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Hand axes have traditionally been oriented with their narrowest part upwards (presupposing that this would have been the most active part, which is not unreasonable given the many hand axes that have unworked bases). The following typological conventions are used to facilitate communication. The axis of symmetry that divides a biface in two is called the morphological axis. The main face is usually the most regular and better worked face. The base (not the heel) is the bottom of the hand axe. | Hand axe | Wikipedia | 101 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Terminal zone—the narrowest end, opposite the base. Its most common shape is pointed, more or less acute or oval. Some hand axes have terminal ends that are rounded or polygonal (i.e. not pointed) while others have terminal ends that are transversal to the axis, called cleaver or spatulate.
Proximal end (base)—opposite the terminal end (usually broader and thicker), it can be described as either reserved (partially or totally worked, but not cut); or cut, with a rounded (polygonal), flat or pointed end.
Edges—convex, rectilinear or concave, and more or less even. Edges on some specimens are denticulate—scalloped—or notched. Some specimens have unsharpened edges. The profile of a hand axe's worked edges can be regular without pronounced rectilinear deviations (the edge is gently curved in the form of an S) or an edge may be more sinuous and wave-formed with pronounced curves or deviations in the edge's profile. On some specimens only selected areas have been formed into a working edge.
Cross section—the horizontal cross-section taken at some distance from the base. It is possible to discern retouching or rebuilding in deteriorated parts of the edges. The following types of cross section are commonly seen: triangular (sub-triangular and backed triangular), rhombic (rhomboidal and backed rhomboidal), trapezium (trapezoid and backed trapezoidal), pentagon (pentagonal and backed pentagonal), polygonal, biconvex or lenticular (sub lenticular).
Profile—By definition, hand axes have a roughly balanced outline, with a morphological axis that also serves as an axis of bilateral symmetry and a plane that serves as an axis of bifacial symmetry. Not all hand axes are perfectly symmetrical. Symmetry was achieved only after millennia of development. Symmetry may not make tools more useful. Hand axes were used in a variety of heavy physical tasks. They deteriorated, wore out and broke and were often repaired with retouching of their edges, recovery of their points or complete reworking. The majority of discovered pieces are remains, pieces that have been discarded after a long life as tools, during which they often were damaged and/or adapted for specialized tasks. Such pieces may have lost whatever symmetry they initially had. Hand axe profiles can be classified into the following categories:
Dimensions and ratios | Hand axe | Wikipedia | 512 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Hand axe measurements use the morphological axis as a reference and for orientation. In addition to length, width, depth, specialists have proposed a wide range of other physical quantities. The most common were proposed by Bordes and Balout:
Maximum length (L)
Maximum width (m)
Maximum depth (e)
Distance from the base to the zone with the maximum width (a)
Width 3/4 of the way along the piece (o)
A and o can be used to delineate the contour's cross section and to measure the angles of the edges (provided this is not an area covered in the stone's original cortex). These angular measurements for the edges are made using a goniometer.
Edge length, weight and the length of the chord described by the edges (if the piece has a transverse terminal bezel) can be measured. These measurements allow morphological and technical ratios to be established (for example, the relationship between the weight and the length of the cutting edges, or the relationship between the hammer used to form the piece and the angle obtained etc.).
The most commonly used coefficients were established by Bordes for the morphological-mathematical classification of what he called "classic bifaces" (Balout proposed other, similar indices):
Bordes hand axe typology
The following guide is strongly influenced by the possibly outdated and basically morphological "Bordes method" classification system. This classification is particularly applicable to classic hand axes, those that can be defined and catalogued by measuring dimensions and mathematical ratios, while disregarding nearly all subjective criteria. "Distinguishing between different types of hand axes is not always easy. There is often no room for doubts, however, there are a number of cases where the difficulty is real." In the majority of cases, this system agrees with previously established categories (although slightly redefining them). Balout made a similar attempt at categorization.
Non-classic specimens
Many specimens defeat objective classification. Bordes created a group he called "non-classic bifaces" to which mathematical indexes do not apply. | Hand axe | Wikipedia | 419 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Tools sometimes categorized as bifaces
Hand axes constitute an important group artefacts from the Acheulean. They are particularly important in open air archaeological sites (Keelley suggested that they are less common in cave sites). Hand axes, chopping tools and trihedral picks are considered core utensils, which were commonly manufactured out of stones, blocks or rock nodules. However this grouping is problematic as these tools were often also fabricated from (large) flakes. Another common suggestion is to refer to flake tools as micro industry, as opposed to the more general size referred to as macro industry, which includes hand axes and cleavers. However, some scrapers are as big as hand axes.
The most elaborated chopping tools and partial hand axes are linked and it is often difficult to distinguish between them. The concept of chopping tools is based on their lack of formal standardization (which is typical of hand axes) and includes the possibility that the pieces are shallow cores, which is unthinkable for the bifaces (except the nucleiforms).
While hand axes and cleavers occasionally served for similar tasks, their design is fundamentally different.
Trihedral picks are no longer considered a specialized type of hand axe. | Hand axe | Wikipedia | 247 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Another group of tools commonly associated with hand axes is the biface leafpoint tools from the Lower and Middle Palaeolithic in the Old World. The difference between the two types is based on the latter's fine, light finishing with a soft hammer and in a morphology that suggests a specific function, possibly as the point of a projectile or a knife. Representatives of these tools include well known examples from the specialized literature:
The biface leafpoint tools of central Europe are called (). They are projectile points belonging to the Middle Palaeolithic with a leaf-shaped form. They are often dual pointed and flat, making them similar to Solutrean laurel leaf blades. It is possible to distinguish the two only from their archaeological context. survived in some Upper Palaeolithic cultures. The pieces from the eastern European Szeletien culture (both and Micoquian bifaces) could be the link that connects the tradition of Lower and Middle Palaeolithic bifacial objects with those from the Upper Palaeolithic and beyond.
Hand axes found in Africa come from both the Aterian culture of North Africa and the Stillbay culture from East Africa. Both these cases relate to Mousterian cultures, although they are relatively late and have their own style, at the end of the so-called African Middle Stone Age. In both cases a variety of objects are found, triangular, oval and other leaf-point. Hand axes and unifaces also came from other cultures.
Importance
The hand axe helped establish that early humans were capable of constructing relatively sophisticated tools that also reflected a sense of aesthetics. The 19th century publications of Frere, and more importantly of Boucher de Perthes, in France, described pieces that were balanced, symmetrical and crafted with a formal purity. Vilanova i Piera published similar works in Spain. This work was continued by Pérez de Barradas and del Prado at the start of the 20th century.
As Leroi-Gourhan explained, it is important to ask what was understood of art at the time, considering the psychologies of non-modern humans. Archaeological records documenting rapid progress towards symmetry and balance surprised Leroi-Gourha. He felt that he could recognize beauty in early prehistoric tools made during the Acheulean: | Hand axe | Wikipedia | 464 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Many authors who comment on the Westfield aspect of hand axes refer only to exceptional pieces. The majority of hand axes tended to symmetry, but lack artistic appeal. Generally, only the most striking pieces are considered, mainly 19th or early 20th century collections. At that time a lack of knowledge regarding prehistoric technology prevented a recognition of human actions in these objects. Other collections were made by aficionados, whose interests were not scientific, so that they collected only objects they considered to be outstanding, abandoning humbler elements that were sometimes necessary to interpret an archaeological site. Exceptions include sites methodically studied by experts where magnificently carved, abundant hand axes caused archaeologists to express admiration for the artists:
The discovery in 1998 of an oval hand axe of excellent workmanship in the Sima de los Huesos in the Atapuerca Mountains mixed in with the fossil remains of Homo heidelbergensis reignited this controversy. Given that this is the only lithic remnant from this section of the site (possibly a burial ground), combined with the piece's qualities led it to receive special treatment, it was even baptized Excalibur and it became a star item. Interest in the symbolic meaning of this example in particular, and hand axes in general, has multiplied in recent years, feeding both scientific and more general debate and literature.
Basch offered this counterargument:
Paradoxically, within the wide range of Acheulean objects, hand axes are one of the simplest tools. They do not require as much planning as other types of object, generally made from flakes, that are less striking but more sophisticated. | Hand axe | Wikipedia | 319 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Archaeologists have evidence of hand axes that are 1.2 million years old in Melka Kunturé (Ethiopia), but the oldest, from Konso-Gardula, could be 1.9 million years old: Although it is now known that they are the heritage of a number of human species, with Homo ergaster the earliest, up until 1954 no solid evidence indicated who had fabricated hand axes: in that year, in Ternifine, Algeria, Arambourg discovered remains that he called Atlanthropus, along with some hand axes. All the species associated with hand axes (from H. ergaster to H. neanderthalensis) show an advanced intelligence that in some cases is accompanied by modern features such as a relatively sophisticated technology, systems to protect against inclement weather (huts, control of fire, clothing), and certain signs of spiritual awareness (early indications of art such as adorning the body, carving of bones, ritual treatment of bodies, articulated language).
Image gallery | Hand axe | Wikipedia | 208 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
A hypodermic needle (from Greek ὑπο- (hypo- = under), and δέρμα (derma = skin)) is a very thin, hollow tube with one sharp tip. It is one of a category of medical tools which enter the skin, called sharps. It is commonly used with a syringe, a hand-operated device with a plunger, to inject substances into the body (e.g., saline solution, solutions containing various drugs or liquid medicines) or extract fluids from the body (e.g., blood). Large-bore hypodermic intervention is especially useful in catastrophic blood loss or treating shock.
A hypodermic needle is used for rapid delivery of liquids, or when the injected substance cannot be ingested, either because it would not be absorbed (as with insulin), or because it would harm the liver. It is also useful to deliver certain medications that cannot be delivered orally due to vomiting. There are many possible routes for an injection, with intramuscular (into a muscle) and intravenous (into a vein) being the most common. A hypodermic syringe has the ability to retain liquid and blood in it up to years after the last use and a great deal of caution should be taken to use a new syringe every time.
The hypodermic needle also serves an important role in research environments where sterile conditions are required. The hypodermic needle significantly reduces contamination during inoculation of a sterile substrate. The hypodermic needle reduces contamination for two reasons: First, its surface is extremely smooth, which prevents airborne pathogens from becoming trapped between irregularities on the needle's surface, which would subsequently be transferred into the media (e.g. agar) as contaminants; second, the needle's surface is extremely sharp, which significantly reduces the diameter of the hole remaining after puncturing the membrane and consequently prevents microbes larger than this hole from contaminating the substrate.
History
Early use and experimentation
The ancient Greeks and Romans knew injection as a method of medicinal delivery from observations of snakebites and poisoned weapons. There are also references to "anointing" and "inunction" in the Old Testament as well as the works of Homer, but injection as a legitimate medical tool was not truly explored until the 17th century. | Hypodermic needle | Wikipedia | 492 | 320351 | https://en.wikipedia.org/wiki/Hypodermic%20needle | Technology | Equipment | null |
Christopher Wren performed the earliest confirmed experiments with crude hypodermic needles, performing intravenous injection into dogs in 1656. These experiments consisted of using animal bladders (as the syringe) and goose quills (as the needle) to administer drugs such as opium intravenously to dogs. Wren and others' main interest was to learn if medicines traditionally administered orally would be effective intravenously. In the 1660s, Johann Daniel Major of Kiel and Johann Sigismund Elsholtz of Berlin were the first to experiment with injections in humans.
19th-century development
The 19th century saw the development of medicines that were effective in small doses, such as opiates and strychnine. This spurred a renewed interest in direct, controlled application of medicine. "Some controversy surrounds the question of priority in hypodermic medication." Irish physician Francis Rynd is generally credited with the first successful injection in 1844, in the Meath Hospital in Dublin, Ireland.
Alexander Wood's main contribution was the all-glass syringe in 1851, which allowed the user to estimate dosage based on the levels of liquid observed through the glass. Wood used hypodermic needles and syringes primarily for the application of localized, subcutaneous injection (localized anesthesia) and therefore was not as interested in precise dosages.
Simultaneous to Wood's work in Edinburgh, Charles Pravaz of Lyon also experimented with sub-dermal injections in sheep using a syringe of his own design. Pravaz designed a hypodermic needle measuring 3 cm (1.18 in) long and 5 mm (0.2 in) in diameter; it was made entirely of silver.
Charles Hunter, a London surgeon, is credited with the coining of the term "hypodermic" to describe subcutaneous injection in 1858. The name originates from two Greek words: hypo, "under", and derma, "skin". Furthermore, Hunter is credited with acknowledging the systemic effects of injection after noticing that a patient's pain was alleviated regardless of the injection's proximity to the pained area. Hunter and Wood were involved in a lengthy dispute over not only the origin of the modern hypodermic needle, but also because of their disagreement as to the medicine's effect once administered. | Hypodermic needle | Wikipedia | 475 | 320351 | https://en.wikipedia.org/wiki/Hypodermic%20needle | Technology | Equipment | null |
Modern improvements
Dr. Francis Rynd used the first "Hollow Needle" as a hypodermic syringe on Ms. Margaret Cox in Ireland on June 3rd, 1844. Dr. Wood can be largely credited with the popularization and acceptance of injection as a medical technique, as well as the widespread use and acceptance of the hypodermic needle. The basic technology of the hypodermic needle has stayed largely unchanged since the 19th century, but as the years progressed and medical and chemical knowledge improved, small refinements have been made to increase safety and efficacy, with needles being designed and tailored for very particular uses. Hypodermic needles remain essential to large volume administration or exchange in settings of trauma or dialysis. The trend of needle specification for use began in the 1920s, particularly for the administration of insulin to diabetics.
The onset of World War II spurred the early development of partially disposable syringes for the administration of morphine and penicillin on the battlefield. Development of the fully disposable hypodermic needle was spurred on in the 1950s for several reasons. The Korean War created blood shortages and in response disposable, sterile syringes were developed for collecting blood. The widespread immunization against polio during the period required the development of a fully disposable syringe system.
The 1950s also saw the rise and recognition of cross-contamination from used needles. This led to the development of the first fully disposable plastic syringe by New Zealand pharmacist Colin Murdoch in 1956. This period also marked a shift in interest from needle specifications to general sterility and safety.
The 1980s saw the rise of the HIV epidemic and with it renewed concern over the safety of cross-contamination from used needles. New safety controls were designed on disposable needles to ensure the safety of medical workers in particular. These controls were implemented on the needles themselves, such as retractable needles, but also in the handling of used needles, particularly in the use of hard-surface disposal receptacles found in every medical office today.
By 2008, all-plastic needles were in production and in limited use. One version was made of Vectra (plastic) aromatic liquid crystal polymer tapered from 1.2 mm at the hub to 0.72 mm at the tip (equivalent to 22 gauge metal needle), with an ID/OD ratio of 70%. | Hypodermic needle | Wikipedia | 500 | 320351 | https://en.wikipedia.org/wiki/Hypodermic%20needle | Technology | Equipment | null |
Manufacture
Hypodermic needles are normally made from a stainless-steel or Niobium tube through a process known as tube drawing where the tube is drawn through progressively smaller dies to make the needle. The end of the needle is bevelled to create a sharp pointed tip, letting the needle easily penetrate the skin.
Gauge
The main system for measuring the diameter of a hypodermic needle is the Birmingham gauge (also known as the Stubs Iron Wire Gauge); the French gauge is used mainly for catheters. Various needle lengths are available for any given gauge. Needles in common medical use range from 7 gauge (the largest) to 34 (the smallest). 21-gauge needles are most commonly used for drawing blood for testing purposes, and 16- or 17-gauge needles are most commonly used for blood donation, as the larger luminal cross-sectional area results in lower fluid shear, reducing harm to red blood cells while also allowing more blood to be collected in a shorter time.
Although reusable needles remain useful for some scientific applications, disposable needles are far more common in medicine. Disposable needles are embedded in a plastic or aluminium hub that attaches to the syringe barrel by means of a press-fit or twist-on fitting. These are sometimes referred to as "Luer Lock" connections, referring to the trademark Luer-Lok. The male and female luer lock and hub—produced by pharmaceutical equipment manufacturers—are two of the most critical parts of disposable hypodermic needles.
Use by non-specialists
Hypodermic needles are usually used by medical professionals (dentists, phlebotomists, physicians, pharmacists, nurses, paramedics), but they are sometimes used by patients themselves. This is most common with type one diabetics, who may require several insulin injections a day. It also occurs with patients who have asthma or other severe allergies. Such patients may need to take desensitization injections or they may need to carry injectable medicines to use for first aid in case of a severe allergic reaction. In the latter case, such patients often carry a syringe loaded with epinephrine (e.g. EpiPen), diphenhydramine (e.g. Benadryl), or dexamethasone. Rapid injection of one of these drugs may stop a severe allergic reaction. | Hypodermic needle | Wikipedia | 502 | 320351 | https://en.wikipedia.org/wiki/Hypodermic%20needle | Technology | Equipment | null |
Multiple sclerosis patients may also treat themselves by injection; several MS therapies, including various interferon preparations, are designed to be self-administered by subcutaneous or intramuscular injection.
Transgender people may also inject their own hormone replacement therapy, using either intramuscular injection or subcutaneous injection methods.
Hypodermic needles are also used for erotic piercing.
Phobia
It is estimated that anywhere from nearly 3.5 to 10% of the world's population may have a phobia of needles (trypanophobia), and it is much more common in children, ages 5–17. Topical anesthetics can be used to desensitize the area where the injection will take place to reduce pain and discomfort. For children, various techniques may be effective at reducing distress or pain related to needles. Techniques include: distraction, hypnosis, combined cognitive behavioral therapy, and breathing techniques. | Hypodermic needle | Wikipedia | 193 | 320351 | https://en.wikipedia.org/wiki/Hypodermic%20needle | Technology | Equipment | null |
Pine nuts, also called piñón (), pinoli (), or pignoli, are the edible seeds of pines (family Pinaceae, genus Pinus). According to the Food and Agriculture Organization, only 29 species provide edible nuts, while 20 are traded locally or internationally owing to their seed size being large enough to be worth harvesting; in other pines, the seeds are also edible but are too small to be of notable value as human food. The biggest producers of pine nuts are China, Russia, North Korea, Pakistan and Afghanistan.
As pines are gymnosperms, not angiosperms (flowering plants), pine nuts are not "true nuts"; they are not botanical fruits, the seed not being enclosed in an ovary which develops into the fruit, but simply bare seeds—"gymnosperm" meaning literally "naked seed" (from and ). The similarity of pine nuts to some angiosperm fruits is an example of convergent evolution.
Species and geographic spread
In Asia, two species, in particular, are widely harvested: Korean pine (Pinus koraiensis) in northeast Asia (the most important species in international trade) and chilgoza pine (P. gerardiana) in the western Himalaya. Four other species, Siberian pine (P. sibirica), Siberian dwarf pine (P. pumila), Chinese white pine (P. armandii) and lacebark pine (P. bungeana), are also used to a lesser extent. Russia is the largest producer of P. sibirica nuts in the world, followed by either Mongolia or Afghanistan. They each produce over annually, most of it exported to China.
Pine nuts produced in Europe mostly come from the stone pine (P. pinea), which has been cultivated for its nuts for over 5,000 years. Pine nuts have been harvested from wild trees for far longer. The Swiss pine (P. cembra) is also used, to a very small extent. | Pine nut | Wikipedia | 413 | 320509 | https://en.wikipedia.org/wiki/Pine%20nut | Biology and health sciences | Nuts | Plants |
In North America, the main species are three of the pinyon pines: Colorado pinyon (P. edulis), single-leaf pinyon (P. monophylla), and Mexican pinyon (P. cembroides). The other eight pinyon species are used to a small extent, as is gray pine (P. sabineana), Coulter pine (P. coulteri), Torrey pine (P. torreyana), sugar pine (P. lambertiana) and Parry pinyon (P. quadrifolia). Here, the nuts themselves are known by the Spanish name for the pinyon pine, piñón (plural: piñones).
In the United States, pine nuts are mainly harvested by Native American and Hispano communities, particularly in the Western United States and Southwestern United States, by the Shoshone, Paiute, Navajo, Pueblo, Hopi, Washoe, and Hispanos of New Mexico. Certain treaties negotiated by tribes and laws in Nevada guarantee Native Americans' right to harvest pine nuts, and the state of New Mexico protects the use of the word piñon for use with pine nuts from certain species of indigenous New Mexican pines.
