual convention is that the application layer (or service layer) is considered a sublayer of the business layer, typically encapsulating the API definition surfacing the supported business functionality. The application/business layers can, in fact, be further subdivided to emphasize additional sublayers of distinct responsibility. For example, if the model--view--presenter pattern is used, the presenter sublayer might be used as an additional layer between the user interface layer and the business/application layer (as represented by the model sublayer).
Some also identify a separate layer called the business infrastructure layer (BI), located between the business layer(s) and the infrastructure layer(s). It is also sometimes called the \"low-level business layer\" or the \"business services layer\". This layer is very general and can be used in several application tiers (e.g. a CurrencyConverter).
The infrastructure layer can be partitioned into different levels (high-level or low-level technical services). Developers often focus on the persistence (data access) capabilities of the infrastructure layer and therefore only talk about the persistence layer or the data access layer (instead of an infrastructure layer or technical services layer). In other words, the other kind of technical services is not always explicitly thought of as part of any particular layer.. The Data Access layer normally contains an object known as the Data Access Object (DAO).
A layer is on top of another, because it depends on it. Every layer can exist without the layers above it, and requires the layers below it to function. Another common view is that layers do not always strictly depend on only the adjacent layer below. For example, in a relaxed layered system (as opposed to a strict layered system) a layer can also depend on all the layers below it. The relaxed layered system has more couplings and subsequently it\'s more difficult to change. Multi-tier architectures can use a hybrid approach so that some layers are strict while other layers are relaxed.
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# Multitier architecture
## Three-tier architecture {#three_tier_architecture}
Three-tier architecture is a client-server software architecture pattern in which the user interface (presentation), functional process logic (\"business rules\"), computer data storage and data access are developed and maintained as independent modules, most often on separate platforms. It was developed by John J. Donovan in Open Environment Corporation (OEC), a tools company he founded in Cambridge, Massachusetts..
Apart from the usual advantages of modular software with well-defined interfaces, the three-tier architecture is intended to allow any of the three tiers to be upgraded or replaced independently in response to changes in requirements or technology. For example, a change of operating system in the *presentation tier* would only affect the user interface code.
Typically, the user interface runs on a desktop PC or workstation and uses a standard graphical user interface, functional process logic that may consist of one or more separate modules running on a workstation or application server, and an RDBMS on a database server or mainframe that contains the computer data storage logic. The middle tier may be multitiered itself (in which case the overall architecture is called an \"*n*-tier architecture\").
Presentation tier
: This is the topmost level of the application. The presentation tier displays information related to such services as browsing merchandise, purchasing and shopping cart contents. It communicates with other tiers by which it puts out the results to the browser/client tier and all other tiers in the network. In simple terms, it is a layer that users can access directly (such as a web page, or an operating system\'s GUI).
Application tier (business logic, logic tier, or middle tier)
: The logical tier is pulled out from the presentation tier and, as its layer, it controls an application's functionality by performing detailed processing.
Data tier
: The data tier includes the data persistence mechanisms (database servers, file shares, etc.) and the data access layer that encapsulates the persistence mechanisms and exposes the data. The data access layer should provide an API to the application tier that exposes methods of managing the stored data without exposing or creating dependencies on the data storage mechanisms. Avoiding dependencies on the storage mechanisms allows for updates or changes without the application tier clients being affected by or even aware of the change. As with the separation of any tier, there are costs for implementation and often costs to performance in exchange for improved scalability and maintainability.
### Web development usage {#web_development_usage}
In the web development field, three-tier is often used to refer to websites, commonly electronic commerce websites, which are built using three tiers:
1. A front-end web server serving static content, and potentially some cached dynamic content. In web-based application, front end is the content rendered by the browser. The content may be static or generated dynamically.
2. A middle dynamic content processing and generation level application server (e.g., Symfony, Spring, ASP.NET, Django, Rails, Node.js).
3. A back-end database or data store, comprising both data sets and the database management system software that manages and provides access to the data.
### Other considerations {#other_considerations}
Data transfer between tiers is part of the architecture. Protocols involved may include one or more of SNMP, CORBA, Java RMI, .NET Remoting, Windows Communication Foundation, sockets, UDP, web services or other standard or proprietary protocols. Often middleware is used to connect the separate tiers. Separate tiers often (but not necessarily) run on separate physical servers, and each tier may itself run on a cluster.
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# Multitier architecture
## Traceability
The end-to-end traceability of data flows through *n*-tier systems is a challenging task which becomes more important when systems increase in complexity. The Application Response Measurement defines concepts and APIs for measuring performance and correlating transactions between tiers. Generally, the term \"tiers\" is used to describe physical distribution of components of a system on separate servers, computers, or networks (processing nodes). A three-tier architecture then will have three processing nodes. The term \"layers\" refers to a logical grouping of components which may or may not be physically located on one processing node
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# Myrinet
**Myrinet**, ANSI/VITA 26-1998, is a high-speed local area networking system designed by the company Myricom to be used as an interconnect between multiple machines to form computer clusters.
## Description
Myrinet was promoted as having lower protocol overhead than standards such as Ethernet, and therefore better throughput, less interference, and lower latency while using the host CPU. Although it can be used as a traditional networking system, Myrinet is often used directly by programs that \"know\" about it, thereby bypassing a call into the operating system.
Earlier versions of Myrinet used a variety of media and connectors:
- Generation 2 used copper media with DC-37 (Myrinet-LAN, M2L-\* controllers and switches) or microribbon (Myrinet-SAN, M2M-\*) connectors.
- Generation 3 used copper media with HSSDC (Myrinet-Serial, M3S-\*) or microribbon (Myrinet-SAN, M3M-\*) connectors, or fiber with LC-connectors (Myrinet-Fiber, M3F-\*).
The later versions of Myrinet physically consist of two fibre optic cables, upstream and downstream, connected to the host computers with a single connector. Machines are connected via low-overhead routers and switches, as opposed to connecting one machine directly to another. Myrinet includes a number of fault-tolerance features, mostly backed by the switches. These include flow control, error control, and \"heartbeat\" monitoring on every link. The \"fourth-generation\" Myrinet, called Myri-10G, supported a 10 Gbit/s data rate and can use 10 Gigabit Ethernet on PHY, the physical layer (cables, connectors, distances, signaling). Myri-10G started shipping at the end of 2005.
Myrinet was approved in 1998 by the American National Standards Institute for use on the VMEbus as ANSI/VITA 26-1998. One of the earliest publications on Myrinet is a 1995 IEEE article.
### Performance
Generation Year Bandwidth
------------ -------------- ------ -------------
1 Myrinet 1994 0.64 Gbit/s
2 Myrinet-LAN 1996 1.28 Gbit/s
Myrinet-SAN
3 Myrinet-2000 2000 2 Gbit/s
4 Myri-10G 2005 10 Gbit/s
Myrinet is a lightweight protocol with little overhead that allows it to operate with throughput close to the basic signaling speed of the physical layer. For supercomputing, the low latency of Myrinet is even more important than its throughput performance, since, according to Amdahl\'s law, a high-performance parallel system tends to be bottlenecked by its slowest sequential process, which in all but the most embarrassingly parallel supercomputer workloads is often the latency of message transmission across the network.
### Deployment
According to Myricom, 141 (28.2%) of the June 2005 TOP500 supercomputers used Myrinet technology. In the November 2005 TOP500, the number of supercomputers using Myrinet was down to 101 computers, or 20.2%, in November 2006, 79 (15.8%), and by November 2007, 18 (3.6%), a long way behind gigabit Ethernet at 54% and InfiniBand at 24.2%.
In the June 2014 TOP500 list, the number of supercomputers using Myrinet interconnect was 1 (0.2%).
In November, 2013, the assets of Myricom (including the Myrinet technology) were acquired by CSP Inc. In 2016, it was reported that Google had also offered to buy the company
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# Microkernel
In computer science, a **microkernel** (often abbreviated as **μ-kernel**) is the near-minimum amount of software that can provide the mechanisms needed to implement an operating system (OS). These mechanisms include low-level address space management, thread management, and inter-process communication (IPC).
If the hardware provides multiple rings or CPU modes, the microkernel may be the only software executing at the most privileged level, which is generally referred to as supervisor or kernel mode. Traditional operating system functions, such as device drivers, protocol stacks and file systems, are typically removed from the microkernel itself and are instead run in user space.
In terms of the source code size, microkernels are often smaller than monolithic kernels. The MINIX 3 microkernel, for example, has only approximately 12,000 lines of code.
## History
Microkernels trace their roots back to Danish computer pioneer Per Brinch Hansen and his tenure in Danish computer company Regnecentralen where he led software development efforts for the RC 4000 computer. In 1967, Regnecentralen was installing a RC 4000 prototype in the Zakłady Azotowe Puławy fertilizer plant in Poland. The computer used a small real-time operating system tailored for the needs of the plant. Brinch Hansen and his team became concerned with the lack of generality and reusability of the RC 4000 system. They feared that each installation would require a different operating system so they started to investigate novel and more general ways of creating software for the RC 4000. In 1969, their effort resulted in the completion of the RC 4000 Multiprogramming System. Its nucleus provided inter-process communication based on message-passing for up to 23 unprivileged processes, out of which 8 at a time were protected from one another. It further implemented scheduling of time slices of programs executed in parallel, initiation and control of program execution at the request of other running programs, and initiation of data transfers to or from peripherals. Besides these elementary mechanisms, it had no built-in strategy for program execution and resource allocation. This strategy was to be implemented by a hierarchy of running programs in which parent processes had complete control over child processes and acted as their operating systems.
Following Brinch Hansen\'s work, microkernels have been developed since the 1970s. The term microkernel itself first appeared no later than 1981. Microkernels were meant as a response to changes in the computer world, and to several challenges adapting existing \"mono-kernels\" to these new systems. New device drivers, protocol stacks, file systems and other low-level systems were being developed all the time. This code was normally located in the monolithic kernel, and thus required considerable work and careful code management to work on. Microkernels were developed with the idea that all of these services would be implemented as user-space programs, like any other, allowing them to be worked on monolithically and started and stopped like any other program. This would not only allow these services to be more easily worked on, but also separated the kernel code to allow it to be finely tuned without worrying about unintended side effects. Moreover, it would allow entirely new operating systems to be \"built up\" on a common core, aiding OS research.
Microkernels were a very hot topic in the 1980s when the first usable local area networks were being introduced.. The AmigaOS Exec kernel was an early example, introduced in 1986 and used in a PC with relative commercial success. The lack of memory protection, considered in other respects a flaw, allowed this kernel to have very high message-passing performance because it did not need to copy data while exchanging messages between user-space programs.
The same mechanisms that allowed the kernel to be distributed into user space also allowed the system to be distributed across network links. The first microkernels, notably Mach created by Richard Rashid, proved to have disappointing performance, but the inherent advantages appeared so great that it was a major line of research into the late 1990s. However, during this time the speed of computers grew greatly in relation to networking systems, and the disadvantages in performance came to overwhelm the advantages in development terms.
Many attempts were made to adapt the existing systems to have better performance, but the overhead was always considerable and most of these efforts required the user-space programs to be moved back into the kernel. By 2000, most large-scale Mach kernel efforts had ended, although Apple\'s macOS, released in 2001, still uses a hybrid kernel called XNU, which combines a heavily modified (hybrid) OSF/1\'s Mach kernel (OSFMK 7.3 kernel) with code from BSD UNIX, and this kernel is also used in iOS, tvOS, and watchOS. Windows NT, starting with NT 3.1 and continuing with Windows 11, uses a hybrid kernel design. `{{As of|2012}}`{=mediawiki}, the Mach-based GNU Hurd is also functional and included in testing versions of Arch Linux and Debian.
Although major work on microkernels had largely ended, experimenters continued development. Using a more pragmatic approach to the problem, including assembly code and relying on the processor to enforce concepts normally supported in software led to a new series of microkernels with dramatically improved performance.
Microkernels are closely related to exokernels. They also have much in common with hypervisors, but the latter make no claim to minimality and are specialized to supporting virtual machines; the L4 microkernel frequently finds use in a hypervisor capacity.
## Introduction
Early operating system kernels were rather small, partly because computer memory was limited. As the capability of computers grew, the number of devices the kernel had to control also grew. Throughout the early history of Unix, kernels were generally small, even though they contained various device drivers and file system implementations. When address spaces increased from 16 to 32 bits, kernel design was no longer constrained by the hardware architecture, and kernels began to grow larger.
The Berkeley Software Distribution (BSD) of Unix began the era of larger kernels. In addition to operating a basic system consisting of the CPU, disks and printers, BSD added a complete TCP/IP networking system and a number of \"virtual\" devices that allowed the existing programs to work \'invisibly\' over the network. This growth continued for many years, resulting in kernels with millions of lines of source code. As a result of this growth, kernels were prone to bugs and became increasingly difficult to maintain.
The microkernel was intended to address this growth of kernels and the difficulties that resulted. In theory, the microkernel design allows for easier management of code due to its division into user space services. This also allows for increased security and stability resulting from the reduced amount of code running in kernel mode. For example, if a networking service crashed due to buffer overflow, only the networking service\'s memory would be corrupted, leaving the rest of the system still functional.
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# Microkernel
## Inter-process communication {#inter_process_communication}
Inter-process communication (IPC) is any mechanism which allows separate processes to communicate with each other, usually by sending messages. Shared memory is, strictly defined, also an inter-process communication mechanism, but the abbreviation IPC usually refers to message passing only, and it is the latter that is particularly relevant to microkernels. IPC allows the operating system to be built from a number of smaller programs called servers, which are used by other programs on the system, invoked via IPC. Most or all support for peripheral hardware is handled in this fashion, with servers for device drivers, network protocol stacks, file systems, graphics, etc.
IPC can be synchronous or asynchronous. Asynchronous IPC is analogous to network communication: the sender dispatches a message and continues executing. The receiver checks (polls) for the availability of the message, or is alerted to it via some notification mechanism. Asynchronous IPC requires that the kernel maintains buffers and queues for messages, and deals with buffer overflows; it also requires double copying of messages (sender to kernel and kernel to receiver). In synchronous IPC, the first party (sender or receiver) blocks until the other party is ready to perform the IPC. It does not require buffering or multiple copies, but the implicit rendezvous can make programming tricky. Most programmers prefer asynchronous send and synchronous receive.
First-generation microkernels typically supported synchronous as well as asynchronous IPC, and suffered from poor IPC performance. Jochen Liedtke assumed the design and implementation of the IPC mechanisms to be the underlying reason for this poor performance. In his L4 microkernel he pioneered methods that lowered IPC costs by an order of magnitude. These include an IPC system call that supports a send as well as a receive operation, making all IPC synchronous, and passing as much data as possible in registers. Furthermore, Liedtke introduced the concept of the *direct process switch*, where during an IPC execution an (incomplete) context switch is performed from the sender directly to the receiver. If, as in L4, part or all of the message is passed in registers, this transfers the in-register part of the message without any copying at all. Furthermore, the overhead of invoking the scheduler is avoided; this is especially beneficial in the common case where IPC is used in a remote procedure call (RPC) type fashion by a client invoking a server. Another optimization, called *lazy scheduling*, avoids traversing scheduling queues during IPC by leaving threads that block during IPC in the ready queue. Once the scheduler is invoked, it moves such threads to the appropriate waiting queue. As in many cases a thread gets unblocked before the next scheduler invocation, this approach saves significant work. Similar approaches have since been adopted by QNX and MINIX 3.
In a series of experiments, Chen and Bershad compared memory cycles per instruction (MCPI) of monolithic Ultrix with those of microkernel Mach combined with a 4.3BSD Unix server running in user space. Their results explained Mach\'s poorer performance by higher MCPI and demonstrated that IPC alone is not responsible for much of the system overhead, suggesting that optimizations focused exclusively on IPC will have a limited effect. Liedtke later refined Chen and Bershad\'s results by making an observation that the bulk of the difference between Ultrix and Mach MCPI was caused by capacity cache-misses and concluding that drastically reducing the cache working set of a microkernel will solve the problem.
In a client-server system, most communication is essentially synchronous, even if using asynchronous primitives, as the typical operation is a client invoking a server and then waiting for a reply. As it also lends itself to more efficient implementation, most microkernels generally followed L4\'s lead and only provided a synchronous IPC primitive. Asynchronous IPC could be implemented on top by using helper threads. However, experience has shown that the utility of synchronous IPC is dubious: synchronous IPC forces a multi-threaded design onto otherwise simple systems, with the resulting synchronization complexities. Moreover, an RPC-like server invocation sequentializes client and server, which should be avoided if they are running on separate cores. Versions of L4 deployed in commercial products have therefore found it necessary to add an asynchronous notification mechanism to better support asynchronous communication. This signal-like mechanism does not carry data and therefore does not require buffering by the kernel. By having two forms of IPC, they have nonetheless violated the principle of minimality. Other versions of L4 have switched to asynchronous IPC completely.
As synchronous IPC blocks the first party until the other is ready, unrestricted use could easily lead to deadlocks. Furthermore, a client could easily mount a denial-of-service attack on a server by sending a request and never attempting to receive the reply. Therefore, synchronous IPC must provide a means to prevent indefinite blocking. Many microkernels provide timeouts on IPC calls, which limit the blocking time. In practice, choosing sensible timeout values is difficult, and systems almost inevitably use infinite timeouts for clients and zero timeouts for servers. As a consequence, the trend is towards not providing arbitrary timeouts, but only a flag which indicates that the IPC should fail immediately if the partner is not ready. This approach effectively provides a choice of the two timeout values of zero and infinity. Recent versions of L4 and MINIX have gone down this path (older versions of L4 used timeouts). QNX avoids the problem by requiring the client to specify the reply buffer as part of the message send call. When the server replies the kernel copies the data to the client\'s buffer, without having to wait for the client to receive the response explicitly.
## Servers
Microkernel servers are essentially daemon programs like any others, except that the kernel grants some of them privileges to interact with parts of physical memory that are otherwise off limits to most programs. This allows some servers, particularly device drivers, to interact directly with hardware.
A basic set of servers for a general-purpose microkernel includes file system servers, device driver servers, networking servers, display servers, and user interface device servers. This set of servers (drawn from QNX) provides roughly the set of services offered by a Unix monolithic kernel. The necessary servers are started at system startup and provide services, such as file, network, and device access, to ordinary application programs. With such servers running in the environment of a user application, server development is similar to ordinary application development, rather than the build-and-boot process needed for kernel development.
Additionally, many \"crashes\" can be corrected by simply stopping and restarting the server, which would not be feasible if the entire kernel had to reboot. However, part of the system state is lost with the failing server, hence this approach requires applications to cope with failure. A good example is a server responsible for TCP/IP connections: If this server is restarted, applications will experience a \"lost\" connection, a normal occurrence in a networked system. For other services, failure is less expected and may require changes to application code. For QNX, restart capability is offered as the QNX High Availability Toolkit.
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# Microkernel
## Device drivers {#device_drivers}
Device drivers frequently perform direct memory access (DMA), and therefore can write to arbitrary locations of physical memory, including various kernel data structures. Such drivers must therefore be trusted. It is a common misconception that this means that they must be part of the kernel. In fact, a driver is not inherently more or less trustworthy by being part of the kernel.
While running a device driver in user space does not necessarily reduce the damage a misbehaving driver can cause, in practice it is beneficial for system stability in the presence of buggy (rather than malicious) drivers: memory-access violations by the driver code itself (as opposed to the device) may still be caught by the memory-management hardware. Furthermore, many devices are not DMA-capable, their drivers can be made untrusted by running them in user space. Recently, an increasing number of computers feature IOMMUs, many of which can be used to restrict a device\'s access to physical memory. This also allows user-mode drivers to become untrusted.
User-mode drivers actually predate microkernels. The Michigan Terminal System (MTS), in 1967, supported user space drivers (including its file system support), the first operating system to be designed with that capability. Historically, drivers were less of a problem, as the number of devices was small and trusted anyway, so having them in the kernel simplified the design and avoided potential performance problems. This led to the traditional driver-in-the-kernel style of Unix, Linux, and Windows NT. With the proliferation of various kinds of peripherals, the amount of driver code escalated and in modern operating systems dominates the kernel in code size.
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# Microkernel
## Essential components and minimality {#essential_components_and_minimality}
As a microkernel must allow building arbitrary operating system services on top, it must provide some core functionality. At a minimum, this includes:
- Some mechanisms for dealing with address spaces, required for managing memory protection
- Some execution abstraction to manage CPU allocation, typically threads or scheduler activations
- Inter-process communication, required to invoke servers running in their own address spaces
This minimal design was pioneered by Brinch Hansen\'s Nucleus and the hypervisor of IBM\'s VM. It has since been formalised in Liedtke\'s *minimality principle*:
> A concept is tolerated inside the microkernel only if moving it outside the kernel, i.e., permitting competing implementations, would prevent the implementation of the system\'s required functionality.
Everything else can be done in a usermode program, although device drivers implemented as user programs may on some processor architectures require special privileges to access I/O hardware.
Related to the minimality principle, and equally important for microkernel design, is the separation of mechanism and policy, it is what enables the construction of arbitrary systems on top of a minimal kernel. Any policy built into the kernel cannot be overwritten at user level and therefore limits the generality of the microkernel. Policy implemented in user-level servers can be changed by replacing the servers (or letting the application choose between competing servers offering similar services).
For efficiency, most microkernels contain schedulers and manage timers, in violation of the minimality principle and the principle of policy-mechanism separation.
Start up (booting) of a microkernel-based system requires device drivers, which are not part of the kernel. Typically, this means that they are packaged with the kernel in the boot image, and the kernel supports a bootstrap protocol that defines how the drivers are located and started; this is the traditional bootstrap procedure of L4 microkernels. Some microkernels simplify this by placing some key drivers inside the kernel (in violation of the minimality principle), LynxOS and the original Minix are examples. Some even include a file system in the kernel to simplify booting. A microkernel-based system may boot via multiboot compatible boot loader. Such systems usually load statically-linked servers to make an initial bootstrap or mount an OS image to continue bootstrapping.
A key component of a microkernel is a good IPC system and virtual-memory-manager design that allows implementing page-fault handling and swapping in usermode servers in a safe way. Since all services are performed by usermode programs, efficient means of communication between programs are essential, far more so than in monolithic kernels. The design of the IPC system makes or breaks a microkernel. To be effective, the IPC system must not only have low overhead, but also interact well with CPU scheduling.
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# Microkernel
## Performance
On most mainstream processors, obtaining a service is inherently more expensive in a microkernel-based system than a monolithic system. In the monolithic system, the service is obtained by a single system call, which requires two *mode switches* (changes of the processor\'s ring or CPU mode). In the microkernel-based system, the service is obtained by sending an IPC message to a server, and obtaining the result in another IPC message from the server. This requires a context switch if the drivers are implemented as processes, or a function call if they are implemented as procedures. In addition, passing actual data to the server and back may incur extra copying overhead, while in a monolithic system the kernel can directly access the data in the client\'s buffers.
Performance is therefore a potential issue in microkernel systems. The experience of first-generation microkernels such as Mach and ChorusOS showed that systems based on them performed very poorly. However, Jochen Liedtke showed that Mach\'s performance problems were the result of poor design and implementation, specifically Mach\'s excessive cache footprint. Liedtke demonstrated with his own L4 microkernel that through careful design and implementation, and especially by following the minimality principle, IPC costs could be reduced by more than an order of magnitude compared to Mach. L4\'s IPC performance is still unbeaten across a range of architectures.
While these results demonstrate that the poor performance of systems based on first-generation microkernels is not representative for second-generation kernels such as L4, this constitutes no proof that microkernel-based systems can be built with good performance. It has been shown that a monolithic Linux server ported to L4 exhibits only a few percent overhead over native Linux. However, such a single-server system exhibits few, if any, of the advantages microkernels are supposed to provide by structuring operating system functionality into separate servers.
A number of commercial multi-server systems exist, in particular the real-time systems QNX and Integrity. No comprehensive comparison of performance relative to monolithic systems has been published for those multiserver systems. Furthermore, performance does not seem to be the overriding concern for those commercial systems, which instead emphasize reliably quick interrupt handling response times (QNX) and simplicity for the sake of robustness. An attempt to build a high-performance multiserver operating system was the IBM Sawmill Linux project. However, this project was never completed.
It has been shown in the meantime that user-level device drivers can come close to the performance of in-kernel drivers even for such high-throughput, high-interrupt devices as Gigabit Ethernet. This seems to imply that high-performance multi-server systems are possible.
## Security
The security benefits of microkernels have been frequently discussed. In the context of security the minimality principle of microkernels is, some have argued, a direct consequence of the principle of least privilege, according to which all code should have only the privileges needed to provide required functionality. Minimality requires that a system\'s trusted computing base (TCB) should be kept minimal. As the kernel (the code that executes in the privileged mode of the hardware) has unvetted access to any data and can thus violate its integrity or confidentiality, the kernel is always part of the TCB. Minimizing it is natural in a security-driven design.
Consequently, microkernel designs have been used for systems designed for high-security applications, including KeyKOS, EROS and military systems. In fact common criteria (CC) at the highest assurance level (Evaluation Assurance Level (EAL) 7) has an explicit requirement that the target of evaluation be \"simple\", an acknowledgment of the practical impossibility of establishing true trustworthiness for a complex system. Again, the term \"simple\" is misleading and ill-defined. At least the Department of Defense Trusted Computer System Evaluation Criteria introduced somewhat more precise verbiage at the B3/A1 classes:
In 2018, a paper presented at the Asia-Pacific Systems Conference claimed that microkernels were demonstrably safer than monolithic kernels by investigating all published critical CVEs for the Linux kernel at the time. The study concluded that 40% of the issues could not occur at all in a formally verified microkernel, and only 4% of the issues would remain entirely unmitigated in such a system.
