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x (consonant)
The Latin letter x, an abbreviation for ks, was also put to other uses in Romance; in Portuguese, Catalan, Sicilian, and Old Spanish it represents a /sh/ sound, in modern Spanish a strong /h/ sound, more commonly spelled with a j, and in northern Italian dialects, the /z/ sound. Other letters pressed into use for new consonantal sounds were z (used in Italy for /ts/......
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X (American rock band)
American band whose tales of urban decay, corruption, and sleaze, delivered with skilled musicianship and unique vocal harmonies, marked them as important contributors to the punk movement. The original members were Exene Cervenka (original name Christine Cervenka; b. Feb. 1, 1956Chicago, Ill., U.S....
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X & Y (album by Coldplay)
...helped drive the band’s total album sales over the 20 million mark. Coldplay followed the concert album Live 2003 (2003) with X & Y (2005), a collection of guitar-driven, arena-friendly rock anthems (including the chart-topping single Speed of Sound) that elevated the group to the rank of......
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X boson (physics)
...lightest stable particles built from quarks, are not in fact stable but can decay to lighter leptons. These interactions between quarks and leptons occur through new gauge bosons, generally called X, which must have masses comparable to the energy scale of grand unification. The mean life for the proton, according to the GUTs, depends on this mass; in the simplest GUTs based on SU(5), the mean....
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X chromosome (genetics)
...the sex chromosomes, designated XX in females and XY in males. The loci of the blood group systems are on the autosomes, except for Xg, which is unique among the blood groups in being located on the X chromosome. Genes carried by the X chromosome are said to be sex-linked. Since the blood groups are inherited in a regular fashion, they can be used as genetic markers in family studies to......
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X Club (British science organization)
private scientific dining club of Victorian London, remarkable for the power that its nine members exerted on the scientific and cultural climate of late-19th-century England....
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X Factor, The (British television program)
In 2006 The X Factor, a talent competition cojudged by Cowell and coproduced by his company, Syco Productions, won the award for best entertainment program from the British Academy of Film and Television Arts. That same year he became executive producer of three new American shows—American Inventor, a competition that promised a......
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x Fatshedera lizei (plant)
Fatsia has been crossed with an English ivy (Hedera helix) to produce the tree ivy, or aralia ivy (× Fatshedera lizei), an intergeneric cross, a most uncommon botanical occurrence....
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X Games
The term extreme sports is generally attributed to the X Games, a made-for-television sports festival created by the cable network ESPN in 1995. The success of the X Games raised the profile and economic viability of these sports. The extreme sports of mountain biking and snowboarding debuted at the Summer and Winter Olympic Games in 1996 and 1998, respectively....
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X inactivation (genetics)
...the X chromosome is gene-rich, most of these genes become transcriptionally silent in all but one X chromosome in each somatic cell (i.e., all cells except eggs and sperm) via a process called X inactivation. The phenomenon of X inactivation prevents a female who carries two copies of the X chromosome in every cell from expressing twice the amount of gene products encoded exclusively on......
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X Olympiad, Games of the (1932)
Only about 1,300 athletes, representing 37 countries, competed in the 1932 Games. The poor participation was the result of the worldwide economic depression and the expense of traveling to California. The Los Angeles Games featured the first Olympic Village, which was located in Baldwin Hills, a suburb of Los Angeles, and covered 321 acres (130 hectares). The male athletes were housed in more......
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X Olympic Winter Games (1968)
Opened by French President Charles de Gaulle, the 1968 Games were a triumph for France but were not without their share of problems. Though a great deal of money was spent to ready the industrial city of Grenoble, its lack of facilities resulted in many contests being held in outlying areas. Spectators had to travel great distances to view events, and seven separate Olympic Villages were......
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X-1 (airplane)
...American James Hart Wyld designed, built, and tested the first U.S. regeneratively cooled liquid rocket engine. In 1947 Wyld’s rocket engine powered the first supersonic research aircraft, the Bell X-1, flown by the U.S. Air Force captain Charles E. Yeager. Supersonic flight offered the aeronautical engineer new challenges in propulsion, structures and materials, high-speed aeroelasticit...