Species list
Commonly used species include:
Old World
Pinus armandii – Chinese white pine
Pinus bungeana – lacebark pine
Pinus cembra – Swiss pine
Pinus gerardiana – Chilgoza pine
Pinus koraiensis – Korean pine
Pinus pinea – Mediterranean stone pine
Pinus pumila – Siberian dwarf pine
Pinus sibirica – Siberian pine
New World
pinyon pine group – in southwestern North America
Pinus albicaulis – Whitebark pine
Pinus cembroides – Mexican pinyon
Pinus coulteri – Coulter pine
Pinus culminicola – Potosi pinyon
Pinus edulis – Two-needle piñon or Colorado pinyon (when grown in Colorado)
Pinus johannis – Johann's pinyon (includes P. discolor – Border pinyon)
Pinus monophylla – Single-leaf pinyon
Pinus orizabensis – Orizaba pinyon
Pinus quadrifolia – Four-leaved pinyon or Parry pinyon
Pinus remota – Papershell pinyon or Texas pinyon
Pinus sabiniana – California foothill pine | Pine nut | Wikipedia | 479 | 320509 | https://en.wikipedia.org/wiki/Pine%20nut | Biology and health sciences | Nuts | Plants |
Pollination and seed development
Pine nuts will not reach full maturity unless the environmental conditions are favorable for the tree and the cone. The time to maturity varies depending on the species.
For some American species, development begins in early spring with pollination. A tiny cone, about the size of a small marble, will form from mid-spring through the end of summer; this immature cone will temporarily cease growing and remain dormant until the following spring, then grow again until it reaches maturity near the end of its second summer. The mature piñon pine cone is ready to harvest ten days before the green cone begins to open. A cone is harvested by placing it in a burlap bag and exposing it to a heat source such as the sun to begin drying. It takes about 20 days until the cone fully opens. Once it is fully open and dry, the seed can be easily extracted in various ways. The most common and practical extraction method used is the repeated striking of the burlap bag containing the cone(s) against a rough surface to cause the cone(s) to shatter, leaving just the job of separating by hand the seed from the residue within the bag.
Another option for harvesting is to wait until the cone opens on the tree (as it naturally will) and harvest the cone from the piñon pine, followed by the extracting process mentioned above. Fallen seeds can also be gathered beneath the trees.
Ecology and status
Because pine nuts are an important food source for many animals, overharvesting of pine nuts threatens local ecosystems, an effect occurring during the early 21st century with increased culinary uses for pine nuts. In the United States, millions of hectares of productive pinyon pine woods have been destroyed due to conversion of lands, and in China and Russia, destructive harvesting techniques (such as breaking off whole branches to harvest the cones) and removal of trees for timber have led to losses in production capacity.
Elevation and pinecone production
Some growers claim that the elevation of the pinyon pine is an important determinant of the quantity of pine cone production and, therefore, will largely determine the number of pine nuts the tree will yield. The US Department of Agriculture notes that variation in cone production between trees growing on identical sites is often observed. | Pine nut | Wikipedia | 453 | 320509 | https://en.wikipedia.org/wiki/Pine%20nut | Biology and health sciences | Nuts | Plants |
American pinyon pine cone production is most commonly found at an elevation between , and ideally at . This is due to higher temperatures at elevations lower than during the spring, which dry up humidity and moisture content (particularly snow packs) that provide for the tree throughout the spring and summer, causing little nourishment for pine cone maturity.
Although several other environmental factors determine the conditions of the ecosystem (such as clouds and rain), the trees tend to abort cones without sufficient water. High humidity encourages cone development. There are certain topographical areas found in lower elevations, such as shaded canyons, where the humidity remains constant throughout the spring and summer, allowing pine cones to fully mature and produce seed.
At elevations above , the temperature substantially drops, drastically affecting the state of the dormant cone. During the winter, frequent dramatic changes in temperature, drying, and gusty winds make the cones susceptible to freeze-drying that permanently damages them; in this case, growth is stunted, and the seeds deteriorate.
Physical characteristics
When first extracted from the pine cone, they are covered with a hard shell (seed coat), thin in some species and thick in others. The nutrition is stored in the embryo (sporophyte) in the center. Although a nut in the culinary sense, in the botanical sense, pine nuts are seeds; being a gymnosperm, they lack a carpel (fruit) outside.
The shell must be removed before the pine nut can be eaten. Unshelled pine nuts have a long shelf life if kept dry and refrigerated (); shelled nuts (and unshelled nuts in warm conditions) deteriorate rapidly, becoming rancid within a few weeks or even days in warm, humid conditions. Pine nuts are commercially available in the shelled form, but due to poor storage, they can have poor flavor and may already be rancid at the time of purchase. Consequently, pine nuts are often frozen to preserve their flavor. | Pine nut | Wikipedia | 403 | 320509 | https://en.wikipedia.org/wiki/Pine%20nut | Biology and health sciences | Nuts | Plants |
European pine nuts may be distinguished from Asian ones by their greater length than girth; Asian pine nuts are stubbier, shaped somewhat like long kernels of corn. The American piñon nuts are known for their large size and ease of shelling. In the United States, Pinus edulis, the hard shell of New Mexico and Colorado, became a sought-after species due to the trading post system and the Navajo people who used the nuts as a means of commerce. The Italian pine nut (P. pinea) was brought to the United States by immigrants and became a favored treat along the East Coast in the early 1930s, when bumper crops of American pine nuts were readily available at low prices.
Nutrition
When dried for eating, pine nuts are 2% water, 13% carbohydrates, 14% protein, and 68% fat (table). In a reference serving, dried pine nuts supply of food energy and are a rich source (20% or more of the Daily Value, DV) of numerous micronutrients, particularly manganese (419% DV), phosphorus (82% DV), magnesium (71% DV), zinc (67% DV), copper (65% DV), vitamin E (62% DV), vitamin K (51% DV), and the B vitamins, thiamin and niacin (29–35% DV), among others (table).
Culinary uses
Pine nuts have been eaten in Europe and Asia since the Paleolithic period. They are frequently added to meat, fish, salads, and vegetable dishes or baked into bread. | Pine nut | Wikipedia | 340 | 320509 | https://en.wikipedia.org/wiki/Pine%20nut | Biology and health sciences | Nuts | Plants |
In Italian, they are called pinoli (in the US, they are often called pignoli, but in Italy, pignolo is actually a word far more commonly used to describe a fussy, overly fastidious or extremely meticulous person) and are an essential component of Italian pesto sauce; the upsurge in the popularity of this sauce since the 1990s has increased the visibility of the nut in America, primarily on the West Coast. Torta della nonna (literally "granny's cake") is a generic Italian dish name that in most families indicates an old family recipe for any cake but often is used for a tart or a pie filled with custard, topped with pine nuts and optionally dusted with icing sugar. Pignoli cookies, an Italian American specialty confection (in Italy, these would be called biscotti ai pinoli), are made of almond flour formed into a dough similar to that of a macaroon and then topped with pine nuts.
In Catalonia, a sweet is made of small marzipan balls covered with pine nuts, painted with egg, and lightly cooked, and those are called "panellets". Pine nuts are also featured in the salade landaise of southwestern France. Nevada, or Great Basin, pine nut has a sweet fruity flavor and is promoted for its large size, sweet flavor, and ease of peeling.
Pine nuts are also widely used in Levantine cuisine, reflected in a diverse range of dishes such as kibbeh, sambusak, fatayer, and Maqluba, desserts such as baklava, meghli, and many others.
Throughout Europe, the Levant, and West Asia, the pine nuts used are traditionally from Pinus pinea (stone pine). They are easily distinguished from the Asian pine nuts by their more slender shape and more homogeneous flesh. Because of the lower price, Asian pine nuts are also often used, especially in cheaper preparations.
Pine nut oil is added to foods for flavor. | Pine nut | Wikipedia | 416 | 320509 | https://en.wikipedia.org/wiki/Pine%20nut | Biology and health sciences | Nuts | Plants |
Taste disturbances
Some raw pine nuts can cause pine mouth syndrome, a taste disturbance lasting from a few days to a few weeks after consumption. A bitter, metallic, unpleasant taste is reported. There are no known lasting effects, with the United States Food and Drug Administration reporting that there are "no apparent adverse clinical side effects". Raw nuts from Pinus armandii, mainly in China, may be the cause of the problem. Metallic taste disturbance is typically reported 1–3 days after ingestion, being worse on day two and typically lasting up to two weeks. Cases are self-limited and resolve without treatment.
Food fraud
In the United States, from 2008 to 2012, some people reported a bitter metallic taste ("pine mouth") that sometimes lasted for weeks after they ate pine nuts. After an international investigation, the FDA found that some manufacturers substituted a non-food species of pine nuts in place of more expensive edible pine nut species as a form of food fraud.
Other uses
Some Native American tribes use the hard outer shell of the pine nut as a bead for decorative purposes in traditional regalia and jewelry. In the Great Basin area of the US, collecting pine nuts is a protected right through state law and treaty.
In northern California, pine nuts are collected from the grey pine or bull pine. Tribes burn designs into the hard shell, reflecting the same design they use in baskets; however, they are often left blank or burned to blacken. These are more often used in women's regalia and jewelry. | Pine nut | Wikipedia | 306 | 320509 | https://en.wikipedia.org/wiki/Pine%20nut | Biology and health sciences | Nuts | Plants |
An air-to-air missile (AAM) is a missile fired from an aircraft for the purpose of destroying another aircraft (including unmanned aircraft such as cruise missiles). AAMs are typically powered by one or more rocket motors, usually solid fueled but sometimes liquid fueled. Ramjet engines, as used on the Meteor, are emerging as propulsion that will enable future medium- to long-range missiles to maintain higher average speed across their engagement envelope.
Air-to-air missiles are broadly put in two groups. Those designed to engage opposing aircraft at ranges of around 30 km to 40 km maximum are known as short-range or "within visual range" missiles (SRAAMs or WVRAAMs) and are sometimes called "dogfight" missiles because they are designed to optimize their agility rather than range. Most use infrared guidance and are called heat-seeking missiles. In contrast, medium- or long-range missiles (MRAAMs or LRAAMs), which both fall under the category of beyond-visual-range missiles (BVRAAMs), tend to rely upon radar guidance, of which there are many forms. Some modern ones use inertial guidance and/or "mid-course updates" to get the missile close enough to use an active homing sensor. The concepts of air-to-air missiles and surface-to-air missiles are closely related, and in some cases versions of the same weapon may be used for both roles, such as the ASRAAM and Sea Ceptor.
History
The air-to-air missile grew out of the unguided air-to-air rockets used during the First World War. Le Prieur rockets were sometimes attached to the struts of biplanes and fired electrically, usually against observation balloons, by such early pilots as Albert Ball and A. M. Walters. Facing the Allied air superiority, Germany in World War II invested limited effort into missile research, initially adapting the projectile of the unguided 21 cm Nebelwerfer 42 infantry barrage rocket system into the air-launched BR 21 anti-aircraft rocket in 1943; leading to the deployment of the R4M unguided rocket and the development of various guided missile prototypes such as the Ruhrstahl X-4. | Air-to-air missile | Wikipedia | 461 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
The US Navy and US Air Force began equipping guided missiles in 1956, deploying the USAF's AIM-4 Falcon and the USN's AIM-7 Sparrow and AIM-9 Sidewinder. Post-war research led the Royal Air Force to introduce Fairey Fireflash into service in 1957 but their results were unsuccessful. The Soviet Air Force introduced its K-5 into service in 1957. As missile systems have continued to advance, modern air warfare consists almost entirely of missile firing. The use of beyond-visual-range combat became so pervasive in the US that early F-4 variants were armed only with missiles in the 1960s. High casualty rates during the Vietnam War caused the US to reintroduce autocannon and traditional dogfighting tactics but the missile remains the primary weapon in air combat.
In the Falklands War British Harriers, using AIM-9L missiles were able to defeat faster Argentinian opponents. Since the late 20th century all-aspect heat-seeking designs can lock-on to a target from various angles, not just from behind, where the heat signature from the engines is strongest. Other types rely on radar guidance (either on-board or "painted" by the launching aircraft).
Use of air-to-air missiles as surface-to-air missiles
In 1999 R-73 missile were adapted by Serb forces for surface to air missiles. The Houthi movement Missile Research and Development Centre and the Missile Force have tried to fire R-27/R-60/R-73/R-77 against Saudi aircraft. Using stockpiles of missiles from Yemeni Air Force stocks. The issue for the R-27 and R-77 is the lack of a radar to support their guidance to the target. However the R-73 and R-60 are infra-red heat seeking missiles. They only require power, liquid nitrogen "to cool the seeker head", and a pylon to launch the missile. These missiles have been paired with a "US made FLIR Systems ULTRA 8500 turrets". Only one near miss has been verified and that was a R-27T fired at Royal Saudi Air Force F-15SA. However the drawback is that these missiles are intended to be fired from one jet fighter against another. So the motors and fuel load are smaller than a purpose built surface to air missile. | Air-to-air missile | Wikipedia | 484 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
On the Western side, the Norwegian-American made NASAMS air defense system has been developed for using AIM-9 Sidewinder, IRIS-T and AMRAAM air-to-air missiles to intercept targets. None of these missiles require modifications and hence it is possible for the system to take missiles straight from an aircraft. After a live-fire test occurred in September 2020 off the coasts of Florida, during which it successfully engaged a simulated cruise missile, in 2022 NASAMS was deployed to Ukraine, where for the first time this missile system was used in real combat conditions, and, according to Ukrainian government, was able to shoot down more than 100 aerial targets.
Warhead
A conventional explosive blast warhead, fragmentation warhead, or continuous rod warhead (or a combination of any of those three warhead types) is typically used in the attempt to disable or destroy the target aircraft. Warheads are typically detonated by a proximity fuze or by an impact fuze if it scores a direct hit. Less commonly, nuclear warheads have been mounted on a small number of air-to-air missile types (such as the AIM-26 Falcon) although these have never been used in combat.
Guidance
Guided missiles operate by detecting their target (usually by either radar or infrared methods, although rarely others such as laser guidance or optical tracking), and then "homing" in on the target on a collision course.
Although the missile may use radar or infra-red guidance to home on the target, the launching aircraft may detect and track the target before launch by other means. Infra-red guided missiles can be "slaved" to an attack radar in order to find the target and radar-guided missiles can be launched at targets detected visually or via an infra-red search and track (IRST) system, although they may require the attack radar to illuminate the target during part or all of the missile interception itself.
Radar guidance
Radar guidance is normally used for medium- or long-range missiles, where the infra-red signature of the target would be too faint for an infra-red detector to track. There are three major types of radar-guided missile – active, semi-active, and passive.
Radar-guided missiles can be countered by rapid maneuvering (which may result in them "breaking lock", or may cause them to overshoot), deploying chaff or using electronic counter-measures.
Active radar homing | Air-to-air missile | Wikipedia | 499 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
Active radar (AR)-guided missiles carry their own radar system to detect and track their target. However, the size of the radar antenna is limited by the small diameter of missiles, limiting its range which typically means such missiles are launched at a predicted future location of the target, often relying on separate guidance systems such as Global Positioning System, inertial guidance, or a mid-course update from either the launching aircraft or other system that can communicate with the missile to get the missile close to the target. At a predetermined point (frequently based on time since launch or arrival near the predicted target location) the missile's radar system is activated (the missile is said to "go active"), and the missile then homes in on the target.
If the range from the attacking aircraft to the target is within the range of the missile's radar system, the missile can "go active" immediately upon launch.
The great advantage of an active radar homing system is that it enables a "fire-and-forget" mode of attack, where the attacking aircraft is free to pursue other targets or escape the area after launching the missile.
Semi-active radar homing
Semi-active radar homing (SARH) guided missiles are simpler and more common. They function by detecting radar energy reflected from the target. The radar energy is emitted from the launching aircraft's own radar system.
However, this means that the launch aircraft has to maintain a "lock" on the target (keep illuminating the target aircraft with its own radar) until the missile makes the interception. This limits the attacking aircraft's ability to maneuver, which may be necessary should threats to the attacking aircraft appear.
An advantage of SARH-guided missiles is that they are homing on the reflected radar signal, so accuracy actually increases as the missile gets closer because the reflection comes from a "point source": the target. Against this, if there are multiple targets, each will be reflecting the same radar signal and the missile may become confused as to which target is its intended victim. The missile may well be unable to pick a specific target and fly through a formation without passing within lethal range of any specific aircraft. Newer missiles have logic circuits in their guidance systems to help prevent this problem. | Air-to-air missile | Wikipedia | 457 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
At the same time, jamming the missile lock-on is easier because the launching aircraft is further from the target than the missile, so the radar signal has to travel further and is greatly attenuated over the distance. This means that the missile may be jammed or "spoofed" by countermeasures whose signals grow stronger as the missile gets closer. One counter to this is a "home on jam" capability in the missile that allows it to home in on the jamming signal.
Beam riding
An early form of radar guidance was "beam-riding" (BR). In this method, the attacking aircraft directs a narrow beam of radar energy at the target. The air-to-air missile was launched into the beam, where sensors on the aft of the missile controlled the missile, keeping it within the beam. So long as the beam was kept on the target aircraft, the missile would ride the beam until making the interception.
While conceptually simple, the move is hard because of the challenge of simultaneously keeping the beam solidly on the target (which could not be relied upon to cooperate by flying straight and level), continuing to fly one's own aircraft, and monitoring enemy countermeasures.
An added complication was that the beam will spread out into a cone shape as the distance from the attacking aircraft increases. This will result in less accuracy for the missile because the beam may actually be larger than the target aircraft when the missile arrives. The missile could be securely within the beam but still not be close enough to destroy the target.
Infrared guidance
Infrared guided (IR) missiles home on the heat produced by an aircraft. Early infra-red detectors had poor sensitivity, so could only track the hot exhaust pipes of an aircraft. This meant an attacking aircraft had to maneuver to a position behind its target before it could fire an infra-red guided missile. This also limited the range of the missile as the infra-red signature soon become too small to detect with increasing distance and after launch the missile was playing "catch-up" with its target. Early infrared seekers were unusable in clouds or rain (which is still a limitation to some degree) and could be distracted by the sun, a reflection of the sun off of a cloud or ground object, or any other "hot" object within its view. | Air-to-air missile | Wikipedia | 473 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
More modern infra-red guided missiles can detect the heat of an aircraft's skin, warmed by the friction of airflow, in addition to the fainter heat signature of the engine when the aircraft is seen from the side or head-on. This, combined with greater maneuverability, gives them an "all-aspect" capability, and an attacking aircraft no longer had to be behind its target to fire. Although launching from behind the target increases the probability of a hit, the launching aircraft usually has to be closer to the target in such a tail-chase engagement.
An aircraft can defend against infra-red missiles by dropping flares that are hotter than the aircraft, so the missile homes in on the brighter, hotter target. In turn, IR missiles may employ filters to enable it to ignore targets whose temperature is not within a specified range.
Towed decoys which closely mimic engine heat and infra-red jammers can also be used. Some large aircraft and many combat helicopters make use of so-called "hot brick" infra-red jammers, typically mounted near the engines. Current research is developing laser devices which can spoof or destroy the guidance systems of infra-red guided missiles. See Infrared countermeasure.
Start of the 21st century missiles such as the ASRAAM use an "imaging infrared" seeker which "sees" the target (much like a digital video camera), and can distinguish between an aircraft and a point heat source such as a flare. They also feature a very wide detection angle, so the attacking aircraft does not have to be pointing straight at the target for the missile to lock on. The pilot can use a helmet mounted sight (HMS) and target another aircraft by looking at it, and then firing. This is called "off-boresight" launch. For example, the Russian Su-27 is equipped with an infra-red search and track (IRST) system with laser rangefinder for its HMS-aimed missiles. | Air-to-air missile | Wikipedia | 402 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
Electro-optical
A recent advancement in missile guidance is electro-optical imaging. The Israeli Python-5 has an electro-optical seeker that scans designated area for targets via optical imaging. Once a target is acquired, the missile will lock-on to it for the kill. Electro-optical seekers can be programmed to target vital area of an aircraft, such as the cockpit. Since it does not depend on the target aircraft's heat signature, it can be used against low-heat targets such as UAVs and cruise missiles. However, clouds can get in the way of electro-optical sensors.
Passive anti-radiation
Evolving missile guidance designs are converting the anti-radiation missile (ARM) design, pioneered during Vietnam and used to home in against emitting surface-to-air missile (SAM) sites, to an air intercept weapon. Current air-to-air passive anti-radiation missile development is thought to be a countermeasure to airborne early warning and control (AEW&C – also known as AEW or AWACS) aircraft which typically mount powerful search radars.
Due to their dependence on target aircraft radar emissions, when used against fighter aircraft passive anti-radiation missiles are primarily limited to forward-aspect intercept geometry. For examples, see Vympel R-27 and Brazo.
Another aspect of passive anti-radiation homing is the "home on jam" mode which, when installed, allows a radar-guided missile to home in on the jammer of the target aircraft if the primary seeker is jammed by the electronic countermeasures of the target aircraft.
