The swordfish (Xiphias gladius), also known as the broadbill, or the forktail, is the only species in the bony fish family Xiphiidae. The swordfish is highly prized as a food fish, and as a game fish. Its most distinguishing characteristic is the remarkable elongation of the upper jaw, which resembles a long, flattened, serrated sword and can extend up to one-third of the body length. The sword is…
Chemical symbols are shorthand abbreviations of the names of the 109 known elements. Each element has its own unique symbol. Since science is an international enterprise, chemical symbols are determined by international agreement. The use of symbols for the chemical elements existed long before a systematic method was developed. The alchemists associated the symbols of the planets not only with th…
The symbolist movement began in France in the 1880s as a literary phenomenon. The term symbolism, however, quickly came to encompass a range of arts, from painting and sculpture to theater and music. While the movement is often said to have spanned the years 1885–1895, the ideas and aesthetic interests of symbolism are often traced back to the middle of the nineteenth century, and many earl…
Many real objects and forces at all size scales—subatomic particles, atoms, crystals, organisms, stars, and galaxies—exhibit symmetry, of which there are many kinds. Line or bilateral symmetry, the simplest and most familiar, is the symmetry of by any figure or object that can be divided along a central line and then restored (geometrically) to wholeness by reflecting its remaining h…
Nerve impulses are transmitted through a functional gap or intercellular space between neural cells (neurons) termed the synapse (also termed the synaptic gap). Although nerve impulses are conducted electrically within the neuron, in the synapse they are continued (propogated) via a special group of chemicals termed neurotransmitters. The synapse is more properly described in structural terms as a…
Syncretism—the process whereby two or more independent cultural systems, or elements thereof, conjoin to form a new and distinct system—is among the most important factors in the evolution of culture in general, but especially in the history of religion. Indeed, all of the so-called world religions, that is, Christianity, Judaism, Islam, Hinduism, Buddhism, and Confucianism, are to a…
A syndrome is a collection of signs, symptoms, and other indications which, taken together, characterize a particular disease or abnormal medical condition. Medical workers place a heavy reliance on the collection of such indicators in the diagnosis of health problems and disorders. The usual approach is to question patients about the nature of their complaints and then to conduct examinations and…
Chemical synthesis is the preparation of a compound, usually an organic compound, from easily available or inexpensive commercial chemicals. Compounds are prepared or synthesized by performing various chemical reactions using an inexpensive starting material and changing its molecular structure, by reactions with other chemicals. The best chemical syntheses are those that use cheap starting materi…
The virtuoso demands that composers placed on musicians at the end of the 1800s were but a foretaste of things to come in the twentieth century. Members of the orchestra were complaining that the music of contemporary composers was unplayable because of the enormous difficulty of complex orchestral writing styles. With the Paris premiere of Igor Stravinsky's "Le Sacre Du Printemps&#x…
The earliest known talking machine was developed in 1778 by Wolfgang von Kempelen. Eyewitnesses reported that it could speak several words in a timid, childlike voice. While the talking machine's success appears genuine, Baron von Kempelen's accomplishments are not above suspicion. Nine years earlier, he had built a chess-playing machine, which defeated many players, including Napole…
When a vertebrate encounters substances that are capable of causing it harm, a protective system known as the "immune system" comes into play. This system is a network of many different organs that work together to recognize foreign substances and destroy them. The immune system can respond to the presence of a disease causing agent (pathogen) in two ways. Immune cells called the B c…
Scarlet tanager (Piranga olivacea). Photograph by Robert J. Huffman. Field Mark Publications. Reproduced by permission. Tanagers are 239 species of extremely colorful, perching birds that make up the family Thraupidae. The evolutionary history and phylogenetic relationships of the tanagers and related birds are not well understood. Recent taxonomic treatments have included the tanagers as a…
Taphonomy is the study of how organisms are preserved in the fossil record (the term is derived from the Greek word taphos, which means grave). Taphonomists seek to understand how an organism died and what happened to its body before and during burial. They also try to determine what factors may have contributed to unequal representation of certain groups in the fossil record due to differences in…
Tapirs, of the family Tapiridae, are large, forest-dwelling mammals with a long flexible snout. They are found in tropical South and Central America, and in southeast Asia. There are four species of tapirs in the single genus, Tapirus. Tapirs are grouped with horses and rhinoceroses in the order Perissodactyla, which are the odd-toed, hoofed mammals. Tapirs have a fourth toe on their front feet. E…
Tarsiers are prosimians, or primitive primates, in the family Tarsiidae, found the islands of Southeast Asia. Tarsiers have only 34 teeth, unlike their closest prosimian relatives, the lemurs and lorises, which have 36 teeth. Also, the upper lip of tarsiers is not fastened to the gum underneath, so that the face can be mobile, rather like the more advanced primates, monkeys and apes. Tarsiers are …
Tartaric acid is used making silver mirrors, in the manufacturing of soft drinks, to provide tartness to foods, in tanning leather and in making blueprints. Tartaric acid is used in cream of tartar (for cooking) and as an emetic (a substance used to induce vomiting). It readily dissolves in water and is used in making blueprints. Tartaric acid is a molecule that demonstrates properties of optical …
The Tasmanian devil (Sarcophilus harrisii) is the largest surviving marsupial predator, occurring only on the island of Tasmania in dense thickets and forests. The Tasmanian devil is one of about 45 species of marsupial predators that make up the family Dasyuridae. The Tasmanian devil once occurred widely in Australia and Tasmania. However, the Tasmanian devil became extirpated from Australia foll…
Taxonomy is the field of biology which deals with the nomenclature, identification, and classification of organisms. There are over one million known species on Earth and probably several million more not yet identified. Taxonomists are responsible for identifying, naming, and classifying all these different species. Systematics is a discipline of biology that explicitly examines the natural varia…
