Oklahoma is a state in the South Central region of the United States, bordered by Kansas on the north, Missouri on the northeast, Arkansas on the east, Texas on the south, New Mexico on the west, Colorado on the northwest. It is the 28th-most populous of the fifty United States; the state's name is derived from the Choctaw words okla and humma, meaning "red people". It is known informally by its nickname, "The Sooner State", in reference to the non-Native settlers who staked their claims on land before the official opening date of lands in the western Oklahoma Territory or before the Indian Appropriations Act of 1889, which increased European-American settlement in the eastern Indian Territory. Oklahoma Territory and Indian Territory were merged into the State of Oklahoma when it became the 46th state to enter the union on November 16, 1907, its residents are known as Oklahomans, its capital and largest city is Oklahoma City. A major producer of natural gas and agricultural products, Oklahoma relies on an economic base of aviation, telecommunications, biotechnology.
Both Oklahoma City and Tulsa serve as Oklahoma's primary economic anchors, with nearly two thirds of Oklahomans living within their metropolitan statistical areas. With ancient mountain ranges, prairie and eastern forests, most of Oklahoma lies in the Great Plains, Cross Timbers, the U. S. Interior Highlands, a region prone to severe weather. More than 25 Native American languages are spoken in Oklahoma, ranking third behind Alaska and California. Oklahoma is on a confluence of three major American cultural regions and served as a route for cattle drives, a destination for Southern settlers, a government-sanctioned territory for Native Americans; the name Oklahoma comes from the Choctaw phrase okla humma meaning red people. Choctaw Nation Chief Allen Wright suggested the name in 1866 during treaty negotiations with the federal government on the use of Indian Territory, in which he envisioned an all-Indian state controlled by the United States Superintendent of Indian Affairs. Equivalent to the English word Indian, okla humma was a phrase in the Choctaw language that described Native American people as a whole.
Oklahoma became the de facto name for Oklahoma Territory, it was approved in 1890, two years after the area was opened to white settlers. The name of the state is Pawnee: Uukuhuúwa, Cayuga: Gahnawiyoˀgeh. In the Chickasaw language, the state is known as Oklahomma', in Arapaho as bo'oobe'. Oklahoma is the 20th-largest state in the United States, covering an area of 69,899 square miles, with 68,595 square miles of land and 1,304 square miles of water, it lies in the Great Plains near the geographical center of the 48 contiguous states. It is bounded on the east by Arkansas and Missouri, on the north by Kansas, on the northwest by Colorado, on the far west by New Mexico, on the south and near-west by Texas. Much of its border with Texas lies along a failed continental rift; the geologic figure defines the placement of the Red River. The Oklahoma panhandle's Western edge is out of alignment with its Texas border; the Oklahoma/New Mexico border is 2.1 miles to 2.2 miles east of the Texas line. The border between Texas and New Mexico was set first as a result of a survey by Spain in 1819.
It was set along the 103rd meridian. In the 1890s, when Oklahoma was formally surveyed using more accurate surveying equipment and techniques, it was discovered the Texas line was not set along the 103rd meridian. Surveying techniques were not as accurate in 1819, the actual 103rd meridian was 2.2 miles to the east. It was much easier to leave the mistake than for Texas to cede land to New Mexico to correct the surveying error; the placement of the Oklahoma/New Mexico border represents the true 103rd meridian. Cimarron County in Oklahoma's panhandle is the only county in the United States that touches four other states: New Mexico, Texas and Kansas. Oklahoma is between the Great Plains and the Ozark Plateau in the Gulf of Mexico watershed sloping from the high plains of its western boundary to the low wetlands of its southeastern boundary, its highest and lowest points follow this trend, with its highest peak, Black Mesa, at 4,973 feet above sea level, situated near its far northwest corner in the Oklahoma Panhandle.
