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Related to Positrons: antimatter, Mesons, neutrinos


the antiparticle of the electron. When a positron is emitted by a radionuclide it combines with an electron and both undergo annihilation, producing two 511-keV gamma rays traveling in opposite directions. This effect is used in positron emission tomography.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

pos·i·tron (β+),

A subatomic particle of mass and charge equal to the electron but of opposite (that is, positive) charge.
Synonym(s): positive electron
Farlex Partner Medical Dictionary © Farlex 2012


+) (poz'i-tron)
A subatomic particle of mass and charge equal to the electron but of opposite (i.e., positive) charge.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


One of the small particles that make up an atom. A positron has the same mass and amount of charge as an electron, but the positron has a positive charge.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
These released positrons subsequently collided with electrons in annihilation events releasing gamma rays.
The [sup.22]Na isotope of low ~50 kBq activity prepared from aqueous [sup.22]NaCl solution (wrapped by Kapton[R] foil of 12 [micro]m thickness and sealed) was used as positron source sandwiched between two identical nanocomposite pellets.
Positron emission tomography is the diagnostic medical procedure of producing a positron emission tomography scan to examine metabolic activity of the tissues particularly the brain tissue, using a radioactive isotope administered intravenously.
The ability to create a large number of positrons in a laboratory, by using energetic lasers, opens the door to several new avenues of antimatter research, including the understanding of the physics underlying extreme astrophysical phenomena such as black holes and gamma-ray bursts.
In 1997, the High-Energy Antimatter Telescope, or HEAT, a cosmic ray detector tethered to a high-altitude balloon, revealed an unexpectedly high concentration of positrons in space.
The present proposal assumes that the BTF will be able to provide 50 bunches per second with duration of 40 ns and [10.sup.4] - [10.sup.5] positrons.
Another telling sign is the direction the positrons are coming from.
In the latter stage (i.e., x>0.7), the lattice contraction has expectedly resulted in a decrease by 0.3% in the grain size, and thereby, the number of positrons reaching out on the grain surfaces has slightly increased.
Sure enough, these frequencies appeared to flip the spin of the positron and eject the antihydrogen from the trap.
In four of them, positrons also struck the satellite.
Champlain, New York-based Positron offers a range of telecommunications equipment: high-density key systems for trader's turrets, answering positrons and dispatch consoles; protection systems for power station communications; telco alarm systems; and 911 emergency call-enhancement systems.