## Third generation {#third_generation}
More recent work on microkernels has been focusing on formal specifications of the kernel API, and formal proofs of the API\'s security properties and implementation correctness. The first example of this is a mathematical proof of the confinement mechanisms in EROS, based on a simplified model of the EROS API. More recently (in 2007) a comprehensive set of machine-checked proofs was performed of the properties of the protection model of seL4, a version of L4.
This has led to what is referred to as *third-generation microkernels*, characterised by a security-oriented API with resource access controlled by capabilities, virtualization as a first-class concern, novel approaches to kernel resource management, and a design goal of suitability for formal analysis, besides the usual goal of high performance. Examples are Coyotos, seL4, Nova, Redox and Fiasco.OC.
In the case of seL4, complete formal verification of the implementation has been achieved, i.e. a mathematical proof that the kernel\'s implementation is consistent with its formal specification. This provides a guarantee that the properties proved about the API actually hold for the real kernel, a degree of assurance which goes beyond even CC EAL7. It was followed by proofs of security-enforcement properties of the API, and a proof demonstrating that the executable binary code is a correct translation of the C implementation, taking the compiler out of the TCB. Taken together, these proofs establish an end-to-end proof of security properties of the kernel.
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# Microkernel
## Examples
Some examples of microkernels are:
- AmigaOS
- Amoeba OS
- BlackBerry QNX
- Genode
- HarmonyOS (HarmonyOS NEXT)
- HelenOS
- Horizon (Nintendo Switch system software)
- The L4 microkernel family
- Mach
- Mac OS 7 to Mac OS 9 (Mac OS nanokernel)
- Minix
- Midori
- Phantom OS
- Qubes OS
- Redox
- Symbian
- SymbOS
- ThreadX
- Zircon
## Nanokernel
The term *nanokernel* or *picokernel* historically referred to:
- A kernel where the total amount of kernel code, i.e. code executing in the privileged mode of the hardware, is very small. The term *picokernel* was sometimes used to further emphasize small size. The term *nanokernel* was coined by Jonathan S. Shapiro in the paper [*The KeyKOS NanoKernel Architecture*](https://web.archive.org/web/20110621235229/http://www.cis.upenn.edu/~KeyKOS/NanoKernel/NanoKernel.html). It was a sardonic response to Mach, which claimed to be a microkernel while Shapiro considered it monolithic, essentially unstructured, and slower than the systems it sought to replace. Subsequent reuse of and response to the term, including the picokernel coinage, suggest that the point was largely missed. Both *nanokernel* and *picokernel* have subsequently come to have the same meaning expressed by the term microkernel.
- A virtualization layer underneath an operating system, which is more correctly referred to as a hypervisor.
- A hardware abstraction layer that forms the lowest-level part of a kernel, sometimes used to provide real-time functionality to normal operating systems, like Adeos.
There is also at least one case where the term nanokernel is used to refer not to a small kernel, but one that supports a nanosecond clock resolution
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# Multics Relational Data Store
The **Multics Relational Data Store**, or **MRDS** for short, was the first commercial relational database management system. It was written in PL/1 by Honeywell for the Multics operating system and first sold in June 1976. Unlike the SQL systems that emerged in the late 1970s and early 80s, MRDS used a command language only for basic data manipulation, equivalent to the `SELECT` or `UPDATE` statements in SQL. Other operations, like creating a new database, or general file management, required the use of a separate command program
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# Maule Air
**Maule Air, Inc.** is a manufacturer of light, single-engined, short take-off and landing (STOL) aircraft, based in Moultrie, Georgia, U.S. The company delivered 2,500 aircraft in its first 50 years of business.
## History
Belford D. Maule (1911--1995) designed his first aircraft, the M-1 starting at age 19. He founded the company Mechanical Products Co. in Napoleon, Michigan to market his own starter design. In 1941 the B.D. Maule Co. was founded, and Maule produced tailwheels and fabric testers. In 1953 he began design work, and started aircraft production with the \"Bee-Dee\" M-4 in 1957.
The company is a family-owned enterprise. Its owner, June Maule, widow of B. D. Maule, remained directly involved with factory production until her death in 2009 at the age of 92.
## Products
The aircraft produced by Maule Air are tube-and-fabric designs and are popular with bush pilots thanks to their very low stall speed, tundra tires and oleo strut landing gear. Most Maules are built with tailwheel or amphibious configurations, although the newer MXT models have tricycle gear.
### Aircraft models {#aircraft_models}
Model Wingspan Engine Gross weight V~so~ V~LD~
----------- ----------- ------------------------------ -------------- -------- ---------
M4-210 29\'8\" 210 HP Continental 2300 lbs 28 mph 145 mph
M4-220 220 HP Franklin
M-5-180C 30\'10\" 180 HP Lycoming Carb 2400 lbs 38 mph 135 mph
M-5-200C 200 HP Lycoming Injected 2500 lbs 38 mph 140 mph
M-5-210TC 210 HP Lycoming Turbo 2500 lbs 38 mph 196 mph
M-5-210C 210 HP Continental Injected 2500 lbs 38 mph 145 mph
M-5-235C 235 HP Lycoming carb 2500 lbs 38 mph 158 mph
M-5-235C 235 HP Lycoming injected 2500 lbs 39 mph 158 mph
M-6-235 32\' 11\" 235 HP Lycoming O-540-J1A5D 2500 lbs 35 mph 160 mph
M-6-235 235 HP Lycoming IO-540-W1A5D
M-7 33\' 6\" 235 HP Lycoming IO-540-W 2500 lbs 40 mph 158 mph
M-9-235 32\' 11\" 235 HP Lycoming O-540-B4B5 2800 lbs 46 mph 158 mph
M-9-235 235 HP Lycoming IO-540-W1A5
M-9-260 260 HP Lycoming IO-540-V4A5 162 mph
## Gallery
<File:maule.mx-7-235.superrocket.g-iton.arp.jpg%7CMaule> MX-7-235 Super Rocket, built 1987 <File:Maule-Amphibian.780.jpg%7CA> Maule amphibian <File:maule.m7-235b.arp
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# Mooney
**Mooney** is a family name which is probably predominantly derived from the Irish Ó Maonaigh, pronounced Om-weeneey. It can also be spelled Moony, Moonie, Mainey, Meaney and Meeney depending on the dialectic pronunciation that was anglicised.
## Origins
The origin of the Moony or Mooney families is lost in antiquity. The name is derived from *maoin*, a Gaelic word meaning *wealth* or *treasure of treasure*, hence when O\'Maonaigh was anglicised to Mooney it meant *the descendant of the wealthy one.*
According to Irish lore, the Mooney family comes from one of the largest and most noble Irish lines. They are said to be descendants of the ancient Irish King Heremon, who, along with his brother Herber, conquered Ireland. Heremon slew his brother shortly after their invasion, took the throne for himself, and fathered a line of kings of Ireland that include Malachi II, and King Niall of the Nine Hostages.
Baptismal records, parish records, ancient land grants, the Annals of the Four Masters, and books by O\'Hart, McLysaght, and O\'Brien were all used in researching the history of the Mooney family name. These varied and often ancient records indicate that distant septs of the name arose in several places throughout Ireland. The most known and most numerous sept came from the county of Offaly. The members of this sept were from Chieftain Monach, son of Ailill Mor, Lord of Ulster, who was descended from the Kings of Connacht. These family members gave their name to town lands called Ballymooney both in that county and in the neighbouring county of Leix.
## People with the surname {#people_with_the_surname}
- James Mooney (Born 1976), Well know Dublin based poet.
- Al Mooney (1906--1986), aircraft designer and founder of Mooney Airplane Company
- Alex Mooney (born 1971), member of Congress from West Virginia
- Bel Mooney (born 1946), English journalist and broadcaster
- Brian Mooney (born 1966), professional football player
- C. P. J. Mooney (1865--1926), American newspaper publisher
- Cameron Mooney (born 1979), Australian rules footballer
- Carol Ann Mooney (fl. 1970s--2010s), president of Saint Mary\'s College in Notre Dame, Indiana
- Charles Mooney (born 1951), American boxer
- Charles (\"Chuck\") W. Mooney Jr. (born 1947), American, the Charles A. Heimbold, Jr. Professor of Law, and former interim dean, at the University of Pennsylvania Law School
- Chris Mooney (basketball) (born 1972), American basketball coach
- Clifton Mooney (born 1986), American Artist/ Photographer
- Darnell Mooney (born 1997), American football player
- Darren Mooney (born 1984) Runner/ Triathlete
- Dave Mooney (born 1984), professional football player
- Debra Mooney (born 1947), American actress
- Edward Aloysius Mooney (1882--1958), Roman Catholic Cardinal Archbishop of Detroit, former Bishop of Rochester
- Edward F. Mooney (born 1941), noted Kierkegaard scholar and Professor of Religion at Syracuse University
- Edward Joseph Mooney (born 1965), United States Air Force/Independent Duty Medic/Veteran of War on Terrorism
- Francie Mooney (1922--2006), musician, fiddler
- Hercules Mooney (1715--1800), American Revolutionary War colonel
- James Mooney (1861--1921), anthropologist whose major works were about Native American Indians
- Jason Mooney (disambiguation), multiple people
- John Mooney (disambiguation), multiple people
- Kathi Mooney (fl. 2010s--2020s), American scientist
- Kevin Mooney (born 1962), Irish musician
- Kyle Mooney (born 1984), American comic actor, *Saturday Night Live*
- Malcolm Mooney (born 1944), original lead singer of rock group Can
- Matt Mooney (born 1997), American basketball player
- Melvin Mooney (1893--1968), American physicist, developed the Mooney viscometer and other testing equipment used in the rubber industry
- Paschal Mooney (born 1947), Irish politician
- Peter Mooney (conductor) (1915--1983), Scottish educationalist and conductor (music)
- Peter Mooney (footballer) (1897--?), English professional footballer
- Paul Mooney (writer) (1904--1939), son of James Mooney
- Paul Mooney (comedian) (1941--2021), American comedian, writer, and actor
- Ralph Mooney (1928--2011), Bakersfield sound steel-guitar player who backed Buck Owens, Merle Haggard and others
- Robert Mooney (1873--1953), Canadian politician
- Sean Mooney (born 1959), sports reporter and former WWF announcer
- Shay Mooney (fl. 2010s--2020s), singer of country duo Dan + Shay
- Shona Mooney (born c. 1984), Scottish fiddler
- Ted Mooney (1951--2022), American author
- Thomas Mooney (1882--1942), American labour leader from San Francisco, California
- Tim Mooney (1958--2012), American musician
- Tom Mooney (rugby league) (born 1952), Australian rugby league footballer
- Tommy Mooney (born 1971), professional football player
- Tony Mooney (fl. 1970s--2010s), Australian politician
- Walter E. Mooney (1925--1990), pilot and model aircraft designer
- Charles A
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# March 8
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# MPEG-1
**MPEG-1** is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to about 1.5 Mbit/s (26:1 and 6:1 compression ratios respectively) without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting (DAB) practical.
Today, MPEG-1 has become the most widely compatible lossy audio/video format in the world, and is used in a large number of products and technologies. Perhaps the best-known part of the MPEG-1 standard is the first version of the MP3 audio format it introduced.
The MPEG-1 standard is published as **ISO/IEC 11172**, titled *Information technology---Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s*.
The standard consists of the following five *Parts*:
1. Systems (defining a format for storage and synchronization of video, audio, and other data together in a single file---later dubbed the MPEG program stream to distinguish it from the MPEG transport stream format introduced as an alternative in MPEG-2).
2. Video (compressed video content)
3. Audio (compressed audio content), including MP3 and MP2
4. Conformance testing (testing the correctness of implementations of the standard)
5. Reference software (example software showing how to encode and decode according to the standard)
## History
The predecessor of MPEG-1 for video coding was the H.261 standard produced by the CCITT (now known as the ITU-T). The basic architecture established in H.261 was the motion-compensated DCT hybrid video coding structure. It uses macroblocks of size 16×16 with block-based motion estimation in the encoder and motion compensation using encoder-selected motion vectors in the decoder, with residual difference coding using a discrete cosine transform (DCT) of size 8×8, scalar quantization, and variable-length codes (like Huffman codes) for entropy coding. H.261 was the first practical video coding standard, and all of its described design elements were also used in MPEG-1.
Modeled on the successful collaborative approach and the compression technologies developed by the Joint Photographic Experts Group and CCITT\'s Experts Group on Telephony (creators of the JPEG image compression standard and the H.261 standard for video conferencing respectively), the Moving Picture Experts Group (MPEG) working group was established in January 1988, by the initiative of Hiroshi Yasuda (Nippon Telegraph and Telephone) and Leonardo Chiariglione (CSELT). MPEG was formed to address the need for standard video and audio formats, and to build on H.261 to get better quality through the use of somewhat more complex encoding methods (e.g., supporting higher precision for motion vectors).
Development of the MPEG-1 standard began in May 1988. Fourteen video and fourteen audio codec proposals were submitted by individual companies and institutions for evaluation. The codecs were extensively tested for computational complexity and subjective (human perceived) quality, at data rates of 1.5 Mbit/s. This specific bitrate was chosen for transmission over T-1/E-1 lines and as the approximate data rate of audio CDs. The codecs that excelled in this testing were utilized as the basis for the standard and refined further, with additional features and other improvements being incorporated in the process.
After 20 meetings of the full group in various cities around the world, and 4½ years of development and testing, the final standard (for parts 1--3) was approved in early November 1992 and published a few months later. The reported completion date of the MPEG-1 standard varies greatly: a largely complete draft standard was produced in September 1990, and from that point on, only minor changes were introduced. The draft standard was publicly available for purchase. The standard was finished with the 6 November 1992 meeting. The Berkeley Plateau Multimedia Research Group developed an MPEG-1 decoder in November 1992. In July 1990, before the first draft of the MPEG-1 standard had even been written, work began on a second standard, MPEG-2, intended to extend MPEG-1 technology to provide full broadcast-quality video (as per CCIR 601) at high bitrates (3--15 Mbit/s) and support for interlaced video. Due in part to the similarity between the two codecs, the MPEG-2 standard includes full backwards compatibility with MPEG-1 video, so any MPEG-2 decoder can play MPEG-1 videos.
Notably, the MPEG-1 standard very strictly defines the bitstream, and decoder function, but does not define how MPEG-1 encoding is to be performed, although a reference implementation is provided in ISO/IEC-11172-5. This means that MPEG-1 coding efficiency can drastically vary depending on the encoder used, and generally means that newer encoders perform significantly better than their predecessors. The first three parts (Systems, Video and Audio) of ISO/IEC 11172 were published in August 1993.
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+------------+---------------------+-------------+
| Part | Number | First public\ | latest\ | Title | Description |
| | | release date\ | correction | | |
| | | (first edition) | | | |
+========+=====================================================================================================================================================================================================+=================+============+=====================+=============+
| Part 1 | [ISO/IEC 11172-1](https://www.iso.org/standard/19180.html) `{{Webarchive|url=https://web.archive.org/web/20170830194543/https://www.iso.org/standard/19180.html |date=2017-08-30 }}`{=mediawiki} | 1993 | 1999 | Systems | |
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+------------+---------------------+-------------+
| Part 2 | [ISO/IEC 11172-2](https://www.iso.org/standard/22411.html) `{{Webarchive|url=https://web.archive.org/web/20170830194202/https://www.iso.org/standard/22411.html |date=2017-08-30 }}`{=mediawiki} | 1993 | 2006 | Video | |
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+------------+---------------------+-------------+
| Part 3 | [ISO/IEC 11172-3](https://www.iso.org/standard/22412.html) `{{Webarchive|url=https://web.archive.org/web/20170515194520/https://www.iso.org/standard/22412.html |date=2017-05-15 }}`{=mediawiki} | 1993 | 1996 | Audio | |
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+------------+---------------------+-------------+
| Part 4 | [ISO/IEC 11172-4](https://www.iso.org/standard/22691.html) `{{Webarchive|url=https://web.archive.org/web/20170830191730/https://www.iso.org/standard/22691.html |date=2017-08-30 }}`{=mediawiki} | 1995 | 2007 | Compliance testing | |
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+------------+---------------------+-------------+
| Part 5 | [ISO/IEC TR 11172-5](https://www.iso.org/standard/25029.html) `{{Webarchive|url=https://web.archive.org/web/20170830193748/https://www.iso.org/standard/25029.html |date=2017-08-30 }}`{=mediawiki} | 1998 | 2007 | Software simulation | |
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+------------+---------------------+-------------+
: MPEG-1 Parts
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# MPEG-1
## Patents
Due to its age, MPEG-1 is no longer covered by any essential patents and can thus be used without obtaining a licence or paying any fees. The ISO patent database lists one patent for ISO 11172, US 4,472,747, which expired in 2003. The near-complete draft of the MPEG-1 standard was publicly available as ISO CD 11172 by December 6, 1991. Neither the July 2008 Kuro5hin article \"Patent Status of MPEG-1, H.261 and MPEG-2\", nor an August 2008 thread on the gstreamer-devel mailing list were able to list a single unexpired MPEG-1 Video and MPEG-1 Audio Layer I/II patent. A May 2009 discussion on the whatwg mailing list mentioned US 5,214,678 patent as possibly covering MPEG-1 Audio Layer II. Filed in 1990 and published in 1993, this patent is now expired.
A full MPEG-1 decoder and encoder, with \"Layer III audio\", could not be implemented royalty free since there were companies that required patent fees for implementations of MPEG-1 Audio Layer III, as discussed in the MP3 article. All patents in the world connected to MP3 expired 30 December 2017, which makes this format totally free for use. On 23 April 2017, Fraunhofer IIS stopped charging for Technicolor\'s MP3 licensing program for certain MP3 related patents and software.
### Former patent holders {#former_patent_holders}
The following corporations filed declarations with ISO saying they held patents for the MPEG-1 Video (ISO/IEC-11172-2) format, although all such patents have since expired.
- BBC
- Daimler Benz AG
- Fujitsu
- IBM
- Matsushita Electric Industrial Co., Ltd.
- Mitsubishi Electric
- NEC
- NHK
- Philips
- Pioneer Corporation
- Qualcomm
- Ricoh
- Sony
- Texas Instruments
- Thomson Multimedia
- Toppan Printing
- Toshiba
- Victor Company of Japan
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# MPEG-1
## Applications
- Most popular software for video playback includes MPEG-1 decoding, in addition to any other supported formats.
- The popularity of MP3 audio has established a massive installed base of hardware that can play back MPEG-1 Audio (all three layers).
- \"Virtually all digital audio devices\" can play back MPEG-1 Audio. Many millions have been sold to-date.
- Before MPEG-2 became widespread, many digital satellite/cable TV services used MPEG-1 exclusively.
- The widespread popularity of MPEG-2 with broadcasters means MPEG-1 is playable by most digital cable and satellite set-top boxes, and digital disc and tape players, due to backwards compatibility.
- MPEG-1 was used for full-screen video on Green Book CD-i, and on Video CD (VCD).
- The Super Video CD standard, based on VCD, uses MPEG-1 audio exclusively, as well as MPEG-2 video.
- The DVD-Video format uses MPEG-2 video primarily, but MPEG-1 support is explicitly defined in the standard.
- The DVD-Video standard originally required MPEG-1 Audio Layer II for PAL countries, but was changed to allow AC-3/Dolby Digital-only discs. MPEG-1 Audio Layer II is still allowed on DVDs, although newer extensions to the format, like MPEG Multichannel, are rarely supported.
- Most DVD players also support Video CD and MP3 CD playback, which use MPEG-1.
- The international Digital Video Broadcasting (DVB) standard primarily uses MPEG-1 Audio Layer II, and MPEG-2 video.
- The international Digital Audio Broadcasting (DAB) standard uses MPEG-1 Audio Layer II exclusively, due to its especially high quality, modest decoder performance requirements, and tolerance of errors.
- The Digital Compact Cassette uses PASC (Precision Adaptive Sub-band Coding) to encode its audio. PASC is an early version of MPEG-1 Audio Layer I with a fixed bit rate of 384 kilobits per second.
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# MPEG-1
## Part 1: Systems {#part_1_systems}
Part 1 of the MPEG-1 standard covers *systems*, and is defined in ISO/IEC-11172-1.
MPEG-1 Systems specifies the logical layout and methods used to store the encoded audio, video, and other data into a standard bitstream, and to maintain synchronization between the different contents. This file format is specifically designed for storage on media, and transmission over communication channels, that are considered relatively reliable. Only limited error protection is defined by the standard, and small errors in the bitstream may cause noticeable defects.
This structure was later named an MPEG program stream: \"The MPEG-1 Systems design is essentially identical to the MPEG-2 Program Stream structure.\" This terminology is more popular, precise (differentiates it from an MPEG transport stream) and will be used here.
### Elementary streams, packets, and clock references {#elementary_streams_packets_and_clock_references}
- Elementary Streams (ES) are the raw bitstreams of MPEG-1 audio and video encoded data (output from an encoder). These files can be distributed on their own, such as is the case with MP3 files.
- Packetized Elementary Streams (PES) are elementary streams packetized into packets of variable lengths, i.e., divided ES into independent chunks where cyclic redundancy check (CRC) checksum was added to each packet for error detection.
- System Clock Reference (SCR) is a timing value stored in a 33-bit header of each PES, at a frequency/precision of 90 kHz, with an extra 9-bit extension that stores additional timing data with a precision of 27 MHz. These are inserted by the encoder, derived from the system time clock (STC). Simultaneously encoded audio and video streams will not have identical SCR values, however, due to buffering, encoding, jitter, and other delay.
### Program streams {#program_streams}
Program Streams (PS) are concerned with combining multiple packetized elementary streams (usually just one audio and video PES) into a single stream, ensuring simultaneous delivery, and maintaining synchronization. The PS structure is known as a multiplex, or a container format.
Presentation time stamps (PTS) exist in PS to correct the inevitable disparity between audio and video SCR values (time-base correction). 90 kHz PTS values in the PS header tell the decoder which video SCR values match which audio SCR values. PTS determines when to display a portion of an MPEG program, and is also used by the decoder to determine when data can be discarded from the buffer. Either video or audio will be delayed by the decoder until the corresponding segment of the other arrives and can be decoded.
PTS handling can be problematic. Decoders must accept multiple *program streams* that have been concatenated (joined sequentially). This causes PTS values in the middle of the video to reset to zero, which then begin incrementing again. Such PTS wraparound disparities can cause timing issues that must be specially handled by the decoder.
Decoding Time Stamps (DTS), additionally, are required because of B-frames. With B-frames in the video stream, adjacent frames have to be encoded and decoded out-of-order (re-ordered frames). DTS is quite similar to PTS, but instead of just handling sequential frames, it contains the proper time-stamps to tell the decoder when to decode and display the next B-frame (types of frames explained below), ahead of its anchor (P- or I-) frame. Without B-frames in the video, PTS and DTS values are identical.
### Multiplexing
To generate the PS, the multiplexer will interleave the (two or more) packetized elementary streams. This is done so the packets of the simultaneous streams can be transferred over the same channel and are guaranteed to both arrive at the decoder at precisely the same time. This is a case of time-division multiplexing.
Determining how much data from each stream should be in each interleaved segment (the size of the interleave) is complicated, yet an important requirement. Improper interleaving will result in buffer underflows or overflows, as the receiver gets more of one stream than it can store (e.g. audio), before it gets enough data to decode the other simultaneous stream (e.g. video). The MPEG Video Buffering Verifier (VBV) assists in determining if a multiplexed PS can be decoded by a device with a specified data throughput rate and buffer size. This offers feedback to the multiplexer and the encoder, so that they can change the multiplex size or adjust bitrates as needed for compliance.
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# MPEG-1
## Part 2: Video {#part_2_video}
Part 2 of the MPEG-1 standard covers video and is defined in ISO/IEC-11172-2. The design was heavily influenced by H.261.
MPEG-1 Video exploits perceptual compression methods to significantly reduce the data rate required by a video stream. It reduces or completely discards information in certain frequencies and areas of the picture that the human eye has limited ability to fully perceive. It also exploits temporal (over time) and spatial (across a picture) redundancy common in video to achieve better data compression than would be possible otherwise. (See: Video compression)
### Color space {#color_space}
Before encoding video to MPEG-1, the color-space is transformed to Y′CbCr (Y′=Luma, Cb=Chroma Blue, Cr=Chroma Red). Luma (brightness, resolution) is stored separately from chroma (color, hue, phase) and even further separated into red and blue components.
The chroma is also subsampled to 4:2:0, meaning it is reduced to half resolution vertically and half resolution horizontally, i.e., to just one quarter the number of samples used for the luma component of the video. This use of higher resolution for some color components is similar in concept to the Bayer pattern filter that is commonly used for the image capturing sensor in digital color cameras. Because the human eye is much more sensitive to small changes in brightness (the Y component) than in color (the Cr and Cb components), chroma subsampling is a very effective way to reduce the amount of video data that needs to be compressed. However, on videos with fine detail (high spatial complexity) this can manifest as chroma aliasing artifacts. Compared to other digital compression artifacts, this issue seems to very rarely be a source of annoyance. Because of the subsampling, Y′CbCr 4:2:0 video is ordinarily stored using even dimensions (divisible by 2 horizontally and vertically).
