Circuit breaker

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Circuit_breaker 

An air circuit breaker for low-voltage (less than 1,000 volt) power distribution switchgear

 

A two-pole miniature circuit breaker

 

Four one-pole miniature circuit breakers

A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by an overcurrent or short circuit. Its basic function is to interrupt current flow to protect equipment and to prevent the risk of fire. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.

Circuit breakers are made in varying sizes, from small devices that protect low-current circuits or individual household appliances, to large switchgear designed to protect high voltage circuits feeding an entire city. The generic function of a circuit breaker, or fuse, as an automatic means of removing power from a faulty system, is often abbreviated as OCPD (Over Current Protection Device).

Origins

An early form of circuit breaker was described by Thomas Edison in an 1879 patent application, although his commercial power distribution system used fuses. Its purpose was to protect lighting circuit wiring from accidental short circuits and overloads. A modern miniature circuit breaker similar to the ones now in use was patented by Brown, Boveri & Cie in 1924. Hugo Stotz, an engineer who had sold his company to BBC, was credited as the inventor on DRP (Deutsches Reichspatent) 458392. Stotz's invention was the forerunner of the modern thermal-magnetic breaker commonly used in household load centers to this day.

Interconnection of multiple generator sources into an electrical grid required the development of circuit breakers with increasing voltage ratings and increased ability to safely interrupt the increasing short-circuit currents produced by networks. Simple air-break manual switches produced hazardous arcs when interrupting high voltages; these gave way to oil-enclosed contacts, and various forms using the directed flow of pressurized air, or pressurized oil, to cool and interrupt the arc. By 1935, the specially constructed circuit breakers used at the Boulder Dam project used eight series breaks and pressurized oil flow to interrupt faults of up to 2,500 MVA, in three cycles of the AC power frequency.

Operation

All circuit breaker systems have common features in their operation, but details vary substantially depending on the voltage class, current rating and type of the circuit breaker.

The circuit breaker must first detect a fault condition. In small mains and low voltage circuit breakers, this is usually done within the device itself. Typically, the heating or magnetic effects of electric current are employed. Circuit breakers for large currents or high voltages are usually arranged with protective relay pilot devices to sense a fault condition and to operate the opening mechanism. These typically require a separate power source, such as a battery, although some high-voltage circuit breakers are self-contained with current transformers, protective relays, and an internal control power source.

Once a fault is detected, the circuit breaker contacts must open to interrupt the circuit; this is commonly done using mechanically stored energy contained within the breaker, such as a spring or compressed air to separate the contacts. Circuit breakers may also use the higher current caused by the fault to separate the contacts, such as thermal expansion or a magnetic field. Small circuit breakers typically have a manual control lever to switch off the load or reset a tripped breaker, while larger units use solenoids to trip the mechanism, and electric motors to restore energy to the springs.

The circuit breaker contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting (opening) the circuit. Contacts are made of copper or copper alloys, silver alloys and other highly conductive materials. Service life of the contacts is limited by the erosion of contact material due to arcing while interrupting the current. Miniature and molded-case circuit breakers are usually discarded when the contacts have worn, but power circuit breakers and high-voltage circuit breakers have replaceable contacts.

When a high current or voltage is interrupted, an arc is generated. The length of the arc is generally proportional to the voltage while the intensity (or heat) is proportional to the current. This arc must be contained, cooled and extinguished in a controlled way, so that the gap between the contacts can again withstand the voltage in the circuit. Different circuit breakers use vacuum, air, insulating gas, or oil as the medium the arc forms in. Different techniques are used to extinguish the arc including:

• Lengthening or deflecting the arc
• Intensive cooling (in jet chambers)
• Division into partial arcs
• Zero point quenching (contacts open at the zero current time crossing of the AC waveform, effectively breaking no load current at the time of opening. The zero-crossing occurs at twice the line frequency; i.e., 100 times per second for 50 Hz and 120 times per second for 60 Hz AC.)
• Connecting capacitors in parallel with contacts in DC circuits.

Finally, once the fault condition has been cleared, the contacts must again be closed to restore power to the interrupted circuit.

Arc interruption

Low-voltage miniature circuit breakers (MCB) use air alone to extinguish the arc. These circuit breakers contain so-called arc chutes, a stack of mutually insulated parallel metal plates that divide and cool the arc. By splitting the arc into smaller arcs the arc is cooled down while the arc voltage is increased and serves as an additional impedance that limits the current through the circuit breaker. The current-carrying parts near the contacts provide easy deflection of the arc into the arc chutes by a magnetic force of a current path, although magnetic blowout coils or permanent magnets could also deflect the arc into the arc chute (used on circuit breakers for higher ratings). The number of plates in the arc chute is dependent on the short-circuit rating and nominal voltage of the circuit breaker.

In larger ratings, oil circuit breakers rely upon vaporization of some of the oil to blast a jet of oil through the arc.

Gas (usually sulfur hexafluoride) circuit breakers sometimes stretch the arc using a magnetic field, and then rely upon the dielectric strength of the sulfur hexafluoride (SF₆) to quench the stretched arc.

Vacuum circuit breakers have minimal arcing (as there is nothing to ionize other than the contact material). The arc quenches when it is stretched a very small amount (less than 2–3 mm (0.08–0.1 in)). Vacuum circuit breakers are frequently used in modern medium-voltage switch gear to 38,000 volts.

Air circuit breakers may use compressed air to blow out the arc, or alternatively, the contacts are rapidly swung into a small sealed chamber, the escaping of the displaced air thus blowing out the arc.

Circuit breakers are usually able to terminate all current very quickly: typically the arc is extinguished between 30 ms and 150 ms after the mechanism has been tripped, depending upon age and construction of the device. The maximum current value and let-through energy determine the quality of the circuit breakers.

Short circuit

Circuit breakers are rated both by the normal current that they are expected to carry, and the maximum short-circuit current that they can safely interrupt. This latter figure is the ampere interrupting capacity (AIC) of the breaker.

Under short-circuit conditions, the calculated or measured maximum prospective short-circuit current may be many times the normal, rated current of the circuit. When electrical contacts open to interrupt a large current, there is a tendency for an arc to form between the opened contacts, which would allow the current to continue. This condition can create conductive ionized gases and molten or vaporized metal, which can cause the further continuation of the arc, or creation of additional short circuits, potentially resulting in the explosion of the circuit breaker and the equipment that it is installed in. Therefore, circuit breakers must incorporate various features to divide and extinguish the arc.

The maximum short-circuit current that a breaker can interrupt is determined by testing. Application of a breaker in a circuit with a prospective short-circuit current higher than the breaker's interrupting capacity rating may result in failure of the breaker to safely interrupt a fault. In a worst-case scenario, the breaker may successfully interrupt the fault, only to explode when reset.

Typical domestic panel circuit breakers are rated to interrupt 6 kA (6000 A) short-circuit current.

Miniature circuit breakers used to protect control circuits or small appliances may not have sufficient interrupting capacity to use at a panel board; these circuit breakers are called "supplemental circuit protectors" to distinguish them from distribution-type circuit breakers.

Standard current ratings

Time till trip versus current as multiple of nominal current

Circuit breakers are manufactured in standard sizes, using a system of preferred numbers to cover a range of ratings. Miniature circuit breakers have a fixed trip setting; changing the operating current value requires changing the whole circuit breaker. Larger circuit breakers can have adjustable trip settings, allowing standardized elements to be applied but with a setting intended to improve protection. For example, a circuit breaker with a 400 ampere "frame size" might have its overcurrent detection set to operate at only 300 amperes, to protect a feeder cable.

For low voltage distribution circuit breakers, International Standards, IEC 60898-1 defines the rated current as the maximum current that the breaker is designed to carry continuously. The commonly available preferred values for the rated current are 1 A, 2 A, 4 A, 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A, 63 A, 80 A, 100 A, and 125 A. The circuit breaker is labeled with the rated current in amperes prefixed by a letter, which indicates the instantaneous tripping current that causes the circuit breaker to trip without intentional time delay expressed in multiples of the rated current:

Type	Instantaneous tripping current
B	3-5 times rated current In For example a 10 A device will trip at 30–50 A
C	5 to 10 times In
D	10-20 times In
K	8 to 12 times In For the protection of loads that cause frequent short duration (approximately 400 ms to 2 s) current peaks in normal operation.
Z	2 to 3 times In for periods in the order of tens of seconds. For the protection of loads such as semiconductor devices or measuring circuits using current transformers.