The state's lowest point is on the Little River near its far southeastern boundary near the town of Idabel, which dips to 289 feet above sea level. Among the most geographically diverse states, Oklahoma is one of four to harbor more than 10 distinct ecological regions, with 11 in its borders—more per square mile than in any other state, its western and eastern halves, are marked by extreme differences in geographical diversity: Eastern Oklahoma touches eight ecological regions and its western half contains three. Although having fewer ecological regions Western Oklahoma contains many relic species. Oklahoma has four primary mountain ranges: the Ouachita Mountains, the Arbuckle Mountains, the Wichita Mountains, the Ozark Mountains. Contained within the U. S. Interior Highlands region, the Ozark and Ouachita Mountains are the only major mountainous region between the Rocky Mountains and the Appalachians. A portion of the Flint Hills stretches into north-central Oklahoma, near the state's eastern border, The Oklahoma Tourism & Recreation Department regards Cavanal Hill as the world's tallest hill.
The semi-arid high
Pinctada is a genus of saltwater oysters, marine bivalve mollusks in the family Pteriidae, the pearl oysters. These oysters have a strong inner shell layer composed of nacre known as "mother of pearl". Pearl oysters are not related to either the edible oysters of family Ostreidae or the freshwater pearl mussels of the families Unionidae and Margaritiferidae. P. margaritifera and P. maxima are used for culturing South Tahitian pearls. They are cultured primarily in the central and eastern Indo-Pacific. A pearl oyster can be seen on the reverse side of the 1,000-peso bill of the Philippines. All species within the genus produce pearls. Attempts have been made to harvest pearls commercially from many Pinctada species. However, the only species that are of significant commercial interest are: Gulf pearl oyster, Pinctada radiata. Black-lip oyster, Pinctada margaritifera. Black South Sea pearls. Pearls are obtained in commercial quantities from some species of the related winged oyster genus Pteria. Pearls are produced from freshwater mussel species unrelated to pearl oysters.
These freshwater species include Hyriopsis cumingii, Hyriopsis schlegelii, a hybrid of the two species. At danger from the large demand for pearls, the typical lifespan of a pearl oyster is around 3 years to 14 years. Pinctada maxima are seeded at about 2 years of age and take 2 years to develop a pearl, they can be reseeded up to 4 times. Akoya pearls are harvested after about 9 to 16 months. Research carried out by biologist Aldemaro Romero Jr. allowed him to discover that the first animal population depleted by Europeans in the American continent was a pearl oyster species off the coast of Venezuela. He analyzed historical records and used information about the biology of these and other species to explain its rapid disappearance; the World Register of Marine Species includes the following species in the genus: Pinctada albina – Shark Bay pearl oyster Pinctada capensis Pinctada chemnitzii Pinctada cumingii Pinctada fucata – Akoya pearl oyster – now accepted as Pinctada imbricata fucata Pinctada galtsoffi Bartsch, 1931 Pinctada imbricata Röding, 1798 – Gulf pearl oyster Pinctada inflata Pinctada longisquamosa Pinctada maculata Pinctada margaritifera – Black-lip oyster Pinctada maxima – White-lip oyster or gold-lip oyster Pinctada mazatlanica Pinctada nigra Pinctada petersii Pinctada radiata – Atlantic pearl-oyster – now accepted as Pinctada imbricata radiata Pinctada reeveana Pinctada sugillata Pinctada vidua Media related to Pinctada at Wikimedia Commons OBIS Indo-Pacific molluscan database entry for Pinctada
The tusk shells or tooth shells referred to by the more-technical term scaphopods, are members of a class of shelled marine mollusc with worldwide distribution, are the only class of infaunal marine molluscs. Shells of species within this class range from about 0.5 to 15 cm in length. Members of the order Dentaliida tend to be larger than those of the order Gadilida; these molluscs live in soft substrates offshore. Because of this subtidal habitat and the small size of most species, many beachcombers are unfamiliar with them. Molecular data suggest that the scaphopods are a sister group to the cephalopods, although higher-level molluscan phylogeny remains somewhat unresolved; the morphological shape of the scaphopod body makes it difficult to orient it satisfactorily. As a result, researchers have disagreed as to which direction is anterior/ posterior and, ventral/ dorsal. According to Shimek and Steiner, "he apex of the shell and mantle are anatomically dorsal, the large aperture is ventral and anterior.