Y′CbCr color is often informally called YUV to simplify the notation, although that term more properly applies to a somewhat different color format. Similarly, the terms luminance and chrominance are often used instead of the (more accurate) terms luma and chroma.
### Resolution/bitrate
MPEG-1 supports resolutions up to 4095×4095 (12 bits), and bit rates up to 100 Mbit/s.
MPEG-1 videos are most commonly seen using Source Input Format (SIF) resolution: 352×240, 352×288, or 320×240. These relatively low resolutions, combined with a bitrate less than 1.5 Mbit/s, make up what is known as a constrained parameters bitstream (CPB), later renamed the \"Low Level\" (LL) profile in MPEG-2. This is the minimum video specifications any decoder should be able to handle, to be considered MPEG-1 compliant. This was selected to provide a good balance between quality and performance, allowing the use of reasonably inexpensive hardware of the time.
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# MPEG-1
## Part 2: Video {#part_2_video}
### Frame/picture/block types {#framepictureblock_types}
MPEG-1 has several frame/picture types that serve different purposes. The most important, yet simplest, is **I-frame**.
#### I-frames {#i_frames}
\"I-frame\" is an abbreviation for \"Intra-frame\", so-called because they can be decoded independently of any other frames. They may also be known as I-pictures, or keyframes due to their somewhat similar function to the key frames used in animation. I-frames can be considered effectively identical to baseline JPEG images.
High-speed seeking through an MPEG-1 video is only possible to the nearest I-frame. When cutting a video it is not possible to start playback of a segment of video before the first I-frame in the segment (at least not without computationally intensive re-encoding). For this reason, I-frame-only MPEG videos are used in editing applications.
I-frame only compression is very fast, but produces very large file sizes: a factor of 3× (or more) larger than normally encoded MPEG-1 video, depending on how temporally complex a specific video is. I-frame only MPEG-1 video is very similar to MJPEG video. So much so that very high-speed and theoretically lossless (in reality, there are rounding errors) conversion can be made from one format to the other, provided a couple of restrictions (color space and quantization matrix) are followed in the creation of the bitstream.
The length between I-frames is known as the group of pictures (GOP) size. MPEG-1 most commonly uses a GOP size of 15--18. i.e. 1 I-frame for every 14-17 non-I-frames (some combination of P- and B- frames). With more intelligent encoders, GOP size is dynamically chosen, up to some pre-selected maximum limit.
Limits are placed on the maximum number of frames between I-frames due to decoding complexing, decoder buffer size, recovery time after data errors, seeking ability, and accumulation of IDCT errors in low-precision implementations most common in hardware decoders (See: IEEE-1180).
#### P-frames {#p_frames}
\"P-frame\" is an abbreviation for \"Predicted-frame\". They may also be called forward-predicted frames or inter-frames (B-frames are also inter-frames).
P-frames exist to improve compression by exploiting the temporal (over time) redundancy in a video. P-frames store only the *difference* in image from the frame (either an I-frame or P-frame) immediately preceding it (this reference frame is also called the *anchor frame*).
The difference between a P-frame and its anchor frame is calculated using *motion vectors* on each *macroblock* of the frame (see below). Such motion vector data will be embedded in the P-frame for use by the decoder.
A P-frame can contain any number of intra-coded blocks (DCT and Quantized), in addition to any forward-predicted blocks (Motion Vectors).
If a video drastically changes from one frame to the next (such as a cut), it is more efficient to encode it as an I-frame.
#### B-frames {#b_frames}
\"B-frame\" stands for \"bidirectional-frame\" or \"bipredictive frame\". They may also be known as backwards-predicted frames or B-pictures. B-frames are quite similar to P-frames, except they can make predictions using both the previous and future frames (i.e. two anchor frames).
It is therefore necessary for the player to first decode the next I- or P- anchor frame sequentially after the B-frame, before the B-frame can be decoded and displayed. This means decoding B-frames requires larger data buffers and causes an increased delay on both decoding and during encoding. This also necessitates the decoding time stamps (DTS) feature in the container/system stream (see above). As such, B-frames have long been subject of much controversy, they are often avoided in videos, and are sometimes not fully supported by hardware decoders.
No other frames are predicted from a B-frame. Because of this, a very low bitrate B-frame can be inserted, where needed, to help control the bitrate. If this was done with a P-frame, future P-frames would be predicted from it and would lower the quality of the entire sequence. However, similarly, the future P-frame must still encode all the changes between it and the previous I- or P- anchor frame. B-frames can also be beneficial in videos where the background behind an object is being revealed over several frames, or in fading transitions, such as scene changes.
A B-frame can contain any number of intra-coded blocks and forward-predicted blocks, in addition to backwards-predicted, or bidirectionally predicted blocks.
#### D-frames {#d_frames}
MPEG-1 has a unique frame type not found in later video standards. \"D-frames\" or DC-pictures are independently coded images (intra-frames) that have been encoded using DC transform coefficients only (AC coefficients are removed when encoding D-frames---see DCT below) and hence are very low quality. D-frames are never referenced by I-, P- or B- frames. D-frames are only used for fast previews of video, for instance when seeking through a video at high speed.
Given moderately higher-performance decoding equipment, fast preview can be accomplished by decoding I-frames instead of D-frames. This provides higher quality previews, since I-frames contain AC coefficients as well as DC coefficients. If the encoder can assume that rapid I-frame decoding capability is available in decoders, it can save bits by not sending D-frames (thus improving compression of the video content). For this reason, D-frames are seldom actually used in MPEG-1 video encoding, and the D-frame feature has not been included in any later video coding standards.
### Macroblocks
MPEG-1 operates on video in a series of 8×8 blocks for quantization. However, to reduce the bit rate needed for motion vectors and because chroma (color) is subsampled by a factor of 4, each pair of (red and blue) chroma blocks corresponds to 4 different luma blocks. That is, for 4 luma blocks of size 8x8, there is one Cb block of 8x8 and one Cr block of 8x8. This set of 6 blocks, with a picture resolution of 16×16, is processed together and called a *macroblock*.
All of these 8x8 blocks are independently put through DCT and quantization.
A macroblock is the smallest independent unit of (color) video. Motion vectors (see below) operate solely at the macroblock level.
If the height or width of the video are not exact multiples of 16, full rows and full columns of macroblocks must still be encoded and decoded to fill out the picture (though the extra decoded pixels are not displayed).
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# MPEG-1
## Part 2: Video {#part_2_video}
### Motion vectors {#motion_vectors}
To decrease the amount of temporal redundancy in a video, only blocks that change are updated, (up to the maximum GOP size). This is known as conditional replenishment. However, this is not very effective by itself. Movement of the objects, and/or the camera may result in large portions of the frame needing to be updated, even though only the position of the previously encoded objects has changed. Through motion estimation, the encoder can compensate for this movement and remove a large amount of redundant information.
The encoder compares the current frame with adjacent parts of the video from the anchor frame (previous I- or P- frame) in a diamond pattern, up to a (encoder-specific) predefined radius limit from the area of the current macroblock. If a match is found, only the direction and distance (i.e. the *vector* of the *motion*) from the previous video area to the current macroblock need to be encoded into the inter-frame (P- or B- frame). The reverse of this process, performed by the decoder to reconstruct the picture, is called motion compensation.
A predicted macroblock rarely matches the current picture perfectly, however. The differences between the estimated matching area, and the real frame/macroblock is called the prediction error. The larger the amount of prediction error, the more data must be additionally encoded in the frame. For efficient video compression, it is very important that the encoder is capable of effectively and precisely performing motion estimation.
Motion vectors record the *distance* between two areas on screen based on the number of pixels (also called pels). MPEG-1 video uses a motion vector (MV) precision of one half of one pixel, or half-pel. The finer the precision of the MVs, the more accurate the match is likely to be, and the more efficient the compression. There are trade-offs to higher precision, however. Finer MV precision results in using a larger amount of data to represent the MV, as larger numbers must be stored in the frame for every single MV, increased coding complexity as increasing levels of interpolation on the macroblock are required for both the encoder and decoder, and diminishing returns (minimal gains) with higher precision MVs. Half-pel precision was chosen as the ideal trade-off for that point in time. (See: qpel)
Because neighboring macroblocks are likely to have very similar motion vectors, this redundant information can be compressed quite effectively by being stored DPCM-encoded. Only the (smaller) amount of difference between the MVs for each macroblock needs to be stored in the final bitstream.
P-frames have one motion vector per macroblock, relative to the previous anchor frame. B-frames, however, can use two motion vectors; one from the previous anchor frame, and one from the future anchor frame.
Partial macroblocks, and black borders/bars encoded into the video that do not fall exactly on a macroblock boundary, cause havoc with motion prediction. The block padding/border information prevents the macroblock from closely matching with any other area of the video, and so, significantly larger prediction error information must be encoded for every one of the several dozen partial macroblocks along the screen border. DCT encoding and quantization (see below) also isn\'t nearly as effective when there is large/sharp picture contrast in a block.
An even more serious problem exists with macroblocks that contain significant, random, *edge noise*, where the picture transitions to (typically) black. All the above problems also apply to edge noise. In addition, the added randomness is simply impossible to compress significantly. All of these effects will lower the quality (or increase the bitrate) of the video substantially.
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# MPEG-1
## Part 2: Video {#part_2_video}
### DCT
Each 8×8 block is encoded by first applying a *forward* discrete cosine transform (FDCT) and then a quantization process. The FDCT process (by itself) is theoretically lossless, and can be reversed by applying an *Inverse* DCT (IDCT) to reproduce the original values (in the absence of any quantization and rounding errors). In reality, there are some (sometimes large) rounding errors introduced both by quantization in the encoder (as described in the next section) and by IDCT approximation error in the decoder. The minimum allowed accuracy of a decoder IDCT approximation is defined by ISO/IEC 23002-1. (Prior to 2006, it was specified by IEEE 1180-1990.)
The FDCT process converts the 8×8 block of uncompressed pixel values (brightness or color difference values) into an 8×8 indexed array of *frequency coefficient* values. One of these is the (statistically high in variance) \"DC coefficient\", which represents the average value of the entire 8×8 block. The other 63 coefficients are the statistically smaller \"AC coefficients\", which have positive or negative values each representing sinusoidal deviations from the flat block value represented by the DC coefficient.
An example of an encoded 8×8 FDCT block:
$$\begin{bmatrix}
-415 & -30 & -61 & 27 & 56 & -20 & -2 & 0 \\
4 & -22 & -61 & 10 & 13 & -7 & -9 & 5 \\
-47 & 7 & 77 & -25 & -29 & 10 & 5 & -6 \\
-49 & 12 & 34 & -15 & -10 & 6 & 2 & 2 \\
12 & -7 & -13 & -4 & -2 & 2 & -3 & 3 \\
-8 & 3 & 2 & -6 & -2 & 1 & 4 & 2 \\
-1 & 0 & 0 & -2 & -1 & -3 & 4 & -1 \\
0 & 0 & -1 & -4 & -1 & 0 & 1 & 2
\end{bmatrix}$$
Since the DC coefficient value is statistically correlated from one block to the next, it is compressed using DPCM encoding. Only the (smaller) amount of difference between each DC value and the value of the DC coefficient in the block to its left needs to be represented in the final bitstream.
Additionally, the frequency conversion performed by applying the DCT provides a statistical decorrelation function to efficiently concentrate the signal into fewer high-amplitude values prior to applying quantization (see below).
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# MPEG-1
## Part 2: Video {#part_2_video}
### Quantization
Quantization is, essentially, the process of reducing the accuracy of a signal, by dividing it by some larger step size and rounding to an integer value (i.e. finding the nearest multiple, and discarding the remainder).
The frame-level quantizer is a number from 0 to 31 (although encoders will usually omit/disable some of the extreme values) which determines how much information will be removed from a given frame. The frame-level quantizer is typically either dynamically selected by the encoder to maintain a certain user-specified bitrate, or (much less commonly) directly specified by the user.
A \"quantization matrix\" is a string of 64 numbers (ranging from 0 to 255) which tells the encoder how relatively important or unimportant each piece of visual information is. Each number in the matrix corresponds to a certain frequency component of the video image.
An example quantization matrix:
$$\begin{bmatrix}
16 & 11 & 10 & 16 & 24 & 40 & 51 & 61 \\
12 & 12 & 14 & 19 & 26 & 58 & 60 & 55 \\
14 & 13 & 16 & 24 & 40 & 57 & 69 & 56 \\
14 & 17 & 22 & 29 & 51 & 87 & 80 & 62 \\
18 & 22 & 37 & 56 & 68 & 109 & 103 & 77 \\
24 & 35 & 55 & 64 & 81 & 104 & 113 & 92 \\
49 & 64 & 78 & 87 & 103 & 121 & 120 & 101 \\
72 & 92 & 95 & 98 & 112 & 100 & 103 & 99
\end{bmatrix}$$
Quantization is performed by taking each of the 64 *frequency* values of the DCT block, dividing them by the frame-level quantizer, then dividing them by their corresponding values in the quantization matrix. Finally, the result is rounded down. This significantly reduces, or completely eliminates, the information in some frequency components of the picture. Typically, high frequency information is less visually important, and so high frequencies are much more *strongly quantized* (drastically reduced). MPEG-1 actually uses two separate quantization matrices, one for intra-blocks (I-blocks) and one for inter-block (P- and B- blocks) so quantization of different block types can be done independently, and so, more effectively.
This quantization process usually reduces a significant number of the *AC coefficients* to zero, (known as sparse data) which can then be more efficiently compressed by entropy coding (lossless compression) in the next step.
An example quantized DCT block:
$$\begin{bmatrix}
-26 & -3 & -6 & 2 & 2 & -1 & 0 & 0 \\
0 & -2 & -4 & 1 & 1 & 0 & 0 & 0 \\
-3 & 1 & 5 & -1 & -1 & 0 & 0 & 0 \\
-4 & 1 & 2 & -1 & 0 & 0 & 0 & 0 \\
1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0
\end{bmatrix}$$
Quantization eliminates a large amount of data, and is the main lossy processing step in MPEG-1 video encoding. This is also the primary source of most MPEG-1 video compression artifacts, like blockiness, color banding, noise, ringing, discoloration, etc. This happens when video is encoded with an insufficient bitrate, and the encoder is therefore forced to use high frame-level quantizers (*strong quantization*) through much of the video.
### Entropy coding {#entropy_coding}
Several steps in the encoding of MPEG-1 video are lossless, meaning they will be reversed upon decoding, to produce exactly the same (original) values. Since these lossless data compression steps don\'t add noise into, or otherwise change the contents (unlike quantization), it is sometimes referred to as noiseless coding. Since lossless compression aims to remove as much redundancy as possible, it is known as entropy coding in the field of information theory.
The coefficients of quantized DCT blocks tend to zero towards the bottom-right. Maximum compression can be achieved by a zig-zag scanning of the DCT block starting from the top left and using Run-length encoding techniques.
The DC coefficients and motion vectors are DPCM-encoded.
Run-length encoding (RLE) is a simple method of compressing repetition. A sequential string of characters, no matter how long, can be replaced with a few bytes, noting the value that repeats, and how many times. For example, if someone were to say \"five nines\", you would know they mean the number: 99999.
RLE is particularly effective after quantization, as a significant number of the AC coefficients are now zero (called sparse data), and can be represented with just a couple of bytes. This is stored in a special 2-dimensional Huffman table that codes the run-length and the run-ending character.
Huffman Coding is a very popular and relatively simple method of entropy coding, and used in MPEG-1 video to reduce the data size. The data is analyzed to find strings that repeat often. Those strings are then put into a special table, with the most frequently repeating data assigned the shortest code. This keeps the data as small as possible with this form of compression. Once the table is constructed, those strings in the data are replaced with their (much smaller) codes, which reference the appropriate entry in the table. The decoder simply reverses this process to produce the original data.
This is the final step in the video encoding process, so the result of Huffman coding is known as the MPEG-1 video \"bitstream.\"
### GOP configurations for specific applications {#gop_configurations_for_specific_applications}
I-frames store complete frame info within the frame and are therefore suited for random access. P-frames provide compression using motion vectors relative to the previous frame ( I or P ). B-frames provide maximum compression but require the previous as well as next frame for computation. Therefore, processing of B-frames requires more buffer on the decoded side. A configuration of the Group of Pictures (GOP) should be selected based on these factors. I-frame only sequences give least compression, but are useful for random access, FF/FR and editability. I- and P-frame sequences give moderate compression but add a certain degree of random access, FF/FR functionality. I-, P- and B-frame sequences give very high compression but also increase the coding/decoding delay significantly. Such configurations are therefore not suited for video-telephony or video-conferencing applications.
The typical data rate of an I-frame is 1 bit per pixel while that of a P-frame is 0.1 bit per pixel and for a B-frame, 0.015 bit per pixel.
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# MPEG-1
## Part 3: Audio {#part_3_audio}
Part 3 of the MPEG-1 standard covers audio and is defined in ISO/IEC-11172-3.
MPEG-1 Audio utilizes psychoacoustics to significantly reduce the data rate required by an audio stream. It reduces or completely discards certain parts of the audio that it deduces that the human ear can\'t *hear*, either because they are in frequencies where the ear has limited sensitivity, or are *masked* by other (typically louder) sounds.
Channel encoding modes:
- Mono
- Joint stereo -- intensity encoded
- Joint stereo -- M/S encoded (Layer III only)
- Stereo
- Dual (two uncorrelated mono channels)
Sampling rates:
- 32000 Hz
- 44100 Hz
- 48000 Hz
Bit rates:
- Layer I: 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416 and 448 kbit/s
- Layer II: 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 and 384 kbit/s
- Layer III: 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256 and 320 kbit/s
MPEG-1 Audio is divided into 3 layers. Each higher layer is more computationally complex, and generally more efficient at lower bitrates than the previous. The layers are semi backwards compatible as higher layers reuse technologies implemented by the lower layers. A \"full\" Layer II decoder can also play Layer I audio, but *not* Layer III audio, although not all higher level players are \"full\".
### Layer I {#layer_i}
MPEG-1 Audio Layer I is a simplified version of MPEG-1 Audio Layer II. Layer I uses a smaller 384-sample frame size for very low delay, and finer resolution. This is advantageous for applications like teleconferencing, studio editing, etc. It has lower complexity than Layer II to facilitate real-time encoding on the hardware available c. 1990.
Layer I saw limited adoption in its time, and most notably was used on Philips\' defunct Digital Compact Cassette at a bitrate of 384 kbit/s. With the substantial performance improvements in digital processing since its introduction, Layer I quickly became unnecessary and obsolete.
Layer I audio files typically use the extension \".mp1\" or sometimes \".m1a\".
### Layer II {#layer_ii}
MPEG-1 Audio Layer II (the first version of MP2, often informally called MUSICAM) is a lossy audio format designed to provide high quality at about 192 kbit/s for stereo sound. Decoding MP2 audio is computationally simple relative to MP3, AAC, etc.
#### History/MUSICAM
MPEG-1 Audio Layer II was derived from the MUSICAM (*Masking pattern adapted Universal Subband Integrated Coding And Multiplexing*) audio codec, developed by Centre commun d\'études de télévision et télécommunications (CCETT), Philips, and Institut für Rundfunktechnik (IRT/CNET) as part of the EUREKA 147 pan-European inter-governmental research and development initiative for the development of digital audio broadcasting.
Most key features of MPEG-1 Audio were directly inherited from MUSICAM, including the filter bank, time-domain processing, audio frame sizes, etc. However, improvements were made, and the actual MUSICAM algorithm was not used in the final MPEG-1 Audio Layer II standard. The widespread usage of the term MUSICAM to refer to Layer II is entirely incorrect and discouraged for both technical and legal reasons.
#### Technical details {#technical_details}
MP2 is a time-domain encoder. It uses a low-delay 32 sub-band polyphased filter bank for time-frequency mapping; having overlapping ranges (i.e. polyphased) to prevent aliasing. The psychoacoustic model is based on the principles of auditory masking, simultaneous masking effects, and the absolute threshold of hearing (ATH). The size of a Layer II frame is fixed at 1152-samples (coefficients).
Time domain refers to how analysis and quantization is performed on short, discrete samples/chunks of the audio waveform. This offers low delay as only a small number of samples are analyzed before encoding, as opposed to frequency domain encoding (like MP3) which must analyze many times more samples before it can decide how to transform and output encoded audio. This also offers higher performance on complex, random and transient impulses (such as percussive instruments, and applause), offering avoidance of artifacts like pre-echo.
The 32 sub-band filter bank returns 32 amplitude coefficients, one for each equal-sized frequency band/segment of the audio, which is about 700 Hz wide (depending on the audio\'s sampling frequency). The encoder then utilizes the psychoacoustic model to determine which sub-bands contain audio information that is less important, and so, where quantization will be inaudible, or at least much less noticeable.
thumb\|right\|upright=1.55\|Example FFT analysis on an audio wave sample
The psychoacoustic model is applied using a 1024-point fast Fourier transform (FFT). Of the 1152 samples per frame, 64 samples at the top and bottom of the frequency range are ignored for this analysis. They are presumably not significant enough to change the result. The psychoacoustic model uses an empirically determined masking model to determine which sub-bands contribute more to the masking threshold, and how much quantization noise each can contain without being perceived. Any sounds below the absolute threshold of hearing (ATH) are completely discarded. The available bits are then assigned to each sub-band accordingly.
Typically, sub-bands are less important if they contain quieter sounds (smaller coefficient) than a neighboring (i.e. similar frequency) sub-band with louder sounds (larger coefficient). Also, \"noise\" components typically have a more significant masking effect than \"tonal\" components.
Less significant sub-bands are reduced in accuracy by quantization. This basically involves compressing the frequency range (amplitude of the coefficient), i.e. raising the noise floor. Then computing an amplification factor, for the decoder to use to re-expand each sub-band to the proper frequency range.
Layer II can also optionally use intensity stereo coding, a form of joint stereo. This means that the frequencies above 6 kHz of both channels are combined/down-mixed into one single (mono) channel, but the \"side channel\" information on the relative intensity (volume, amplitude) of each channel is preserved and encoded into the bitstream separately. On playback, the single channel is played through left and right speakers, with the intensity information applied to each channel to give the illusion of stereo sound. This perceptual trick is known as \"stereo irrelevancy\". This can allow further reduction of the audio bitrate without much perceivable loss of fidelity, but is generally not used with higher bitrates as it does not provide very high quality (transparent) audio.
#### Quality
Subjective audio testing by experts, in the most critical conditions ever implemented, has shown MP2 to offer transparent audio compression at 256 kbit/s for 16-bit 44.1 kHz CD audio using the earliest reference implementation (more recent encoders should presumably perform even better). That (approximately) 1:6 compression ratio for CD audio is particularly impressive because it is quite close to the estimated upper limit of perceptual entropy, at just over 1:8. Achieving much higher compression is simply not possible without discarding some perceptible information.
MP2 remains a favoured lossy audio coding standard due to its particularly high audio coding performances on important audio material such as castanet, symphonic orchestra, male and female voices and particularly complex and high energy transients (impulses) like percussive sounds: triangle, glockenspiel and audience applause. More recent testing has shown that MPEG Multichannel (based on MP2), despite being compromised by an inferior matrixed mode (for the sake of backwards compatibility) rates just slightly lower than much more recent audio codecs, such as Dolby Digital (AC-3) and Advanced Audio Coding (AAC) (mostly within the margin of error---and substantially superior in some cases, such as audience applause). This is one reason that MP2 audio continues to be used extensively. The MPEG-2 AAC Stereo verification tests reached a vastly different conclusion, however, showing AAC to provide superior performance to MP2 at half the bitrate. The reason for this disparity with both earlier and later tests is not clear, but strangely, a sample of applause is notably absent from the latter test.
Layer II audio files typically use the extension \".mp2\" or sometimes \".m2a\".
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# MPEG-1
## Part 3: Audio {#part_3_audio}
### Layer III {#layer_iii}
MPEG-1 Audio Layer III (the first version of MP3) is a lossy audio format designed to provide acceptable quality at about 64 kbit/s for monaural audio over single-channel (BRI) ISDN links, and 128 kbit/s for stereo sound.
#### History/ASPEC
MPEG-1 Audio Layer III was derived from the *Adaptive Spectral Perceptual Entropy Coding* (ASPEC) codec developed by Fraunhofer as part of the EUREKA 147 pan-European inter-governmental research and development initiative for the development of digital audio broadcasting. ASPEC was adapted to fit in with the Layer II model (frame size, filter bank, FFT, etc.), to become Layer III.
ASPEC was itself based on *Multiple adaptive Spectral audio Coding* (MSC) by E. F. Schroeder, *Optimum Coding in the Frequency domain* (OCF) the doctoral thesis by Karlheinz Brandenburg at the University of Erlangen-Nuremberg, *Perceptual Transform Coding* (PXFM) by J. D. Johnston at AT&T Bell Labs, and *Transform coding of audio signals* by Y. Mahieux and J. Petit at Institut für Rundfunktechnik (IRT/CNET).
#### Technical details {#technical_details_1}
MP3 is a frequency-domain audio transform encoder. Even though it utilizes some of the lower layer functions, MP3 is quite different from MP2.
MP3 works on 1152 samples like MP2, but needs to take multiple frames for analysis before frequency-domain (MDCT) processing and quantization can be effective. It outputs a variable number of samples, using a bit buffer to enable this variable bitrate (VBR) encoding while maintaining 1152 sample size output frames. This causes a significantly longer delay before output, which has caused MP3 to be considered unsuitable for studio applications where editing or other processing needs to take place.