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X-13 Vertijet (aircraft)
...to lift an aircraft vertically from the ground and then shift to forward flight, but in every case the difficulties involved in recovery have inhibited the program. An early example, the Ryan X-13 Vertijet, was launched from a trailer bed that was erected vertically prior to takeoff. The aircraft flew successfully in vertical and horizontal modes, including takeoff and......
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X-15 (rocket plane)
...in propulsion, structures and materials, high-speed aeroelasticity, and transonic, supersonic, and hypersonic aerodynamics. The experience gained in the X-1 tests led to the development of the X-15 research rocket plane, which flew nearly 200 flights over a nine-year period. The X-15 established an extensive database in transonic and supersonic flight (up to five times the speed of sound)......
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X-ALD (pathology)
...manifesting heterozygotes. Examples of X-linked disorders include ornithine transcarbamylase deficiency (an enzyme deficiency resulting in high blood levels of ammonia and impaired urea formation), X-linked adrenoleukodystrophy (a disorder that is characterized by progressive mental and physical deterioration and adrenal insufficiency), and Lesch-Nyhan syndrome (a disorder of purine metabolism....
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X-chair
chair supported by two crossed and curved supports either at the sides or at the back and front. Because of its basic simplicity, it is one of the oldest forms of chair or stool, with examples reaching back to the 2nd millennium bc. The seat, which was originally made of leather or fabric, could be stretched across the upper terminals of the X-shape or inserted at a lower level, just...
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X-disease (veterinary science)
in cattle, a disease characterized by inflammation and thickening of the horny covering of the epidermis, the outermost layer of the skin. Other symptoms include weight loss, wartlike swellings in the mouth, drooling, and a runny nose. Severely afflicted animals usually die. Although once attributed to a virus, the disease is now known to be caused by the ingestion of feed contaminated with chlori...
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X-Force (Chinese military unit)
...across northern Burma. Already in India, the United States was training two Chinese divisions from remnants of the Burma campaign, plus artillery and engineering regiments (this became known as X-Force). Also in training were Chinese instructors to help retrain other divisions in China. Both air development and army modernizing were being pushed in early 1943, with a training centre created......
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X-Group (Nubian people)
The 200 years from the fall of Kush to the middle of the 6th century is an unknown age in the Sudan. Nubia was inhabited by a people called the Nobatae by the ancient geographers and the X-Group by modern archaeologists, who are still at a loss to explain their origins. The X-Group were clearly, however, the heirs of Kush, for their whole cultural life was dominated by Meroitic crafts and......
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X-linked adrenoleukodystrophy (pathology)
...manifesting heterozygotes. Examples of X-linked disorders include ornithine transcarbamylase deficiency (an enzyme deficiency resulting in high blood levels of ammonia and impaired urea formation), X-linked adrenoleukodystrophy (a disorder that is characterized by progressive mental and physical deterioration and adrenal insufficiency), and Lesch-Nyhan syndrome (a disorder of purine metabolism....
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X-linked infantile agammaglobulinemia (disease)
...from hereditary and congenital defects are rare, but they can affect all major aspects of the immune system. Luckily many of those conditions can be treated. In the rare hereditary disorder called X-linked infantile agammaglobulinemia, which affects only males, B lymphocytes are unable to secrete all classes of immunoglobulins. (An immunoglobulin is a type of protein, also called an antibody,.....
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X-linked mutation (genetics)
...Females have two X chromosomes, while males have an X and a Y chromosome. If a mutant gene is part of the X chromosome, the resulting disease is called X-linked. All male offspring who inherit an X-linked mutation are affected, because the Y chromosome of the XY pair does not have a compensating normal gene. Because the mutation is on the X chromosome and males transmit only the Y chromosome......
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X-organ
The X-organ–sinus-gland complex is located in the eyestalk. The X-organ passes its secretions to the sinus gland, which acts as a release centre into the blood. Hormones liberated from the sinus gland have been shown to influence molting, gonad development, water balance, blood glucose, and the expansion and contraction of pigment cells both in the general body and in the retina of the......
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X-organ–sinus-gland complex (anatomy)
The X-organ–sinus-gland complex is located in the eyestalk. The X-organ passes its secretions to the sinus gland, which acts as a release centre into the blood. Hormones liberated from the sinus gland have been shown to influence molting, gonad development, water balance, blood glucose, and the expansion and contraction of pigment cells both......
