- polyarylate (chemical compound)
polyarylate, a family of high-performance engineering plastics noted for their strength, toughness, chemical resistance, and high melting points. They are employed in automotive parts, ovenware, and electronic devices, among other applications. Polyarylates are a type of aromatic polyester. As in
- polyatomic ion (chemistry)
chemical compound: Ionic compounds containing polyatomic ions: A special type of ionic compound is exemplified by ammonium nitrate (NH4NO3), which contains two polyatomic ions, NH4+ and NO3−. As the name suggests, a polyatomic ion is a charged entity composed of several atoms bound together. Polyatomic ions have special names that…
- polyatomic molecule (chemistry)
molecule: Characteristics of molecules: …than two atoms are termed polyatomic molecules, e.g., carbon dioxide (CO2) and water (H2O). Polymer molecules may contain many thousands of component atoms.
- polybasite (mineral)
polybasite, heavy, black sulfosalt mineral, a sulfide of the elements silver, copper, and antimony ([Ag, Cu]16Sb2S11), that occurs as monoclinic crystals and masses in silver veins, sometimes in large amounts. Polybasite is found in Chile, Peru, the Czech Republic, and many localities in Mexico and
- polybenzimidazole (chemical compound)
Carl Shipp Marvel: …during the 1960s, Marvel synthesized polybenzimidazoles (PBIs), a type of polyimide that is resistant to temperatures as high as 600 °C (1,100 °F) and is used in suits for astronauts and firefighters. In 1980 PBIs became the first man-made fibres to be produced commercially in almost a decade. Marvel continued…
- Polybia (insect genus)
hymenopteran: Social forms: …division of labour occurs in Polybia. Some female Polybia only lay eggs. In others, called assisting females, the gonads are poorly developed; these females take charge of repair and construction, larvae care, and food gathering. They thus are useful in the society, even though they produce no offspring. This society…
- polybisphenol-A terephthalate (chemical compound)
polyarylate: Polybisphenol-A terephthalate does not begin to soften until heated above approximately 170 °C (340 °F). Its transparency and resistance to degradation from ultraviolet radiation make it suitable for use in solar-energy panels. Poly-4-hydroxybenzoate, a highly crystalline polymer consisting solely of aromatic rings linked by ester…
- Polybius (Greek historian)
Polybius was a Greek statesman and historian who wrote of the rise of Rome to world prominence. Polybius was the son of Lycortas, a distinguished Achaean statesman, and he received the upbringing considered appropriate for a son of rich landowners. His youthful biography of Philopoemen reflected
- Polybius checkerboard (device)
cryptology: Early cryptographic systems and applications: …by a device called the Polybius checkerboard, which is a true biliteral substitution and presages many elements of later cryptographic systems. Similar examples of primitive substitution or transposition ciphers abound in the history of other civilizations. The Romans used monoalphabetic substitution with a simple cyclic displacement of the alphabet. Julius…
- Polyboroides typus (bird)
hawk: The African harrier hawk (Polyboroides typus) and the crane hawk (Geranospiza nigra) of tropical America are medium-sized gray birds resembling the harriers but having short broad wings.
- Polyborus plancus (bird)
caracara: …crested caracara (Caracara plancus or Polyborus plancus) occurs from Florida, Texas, Arizona, Cuba, and the Isle of Pines south to the Falkland Islands and Tierra del Fuego. Some authorities classify the entire population of caracaras within this range as crested caracaras, dividing them into several subspecies, while others define only…
- polybrominated diphenyl ether (chemical compound)
biomonitoring: Studies and surveillance programs: …that human milk levels of polybrominated diphenyl ethers (PBDEs), chemicals used as flame retardants in many consumer products, had doubled every five years. Other studies detected these chemicals in breast milk from women in Japan, Germany, the United States, and Canada, as well as in killer whales and polar bears…
- polybutadiene (chemistry)
butadiene rubber: It consists of polybutadiene, an elastomer (elastic polymer) built up by chemically linking multiple molecules of butadiene to form giant molecules, or polymers. The polymer is noted for its high resistance to abrasion, low heat buildup, and resistance to cracking.