Circuit breakers are also rated by the maximum fault current that they can interrupt; this allows use of more economical devices on systems unlikely to develop the high short-circuit current found on, for example, a large commercial building distribution system.

In the United States, Underwriters Laboratories (UL) certifies equipment ratings, called Series Ratings (or "integrated equipment ratings") for circuit breaker equipment used for buildings. Power circuit breakers and medium- and high-voltage circuit breakers used for industrial or electric power systems are designed and tested to ANSI or IEEE standards in the C37 series. For example, standard C37.16 lists preferred frame size current ratings for power circuit breakers in the range ofo 600 to 5000 amperes. Trip current settings dn time-current characteristics of these breakers are generally adjustable.

For medium and high voltage circuit breakers used in switchgear or substations and generating stations, relatively few standard frame sizes are generally manufactured. These circuit breakers are usually controlled by separate protective relay systems, offering adjustable tripping current and time settings as well as allowing for more complex protection schemes.

Types

Front panel of a 1250 A air circuit breaker manufactured by ABB. This low-voltage power circuit breaker can be withdrawn from its housing for servicing. Trip characteristics are configurable via DIP switches on the front panel.

Many classifications of circuit breakers can be made, based on their features such as voltage class, construction type, interrupting type, and structural features.

Low-voltage

Low-voltage (less than 1,000 V_AC) types are common in domestic, commercial and industrial application, and include:

• Miniature circuit breaker (MCB)—rated current up to 125 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above are in this category.
• Molded Case Circuit Breaker (MCCB)—rated current up to 1,600 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in larger ratings.
• Low-voltage power circuit breakers can be mounted in multi-tiers in low-voltage switchboards or switchgear cabinets.

The characteristics of low-voltage circuit breakers are given by international standards such as IEC 947. These circuit breakers are often installed in draw-out enclosures that allow removal and interchange without dismantling the switchgear.

Large low-voltage molded case and power circuit breakers may have electric motor operators so they can open and close under remote control. These may form part of an automatic transfer switch system for standby power.

Low-voltage circuit breakers are also made for direct-current (DC) applications, such as DC for subway lines. Direct current requires special breakers because the arc is continuous—unlike an AC arc, which tends to go out on each half cycle, direct current circuit breaker has blow-out coils that generate a magnetic field that rapidly stretches the arc. Small circuit breakers are either installed directly in equipment, or are arranged in a breaker panel.

Inside a miniature circuit breaker

The DIN rail-mounted thermal-magnetic miniature circuit breaker is the most common style in modern domestic consumer units and commercial electrical distribution boards throughout Europe. The design includes the following components:

1. Actuator lever - used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped). Most breakers are designed so they can still trip even if the lever is held or locked in the "on" position. This is sometimes referred to as "free trip" or "positive trip" operation.
2. Actuator mechanism - forces the contacts together or apart.
3. Contacts - allow current when touching and break the current when moved apart.
4. Terminals
5. Bimetallic strip - separates contacts in response to smaller, longer-term overcurrents
6. Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.
7. Solenoid - separates contacts rapidly in response to high overcurrents
8. Arc divider/extinguisher

Solid state

Solid-state circuit breakers, also known as digital circuit breakers are a technological innovation which promises advance circuit breaker technology out of the mechanical level, into the electrical. This promises several advantages, such as cutting the circuit in fractions of microseconds, better monitoring of circuit loads and longer lifetimes.

Magnetic

Magnetic circuit breakers use a solenoid (electromagnet) whose pulling force increases with the current. Certain designs utilize electromagnetic forces in addition to those of the solenoid. The circuit breaker contacts are held closed by a latch. As the current in the solenoid increases beyond the rating of the circuit breaker, the solenoid's pull releases the latch, which lets the contacts open by spring action. They are the most commonly used circuit breakers in the United States.

Thermal-magnetic

Shihlin Electric MCCB with SHT

Thermal magnetic circuit breakers, which are the type found in most distribution boards in Europe and countries with a similar wiring arrangements, incorporate both techniques with the electromagnet responding instantaneously to large surges in current (short circuits) and the bimetallic strip responding to less extreme but longer-term over-current conditions. The thermal portion of the circuit breaker provides a time response feature, that trips the circuit breaker sooner for larger over currents but allows smaller overloads to persist for a longer time. This allows short current spikes such as are produced when a motor or other non-resistive load is switched on. With very large over-currents during a short circuit, the magnetic element trips the circuit breaker with no intentional additional delay.

Magnetic-hydraulic

A magnetic-hydraulic circuit breaker uses a solenoid coil to provide operating force to open the contacts. Magnetic-hydraulic breakers incorporate a hydraulic time delay feature using a viscous fluid. A spring restrains the core until the current exceeds the breaker rating. During an overload, the speed of the solenoid motion is restricted by the fluid. The delay permits brief current surges beyond normal running current for motor starting, energizing equipment, etc. Short-circuit currents provide sufficient solenoid force to release the latch regardless of core position thus bypassing the delay feature. Ambient temperature affects the time delay but does not affect the current rating of a magnetic breaker.

Large power circuit breakers, applied in circuits of more than 1000 volts, may incorporate hydraulic elements in the contact operating mechanism. Hydraulic energy may be supplied by a pump, or stored in accumulators. These form a distinct type from oil-filled circuit breakers where oil is the arc extinguishing medium.

Common trip (ganged) breakers

Three-pole common trip breaker for supplying a three-phase device. This breaker has a 2 A rating.

To provide simultaneous breaking on multiple circuits from a fault on any one, circuit breakers may be made as a ganged assembly. This is a very common requirement for 3 phase systems, where breaking may be either 3 or 4 pole (solid or switched neutral). Some makers make ganging kits to allow groups of single phase breakers to be interlinked as required.

In the US, where split phase supplies are common, in branch circuits with more than one live conductor, each live conductor must be protected by a breaker pole. To ensure that all live conductors are interrupted when any pole trips, a "common trip" breaker must be used. These may either contain two or three tripping mechanisms within one case, or for small breakers, may externally tie the poles together via their operating handles. Two-pole common trip breakers are common on 120/240-volt systems where 240 volt loads (including major appliances or further distribution boards) span the two live wires. Three-pole common trip breakers are typically used to supply three-phase electric power to large motors or further distribution boards.

Separate circuit breakers must never be used for live and neutral, because if the neutral is disconnected while the live conductor stays connected, a very dangerous condition arises: the circuit appears de-energized (appliances don't work), but wires remain live and some residual-current devices (RCDs) may not trip if someone touches the live wire (because some RCDs need power to trip). This is why only common trip breakers must be used when neutral wire switching is needed.

Shunt-trip units

A shunt-trip unit appears similar to a normal breaker and the moving actuators are 'ganged' to a normal breaker mechanism to operate together in a similar way, but the shunt trip is a solenoid intended to be operated by an external constant voltage signal, rather than a current, commonly the local mains voltage or   DC. These are often used to cut the power when a high risk event occurs, such as a fire or flood alarm, or another electrical condition, such as over voltage detection. Shunt trips may be a user fitted accessory to a standard breaker, or supplied as an integral part of the circuit breaker.

Medium-voltage

A Siemens air circuit breaker mounted on a motor control cubicle

Medium-voltage circuit breakers rated between 1 and 72 kV may be assembled into metal-enclosed switchgear line ups for indoor use, or may be individual components installed outdoors in a substation. Air-break circuit breakers replaced oil-filled units for indoor applications, but are now themselves being replaced by vacuum circuit breakers (up to about 40.5 kV). Like the high voltage circuit breakers described below, these are also operated by current sensing protective relays operated through current transformers. The characteristics of MV breakers are given by international standards such as IEC 62271. Medium-voltage circuit breakers nearly always use separate current sensors and protective relays, instead of relying on built-in thermal or magnetic overcurrent sensors.

