ground pearl, (genus Margarodes), any of a group of scale insects in the family Margarodidae (order Homoptera) that have an iridescent globular body 2 to 4 mm (0.08 to 0.16 inch) in length. Ground pearl insects vary in colour from metallic bronze, red, or gold to cream or silver. They are worldwide

club moss: Major genera and species: Ground pine (Dendrolycopodium obscurum), a 25-cm- (10-inch-) tall plant, has underground-running stems. It is native to moist woods and bog margins in northern North America, to mountain areas farther south, and to eastern Asia.

club moss, (family Lycopodiaceae), any of some 400 species of seedless vascular plants constituting the only family of the lycophyte order Lycopodiales. The taxonomy of the family has been contentious, and the number of genera vary depending on the source. The plants are native mainly to tropical

bugleweed: Ground pine, or yellow bugle (A. chamaepitys), is shorter and has yellow flowers and three-parted needlelike leaves that are pine-scented.

celestial navigation: This location is called the ground position (GP). GP can thus be stated in terms of celestial coordinates, with the declination of the celestial object equal to latitude and the Greenwich hour angle equal to longitude. Almanacs such as those published by the Nautical Almanac Office of the U.S. Naval…

telecommunications media: Reflected propagation: …of reflected wave propagation are ground reflection, where the wave is reflected off land or water, and ionospheric reflection, where the wave is reflected off an upper layer of the Earth’s ionosphere (as in shortwave radio; see below The radio-frequency spectrum: HF).

ground roller, any of five species of pigeon-sized birds that comprise the family Brachypteracidae (order Coraciiformes) known for their tumbling flight. They are found only in Madagascar. Four species inhabit deep forest; one, the long-tailed ground roller (Uratelornis chimaera), confined to a

carcharhinid, any member of the shark family Carcharhinidae, which includes 12 genera and about 50 species found worldwide. Carcharhinids are found primarily in warm and temperate ocean waters, though a few species inhabit fresh or brackish water. The Carcharhinidae is one of the largest families

bull shark, (Carcharhinus leucas), species of large predatory shark found in shallow coastal lagoons, estuaries, and harbours in tropical and subtropical oceans and seas worldwide. The bull shark is one of only a few shark species also capable of living and breeding in freshwater environments. Bull

sloth: Classification and paleontology: …Megalonychidae, whose extinct relatives, the ground sloths, once ranged into areas of North America as far north as Alaska and southern Canada. Different species of ground sloths varied greatly in size. Most were small, but one, the giant ground sloth (Megatherium americanum), was the size of an elephant; others were…

mining: Mechanized methods: Ground sluicing is a special technique for the mining of natural placers as well as artificial ones (tailings piles, for example). A natural flow of water is used to disintegrate and then transport the material through a sluice, where the valuable mineral is concentrated. In…

wolf spider, (family Lycosidae), large family of more than 2,300 species and 135 genera of spiders named for their wolflike habit of chasing and pouncing upon prey. The group is widespread, with about 240 species occurring in North America and about 50 in Europe. Interestingly, numerous species

ground squirrel, any of 62 species of long-bodied terrestrial rodents that are active during the day and have short legs, strong claws, small rounded ears, and a short or moderately long tail. Colour varies widely among species from gray, tawny, or pale brown to olive, reddish, or very dark brown.

spectroscopy: Basic properties of atoms: …possible energy state (called the ground state) can be excited to a higher state only if energy is added by an amount that is equal to the difference between the two levels. Thus, by measuring the energy of the radiation that has been absorbed by the atom, the difference in…

tennis: Strategy and technique: …players whose strength is their ground stroke, the priority is to maneuver the opponent into a vulnerable position for a winning passing shot, placement, or drive that forces an error. All shots after the serve—volley or ground stroke—can be played on either the forehand (where, if the racket were viewed…

ground substance, an amorphous gel-like substance present in the composition of the various connective tissues. It is most clearly seen in cartilage, in the vitreous humour of the eye, and in the Wharton’s jelly of the umbilical cord. It is transparent or translucent and viscous in composition; the