- polybutylene pipe (technology)
polybutylene terephthalate: Pipe made with PBT (so-called polybutylene pipe, or PB pipe) was formerly popular for residential plumbing as a low-cost and easily handled substitute for copper, but it was found to degrade after prolonged contact with oxidizing chemicals such as chlorine in municipal water supplies, so it is no longer used.…
- polybutylene terephthalate (chemical compound)
polybutylene terephthalate (PBT), a strong and highly crystalline synthetic resin, produced by the polymerization of butanediol and terephthalic acid. PBT is similar in structure to polyethylene terephthalate (PET)—the difference being in the number of methylene (CH2) groups present in the
- Polycaon (beetle)
branch and twig borer: …dead wood, and the genus Polycaon is often destructive in orchards.
- polycaprolactam (fibre)
major industrial polymers: Nylon: …the DuPont fibre was marketed, nylon 6 (polycaprolactam) was produced in Europe based on the polymerization of caprolactam. Nylon 6 and nylon 6,6 have almost the same structure and similar properties and are still the most important polyamide fibres worldwide. Their repeating units have the following structure:
- polycaprolactone (chemical compound)
major industrial polymers: Degradable polyesters: … (PLA), poly-2-hydroxy butyrate (PHB), and polycaprolactone (PCL), as well as their copolymers:
- polycarbonate (chemical compound)
polycarbonate (PC), a tough, transparent synthetic resin employed in safety glass, eyeglass lenses, and compact discs, among other applications. PC is a special type of polyester used as an engineering plastic owing to its exceptional impact resistance, tensile strength, ductility, dimensional
- polycarboxylic acid (chemical compound)
carboxylic acid: Polycarboxylic acids: Unbranched-chain dicarboxylic acids contain two COOH groups. As a result they can yield two kinds of salts. For example, if oxalic acid, HOOCCOOH, is half-neutralized with sodium hydroxide, NaOH (i.e., the acid and base are in a 1:1 molar ratio), HOOCCOONa, called
- Polycarp, Martyrdom of (patristic literature)
Martyrdom of Polycarp, early Christian letter that describes the death by burning of St. Polycarp, bishop of Smyrna in Asia Minor. It was sent to the church in Philomelium, Asia Minor, from the church in Smyrna (modern İzmir, Turkey). The work is the oldest authentic account of an early Christian
- Polycarp, St. (Greek bishop)
St. Polycarp ; feast day February 23) was a Greek bishop of Smyrna and Apostolic Father who was the leading 2nd-century Christian figure in Roman Asia by virtue of his work during the initial appearance of the fundamental theological literature of Christianity. Historically, he formed a link
- polycentrism (political concept)
Democrats of the Left: …proposing the concept of “polycentrism,” a form of limited independence among communist parties. After Togliatti’s death in 1964, the PCI nearly split into “Russian” and “Italian” wings over this concept. Despite this conflict and other splits to the left, the PCI won 27 percent of the vote in the…
- Polychaeta (annelid)
polychaete, any worm of the class Polychaeta (phylum Annelida). About 8,000 living species are known. Polychaetes, which include rag worms, lugworms, bloodworms, sea mice, and others, are marine worms notable for well-defined segmentation of the body. Unique among annelids, most polychaete body
- polychaete (annelid)
polychaete, any worm of the class Polychaeta (phylum Annelida). About 8,000 living species are known. Polychaetes, which include rag worms, lugworms, bloodworms, sea mice, and others, are marine worms notable for well-defined segmentation of the body. Unique among annelids, most polychaete body
- polychaete hypothesis (paleontology)
polychaete hypothesis, theory that conodonts (minute toothlike structures found as fossils in marine rocks) are parts of the jaw apparatus of polychaete worms, a class of the annelid, or segmented, worms. Conodonts resemble the jaws (scolecodonts) of polychaete worms in form, and they are found in
- Polychelidae (crustacean family)
lobster: Deep-sea lobsters (Polychelidae) are soft, weak animals with claws; some are blind. None is commercially important.
