Science & Philosophy: Ambiguity - Ambiguity to Anticolonialism in Middle East - Ottoman Empire And The Mandate System
America - The Indians, The United States, Critical Reflections, Bibliography
America is one of the greatest political-philosophical symbols in world history. It is equal in importance to Athens representing philosophy, Jerusalem representing biblical religion, Rome representing both its pagan and Catholic manifestations, and Mecca representing the home of Islam. But what is meant by America? When people refer to it are they signifying the precise measurements of the landma…
American Standard Code for Information Interchange
The American Standard Code for Information Interchange (ASCII; pronounced "askee") was first introduced in 1968 as a method of encoding alphabetic and numeric data in digital format. Although ASCII code was originally developed for the teletypewriter industry, it has since found widespread use in computer and information-transfer technologies. Because ASCII code is standardized, comp…
U.S. Americanization - American National Identity And Ideologies Of Americanization, Conclusion, Bibliography
Americanization refers to processes of "becoming American," and to organized efforts to encourage the transformation of immigrants into "Americans." The term was in informal use in the United States in the mid-nineteenth century, but it is most prominently associated with the movement of that name during the 1910s and early 1920s. The term is often used interchangeably …
Ames Test
The Ames test, named for its developer, Bruce Ames, is a method to test chemicals for their cancer-causing properties. It is used by cosmetic companies, pharmaceutical manufacturers, and other industries that must prove that their products will not cause cancer in humans. Ames, a cancer researcher at the University of California, began development of his method in the late 1950s. He believed an ef…
Amicable Numbers
Two numbers are said to be amicable (i.e., friendly) if each one of them is equal to the sum of the proper divisors of the others, i.e., whole numbers less than the given numbers that divide the given number with no remainder. For example, 220 has proper divisors 1, 2, 4, 5, 10, 11, 20, 22, 44, 55, and 110. The sum of these divisors is 284. The proper divisors of 284 are 1, 2, 4, 71, and 142. Thei…
Amides - Classification And Properties, Important Synthetic Amides - Some familiar amides
The synthesis of a protein results in a protein in the formation of an amide bond between adjacent amino acids. Proteins can be considered the most common examples of amides in the natural world. A naturally occurring amide is nicotinamide, one of the B vitamins. A third familiar natural amide is urea, also known as carbamide. Urea is the compound by which otherwise toxic wastes are excreted from …
Amino Acid - Chemical Structure, Bonding
A chemical reaction that is characteristic of amino acids involves the formation of a bond, called a peptide linkage, between the carboxyl group of one amino acid and the amino group of a second amino acid. Very long chains of amino acids can bond together in this way to form proteins. The importance of the amino acids in nature arises from their ability to form proteins, which are the basic build…
Ammonification - Ammonification, Humans And Ammonification
Ammonification is a key component in the nitrogen cycle of ecosystems. The nitrogen cycle consists of a complex of integrated processes by which nitrogen circulates among its major compartments in the atmosphere, water, soil, and organisms. During various phases of the nitrogen cycle, this element is transformed among its various organic and inorganic compounds. …
Amnesia - How amnesia is manifested, Causes of amnesia
Amnesia is a dissociative psychological disorder manifested by total or partial loss of memory and usually caused by a trauma. Unlike ordinary forgetfulness (the inability to remember a friend's telephone number), amnesia is a serious threat to a person's professional and social life. Amnesia, which depending on its cause can be either organic and psychogenic, has several types. Glob…
Amniocentesis
Amniocentesis is an invasive procedure used to obtain amniotic fluid for prenatal diagnosis of a fetus (e.g., assessment of fetal lung maturity). In the 1950s the measurement of bilirubin concentrations present in amniotic fluid in monitoring the rhesus diseases was first reported. Amniocentesis for fetal chromosome analysis was also initiated in the 1950s. The first application was for fetal sex …
Amoeba
Amoebas are single-celled protozoans of the order Amoebida. They consist of a mass of cellular fluid surrounded by a membrane, and containing one or more nuclei (depending upon the species), as well as other cell organelles, such as food vacuoles. The word amoeba is derived from the Greek word ameibein (to change), which describes the amoeba's most easily distinguishable feature, the contin…
Amphetamines - History, Ice, Action, Physical And Psychological Effects, Treatment
Amphetamines are a group of nervous system stimulants that includes amphetamine, dextroamphetamine, and methamphetamine. They are used to induce a state of alert wakefulness and euphoria, and since they inhibit appetite, they also serve as diet pills. After World War II, they were widely prescribed by physicians as diet pills, but they are generally no longer recommended for weight loss programs s…
