1.
Bicycle helmet
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A bicycle helmet is designed to attenuate impacts to the head of a cyclist in falls while minimizing side effects such as interference with peripheral vision. The dominant form of helmet up to the 1970s was the leather hairnet style and this offered acceptable protection from scrapes and cuts, but only minimal impact protection, and was mainly used by racing cyclists. More widespread use of helmets began in the U. S. in the 1970s, after many decades, when bicycles were regarded only as childrens toys, many American adults took up cycling during and after the bike boom of the 1970s. Two of the first modern bicycle helmets were made by MSR, a manufacturer of mountaineering equipment, and Bell Sports and these helmets were a spin-off from the development of expanded polystyrene foam liners for motorcycling and motorsport helmets, and had hard polycarbonate plastic shells. The bicycle helmet arm of Bell was split off in 1991 as Bell Sports Inc. having completely overtaken the motorcycle, the first commercially successful purpose-designed bicycle helmet was the Bell Biker, a polystyrene-lined hard shell released in 1975. At the time there was no standard, the only applicable one, from Snell. Over time the design was refined and by 1983 Bell were making the V1-Pro, in 1984 Bell produced the Lil Bell Shell, a no-shell childrens helmet. These early helmets had little ventilation, in 1985, Snell B85 was introduced, the first widely adopted standard for bicycle helmets, this has subsequently been refined into B90 and B95. At this time helmets were almost all either hard-shell or no-shell, ventilation was still minimal due mainly to technical limitations of the foams and shells in use. Around 1990 a new technique was invented, in-mould microshell. A very thin shell was incorporated during the moulding process and this rapidly became the dominant technology, allowing for larger vents and more complex shapes than hard shells. The late 1990s and early 2000s saw advances in retention and fitting systems, with cradles which adjust precisely to the riders head and this resulted in the back of the head being less covered by the helmet, although more recent designs have largely addressed this. Since more advanced helmets began being used in the Tour de France, carbon fiber inserts are often used to increase strength, the Giro Atmos and Ionos, as well as the Bell Alchera were among the first to use carbon fiber. Some modern road and track racing bicycle helmets have a long tapering back end for streamlining and this type of helmet is mainly dedicated to time trial racing as they lack significant ventilation, making them uncomfortable for long races. Snells standard includes testing of random samples, in 1990 the Consumers Association market survey showed that around 90 % of helmets on sale were Snell B90 certified. By their 1998 survey the number of Snell certified helmets was around zero, there are two main types of helmet, hard shell and soft/micro shell. The American National Standards Institute created a standard called ANSI Z80.4 in 1984, later, the United States Consumer Product Safety Commission created its own mandatory standard for all bicycle helmets sold in the United States, which took effect in March 1999. In the European Union the currently applicable standards are EN1078,1997, in Australia and New Zealand, the current legally-required standard is AS/NZS2063
2.
Personal protective equipment
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Personal protective equipment refers to protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearers body from injury or infection. The hazards addressed by protective equipment include physical, electrical, heat, chemicals, biohazards, Protective equipment may be worn for job-related occupational safety and health purposes, as well as for sports and other recreational activities. Protective clothing is applied to categories of clothing, and protective gear applies to items such as pads, guards, shields, or masks. PPE is needed there are hazards present. PPE has the limitation that it does not eliminate the hazard at source. Any item of PPE imposes a barrier between the wearer/user and the working environment and this can create additional strains on the wearer, impair their ability to carry out their work and create significant levels of discomfort. Any of these can discourage wearers from using PPE correctly, therefore placing them at risk of injury, ill-health or, under extreme circumstances, death. Good ergonomic design can help to minimise these barriers and can help to ensure safe. Practices of occupational safety and health can use hazard controls and interventions to mitigate workplace hazards, the hierarchy of hazard controls provides a policy framework which ranks the types of hazard controls in terms of absolute risk reduction. At the top of the hierarchy are elimination and substitution, which remove the hazard entirely or replace the hazard with a safer alternative. If elimination or substitution measures cannot apply, engineering controls and administrative controls, Personal protective equipment ranks last on the hierarchy of controls, as the workers are regularly exposed to the hazard, with a barrier of protection. The hierarchy of controls is important in acknowledging that, while personal protective equipment has tremendous utility, Personal protective equipment can be categorized by the area of the body protected, by the types of hazard, and by the type of garment or accessory. The protective attributes of each piece of equipment must be compared with the expected to be found in the workplace. More breathable types of protective equipment may not lead to more contamination. Respirators serve to protect the user from breathing in contaminants in the air, there are two main types of respirators. One type functions by filtering out chemicals and gases, or airborne particles, the filtration may be either passive or active. Gas masks and particulate respirators are examples of type of respirator. A second type protects users by providing clean, respirable air from another source and this type includes airline respirators and self-contained breathing apparatus
3.
