- 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.
Skin diving, or diving without the aid of special equipment, is a technique to investigate underwater environments and to gather shellfish or other items of commercial importance. In breath-hold diving, fins and faceplate are usually employed to facilitate the diver's activities. For longer periods of time, divers can function by using air pumped to them from the surface. This restricts the area that can be explored since movement of the diver is limited by the length of the air hose. Diving with scuba (self-contained underwater breathing apparatus) provides an almost limitless amount of freedom. With this equipment, the amount of time the diver can stay beneath the surface and the distance traveled are limited only by the volume of compressed air in the diver's tanks or aqua-lung.
Industry:Science
Precipitation that incorporates anthropogenic acids and acidic materials. The deposition of acidic materials on the Earth's surface occurs in both wet and dry forms as rain, snow, fog, dry particles, and gases. Although 30% or more of the total deposition may be dry, very little information that is specific to this dry form is available. In contrast, there is a large and expanding body of information related to the wet form: acid rain or acid precipitation. Acid precipitation, strictly defined, contains a greater concentration of hydrogen (H<sup>+</sup>) than of hydroxyl (OH<sup>−</sup>) ions, resulting in a solution pH less than 7. Under this definition, nearly all precipitation is acidic. The phenomenon of acid deposition, however, is generally regarded as resulting from human activity.
Industry:Science
Instruments used to measure the amount of rain or snow that falls on a level surface. Such measurements are made with instruments known as precipitation gages. A precipitation gage can be as simple as an open container on the ground to collect rain, snow, and hail; it is usually more complex, however, because of the need to avoid wind effects, enhance accuracy and resolution, and make a measurement representative of a large area. Precipitation is measured as the depth to which a flat horizontal surface would have been covered per unit time if no water were lost by runoff, evaporation, or percolation. Depth is expressed in inches or millimeters, typically per day. The unit of time is often understood and not stated explicitly. Snow and hail are converted to equivalent depth of liquid water.
Industry:Science
Interfering and unwanted currents or voltages in an electrical device or system. Electrical noise, or simply noise, has a significant effect on the design and operation of almost all electrical and optical systems which are used to communicate or process information. Noise is responsible for the familiar static observed on home radio receivers, the clicking sounds on frequency-modulation (FM) radios operating in fringe (near-threshold) areas, and the “snow”-type granularity on the viewing screen of a television receiver displaying a weak signal. In general, noise provides the fundamental limitation to the range over which radio or optical signals can be transmitted and received with integrity. Noise is, therefore, of great importance to the engineers who design and operate such systems.
Industry:Science
Most people have a strong belief in the accuracy and completeness of their visual experience. Indeed, it is often said that “seeing is believing,” indicating that visual perception is considered to be a trustworthy means of obtaining information about the world, distorting little and missing less. However, research has shown that visual perception does not capture as much of the world as we think. For example, drivers might believe that simply by looking around they would always be able to see an oncoming car, always notice the sudden veering of a nearby child on a bicycle, or always see an animal that suddenly rushes in front of their car. But they would be wrong. Even if viewing conditions were excellent, they could still miss such events—for example, if they were talking on a cell phone.
Industry:Science
Instrumentation located on the Earth for monitoring, tracking, and communicating with satellites, space probes, and crewed spacecraft. Radars, communication antennas, and optical instruments are classified as ground instrumentation. They are deployed in networks and, to a lesser extent, in ranges. Ranges are relatively narrow chains of ground instruments used to follow the flights of missiles, sounding rockets, and spacecraft ascending to orbit. Some ranges are a few miles long; others, such as the U.S. Air Force's Eastern Test Range, stretch for thousands of miles. Networks, in contrast, are dispersed over wide geographical areas so that their instruments can follow satellites in orbit as the Earth rotates under them at 15° per hour, or space probes on their flights through deep space.
Industry:Science
Rabies is one of the oldest and deadliest zoonotic diseases, killing tens of thousands of people worldwide each year. It is a viral infection typically transmitted to people via bites from infected animals, especially bats and carnivores or domestic mammals. The disease has no cure, but pre- and postexposure prophylaxes are available; therefore, human deaths due to rabies are relatively rare in North America. Because of aggressive vaccination programs for pets, most rabies cases in developed countries such as the United States come from wildlife species, and current rabies management programs are focused on the challenging goal of reducing infection within wildlife (in contrast to reducing infection within domestic species (especially domestic dogs), as is the case in under-developed countries).
Industry:Science
Members of the family Gramineae cultivated as forage and grain for consumption. The grasses are the most useful of all the plants that cover the Earth. The cereal grasses (rice, wheat, maize, rye, barley, oats, sorghum, and the millets) supply directly three-fourths of the energy and over half of the protein in food consumed by humans. Indirectly, these cereals together with the forage grasses supply most of the food for the domestic animals that provide milk, meat, eggs, and much of the draft power required to grow crops. Deer, antelope, rabbits, and many other wild game depend on grasses for much of their sustenance. Sugarcane produces more than half of the world supply of sugar. Starch, and most of the alcohol for beverage and industrial uses, comes from the cereal grasses.
Industry:Science
Since the late 1980s, satellites have been used to provide distance education to large numbers of students and adults. Teachers can extend their reach to remote parts of the world, providing students with access to advanced courses that are unavailable locally. Until recently, most of these courses have been delivered in the traditional educational style with students watching the teacher on video. However, emerging technologies are reshaping distance education. The ability of these technologies to handle video, data, and voice gives designers the opportunity to take maximum advantage of a rich distributed-learning environment. Individuals can be offered a chance to engage in learning at their convenience and in a variety of modes, and they can have access to experts as well as current resources.
Industry:Science
In the late 1980s, the universality of the accepted paradigm for how spontaneous gene mutations form was challenged. The paradigm of S. E. Luria and M. Delbrück (1943) described spontaneous mutation as a process akin to random thermal noise—that is, spontaneous mutation occurred before cells encounter an environment in which the mutation might prove beneficial, in a cell generation–dependent manner, and more or less randomly in the genome. This was in harmony with neo-Darwinian evolutionary thought, in which rare, randomly formed mutants gain the ability to survive by accidentally acquiring genotypes more favorable for their environment than their competitors' genotypes. In this view, the environment and its role in selection of favorable genotypes is not linked to the generation of new genotypes.
Industry:Science
