A tank gun is the main armament of a tank. Modern tank guns are large-caliber high-velocity guns, capable of firing kinetic energy penetrators, high explosive anti-tank rounds, in some cases guided missiles. Anti-aircraft guns can be mounted to tanks; as the tank's primary armament, they are always employed in a direct fire mode to defeat a variety of ground targets at all ranges, including dug-in infantry armored vehicles, other armored tanks. They must provide accuracy, range and rapid fire in a package, as compact and lightweight as possible, to allow mounting in the cramped confines of an armored gun turret. Tank guns use self-contained ammunition, allowing rapid loading, they display a bulge in the barrel, a bore evacuator, or a device on the muzzle, a muzzle brake. The first tanks were used to break through trench defences in support of infantry actions machine gun positions during the First World War and they were fitted with machine guns or high explosive firing guns of modest calibre.
These were naval or field artillery pieces stripped from their carriages and mounted in sponsons or casemates on armored vehicles. The early British Mark I tanks of 1916 used naval 57 mm QF 6 pounder Hotchkiss mounted at the sides in sponsons; these guns proved too long for use in the British tank designs as they would come into contact with obstacles and the ground on uneven terrain, the succeeding Mark IV tank of 1917 was equipped with the shortened 6 pounder 6 cwt version which can be considered the first specialised tank gun. The first German tank, the A7V, utilized 57 mm Maxim-Nordenfelt fortification guns captured from Belgium and Russia, but mounted at the front; the early French Schneider CA1 mounted a short 75 mm mortar on one side, while the Saint-Chamond mounted a standard 75 mm field gun in the nose. The thin armour of the tanks meant that such weapons were effective against other vehicles, though the Germans fielded few tanks anyway and the Allied tanks concentrated on anti-infantry and infantry support activities.
This thinking remained pervasive into the dawn of World War II, when most tank guns were still modifications of existing artillery pieces, were expected to be used against unarmored targets. The larger caliber, shorter range artillery mounting did not go away however. Tanks intended for infantry support, expected to take out emplacements and infantry concentrations, carried large calibre weapons to fire large high-explosive shells—though these could be quite effective against other vehicles at close ranges. In some designs - for example, M3 Lee, Char B1 - the larger bore weapons were mounted within the tank hull while a second gun for use against tanks was fitted in a turret. However, other strategists saw new roles for tanks in war, wanted more developed guns tailored to these missions; the ability to destroy enemy tanks was foremost on their minds. To this end, the emerging anti-tank gun designs were modified to fit tanks; these weapons fired smaller shells, but at higher velocities with higher accuracy, improving their performance against armor.
Such light guns as the QF 2-pounder and 37 mm equipped British cruiser tanks and infantry tanks in the late 1930s. These weapons lacked a good high-explosive shell for attacking infantry and fortifications, but were effective against the light armor of the time. World War II saw a leapfrog growth in all areas of military technology. Battlefield experience led to powerful weapons being adopted. Guns with calibres from 20 mm to 40 mm soon gave way to 50 mm, 75 mm, 85 mm, 88 mm, 90 mm and 122 mm calibre. In 1939, the standard German panzer had either a 20 mm or 37 mm medium-velocity weapon, but by 1945 long-barrelled 75 mm and 88 mm high-velocity guns were common; the Soviets introduced their 122 mm in the Iosef Stalin tanks. Shells were improved to provide better penetration with scientific shaping. All of these meant improvements in accuracy and range, although the average tank had to grow as well to carry the ammunition and protection for these powerful guns. While high velocity tank guns were effective against other tanks, for the most part British tanks moved to a dual purpose 75 mm gun capable of firing a useful HE shell.