The concave side of the shell and viscera are anatomically dorsal. The convex side has to be divided into anteriorly ventral and dorsally posterior portions, with the anus as the demarcation. Functionally, as in cephalopods, the large aperture with the foot is anterior, the apical area posterior, the concave side dorsal and the convex side ventral." The shells of the members of the Gadilida are glassy-smooth in addition to being quite narrow and with a reduced aperture. This along with other structures of their anatomy allows them to move with surprising speed through loose sediment to escape potential bottom-dwelling predators; the Dentalids, on the other hand, tend to have ribbed and rather rough shells. When they sense vibrations anywhere around them, their defensive response is to freeze; this makes them harder to detect by animals such as ratfish which can sense the electrical signals given off by the most minute muscle movement. The mantle of a scaphopod is within the shell; the foot extends from the larger end of the shell, is used to burrow through the substrate.
The scaphopod positions itself head down in the substrate, with the apical end of the shell projecting upward. This end appears above the level of the substrate, however, as doing so exposes the animal to numerous predators. Most adult scaphopods live their lives buried within the substrate. Water enters the mantle cavity through the apical aperture, is wafted along the body surface by cilia. There are no gills. Unlike most other molluscs, there is no continuous flow of water with a separate exhalant stream. Instead, deoxygenated water is expelled back through the apical aperture through muscular action once every ten to twelve minutes. A number of minute tentacles around the foot, called captacula, sift through the sediment and latch onto bits of food, which they convey to the mouth; the mouth has a grinding radula. The radulae and cartilaginous oral bolsters of the Gadilidae are structured like zippers where the teeth crush the prey by opening and closing on it while the radulae and bolsters of the Dentaliidae work rachet-like to pull the prey into the esophagus, sometimes whole.
The massive radula of the scaphopods is the largest such organ relative to body size of any mollusc. The remainder of the digestive system consists of a digestive diverticulum, esophagus and intestine. A digestive gland secretes enzymes into the stomach, unlike some other molluscs, does not digest the food directly itself; the anus opens on the ventral/ underside of the animal in the middle of the mantle cavity. The scaphopod vascular system is rudimentary lacking heart auricles as well as corresponding ctenidia and blood vessels; the heart, a characteristic feature of all other groups of mollusca, has been considered lost or reduced to a thin fold of the pericardium. Metabolic waste is excreted through a pair of nephridia close to the anus; the tusk shells appear to be the only extant molluscs which lack the otherwise standard molluscan reno-pericardial apertures. Furthermore, they appear to be the only molluscs with openings that directly connect the hemocoel with the surrounding water; these openings may serve to allow the animal to relieve internal pressure by ejecting body fluid during moments of extreme muscular contraction of the foot.
The nervous system is similar to that of gastropods. One pair each of cerebral and pleural ganglia lie close to the oesophagus, form the animal's brain. A separate set of pedal ganglia lie in the foot, a pair of visceral ganglia are set further back in the body, connect to pavilion ganglia via long connectives. Radular and sub-radular ganglia are present, as are statocysts with staticonia. Scaphopods have no osphradia, or other distinct sensory organs. Scaphopods have separate sexes, external fertilisation
Horseshoe crabs are marine and brackish water arthropods of the family Limulidae, suborder Xiphosurida, order Xiphosura. Their popular name is a misnomer, for they are not true crabs. Horseshoe crabs live in and around shallow coastal waters on soft sandy or muddy bottoms, they tend to spawn in the intertidal zone at spring high tides. They are eaten in Asia, used as fishing bait, in fertilizer and in science. In recent years, population declines have occurred as a consequence of coastal habitat destruction and overharvesting. Tetrodotoxin may be present in Carcinoscorpius rotundicauda; because of their origin 450 million years ago, horseshoe crabs are considered living fossils. A 2019 molecular analysis places them as the sister group of Ricinulei within Arachnida. Horseshoe crabs resemble crustaceans but belong to a separate subphylum of the arthropods and are related to arachnids. Horseshoe crabs are related to the extinct eurypterids, which include some of the largest arthropods to have existed, the two may be sister groups.
