History and etymology.

Tries were first described by René de la Briandais in 1959. The term "trie" was coined two years later by Edward Fredkin, who pronounces it (as "tree"), after the middle syllable of "retrieval". However, other authors pronounce it (as "try"), in an attempt to distinguish it verbally from "tree".

Applications.

As a replacement for other data structures.

As discussed below, a trie has a number of advantages over binary search trees.  A trie can also be used to replace a hash table, over which it has the following advantages:  However, a trie also has some drawbacks compared to a hash table:

Dictionary representation.

A common application of a trie is storing a predictive text or autocomplete dictionary, such as found on a mobile telephone. Such applications take advantage of a trie's ability to quickly search for, insert, and delete entries; however, if storing dictionary words is all that is required (i.e., storage of information auxiliary to each word is not required), a minimal deterministic acyclic finite state automaton (DAFSA) would use less space than a trie. This is because a DAFSA can compress identical branches from the trie which correspond to the same suffixes (or parts) of different words being stored.  Tries are also well suited for implementing approximate matching algorithms, including those used in spell checking and hyphenation software.

Term indexing.

A discrimination tree term index stores its information in a trie data structure.

Algorithms.

The trie is a tree of nodes which supports Find and Insert operations. Find returns the value for a key string, and Insert inserts a string (the key) and a value into the trie. Both Insert and Find run in time, where m is the length of the key.  A simple Node class can be used to represent nodes in the trie: class Node: Note that codice_1 is a dictionary of characters to a node's children; and it is said that a "terminal" node is one which represents a complete string.<br>A trie's value can be looked up as follows: def find(node: Node, key: str) -> Optional[Any]: A slight modifications of this routine can be utilized  Insertion proceeds by walking the trie according to the string to be inserted, then appending new nodes for the suffix of the string that is not contained in the trie: def insert(node: Node, key: str, value: Any) -> None:

Sorting.

Lexicographic sorting of a set of keys can be accomplished by building a trie from them, with the children of each node sorted lexicographically, and traversing it in pre-order, printing only the leaves' values. This algorithm is a form of radix sort.  A trie is the fundamental data structure of Burstsort, which (in 2007) was the fastest known string sorting algorithm due to its efficient cache use. Now there are faster ones.

Full-text search.

A special kind of trie, called a suffix tree, can be used to index all suffixes in a text in order to carry out fast full text searches.

Implementation strategies.

There are several ways to represent tries, corresponding to different trade-offs between memory use and speed of the operations. The basic form is that of a linked set of nodes, where each node contains an array of child pointers, one for each symbol in the alphabet (so for the English alphabet, one would store 26 child pointers and for the alphabet of bytes, 256 pointers). This is simple but wasteful in terms of memory: using the alphabet of bytes (size 256) and four-byte pointers, each node requires a kilobyte of storage, and when there is little overlap in the strings' prefixes, the number of required nodes is roughly the combined length of the stored strings. Put another way, the nodes near the bottom of the tree tend to have few children and there are many of them, so the structure wastes space storing null pointers.  The storage problem can be alleviated by an implementation technique called "alphabet reduction", whereby the original strings are reinterpreted as longer strings over a smaller alphabet. E.g., a string of bytes can alternatively be regarded as a string of four-bit units and stored in a trie with sixteen pointers per node. Lookups need to visit twice as many nodes in the worst case, but the storage requirements go down by a factor of eight.  An alternative implementation represents a node as a triple and links the children of a node together as a singly linked list: points to the node's first child, to the parent node's next child. The set of children can also be represented as a binary search tree; one instance of this idea is the ternary search tree developed by Bentley and Sedgewick.  Another alternative in order to avoid the use of an array of 256 pointers (ASCII), as suggested before, is to store the alphabet array as a bitmap of 256 bits representing the ASCII alphabet, reducing dramatically the size of the nodes.

Bitwise tries.

Bitwise tries are much the same as a normal character-based trie except that individual bits are used to traverse what effectively becomes a form of binary tree. Generally, implementations use a special CPU instruction to very quickly find the first set bit in a fixed length key (e.g., GCC's codice_2 intrinsic). This value is then used to index a 32- or 64-entry table which points to the first item in the bitwise trie with that number of leading zero bits. The search then proceeds by testing each subsequent bit in the key and choosing codice_3 or codice_4 appropriately until the item is found.  Although this process might sound slow, it is very cache-local and highly parallelizable due to the lack of register dependencies and therefore in fact has excellent performance on modern out-of-order execution CPUs. A red-black tree for example performs much better on paper, but is highly cache-unfriendly and causes multiple pipeline and TLB stalls on modern CPUs which makes that algorithm bound by memory latency rather than CPU speed. In comparison, a bitwise trie rarely accesses memory, and when it does, it does so only to read, thus avoiding SMP cache coherency overhead. Hence, it is increasingly becoming the algorithm of choice for code that performs many rapid insertions and deletions, such as memory allocators (e.g., recent versions of the famous Doug Lea's allocator (dlmalloc) and its descendants). The worst case of steps for lookup is the same as bits used to index bins in the tree.  Alternatively, the term "bitwise trie" can more generally refer to a binary tree structure holding integer values, sorting them by their binary prefix. An example is the x-fast trie.

Compressing tries.

Compressing the trie and merging the common branches can sometimes yield large performance gains. This works best under the following conditions: For example, it may be used to represent sparse bitsets; i.e., subsets of a much larger, fixed enumerable set. In such a case, the trie is keyed by the bit element position within the full set. The key is created from the string of bits needed to encode the integral position of each element. Such tries have a very degenerate form with many missing branches. After detecting the repetition of common patterns or filling the unused gaps, the unique leaf nodes (bit strings) can be stored and compressed easily, reducing the overall size of the trie.  Such compression is also used in the implementation of the various fast lookup tables for retrieving Unicode character properties. These could include case-mapping tables (e.g., for the Greek letter pi, from Π to π), or lookup tables normalizing the combination of base and combining characters (like the a-umlaut in German, ä, or the dalet-patah-dagesh-ole in Biblical Hebrew, ). For such applications, the representation is similar to transforming a very large, unidimensional, sparse table (e.g., Unicode code points) into a multidimensional matrix of their combinations, and then using the coordinates in the hyper-matrix as the string key of an uncompressed trie to represent the resulting character. The compression will then consist of detecting and merging the common columns within the hyper-matrix to compress the last dimension in the key. For example, to avoid storing the full, multibyte Unicode code point of each element forming a matrix column, the groupings of similar code points can be exploited. Each dimension of the hyper-matrix stores the start position of the next dimension, so that only the offset (typically a single byte) need be stored. The resulting vector is itself compressible when it is also sparse, so each dimension (associated to a layer level in the trie) can be compressed separately.  Some implementations do support such data compression within dynamic sparse tries and allow insertions and deletions in compressed tries. However, this usually has a significant cost when compressed segments need to be split or merged. Some tradeoff has to be made between data compression and update speed. A typical strategy is to limit the range of global lookups for comparing the common branches in the sparse trie.  The result of such compression may look similar to trying to transform the trie into a directed acyclic graph (DAG), because the reverse transform from a DAG to a trie is obvious and always possible. However, the shape of the DAG is determined by the form of the key chosen to index the nodes, in turn constraining the compression possible.  Another compression strategy is to "unravel" the data structure into a single byte array. This approach eliminates the need for node pointers, substantially reducing the memory requirements. This in turn permits memory mapping and the use of virtual memory to efficiently load the data from disk.  One more approach is to "pack" the trie. Liang describes a space-efficient implementation of a sparse packed trie applied to automatic hyphenation, in which the descendants of each node may be interleaved in memory.

External memory tries.

Several trie variants are suitable for maintaining sets of strings in external memory, including suffix trees. A combination of trie and B-tree, called the "B-trie" has also been suggested for this task; compared to suffix trees, they are limited in the supported operations but also more compact, while performing update operations faster.

In computer science, a trie, also called digital tree or prefix tree, is a kind of search tree—an ordered tree data structure used to store a dynamic set or associative array where the keys are usually strings. Unlike a binary search tree, no node in the tree stores the key associated with that node; instead, its position in the tree defines the key with which it is associated; i.e., the value of the key is distributed across the structure. All the descendants of a node have a common prefix of the string associated with that node, and the root is associated with the empty string. Keys tend to be associated with leaves, though some inner nodes may correspond to keys of interest. Hence, keys are not necessarily associated with every node. For the space-optimized presentation of prefix tree, see compact prefix tree.

Trie nebo prefixový strom je datová struktura, která se používá pro uchovávání dvojic klíč-hodnota, kde klíči jsou obvykle řetězce. Na rozdíl od binárního vyhledávacího stromu, kde se podle hodnoty uzlu rozhoduje, do které větve sestoupit, trie v každém uzlu obsahuje všechny podřetězce, kterými může pokračovat řetězec v dosud prohledané cestě. Všichni následníci uzlu mají společný prefix, který je shodný s řetězcem přiřazeným k danému uzlu. Kořen je asociovaný s prázdným řetězcem. Hodnoty obvykle nejsou asociovány se všemi uzly, ale jen s listy a některými vnitřními uzly, které odpovídají klíčům.


Development.