MP3 does not benefit from the 32 sub-band polyphased filter bank, instead just using an 18-point MDCT transformation on each output to split the data into 576 frequency components, and processing it in the frequency domain. This extra granularity allows MP3 to have a much finer psychoacoustic model, and more carefully apply appropriate quantization to each band, providing much better low-bitrate performance.
Frequency-domain processing imposes some limitations as well, causing a factor of 12 or 36 × worse temporal resolution than Layer II. This causes quantization artifacts, due to transient sounds like percussive events and other high-frequency events that spread over a larger window. This results in audible smearing and pre-echo. MP3 uses pre-echo detection routines, and VBR encoding, which allows it to temporarily increase the bitrate during difficult passages, in an attempt to reduce this effect. It is also able to switch between the normal 36 sample quantization window, and instead using 3× short 12 sample windows instead, to reduce the temporal (time) length of quantization artifacts. And yet in choosing a fairly small window size to make MP3\'s temporal response adequate enough to avoid the most serious artifacts, MP3 becomes much less efficient in frequency domain compression of stationary, tonal components.
Being forced to use a *hybrid* time domain (filter bank) /frequency domain (MDCT) model to fit in with Layer II simply wastes processing time and compromises quality by introducing aliasing artifacts. MP3 has an aliasing cancellation stage specifically to mask this problem, but which instead produces frequency domain energy which must be encoded in the audio. This is pushed to the top of the frequency range, where most people have limited hearing, in hopes the distortion it causes will be less audible.
Layer II\'s 1024 point FFT doesn\'t entirely cover all samples, and would omit several entire MP3 sub-bands, where quantization factors must be determined. MP3 instead uses two passes of FFT analysis for spectral estimation, to calculate the global and individual masking thresholds. This allows it to cover all 1152 samples. Of the two, it utilizes the global masking threshold level from the more critical pass, with the most difficult audio.
In addition to Layer II\'s intensity encoded joint stereo, MP3 can use middle/side (mid/side, m/s, MS, matrixed) joint stereo. With mid/side stereo, certain frequency ranges of both channels are merged into a single (middle, mid, L+R) mono channel, while the sound difference between the left and right channels is stored as a separate (side, L-R) channel. Unlike intensity stereo, this process does not discard any audio information. When combined with quantization, however, it can exaggerate artifacts.
If the difference between the left and right channels is small, the side channel will be small, which will offer as much as a 50% bitrate savings, and associated quality improvement. If the difference between left and right is large, standard (discrete, left/right) stereo encoding may be preferred, as mid/side joint stereo will not provide any benefits. An MP3 encoder can switch between m/s stereo and full stereo on a frame-by-frame basis.
Unlike Layers I and II, MP3 uses variable-length Huffman coding (after perceptual) to further reduce the bitrate, without any further quality loss.
#### Quality {#quality_1}
MP3\'s more fine-grained and selective quantization does prove notably superior to MP2 at lower-bitrates. It is able to provide nearly equivalent audio quality to Layer II, at a 15% lower bitrate (approximately). 128 kbit/s is considered the \"sweet spot\" for MP3; meaning it provides generally acceptable quality stereo sound on most music, and there are diminishing quality improvements from increasing the bitrate further. MP3 is also regarded as exhibiting artifacts that are less annoying than Layer II, when both are used at bitrates that are too low to possibly provide faithful reproduction.
Layer III audio files use the extension \".mp3\".
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# MPEG-1
## Part 3: Audio {#part_3_audio}
### MPEG-2 audio extensions {#mpeg_2_audio_extensions}
The MPEG-2 standard includes several extensions to MPEG-1 Audio. These are known as MPEG-2 BC -- backwards compatible with MPEG-1 Audio. MPEG-2 Audio is defined in ISO/IEC 13818-3.
- MPEG Multichannel -- Backward compatible 5.1-channel surround sound.
- Sampling rates: 16000, 22050, and 24000 Hz
- Bitrates: 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144 and 160 kbit/s
These sampling rates are exactly half that of those originally defined for MPEG-1 Audio. They were introduced to maintain higher quality sound when encoding audio at lower-bitrates. The even-lower bitrates were introduced because tests showed that MPEG-1 Audio could provide higher quality than any existing (c. 1994) very low bitrate (i.e. speech) audio codecs.
## Part 4: Conformance testing {#part_4_conformance_testing}
Part 4 of the MPEG-1 standard covers conformance testing, and is defined in ISO/IEC-11172-4.
Conformance: Procedures for testing conformance.
Provides two sets of guidelines and reference bitstreams for testing the conformance of MPEG-1 audio and video decoders, as well as the bitstreams produced by an encoder.
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# MPEG-1
## Part 5: Reference software {#part_5_reference_software}
Part 5 of the MPEG-1 standard includes reference software, and is defined in ISO/IEC TR 11172--5.
Simulation: Reference software.
C reference code for encoding and decoding of audio and video, as well as multiplexing and demultiplexing.
This includes the *ISO Dist10* audio encoder code, which LAME and TooLAME were originally based upon.
## File extension {#file_extension}
.mpg is one of a number of file extensions for MPEG-1 or MPEG-2 audio and video compression. MPEG-1 Part 2 video is rare nowadays, and this extension typically refers to an MPEG program stream (defined in MPEG-1 and MPEG-2) or MPEG transport stream (defined in MPEG-2). Other suffixes such as .m2ts also exist specifying the precise container, in this case MPEG-2 TS, but this has little relevance to MPEG-1 media.
.mp3 is the most common extension for files containing MP3 audio (typically MPEG-1 Audio, sometimes MPEG-2 Audio). An MP3 file is typically an uncontained stream of raw audio; the conventional way to tag MP3 files is by writing data to \"garbage\" segments of each frame, which preserve the media information but are discarded by the player. This is similar in many respects to how raw .AAC files are tagged (but this is less supported nowadays, e.g. iTunes).
Note that although it would apply, .mpg does not normally append raw AAC or AAC in MPEG-2 Part 7 Containers. The .aac extension normally denotes these audio files
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# Mumia Abu-Jamal
**Mumia Abu-Jamal** (born **Wesley Cook**;`{{r|Smith 2018}}`{=mediawiki} April 24, 1954) is an American political activist and journalist who was convicted of murder and sentenced to death in 1982 for the 1981 murder of Philadelphia police officer Daniel Faulkner. While on death row, he wrote and commented on the criminal justice system in the United States. After numerous appeals, his death sentence was overturned by a federal court. In 2011, the prosecution agreed to a sentence of life imprisonment without parole. He entered the general prison population early the following year.
Beginning at the age of 14 in 1968, Abu-Jamal became involved with the Black Panther Party and was a member until October 1970, leaving the party at age 16. After leaving, he completed his high school education, and later became a radio reporter. He eventually served as president of the Philadelphia Association of Black Journalists (1978--1980). He supported MOVE, a Philadelphia-based organization, and covered the 1978 confrontation in which one police officer was killed. The MOVE Nine were the members who were arrested and convicted of murder in that case.
Since 1982, the murder trial of Abu-Jamal has been seriously criticized for constitutional failings; some have claimed that he is innocent, and many opposed his death sentence. The Faulkner family, politicians, and other groups involved with law enforcement, state and city governments argue that Abu-Jamal\'s trial was fair, his guilt beyond question, and his death sentence justified.
When his death sentence was overturned by a federal court in 2001, he was described as \"perhaps the world\'s best-known death-row inmate\" by *The New York Times*. During his imprisonment, Abu-Jamal has published books and commentaries on social and political issues; his first book was *Live from Death Row* (1995).
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# Mumia Abu-Jamal
## Early life and activism {#early_life_and_activism}
Abu-Jamal was born Wesley Cook in Philadelphia, Pennsylvania, where he grew up. He has a younger brother named William. They attended local public schools. In 1968, a high school teacher, a Kenyan man instructing a class on African cultures, encouraged the students to take African or Arabic names for classroom use; he gave Cook the name \"Mumia\". According to Abu-Jamal, \"Mumia\" means \"Prince\" and was the name of several Kenyan anti-colonial African nationalists who fought in the Mau Mau uprising before Kenyan independence.
### Involvement with the Black Panthers {#involvement_with_the_black_panthers}
Abu-Jamal has described being \"kicked \... into the Black Panther Party\" as a teenager of 14, after suffering a beating from \"white racists\" and a policeman for trying to disrupt a 1968 rally for Independent candidate George Wallace, former governor of Alabama, who was running on a racist platform. From then, he helped form the Philadelphia branch of the Black Panther Party with Defense Captain Reggie Schell, and other Panthers. He was appointed as the chapter\'s \"Lieutenant of Information,\" responsible for writing information and news communications. In an interview in the early years, Abu-Jamal quoted Mao Zedong, saying, \"Political power grows out of the barrel of a gun\". That same year, he dropped out of Benjamin Franklin High School and began living at the branch\'s headquarters.
He spent late 1969 in New York City and early 1970 in Oakland, living and working with BPP colleagues in those cities; the party\'s headquarters based in Oakland. He was a party member from May 1969 until October 1970. During this period, he was subject to illegal surveillance as part of the Federal Bureau of Investigation\'s COINTELPRO program, with which the Philadelphia police cooperated. The FBI was working to infiltrate black radical groups and to disrupt them by creating internal dissension.
## Return to education {#return_to_education}
After leaving the Panthers, Abu-Jamal returned as a student to his former high school. He was suspended for distributing literature calling for \"black revolutionary student power\". He led unsuccessful protests to change the school name to Malcolm X High, to honor the major African-American leader who had been killed in New York by political opponents.
After attaining his GED, Abu-Jamal studied briefly at Goddard College in rural Vermont. He returned to Philadelphia.
## Marriages and family {#marriages_and_family}
Cook adopted the surname Abu-Jamal (\"father of Jamal\" in Arabic) after the birth of his first child, son Jamal, on July 18, 1971. He married Jamal\'s mother Biba in 1973, but they did not stay together long. Their daughter, Lateefa, was born shortly after the wedding. The couple divorced.
In 1977, Abu-Jamal married again, to his second wife, Marilyn (known as \"Peachie\"). Their son, Mazi, was born in early 1978. By 1981, Abu-Jamal had divorced Peachie and had married his third (and last) wife, Wadiya, who died unexpectedly on December 27, 2022.
## Radio journalism career {#radio_journalism_career}
By 1975, Abu-Jamal was working in radio newscasting, first at Temple University\'s WRTI and then at commercial enterprises. In 1975, he was employed at radio station WHAT, and he became host of a weekly feature program at WCAU-FM in 1978. He also worked for brief periods at radio station WPEN. He became active in the local chapter of the Marijuana Users Association of America.
From 1979 to 1981, he worked at National Public Radio (NPR) affiliate WHYY. The management asked him to resign, saying that he did not maintain a sufficiently objective approach in his presentation of news. As a radio journalist, Abu-Jamal was renowned for identifying with and covering the MOVE anarcho-primitivist commune in West Philadelphia\'s Powelton Village neighborhood. He reported on the 1979--80 trial of the \"MOVE Nine\", who were convicted of the murder of police officer James Ramp. Abu-Jamal had several high-profile interviews, including with Julius Erving, Bob Marley, and Alex Haley. He was elected president of the Philadelphia Association of Black Journalists.
Before joining MOVE, Abu-Jamal reported on the organization. When he joined MOVE, he said it was because of his love of the people in the organization. Thinking back on it later, he said he \"was probably enraged as well\".
In December 1981, Abu-Jamal was working as a taxicab driver in Philadelphia two nights a week to supplement his income. He had been working part-time as a reporter for WDAS, then an African American oriented and minority-owned radio station.
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# Mumia Abu-Jamal
## Traffic stop and murder of officer Faulkner {#traffic_stop_and_murder_of_officer_faulkner}
At 3:55 am on December 9, 1981, in Philadelphia, close to the intersection at 13th and Locust Streets, Philadelphia Police Department officer Daniel Faulkner conducted a traffic stop on a vehicle belonging to and driven by William Cook, Abu-Jamal\'s younger brother. Faulkner and Cook became engaged in a physical confrontation. Driving his cab in the vicinity, Abu-Jamal observed the altercation, parked, and ran across the street toward Cook\'s car. Faulkner was shot in the back and face. He shot Abu-Jamal in the stomach. Faulkner died at the scene from the gunshot to his head.
### Arrest and trial {#arrest_and_trial}
Police arrived and arrested Abu-Jamal, who was found to be wearing a shoulder holster. His revolver, which had five spent cartridges, was beside him. He was taken directly from the scene of the shooting to Thomas Jefferson University Hospital, where he received treatment for his wound. He was next taken to Police Headquarters, where he was charged and held for trial in the first-degree murder of Officer Faulkner.
### Prosecution case at trial {#prosecution_case_at_trial}
The prosecution presented four witnesses to the court about the shootings. Robert Chobert, a cab driver who testified he was parked behind Faulkner, identified Abu-Jamal as the shooter. Cynthia White testified that Abu-Jamal emerged from a nearby parking lot and shot Faulkner. Michael Scanlan, a motorist, testified that from two car lengths away he saw a man matching Abu-Jamal\'s description run across the street from a parking lot and shoot Faulkner. Albert Magilton testified to seeing Faulkner pull over Cook\'s car. As Abu-Jamal started to cross the street toward them, Magilton turned away and did not see what happened next.
The prosecution presented two witnesses from the hospital where Abu-Jamal was treated. Hospital security guard Priscilla Durham and police officer Garry Bell testified that Abu-Jamal said in the hospital, \"I shot the motherfucker, and I hope the motherfucker dies.\"
A .38 caliber Charter Arms revolver, belonging to Abu-Jamal, with five spent cartridges, was retrieved beside him at the scene. He was wearing a shoulder holster. Anthony Paul, the Supervisor of the Philadelphia Police Department\'s firearms identification unit, testified at trial that the cartridge cases and rifling characteristics of the weapon were consistent with bullet fragments taken from Faulkner\'s body. Tests to confirm that Abu-Jamal had handled and fired the weapon were not performed. Contact with arresting police and other surfaces at the scene could have compromised the forensic value of such tests.
### Defense case at trial {#defense_case_at_trial}
The defense maintained that Abu-Jamal was innocent, and that the prosecution witnesses were unreliable. The defense presented nine character witnesses, including poet Sonia Sanchez, who testified that Abu-Jamal was \"viewed by the black community as a creative, articulate, peaceful, genial man\". Another defense witness, Dessie Hightower, testified that he saw a man running along the street shortly after the shooting, although he did not see the shooting itself. His testimony contributed to the development of a \"running man theory\", based on the possibility that a \"running man\" may have been the shooter. Veronica Jones also testified for the defense, but she did not testify to having seen another man. Other potential defense witnesses refused to appear in court. Abu-Jamal did not testify in his own defense, nor did his brother, William Cook. Cook had repeatedly told investigators at the crime scene: \"I ain\'t got nothing to do with this!\"
### Verdict and sentence {#verdict_and_sentence}
After three hours of deliberations, the jury presented a unanimous guilty verdict.
In the sentencing phase of the trial, Abu-Jamal read to the jury from a prepared statement. He was cross-examined about issues relevant to the assessment of his character by Joseph McGill, the prosecuting attorney.
In his statement, Abu-Jamal criticized his attorney as a \"legal trained lawyer\", who was imposed on him against his will and who \"knew he was inadequate to the task and chose to follow the directions of this black-robed conspirator \[referring to the judge\], Albert Sabo, even if it meant ignoring my directions.\" He claimed that his rights had been \"deceitfully stolen\" from him by Sabo, particularly focusing on the denial of his request to receive defense assistance from John Africa, who was not an attorney, and being prevented from proceeding *pro se*. He quoted remarks of John Africa, and said:
Abu-Jamal was sentenced to death by the unanimous decision of the jury.
Amnesty International has objected to the introduction by the prosecution at the time of his sentencing of statements from when he was an activist as a youth. It also protested the politicization of the trial, noting that there was documented recent history in Philadelphia of police abuse and corruption, including fabricated evidence and use of excessive force. Amnesty International concluded \"that the proceedings used to convict and sentence Mumia Abu-Jamal to death were in violation of minimum international standards that govern fair trial procedures and the use of the death penalty\".
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# Mumia Abu-Jamal
## Appeals and review {#appeals_and_review}
### State appeals {#state_appeals}
The Supreme Court of Pennsylvania on March 6, 1989, heard and rejected a direct appeal of his conviction. It subsequently denied rehearing. The Supreme Court of the United States denied his petition for writ of *certiorari* on October 1, 1990, and denied his petition for rehearing twice up to June 10, 1991.
On June 1, 1995, Abu-Jamal\'s death warrant was signed by Pennsylvania Governor Tom Ridge. Its execution was suspended while Abu-Jamal pursued state post-conviction review. At the post-conviction review hearings, new witnesses were called. William \"Dales\" Singletary testified that he saw the shooting, and that the gunman was the passenger in Cook\'s car. Singletary\'s account contained discrepancies which rendered it \"not credible\" in the opinion of the court.
The six judges of the Supreme Court of Pennsylvania ruled unanimously that all issues raised by Abu-Jamal, including the claim of ineffective assistance of counsel, were without merit. The Supreme Court of the United States denied a petition for *certiorari* against that decision on October 4, 1999, enabling Ridge to sign a second death warrant on October 13, 1999. Its execution was stayed as Abu-Jamal began to seek federal *habeas corpus* review.
In 1999, Arnold Beverly claimed that he and an unnamed assailant, not Mumia Abu-Jamal, shot Daniel Faulkner as part of a contract killing because Faulkner was interfering with graft and payoff to corrupt police. As Abu-Jamal\'s defense team prepared another appeal in 2001, they were divided over use of the Beverly affidavit. Some thought it usable and others rejected Beverly\'s story as \"not credible\".
Private investigator George Newman claimed in 2001 that Chobert had recanted his testimony. Commentators noted that police and news photographs of the crime scene did not show Chobert\'s taxi, and that Cynthia White, the only witness at the original trial to testify to seeing the taxi, had previously provided crime scene descriptions that omitted it. Cynthia White was declared dead by the state of New Jersey in 1992, but Pamela Jenkins claimed that she saw White alive as late as 1997. The Free Mumia Coalition has claimed that White was a police informant and that she falsified her testimony against Abu-Jamal.
Kenneth Pate, who was imprisoned with Abu-Jamal on other charges, has since claimed that his step-sister Priscilla Durham, a hospital security guard, admitted later she had not heard the \"hospital confession\" to which she had testified at trial. The hospital doctors said that Abu-Jamal was \"on the verge of fainting\" when brought in, and they did not hear any such confession.
In 2008, the Supreme Court of Pennsylvania rejected a further request from Abu-Jamal for a hearing into claims that the trial witnesses perjured themselves, on the grounds that he had waited too long before filing the appeal.
On March 26, 2012, the Supreme Court of Pennsylvania rejected his appeal for retrial. His defense had asserted, based on a 2009 report by the National Academy of Sciences, that forensic evidence presented by the prosecution and accepted into evidence in the original trial was unreliable. This was reported as Abu-Jamal\'s last legal appeal.
On April 30, 2018, the Pennsylvania Supreme Court ruled that Abu-Jamal would not be immediately granted another appeal and that the proceedings had to continue until August 30 of that year. The defense argued that former Pennsylvania Supreme Court Chief justice Ronald D. Castille should have recused himself from the 2012 appeals decision after his involvement as Philadelphia District Attorney (DA) in the 1989 appeal. Both sides of the 2018 proceedings repeatedly cited a 1990 letter sent by Castille to then-Governor Bob Casey, urging Casey to sign the execution warrants of those convicted of murdering police. This letter, demanding Casey send \"a clear and dramatic message to all cop killers,\" was claimed as one of many reasons to suspect Castille\'s bias in the case. Philadelphia\'s current DA Larry Krasner stated he could not find any document supporting the defense\'s claim. On August 30, 2018, the proceedings to determine another appeal were once again extended and a ruling on the matter was delayed for at least 60 more days.
In April 2019, Krasner agreed drop his opposition a new appeal effort for Abu-Jamal, thus paving the way for a new hearing. In March 2023, Philadelphia-based Common Pleas Court Judge Lucretia Clemons would block this latest appeal effort.
### Federal District Court 2001 ruling {#federal_district_court_2001_ruling}
The Free Mumia Coalition published statements by William Cook and his brother Abu-Jamal in the spring of 2001. Cook, who had been stopped by the police officer, had not made any statement before April 29, 2001, and did not testify at his brother\'s trial. In 2001 he said that he had not seen who had shot Faulkner. Abu-Jamal did not make any public statements about Faulkner\'s murder until May 4, 2001. In his version of events, he claimed that he was sitting in his cab across the street when he heard shouting, saw a police vehicle, and heard the sound of gunshots. Upon seeing his brother appearing disoriented across the street, Abu-Jamal ran to him from the parking lot and was shot by a police officer.
In 2001, Judge William H. Yohn, Jr. of the United States District Court for the Eastern District of Pennsylvania upheld the conviction, saying that Abu-Jamal did not have the right to a new trial. He vacated the sentence of death on December 18, 2001, citing irregularities in the penalty phase of the trial and the original process of sentencing. He said that \"the jury instructions and verdict sheet in this case involved an unreasonable application of federal law. The charge and verdict form created a reasonable likelihood that the jury believed it was precluded from considering any mitigating circumstance that had not been found unanimously to exist.\" He ordered the State of Pennsylvania to commence new sentencing proceedings within 180 days, and ruled unconstitutional the requirement that a jury be unanimous in its finding of circumstances mitigating against a sentence of death.
Eliot Grossman and Marlene Kamish, attorneys for Abu-Jamal, criticized the ruling on the grounds that it denied the possibility of a *trial de novo*, at which they could introduce evidence that their client had been framed. Prosecutors also criticized the ruling. Officer Faulkner\'s widow Maureen said the judgment would allow Abu-Jamal, whom she described as a \"remorseless, hate-filled killer\", to \"be permitted to enjoy the pleasures that come from simply being alive\". Both parties appealed.
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# Mumia Abu-Jamal
## Appeals and review {#appeals_and_review}
### Federal appeal and review {#federal_appeal_and_review}
On December 6, 2005, the Third Circuit Court of Appeals admitted four issues for appeal of the ruling of the District Court:
1. in relation to sentencing, whether the jury verdict form had been flawed and the judge\'s instructions to the jury had been confusing;
2. in relation to conviction and sentencing, whether racial bias in jury selection existed to an extent tending to produce an inherently biased jury and therefore an unfair trial (the *Batson* claim);
3. in relation to conviction, whether the prosecutor improperly attempted to reduce jurors\' sense of responsibility by telling them that a guilty verdict would be subsequently vetted and subject to appeal; and
4. in relation to post-conviction review hearings in 1995--1996, whether the presiding judge, who had also presided at the trial, demonstrated unacceptable bias in his conduct.
The Third Circuit Court heard oral arguments in the appeals on May 17, 2007, at the United States Courthouse in Philadelphia. The appeal panel consisted of Chief Judge Anthony Joseph Scirica, Judge Thomas Ambro, and Judge Robert Cowen. The Commonwealth of Pennsylvania sought to reinstate the sentence of death, on the basis that Yohn\'s ruling was flawed, as he should have deferred to the Pennsylvania Supreme Court which had already ruled on the issue of sentencing. The prosecution said that the *Batson* claim was invalid because Abu-Jamal made no complaints during the original jury selection.
The resulting jury was racially mixed, with 2 blacks and 10 whites at the time of the unanimous conviction, but defense counsel told the Third Circuit Court that Abu-Jamal did not get a fair trial because the jury was racially biased, misinformed, and the judge was a racist. He noted that the prosecution used eleven out of fourteen peremptory challenges to eliminate prospective black jurors. Terri Maurer-Carter, a former Philadelphia court stenographer, stated in a 2001 affidavit that she overheard Judge Sabo say \"Yeah, and I\'m going to help them fry the nigger,\" in the course of a conversation with three people present regarding Abu-Jamal\'s case. Sabo denied having made any such comment.
On March 27, 2008, the three-judge panel issued a majority 2--1 opinion upholding Yohn\'s 2001 opinion but rejecting the bias and *Batson* claims, with Judge Ambro dissenting on the *Batson* issue. On July 22, 2008, Abu-Jamal\'s formal petition seeking reconsideration of the decision by the full Third Circuit panel of 12 judges was denied. On April 6, 2009, the United States Supreme Court refused to hear Abu-Jamal\'s appeal, allowing his conviction to stand.
On January 19, 2010, the Supreme Court ordered the appeals court to reconsider its decision to rescind the death penalty. The same three-judge panel convened in Philadelphia on November 9, 2010, to hear oral argument. On April 26, 2011, the Third Circuit Court of Appeals reaffirmed its prior decision to vacate the death sentence on the grounds that the jury instructions and verdict form were ambiguous and confusing. The Supreme Court declined to hear the case in October.
### Death penalty dropped {#death_penalty_dropped}
On December 7, 2011, District Attorney of Philadelphia R. Seth Williams announced that prosecutors, with the support of the victim\'s family, would no longer seek the death penalty for Abu-Jamal and would accept a sentence of life imprisonment without parole. This sentence was reaffirmed by the Superior Court of Pennsylvania on July 9, 2013.
After the press conference on the sentence, widow Maureen Faulkner said that she did not want to relive the trauma of another trial. She understood that it would be extremely difficult to present the case against Abu-Jamal again, after the passage of 30 years and the deaths of several key witnesses. She also reiterated her belief that Abu-Jamal will be punished further after death.
