Darts is a sport in which small missiles are thrown at a circular target fixed to a wall. Though various boards and rules have been used in the past, the term "darts" now refers to a standardised game involving a specific board design and set of rules; as well as being a professional competitive game, darts is a traditional pub game played in the United Kingdom and the Republic of Ireland, across the Commonwealth, the Netherlands, Germany, the Scandinavian countries, the United States and elsewhere. The dartboard may have its origins in the cross-section of a tree. An old name for a dartboard is "butt", it is said that the standard numbering plan with a 20 on top was created in 1896 by Lancashire carpenter Brian Gamlin to penalise inaccuracy. Though this is disputed. However, a great many other configurations have been used throughout the years and in different geographical locations. In particular, the Yorkshire and Manchester Log End boards differ from the standard board in that they have no triple, only double and bullseye, the Manchester board being of a smaller diameter, with a playing area of only 25 cm across with double and bull areas measuring just 4 mm.
The London Fives board is another variation. This has only 12 equal segments numbered 20, 5, 15, 10, 20, 5, 15, 10, 20, 5, 15, 10 with the doubles and trebles being a quarter of an inch wide. Mathematically, removing the rotational symmetry by placing the "20" at the top, there are 19!, or 121,645,100,408,832,000 possible dartboards. Many different layouts would penalise a player more than the current setup. There have been several mathematical papers published. Before the First World War, pubs in the United Kingdom had dartboards made from solid blocks of wood elm. Elm dart boards had two problems. Darts broke up the surface; the other problem was. This changed when a company called Nodor, whose primary business was making modelling clay, started producing clay dartboards in 1923; the clay dartboards never caught on, Nodor switched to making the traditional elm dartboards that were popular at the time. In 1935, chemist Ted Leggatt and pub owner Frank Dabbs began using the century plant, a type of agave, to make dartboards.
Small bundles of sisal fibres of the same length were bundled together. The bundles were compressed into a disk and bound with a metal ring, it was an instant success, as the darts did little or no damage to the board—they just parted the fibres when they entered the board. In the late'70s, companies began producing electronic dartboards; these dartboards have electronic scoring computers that are preprogrammed with a wide variety of game types. The board is made of plastic facings with small holes; the holes slant out. When a dart strikes the board, the section makes contact with a metal plate, telling the computer where the player has thrown; these "soft-tip" darts and automated boards increased the game's popularity in the United States. The darts were cut down arrows or crossbow bolts; the first purpose-made darts were manufactured in one piece from wood. These darts were imported from France and became known as French darts. Metal barrels were patented in 1906 but wood continued to be used into the 1950s.
The first metal barrels were made from brass, cheap and easy to work. The wooden shafts, which were now threaded to fit the tapped barrel, were either fletched as before or designed to take a paper flight; this type of dart continued to be used into the 1970s. When the advantages of using plastic were realised, the shaft and flight became separate entities, although one piece moulded plastic shaft and flights were available. According to the Darts Regulation Authority, a regulation board is 451 mm in diameter and is divided into 20 radial sections; each section is separated with a thin band of sheet metal. The best dartboards have the thinnest wire, so that the darts have less chance of hitting a wire and bouncing out; the numbers indicating the various scoring sections of the board are normally made of wire on tournament-quality boards. The wire ring on which the numbers are welded can be turned to facilitate wear of the board. Boards of lesser quality have the numbers printed directly on the board.