Sweden: Political stagnation (1866–1900): …demand for an abolition of ground tax, which had been levied from ancient times, and the defense question, where the demand was for an abolition of the military system of indelningsverket—i.e., an army organization in which the soldiers were given small holdings to live on. The defense system was to…

ground thrush, any of about 37 species of thrushes of the genus Zoothera (family Turdidae), including birds sometimes placed in the genera Geokichla, Ixoreus, Oreocincla, and Ridgwayia and some that have been assigned to Turdus. All are more than 20 centimetres (8 inches) long and have pale

angiosperm: Ground tissue: The ground tissue system arises from a ground tissue meristem and consists of three simple tissues: parenchyma, collenchyma, and sclerenchyma (Figure 5). The cells of each simple tissue bear the same name as their respective tissue.

hand tool: Neolithic tools: A ground tool is one that was chipped to rough shape in the old manner and then rubbed on or with a coarse abrasive rock to remove the chip scars either from the entire surface or around the working edge. Polishing was a last step, a…

airport: Links to local ground transportation: An airport should always be considered an interchange where different modes of transportation connect. Since the airport itself is not a primary destination, consideration must be given to access by surface vehicles. This is as critical a factor in airport layout and design…

Uta: The common side-blotched lizard, or ground uta (Uta stansburiana), is widespread in the western United States. Uta species range in length from 10 to 27 cm (4 to 11 inches). They are usually dull-coloured; the males of some species have a blue throat and abdomen. These lizards…

electromagnetic radiation: Radio waves: …further facilitated by the so-called ground wave. This form of electromagnetic wave closely follows Earth’s surface, particularly over water, as a result of the wave’s interaction with the terrestrial surface. The range of the ground wave (up to 1,600 km [1,000 miles]) and the bending and reflection of the sky…

World Trade Center, complex of several buildings around a central plaza in New York City that in 2001 was the site of the deadliest terrorist attack in American history. (See September 11 attacks.) The complex—located at the southwestern tip of Manhattan, near the shore of the Hudson River and a

Feisal Abdul Rauf: …community centre, to be called Park51, would house a Muslim prayer area, athletic facilities, a day-care centre, and a memorial to the September 11 attacks that would serve as a nondenominational space for prayer and meditation. Abdul Rauf emphasized that the centre would be open to non-Muslims as well as…

tunnels and underground excavations: Ground support: …of the opening, termed the ground-arch effect. At the heading the effect is three-dimensional, locally creating a ground dome in which the load is arched not only to the sides but also forward and back. If permanence of the ground arch is completely assured, stand-up time is infinite, and no…

history of flight: Avionics, passenger support, and safety: The ground-controlled approach (GCA), in which a ground observer monitors the course and descent angle of an aircraft via radar, enables pilots to land under extremely adverse weather conditions. GCA was used extensively by the U.S. military during the 1948 Berlin blockade and airlift and was…

military communication: World War II and after: …aircraft—the system called GCI (ground-controlled intercept). Radio-controlled guidance of falling bombs enabled an operator in a bomber to direct a bomb to the target. Electronic countermeasures made their appearance in the form of jamming transmitters to jam radio channels and radar, navigation, and other military electronics.

air-cushion machine, any of the machines characterized by movement in which a significant portion of the weight is supported by forces arising from air pressures developed around the craft, as a result of which they hover in close proximity to the Earth’s surface. It is this proximity to the

technology of photography: Methods of focusing and framing: The ground-glass (now mostly grained plastic) screen is the most direct way of viewing the image for framing and for sharpness control. The screen localizes the image plane for observation. The image is also visible without a screen, but then the eye can locate the image…

Intermediate-Range Nuclear Forces Treaty: …intermediate-range ballistic missiles (IRBMs) and ground-launched cruise missiles (GLCMs) as those having ranges of 1,000 to 5,500 km (620 to 3,400 miles) and shorter-range ballistic missiles (SRBMs) as those having ranges from 500 to 1,000 km.