Design
Air-to-air missiles are typically long, thin cylinders in order to reduce their cross section and thus minimize drag at the high speeds at which they travel. Missiles are divided into five primary systems (moving forward to aft): seeker, guidance, warhead, motor, and control actuation.
At the front is the seeker, either a radar system, radar homer, or infra-red detector. Behind that lies the avionics which control the missile. Typically after that, in the centre of the missile, is the warhead, usually several kilograms of high explosive surrounded by metal that fragments on detonation (or in some cases, pre-fragmented metal). | Air-to-air missile | Wikipedia | 458 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
The rear part of the missile contains the propulsion system, usually a rocket of some type and the control actuation system or CAS. Dual-thrust solid-fuel rockets are common, but some longer-range missiles use liquid-fuel motors that can "throttle" to extend their range and preserve fuel for energy-intensive final maneuvering. Some solid-fuelled missiles mimic this technique with a second rocket motor which burns during the terminal homing phase. There are missiles, such as the MBDA Meteor, that "breathe" air (using a ramjet, similar to a jet engine) in order to extend their range.
Modern missiles use "low-smoke" motors – early missiles produced thick smoke trails, which were easily seen by the crew of the target aircraft alerting them to the attack and helping them determine how to evade it.
The CAS is typically an electro-mechanical, servo control actuation system, which takes input from the guidance system and manipulates the airfoils or fins at the rear of the missile that guide or steers the weapon to target.
Nowadays, countries start developing hypersonic air-to-air missile using scramjet engines (such as R-37, or AIM-260 JATM), which not only increases efficiency for BVR battles, but it also makes survival chances of target aircraft drop to nearly zero.
Performance
A number of terms frequently crop up in discussions of air-to-air missile performance. | Air-to-air missile | Wikipedia | 292 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
Launch success zone The Launch Success Zone is the range within which there is a high (defined) kill probability against a target that remains unaware of its engagement until the final moment. When alerted visually or by a warning system the target attempts a last-ditch-manoeuvre sequence.
F-pole A closely related term is the F-Pole. This is the slant range between the launch aircraft and target, at the time of interception. The greater the F-Pole, the greater the confidence that the launch aircraft will achieve air superiority with that missile.
A-pole This is the slant range between the launch aircraft and target at the time that the missile begins active guidance or acquires the target with the missile's active seeker. The greater the A-Pole means less time and possibly greater distance that the launch aircraft needs to support the missile guidance until missile seeker acquisition.
No-escape zone The no-escape zone is the zone within which there is a high (defined) kill probability against a target even if it has been alerted. This zone is defined as a conical shape with the tip at the missile launch. The cone's length and width are determined by the missile and seeker performance. A missile's speed, range and seeker sensitivity will mostly determine the length of this imaginary cone, while its agility (turn rate) and seeker complexity (speed of detection and ability to detect off axis targets) will determine the width of the cone.
Missile minimum range
A missile is subject to a minimum range, before which it cannot maneuver effectively. In order to maneuver sufficiently from a poor launch angle at short ranges to hit its target, some missiles use thrust vectoring, which allow the missile to start turning "off the rail", before its motor has accelerated it up to high enough speeds for its small aerodynamic surfaces to be useful.
Short-range air-to-air missile
Short-range air-to-air missiles (SRAAMs), typically used in "dogfighting" or close range air combat compare to the beyond-visual-range missiles. Most of the short-range air-to-air missiles are infrared guided.
SRAAM missile evolution
Those missiles usually classified into five "generations" according to the historical technological advances. Most of these advances were in infrared seeker technology (later combined with digital signal processing). | Air-to-air missile | Wikipedia | 469 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
First generation
Early short-range missiles such as the early Sidewinders and K-13 (missile) (AA-2 Atoll) had infrared seekers with a narrow (30-degree) field of view and required the attacker to position himself behind the target (rear aspect engagement). This meant that the target aircraft only had to perform a slight turn to move outside the missile seeker's field of view and cause the missile to lose track of the target ("break lock").
Second generation
The second-generation of short-range missiles utilized more effective seekers that were better cooled than its predecessors while being typically "uncaged"; resulting in improved sensitivity to heat signatures, an increase in field of view as well as allowing the possibility of leading a missile within its FOV for an increased probability of kill against a maneuvering target. In some cases, the improved sensitivity to heat signatures allows for a very limited side and even all-aspect tracking, as is the case with the Red Top missile. In conjunction with improved control surfaces and propulsion motors over the first generation of dogfight missiles, the technological advances of the second-generation short-range missiles allowed them to be used not just on non-maneuvering bombers, but also actively maneuvering fighters. Examples include advanced derivatives of the K-13 (missile) and AIM-9 such as K-13M (R-13M, Object 380) or AIM-9D / G / H.
Third generation
This generation introduced much more sensitive seekers that are capable of locking onto the warm heat irradiated by the skins of aircraft from the front or side aspects, as opposed to just the hotter engine nozzle(s) from rear-aspect, allowing for a true all-aspect capability. This significantly expanded potential attacking envelopes, allowing the attacker to fire at a target which was side-on or front-on to itself as opposed to just the rear. While the field-of-view was still restricted to a fairly narrow cone, the attack at least did not have to be behind the target.
Also typical of the third generation of short-range missiles are further improved agility over the previous generation as well as their ability to radar-slave; which is acquiring tracking data from the launching aircraft's radar or IRST systems, allowing attackers to launch missiles without ever pointing the nose of the aircraft at an enemy prior to leading the missile. Examples of this generation of dogfight missiles include the R-60M or the Python-3. | Air-to-air missile | Wikipedia | 505 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
Fourth generation
The R-73 (missile) (AA-11 Archer) entered service in 1985 and marked a new generation of dogfight missile. It had a wider field of view and could be cued onto a target using a helmet mounted sight. This allowed it to be launched at targets that would otherwise not be seen by older generation missiles that generally stared forward while waiting to be launched. This capability, combined with a more powerful motor that allows the missile to maneuver against crossing targets and launch at greater ranges, gives the launching aircraft improved tactical freedom.
Other members of the 4th generation use focal plane arrays to offer greatly improved scanning and countermeasures resistance (especially against flares). These missiles are also much more agile, some by employing thrust vectoring (typically gimballed thrust).
Fifth generation
The latest generation of short-range missiles again defined by advances in seeker technologies, this time electro-optical imaging infrared (IIR) seekers that allow the missiles to "see" images rather than single "points" of infrared radiation (heat). The sensors combined with more powerful digital signal processing provide the following benefits:
greater infrared counter countermeasures (IRCCM) ability, by being able to distinguish aircraft from infrared countermeasures (IRCM) such as flares.
greater sensitivity means greater range and ability to identify smaller low flying targets such as UAVs.
more detailed target image allows targeting of more vulnerable parts of aircraft instead of just homing in on the brightest infrared source (exhaust).
Examples of fifth generation short-range missiles include:
R-74M2 ("AA-11 Archer") – Russia (1983–)
R-77T ("AA-12 Adder") – Russia (1994–)
ASRAAM – UK (1998–)
AIM-9X Sidewinder – US (2003–)
Python 5 – Israel (2003–)
AAM-5 – Japan (2004–)
IRIS-T – Germany (2005–)
PL-10 – China (2015–)
A-Darter – South Africa and Brazil (2019–)
Merlin – Turkey (2024–)
List of missiles by country
For each missile, short notes are given, including an indication of its range and guidance mechanism.
Brazil
MAA-1A Piranha – Short-range IR
MAA-1B Piranha – IR-guided missile.
A-Darter – Short-range IR (With South Africa)
Canada
Velvet Glove - short range, semi-active radar-guided | Air-to-air missile | Wikipedia | 510 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
France
Nord AA.20, AA.25 – radio-guided, beam-riding
Matra R.510 – IR-guided
Matra R.511 – radar-guided
Matra R.550 Magic – short-range, IR-guided
Matra Magic II – IR-guided
Matra R.530 – medium-range, IR- or radar-guided
Matra Super 530F/Super 530D – medium-range, radar-guided
Matra Mistral – IR-guided
MBDA MICA – medium-range, IR- or active radar-guided
MBDA Meteor – long-range active radar-guided missile, integrated on Rafale.
TRIGAT LR
Germany
Henschel Hs 298 – World War II design, MCLOS, never saw service
IRIS-T
MBDA Meteor long-range, active radar-guided, pending contract for integration on Eurofighter.
Ruhrstahl X-4 – World War II design, first practical anti-aircraft missile, MCLOS, never saw service
RZ 65 missile project developed by Rheinmetall-Borsig in 1941. After about 3000 tests it revealed itself unsatisfactory owing to an accuracy of only 15%. The project was terminated by the end of the war.
Dornier Viper
India
Astra Mk 1 – Long-range radar-guided
Astra Mk 2 – Long-range radar-guided
Astra Mk 3 – Long-range radar-guided
Astra IR – Short-range infrared homing
K-100 (missile) – Inertial navigation and active radar homing (with Russia)
Iran
Fatter – copy of U.S. AIM-9 Sidewinder
Sedjil – copy of U.S. MIM-23 Hawk converted to be carried by aircraft
Fakour-90 – copy of U.S. AIM-54 Phoenix
Iraq
Al Humurrabi – Long-range, semi active radar
Israel | Air-to-air missile | Wikipedia | 389 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
Python:
Rafael Shafrir – first Israeli domestic AAM
Rafael Shafrir 2 – improved Shafrir missile
Rafael Python 3 – medium-range IR-homing missile with all aspect capability
Rafael Python 4 – medium-range IR-homing missile with HMS-guidance capability
Python-5 – improved Python 4 with electro-optical imaging seeker, and 360 degrees lock on. (and launch)
Rafael Derby – Also known as the Alto, this is a medium-range, BVR active radar-homing missile
I-Derby ER – long range BVR active radar-homing missile
Sky Spear – 6th generation long-range, air-to-air missile
Italy
Alenia Aspide – Copy of the U.S.AIM-7 Sparrow, based on the AIM-7E.
Japan
AAM-1 – (Type 69 air-to-air missile) short-range, IR-seeking air-to-air missile; copy of U.S. AIM-9B Sidewinder.
AAM-2 – short-range, IR-seeking air-to-air missile; similar to AIM-4D, prototype-only.
AAM-3 – (Type 90 air-to-air missile) short-range, all-aspect IR-seeking air-to-air missile.
AAM-4 – (Type 99 air-to-air missile) medium-range, active radar-guided air-to-air missile.
AAM-5 – (Type 04 air-to-air missile) short-range, all-aspect IR-seeking air-to-air missile. | Air-to-air missile | Wikipedia | 329 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
People's Republic of China
PL-1 – PRC version of the Soviet K-5 (missile) (AA-1 Alkali), retired.
PL-2 – PRC version of the Soviet Vympel K-13 (AA-2 Atoll), which was based on AIM-9B Sidewinder. Retired & replaced by PL-5 in PLAAF service.
PL-3 – updated version of the PL-2, did not enter service.
PL-4 – experimental BVR missile based on AIM-7D, did not enter service.
PL-6 – updated version of PL-3, also did not enter service.
PL-5 – updated version of the PL-2, known versions include:
PL-5A – semi-active radar-homing AAM intended to replace the PL-2, did not enter service. Resembles AIM-9G in appearance.
PL-5B – IR version, entered service in the 1990s to replace the PL-2 SRAAM. Limited off-boresight
PL-5C – Improved version comparable to AIM-9H or AIM-9L in performance
PL-5E – All-aspect attack version, resembles AIM-9P in appearance.
PL-7 – PRC version of the IR-homing French R550 Magic AAM, did not enter service.
PL-8 – PRC version of the Israeli Rafael Python 3
PL-9 – short-range IR-guided missile, marketed for export. One known improved version (PL-9C).
PL-10(old);– semi-active radar-homing medium-range missile based on the HQ-61 SAM, often confused with PL-11. Did not enter service.
PL-10(new)/PL-ASR – short-range off-boresight all-aspect IR-guided missile.
PL-11 – medium-range air-to-air missile (MRAAM), based on the HQ-61C & Italian Aspide (AIM-7) technology. Limited service with J-8-B/D/H fighters. Known versions include:
PL-11 – MRAAM with semi-active radar homing, based on the HQ-61C SAM and Aspide seeker technology, exported as FD-60 | Air-to-air missile | Wikipedia | 472 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
PL-11A – Improved PL-11 with increased range, warhead, and more effective seeker. The new seeker only requires fire-control radar guidance during the terminal stage, providing a basic LOAL (lock-on after launch) capability.
PL-11B – Also known as PL-11 AMR, improved PL-11 with AMR-1 active radar-homing seeker.
LY-60 – PL-11 adopted for navy ships for air-defense, sold to Pakistan but does not appear to be in service with the Chinese Navy.
PL-12 (SD-10) – medium-range active radar missile
PL-12A – with upgraded motor
PL-12B – with upgraded guidance
PL-12C – with foldable tailfins
PL-12D – with belly inlet and ramjet motors
F80 – medium-range active radar missile
PL-15 – long-range active radar missile
PL-17 – extreme long-range active radar missile
PL-21 - long-range active radar missile (In Development)
TY-90 – light IR-homing air-to-air missile designed for helicopters | Air-to-air missile | Wikipedia | 229 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
Soviet Union/Russian Federation
K-5 (missile) (NATO reporting name AA-1 'Alkali') – beam-riding
Vympel K-13 (NATO reporting name AA-2 'Atoll') – short-range IR or SARH
Kaliningrad K-8 (NATO reporting name AA-3 'Anab') – IR or SARH
Raduga K-9 (NATO reporting name AA-4 'Awl') – IR or SARH
Bisnovat R-4 (NATO reporting name AA-5 'Ash') – IR or SARH
Bisnovat R-40 (NATO reporting name AA-6 'Acrid') – long-range IR or SARH
Vympel R-23/R-24 (NATO reporting name AA-7 'Apex') – medium-range SARH or IR
Molniya R-60 (NATO reporting name AA-8 'Aphid') – short-range IR
Vympel R-33 (NATO reporting name AA-9 'Amos') – long-range active radar
Vympel R-27 (NATO reporting name AA-10 'Alamo') – medium-range SARH or IR
Vympel R-73 (NATO reporting name AA-11 'Archer') – short-range IR
Vympel R-77 (NATO reporting name AA-12 'Adder') – medium-range active radar
Vympel R-37 (NATO reporting name AA-13 'Axehead') – long-range SARH or active radar homing
Novator KS-172 AAM-L – extreme long-range, inertial navigation with terminal active radar homing
South Africa
A-Darter – Short-range IR (With Brazil)
V3 Kukri – Short-range IR
R-Darter – Beyond-visual-range (BVR) radar-guided missile
Taiwan
Sky Sword I (TC-1) – air-to-air
Sky Sword II (TC-2) – air-to-air | Air-to-air missile | Wikipedia | 419 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
Turkey
Bozdoğan (Merlin) – WVRAAM (within-visual-range air-to-air missile)
Gökdoğan (Peregrine) – BVRAAM (beyond-visual-range air-to-air missile)
Akdoğan (Gyrfalcon) – Akdoğan is a 'mini' air-to-air missile intended to be cost-effective and to be used in UAVs such as Bayraktar Akıncı and TAI Aksungur.
Gökhan – it was officially confirmed that this variant would have a Ramjet.
United Kingdom
Fireflash – short-range beam-riding
Firestreak – short-range IR
Red Top – short-range IR
Taildog/SRAAM – short-range IR
Skyflash – medium-range radar-guided missile based on the AIM-7E2, said to have quick warm-up times of 1 to 2 seconds.
AIM-132 ASRAAM – short-range IR
MBDA Meteor – long-range active radar-guided missile with a solid fuel ducted ramjet
United States
Retired
AIM-4 Falcon – radar-guided (later IR-seeking)
AIM-26 Falcon
AIM-54 Phoenix – long-range, semi-active-guided and active radar-guided; retired in 2004
AIM-47 Falcon
Operational
AIM-7 Sparrow – medium-range, semi-active radar-guided
AIM-9 Sidewinder – short-range, IR-seeking
AIM-92 Stinger – short-range, IR-seeking; launched from helicopters
AIM-120 AMRAAM – medium-range, active radar-guided; replaces AIM-7 Sparrow
AIM-174 - extreme long-range, active radar-guided
In development
AIM-260 JATM – Under development by Lockheed Martin
AIM-160 CUDA/SACM – Under development
Boeing LRAAM
LREW (Long-Range Engagement Weapon programme)
MAM (Modular Advanced Missile)
Raytheon Peregrine – Compact medium-range active radar missile
Typical air-to-air missiles | Air-to-air missile | Wikipedia | 419 | 320568 | https://en.wikipedia.org/wiki/Air-to-air%20missile | Technology | Missiles | null |
Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the body of an organism. In lean healthy adult men, the total body water is about 60% (60–67%) of the total body weight; it is usually slightly lower in women (52–55%). The exact percentage of fluid relative to body weight is inversely proportional to the percentage of body fat. A lean man, for example, has about 42 (42–47) liters of water in his body.
The total body of water is divided into fluid compartments, between the intracellular fluid compartment (also called space, or volume) and the extracellular fluid (ECF) compartment (space, volume) in a two-to-one ratio: 28 (28–32) liters are inside cells and 14 (14–15) liters are outside cells.
The ECF compartment is divided into the interstitial fluid volume – the fluid outside both the cells and the blood vessels – and the intravascular volume (also called the vascular volume and blood plasma volume) – the fluid inside the blood vessels – in a three-to-one ratio: the interstitial fluid volume is about 12 liters; the vascular volume is about 4 liters.
The interstitial fluid compartment is divided into the lymphatic fluid compartment – about 2/3, or 8 (6–10) liters, and the transcellular fluid compartment (the remaining 1/3, or about 4 liters).
The vascular volume is divided into the venous volume and the arterial volume; and the arterial volume has a conceptually useful but unmeasurable subcompartment called the effective arterial blood volume.
Compartments by location
intracellular fluid (ICF), which consist of cytosol and fluids in the cell nucleus
Extracellular fluid
Intravascular fluid (blood plasma)
Interstitial fluid
Lymphatic fluid (sometimes included in interstitial fluid)
Transcellular fluid
Health
Clinical samples
Clinical samples are generally defined as non-infectious human or animal materials including blood, saliva, excreta, body tissue and tissue fluids, and also FDA-approved pharmaceuticals that are blood products. In medical contexts, it is a specimen taken for diagnostic examination or evaluation, and for identification of disease or condition. | Body fluid | Wikipedia | 472 | 320760 | https://en.wikipedia.org/wiki/Body%20fluid | Biology and health sciences | Animal anatomy and morphology | Biology |
In mathematics, a constant function is a function whose (output) value is the same for every input value.
Basic properties
As a real-valued function of a real-valued argument, a constant function has the general form or just For example, the function is the specific constant function where the output value is . The domain of this function is the set of all real numbers. The image of this function is the singleton set . The independent variable does not appear on the right side of the function expression and so its value is "vacuously substituted"; namely , , , and so on. No matter what value of is input, the output is .
The graph of the constant function is a horizontal line in the plane that passes through the point . In the context of a polynomial in one variable , the constant function is called non-zero constant function because it is a polynomial of degree 0, and its general form is , where is nonzero. This function has no intersection point with the axis, meaning it has no root (zero). On the other hand, the polynomial is the identically zero function. It is the (trivial) constant function and every is a root. Its graph is the axis in the plane. Its graph is symmetric with respect to the axis, and therefore a constant function is an even function.
In the context where it is defined, the derivative of a function is a measure of the rate of change of function values with respect to change in input values. Because a constant function does not change, its derivative is 0. This is often written: . The converse is also true. Namely, if for all real numbers , then is a constant function. For example, given the constant function The derivative of is the identically zero function
Other properties
For functions between preordered sets, constant functions are both order-preserving and order-reversing; conversely, if is both order-preserving and order-reversing, and if the domain of is a lattice, then must be constant. | Constant function | Wikipedia | 407 | 320861 | https://en.wikipedia.org/wiki/Constant%20function | Mathematics | Specific functions | null |
Every constant function whose domain and codomain are the same set is a left zero of the full transformation monoid on , which implies that it is also idempotent.
It has zero slope or gradient.
Every constant function between topological spaces is continuous.
A constant function factors through the one-point set, the terminal object in the category of sets. This observation is instrumental for F. William Lawvere's axiomatization of set theory, the Elementary Theory of the Category of Sets (ETCS).
For any non-empty , every set is isomorphic to the set of constant functions in . For any and each element in , there is a unique function such that for all . Conversely, if a function satisfies for all , is by definition a constant function.
As a corollary, the one-point set is a generator in the category of sets.