- polychlorinated biphenyl (chemical compound)
polychlorinated biphenyl (PCB), any of a class of organohalogen compounds prepared by the reaction of chlorine with biphenyl. A typical mixture of PCBs may contain over 100 compounds and is a colourless, viscous liquid. The mixture is relatively insoluble in water, is stable at high temperatures,
- polychlorinated dibenzodioxin (chemical compound)
dioxin, any of a group of aromatic hydrocarbon compounds known to be environmental pollutants that are generated as undesirable by-products in the manufacture of herbicides, disinfectants, and other agents. In popular terminology, dioxin has become a synonym for one specific dioxin,
- polychloroethene (chemical compound)
PVC, a synthetic resin made from the polymerization of vinyl chloride. Second only to polyethylene among the plastics in production and consumption, PVC is used in an enormous range of domestic and industrial products, from raincoats and shower curtains to window frames and indoor plumbing. A
- polychloroprene (chemical compound)
neoprene (CR), synthetic rubber produced by the polymerization (or linking together of single molecules into giant, multiple-unit molecules) of chloroprene. A good general-purpose rubber, neoprene is valued for its high tensile strength, resilience, oil and flame resistance, and resistance to
- polychlorotrifluoroethylene (chemical compound)
polychlorotrifluoroethylene (PCTFE), synthetic resin formed by the polymerization of chlorotrifluoroethylene. It is a moldable, temperature-resistant, and chemical-resistant plastic that finds specialty applications in the chemical, electrical, and aerospace industries. PCTFE can be prepared as a
- polychondritis (pathology)
polychondritis, chronic disease characterized by inflammation and destruction of the cartilage of various tissues of the body. The cause of polychondritis is unknown, but the disease may be the result of an abnormal immune response. Symptoms include pain, redness, and swelling of the affected
- polychromatism (biological pigmentation)
coloration: Coloration changes in populations: …species is said to be polychromatic. The white-throated sparrow (Zonotrichia albicollis) of North America, for example, has individuals with white-and-black head stripes and other individuals with tan-and-brown head stripes. The different colorations are not associated with age, sex, or geographic region. Polychromatism may evolve in response to predation. A predator…
- polychromy (visual arts)
Aegean civilizations: Period of the Early Palaces in Crete (c. 2000–1700): …red to create a striking polychrome effect. This kind of pottery, which flourished in Crete throughout the time of the first palaces and later (c. 2200 to 1600), is known as Kamáres ware from a sacred cave of that name on Mount Ida, where vases with fine polychrome decoration were…
- Polychronicon (work by Higden)
Ranulf Higden: …and chronicler remembered for his Polychronicon, a compilation of much of the knowledge of his age.
- Polycillin (drug)
ampicillin, drug used in the treatment of various infections, including otitis media (middle ear infection), sinusitis, and acute bacterial cystitis. Ampicillin (or alpha-aminobenzylpenicillin) is a semisynthetic penicillin, one of the first such antibiotics developed. Similar in action to
- Polycladida (flatworm order)
flatworm: Annotated classification: Order Polycladida Pharynx simple, bulbose, or plicate (many ridges); intestine may have short diverticula, or pockets; protonephridia paired; testes usually numerous; penis papilla generally present; nervous system with 3–4 trunks; nearly 800 species. Class Monogenea Oral sucker lacking or weakly developed; posterior end with
- Polycleitus (Greek sculptor)
Polyclitus was a Greek sculptor from the school of Árgos, known for his masterly bronze sculptures of young athletes; he was also one of the most significant aestheticians in the history of art. Polyclitus’s two greatest statues were the Diadumenus (430 bce; “Man Tying on a Fillet”) and the
- polyclinic (medicine)
medicine: Russia: …in varying specialties work from polyclinics or outpatient units, where many types of diseases are treated. Small towns usually have one polyclinic to serve all purposes. Large cities commonly have separate polyclinics for children and adults, as well as clinics with specializations such as women’s health care, mental illnesses, and…
- Polyclitus (Greek sculptor)
Polyclitus was a Greek sculptor from the school of Árgos, known for his masterly bronze sculptures of young athletes; he was also one of the most significant aestheticians in the history of art. Polyclitus’s two greatest statues were the Diadumenus (430 bce; “Man Tying on a Fillet”) and the
- polycrase (mineral)
euxenite: …to form the similar mineral polycrase; both it and euxenite often contain rare earths. These minerals are widespread in Norway, Madagascar, and Canada and also occur in Sweden, Finland, Greenland, Australia, Brazil, and the U.S. For chemical formula and detailed physical properties, see oxide mineral (table).