The earliest horseshoe crab fossils are found in strata from the late Ordovician period 450 million years ago. The Limulidae are the only recent family of the order Xiphosura, contains all four living species of horseshoe crabs: Carcinoscorpius rotundicauda, the mangrove horseshoe crab, found in South and Southeast Asia Limulus polyphemus, the Atlantic or American horseshoe crab, found along the American Atlantic coast and in the Gulf of Mexico Tachypleus gigas, the Indo-Pacific, Indian or southern horseshoe crab, found in South and Southeast Asia Tachypleus tridentatus, the Chinese, Japanese or tri-spine horseshoe crab, found in Southeast and East Asia The entire body of the horseshoe crab is protected by a hard carapace, it has two compound lateral eyes, each composed of about 1,000 ommatidia, plus a pair of median eyes that are able to detect both visible light and ultraviolet light, a single endoparietal eye, a pair of rudimentary lateral eyes on the top. The latter become functional.
A pair of ventral eyes is located near the mouth, as well as a cluster of photoreceptors on the telson. The horseshoe crab has five additional eyes on top of its shell. Despite having poor eyesight, the animals have the largest rods and cones of any known animal, about 100 times the size of humans', their eyes are a million times more sensitive to light at night than during the day; the mouth is located in the center of the legs, whose bases are referred to as gnathobases and have the same function as jaws and help grind up food. The horseshoe crab has five pairs of legs for walking and moving food into the mouth, each with a claw at the tip, except for the last pair. Behind its legs, the horseshoe crab has book gills, which exchange respiratory gases, are occasionally used for swimming; as in other arthropods, a true endoskeleton is absent, but the body does have an endoskeletal structure made up of cartilaginous plates that support the book gills. They are more found on the ocean floor searching for worms and molluscs, which are their main food.
They may feed on crustaceans and small fish. Females are about 20–30% larger than males; the smallest species is the largest is T. tridentatus. On average, males of C. rotundicauda are about 30 cm long, including a tail, about 15 cm, their carapace is about 15 cm wide. Some southern populations of L. polyphemus are somewhat smaller, but otherwise this species is larger. In the largest species, T. tridentatus, females can reach as much as 79.5 cm long, including their tail, up to 4 kg in weight. This is only about 10–20 cm longer than the largest females of L. polyphemus and T. gigas, but twice the weight. The juveniles grow about 33% larger with every molt until reaching adult size. During the breeding season, horseshoe crabs migrate to shallow coastal waters. A male selects a female and clings to her back. Several males surround the female and all fertilize together, which makes it easy to spot and count females as they are the large center carapace surrounded by 3-5 smaller ones; the female lays her eggs while the male fertilize them.
The female can lay between 120,000 eggs in batches of a few thousand at a time. In L. polyphemus, the eggs take about two weeks to hatch. The larvae molt six times during the first year. Natural breeding of horseshoe crabs in captivity has proven to be difficult; some evidence indicates that mating takes place only in the presence of the sand or mud in which the horseshoe crab's eggs were hatched. It is not known with certainty what is in the sand how they sense it. Artificial insemination and induced spawning have been done on a large scale in captivity, eggs and juveniles collected from the wild are raised to adulthood in captivity. Horseshoe crabs use hemocyanin to carry oxygen through their blood; because of the copper present in hemocyanin, their blood is blue. Their blood contains amebocytes, which play a similar role to the white blood cells of vertebrates in defending the organism against pathogens. Amebocytes from the blood of L. polyphemus are used to make Limulus amebocyte lysate, used for the detection of bacterial endotoxins in medical applications.
