1. The third letter of the Greek alphabet; Γ, γ.
2. The third item in a series or system of classification.
3. A unit of magnetic intensity equal to one hundred thousandth (10^-5) of an oersted (unit measure of magnetic field strength in the centimeter-gram-second system).
4. A unit of mass equal to one millionth (10^-6) of a gram.
5. In chemistry, the third position from a designated carbon atom in an organic molecule at which an atom or a radical may be substituted.
6. A number expressing the degree to which a negative has been developed as compared with the range of light values in the subject photographed.

Rays coming from pulsars, radio galaxies, and quasars, although it is believed that they cannot penetrate the earth's atmosphere.

1. A correction to the contrast of images and displays, performed by either software or hardware, and designed to correct for the fact that the intensity displayed on a cathode-ray tube is not linearly related to the input voltage.
2. Adjustments applied during the display of a digital representation of color on a screen in order to compensate for the fact that the Cathode Ray Tubes used in computer monitors, and televisions, produce a light intensity which is not proportional to the input voltage.

The light intensity is actually proportional to the input voltage raised to the inverse power of some constant, called gamma.

A device for detecting gamma radiation, primarily through the detection of fast electrons produced by the gamma rays; it either yields information about integrated intensity within a time interval or detects each photon separately.

The cross section for absorption or scattering of gamma rays by a nucleus or atom.

A quantum transition between two energy levels of a nucleus in which a gamma ray is emitted.

Any of the motor nerve fibers that transmit impulses from the central nervous system to the intrafusal fibers (the striated fibers within a muscle spindle or a stretch receptor) of the muscle spindle.

The gamma efferent fibers are responsible for deep tendon reflexes, spasticity (increased tone of a muscle), and rigidity, but not for the degree of contractile response. They function in regulating the sensitivity of the spindle and the total tension of the muscle.

The number of gamma rays passing through a unit area in a unit of time.

A penetration-type thickness gage that measures the thickness or density of a sample by measuring its absorption of gamma rays.

1. A globulin present in blood plasma which contains antibodies effective against certain pathogenic micro-organisms.
2. Any of the serum proteins with antibody activity.

Heating resulting from absorption of gamma-ray energy by a material.

Exposure of a material to gamma rays.

A method for destroying deep-seated brain tumors with a focused beam of gamma radiation.

By using three-dimensional stereoscopic techniques to aim the radiation from several angles, it is possible to concentrate the energy on the tumor while minimizing damage to surrounding tissues.

Radiosurgery in which an intracranial target can be destroyed by ionizing beams of radiation that are directed with stereotaxic precision.

A normal surgical incision is not needed. The therapy is used to treat brain tumors and vascular lesions.

A small nerve originating in the anterior horns of the spinal cord that transmits impulses through type A gamma fibers to intrafusal fibers of the muscle spindle for muscle control.

Radiation of gamma rays which consist of very high-frequency electromagnetic radiation, similar in nature to X-rays but of shorter wavelength emitted by the nuclei of radioactive substances during decay or by the interactions of high-energy electrons with matter.

Gamma emission usually occurs as part of alpha or beta emissions; however, they are less ionizing in their effect than alpha and beta particles, but are dangerous nevertheless because they can penetrate deeply into body tissues; such as, bone marrow.

Controlled application of gamma radiation is important in the diagnosis and treatment of various conditions, including skin cancer and malignancies deep within the body.

Gamma radiation is also used to kill bacteria and other micro-organisms, to sterilize medical devices, and to change the molecular structure of plastics to modify their properties.

1. A type of emission from radioactive substances, consisting of electromagnetic radiation of great penetrating power and of wavelengths lying beyond the region of the shortest X-rays.
2. A high-energy photon, especially as emitted by a nucleus in a transition between two energy levels.

A test using a strip of film to determine the degree of density in a photographic image in comparison with the degree of illumination of the object photographed.

Any nuclide that emits gamma photons.

An altimeter, used at altitudes under several hundred feet, that measures the photon back-scatter from the earth resulting from the transmission of photons to earth from a cobalt-60 gamma source.

The study of gamma rays from extraterrestrial sources, especially gamma-ray bursts.

Gamma-ray astronomy is the study of astronomical objects by analysis of the most energetic electromagnetic radiation they emit.

Gamma rays are shorter in wavelength and hence more energetic than X-rays, but much harder to detect and to pinpoint.

X-rays and some gamma rays are produced throughout the universe by the same catastrophic astrophysical events; such as, supernovas and black holes, and gamma-ray astronomy can be considered an extension of X-ray astronomy to the extreme shortwave end of the spectrum.

Intense blasts of soft gamma rays of unknown origin, which range in duration from a tenth of a second to tens of seconds and occur several times a year from sources widely distributed over the sky.

An instrument used on ships to identify and measure abnormal concentrations of gamma rays in the oceans.

A level indicator in which the rising level of the liquid or other material reduces the amount of radiation passing from a gamma-ray source through the container to a Geiger counter or other radiation detector.

A gamma-ray counter built into a watertight case small enough to be lowered into a borehole.

A quantity of radioactive material that emits gamma radiation and is in a form that is convenient for radiology.

Measurement of gamma-ray intensity versus depth down a well bore.

Used to identify rock strata, their positions, and their thicknesses.