In the wake of the Cuban Missile Crisis, the army was instructed to consider putting more emphasis on means to project power outside of the normal sphere of Soviet influence. As a result, there was a major effort to develop the VDV (Soviet airborne forces) as a rapid deployment force. Soviet studies of airborne operations had shown that lightly armed paratroops were unable to deal with armoured forces. Also, in the early 1960s, the BMP-1 infantry fighting vehicle was being developed. Before the BMP-1 entered service in 1966, the Soviet Army high command decided to equip the newly created airborne divisions with similar vehicles.  The use of Antonov An-12 aircraft at the time of the BMD development allowed the transport of only light armoured vehicles for an airborne drop that weighed less than seven tons. Because the existing BMP-1 weighed 13 tonnes, it was effectively ruled out of being considered for the VDV service.  The task of designing the BMD fell to the Volgograd Tractor Factory, which had produced an unsuccessful competitor to the Ob'yekt 764 that eventually became the BMP-1 – the Ob'yekt 914. The BMD design, Ob'yekt 915, was basically a trimmed down version of the Ob'yekt 914 – smaller, lighter aluminium armour, while retaining the 73 mm 2A28 "Grom" low pressure smoothbore short-recoil semi-automatic gun. The compromise made is the extremely cramped crew compartment.  Development started in 1965 and trials began in 1967. A limited production began in 1968. After operational trials, it was commissioned on 14 April 1969 and serial production started in 1970, although the vehicle weighed 500 kg more than what the requirements stated (7.5 tonnes and 13.3 tonnes when loaded with equipment).  Starting from 1977 a new modernized vehicle received a designation BMD-1P following adoption of the new 9P135M-1 ATGM launcher instead of 9S428 ATGM launcher, firing the 9M113 Konkurs (AT-5 Spandrel) and 9M111M Fagot or 9M111-2 (standard load: two 9M113 and one 9M111M missiles). Most of older BMD-1s were subsequently modernized this way.  In 1983, based on the combat experience in Afghanistan, a decision was made to produce a new variant of the BMD with a weapon capable of engaging targets such as those faced by the airborne troops in that conflict. This resulted in "Ob'yekt 916", which later became the BMD-2.  A lengthened BMD-1 chassis served as the basis for the BTR-D airborne multi-purpose tracked APC, which itself served as a basis for many specialized airborne vehicles.

Description.

Overview.

The BMD-1 can be thought of as a BMP intended for airborne troops. The vehicle therefore must be lighter and smaller in order to meet airdrop weight requirements (the BMD-1 is secured to a pallet and parachute-dropped from cargo planes).  The BMD-1 has an unconventional layout for an IFV. From the front to the back of the vehicle, the compartments are located in the following formation: steering, fighting, troop and engine. This is because the BMD-1 is based on Ob'yekt 914, which in turn is based on the PT-76 amphibious light tank (refer Prototypes section in the BMP-1 article for details). This meant that transported troops had to mount and dismount the vehicle via the roof hatches, which made them an easy target on the battlefield when these actions were performed.

Crew.

The crew consist of four soldiers: driver, commander, gunner and bow machine gunner, two of which (commander and machine gunner) are included in the number of soldiers carried. The driver's station is located centrally in the front of the vehicle and has a hatch that is opened by raising it and rotating it to the right. The driver is provided with three periscope vision blocks, which allow him to view the outer environment when his hatch is closed. The center one can be replaced with a night vision device for use in night and bad visibility conditions or with an extended periscope for swimming with the trim vane erected. The commander's station is on the driver's left. It is provided with a hatch, one periscope vision block, an outer environment observation device and an R-123 radio set for communications. He also fires the left bow machine gun. The right one is operated by a bow machine gun gunner, who sits to the right of the driver. The gunner's station is located on the left side of the turret, like in the BMP-1, and has the same equipment (see Gunner's station section in BMP-1 article for details).

Turret.

The BMD-1 has the same turret as the BMP-1.

Armament.

The vehicle is armed with a 73 mm 2A28 Grom gun and a 7.62 mm PKT coaxial tank machine gun. Mounted on the mantlet is the 9S428 ATGM launcher capable of firing 9M14 Malyutka (NATO: AT-3A Sagger A) and 9M14M Malyutka-M (NATO: AT-3B Sagger B) ATGMs (for which the vehicle carries two ATGMs in the turret). There are also two 7.62 mm PKT machine guns in fixed mounts, one in each corner of the bow.

Mobility.

Maneuverability.

The vehicle is powered by a 5D-20 6-cylinder 4-stroke V-shaped liquid-cooled 15.9-liter diesel engine, which develops 270 hp (201 kW) at 2,600 revolutions per minute. The engine drives a manual gearbox with five forward and one reverse gear.  The BMD-1 has a maximum road speed of 80 kilometers per hour, reducing to around 45 kilometers per hour off-road and 10 kilometers per hour while swimming.  The BMD-1 can climb vertical obstacles, cross trenches and 30% side slopes. It can climb 60% gradients. The BMD-1 has a ground pressure of 0.57 kg/cm2.  The 230 mm wide track is driven at the rear and passes over five small evenly spaced road wheels suspended on independent torsion bars. On each side there is an idler wheel at the front, a rear drive sprocket and four track-return rollers. The independent suspension combines a hydraulic system for altering the ground clearance and maintaining the track tension with pneumatic springs, which enables the ground clearance to be altered from 100 mm to 450 mm. Alterable ground clearance allows easier transportation in an airplane.

Amphibious ability.

The BMD-1 is fully amphibious, it can swim after switching on the two electric bilge pumps, erecting the two-piece trim vane which improves vehicle's stability and displacement in water and prevents the water from flooding the bow of the tank and switching the driver's periscope for a swimming periscope that enables the driver to see over the trim vane. When not in use the trim vane is placed in its laying position in the front of the bow under the barrel of the main gun and serves as additional armour. There is also a manual bilge pump for emergency use. The bilge pumps keep the vehicle afloat even if it is hit, damaged or leaks. In water it is propelled by two hydrojets, one in each side of the hull, with the entrance under the hull and exits at the rear of the hull. The rear exits have lids that can be fully or partially closed, redirecting the water stream to the forward-directed exits at the sides of the hull, thus enabling the vehicle to turn or float reverse, for example, to go left, the left water-jet is covered, to go right, the right water-jet is covered and to make a 180° turn the left water-jet sucks in water and the right water-jet pushes it out.

Air-drop techniques.

The vehicle can be transported by An-12, An-22, Il-76, An-124 airplanes and Mi-6 and Mi-26 helicopters.  The BMD was originally dropped under the MKS-350-9 multi-canopy parachute with a descending speed between 15 m/s and 20 m/s. The intention was to drop the vehicle without the crew. This proved to be very problematic, since the crew frequently landed at a considerable distance from the vehicle and often had trouble finding it. Also, the vehicle itself could easily land in a location from which it couldn't be extracted (either because of a lack of suitable equipment or because of the location being virtually inaccessible). Several experiments were done in the 1970s in order to find a way to circumvent these limitations, including dropping the BMD with the two key crew members, the driver and gunner, seated inside the vehicle during the descent. The first such test took place in January 1973, and the concept was proved to be valid in a subsequent series of tests.  A rocket parachute, the PRSM-915, was developed to ensure the vehicle's safe landing. To use the parachute, the BMD is first packed onto a special pallet before takeoff. To drop the BMD, a drogue chute is released that initially drags the BMD out of the Il-76 transport plane. Once clear of the plane a single large main chute opens. The deployment of the main chute triggers the deployment of four long rods which hang beneath the pallet. As soon as the rods touch the ground a retrorocket fires, slowing the BMD to a descending speed between 6 m/s and 7 m/s and giving it a relatively soft landing. This system entered service in 1975 and allows a BMD to be relatively safely parachuted with both the driver and the gunner.  An alternative radio location system also exists. Each crew member is given a radio receiver locked onto a transponder in its particular BMD, allowing each BMD crewman to quickly locate his respective vehicle after the airdrop.

Armour protection.

The BMD-1's armour is made of ABT-101 an alloy composed of 91% Aluminum, 6% Zinc and 3% Magnesium. The BMD-2 on the other-hand is composed of ABT-102, which 94% Aluminum, 4% Zinc and 2% Magnesium.  Armour thickness is 23 mm at 42° on the front of the turret, 19 mm at 36° on the sides of the turret, 13 mm at 30° on the rear of the turret, 6 mm on the top of the turret, 15 mm on the front of the hull and 10 mm on the rest of the hull. The hull's front armour has two sections: upper and lower. The upper section is angled at 78° while the lower one is angled at 50°. It is resistant to small arms fire and shrapnel.

Troop compartment.

Many compromises had to be made to the design in order to save the necessary weight, not least to crew comfort. The BMD-1 has an extremely cramped interior space, which is much smaller than that found in the BMP-1 and BMP-2 IFVs. It can carry five infantrymen, comprising vehicle's commander, bow machine gunner and three soldiers seated behind a turret.  Nevertheless, it is equipped with periscope vision blocks on the sides and rear of the vehicle. There are only three firing ports, one on each side of the hull and one in the rear. As standard, the vehicle carries the following weapons inside the troop compartment: an RPG-7 or RPG-16 shoulder-launched anti-tank rocket propelled grenade launcher, which is to be operated by two soldiers, RPKS light machine gun and five AKMS assault rifles. It also carries portable launchers for 9M14M Malyutka missiles (9M111/9M113 missiles in BMD-1P).

Equipment.

The vehicle has electric and manual bilge pumps, Gpk-S9 gyro-compass, engine pre-heater, TDA smoke-generating equipment, FTP-100M NBC system, R-123 transceiver, R-124 intercom and a centralized methyl bromide fire extinguishing system, the same as the one fitted to other former Soviet armoured vehicles.

Service history.