Every set is canonically isomorphic to the function set , or hom set in the category of sets, where 1 is the one-point set. Because of this, and the adjunction between Cartesian products and hom in the category of sets (so there is a canonical isomorphism between functions of two variables and functions of one variable valued in functions of another (single) variable, ) the category of sets is a closed monoidal category with the Cartesian product of sets as tensor product and the one-point set as tensor unit. In the isomorphisms natural in , the left and right unitors are the projections and the ordered pairs and respectively to the element , where is the unique point in the one-point set.
A function on a connected set is locally constant if and only if it is constant. | Constant function | Wikipedia | 345 | 320861 | https://en.wikipedia.org/wiki/Constant%20function | Mathematics | Specific functions | null |
A birth defect is an abnormal condition that is present at birth, regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can range from mild to severe. Birth defects are divided into two main types: structural disorders in which problems are seen with the shape of a body part and functional disorders in which problems exist with how a body part works. Functional disorders include metabolic and degenerative disorders. Some birth defects include both structural and functional disorders.
Birth defects may result from genetic or chromosomal disorders, exposure to certain medications or chemicals, or certain infections during pregnancy. Risk factors include folate deficiency, drinking alcohol or smoking during pregnancy, poorly controlled diabetes, and a mother over the age of 35 years old. Many birth defects are believed to involve multiple factors. Birth defects may be visible at birth or diagnosed by screening tests. A number of defects can be detected before birth by different prenatal tests.
Treatment varies depending on the defect in question. This may include therapy, medication, surgery, or assistive technology. Birth defects affected about 96 million people . In the United States, they occur in about 3% of newborns. They resulted in about 628,000 deaths in 2015, down from 751,000 in 1990. The types with the greatest numbers of deaths are congenital heart disease (303,000), followed by neural tube defects (65,000).
Classification
Much of the language used for describing congenital conditions antedates genome mapping, and structural conditions are often considered separately from other congenital conditions. Many metabolic conditions are now known to have subtle structural expression, and structural conditions often have genetic links. Still, congenital conditions are often classified on a structural basis, organized when possible by primary organ system affected.
Primarily structural
Several terms are used to describe congenital abnormalities. (Some of these are also used to describe noncongenital conditions, and more than one term may apply in an individual condition.) | Birth defect | Wikipedia | 397 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Terminology
A congenital physical anomaly is an abnormality of the structure of a body part. It may or may not be perceived as a problem condition. Many, if not most, people have one or more minor physical anomalies if examined carefully. Examples of minor anomalies can include curvature of the fifth finger (clinodactyly), a third nipple, tiny indentations of the skin near the ears (preauricular pits), shortness of the fourth metacarpal or metatarsal bones, or dimples over the lower spine (sacral dimples). Some minor anomalies may be clues to more significant internal abnormalities.
Birth defect is a widely used term for a congenital malformation, i.e. a congenital, physical anomaly that is recognizable at birth, and which is significant enough to be considered a problem. According to the Centers for Disease Control and Prevention (CDC), most birth defects are believed to be caused by a complex mix of factors including genetics, environment, and behaviors, though many birth defects have no known cause. An example of a birth defect is cleft palate, which occurs during the fourth through seventh weeks of gestation. Body tissue and special cells from each side of the head grow toward the center of the face. They join to make the face. A cleft means a split or separation; the "roof" of the mouth is called the palate.
A congenital malformation is a physical anomaly that is deleterious, i.e. a structural defect perceived as a problem. A typical combination of malformations affecting more than one body part is referred to as a malformation syndrome.
Some conditions are due to abnormal tissue development:
A malformation is associated with a disorder of tissue development. Malformations often occur in the first trimester.
A dysplasia is a disorder at the organ level that is due to problems with tissue development.
Conditions also can arise after tissue is formed:
A deformation is a condition arising from mechanical stress to normal tissue. Deformations often occur in the second or third trimester, and can be due to oligohydramnios.
A disruption involves breakdown of normal tissues.
When multiple effects occur in a specified order, they are known as a sequence. When the order is not known, it is a syndrome. | Birth defect | Wikipedia | 477 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Examples of primarily structural congenital disorders
A limb anomaly is called a dysmelia. These include all forms of limbs anomalies, such as amelia, ectrodactyly, phocomelia, polymelia, polydactyly, syndactyly, polysyndactyly, oligodactyly, brachydactyly, achondroplasia, congenital aplasia or hypoplasia, amniotic band syndrome, and cleidocranial dysostosis.
Congenital heart defects include patent ductus arteriosus, atrial septal defect, ventricular septal defect, and tetralogy of Fallot.
Congenital anomalies of the nervous system include neural tube defects such as spina bifida, encephalocele, and anencephaly. Other congenital anomalies of the nervous system include the Arnold–Chiari malformation, the Dandy–Walker malformation, hydrocephalus, microencephaly, megalencephaly, lissencephaly, polymicrogyria, holoprosencephaly, and agenesis of the corpus callosum.
Congenital anomalies of the gastrointestinal system include numerous forms of stenosis and atresia, and perforation, such as gastroschisis.
Congenital anomalies of the kidney and urinary tract include renal parenchyma, kidneys, and urinary collecting system.
Defects can be bilateral or unilateral, and different defects often coexist in an individual child.
Primarily metabolic
A congenital metabolic disease is also referred to as an inborn error of metabolism. Most of these are single-gene defects, usually heritable. Many affect the structure of body parts, but some simply affect the function.
Other
Other well-defined genetic conditions may affect the production of hormones, receptors, structural proteins, and ion channels.
Causes
Alcohol exposure
The mother's consumption of alcohol during pregnancy can cause a continuum of various permanent birth defects: craniofacial abnormalities, brain damage, intellectual disability, heart disease, kidney abnormality, skeletal anomalies, ocular abnormalities.
The prevalence of children affected is estimated at least 1% in U.S. as well in Canada.
Very few studies have investigated the links between paternal alcohol use and offspring health. | Birth defect | Wikipedia | 496 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
However, recent animal research has shown a correlation between paternal alcohol exposure and decreased offspring birth weight. Behavioral and cognitive disorders, including difficulties with learning and memory, hyperactivity, and lowered stress tolerance have been linked to paternal alcohol ingestion. The compromised stress management skills of animals whose male parent was exposed to alcohol are similar to the exaggerated responses to stress that children with fetal alcohol syndrome display because of maternal alcohol use. These birth defects and behavioral disorders were found in cases of both long- and short-term paternal alcohol ingestion. In the same animal study, paternal alcohol exposure was correlated with a significant difference in organ size and the increased risk of the offspring displaying ventricular septal defects at birth.
Toxic substances
Substances whose toxicity can cause congenital disorders are called teratogens, and include certain pharmaceutical and recreational drugs in pregnancy, as well as many environmental toxins in pregnancy.
A review published in 2010 identified six main teratogenic mechanisms associated with medication use: folate antagonism, neural crest cell disruption, endocrine disruption, oxidative stress, vascular disruption, and specific receptor- or enzyme-mediated teratogenesis.
An estimated 10% of all birth defects are caused by prenatal exposure to a teratogenic agent. These exposures include medication or drug exposures, maternal infections and diseases, and environmental and occupational exposures. Paternal smoking has also been linked to an increased risk of birth defects and childhood cancer for the offspring, where the paternal germline undergoes oxidative damage due to cigarette use. Teratogen-caused birth defects are potentially preventable. Nearly 50% of pregnant women have been exposed to at least one medication during gestation. During pregnancy, a woman can also be exposed to teratogens from contaminated clothing or toxins within the seminal fluid of a partner. An additional study found that of 200 individuals referred for genetic counseling for a teratogenic exposure, 52% were exposed to more than one potential teratogen.
The United States Environmental Protection Agency studied 1,065 chemical and drug substances in their ToxCast program (part of the CompTox Chemicals Dashboard) using in silico modeling and a human pluripotent stem cell-based assay to predict in vivo developmental intoxicants based on changes in cellular metabolism following chemical exposure. Findings of the study published in 2020 were that 19% of the 1065 chemicals yielded a prediction of developmental toxicity. | Birth defect | Wikipedia | 492 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Medications and supplements
Probably, the most well-known teratogenic drug is thalidomide. It was developed near the end of the 1950s by Chemie Grünenthal as a sleep-inducing aid and antiemetic. Because of its ability to prevent nausea, it was prescribed for pregnant women in almost 50 countries worldwide between 1956 and 1962. Until William McBride published the study leading to its withdrawal from the market in 1961, about 8,000 to 10,000 severely malformed children were born. The most typical disorders induced by thalidomide were reductional deformities of the long bones of the extremities. Phocomelia, otherwise a rare deformity, therefore helped to recognise the teratogenic effect of the new drug. Among other malformations caused by thalidomide were those of ears, eyes, brain, kidney, heart, and digestive and respiratory tracts; 40% of the prenatally affected children died soon after birth. As thalidomide is used today as a treatment for multiple myeloma and leprosy, several births of affected children were described in spite of the strictly required use of contraception among female patients treated by it. | Birth defect | Wikipedia | 246 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Vitamin A is the sole vitamin that is embryotoxic even in a therapeutic dose, for example in multivitamins, because its metabolite, retinoic acid, plays an important role as a signal molecule in the development of several tissues and organs. Its natural precursor, β-carotene, is considered safe, whereas the consumption of animal liver can lead to malformation, as the liver stores lipophilic vitamins, including retinol. Isotretinoin (13-cis-retinoic-acid; brand name Roaccutane), vitamin A analog, which is often used to treat severe acne, is such a strong teratogen that just a single dose taken by a pregnant woman (even transdermally) may result in serious birth defects. Because of this effect, most countries have systems in place to ensure that it is not given to pregnant women and that the patient is aware of how important it is to prevent pregnancy during and at least one month after treatment. Medical guidelines also suggest that pregnant women should limit vitamin A intake to about 700 μg/day, as it has teratogenic potential when consumed in excess. Vitamin A and similar substances can induce spontaneous abortions, premature births, defects of eyes (microphthalmia), ears, thymus, face deformities, and neurological (hydrocephalus, microcephalia) and cardiovascular defects, as well as intellectual disability.
Tetracycline, an antibiotic, should never be prescribed to women of reproductive age or to children, because of its negative impact on bone mineralization and teeth mineralization. The "tetracycline teeth" have brown or grey colour as a result of a defective development of both the dentine and the enamel of teeth. | Birth defect | Wikipedia | 367 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Several anticonvulsants are known to be highly teratogenic. Phenytoin, also known as diphenylhydantoin, along with carbamazepine, is responsible for the fetal hydantoin syndrome, which may typically include broad nose base, cleft lip and/or palate, microcephalia, nails and fingers hypoplasia, intrauterine growth restriction, and intellectual disability. Trimethadione taken during pregnancy is responsible for the fetal trimethadione syndrome, characterized by craniofacial, cardiovascular, renal, and spine malformations, along with a delay in mental and physical development. Valproate has antifolate effects, leading to neural tube closure-related defects such as spina bifida. Lower IQ and autism have recently also been reported as a result of intrauterine valproate exposure.
Hormonal contraception is considered harmless for the embryo. Peterka and Novotná do, however, state that synthetic progestins used to prevent miscarriage in the past frequently caused masculinization of the outer reproductive organs of female newborns due to their androgenic activity. Diethylstilbestrol is a synthetic estrogen used from the 1940s to 1971, when the prenatal exposition has been linked to the clear-cell adenocarcinoma of the vagina. Following studies showed elevated risks for other tumors and congenital malformations of the sex organs for both sexes.
All cytostatics are strong teratogens; abortion is usually recommended when pregnancy is discovered during or before chemotherapy. Aminopterin, a cytostatic drug with antifolate effect, was used during the 1950s and 1960s to induce therapeutic abortions. In some cases, the abortion did not happen, but the newborns had a fetal aminopterin syndrome consisting of growth retardation, craniosynostosis, hydrocephalus, facial dismorphities, intellectual disability, or leg deformities
Toxic substances
Drinking water is often a medium through which harmful toxins travel. Heavy metals, elements, nitrates, nitrites, and fluoride can be carried through water and cause congenital disorders. | Birth defect | Wikipedia | 455 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Nitrate, which is found mostly in drinking water from ground sources, is a powerful teratogen. A case-control study in rural Australia that was conducted following frequent reports of prenatal mortality and congenital malformations found that those who drank the nitrate-containing groundwater, as opposed to rain water, ran the risk of giving birth to children with central nervous system disorders, muscoskeletal defects, and cardiac defects.
Chlorinated and aromatic solvents such as benzene and trichloroethylene sometimes enter the water supply due to oversights in waste disposal. A case-control study on the area found that by 1986, leukemia was occurring in the children of Woburn, Massachusetts, at a rate that was four times the expected rate of incidence. Further investigation revealed a connection between the high occurrence of leukemia and an error in water distribution that delivered water to the town with significant contamination with manufacturing waste containing trichloroethylene.
As an endocrine disruptor, DDT was shown to induce miscarriages, interfere with the development of the female reproductive system, cause the congenital hypothyroidism, and suspectably childhood obesity.
Fluoride, when transmitted through water at high levels, can also act as a teratogen. Two reports on fluoride exposure from China, which were controlled to account for the education level of parents, found that children born to parents who were exposed to 4.12 ppm fluoride grew to have IQs that were, on average, seven points lower than their counterparts whose parents consumed water that contained 0.91 ppm fluoride. In studies conducted on rats, higher fluoride in drinking water led to increased acetylcholinesterase levels, which can alter prenatal brain development. The most significant effects were noted at a level of 5 ppm. | Birth defect | Wikipedia | 376 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
The fetus is even more susceptible to damage from carbon monoxide intake, which can be harmful when inhaled during pregnancy, usually through first- or second-hand tobacco smoke. The concentration of carbon monoxide in the infant born to a nonsmoking mother is around 2%, and this concentration drastically increases to a range of 6%–9% if the mother smoked tobacco. Other possible sources of prenatal carbon monoxide intoxication are exhaust gas from combustion motors, use of dichloromethane (paint thinner, varnish removers) in enclosed areas, defective gas water heaters, indoor barbeques, open flames in poorly ventilated areas, and atmospheric exposure in highly polluted areas. Exposure to carbon monoxide at toxic levels during the first two trimesters of pregnancy can lead to intrauterine growth restriction, leading to a baby who has stunted growth and is born smaller than 90% of other babies at the same gestational age. The effect of chronic exposure to carbon monoxide can depend on the stage of pregnancy in which the mother is exposed. Exposure during the embryonic stage can have neurological consequences, such as telencephalic dysgenesis, behavioral difficulties during infancy, and reduction of cerebellum volume. Also, possible skeletal defects could result from exposure to carbon monoxide during the embryonic stage, such as hand and foot malformations, hip dysplasia, hip subluxation, agenesis of a limb, and inferior maxillary atresia with glossoptosis. Also, carbon monoxide exposure between days 35 and 40 of embryonic development can lead to an increased risk of the child developing a cleft palate. Exposure to carbon monoxide or polluted ozone exposure can also lead to cardiac defects of the ventrical septal, pulmonary artery, and heart valves. The effects of carbon monoxide exposure are decreased later in fetal development during the fetal stage, but they may still lead to anoxic encephalopathy. | Birth defect | Wikipedia | 410 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Industrial pollution can also lead to congenital defects. Over a period of 37 years, the Chisso Corporation, a petrochemical and plastics company, contaminated the waters of Minamata Bay with an estimated 27 tons of methylmercury, contaminating the local water supply. This led many people in the area to develop what became known as the "Minamata disease". Because methylmercury is a teratogen, the mercury poisoning of those residing by the bay resulted in neurological defects in the offspring. Infants exposed to mercury poisoning in utero showed predispositions to cerebral palsy, ataxia, inhibited psychomotor development, and intellectual disability.
Landfill sites have been shown to have adverse effects on fetal development. Extensive research has shown that landfills have several negative effects on babies born to mothers living near landfill sites: low birth weight, birth defects, spontaneous abortion, and fetal and infant mortality. Studies done around the Love Canal site near Niagara Falls and the Lipari Landfill in New Jersey have shown a higher proportion of low birth-weight babies than communities farther away from landfills. A study done in California showed a positive correlation between time and quantity of dumping and low birth weights and neonatal deaths. A study in the United Kingdom showed a correlation between pregnant women living near landfill sites and an increased risk of congenital disorders, such as neural tube defects, hypospadias, epispadia, and abdominal wall defects, such as gastroschisis and exomphalos. A study conducted on a Welsh community also showed an increased incidence of gastroschisis. Another study on 21 European hazardous-waste sites showed that those living within 3 km had an increased risk of giving birth to infants with birth defects and that as distance from the land increased, the risk decreased. These birth defects included neural tube defects, malformations of the cardiac septa, anomalies of arteries and veins, and chromosomal anomalies. Looking at communities that live near landfill sites brings up environmental justice. A vast majority of sites are located near poor, mostly black, communities. For example, between the early 1920s and 1978, about 25% of Houston's population was black. However, over 80% of landfills and incinerators during this time were located in these black communities. | Birth defect | Wikipedia | 469 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Another issue regarding environmental justice is lead poisoning. A fetus exposed to lead during the pregnancy can result in learning difficulties and slowed growth. Some paints (before 1978) and pipes contain lead. Therefore, pregnant women who live in homes with lead paint inhale the dust containing lead, leading to lead exposure in the fetus. When lead pipes are used for drinking water and cooking water, this water is ingested, along with the lead, exposing the fetus to this toxin. This issue is more prevalent in poorer communities because more well-off families are able to afford to have their homes repainted and pipes renovated.
Endometriosis
Endometriosis can impact a woman's fetus, causing a 30% higher risk for congenital malformations and a 50% higher risk of neonates being under-sized for their gestational age.
Smoking
Paternal smoking prior to conception has been linked with the increased risk of congenital abnormalities in offspring.
Smoking causes DNA mutations in the germline of the father, which can be inherited by the offspring. Cigarette smoke acts as a chemical mutagen on germ cell DNA. The germ cells suffer oxidative damage, and the effects can be seen in altered mRNA production, infertility issues, and side effects in the embryonic and fetal stages of development. This oxidative damage may result in epigenetic or genetic modifications of the father's germline. Fetal lymphocytes have been damaged as a result of a father's smoking habits prior to conception.
Correlations between paternal smoking and the increased risk of offspring developing childhood cancers (including acute leukemia, brain tumors, and lymphoma) before age five have been established. Little is currently known about how paternal smoking damages the fetus, and what window of time in which the father smokes is most harmful to offspring.
Infections
A vertically transmitted infection is an infection caused by bacteria, viruses, or in rare cases, parasites transmitted directly from the mother to an embryo, fetus, or baby during pregnancy or childbirth. | Birth defect | Wikipedia | 416 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Congenital disorders were initially believed to be the result of only hereditary factors. However, in the early 1940s, Australian pediatric ophthalmologist Norman Gregg began recognizing a pattern in which the infants arriving at his surgery were developing congenital cataracts at a higher rate than those who developed it from hereditary factors. On October 15, 1941, Gregg delivered a paper that explained his findings-68 out of the 78 children with congenital cataracts had been exposed in utero to rubella due to an outbreak in Australian army camps. These findings confirmed, to Gregg, that, in fact, environmental causes for congenital disorders could exist.
Rubella is known to cause abnormalities of the eye, internal ear, heart, and sometimes the teeth. More specifically, fetal exposure to rubella during weeks five to ten of development (the sixth week particularly) can cause cataracts and microphthalmia in the eyes. If the mother is infected with rubella during the ninth week, a crucial week for internal ear development, destruction of the organ of Corti can occur, causing deafness. In the heart, the ductus arteriosus can remain after birth, leading to hypertension. Rubella can also lead to atrial and ventricular septal defects in the heart. If exposed to rubella in the second trimester, the fetus can develop central nervous system malformations. However, because infections of rubella may remain undetected, misdiagnosed, or unrecognized in the mother, and/or some abnormalities are not evident until later in the child's life, precise incidence of birth defects due to rubella are not entirely known. The timing of the mother's infection during fetal development determines the risk and type of birth defect. As the embryo develops, the risk of abnormalities decreases. If exposed to the rubella virus during the first four weeks, the risk of malformations is 47%. Exposure during weeks five through eight creates a 22% chance, while weeks 9–12, a 7% chance exists, followed by 6% if the exposure is during the 13th-16th weeks. Exposure during the first eight weeks of development can also lead to premature birth and fetal death. These numbers are calculated from immediate inspection of the infant after birth. Therefore, mental defects are not accounted for in the percentages because they are not evident until later in the child's life. If they were to be included, these numbers would be much higher. | Birth defect | Wikipedia | 501 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Other infectious agents include cytomegalovirus, the herpes simplex virus, hyperthermia, toxoplasmosis, and syphilis. Maternal exposure to cytomegalovirus can cause microcephaly, cerebral calcifications, blindness, chorioretinitis (which can cause blindness), hepatosplenomegaly, and meningoencephalitis in fetuses. Microcephaly is a disorder in which the fetus has an atypically small head, cerebral calcifications means certain areas of the brain have atypical calcium deposits, and meningoencephalitis is the enlargement of the brain. All three disorders cause abnormal brain function or intellectual disability. Hepatosplenomegaly is the enlargement of the liver and spleen which causes digestive problems. It can also cause some kernicterus and petechiae. Kernicterus causes yellow pigmentation of the skin, brain damage, and deafness. Petechaie is when the capillaries bleed resulting in red/purple spots on the skin. However, cytomegalovirus is often fatal in the embryo. The Zika virus can also be transmitted from the pregnant mother to her baby and cause microcephaly.