Quality dartboards are still made of sisal fibres. However, several types of sisal fibre are used in dartboards today, originating from East Africa, Brazil, or China. Illumination is arranged to minimize shadows of thrown darts; the main supply for the illumination should be protected against accidental piercing, or placed away from the board. Modern darts have four parts: the barrels, the shafts and the flights; the points come in 2 common lengths, 32mm and 41mm and are sometimes knurled or coated to improve grip. Others are designed to retract on impact to lessen the chance of bouncing out; the barrels come in a variety of weights and are constructed from brass, silver-nickel, or a tungsten alloy. Brass is cheap but light and therefore brass barrels tend to be bulky. Tungsten on the other hand, is twice as dense
Blunt trauma is physical trauma to a body part, either by impact, injury or physical attack. The latter is referred to as blunt force trauma. Blunt trauma is the initial trauma, from which develops more specific types such as contusions, lacerations, and/or bone fractures. Blunt trauma is contrasted with penetrating trauma, in which an object such as a projectile or knife enters the body. Blunt abdominal trauma represents 75% of all blunt trauma and is the most common example of this injury; the majority occurs in motor vehicle accidents, in which rapid deceleration may propel the driver into the steering wheel, dashboard, or seatbelt causing contusions in less serious cases, or rupture of internal organs from increased intraluminal pressure in the more serious, depending on the force applied. There may be few indications that serious internal abdominal injury has occurred, making assessment more challenging and requiring a high degree of clinical suspicion. There are two basic physical mechanisms at play with the potential of injury to intra-abdominal organs: compression and deceleration.
The former occurs from a direct blow, such as a punch, or compression against a non-yielding object such as a seat belt or steering column. This force may deform a hollow organ, increasing its intraluminal or internal pressure and lead to rupture. Deceleration, on the other hand, causes stretching and shearing at the points where mobile contents in the abdomen, like bowel, are anchored; this can cause tearing of the mesentery of the bowel and injury to the blood vessels that travel within the mesentery. Classic examples of these mechanisms are a hepatic tear along the ligamentum teres and injuries to the renal arteries; when blunt abdominal trauma is complicated by'internal injury,' the liver and spleen are most involved, followed by the small intestine. In rare cases, this injury has been attributed to medical techniques such as the Heimlich Maneuver, attempts at CPR and manual thrusts to clear an airway. Although these are rare examples, it has been suggested that they are caused by applying excessive pressure when performing these life-saving techniques.
The occurrence of splenic rupture with mild blunt abdominal trauma in those recovering from infectious mononucleosis or ‘mono’ is well reported. The term blunt thoracic trauma or, put in a more familiar way, blunt chest injury, encompasses a variety of injuries to the chest. Broadly, this includes damage caused by direct blunt force, acceleration or deceleration, shear force and blasts. Common signs and symptoms include something as simple as bruising, but as complicated as hypoxia, ventilation-perfusion mismatch and reduced cardiac output due to the way the thoracic organs may have been affected. Blunt thoracic trauma is not always visible from the outside and such internal injuries may not show signs or symptoms at the time the trauma occurs or until hours after. A high degree of clinical suspicion may sometimes be required to identify such injuries, a CT scan may prove useful in such instances; those experiencing more obvious complications from a blunt chest injury will undergo a focused assessment with sonography for trauma which can reliably detect a significant amount of blood around the heart or in the lung by using a special machine that visualizes sound waves sent through the body.
Only 10-15% of thoracic traumas require surgery, but they can have serious impacts on the heart and great vessels. The most immediate life-threatening injuries that may occur include tension pneumothorax, open pneumothorax, flail chest, cardiac tamponade, airway obstruction/rupture; the injuries may necessitate a procedure, with the most common being the insertion of an intercostal drain, more referred to as a chest tube. This tube is placed because it helps restore a certain balance in pressures that are impeding the lungs ability to inflate and thus exchange vital gases that allow the body to function. A less common procedure that may be employed is a pericardiocentesis which by removing blood surrounding the heart, permits the heart to regain some ability to appropriately pump blood. In certain dire circumstances an emergent thoracotomy may be employed; the primary clinical concern when blunt trauma to the head occurs is damage to the brain, although other structures, including the skull, face and neck are at risk.