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# Mumia Abu-Jamal
## Life as a prisoner {#life_as_a_prisoner}
In 1991, Abu-Jamal published an essay in the *Yale Law Journal*, on the death penalty and his death row experience. In May 1994, Abu-Jamal was engaged by NPR\'s *All Things Considered* program to deliver a series of monthly three-minute commentaries on crime and punishment. The broadcast plans and commercial arrangement were canceled following condemnations from, among others, the Fraternal Order of Police and Senate Minority Leader Bob Dole. Abu-Jamal sued NPR for not airing his work, but a federal judge dismissed the suit. His commentaries later were published in May 1995 as part of his first book, *Live from Death Row.*
In 1996, he completed a B.A. degree via correspondence classes at Goddard College, which he had attended for a time as a young man. He has been invited as commencement speaker by a number of colleges and has participated via recordings. In 1999, Abu-Jamal was invited to record a keynote address for the graduating class at Evergreen State College in Washington State. The event was protested by some. In 2000, he recorded a commencement address for Antioch College. The now defunct New College of California School of Law presented him with an honorary degree \"for his struggle to resist the death penalty.\"
On October 5, 2014, he gave the commencement speech at Goddard College, via playback of a recording. As before, the choice of Abu-Jamal was controversial. Ten days later the Pennsylvania legislature had passed an addition to the Crime Victims Act called \"Revictimization Relief.\" The new provision is intended to prevent actions that cause \"a temporary or permanent state of mental anguish\" to those who have previously been victimized by crime. It was signed by Republican governor Tom Corbett five days later. Commentators suggest that the bill was directed to control Abu-Jamal\'s journalism, book publication, and public speaking, and that it would be challenged on the grounds of free speech.
With occasional interruptions due to prison disciplinary actions, Abu-Jamal has for many years been a regular commentator on an online broadcast, sponsored by Prison Radio. He also is published as a regular columnist for *Junge Welt,* a Marxist newspaper in Germany. For almost a decade, Abu-Jamal taught introductory courses in Georgist economics by correspondence to other prisoners around the world.
In addition, he has written and published several books: *Live From Death Row* (1995), a diary of life on Pennsylvania\'s death row; *All Things Censored* (2000), a collection of essays examining issues of crime and punishment; *Death Blossoms: Reflections from a Prisoner of Conscience* (2003), in which he explores religious themes; and *We Want Freedom: A Life in the Black Panther Party* (2004), a history of the Black Panthers that draws on his own experience and research, and discusses the federal government\'s program known as COINTELPRO to disrupt black activist organizations.
In 1995, Abu-Jamal was punished with solitary confinement for engaging in entrepreneurship contrary to prison regulations. Subsequent to the airing of the 1996 HBO documentary *Mumia Abu-Jamal: A Case for Reasonable Doubt?,* which included footage from visitation interviews conducted with him, the Pennsylvania Department of Corrections banned outsiders from using any recording equipment in state prisons.
In litigation before the U.S. Court of Appeals, in 1998, Abu-Jamal successfully established his right while in prison to write for financial gain. The same litigation also established that the Pennsylvania Department of Corrections had illegally opened his mail in an attempt to establish whether he was earning money by his writing.
When, for a brief time in August 1999, Abu-Jamal began delivering his radio commentaries live on the Pacifica Network\'s *Democracy Now!* weekday radio newsmagazine, prison staff severed the connecting wires of his telephone from their mounting in mid-performance. He was later allowed to resume his broadcasts, and hundreds of his broadcasts have been aired on Pacifica Radio.
Following the overturning of his death sentence, Abu-Jamal was sentenced to life in prison in December 2011. At the end of January 2012, he was shifted from the isolation of death row into the general prison population at State Correctional Institution -- Mahanoy.
In August 2015, his attorneys filed suit in the U.S. District Court for the Middle District of Pennsylvania, alleging that he has not received appropriate medical care for his serious health conditions. In April 2021, he tested positive for COVID-19 and was scheduled for heart surgery to relieve blocked coronary arteries.
In 2022, Brown University\'s John Hay Library acquired Abu-Jamal\'s personal papers as part of its Voices of Mass Incarceration collecting initiative. According to a Brown University archivist, the Abu-Jamal collection \"is the largest and only collection relating to a person who is still incarcerated.\"
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# Mumia Abu-Jamal
## Popular support and opposition {#popular_support_and_opposition}
Labor unions, politicians, advocates, educators, the NAACP Legal Defense and Educational Fund, and human rights advocacy organizations such as Human Rights Watch and Amnesty International have expressed concern about the impartiality of the trial of Abu-Jamal. Amnesty International neither takes a position on the guilt or innocence of Abu-Jamal nor classifies him as a political prisoner.
The family of Daniel Faulkner, the Commonwealth of Pennsylvania, the City of Philadelphia, politicians, and the Fraternal Order of Police have continued to support the original trial and sentencing of the journalist. In August 1999, the Fraternal Order of Police called for an economic boycott against all individuals and organizations that support Abu-Jamal. Many such groups operate within the Prison-Industrial Complex, a system which Abu-Jamal has frequently criticized.
Partly based on his own writing, Abu-Jamal and his cause have become widely known internationally, and other groups have classified him as a political prisoner. About 25 cities, including Montreal, Palermo, and Paris, have made him an honorary citizen.
In 2001, he received the sixth biennial Erich Mühsam Prize, named after an anarcho-communist essayist, which recognizes activism in line with that of its namesake. In October 2002, he was made an honorary member of the German political organization Union of Persecutees of the Nazi Regime.
On April 29, 2006, a newly paved road in the Parisian suburb of Saint-Denis was named Rue Mumia Abu-Jamal in his honor. In protest of the street-naming, U.S. Congressman Michael Fitzpatrick and Senator Rick Santorum, both members of the Republican Party of Pennsylvania, introduced resolutions in both Houses of Congress condemning the decision. The House of Representatives voted 368--31 in favor of Fitzpatrick\'s resolution. In December 2006, the 25th anniversary of the murder, the executive committee of the Republican Party for the 59th Ward of the City of Philadelphia---covering approximately Germantown, Philadelphia---filed two criminal complaints in the French legal system against the city of Paris and the city of Saint-Denis, accusing the municipalities of \"glorifying\" Abu-Jamal and alleging the offense \"apology or denial of crime\" in respect of their actions.
In 2007, the widow of Officer Faulkner co-authored a book with Philadelphia radio journalist Michael Smerconish titled *Murdered by Mumia: A Life Sentence of Pain, Loss, and Injustice.* The book was part memoir of Faulkner\'s widow and part discussion in which they chronicled Abu-Jamal\'s trial and discussed evidence for his conviction. They also discussed support for the death penalty.
In early 2014, President Barack Obama nominated Debo Adegbile, a former lawyer for the NAACP Legal Defense Fund, to head the civil rights division of the Justice Department. He had worked on Abu-Jamal\'s case, and his nomination was rejected by the U.S. Senate on a bipartisan basis because of that.
After Goddard College invited Abu-Jamal to give a recorded commencement speech in 2014 and an outcry by the police union against this, the Revictimization Relief Act was introduced, passed and signed into Pennsylvania law. It allowed victims and prosecutors to sue if a perpetrator causes a \"state of mental anguish\" by perpetuating \"the continuing effect of a crime on the victim.\" The law was struck down in April 2015 as a vague and overbroad restriction on free speech.
On April 10, 2015, Marylin Zuniga, a teacher at Forest Street Elementary School in Orange, New Jersey, was suspended without pay after asking her students to write cards to Abu-Jamal, who was ill in prison due to complications from diabetes, without approval from the school or parents. Some parents and police leaders denounced her actions. Conversely, some community members, parents, teachers, and professors expressed support for Zuniga and condemned her suspension. Scholars and educators nationwide, including Noam Chomsky, Chris Hedges and Cornel West among others, signed a letter calling for her immediate reinstatement. On May 13, 2015, the Orange Preparatory Academy board voted to dismiss Marylin Zuniga after hearing from her and several of her supporters.
## Written works {#written_works}
- *Beneath the Mountain: An Anti-Prison Reader*, City Lights Publishers (2024), `{{ISBN|9780872869264}}`{=mediawiki}
- *Murder Incorporated - Dreaming of Empire: Book One (Empire, Genocide, and Manifest Destiny)* (2018), Prison Radio, `{{ISBN|9780998960012}}`{=mediawiki}, co-authored by Stephen Vittoria
- *Have Black Lives Ever Mattered?* City Lights Publishers (2017), `{{ISBN|9780872867383}}`{=mediawiki}
- *Writing on the Wall: Selected Prison Writings of Mumia Abu-Jamal*, City Lights Publishers (2015), `{{ISBN|978-0872866751}}`{=mediawiki}
- *The Classroom and the Cell: Conversations on Black Life in America*, Third World Press (2011), `{{ISBN|978-0883783375}}`{=mediawiki}
- *Jailhouse Lawyers: Prisoners Defending Prisoners v. the U.S.A.*, City Lights Publishers (2009), `{{ISBN|978-0872864696}}`{=mediawiki}
- *We Want Freedom: A Life in the Black Panther Party*, South End Press (2008), `{{ISBN|978-0896087187}}`{=mediawiki}
- *Faith of Our Fathers: An Examination of the Spiritual Life of African and African-American People*, Africa World Press (2003), `{{ISBN|978-1592210190}}`{=mediawiki}
- *All Things Censored*, Seven Stories Press (2000), `{{ISBN|978-1583220221}}`{=mediawiki}
- *Death Blossoms: Reflections from a Prisoner of Conscience*, Plough Publishing House (1997), `{{ISBN|978-0874860863}}`{=mediawiki}
- *Live from Death Row*, Harper Perennial (1996), `{{ISBN|978-0380727667}}`{=mediawiki}
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# Mumia Abu-Jamal
## Representation in popular culture {#representation_in_popular_culture}
- HBO aired the documentary film *Mumia Abu-Jamal: A Case for Reasonable Doubt?* in 1996; this 57-minute film about the 1982 murder trial is directed by John Edginton. There are two versions by Edginton, both produced by Otmoor Productions. The second is 72 minutes long and contains additional information by witnesses.
- An album containing spoken word from Abu-Jamal with four tracks by powerviolence band Man Is the Bastard was released in 2002.
- Political hip hop artist Immortal Technique featured Abu-Jamal on his second album *Revolutionary Vol. 2*.
- The punk band Anti-Flag has a speech from Mumia Abu-Jamal in the intro to their song \"The Modern Rome Burning\" from their 2008 album *The Bright Lights of America*. The speech also appears on the end of their preceding track \"Vices\".
- The rock band Rage Against the Machine mentions Mumia in 2 of their songs --- \"Guerrilla Radio\" and \"Voice of the Voiceless\" --- on their 1999 album *The Battle of Los Angeles.*
- Alternative hip-hop band Flobots, known for criticizing US politics and calls for action, referenced Abu-Jamal in their song \"Same Thing\" from their 2007 debut album *Fight with Tools*. The song mentions many people and topics, and the line that references Abu-Jamal also references Leonard Peltier; it reads \"Free Mumia and Leonard Peltier\".
- The documentary film *In Prison My Whole Life* (2008), directed by Marc Evans, and written by Evans and William Francome, explores the life of Abu-Jamal
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# MPEG-3
**MPEG-3** was the designation for an abandoned plan to create a group of audio and video coding standards agreed upon by the Moving Picture Experts Group (MPEG) designed to handle HDTV signals at 1080p in the range of 20 to 40 megabits per second. MPEG-3 was launched as an effort to address the need of an HDTV standard while work on MPEG-2 was underway, but it was soon discovered that MPEG-2, at high data rates, would accommodate HDTV. Thus, in 1992 HDTV was included as a separate profile in the MPEG-2 standard and MPEG-3 was rolled into MPEG-2
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# MPEG-4
**MPEG-4** is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) (ISO/IEC JTC 1/SC29/WG11) under the formal standard ISO/IEC 14496 -- *Coding of audio-visual objects*. Uses of MPEG-4 include compression of audiovisual data for Internet video and CD distribution, voice (telephone, videophone) and broadcast television applications. The MPEG-4 standard was developed by a group led by Touradj Ebrahimi (later the JPEG president) and Fernando Pereira.
## Background
MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2 and other related standards, adding new features such as (extended) VRML support for 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for externally specified digital rights management and various types of interactivity. AAC (Advanced Audio Coding) was standardized as an adjunct to MPEG-2 (as Part 1) before MPEG-4 was issued.
MPEG-4 is still an evolving standard and is divided into a number of parts. Companies promoting MPEG-4 compatibility do not always clearly state which \"part\" level compatibility they are referring to. The key parts to be aware of are MPEG-4 Part 2 (including Advanced Simple Profile, used by codecs such as DivX, Xvid, Nero Digital, RealMedia, 3ivx, H.263 and by QuickTime 6) and MPEG-4 part 10 (MPEG-4 AVC/H.264 or Advanced Video Coding, used by the x264 encoder, Nero Digital AVC, QuickTime 7, Flash Video, and high-definition video media like Blu-ray Disc).
Most of the features included in MPEG-4 are left to individual developers to decide whether or not to implement. This means that there are probably no complete implementations of the entire MPEG-4 set of standards. To deal with this, the standard includes the concept of \"profiles\" and \"levels\", allowing a specific set of capabilities to be defined in a manner appropriate for a subset of applications.
Initially, MPEG-4 was aimed primarily at low-bit-rate video communications; however, its scope as a multimedia coding standard was later expanded. MPEG-4 is efficient across a variety of bit rates ranging from a few kilobits per second to tens of megabits per second. MPEG-4 provides the following functions:
- Improved coding efficiency over MPEG-2
- Ability to encode mixed media data (video, audio, speech)
- Error resilience to enable robust transmission
- Ability to interact with the audio-visual scene generated at the receiver
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# MPEG-4
## Overview
MPEG-4 provides a series of technologies for developers, for various service-providers and for end users:
- MPEG-4 enables different software and hardware developers to create multimedia objects possessing better abilities of adaptability and flexibility to improve the quality of such services and technologies as digital television, animation graphics, the World Wide Web and their extensions.
- Data network providers can use MPEG-4 for data transparency. With the help of standard procedures, MPEG-4 data can be interpreted and transformed into other signal types compatible with any available network.
- The MPEG-4 format provides end users with a wide range of interaction with various animated objects.
- Standardized digital rights management signaling, otherwise known in the MPEG community as Intellectual Property Management and Protection (IPMP).
The MPEG-4 format can perform various functions, among which might be the following:
- Multiplexes and synchronizes data, associated with media objects, in such a way that they can be efficiently transported further via network channels.
- Interaction with the audio-visual scene, which is formed on the side of the receiver.
### Profiles and Levels {#profiles_and_levels}
MPEG-4 provides a large and rich set of tools for encoding.`{{vague|date=August 2023}}`{=mediawiki} Subsets of the MPEG-4 tool sets have been provided for use in specific applications.`{{vague|date=August 2023}}`{=mediawiki} These subsets, called \'Profiles\', limit the size of the tool set a decoder is required to implement. In order to restrict computational complexity, one or more \'Levels\' are set for each Profile. A Profile and Level combination allows:
- A codec builder to implement only the subset of the standard needed, while maintaining interworking with other MPEG-4 devices that implement the same combination.
- Checking whether MPEG-4 devices comply with the standard, referred to as conformance testing.
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# MPEG-4
## MPEG-4 Parts {#mpeg_4_parts}
MPEG-4 consists of several standards---termed \"parts\"---including the following (each part covers a certain aspect of the whole specification):
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part | Number | First public release date (first edition) | Latest public release date (last edition) | Latest amendment | Title | Description |
+=========+=======================+===========================================+===========================================+==================+==============================================================================================================+========================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================+
| Part 1 | ISO/IEC 14496-1 | 1999 | 2010 | 2014 | Systems | Describes synchronization and multiplexing of video and audio. For example, the MPEG-4 file format version 1 (obsoleted by version 2 defined in MPEG-4 Part 14). The functionality of a transport protocol stack for transmitting and/or storing content complying with ISO/IEC 14496 is not within the scope of 14496-1 and only the interface to this layer is considered (DMIF). Information about transport of MPEG-4 content is defined e.g. in MPEG-2 Transport Stream, RTP Audio Video Profiles and others. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 2 | ISO/IEC 14496-2 | 1999 | 2004 | 2009 | Visual | A compression format for visual data (video, still textures, synthetic images, etc.). Contains many profiles, including the Advanced Simple Profile (ASP), and the Simple Profile (SP). |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 3 | ISO/IEC 14496-3 | 1999 | 2009 | 2017 | Audio | A set of compression formats for perceptual coding of audio signals, including some variations of Advanced Audio Coding (AAC) as well as other audio/speech coding formats and tools (such as Audio Lossless Coding (ALS), Scalable Lossless Coding (SLS), Structured Audio, Text-To-Speech Interface (TTSI), HVXC, CELP and others) |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 4 | ISO/IEC 14496-4 | 2000 | 2004 | 2016 | Conformance testing | Describes procedures for testing conformance to other parts of the standard. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 5 | ISO/IEC 14496-5 | 2000 | 2001 | 2017 | Reference software | Provides reference software for demonstrating and clarifying the other parts of the standard. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 6 | ISO/IEC 14496-6 | 1999 | 2000 | | Delivery Multimedia Integration Framework (DMIF) | |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 7 | ISO/IEC TR 14496-7 | 2002 | 2004 | | Optimized reference software for coding of audio-visual objects | Provides examples of how to make improved implementations (e.g., in relation to Part 5). |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 8 | ISO/IEC 14496-8 | 2004 | 2004 | | Carriage of ISO/IEC 14496 contents over IP networks | Specifies a method to carry MPEG-4 content on IP networks. It also includes guidelines to design RTP payload formats, usage rules of SDP to transport ISO/IEC 14496-1-related information, MIME type definitions, analysis on RTP security and multicasting. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 9 | ISO/IEC TR 14496-9 | 2004 | 2009 | | Reference hardware description | Provides hardware designs for demonstrating how to implement the other parts of the standard. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 10 | ISO/IEC 14496-10 | 2003 | 2014 | 2016 | Advanced Video Coding (AVC) | A compression format for video signals which is technically identical to the ITU-T H.264 standard. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 11 | ISO/IEC 14496-11 | 2005 | 2015 | | Scene description and application engine | Can be used for rich, interactive content with multiple profiles, including 2D and 3D versions. MPEG-4 Part 11 revised MPEG-4 Part 1 -- ISO/IEC 14496-1:2001 and two amendments to MPEG-4 Part 1. It describes a system level description of an application engine (delivery, lifecycle, format and behaviour of downloadable Java byte code applications) and the Binary Format for Scene (BIFS) and the Extensible MPEG-4 Textual (XMT) format -- a textual representation of the MPEG-4 multimedia content using XML, etc. (It is also known as BIFS, XMT, MPEG-J. MPEG-J was defined in MPEG-4 Part 21) |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 12 | ISO/IEC 14496-12 | 2004 | 2015 | 2017 | ISO base media file format | A file format for storing time-based media content. It is a general format forming the basis for a number of other more specific file formats (e.g. 3GP, Motion JPEG 2000, MPEG-4 Part 14). It is technically identical to ISO/IEC 15444-12 (JPEG 2000 image coding system -- Part 12). |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 13 | ISO/IEC 14496-13 | 2004 | 2004 | | Intellectual Property Management and Protection (IPMP) Extensions | MPEG-4 Part 13 revised an amendment to MPEG-4 Part 1 -- ISO/IEC 14496-1:2001/Amd 3:2004. It specifies common Intellectual Property Management and Protection (IPMP) processing, syntax and semantics for the carriage of IPMP tools in the bit stream, IPMP information carriage, mutual authentication for IPMP tools, a list of registration authorities required for the support of the amended specifications (e.g. CISAC), etc. It was defined due to the lack of interoperability of different protection mechanisms (different DRM systems) for protecting and distributing copyrighted digital content such as music or video. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 14 | ISO/IEC 14496-14 | 2003 | 2003 | 2010 | MP4 file format | It is also known as \"MPEG-4 file format version 2\". The designated container file format for MPEG-4 content, which is based on Part 12. It revises and completely replaces Clause 13 of ISO/IEC 14496-1 (MPEG-4 Part 1: Systems), in which the MPEG-4 file format was previously specified. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 15 | ISO/IEC 14496-15 | 2004 | 2022 | 2023 | Part 15: Carriage of network abstraction layer (NAL) unit structured video in the ISO base media file format | For storage of Part 10 video. File format is based on Part 12, but also allows storage in other file formats. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 16 | ISO/IEC 14496-16 | 2004 | 2011 | 2016 | Animation Framework eXtension (AFX) | It specifies MPEG-4 Animation Framework eXtension (AFX) model for representing 3D Graphics content. MPEG-4 is extended with higher-level synthetic objects for specifying geometry, texture, animation and dedicated compression algorithms. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 17 | ISO/IEC 14496-17 | 2006 | 2006 | | Streaming text format | Timed Text subtitle format |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 18 | ISO/IEC 14496-18 | 2004 | 2004 | 2014 | Font compression and streaming | For Open Font Format defined in Part 22. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 19 | ISO/IEC 14496-19 | 2004 | 2004 | | Synthesized texture stream | Synthesized texture streams are used for creation of very low bitrate synthetic video clips. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 20 | ISO/IEC 14496-20 | 2006 | 2008 | 2010 | Lightweight Application Scene Representation (LASeR) and Simple Aggregation Format (SAF) | LASeR requirements (compression efficiency, code and memory footprint) are fulfilled by building upon the existing the Scalable Vector Graphics (SVG) format defined by the World Wide Web Consortium. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 21 | ISO/IEC 14496-21 | 2006 | 2006 | | MPEG-J Graphics Framework eXtensions (GFX) | Describes a lightweight programmatic environment for advanced interactive multimedia applications -- a framework that marries a subset of the MPEG standard Java application environment (MPEG-J) with a Java API. (at \"FCD\" stage in July 2005, FDIS January 2006, published as ISO standard on 2006-11-22). |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 22 | ISO/IEC 14496-22 | 2007 | 2015 | 2017 | Open Font Format | OFFS is based on the OpenType version 1.4 font format specification, and is technically equivalent to that specification. Reached \"CD\" stage in July 2005, published as ISO standard in 2007 |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 23 | ISO/IEC 14496-23 | 2008 | 2008 | | Symbolic Music Representation (SMR) | Reached \"FCD\" stage in October 2006, published as ISO standard in 2008-01-28 |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 24 | ISO/IEC TR 14496-24 | 2008 | 2008 | | Audio and systems interaction | Describes the desired joint behavior of MPEG-4 File Format and MPEG-4 Audio. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 25 | ISO/IEC 14496-25 | 2009 | 2011 | | 3D Graphics Compression Model | Defines a model for connecting 3D Graphics Compression tools defined in MPEG-4 standards to graphics primitives defined in any other standard or specification. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 26 | ISO/IEC 14496-26 | 2010 | 2010 | 2016 | Audio Conformance | |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 27 | ISO/IEC 14496-27 | 2009 | 2009 | 2015 | 3D Graphics conformance | 3D Graphics Conformance summarizes the requirements, cross references them to characteristics, and defines how conformance with them can be tested. Guidelines are given on constructing tests to verify decoder conformance. |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 28 | ISO/IEC 14496-28 | 2012 | 2012 | | Composite font representation | |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 29 | ISO/IEC 14496-29 | 2014 | 2015 | | Web video coding | Text of Part 29 is derived from Part 10 - ISO/IEC 14496-10. Web video coding is a technology that is compatible with the Constrained Baseline Profile of ISO/IEC 14496-10 (the subset that is specified in Annex A for Constrained Baseline is a normative specification, while all remaining parts are informative). |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 30 | ISO/IEC 14496-30 | 2014 | 2014 | | Timed text and other visual overlays in ISO base media file format | It describes the carriage of some forms of timed text and subtitle streams in files based on ISO/IEC 14496-12 - W3C Timed Text Markup Language 1.0, W3C WebVTT (Web Video Text Tracks). The documentation of these forms does not preclude other definition of carriage of timed text or subtitles; see, for example, 3GPP Timed Text (3GPP TS 26.245). |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 31 | ISO/IEC 14496-31 | Under development (2018-05) | | | Video Coding for Browsers | Video Coding for Browsers (VCB) - a video compression technology that is intended for use within World Wide Web browser |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 32 | ISO/IEC CD 14496-32 | Under development | | | Conformance and reference software | |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Part 33 | ISO/IEC FDIS 14496-33 | Under development | | | Internet video coding | |
+---------+-----------------------+-------------------------------------------+-------------------------------------------+------------------+--------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
: MPEG-4 parts
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# MPEG-4
## MPEG-4 Parts {#mpeg_4_parts}
Profiles are also defined within the individual \"parts\", so an implementation of a part is ordinarily not an implementation of an entire part.
MPEG-1, MPEG-2, MPEG-7 and MPEG-21 are other suites of MPEG standards.
## Licensing
MPEG-4 contains patented technologies, the use of which requires licensing in countries that acknowledge software algorithm patents. Over two dozen companies claim to have patents covering MPEG-4. MPEG LA licenses patents required for MPEG-4 Part 2 Visual from a wide range of companies (audio is licensed separately) and lists all of its licensors and licensees on the site. New licenses for MPEG-4 System patents are under development and no new licenses are being offered while holders of its old MPEG-4 Systems license are still covered under the terms of that license for the patents listed.
The majority of patents used for the MPEG-4 Visual format are held by three Japanese companies: Mitsubishi Electric (255 patents), Hitachi (206 patents), and Panasonic (200 patents)
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# Morihei Ueshiba
was a Japanese martial artist and founder of the martial art of aikido. He is often referred to as \"the founder\" `{{Nihongo|''Kaiso''|開祖}}`{=mediawiki} or `{{Nihongo|[[sensei|''Ōsensei'']]|大先生/翁先生}}`{=mediawiki}, \"Great Teacher\".