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X-radiation (radiation beam)
electromagnetic radiation of extremely short wavelength and high frequency, with wavelengths ranging from about 10−8 to 10−12 metre and corresponding frequencies from about 1016 to 1020 hertz (Hz)....
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X-ray (radiation beam)
electromagnetic radiation of extremely short wavelength and high frequency, with wavelengths ranging from about 10−8 to 10−12 metre and corresponding frequencies from about 1016 to 1020 hertz (Hz)....
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X-ray absorptiometry
Absorbed X rays cause excitation of electrons from inner orbitals (those near the nucleus) to unoccupied outer orbitals. In some cases, the energy of the incident X ray is sufficient to ionize the analyte by completely removing the electron from the atom or molecule. The energy required to excite the electron from an inner orbital is greater than that which is available in the......
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X-ray astronomy
Emission of X rays from high-temperature laboratory plasmas is used to probe the conditions within them; X-ray spectral measurements show both the composition and temperature of a source. X-ray and gamma-ray astrophysics is also an active area of research. X-ray sources include stars and galactic centres. The most intense astronomical X-ray sources are extremely dense gravitational objects such......
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X-ray crystallography
...black, dissected into quarters. For crystals, of course, the unit cell is three-dimensional. A very wide variety of arrangements is exhibited by different substances, and it is the great triumph of X-ray crystallography to have provided the means for determining experimentally what arrangement is involved in each case....
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X-ray diffraction (physics)
a phenomenon in which the atoms of a crystal, by virtue of their uniform spacing, cause an interference pattern of the waves present in an incident beam of X rays. The atomic planes of the crystal act on the X rays in exactly the same manner as does a uniformly ruled grating on a beam of light. See also Bragg law; Laue diffraction pattern. ...
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X-ray diffraction analysis (physics)
a phenomenon in which the atoms of a crystal, by virtue of their uniform spacing, cause an interference pattern of the waves present in an incident beam of X rays. The atomic planes of the crystal act on the X rays in exactly the same manner as does a uniformly ruled grating on a beam of light. See also Bragg law; Laue diffraction pattern. ...
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X-ray diffraction analysis, precession method of (physics)
Among the most important of Buerger’s innovations is the precession method of X-ray diffraction analysis (the determination of the spatial arrangement of atoms in crystals by observing the pattern in which they scatter a beam of X rays), one of the two most commonly used methods of recording diffraction intensities....
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X-ray diffraction spectrometer (instrument)
...a crystal of zinc sulfide. Because the details of the diffraction patterns depended on the wavelength of the radiation, these experiments formed the basis for the spectroscopy of X rays. The first spectrographs for this radiation were devised in 1912–13 by two British physicists—father and son—William Henry and Lawrence Bragg, who showed that there existed not only continuu...
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X-ray emission spectrometry
A penetrating, electrically uncharged radiation was discovered in 1895 by the German physicist Wilhelm Conrad Röntgen and was named X-radiation because its origin was unknown. This radiation is produced when electrons (cathode rays) strike glass or metal surfaces in high-voltage evacuated tubes and is detected by the fluorescent glow of coated screens and by the exposure of photographic......
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X-ray fluorescence (radiation beam)
The chemical analysis of minerals is undertaken with the electron microprobe (see above). Instruments and techniques used for the chemical analysis of rocks are as follows: The X-ray fluorescent (XRF) spectrometer excites atoms with a primary X-ray beam and causes secondary (or fluorescent) X rays to be emitted. Each element produces a diagnostic X radiation, the intensity of which is measured.......
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X-ray galaxy (astronomy)
Synchrotron radiation is characteristically emitted at virtually all wavelengths at almost the same intensity. A synchrotron source therefore ought to be detectable at optical and radio wavelengths, as well as at others (e.g., infrared, ultraviolet, X-ray, and gamma-ray wavelengths). For radio galaxies this does seem to be the case, at least in circumstances where the radiation is not screened......