radar: Ground-probing radar: Radar waves are usually thought of as being reflected from the surface of the ground. However, at the lower frequencies (below several hundred megahertz), radar energy can penetrate into the ground and be reflected from buried objects. The loss in propagating in the…

A geothermal heat pump (GHP) is a heating and cooling system that takes advantage of the relatively stable moderate temperature conditions within the first 300 meters (1,000 feet) below Earth’s surface to heat a building in the winter and cool it in the summer. Unlike boilers or furnaces, GHPs do

ground cherry, (genus Physalis), genus of some 80 species of small herbaceous plants in the nightshade family (Solanaceae), the majority of which are native to the New World. The berries of some ground cherry species are edible, and several species are commercially important as food crops,

semiconductor device: Bipolar transistors: …4B is known as a common-base configuration. The arrows indicate the directions of current flow under normal operating conditions—namely, the emitter-base junction is forward-biased and the base-collector junction is reverse-biased. The complementary structure of the p-n-p bipolar transistor is the n-p-n bipolar transistor, which is obtained by interchanging p for…

Newfoundland and Labrador: Agriculture, forestry, and fishing: …based on catching and processing groundfish (cod, hake, flounder, and redfish) in large plants in order to produce frozen goods for the North American market. In the second half of the 20th century, the industry was allowed to overexpand, and heavy fishing by Canadian and foreign trawlers severely depleted groundfish…

groundhog, (Marmota monax), one of 14 species of marmots (Marmota), considered basically a giant North American ground squirrel. It is sometimes destructive to gardens and pasturelands. Classified as a marmot, the groundhog is a member of the squirrel family, Sciuridae, within the order Rodentia.

Groundhog Day, in the United States and Canada, day (February 2) on which the emergence of the groundhog (woodchuck) from its burrow is said to foretell the weather for the following six weeks. The beginning of February, which falls roughly halfway between the winter solstice and the spring

Bill Murray: …weatherman in the existential comedy Groundhog Day (1993), Murray began tackling more thoughtful and challenging parts, including supporting roles in Tim Burton’s Ed Wood (1994) and Wes Anderson’s Rushmore (1998).

Will Ferrell: Early life and SNL: …Los Angeles improv comedy group the Groundlings, he became a member of the company, and in 1995 he was invited to join the television sketch show Saturday Night Live (SNL).

matrix: …a crystalline rock, sometimes called groundmass.

peanut, (Arachis hypogaea), legume of the pea family (Fabaceae), grown for its edible seeds. Native to tropical South America, the peanut was at an early time introduced to the Old World tropics. The seeds are a nutritionally dense food, rich in protein and fat. Despite its several common names,

groundnut, any of several plants that bear edible fruit or other nutlike parts. Three are members of the family Fabaceae (or Leguminosae): Arachis hypogaea, the peanut (q.v.), the fruit of which is a legume or pod rather than a true nut; Apois americana, also called wild bean and potato bean, the

Tanzania: Tanganyika Territory: …the production of peanuts (the Groundnuts Scheme). The plan, which was to be financed by the British government, was to cost £25 million, and, in addition, a further £4.5 million would be required for the construction of a railway in southern Tanganyika. It failed because of the lack of adequate…

Robert Z. Leonard: Later films: Grounds for Marriage (1951) was a romantic comedy about an opera singer (Kathryn Grayson) who still loves her ex-husband (Johnson). Too Young to Kiss (1951) was an entertaining romance about a pianist (Allyson) who disguises herself as a 14-year-old prodigy in order to land an…

groundsel, (genus Senecio), large genus of about 1,200 species of flowering plants in the aster family (Asteraceae) distributed throughout the world. Some species are cultivated as border plants or houseplants, and many species contain alkaloids that are poisonous to grazing animals. A diverse

Maya Lin: …of women at Yale; and Groundswell (1993), an installation of 43 tons of glass pebbles at the Wexner Center for the Arts in Columbus, Ohio. Her architectural achievements, which were noted for their emphasis on sustainability, include designs for the Langston Hughes Library (1999), a converted barn in Clinton, Tennessee;…

groundwater, water that occurs below the surface of Earth, where it occupies all or part of the void spaces in soils or geologic strata. It is also called subsurface water to distinguish it from surface water, which is found in large bodies like the oceans or lakes or which flows overland in

