- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- Company Profile:
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.
Electric vehicles competed head to head with gasoline cars around the beginning of the twentieth century but soon faded from the marketplace. They failed in the United States and elsewhere because electricity-recharging infrastructure was too sparse, batteries were far inferior to present ones, and the technology did not match well with the contemporary market. After batteries were made more reliable around 1907, electric vehicles made a brief resurgence, but limited-range cars had little appeal. In recent times, circumstances have changed, environmental issues are more central, and batteries continue to be improved. It remains to be seen whether the rapid pace of electric vehicle technology will continue and whether it will lead to other types of electric drive vehicles.
Industry:Science
Cells maintain their content separate and distinct from the external environment by a semifluid lipid bilayer that prevents the free exchange of most biological molecules and acts as a barrier between the inside and the outside of a cell. Prokaryotic cells contain only one such membrane, the plasma membrane that delineates the border of the cell. Eukaryotic cells, in addition to the plasma membrane, contain a multitude of internal membranes that define distinct intracellular organelles. The role of the plasma membrane and the internal membranes is analogous—all prevent the free exchange of molecules between the inside and the outside of the enclosed compartment, thus allowing the generation and maintenance of specialized microenvironments within each membrane-enclosed space.
Industry:Science
Any of the organic compounds in which all of the hydrogen atoms attached to a carbon atom have been replaced by fluorine; also referred to as a perfluorocarbon. Fluorocarbons are usually gases or liquids at room temperature, depending on the number of carbon atoms in the molecule. A major use of gaseous fluorocarbons is in radiation-induced etching processes for the microelectronics industry; the most common one is tetrafluoromethane. Liquid fluorocarbons possess a unique combination of properties that has led to their use as inert fluids for cooling of electronic devices and soldering. Solubility of gases in fluorocarbons has also been used to advantage. For example, they have been used in biological cultures requiring oxygen, and as liquid barrier filters for purifying air.
Industry:Science
Applying risk analysis to strategies against terrorism requires an innovative combination of approaches. Assessing the risk of terrorism (which is dynamic and adaptable) is fundamentally different from assessing the risk of accidents or acts of nature. In particular, terrorists can adopt different strategies in response to our defenses. Game theory, an economic tool for mathematically modeling optimal strategies, provides a way of accounting for this. Counterterrorism can benefit from the combination of risk analysis and game theory. While game theory quickly becomes mathematically complex and may not be applicable to problems of realistic scale and complexity, the results of such analyses can yield useful qualitative insights into the nature of optimal defensive investments.
Industry:Science
Energy metabolism, or bioenergetics, is the study of energy changes that accompany biochemical reactions. Animals, plants, and bacteria require energy to sustain life. Energy sustains the work of biosynthesis of cellular and extracellular components, the transport of ions and organic chemicals against concentration gradients (osmotic work), the conduction of electrical impulses in the nervous system, and the movement of cells and the whole organism. Sunlight is the ultimate source of energy for life. Photosynthetic cells use light energy to produce chemical energy and reducing compounds, used to convert carbon dioxide into organic chemicals such as glucose. The energy from the oxidation of carbohydrates, fats, and proteins sustains the biochemical reactions required for life.
Industry:Science
Apes and humans are closely related primates in the superfamily Hominoidea. The living hominoids are subdivided into the families Hylobatidae and Hominidae. The hylobatids or lesser apes (genus <i>Hylobates</i>) are represented by approximately nine species found throughout Southeast Asia. Humans and the great apes—the orangutan (<i>Pongo pygmaeus</i>), the gorilla (<i>Gorilla gorilla</i>), the common chimpanzee (<i>Pan troglodytes</i>), and the pygmy chimpanzee or bonobo (<i>Pan paniscus</i>)—are grouped in the Hominidae. In the past, the great apes were included in a separate family, the Pongidae, but subsequent anatomical and molecular studies showed that the African apes (<i>Gorilla</i> and <i>Pan</i>) are more closely related to humans than they are to the Asian orangutan.
Industry:Science
Biological diversity arises through speciation—the evolution of two species from a single common ancestor. Under the standard (allopatric) speciation model, new species begin as geographically isolated populations that evolve independently, gradually accumulating genetic differences that render them reproductively isolated from one another. Should such diverging populations later come into secondary geographic contact, incompatible courtship signals could prevent them from forming hybrids (prezygotic isolation) or, if hybrids are formed, incompatible genetic interactions could cause them to be sterile or inviable (postzygotic isolation). Both pre- and postzygotic forms of reproductive isolation prevent genetic exchange, allowing the recently diverged species to remain distinct.
Industry:Science
For more than a century, physical oceanographers—those who study the physics of the ocean—have been expanding their ability to interpret oceanic observations. The first crucial step is the application of dynamical equations, the fundamental equations of fluid mechanics. The task of developing dynamical models, written out as equations, is not yet complete. There remain unresolved issues such as turbulence, mixing, and friction, and the appropriate way in which to represent them. Nonetheless, the fundamental equations are well accepted and, in many different case studies, well understood. With especially rapid progress in recent years, oceanographers have developed computer models of ocean currents, just as meteorologists have developed numerical models of winds in the atmosphere.
Industry:Science
Helium boils at a substantially lower temperature, 4.2 K (−452°F or −269°C), than any other substance; and below 2.172 K (−455.76°F) the liquid exhibits the extraordinary properties of superfluidity, notably the ability to flow through narrow channels with complete absence of friction. In addition to the common isotope of atomic weight 4, helium has a rare isotope of atomic weight 3 with a normal boiling point of 3.2 K (−454°F) and a superfluid transition at a very much lower temperature near 0.001 K. Both forms of helium remain in a liquid state at absolute zero. All of these characteristics are due to the weakness of the attractive force between two helium atoms and to the small atomic mass, which according to the laws of quantum mechanics makes the atoms difficult to localize.
Industry:Science
Any compound having highly basic properties, strong acrid taste, and ability to neutralize acids. Aqueous solutions of alkalies are high in hydroxyl ions, have a pH above 7, and turn litmus paper from red to blue. Caustic alkalies include sodium hydroxide (caustic soda), the sixth-largest-volume chemical produced in the United States, and potassium hydroxide. They are extremely destructive to human tissue; external burns should be washed with large amounts of water. The milder alkalies are the carbonates of the alkali metals; these include the industrially important sodium carbonate (soda ash) and potassium carbonate (potash), as well as the carbonates of lithium, rubidium, and cesium, and the volatile ammonium hydroxide. Sodium bicarbonate is a still milder alkaline material.
Industry:Science