The herpes simplex virus can cause microcephaly, microphthalmus (abnormally small eyeballs), retinal dysplasia, hepatosplenomegaly, and intellectual disability. Both microphthalmus and retinal dysplasia can cause blindness. However, the most common symptom in infants is an inflammatory response that develops during the first three weeks of life. Hyperthermia causes anencephaly, which is when part of the brain and skull are absent in the infant. Mother exposure to toxoplasmosis can cause cerebral calcification, hydrocephalus (causes mental disabilities), and intellectual disability in infants. Other birth abnormalities have been reported as well, such as chorioretinitis, microphthalmus, and ocular defects. Syphilis causes congenital deafness, intellectual disability, and diffuse fibrosis in organs, such as the liver and lungs, if the embryo is exposed.
Malnutrition | Birth defect | Wikipedia | 476 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
For example, a lack of folic acid, a B vitamin, in the diet of a mother can cause cellular neural tube deformities that result in spina bifida. Congenital disorders such as a neural tube deformity can be prevented by 72% if the mother consumes 4 mg of folic acid before the conception and after twelve weeks of pregnancy. Folic acid, or vitamin B9, aids the development of the foetal nervous system.
Studies with mice have found that food deprivation of the male mouse prior to conception leads to the offspring displaying significantly lower blood glucose levels.
Physical restraint
External physical shocks or constraints due to growth in a restricted space may result in unintended deformation or separation of cellular structures resulting in an abnormal final shape or damaged structures unable to function as expected. An example is Potter syndrome due to oligohydramnios. This finding is important for future understanding of how genetics may predispose individuals for diseases such as obesity, diabetes, and cancer.
For multicellular organisms that develop in a womb, the physical interference or presence of other similarly developing organisms such as twins can result in the two cellular masses being integrated into a larger whole, with the combined cells attempting to continue to develop in a manner that satisfies the intended growth patterns of both cell masses. The two cellular masses can compete with each other, and may either duplicate or merge various structures. This results in conditions such as conjoined twins, and the resulting merged organism may die at birth when it must leave the life-sustaining environment of the womb and must attempt to sustain its biological processes independently.
Genetics
Genetic causes of birth defects include inheritance of abnormal genes from the mother or the father, as well as new mutations in one of the germ cells that gave rise to the fetus. Male germ cells mutate at a much faster rate than female germ cells, and as the father ages, the DNA of the germ cells mutates quickly. If an egg is fertilized with sperm that has damaged DNA, a possibility exists that the fetus could develop abnormally. | Birth defect | Wikipedia | 424 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Genetic disorders are all congenital (present at birth), though they may not be expressed or recognized until later in life. Genetic disorders may be grouped into single-gene defects, multiple-gene disorders, or chromosomal defects. Single-gene defects may arise from abnormalities of both copies of an autosomal gene (a recessive disorder) or of only one of the two copies (a dominant disorder). Some conditions result from deletions or abnormalities of a few genes located contiguously on a chromosome. Chromosomal disorders involve the loss or duplication of larger portions of a chromosome (or an entire chromosome) containing hundreds of genes. Large chromosomal abnormalities always produce effects on many different body parts and organ systems.
Defective sperm
Non-genetic defects in sperm cells, such as deformed centrioles and other components in the tail and neck of the sperm which are important for the embryonic development, may result in defects. | Birth defect | Wikipedia | 190 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Socioeconomics
A low socioeconomic status in a deprived neighborhood may include exposure to "environmental stressors and risk factors". Socioeconomic inequalities are commonly measured by the Cartairs-Morris score, Index of Multiple Deprivation, Townsend deprivation index, and the Jarman score. The Jarman score, for example, considers "unemployment, overcrowding, single parents, under-fives, elderly living alone, ethnicity, low social class and residential mobility". In Vos' meta-analysis these indices are used to view the effect of low SES neighborhoods on maternal health. In the meta-analysis, data from individual studies were collected from 1985 up until 2008. Vos concludes that a correlation exists between prenatal adversities and deprived neighborhoods. Other studies have shown that low SES is closely associated with the development of the fetus in utero and growth retardation. Studies also suggest that children born in low SES families are "likely to be born prematurely, at low birth weight, or with asphyxia, a birth defect, a disability, fetal alcohol syndrome, or AIDS". Bradley and Corwyn also suggest that congenital disorders arise from the mother's lack of nutrition, a poor lifestyle, maternal substance abuse and "living in a neighborhood that contains hazards affecting fetal development (toxic waste dumps)". In a meta-analysis that viewed how inequalities influenced maternal health, it was suggested that deprived neighborhoods often promoted behaviors such as smoking, drug and alcohol use. After controlling for socioeconomic factors and ethnicity, several individual studies demonstrated an association with outcomes such as perinatal mortality and preterm birth.
Radiation
For the survivors of the atomic bombing of Hiroshima and Nagasaki, who are known as the Hibakusha, no statistically demonstrable increase of birth defects/congenital malformations was found among their later conceived children, or found in the later conceived children of cancer survivors who had previously received radiotherapy.
The surviving women of Hiroshima and Nagasaki who were able to conceive, though exposed to substantial amounts of radiation, later had children with no higher incidence of abnormalities/birth defects than in the Japanese population as a whole. | Birth defect | Wikipedia | 445 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Relatively few studies have researched the effects of paternal radiation exposure on offspring. Following the Chernobyl disaster, it was assumed in the 1990s that the germ line of irradiated fathers suffered minisatellite mutations in the DNA, which was inherited by descendants. More recently, however, the World Health Organization states, "children conceived before or after their father's exposure showed no statistically significant differences in mutation frequencies". This statistically insignificant increase was also seen by independent researchers analyzing the children of the liquidators. Animal studies have shown that incomparably massive doses of X-ray irradiation of male mice resulted in birth defects of the offspring.
In the 1980s, a relatively high prevalence of pediatric leukemia cases in children living near a nuclear processing plant in West Cumbria, UK, led researchers to investigate whether the cancer was a result of paternal radiation exposure. A significant association between paternal irradiation and offspring cancer was found, but further research areas close to other nuclear processing plants did not produce the same results. Later this was determined to be the Seascale cluster in which the leading hypothesis is the influx of foreign workers, who have a different rate of leukemia within their race than the British average, resulted in the observed cluster of 6 children more than expected around Cumbria.
Parent's age
Certain birth complications can occur more often in advanced maternal age (greater than 35 years). Complications include fetal growth restriction, preeclampsia, placental abruption, pre-mature births, and stillbirth. These complications not only may put the child at risk, but also the mother.
The effects of the father's age on offspring are not yet well understood and are studied far less extensively than the effects of the mother's age. Fathers contribute proportionally more DNA mutations to their offspring via their germ cells than the mother, with the paternal age governing how many mutations are passed on. This is because, as humans age, male germ cells acquire mutations at a much faster rate than female germ cells. | Birth defect | Wikipedia | 410 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Around a 5% increase in the incidence of ventricular septal defects, atrial septal defects, and patent ductus arteriosus in offspring has been found to be correlated with advanced paternal age. Advanced paternal age has also been linked to increased risk of achondroplasia and Apert syndrome. Offspring born to fathers under the age of 20 show increased risk of being affected by patent ductus arteriosus, ventricular septal defects, and the tetralogy of Fallot. It is hypothesized that this may be due to environmental exposures or lifestyle choices.
Research has found that there is a correlation between advanced paternal age and risk of birth defects such as limb anomalies, syndromes involving multiple systems, and Down syndrome. Recent studies have concluded that 5-9% of Down syndrome cases are due to paternal effects, but these findings are controversial.
There is concrete evidence that advanced paternal age is associated with the increased likelihood that a mother will have a miscarriage or that fetal death will occur.
Unknown
Although significant progress has been made in identifying the etiology of some birth defects, approximately 65% have no known or identifiable cause. These are referred to as sporadic, a term that implies an unknown cause, random occurrence regardless of maternal living conditions, and a low recurrence risk for future children. For 20-25% of anomalies there seems to be a "multifactorial" cause, meaning a complex interaction of multiple minor genetic anomalies with environmental risk factors. Another 10–13% of anomalies have a purely environmental cause (e.g. infections, illness, or drug abuse in the mother). Only 12–25% of anomalies have a purely genetic cause. Of these, the majority are chromosomal anomalies.
Congenital disorders are not limited to humans and can be found in a variety of other species, including cattle. One such condition is called schistosomus reflexus and is defined by spinal inversion, exposure of abdominal viscera, and limb abnormalities.
Prevention
Folate supplements decrease the risk of neural tube defects. Tentative evidence supports the role of L-arginine in decreasing the risk of intrauterine growth restriction.
Screening | Birth defect | Wikipedia | 453 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Newborn screening tests were introduced in the early 1960s and initially dealt with just two disorders. Since then tandem mass spectrometry, gas chromatography–mass spectrometry, and DNA analysis has made it possible for a much larger range of disorders to be screened. Newborn screening mostly measures metabolite and enzyme activity using a dried blood spot sample. Screening tests are carried out in order to detect serious disorders that may be treatable to some extent. Early diagnosis makes possible the readiness of therapeutic dietary information, enzyme replacement therapy and organ transplants. Different countries support the screening for a number of metabolic disorders (inborn errors of metabolism (IEM)), and genetic disorders including cystic fibrosis and Duchenne muscular dystrophy.
Tandem mass spectroscopy can also be used for IEM, and investigation of sudden infant death, and shaken baby syndrome.
Screening can also be carried out prenatally and can include obstetric ultrasonography to give scans such as the nuchal scan. 3D ultrasound scans can give detailed information of structural anomalies.
Epidemiology
Congenital anomalies resulted in about 632,000 deaths per year in 2013 down from 751,000 in 1990. The types with the greatest death are congenital heart defects (323,000), followed by neural tube defects (69,000).
Many studies have found that the frequency of occurrence of certain congenital malformations depends on the sex of the child (table). For example, pyloric stenosis occurs more often in males while congenital hip dislocation is four to five times more likely to occur in females. Among children with one kidney, there are approximately twice as many males, whereas among children with three kidneys there are approximately 2.5 times more females. The same pattern is observed among infants with excessive number of ribs, vertebrae, teeth and other organs which in a process of evolution have undergone reduction—among them there are more females. Contrarily, among the infants with their scarcity, there are more males. Anencephaly is shown to occur approximately twice as frequently in females. The number of boys born with 6 fingers is two times higher than the number of girls. Now various techniques are available to detect congenital anomalies in fetus before birth. | Birth defect | Wikipedia | 464 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
About 3% of newborns have a "major physical anomaly", meaning a physical anomaly that has cosmetic or functional significance.
Physical congenital abnormalities are the leading cause of infant mortality in the United States, accounting for more than 20% of all infant deaths. Seven to ten percent of all children will require extensive medical care to diagnose or treat a birth defect. | Birth defect | Wikipedia | 73 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
{| class="wikitable"
|+ The sex ratio of patients with congenital malformations
! Congenital anomaly !! Sex ratio, ♂♂:♀♀
|-
| Defects with female predominance ||
|-
| Congenital hip dislocation || 1 : 5.2; 1 : 5; 1 : 8; 1 : 3.7
|-
| Cleft palate || 1 : 3
|-
| Anencephaly || 1 : 1.9; 1 : 2
|-
| Craniocele || 1 : 1.8
|-
| Aplasia of lung || 1 : 1.51
|-
| Spinal herniation || 1 : 1.4
|-
| Diverticulum of the esophagus || 1 : 1.4
|-
| Stomach || 1 : 1.4
|-
| Neutral defects ||
|-
| Hypoplasia of the tibia and femur || 1 : 1.2
|-
| Spina bifida || 1 : 1.2
|-
| Atresia of small intestine || 1 : 1
|-
| Microcephaly || 1.2 : 1
|-
| Esophageal atresia || 1.3 : 1; 1.5 : 1
|-
| Hydrocephalus || 1.3 : 1
|-
| Defects with male predominance ||
|-
| Diverticula of the colon || 1.5 : 1
|-
| Atresia of the rectum || 1.5 : 1; 2 : 1
|-
| Unilateral renal agenesis || 2 : 1; 2.1 : 1
|-
| Schistocystis || 2 : 1
|-
| Cleft lip and palate || 2 : 1; 1.47 : 1
|-
| Bilateral renal agenesis || 2.6 : 1
|-
| Congenital anomalies of the genitourinary system || 2.7 : 1
|-
| Pyloric stenosis, congenital || 5 : 1; 5.4 : 1
|-
| Meckel's diverticulum || More common in boys
|-
| Congenital megacolon || More common in boys
|-
| All defects || 1.22 : 1; 1.29 : 1
|} | Birth defect | Wikipedia | 499 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
Data obtained on opposite-sex twins. ** — Data were obtained in the period 1983–1994. | Birth defect | Wikipedia | 21 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
P. M. Rajewski and A. L. Sherman (1976) have analyzed the frequency of congenital anomalies in relation to the system of the organism. Prevalence of men was recorded for the anomalies of phylogenetically younger organs and systems.
In respect of an etiology, sexual distinctions can be divided on appearing before and after differentiation of male's gonads during embryonic development, which begins from the eighteenth week. The testosterone level in male embryos thus raises considerably. The subsequent hormonal and physiological distinctions of male and female embryos can explain some sexual differences in frequency of congenital defects. It is difficult to explain the observed differences in the frequency of birth defects between the sexes by the details of the reproductive functions or the influence of environmental and social factors.
United States
The CDC and National Birth Defect Project studied the incidence of birth defects in the US. Key findings include:
Down syndrome was the most common condition with an estimated prevalence of 14.47 per 10,000 live births, implying about 6,000 diagnoses each year.
About 7,000 babies are born with a cleft palate, cleft lip or both. | Birth defect | Wikipedia | 234 | 321263 | https://en.wikipedia.org/wiki/Birth%20defect | Biology and health sciences | Disabilities | Health |
A railway track ( and UIC terminology) or railroad track (), also known as permanent way () or "P Way" ( and Indian English), is the structure on a railway or railroad consisting of the rails, fasteners, sleepers (railroad ties in American English) and ballast (or slab track), plus the underlying subgrade. It enables trains to move by providing a dependable, low-friction surface on which their wheels can roll. Early tracks were constructed with wooden or cast-iron rails, and wooden or stone sleepers. Since the 1870s, rails have almost universally been made from steel.
Historical development
The first railway in Britain was the Wollaton wagonway, built in 1603 between Wollaton and Strelley in Nottinghamshire. It used wooden rails and was the first of about 50 wooden-railed tramways built over the subsequent 164 years. These early wooden tramways typically used rails of oak or beech, attached to wooden sleepers with iron or wooden nails. Gravel or small stones were packed around the sleepers to hold them in place and provide a walkway for the people or horses that moved wagons along the track. The rails were usually about long and were not joined - instead, adjacent rails were laid on a common sleeper. The straight rails could be angled at these joints to form primitive curved track.
The first iron rails laid in Britain were at the Darby Ironworks in Coalbrookdale in 1767.
When steam locomotives were introduced, starting in 1804, the track then in use proved too weak to carry the additional weight. Richard Trevithick's pioneering locomotive at Pen-y-darren broke the plateway track and had to be withdrawn. As locomotives became more widespread in the 1810s and 1820s, engineers built rigid track formations, with iron rails mounted on stone sleepers, and cast-iron chairs holding them in place. This proved to be a mistake, and was soon replaced with flexible track structures that allowed a degree of elastic movement as trains passed over them.
Structure
Traditional track structure
Traditionally, tracks are constructed using flat-bottomed steel rails laid on and spiked or screwed into timber or pre-stressed concrete sleepers (known as ties in North America), with crushed stone ballast placed beneath and around the sleepers. | Railway track | Wikipedia | 459 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Most modern railroads with heavy traffic use continuously welded rails that are attached to the sleepers with base plates that spread the load. When concrete sleepers are used, a plastic or rubber pad is usually placed between the rail and the tie plate. Rail is usually attached to the sleeper with resilient fastenings, although cut spikes are widely used in North America. For much of the 20th century, rail track used softwood timber sleepers and jointed rails, and a considerable amount of this track remains on secondary and tertiary routes.
In North America and Australia, flat-bottomed rails were typically fastened to the sleepers with dog spikes through a flat tie plate. In Britain and Ireland, bullhead rails were carried in cast-iron chairs which were spiked to the sleepers. In 1936, the London, Midland and Scottish Railway pioneered the conversion to flat-bottomed rail in Britain, though earlier lines had made some use of it.
Jointed rails were used at first because contemporary technology did not offer any alternative. However, the intrinsic weakness in resisting vertical loading results in the ballast becoming depressed and a heavy maintenance workload is imposed to prevent unacceptable geometrical defects at the joints. The joints also needed to be lubricated, and wear at the fishplate (joint bar) mating surfaces needed to be rectified by shimming. For this reason jointed track is not financially appropriate for heavily operated railroads.
Timber sleepers are of many available timbers, and are often treated with creosote, chromated copper arsenate, or other wood preservatives. Pre-stressed concrete sleepers are often used where timber is scarce and where tonnage or speeds are high. Steel is used in some applications.
Track ballast is usually stone crushed to particular specifications. Its purpose is to support the sleepers and allow some adjustment of their position while allowing free drainage.
Ballastless track
A disadvantage of traditional track structures is the heavy demand for maintenance, particularly surfacing (tamping) and lining to restore the desired track geometry and smoothness of vehicle running. Weakness of the subgrade and drainage deficiencies also lead to heavy maintenance costs. This can be overcome by using ballastless track. In its simplest form this consists of a continuous slab of concrete (like a highway structure) with the rails supported directly on its upper surface (using a resilient pad). | Railway track | Wikipedia | 479 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
There are a number of proprietary systems; variations include a continuous reinforced concrete slab and the use of pre-cast pre-stressed concrete units laid on a base layer. Many permutations of design have been put forward.
However, ballastless track has a high initial cost, and in the case of existing railroads the upgrade to such requires closure of the route for a long period. Its whole-life cost can be lower because of the reduction in maintenance. Ballastless track is usually considered for new very high speed or very high loading routes, in short extensions that require additional strength (e.g. railway stations), or for localised replacement where there are exceptional maintenance difficulties, for example in tunnels. Most rapid transit lines and rubber-tyred metro systems use ballastless track.
Continuous longitudinally supported track
Early railways (c. 1840s) experimented with continuous bearing railtrack, in which the rail was supported along its length, with examples including Brunel's baulk road on the Great Western Railway, as well as use on the Newcastle and North Shields Railway, on the Lancashire and Yorkshire Railway to a design by John Hawkshaw, and elsewhere. Continuous-bearing designs were also promoted by other engineers. The system was tested on the Baltimore and Ohio railway in the 1840s, but was found to be more expensive to maintain than rail with cross sleepers.
This type of track still exists on some bridges on Network Rail where the timber baulks are called waybeams or longitudinal timbers. Generally the speed over such structures is low.
Later applications of continuously supported track include Balfour Beatty's 'embedded slab track', which uses a rounded rectangular rail profile (BB14072) embedded in a slipformed (or pre-cast) concrete base (development 2000s). The 'embedded rail structure', used in the Netherlands since 1976, initially used a conventional UIC 54 rail embedded in concrete, and later developed (late 1990s) to use a 'mushroom' shaped SA42 rail profile; a version for light rail using a rail supported in an asphalt concrete–filled steel trough has also been developed (2002).
Modern ladder track can be considered a development of baulk road. Ladder track utilizes sleepers aligned along the same direction as the rails with rung-like gauge restraining cross members. Both ballasted and ballastless types exist.
Rail | Railway track | Wikipedia | 477 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Modern track typically uses hot-rolled steel with a profile of an asymmetrical rounded I-beam. Unlike some other uses of iron and steel, railway rails are subject to very high stresses and have to be made of very high-quality steel alloy. It took many decades to improve the quality of the materials, including the change from iron to steel. The stronger the rails and the rest of the trackwork, the heavier and faster the trains the track can carry.
Other profiles of rail include: bullhead rail; grooved rail; flat-bottomed rail (Vignoles rail or flanged T-rail); bridge rail (inverted U–shaped used in baulk road); and Barlow rail (inverted V).