Medium-voltage circuit breakers can be classified by the medium used to extinguish the arc:

• Vacuum circuit breakers—With rated current up to 6,300 A, and higher for generator circuit breakers application (up to 16,000 A & 140 kA). These breakers interrupt the current by creating and extinguishing the arc in a vacuum container - aka "bottle". Long life bellows are designed to travel the 6–10 mm the contacts must part. These are generally applied for voltages up to about 40,500 V, which corresponds roughly to the medium-voltage range of power systems. Vacuum circuit breakers have longer life expectancy between overhaul than do other circuit breakers. In addition their global warming potential is by far lower than SF₆ circuit breaker.
• Air circuit breakers—Rated current up to 6,300 A and higher for generator circuit breakers. Trip characteristics are often fully adjustable including configurable trip thresholds and delays. Usually electronically controlled, though some models are microprocessor controlled via an integral electronic trip unit. Often used for main power distribution in large industrial plant, where the breakers are arranged in draw-out enclosures for ease of maintenance.
• SF₆ circuit breakers extinguish the arc in a chamber filled with sulfur hexafluoride gas.

Medium-voltage circuit breakers may be connected into the circuit by bolted connections to bus bars or wires, especially in outdoor switchyards. Medium-voltage circuit breakers in switchgear line-ups are often built with draw-out construction, allowing breaker removal without disturbing power circuit connections, using a motor-operated or hand-cranked mechanism to separate the breaker from its enclosure.

High-voltage

Main article: High-voltage switchgear

 

Three single-phase Soviet/Russian 110-kV oil circuit breakers

 

400 kV SF₆ live-tank circuit breakers

Electrical power transmission networks are protected and controlled by high-voltage breakers. The definition of high voltage varies but in power transmission work is usually thought to be 72.5 kV or higher, according to a recent definition by the International Electrotechnical Commission (IEC). High-voltage breakers are nearly always solenoid-operated, with current sensing protective relays operated through current transformers. In substations the protective relay scheme can be complex, protecting equipment and buses from various types of overload or ground/earth fault.

High-voltage breakers are broadly classified by the medium used to extinguish the arc:

• Bulk oil
• Minimum oil
• Air blast
• Vacuum
• SF₆
• CO₂

Due to environmental and cost concerns over insulating oil spills, most new breakers use SF₆ gas to quench the arc.

Circuit breakers can be classified as live tank, where the enclosure that contains the breaking mechanism is at line potential, or dead tank with the enclosure at earth potential. High-voltage AC circuit breakers are routinely available with ratings up to 765 kV. 1,200 kV breakers were launched by Siemens in November 2011, followed by ABB in April the following year.

High-voltage circuit breakers used on transmission systems may be arranged to allow a single pole of a three-phase line to trip, instead of tripping all three poles; for some classes of faults this improves the system stability and availability.

High-voltage direct current circuit breakers are still a field of research as of 2015. Such breakers would be useful to interconnect HVDC transmission systems.

Sulfur hexafluoride (SF₆) high-voltage

Main article: Sulfur hexafluoride circuit breaker

A sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur hexafluoride gas to quench the arc. They are most often used for transmission-level voltages and may be incorporated into compact gas-insulated switchgear. In cold climates, supplemental heating or de-rating of the circuit breakers may be required due to liquefaction of the SF₆ gas.

Disconnecting circuit breaker (DCB)

The disconnecting circuit breaker (DCB) was introduced in 2000 and is a high-voltage circuit breaker modeled after the SF₆-breaker. It presents a technical solution where the disconnecting function is integrated in the breaking chamber, eliminating the need for separate disconnectors. This increases the availability, since open-air disconnecting switch main contacts need maintenance every 2–6 years, while modern circuit breakers have maintenance intervals of 15 years. Implementing a DCB solution also reduces the space requirements within the substation, and increases the reliability, due to the lack of separate disconnectors.

In order to further reduce the required space of substation, as well as simplifying the design and engineering of the substation, a fiber optic current sensor (FOCS) can be integrated with the DCB. A 420 kV DCB with integrated FOCS can reduce a substation's footprint with over 50% compared to a conventional solution of live tank breakers with disconnectors and current transformers, due to reduced material and no additional insulation medium.

Carbon dioxide (CO₂) high-voltage

In 2012, ABB presented a 75 kV high-voltage breaker that uses carbon dioxide as the medium to extinguish the arc. The carbon dioxide breaker works on the same principles as an SF₆ breaker and can also be produced as a disconnecting circuit breaker. By switching from SF₆ to CO₂, it is possible to reduce the CO₂ emissions by 10 tons during the product's life cycle.

"Smart" circuit breakers

Several firms have looked at adding monitoring for appliances via electronics or using a digital circuit breaker to monitor the breakers remotely. Utility companies in the United States have been reviewing use of the technology to turn on and off appliances, as well as potentially turning off charging of electric cars during periods of high electrical grid load. These devices under research and testing would have wireless capability to monitor the electrical usage in a house via a smartphone app or other means.

Other breakers

Residual current circuit breaker with overcurrent protection

The following types are described in separate articles.

• Breakers for protections against earth faults too small to trip an over-current device:
  • Residual-current device (RCD), or residual-current circuit breaker (RCCB) — detects current imbalance, but does not provide over-current protection. In the United States and Canada, these are called ground fault circuit interrupters (GFCI).
  • Residual-current circuit breaker with overcurrent protection (RCBO) — combines the functions of a RCD and a MCB in one package. In the United States and Canada, these are called GFCI breakers.
  • Earth leakage circuit breaker (ELCB) — This detects current in the earth wire directly rather than detecting imbalance. They are no longer seen in new installations as they cannot detect any dangerous condition where the current is returning to earth by another route - such as via a person on the ground or via plumbing. (also called VOELCB in the UK).
• Recloser — A type of circuit breaker that closes automatically after a delay. These are used on overhead electric power distribution systems, to prevent short duration faults from causing sustained outages.
• Polyswitch (polyfuse) — A small device commonly described as an automatically resetting fuse rather than a circuit breaker.

Polyphenol

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Polyphenol 

 

Plant-derived polyphenol, tannic acid, formed by esterification of ten equivalents of the phenylpropanoid-derived gallic acid to a monosaccharide (glucose) core from primary metabolism

Polyphenols (/ˌpɒliˈfiːnoʊl, -nɒl/) are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments.

Curcumin, a bright yellow component of turmeric (Curcuma longa) is a well-studied polyphenol.

Etymology

The name derives from the Ancient Greek word πολύς (polus, meaning "many, much") and the word phenol which refers to a chemical structure formed by attaching to an aromatic benzenoid (phenyl) ring to a hydroxyl (-OH) group as is found in alcohols (hence the -ol suffix). The term polyphenol has been in use at least since 1894.

Definition

Ellagic acid, a polyphenol.

 

Raspberry ellagitannin, a tannin composed of 14 gallic acid units around a core of three units of glucose, with two gallic acids as simple esters, and the remaining 12 appearing in 6 ellagic acid-type units. Ester, ether, and biaryl linkages are present, see below.

The term polyphenol is not well-defined, but is generally agreed that they are natural products "having a polyphenol structure (i.e., several hydroxyl groups on aromatic rings)" including four principal classes: "phenolic acids, flavonoids, stilbenes, and lignans".

• Flavonoids include flavones, flavonols, flavanols, flavanones, isoflavones, proanthocyanidins, and anthocyanins. Particularly abundant flavanoids in foods are catechin (tea, fruits), hesperetin (citrus fruits), cyanidin (red fruits and berries), daidzein (soybean), proanthocyanidins (apple, grape, cocoa), and quercetin (onion, tea, apples).
• Phenolic acid include caffeic acid
• Lignans are polyphenols derived from phenylalanine found in Flax seed and other cereals.

WBSSH definition

The White–Bate-Smith–Swain–Haslam (WBSSH) definition characterized structural characteristics common to plant phenolics used in tanning (i.e., the tannins).