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X-ray microprobe analyzer (microscopy)
X-ray microprobe analysis has proven to be so valuable that a majority of SEMs, as well as many TEMs, are now equipped with X-ray spectrometers as accessories. The technique has found wide applications in mineralogy, metallurgy, and solid-state science, as well as in the clinical and life sciences....
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X-ray microscopy
Little use has been found for the X-ray microscope. The basic device uses the emission of X-rays from a point source to cast an enlarged image on a phosphor screen, and a successful X-ray microscope was made in 1951 by British physicists Ellis Coslett and William Nixon. It was the first such instrument whose resolution was comparable to that of an optical microscope and was hailed as a means of......
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X-ray monochromator (instrument)
X-ray monochromators are analogous to grating monochromators and spectrometers in the visible portion of the spectrum. If the lattice spacing for a crystal is accurately known, the observed angles of diffraction can be used to measure and identify unknown X-ray wavelengths. Because of the sensitive wavelength dependence of Bragg reflection exhibited by materials such as silicon, a small portion......
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X-Ray of the Pampa (work by Martínez Estrada)
...and economic crises of the early 1930s and of what he saw as factors contributing to moral and social decay in Argentina led him to write Radiografía de la pampa (1933; X-Ray of the Pampa), a comprehensive psychological study of the Argentine character laden with fatalistic overtones. La cabeza de Goliat: Microscopía de Buenos Aires (1940;......
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X-ray optics (physics)
X rays are strongly absorbed by solid matter so that the optics used in the visible and near-infrared portions of the electromagnetic spectrum cannot be used to focus or reflect the radiation. Over a fairly wide range of X-ray energies, however, radiation hitting a metal surface at grazing incidence can be reflected. For X rays where the wavelengths are comparable to the lattice spacings in......
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X-ray photoelectron spectroscopy
Since the binding energies of the electrons emitted through XPS are discrete and atoms of different elements have different characteristic electron-binding energies, the emitted electron beam can provide a simple method of elemental analysis. The specificity of XPS is very good, since there is little systematic overlap of spectral lines between elements....
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X-ray scattering (physics)
...Over the next several years, a number of researchers determined that the rays carried no electric charge, traveled in straight trajectories, and had a transverse nature (could be polarized) by scattering from certain materials. These properties suggested that the rays were another form of electromagnetic radiation, a possibility that was postulated earlier by the British physicist J.J.......
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X-ray source (astronomy)
in astronomy, any of a class of cosmic objects that emit radiation at X-ray wavelength. Because the Earth’s atmosphere absorbs X rays very efficiently, X-ray telescopes and detectors must be carried high above it by spacecraft to observe objects that produce such electromagnetic radiation....
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X-ray spectroscopy
A penetrating, electrically uncharged radiation was discovered in 1895 by the German physicist Wilhelm Conrad Röntgen and was named X-radiation because its origin was unknown. This radiation is produced when electrons (cathode rays) strike glass or metal surfaces in high-voltage evacuated tubes and is detected by the fluorescent glow of coated screens and by the exposure of photographic......
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X-ray style (art)
manner of depicting animals by drawing or painting the skeletal frame and internal organs. It is one of the characteristic styles of the art of some prehistoric hunting cultures....
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X-ray telescope
instrument designed to detect and resolve X rays from sources outside the Earth’s atmosphere. Because of atmospheric absorption, X-ray telescopes must be carried to high altitudes by rockets or balloons or placed in orbit outside the atmosphere. Balloon-borne telescopes are used to detect the more penetrating (harder) X rays, whereas those carried aloft by rockets or in satellites are used...
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X-ray treatment
use of radiation sources in the treatment or relief of diseases. Radiation therapy almost always makes use of ionizing radiation, deep tissue-penetrating rays, which can physically and chemically react with diseased cells to destroy them. The other forms of radiation, infrared and ultraviolet, can be employed in heat lamps for neuritis and a...
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X-ray tube (electronics)
evacuated electron tube that produces X rays by accelerating electrons to a high velocity with a high-voltage field and causing them to collide with a target, the anode plate. The tube consists of a source of electrons, the cathode, which is usually a heated filament, and a thermally rugged anode, usuall...