- Polycrates (tyrant of Samos)
Polycrates was a tyrant (c. 535–522 bc) of the island of Samos, in the Aegean Sea, who established Samian naval supremacy in the eastern Aegean and strove for control of the archipelago and mainland towns of Ionia. Polycrates seized control of the city of Samos during a celebration of a festival of
- Polycrates (bishop of Ephesus)
councils of Ephesus: First Council of Ephesus: In 190 Polycrates, bishop of Ephesus, convened a synod to establish the 14th of Nisan (the date of the Jewish Passover) as the official date of Easter. Pope Victor I, preferring a Sunday as more convenient and desiring uniformity, repudiated the decision and separated those who disagreed…
- polycrystal (crystallography)
polycrystal, any solid object composed of randomly oriented crystalline regions, called crystallites, especially as distinguished from a single crystal (q.v.). Polycrystalline materials result when a substance solidifies rapidly; crystallization commences at many sites (see nucleation), and the
- Polyctenidae (insect)
bat bug, (family Polyctenidae), any of about 20 species of bloodsucking insects (order Heteroptera) that are external parasites found mainly in the fur of tropical bats. The adult (between 3.5 and 5 mm [0.14 and 0.2 inch] long) lacks eyes and wings. Its forelegs are short and thick, and its middle
- polycyclic aromatic hydrocarbon (chemical compound)
David S. McKay: First was the presence of polycyclic aromatic hydrocarbons (PAHs). While these organic compounds are commonplace, found throughout the solar system, the PAHs in the meteorite were unusual in appearance, resembling the type that result from the decay of organic matter. The presence of the molecules within the rock and their…
- polycyclic dictyostele (botany)
fern: Vascular tissues: … fern (Pteridium), which has a polycyclic dictyostele, in which one stele occurs within another stele. Large strands of fibrelike cells running between the two steles form mechanically specialized hard tissue, or sclerenchyma. As herbaceous plants, ferns do not form true woody tissues.
- polycyclic nonaromatic compound (chemical compound)
hydrocarbon: Polycyclic nonaromatic compounds: The Hückel rule is not designed to apply to polycyclic compounds. Nevertheless, a similar dependence on the number of π electrons is apparent. The bicyclic hydrocarbon azulene has the same number of π electrons (10) as naphthalene and, like naphthalene, is aromatic.…
- polycyclic quinone (chemical compound)
coloration: Polycyclic quinones: The polycyclic quinones occur in some bacteria, fungi, and parts of higher plants. One of the more interesting representatives is the aphin group, so called because of their initial recovery from the hemolymph (circulating fluid) of several coloured species of aphids; aphids parasitize…
- polycystic ovary syndrome (medical disorder)
Stein-Leventhal syndrome, disorder in women that is characterized by an elevated level of male hormones (androgens) and infrequent or absent ovulation (anovulation). About 5 percent of women are affected by Stein-Leventhal syndrome, which is responsible for a substantial proportion of cases of
- polycystic renal disease
renal system disease: Other tumours: The form of polycystic (multiple-cyst) renal disease that allows survival into adult life is a familial condition, in which several members of the family have little trouble until middle life but then are progressively affected by kidney malfunction. Episodes of blood in the urine and urinary infection are…
- Polycystinea (organism)
radiolarian, any protozoan of the class Polycystinea (superclass Actinopoda), found in the upper layers of all oceans. Radiolarians, which are mostly spherically symmetrical, are known for their complex and beautifully sculptured, though minute, skeletons, referred to as tests. Usually composed of
- polycythemia (pathology)
polycythemia, abnormal increase in red blood cells (erythrocytes) and hemoglobin in the circulation, a situation that results in thickened blood, retarded flow, and an increased danger of clot formation within the circulatory system. The condition often results in an increase in the volume of
- polycythemia vera (pathology)
bloodletting: Bloodletting in the modern world: Polycythemia vera is a condition marked by the overproduction of platelets as well as red and white blood cells; blood is drawn in such cases to prevent the formation of blood clots. Leech therapy continues to be used to reduce blood congestion in veins and prevent tissue necrosis, especially…
- polycythemia, absolute (pathology)
polycythemia: Types of polycythemia: …cause is known, is called erythrocytosis.