The son of a landowner from Tanabe, Ueshiba studied a number of martial arts in his youth, and served in the Japanese Army during the Russo-Japanese War. After being discharged in 1907, he moved to Hokkaido as the head of a pioneer settlement; here he met and studied with Takeda Sōkaku, the headmaster of Daitō-ryū Aiki-jūjutsu. On leaving Hokkaido in 1919, Ueshiba joined the Ōmoto-kyō movement, a Shinto sect, in Ayabe, where he served as a martial arts instructor and opened his first dojo. He accompanied the head of the Ōmoto-kyō group, Onisaburo Deguchi, on an expedition to Mongolia in 1924, where they were captured by Chinese troops and returned to Japan. The following year, he had a profound spiritual experience, stating that, \"a golden spirit sprang up from the ground, veiled my body, and changed my body into a golden one.\" After this experience, his martial arts technique became gentler, with a greater emphasis on the control of ki.
Ueshiba moved to Tokyo in 1926, where he set up what would become the Aikikai Hombu Dojo. By this point he was comparatively famous in martial arts circles, and taught at this dojo and others around Japan, including in several military academies. In the aftermath of World War II the Hombu dojo was temporarily closed, but Ueshiba had by this point left Tokyo and retired to Iwama, and he continued training at the dojo he had set up there. From the end of the war until the 1960s, he worked to promote aikido throughout Japan and abroad. He died from liver cancer in 1969.
After Ueshiba\'s death, aikido continued to be promulgated by his students (many of whom became noted martial artists in their own right). It is now practiced around the world.
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# Morihei Ueshiba
## Tanabe, 1883--1912 {#tanabe_18831912}
Morihei Ueshiba was born in Nishinotani village (now part of the city of Tanabe), Wakayama Prefecture, Japan, on December 14, 1883, the fourth child (and only son) born to Yoroku Ueshiba and his wife Yuki.
The young Ueshiba was raised in a somewhat privileged setting. His father Yoroku was a wealthy gentleman farmer and minor politician, being an elected member of the Nishinotani village council for 22 consecutive years. His mother Yuki was from the Itokawa clan, a prominent local family who could trace their lineage back to the Heian period. Ueshiba was a rather weak, sickly child and bookish in his inclinations. At a young age his father encouraged him to take up sumo wrestling and swimming and entertained him with stories of his great-grandfather Kichiemon, who was considered a very strong samurai in his era. The need for such strength was further emphasized when the young Ueshiba witnessed his father being attacked by followers of a competing politician.
A major influence on Ueshiba\'s early education was his elementary schoolteacher Tasaburo Nasu, who was a Shinto priest and who introduced Ueshiba to the religion. At the age of six Ueshiba was sent to study at the Jizōderu Temple, but had little interest in the rote learning of Confucian education. However, his schoolmaster Mitsujo Fujimoto was also a priest of Shingon Buddhism, and taught the young Ueshiba some of the esoteric chants and ritual observances of the sect, which Ueshiba found intriguing. His interest in Buddhism was sufficiently great that his mother considered enrolling him in the priesthood, but his father Yoroku vetoed the idea. Ueshiba went to Tanabe Higher Elementary School and then to Tanabe Prefectural Middle School, but left formal education in his early teens, enrolling instead at a private abacus academy, the Yoshida Institute, to study accountancy. On graduating from the academy, he worked at a local tax office for a few months, but the job did not suit him and in 1901 he left for Tokyo, funded by his father. Ueshiba Trading, the stationery business which he opened there, was short-lived; unhappy with life in the capital, he returned to Tanabe less than a year later after suffering a bout of beri-beri. Shortly thereafter he married his childhood acquaintance Hatsu Itokawa.
In 1903, Ueshiba was called up for military service. He failed the initial physical examination, being shorter than the regulation 5 ft. To overcome this, he stretched his spine by attaching heavy weights to his legs and suspending himself from tree branches; when he re-took the physical exam he had increased his height by the necessary half-inch to pass. He was assigned to the Osaka Fourth Division, 37th Regiment, and was promoted to corporal of the 61st Wakayama regiment by the following year; after serving on the front lines during the Russo-Japanese War he was promoted to sergeant. He was discharged in 1907, and again returned to his father\'s farm in Tanabe. Here he befriended the writer and philosopher Minakata Kumagusu, becoming involved with Minakata\'s opposition to the Meiji government\'s Shrine Consolidation Policy. He and his wife had their first child, a daughter named Matsuko, in 1911.
Ueshiba studied several martial arts during his early life, and was renowned for his physical strength during his youth. During his sojourn in Tokyo he studied Kitō-ryū jujutsu under Takisaburo Tobari, and briefly enrolled in a school teaching Shinkage-ryū. His training in Gotō-ha Yagyū-ryu under Masakatsu Nakai started in 1903 and continued until 1908; although this training was sporadic due to his military service, Ueshiba was granted a Menkyo Kaiden (certificate of \"Total Transmission\") in 1908. In 1901 he received some instruction from Tozawa Tokusaburōin in Tenjin Shin\'yō-ryū jujutsu and he studied judo with Kiyoichi Takagi in Tanabe in 1911, after his father had a dojo built on the family compound to encourage his son\'s training. In 1907, after his return from the war, he was also presented with a certificate of enlightenment (*shingon inkyo*) by his childhood teacher Mitsujo Fujimoto.
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# Morihei Ueshiba
## Hokkaido, 1912--1920 {#hokkaido_19121920}
In the early part of the 20th century, the prefectural government of Hokkaido, Japan\'s northernmost island, were offering various grants and incentives for mainland Japanese groups willing to relocate there. At the time, Hokkaido was still largely unsettled by the Japanese, being occupied primarily by the indigenous Ainu. In 1910, Ueshiba travelled to Hokkaido in the company of his acquaintance Denzaburo Kurahashi, who had lived on the northern island before. His intent was to scout out a propitious location for a new settlement, and he found the site at Shirataki suitable for his plans. Despite the hardships he suffered on this journey (which included getting lost in snowstorms several times and an incident in which he nearly drowned in a freezing river), Ueshiba returned to Tanabe filled with enthusiasm for the project, and began recruiting families to join him. He became the leader of the Kishū Settlement Group, a collective of eighty-five pioneers who intended to settle in the Shirataki district and live as farmers; the group founded the village of Yubetsu (later Shirataki village) in August, 1912. Much of the funding for this project came from Ueshiba\'s father and his brothers-in-law Zenzo and Koshiro Inoue. Zenzo\'s son Noriaki was also a member of the settlement group.
Poor soil conditions and bad weather led to crop failures during the first three years of the project, but the group still managed to cultivate mint and farm livestock. The burgeoning timber industry provided a boost to the settlement\'s economy, and by 1918 there were over 500 families residing there. A fire in 1917 razed the entire village, leading to the departure of around twenty families. Ueshiba was attending a meeting over railway construction around 50 miles away, but on learning of the fire travelled back the entire distance on foot. He was elected to the village council that year, and took a prominent role in leading the reconstruction efforts. In the summer of 1918, Hatsu gave birth to their first son, Takemori.
The young Ueshiba met Takeda Sōkaku, the founder of Daitō-ryū Aiki-jūjutsu, at the Hisada Inn in Engaru, in March 1915. Ueshiba was deeply impressed with Takeda\'s martial art, and despite being on an important mission for his village at the time, abandoned his journey to spend the next month studying with Takeda. He requested formal instruction and began studying Takeda\'s style of jūjutsu in earnest, going so far as to construct a dojo at his home and inviting his new teacher to be a permanent house guest. He received a *kyōju dairi* certificate, a teaching license, for the system from Takeda in 1922, when Takeda visited him in Ayabe. Takeda also gave him a Yagyū Shinkage-ryū sword transmission scroll. Ueshiba then became a representative of Daitō-ryū, toured with Takeda as a teaching assistant and taught the system to others. The relationship between Ueshiba and Takeda was a complicated one. Ueshiba was an extremely dedicated student, dutifully attending to his teacher\'s needs and displaying great respect. However, Takeda overshadowed him throughout his early martial arts career, and Ueshiba\'s own students recorded the need to address what they referred to as \"the Takeda problem\".
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# Morihei Ueshiba
## Ayabe, 1920--1927 {#ayabe_19201927}
In November 1919, Ueshiba learned that his father Yoroku was ill, and was not expected to survive. Leaving most of his possessions to Takeda, Ueshiba left Shirataki with the apparent intention of returning to Tanabe to visit his ailing parent. En route he made a detour to Ayabe, near Kyoto, intending to visit Onisaburo Deguchi, the spiritual leader of the Ōmoto-kyō religion (Ueshiba\'s nephew Noriaki Inoue had already joined the religion and may have recommended it to his uncle). Ueshiba stayed at the Ōmoto-kyō headquarters for several days, and met with Deguchi, who told him that, \"There is nothing to worry about with your father\". On his return to Tanabe, Ueshiba found that Yoroku had died. Criticised by family and friends for arriving too late to see his father, Ueshiba went into the mountains with a sword and practised solo sword exercises for several days; this almost led to his arrest when the police were informed of a sword-wielding madman on the loose.
Within a few months, Ueshiba was back in Ayabe, having decided to become a full-time student of Ōmoto-kyō. In 1920 he moved his entire family, including his mother, to the Ōmoto compound; at the same time he also purchased enough rice to feed himself and his family for several years. That same year, Deguchi asked Ueshiba to become the group\'s martial arts instructor, and a dojo---the first of several that Ueshiba was to lead---was constructed on the centre\'s grounds. Ueshiba also taught Takeda\'s Daitō-ryū in neighbouring Hyōgo Prefecture during this period. His second son, Kuniharu, was born in 1920 in Ayabe, but died from illness the same year, along with three-year-old Takemori.
Takeda visited Ueshiba in Ayabe to provide instruction, although he was not a follower of Ōmoto and did not get along with Deguchi, which led to a cooling of the relationship between him and Ueshiba. Ueshiba continued to teach his martial art under the name \"Daitō-ryū Aiki-jūjutsu\", at the behest of his teacher. However, Deguchi encouraged Ueshiba to create his own style of martial arts, \"Ueshiba-ryū\", and sent many Ōmoto followers to study at the dojo. He also brought Ueshiba into the highest levels of the group\'s bureaucracy, making Ueshiba his executive assistant and putting him in charge of the Showa Seinenkai (Ōmoto-kyō\'s national youth organisation) and the Ōmoto Shobotai, a volunteer fire service.
His close relationship with Deguchi introduced Ueshiba to various members of Japan\'s far-right; members of the ultranationalist group the Sakurakai would hold meetings at Ueshiba\'s dojo, and he developed a friendship with the philosopher Shūmei Ōkawa during this period, as well as meeting with Nisshō Inoue and Kozaburō Tachibana. Deguchi also offered Ueshiba\'s services as a bodyguard to Kingoro Hashimoto, the Sakurakai\'s founder. Ueshiba\'s commitment to the goal of world peace, stressed by many biographers, must be viewed in the light of these relationships and his Ōmoto-kyō beliefs. His association with the extreme right-wing is understandable when one considers that Ōmoto-kyō\'s view of world peace was of a benevolent dictatorship by the Emperor of Japan, with other nations being subjugated under Japanese rule.
In 1921, in an event known as the `{{nihongo|First Ōmoto-kyō Incident|大本事件|''Ōmoto jiken''}}`{=mediawiki}, the Japanese authorities raided the compound, destroying the main buildings on the site and arresting Deguchi on charges of lèse-majesté. Ueshiba\'s dojo was undamaged and, over the following two years, he worked closely with Deguchi to reconstruct the group\'s centre, becoming heavily involved in farming work and serving as the group\'s \"Caretaker of Forms\", a role which placed him in charge of overseeing Ōmoto\'s move towards self-sufficiency. His son Kisshomaru was born in the summer of 1921.
Three years later, in 1924, Deguchi led a small group of Ōmoto-kyō disciples, including Ueshiba, on a journey to Mongolia at the invitation of retired naval captain Yutaro Yano and his associates within the ultra-nationalist Black Dragon Society. Deguchi\'s intent was to establish a new religious kingdom in Mongolia, and to this end he had distributed propaganda suggesting that he was the reincarnation of Genghis Khan. Allied with the Mongolian bandit Lu Zhankui, Deguchi\'s group were arrested in Tongliao by the Chinese authorities. Fortunately for Ueshiba, whilst Lu and his men were executed by firing squad, the Japanese group was released into the custody of the Japanese consul. They were returned under guard to Japan, where Deguchi was imprisoned for breaking the terms of his bail. During this expedition Ueshiba was given the Chinese alias Wang Shou-gao, rendered in Japanese as \"Moritaka\" -- he was reportedly very taken with this name and continued to use it intermittently for the rest of his life.
After returning to Ayabe, Ueshiba began a regimen of spiritual training, regularly retreating to the mountains or performing *misogi* in the Nachi Falls. As his prowess as a martial artist increased, his fame began to spread. He was challenged by many established martial artists, some of whom later became his students after being defeated by him. In the autumn of 1925 he was asked to give a demonstration of his art in Tokyo, at the behest of Admiral Isamu Takeshita; one of the spectators was Yamamoto Gonnohyōe, who requested that Ueshiba stay in the capital to instruct the Imperial Guard in his martial art. After a couple of weeks, however, Ueshiba took issue with several government officials who voiced concerns about his connections to Deguchi; he cancelled the training and returned to Ayabe.
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# Morihei Ueshiba
## Tokyo, 1927--1942 {#tokyo_19271942}
In 1926 Takeshita invited Ueshiba to visit Tokyo again. Ueshiba relented and returned to the capital, but while residing there was stricken with a serious illness. Deguchi visited his ailing student and, concerned for his health, commanded Ueshiba to return to Ayabe. The appeal of returning increased after Ueshiba was questioned by the police following his meeting with Deguchi; the authorities were keeping the Ōmoto-kyō leader under close surveillance. Angered at the treatment he had received, Ueshiba went back to Ayabe again. Six months later, this time with Deguchi\'s blessing, he and his family moved permanently to Tokyo. This move allowed Ueshiba to teach politicians, high-ranking military personnel, and members of the Imperial household; suddenly he was no longer an obscure provincial martial artist, but a sensei to some of Japan\'s most important citizens. Arriving in October 1927, the Ueshiba family set up home in the Shirokane district. The building proved too small to house the growing number of aikido students, and so the Ueshibas moved to larger premises, first in Mita district, then in Takanawa, and finally to a purpose-built hall in Shinjuku. This last location, originally named the Kobukan (*皇武館*), would eventually become the Aikikai Hombu Dojo. During its construction, Ueshiba rented a property nearby, where he was visited by Kanō Jigorō, the founder of judo.
During this period, Ueshiba was invited to teach at a number of military institutes, due to his close personal relationships with key figures in the military (among them Sadao Araki, the Japanese Minister of War). He accepted an invitation from Admiral Sankichi Takahashi to be the martial arts instructor at the Imperial Japanese Naval Academy, and also taught at the Nakano Spy School, although aikido was later judged to be too technical for the students there and karate was adopted instead. He also became a visiting instructor at the Imperial Japanese Army Academy after being challenged by (and defeating) General Makoto Miura, another student of Takeda Sōkaku\'s Daitō-ryū. Takeda himself met Ueshiba for the last time around 1935, while Ueshiba was teaching at the Osaka headquarters of the *Asahi Shimbun* newspaper. Frustrated by the appearance of his teacher, who was openly critical of Ueshiba\'s martial arts and who appeared intent on taking over the classes there, Ueshiba left Osaka during the night, bowing to the residence in which Takeda was staying and thereafter avoiding all contact with him. Between 1940 and 1942 he made several visits to Manchukuo (Japanese occupied Manchuria) where he was the principal martial arts instructor at Kenkoku University. Whilst in Manchuria, he met and defeated the sumo wrestler Tenryū Saburō during a demonstration.
The \"Second Ōmoto Incident\" in 1935 saw another government crackdown on Deguchi\'s sect, in which the Ayabe compound was destroyed and most of the group\'s leaders imprisoned. Although he had relocated to Tokyo, Ueshiba had retained links with the Ōmoto-kyō group (he had in fact helped Deguchi to establish a paramilitary branch of the sect only three years earlier) and expected to be arrested as one of its senior members. However, he had a good relationship with the local police commissioner Kenji Tomita and the chief of police Gīchi Morita, both of whom had been his students. As a result, although he was taken in for interrogation, he was released without charge on Morita\'s authority.
In 1932, Ueshiba\'s daughter Matsuko was married to the swordsman Kiyoshi Nakakura, who was adopted as Ueshiba\'s heir under the name Morihiro Ueshiba. The marriage ended after a few years, and Nakakura left the family in 1937. Ueshiba later designated his son Kisshomaru as the heir to his martial art.
The 1930s saw Japan\'s invasion of mainland Asia and increased military activity in Europe. Ueshiba was concerned about the prospect of war, and became involved in a number of efforts to try and forestall the conflict that would eventually become World War II. He was part of a group, along with Shūmei Ōkawa and several wealthy Japanese backers, that tried to broker a deal with Harry Chandler to export aviation fuel from the United States to Japan (in contravention of the oil embargo that was currently in force), although this effort ultimately failed. In 1941 Ueshiba also undertook a secret diplomatic mission to China at the behest of Prince Fumimaro Konoe. The intended goal was a meeting with Chiang Kai-shek to establish peace talks, but Ueshiba was unable to meet with the Chinese leader, arriving too late to fulfil his mission.
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# Morihei Ueshiba
## Iwama, 1942--1969 {#iwama_19421969}
thumb\|upright=1.2\|alt=A small Shinto shrine surrounded by trees, with a stone tablet in the foreground\|The Aiki Shrine in Iwama From 1935 onwards, Ueshiba had been purchasing land in Iwama in Ibaraki Prefecture, and by the early 1940s had acquired around 17 acre of farmland there. In 1942, disenchanted with the war-mongering and political manoeuvring in the capital, he left Tokyo and moved to Iwama permanently, settling in a small farmer\'s cottage. Here he founded the Aiki Shuren Dojo, also known as the Iwama dojo, and the Aiki Shrine, a devotional shrine to the \"Great Spirit of Aiki\". During this time he travelled extensively in Japan, particularly in the Kansai region, teaching his aikido. Despite the prohibition on the teaching of martial arts after World War II, Ueshiba and his students continued to practice in secret at the Iwama dojo; the Hombu dojo in Tokyo was in any case being used as a refugee centre for citizens displaced by the severe firebombing. It was during this period that Ueshiba met and befriended Koun Nakanishi, an expert in kotodama. The study of kotodama was to become one of Ueshiba\'s passions in later life, and Nakanishi\'s work inspired Ueshiba\'s concept of *takemusu aiki*.
The rural nature of his new home in Iwama allowed Ueshiba to concentrate on the second great passion of his life: farming. He had been born into a farming family and spent much of his life cultivating the land, from his settlement days in Hokkaido to his work in Ayabe trying to make the Ōmoto-kyō compound self-sufficient. He viewed farming as a logical complement to martial arts; both were physically demanding and required single-minded dedication. Not only did his farming activities provide a useful cover for martial arts training under the government\'s restrictions, it also provided food for Ueshiba, his students and other local families at a time when food shortages were commonplace.
The government prohibition (on aikido, at least) was lifted in 1948 with the creation of the Aiki Foundation, established by the Japanese Ministry of Education with permission from the Occupation forces. The Hombu dojo re-opened the following year. After the war Ueshiba effectively retired from aikido. He delegated most of the work of running the Hombu dojo and the Aiki Federation to his son Kisshomaru, and instead chose to spend much of his time in prayer, meditation, calligraphy and farming. He still travelled extensively to promote aikido, even visiting Hawaii in 1961. He also appeared in a television documentary on aikido: NTV\'s *The Master of Aikido*, broadcast in January 1960. Ueshiba maintained links with the Japanese nationalist movement even in later life; his student Kanshu Sunadomari reported that Ueshiba temporarily sheltered Mikami Taku, one of the naval officers involved in the May 15 Incident, at Iwama.
In 1969, Ueshiba became ill. He led his last training session on March 10, and was taken to hospital where he was diagnosed with cancer of the liver. He died suddenly on April 26, 1969. His body was buried at Kozan-ji Temple Tanabe-shi Wakayama Japan, and he was given the posthumous Buddhist title \"Aiki-in Moritake En\'yū Daidōshi\" (*合気院盛武円融大道士*); parts of his hair were enshrined at Ayabe, Iwama and Kumano. Two months later, his wife Hatsu (*植芝 はつ* *Ueshiba Hatsu*, née *Itokawa Hatsu*; 1881--1969) also died.
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# Morihei Ueshiba
## Development of aikido {#development_of_aikido}
Aikido---usually translated as the *Way of Unifying Spirit* or the *Way of Spiritual Harmony*---is a fighting system that focuses on throws, pins, and joint locks together with some striking techniques. It emphasizes protecting the opponent and promotes spiritual and social development.
The technical curriculum of aikido was derived from the teachings of Takeda Sōkaku; the basic techniques of aikido stem from his Daitō-ryū system. In the earlier years of his teaching, from the 1920s to the mid-1930s, Ueshiba taught the Daitō-ryū Aiki-jūjutsu system; his early students\' documents bear the term Daitō-ryū. Indeed, Ueshiba trained one of the future highest grade earners in Daitō-ryū, Takuma Hisa, in the art before Takeda took charge of Hisa\'s training.
The early form of training under Ueshiba was noticeably different from later forms of aikido. It had a larger curriculum, increased use of strikes to vital points (*atemi*), and greater use of weapons. The schools of aikido developed by Ueshiba\'s students from the pre-war period tend to reflect the harder style of the early training. These students included Kenji Tomiki (who founded the Shodokan Aikido sometimes called Tomiki-ryū), Noriaki Inoue (who founded Shin\'ei Taidō), Minoru Mochizuki (who founded Yoseikan Budo) and Gozo Shioda (who founded Yoshinkan Aikido). Many of these styles are therefore considered \"pre-war styles\", although some of these teachers continued to train with Ueshiba in the years after World War II.
During his lifetime, Ueshiba had three spiritual experiences that impacted greatly his understanding of the martial arts. The first occurred in 1925, after Ueshiba had defeated a naval officer\'s *bokken* (wooden katana) attacks unarmed and without hurting the officer. Ueshiba then walked to his garden, where he had the following realization: `{{Blockquote|I felt the universe suddenly quake and a golden spirit sprang up from the ground, veiled my body, and changed my body into a golden one. At the same time, my body became light. I was able to understand the whispering of the birds and was aware of the mind of God, the creator of the universe. At that moment I was enlightened: the source of [[budō]] [''the martial way''] is God's love – the spirit of loving protection for all beings ...
Budō is not the felling of an opponent by force; nor is it a tool to lead the world to destruction with arms. True Budō is to accept the spirit of the universe, keep the peace of the world, correctly produce, protect and cultivate all beings in nature.<ref name="AutoS5-3"/>}}`{=mediawiki}
His second experience occurred in 1940 when engaged in the ritual purification process of *misogi*.
His third experience was in 1942 during the worst fighting of World War II when Ueshiba had a vision of the \"Great Spirit of Peace\". `{{quote|The Way of the Warrior has been misunderstood. It is not a means to kill and destroy others. Those who seek to compete and better one another are making a terrible mistake. To smash, injure, or destroy is the worst thing a human being can do. The real Way of a Warrior is to prevent such slaughter – it is the Art of Peace, the power of love.<ref name="Wagner2015"/>{{rp|223}}}}`{=mediawiki}
After these events, Ueshiba seemed to slowly grow away from Takeda, and he began to change his art. These changes are reflected in the differing names with which he referred to his system, first as *aiki-jūjutsu*, then Ueshiba-ryū, Asahi-ryū, and *aiki budō*. In 1942, when Ueshiba\'s group joined the Dai Nippon Butoku Kai, the martial art that he developed finally came to be known as aikido.
As Ueshiba grew older, more skilled, and more spiritual in his outlook, his art also changed and became softer and more gentle. Martial techniques became less important, and more focus was given to the control of ki. In his expression of the art there was a greater emphasis on what is referred to as *kokyū-nage*, or \"breath throws\" which are soft and blending, utilizing the opponent\'s movement to throw them. Ueshiba regularly practiced cold water *misogi*, as well as other spiritual and religious rites, and viewed his studies of aikido as part of this spiritual training.
thumb\|upright=1.3\|alt=Black-and-white photograph of a group of people kneeling around an elderly Japanese man\|Ueshiba with a group of his international students at the Hombu dojo in 1967. Over the years, Ueshiba trained a large number of students, many of whom later became famous teachers in their own right and developed their styles of aikido. Some of them were *uchi-deshi*, live-in students. Ueshiba placed many demands on his *uchi-deshi*, expecting them to attend to him at all times, act as training partners (even in the middle of the night), arrange his travel plans, massage, and bathe him, and assist with household chores.
There were roughly four generations of students, comprising the pre-war students (training c. 1921--1935), students who trained during the Second World War (c.1936--1945), the post-war students in Iwama (c.1946--1955) and the students who trained with Ueshiba during his final years (c.1956--c.1969). As a result of Ueshiba\'s martial development throughout his life, students from each of these generations tend to have markedly different approaches to aikido. These variations are compounded by the fact that few students trained with Ueshiba for a protracted period; only Yoichiro Inoue, Kenji Tomiki, Gozo Shioda, Morihiro Saito, Tsutomu Yukawa and Mitsugi Saotome studied directly under Ueshiba for more than five or six years. After the war, Ueshiba and the Hombu Dojo dispatched some of their students to various other countries, resulting in aikido spreading around the world
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# Memory address register
In a computer, the **memory address register** (**MAR**) is the CPU register that either stores the memory address from which data will be fetched to the CPU registers, or the address to which data will be sent and stored via system bus.
