The X chromosome occupies an exceptional place in the mammalian genome. Together with the Y chromosome, the X chromosome differentiates the sexes. Males have one X chromosome and a Y chromosome and females have two X chromosomes. Because o...

An X terminal is a computer that lacks a disk. Accordingly, X terminals do not have (house) resident applications. X terminals are designed to connect a user to network applications that are running in an X server; a server operating in a ...

(b. 1946), East Timorese resistance leader. As the leader of the struggle for independence, Xanana Gusmão became the most important resistance figure of East Timor. Born on 20 June 1946 in Laleia, East Timor, José Alexandre &...

Zubiri, Xavier(1898–1983) Xavier Zubiri, the Spanish Christian ontologist, was born in San Sebastián. He was professor of the history of philosophy in Madrid from 1926 to 1936 and in Barcelona from 1940 to 1942, after an abse...

Designating a foreign and usually harmful substance or organism in a biological system. Xenobiotic, derived from the Greek root xeno, meaning "stranger" or "foreign," and bio, meaning "life," descr...

Xenogamy (also called outbreeding) is a term used to describe the union of genetically unrelated organisms within the same species. Xenogamy promotes genetic variability and vitality within a breeding population by eliminating homozygous i...

Chemical element, chemical symbol Xe, atomic number 54. One of the noble gases, it is colourless, odourless, tasteless, and nearly inert, combining only with fluorine and oxygen and in complexes (&see; bonding). Xenon occurs in slight trac...

The Greek historian, essayist, and military expert Xenophon (ca. 430-ca. 355 BC) was the most popular of the Greek historians. He facilitated the change from the Thucydidean tradition of history to rhetoric. The son of Gryllus of the Athen...

major U.S. corporation and first manufacturer of xerographic, plain-paper copiers. Headquarters are in Stamford, Connecticut. The company was founded in 1906 as the Haloid Company, a manufacturer and distributor of photographic paper. In 1...

In 1998 the motion picture The X-Files: Fight the Future--released in June and becoming the number one box-office hit, with a take of over $30 million in its first weekend--brought to the big screen one of the hottest television shows an...

city and capital of Shaanxi sheng (province), north-central China. It is located in the south-central part of the province, at the southern limit of the Loess Plateau. The city site is on a low plain on the south bank of the Wei River. Jus...

The term "Xiang" refers to the people and the local sublanguage used in Hunan, a province in southeast-central China; Xiang is derived from the older literary name of Hunan. It is estimated that more than 25 million Chinese (...

By the end of the nineteenth century, nearly every political and intellectual leader in China saw the need for change. Some, such as Sun Yat-sen (1866–1925), felt that rather than reforming the imperial system, China needed a thorou...

X-linked agammaglobulinemia (XLA) or Bruton's agammaglobulinemia is present at birth (congenital) and is characterized by low or completely absent levels of immunoglobulins in the bloodstream. Immunoglobulins are protein molecules in blood...

Electromagnetic radiation of extremely short wavelength (100 nanometres to 0.001 nanometre) produced by the deceleration of charged particles or the transitions of electrons in atoms. X-rays travel at the speed of light and exhibit phenome...

Phenomenon in which the atoms of a crystal, by virtue of their uniform spacing, cause an interference pattern of the waves in an incident beam of X-rays. The crystal's atomic planes act on the X-rays in the same way a uniformly ruled grati...

Stars radiate energy in many wavelengths. Visible light, the wavelength we see with the naked eye, is only one small part of the electromagnetic spectrum. Toward the short-wavelength end, beyond visible blue light and invisible ultraviolet...

Xu Guangqi (1562-1633) was a Chinese scholar-official, who rose to one of the highest government positions in the Ming dynasty, pioneered in the introduction of Western science and technology into China, and became one of the "Three Pillar...

Hsüan Tsang (ca. 602-664) was the most famous Chinese Buddhist pilgrim and traveler in India and a translator of Buddhist texts. His "Hsi-yü Chi," or "Record of Western Countries," remains an indispensable source book to students...

XX male syndrome occurs when the affected individual appears as a normal male, but has a female genotype (two X chromosomes). Two types of XX male syndrome can occur: those with detectable SRY gene and those without detectable SRY. SRY is ...

The term "xylene" refers to any of three benzene derivative isomers that share the same chemical formula, C6H4(CH3)2, but differ in their molecular structure. They are useful as solvents, as additives to improve the octane ra...