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X-trisomy (genetics)
sex chromosome disorder of human females, in which three X chromosomes are present, rather than the normal pair. More common than Turner’s syndrome, where only one X chromosome is present, X-trisomy usually remains undetected because affected individuals appear normal, experience puberty, and are usually fertile. Statistical studies ...
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Xai-Xai (Mozambique)
port town, southern Mozambique. Located on the eastern bank of the Limpopo River near its mouth, the town is a market centre for cashew nuts, rice, corn (maize), cassava, and sorghum raised in the surrounding area, which is irrigated by the lower Limpopo irrigation project; dairy cattle also are raised. A light railway system runs inland and provides access to the port, which has declined in impor...
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Xaimaca (work by Güiraldes)
...approaches with his deep and sentimental feeling for his native land and its traditional themes, as in Cuentos de muerte y de sangre (1915; “Tales of Death and of Blood”) and Xaimaca (1923; “Jamaica”). In Don Segundo Sombra, the work considered his masterpiece, he combined poetic description of country life with a subtle portrayal of the cattlema...
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Xalapa (Mexico)
city, capital of Veracruz estado (state), east-central Mexico. About 55 miles (90 km) northwest of Veracruz city, Xalapa is located beneath towering volcanic peaks in the Sierra Madre Oriental, at an elevation of about 4,680 feet (1,425 metres). Known for its scenic backdrop and its ...
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Xalapa Enríquez (Mexico)
city, capital of Veracruz estado (state), east-central Mexico. About 55 miles (90 km) northwest of Veracruz city, Xalapa is located beneath towering volcanic peaks in the Sierra Madre Oriental, at an elevation of about 4,680 feet (1,425 metres). Known for its scenic backdrop and its ...
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Xamar (Somalia)
capital, largest city, and a major port of Somalia, located just north of the Equator on the Indian Ocean. One of the earliest Arab settlements on the East African coast, its origins date to the 10th century. It declined in the 16th century after a period of extensive trade with the Arab states, but it had commercial relations with the Portuguese and the imams of Muscat before c...
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Xanadu (poetic name)
...of the homeland because he was the youngest, was planning to have himself elected khan, he patched up a truce with Sung. In April 1260 he arrived at his residence of K’ai-p’ing, or Shang-tu (the Xanadu of Samuel Taylor Coleridge’s famous poem), in southeastern Mongolia. Here his associates held a kuriltai, or “great assembly,” and on May 5 Kublai was un...
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Xanadu Regio (astronomy)
...this property were able to show that the surface is not uniform. Images taken in near-infrared wavelengths by the Hubble Space Telescope in 1994 revealed a bright continent-sized region, later named Xanadu Regio, on Titan’s leading face. This region was also discerned from Earth and from the Cassini spacecraft at radar wavelengths, which can penetrate the haze....
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Xanax (drug)
...system when used at high doses. They also require a much smaller dosage than do barbiturates to achieve their effects. The benzodiazepines include chlordiazepoxide (Librium), diazepam (Valium), alprazolam (Xanax), oxazepam (Serax), and triazolam (Halcion). They are, however, intended only for short- or medium-term use, since the body does develop a tolerance to them and withdrawal symptoms......
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Xandrames (ruler of Magadha)
...genealogy of the Nanda dynasty is perfunctory in the Puranas, which mention only Sukalpa (Sahalya, Sumalya), while the Buddhist text Mahabodhivamsa enumerates eight names. Dhanananda, the last of this list, possibly figures as Agrammes, or Xandrames, in classical sources, a powerful contemporary of Alexander the Great. The Nanda line ended with him in about 321 bc......
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Xankändi (Azerbaijan)
city, southwestern Azerbaijan. Situated at the foot of the eastern slopes of the Karabakh Range, the city was founded after the October Revolution (1917) on the site of the village of Khankendy and was renamed Stepanakert in 1923 for Stepan Shaumyan, a Baku Communist leader. After Azerbaijan gained independence the name was changed to Xankändi, though Armenians continue to call the city Ste...
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Xanten, Treaty of (Europe [1614])
...Sigismund, elector of Brandenburg, and Wolfgang William of Palatinate-Neuburg, backed by France, the United Provinces, and the German Protestant princes, jointly occupied the duchies (1610). By the Treaty of Xanten (1614), they agreed to a division of the territories. Cleves-Mark and Ravensberg went to John Sigismund, Jülich-Berg and Ravensstein, to Wolfgang William....
