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Overview

A20

A cytoplasmic zinc finger protein (790 aa) that inhibits NFκB activity and TNF-mediated programmed cell death. The expression of the A20 mRNA is upregulated by TNFα. It is a dual function ...

prompt neutrons

prompt neutrons  

The neutrons emitted during a nuclear fission process within less than a microsecond of fission. Compare delayed neutrons.
slow neutron

slow neutron  

A neutron with a kinetic energy of less than 102 eV (10−17 joule). See also fast neutron; thermalization.
breakdown

breakdown  

The sudden passage of a current through an insulator. The voltage at which this occurs is the breakdown voltage.
quantum electronics

quantum electronics  

The application of quantum optics and the specifically quantum-mechanical properties of electrons to the design of electronic devices.
speed of sound

speed of sound  

Symbol c or cs. The speed at which sound waves are propagated through a material medium. In air at 20°C sound travels at 344 m s−1, in water at 20°C it travels at 1461 m s−1, and in steel at 20°C at ...
magic numbers

magic numbers  

Numbers of neutrons or protons that occur in atomic nuclei to produce very stable structures. The magic numbers for both protons and neutrons are 2, 8, 20, 28, 50, and 82. For neutrons 126 and 184 ...
loudspeaker

loudspeaker  

A transducer for converting an electrical signal into an acoustic signal. Usually it is important to preserve as many characteristics of the electrical waveform as possible. The device must be ...
nucleon emission

nucleon emission  

A decay mechanism in which a particularly unstable nuclide regains some stability by the emission of a nucleon (i.e. a proton or neutron). Proton emitters have fewer neutrons than their stable ...
coercive force

coercive force  

The magnetizing force necessary to reduce the flux density in a magnetic material to zero. See hysteresis.
differential amplifier

differential amplifier  

An amplifier with two inputs in which the output is a function of the difference between the inputs.
soft radiation

soft radiation  

Ionizing radiation of low penetrating power, usually used with reference to X-rays of long wavelength. Compare hard radiation.
resistivity

resistivity  

Symbol ρ. A measure of a material's ability to oppose the flow of an electric current. The resistivity of a material is given by RA/l, where R is the resistance of a uniform specimen of the material, ...
twinning

twinning  

A process in which two crystals of the same material form with orientations such that the crystals are related to each other by a symmetry operation. This may be either reflection in a plane (the ...
sigma particle

sigma particle  

A type of spin ½ baryon. There are three types of sigma particles, denoted Σ−, Σ0, Σ+, for the negatively charged, electrically neutral, and positively charged forms, respectively. The quark content ...
thermal imagery

thermal imagery  

The production of images by detecting, measuring, and recording the thermal (infrared) radiation emitted by objects. Applications of thermal imaging include mapping of the surface of the earth from ...
motor

motor  

Any device for converting chemical energy or electrical energy into mechanical energy. See electric motor; internal-combustion engine; linear motor.
Van de Graaff generator

Van de Graaff generator  

An electrostatic generator used to produce a high voltage, usually in the megavolt range. It consists of a large metal dome-shaped terminal mounted on a hollow insulating support. An endless ...
simultaneity

simultaneity  

The condition in which two or more events occur at the same instant. In Newtonian physics any two events found to be simultaneous by one observer will also appear to be simultaneous to any other ...
wind power

wind power  

The use of winds in the earth's atmosphere to drive machinery, especially to drive an electrical generator. Practical land-based wind generators ( aerogenerators) are probably capable of providing ...
oscillator

oscillator  

An electronic device that produces an alternating output of known frequency. If the output voltage or current has the form of a sine wave with respect to time, the device is called a sinusoidal (or ...

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