Darcy’s law: …Henri Darcy that governs the flow of groundwater through granular media or the flow of other fluids through permeable material, such as petroleum through sandstone or limestone. As the basic relationship from which many sophisticated theoretical and practical derivations have been devised, it has become the foundation for quantitative work…

aquifer: Recharge: …climatic regime, is known as groundwater mining.

aquifer: Recharge: …drainage is referred to as groundwater recharge. Rates of groundwater recharge are greatest when rainfall inputs to the soil exceed evapotranspiration losses. When the water table is deep underground, the water of the aquifer may be exceedingly old, possibly a result of a past climatic regime. A good example is…

water table, upper level of an underground surface in which the soil or rocks are permanently saturated with water. The water table separates the groundwater zone that lies below it from the capillary fringe, or zone of aeration, that lies above it. The water table fluctuates both with the seasons

paper: …grades are bond, book, bristol, groundwood and newsprint, kraft, paperboard, and sanitary.

papermaking: Improvements in materials and processes: Made by mechanical methods, groundwood pulp contains all the components of wood and thus is not suitable for papers in which high whiteness and permanence are required. Chemical wood pulps such as soda and sulfite pulp (described below) are used when high brightness, strength, and permanence are required. Groundwood…

Haki R. Madhubuti: …Memory, Seeking Ancestors (1987), and GroundWork (1996). He also wrote several nonfiction works about African American social issues, including From Plan to Planet—Life Studies: The Need for Afrikan Minds and Institutions (1973), Black Men: Obsolete, Single, Dangerous?: Afrikan American Families in Transition: Essays in Discovery, Solution, and Hope (1990), and…

group, in chemistry, a column in the periodic table of the chemical elements. In a group, the chemical elements have atoms with identical valence electron counts and identical valence vacancy counts. This similarity in both the composition and structure of their atomic valence shells implies a

galaxy: Groups: The groups class is composed of small compact groups of 10 to 50 galaxies of mixed types, spanning roughly five million light-years. An example of such an entity is the Local Group, which includes the Milky Way Galaxy, the Magellanic Clouds, the Andromeda Galaxy,…

group, in mathematics, set that has a multiplication that is associative [a(bc) = (ab)c for any a, b, c] and that has an identity element and inverses for all elements of the set. Systems obeying the group laws first appeared in 1770 in Joseph-Louis Lagrange’s studies of permutations of roots of

group, in chemistry, a column in the periodic table of the chemical elements. In a group, the chemical elements have atoms with identical valence electron counts and identical valence vacancy counts. This similarity in both the composition and structure of their atomic valence shells implies a

functional group, any of numerous combinations of atoms that form parts of chemical molecules, that undergo characteristic reactions themselves, and that in many cases influence the reactivity of the remainder of each molecule. In organic chemistry the concept of functional groups is useful as a

noble gas, any of the seven chemical elements that make up Group 18 (VIIIa) of the periodic table. The elements are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and oganesson (Og). The noble gases are colourless, odourless, tasteless, nonflammable gases. They

alkali metal, any of the six chemical elements that make up Group 1 (Ia) of the periodic table—namely, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). The alkali metals are so called because reaction with water forms alkalies (i.e., strong bases capable of

fax: Analog telephone facsimile: Group 1 fax machines were capable of transmitting a one-page document in about six minutes with a resolution of 4 lines per mm using an analog signal format. This standard was followed in 1976 by a CCITT Group 2 fax standard, which permitted transmission of…

zinc group element, any of the four chemical elements that constitute Group 12 (IIb) of the periodic table—namely, zinc (Zn), cadmium (Cd), mercury (Hg), and copernicium (Cn). They have properties in common, but they also differ in significant respects. Zinc, cadmium, and mercury are metals with a

boron group element, any of the six chemical elements constituting Group 13 (IIIa) of the periodic table. The elements are boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), and nihonium (Nh). They are characterized as a group by having three electrons in the outermost parts of