The BMD-1 entered serial production in 1968. It was produced by Volgograd Tractor Plant. Two airborne regiments of each airborne division were equipped with BMD-1 IFVs. Overall, each division operated 220 BMD-1 IFVs. It was displayed publicly for the first time during the Dvina exercise in the USSR in 1970. The BMD-1 was showcased for the second time during the Moscow Red Square parade in November 1973. Western governments originally classified the BMD-1 as a light tank before its true nature was known. Because of its small crew, the introduction of the BMD led to a reduction in the number of soldiers in an airborne battalion, from 610 to 316 men. The firepower of the BMD also meant that some of the battalion's integral fire support could be done away with. In 1973, the BMD-1 completely replaced the ASU-57 airborne assault guns in the Soviet airborne forces, increasing the firepower and maneuverability of the airborne division. Since 1977 a number of Soviet BMD-1 IFVs underwent a modernization to BMD-1P standard.

Ogaden War.

In 1978, a force of 70 Cuban Army BMD-1s and ASU-57s fighting on behalf of the Ethiopian government was airlifted by Mi-6 helicopters behind the lines of Somali forces holding the town of Jijiiga. This attack formed a pincer with a conventional Cuban armored push and routed the Somali forces in Ogaden.

Soviet–Afghan War.

It was widely used by airborne units during Soviet–Afghan War. During the initial Soviet invasion of Afghanistan in 1979, BMD-1s of the Soviet 103rd Guards Airborne Division and 345th Separate Parachute Regiment were airlanded by IL-76 transports into Kabul airport and Bagram Airfield, enabling the rapid seizure of critical cities and facilities throughout Afghanistan. The 56th Air Assault Brigade executed a similar capture of Kunduz. For the remainder of the Soviet occupation of Afghanistan through 1989, airborne forces under the 40th Army used BMD-1s as infantry fighting vehicles for transportation and fire support in operations against the mujahideen.  BMD-1 IFVs were not suited for fighting in the hot mountain regions of Afghanistan, as they were originally developed to provide airborne units with an IFV to give them a chance in engagements with enemy armour and allow them to operate in Nuclear-Biological-Chemical (NBC) warfare conditions. In Afghanistan, the main enemies were not AFVs but land mines and ambushes prepared by skillful Afghan Mujahideen armed with light anti-tank weapons, which meant that the BMD-1's anti-tank firepower was useless. Many BMD-1 IFVs fell victim to Mujahideen attacks and, especially, antitank landmines like quite a lot of Soviet light AFVs sent there. The Soviet Army lost 1,317 APCs and IFVs of all types during nine years of war in Afghanistan.

Iraq.

In 1990, BMD-1 IFVs were used by the Iraqi Army during the First Gulf War. They were used for a second time during the 2003 invasion of Iraq.

Former Yugoslavia.

BMD-1 and BMD-1PK IFVs are used by the Russian airborne units in KFOR. BMD-1 IFVs were used by Russian airborne units in SFOR.

2008 Georgia–Russia War.

During the Russo-Georgian War, BMD-1s of the 104th Airborne Assault Regiment of the 76th Guards Air Assault Division advanced into South Ossetia and successfully engaged Georgian Army troops and vehicles. However, the BMDs visual and sighting equipment was criticized as being primitive.

2014 Ukraine Donbass Conflict.

During the War in Donbass in 2014 in Eastern Ukraine, BMD-1s were used both by mechanized units of the Ukrainian Army and in smaller number by the separatists of the Donetsk People's Republic. It was claimed that a BMD-1 was one of the six armored vehicles in Separatist forces defending Sloviansk when it was besieged.

Present service.

As of now, BMD-1 and vehicles based on it are used by the following units of Russian Airborne Troops or are stationed in following bases (this list does not include BTR-D APCs and BTR-D variants):  76th Guards Air Assault Division (CDO) from Pskov, which is part of Leningrad Military District (210 BMD vehicles as of 2000), the subunits of this division include 104th airborne regiment from Pskov (51 BMD-1) and 234th airborne regiment from Pskov (98 BMD-1).  98th Guards Airborne Division from Ivanovo (220 BMD vehicles as of 2000), the subunits of this division include 217th Guards Airborne Regiment from Ivanovo (109 BMD-1) and 331st airborne regiment from Kostroma (102 BMD-1).  106th Guards Airborne Division from Tula, which is a part of the Moscow Military District (306 BMD as of 2000), the subunits of this division include 51st airborne regiment from Tula (93 BMD-1) and 137th airborne regiment from Ryazan (10 BMD-1).  7th Guards Airborne Mountain Division CDO from Novorossyysk (190 BMD and BMP vehicles as of 2000), the subunits of this division include 108th Guards Air Assault Regiment from Novorossyysk (70 BMD-1) and 743rd commandos battalion from Novorossyysk (6 BMD-1).  31st Separate Airborne Brigade from Ul'yanovsk, which is a part of the Volga-Ural Military District (26 BMD-1 as of 2000).  Ryazan Higher Airborne Command School (51 BMD-1).  99th Internal Troops division from Rostov, Persianovka, which is a part of the North Caucasus Military District (4 BMD-1 and 33 BMD-1 IFVs in the Cherkmen regiment).  81st tank repair plant from Armavir (Krasnodar) (1 BMD-1).

BMD's replacement.

The Russian military was considering replacing the BMD series altogether with the GAZ-3937. This very lightweight wheeled armoured personnel carrier that incorporates plastic and carbon fibre in its construction, as well as aluminum. The GAZ-3937 can be air-dropped like the BMD, but is considerably lighter and less expensive to manufacture. Since the GAZ-3937 lacks the armor protection, cross-country mobility, and heavy armament of the BMD series, and is armed only with a 7.62 mm PKM machine gun in front of the commander's hatch, the BMD-4 (an upgraded BMD-3) has been selected for the future use of the Russian airborne and naval infantry. The BMD-4 uses the same 100 mm main gun with 30 mm autocannon and 7.62 mm medium machine gun turret on an improved, larger hull raising overall weight to the 15-ton class. The waterjet swim propulsion systems of the BMD-3/4 are strong enough to enable ship-to-shore transport, resulting in Russian naval infantry use.

The BMD-1 is a Soviet airborne amphibious tracked infantry fighting vehicle, which was introduced in 1969 and first seen by the West in 1970. BMD stands for "Boyevaya Mashina Desanta" (Боевая Машина Десанта, which literally translates to "Combat Vehicle of the Airborne"). It can be dropped by parachute and although it resembles the BMP-1 it is in fact much smaller. The BMD-1 was used as an IFV by the Soviet Army's airborne divisions. An improved variant of the BMD-1 was developed, the BMD-2. The BMD-1 also provided a basis for the BTR-D airborne multi-purpose tracked APC.

BMD-1 ("bojevaja mašina děsantnaja") je sovětské obojživelné obrněné vozidlo určené pro přepravu menší skupiny výsadkářů. Jedná se o lehký stroj, který je schopen shozu na padácích. Prototyp stroje byl sestrojen koncem šedesátých let 20. století, sériově se začal vyrábět od roku 1970. Vozidlo je vybavené gyrokompasem, zařízením pro ochranu proti zbraním hromadného ničení, zadýmovacím zařízením a hasicím systémem.


Gameplay.

WarRock is developed in Episodes; similar to TV programming but inverted (four seasons make up one episode). Currently WarRock is on Episode IV, Season 2 - suggesting that WarRock is in its 10th incarnation.  The game is set in the midst of a nuclear war in the fictional Republic of Derbaran. Players select between the two teams and engage in battles using 20th and 21st century military equipment, including a large assortment of infantry weapons and vehicles. Derbaran is the government army (yellow camouflage) and NIU is the rebel army (green camouflage). During most combat modes, players are divided into these two teams and compete as an army against each other.  "War Rock" games are divided into six main modes of play: Conquest Mode, Capture the Base, Individual Death Match - One Man Army, Bombing Mission,Team Death Match and AI mode.  The game features deathmatch-based multiplayer modes, all of which feature objectives that must be completed in order for teams to win. Sessions end either when a team has reached a preset number of points, or the allotted time expires in which case the team with the most points wins. Not all the game modes are kill based.  The player's performance is tracked with experience points and in-game money which players can earn several ways including defeating opponents, or completing objectives. As players gain experience, they will advance in level, allowing access to new weapons and items, which can be bought with money earned in the game. War Rock features a clan system, that allows members to engage in clan wars whilst representing their specific clans.

Reception.

IGN rated it a "mediocre" 5.9 and GameSpot rated the game 5.5 out of 10.

War Rock () is a multiplayer first-person shooter made by the South Korean company, Dream Execution. The game is distributed as a free-to-play, a common form of freeware EULA and available through online downloading. Outside of the Far East, the game is hosted by PapayaPlay, who services the game for both Europe and North America.

Michael Dale Huckabee (24. srpna 1955) je americký politik, v letech 1996 až 2007 guvernér státu Arkansas a neúspěšný kandidát na republikánskou nominaci pro prezidentské volby v roce 2008. Zároveň je Huckabee autorem několika knih, bývalým baptistickým pastorem, komentátorem pro stanici Fox News Channel, řečníkem a muzikantem. Je také znám tím, že během velmi krátké doby dokázal zhubnout o 50 kg a poté začal propagovat zdravý životní styl. V roce 2010 se v souvislosti s únikem amerických diplomatických kabelogramů na serveru WikiLeaks vyslovil pro smrt Juliana Assangeho a „toho zodpovědného za únik diplomatických depeší“ – ten označil za velezradu a o trestu za tento čin řekl, že „cokoli méně než poprava by bylo příliš vlídný trest“. Se svojí ženou má tři dospělé děti.


History.