North American railroads until the mid- to late-20th century used rails long so they could be carried in gondola cars (open wagons), often long; as gondola sizes increased, so did rail lengths.
According to the Railway Gazette International the planned-but-cancelled 150-kilometre rail line for the Baffinland Iron Mine, on Baffin Island, would have used older carbon steel alloys for its rails, instead of more modern, higher performance alloys, because modern alloy rails can become brittle at very low temperatures.
Iron-topped wooden rails
Early North American railroads used iron on top of wooden rails as an economy measure but gave up this method of construction after the iron came loose, began to curl, and intruded into the floors of the coaches, leading early railroaders to refer to them as "snake heads".
The Deeside Tramway in North Wales used this form of rail. It opened around 1870 and closed in 1947, with long sections still using these rails. It was one of the last uses of iron-topped wooden rails.
Rail classification (weight)
Rail is graded by its linear density, that is, its mass over a standard length. Heavier rail can support greater axle loads and higher train speeds without sustaining damage than lighter rail, but at a greater cost. In North America and the United Kingdom, rail is graded in pounds per yard (usually shown as pound or lb), so 130-pound rail would weigh . The usual range is . In Europe, rail is graded in kilograms per metre and the usual range is . The heaviest mass-produced rail was , rolled for the Pennsylvania Railroad. | Railway track | Wikipedia | 478 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Rail lengths
The rails used in rail transport are produced in sections of fixed length. Rail lengths are made as long as possible, as the joints between rails are a source of weakness. Throughout the history of rail production, lengths have increased as manufacturing processes have improved.
Timeline
The following are lengths of single sections produced by steel mills, without any thermite welding. Shorter rails may be welded with flashbutt welding, but the following rail lengths are unwelded.
(1767) Richard Reynolds laid the first iron rails at Coalbrookdale.
(1825) Stockton and Darlington Railway
(1830) Liverpool and Manchester Railway. Fish-belly rails at , laid mostly on stone blocks
(1831) long and weighing , reached Philadelphia the first use of the flanged T-rail in the United States
(1880) United States to suit gondola waggons
(1928) London, Midland and Scottish Railway
(1950) British Rail
(1900) – steel works weighing machine for rails (steelyard balance)
(1940s) – double 39 ft
(1953) Australia
Welding of rails into longer lengths was first introduced around 1893, making train rides quieter and safer. With the introduction of thermite welding after 1899, the process became less labour-intensive, and ubiquitous.
(1895) Hans Goldschmidt developed exothermic welding
(1899) the Essen Tramway became the first railway to use thermite welding; also suited track circuits
(1904) George Pellissier welded the Holyoke Street Railway, first to use the process in the Americas
(1935) Charles Cadwell developed non-ferrous exothermic welding
(1950) welded – (4 x )
Modern production techniques allowed the production of longer unwelded segments.
(2007) Corus (now British Steel (2016–present))
(2011) Tata Steel Europe
(2011) Voestalpine,
(2011) Jindal
Multiples
Newer longer rails tend to be made as simple multiples of older shorter rails, so that old rails can be replaced without cutting. Some cutting would be needed as slightly longer rails are needed on the outside of sharp curves compared to the rails on the inside.
Boltholes
Rails can be supplied pre-drilled with boltholes for fishplates or without where they will be welded into place. There are usually two or three boltholes at each end. | Railway track | Wikipedia | 475 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Joining rails
Rails are produced in fixed lengths and need to be joined end-to-end to make a continuous surface on which trains may run. The traditional method of joining the rails is to bolt them together using metal fishplates (jointbars in the US), producing jointed track. For more modern usage, particularly where higher speeds are required, the lengths of rail may be welded together to form continuous welded rail (CWR).
Jointed track
Jointed track is made using lengths of rail, usually about long (in the UK) and long (in North America), bolted together using perforated steel plates known as fishplates (UK) or joint bars (North America).
Fishplates are usually long, used in pairs either side of the rail ends and bolted together (usually four, but sometimes six bolts per joint). The bolts have alternating orientations so that in the event of a derailment and a wheel flange striking the joint, only some of the bolts will be sheared, reducing the likelihood of the rails misaligning with each other and worsening the derailment. This technique is not applied universally; European practice is to have all the bolt heads on the same side of the rail.
Small gaps which function as expansion joints are deliberately left between the rail ends to allow for expansion of the rails in hot weather. European practice was to have the rail joints on both rails adjacent to each other; North American practice is to stagger them. Because of these small gaps, when trains pass over jointed tracks they make a "clickety-clack" sound, and in time the rail ends are deflected downwards. Unless it is well-maintained, jointed track does not have the ride quality of welded rail and is not suitable for high speed trains. However, jointed track is still used in many countries on lower-speed lines and sidings, and is used extensively in poorer countries due to the lower construction cost and the simpler equipment required for its installation and maintenance.
A major problem of jointed track is cracking around the bolt holes, which can lead to breaking of the rail head (the running surface). This was the cause of the Hither Green rail crash which caused British Railways to begin converting much of its track to continuous welded rail. | Railway track | Wikipedia | 469 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Insulated joints
Where track circuits exist for signalling purposes, insulated block joints are required. These compound the weaknesses of ordinary joints. Specially-made glued joints, where all the gaps are filled with epoxy resin, increase the strength again.
As an alternative to the insulated joint, audio frequency track circuits can be employed using a tuned loop formed in approximately of the rail as part of the blocking circuit. Some insulated joints are unavoidable within turnouts.
Another alternative is an axle counter, which can reduce the number of track circuits and thus the number of insulated rail joints required.
Continuous welded rail
Most modern railways use continuous welded rail, sometimes referred to as ribbon rails or seamless rails. In this form of track, the rails are welded together by utilising flash butt welding to form one continuous rail that may be several kilometres long. Because there are few joints, this form of track is very strong, gives a smooth ride, and needs less maintenance; trains can travel on it at higher speeds and with less friction. Welded rails are more expensive to lay than jointed tracks, but have much lower maintenance costs. The first welded track was used in Germany in 1924. and has become common on main lines since the 1950s.
The preferred process of flash butt welding involves an automated track-laying machine running a strong electric current through the touching ends of two unjoined rails. The ends become white hot due to electrical resistance and are then pressed together forming a strong weld. Thermite welding is used to repair or splice together existing continuous welded rail segments. This manual process requires a reaction crucible and form to contain the molten iron.
North American practice is to weld segments of rail at a rail facility and load it on a special train to carry it to the job site. This train is designed to carry many segments of rail which are placed so they can slide off their racks to the rear of the train and be attached to the ties (sleepers) in a continuous operation. | Railway track | Wikipedia | 405 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
If not restrained, rails would lengthen in hot weather and shrink in cold weather. To provide this restraint, the rail is prevented from moving in relation to the sleeper by use of clips or anchors. Attention needs to be paid to compacting the ballast effectively, including under, between, and at the ends of the sleepers, to prevent the sleepers from moving. Anchors are more common for wooden sleepers, whereas most concrete or steel sleepers are fastened to the rail by special clips that resist longitudinal movement of the rail. There is no theoretical limit to how long a welded rail can be. However, if longitudinal and lateral restraint are insufficient, the track could become distorted in hot weather and cause a derailment. Distortion due to heat expansion is known in North America as sun kink, and elsewhere as buckling. In extreme hot weather special inspections are required to monitor sections of track known to be problematic. In North American practice, extreme temperature conditions will trigger slow orders to allow for crews to react to buckling or "sun kinks" if encountered. The German railway company Deutsche Bahn is starting to paint rails white to lower the peak temperatures reached in summer days.
After new segments of rail are laid, or defective rails replaced (welded-in), the rails can be artificially stressed if the temperature of the rail during laying is cooler than what is desired. The stressing process involves either heating the rails, causing them to expand, or stretching the rails with hydraulic equipment. They are then fastened (clipped) to the sleepers in their expanded form. This process ensures that the rail will not expand much further in subsequent hot weather. In cold weather the rails try to contract, but because they are firmly fastened, cannot do so. In effect, stressed rails are a bit like a piece of stretched elastic firmly fastened down. In extremely cold weather, rails are heated to prevent "pull aparts".
Continuous welded rails, complete with fastenings, are laid at a temperature known as "rail neutral temperature" that is approximately midway between the extremes experienced at that location. This installation procedure is intended to prevent tracks from buckling in summer heat or pulling apart in the winter cold. In North America, because broken rails are typically detected by interruption of the current in the signaling system, they are seen as less of a potential hazard than undetected heat kinks. | Railway track | Wikipedia | 478 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Joints are used in the continuous welded rail when necessary, usually for signal circuit gaps. Instead of a joint that passes straight across the rail, the two rail ends are sometimes cut at an angle to give a smoother transition. In extreme cases, such as at the end of long bridges, a breather switch (referred to in North America and Britain as an expansion joint) gives a smooth path for the wheels while allowing the end of one rail to expand relative to the next rail.
Sleepers
A sleeper (tie or crosstie) is a rectangular object on which the rails are supported and fixed. The sleeper has two main roles: to transfer the loads from the rails to the track ballast and the ground underneath, and to hold the rails to the correct width apart (to maintain the rail gauge). They are generally laid transversely to the rails.
Fixing rails to sleepers
Various methods exist for fixing the rail to the sleeper. Historically, rails were spiked directly on to ties, the practice giving way baseplates being fitted between the rails and sleepers; subsequently, spikes were replaced by sprung steel clips, such as Pandrol clips, to fix the rail to the baseplates.
Portable track
Sometimes rail tracks are designed to be portable and moved from one place to another as required. During construction of the Panama Canal, tracks were moved around excavation works. These track gauge were and the rolling stock full size. Portable tracks have often been used in open pit mines. In 1880 in New York City, sections of heavy portable track (along with much other improvised technology) helped in the move of the ancient obelisk in Central Park to its final location from the dock where it was unloaded from the cargo ship SS Dessoug.
Cane railways often had permanent tracks for the main lines, with portable tracks serving the canefields themselves. These tracks were narrow gauge (for example, ) and the portable track came in straights, curves, and turnouts, rather like on a model railway.
Decauville was a source of many portable light rail tracks, also used for military purposes.
The permanent way is so called because temporary way tracks were often used in the construction of that permanent way.
Layout
The geometry of the tracks is three-dimensional by nature, but the standards that express the speed limits and other regulations in the areas of track gauge, alignment, elevation, curvature and track surface are usually expressed in two separate layouts for horizontal and vertical. | Railway track | Wikipedia | 494 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Horizontal layout is the track layout on the horizontal plane. This involves the layout of three main track types: tangent track (straight line), curved track, and track transition curve (also called transition spiral or spiral) which connects between a tangent and a curved track.
Vertical layout is the track layout on the vertical plane including the concepts such as crosslevel, cant and gradient.
A sidetrack is a railroad track other than siding that is auxiliary to the main track. The word is also used as a verb (without object) to refer to the movement of trains and railcars from the main track to a siding, and in common parlance to refer to giving in to distractions apart from a main subject. Sidetracks are used by railroads to order and organise the flow of rail traffic.
Gauge
During the early days of rail, there was considerable variation in the gauge used by different systems, and in the UK during the railway building boom of the 1840s Brunel's broad gauge of was in competition with what was referred to at the time as the 'narrow' gauge of . Eventually the gauge won the battle, and became the standard gauge, with the term 'narrow gauge' henceforth used for gauges narrower than the new standard. , about 60% of the world's railways use a gauge of , known as standard or international gauge Gauges wider than standard gauge are called broad gauge; narrower, narrow gauge. Some stretches of track are dual gauge, with three (or sometimes four) parallel rails in place of the usual two, to allow trains of two different gauges to use the same track.
Gauge can safely vary over a range. For example, U.S. federal safety standards allow standard gauge to vary from to for operation up to .
Maintenance
Track needs regular maintenance to remain in good order, especially when high-speed trains are involved. Inadequate maintenance may lead to a "slow order" (North American terminology, or temporary speed restriction in the United Kingdom) being imposed to avoid accidents (see Slow zone). Track maintenance was at one time hard manual labour, requiring teams of labourers, or trackmen (US: gandy dancers; UK: platelayers; Australia: fettlers or packers) under the supervision of a skilled ganger, who used lining bars to correct irregularities in horizontal alignment (line) of the track, and tamping and jacks to correct vertical irregularities (surface). Currently, maintenance is facilitated by a variety of specialised machines. | Railway track | Wikipedia | 504 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
The surface of the head of each of the two rails can be maintained by using a railgrinder.
Common maintenance jobs include changing sleepers, lubricating and adjusting switches, tightening loose track components, and surfacing and lining track to keep straight sections straight and curves within maintenance limits. The process of sleeper and rail replacement can be automated by using a track renewal train.
Spraying ballast with herbicide to prevent weeds growing through and redistributing the ballast is typically done with a special weed killing train.
Over time, ballast is crushed or moved by the weight of trains passing over it, periodically requiring relevelling ("tamping") and eventually to be cleaned or replaced. If this is not done, the tracks may become uneven, causing swaying, rough riding and possibly derailments. An alternative to tamping is to lift the rails and sleepers and reinsert the ballast beneath. For this, specialist "stoneblower" trains are used.
Rail inspections utilize nondestructive testing methods to detect internal flaws in the rails. This is done by using specially equipped HiRail trucks, inspection cars, or in some cases, handheld inspection devices.
Rails must be replaced before the railhead profile wears to a degree that may trigger a derailment. Worn mainline rails usually have sufficient life remaining to be used on a branch line, siding or stub afterwards and are "cascaded" to those applications.
The environmental conditions along railroad track create a unique railway ecosystem. This is particularly so in the United Kingdom, where steam locomotives are only used on special services and vegetation has not been trimmed back so thoroughly. This creates a fire risk in prolonged dry weather.
In the UK, the cess is used by track repair crews to walk to a work site, and as a safe place to stand when a train is passing. This helps when doing minor work, while needing to keep trains running, by not needing a Hi-railer or transport vehicle blocking the line to transport crew to get to the site.
Bed and foundation | Railway track | Wikipedia | 410 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Railway tracks are generally laid on a bed of stone track ballast or track bed, which in turn is supported by prepared earthworks known as the track formation. The formation comprises the subgrade and a layer of sand or stone dust (often sandwiched in impervious plastic), known as the blanket, which restricts the upward migration of wet clay or silt. There may also be layers of waterproof fabric to prevent water penetrating to the subgrade. The track and ballast form the permanent way. The foundation may refer to the ballast and formation, i.e. all man-made structures below the tracks.
Some railroads are using asphalt pavement below the ballast in order to keep dirt and moisture from moving into the ballast and spoiling it. The fresh asphalt also serves to stabilize the ballast so it does not move around so easily.
Additional measures are required where the track is laid over permafrost, such as on the Qingzang Railway in Tibet. For example, transverse pipes through the subgrade allow cold air to penetrate the formation and prevent that subgrade from melting.
Geosynthetic reinforcement
Geosynthetics are used to reduce or replace traditional layers in trackbed construction and rehabilitation worldwide to improve track support and reduce track maintenance costs. Reinforcement geosynthetics, such as geocells (which rely on 3D soil confinement mechanisms) have demonstrated efficacy in stabilizing soft subgrade soils and reinforcing substructural layers to limit progressive track degradation. Reinforcement geosynthetics increase soil bearing capacity, limit ballast movement and degradation and reduce differential settlement that affects track geometry. They also reduce construction time and cost, while reducing environmental impact and carbon footprint. The increased use of geosynthetic reinforcement solutions is supported by new high-performance geocell materials (e.g., NPA - Novel Polymeric Alloy), published research, case studies projects and international standards (ISO, ASTM, CROW/SBRCURnet) | Railway track | Wikipedia | 400 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
The hybrid use of high-performance geogrids at the subgrade and high-performance geocell in the upper subbase/subballast layer has been shown to increase the reinforcement factor greater than their separate sums, and is particularly effective in attenuating heaving of expansive subgrade clay soils. A field test project on Amtrak's NE Corridor suffering clay mud-pumping demonstrated how the hybrid solution improved track quality index (TQI) significantly reduced track geometry degradation and lowered track surface maintenance by factor of 6.7x utilizing high-performance NPA geocell. Geosynthetic reinforcement is also used to stabilize railway embankments, which must be robust enough to withstand repeated cyclical loading. Geocells can utilize recycled marginal or poorly graded granular material to create stable embankments, make railway construction more economical and sustainable.
Buses
Some buses can use tracks. This concept came out of Germany and was called . The first such track, the O-Bahn Busway, was built in Adelaide, Australia. | Railway track | Wikipedia | 205 | 321365 | https://en.wikipedia.org/wiki/Railway%20track | Technology | Trains | null |
Energy flow is the flow of energy through living things within an ecosystem. All living organisms can be organized into producers and consumers, and those producers and consumers can further be organized into a food chain. Each of the levels within the food chain is a trophic level. In order to more efficiently show the quantity of organisms at each trophic level, these food chains are then organized into trophic pyramids. The arrows in the food chain show that the energy flow is unidirectional, with the head of an arrow indicating the direction of energy flow; energy is lost as heat at each step along the way.
The unidirectional flow of energy and the successive loss of energy as it travels up the food web are patterns in energy flow that are governed by thermodynamics, which is the theory of energy exchange between systems. Trophic dynamics relates to thermodynamics because it deals with the transfer and transformation of energy (originating externally from the sun via solar radiation) to and among organisms.
Energetics and the carbon cycle
The first step in energetics is photosynthesis, where in water and carbon dioxide from the air are taken in with energy from the sun, and are converted into oxygen and glucose. Cellular respiration is the reverse reaction, wherein oxygen and sugar are taken in and release energy as they are converted back into carbon dioxide and water. The carbon dioxide and water produced by respiration can be recycled back into plants.
Energy loss can be measured either by efficiency (how much energy makes it to the next level), or by biomass (how much living material exists at those levels at one point in time, measured by standing crop). Of all the net primary productivity at the producer trophic level, in general only 10% goes to the next level, the primary consumers, then only 10% of that 10% goes on to the next trophic level, and so on up the food pyramid. Ecological efficiency may be anywhere from 5% to 20% depending on how efficient or inefficient that ecosystem is. This decrease in efficiency occurs because organisms need to perform cellular respiration to survive, and energy is lost as heat when cellular respiration is performed. That is also why there are fewer tertiary consumers than there are producers.
Primary production | Energy flow (ecology) | Wikipedia | 467 | 321382 | https://en.wikipedia.org/wiki/Energy%20flow%20%28ecology%29 | Biology and health sciences | Ecology | Biology |
A producer is any organism that performs photosynthesis. Producers are important because they convert energy from the sun into a storable and usable chemical form of energy, glucose, as well as oxygen. The producers themselves can use the energy stored in glucose to perform cellular respiration. Or, if the producer is consumed by herbivores in the next trophic level, some of the energy is passed on up the pyramid. The glucose stored within producers serves as food for consumers, and so it is only through producers that consumers are able to access the sun’s energy. Some examples of primary producers are algae, mosses, and other plants such as grasses, trees, and shrubs.
Chemosynthetic bacteria perform a process similar to photosynthesis, but instead of energy from the sun they use energy stored in chemicals like hydrogen sulfide. This process, referred to as chemosynthesis, usually occurs deep in the ocean at hydrothermal vents that produce heat and chemicals such as hydrogen, hydrogen sulfide and methane. Chemosynthetic bacteria can use the energy in the bonds of the hydrogen sulfide and oxygen to convert carbon dioxide to glucose, releasing water and sulfur in the process. Organisms that consume the chemosynthetic bacteria can take in the glucose and use oxygen to perform cellular respiration, similar to herbivores consuming producers.
One of the factors that controls primary production is the amount of energy that enters the producer(s), which can be measured using productivity. Only one percent of solar energy enters the producer, the rest bounces off or moves through. Gross primary productivity is the amount of energy the producer actually gets. Generally, 60% of the energy that enters the producer goes to the producer’s own respiration. The net primary productivity is the amount that the plant retains after the amount that it used for cellular respiration is subtracted. Another factor controlling primary production is organic/inorganic nutrient levels in the water or soil that the producer is living in. | Energy flow (ecology) | Wikipedia | 404 | 321382 | https://en.wikipedia.org/wiki/Energy%20flow%20%28ecology%29 | Biology and health sciences | Ecology | Biology |
Secondary production
Secondary production is the use of energy stored in plants converted by consumers to their own biomass. Different ecosystems have different levels of consumers, all end with one top consumer. Most energy is stored in organic matter of plants, and as the consumers eat these plants they take up this energy. This energy in the herbivores and omnivores is then consumed by carnivores. There is also a large amount of energy that is in primary production and ends up being waste or litter, referred to as detritus. The detrital food chain includes a large amount of microbes, macroinvertebrates, meiofauna, fungi, and bacteria. These organisms are consumed by omnivores and carnivores and account for a large amount of secondary production. Secondary consumers can vary widely in how efficient they are in consuming. The efficiency of energy being passed on to consumers is estimated to be around 10%. Energy flow through consumers differs in aquatic and terrestrial environments.