In terms of properties, the WBSSH describes the polyphenols thusly:

• generally moderately water-soluble compounds
• with molecular weight of 500–4000 Da
• with >12 phenolic hydroxyl groups
• with 5–7 aromatic rings per 1000 Da

In terms of structures, the WBSSH recognizes two structural family that have these properties:

• proanthocyanidins and its derivatives
• galloyl and hexahydroxydiphenoyl esters and their derivatives

Quideau definition

According to Stéphane Quideau, the term "polyphenol" refers to compounds derived from the shikimate/phenylpropanoid and/or the polyketide pathway, featuring more than one phenolic unit and deprived of nitrogen-based functions.

Ellagic acid, a molecule at the core of naturally occurring phenolic compounds of varying sizes, is itself not a polyphenol by the WBSSH definition, but is by the Quideau definition. The raspberry ellagitannin, on the other hand, with its 14 gallic acid moieties (most in ellagic acid-type components), and more than 40 phenolic hydroxyl groups, meets the criteria of both definitions of a polyphenol. Other examples of compounds that fall under both the WBSSH and Quideau definitions include the black tea theaflavin-3-gallate shown below, and the hydrolyzable tannin, tannic acid.

Theaflavin-3-gallate, a plant-derived polyphenol, an ester of gallic acid and a theaflavin core. There are 9 phenolic hydroxyl groups and two phenolic ether linkages.

Chemistry

Polyphenols are reactive species toward oxidation, hence their description as antioxidants in vitro.

Structural chemistry

Polyphenols are often larger molecules (macromolecules). Their upper molecular weight limit is about 800 daltons, which allows for the possibility to rapidly diffuse across cell membranes so that they can reach intracellular sites of action or remain as pigments once the cell senesces. Hence, many larger polyphenols are biosynthesized in-situ from smaller polyphenols to non-hydrolyzable tannins and remain undiscovered in the plant matrix. Most polyphenols contain repeating phenolic moieties of pyrocatechol, resorcinol, pyrogallol, and phloroglucinol connected by esters (hydrolyzable tannins) or more stable C-C bonds (nonhydrolyzable condensed tannins). Proanthocyanidins are mostly polymeric units of catechin and epicatechin.

The C-glucoside substructure of polyphenols is exemplified by the phenol-saccharide conjugate puerarin, a midmolecular-weight plant natural product. The attachment of the phenol to the saccharide is by a carbon-carbon bond. The isoflavone and its 10-atom benzopyran "fused ring" system, also a structural feature here, is common in polyphenols.

Polyphenols often have functional groups beyond hydroxyl groups. Ether ester linkages are common, as are carboxylic acids.

An example of a synthetically achieved small ellagitannin, tellimagrandin II, derived biosynthetically and sometimes synthetically by oxidative joining of two of the galloyl moieties of 1,2,3,4,6-pentagalloyl-glucose

Analytical chemistry

The analysis techniques are those of phytochemistry: extraction, isolation, structural elucidation, then quantification.

Extraction

Extraction of polyphenols can be performed using a solvent like water, hot water, methanol, methanol/formic acid, methanol/water/acetic or formic acid. Liquid–liquid extraction can be also performed or countercurrent chromatography. Solid phase extraction can also be made on C18 sorbent cartridges. Other techniques are ultrasonic extraction, heat reflux extraction, microwave-assisted extraction, critical carbon dioxide, high-pressure liquid extraction or use of ethanol in an immersion extractor. The extraction conditions (temperature, extraction time, ratio of solvent to raw material, solvent and concentrations) have to be optimized.

Mainly found in the fruit skins and seeds, high levels of polyphenols may reflect only the measured extractable polyphenol (EPP) content of a fruit which may also contain non-extractable polyphenols. Black tea contains high amounts of polyphenol and makes up for 20% of its weight.

Concentration can be made by ultrafiltration. Purification can be achieved by preparative chromatography.

Analysis techniques

Reversed-phase HPLC plot of separation of phenolic compounds. Smaller natural phenols formed individual peaks while tannins form a hump.

Phosphomolybdic acid is used as a reagent for staining phenolics in thin layer chromatography. Polyphenols can be studied by spectroscopy, especially in the ultraviolet domain, by fractionation or paper chromatography. They can also be analysed by chemical characterisation.

Instrumental chemistry analyses include separation by high performance liquid chromatography (HPLC), and especially by reversed-phase liquid chromatography (RPLC), can be coupled to mass spectrometry. Purified compounds can be identified by the means of nuclear magnetic resonance.

Microscopy analysis

The DMACA reagent is an histological dye specific to polyphenols used in microscopy analyses. The autofluorescence of polyphenols can also be used, especially for localisation of lignin and suberin. Where fluorescence of the molecules themselves is insufficient for visualization by light microscopy, DPBA (diphenylboric acid 2-aminoethyl ester, also referred to as Naturstoff reagent A) has traditionally been used, at least in plant science, to enhance the fluorescence signal.

Quantification

Polyphenolic content in vitro can be quantified by volumetric titration. An oxidizing agent, permanganate, is used to oxidize known concentrations of a standard tannin solution, producing a standard curve. The tannin content of the unknown is then expressed as equivalents of the appropriate hydrolyzable or condensed tannin.

Some methods for quantification of total polyphenol content in vitro are based on colorimetric measurements. Some tests are relatively specific to polyphenols (for instance the Porter's assay). Total phenols (or antioxidant effect) can be measured using the Folin-Ciocalteu reaction. Results are typically expressed as gallic acid equivalents. Polyphenols are seldom evaluated by antibody technologies.

Other tests measure the antioxidant capacity of a fraction. Some make use of the ABTS radical cation which is reactive towards most antioxidants including phenolics, thiols and vitamin C. During this reaction, the blue ABTS radical cation is converted back to its colorless neutral form. The reaction may be monitored spectrophotometrically. This assay is often referred to as the Trolox equivalent antioxidant capacity (TEAC) assay. The reactivity of the various antioxidants tested are compared to that of Trolox, which is a vitamin E analog.

Other antioxidant capacity assays which use Trolox as a standard include the diphenylpicrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), ferric reducing ability of plasma (FRAP) assays or inhibition of copper-catalyzed in vitro human low-density lipoprotein oxidation.

New methods including the use of biosensors can help monitor the content of polyphenols in food.

Quantitation results produced by the mean of diode array detector–coupled HPLC are generally given as relative rather than absolute values as there is a lack of commercially available standards for all polyphenolic molecules.

Industrial applications

Some polyphenols are traditionally used as dyes. For instance, in the Indian subcontinent, the pomegranate peel, high in tannins and other polyphenols, or its juice, is employed in the dyeing of non-synthetic fabrics.

Polyphenols, especially tannins, were used traditionally for tanning leather and today also as precursors in green chemistry notably to produce plastics or resins by polymerisation with or without the use of formaldehyde or adhesives for particleboards. The aims are generally to make use of plant residues from grape, olive (called pomaces) or pecan shells left after processing.

Pyrogallol and pyrocatechin are among the oldest photographic developers.

Biochemistry

Polyphenols are thought to play diverse roles in the ecology of plants. These functions include:

• Release and suppression of growth hormones such as auxin.
• UV screens to protect against ionizing radiation and to provide coloration (plant pigments).
• Deterrence of herbivores (sensory properties).
• Prevention of microbial infections (phytoalexins).
• Signaling molecules in ripening and other growth processes.

Occurrence in nature

The most abundant polyphenols are the condensed tannins, found in virtually all families of plants. Larger polyphenols are often concentrated in leaf tissue, the epidermis, bark layers, flowers and fruits but also play important roles in the decomposition of forest litter, and nutrient cycles in forest ecology. Absolute concentrations of total phenols in plant tissues differ widely depending on the literature source, type of polyphenols and assay; they are in the range of 1–25% total natural phenols and polyphenols, calculated with reference to the dry green leaf mass.

High levels of polyphenols in some woods can explain their natural preservation against rot.

Flax and Myriophyllum spicatum (a submerged aquatic plant) secrete polyphenols that are involved in allelopathic interactions.