In other words, this register is used to access data and instructions from memory during the execution phase of instruction. MAR holds the memory location of data that needs to be accessed. When reading from memory, data addressed by MAR is fed into the MDR (memory data register) and then used by the CPU. When writing to memory, the CPU writes data from MDR to the memory location whose address is stored in MAR. MAR, which is found inside the CPU, goes either to the RAM (random-access memory) or cache.
The MAR register is half of a minimal interface between a microprogram and computer storage; the other half is a MDR.
In general, MAR is a parallel load register that contains the next memory address to be manipulated, for example the next address to be read or written
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# Microassembler
A **microassembler** is a computer program that helps prepare a microprogram, called *firmware*, to control the low level operation of a computer in much the same way an assembler helps prepare higher level code for a processor. The difference is that the microprogram is usually only developed by the processor manufacturer and works intimately with the computer hardware. On a microprogrammed computer the microprogram implements the operations of the instruction set in which any normal program (including both application programs and operating systems) is written. The use of a microprogram allows the manufacturer to fix certain mistakes, including working around hardware design errors, without modifying the hardware. Another means of employing microassembler-generated microprograms is in allowing the same hardware to run different instruction sets. After it is assembled, the microprogram is then loaded to a control store to become part of the logic of a CPU\'s control unit.
Some microassemblers are more generalized and are not targeted at a single computer architecture. For example, through the use of macro-assembler-like capabilities, Digital Equipment Corporation used their *MICRO2* microassembler for a very wide range of computer architectures and implementations.
If a given computer implementation supports a writeable control store, the microassembler is usually provided to customers as a means of writing customized microcode.
In the process of microcode assembly it is helpful to verify the microprogram with emulation tools before distribution. Nowadays, microcoding has experienced a revival, since it is possible to correct and optimize the firmware of processing units already manufactured or sold, in order to adapt to specific operating systems or to fix hardware bugs. However, a commonly usable microassembler for today\'s CPUs is not available to manipulate the microcode. Knowledge of a processor\'s microcode is usually considered proprietary information so it is difficult to obtain information about how to modify it
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# Marino Marini (sculptor)
**Marino Marini** (27 February 1901 -- 6 August 1980) was an Italian sculptor and educator.
## Biography
He attended the Accademia di Belle Arti in Florence in 1917. Although he never abandoned painting, Marini devoted himself primarily to sculpture from about 1922. From this time his work was influenced by Etruscan art and the sculpture of Arturo Martini. Marini succeeded Martini as professor at the Scuola d'Arte di Villa Reale in Monza, near Milan, in 1929, a position he retained until 1940.
During this period, Marini traveled frequently to Paris, where he associated with Massimo Campigli, Giorgio de Chirico, Alberto Magnelli, and Filippo Tibertelli de Pisis. In 1936 he moved to Tenero-Locarno, in Ticino Canton, Switzerland; during the following few years the artist often visited Zürich and Basel, where he became a friend of Alberto Giacometti, Germaine Richier, and Fritz Wotruba. In 1936, he received the Prize of the Quadriennale of Rome. In 1938, he married Mercedes Pedrazzini.
In 1940, he accepted a professorship in sculpture at the Accademia di Belle Arti di Brera (now Brera Academy) in Milan. Notable students of his include sculptor Parviz Tanavoli. In 1943, he went into exile in Switzerland, exhibiting in Basel, Bern, and Zurich. In 1946, the artist settled permanently in Milan.
He is buried at Cimitero Comunale of Pistoia, Toscana, Italy.
## Career
He participated in the \'Twentieth-Century Italian Art\' show at the Museum of Modern Art in New York City in 1944. Curt Valentin began exhibiting Marini\'s work at his Buchholz Gallery in New York in 1950, on which occasion the sculptor visited the city and met Jean Arp, Max Beckmann, Alexander Calder, Lyonel Feininger, and Jacques Lipchitz. On his return to Europe, he stopped in London, where the Hanover Gallery had organized a solo show of his work, and there met Henry Moore. In 1951 a Marini exhibition traveled from the Kestner-Gesellschaft Hannover to the Kunstverein in Hamburg and the Haus der Kunst of Munich. He was awarded the Grand Prize for Sculpture at the Venice Biennale in 1952 and the Feltrinelli Prize at the Accademia dei Lincei in Rome in 1954. One of his monumental sculptures was installed in The Hague in 1959.
Retrospectives of Marini\'s work took place at the Kunsthaus Zürich in 1962 and at the Palazzo Venezia in Rome in 1966. His paintings were exhibited for the first time at Toninelli Arte Moderna in Milan in 1963--64. In 1973 a permanent installation of his work opened at the Galleria d'Arte Moderna in Milan, and in 1978 a Marini show was presented at the National Museum of Modern Art in Tokyo.
There is a museum dedicated to his work in Florence in the former church of San Pancrazio. His work may also be found in museums such as the Civic Gallery of Modern Art in Milan, the Tate Collection, *The Angel of the City* at the Peggy Guggenheim Collection, Venice, the Norton Simon Museum, Museum de Fundatie and the Hirshhorn Museum and Sculpture Garden in Washington, D.C.
## Work
Marini developed several themes in sculpture: equestrian, Pomonas (nudes), portraits, and circus figures. He drew on traditions of Etruscan and Northern European sculpture in developing these themes. His aim was to develop mythical images by interpreting classical themes in light of modern concerns and techniques.
Marini is particularly famous for his series of stylised equestrian statues, which feature a man with outstretched arms on a horse. The evolution of the horse and rider as a subject in Marini\'s works reflects the artist\'s response to the changing context of the modern world. This theme appeared in his work in 1936. At first the proportions of horse and rider are slender and both are \"poised, formal, and calm.\" By the next year the horse is depicted rearing and the rider gesturing. By 1940 the forms are simpler and more archaic in spirit; the proportions squatter.
After World War II, in the late 1940s, the horse is planted, immobile, with neck extended, ears pinned back, mouth open. An example, in the Peggy Guggenheim Collection in Venice, is \"The Angel of the City,\" depicting \"affirmation and charged strength associated explicitly with sexual potency.\" In later works, the rider is, increasingly, oblivious of his mount, \"involved in his own visions or anxieties.\" In the artist\'s final work, the rider is unseated as the horse falls to the ground in an \"apocalyptic image of lost control\" which parallels Marini\'s growing despair for the future of the world.
## Exhibition Catalogues {#exhibition_catalogues}
- Marini, Marino. \"Sculture, Opere Su Carta.\" (Galleria Pieter Coray, Lugano: Kent Fine Art, New York. Milano: Electa, 1991
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# Mancala
**Mancala** (*منقلة* *manqalah*) is a family of two-player turn-based strategy board games played with small stones, beans, marbles or seeds and rows of holes or pits in the earth, a board or other playing surface. The objective is usually to capture all or some set of the opponent\'s pieces.
Versions of the game date back past the 3rd century and evidence suggests such games existed in Ancient Egypt. It is among the oldest known family of games to still be widely played today.
## History
According to some experts, the oldest discovered mancala boards are in \'Ain Ghazal, Jordan in the floor of a Neolithic dwelling as early as \~5,870 BC although this claim has been disputed by others. More recent and undisputed claims concern artifacts from the city of Gedera in an excavated Roman bathhouse where pottery boards and rock cuts that were unearthed dating back to between the 2nd and 3rd century AD. Among other early evidence of the game are fragments of a pottery board and several rock cuts found in Aksumite areas in Matara (in Eritrea) and Yeha (in Ethiopia), which are dated by archaeologists to between the 6th and 7th centuries AD.
The oldest mention of the game is in the \"Kitab al-Aghani\" (\"*Book of Songs*\") of the 10th-century, attributed to Abu al-Faraj al-Isfahani. The game may have been mentioned by Giyorgis of Segla in his 14th century Geʽez text *Mysteries of Heaven and Earth*, where he refers to a game called qarqis, a term used in Geʽez to refer to both Gebet\'a (mancala) and *Sant\'araz* (modern *sent\'erazh*, Ethiopian chess). Evidence of the game has also been uncovered in Kenya.
The games have also existed in Eastern Europe. In Estonia, it was once very popular (see \"Bohnenspiel\"), and likewise in Bosnia (where it is called Ban-Ban and still played today), Serbia, and Greece (\"Mandoli\", Cyclades). Two mancala tables from the early 18th century are to be found in Weikersheim Castle in southern Germany. In western Europe, it never caught on but was documented by Oxford University orientalist Thomas Hyde.
In the United States a traditional mancala game called Warra was still played in Louisiana in the early 20th century, and a commercial version called Kalah became popular in the 1940s. In Cape Verde, mancala is known as \"ouril\". It is played on the Islands and was brought to the United States by Cape Verdean immigrants. It is played to this day in Cape Verdean communities in New England.
Historians may have found evidence of mancala in slave communities of the Americas. The game was brought to the Americas by enslaved Africans during the trans-Atlantic slave trade. The game was played by enslaved Africans to foster community and develop social skills. Archeologists may have found evidence of the game mancala played in Nashville, Tennessee at the Hermitage Plantation.
Recent studies of mancala rules have given insight into the distribution of mancala. This distribution has been linked to migration routes, which may go back several hundred years.
## Etymology
The word *mancala* (*minqalah*) is a tool noun derived from an Arabic root *naqala* (*ن-ق-ل\]\]*) meaning \"to move\".
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# Mancala
## General gameplay {#general_gameplay}
Most mancala games have a common gameplay. Players begin by placing a certain number of seeds, prescribed for the particular game, in each of the pits on the game board. A player may count their stones to plot the game. A turn consists of removing all seeds from a pit, \"sowing\" the seeds (placing one in each of the following pits in sequence), and capturing based on the state of the board. The game\'s object is to plant the most seeds in the bank. This leads to the English phrase \"count and capture\" sometimes used to describe the gameplay. Although the details differ greatly, this general sequence applies to all games.
If playing in capture mode, once a player ends their turn in an empty pit on their own side, they capture the opponent\'s pieces directly across. Once captured, the player gets to put the seeds in their own bank. After capturing, the opponent forfeits a turn.
### Equipment
Equipment is typically a board, constructed of various materials, with a series of holes arranged in rows, usually two or four. The materials include clay and other shapeable materials. Some games are more often played with holes dug in the earth, or carved in stone. The holes may be referred to as \"depressions\", \"pits\", or \"houses\". Sometimes, large holes on the ends of the board called *stores*, are used for holding the pieces.
Playing pieces are seeds, beans, stones, cowry shells, half-marbles or other small undifferentiated counters that are placed in and transferred about the holes during play.
Board configurations vary among different games but also within variations of a given game; for example Endodoi is played on boards from 2×6 to 2×10. The largest are Tchouba (Mozambique) with a board of 160 (4×40) holes requiring 320 seeds, and En Gehé (Tanzania), played on longer rows with up to 50 pits (a total of 2×50=100) and using 400 seeds. The most minimalistic variants are Nano-Wari and Micro-Wari, created by the Bulgarian ethnologue Assia Popova. The Nano-Wari board has eight seeds in just two pits; Micro-Wari has a total of four seeds in four pits.
With a two-rank board, players usually are considered to control their respective sides of the board, although moves often are made into the opponent\'s side. With a four-rank board, players control an inner row and an outer row, and a player\'s seeds will remain in these closest two rows unless the opponent captures them.
### Objective
The objective of most two- and three-row mancala games is to capture more stones than the opponent; in four-row games, one usually seeks to leave the opponent with no legal move or sometimes to capture all counters in their front row.
At the beginning of a player\'s turn, they select a hole with seeds that will be sown around the board. This selection is often limited to holes on the current player\'s side of the board, as well as holes with a certain minimum number of seeds.
In a process known as *sowing*, all the seeds from a hole are dropped one by one into subsequent holes in a motion wrapping around the board. Sowing is an apt name for this activity, since not only are many games traditionally played with seeds but placing seeds one at a time in different holes reflects the physical act of sowing. If the sowing action stops after dropping the last seed, the game is considered a *single lap* game.
*Multiple laps* or *relay sowing* is a frequent feature of mancala games, although not universal. When relay sowing, if the last seed during sowing lands in an occupied hole, all the contents of that hole, including the last sown seed, are immediately re-sown from the hole. The process usually will continue until sowing ends in an empty hole. Another common way to receive \"multiple laps\" is when the final seed sown lands in your designated hole.
Many games from the Indian subcontinent use *pussakanawa laps*. These are like standard multi-laps, but instead of continuing the movement with the contents of the last hole filled, a player continues with the next hole. A pussakanawa lap move will then end when a lap ends just before an empty hole.
If a player ends their stone with a point move they get a \"free turn\".
### Capturing
Depending on the last hole sown in a lap, a player may *capture* stones from the board. The exact requirements for capture, as well as what is done with captured stones, vary considerably among games. Typically, a capture requires sowing to end in a hole with a certain number of stones, ending across the board from stones in specific configurations or landing in an empty hole adjacent to an opponent\'s hole that contains one or more pieces.
Another common way of capturing is to capture the stones that reach a certain number of seeds at any moment.
Also, several games include the notion of capturing holes, and thus all seeds sown on a captured hole belong at the end of the game to the player who captured it.
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# Mancala
## Names and variants {#names_and_variants}
The name is a classification or type of game, rather than any specific game. Some of the most popular mancala games (concerning distribution area, the numbers of players and tournaments, and publications) are:
- Bao -- played in most of East Africa including Kenya, Tanzania, Comoros, Madagascar, Malawi, as well as some areas of DR Congo, and Burundi.
- Gebeta (Tigrinya: ገበጣ) -- played in Ethiopia and Eritrea (especially in Tigray).
- Kalah -- North American variation, the most popular variant in the Western world.
- Omweso (*mweso*) -- played in Uganda, some players and tournaments also in the UK.
- Oware (*awalé, awélé, awari*) -- Ashanti, but played world-wide including Europe (England, France, Catalonia, Portugal), where it is mostly played (but not exclusively) by expatriates; close variants in West Africa (e.g., Ayo by Yorubas (Nigeria), Ouri (Cape Verde)) and Warri in the Caribbean.
- Pallanguzhi -- played in Tamil Nadu, India.
- Ovvaḷugoṇḍi -- played in Maldives
- Songo -- played in Cameroon, Equatorial Guinea and Gabon, also among expatriates in France.
- Sungka -- Popular variants are known as Congklak (a.k.a. *congkak*, *congka*, *tjongklak*, *jongklak*) and Dakon (or *dhakon*) -- played in Indonesia, Singapore, Malaysia, the Philippines and Brunei; boards are often sold in fairtrade shops in Germany and other European countries.
- Toguz korgool or Toguz kumalak -- played in Kyrgyzstan and Kazakhstan, tournaments also in Europe.
- Eson Khorgol (Mongolian: \"nine balls\"), also Eson Xorgol, played by the Kazakh minority in the aimag province of Bayan Ölgii in north-western Mongolia. The game was first described in 1963.
Although more than 800 names of traditional mancala games are known, some names denote the same game, while others are used for more than one game. Almost 200 modern invented versions have also been described.
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# Mancala
## Psychology
Like other board games, mancala games have led to psychological studies. Retschitzki has studied the cognitive processes used by awalé players. Some of Restchitzki\'s results on memory and problem solving have recently been simulated by Fernand Gobet with the CHREST computer model. De Voogt has studied the psychology of Bao playing.
## Competition
Several groups of mancala games have their own tournaments. A medley tournament including at least two modalities has been part of the Mind Sports Olympiad, including in the in-person event and the online Grand Prix
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# Mixmaster Morris
**Mixmaster Morris** (born **Morris Gould**; 30 December 1960) is an English electronica DJ and underground musician who has also recorded as **The Irresistible Force**. His work in the 1990s blended ambient music and chill-out influences with UK dance styles.
## Life and career {#life_and_career}
Morris Gould was born in Brighton, Sussex, England, but grew up in Lincolnshire and was educated at Millfield in Somerset, and King\'s College London. At 15 he founded a punk rock band, The Ripchords, whose sole release, an eponymous EP with four tracks, was championed by the BBC Radio One DJ John Peel. After leaving university, he began working as a DJ in 1985 with his \"Mongolian Hip Hop Show\" on pirate radio station Network 21 in London -- the handle Mixmaster Morris was suggested by the station director. After a year of managing a club called \"The Gift\" in New Cross, which had been founded by Keith Gallagher and named after a Velvet Underground song, Morris began releasing material as **The Irresistible Force** in 1987 in collaboration with singer-songwriter Des de Moor. He became involved with the emerging UK acid house scene, after organising Madhouse at The Fridge, Brixton in 1988 -- which was the subject of a piece by Peel in *The Observer*.
A show with the band Psychic TV led to him becoming full-time DJ with The Shamen, and touring with them on their \'Synergy\' tours for nearly two years.
The first release as The Irresistible Force was the single, \"I Want To\" (1988), but success came with the first album, *Flying High*, released in 1992 on Rising High Records. In 1994, Morris released the second album *Global Chillage* which featured a holographic sleeve, and was released in the US on Astralwerks. After a period of legal problems, the third album *It\'s Tomorrow Already* came out on Ninja Tune.
In 1990, he made one of the first chillout compilations, *Give Peace a Dance 2: The Ambient Collection* for the Campaign for Nuclear Disarmament, followed by the series *Chillout or Die* for Rising High Records. A mix tape for *Mixmag* shared with Alex Patterson was also released as a CD. *The Morning After* became his first major-label mix album, followed by *Abstract Funk Theory* for Obsessive.
Through the 1990s he was a regular DJ in the chill out room at Return to the Source parties in London, around the UK and abroad. In 2003 he released the mix CD *God Bless the Chilled* for the Return to the Source Ambient Meditations series.
He has produced many remixes since 1985, including Coldcut\'s \"Autumn Leaves\". This remix was nominated by Norman Cook as his favourite chillout track on BBC Television. His mix for INXS was a Top 20 hit in the UK. Other early remixes were of Lloyd Cole, Dave Howard Singers, Bang Bang Machine, Stump, Higher Intelligence Agency, Sven Väth and Rising High Collective.
In the early 1990s his key residencies were alongside the Detroit masters at Lost, Megatripolis at London\'s Heaven, and also the Tribal Gathering parties. He became known for wearing holographic suits, produced by the company Spacetime, which he modelled for *Vogue* magazine. Throughout the decade, Morris wrote about electronic music for the *NME*, *Mixmag*, and *i-D*. He was resident on Kiss FM for several years, and then a regular on Solid Steel, the Ninja Tune syndicated radio show. He made his film debut in *Modulations* (Caipirinha Films), and his music was used in a number of other films including *Groove* and *Hey Happy*.
Morris has played in over fifty countries at nightclubs and parties, and particularly music festivals such as the Full Moon parties in the Mojave Desert, Glastonbury Festival, Rainbow 2000 and Mother SOS in Japan, Chillits in Northern California, and Berlin\'s Love Parade. He also ran the downtempo night Nubient in Brixton. In 1995, he played at the first The Big Chill festival, and then became a resident for the next 16 years.
He also collaborated with the German musician Pete Namlook under the name Dreamfish, recording two albums. Also with SF-based musician Jonah Sharp and Haruomi Hosono of Yellow Magic Orchestra he made the album *Quiet Logic* for the Japanese label Daisyworld.
In 1998 he joined the UK\'s Ninja Tune record label, with whom he toured as a DJ and made three releases. 1999 saw him win \'Best Chillout DJ\' at the Ibiza DJ Awards at Pacha, Ibiza, and in 2001 he won the title for a second time, becoming the first DJ to achieve this. He has appeared in many lists of the world\'s top DJ\'s including the Ministry of Sound book *The Annual* and 2003\'s *DJs by Lopez*, and *URB Magazine*\'s Top 100 DJ list. Morris records regular radio shows for the Japanese internet radio station Samurai FM. In 2006 he started a new club at the Big Chill House in Kings Cross, London, and did a guest mix for BBC Radio 1\'s *The Blue Room* show. His essay about jazz was published in the book, *Crossfade*, and he made a one-off appearance reading it aloud.
In March 2007, together with Coldcut, he organised a tribute show to the writer and philosopher Robert Anton Wilson, which they performed at the Queen Elizabeth Hall. He also played in Goa for the first time with The Big Chill, and started a new residency at The Prince in Brixton. In May 2008 Morris undertook an ambient mix on BBC Radio 1, and put a The Irresistible Force band together to play at The Big Chill festival. In 2009, he compiled a podcast for Tate Britain to accompany their Altermodern exhibition, and opened a new AV night called MMMTV in Camden. The mix CD, *Calm Down My Selector* was released in January by Wakyo Records, and he made a tour of Japan to promote it.
In 2010, he won another Ibiza DJ Award, for the third time. In October that year, he was announced as Head of A+R for Apollo Records. 2011 saw him rejoin Bestival as part of their \"Ambient Forest\" team.
2017 saw Morris continue to stay at the top of the psybient/downtempo movement and charts, especially Mixcloud where he held top positions in most categories relating to ambient music for the full year. 2017 also saw the triumphant return of Mixmaster Morris with his acclaimed release \"Kira Kira\", a lush soundscape that was received well by many publications and listeners and earned a spot in \"Extreme Chill\'s\" top twenty of 2017 along with releases by Brian Eno and Steve Roach
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# Maroboduus
**Maroboduus** (d. AD 37), also known as **Marbod**, was a king of the Marcomanni, who were a Germanic Suebian people. He spent part of his youth in Rome, and returning, found his people under pressure from invasions by the Roman Empire between the Rhine and Elbe. He led them into the forests of Bohemia, near to the Quadi who already lived nearby, and established a large alliance.
## Name
The name appears in Latin and Greek texts spelt variously: *Maroboduus, Marobodus, Maraboduus, Meroboduus, Morobuduus, Moroboduus, Marbodus* and *Marabodus* in Latin sources; *Maroboudos* and *Baroboudos* in Greek ones.`{{citationneeded|date=January 2023}}`{=mediawiki}
According to linguist Xavier Delamarre, the personal name *Maroboduus* is a latinized form of Gaulish *Maro-boduos*, from *maro*- (\'great\') attached to *boduos* (\'crow\'; cf. Middle Irish *bodb* \'scald-crow, war-divinity\', Old Breton *bodou* \'ardea\'; also Common Brittonic *Boduoci*). The Celtic personal names *Boduus*, *Teuto-boduus*, *Ate-boduus*, *Soli-boduus*, *Boduo-genus*, and *Buduo-gnatus* are related. Philologist John T. Koch argues that Middle Irish *bodb* must be understood as the \'bird on the battlefield and manifestation of the war-goddess\'.
The second element of the name, *boduos*, is a term shared by Celtic and Germanic languages, where it is found as the common noun \**badwō* (\'battle\'; cf. ON *bǫð*, OE *beado*, OS *badu*-*,* OHG *batu-*) and in the name of the war goddess *Baduhenna*. The original meaning of Celtic--Germanic \**b^h^od^h^wo*- must have been \'battle, fight\', later metaphorised in Celtic as \'crow\', a bird symbolizing the carnage in battle.
## Biography
Maroboduus was born into a noble family of the Marcomanni. As a young man, he lived in Italy and enjoyed the favour of the Emperor Augustus. The Marcomanni had been beaten utterly by the Romans in 10 BC. About 9 BC, Maroboduus returned to Germania and became ruler of his people. To deal with the threat of Roman expansion into the Rhine-Danube basin, he led the Marcomanni to the area later known as Bohemia to be outside the range of the Roman influence. There, he took the title of king and organized a confederation of several neighboring Germanic tribes. He was the first documented ruler of Bohemia with a government.
Augustus planned in 6 AD to destroy the kingdom of Maroboduus, which he considered to be too dangerous for the Romans. The future emperor Tiberius commanded 12 legions to attack the Marcomanni, but the outbreak of a revolt in Illyria, and the need for troops there, forced Tiberius to conclude a treaty with Maroboduus and to recognize him as king.
## War with Arminius and death {#war_with_arminius_and_death}
His rivalry with Arminius, the Cheruscan leader who inflicted the devastating defeat at the Battle of the Teutoburg Forest on the Romans under Publius Quinctilius Varus in 9 AD, prevented a concerted attack on Roman territory across the Rhine in the north (by Arminius) and in the Danube basin in the south (by Maroboduus).
However, according to the first-century AD historian Marcus Velleius Paterculus, Arminius sent Varus\'s head to Maroboduus, but the king of the Marcomanni sent it to Augustus. In the revenge war of Tiberius and Germanicus against the Cherusci, in 16 AD, Maroboduus stayed neutral.
In 17 AD, war broke out between Arminius and Maroboduus, and after an indecisive battle, Maroboduus withdrew into the hilly forests of Bohemia in 18 AD. In the next year, Catualda, a young Marcomannic nobleman living in exile among the Gutones, returned, perhaps by a subversive Roman intervention, and defeated Maroboduus. The deposed king had to flee to Italy, and Tiberius detained him for 18 years in Ravenna. There, Maroboduus died in 37 AD. Catualda was, in turn, defeated by the Hermunduri Vibilius, after which the realm was ruled by the Quadian Vannius. Vannius was himself also deposed by Vibilius, in coordination with his nephews Vangio and Sido, who then ruled as Roman client kings
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# Mike Muuss
**Michael John Muuss** (October 16, 1958 -- November 20, 2000) was the American author of the freeware network tool ping, as well as the first interactive ray tracing program.
