Positron

The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1 e, a spin of ½, and has the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production of two or more gamma ray photons (see electron–positron annihilation).

Positrons may be generated by positron emission radioactive decay (through weak interactions), or by pair production from a sufficiently energetic photon which is interacting with an atom in a material.

History

Theory

In 1928, Paul Dirac published a paper proposing that electrons can have both a positive charge and negative energy. This paper introduced the Dirac equation, a unification of quantum mechanics, special relativity, and the then-new concept of electron spin to explain the Zeeman effect. The paper did not explicitly predict a new particle, but did allow for electrons having either positive or negative energy as solutions. Hermann Weyl then published "Gravitation and the Electron" (Proceedings of the National Academy of Sciences of the United States of America, Vol. 15, No. 4-Apr. 15, 1929, pp. 323–334) discussing the mathematical implications of the negative energy solution. The positive-energy solution explained experimental results, but Dirac was puzzled by the equally valid negative-energy solution that the mathematical model allowed. Quantum mechanics did not allow the negative energy solution to simply be ignored, as classical mechanics often did in such equations; the dual solution implied the possibility of an electron spontaneously jumping between positive and negative energy states. However, no such transition had yet been observed experimentally. He referred to the issues raised by this conflict between theory and observation as "difficulties" that were "unresolved".

Positron Corporation

Positron Corporation is an American nuclear medicine healthcare company specializing in cardiac Positron Emission Tomography (PET) imaging. Positron operates in a variety of business areas combining cardiac PET imaging technology, radiopharmaceuticals and radioisotopes. Positron is headquartered in Westmont, Illinois and holds three facilities: a radioisotope manufacturing facility in Lubbock, Texas, a clinical and technical cardiovascular PET training institute in Niagara Falls, New York and an automation manufacturing facility in Fishers, Indiana.

The company's products and services enable healthcare providers to diagnose cardiac disease and improve patient outcomes. Positron Corporation is a public company and traded on the Financial Industry Regulatory Authority, Inc.'s OTC Bulletin Board under the ticker symbol POSC.

History

Positron was originally founded in 1983 as a research and development company. The company expanded from a medical imaging device manufacturer to a nuclear healthcare company integrating the key components of the cardiac PET supply chain. Positron's strategy focuses on stabilizing and securing the Sr-82 supply chain.

Positron (video game)

Positron is a video game which was published for the BBC Micro and Acorn Electron computers by Micro Power in 1983. It was developed on a pre-release Electron and was one of the few games (other than those produced by Acornsoft) available for the machine on its launch.

Gameplay

The player controls a laser base which can move left and right and fire vertically. The object of the game is to destroy all alien creatures on each screen, then proceed to the next. The first sheet of aliens follows the classic Space Invaders style of moving, that being left to right, then moving down one row before moving right to left. The standard Invaders strategy of picking off the end columns to stop a rapid descent also applies to the first sheet of Positron. This first sheet however is not representative of the rest of the game and serves only to lull the player into a false sense of security.

All subsequent sheets follow a pseudo-random formation, generally moving down the screen but at various speeds and with greatly varying levels of firepower for each individual enemy. This means the strategy must change to looking to find which enemies are descending fastest and picking them off while also trying to break up big groups.