- 行业: Printing & publishing
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McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
In mathematics, the concept zero is used in two ways: as a number and as a value of a variable. The positional system of number notation, developed first by the Babylonians with the base 60, and later by the Hindus and the Chinese with the base 10, required for greater clarity a special marker of the empty, nonoccupied position. As such, the symbol for zero was introduced by the Babylonians (about 500 <small>B.C.</small>), and a millennium later it appeared in the Indian system of notation, which came to the West through the Arabs as the arabic number system.
Industry:Science
One of the oldest and most important of the spices. It is the dried, unripe fruit of a weak climbing vine, <i>Piper nigrum</i>, a member of the pepper family (Piperaceae), and a native of India or Indomalaysia. The fruits are small one-seeded berries which, in ripening, undergo a color change from green to red to yellow. When in the red stage, they are picked, sorted, and dried. The dry, wrinkled berries (peppercorns) are ground to make the familiar black pepper of commerce. White pepper is obtained by grinding the seed separately from the surrounding pulp.
Industry:Science
Quantum effects have opened a new era in metrology for realizing (providing standards for) the physical units. The conventional standards of our macroscopic world (collectively termed “artifacts”) alter with time, temperature, and weather; suffer from mechanical shock during transportation; and depend on unwanted side effects and on geometric dimensions that often cannot be measured with sufficient precision. In contrast, quantum effects in the atomic world are unchangeable and can be described with extraordinary precision using only a few fundamental constants.
Industry:Science
In the early 1990s, some persons in New York City were diagnosed with a new, virtually untreatable form of tuberculosis. Called Strain W, it very rapidly killed 80–90% of those infected: most died within 4 months. All of the drugs routinely used to treat tuberculosis were useless. Strain W has now spread to at least 10 states and to France. By 1996 it accounted for one-quarter of the drug-resistant tuberculosis cases in the United States. This virulent outbreak demonstrates how multidrug-resistant tuberculosis is transforming treatment and control of the disease.
Industry:Science
In the early part of the twentieth century, liquid helium was found to have zero viscosity at temperatures below about 2.2 K. The condition of matter displaying this property was named the superfluid state. This property was later explained as a consequence of the fact that helium-4 (<sup>4</sup>He) atoms are Bose particles which, at sufficiently low temperatures and sufficiently high density, can display the quantum statistical phenomenon called Bose-Einstein condensation. This occurs when a fraction of the atoms occupy the same zero-kinetic-energy quantum state.
Industry:Science
Natural salt deposits contain microorganisms reported to be up to hundreds of millions of years old. Recent studies have concluded that salt-loving (halophilic) microbes living in ancient surface environments became trapped inside salt crystals and survived in a dormant state within the buried deposits. Protracted survival of microorganisms in ancient salt formations and other materials has redefined views of long-term survival and led to the realization that the biosphere on Earth and perhaps other parts of the solar system extends well into the solid subsurface.
Industry:Science
Snow that falls on Antarctica is gradually compressed, by the weight of the snow that accumulates above it, into ice. This ice flows toward the coast, where it eventually melts or calves (breaks) off into the ocean as icebergs. Most of the ice flows in the form of a large, continuous, slowly moving ice sheet, but in many places drainage basins occur in the ice sheet that contain faster-moving ice streams and their tributaries. The flow dynamics of these systems can be monitored and the findings used to shed light on many phenomena, including global climate change.
Industry:Science
Lithography is a photographic process that is used to transfer the geometric patterns describing an integrated circuit to the silicon wafer. After a lithography step, chemical, etching, impurity deposition, or oxidation process steps are performed on the silicon wafer to further delineate the circuit structure. These sequential lithography and processing steps precisely form the three-dimensional electrical circuit on the silicon surface, thus producing the integrated circuits used in all types of electronic communications, displays, and signal processing equipment.
Industry:Science
Recent research to determine the age of the Earth's core used hafnium–tungsten chronometry. The iron-rich metallic core is the most inaccessible part of the Earth, so determining how it has developed is very difficult. Furthermore, the first 500 million years of Earth history are the most obscure; no indigenous rocks from that period have survived the intense meteorite bombardment of the Earth. The development of a new way of determining the timetable for the growth of the core during the very earliest evolution of the Earth therefore represents a major breakthrough.
Industry:Science
Methods of converting electric energy to heat energy by resisting the free flow of electric current. Electric heating has several advantages: it can be precisely controlled to allow a uniformity of temperature within very narrow limits; it is cleaner than other methods of heating because it does not involve any combustion; it is considered safe because it is protected from overloading by automatic breakers; it is quick to use and to adjust; and it is relatively quiet. For these reasons, electric heat is widely chosen for industrial, commercial, and residential use.
Industry:Science