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xanthate (chemical compound)
any of a class of organic salts formed by treatment of an alcohol with carbon disulfide in the presence of an alkali. The term is derived from the Greek word xanthos, for “yellow,” in reference to the compound potassium ethyl xanthate (C2H5OCS2K), which gives a yellow precipitate when combined with copper sulfate. The most important group of x...
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Xanthé (Greece)
city and nomós (department) in the Thrace (Thráki) region of eastern Greece. The city, which is situated below the Rhodope massif at the head of the narrow Eskejé (Esketzé) Valley, is the seat of a metropolitan bishop of the Greek Orthodox Church....
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xanthene (chemical compound)
In 1871 the German chemist Adolph von Baeyer discovered a new dye class closely related to the triphenylmethane series and also without natural counterparts. Heating phthalic anhydride with resorcinol (1,3-dihydroxybenzene) produced a yellow compound he named fluorescein, because aqueous solutions show an intense fluorescence. Although not useful as a dye, its value as a marker for accidents at......
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Xánthi (Greece)
city and nomós (department) in the Thrace (Thráki) region of eastern Greece. The city, which is situated below the Rhodope massif at the head of the narrow Eskejé (Esketzé) Valley, is the seat of a metropolitan bishop of the Greek Orthodox Church....
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xanthine (chemical compound)
Uric acid, the first purine derivative to be discovered, was isolated in 1776 from urinary calculi; xanthine was obtained from the same source in 1817. Xanthine also occurs in tea, as does caffeine, another purine compound. Guanine, found in guano, the accumulated excrement and dead bodies of birds, bats, and seals, and adenine were identified in 1891 as products of the chemical decomposition......
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xanthinuria (pathology)
rare inherited disorder of purine metabolism that results from a deficiency in the enzyme xanthine oxidase. Normally this enzyme breaks down the purine base xanthine to uric acid, which is then excreted. In the absence of the enzyme, xanthine is not metabolized by the body and its concentration builds up in the blood and urine. Xanthinuria is not a serious condition, and many i...
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Xanthippus (Greek leader)
Pericles was born into the first generation able to use the new weapon of the popular vote against the old power of family politics. His father, Xanthippus, a typical member of this generation, almost certainly of an old family, began his political career by a dynastic marriage into the controversial family of the Alcmaeonids. He soon left their political camp, probably on the question of......
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Xanthium (plant)
weedy annual plant of the genus Xanthium of the family Asteraceae, distributed throughout much of Europe and parts of North America. Some authorities consider that the genus contains about 15 species, others say from 2 to 4....
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Xanthium strumarium (plant)
...enclosed in oval green, yellow, or brown burs that have many hooked spines and two large hornlike spines. The ripe burs adhere to the hair of animals, which widely disseminate the plant. Cocklebur (X. strumarium) is poisonous to grazing animals and was formerly used in herbal remedies....
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Xanthomonas (bacterium)
The principal genera of plant pathogenic bacteria are Agrobacterium, Clavibacter, Erwinia, Pseudomonas, Xanthomonas, Streptomyces, and Xylella. With the exception of Streptomyces species, all are small, single, rod-shaped cells approximately 0.5 to 1.0 micrometre (0.00002 to 0.00004 inch) in width and 1.0 to 3.5 micrometres in length.......
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Xanthopan morganii (insect)
...Madagascar orchid, Angraecum sesquipedale, with a nectar receptacle 20 to 35 centimetres (eight to 14 inches) long, depends for its pollination exclusively on the local race of a hawkmoth, Xanthopan morganii, which has a proboscis of 2212 centimetres (nine inches). Interestingly enough, the existence of the hawkmoth was predicted by Charles Darwi...
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Xanthopan morganii praedicta (insect)
The species Xanthopan morganii praedicta, named in honour of its predicted existence by Charles Darwin and Alfred Russel Wallace, exclusively pollinates the Madagascar orchid, Angraecum sesquipedale. The proboscis of this hawk moth is long enough to reach the nectar receptacle of the orchid, which is between 20 and 35 cm (8 and 14 inches)......