Amphibians
The vertebrate class Amphibia, to date, includes about 3,500 species in three orders: frogs and toads (order Anura), salamanders and newts (order Caudata), and caecilians (order Gymnophiona). There is, however, a much larger number of extinct species, because this ancient group of animals were the first vertebrates to begin exploiting terrestrial environments. Fossil amphibians are known from at l…
Amplifier - Amplifiers And Energy, Cascading Amplifiers, Discrete And Integrated Amplifiers - Efficiency
An amplifier is a device, usually electronic, that magnifies information to a more powerful signal at the amplifier's output. Amplifiers are usually based on electronic principles but may utilize hydraulics or magnetics. Amplifiers are used when the electrical power of a signal must be increased. Audio amplifiers can increase the microwatts developed by a microphone to more than a million w…
Anabolism
Anabolism, or biosynthesis, is the process by which living organisms synthesize complex molecules of life from simpler ones. Anabolism, together with catabolism, are the two series of chemical processes in cells that are, together, called metabolism. Anabolic reactions are divergent processes. That is, relatively few types of raw materials are used to synthesize a wide variety of end products. Thi…
Analemma
The Earth's orbit around the Sun is not a perfect circle. It is an ellipse, albeit not a very flattened one, and this leads to a number of interesting observational effects. One of these is the analemma, the apparent path traced by the Sun in the sky when observed at the same time of day over the course of a year. The path resembles a lopsided figure eight, which you sometimes see printed o…
Analgesia - Nonaddictive Analgesics, Mechanism Of Nonaddictive Analgesics, Addictive Analgesics, Mechanism Of Addictive Analgesics, Development Of New Analgesics
Analgesia is the loss of pain without the loss of consciousness. Techniques for controlling and relieving pain include acupuncture, anesthesia, hypnosis, biofeedback, and the use of analgesic drugs. Acupuncture is the ancient Chinese practice of inserting fine needles along certain pathways of the body and is used to relieve pain, especially in surgery, and to cure disease. In Western medicine the…
Analytical Philosophy - Moore, Russell, Frege, Wittgenstein, The Vienna Circle, Ordinary Language Philosophy, Quine
It was only in the 1960s that the phrase "analytical philosophy" came into frequent use as a way of describing the kind of philosophy characteristic of much English-language philosophy of the twentieth century. But occasional references to "analytical" (or "analytic") philosophy as a new kind of philosophy can be found much earlier, where it is primarily u…
Anaphylaxis
Anaphylaxis is a severe, sudden, often fatal bodily reaction to a foreign substance or antigen. C. R. Richet first coined the term to define the puzzling reactions that occurred in dogs following injection of an eel toxin. Instead of acquiring immunity from the toxin as expected, the dogs experienced acute reactions, including often fatal respiratory difficulties, shock, and internal hemorrhaging.…
Anarchism - Anarchist Principles In Context, Contemporary Anarchism, Bibliography
The term anarchy comes from an ancient Greek word meaning "without a leader or ruler." However, proponents of anarchism have most often used the term to refer to a natural state of society in which people are not governed by submission to human-made laws or to any external authority. Anarchism is above all a moral doctrine concerned with maximizing the personal freedom of individuals…
Comparative Anatomy
There are many forms of evidence for evolution. One of the strongest forms of evidence is comparative anatomy; comparing structural similarities of organisms to determine their evolutionary relationships. Organisms with similar anatomical features are assumed to be relatively closely related evolutionarily, and they are assumed to share a common ancestor. As a result of the study of evolutionary r…
Ancestor Worship - Ancestors In Africa And Asia, Among The Inca, Ancestral Ambivalence, Bibliography
Ancestor worship is the reverent devotion expressed by descendants for their deceased forebears through a culturally prescribed set of rituals and observances. The prominence of ancestors as a focus of worship within a broader religious tradition is common in many parts of the world, including Asia, Africa, and Native America, but there are few unifying characteristics cross-culturally. Commonalit…
Anchovy
Anchovies are small, bony fish in the order Clupeiformes, a large group that also includes herring, salmon, and trout. Anchovies are in the family Engraulidae, and all of the more than 100 species are in the genus Engraulis. Anchovies are predominantly marine fish, but are occasionally found in brackish waters and even in freshwater. Species of anchovies are found in the Mediterranean Sea, Black S…
Anemia - Causes Of Anemia, Trauma And Surgery, Low Red Blood Cell Production, Aplastic Anemia, Megaloblastic Anemia - Sickle cell anemia, Others
Anemia means literally lack of blood. In fact it is a reduction in the number of red blood cells, plasma, or packed red blood cells to a level that is lower than necessary for normal functioning. This is the result of the inability to replace lost cells or plasma volume at the rate they are being lost. The underlying cause for anemia may be one of several conditions. Although blood cell levels are…