Many nations devised "tank destroyers" during the war - a vehicle designed for anti-tank work, armed more than a tank on the same chassis could be. They fell into three overlapping categories: improvised modifications of old or captured tanks to render them viable again with haphazard, poorly protected, limited-traverse weapon mounts; the relative superiority in armament of tank destroyers was only relative, however: for instance, the SU-85 was a casemate-type TD on the T-34 chassis, rendered obsolete once the basic T-34 switched from the 76 mm gun to the same 85 mm cannon, producing the T-34-85. By the end of the war the variety in tank designs was narrowed and the concept of the main battle tank emerged. After World War II, the race to increase caliber slowed. Slight incre
Token (railway signalling)
In railway signalling, a token is a physical object which a train driver is required to have or see before entering onto a particular section of single track. The token is endorsed with the names of the section it belongs to. A token system is more used for single lines because of the greater risk of collision in the event of a mistake being made by a signaller or traincrew, than on double lines; the operation of a bidirectional single track line has obvious dangers, the most serious of, the possibility of two trains colliding from opposite directions. The simplest method of controlling such a line is to have only one train operational, on the basis that a single train cannot collide with itself; such a system is known as "one-train working". This system is used on some branches of rail networks, on heritage railways; the main disadvantage is. For a larger railway system, it becomes exceptionally limiting in the level of operations that it allows, with the increased risk of mistakes being made leading to a collision.
Instead, reliance is placed not on employing only one train but on having a single physical object available for the single track section, ruling that a driver may enter the single line section only if in physical possession of that object. That object is known as a token, is marked to indicate to which single track section it belongs. Tokens have existed in a variety of physical forms: staff tablet ball key The token system was developed in Britain in the 19th century, to enable safe working of single-line railways. If a branch line is a dead end with a simple shuttle train service a single token is sufficient; the driver of any train entering the branch line must be in possession of the token, no collision with another train is possible. For convenience in passing it from hand to hand, the token was in the form of a staff 800 mm long and 40 mm diameter, is referred to as a train staff; such a staff is literally a wooden staff with a brass plate stating the two signal boxes between which it is valid.
In UK terminology, this method of working on simple branch lines was referred to as One Engine in Steam, One-Train Working. However the system was used on long through lines as well; that does cause a great delay because if the staff is not there, the train must stop while a man is sent on a horse to get it ". Using only a single token does not provide convenient operation when consecutive trains are to be worked in the same direction; the simple token system was therefore extended: if one train was to be followed by another in the same direction, the driver of the first train was required to be shown the token, but not take possession of it. He was given a written authority to enter the single line section, referred to as the ticket, he could proceed, a second train could follow. In the earliest days the second train could proceed after a designated time interval, as on double lines at the time. However, following the Armagh rail disaster of 1889, block working became mandatory. Seeing the train staff provided assurance that there could be no head-on collision.
To ensure that the ticket is not issued incorrectly, a book of numbered tickets is kept in a locked box, the key to, permanently fastened to the token, or is the token. In addition, the lock prevents the token being removed until the ticket box is closed, it cannot be closed unless the book of tickets is in the box. Once a ticket is issued, its number is recorded in a Train Register book, the token is locked in a secure place; this system is known as ticket. In a variation on this principle, called divisible train staff, a section of the token referred to as the ticket portion was designed to be removed and handed to the driver instead of a paper ticket; the staff and ticket system was still too inflexible for busy lines, as it did not allow for the situation where the train intended to carry the actual token was cancelled or running late. To provide for this, the electric train token system was developed; each single-line section is provided with a pair of token instruments, one at the signal box at each end.