## Career
A graduate of Johns Hopkins University, Muuss was a senior scientist specializing in geometric solid modeling, ray-tracing, MIMD architectures and digital computer networks at the United States Army Research Laboratory at Aberdeen Proving Ground, Maryland when he died. He wrote a number of software packages (including BRL-CAD) and network tools (including ttcp and the concept of the default route or \"default gateway\") and contributed to many others (including BIND).
However, the thousand-line ping, which he wrote in December 1983 while working at the Ballistic Research Laboratory, is the program for which he is most remembered. Due to its usefulness, ping has been implemented on a large number of operating systems, initially Berkeley Software Distribution (BSD) and Unix, but later others including Windows and Mac OS X.
In 1993, the USENIX Association gave a Lifetime Achievement Award (*Flame*) to the Computer Systems Research Group at University of California, Berkeley, honoring 180 individuals, including Muuss, who contributed to the CSRG\'s 4.4BSD-Lite release.
Muuss is mentioned in two books, *The Cuckoo\'s Egg* (`{{ISBN|0-7434-1146-3}}`{=mediawiki}) and *Cyberpunk: Outlaws and Hackers on the Computer Frontier* (`{{ISBN|0-684-81862-0}}`{=mediawiki}), for his role in tracking down crackers. He is also mentioned in Peter Salus\'s *A Quarter Century of UNIX* and a link to his website's ping page is included in *How Linux Works* (`{{ISBN|1718500408}}`{=mediawiki}).
Muuss died in an automobile collision on Interstate 95 on November 20, 2000. The **Michael J. Muuss Research Award**, set up by friends and family of Muuss, memorializes him at Johns Hopkins University
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# Metallocene
A **metallocene** is a compound typically consisting of two cyclopentadienyl anions (`{{chem|C|5|H|5|−}}`{=mediawiki}, abbreviated Cp) bound to a metal center (M) in the oxidation state II, with the resulting general formula `{{nowrap|(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>M.}}`{=mediawiki} Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride or vanadocene dichloride. Certain metallocenes and their derivatives exhibit catalytic properties, although metallocenes are rarely used industrially. Cationic group 4 metallocene derivatives related to \[Cp~2~ZrCH~3~\]^+^ catalyze olefin polymerization.
Some metallocenes consist of metal plus two cyclooctatetraenide anions (`{{chem|C|8|H|8|2−}}`{=mediawiki}, abbreviated cot^2−^), namely the lanthanocenes and the actinocenes (uranocene and others).
Metallocenes are a subset of a broader class of compounds called sandwich compounds. In the structure shown at right, the two pentagons are the cyclopentadienyl anions with circles inside them indicating they are aromatically stabilized. Here they are shown in a staggered conformation.
## History
The first metallocene to be classified was ferrocene, and was discovered simultaneously in 1951 by Kealy and Pauson, and Miller et al. Kealy and Pauson were attempting to synthesize fulvalene through the oxidation of a cyclopentadienyl salt with anhydrous FeCl~3~ but obtained instead the substance C~10~H~10~Fe At the same time, Miller *et al* reported the same iron product from a reaction of cyclopentadiene with iron in the presence of aluminum, potassium, or molybdenum oxides. The structure of \"C~10~H~10~Fe\" was determined by Geoffrey Wilkinson et al. and by Ernst Otto Fischer et al. These two were awarded the Nobel Prize in Chemistry in 1973 for their work on sandwich compounds, including the structural determination of ferrocene. They determined that the carbon atoms of the cyclopentadienyl (Cp) ligand contributed equally to the bonding and that bonding occurred due to the metal `{{nowrap|[[d-orbital]]s}}`{=mediawiki} and the `{{nowrap|π-[[electron]]s}}`{=mediawiki} in the `{{nowrap|[[p-orbital]]s}}`{=mediawiki} of the Cp ligands. This complex is now known as ferrocene, and the group of transition metal dicyclopentadienyl compounds is known as metallocenes. Metallocenes have the general formula `{{nowrap|[(''η''<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>M].}}`{=mediawiki} Fischer et al. first prepared the ferrocene derivatives involving Co and Ni. Often derived from substituted derivatives of cyclopentadienide, metallocenes of many elements have been prepared.
One of the very earliest commercial manufacturers of metallocenes was Arapahoe Chemicals in Boulder, Colorado
## Definition
The general name metallocene is derived from ferrocene, (C~5~H~5~)~2~Fe or Cp~2~Fe, systematically named `{{nowrap|bis(''η''<sup>5</sup>-[[cyclopentadienyl complex|cyclopentadienyl]])iron(II).}}`{=mediawiki} According to the International Union of Pure and Applied Chemistry definition, a metallocene contains a transition metal and two cyclopentadienyl ligands coordinated in a sandwich structure, i.e., the two cyclopentadienyl anions are on parallel planes with equal bond lengths and strengths. Using the nomenclature of \"hapticity\", the equivalent bonding of all 5 carbon atoms of a cyclopentadienyl ring is denoted as *η*^5^, pronounced \"pentahapto\". There are exceptions, such as uranocene, which has two cyclooctatetraene rings sandwiching a uranium atom.
In metallocene names, the prefix before the *`{{not a typo|-ocene}}`{=mediawiki}* ending indicates what metallic element is between the Cp groups. For example, in ferrocene, iron(II), ferrous iron is present.
In contrast to the more strict definition proposed by International Union of Pure and Applied Chemistry, which requires a d-block metal and a sandwich structure, the term metallocene and thus the denotation *`{{not a typo|-ocene}}`{=mediawiki}*, is applied in the chemical literature also to non-transition metal compounds, such as barocene (Cp~2~Ba), or structures where the aromatic rings are not parallel, such as found in manganocene or titanocene dichloride (Cp~2~TiCl~2~).
Some metallocene complexes of actinides have been reported where there are three cyclopentadienyl ligands for a monometallic complex, all three of them bound η^5^.
## Classification
There are many (*η*^5^-C~5~H~5~)--metal complexes and they can be classified by the following formulas:
Formula Description
--------------------------------- ---------------------------------------------------------------------------
\[(*η*^5^-C~5~H~5~)~2~M\] Symmetrical, classical \'sandwich\' structure
\[(*η*^5^-C~5~H~5~)~2~ML~*x*~\] Bent or tilted Cp rings with additional ligands, L
\[(*η*^5^-C~5~H~5~)ML~*x*~\] Only one Cp ligand with additional ligands, L (\'piano-stool\' structure)
Cp-based complexes can also be classified by type:
1. Parallel
2. Multi-decker
3. Half-sandwich compound
4. Bent metallocene or tilted
5. More than two Cp ligands
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# Metallocene
## Synthesis
Three main routes are normally employed in the formation of these types of compounds:
### Using a metal salt and cyclopentadienyl reagents {#using_a_metal_salt_and_cyclopentadienyl_reagents}
Sodium cyclopentadienide (NaCp) is the preferred reagent for these types of reactions. It is most easily obtained by the reaction of molten sodium and dicyclopentadiene. Traditionally, the starting point is the cracking of dicyclopentadiene, the dimer of cyclopentadiene. Cyclopentadiene is deprotonated by strong bases or alkali metals.
: MCl~2~ + 2 NaC~5~H~5~ → (C~5~H~5~)~2~M + 2 NaCl `{{space|10}}`{=mediawiki} (M = V, Cr, Mn, Fe, Co; solvent = THF, DME, NH~3~)
```{=html}
<!-- -->
```
: CrCl~3~ + 3 NaC~5~H~5~ → \[(C~5~H~5~)~2~Cr\] + `{{1/2}}`{=mediawiki} \"C~10~H~10~\" + 3 NaCl
NaCp acts as a reducing agent and a ligand in this reaction.
### Using a metal and cyclopentadiene {#using_a_metal_and_cyclopentadiene}
This technique provides using metal atoms in the gas phase rather than the solid metal. The highly reactive atoms or molecules are generated at a high temperature under vacuum and brought together with chosen reactants on a cold surface.
: M + C~5~H~6~ → MC~5~H~5~ + `{{1/2}}`{=mediawiki} H~2~ `{{space|10}}`{=mediawiki} (M = Li, Na, K)
: M + 2 C~5~H~6~ → \[(C~5~H~5~)~2~M\] + H~2~ `{{space|10}}`{=mediawiki} (M = Mg, Fe)
### Using cyclopentadienyl reagents {#using_cyclopentadienyl_reagents}
A variety of reagents have been developed that transfer Cp to metals. Once popular was thallium cyclopentadienide. It reacts with metal halides to give thallium chloride, which is poorly soluble, and the cyclopentadienyl complex. Trialkyltin derivatives of Cp^−^ have also been used.
Many other methods have been developed. Chromocene can be prepared from chromium hexacarbonyl by direct reaction with cyclopentadiene in the presence of diethylamine; in this case, the formal deprotonation of the cyclopentadiene is followed by reduction of the resulting protons to hydrogen gas, facilitating the oxidation of the metal centre.
: Cr(CO)~6~ + 2 C~5~H~6~ → Cr(C~5~H~5~)~2~ + 6 CO + H~2~
Metallocenes generally have high thermal stability. Ferrocene can be sublimed in air at over 100 °C with no decomposition; metallocenes are generally purified in the laboratory by vacuum sublimation. Industrially, sublimation is not practical so metallocenes are isolated by crystallization or produced as part of a hydrocarbon solution. For Group IV metallocenes, donor solvents like ether or THF are distinctly undesirable for polyolefin catalysis. Charge-neutral metallocenes are soluble in common organic solvents. Alkyl substitution on the metallocene increases the solubility in hydrocarbon solvents.
## Structure
A structural trend for the series MCp~2~ involves the variation of the M-C bonds, which elongate as the valence electron count deviates from 18.
M(C~5~H~5~)~2~ *r*~M--C~ (pm) Valence electron count
---------------- ---------------- ------------------------
Fe 203.3 18
Co 209.6 19
Cr 215.1 16
Ni 218.5 20
V 226 15
In metallocenes of the type (C~5~R~5~)~2~M, the cyclopentadienyl rings rotate with very low barriers. Single crystal X-ray diffraction studies reveal both eclipsed or staggered rotamers. For non-substituted metallocenes the energy difference between the staggered and eclipsed conformations is only a few kJ/mol. Crystals of ferrocene and osmocene exhibit eclipsed conformations at low temperatures, whereas in the related bis(pentamethylcyclopentadienyl) complexes the rings usually crystallize in a staggered conformation, apparently to minimize steric hindrance between the methyl groups.
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# Metallocene
## Spectroscopic properties {#spectroscopic_properties}
### Vibrational (infrared and Raman) spectroscopy of metallocenes {#vibrational_infrared_and_raman_spectroscopy_of_metallocenes}
Infrared and Raman spectroscopies have proved to be important in the analysis of cyclic polyenyl metal sandwich species, with particular use in elucidating covalent or ionic M--ring bonds and distinguishing between central and coordinated rings. Some typical spectral bands and assignments of iron group metallocenes are shown in the following table:
Ferrocene (cm^−1^) Ruthenocene (cm^−1^) Osmocene (cm^−1^)
------------------------ -------------------- ---------------------- -------------------
C--H stretch 3085 3100 3095
C--C stretch 1411 1413 1405
Ring deformation 1108 1103 1096
C--H deformation 1002 1002 995
C--H out-of-plane bend 811 806 819
Ring tilt 492 528 428
M--ring stretch 478 446 353
M--ring bend 170 185 --
: Spectral frequencies of group 8 metallocenes
### NMR (^1^H and ^13^C) spectroscopy of metallocenes {#nmr_1h_and_13c_spectroscopy_of_metallocenes}
Nuclear magnetic resonance (NMR) is the most applied tool in the study of metal sandwich compounds and organometallic species, giving information on nuclear structures in solution, as liquids, gases, and in the solid state. ^1^H NMR chemical shifts for paramagnetic organotransition-metal compounds is usually observed between 25 and 40 ppm, but this range is much more narrow for diamagnetic metallocene complexes, with chemical shifts usually observed between 3 and 7 ppm.
### Mass spectrometry of metallocenes {#mass_spectrometry_of_metallocenes}
Mass spectrometry of metallocene complexes has been very well studied and the effect of the metal on the fragmentation of the organic moiety has received considerable attention and the identification of metal-containing fragments is often facilitated by the isotope distribution of the metal. The three major fragments observed in mass spectrometry are the molecular ion peak, \[C~10~H~10~M\]^+^, and fragment ions, \[C~5~H~5~M\]^+^ and M^+^.
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# Metallocene
## Derivatives
After the discovery of ferrocene, the synthesis and characterization of derivatives of metallocene and other sandwich compounds attracted researchers' interests.
### Metallocenophanes
Metallocenophanes feature linking of the cyclopentadienyl or polyarenyl rings by the introduction of one or more heteroannular bridges. Some of these compounds undergo thermal ring-opening polymerizations to give soluble high molecular weight polymers with transition metals in the polymer backbone. Ansa-metallocenes are derivatives of metallocenes with an intramolecular bridge between the two cyclopentadienyl rings.
### Polynuclear and heterobimetallic metallocenes {#polynuclear_and_heterobimetallic_metallocenes}
- Ferrocene derivatives: biferrocenophanes have been studied for their mixed valence properties. Upon one-electron oxidation of a compound with two or more equivalent ferrocene moieties, the electron vacancy could be localized on one ferrocene unit or completely delocalized.
- Ruthenocene derivatives: in the solid state biruthenocene is disordered and adopts the transoid conformation with the mutual orientation of Cp rings depending on the intermolecular interactions.
- Vanadocene and rhodocene derivatives: vanadocene complexes have been used as starting materials for the synthesis of heterobimetallic complexes. The 18 valence electron ions \[Cp~2~Rh\]^+^ are very stable, unlike the neutral monomers Cp~2~Rh which dimerize immediately at room temperature and they have been observed in matrix isolation.
### Multi-decker sandwich compounds {#multi_decker_sandwich_compounds}
Triple-decker complexes are composed of three Cp anions and two metal cations in alternating order. The first triple-decker sandwich complex, `{{chem2|[Ni2Cp3](+)}}`{=mediawiki}, was reported in 1972. Many examples have been reported subsequently, often with boron-containing rings.
### Metallocenium ions {#metallocenium_ions}
The most famous example is ferrocenium, `{{chem2|[Fe(C5H5)2](+)}}`{=mediawiki}, the blue iron(III) complex derived from oxidation of orange iron(II) ferrocene. The lithocene anion, \[Li(C~5~H~5~)~2~\]^--^, is the best-documented example of a metallocene anion; otherwise such ions are little known.
## Applications
Many derivatives of early metal metallocenes are active catalysts for olefin polymerization. Unlike traditional and still dominant heterogeneous Ziegler--Natta catalysts, metallocene catalysts are homogeneous. Early metal metallocene derivatives, e.g. Tebbe\'s reagent, Petasis reagent, and Schwartz\'s reagent are useful in specialized organic synthetic operations.
### Potential applications {#potential_applications}
The ferrocene/ferrocenium biosensor has been discussed for determining the levels of glucose in a sample electrochemically through a series of connected redox cycles.
Metallocene dihalides \[Cp~2~MX~2~\] (M = Ti, Mo, Nb) exhibit anti-tumor properties, although none have proceeded far in clinical trials
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# Mariner program
The **Mariner program** was conducted by the American space agency NASA to explore other planets. Between 1962 and late 1973, NASA\'s Jet Propulsion Laboratory (JPL) designed and built 10 robotic interplanetary probes named Mariner to explore the inner Solar System -- visiting the planets Venus, Mars and Mercury for the first time, and returning to Venus and Mars for additional close observations.
The program included a number of interplanetary firsts, including the first successful planetary flyby, the planetary orbiter, and the first gravity assist maneuver. Of the 10 vehicles in the Mariner series, seven were successful, forming the starting point for many subsequent NASA/JPL space probe programs. The planned Mariner Jupiter-Saturn vehicles were adapted into the Voyager program, while the Viking program orbiters were enlarged versions of the Mariner 9 spacecraft. Later Mariner-based spacecraft include Galileo and Magellan, while the second-generation Mariner Mark II series evolved into the Cassini--Huygens probe.
The total cost of the Mariner program was approximately \$554 million.
## Early concept {#early_concept}
The Mariner program began in 1960 with a series of JPL mission studies for small-scale, frequent exploration of the nearest planets. They were to take advantage of the soon-to-be-available Atlas launch vehicles as well as the developing capability of JPL\'s Deep Space Instrumentation Facility (later named the Deep Space Network), a global network of ground stations designed to communicate with spacecraft in deep space. The name of the Mariner program was decided in \"May 1960 -- at the suggestion of Edgar M. Cortright\" to have the \"planetary mission probes \... patterned after nautical terms, to convey \'the impression of travel to great distances and remote lands.\'\" That \"decision was the basis for naming Mariner, Ranger, Surveyor, and Viking probes.\"
Each spacecraft was to carry solar panels that would be pointed toward the Sun and a dish antenna that would be pointed at Earth. Each would also carry a host of scientific instruments. Some of the instruments, such as cameras, would need to be pointed at the target body it was studying. Other instruments were non-directional and studied phenomena such as magnetic fields and charged particles. JPL engineers proposed to make the Mariners \"three-axis-stabilized,\" meaning that unlike other space probes they would not spin.
Each of the Mariner projects was designed to have two spacecraft launched on separate rockets, in case of difficulties with the nearly untried launch vehicles. Mariner 1, Mariner 3, and Mariner 8 were in fact lost during launch, but their backups were successful. No Mariners were lost in later flight to their destination planets or before completing their scientific missions.
## Basic layout {#basic_layout}
All Mariner spacecraft were based on a hexagonal or octagonal bus, which housed all of the electronics, and to which all components were attached, such as antennae, cameras, propulsion, and power sources. Mariner 2 was based on the Ranger Lunar probe. All of the Mariners launched after Mariner 2 had four solar panels for power, except for Mariner 10, which had two. Additionally, all except Mariner 1, Mariner 2 and Mariner 5 had TV cameras.
The first five Mariners were launched on Atlas-Agena rockets, while the last five used the Atlas-Centaur. All Mariner-based probes after Mariner 10 used the Titan IIIE, Titan IV uncrewed rockets or the Space Shuttle with a solid-fueled Inertial Upper Stage and multiple planetary flybys.
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# Mariner program
## Mariners
The Mariners were all relatively small robotic explorers, each launched on an Atlas rocket with either an Agena or Centaur upper-stage booster, and weighing less than half a ton (without onboard rocket propellant). Each of their missions was completed within a few months to a year or two, though one of them outlived its original mission and continued to send useful scientific data for three years.
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Spacecraft | Mass | Carrier rocket | Launch date | Last contact | Destination | Mission | Outcome | Remarks |
+================================+============+==========================+=============+====================================+================+=========+=========+======================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================+
| Mariner 1\ | | Atlas-LV3 Agena-B | | \ | Venus | Flyby | | Failed to orbit; destroyed by range safety following guidance failure |
| (P-37) | | | | (destroyed) | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 2\ | 203 kg\ | Atlas-LV3 Agena-B | | 7:00 UT | Venus | Flyby | | First flyby of Venus with data returned, on 14 December 1962. A copy of Mariner 1. |
| (P-38, Mariner R-2) | (446 lb) | | | | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 3 (Mariner C-2) | | Atlas LV-3 Agena-D | | | Mars | Flyby | | Payload fairing failed to separate |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 4 (Mariner C-3) | 261 kg\ | Atlas LV-3 Agena-D | | | Mars | Flyby | | First flyby of Mars, on 15 July 1965. A copy of Mariner 3. |
| | (575 lb) | | | | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 5 (Mariner Venus \'67) | 245 kg\ | Atlas SLV-3 Agena-D | | \ | Venus | Flyby | | Flyby on 19 October 1967, closest approach at 17:34:56 UTC. Designed to measure magnetic fields and various emissions of the Venusian atmosphere. |
| | (540 lb) | | | (Briefly regained 14 October 1968) | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 6 (Mariner Mars 69A) | 413 kg\ | | | December 23, 1970 (decommissioned) | Mars | Flyby | | Dual mission |
| | (908 lb) | | | | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 7 (Mariner Mars 69B) | 413 kg\ | Atlas SLV-3C Centaur-D | | December 28, 1970 (decommissioned) | Mars | Flyby | | |
| | (908 lb) | | | | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 8 (Mariner-H) | | Atlas SLV-3C Centaur-D | | \ | Mars | Orbiter | | One of two probes designed to orbit Mars and return images and data. Lost in a vehicle malfunction. |
| | | | | (destroyed) | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 9 (Mariner-I) | 998 kg\ | Atlas SLV-3C Centaur-D | | | Mars | Orbiter | | First orbiter of Mars. Entered orbit on 14 November 1971, deactivated 516 days later. A copy of Mariner 8. |
| | (2,200 lb) | | | | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mariner 10 (Mariner-J) | 433 kg\ | Atlas SLV-3D Centaur-D1A | | | Venus, Mercury | Flyby | | First flyby of Mercury and the last Mariner probe launched`{{refn|group=note|An eleventh spacecraft, the Mariner 10 [[flight spare]], was constructed but did not fly. NASA gave it to the [[Smithsonian Institution]] in 1982, which currently displays it in the Time and Navigation exhibition at the [[National Air and Space Museum]].<ref>{{cite web |url=https://www.si.edu/object/spacecraft-mariner-10-flight-spare:nasm_A19830006000 |title=Spacecraft, Mariner 10, Flight Spare |author=<!--Not stated--> |access-date=2020-10-18 }}</ref>}}`{=mediawiki} |
| | (952 lb) | | | | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| | | | | | | | | |
+--------------------------------+------------+--------------------------+-------------+------------------------------------+----------------+---------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
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# Mariner program
## Mariners 1 and 2 {#mariners_1_and_2}
thumb\|upright=0.8\|Diagram of Mariner 1 and 2 with Atlas-Agena launch vehicle
Mariner 1 (P-37) and Mariner 2 (P-38) were two deep-space probes making up NASA\'s Mariner-R project. The primary goal of the project was to develop and launch two spacecraft sequentially to the near vicinity of Venus, receive communications from the spacecraft and to perform radiometric temperature measurements of the planet. A secondary objective was to make interplanetary magnetic field and/or particle measurements on the way to, and in the vicinity of, Venus. Mariner 1 (designated Mariner R-1) was launched on July 22, 1962, but was destroyed approximately 5 minutes after liftoff by the Air Force Range Safety Officer when its malfunctioning Atlas-Agena rocket went off course. Mariner 2 (designated Mariner R-2) was launched on August 27, 1962, sending it on a 3½-month flight to Venus. The mission was a success, and Mariner 2 became the first spacecraft to have flown by another planet.
On the way it measured for the first time the solar wind, a constant stream of charged particles flowing outward from the Sun. It also measured interplanetary dust, which turned out to be more scarce than predicted. In addition, Mariner 2 detected high-energy charged particles coming from the Sun, including several brief solar flares, as well as cosmic rays from outside the Solar System. As it flew by Venus on December 14, 1962, Mariner 2 scanned the planet with infrared and microwave radiometers, revealing that Venus has cool clouds and an extremely hot surface (because the bright, opaque clouds hide the planet\'s surface, Mariner 2 was not outfitted with a camera).
- Mission: Venus flyby
- Mass: 203 kg (446 lb)
- Sensors: microwave and infrared radiometers, cosmic dust, solar plasma and high-energy radiation, magnetic fields
Status:
- Mariner 1 -- Destroyed shortly after liftoff.
- Mariner 2 -- Defunct after successful mission, occupies a heliocentric orbit.
## Mariners 3 and 4 {#mariners_3_and_4}
Sisterships Mariner 3 and Mariner 4 were Mars flyby missions.
Mariner 3 was launched on November 5, 1964, but the shroud encasing the spacecraft atop its rocket failed to open properly and Mariner 3 did not get to Mars.
Mariner 4, launched on November 28, 1964, was the first successful flyby of the planet Mars and gave the first glimpse of Mars at close range. The spacecraft flew past Mars on July 14, 1965, collecting the first close-up photographs of another planet. The pictures, played back from a small tape recorder over a long period, showed lunar-type impact craters (just beginning to be photographed at close range from the Moon), some of them touched with frost in the chill Martian evening. The Mariner 4 spacecraft, expected to survive something more than the eight months to Mars encounter, actually lasted about three years in solar orbit, continuing long-term studies of the solar wind environment and making coordinated measurements with Mariner 5, a sister ship launched to Venus in 1967.
- Mission: Mars flyby
- Mass: 261 kg (575 lb)
- Sensors: camera with digital tape recorder (about 20 pictures), cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics
Status:
- Mariner 3 -- Malfunctioned. Derelict in heliocentric orbit.
- Mariner 4 -- Communications lost after bombardment by micrometeoroids. Derelict in heliocentric orbit.
## Mariner 5 {#mariner_5}
The Mariner 5 spacecraft was launched to Venus on June 14, 1967, and arrived in the vicinity of the planet in October 1967. It carried a complement of experiments to probe Venus\' atmosphere with radio waves, scan its brightness in ultraviolet light, and sample the solar particles and magnetic field fluctuations above the planet.
- Mission: Venus flyby
- Mass: 245 kg (540 lb)
- Sensors: ultraviolet photometer, cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics
Status: Mariner 5 -- Defunct and now in a heliocentric orbit.
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