As a successful theoretical framework today, quantum field theory emerged from the work of generations of theoretical physicists spanning much of the 20th century. Its development began in the 1920s with the description of interactions between light and electrons, culminating in the first quantum field theory — quantum electrodynamics. A major theoretical obstacle soon followed with the appearance and persistence of various infinities in perturbative calculations, a problem only resolved in the 1950s with the invention of the renormalization procedure. A second major barrier came with QFT's apparent inability to describe the weak and strong interactions, to the point where some theorists called for the abandonment of the field theoretic approach. The development of gauge theory and the completion of the Standard Model in the 1970s led to a renaissance of quantum field theory.

Theoretical background.

Quantum field theory is the result of the combination of classical field theory, quantum mechanics, and special relativity. A brief overview of these theoretical precursors is in order.  The earliest successful classical field theory is one that emerged from Newton's law of universal gravitation, despite the complete absence of the concept of fields from his 1687 treatise "Philosophiæ Naturalis Principia Mathematica". The force of gravity as described by Newton is an "action at a distance" — its effects on faraway objects are instantaneous, no matter the distance. In an exchange of letters with Richard Bentley, however, Newton stated that "it is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter without mutual contact." It was not until the 18th century that mathematical physicists discovered a convenient description of gravity based on fields — a numerical quantity (a vector) assigned to every point in space indicating the action of gravity on any particle at that point. However, this was considered merely a mathematical trick.  Fields began to take on an existence of their own with the development of electromagnetism in the 19th century. Michael Faraday coined the English term "field" in 1845. He introduced fields as properties of space (even when it is devoid of matter) having physical effects. He argued against "action at a distance", and proposed that interactions between objects occur via space-filling "lines of force". This description of fields remains to this day.  The theory of classical electromagnetism was completed in 1864 with Maxwell's equations, which described the relationship between the electric field, the magnetic field, electric current, and electric charge. Maxwell's equations implied the existence of electromagnetic waves, a phenomenon whereby electric and magnetic fields propagate from one spatial point to another at a finite speed, which turns out to be the speed of light. Action-at-a-distance was thus conclusively refuted.  Despite the enormous success of classical electromagnetism, it was unable to account for the discrete lines in atomic spectra, nor for the distribution of blackbody radiation in different wavelengths. Max Planck's study of blackbody radiation marked the beginning of quantum mechanics. He treated atoms, which absorb and emit electromagnetic radiation, as tiny oscillators with the crucial property that their energies can only take on a series of discrete, rather than continuous, values. These are known as quantum harmonic oscillators. This process of restricting energies to discrete values is called quantization. Building on this idea, Albert Einstein proposed in 1905 an explanation for the photoelectric effect, that light is composed of individual packets of energy called photons (the quanta of light). This implied that the electromagnetic radiation, while being waves in the classical electromagnetic field, also exists in the form of particles.  In 1913, Niels Bohr introduced the Bohr model of atomic structure, wherein electrons within atoms can only take on a series of discrete, rather than continuous, energies. This is another example of quantization. The Bohr model successfully explained the discrete nature of atomic spectral lines. In 1924, Louis de Broglie proposed the hypothesis of wave-particle duality, that microscopic particles exhibit both wave-like and particle-like properties under different circumstances. Uniting these scattered ideas, a coherent discipline, quantum mechanics, was formulated between 1925 and 1926, with important contributions from de Broglie, Werner Heisenberg, Max Born, Erwin Schrödinger, Paul Dirac, and Wolfgang Pauli.  In the same year as his paper on the photoelectric effect, Einstein published his theory of special relativity, built on Maxwell's electromagnetism. New rules, called Lorentz transformation, were given for the way time and space coordinates of an event change under changes in the observer's velocity, and the distinction between time and space was blurred. It was proposed that all physical laws must be the same for observers at different velocities, "i.e." that physical laws be invariant under Lorentz transformations.  Two difficulties remained. Observationally, the Schrödinger equation underlying quantum mechanics could explain the stimulated emission of radiation from atoms, where an electron emits a new photon under the action of an external electromagnetic field, but it was unable to explain spontaneous emission, where an electron spontaneously decreases in energy and emits a photon even without the action of an external electromagnetic field. Theoretically, the Schrödinger equation could not describe photons and was inconsistent with the principles of special relativity — it treats time as an ordinary number while promoting spatial coordinates to linear operators.

Quantum electrodynamics.

Quantum field theory naturally began with the study of electromagnetic interactions, as the electromagnetic field was the only known classical field as of the 1920s.  Through the works of Born, Heisenberg, and Pascual Jordan in 1925–1926, a quantum theory of the free electromagnetic field (one with no interactions with matter) was developed via canonical quantization by treating the electromagnetic field as a set of quantum harmonic oscillators. With the exclusion of interactions, however, such a theory was yet incapable of making quantitative predictions about the real world.  In his seminal 1927 paper "The quantum theory of the emission and absorption of radiation", Dirac coined the term quantum electrodynamics (QED), a theory that adds upon the terms describing the free electromagnetic field an additional interaction term between electric current density and the electromagnetic vector potential. Using first-order perturbation theory, he successfully explained the phenomenon of spontaneous emission. According to the uncertainty principle in quantum mechanics, quantum harmonic oscillators cannot remain stationary, but they have a non-zero minimum energy and must always be oscillating, even in the lowest energy state (the ground state). Therefore, even in a perfect vacuum, there remains an oscillating electromagnetic field having zero-point energy. It is this quantum fluctuation of electromagnetic fields in the vacuum that "stimulates" the spontaneous emission of radiation by electrons in atoms. Dirac's theory was hugely successful in explaining both the emission and absorption of radiation by atoms; by applying second-order perturbation theory, it was able to account for the scattering of photons, resonance fluorescence, as well as non-relativistic Compton scattering. Nonetheless, the application of higher-order perturbation theory was plagued with problematic infinities in calculations.  In 1928, Dirac wrote down a wave equation that described relativistic electrons — the Dirac equation. It had the following important consequences: the spin of an electron is 1/2; the electron "g"-factor is 2; it led to the correct Sommerfeld formula for the fine structure of the hydrogen atom; and it could be used to derive the Klein–Nishina formula for relativistic Compton scattering. Although the results were fruitful, the theory also apparently implied the existence of negative energy states, which would cause atoms to be unstable, since they could always decay to lower energy states by the emission of radiation.  The prevailing view at the time was that the world was composed of two very different ingredients: material particles (such as electrons) and quantum fields (such as photons). Material particles were considered to be eternal, with their physical state described by the probabilities of finding each particle in any given region of space or range of velocities. On the other hand, photons were considered merely the excited states of the underlying quantized electromagnetic field, and could be freely created or destroyed. It was between 1928 and 1930 that Jordan, Eugene Wigner, Heisenberg, Pauli, and Enrico Fermi discovered that material particles could also be seen as excited states of quantum fields. Just as photons are excited states of the quantized electromagnetic field, so each type of particle had its corresponding quantum field: an electron field, a proton field, etc. Given enough energy, it would now be possible to create material particles. Building on this idea, Fermi proposed in 1932 an explanation for beta decay known as Fermi's interaction. Atomic nuclei do not contain electrons "per se", but in the process of decay, an electron is created out of the surrounding electron field, analogous to the photon created from the surrounding electromagnetic field in the radiative decay of an excited atom.  It was realized in 1929 by Dirac and others that negative energy states implied by the Dirac equation could be removed by assuming the existence of particles with the same mass as electrons but opposite electric charge. This not only ensured the stability of atoms, but it was also the first proposal of the existence of antimatter. Indeed, the evidence for positrons was discovered in 1932 by Carl David Anderson in cosmic rays. With enough energy, such as by absorbing a photon, an electron-positron pair could be created, a process called pair production; the reverse process, annihilation, could also occur with the emission of a photon. This showed that particle numbers need not be fixed during an interaction. Historically, however, positrons were at first thought of as "holes" in an infinite electron sea, rather than a new kind of particle, and this theory was referred to as the Dirac hole theory. QFT naturally incorporated antiparticles in its formalism.

Infinities and renormalization.

Robert Oppenheimer showed in 1930 that higher-order perturbative calculations in QED always resulted in infinite quantities, such as the electron self-energy and the vacuum zero-point energy of the electron and photon fields, suggesting that the computational methods at the time could not properly deal with interactions involving photons with extremely high momenta. It was not until 20 years later that a systematic approach to remove such infinities was developed.  A series of papers was published between 1934 and 1938 by Ernst Stueckelberg that established a relativistically invariant formulation of QFT. In 1947, Stueckelberg also independently developed a complete renormalization procedure. Unfortunately, such achievements were not understood and recognized by the theoretical community.  Faced with these infinities, John Archibald Wheeler and Heisenberg proposed, in 1937 and 1943 respectively, to supplant the problematic QFT with the so-called S-matrix theory. Since the specific details of microscopic interactions are inaccessible to observations, the theory should only attempt to describe the relationships between a small number of observables ("e.g." the energy of an atom) in an interaction, rather than be concerned with the microscopic minutiae of the interaction. In 1945, Richard Feynman and Wheeler daringly suggested abandoning QFT altogether and proposed action-at-a-distance as the mechanism of particle interactions.  In 1947, Willis Lamb and Robert Retherford measured the minute difference in the "S" and "P" energy levels of the hydrogen atom, also called the Lamb shift. By ignoring the contribution of photons whose energy exceeds the electron mass, Hans Bethe successfully estimated the numerical value of the Lamb shift. Subsequently, Norman Myles Kroll, Lamb, James Bruce French, and Victor Weisskopf again confirmed this value using an approach in which infinities cancelled other infinities to result in finite quantities. However, this method was clumsy and unreliable and could not be generalized to other calculations.  The breakthrough eventually came around 1950 when a more robust method for eliminating infinities was developed by Julian Schwinger, Feynman, Freeman Dyson, and Shinichiro Tomonaga. The main idea is to replace the initial, so-called "bare" parameters (mass, electric charge, etc.), which have no physical meaning, by their finite measured values. To cancel the apparently infinite parameters, one has to introduce additional, infinite, "counterterms" into the Lagrangian. This systematic computational procedure is known as renormalization and can be applied to arbitrary order in perturbation theory.  By applying the renormalization procedure, calculations were finally made to explain the electron's anomalous magnetic moment (the deviation of the electron "g"-factor from 2) and vacuum polarisation. These results agreed with experimental measurements to a remarkable degree, thus marking the end of a "war against infinities".  At the same time, Feynman introduced the path integral formulation of quantum mechanics and Feynman diagrams. The latter can be used to visually and intuitively organise and to help compute terms in the perturbative expansion. Each diagram can be interpreted as paths of particles in an interaction, with each vertex and line having a corresponding mathematical expression, and the product of these expressions gives the scattering amplitude of the interaction represented by the diagram.  It was with the invention of the renormalization procedure and Feynman diagrams that QFT finally arose as a complete theoretical framework.