Polyphenols are also found in animals. In arthropods, such as insects, and crustaceans polyphenols play a role in epicuticle hardening (sclerotization). The hardening of the cuticle is due to the presence of a polyphenol oxidase. In crustaceans, there is a second oxidase activity leading to cuticle pigmentation. There is apparently no polyphenol tanning occurring in arachnids cuticle.

Biosynthesis and metabolism

Polyphenols incorporate smaller parts and building blocks from simpler natural phenols, which originate from the phenylpropanoid pathway for the phenolic acids or the shikimic acid pathway for gallotannins and analogs. Flavonoids and caffeic acid derivatives are biosynthesized from phenylalanine and malonyl-CoA. Complex gallotannins develop through the in-vitro oxidation of 1,2,3,4,6-pentagalloylglucose or dimerization processes resulting in hydrolyzable tannins. For anthocyanidins, precursors of the condensed tannin biosynthesis, dihydroflavonol reductase and leucoanthocyanidin reductase (LAR) are crucial enzymes with subsequent addition of catechin and epicatechin moieties for larger, non-hydrolyzable tannins.

The glycosylated form develops from glucosyltransferase activity and increases the solubility of polyphenols.

Polyphenol oxidase (PPO) is an enzyme that catalyses the oxidation of o-diphenols to produce o-quinones. It is the rapid polymerisation of o-quinones to produce black, brown or red polyphenolic pigments that causes fruit browning. In insects, PPO is involved in cuticle hardening.

Occurrence in food

See also: List of phytochemicals in food

Main articles: Natural phenols and polyphenols in wine and Natural phenols and polyphenols in tea

Polyphenols comprise up to 0.2–0.3% fresh weight for many fruits. Consuming common servings of wine, chocolate, legumes or tea may also contribute to about one gram of intake per day. According to a 2005 review on polyphenols:

The most important food sources are commodities widely consumed in large quantities such as fruit and vegetables, green tea, black tea, red wine, coffee, chocolate, olives, and extra virgin olive oil. Herbs and spices, nuts and algae are also potentially significant for supplying certain polyphenols. Some polyphenols are specific to particular food (flavanones in citrus fruit, isoflavones in soya, phloridzin in apples); whereas others, such as quercetin, are found in all plant products such as fruit, vegetables, cereals, leguminous plants, tea, and wine.

Some polyphenols are considered antinutrients – compounds that interfere with the absorption of essential nutrients – especially iron and other metal ions, which may bind to digestive enzymes and other proteins, particularly in ruminants.

In a comparison of cooking methods, phenolic and carotenoid levels in vegetables were retained better by steaming compared to frying. Polyphenols in wine, beer and various nonalcoholic juice beverages can be removed using finings, substances that are usually added at or near the completion of the processing of brewing.

Astringency

With respect to food and beverages, the cause of astringency is not fully understood, but it is measured chemically as the ability of a substance to precipitate proteins.

A review published in 2005 found that astringency increases and bitterness decreases with the mean degree of polymerization. For water-soluble polyphenols, molecular weights between 500 and 3000 were reported to be required for protein precipitation. However, smaller molecules might still have astringent qualities likely due to the formation of unprecipitated complexes with proteins or cross-linking of proteins with simple phenols that have 1,2-dihydroxy or 1,2,3-trihydroxy groups. Flavonoid configurations can also cause significant differences in sensory properties, e.g. epicatechin is more bitter and astringent than its chiral isomer catechin. In contrast, hydroxycinnamic acids do not have astringent qualities, but are bitter.

Potential health effects

Main article: Health effects of polyphenols

Polyphenols are a large, diverse group of compounds, making it difficult to determine their biological effects. Postulated health effects have been attributed to polyphenols in food, different classes of polyphenols and individual compounds, but studies through 2014 were largely from small, short-term clinical trials, and therefore were insufficient to establish an effect in humans. The bioavailability of polyphenols is low and their excretion as metabolites is rapid, two fates that depend on the metabolite and whether the polyphenol was glycosylated (bound to a sugar molecule). They are extensively metabolized, both upon uptake from the intestinal tract and by the gut microbiome.

In the US, the Food and Drug Administration issued guidance to manufacturers that polyphenols cannot be mentioned on food labels as antioxidant nutrients unless physiological evidence exists to verify such a qualification and a Dietary Reference Intake value has been established, characteristics which have not been determined for polyphenols.

As of 2014, the European Food Safety Authority approved two health claims for polyphenols, flavan-3-ols in cocoa (200 mg per day) contributing to a normal function of the vascular endothelium, and olive oil polyphenols (5 mg of hydroxytyrosol and its derivatives per day (e.g. oleuropein complex and tyrosol) contributing to the protection of blood lipids from oxidative damage.

Bullying

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Bullying

Share of children who report being bullied (2015)

Bullying is the use of force, coercion, hurtful teasing or threat, to abuse, aggressively dominate or intimidate. The behavior is often repeated and habitual. One essential prerequisite is the perception (by the bully or by others) of an imbalance of physical or social power. This imbalance distinguishes bullying from conflict. Bullying is a subcategory of aggressive behavior characterized by hostile intent, imbalance of power and repetition over a period of time. Bullying is the activity of repeated, aggressive behavior intended to hurt another individual, physically, mentally or emotionally.

Bullying can be done individually or by a group, called mobbing, in which the bully may have one or more "lieutenants" who are willing to assist the primary bully. Bullying in school and the workplace is also referred to as "peer abuse". Robert W. Fuller has analyzed bullying in the context of rankism. The Swedish-Norwegian researcher Dan Olweus says bullying occurs when a person is "exposed, repeatedly and over time, to negative actions on the part of one or more other persons", and that negative actions occur "when a person intentionally inflicts injury or discomfort upon another person, through physical contact, through words or in other ways". Individual bullying is usually characterized by a person behaving in a certain way to gain power over another person.

A bullying culture can develop in any context in which humans interact with each other. This may include school, family, the workplace, the home, and neighborhoods. The main platform for bullying in contemporary culture is on social media websites. In a 2012 study of male adolescent American football players, "the strongest predictor [of bullying] was the perception of whether the most influential male in a player's life would approve of the bullying behavior." A study by The Lancet Child & Adolescent Health in 2019 showed a relationship between social media use by girls and an increase in their exposure to bullying.

Bullying may be defined in many different ways. In the United Kingdom, there is no legal definition of bullying, while some states in the United States have laws against it. Bullying is divided into four basic types of abuse – psychological (sometimes called emotional or relational), verbal, physical, and cyber.

Behaviors used to assert such domination may include physical assault or coercion, verbal harassment, or threat, and such acts may be directed repeatedly toward particular targets. Rationalizations of such behavior sometimes include differences of social class, race, religion, gender, sexual orientation, appearance, behavior, body language, personality, reputation, lineage, strength, size, or ability. If bullying is done by a group, it is called mobbing.

Etymology

The word "bully" was first used in the 1530s meaning "sweetheart", applied to either sex, from the Dutch boel "lover, brother", probably diminutive of Middle High German buole "brother", of uncertain origin (compare with the German buhle "lover"). The meaning deteriorated through the 17th century through "fine fellow", "blusterer", to "harasser of the weak". This may have been as a connecting sense between "lover" and "ruffian" as in "protector of a prostitute", which was one sense of "bully" (though not specifically attested until 1706). The verb "to bully" is first attested in 1710.

In the past, in American culture, the term has been used differently, as an exclamation/exhortation, in particular famously associated with Theodore Roosevelt and continuing to the present in the bully pulpit, Roosevelt's coining and also as faint/deprecating praise ("bully for him").

Types

Bullying has been classified by the body of literature into different types. These can be in the form of nonverbal, verbal, or physical behavior. Another classification is based on perpetrators or the participants involved, so that the types include individual and collective bullying. Other interpretation also cite emotional and relational bullying in addition to physical harm inflicted towards another person or even property. There is also the case of the more recent phenomenon called cyberbullying.

Physical, verbal, and relational bullying are most prevalent in primary school and could also begin much earlier while continuing into later stages in individuals lives.