Anesthesia - History Of Anesthesia, Nitrous Oxide, Chloroform, Emergence Of Anesthesiology, Types Of Anesthesia, Theory Of The Mechanism Of Anesthesia - Ether
Anesthesia is the loss of feeling or sensation. It may be accomplished without the loss of consciousness, or with partial or total loss of consciousness. Anesthesiology is a branch of medical science that relates to anesthesia and anesthetics. The anesthetist is a specialized physician in charge of supervising and administering anesthesia in the course of a surgical operation. Depending on the typ…
Aneurism
An aneurism is a weak spot in the wall of an artery or a vein that dilates or balloons out, forming a blood-filled sack or pouch. Aneurisms can occur almost anywhere in the body and are found in all age groups, although they occur primarily in the elderly. The foremost cause of aneurisms is atherosclerosis, or fatty deposits in the arteries. If an aneurism bursts, a massive amount of blood is rele…
Angelfish
The word angelfish is a general term that refers to many different kinds of fish. Typically, angelfish have thin bodies that are flattened laterally. They tend to have elongated dorsal, anal, and pelvic fins, and display a wide variety of colors, making them popular aquarium species. The association of these fish with angels may be due to the fins resembling wings. All angelfish belong to the taxo…
Angiography
Angiography is a medical diagnostic test in which a fluid that is visible on x rays is used to take photographs of the arteries of the heart or other organs. First used in the early 1950s, angiography is now a standard procedure to locate areas where an artery is closed or constricted and interfering with the circulation of blood. Angiography applied to the heart is called coronary angiography. A …
Angiosperm
Angiosperm is the name given to those plants that produce flowers during sexual reproduction. The term literally means "vessel seed" and refers to the fact that seeds are contained in a highly specialized organ called an ovary. Flowering plants are the most recently evolved of the major groups of plants, arising only about 130 million years ago. Despite their geological youthfulness,…
Angle - Units Of Measurement Of An Angle, Geometric Characteristics Of Angles
An angle is a geometric figure created by two line segments that extend from a single point or two planes which extend from a single line. The size of an angle, measured in units of degrees or radians, is related to the amount of rotation required to superimpose one of its sides on the other. First used by ancient civilizations, angles continue to be an important tool to science and industry today…
Anglerfish
Anglerfish are marine fish that attract prey by dangling a fleshy, bait-like appendage (the esca) in front of their heads. The appendage, which resembles a fishing pole, is attached to the end of the dorsal fin's foremost spine (the illicium), which is separated from the rest of the fin. Anglerfish belong to the order Lophiiformes, which includes three suborders, 15 families, and about 215 …
Animal
Animals are creatures in the kingdom Animalia, one of the five major divisions of organisms (the others are: Monera or bacteria, Fungi, Protists or protozoans, and Plantae or plants). Animals are multicellular, eukaryotic organisms, with cells that do not have walls made of cellulose. Animals are capable of voluntary, spontaneous movements, often in response to sensory perceptions. For their nutri…
Animal Cancer Tests - Mice—the best animal model for cancer research
The chemical causation of cancer is not a simple process. Many, perhaps most, chemical carcinogens do not have the potency to cause cancer in their usual condition. The non-cancer causing form of the chemical is called a procarcinogen. Procarcinogens are frequently complex organic compounds that the human body attempts to dispose of when ingested. Hepatic enzymes chemically change the procarcinoge…
Anoles
Anoles are small lizards in the genus Anolis (family Iguanidae), found only in the Americas, mostly in the tropical countries. Because anoles can change the color of their skin according to their mood, temperature, humidity, and light intensity, these animals are sometimes called chameleons. However, none of the more than 300 species of anoles is closely related to the true chameleons (family Cham…
Ant-Pipits
The ant-pipits are 10-11 species of birds that make up the family Conopophagidae. These birds are exclusively South American, occurring in tropical rain forests of Amazonia. The usual habitat of ant-pipits is thick and lush with foliage, and the birds are rather shy. Consequently, these small birds are difficult to see and demanding to study. Therefore, little is known about their biology and ecol…
Antarctica - Antarctica—an Overview, Geology, Climate, Plants And Animals, Exploration Of The Continent, Scientific Exploration
Of the seven continents on planet Earth—North America, South America, Europe, Africa, Asia, Australia, and Antarctica—the last lies at the southernmost tip of the world. It is the coldest, driest, and windiest continent. Ice covers 98% of the land, and its 5,100,000 sq mi (13,209,000 sq km) occupy nearly one-tenth of the Earth's land surface, or the same area as Europe and the…
Antbirds and Gnat-Eaters