Non-renormalizability.

Given the tremendous success of QED, many theorists believed, in the few years after 1949, that QFT could soon provide an understanding of all microscopic phenomena, not only the interactions between photons, electrons, and positrons. Contrary to this optimism, QFT entered yet another period of depression that lasted for almost two decades.  The first obstacle was the limited applicability of the renormalization procedure. In perturbative calculations in QED, all infinite quantities could be eliminated by redefining a small (finite) number of physical quantities (namely the mass and charge of the electron). Dyson proved in 1949 that this is only possible for a small class of theories called "renormalizable theories", of which QED is an example. However, most theories, including the Fermi theory of the weak interaction, are "non-renormalizable". Any perturbative calculation in these theories beyond the first order would result in infinities that could not be removed by redefining a finite number of physical quantities.  The second major problem stemmed from the limited validity of the Feynman diagram method, which is based on a series expansion in perturbation theory. In order for the series to converge and low-order calculations to be a good approximation, the coupling constant, in which the series is expanded, must be a sufficiently small number. The coupling constant in QED is the fine-structure constant, which is small enough that only the simplest, lowest order, Feynman diagrams need to be considered in realistic calculations. In contrast, the coupling constant in the strong interaction is roughly of the order of one, making complicated, higher order, Feynman diagrams just as important as simple ones. There was thus no way of deriving reliable quantitative predictions for the strong interaction using perturbative QFT methods.  With these difficulties looming, many theorists began to turn away from QFT. Some focused on symmetry principles and conservation laws, while others picked up the old S-matrix theory of Wheeler and Heisenberg. QFT was used heuristically as guiding principles, but not as a basis for quantitative calculations.

Standard Model.

In 1954, Yang Chen-Ning and Robert Mills generalised the local symmetry of QED, leading to non-Abelian gauge theories (also known as Yang–Mills theories), which are based on more complicated local symmetry groups. In QED, (electrically) charged particles interact via the exchange of photons, while in non-Abelian gauge theory, particles carrying a new type of "charge" interact via the exchange of massless gauge bosons. Unlike photons, these gauge bosons themselves carry charge.  Sheldon Glashow developed a non-Abelian gauge theory that unified the electromagnetic and weak interactions in 1960. In 1964, Abdus Salam and John Clive Ward arrived at the same theory through a different path. This theory, nevertheless, was non-renormalizable.  Peter Higgs, Robert Brout, and François Englert proposed in 1964 that the gauge symmetry in Yang–Mills theories could be broken by a mechanism called spontaneous symmetry breaking, through which originally massless gauge bosons could acquire mass.  By combining the earlier theory of Glashow, Salam, and Ward with the idea of spontaneous symmetry breaking, Steven Weinberg wrote down in 1967 a theory describing electroweak interactions between all leptons and the effects of the Higgs boson. His theory was at first mostly ignored, until it was brought back to light in 1971 by Gerard 't Hooft's proof that non-Abelian gauge theories are renormalizable. The electroweak theory of Weinberg and Salam was extended from leptons to quarks in 1970 by Glashow, John Iliopoulos, and Luciano Maiani, marking its completion.  Harald Fritzsch, Murray Gell-Mann, and Heinrich Leutwyler discovered in 1971 that certain phenomena involving the strong interaction could also be explained by non-Abelian gauge theory. Quantum chromodynamics (QCD) was born. In 1973, David Gross, Frank Wilczek, and Hugh David Politzer showed that non-Abelian gauge theories are "asymptotically free", meaning that under renormalization, the coupling constant of the strong interaction decreases as the interaction energy increases. (Similar discoveries had been made numerous times previously, but they had been largely ignored.) Therefore, at least in high-energy interactions, the coupling constant in QCD becomes sufficiently small to warrant a perturbative series expansion, making quantitative predictions for the strong interaction possible.  These theoretical breakthroughs brought about a renaissance in QFT. The full theory, which includes the electroweak theory and chromodynamics, is referred to today as the Standard Model of elementary particles. The Standard Model successfully describes all fundamental interactions except gravity, and its many predictions have been met with remarkable experimental confirmation in subsequent decades. The Higgs boson, central to the mechanism of spontaneous symmetry breaking, was finally detected in 2012 at CERN, marking the complete verification of the existence of all constituents of the Standard Model.

Other developments.

The 1970s saw the development of non-perturbative methods in non-Abelian gauge theories. The 't Hooft–Polyakov monopole was discovered by 't Hooft and Alexander Polyakov, flux tubes by Holger Bech Nielsen and Poul Olesen, and instantons by Polyakov "et al.". These objects are inaccessible through perturbation theory.  Supersymmetry also appeared in the same period. The first supersymmetric QFT in four dimensions was built by Yuri Golfand and Evgeny Likhtman in 1970, but their result failed to garner widespread interest due to the Iron Curtain. Supersymmetry only took off in the theoretical community after the work of Julius Wess and Bruno Zumino in 1973.  Among the four fundamental interactions, gravity remains the only one that lacks a consistent QFT description. Various attempts at a theory of quantum gravity led to the development of string theory, itself a type of two-dimensional QFT with conformal symmetry. Joël Scherk and John Schwarz first proposed in 1974 that string theory could be "the" quantum theory of gravity.

Condensed matter physics.

Although quantum field theory arose from the study of interactions between elementary particles, it has been successfully applied to other physical systems, particularly to many-body systems in condensed matter physics.  Historically, the Higgs mechanism of spontaneous symmetry breaking was a result of Yoichiro Nambu's application of superconductor theory to elementary particles, while the concept of renormalization came out of the study of second-order phase transitions in matter.  Soon after the introduction of photons, Einstein performed the quantization procedure on vibrations in a crystal, leading to the first quasiparticle — phonons. Lev Landau claimed that low-energy excitations in many condensed matter systems could be described in terms of interactions between a set of quasiparticles. The Feynman diagram method of QFT was naturally well suited to the analysis of various phenomena in condensed matter systems.  Gauge theory is used to describe the quantization of magnetic flux in superconductors, the resistivity in the quantum Hall effect, as well as the relation between frequency and voltage in the AC Josephson effect.

Principles.

For simplicity, natural units are used in the following sections, in which the reduced Planck constant and the speed of light are both set to one.

Classical fields.

A classical field is a function of spatial and time coordinates. Examples include the gravitational field in Newtonian gravity and the electric field and magnetic field in classical electromagnetism. A classical field can be thought of as a numerical quantity assigned to every point in space that changes in time. Hence, it has infinitely many degrees of freedom.  Many phenomena exhibiting quantum mechanical properties cannot be explained by classical fields alone. Phenomena such as the photoelectric effect are best explained by discrete particles (photons), rather than a spatially continuous field. The goal of quantum field theory is to describe various quantum mechanical phenomena using a modified concept of fields.  Canonical quantisation and path integrals are two common formulations of QFT. To motivate the fundamentals of QFT, an overview of classical field theory is in order.  The simplest classical field is a real scalar field — a real number at every point in space that changes in time. It is denoted as, where is the position vector, and is the time. Suppose the Lagrangian of the field is where formula_2 is the time-derivative of the field, is the gradient operator, and is a real parameter (the "mass" of the field). Applying the Euler–Lagrange equation on the Lagrangian: we obtain the equations of motion for the field, which describe the way it varies in time and space: This is known as the Klein–Gordon equation.  The Klein–Gordon equation is a wave equation, so its solutions can be expressed as a sum of normal modes (obtained via Fourier transform) as follows: where is a complex number (normalised by convention), denotes complex conjugation, and is the frequency of the normal mode: where, and denotes the covariant derivative. The Lagrangian of a QFT, hence its calculational results and physical predictions, depends on the geometry of the spacetime background.

Topological quantum field theory.

The correlation functions and physical predictions of a QFT depend on the spacetime metric. For a special class of QFTs called topological quantum field theories (TQFTs), all correlation functions are independent of continuous changes in the spacetime metric. QFTs in curved spacetime generally change according to the "geometry" (local structure) of the spacetime background, while TQFTs are invariant under spacetime diffeomorphisms but are sensitive to the "topology" (global structure) of spacetime. This means that all calculational results of TQFTs are topological invariants of the underlying spacetime. Chern–Simons theory is an example of TQFT and has been used to construct models of quantum gravity. Applications of TQFT include the fractional quantum Hall effect and topological quantum computers. The world line trajectory of fractionalized particles (known as anyons) can form a link configuration in the spacetime, which relates the braiding statistics of anyons in physics to the link invariants in mathematics. Topological quantum field theories (TQFTs) applicable to the frontier research of topological quantum matters include Chern-Simons-Witten gauge theories in 2+1 spacetime dimensions, other new exotic TQFTs in 3+1 spacetime dimensions and beyond.