The tea plant Camellia sinensis, which is a member of the plant family Theaceae, is a small evergreen tree that is related to the camellias commonly grown in gardens. Although there are more than 3,000 different types, or grades, of true tea that are produced, nearly all are derived from this single species. Other plants such as peppermint and jasmine, which are also often steeped to yield a hot d…
Introduced in the first decades of the nineteenth century, the word technology signified the pursuit of a science to encompass all the industrial arts. Mechanical arts, a term used in medieval and early modern Europe, indicated something different because it included, for example, painting and sculpture. The introduction of the term technology corresponded somewhat contemporaneously with the intro…
Tectonics is the study of the deformation of Earth's lithosphere—both the causes of deformation and its effects. Tectonics focuses primarily on mountain-building, but involves other unrelated activities as well. Since the development of the theory of plate tectonics, tectonics has become an especially active area of research in geology. Deformation of rocks, known as tectonism or dia…
A telegraph is any system that transmits encoded information by signal across a distance. Although it is associated with sending messages via an electric current, the word telegraph was coined to describe an optical system of sending coded messages. From its invention until the telephone became a viable system, the telegraph was the standard means of communicating both between and within metropoli…
The term telephone (from Greek tele, afar, and phone, sound) in a broad sense means a specific type of Figure 1. Telephone set simplified circuit. Illustration by Hans & Cassidy. Courtesy of Gale Group. telecommunications which permits people to carry direct conversations over almost any distance. The articulate speech is transmitted in a form of either modulated electric current pr…
The telescope is an instrument which collects and analyzes the radiation emitted by distant sources. The most common type is the optical telescope, a collection of lenses and/or mirrors that is used to allow the viewer to see distant objects more clearly by magnifying them or to increase the effective brightness of a faint object. In a broader sense, telescopes can operate at most frequencies of t…
The invention of the cathode ray tube in 1897 by Ferdinand Braun quickly made possible the technology that we call television. Indeed, by 1907, the cathode ray tube was supplying television images. Within 50 years, television had become a dominant form of entertainment and an important way to acquire information. This remains true today, as the average American spends between two and five hours ea…
In classical and medieval thought, temperance, or sōphrosynē, could signify one or more of a congeries of traits, such as moderation, self-knowledge, self-restraint, or independence. These virtues were to be cultivated by the individual. In modern history, however, the meaning of temperance has become narrowed to refer only to limits on the consumption of alcoholic beverages, whether t…
An organism maintains homeostasis, a steady internal state, only if its body temperature stays within prescribed limits. Cellular activities require an optimum amount of heat. They depend on enzyme action, and enzymes function within a narrow range of temperature. For this reason, living things can only tolerate a limited rise or drop in temperature from the optimum. Mechanisms exist that regulate…
Tenrecs are four-legged nocturnal mammals belonging to the order Insectivora. Tenrecs have evolved into more distinct forms than any other family of animals within the order. Tenrecs can resemble hedgehogs, moles, shrews, or muskrats, depending on the species. Some species of tenrecs have a long tail and long hind legs, while others have a stumpy tail and short hind legs. A stripped tenrec. P…
In general, there are three types of algebraic expressions which can be classified as terms. These include expressions made up of a single variable or constant, ones that are the product or quotient of two or more variables and/or constants, and those that are the product or quotient of other expressions. For example, the number 4 and the variable x are both terms because they consist of a single …
Termites are slender, social insects, ranging in size from 0.007-0.072 in (2-22 mm) long. The reproductive members of the species have wing spans of 0.03-0.3 in (10-90 mm). Inhabiting nests of their own construction, they live in permanent and often highly developed communities. While termites thrive in warm, humid environments, some species have also adapted to open savannas and temperate zones. …
The word terrace is applied to geological formations, architecture such as a housing complex built on a slope, or an island between two paved roads. However, Rice terraces in Bali, Indonesia. JLM Visuals. Reproduced by permission. the act of terracing specifies an agricultural method of cultivating on steeply graded land. This form of conservation tillage breaks a hill into a series of ste…
While terrorism has arisen in a variety of cultures and historical periods, much of the world's attention on this phenomenon in the late twentieth and early twenty-first centuries has centered on the Middle East. Middle Eastern terrorism emerged in Western consciousness during the 1970s, primarily through the rise of secular leftist and nationalist groups among Palestinian exiles, which tar…
Tetanus, also known as lockjaw, is a disease caused by a type of bacteria that lives in the soil and the intestines of people and animals. When these bacteria get into the body, the poisons they produce affect the nervous system, causing muscle spasms and, in many cases, death. Tetanus is not contagious and can be prevented with a vaccine. Tetanus is caused by the bacteria Clostridium tetani. Teta…
Textiles are generally considered to be woven fabrics. They may be woven from any natural or synthetic fibers, filaments, or yarns that are suitable for being spun and woven into cloth. Spinning is the process of making yarn or thread by the twisting of vegetable fibers, animal hairs, or man-made fibers, i.e., filament-like elements only a few inches in length. In the spinning mill, the raw materi…
Thalidomide is a drug that was marketed in the late 1950s and early 1960s in Great Britain and Europe. It was used both as a sleeping pill and as an antidote to morning sickness in pregnant women. In 1962, a host of usually rare limb abnormalities suddenly became much more common. About 10,000 babies were born displaying, in particular, a shortening of the arms and/or legs called phocomelia. In ph…