In aquatic environments
Heterotrophs contribute to secondary production and it is dependent on primary productivity and the net primary products. Secondary production is the energy that herbivores and decomposers use and thus depends on primary productivity. Primarily herbivores and decomposers consume all the carbon from two main organic sources in aquatic ecosystems, autochthonous and allochthonous. Autochthonous carbon comes from within the ecosystem and includes aquatic plants, algae and phytoplankton. Allochthonous carbon from outside the ecosystem is mostly dead organic matter from the terrestrial ecosystem entering the water. In stream ecosystems, approximately 66% of annual energy input can be washed downstream. The remaining amount is consumed and lost as heat.
In terrestrial environments | Energy flow (ecology) | Wikipedia | 357 | 321382 | https://en.wikipedia.org/wiki/Energy%20flow%20%28ecology%29 | Biology and health sciences | Ecology | Biology |
Secondary production is often described in terms of trophic levels, and while this can be useful in explaining relationships it overemphasizes the rarer interactions. Consumers often feed at multiple trophic levels. Energy transferred above the third trophic level is relatively unimportant. The assimilation efficiency can be expressed by the amount of food the consumer has eaten, how much the consumer assimilates and what is expelled as feces or urine. While a portion of the energy is used for respiration, another portion of the energy goes towards biomass in the consumer. There are two major food chains: The primary food chain is the energy coming from autotrophs and passed on to the consumers; and the second major food chain is when carnivores eat the herbivores or decomposers that consume the autotrophic energy. Consumers are broken down into primary consumers, secondary consumers and tertiary consumers. Carnivores have a much higher assimilation of energy, about 80% and herbivores have a much lower efficiency of approximately 20 to 50%. Energy in a system can be affected by animal emigration/immigration. The movements of organisms are significant in terrestrial ecosystems. Energetic consumption by herbivores in terrestrial ecosystems has a low range of ~3-7%. The flow of energy is similar in many terrestrial environments. The fluctuation in the amount of net primary product consumed by herbivores is generally low. This is in large contrast to aquatic environments of lakes and ponds where grazers have a much higher consumption of around ~33%. Ectotherms and endotherms have very different assimilation efficiencies.
Detritivores
Detritivores consume organic material that is decomposing and are in turn consumed by carnivores. Predator productivity is correlated with prey productivity. This confirms that the primary productivity in ecosystems affects all productivity following.
Detritus is a large portion of organic material in ecosystems. Organic material in temperate forests is mostly made up of dead plants, approximately 62%. | Energy flow (ecology) | Wikipedia | 413 | 321382 | https://en.wikipedia.org/wiki/Energy%20flow%20%28ecology%29 | Biology and health sciences | Ecology | Biology |
In an aquatic ecosystem, leaf matter that falls into streams gets wet and begins to leech organic material. This happens rather quickly and will attract microbes and invertebrates. The leaves can be broken down into large pieces called coarse particulate organic matter (CPOM). The CPOM is rapidly colonized by microbes. Meiofauna is extremely important to secondary production in stream ecosystems. Microbes breaking down and colonizing this leaf matter are very important to the detritovores. The detritovores make the leaf matter more edible by releasing compounds from the tissues; it ultimately helps soften them. As leaves decay nitrogen will decrease since cellulose and lignin in the leaves is difficult to break down. Thus the colonizing microbes bring in nitrogen in order to aid in the decomposition. Leaf breakdown can depend on initial nitrogen content, season, and species of trees. The species of trees can have variation when their leaves fall. Thus the breakdown of leaves is happening at different times, which is called a mosaic of microbial populations.
Species effect and diversity in an ecosystem can be analyzed through their performance and efficiency. In addition, secondary production in streams can be influenced heavily by detritus that falls into the streams; production of benthic fauna biomass and abundance decreased an additional 47–50% during a study of litter removal and exclusion.
Energy flow across ecosystems
Research has demonstrated that primary producers fix carbon at similar rates across ecosystems. Once carbon has been introduced into a system as a viable source of energy, the mechanisms that govern the flow of energy to higher trophic levels vary across ecosystems. Among aquatic and terrestrial ecosystems, patterns have been identified that can account for this variation and have been divided into two main pathways of control: top-down and bottom-up. The acting mechanisms within each pathway ultimately regulate community and trophic level structure within an ecosystem to varying degrees. Bottom-up controls involve mechanisms that are based on resource quality and availability, which control primary productivity and the subsequent flow of energy and biomass to higher trophic levels. Top-down controls involve mechanisms that are based on consumption by consumers. These mechanisms control the rate of energy transfer from one trophic level to another as herbivores or predators feed on lower trophic levels. | Energy flow (ecology) | Wikipedia | 459 | 321382 | https://en.wikipedia.org/wiki/Energy%20flow%20%28ecology%29 | Biology and health sciences | Ecology | Biology |
Aquatic vs terrestrial ecosystems
Much variation in the flow of energy is found within each type of ecosystem, creating a challenge in identifying variation between ecosystem types. In a general sense, the flow of energy is a function of primary productivity with temperature, water availability, and light availability. For example, among aquatic ecosystems, higher rates of production are usually found in large rivers and shallow lakes than in deep lakes and clear headwater streams. Among terrestrial ecosystems, marshes, swamps, and tropical rainforests have the highest primary production rates, whereas tundra and alpine ecosystems have the lowest. The relationships between primary production and environmental conditions have helped account for variation within ecosystem types, allowing ecologists to demonstrate that energy flows more efficiently through aquatic ecosystems than terrestrial ecosystems due to the various bottom-up and top-down controls in play.
Bottom-up
The strength of bottom-up controls on energy flow are determined by the nutritional quality, size, and growth rates of primary producers in an ecosystem. Photosynthetic material is typically rich in nitrogen (N) and phosphorus (P) and supplements the high herbivore demand for N and P across all ecosystems. Aquatic primary production is dominated by small, single-celled phytoplankton that are mostly composed of photosynthetic material, providing an efficient source of these nutrients for herbivores. In contrast, multi-cellular terrestrial plants contain many large supporting cellulose structures of high carbon but low nutrient value. Because of this structural difference, aquatic primary producers have less biomass per photosynthetic tissue stored within the aquatic ecosystem than in the forests and grasslands of terrestrial ecosystems. This low biomass relative to photosynthetic material in aquatic ecosystems allows for a more efficient turnover rate compared to terrestrial ecosystems. As phytoplankton are consumed by herbivores, their enhanced growth and reproduction rates sufficiently replace lost biomass and, in conjunction with their nutrient dense quality, support greater secondary production. | Energy flow (ecology) | Wikipedia | 389 | 321382 | https://en.wikipedia.org/wiki/Energy%20flow%20%28ecology%29 | Biology and health sciences | Ecology | Biology |
Additional factors impacting primary production includes inputs of N and P, which occurs at a greater magnitude in aquatic ecosystems. These nutrients are important in stimulating plant growth and, when passed to higher trophic levels, stimulate consumer biomass and growth rate. If either of these nutrients are in short supply, they can limit overall primary production. Within lakes, P tends to be the greater limiting nutrient while both N and P limit primary production in rivers. Due to these limiting effects, nutrient inputs can potentially alleviate the limitations on net primary production of an aquatic ecosystem. Allochthonous material washed into an aquatic ecosystem introduces N and P as well as energy in the form of carbon molecules that are readily taken up by primary producers. Greater inputs and increased nutrient concentrations support greater net primary production rates, which in turn supports greater secondary production.
Top-down
Top-down mechanisms exert greater control on aquatic primary producers due to the roll of consumers within an aquatic food web. Among consumers, herbivores can mediate the impacts of trophic cascades by bridging the flow of energy from primary producers to predators in higher trophic levels. Across ecosystems, there is a consistent association between herbivore growth and producer nutritional quality. However, in aquatic ecosystems, primary producers are consumed by herbivores at a rate four times greater than in terrestrial ecosystems. Although this topic is highly debated, researchers have attributed the distinction in herbivore control to several theories, including producer to consumer size ratios and herbivore selectivity.
Modeling of top-down controls on primary producers suggests that the greatest control on the flow of energy occurs when the size ratio of consumer to primary producer is the highest. The size distribution of organisms found within a single trophic level in aquatic systems is much narrower than that of terrestrial systems. On land, the consumer size ranges from smaller than the plant it consumes, such as an insect, to significantly larger, such as an ungulate, while in aquatic systems, consumer body size within a trophic level varies much less and is strongly correlated with trophic position. As a result, the size difference between producers and consumers is consistently larger in aquatic environments than on land, resulting in stronger herbivore control over aquatic primary producers. | Energy flow (ecology) | Wikipedia | 456 | 321382 | https://en.wikipedia.org/wiki/Energy%20flow%20%28ecology%29 | Biology and health sciences | Ecology | Biology |
Herbivores can potentially control the fate of organic matter as it is cycled through the food web. Herbivores tend to select nutritious plants while avoiding plants with structural defense mechanisms. Like support structures, defense structures are composed of nutrient poor, high carbon cellulose. Access to nutritious food sources enhances herbivore metabolism and energy demands, leading to greater removal of primary producers. In aquatic ecosystems, phytoplankton are highly nutritious and generally lack defense mechanisms. This results in greater top-down control because consumed plant matter is quickly released back into the system as labile organic waste. In terrestrial ecosystems, primary producers are less nutritionally dense and are more likely to contain defense structures. Because herbivores prefer nutritionally dense plants and avoid plants or plant parts with defense structures, a greater amount of plant matter is left unconsumed within the ecosystem. Herbivore avoidance of low-quality plant matter may be why terrestrial systems exhibit weaker top-down control on the flow of energy. | Energy flow (ecology) | Wikipedia | 210 | 321382 | https://en.wikipedia.org/wiki/Energy%20flow%20%28ecology%29 | Biology and health sciences | Ecology | Biology |
In economics, perfect information (sometimes referred to as "no hidden information") is a feature of perfect competition. With perfect information in a market, all consumers and producers have complete and instantaneous knowledge of all market prices, their own utility, and own cost functions.
In game theory, a sequential game has perfect information if each player, when making any decision, is perfectly informed of all the events that have previously occurred, including the "initialization event" of the game (e.g. the starting hands of each player in a card game).
Perfect information is importantly different from complete information, which implies common knowledge of each player's utility functions, payoffs, strategies and "types". A game with perfect information may or may not have complete information.
Games where some aspect of play is hidden from opponents – such as the cards in poker and bridge – are examples of games with imperfect information.
Examples
Chess is an example of a game with perfect information, as each player can see all the pieces on the board at all times. Other games with perfect information include tic-tac-toe, Reversi, checkers, and Go.
Academic literature has not produced consensus on a standard definition of perfect information which defines whether games with chance, but no secret information, and games with simultaneous moves are games of perfect information.
Games which are sequential (players alternate in moving) and which have chance events (with known probabilities to all players) but no secret information, are sometimes considered games of perfect information. This includes games such as backgammon and Monopoly. But there are some academic papers which do not regard such games as games of perfect information because the results of chance themselves are unknown prior to them occurring.
Games with simultaneous moves are generally not considered games of perfect information. This is because each player holds information which is secret, and must play a move without knowing the opponent's secret information. Nevertheless, some such games are symmetrical, and fair. An example of a game in this category includes rock paper scissors. | Perfect information | Wikipedia | 411 | 321438 | https://en.wikipedia.org/wiki/Perfect%20information | Mathematics | Game theory | null |
The thoracic diaphragm, or simply the diaphragm (; ), is a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity. The diaphragm is the most important muscle of respiration, and separates the thoracic cavity, containing the heart and lungs, from the abdominal cavity: as the diaphragm contracts, the volume of the thoracic cavity increases, creating a negative pressure there, which draws air into the lungs. Its high oxygen consumption is noted by the many mitochondria and capillaries present; more than in any other skeletal muscle.
The term diaphragm in anatomy, created by Gerard of Cremona, can refer to other flat structures such as the urogenital diaphragm or pelvic diaphragm, but "the diaphragm" generally refers to the thoracic diaphragm. In humans, the diaphragm is slightly asymmetric—its right half is higher up (superior) to the left half, since the large liver rests beneath the right half of the diaphragm. There is also speculation that the diaphragm is lower on the other side due to heart's presence.
Other mammals have diaphragms, and other vertebrates such as amphibians and reptiles have diaphragm-like structures, but important details of the anatomy may vary, such as the position of the lungs in the thoracic cavity.
Structure
The diaphragm is an upward curved, c-shaped structure of muscle and fibrous tissue that separates the thoracic cavity from the abdomen. The superior surface of the dome forms the floor of the thoracic cavity, and the inferior surface the roof of the abdominal cavity.
As a dome, the diaphragm has peripheral attachments to structures that make up the abdominal and chest walls. The muscle fibres from these attachments converge in a central tendon, which forms the crest of the dome. Its peripheral part consists of muscular fibers that take origin from the circumference of the inferior thoracic aperture and converge to be inserted into a central tendon. | Thoracic diaphragm | Wikipedia | 457 | 321567 | https://en.wikipedia.org/wiki/Thoracic%20diaphragm | Biology and health sciences | Respiratory system | Biology |
The muscle fibres of the diaphragm radiate outward from the central tendon. While the diaphragm is one muscle, it is composed of two distinct muscle regions: the costal, which serves as the driver in the work of breathing, and crural diaphragm, which serves as an "anchor;" attaching the muscle to the lower ribs and lumbar vertebrae. The costal diaphragm is further divided into ventral, medial, and dorsal costal portions.
The vertebral part of the diaphragm arises from the crura and arcuate ligaments. Right crus arises from L1-L3 vertebral bodies and their intervertebral discs. Smaller left crus arises from L1, L2 vertebral bodies and their intervertebral discs. Medial arcuate ligament arises from the fascia thickening from body of L2 vertebrae to transverse process of L1 vertebrae, crossing over the body of the psoas major muscle. The lateral arcuate ligament arises from the transverse process of L1 vertebrae and is attached laterally to the 12th rib. The lateral arcuate ligament also arises from fascia thickening that covers the quadratus lumborum muscle. The median arcuate ligament arises from the fibrous parts of right and left crura where descending thoracic aorta passes behind it. No diaphragmatic muscle arises from the median arcuate ligament. Both adrenal glands lie near the diaphragmatic crus and arcuate ligament.
The costal part of diaphragm arises from the lower four ribs (7 to 10) costal cartilages.
The central tendon of the diaphragm is a thin but strong aponeurosis near the center of the vault formed by the muscle, closer to the front than to the back of the thorax. The central part of the tendon is attached above to pericardium. The both sides of the posterior fibres are attached to paracolic gutters (the curving of ribs before attaching to both sides of the vertebral bodies).
Openings | Thoracic diaphragm | Wikipedia | 443 | 321567 | https://en.wikipedia.org/wiki/Thoracic%20diaphragm | Biology and health sciences | Respiratory system | Biology |
There are a number of openings in the diaphragm through which structures pass between the thorax and abdomen. There are three large openings — one for the aorta (aortic hiatus), one for the esophagus (esophageal hiatus), and one for the inferior vena cava (the caval opening), as well as a series of smaller openings.
The inferior vena cava passes through the caval opening, a quadrilateral opening at the junction of the right and middle leaflets of the central tendon, so that its margins are tendinous. Surrounded by tendons, the opening is stretched open every time inspiration occurs. However, there has been argument that the caval opening actually constricts during inspiration. Since thoracic pressure decreases upon inspiration and draws the caval blood upwards toward the right atrium, increasing the size of the opening allows more blood to return to the heart, maximizing the efficacy of lowered thoracic pressure returning blood to the heart. The aorta does not pierce the diaphragm but rather passes behind it in between the left and right crus.
There are several structures that pierce through the diaphragm, including: left phrenic nerve pierces through the central tendon, greater, lesser, and least thoracic splanchnic nerves pierces through bilateral crura, and lymphatic vessels that pierce throughout the diaphragm, especially behind the diaphragm.
Nerve supply
The diaphragm is primarily innervated by the phrenic nerve which is formed from the cervical nerves C3, C4 and C5. While the central portion of the diaphragm sends sensory afferents via the phrenic nerve, the peripheral portions of the diaphragm send sensory afferents via the intercostal (T5–T11) and subcostal nerves (T12).
Blood supply
Arteries and veins above and below the diaphragm supply and drain blood.
From above, the diaphragm receives blood from branches of the internal thoracic arteries, namely the pericardiacophrenic artery and musculophrenic artery; from the superior phrenic arteries, which arise directly from the thoracic aorta; and from the lower internal intercostal arteries. From below, the inferior phrenic arteries supply the diaphragm. | Thoracic diaphragm | Wikipedia | 501 | 321567 | https://en.wikipedia.org/wiki/Thoracic%20diaphragm | Biology and health sciences | Respiratory system | Biology |
The diaphragm drains blood into the brachiocephalic veins, azygos veins, and veins that drain into the inferior vena cava and left suprarenal vein.
Variation
The sternal portion of the muscle is sometimes wanting and more rarely defects occur in the lateral part of the central tendon or adjoining muscle fibers.
Development
The thoracic diaphragm develops during embryogenesis, beginning in the third week after fertilization with two processes known as transverse folding and longitudinal folding. The septum transversum, the primitive central tendon of the diaphragm, originates at the rostral pole of the embryo and is relocated during longitudinal folding to the ventral thoracic region. Transverse folding brings the body wall anteriorly to enclose the gut and body cavities. The pleuroperitoneal membrane and body wall myoblasts, from somatic lateral plate mesoderm, meet the septum transversum to close off the pericardio-peritoneal canals on either side of the presumptive esophagus, forming a barrier that separates the peritoneal and pleuropericardial cavities. Furthermore, dorsal mesenchyme surrounding the presumptive esophagus form the muscular crura of the diaphragm.
Because the earliest element of the embryological diaphragm, the septum transversum, forms in the cervical region, the phrenic nerve that innervates the diaphragm originates from the cervical spinal cord (C3,4, and 5). As the septum transversum descends inferiorly, the phrenic nerve follows, accounting for its circuitous route from the upper cervical vertebrae, around the pericardium, finally to innervate the diaphragm.
Function
The diaphragm is the main muscle of respiration and functions in breathing. During inhalation, the diaphragm contracts and moves in the inferior direction, enlarging the volume of the thoracic cavity and reducing intra-thoracic pressure (the external intercostal muscles also participate in this enlargement), forcing the lungs to expand. In other words, the diaphragm's movement downwards creates a partial vacuum in the thoracic cavity, which forces the lungs to expand to fill the void, drawing air in the process. | Thoracic diaphragm | Wikipedia | 496 | 321567 | https://en.wikipedia.org/wiki/Thoracic%20diaphragm | Biology and health sciences | Respiratory system | Biology |
Cavity expansion happens in two extremes, along with intermediary forms. When the lower ribs are stabilized and the central tendon of the diaphragm is mobile, a contraction brings the insertion (central tendon) towards the origins and pushes the lower cavity towards the pelvis, allowing the thoracic cavity to expand downward. This is often called belly breathing. When the central tendon is stabilized and the lower ribs are mobile, a contraction lifts the origins (ribs) up towards the insertion (central tendon) which works in conjunction with other muscles to allow the ribs to slide and the thoracic cavity to expand laterally and upwards.
When the diaphragm relaxes (moves in the superior direction), air is exhaled by elastic recoil process of the lung and the tissues lining the thoracic cavity. Assisting this function with muscular effort (called forced exhalation) involves the internal intercostal muscles used in conjunction with the abdominal muscles, which act as an antagonist paired with the diaphragm's contraction. Diaphragm dysfunction is a well-known factor associated with various complications in patients, such as prolonged respiratory failure, difficulties in weaning from mechanical ventilation, extended hospitalization, increased morbidity, and mortality. Studies have reported that a thin diaphragm leads to greater lung compliance, which can contribute to respiratory failure. Furthermore, reduction in diaphragm thickness during the early stages of disease can serve as a prognostic marker in sepsis patients, and COVID-19 patients.
The diaphragm is also involved in non-respiratory functions. It helps to expel vomit, feces, and urine from the body by increasing intra-abdominal pressure, aids in childbirth, and prevents acid reflux by exerting pressure on the esophagus as it passes through the esophageal hiatus.
In some non-human animals, the diaphragm is not crucial for breathing; a cow, for instance, can survive fairly asymptomatically with diaphragmatic paralysis as long as no massive aerobic metabolic demands are made of it.