Following assessment of the patient's airway and breathing, a cervical collar may be placed if there is suspicion of trauma to the neck. Evaluation of blunt trauma to the head continues with the secondary survey in which evidence of cranial trauma, including bruises, contusions and abrasions are noted. In addition to noting external injury, a comprehensive neurologic exam is performed to assess for damage to the brain. Depending on the mechanism of injury and examination, a CT scan of the skull and brain may be ordered; this is done to assess for blood within the skull, or fracture of the skull bones. Traumatic brain injury is a significant cause of morbidity and mortality and is most caused by falls, motor vehicle accidents, sports- and work-related injuries, assaults, it is the most common cause of death in patients under the age of 25. TBI is graded from mild to severe, with greater severity correlating with increased morbidity and mortality. Most patients with more severe traumatic b
Wound healing is a complex process in which the skin, the tissues under it, repair themselves after injury. In this article, wound healing is depicted in a discrete timeline of physical attributes constituting the post-trauma repairing process. In undamaged skin, the epidermis and dermis form a protective barrier against the external environment; when the barrier is broken, a regulated sequence of biochemical events is set into motion to repair the damage. This process is divided into predictable phases: blood clotting, tissue growth, tissue remodeling. Blood clotting may be considered to be part of the inflammation stage instead of a separate stage; the wound healing process is not only complex but fragile, it is susceptible to interruption or failure leading to the formation of non-healing chronic wounds. Factors that contribute to non-healing chronic wounds are diabetes, venous or arterial disease and metabolic deficiencies of old age. Wound care encourages and speeds wound healing via cleaning and protection from reinjury or infection.
Depending on each patient's needs, it can range from the simplest first aid to entire nursing specialties such as wound and continence nursing and burn center care. Hemostasis: Within the first few minutes of injury, platelets in the blood begin to stick to the injured site; this activates the platelets. They change into an amorphous shape, more suitable for clotting, they release chemical signals to promote clotting; this results in the activation of fibrin, which forms a mesh and acts as "glue" to bind platelets to each other. This makes a clot that serves to plug the break in the blood vessel, slowing/preventing further bleeding. Inflammation: During this phase and dead cells are cleared out, along with bacteria and other pathogens or debris; this happens through the process of phagocytosis, where white blood cells "eat" debris by engulfing it. Platelet-derived growth factors are released into the wound that cause the migration and division of cells during the proliferative phase. Proliferation: In this phase, collagen deposition, granulation tissue formation, epithelialization, wound contraction occur.
In angiogenesis, vascular endothelial cells form new blood vessels. In fibroplasia and granulation tissue formation, fibroblasts grow and form a new, provisional extracellular matrix by excreting collagen and fibronectin. Concurrently, re-epithelialization of the epidermis occurs, in which epithelial cells proliferate and'crawl' atop the wound bed, providing cover for the new tissue. In wound contraction, myofibroblasts decrease the size of the wound by gripping the wound edges and contracting using a mechanism that resembles that in smooth muscle cells; when the cells' roles are close to complete, unneeded cells undergo apoptosis. Maturation: During maturation and remodeling, collagen is realigned along tension lines, cells that are no longer needed are removed by programmed cell death, or apoptosis. Timing is important to wound healing. Critically, the timing of wound reepithelialization can decide the outcome of the healing. If the epithelization of tissue over a denuded area is slow, a scar will form over many weeks, or months.
Wound healing is classically divided into hemostasis, inflammation and remodeling. Although a useful construct, this model employs considerable overlapping among individual phases. A complementary model has been described where the many elements of wound healing are more delineated; the importance of this new model becomes more apparent through its utility in the fields of regenerative medicine and tissue engineering. In this construct, the process of wound healing is divided into two major phases: the early phase and the cellular phase:The early phase, which begins following skin injury, involves cascading molecular and cellular events leading to hemostasis and formation of an early, makeshift extracellular matrix that provides structural staging for cellular attachment and subsequent cellular proliferation; the cellular phase involves several types of cells working together to mount an inflammatory response, synthesize granulation tissue, restore the epithelial layer. Subdivisions of the cellular phase are: Macrophages and inflammatory components, Epithelial-mesenchymal interaction: re-epithelialization and myofibroblasts: progressive alignment, collagen production, matrix contraction, Endothelial cells and angiogenesis, Dermal matrix: elements of fabrication and alteration/remodeling.
