Until the early years of the twentieth century, there was no way to observe the functions of a living organism without surgery. Then came the invention of the x-ray machine, the first device that allowed doctors to actually see inside a li...

Radioactivity was one of several discoveries made at the turn of the twentieth century that led to revolutionary changes in physics. Unlike some discoveries, it was completely unexpected. The discoverer was looking for something else when...

Radiation chemistry is the study of how radioactive elements interact with other materials and how these radioactive materials can be used for different processes. Radiation exists as three different types: alpha rays, beta rays, and gamma...

In radiology, the maximum permissible concentration refers to the recommended upper limit for the dose which may be safely received during a specific period by a person exposed to ionizing radiation.Itis also sometimes called permissible d...

Radioisotopes, containing unstable combinations of protons and neutrons, are created by neutron activation that involves the capture of a neutron by the nucleus of an atom. Such a capture results in an excess of neutrons (neutron rich). Pr...

Although the number system commonly used for counting and measuring is based on the number 10 and is known as the decimal system, there are counting systems based on other numbers. For example, base-2 and base-60 number systems are also us...

Rafello Bombelli was the last of a long line of Italian algebraists who contributed to the theory of equations during the Renaissance. He was the first to develop a consistent theory of imaginary numbers which included the rules for the fo...

Ragged Dick; or, Street Life in New York with the Boot Blacks by Horatio Alger Horatio Alger began a long career as a popular novelist for boys with the publication of Ragged Dick, his most successful book. So widely known were Alger's 119 ...

When Raging Bull, Martin Scorsese's biopic of 1940s middle-weight boxing champion Jake LaMotta, premiered in November of 1980, critics and audiences alike hailed it as a masterpiece. The film's expressionistic black-and-white...

fl. 800s Scandinavian monarch whose military exploits, including a battle with Charlemagne, became legendary in medieval European literature. Lothbrok's story was recounted in several Icelandic sagas and the twelfth-century Gesta Da...

RAID is an acronym that stands for Redundant Array of Independent Disks. It is a method of spreading information across several disks. Information can be duplicated on several disks, hence the word redundancy in the technique's name. By sp...

In 1985, the Rails-to-Trails Conservancy, a non-profit organization, was established to convert abandoned railroad corridors into open spaces for public use. During the nineteenth century, the railroad industry in the United States boome...

Even as transportation improvements accelerated through the twentieth century, the railroad still best symbolized the ability of mechanized invention to conquer distance; electric trains continue to epitomize this cultural belief in such t...

United States 1898 The Erdman Act, an early step toward the passage of the more comprehensive Railway Labor Act of 1926, was a federal law that attempted to alleviate labor unrest in the railroad industry by requiring mediation of any lab...

A rain shadow in Hawaii on the eastern side of Mount Waialeale. () A region of relative dryness found on the downwind side of a mountain range or other upland...

RAINBOW SNAKE (Rainbow Serpent) is an almost ubiquitous but elusive mythological figure throughout the Australian continent. To A. R. Radcliffe-Brown (1930), the Rainbow Snake was "perhaps the most important nature-deity, … t...

Rainforest Action Network (RAN), founded in 1985, is an activist group that works to protect rain forests and their inhabitants worldwide. Its strategy includes imposing public pressure on those corporations, agencies, nations, and polit...

Langston Hughes raised the question, "What happens to a dream deferred?" in his famous poem, "Montage of a Dream Deferred." A dream deferred, or a goal that is postponed, has several possible fates. It could totally di...

(b. 1909), Indian novelist. Raja Rao was born in Hassan, a provincial town of Karnataka, India. He graduated from the University of Madras and continued his studies at Montpellier and the Sorbonne. His remarkable literary reputation is bas...

(2002 est. pop. 57.6 million). Home of the inhospitable Thar Desert and with an overall arid climate, site of nuclear tests, and defender of a politically sensitive border with Pakistan, Rajasthan is nonetheless regarded as the major touri...

(2001 est. pop. 654,000). Rajkot is a city in Gujarat state, India. It was once the capital of the princely state of Rajkot, and is now the headquarters of Rajkot District. It is located in the middle of the peninsula of Kathiawar, some 70...

Rajput is a category of Indian warrior castes that is widespread across northwestern India, some neighboring Himalayan valleys, the Ganges plains, and Madhya Pradesh. Following India's independence in 1947, twenty-three small Rajput...

Suave, elegant, and incredibly versatile, Raul Julia (1940-1994) was among the most critically respected stage and screen actors of his generation. Though perhaps best known for his role as Gomez Addams in the Addams Family films of the 19...

The American philosopher Ralph Barton Perry (1876-1957) was a leader of the New Realist movement and the originator of the interest theory of value. Ralph Barton Perry was born on July 3, 1876, in Poultney, Vt. He received his bachelor of ...

Ralph GonsalvesPrime Minister (pronounced "RALF gon-SAHL-vayz") "Let us again put the issue of political union [among Caribbean nations] on the agenda…For my part, it is a noise in my blood, an echo in my b...