Individual

Individual bullying tactics are perpetrated by a single person against a victim or victims. Individual bullying can be classified into four types outlined below:

Physical

Physical bullying is any bullying that hurts someone's body or damages their possessions. Stealing, shoving, hitting, fighting, and intentionally destroying someone's property are types of physical bullying. Physical bullying is rarely the first form of bullying that a victim will experience. Often bullying will begin in a different form and later progress to physical violence. In physical bullying the main weapon the bully uses is his/her body, or some part thereof; or an object as a weapon when attacking his/her victim. Sometimes groups of young adults will target and alienate a peer because of some adolescent prejudice. This can quickly lead to a situation where they are being taunted, tortured, and "beaten up" by their classmates. Physical bullying will often escalate over time, and can lead to a detrimental or fatal ending, and therefore many try to stop it quickly to prevent any further escalation.

Verbal

Verbal bullying is one of the most common types of bullying. This is any bullying that is conducted by speaking, other use of the voice, or some form of body language and does not involve any physical contact. Bullying usually begins at this stage and includes any of the following:

• Derogatory name-calling and nicknaming
• Spreading rumors or lying about someone
• Threatening someone
• Yelling at or talking to someone in a rude or unkind tone of voice, especially without justifiable cause
• Mocking someone's voice or style of speaking
• Laughing at someone
• Use of body language (i.e., the middle finger) to torture someone
• Making insults or otherwise making fun of someone

In verbal bullying, the main weapon the bully uses is voice. In many cases, verbal bullying is common in both genders, but girls are more likely to perform it. Girls, in general, are more subtle with insults than boys. Girls use verbal bullying, as well as social exclusion techniques, to dominate and control other individuals and show their superiority and power, often to try to impress someone they idolize. Many boys are subtle enough to use verbal techniques for domination when they want to avoid the trouble that can come with physically bullying someone else.

Relational

Relational bullying (sometimes referred to as social aggression) is the type of bullying that uses relationships to hurt others. The term also denotes any bullying that is done with the intent to hurt somebody's reputation or social standing which can also link in with the techniques included in physical and verbal bullying. Relational bullying is a form of bullying common among youth, but particularly upon girls. Social exclusion (slighting or making someone feel "left out") is one of the most common types of relational bullying. Relational bullying can be used as a tool by bullies to both improve their social standing and control others. Unlike physical bullying which is obvious, relational bullying is not overt and can continue for a long time without being noticed.

Cyber

Cyberbullying is the use of technology to harass, threaten, embarrass, or target another person. When an adult is involved, it may meet the definition of cyber-harassment or cyberstalking, a crime that can have legal consequences and involve jail time. This includes bullying by use of email, instant messaging, social media websites (such as Facebook), text messages, and cell phones. It is stated that Cyberbullying is more common in secondary school than in primary school.

Collective

Collective bullying tactics are employed by more than one individual against a victim or victims. Collective bullying is known as mobbing, and can include any of the individual types of bullying. Trolling behavior on social media, although generally assumed to be individual in nature by the casual reader, is sometime organized efforts by sponsored astroturfers.

Mobbing

Main article: Mobbing

Mobbing refers to the bullying of an individual by a group, in any context, such as a family, peer group, school, workplace, neighborhood, community, or online. When it occurs as emotional abuse in the workplace, such as "ganging up" by co-workers, subordinates or superiors, to force someone out of the workplace through rumor, innuendo, intimidation, humiliation, discrediting, and isolation, it is also referred to as malicious, nonsexual, nonracial/racial, general harassment.

Characteristics

Bullies and accomplices

Studies have shown that envy and resentment may be motives for bullying. Research on the self-esteem of bullies has produced equivocal results. While some bullies are arrogant and narcissistic, they can also use bullying as a tool to conceal shame or anxiety or to boost self-esteem: by demeaning others, the abuser feels empowered. Bullies may bully out of jealousy or because they themselves are bullied. Psychologist Roy Baumeister asserts that people who are prone to abusive behavior tend to have inflated but fragile egos. Because they think too highly of themselves, they are frequently offended by the criticisms and lack of deference of other people, and react to this disrespect with violence and insults.

Researchers have identified other risk factors such as depression and personality disorders, as well as quickness to anger and use of force, addiction to aggressive behaviors, mistaking others' actions as hostile, concern with preserving self-image, and engaging in obsessive or rigid actions. A combination of these factors may also be causes of this behavior. In one study of youth, a combination of antisocial traits and depression was found to be the best predictor of youth violence, whereas video game violence and television violence exposure were not predictive of these behaviors.

Bullying may also result from a genetic predisposition or a brain abnormality in the bully. While parents can help a toddler develop emotional regulation and control to restrict aggressive behavior, some children fail to develop these skills due to insecure attachment with their families, ineffective discipline, and environmental factors such as a stressful home life and hostile siblings. Moreover, according to some researchers, bullies may be inclined toward negativity and perform poorly academically. Dr. Cook says, "A typical bully has trouble resolving problems with others and also has trouble academically. He or she usually has negative attitudes and beliefs about others, feels negatively toward himself/herself, comes from a family environment characterized by conflict and poor parenting, perceives school as negative and is negatively influenced by peers."

Contrarily, some researchers have suggested that some bullies are psychologically strongest and have high social standing among their peers, while their targets are emotionally distressed and socially marginalized. Peer groups often promote the bully's actions, and members of these peer groups also engage in behaviors, such as mocking, excluding, punching, and insulting one another as a source of entertainment. Other researchers also argued that a minority of the bullies, those who are not in-turn bullied, enjoy going to school, and are least likely to take days off sick.

Research indicates that adults who bully have authoritarian personalities, combined with a strong need to control or dominate. It has also been suggested that a prejudicial view of subordinates can be a particularly strong risk factor.

In a recent study, bullies showed lower school performance-related self-esteem than non-involved students. They also showed higher social self-esteem than victims of traditional bullying.

Brain studies have shown that the section of the brain associated with reward becomes active when bullies are shown a video of someone inflicting pain on another.

Bystanders

Often, bullying takes place in the presence of a large group of relatively uninvolved bystanders. In many cases, it is the bully's ability to create the illusion they have the support of the majority present that instills the fear of "speaking out" in protestation of the bullying activities being observed by the group. Unless the "bully mentality" is effectively challenged in any given group in its early stages, it often becomes an accepted, or supported, norm within the group.

Unless action is taken, a "culture of bullying" is often perpetuated within a group for months, years, or longer.

Bystanders who have been able to establish their own "friendship group" or "support group" have been found to be far more likely to opt to speak out against bullying behavior than those who have not.

In addition to communication of clear expectations that bystanders should intervene and increasing individual self-efficacy, there is growing research to suggest interventions should build on the foundation that bullying is morally wrong.

Among adults, being a bystander to workplace bullying was linked to depression.

Victims

Dr. Cook says, "A typical victim is likely to be aggressive, lack social skills, think negative thoughts, experience difficulties in solving social problems, come from a negative family, school and community environments and be noticeably rejected and isolated by peers." Victims often have characteristics such as being physically and mentally weak, as well as being easily distraught emotionally. They may also have physical characteristics that make them easier targets for bullies such as being overweight or having some type of physical deformity. Boys are more likely to be victims of physical bullying while girls are more likely to be bullied indirectly.

Low levels of self-esteem has been identified as a frequent antecedent of bullying victimization. Victims of traditional bullying tend to have lower global, social, body-related, and emotional self-esteem compared to uninvolved students. Victims of cyberbullying, on the other hand, may not have lower self-esteem scores than uninvolved students but might have higher body-related self-esteem than both victims of traditional bullying and bullies.

The results of a meta-analysis conducted by Cook and published by the American Psychological Association in 2010 concluded the main risk factors for children and adolescents being bullied, and also for becoming bullies, are the lack of social problem-solving skills.

Children who are bullied often show physical or emotional signs, such as: being afraid to attend school, complaining of headaches or a loss of appetite, a lack of interest in school activities, spending time with friends or family, reluctance to go out in public for fear they may encounter their bullies in public places other than school, and having an overall sense of sadness.