- polydactylism (medical condition)
polydactyly, condition that is present at birth in which a person has more than five fingers on a hand or more than five toes on a foot. The term polydactyly is derived from the Greek words poly, meaning “many,” and daktylos, meaning “digit.” Polydactyly occurs in an estimated 1 in 500–1,000
- polydactyly (medical condition)
polydactyly, condition that is present at birth in which a person has more than five fingers on a hand or more than five toes on a foot. The term polydactyly is derived from the Greek words poly, meaning “many,” and daktylos, meaning “digit.” Polydactyly occurs in an estimated 1 in 500–1,000
- polydaemonistic magical religion
classification of religions: Morphological: …the nature religions is called polydaemonistic (many spirits) magical religion, which is dominated by animism and characterized by a confused mythology, a firm faith in magic, and the preeminence of fear above other religious emotions. At a higher stage of nature religions is therianthropic polytheism, in which the deities are…
- Polydectes (Greek mythology)
Perseus: …the chest had grounded, King Polydectes of Seriphus, who desired Danaë, tricked Perseus into promising to obtain the head of Medusa, the only mortal among the Gorgons.
- polydentate ligand (chemistry)
coordination compound: Ligands and chelates: Because a polydentate ligand is joined to the metal atom in more than one place, the resulting complex is said to be cyclic—i.e., to contain a ring of atoms. Coordination compounds containing polydentate ligands are called chelates (from Greek chele, “claw”), and their formation is termed chelation.…
- Polydeuces (astronomy)
Dione: …much smaller moons, Helene and Polydeuces (also named for Greek mythological figures). Helene, which has a diameter of about 30 km (20 miles), maintains a gravitationally stable position 60° ahead of Dione. Polydeuces has less than half the diameter of Helene and follows Dione by 60°, though with large deviations…
- polydimethylsiloxane (chemical compound)
major industrial polymers: Polysiloxanes (silicones): The most common siloxane polymer, polydimethylsiloxane, is formed when the chlorine atoms of the monomer, dichlorodimethylsilane (Cl2Si[CH3]2), are replaced by hyroxyl (OH) groups by hydrolysis. The resultant unstable compound, silanol (Cl2Si[OH]2), condenses in step-growth fashion to form the polymer, with concomitant loss of water. Some cyclic products are also formed,…
- Polydora (polychaete genus)
annelid: Annotated classification: …cm; examples of genera: Spio, Polydora. Order Chaetopterida Two to 3 distinct body regions; prostomium with palpi; modified setae on segment 4; tube dweller; examples of genera: Chaetopterus (parchment worm), Spiochaetopterus. Order Magelonida
- Polydorian (Turkey)
Burdur, city, southwestern Turkey. It is located near the eastern shore of Lake Burdur. Called Polydorion in the Middle Ages, it fell to the Seljuq Turks in the 12th century and came under Ottoman domination in the 15th. Its size and economy expanded after World War II. Industries include textiles,
- Polydoúre, Maria (Greek poet)
Maria Polidoúri was a Greek poet known for her impassioned, eloquent farewell to life. Polidoúri was orphaned as a small child, and in 1921 she went to Athens to study law. There she began a friendship with another poet, Kóstas Kariotákis. In 1926 she went to Paris, returning two years later,
- Polyeidus (Greek mythology)
Glaucus: The seer Polyeidus finally discovered the child but on confessing his inability to restore him to life was shut up in a vault with the corpse. There he killed a serpent and, seeing it revived by a companion that laid a certain herb upon it, brought the…
- polyelectrolyte (chemical compound)
liquid: Solutions of electrolytes: …charges; such molecules are called polyelectrolytes. In solution, the conformation (i.e., the three-dimensional structure) of a large, charged molecule is strongly dependent on the ionic strength of the dissolving medium; for example, depending on the nature and concentration of salts present in the solvent, a polyelectrolyte molecule may coagulate into…
- polyembryony (biology)
polyembryony, a condition in which two or more embryos develop from a single fertilized egg, forming what in humans is known as identical twins. A common phenomenon in many plant and animal species, polyembryony occurs regularly in the nine-banded armadillo, which usually gives birth to four
- polyene (chemical compound)
antifungal drug: The polyenes: Polyenes, such as amphotericin B and nystatin, are macrolide antibiotics made up of alternating conjugated double bonds. The polyene drugs work by interacting with ergosterol, a type of steroid that is found in fungal membranes; this binding causes channels to form in
- polyepiphyseal dysplasia (pathology)
joint disease: Congenital and hereditary abnormalities: Polyepiphyseal dysplasias (abnormal development in childhood of a number of epiphyses—the ends or outlying portions of bones separated from the main body of the bone by cartilage) are a vaguely similar, though much milder, group of conditions in which precocious osteoarthritis and spondylosis are the…
- polyester (chemical compound)
polyester, a class of synthetic polymers built up from multiple chemical repeating units linked together by ester (CO-O) groups. Polyesters display a wide array of properties and practical applications. Permanent-press fabrics, disposable soft-drink bottles, compact discs, rubber tires, and enamel
- polyester bee (insect)
plasterer bee, (family Colletidae), large family of bees with more than 2,500 species found worldwide. Their common name, which is often used to refer to the bees of the genus Colletes, is derived from the protective, cellophane-like material that females secrete and plaster to the walls of their
- polyesterurethane
materials science: General requirements of biomaterials: In addition, degradable polyesterurethane foam was abandoned as a fixation patch for breast prostheses, because it offered a distinct possibility for the release of carcinogenic by-products as it degraded.