carbon group element, any of the six chemical elements that make up Group 14 (IVa) of the periodic table—namely, carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). Except for germanium and the artificially produced flerovium, all of these elements are familiar in

nitrogen group element, any of the chemical elements that constitute Group 15 (Va) of the periodic table. The group consists of nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), and moscovium (Mc). The elements share certain general similarities in chemical behaviour, though

oxygen group element, any of the six chemical elements making up Group 16 (VIa) of the periodic classification—namely, oxygen (O), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and livermorium (Lv). A relationship between the first three members of the group was recognized as early as

halogen, any of the six nonmetallic elements that constitute Group 17 (Group VIIa) of the periodic table. The halogen elements are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). They were given the name halogen, from the Greek roots hal- (“salt”) and -gen

noble gas, any of the seven chemical elements that make up Group 18 (VIIIa) of the periodic table. The elements are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and oganesson (Og). The noble gases are colourless, odourless, tasteless, nonflammable gases. They

alkaline-earth metal, any of the six chemical elements that comprise Group 2 (IIa) of the periodic table. The elements are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Prior to the 19th century, substances that were nonmetallic, insoluble in water, and

fax: Analog telephone facsimile: …in 1976 by a CCITT Group 2 fax standard, which permitted transmission of a one-page document in about three minutes using an improved modulation scheme.

fax: Standard fax transmission: …fax machines conform to the Group 3 standard, which was adopted in 1980 in order to ensure the compatibility of digital machines operating through public telephone systems worldwide. As a standard letter-size sheet is fed through a machine, it is scanned repeatedly across its width by a charge-coupled device (CCD),…

fax: Digital facsimile: Group 4 fax was intended to supplant Group 3 fax by permitting error-free transmission of documents over digital networks, such as the integrated services digital network (ISDN), at speeds up to 64,000 bits per second. At such rates, transmission time for a single page could…

Gruppe 47, informal association of German-speaking writers that was founded in 1947 (hence its name). Gruppe 47 originated with a group of war prisoners in the United States who were concerned with reestablishing the broken traditions of German literature. Feeling that Nazi propaganda had corrupted

Kazimierz Serocki: …and Tadeusz Baird, of the Group 49 movement, which helped gain international recognition for post-World War II Polish music. In 1956, Serocki participated with Tadeusz Baird in the foundation of the Warsaw Autumn festival of international contemporary music.

Gruppo 63, avant-garde Italian literary movement of the 1960s. It was composed of Italian intellectuals who shared the desire for a radical break from the conformity present in traditional Italian society. The group was organized at a 1963 meeting in Palermo. Edoardo Sanguineti, Elio Pagliarani,

streptococcus: Streptococcus pyogenes, often referred to as group A streptococcus bacteria, can cause rheumatic fever, impetigo, scarlet fever, puerperal fever, streptococcal toxic shock syndrome, strep throat, tonsillitis, and other upper respiratory infections. Necrotizing

insurance: Group annuities: An annuity in the literal sense is a series of annual payments. More broadly it may be defined as a series of equal payments over equal intervals of time. A life annuity, a subclass of annuities in general, is one in which the…

Group Areas Act, one of three acts, the first promulgated in 1950, in South Africa that provided for the division of the country into areas based on racial categories determined by the government. This occurred during the country’s apartheid era, when the white minority government implemented

Cape Town: The people of Cape Town: South Africa’s Group Areas Act of 1966 consolidated earlier acts aimed at enforcing the policy of racial segregation known as apartheid, and it provided for the reservation of certain areas for residence and occupation by specific racial groups within the population. The act brought about many changes…

history of the organization of work: Effect on skilled labour: …is what is known as group assembly, which started in Swedish automobile plants and was also adopted by the Japanese and then by the Americans. With this system a group of workers is responsible for the entire product (as opposed to individual workers who perform only one small task). If…

streptococcus: ” Streptococcus agalactiae, or group B streptococcus bacteria, can cause infections of the bladder and uterus in pregnant women; in newborn infants infection with the bacterium may result in sepsis (blood poisoning), meningitis (inflammation of the membranes covering the brain and spinal cord), or pneumonia.