Just before the inflammatory phase is initiated, the clotting cascade occurs in order to achieve hemostasis, or stop blood loss by way of a fibrin clot. Thereafter, various soluble factors are released to attract cells that phagocytise debris and damaged tissue, in addition to releasing signaling molecules that initiate the proliferative phase of wound healing; when tissue is first wounded, blood comes in contact with collagen, triggering blood platelets to begin secreting inflammatory factors. Platelets express sticky glycoproteins on their cell membranes that allow them to aggregate, forming a mass. Fibrin and fibronectin cross-link together and form a plug that traps proteins and
The blood vessels are a part of the circulatory system, microcirculation, that transports blood throughout the human body. These vessels are designed to transport nutrients and oxygen to the tissues of the body, they take waste and carbon dioxide and carry them away from the tissues and back to the heart. Blood vessels are needed to sustain life. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the word vascular, meaning relating to the blood vessels, is derived from the Latin vas, meaning vessel. Some structures -- such as cartilage, the epithelium, the lens and cornea of the eye -- do not contain blood vessels and are labeled avascular; the arteries and veins have three layers. The middle layer is thicker in the arteries than it is in the veins: The inner layer, tunica intima, is the thinnest layer, it is a single layer of flat cells glued by a polysaccharide intercellular matrix, surrounded by a thin layer of subendothelial connective tissue interlaced with a number of circularly arranged elastic bands called the internal elastic lamina.
A thin membrane of elastic fibers in the tunica intima run parallel to the vessel. The middle layer tunica media is the thickest layer in arteries, it consists of circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina. The tunica media may be rich in vascular smooth muscle. Veins don't have the external elastic lamina, but only an internal one; the tunica media is thicker in the arteries rather than the veins. The outer layer is the thickest layer in veins, it is made of connective tissue. It contains nerves that supply the vessel as well as nutrient capillaries in the larger blood vessels. Capillaries consist of little more than a layer of endothelium and occasional connective tissue; when blood vessels connect to form a region of diffuse vascular supply it is called an anastomosis. Anastomoses provide critical alternative routes for blood to flow in case of blockages. There is a layer of muscle surrounding the arteries and the veins which help contract and expand the vessels.
This creates enough pressure for blood to be pumped around the body. Blood vessels are part of the circulatory system, together with the blood; the biggest difference in the structure of arteries and veins is the presence of valves. Backflow of blood is prevented in arteries by the heart; however in veins, one-direction valves are used to prevent backflow as a result of a decrease in blood pressure as the blood passes through the circulatory system. There are various kinds of blood vessels: Arteries Elastic arteries Distributing arteries Arterioles Capillaries Venules Veins Large collecting vessels, such as the subclavian vein, the jugular vein, the renal vein and the iliac vein. Venae cavae. Sinusoids Extremely small vessels located within bone marrow, the spleen, the liver, they are grouped as "arterial" and "venous", determined by whether the blood in it is flowing away from or toward the heart. The term "arterial blood" is used to indicate blood high in oxygen, although the pulmonary artery carries "venous blood" and blood flowing in the pulmonary vein is rich in oxygen.
This is because they are carrying the blood to and from the lungs to be oxygenated. Blood vessels function to transport blood. In general and arterioles transport oxygenated blood from the lungs to the body and its organs, veins and venules transport deoxygenated blood from the body to the lungs. Blood vessels circulate blood throughout the circulatory system Oxygen is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is saturated with oxygen. In all veins apart from the pulmonary vein, the saturation of hemoglobin is about 75%. In addition to carrying oxygen, blood carries hormones, waste products and nutrients for cells of the body. Blood vessels do not engage in the transport of blood. Blood is propelled through arterioles through pressure generated by the heartbeat. Blood vessels transport red blood cells which contain the oxygen necessary for daily activities; the amount of red blood cells present in your vessels has an effect on your health.