- polyestrous (zoology)
estrus: , ground squirrels) are polyestrous: if not impregnated, they will come into heat repeatedly during the breeding season. Males can recognize a female in heat by smell; certain substances (pheromones) are secreted only at this portion of her cycle. The female’s genital area may be swollen during estrus, and…
- polyethene (chemical compound)
polyethylene (PE), light, versatile synthetic resin made from the polymerization of ethylene. Polyethylene is a member of the important family of polyolefin resins. It is the most widely used plastic in the world, being made into products ranging from clear food wrap and shopping bags to detergent
- polyether (chemical compound)
polyether, any of a class of organic substances prepared by joining together or polymerizing many molecules of simpler compounds (monomers) by establishing ether links between them; polyethers, which may be either chainlike or networklike in molecular structure, comprise an unusually diverse group
- polyetheretherketone (chemical compound)
major industrial polymers: Polyetherketone (PEK) and polyetheretherketone (PEEK): PEK and PEEK are high-strength, radiation-resistant engineering plastics whose structures combine both ether and ketone groups. Both are thermally stable and highly resistant to chemicals. Principal uses are in machine parts, nuclear power-plant equipment, automobile parts, aerospace components, cable insulation, and pump parts.
- polyetherimide (chemical compound)
major industrial polymers: Polyimides: …Torlon by Amoco Corporation) and polyetherimide (PEI; trademark Ultem); these two compounds combine the imide function with amide and ether groups, respectively.
- polyetherketone (chemical compound)
major industrial polymers: Polyetherketone (PEK) and polyetheretherketone (PEEK): PEK and PEEK are high-strength, radiation-resistant engineering plastics whose structures combine both ether and ketone groups. Both are thermally stable and highly resistant to chemicals. Principal uses are in machine parts, nuclear power-plant equipment, automobile parts, aerospace components, cable insulation,…
- polyethyl acrylate (chemical compound)
major industrial polymers: Polymethyl acrylate and polyethyl acrylate: These materials are polymers of acrylic esters (CH2=CHCO2R), which have the following repeating unit structure:
- polyethylene (chemical compound)
polyethylene (PE), light, versatile synthetic resin made from the polymerization of ethylene. Polyethylene is a member of the important family of polyolefin resins. It is the most widely used plastic in the world, being made into products ranging from clear food wrap and shopping bags to detergent
- polyethylene glycol (chemical compound)
polyethylene glycol (PEG), synthetic chemical compound derived from petroleum that is widely used as a laxative for the treatment of constipation and that has various other uses, including as a moisture carrier, solvent, and thickener. Polyethylene glycol is a hydrophilic (“water-loving”) polymer
- polyethylene oxide (chemical compound)
polyethylene glycol (PEG), synthetic chemical compound derived from petroleum that is widely used as a laxative for the treatment of constipation and that has various other uses, including as a moisture carrier, solvent, and thickener. Polyethylene glycol is a hydrophilic (“water-loving”) polymer
- polyethylene terephthalamide (chemical compound)
man-made fibre: Polyesters and polyamides: This compound, polyethylene terephthalamide, can only be spun from solution, using costly solvents; therefore, it is not made into fibres.