Human head
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In human anatomy, the head is the upper portion of the human body. It supports the face and is maintained by the skull, which encloses the brain. The human head consists of an outer portion surrounding the bony skull. The head rests on the neck, and is provided bony support for movement by the seven cervical vertebrae, the face is the anterior part of the head, containing the sensory organs the eyes, nose and mouth. The cheeks, on side of the mouth, provide a fleshy border to the oral cavity. To either side of the sit the ears. The twelve pairs of cranial nerves provide the majority of control to the head. The sensation to the face is provided by the branches of the trigeminal nerve, the sensation to other portions of the head is provided by the cervical nerves. The head receives blood supply through the internal and external carotid arteries and these supply the area outside of the skull and inside of the skull. The area inside the skull also receives blood supply from the vertebral arteries, the head contains sensory organs, two eyes, two ears, a nose and inside the mouth a tongue. The human head typically weighs between 5 and 11 pounds, human faces are easily differentiable to us due to our brains predispositions toward discriminating human facial forms. When observing a relatively unfamiliar species, all faces seem nearly identical, ancient Greeks had a method for evaluating sexual attractiveness based on the Golden Ratio, part of which included measurements of the head. In many cultures, covering the head is seen as a sign of respect, often, some or all of the head must be covered and veiled when entering holy places, or places of prayer. For many centuries, women in Europe, the Middle East and this trend has changed drastically in Europe in the 20th century, although is still observed in other parts of the world. People may cover the head for other reasons, a hat is a piece of clothing covering just the top of the head. This may be part of a uniform, such as a uniform, a protective device such as a hard hat. Different headpieces can also signify status, origin, religious/spiritual beliefs, social grouping, team affiliation, occupation, while numerous charts detailing head sizes in infants and children exist, most do not measure average head circumference past the age of 21. Reference charts for adult head circumference also generally feature homogeneous samples, one study in the United States estimated the average human head circumference to be 55 centimetres in females and 57 centimetres in males
4.
Brain
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The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is located in the head, usually close to the organs for senses such as vision. The brain is the most complex organ in a vertebrates body, in a human, the cerebral cortex contains approximately 15–33 billion neurons, each connected by synapses to several thousand other neurons. Physiologically, the function of the brain is to exert centralized control over the other organs of the body, the brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment, the operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. This article compares the properties of brains across the range of animal species. It deals with the human brain insofar as it shares the properties of other brains, the ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because more can be said about them in a human context. The most important is brain disease and the effects of brain damage, the shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of architecture that apply across a wide range of species. Some aspects of structure are common to almost the entire range of animal species, others distinguish advanced brains from more primitive ones. The simplest way to gain information about brain anatomy is by visual inspection, Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the consists of areas of so-called grey matter, with a dark color, separated by areas of white matter. Further information can be gained by staining slices of tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, the brains of all species are composed primarily of two broad classes of cells, neurons and glial cells. Glial cells come in types, and perform a number of critical functions, including structural support, metabolic support, insulation. Neurons, however, are considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to target cells over long distances
5.