The antbirds and gnat-eaters are 231 species of birds that comprise the relatively large family, Formicariidae. These birds only occur in Central and South America, mostly in lowland tropical forests. The antbirds and gnat-eaters are variable in their body form and size. Their body length ranges from 4–14 in (10–36 cm), and they have short, rounded wings, and a rounded tail that can …
Anteaters
Anteaters belong to the family Myrmecophagidae, which includes four species in three genera. They are found in Trinidad and range from southern Mexico to northern Argentina. The spiny anteater (echidna) of Australia is an egg-laying mammal and is not related to the placental anteaters of the New World. The banded anteater (or numbat) of Australia is a marsupial mammal, and not a close relative of …
Antelopes and Gazelles
Antelopes and gazelles belong to the family Bovidae, which includes even-toed hoofed animals with hollow horns and a four-chambered stomach. Sheep, cattle, and goats are also bovids. The family Bovidae in Africa includes nine tribes of antelopes, one of which includes the 12 species of gazelles (Antilopini). Other tribes are the duikers (Cephalophini), dwarf antelopes (Neotragini), reedbuck, kob, …
Antenna
An antenna is a device used to transmit and receive electromagnetic waves such as radio waves and microwaves. Antenna for a Doppler weather radar site. Doppler radar can be used to detect wind shear and microburst weather conditions. Photograph by Brownie Harris. Stock Market. Reproduced by permission. Antennas provide the transition between a guided wave (flowing in a wire) and a free spa…
Anthrax
Anthrax is the name given to an infection that is caused by the bacterium Bacillus anthracis. The bacterium is common in cattle, sheep, goats, camels, antelopes, and other plant-eating animals. Humans can also become contaminated with the anthrax bacterium. In the past, such human contamination was only associated with farmers or sheepherders, people who worked in close contact with infected anima…
Anthropocentrism
Anthropocentrism is a world view that considers humans to be the most important factor and value in the Universe. In contrast, the biocentric world view considers humans to be no more than a particular species of animal, without greater intrinsic value than any of the other species of organisms that occur on Earth. The ecocentric world view incorporates the biocentric one, while additionally propo…
Anthropology - Biological Anthropology, Archaeology, Linguistics, Sociocultural Anthropology, Bibliography
As an academic discipline, anthropology is somewhat less than two centuries old, but speculations, if not rigorous scientific theories, about where we human beings came from and how to account for the physical and cultural differences that distinguish our communities and nations from one another probably began during prehistory. In the United States (but not in most other academic settings, for ex…
Anti-Inflammatory Agents
Anti-inflammatory agents are compounds that reduce the pain and swelling associated with inflammation. Inflammation is a response of the body to injuries such as a blow or a burn. The swelling of the affected region of the body occurs because fluid is directed to that region. The inflammatory response can aid the healing process. In conditions such as rheumatoid arthritis, however, the swelling an…
Antibiotics - Antibiotic Classes, Antibiotic Resistance
Antibiotics are natural or synthetic compounds that kill bacteria. Antibiotics are not active against viruses. There are many different antibiotics that have different bacterial targets. Some antibiotics are specific in their activity, affecting only one or a few types (genera) of bacteria. Other antibiotics, such as penicillin, are active against a wide variety of bacteria. Such antibiotics are d…
Antibody and Antigen - Igg, Iga, Igm, Ige, Types Of Antigens, Vaccination, Monoclonal Antibodies - Functions of antibody types, IgD
The antibody and antigen reaction is an important protective mechanism against invading foreign substances. The antibody and antigen reaction, together with phagocytosis, constitute the immune response (humoral immune response). Invading foreign substances are antigens while the antibodies, or immunoglobulins, are specific proteins generated (or previously and present in blood, lymph or mucosal se…
Anticolonialism in Africa - Aims And Objectives, The Development Of Nationalism, After Political Independence: The Struggle Continues, Bibliography
In post–World War II history, decolonization is a term generally employed to describe and explain the struggle for, and attainment of, freedom from colonial rule by most countries in Asia and Africa. This attainment was marked by a transfer of power; national political elites assumed the administrative responsibilities and duties previously discharged by the colonial authorities. Thus, new…
Anticolonialism in Latin America - Independence, Neocolonialism, Anti-imperialism, Non-spanish Caribbean, Bibliography
Over the past five hundred years, Latin America has experienced three and possibly four periods of colonization, all of which gave rise to anticolonial movements. The first period symbolically began with Christopher Columbus's arrival in the Americas on 12 October 1492, launching three centuries of Spanish, Portuguese, and British colonial control over the hemisphere, with the French, Dutch…