Effects

Mona O'Moore of the Anti-Bullying Centre at Trinity College in Dublin, has written, "There is a growing body of research which indicates that individuals, whether child or adult, who are persistently subjected to abusive behavior are at risk of stress related illness which can sometimes lead to suicide" Those who have been the targets of bullying can develop long-term emotional and behavioral problems. Bullying can cause loneliness, depression, anxiety, lead to low self-esteem and increased susceptibility to illness. Bullying has also been shown to cause maladjustment in young children, and targets of bullying who were also bullies themselves exhibit even greater social difficulties. A mental health report also found that bullying was linked to eating disorders, anxiety, body dysmorphia and other negative psychological effects. Both victims and perpetrators have been shown to exhibit higher levels of loneliness.

Suicide

Main articles: Bullying and suicide and List of suicides that have been attributed to bullying

Even though there is evidence that bullying increases the risk of suicide, bullying alone does not cause suicide. Depression is one of the main reasons why kids who are bullied die by suicide. It is estimated that between 15 and 25 children die by suicide every year in the UK alone because they are being bullied. Certain groups seem to incur a higher risk for suicide, such as Native Americans, Alaskan Natives, Asian Americans, and LGBT people. When someone feels unsupported by family or friends, it can make the situation much worse for the victim.

In a self-report study completed in New York by 9th through 12th graders, victims of bullying reported more depressive symptoms and psychological distress than those who did not experience bullying. All types of involvement in bullying among both boys and girls is associated with depression even a couple years later. Another study that followed up with Finnish teens two years after the initial survey showed that depression and suicidal ideation is higher with teens who are bullied than those who did not report experiencing bullying. A Dutch longitudinal study on elementary students reported that boys who are bully-victims, who play both roles of a victim and a bully, were more likely to experience depression or serious suicidal ideation than the other roles, victims or bullies only, while girls who have any involvement in bullying have a higher level of risk for depression. In a study of high school students completed in Boston, students who self reported being victims of bullying were more likely to consider suicide when compared to youth who did not report being bullied. The same study also showed a higher risk of suicidal consideration in youth who report being a perpetrator, victim, or victim-perpetrator. Victims and victim-bullies are associated with a higher risk of suicide attempts. The place where youth live also appears to differentiate their bullying experiences such that those living in more urban areas who reported both being bullied and bullying others appear to show higher risk of suicidal ideation and suicide attempts. A national survey given to American 6th through 10th grade students found that cyberbullying victims experience a higher level of depression than victims experiencing other forms of bullying. This can be related to the anonymity behind social media. If a teen is being bullied and is displaying symptoms of depression it should be questioned and interventions should be implemented. The Danish study showed that kids who are bullied talked to their parents and teachers about it and some reported a decrease in bullying or a stop in the bullying after a teacher or parent intervened. The study emphasizes the importance of implementing program-collaborations in schools to have programs and anti-bullying interventions in place to prevent and properly intervene when it occurs. The study also shows the importance of having parents and teachers talk to the bullies about their bullying behavior in order to provide the necessary support for those experiencing bullying.

While some people find it very easy to ignore a bully, others may find it very difficult and reach a breaking point. There have been cases of apparent bullying suicides that have been reported closely by the media. These include the deaths of Ryan Halligan, Phoebe Prince, Dawn-Marie Wesley, Nicola Ann Raphael, Megan Meier, Audrie Pott, Tyler Clementi, Jamey Rodemeyer, Kenneth Weishuhn, Jadin Bell, Kelly Yeomans, Rehtaeh Parsons, Amanda Todd, Brodie Panlock, Jessica Haffer, Hamed Nastoh, Sladjana Vidovic, April Himes, Cherice Moralez and Rebecca Ann Sedwick. According to the suicide awareness voices for education, suicide is one of the leading causes of death for youth from 15 to 24 years old. Over 16 percent of students seriously consider suicide, 13 percent create a plan, and 8 percent have made a serious attempt.

Strength and wisdom

Some have argued that bullying can teach life lessons and instill strength. Helene Guldberg, a child development academic, sparked controversy when she argued that being a target of bullying can teach a child "how to manage disputes and boost their ability to interact with others", and that teachers should not intervene but leave children to respond to the bullying themselves.

The teaching of anti-bullying coping skills to children, carers and teachers has been found to be an effective long-term means of reducing bullying incidence rates and a valuable skill-set for individuals.

Testosterone production

Statistically controlling for age and pubertal status, results indicated that on average verbally bullied girls produced less testosterone, and verbally bullied boys produced more testosterone than their nonbullied counterparts.

Dark triad

Main article: Dark triad

Research on the dark triad (narcissism, Machiavellianism, and psychopathy) indicate a correlation with bullying as part of evidence of the aversive nature of those traits.

Projection

Main article: Psychological projection

A bully may project his/her own feelings of vulnerability onto the target(s) of the bullying activity. Despite the fact that a bully's typically denigrating activities are aimed at the bully's targets, the true source of such negativity is ultimately almost always found in the bully's own sense of personal insecurity and/or vulnerability. Such aggressive projections of displaced negative emotions can occur anywhere from the micro-level of interpersonal relationships, all the way up through to the macro-level of international politics, or even international armed conflict.

Emotional intelligence

Main article: Bullying and emotional intelligence

Bullying is abusive social interaction between peers which can include aggression, harassment, and violence. Bullying is typically repetitive and enacted by those who are in a position of power over the victim. A growing body of research illustrates a significant relationship between bullying and emotional intelligence (EI). Mayer et al., (2008) defines the dimensions of overall EI as "accurately perceiving emotion, using emotions to facilitate thought, understanding emotion, and managing emotion". The concept combines emotional and intellectual processes. Lower emotional intelligence appears to be related to involvement in bullying, as the bully and/or the victim of bullying. EI seems to play an important role in both bullying behavior and victimization in bullying; given that EI is illustrated to be malleable, EI education could greatly improve bullying prevention and intervention initiatives.

Context

Internet

Main article: Cyberbullying

Cyberbullying is any bullying done through the use of technology. This form of bullying can easily go undetected because of lack of parental/authoritative supervision. Because bullies can pose as someone else, it is the most anonymous form of bullying. Cyberbullying includes, but is not limited to, abuse using email, instant messaging, text messaging, websites, social networking sites, etc. With the creation of social networks like Facebook, Myspace, Instagram, and Twitter, cyberbullying has increased. Particular watchdog organizations have been designed to contain the spread of cyberbullying.

Disability

Main article: Disability bullying

It has been noted that disabled people are disproportionately affected by bullying and abuse, and such activity has been cited as a hate crime. The bullying is not limited to those who are visibly disabled, such as wheelchair-users or physically deformed such as those with a cleft lip, but also those with developmental disabilities such as autism and developmental coordination disorder.

There is an additional problem that those with learning disabilities are often not as able to explain things to other people, so are more likely to be disbelieved or ignored if they do complain.

Homosexuality

Main article: Gay bashing

Gay bullying and gay bashing designate direct or indirect verbal or physical actions by a person or group against someone who is gay or lesbian, or perceived to be so due to rumors or because they are considered to fit gay stereotypes. Gay and lesbian youth are more likely than straight youth to report bullying, as well as be bullied.

Law

Main article: Legal abuse

Legal bullying is the bringing of a vexatious legal action to control and punish a person. Legal bullying can often take the form of frivolous, repetitive, or burdensome lawsuits brought to intimidate the defendant into submitting to the litigant's request, not because of the legal merit of the litigant's position, but principally due to the defendant's inability to maintain the legal battle. This can also take the form of Strategic Lawsuit Against Public Participation (SLAPP). It was partially concern about the potential for this kind of abuse that helped to fuel the protests against SOPA and PIPA in the United States in 2011 and 2012.

Military

Main articles: Bullying in the military and Dedovshchina

In 2000, the UK Ministry of Defence (MOD) defined bullying as "the use of physical strength or the abuse of authority to intimidate or victimize others, or to give unlawful punishments".