Perturbative and non-perturbative methods.

Using perturbation theory, the total effect of a small interaction term can be approximated order by order by a series expansion in the number of virtual particles participating in the interaction. Every term in the expansion may be understood as one possible way for (physical) particles to interact with each other via virtual particles, expressed visually using a Feynman diagram. The electromagnetic force between two electrons in QED is represented (to first order in perturbation theory) by the propagation of a virtual photon. In a similar manner, the W and Z bosons carry the weak interaction, while gluons carry the strong interaction. The interpretation of an interaction as a sum of intermediate states involving the exchange of various virtual particles only makes sense in the framework of perturbation theory. In contrast, non-perturbative methods in QFT treat the interacting Lagrangian as a whole without any series expansion. Instead of particles that carry interactions, these methods have spawned such concepts as 't Hooft–Polyakov monopole, domain wall, flux tube, and instanton. Examples of QFTs that are completely solvable non-perturbatively include minimal models of conformal field theory and the Thirring model.

Mathematical rigour.

In spite of its overwhelming success in particle physics and condensed matter physics, QFT itself lacks a formal mathematical foundation. For example, according to Haag's theorem, there does not exist a well-defined interaction picture for QFT, which implies that perturbation theory of QFT, which underlies the entire Feynman diagram method, is fundamentally ill-defined.  Since the 1950s, theoretical physicists and mathematicians have attempted to organise all QFTs into a set of axioms, in order to establish the existence of concrete models of relativistic QFT in a mathematically rigorous way and to study their properties. This line of study is called constructive quantum field theory, a subfield of mathematical physics, which has led to such results as CPT theorem, spin–statistics theorem, and Goldstone's theorem.  Compared to ordinary QFT, topological quantum field theory and conformal field theory are better supported mathematically — both can be classified in the framework of representations of cobordisms.  Algebraic quantum field theory is another approach to the axiomatisation of QFT, in which the fundamental objects are local operators and the algebraic relations between them. Axiomatic systems following this approach include Wightman axioms and Haag–Kastler axioms. One way to construct theories satisfying Wightman axioms is to use Osterwalder–Schrader axioms, which give the necessary and sufficient conditions for a real time theory to be obtained from an imaginary time theory by analytic continuation (Wick rotation).  Yang–Mills existence and mass gap, one of the Millennium Prize Problems, concerns the well-defined existence of Yang–Mills theories as set out by the above axioms. The full problem statement is as follows.

In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines classical field theory, special relativity and quantum mechanics, but "not" general relativity's description of gravity. QFT is used in particle physics to construct physical models of subatomic particles and in condensed matter physics to construct models of quasiparticles.

Copland byl koncept operačního systému pro počítače Macintosh společnosti Apple. Byl ohlášen v březnu 1994 při představení Maců s procesory PowerPC jako operační systém nové generace. Vývojáři firmy Apple zamýšleli Copland jako úplně původní operační systém pro PowerPC nabízející inteligentní agenty, upravitelné rozhraní a relační databázi integrovanou do vyhledávače. Copland byl následován operačním systémem Gershwin, který sliboval chráněný paměťový prostor a plně preemptivní multitasking. Tento operační systém měl být úplným přepisem systému Mac OS a firma Apple doufala, že s ním na trhu porazí Windows 95 během pouhého jednoho roku.


The standing martingale.

The standing martingale, also known as a "tiedown" or a "head check", has a single strap which is attached to the girth, passes between the horse's front legs and is fixed to the back of the noseband. To prevent it from catching on other objects, it also has a neck strap. A variation is attached to a breastplate in lieu of a neck strap. When correctly fitted for English riding, it should be possible to push the martingale strap up to touch the horse's throatlatch.  A variation of the standing martingale, called a "tiedown", is seen almost exclusively in the western riding disciplines. A tiedown is adjusted much shorter than a standing martingale and is intended primarily to prevent the horse from flipping its head up when asked to abruptly stop or turn in speed events. Users also claim that it gives the horse something to brace against for balance. It consists of an adjustable strap, one end which attaches to the horse's breastplate and the other which attaches to a noseband on the bridle. The noseband can be of leather, but may also be of lariat rope, or even plastic-covered cable, which can make the western tiedown considerably harsher than the English-style standing martingale. It is properly adjusted when it puts no pressure on the horse's nose when held at a normal position, but will immediately act if the horse raises its nose more than a few inches.  With both pieces of equipment, the slack is taken up out of the strap when the horse raises its head above the desired point, and pressure is placed on the horse's nose.  The standing martingale is competition legal for show hunter and hunt seat equitation riders over fences in the US, show jumping competitions in the UK, and is permissible and in common use in fox hunting, polocrosse, horseball, and polo. It is also seen on some military and police horses, partly for style and tradition, but also in the event of an emergency that may require the rider to handle the horse in an abrupt manner. It is not legal for flat classes. The tiedown is commonly seen in rodeo and speed events such as gymkhana games, but is not show legal in any other western-style horse show competition.

Safety and risks.

The standing martingale is more restrictive than the running martingale because it cannot be loosened in an emergency. A horse that trips in a standing martingale could potentially fall more easily because its range of motion is restricted. If a horse falls wearing an incorrectly fitted standing martingale, the animal cannot extend its neck fully, plus will have a more difficult time getting back up.  Due to the risk of injury to the cartilage of the nose, the martingale strap is never attached to a drop noseband. Because of the risk of both nose and jaw injuries, it also should not be attached to any type of "figure 8" or "grackle" noseband. A standing martingale can be attached to the cavesson (the upper, heavier strap) of a flash noseband, but not to the lower, "flash" or "drop" strap.  Any martingale may cause pain to the horse if misused in combination with certain other equipment. If used in conjunction with a gag bit, a standing martingale can trap the head of the horse, simultaneously asking the horse to raise and lower its head and providing no source of relief in either direction. This combination is sometimes seen in polo, in some rodeo events, and occasionally in the lower levels of jumping.  Overuse or misuse of a martingale or tiedown, particularly as a means to prevent a horse from head-tossing, can lead to the overdevelopment of the muscles on the underside of the neck, creating an undesirable "upside down" neck that makes it more difficult for the horse work properly under saddle. It may also lead to the horse tensing the back muscles and moving incorrectly, especially over fences. This may put excessive pressure on the horse's spine, reduce the shock-absorbing capacity of the leg anatomy, and can over time lead to lameness. There is also a risk of accidents: If a horse is sufficiently "trapped" by a combination of a too-short martingale and too-harsh bit, the horse may attempt to rear and, inhibited by the action of the martingale, fall, potentially injuring both horse and rider.

The running martingale and German martingale.

The "running martingale" consists of a strap which is attached to the girth and passes between the horse's front legs before dividing into two pieces. At the end of each of these straps is a small metal ring through which the reins pass. It is held in the correct position by a neck strap or breastplate.  A running martingale is adjusted so that each of the "forks" has about an inch of slack when the horse holds its head in the normal position. When correctly adjusted, the reins make a straight line from the rider's hand to the bit ring when the horse's head in at the correct height and the running martingale is not in effect.  When the horse raises its head above the desired point, the running martingale adds leverage through the reins to the bit on the bars of the horse's mouth. The leverage created by this pressure encourages the horse to lower its head. A running martingale provides more freedom for the horse than a standing martingale, as the rider can release pressure as soon as the desired result is achieved. Additionally, if a horse happens to trip on landing after a fence, the rider can loosen the reins and the horse will have full use of its head and neck.  Because of this safety factor, the running martingale is the only style of martingale permitted for use in eventing competitions and horse racing. Some show jumpers also prefer the running martingale due to the extra freedom it provides. Running martingales are also used outside of the competition arena on young horses being trained in the Saddle seat, western riding, and many other disciplines.  The German martingale, also called a Market Harborough, consists of a split fork that comes up from the chest, runs through the rings of the bit and attaches to rings on the reins of the bridle between the bit and the rider's hand. It acts in a manner similar to a running martingale, but with additional leverage. It is not show legal and is used primarily as a training aid.

Safety and risks.

A running martingale is generally used with rein stops, which are rubber or leather stops slipped onto the rein between the bit and the ring of the martingale. Rein stops are compulsory at Pony Club and British Eventing Events. They are an important safety feature that stops the martingale from sliding too far forward and getting caught on the bit ring or on the buckles or studs that attach the reins to the bit. Sanctioning organizations require a running martingale to be used in conjunction with rein stops if the reins are buckled to the bit.  The primary difficulty in use of a running martingale is the inability to raise the horse's head in the event of the animal bucking. If adjusted too short, lateral use of the reins may be impeded. If used improperly, the force exerted by the running martingale on the horse's mouth can be severe and for this reason the standing martingale is preferred in some circles. Improper use includes use on the reins of a curb bit; adjustment too short, so that the equipment pulls the horse's head below the proper position.

The Irish martingale.

The Irish martingale is not a true martingale in the sense of a device that affects the rider's control over the horse. Thus, it is sometimes known as a semi-martingale. It is a simple short strap with a ring on either end. The reins are each run through a ring on either side before being buckled. The Irish martingale's purpose is not to control the head, but to prevent the reins from coming over the horse's head, risking entanglement, should a rider fall. It is used mostly in European horse racing.