This means there is a high demand for the blood, the harvest of which involves collecting and bleeding the animal
Silicon is a chemical element with symbol Si and atomic number 14. It is a brittle crystalline solid with a blue-grey metallic lustre, it is a member of group 14 in the periodic table: carbon is above it. It is unreactive; because of its high chemical affinity for oxygen, it was not until 1823 that Jöns Jakob Berzelius was first able to prepare it and characterize it in pure form. Its melting and boiling points of 1414 °C and 3265 °C are the second-highest among all the metalloids and nonmetals, being only surpassed by boron. Silicon is the eighth most common element in the universe by mass, but rarely occurs as the pure element in the Earth's crust, it is most distributed in dusts, sands and planets as various forms of silicon dioxide or silicates. More than 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust after oxygen. Most silicon is used commercially without being separated, with little processing of the natural minerals.
Such use includes industrial construction with clays, silica sand, stone. Silicates are used in Portland cement for mortar and stucco, mixed with silica sand and gravel to make concrete for walkways and roads, they are used in whiteware ceramics such as porcelain, in traditional quartz-based soda-lime glass and many other specialty glasses. Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics. Silicon is the basis of the used synthetic polymers called silicones. Elemental silicon has a large impact on the modern world economy. Most free silicon is used in the steel refining, aluminium-casting, fine chemical industries. More visibly, the small portion of highly purified elemental silicon used in semiconductor electronics is essential to integrated circuits – most computers, cell phones, modern technology depend on it. Silicon is an essential element in biology. However, various sea sponges and microorganisms, such as diatoms and radiolaria, secrete skeletal structures made of silica.
Silica is deposited in many plant tissues. In 1787 Antoine Lavoisier suspected that silica might be an oxide of a fundamental chemical element, but the chemical affinity of silicon for oxygen is high enough that he had no means to reduce the oxide and isolate the element. After an attempt to isolate silicon in 1808, Sir Humphry Davy proposed the name "silicium" for silicon, from the Latin silex, silicis for flint, adding the "-ium" ending because he believed it to be a metal. Most other languages use transliterated forms of Davy's name, sometimes adapted to local phonology. A few others use instead a calque of the Latin root. Gay-Lussac and Thénard are thought to have prepared impure amorphous silicon in 1811, through the heating of isolated potassium metal with silicon tetrafluoride, but they did not purify and characterize the product, nor identify it as a new element. Silicon was given its present name in 1817 by Scottish chemist Thomas Thomson, he retained part of Davy's name but added "-on" because he believed that silicon was a nonmetal similar to boron and carbon.
In 1823, Jöns Jacob Berzelius prepared amorphous silicon using the same method as Gay-Lussac, but purifying the product to a brown powder by washing it. As a result, he is given credit for the element's discovery; the same year, Berzelius became the first to prepare silicon tetrachloride. Silicon in its more common crystalline form was not prepared until 31 years by Deville. By electrolyzing a mixture of sodium chloride and aluminium chloride containing 10% silicon, he was able to obtain a impure allotrope of silicon in 1854. More cost-effective methods have been developed to isolate several allotrope forms, the most recent being silicene in 2010. Meanwhile, research on the chemistry of silicon continued; the first organosilicon compound, was synthesised by Charles Friedel and James Crafts in 1863, but detailed characterisation of organosilicon chemistry was only done in the early 20th century by Frederic Kipping. Starting in the 1920s, the work of William Lawrence Bragg on X-ray crystallography elucidated the compositions of the silicates, known from analytical chemistry but had not yet been understood, together with Linus Pauling's development of crystal chemistry and Victor Goldschmidt's development of geochemistry.
The middle of the 20th century saw the development of the chemistry and industrial use of siloxanes and the growing use of silicone polymers and resins. In the late 20th century, the complexity of the crystal chemistry of silicides was mapped, along with the solid-state chemistry of doped semiconductors; because silicon is an important element in high-technology semiconductor devi
Conch is a common name applied to a number of different medium to large-sized shells. The term applies to large snails whose shell has a high spire and a noticeable siphonal canal. In North America, a conch is identified as a queen conch, indigenous to the waters of the Bahamas. Queen conchs are valued for seafood, are used as fish bait; the group of conchs that are sometimes referred to as "true conchs" are marine gastropod molluscs in the family Strombidae in the genus Strombus and other related genera. For example, see Lobatus gigas, the queen conch, Laevistrombus canarium, the dog conch. Many other species are often called "conch", but are not at all related to the family Strombidae, including Melongena species, the horse conch Triplofusus papillosus. Species referred to as conchs include the sacred chank or more shankha shell and other Turbinella species in the family Turbinellidae; the English word "conch" is attested in Middle English, coming from Latin concha, which in turn comes from Greek konchē from Proto-Indo-European root *konkho-, cognate with Sanskrit śaṅkha.