A supply of identical tokens is stored in the instruments. A token can be removed from one instrument only if both signalmen co-operate in agreeing to the release. Once a token has been removed, another cannot be removed until the token, "out" is replaced in either instrument. By this means, it can be ensured that at any one time, only one token is available to be issued to a driver. Tokens belonging to adjacent sections have different configurations to prevent them being inserted into the wrong instrument. In the Abermule train collision in 1921, lax working procedures allowed the safeguards provided by the electric token system to be circumvented. To prevent this, it became a requirement in the UK for the signals controlling entry to the single line section to be locked at danger unless a token has been released from the relevant token instrument. In a basic railway situation, the token can be collected by the d
A Scout staff is a shoulder-high wooden pole or quarterstaff, traditionally carried by Boy Scouts as part of their accoutrements. Its main purpose was as a walking stick, but it had a number of other uses in emergency situations and can be used for Scout pioneering; when Robert Baden-Powell devised his scheme of Scout citizenship training for boys, published in 1908 in Scouting for Boys, he recommended that Scouts should carry "a strong stick, about as high as your nose, marked in feet and inches for measuring". After listing the various uses to which the staff could be put, he added "If you get the chance, cut your own staff, but remember to get permission first", it was said to have been based on a staff used by a Royal Engineers officer during the Fourth Anglo-Ashanti War. In August 1917, Baden-Powell wrote a critical article in the Headquarters Gazette about "the matter of Scouts being allowed to parade without their staffs, which for several reasons is regrettable". In the same article, he lists the cultural roots of the Scout staff which he claimed were "the scouts of Cuhulain armed with staffs, the pilgrims... with their cockle-shells and staffs, the'prentice bands of London with their cloth yards and their staffs, the merry men of Robin Hood with bows and quarter staffs, down to the present-day mountaineers, war-scouts, explorers".
At the 3rd World Scout Jamboree in 1929, French Scouts constructed an 80-foot replica of the Eiffel Tower constructed of lashed Scout staves. In the United Kingdom, the cost and awkwardness of the staff meant that it became common for Scout Troops to hold a stock of staves in their meeting place, rather than have Scouts carry them about; the final blow came with the 1966 Advance Party Report, which recommended that "With the exception of a knife, no present optional items of uniform may in future be worn". The official Policy and Rules of the Boy Scouts Association stipulated that the staff must be "Marked in feet and inches, five feet six inches in length". Patrol Leaders carried a white pennant on their staves. Modern commercially produced Scout staves are still available in the United Kingdom made from coppice grown ash; some uses of the Scout staff that have been recommended by various Scouting publications: Making an improvised stretcher Holding back a crowd Jumping over a ditch Testing the depth of a river Helping another Scout over a high wall Construction of a light bridge, hut or flag staff Stopping a car by jamming a staff through the spokes of the wheel Self-defence A tent pole for a small tent Feeling your way over rough or marshy ground Measuring distances Estimating the height of trees or tall buildings Linking Scouts together on a night hike Making a splint for an injured leg Stopping an aggressive dog Beating out bush fires
Staphylococcus is a genus of Gram-positive bacteria in the family Staphylococcaceae in the order Bacillales. Under the microscope, they appear spherical, form in grape-like clusters. Staphylococcus species are facultative anaerobic organisms; the name was coined in 1882 by Scottish surgeon and bacteriologist Alexander Ogston, following the pattern established five years earlier with the naming of Streptococcus. It combines the prefix "staphylo-", suffixed by the Modern Latin: coccus, lit.'spherical bacterium'. Staphylococcus includes at least 40 species. Of these, nine have two subspecies, one has three subspecies, one has four subspecies. Most are harmless and reside on the skin and mucous membranes of humans and other organisms. Staphylococcus has been found to be a nectar-inhabiting microbe. Found worldwide, they are a small component of soil microbial flora; the taxonomy is based on 16s rRNA sequences, most of the staphylococcal species fall into 11 clusters: S. aureus group – S. argenteus, S. aureus, S. schweitzeri, S. simiae S. auricularis group – S. auricularis S. carnosus group – S. carnosus, S. condimenti, S. massiliensis, S. piscifermentans, S. simulans S. epidermidis group – S. capitis, S. caprae, S. epidermidis, S. saccharolyticus S. haemolyticus group – S. devriesei, S. haemolyticus, S. hominis S. hyicus-intermedius group – S. agnetis, S. chromogenes, S. cornubiensis, S. felis, S. delphini, S. hyicus, S. intermedius, S. lutrae, S. microti, S. muscae, S. pseudintermedius, S. rostri, S. schleiferi S. lugdunensis group – S. lugdunensis S. saprophyticus group – S. arlettae, S. caeli, S. cohnii, S. equorum, S. gallinarum, S. kloosii, S. leei, S. nepalensis, S. saprophyticus, S. succinus, S. xylosus S. sciuri group – S. fleurettii, S. lentus, S. sciuri, S. stepanovicii, S. vitulinus S. simulans group – S. simulans S. warneri group – S. pasteuri, S. warneriA 12th group – that of S. caseolyticus – has now been removed to a new genus, the species of which are the closest known relatives of Staphylococcus.