A martingale is any of several designs of tack that are used on horses to control head carriage. Martingales may be seen in a wide variety of equestrian disciplines, both riding and driving. Rules for their use vary widely; in some disciplines they are never used, others allow them for schooling but not in judged performance, and some organizations allow certain designs in competition.

Martingal je pomocné řemení s kroužky jimiž se provlékají otěže. Používá se v jezdectví a je povolen v parkurových sportech. V případě správného použití martingal zabraňuje koním zvedat příliš vysoko hlavu a pohazovat s ní nahoru nebo dolů. Zmírňuje půsebení otěží. V drezuře je zakázán, v parkuru naopak povolen.


Architecture.

The S-100 bus is a passive backplane of 100-pin printed circuit board edge connectors wired in parallel. Circuit cards measuring 5 × 10-inches serving the functions of CPU, memory, or I/O interface plugged into these connectors. The bus signal definitions closely follow those of an 8080 microprocessor system, since the Intel 8080 microprocessor was the first microprocessor hosted on the S-100 bus. The 100 lines of the S-100 bus can be grouped into four types: 1) Power, 2) Data, 3) Address, and 4) Clock and control.  Power supplied on the bus is bulk unregulated +8 Volt DC and ±16 Volt DC, designed to be regulated on the cards to +5 V (used by TTL ICs), -5 V and +12 V for Intel 8080 CPU IC, ±12 V RS-232 line driver ICs, +12 V for disk drive motors. The onboard voltage regulation is typically performed by devices of the 78xx family (for example, a 7805 device to produce +5 volts). These were linear regulators which are commonly mounted on heat sinks.  The bi-directional 8-bit data bus of the Intel 8080 is split into two unidirectional 8-bit data buses. The processor could use only one of these at a time. The Sol-20 used a variation that had only a single 8-bit bus and used the now-unused pins as signal grounds to reduce electronic noise. The direction of the bus, in or out, was signaled using the otherwise unused DBIN pin. This became universal in the S-100 market as well, making the second bus superfluous. Later, these two 8-bit busses would be combined to support a 16-bit data width for more advanced processors, using the Sol's system to signal the direction.  The address bus is 16-bits wide in the initial implementation and later extended to 24-bits wide. A bus control signal can put these lines in a tri-state condition to allow direct memory access. The Cromemco Dazzler, for example, is an early S-100 card that retrieved digital images from memory using direct memory access.  Clock and control signals are used to manage the traffic on the bus. For example, the "DO Disable" line will tristate the address lines during direct memory access. Unassigned lines of the original bus specification were later assigned to support more advanced processors. For example, the Zilog Z-80 processor has a non-maskable interrupt line that the Intel 8080 processor does not. One unassigned line of the S-100 bus then was reassigned to support the non-maskable interrupt request.

History.

During the design of the Altair, the hardware required to make a usable machine was not available in time for the January 1975 launch date. The designer, Ed Roberts, also had the problem of the backplane taking up too much room. Attempting to avoid these problems, he placed the existing components in a case with additional "slots", so that the missing components could be plugged in later when they became available. The backplane is split into four separate cards, with the CPU on a fifth. He then looked for an inexpensive source of connectors, and he came across a supply of military surplus 100-pin edge connectors. The 100-pin bus was created by an anonymous draftsman, who selected the connector from a parts catalog and arbitrarily assigned signal names to groups of connector pins.  A burgeoning industry of "clone" machines followed the introduction of the Altair in 1975. Most of these used the same bus layout as the Altair, creating a new industry standard. These companies were forced to refer to the system as the "Altair bus", and wanted another name in order to avoid referring to their competitor when describing their own system. The "S-100" name, short for "Standard 100", was coined by Harry Garland and Roger Melen, co-founders of Cromemco. While on a flight to attend the Atlantic City PC '76 microcomputer conference in August 1976, they shared the cabin with Bob Marsh and Lee Felsenstein of Processor Technology. Melen went over to them to convince them to adopt the same name. He had a beer in his hand and when the plane hit a bump, Melen spilt some the beer on Marsh. Marsh agreed to use the name, which Melen ascribes to him wanting to get Melen to leave with his beer.  The term first appeared in print in a Cromemco advertisement in the November 1976 issue of Byte magazine. The first symposium on the S-100 bus, moderated by Jim Warren, was held November 20, 1976 at Diablo Valley College with a panel consisting of Harry Garland, George Morrow, and Lee Felsenstein. Just one year later, the S-100 Bus would be described as "the most used busing standard ever developed in the computer industry."  Cromemco was the largest of the S-100 manufacturers, followed by Vector Graphic and North Star Computers. Other innovators were companies such as Alpha Microsystems, IMS Associates, Inc., Godbout Electronics (later CompuPro), and Ithaca Intersystems. In May 1984, "Microsystems" published a comprehensive S-100 product directory listing over 500 "S-100/IEEE-696" products from over 150 companies.  The S-100 bus signals were simple to create using an 8080 CPU, but increasingly less so when using other processors like the 68000. More board space was occupied by signal conversion logic. Nonetheless by 1984, eleven different processors were hosted on the S-100 bus, from the 8-bit Intel 8080 to the 16-bit Zilog Z-8000. In 1986, Cromemco introduced the XXU card, designed by Ed Lupin, utilizing a 32-bit Motorola 68020 processor.

IEEE-696 Standard.

As the S-100 bus gained momentum, there was a need to develop a formal specification of the bus to help assure compatibility of products produced by different manufacturers. There was also a need to extend the bus so that it could support processors more capable than the Intel 8080 used in the original Altair Computer. In May 1978, George Morrow and Howard Fullmer published a “Proposed Standard for the S-100 Bus” noting that 150 vendors were already supplying products for the S-100 Bus. This proposed standard documented the 8-bit data path and 16-bit address path of the bus and stated that consideration was being given to extending the data path to 16 bits and the address path to 24 bits.  In July 1979 Kells Elmquist, Howard Fullmer, David Gustavson, and George Morrow published a “Standard Specification for S-100 Bus Interface Devices.” In this specification the data path was extended to 16 bits and the address path was extended to 24 bits. The IEEE 696 Working Group, chaired by Mark Garetz, continued to develop the specification which was proposed as an IEEE Standard and approved by the IEEE Computer Society on June 10, 1982.  The American National Standards Institute (ANSI) approved the IEEE standard on September 8, 1983. The computer bus structure developed by Ed Roberts for the Altair 8800 computer had been extended, rigorously documented, and now designated as the American National Standard IEEE Std 696-1983.

Retirement.

IBM introduced the IBM Personal Computer in 1981 and followed it with increasingly capable models: the XT in 1983 and the AT in 1984. The success of these computers cut deeply into the market for S-100 bus products. In May 1984, Sol Libes (who had been a member of the IEEE-696 Working Group) wrote in "Microsystems": “there is no doubt that the S-100 market can now be considered a mature industry with only moderate growth potential, compared to the IBM PC-compatible market.”  As the IBM PC products captured the low-end of the market, S-100 machines moved up-scale to more powerful OEM and multiuser systems. Banks of S-100 bus computers were used, for example, to process the trades at the Chicago Mercantile Exchange; the United States Air Force deployed S-100 bus machines for their mission planning systems. However throughout the 1980s the market for S-100 bus machines for the hobbyist, for personal use, and even for small business was on the decline.  The market for S-100 bus products continued to contract through the early 1990s, as IBM-compatible computers became more capable. In 1992, the Chicago Mercantile Exchange, for example, replaced their S-100 bus computers with the IBM model PS/2. By 1994 the S-100 bus industry had contracted sufficiently that the IEEE did not see a need to continue supporting the IEEE-696 standard. The IEEE-696 standard was retired on June 14, 1994.

The S-100 bus or Altair bus, "IEEE696-1983 (withdrawn)", is an early computer bus designed in 1974 as a part of the Altair 8800. The S-100 bus was the first industry standard expansion bus for the microcomputer industry. S-100 computers, consisting of processor and peripheral cards, were produced by a number of manufacturers. The S-100 bus formed the basis for homebrew computers whose builders (e.g., the Homebrew Computer Club) implemented drivers for CP/M and MP/M. These S-100 microcomputers ran the gamut from hobbyist toy to small business workstation and were common in early home computers until the advent of the IBM PC (which some of them outperformed).

Sběrnice S-100 (IEEE 696-1983) je jednou z prvních počítačových sběrnic. Byla vyvinuta v roce 1974 jako část 8bitového počítače Altair 8800, který se dnes považuje za první osobní počítač. Sběrnice S-100 byla první standardizovanou sběrnicí v mikropočítačovém průmyslu.


Plot introduction.