Custodian helmet
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The custodian helmet is the modern name applied to the helmet worn by male police officers in England and Wales and certain other places around the world. It is synonymous with the bobby on the beat image, the custodian helmet is the headgear traditionally worn by male police constables and sergeants while on foot patrol in England and Wales. Officers of all ranks in most forces are issued a flat. Ranks above sergeant wear the cap only. It was first adopted by the London Metropolitan Police in 1863 to replace the top hat worn since 1829. The early Metropolitan Police helmet had a garter style badge on the front of the helmet which had the personal number and divisional letter in the centre. This was surrounded by a design which had the words Metropolitan Police around the outside and was topped with the reigning monarchs crown. This style changed in 1875, when a version of the brunswick star was adopted without the upturned brim seen in the previous style. There was much variety in the style of helmets during this period, the form of the helmets gradually converged with the foreign service and home service helmets adopted by the British army in the late-1870s. Some forces adopted the helmet without any badge, others designed their own, one force adopted an Australian style bush hat and one wore a helmet constructed of straw. The Home Office Pattern consisted of a helmet with the Brunswick star badge which would feature the reigning monarchs cipher, the top of the helmet had a rose top, which was a raised metal rose, largely used as an ornament to cover the ventilation hole. However, this process was largely unsuccessful, with many different designs being worn by todays police forces nationally. Internally, helmets up until the 1970s, and in areas the 1980s, had only a sweat band to allow it to sit correctly on the wearers head. Other helmet furniture included a top and in some cases a spike top. During the 1970s and 1980s, before specially adapted riot helmets were produced, officers were expected to conduct public order, the cork construction provided little protection against attack and hand-thrown missiles. In order to more protection, the construction of the helmets changed. Visually they remained the same, however instead of being constructed of cork they were now out of a very hard wearing plastic material. Internally, they were padded with foam which was fitted into the shell of the helmet with a webbing-style harness to allow it to sit on the head in the correct manner
6.
Military history of the Neo-Assyrian Empire
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The Neo-Assyrian Empire arises in the 10th century BC. Ashurnasirpal II is credited for utilizing sound strategy in his wars of conquest, while aiming to secure defensible frontiers, he would launch raids further inland against his opponents as a means of securing economic benefit, as he did when campaigning in the Levant. The result meant that the prosperity of the region would fuel the Assyrian war machine. Ashurnasirpal II was succeeded by Shalmaneser III, although he campaigned for 31 years of his 35-year reign, he failed to achieve or equal the conquests of his predecessor, and his death led to another period of weakness in Assyrian rule. As such, costly battles raged taking tolls on Assyrian manpower, Esarhaddon succeeded in taking lower Egypt and his successor, Ashurbanipal, took the southern upper half of Egypt. However, by the end of the Ashurbanipals reign it appears that the Assyrian Empire was falling into another period of weakness and it appears that years of costly battles followed by constant rebellions meant that it was a matter of time before Assyria ran out of troops. The loss of the outer regions meant that troops were gone too. By 605 BC, independent political Assyrian records vanish from history, Mesopotamia was the site of some of the earliest recorded battles in history. In fact, the first recorded battle was between the forces of Lagash and Umma c.2450 BC, like many Mesopotamian records, it contains elements of fiction. The ruler of Lagash, Eanatum, was inspired by the god Ningirsu to attack the kingdom of Umma. Eanatum, although having triumphed, was struck in the eye by an arrow, after the battle, he proudly documented the behavior of the vultures. The Assyrian empire has at times described as the first military power in history. The earliest Old Assyrian king Tudiya was a contemporary of Ibrium of Ebla and it evolved from the Akkadian Empire of the late 3rd millennium BC. Assyria was a nation under the rule of Ilushuma, who founded colonies in Asia Minor and raided Isin. According to legend, Sargon, the first king of the Akkadian Kingdom, was discovered by a gardener in Mesopotamia in a basket. In time, he would found the city of Agade and raise an army of 5,400 men and his inscriptions boast of 34 victories and 5,400 men eating bread before Sargon, exemplifying both the vast manpower and the obedience of his troops. Though small by the standards of later kings, Sargons army was larger and more sophisticated than others of the time, utilizing a combination of spears and missile weapons. Bronze swords and four wheeled chariots brushed aside any resistance as he carved out his empire, which may well have included parts of the Mediterranean, Anatolia and western Iran
7.