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xanthophore (biology)
pigment-containing cell in the deeper layers of the skin of animals. Depending on the colour of their pigment, chromatophores are termed melanophores (black), erythrophores (red), xanthophores (yellow), or leucophores (white). The distribution of the chromatophores and the pigments they contain determine the colour patterns of an organism. ...
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Xanthophyceae (class of algae)
members of the class Xanthophyceae (division Chromophyta), consisting of approximately 600 species, once classified with the green algae on the basis of similarity of body organization. The Xanthophyceae are distinguished by their food reserve (oil), the quantity of β-carotene in their plastids, and motile cells with unequal flagella. Frequently their cell walls are two overlapping halves. ...
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xanthophyll (pigment)
...or red pigments (biochromes) that are almost universally distributed in living things. There are two major types: the hydrocarbon class, or carotenes, and the oxygenated (alcoholic) class, or xanthophylls. Synthesized by bacteria, fungi, lower algae, and green plants, carotenoids are most conspicuous in the petals, pollen, and fruit (e.g., carrots, sweet potatoes, tomatoes, and......
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Xanthophyta (protist phylum)
division or phylum of algae commonly known as yellow-green algae....
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xanthopterin (chemical compound)
...pteron, “wing”) has become apparent since the first known members of the group were discovered as pigments of butterfly wings. One example is the yellow pigment 2-amino-4,6-pteridinedione (xanthopterin)....
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Xanthoria parietina (plant)
(Xanthoria parietina), lichen species characterized by lobed margins and a wrinkled centre. It is usually found where the air is filled with mineral salts, especially near the sea and on rocks and walls. It was once considered a valuable medication for jaundice because of its yellow or orange colour....
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Xanthorrhoea (plant)
any plant of the genus Xanthorrhoea of the family Xanthorrhoeaceae, with about 17 species native to eastern Australia. They have thick, woody, often palmlike stems about 5 m (16 feet) tall that end in a tuft of rigid, grasslike leaves from which flower spikes resembling those of the bulrush extend 3 m or more....
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Xanthorrhoea hastilis (plant)
...as grass gums because of the red or yellow gumlike resins that exude from the bases of old leaves. The resins are used for varnish. In some areas grass trees are known as yaccas (or yuccas) and as blackboys, especially X. hastilis. In western Australia a monotypic species, Kingia australis, is known as grass tree....
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Xanthos (Turkey)
principal city of ancient Lycia. The ruined city, situated on a cliff above the mouth of the Koca (Xanthus) River in what is now southwestern Turkey, was designated (along with the nearby Letoon religious centre) a UNESCO World Heritage site in 1988....
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Xanthos, Emmanuil (Greek revolutionary)
...the Philikí Etaireía, or “Friendly Society,” with the specific aim of laying the foundations for a coordinated, armed uprising against the Turks. The three founders, Emmanuil Xanthos, Nicholas Skouphas, and Athanasios Tsakalov, had little vision of the shape of the independent Greece for which they aimed beyond the liberation of the motherland....
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xanthosis (pathology)
yellow skin discoloration caused by excess blood carotene; it may follow overeating of such carotenoid-rich foods as carrots, sweet potatoes, or oranges....
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Xanthoura yncas (bird)
...Africa; about 33 cm (13 inches) long, it is pinkish brown, with blue-and-black-barred shoulders, white rump, and white wing-patches. Among brightly coloured forms in tropical America is the green jay (Cyanocorax, sometimes Xanthoura, yncas)....
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Xanthus (Turkey)
principal city of ancient Lycia. The ruined city, situated on a cliff above the mouth of the Koca (Xanthus) River in what is now southwestern Turkey, was designated (along with the nearby Letoon religious centre) a UNESCO World Heritage site in 1988....
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Xantusiidae (reptile)
any of 26 species of small, secretive New World lizards that live under rocks and decaying vegetation and in crevices and caves. Three genera are known. Xantusia (six species) occurs from southern California to the tip of the Baja California peninsula, with one species in Durango state, Mexico. The 19 species of Lepidophyma...