This novel is an imaginative reconstruction of the life of a band of Neanderthals. It is written in such a way that the reader might assume the group to be modern "Homo sapiens" as they gesture and speak simply among themselves, and bury their dead with heartfelt, solemn rituals. They also have powerful sense impressions and feelings, and appear sometimes to share thoughts in a near-telepathic way. As the novel progresses it becomes more and more apparent that they live very simply, using their considerable mental abilities to connect to one another without extensive vocabulary or the kinds of memories that create culture. They have wide knowledge of food sources, mostly roots and vegetables. They chase hyenas from a larger beast's kill and eat meat, but they don't kill mammals themselves. They have a spiritual system centring on a female principle of bringing forth, but their lives are lived so much in the present that the reader realizes they are very different from us, living in something like an eternal present, or at most a present broken and shaped by seasons.  One of the band, Lok, is a point of view character. He is the one we follow as one by one the adults of the band die or are killed, then the young are stolen by the "new people," a group of early modern humans. Lok and Fa, the remaining adults, are fascinated and repelled by the new people. They observe their actions and rituals with amazement, only slowly understanding that harm is meant by the sticks of the new people.  The humans are portrayed as strange, godlike beings as the neanderthals witness their mastery of fire, Upper Palaeolithic weaponry and sailing.  All save the last chapters of the novel are written from the Neanderthals' stark, simple stylistic perspective. Their observations of early human behaviour serve as a filter for Golding's exercise in paleoanthropology, in which modern readers will recognize precursors of later human societal constructs, e.g., religion, culture, sacrifice and war.  The penultimate chapter employs an omniscient viewpoint, observing Lok. For the first time, the novel describes the people the reader has been inhabiting through the first-person perspective. Lok, totally alone, gives up in despair. In the final chapter, we move to the point of view of the new race, more or less modern humans fleeing in their boats, revealing that they are terribly afraid of the Neanderthals (whom they believe to be devils of the forest) and of pretty much everything around. This last chapter, the only one written from the humans' point of view, reinforces the inheritance of the world by the new species.  The fleeing humans carry with them an infant Neanderthal, of whom they are simultaneously afraid and enamoured, hinting at the later hypothesis of inter-breeding between Neanderthals and modern humans.  The book, particularly the last chapter, was the inspiration for the song "A Trick of the Tail" by British rock band Genesis.

The Inheritors is a work of prehistoric fiction and the second novel, published in 1955, by the British author William Golding, best known for "Lord of the Flies". It concerns the extinction of one of the last remaining tribes of Neanderthals at the hands of the more sophisticated "Homo sapiens".

Dědicové ("The Inheritors", 1955) je druhý román držitele Nobelovy ceny za literaturu, anglického spisovatele Williama Goldinga. Vypráví o setkání dvou tlup odlišných druhů člověka ("Homo sapiens" a "Homo neanderthalensis") v době zhruba před 50 000 lety, které skončí pro méně vyvinuté neandrtálce katastroficky. Podobně jako "Pánem much" polemizuje Golding s "Korálovým ostrovem" R. M. Ballantyna, románem Dědicové pak s "Dějinami světa" a "Chlupatci" H. G. Wellse.


Developers.

Dan Ingalls, an important contributor to the Squeak project, wrote the paper upon which Squeak is built and constructed the architecture for five generations of the Smalltalk language.  Squeak incorporates many of the elements Alan Kay proposed in the Dynabook concept, which he formulated in the 1960s. Kay is an important contributor to the Squeak project.

User interface frameworks.

Squeak includes four user interface frameworks:

Uses.

Many Squeak contributors collaborate on Open Cobalt, a free and open source virtual world browser and construction toolkit application which is built on Squeak.  Squeak is also used in the Nintendo ES operating system and was used for implementing the first version of Scratch programming language for beginning programmers. In May 2011 the OpenQwaq virtual conferencing and collaboration system based on Squeak, an open source release of Teleplace, was announced on the Teleplace blog.

License.

Squeak 4.0 and later may be downloaded at no cost, including source code, as a prebuilt virtual machine image licensed under the MIT License, with the exception of some of the original Apple code, which is governed by the Apache License.  Originally, Apple actually released Squeak under a license called the "Squeak License". While source code was available and modification permitted, the Squeak License contained an indemnity clause that prevented it from qualifying as true free and open-source software.  In 2006, Apple relicensed Squeak twice. First, in May, Apple used its own Apple Public Source License, which satisfies the Free Software Foundation's concept of a Free Software License and has attained official approval from the Open Source Initiative as an Open Source License. The Apple Public Source License, as it turns out, fails to pass the third standard that Free and Open Source Software licenses are held to: the Debian Free Software Guidelines promulgated by the Debian project, an influential volunteer-run Linux distribution. To enable inclusion of Etoys in the One Laptop Per Child project, a second relicensing was undertaken using the Apache License. At this point, an effort was also made to address the issue of code contributed by members of the Squeak community, which it was not in Apple's power to unilaterally relicense.  For each contribution made under the Squeak License since 1996, a relicensing statement was obtained authorizing distribution under the MIT license, and finally in March 2010, the end result was released as Squeak 4.0, now under combined MIT and Apache licenses.

Squeak virtual machine.

The "Squeak virtual machine" is a family of virtual machines (VMs) used in Smalltalk programming language implementations. They are an essential part of any Smalltalk implementation. All are open-source software. The current VM is a high performance dynamic translation system. The relevant code is maintained on GitHub at OpenSmalltalk

The Squeak programming language is a dialect of Smalltalk. It is object-oriented, class-based, and reflective. It was derived directly from Smalltalk-80 by a group at Apple Computer that included some of the original Smalltalk-80 developers. Its development was continued by the same group at Walt Disney Imagineering, where it was intended for use in internal Disney projects. Later on the group moved on to be supported by HP labs, SAP Labs and most recently Y Combinator.

Squeak je open source implementace programovacího jazyka a prostředí Smalltalk. Squeak je k dispozici pro mnoho platforem (Windows, Linux, MacOS, RiscOS, UNIX). Skládá se z virtuálního stroje, obrazu prostředí, logu změn a zdrojových kódů. Prostředí je objektově orientované, založené na třídách a reflexivní. Uživatelské rozhraní umožňuje různé modifikace widgetů (např. rotaci okna). Na Squeaku jsou založeny projekty Croquet Project nebo SmallDEVS.


Description.

"Leiurus quinquestriatus" is yellow, and long, with an average of.

Geographic range.

"Leiurus quinquestriatus" can be found in desert and scrubland habitats ranging from North Africa through to the Middle East. Its range covers a wide sweep of territory in the Sahara, Arabian Desert, Thar Desert, and Central Asia, from Algeria and Mali in the west through to Egypt, Ethiopia, Asia Minor and the Arabian Peninsula, eastwards to Kazakhstan and western India in the northeast and southeast.

Venom.

Neurotoxins in "L. quinquestriatus" venom include:

Hazards.

The deathstalker is one of the most dangerous species of scorpions. Its venom is a powerful mixture of neurotoxins, with a low lethal dose. While a sting from this scorpion is extraordinarily painful, it normally would not kill a healthy adult human. However, young children, the elderly, or infirm (such as those with a heart condition and those who are allergic) are at much greater risk. Any envenomation runs the risk of anaphylaxis, a potentially life-threatening allergic reaction to the venom. A study from Israel shows a high rate of pancreatitis following envenomation. If a sting from "Leiurus quinquestriatus" does prove deadly, the cause of death is usually pulmonary edema.  Antivenom for the treatment of deathstalker envenomations is produced by pharmaceutical companies Twyford (German) and Sanofi Pasteur (French), and by the Antivenom and Vaccine Production Center in Riyadh. Envenomation by the deathstalker is considered a medical emergency even with antivenom treatment, as its venom is unusually resistant to treatment and typically requires large doses of antivenom.  In the United States and other countries outside of the typical range of the deathstalker, there is the additional complicating factor that none of the existing antivenoms are approved by the Food and Drug Administration (or equivalent agencies) and are only available as investigational drugs (INDs). The US Armed Forces maintain an investigational drug application for the AVPC-Riyadh antivenom in the event of envenomation of soldiers in the Gulf War theater of operations, and the Florida Antivenin Bank, managed by the Miami-Dade Fire Rescue Department, maintains Sanofi Pasteur's Scorpifav antivenom for the deathstalker.

Uses.

A component of the deathstalker's venom, the peptide chlorotoxin, has shown potential for treating human brain tumors. There has also been some evidence to show that other components of the venom may aid in the regulation of insulin and could be used to treat diabetes.  In 2015 clinical trials were beginning of the use of chlorotoxin with a fluorescent molecule attached as brain tumour "paint" (BLZ-100), to mark cancerous cells in real time during an operation. This is important in brain cancer surgery, where it is vital both to remove as many cancerous cells as possible, but not to remove healthy tissue necessary for brain functioning. In preclinical animal trials the technique could highlight extremely small clusters of as few as 200 cancer cells, compared to the standard use of MRI, with a lower limit in excess of 500,000.

Legality.

Possession of "L.quinquestriatus" may be illegal or regulated in countries with laws prohibiting the keeping of dangerous animals in general. Jurisdictions are increasingly and explicitly including "L.quinquestriatus" in laws requiring permits to keep animals which are not usual pets, or restricting possession of dangerous animals, and in some cases have prohibited the keeping of "L.quinquestriatus" save by licensed zoos and educational facilities.  In several jurisdictions departments of fish and wildlife require permits for many animals, and a number of cities and municipal governments have prohibited their possession in their bylaws.

The deathstalker ("Leiurus quinquestriatus") is a species of scorpion, a member of the family Buthidae. It is also known as the Palestine yellow scorpion, Omdurman scorpion, Naqab desert scorpion and by many other colloquial names, which generally originate from the commercial captive trade of the animal. To eliminate confusion, especially important with potentially dangerous species, the scientific name is normally used to refer to them. The name "Leiurus quinquestriatus" roughly translates into English as "five-striped smooth-tail". In 2014, the subspecies "L. q. hebraeus" was separated from it and elevated to its own species "Leiurus hebraeus". Other species of the genus "Leiurus" are also often referred to as "deathstalkers".

Štír nejjedovatější ("Leiurus quinquestriatus"), je druh štíra, který má nejúčinnější jed ze všech štírů na světě. Vzhledem k malé kapacitě jedového váčku uvnitř telsonu způsobí méně úmrtí než štír tlustorepý ("Androctonus australis").