Two species were described in 2015 - Staphylococcus argenteus and Staphylococcus schweitzeri - both of which were considered variants of S. aureus. A new coagulase negative species - Staphylococcus edaphicus - has been isolated from Antarctica; this species is a member of the S. saprophyticus group. S. aureus subsp. AureusS. Aureus subsp. Anaerobius S. capitis subsp. CapitisS. Capitis subsp. Urealyticus S. carnosus subsp. CarnosusS. Carnosus subsp. Utilis S. cohnii subsp. CohniiS. Cohnii subsp. Urealyticus S. equorum subsp. EquorumS. Equorum subsp. Linens S. hominis subsp. HominisS. Hominis subsp. Novobiosepticus S petrasii subsp. CroceilyticusS petrasii subsp. JettensisS petrasii subsp. PetrasiiS petrasii subsp. Pragensis S. saprophyticus subsp. BovisS. Saprophyticus subsp. Saprophyticus S. schleiferi subsp. CoagulansS. Schleiferi subsp. Schleiferi S. sciuri subsp. CarnaticusS. Sciuri subsp. RodentiumS. Sciuri subsp. Sciuri S. succinus subsp. CaseiS. Succinus subsp. Succinus Based on an analysis of orthologous gene content three groups have been proposed.
Group A includes S. aureus, S. capitis, S. epidermidis, S. haemolyticus, S. hominis, S. lugdunensis, S. pettenkoferi, S. simiae and S. warneri. Group B includes S. cohnii, S. equorum, S. saprophyticus and S. xylosus. Group C includes S. intermedius and S. pseudintermedius. The S. saprophyticus and S. sciuri groups are novobiocin-resistant, as is S. hominis subsp. Novobiosepticus. Members of the S. sciuri group are oxidase-positive due to their possession of the enzyme cytochrome c oxidase. This group is the only clade within the staphylococci to possess this gene; the S. sciuri group appears to be the closest relations to the genus Macrococcus. S. pulvereri has been shown to be a junior synonym of S. vitulinus. Within these clades, the S. haemolyticus and S. simulans groups appear to be related, as do the S. aureus and S. epidermidis groups. S. Lugdunensis appears to be related to the S. haemolyticus group. S. petrasii may be related to S. haemolyticus. The taxonomic position of S. lyticans, S. pettenkoferi, S. petrasii, S. pseudolugdunensis has yet to be clarified.
The published descriptions of these species do not appear to have been validly published. Assignment of a strain to the genus Staphylococcus requires it to be a Gram-positive coccus that forms clusters, has an appropriate cell wall structure and G + C content of DNA in a range of 30–40 mol%. Staphylococcus species can be differentiated from other aerobic and facultative anaerobic, Gram-positive cocci by several simple tests. Staphylococcus species are facultative anaerobes. All species grow in the presence of bile salts. All species of Staphylococcus aureus were once thought to be coagulase-positive, but this has since been disproven. Growth can occur in a 6.5% NaCl solution. On Baird Parker medium, Staphylococcus species grow fermentatively, except for S. saprophyticus, which grows oxidatively. Staphylococcus species are susceptible to furazolidone. Further biochemical testing is needed to identify to the species level; when these bacteria divide, they do so along two axes. This is as opposed to streptococci.