animal social behaviour, the suite of interactions that occur between two or more individual animals, usually of the same species, when they form simple aggregations, cooperate in sexual or parental behaviour, engage in disputes over territory and access to mates, or simply communicate across

clinic: Private clinics: The advantages of group medical service, with facilities and technical personnel beyond the means of an individual practitioner plus the benefit of group consultation, have encouraged the establishment of pay or private clinics. Such a clinic is essentially a voluntary association of physicians engaged in the practice of…

galaxy: Groups: The groups class is composed of small compact groups of 10 to 50 galaxies of mixed types, spanning roughly five million light-years. An example of such an entity is the Local Group, which includes the Milky Way Galaxy, the Magellanic Clouds, the Andromeda Galaxy,…

Kurt Lewin: …his life to research on group dynamics, believing that groups alter the individual behaviour of their constituents. On the basis of research examining the effects of democratic, autocratic, and laissez-faire methods of leadership on groups of children, Lewin claimed that small groups operated most successfully when they were conducted in…

Group f.64, loose association of California photographers who promoted a style of sharply detailed, purist photography. The group, formed in 1932, constituted a revolt against Pictorialism, the soft-focused, academic photography that was then prevalent among West Coast artists. The name of the

aerobics, system of physical conditioning that increases the efficiency of the body’s intake of oxygen, thereby stimulating the cardiovascular system, developing endurance, and reducing body fat. Increased energy, lower blood pressure and cholesterol, greater suppleness, stronger bones, better

Memorial, Russian human rights organization. It documented human rights abuses during the Soviet era and played an important role in the transition to democracy after the Soviet Union’s collapse. It won (with Ales Bialiatski and the Center for Civil Liberties) the Nobel Prize for Peace in 2022 and

health maintenance organization: …Greater New York, and the Group Health Cooperative of Puget Sound are generally regarded as innovators of this type of HMO. The MCF usually involves a number of insurance companies. The organization is a loose network of individual physicians, practicing individually and paid on a fee-for-service basis. The medical-care foundation…

architecture: Group housing: A third type of domestic architecture accommodates the group rather than the unit and is therefore public as well as private. It is familiar through the widespread development of mass housing in the modern world, in which individuals or families find living space…

alkali metal, any of the six chemical elements that make up Group 1 (Ia) of the periodic table—namely, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). The alkali metals are so called because reaction with water forms alkalies (i.e., strong bases capable of

alkaline-earth metal, any of the six chemical elements that comprise Group 2 (IIa) of the periodic table. The elements are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Prior to the 19th century, substances that were nonmetallic, insoluble in water, and

zinc group element, any of the four chemical elements that constitute Group 12 (IIb) of the periodic table—namely, zinc (Zn), cadmium (Cd), mercury (Hg), and copernicium (Cn). They have properties in common, but they also differ in significant respects. Zinc, cadmium, and mercury are metals with a

boron group element, any of the six chemical elements constituting Group 13 (IIIa) of the periodic table. The elements are boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), and nihonium (Nh). They are characterized as a group by having three electrons in the outermost parts of

group insurance, insurance provided to members of a formal group such as employees of a firm or members of an association. Group insurance is distinguished from individual insurance in which single policies are sold to one person at a time and from social insurance (e.g., unemployment insurance,

carbon group element, any of the six chemical elements that make up Group 14 (IVa) of the periodic table—namely, carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). Except for germanium and the artificially produced flerovium, all of these elements are familiar in

group marriage, the marriage of several men with several women. As an institutionalized social practice, group marriage is extremely rare; nowhere does it appear to have existed as the prevailing form of marital arrangement. Of the 250 societies reported by the American anthropologist George P.

stagecraft: Control consoles: …by the century’s final decades: group master and preset. (A combination board is sometimes identified as a separate category of control console, but it simply combined group master and preset controls.) The group master and preset boards were a direct carryover from the layouts first used on gas tables. On…