Clinical significance | Thoracic diaphragm | Wikipedia | 436 | 321567 | https://en.wikipedia.org/wiki/Thoracic%20diaphragm | Biology and health sciences | Respiratory system | Biology |
Paralysis
If either the phrenic nerve, cervical spine or brainstem is damaged, this will sever the nervous supply to the diaphragm. The most common damage to the phrenic nerve is by bronchial cancer, which usually only affects one side of the diaphragm. Other causes include Guillain–Barré syndrome and systemic lupus erythematosus.
Herniation
A hiatus hernia is a hernia in which parts of the lower esophagus or stomach that are normally in the abdomen pass abnormally through the diaphragm and are present in the thorax. Hernias are described as rolling, in which the hernia is beside the oesophagus, or sliding, in which the hernia directly involves the esophagus. These hernias are implicated in the development of reflux, as the different pressures between the thorax and abdomen normally act to keep pressure on the esophageal hiatus. With herniation, this pressure is no longer present, and the angle between the cardia of the stomach and the oesophagus disappears. Not all hiatus hernias cause symptoms, although almost all people with Barrett's oesophagus or oesophagitis have a hiatus hernia.
Hernias may also occur as a result of congenital malformation, a congenital diaphragmatic hernia. When the pleuroperitoneal membranes fail to fuse, the diaphragm does not act as an effective barrier between the abdomen and thorax. Herniation is usually of the left, and commonly through the posterior lumbocostal triangle, although rarely through the anterior foramen of Morgagni. The contents of the abdomen, including the intestines, may be present in the thorax, which may impact development of the growing lungs and lead to hypoplasia. This condition is present in 0.8 - 5/10,000 births. A large herniation has high mortality rate, and requires immediate surgical repair.
Imaging | Thoracic diaphragm | Wikipedia | 425 | 321567 | https://en.wikipedia.org/wiki/Thoracic%20diaphragm | Biology and health sciences | Respiratory system | Biology |
Due to its position separating the thorax and abdomen, fluid abnormally present in the thorax, or air abnormally present in the abdomen, may collect on one side of the diaphragm. An X-ray may reveal this. Pleural effusion, in which there is fluid abnormally present between the two pleurae of the lungs, is detected by an X-ray of the chest, showing fluid collecting in the angle between the ribs and diaphragm. An X-ray may also be used to reveal a pneumoperitoneum, in which there is gas in the abdomen.
An X-ray may also be used to check for herniation.
Significance in strength training
The adoption of a deeper breathing pattern typically occurs during physical exercise in order to facilitate greater oxygen absorption. During this process the diaphragm more consistently adopts a lower position within the body's core. In addition to its primary role in breathing, the diaphragm also plays a secondary role in strengthening the posture of the core. This is especially evident during deep breathing where its generally lower position increases intra-abdominal pressure, which serves to strengthen the lumbar spine.
The key to real core stabilization is to maintain the increased IAP while going through normal breathing cycles. [...] The diaphragm then performs its breathing function at a lower position to facilitate a higher IAP.
Therefore, if a person's diaphragm position is lower in general, through deep breathing, then this assists the strengthening of their core during that period. This can be an aid in strength training and other forms of athletic endeavour. For this reason, taking a deep breath or adopting a deeper breathing pattern is typically recommended when lifting heavy weights.
Other animals
The existence of a membrane separating the pharynx from the stomach can be traced widely among the chordates. Thus the model organism, the marine chordate lancelet, possesses an atriopore by which water exits the pharynx, which has been claimed (and disputed) to be homologous to structures in ascidians and hagfishes. The tunicate epicardium separates digestive organs from the pharynx and heart, but the anus returns to the upper compartment to discharge wastes through an outgoing siphon. | Thoracic diaphragm | Wikipedia | 473 | 321567 | https://en.wikipedia.org/wiki/Thoracic%20diaphragm | Biology and health sciences | Respiratory system | Biology |
Thus the diaphragm emerges in the context of a body plan that separated an upper feeding compartment from a lower digestive tract, but the point at which it originates is a matter of definition. Structures in fish, amphibians, reptiles, and birds have been called diaphragms, but it has been argued that these structures are not homologous. For instance, the alligator diaphragmaticus muscle does not insert on the esophagus and does not affect pressure of the lower esophageal sphincter. The lungs are located in the abdominal compartment of amphibians and reptiles, so that contraction of the diaphragm expels air from the lungs rather than drawing it into them. In birds and mammals, lungs are located above the diaphragm. The presence of an exceptionally well-preserved fossil of Sinosauropteryx, with lungs located beneath the diaphragm as in crocodiles, has been used to argue that dinosaurs could not have sustained an active warm-blooded physiology, or that birds could not have evolved from dinosaurs. An explanation for this (put forward in 1905), is that lungs originated beneath the diaphragm, but as the demands for respiration increased in warm-blooded birds and mammals, natural selection came to favor the parallel evolution of the herniation of the lungs from the abdominal cavity in both lineages.
However, birds lack diaphragms. They do not breathe in the same way as mammals and do not rely on creating a negative pressure in the thoracic cavity, at least not to the same extent. They rely on a rocking motion of the keel of the sternum to create local areas of reduced pressure to supply thin, membranous airsacs cranially and caudally to the fixed-volume, non-expansive lungs. A complicated system of valves and air sacs cycles air constantly over the absorption surfaces of the lungs so allowing maximal efficiency of gaseous exchange. Thus, birds do not have the reciprocal tidal breathing flow of mammals. On careful dissection, around eight air sacs can be clearly seen. They extend quite far caudally into the abdomen. | Thoracic diaphragm | Wikipedia | 446 | 321567 | https://en.wikipedia.org/wiki/Thoracic%20diaphragm | Biology and health sciences | Respiratory system | Biology |
A tessellation or tiling is the covering of a surface, often a plane, using one or more geometric shapes, called tiles, with no overlaps and no gaps. In mathematics, tessellation can be generalized to higher dimensions and a variety of geometries.
A periodic tiling has a repeating pattern. Some special kinds include regular tilings with regular polygonal tiles all of the same shape, and semiregular tilings with regular tiles of more than one shape and with every corner identically arranged. The patterns formed by periodic tilings can be categorized into 17 wallpaper groups. A tiling that lacks a repeating pattern is called "non-periodic". An aperiodic tiling uses a small set of tile shapes that cannot form a repeating pattern (an aperiodic set of prototiles). A tessellation of space, also known as a space filling or honeycomb, can be defined in the geometry of higher dimensions.
A real physical tessellation is a tiling made of materials such as cemented ceramic squares or hexagons. Such tilings may be decorative patterns, or may have functions such as providing durable and water-resistant pavement, floor, or wall coverings. Historically, tessellations were used in Ancient Rome and in Islamic art such as in the Moroccan architecture and decorative geometric tiling of the Alhambra palace. In the twentieth century, the work of M. C. Escher often made use of tessellations, both in ordinary Euclidean geometry and in hyperbolic geometry, for artistic effect. Tessellations are sometimes employed for decorative effect in quilting. Tessellations form a class of patterns in nature, for example in the arrays of hexagonal cells found in honeycombs.
History
Tessellations were used by the Sumerians (about 4000 BC) in building wall decorations formed by patterns of clay tiles.
Decorative mosaic tilings made of small squared blocks called tesserae were widely employed in classical antiquity, sometimes displaying geometric patterns.
In 1619, Johannes Kepler made an early documented study of tessellations. He wrote about regular and semiregular tessellations in his ; he was possibly the first to explore and to explain the hexagonal structures of honeycomb and snowflakes. | Tessellation | Wikipedia | 465 | 321671 | https://en.wikipedia.org/wiki/Tessellation | Mathematics | Geometry | null |
Some two hundred years later in 1891, the Russian crystallographer Yevgraf Fyodorov proved that every periodic tiling of the plane features one of seventeen different groups of isometries. Fyodorov's work marked the unofficial beginning of the mathematical study of tessellations. Other prominent contributors include Alexei Vasilievich Shubnikov and Nikolai Belov in their book Colored Symmetry (1964), and Heinrich Heesch and Otto Kienzle (1963).
Etymology
In Latin, tessella is a small cubical piece of clay, stone, or glass used to make mosaics. The word "tessella" means "small square" (from tessera, square, which in turn is from the Greek word τέσσερα for four). It corresponds to the everyday term tiling, which refers to applications of tessellations, often made of glazed clay.
Overview
Tessellation in two dimensions, also called planar tiling, is a topic in geometry that studies how shapes, known as tiles, can be arranged to fill a plane without any gaps, according to a given set of rules. These rules can be varied. Common ones are that there must be no gaps between tiles, and that no corner of one tile can lie along the edge of another. The tessellations created by bonded brickwork do not obey this rule. Among those that do, a regular tessellation has both identical regular tiles and identical regular corners or vertices, having the same angle between adjacent edges for every tile. There are only three shapes that can form such regular tessellations: the equilateral triangle, square and the regular hexagon. Any one of these three shapes can be duplicated infinitely to fill a plane with no gaps.
Many other types of tessellation are possible under different constraints. For example, there are eight types of semi-regular tessellation, made with more than one kind of regular polygon but still having the same arrangement of polygons at every corner. Irregular tessellations can also be made from other shapes such as pentagons, polyominoes and in fact almost any kind of geometric shape. The artist M. C. Escher is famous for making tessellations with irregular interlocking tiles, shaped like animals and other natural objects. If suitable contrasting colours are chosen for the tiles of differing shape, striking patterns are formed, and these can be used to decorate physical surfaces such as church floors. | Tessellation | Wikipedia | 508 | 321671 | https://en.wikipedia.org/wiki/Tessellation | Mathematics | Geometry | null |
More formally, a tessellation or tiling is a cover of the Euclidean plane by a countable number of closed sets, called tiles, such that the tiles intersect only on their boundaries. These tiles may be polygons or any other shapes. Many tessellations are formed from a finite number of prototiles in which all tiles in the tessellation are congruent to the given prototiles. If a geometric shape can be used as a prototile to create a tessellation, the shape is said to tessellate or to tile the plane. The Conway criterion is a sufficient, but not necessary, set of rules for deciding whether a given shape tiles the plane periodically without reflections: some tiles fail the criterion, but still tile the plane. No general rule has been found for determining whether a given shape can tile the plane or not, which means there are many unsolved problems concerning tessellations.
Mathematically, tessellations can be extended to spaces other than the Euclidean plane. The Swiss geometer Ludwig Schläfli pioneered this by defining polyschemes, which mathematicians nowadays call polytopes. These are the analogues to polygons and polyhedra in spaces with more dimensions. He further defined the Schläfli symbol notation to make it easy to describe polytopes. For example, the Schläfli symbol for an equilateral triangle is {3}, while that for a square is {4}. The Schläfli notation makes it possible to describe tilings compactly. For example, a tiling of regular hexagons has three six-sided polygons at each vertex, so its Schläfli symbol is {6,3}.
Other methods also exist for describing polygonal tilings. When the tessellation is made of regular polygons, the most common notation is the vertex configuration, which is simply a list of the number of sides of the polygons around a vertex. The square tiling has a vertex configuration of 4.4.4.4, or 44. The tiling of regular hexagons is noted 6.6.6, or 63.
In mathematics
Introduction to tessellations | Tessellation | Wikipedia | 454 | 321671 | https://en.wikipedia.org/wiki/Tessellation | Mathematics | Geometry | null |
Mathematicians use some technical terms when discussing tilings. An edge is the intersection between two bordering tiles; it is often a straight line. A vertex is the point of intersection of three or more bordering tiles. Using these terms, an isogonal or vertex-transitive tiling is a tiling where every vertex point is identical; that is, the arrangement of polygons about each vertex is the same. The fundamental region is a shape such as a rectangle that is repeated to form the tessellation. For example, a regular tessellation of the plane with squares has a meeting of four squares at every vertex.
The sides of the polygons are not necessarily identical to the edges of the tiles. An edge-to-edge tiling is any polygonal tessellation where adjacent tiles only share one full side, i.e., no tile shares a partial side or more than one side with any other tile. In an edge-to-edge tiling, the sides of the polygons and the edges of the tiles are the same. The familiar "brick wall" tiling is not edge-to-edge because the long side of each rectangular brick is shared with two bordering bricks.
A normal tiling is a tessellation for which every tile is topologically equivalent to a disk, the intersection of any two tiles is a connected set or the empty set, and all tiles are uniformly bounded. This means that a single circumscribing radius and a single inscribing radius can be used for all the tiles in the whole tiling; the condition disallows tiles that are pathologically long or thin.
A is a tessellation in which all tiles are congruent; it has only one prototile. A particularly interesting type of monohedral tessellation is the spiral monohedral tiling. The first spiral monohedral tiling was discovered by Heinz Voderberg in 1936; the Voderberg tiling has a unit tile that is a nonconvex enneagon. The Hirschhorn tiling, published by Michael D. Hirschhorn and D. C. Hunt in 1985, is a pentagon tiling using irregular pentagons: regular pentagons cannot tile the Euclidean plane as the internal angle of a regular pentagon, , is not a divisor of 2. | Tessellation | Wikipedia | 475 | 321671 | https://en.wikipedia.org/wiki/Tessellation | Mathematics | Geometry | null |
An isohedral tiling is a special variation of a monohedral tiling in which all tiles belong to the same transitivity class, that is, all tiles are transforms of the same prototile under the symmetry group of the tiling. If a prototile admits a tiling, but no such tiling is isohedral, then the prototile is called anisohedral and forms anisohedral tilings.
A regular tessellation is a highly symmetric, edge-to-edge tiling made up of regular polygons, all of the same shape. There are only three regular tessellations: those made up of equilateral triangles, squares, or regular hexagons. All three of these tilings are isogonal and monohedral.
A semi-regular (or Archimedean) tessellation uses more than one type of regular polygon in an isogonal arrangement. There are eight semi-regular tilings (or nine if the mirror-image pair of tilings counts as two). These can be described by their vertex configuration; for example, a semi-regular tiling using squares and regular octagons has the vertex configuration 4.82 (each vertex has one square and two octagons). Many non-edge-to-edge tilings of the Euclidean plane are possible, including the family of Pythagorean tilings, tessellations that use two (parameterised) sizes of square, each square touching four squares of the other size. An edge tessellation is one in which each tile can be reflected over an edge to take up the position of a neighbouring tile, such as in an array of equilateral or isosceles triangles.
Wallpaper groups
Tilings with translational symmetry in two independent directions can be categorized by wallpaper groups, of which 17 exist. It has been claimed that all seventeen of these groups are represented in the Alhambra palace in Granada, Spain. Although this is disputed, the variety and sophistication of the Alhambra tilings have interested modern researchers. Of the three regular tilings two are in the p6m wallpaper group and one is in p4m. Tilings in 2-D with translational symmetry in just one direction may be categorized by the seven frieze groups describing the possible frieze patterns. Orbifold notation can be used to describe wallpaper groups of the Euclidean plane.
Aperiodic tilings | Tessellation | Wikipedia | 501 | 321671 | https://en.wikipedia.org/wiki/Tessellation | Mathematics | Geometry | null |
Penrose tilings, which use two different quadrilateral prototiles, are the best known example of tiles that forcibly create non-periodic patterns. They belong to a general class of aperiodic tilings, which use tiles that cannot tessellate periodically. The recursive process of substitution tiling is a method of generating aperiodic tilings. One class that can be generated in this way is the rep-tiles; these tilings have unexpected self-replicating properties. Pinwheel tilings are non-periodic, using a rep-tile construction; the tiles appear in infinitely many orientations. It might be thought that a non-periodic pattern would be entirely without symmetry, but this is not so. Aperiodic tilings, while lacking in translational symmetry, do have symmetries of other types, by infinite repetition of any bounded patch of the tiling and in certain finite groups of rotations or reflections of those patches. A substitution rule, such as can be used to generate Penrose patterns using assemblies of tiles called rhombs, illustrates scaling symmetry. A Fibonacci word can be used to build an aperiodic tiling, and to study quasicrystals, which are structures with aperiodic order.
Wang tiles are squares coloured on each edge, and placed so that abutting edges of adjacent tiles have the same colour; hence they are sometimes called Wang dominoes. A suitable set of Wang dominoes can tile the plane, but only aperiodically. This is known because any Turing machine can be represented as a set of Wang dominoes that tile the plane if, and only if, the Turing machine does not halt. Since the halting problem is undecidable, the problem of deciding whether a Wang domino set can tile the plane is also undecidable.
Truchet tiles are square tiles decorated with patterns so they do not have rotational symmetry; in 1704, Sébastien Truchet used a square tile split into two triangles of contrasting colours. These can tile the plane either periodically or randomly.
An einstein tile is a single shape that forces aperiodic tiling. The first such tile, dubbed a "hat", was discovered in 2023 by David Smith, a hobbyist mathematician. The discovery is under professional review and, upon confirmation, will be credited as solving a longstanding mathematical problem.
Tessellations and colour | Tessellation | Wikipedia | 488 | 321671 | https://en.wikipedia.org/wiki/Tessellation | Mathematics | Geometry | null |
Sometimes the colour of a tile is understood as part of the tiling; at other times arbitrary colours may be applied later. When discussing a tiling that is displayed in colours, to avoid ambiguity, one needs to specify whether the colours are part of the tiling or just part of its illustration. This affects whether tiles with the same shape, but different colours, are considered identical, which in turn affects questions of symmetry. The four colour theorem states that for every tessellation of a normal Euclidean plane, with a set of four available colours, each tile can be coloured in one colour such that no tiles of equal colour meet at a curve of positive length. The colouring guaranteed by the four colour theorem does not generally respect the symmetries of the tessellation. To produce a colouring that does, it is necessary to treat the colours as part of the tessellation. Here, as many as seven colours may be needed, as demonstrated in the image at left.
Tessellations with polygons
Next to the various tilings by regular polygons, tilings by other polygons have also been studied.
Any triangle or quadrilateral (even non-convex) can be used as a prototile to form a monohedral tessellation, often in more than one way. Copies of an arbitrary quadrilateral can form a tessellation with translational symmetry and 2-fold rotational symmetry with centres at the midpoints of all sides. For an asymmetric quadrilateral this tiling belongs to wallpaper group p2. As fundamental domain we have the quadrilateral. Equivalently, we can construct a parallelogram subtended by a minimal set of translation vectors, starting from a rotational centre. We can divide this by one diagonal, and take one half (a triangle) as fundamental domain. Such a triangle has the same area as the quadrilateral and can be constructed from it by cutting and pasting.
If only one shape of tile is allowed, tilings exist with convex N-gons for N equal to 3, 4, 5, and 6. For , see Pentagonal tiling, for , see Hexagonal tiling, for , see Heptagonal tiling and for , see octagonal tiling.
With non-convex polygons, there are far fewer limitations in the number of sides, even if only one shape is allowed. | Tessellation | Wikipedia | 493 | 321671 | https://en.wikipedia.org/wiki/Tessellation | Mathematics | Geometry | null |
Polyominoes are examples of tiles that are either convex of non-convex, for which various combinations, rotations, and reflections can be used to tile a plane. For results on tiling the plane with polyominoes, see Polyomino § Uses of polyominoes.
Voronoi tilings
Voronoi or Dirichlet tilings are tessellations where each tile is defined as the set of points closest to one of the points in a discrete set of defining points. (Think of geographical regions where each region is defined as all the points closest to a given city or post office.) The Voronoi cell for each defining point is a convex polygon. The Delaunay triangulation is a tessellation that is the dual graph of a Voronoi tessellation. Delaunay triangulations are useful in numerical simulation, in part because among all possible triangulations of the defining points, Delaunay triangulations maximize the minimum of the angles formed by the edges. Voronoi tilings with randomly placed points can be used to construct random tilings of the plane.
Tessellations in higher dimensions
Tessellation can be extended to three dimensions. Certain polyhedra can be stacked in a regular crystal pattern to fill (or tile) three-dimensional space, including the cube (the only Platonic polyhedron to do so), the rhombic dodecahedron, the truncated octahedron, and triangular, quadrilateral, and hexagonal prisms, among others. Any polyhedron that fits this criterion is known as a plesiohedron, and may possess between 4 and 38 faces. Naturally occurring rhombic dodecahedra are found as crystals of andradite (a kind of garnet) and fluorite.
Tessellations in three or more dimensions are called honeycombs. In three dimensions there is just one regular honeycomb, which has eight cubes at each polyhedron vertex. Similarly, in three dimensions there is just one quasiregular honeycomb, which has eight tetrahedra and six octahedra at each polyhedron vertex. However, there are many possible semiregular honeycombs in three dimensions. Uniform honeycombs can be constructed using the Wythoff construction.
The Schmitt-Conway biprism is a convex polyhedron with the property of tiling space only aperiodically. | Tessellation | Wikipedia | 504 | 321671 | https://en.wikipedia.org/wiki/Tessellation | Mathematics | Geometry | null |
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