Hematocrit tests can be performed to calculate the proportion of red blood cells in your blood. Higher proportions result in conditions such as dehydration or heart disease while lower proportions could lead to anemia and long-term blood loss. Blood vessels transport red blood cells which contain the oxygen necessary for daily activities; the amount of red blood cells present in your vessels has an effect on your health. Hematocrit tests can be performed to calculate the proportion of red blood cells in your blood. Higher proportions result in conditions such as dehydration or heart disease while lower proportions could lead to anemia and long-term blood loss. Permeability of the endothelium is pivotal in the release of nutrients to the tissue, it is increased in inflammation in response to histamine and interleukins, which leads to most of the
Emergency medicine known as accident and emergency medicine, is the medical specialty concerned with the care of illnesses or injuries requiring immediate medical attention. Emergency physicians care for undifferentiated patients of all ages; as first-line providers, their primary responsibility is to initiate resuscitation and stabilization and to start investigations and interventions to diagnose and treat illnesses in the acute phase. Emergency physicians practice in hospital emergency departments, pre-hospital settings via emergency medical services, intensive care units, but may work in primary care settings such as urgent care clinics. Sub-specializations of emergency medicine include disaster medicine, medical toxicology, critical care medicine, hyperbaric medicine, sports medicine, palliative care, or aerospace medicine. Different models for emergency medicine exist internationally. In countries following the Anglo-American model, emergency medicine was the domain of surgeons, general practitioners, other generalist physicians, but in recent decades it has become recognised as a speciality in its own right with its own training programmes and academic posts, the specialty is now a popular choice among medical students and newly qualified medical practitioners.
By contrast, in countries following the Franco-German model, the speciality does not exist and emergency medical care is instead provided directly by anesthesiologists, specialists in internal medicine, cardiologists or neurologists as appropriate. In developing countries, emergency medicine is still evolving and international emergency medicine programs offer hope of improving basic emergency care where resources are limited. Emergency Medicine is a medical specialty—a field of practice based on the knowledge and skills required for the prevention and management of acute and urgent aspects of illness and injury affecting patients of all age groups with a full spectrum of undifferentiated physical and behavioral disorders, it further encompasses an understanding of the development of pre-hospital and in-hospital emergency medical systems and the skills necessary for this development. The field of emergency medicine encompasses care involving the acute care of internal medical and surgical conditions.
In many modern emergency departments, emergency physicians are tasked with seeing a large number of patients, treating their illnesses and arranging for disposition—either admitting them to the hospital or releasing them after treatment as necessary. They provide episodic primary care to patients during off hours and for those who do not have primary care providers. Most patients present to emergency departments with low-acuity conditions, but a small proportion will be critically ill or injured. Therefore, the emergency physician requires a broad field of knowledge and procedural skills including surgical procedures, trauma resuscitation, advanced cardiac life support and advanced airway management, they must have some of the core skills from many medical specialities—the ability to resuscitate a patient, manage a difficult airway, suture a complex laceration, set a fractured bone or dislocated joint, treat a heart attack, manage strokes, work-up a pregnant patient with vaginal bleeding, control a patient with mania, stop a severe nosebleed, place a chest tube, conduct and interpret x-rays and ultrasounds.
This generalist approach can obviate barrier-to-care issues seen in systems without specialists in emergency medicine, where patients requiring immediate attention are instead managed from the outset by speciality doctors such as surgeons or internal physicians. However, this may lead to barriers through acute and critical care specialties disconnecting from emergency care. Emergency medicine can be distinguished from urgent care, which refers to immediate healthcare for less emergent medical issues, but there is obvious overlap and many emergency physicians work in urgent care settings. Emergency medicine includes many aspects of acute primary care, shares with family medicine the uniqueness of seeing all patients regardless of age, gender or organ system; the emergency physician workforce includes many competent physicians who trained in other specialties. Physicians specializing in emergency medicine can enter fellowships to receive credentials in subspecialties such as palliative care, critical-care medicine, medical toxicology, wilderness medicine, pediatric emergency medicine, sports medicine, disaster medicine, tactical medicine, pain medicine, pre-hospital emergency medicine, or undersea and hyperbaric medicine.