The meat of conchs is eaten raw in salads, or cooked, as in burgers, chowders and gumbos. All parts of the conch meat are edible. Conch is most indigenous to the Bahamas, is served in fritter and soup forms. Conch is eaten in the West Indies. Restaurants all over the islands serve this particular meat. In the Dominican Republic and Haiti, conch is eaten in curries or in a spicy soup, it is locally referred to as lambi. In the Turks and Caicos Islands, the Annual Conch Festival is held in November each year, located at the Three Queens Bar/Restaurant in Blue Hills. Local restaurateurs compete for the best and most original conch dishes, which are judged by international chefs. Free sampling of the dishes follows the judging. In Puerto Rico, conch is served as a ceviche called ensalada de carrucho, consisting of raw conch marinated in lime juice, olive oil, garlic, green peppers, onions, it is used to fill empanadas. In Panama, conch is known as cambombia and is served as ceviche de cambombia consisting of raw conch marinated in lime juice, chopped onions, finely chopped habaneros, vinegar.
Conch is popular in Italy and among Italian Americans. Called scungille, it is eaten in a variety of ways, but most in salads or cooked in a sauce for pasta, it is included as one of the dishes prepared for the Feast of the Seven Fishes. In East Asian cuisines, this seafood is cut into thin slices and steamed or stir-fried. Eighty-percent of the queen conch meat in international trade is imported into the United States; the Florida Keys were a major source of queen conchs until the 1970s, but the conchs are now scarce and all harvesting of them in Florida waters is prohibited. Conch shells can be used as wind instruments, they are prepared by cutting a hole in the spire of the shell near the apex, blowing into the shell as if it were a trumpet, as in blowing horn. Sometimes, a mouthpiece is used. Pitch is adjusted by moving one's hand out of the aperture. Various species of large marine gastropod shells can be turned into "blowing shells", but some of the best-known species used are the sacred chank or shankha Turbinella pyrum, the Triton's trumpet Charonia tritonis, the queen conch Strombus gigas.
Many different kinds of mollusks can produce pearls. Pearls from the queen conch, S. gigas, are rare and have been collectors' items since Victorian times. Conch pearls occur in a range of hues, including white and orange, with many intermediate shades, but pink is the colour most associated with the conch pearl, such that these pearls are sometimes referred to as "pink pearls". In some gemological texts, non-nacreous gastropod pearls used to be referred to as "calcareous concretions" because they were "porcellaneous", rather than "nacreous", sometimes known as "orient"; the GIA and CIBJO now use the term "pearl"—or, where appropriate, the more descriptive term "non-nacreous pearl"—when referring to such items, under Federal Trade Commission rules, various mollusc pearls may be referred to as "pearls" without qualification. Although not nacreous, the surfaces of fine conch pearls have a unique and attractive appearance of their own; the microstructure of conch pearls comprises aligned bundles of microcrystalline fibres that create a shimmering iridescent effect known as "flame structure".