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Xantusiidae henshawi (reptile)
...the smallest night lizards, X. vigilis is less than 4 cm (1.6 inches) from snout to vent. It eats small insects and termites that live under logs. A close relative, the granite night lizard (X. henshawi), lives in crevices, where it moves about during the day....
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Xantusiidae vigilis (reptile)
The desert night lizard (X. vigilis) lives underneath decaying Joshua trees in the Mojave and Sonoran deserts. Among the smallest night lizards, X. vigilis is less than 4 cm (1.6 inches) from snout to vent. It eats small insects and termites that live under logs. A close relative, the granite night lizard (X.......
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Xantus’s murrelet (bird)
...in Alaska are the marbled murrelet (Brachyramphus marmoratus), seen as far south as California, and Kittlitz’s murrelet, (B. brevirostris), which reaches Japan. Most southerly is Xantus’s murrelet (Endomychura hypoleucus), which nests on the hot coast of Baja California and (like some gulls of the region) travels north in winter. ...
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Xarays, Lago (floodplain, Brazil)
floodplain in south-central Brazil that extends into northeast Paraguay and southeast Bolivia. It lies mainly within the Brazilian estados (states) of Mato Grosso do Sul and Mato Grosso. The Pantanal is one of the world’s largest freshwater wetlands, and the extent of its dynamic area is estimated to be from 54,000 square miles (140,000 square km) t...
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Xasan, Sayyid Maxamed Cabdulle (Somalian leader)
Somali religious and nationalist leader (called the “Mad Mullah” by the British) who for 20 years led armed resistance to the British, Italian, and Ethiopian colonial forces in Somaliland. Because of his active resistance to the British and his vision of a Somalia united in a Muslim brotherhood transcending clan divisions, Sayyid Maxamed is seen as a forerunner of modern Somali natio...
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Xauen (Morocco)
town, northern Morocco, situated in the Rif mountain range. Founded as a holy city in 1471 by the warrior Abū Youma and later moved by Sīdī ʿAlī ibn Rashīd to its present site at the base of Mount El-Chaouene, it became a refuge for Moors expelled from Spain. A site long closed to ...
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Xauen, Dámaso Berenguer y Fusté, Count de (Spanish statesman)
Spanish general who served briefly as prime minister (January 1930–February 1931) before the establishment of the Second Republic....
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Xavante (people)
Brazilian Indian group speaking Xavante, a language of the Macro-Ge language family. The Xavante, who numbered about 10,000 in the early 21st century, live in the southeastern corner of Mato Grosso state, between the Rio das Mortes and the Araguaia River, in a region of upland savannah laced with narrow bands of forest running alongside the rivers. The Xavante and the closely re...
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Xavier, Saint Francis (Christian missionary)
the greatest Roman Catholic missionary of modern times, who was instrumental in the establishment of Christianity in India, the Malay Archipelago, and Japan. In Paris in 1534 he pronounced vows as one of the first seven members of the Society of Jesus, or Jesuits, under the leadership of Ignatius of Loyola....
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Xavier University (university, Cincinnati, Ohio, United States)
private, coeducational institution of higher learning in Cincinnati, Ohio, U.S. It is affiliated with the Jesuit order (Society of Jesus) of the Roman Catholic church. The university comprises colleges of arts and sciences, business administration, and social sciences. In addition to undergraduate studies, Xavier offers about a dozen master’s degree programs, notably in t...
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Xavier University (university, New Orleans, Lousiana, United States)
private, coeducational institution of higher learning in Cincinnati, Ohio, U.S. It is affiliated with the Jesuit order (Society of Jesus) of the Roman Catholic church. The university comprises colleges of arts and sciences, business administration, and social sciences. In addition to undergraduate studies, Xavier offers about a dozen master’s degree programs, notably in t...
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Xaymaca
island nation of the West Indies. It is the third largest island in the Caribbean Sea, after Cuba and Hispaniola. Jamaica is about 146 miles (235 km) long and varies from 22 to 51 miles (35 to 82 km) wide. It is situated some 100 miles (160 km) west of Haiti, 90 miles (150 km) south of Cuba, and 390 miles (630 km) northeast of Cape Gracias a Dios, Nicaragua, the nearest point on the mainland. The ...
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