One of the most important phenot
A shepherd's crook is a long and sturdy stick with a hook at one end used by a shepherd to manage and sometimes catch sheep. In addition, the crook may aid in defending against attack by predators; when traversing rough terrain, a crook is an aid to balance. Shepherds may use the long implement to part thick undergrowth when searching for lost sheep or potential predators; the innovation of a hook facilitates the recovery of fallen animals by ensnaring them by neck or leg. For this reason the crook has been used as a religious symbol of care, including the Christian bishop's crosier. In medicine, the term shepherd’s crook is used to describe a right coronary artery that follows an unusually high and winding route; this variant, which has a prevalence of about 5%, imposes technical problems in angioplasty procedures. Thalia, Muse of comedy in Greek mythology, was seen holding a shepherd's crook; the shepherd's crook and the flail are insignia of pharaonic authority: the Crook and flail
Stick-fighting, stickfighting, or stick fighting is a variety of martial arts which use simple long slender, hand-held wooden "sticks" for fighting. Some techniques can be used with a sturdy umbrella or a sword in its scabbard. Thicker and/or heavier blunt weapons such as clubs or the mace are outside the scope of "stick-fighting". Although many systems are defensive combat techniques intended for use if attacked while armed, others such as kendo and gatka were developed as safe training methods for dangerous weapons. Whatever their history, many stick-fighting techniques lend themselves to being treated as sports. In addition to systems devoted to stick-fighting, certain other disciplines include it, either in its own right, as in the Tamil martial art silambam, or as part of a polyvalent training including other weapons and/or bare handed fighting, as in Kerala's kalaripayattu tradition, where these wooden weapons serve as preliminary training before practice of the more dangerous metal weapons.
Stick-fights between individuals or large gatherings between sub-tribes where men fight duels are an important part of the anthropological heritage of various cultures tribes such as the Surma people of Ethiopia, where donga stick-fighting is an important cultural practice and the best means of showing off to look for a bride, nude or nearly so, their more warlike neighbors, the Nyangatom people, who fight duels bare-chested, the aim being to inflict visible stripes on the back of the adversary, using not plain staffs but sticks with a flexible, whipping tail-end. Traditional European systems of stick-fighting included a wide variety of methods of quarterstaff combat, which were detailed in numerous manuscripts written by masters-at-arms. Many of these methods became extinct but others adapted and survived as folk-sports and self-defence systems. Examples include Portugal's jogo do pau, the related juego del palo of the Canary Islands, France's canne de combat or la canne, Poland's palcaty and Italy's scherma di bastone.
Giuseppe Cerri's 1854 manual Trattato teorico e pratico della scherma di bastone is influenced by masters of the Italian school of swordsmanship, Achille Marozzo and Francesco Alfieri. The French system of la canne is still practiced as a competitive sport. A self-defense adaptation of la canne developed by Swiss master-at-arms Pierre Vigny in the early 1900s has been revived as part of the curriculum of bartitsu. Nivkh people from Sakhalin used. In the US during the early years of the 1900s, fencer and self-defense specialist A. C. Cunningham developed a unique system of stick-fighting using a walking stick or umbrella, which he recorded in his book The Cane as a Weapon. Singlestick was developed as a method of training in the use of backswords such as the cavalry sabre and naval cutlass, it was a popular pastime in the UK from the 18th to the early 20th century, was a fencing event at the 1904 Summer Olympics. Although interest in the art declined, a few fencing coaches continued to train with the stick and competitions in this style of stick-fighting was reintroduced into the Royal Navy in the 1980s by commander Locker Madden.
The art continues to gain a small following amongst the martial art community in the UK, Australia and the US. Latin America has its share of martial arts devoted to stick-fighting, including Venezuela's juego del garrote, Brazil's palo do Brasil and Maculelê, Trinidad's calinda and the South Americans' Eskrima Kombat. Sticks and staves of various sizes are common weapons in Asian martial arts, in which they vary in design, weight and methodology, are used interchangeably and alongside open-hand techniques. For example, eskrima or arnis of the Philippines uses sticks traditionally crafted from rattan or from butterfruit tree and may be wielded singly or as a pair. Stick-fighting portal Bataireacht Krabi–krabong Kalarippayattu stick-fighting Shillelagh Silambam Tahtib Matrague