The effect is a form of chatoyancy, caused by the interaction of light rays with the microcrystals in the pearl's surface, it somewhat resembles moiré silk. Conch shells are sometimes used as decoration, as decorative planters, in cameo making. In classic Maya art, conchs are shown being used in many ways, including as paint and ink holders for elite scribes, as bugles or trumpets, as hand weapons. Conch shells have been used as shell money in several cultures; some American Aboriginals used cylindrical conch columella beads as part of breastplates and other personal adornment. In India, the Bengali bride-to-be is adorned with conch shell and coral bangles
A composite material is a material made from two or more constituent materials with different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure, differentiating composites from mixtures and solid solutions; the new material may be preferred for many reasons: common examples include materials which are stronger, lighter, or less expensive when compared to traditional materials. More researchers have begun to include sensing, actuation and communication into composites, which are known as Robotic Materials. Typical engineered composite materials include: Reinforced concrete and masonry Composite wood such as plywood Reinforced plastics, such as fibre-reinforced polymer or fiberglass Ceramic matrix composites Metal matrix composites and other Advanced composite materialsComposite materials are used for buildings and structures such as boat hulls, swimming pool panels, racing car bodies, shower stalls, storage tanks, imitation granite and cultured marble sinks and countertops.
The most advanced examples perform on spacecraft and aircraft in demanding environments. The earliest man-made composite materials were straw and mud combined to form bricks for building construction. Ancient brick-making was documented by Egyptian tomb paintings. Wattle and daub is one of the oldest man-made composite materials, at over 6000 years old. Concrete is a composite material, is used more than any other man-made material in the world; as of 2006, about 7.5 billion cubic metres of concrete are made each year—more than one cubic metre for every person on Earth. Woody plants, both true wood from trees and such plants as palms and bamboo, yield natural composites that were used prehistorically by mankind and are still used in construction and scaffolding. Plywood 3400 BC by the Ancient Mesopotamians. Cartonnage layers of linen or papyrus soaked in plaster dates to the First Intermediate Period of Egypt c. 2181–2055 BC and was used for death masks. Cob Mud Bricks, or Mud Walls, have been used for thousands of years.
Concrete was described by Vitruvius, writing around 25 BC in his Ten Books on Architecture, distinguished types of aggregate appropriate for the preparation of lime mortars. For structural mortars, he recommended pozzolana, which were volcanic sands from the sandlike beds of Pozzuoli brownish-yellow-gray in colour near Naples and reddish-brown at Rome. Vitruvius specifies a ratio of 1 part lime to 3 parts pozzolana for cements used in buildings and a 1:2 ratio of lime to pulvis Puteolanus for underwater work the same ratio mixed today for concrete used at sea. Natural cement-stones, after burning, produced cements used in concretes from post-Roman times into the 20th century, with some properties superior to manufactured Portland cement. Papier-mâché, a composite of paper and glue, has been used for hundreds of years; the first artificial fibre reinforced plastic was bakelite which dates to 1907, although natural polymers such as shellac predate it. One of the most common and familiar composite is fibreglass, in which small glass fibre are embedded within a polymeric material.
The glass fibre is strong and stiff, whereas the polymer is ductile. Thus the resulting fibreglass is stiff, strong and ductile. Concrete is the most common artificial composite material of all and consists of loose stones held with a matrix of cement. Concrete is an inexpensive material, will not compress or shatter under quite a large compressive force. However, concrete cannot survive tensile loading. Therefore, to give concrete the ability to resist being stretched, steel bars, which can resist high stretching forces, are added to concrete to form reinforced concrete. Fibre-reinforced polymers s include glass-reinforced plastic. If classified by matrix there are thermoplastic composites, short fibre thermoplastics, long fibre thermoplastics or long fibre-reinforced thermoplastics. There are numerous thermoset composites, including paper composite panels. Many advanced thermoset polymer matrix systems incorporate aramid fibre and carbon fibre in an epoxy resin matrix. Shape memory polymer composites are high-performance composites, formulated using fibre or fabric reinforcement and shape memory polymer resin as the matrix.
Since a shape memory polymer resin is used as the matrix, these composites have the ability to be manipulated into various configurations when they are heated above their activation temperatures and will exhibit high strength and stiffness at lower temperatures. They can be reheated and reshaped without losing their material properties; these composites are ideal for applications such as lightweight, deployable structures. High strain composites are another type of high-performance composites that are designed to perform in a high deformation setting and are used in deployable systems where structural flexing is advantageous. Although high strain composites exhibit many similarities to shape memory polymers, their performance is dependent on the fibre layout as opposed to the resin content of the matrix. Comp