- polyethylene terephthalate (chemical compound)
polyethylene terephthalate (PET or PETE), a strong, stiff synthetic fibre and resin and a member of the polyester family of polymers. PET is spun into fibres for permanent-press fabrics and blow-molded into disposable beverage bottles. PET is produced by the polymerization of ethylene glycol and
- Polyeucte (play by Corneille)
Polyeucte, Neoclassical verse tragedy in five acts by Pierre Corneille, produced about 1641–42 and published in 1643. It is known in English as Polyeuctes. With Le Cid, Horace, and Cinna, Polyeucte forms Corneille’s classical tetralogy. The title character is a recent Christian convert who would
- polyextremophile (biology)
extremophile: …simultaneously to multiple stresses (polyextremophile); common examples include thermoacidophiles and haloalkaliphiles.
- polyextremophilic organism (biology)
extremophile: …simultaneously to multiple stresses (polyextremophile); common examples include thermoacidophiles and haloalkaliphiles.
- polyfidelity (society)
polyamory: Polyfidelity is a type of polyamorous relationship in which three or more people are involved in an exclusive relationship or relationships and do not date outside the group. In a group of three, for instance, all three people might be involved with each other, or…
- Polyflon (chemical compound)
polytetrafluoroethylene (PTFE), a strong, tough, waxy, nonflammable synthetic resin produced by the polymerization of tetrafluoroethylene. Known by such trademarks as Teflon, Fluon, Hostaflon, and Polyflon, PTFE is distinguished by its slippery surface, high melting point, and resistance to attack
- polyformaldehyde (chemical compound)
polymer: Synthetic polymers: The simplest polyacetal is polyformaldehyde. It has a high melting point and is crystalline and resistant to abrasion and the action of solvents. Acetal resins are more like metal than are any other plastics and are used in the manufacture of machine parts such as gears and bearings.
- polyfunctional compound (chemical compound)
monomer: …feature of a monomer is polyfunctionality, the capacity to form chemical bonds to at least two other monomer molecules. Bifunctional monomers can form only linear, chainlike polymers, but monomers of higher functionality yield cross-linked, network polymeric products.
- polyfunctional heterogeneous catalysis (chemistry)
catalysis: Other catalytic compounds: The term polyfunctional heterogeneous catalysis is applied to a group of catalysts in which more than one component of the surface is active in the processes under study. One example of a bifunctional heterogeneous catalyst is the catalyst of metal (platinum or nickel) deposited on a silica-alumina…
- polygamy (marriage)
polygamy, marriage to more than one spouse at a time. The most typical forms of polygamy have been polygyny, in which cowives share a husband, or polyandry, in which cohusbands share a wife. However, same-sex marriage may instigate new forms of polygamy. Similar but without the commitment of
- polygamy (animal behavior)
animal social behaviour: Social interactions involving sex: Although polygamy also involves mating with multiple partners, it often refers to cases in which individuals form relatively stable associations with two or more mates. Most such species exhibit polygyny, in which males have multiple partners. Some examples include the red-winged blackbird (Agelaius phoeniceus) and house…
- polygamy (botany)
flower: Form and types: …plant, the plant is termed polygamous.
- polygene (genetics)
heredity: Polygenic inheritance: The greatest difficulties of analysis and interpretation are presented by the inheritance of many quantitative or continuously varying traits. Inheritance of this kind produces variations in degree rather than in kind, in contrast to the inheritance of discontinuous traits resulting from single genes…
- polygenetic landform (geology)
continental landform: The concept of periodic random dominance: …with it the implication of polygenetic landforms and landscapes where geomorphic system dominance fails to develop. Indeed, dominance becomes the special case because it is dependent on a particular juxtaposition of tectonic and/or climatic elements over a protracted interval in a given area. One estimate places polygenetic landforms over approximately…
- polygenic character (biology)
plant breeding: Quantitative characters: In other cases, however, plant traits grade gradually from one extreme to another in a continuous series, and classification into discrete classes is not possible. Such variability is termed quantitative. Many traits of economic importance are of this type; e.g., height, cold and…