Some argue that this behaviour should be allowed, due to ways in which "soldiering" is different from other occupations. Soldiers expected to risk their lives should, according to them, develop strength of body and spirit to accept bullying.

Parenting

See also: Child abuse, Narcissistic parent, and Parental narcissistic abuse

Parents who may displace their anger, insecurity, or a persistent need to dominate and control upon their children in excessive ways have been proven to increase the likelihood that their own children will in turn become overly aggressive or controlling towards their peers. The American Psychological Association advises on its website that parents who may suspect their own children may be engaging in bullying activities among their peers should carefully consider the examples which they themselves may be setting for their own children regarding how they typically interact with their own peers, colleagues, and children.

Prison

Main article: Prisoner abuse

The prison environment is known for bullying. An additional complication is the staff and their relationships with the inmates. Thus, the following possible bullying scenarios are possible:

• Inmate bullies inmate (echoing school bullying)
• Staff bullies inmate
• Staff bullies staff (a manifestation of workplace bullying)
• Inmate bullies staff

School

Main article: School bullying

 

A Centers for Disease Control and Prevention graphic presenting school anti-bullying guidelines.

Bullying can occur in nearly any part in or around the school building, although it may occur more frequently during physical education classes and activities such as recess. Bullying also takes place in school hallways, bathrooms, on school buses and while waiting for buses, and in classes that require group work and/or after school activities. Bullying in school sometimes consists of a group of students taking advantage of or isolating one student in particular and gaining the loyalty of bystanders who want to avoid becoming the next target. In the 2011 documentary Bully, we see first hand the torture that kids go through both in school and while on the school bus. As the movie follows around a few kids we see how bullying affects them both at school as well as in their homes. While bullying has no age limit, these bullies may taunt and tease their target before finally physically bullying them. Bystanders typically choose to either participate or watch, sometimes out of fear of becoming the next target.

Bullying can also be perpetrated by teachers and the school system itself; there is an inherent power differential in the system that can easily predispose to subtle or covert abuse (relational aggression or passive aggression), humiliation, or exclusion—even while maintaining overt commitments to anti-bullying policies.

In 2016, in Canada, a North American legal precedent was set by a mother and her son, after the son was bullied in his public school. The mother and son won a court case against the Ottawa-Carleton District School Board, making this the first case in North America where a school board has been found negligent in a bullying case for failing to meet the standard of care (the "duty of care" that the school board owes to its students). Thus, it sets a precedent of a school board being found liable in negligence for harm caused to a child, because they failed to protect a child from the bullying actions of other students. There has been only one other similar bullying case and it was won in Australia in 2013 (Oyston v. St. Patricks College, 2013).

Heterosexuality

Main article: Sexual bullying

See also: Slut-shaming

Sexual bullying is "any bullying behaviour, whether physical or non-physical, that is based on a person's sexuality or gender. It is when sexuality or gender is used as a weapon by boys or girls towards other boys or girls – although it is more commonly directed at girls. It can be carried out to a person's face, behind their back or through the use of technology."

Transsexuality

Main article: Trans bashing

Trans bashing is the act of victimizing a person physically, sexually, or verbally because they are transgender or transsexual. Unlike gay bashing, it is committed because of the target's actual or perceived gender identity, not sexual orientation.

Work

Main article: Workplace bullying

Workplace bullying occurs when an employee experiences a persistent pattern of mistreatment from others in the workplace that causes harm. Workplace bullying can include such tactics as verbal, nonverbal, psychological, physical abuse and humiliation. This type of workplace aggression is particularly difficult because, unlike the typical forms of school bullying, workplace bullies often operate within the established rules and policies of their organization and their society. Bullying in the workplace is in the majority of cases reported as having been perpetrated by someone in authority over the target. Bullies can also be peers, and occasionally can be subordinates.

The first known documented use of "workplace bullying" is in 1992 in a book by Andrea Adams called Bullying at Work: How to Confront and Overcome It.

Research has also investigated the impact of the larger organizational context on bullying as well as the group-level processes that impact on the incidence, and maintenance of bullying behavior. Bullying can be covert or overt. It may be missed by superiors or known by many throughout the organization. Negative effects are not limited to the targeted individuals, and may lead to a decline in employee morale and a change in organizational culture. A Cochrane Collaboration systematic review has found very low quality evidence to suggest that organizational and individual interventions may prevent bullying behaviors in the workplace.

Academia

Main article: Bullying in academia

Bullying in academia is workplace bullying of scholars and staff in academia, especially places of higher education such as colleges and universities. It is believed to be common, although has not received as much attention from researchers as bullying in some other contexts.

Blue collar jobs

Bullying has been identified as prominent in blue collar jobs, including on oil rigs and in mechanic shops and machine shops. It is thought that intimidation and fear of retribution cause decreased incident reports. In industry sectors dominated by males, typically of little education, where disclosure of incidents are seen as effeminate, reporting in the socioeconomic and cultural milieu of such industries would likely lead to a vicious circle. This is often used in combination with manipulation and coercion of facts to gain favour among higher-ranking administrators.

Information technology

Main article: Bullying in information technology

A culture of bullying is common in information technology (IT), leading to high sickness rates, low morale, poor productivity, and high staff-turnover. Deadline-driven project work and stressed-out managers take their toll on IT workers.

Courts

Main article: Bullying in the legal profession

Bullying in the legal profession is believed to be more common than in some other professions. It is believed that its adversarial, hierarchical tradition contributes towards this. Women, trainees and solicitors who have been qualified for five years or less are more impacted, as are ethnic minority lawyers and lesbian, gay and bisexual lawyers.

Medicine

Main articles: Bullying in medicine and Bullying in nursing

Bullying in the medical profession is common, particularly of student or trainee doctors and of nurses. It is thought that this is at least in part an outcome of conservative traditional hierarchical structures and teaching methods in the medical profession, which may result in a bullying cycle.

Even though The American Nurses Association believes that all nursing personnel have the right to work in safe, non-abusive environments, bullying has been identified as being particularly prevalent in the nursing profession although the reasons are not clear. It is thought that relational aggression (psychological aspects of bullying such as gossiping and intimidation) are relevant. Relational aggression has been studied among girls but not so much among adult women.

Teaching

Main article: Bullying in teaching

School teachers are commonly the subject of bullying but they are also sometimes the originators of bullying within a school environment.

Machines

Children have been observed bullying anthropomorphic robots designed to assist the elderly. Their attacks start with blocking the robots' paths of movement and then escalate to verbal abuse, hitting and destroying the object. Seventy-five percent of the kids interviewed perceived the robot as "human-like" yet decided to abuse it anyway, while 35% of the kids who beat up the robot did so "for enjoyment".

Prevention

Bullying prevention is the collective effort to prevent, reduce and stop bullying. Many campaigns and events are designated to bullying prevention throughout the world. Bullying prevention campaigns and events include: Anti-Bullying Day, Anti-Bullying Week, International Day of Pink, International STAND UP to Bullying Day and National Bullying Prevention Month. Anti-Bullying laws in the U.S. have also been enacted in 23 of its 50 states, making bullying in schools illegal.

Responses

Bullying is typically ongoing and not isolated behaviour. Common ways that people try to respond, are to try to ignore it, to confront the bullies or to turn to an authority figure to try to address it.

Ignoring it often does nothing to stop the bullying continuing, and it can become worse over time. It can be important to address bullying behaviour early on, as it can be easier to control the earlier it is detected. Bystanders play an important role in responding to bullying, as doing nothing can encourage it to continue, while small steps that oppose the behaviour can reduce it.

Authority figures can play an important role, such as parents in child or adolescent situations, or supervisors, human-resources staff or parent-bodies in workplace and volunteer settings. Authority figures can be influential in recognising and stopping bullying behaviour, and creating an environment where it doesn't continue. In many situations, authority figures are untrained and unqualified, do not know how to respond, and can make the situation worse. In some cases the authority figures even support the people doing the bullying, facilitating it continuing and increasing the isolation and marginalising of the target. Some of the most effective ways to respond, are to recognise that harmful behaviour is taking place, and creating an environment where it won't continue.