The practice of emergency medicine is quite different in rural areas where there are far fewer other specialties and healthcare resources. In these areas, family physicians with additional skills in emergency medicine staff emergency departments. Rural emergency physicians may be the only health care providers in the community, require skills that include primary care and obstetrics. Patterns vary by region. In the United States, the employment arrangement of emergency physician practices are either private, corporate, or governmental
X-rays make up X-radiation, a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 100 eV to 100 keV. X-ray wavelengths are shorter than those of UV rays and longer than those of gamma rays. In many languages, X-radiation is referred to with terms meaning Röntgen radiation, after the German scientist Wilhelm Röntgen who discovered these on November 8, 1895, credited as its discoverer, who named it X-radiation to signify an unknown type of radiation. Spelling of X-ray in the English language includes the variants x-ray, X ray. Before their discovery in 1895 X-rays were just a type of unidentified radiation emanating from experimental discharge tubes, they were noticed by scientists investigating cathode rays produced by such tubes, which are energetic electron beams that were first observed in 1869. Many of the early Crookes tubes undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below.
Crookes tubes created free electrons by ionization of the residual air in the tube by a high DC voltage of anywhere between a few kilovolts and 100 kV. This voltage accelerated the electrons coming from the cathode to a high enough velocity that they created X-rays when they struck the anode or the glass wall of the tube; the earliest experimenter thought to have produced. In 1785 he presented a paper to the Royal Society of London describing the effects of passing electrical currents through a evacuated glass tube, producing a glow created by X-rays; this work was further explored by his assistant Michael Faraday. When Stanford University physics professor Fernando Sanford created his "electric photography" he unknowingly generated and detected X-rays. From 1886 to 1888 he had studied in the Hermann Helmholtz laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as studied by Heinrich Hertz and Philipp Lenard.
His letter of January 6, 1893 to The Physical Review was duly published and an article entitled Without Lens or Light, Photographs Taken With Plate and Object in Darkness appeared in the San Francisco Examiner. Starting in 1888, Philipp Lenard, a student of Heinrich Hertz, conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air, he built a Crookes tube with a "window" in the end made of thin aluminum, facing the cathode so the cathode rays would strike it. He found that something came through, that would cause fluorescence, he measured the penetrating power of these rays through various materials. It has been suggested that at least some of these "Lenard rays" were X-rays. In 1889 Ukrainian-born Ivan Pulyui, a lecturer in experimental physics at the Prague Polytechnic who since 1877 had been constructing various designs of gas-filled tubes to investigate their properties, published a paper on how sealed photographic plates became dark when exposed to the emanations from the tubes.
Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his announcement, it was formed on the basis of the electromagnetic theory of light. However, he did not work with actual X-rays. In 1894 Nikola Tesla noticed damaged film in his lab that seemed to be associated with Crookes tube experiments and began investigating this radiant energy of "invisible" kinds. After Röntgen identified the X-ray, Tesla began making X-ray images of his own using high voltages and tubes of his own design, as well as Crookes tubes. On November 8, 1895, German physics professor Wilhelm Röntgen stumbled on X-rays while experimenting with Lenard tubes and Crookes tubes and began studying them, he wrote an initial report "On a new kind of ray: A preliminary communication" and on December 28, 1895 submitted it to Würzburg's Physical-Medical Society journal. This was the first paper written on X-rays. Röntgen referred to the radiation as "X"; the name stuck.
They are still referred to as such in many languages, including German, Danish, Swedish, Estonian, Japanese, Georgian and Norwegian. Röntgen received the first Nobel Prize in Physics for his discovery. There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a reconstruction by his biographers: Röntgen was investigating cathode rays from a Crookes tube which he had wrapped in black cardboard so that the visible light from the tube would not interfere, using a fluorescent screen painted with barium platinocyanide, he noticed a faint green glow from the screen, about 1 meter away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow, he found they could pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper. Röntgen discovered their medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays.
