- 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.
An instrument designed to collect and detect x-rays emitted from a source outside the Earth's atmosphere and to resolve the x-rays into an image. Absorption by the atmosphere requires that x-ray telescopes be carried to high altitudes. Balloons are used for detection systems designed for higher-energy (hard) x-ray observations, whereas rockets and satellites are required for softer x-ray detectors.
Industry:Science
An instrument designed to measure electrical quantities. A typical multimeter can measure alternating- and direct-current potential differences (voltages), current, and resistance, with several full-scale ranges provided for each quantity. Sometimes referred to as a volt-ohm meter (VOM), it is a logical development of the electrical meter, providing a general-purpose instrument. Many kinds of special-purpose multimeters are manufactured to meet the needs of such specialists as telephone engineers and automobile mechanics testing ignition circuits.
Industry:Science
An instrument for detecting ionizing radiation by measuring the amount of charge liberated by the interaction of ionizing radiation with suitable gases, liquids, or solids. These radiation detectors have played an important part in the development of modern physics and have found many applications in basic scientific research, in industry, and in medicine.
Industry:Science
An instrument for detecting the presence and sign of an electric charge. It is the simplest type of ionization chamber.
Industry:Science
An instrument for measuring vacuum by ionizing the gas present and measuring the ion current. There are two types of ionization gages.
Industry:Science
An instrument for observing moving bodies by making them visible intermittently and thereby giving them the optical illusion of being stationary. A stroboscope (sometimes called strobe) may operate by illuminating the object with brilliant flashes of light or by imposing an intermittent shutter between the viewer and the object. The rate and duration of the visible periods are adjustable.
Industry:Science
An instrument for telling time by the Sun. It is composed of a style that casts a shadow and a dial plate, which is the surface upon which hour lines are marked and upon which the shadow falls. The style lies parallel to Earth's axis. The construction of the hour lines is based on the assumption that the apparent motion of the Sun is always on the celestial equator.
Industry:Science
An instrument for the analysis and measurement of signals throughout the electromagnetic spectrum. Spectrum analyzers are available for subaudio, audio, and radio-frequency measurements, as well as for microwave and optical signal measurements.
Industry:Science
An instrument for the measurement of the electric potential difference between two conductors. Many different kinds of instruments are available to suit different purposes. Voltages of the order of picovolts (10<sup>−12</sup> V) to megavolts (10<sup>6</sup> V) can be measured. Frequencies from zero (dc) to many megahertz and accuracies in the range from a fraction of part per million (ppm) to a few percent may be covered.
Industry:Science
An instrument for the observation and study of microscopic specimens that absorb light and emit fluorescence. The ability of substances to emit light when excited by a strong light source is called luminescence, which encompasses the phenomena of phosphorescence and fluorescence. If the secondary emission continues for some time (milliseconds) after the light source has been turned off, it is referred to as phosphorescence. The ability to emit light only very briefly (nanoseconds) after the absorption of light is termed fluorescence. Many specimens obtained from plants, animals, and minerals have the ability to emit a weak to strong fluorescence when excited with appropriate light and without being specifically treated or stained. That phenomenon is called autofluorescence. In most cases, in order to obtain specific and meaningful fluorescence, staining with fluorescing dyes called fluorophores or fluorochromes is necessary. Fluorescence microscopy is a highly sensitive method, since often minute quantities of a fluorophore can be visualized with good microscopic contrast. In appropriate applications, brightly fluorescing images can be observed against a dark background. Individual fluorophores have different absorption and emission spectra and a different quantum efficiency (the ratio between the energy absorbed and the energy emitted), factors that must be considered for optimum fluorescence.
Industry:Science