Sword
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A sword is a long bladed weapon intended for slashing or thrusting. The precise definition of the term varies with the epoch or the geographical region under consideration. A sword consists of a blade attached to a hilt. The blade can be straight or curved, thrusting swords have a pointed tip on the blade, and tend to be straighter, slashing swords have sharpened cutting edge on one or both sides of the blade, and are more likely to be curved. Many swords are designed for thrusting and slashing. Historically, the sword developed in the Bronze Age, evolving from the dagger, the later Iron Age sword remained fairly short and without a crossguard. The word sword continues the Old English, sweord, the use of a sword is known as swordsmanship or as fencing. In the Early Modern period, western sword design diverged into two forms, the thrusting swords and the sabers. The thrusting swords such as the rapier and eventually the smallsword were designed to impale their targets quickly and their long and straight yet light and well balanced design made them highly maneuverable and deadly in a duel but fairly ineffective when used in a slashing or chopping motion. A well aimed lunge and thrust could end a fight in seconds with just the swords point, the saber and similar blades such as the cutlass were built more heavily and were more typically used in warfare. Built for slashing and chopping at multiple enemies, often from horseback, most sabers also had sharp points and double edged blades, making them capable of piercing soldier after soldier in a cavalry charge. Sabers continued to see use until the early 20th century. The US Navy kept tens of thousands of sturdy cutlasses in their armory well into World War II, non-European weapons called sword include single-edged weapons such as the Middle Eastern scimitar, the Chinese dao and the related Japanese katana. The Chinese jian is an example of a non-European double-edged sword, the first weapons that can be described as swords date to around 3300 BC. They have been found in Arslantepe, Turkey, are made from arsenical bronze, some of them are inlaid with silver. The sword developed from the dagger when the construction of longer blades became possible, from the late 3rd millennium BC in the Middle East, first in arsenic copper, then in tin-bronze. Blades longer than 60 cm were rare and not practical until the late Bronze Age because the strength of bronze is relatively low. These are the type A swords of the Aegean Bronze Age, one of the most important, and longest-lasting, types swords of the European Bronze Age was the Naue II type, also known as Griffzungenschwert
8.
Arrow
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An arrow is a shafted projectile that is shot with a bow. It predates recorded history and is common to most cultures, an arrow usually consists of a shaft with an arrowhead attached to the front end, with fletchings and a nock at the other. The oldest evidence of stone-tipped projectiles, which may or may not have been propelled by a bow, dating to c.64,000 years ago, were found in Sibudu Cave, South Africa. The oldest evidence of the use of bows to shoot arrows dates to about 10,000 years ago and they had shallow grooves on the base, indicating that they were shot from a bow. The oldest bow so far recovered is about 8,000 years old, archery seems to have arrived in the Americas with the Arctic small tool tradition, about 4,500 years ago. Arrow sizes vary greatly across cultures, ranging from eighteen inches to five feet, however, most modern arrows are 75 centimetres to 96 centimetres, most war arrows from an English ship sunk in 1545 were 76 centimetres. Very short arrows have been used, shot through a guide attached either to the bow or to the archers wrist and these may fly farther than heavier arrows, and an enemy without suitable equipment may find himself unable to return them. The shaft is the structural element of the arrow, to which the other components are attached. Traditional arrow shafts are made from wood, bamboo or reeds, while modern shafts may be made from aluminium, carbon fibre reinforced plastic. Such shafts are made from an aluminium core wrapped with a carbon fibre outer. The stiffness of the shaft is known as its spine, referring to how little the shaft bends when compressed, hence, an arrow which bends less is said to have more spine. In order to strike consistently, a group of arrows must be similarly spined, center-shot bows, in which the arrow passes through the central vertical axis of the bow riser, may obtain consistent results from arrows with a wide range of spines. Higher draw-weight bows will generally require stiffer arrows, with more spine to give the amount of flex when shot. The weight of a shaft can be expressed in GPI. The length of a shaft in inches multiplied by its GPI rating gives the weight of the shaft in grains, for example, a shaft that is 30 inches long and has a GPI of 9.5 weighs 285 grains, or about 18 grams. This does not include the elements of a finished arrow. Sometimes a shaft will be made of two different types of wood fastened together, resulting in what is known as a footed arrow, known by some as the finest of wood arrows, footed arrows were used both by early Europeans and Native Americans. Footed arrows will typically consist of a length of hardwood near the head of the arrow
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