The photograph of his wife's hand was the first photograph of a human body part using X-rays. When she saw the picture, she said "I have seen my death."The discovery of X-rays stimul
A knife is a tool with a cutting edge or blade attached to a handle. Mankind's first tool, knives were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools. Made of rock, bone and obsidian, over the centuries, in step with improvements in metallurgy or manufacture, knife blades have been made from bronze, iron, steel and titanium. Most modern knives have either folding blades. Knives can serve various purposes. Hunters use a hunting knife, soldiers use the combat knife, scouts and hikers carry a pocket knife. A modern knife consists of: the blade the handle the point – the end of the knife used for piercing the edge – the cutting surface of the knife extending from the point to the heel the grind – the cross section shape of the blade the spine – the thickest section of the blade. Single-edged knives may have a reverse edge or false edge occupying a section of the spine; these edges are serrated and are used to further enhance function. The handle, used to grip and manipulate the blade safely, may include a tang, a portion of the blade that extends into the handle.
Knives are made with full tangs. The handle may include a bolster, a piece of heavy material situated at the front or rear of the handle; the bolster, as its name suggests, is used to mechanically strengthen the knife. Knife blades can be manufactured from a variety of materials, each of which has advantages and disadvantages. Carbon steel, an alloy of iron and carbon, can be sharp, it holds its edge well, remains easy to sharpen, but is vulnerable to rust and stains. Stainless steel is an alloy of iron, chromium nickel, molybdenum, with only a small amount of carbon, it is not able to take quite as sharp an edge as carbon steel, but is resistant to corrosion. High carbon stainless steel is stainless steel with a higher amount of carbon, intended to incorporate the better attributes of carbon steel and stainless steel. High carbon stainless steel blades do not discolor or stain, maintain a sharp edge. Laminated blades use combining the attributes of both. For example, a harder, more brittle steel may be sandwiched between an outer layer of softer, stainless steel to reduce vulnerability to corrosion.
In this case, the part most affected by corrosion, the edge, is still vulnerable. Damascus steel is a form of pattern welding with similarities to laminate construction. Layers of different steel types are welded together, but the stock is manipulated to create patterns in the steel. Titanium is a metal that has a better strength-to-weight ratio, is more wear resistant, more flexible than steel. Although less hard and unable to take as sharp an edge, carbides in the titanium alloy allow them to be heat-treated to a sufficient hardness. Ceramic blades are hard and lightweight: they may maintain a sharp edge for years with no maintenance at all, but are as fragile as glass and will break if dropped on a hard surface, they are immune to common corrosion, can only be sharpened on silicon carbide sandpaper and some grinding wheels. Plastic blades are not sharp and serrated, they are disposable. Steel blades are shaped by forging or stock removal. Forged blades are made by heating a single piece of steel shaping the metal while hot using a hammer or press.
Stock removal blades are shaped by removing metal. With both methods, after shaping, the steel must be heat treated; this involves heating the steel above its critical point quenching the blade to harden it. After hardening, the blade is tempered to make the blade tougher. Mass manufactured kitchen cutlery uses both the stock removal processes. Forging tends to be reserved for manufacturers' more expensive product lines, can be distinguished from stock removal product lines by the presence of an integral bolster, though integral bolsters can be crafted through either shaping method. Knives are sharpened in various ways. Flat ground blades have a profile that tapers from the thick spine to the sharp edge in a straight or convex line. Seen in cross section, the blade would form a long, thin triangle, or where the taper does not extend to the back of the blade, a long thin rectangle with one peaked side. Hollow ground blades have beveled edges; the resulting blade has a thinner edge, so it may have better cutting ability for shallow cuts, but it is lighter and less durable than flat ground blades and will tend to bind in deep cuts.