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In this issue:
Symmetry Explains it in 60 Seconds: Positron
Safety Today: 911 versus 9-911
Reuse of Government Property—Part I

SLAC Today

Tuesday - September 16, 2008

Symmetry Explains it in 60 Seconds: Positron


A positron is the antimatter partner of an electron. It has exactly the same mass as an electron but has the opposite electric charge. When kept separate from matter, positrons can exist forever. However, when a positron meets an electron, the two particles annihilate into a flash of energy.

Theorist Paul Dirac predicted positrons and other antiparticles in 1928. Combining the classical description of an electron’s motion with the new theories of relativity and quantum mechanics, Dirac found a puzzling solution to his equations: an electron moving with negative energy, which is impossible in classical physics. He interpreted his result as an antiparticle moving with positive energy. Four years later, physicist Carl Anderson observed in a cloud chamber experiment the positron predicted by Dirac. For their discoveries, both Dirac and Anderson received Nobel Prizes.

Today, positrons have numerous applications in particle physics research and medical imaging techniques. Scientists can "reverse" the annihilation process and create large numbers of positrons by, for example, bombarding a piece of metal with an intense electron beam. Another source of positrons are radioactive isotopes such as carbon-11. Hospitals use accelerators to produce these short-lived isotopes and use them as medical markers in Positron Emission Tomography. The PET technique allows for the visualization of biological processes and systems such as blood flow, metabolism and neuron receptors. 

(Column - Safety Today)

911 versus 9-911

Over the past several weeks, the question of using 911, versus 9‑911, for life threatening emergencies has come up during safety meetings. Both numbers work. Both go directly to the Palo Alto Fire Department Dispatch office and emergency responders from SLAC's Station 7 will be dispatched to your emergency. If it's easier for you to remember, just dial 911 (like you would at home).

SLAC's Emergency Management Program is migrating the entire SLAC site to a common process for contacting emergency responders. This migration includes contractors, visitors and guests who may not know our phone system. By now, you should have all received your new badge cards with the incident notification information (above image).  Read more...

Reuse of Government Property—Part I

SLAC departments and groups can save hundreds—even thousands—of dollars by using re-issued property here at SLAC.

The first priority is to re-use items. Reallocation of existing resources to the maximum extent possible is essential to prevent unnecessary procurements and make best use of resources. 

Stop by and visit the salvage group, located at the south end of Building 28, or check the online Property Utilization Catalog, viewable through the Business Information Systems property control Web site, for some of the items currently available. The catalog includes a brief description and photo of each item. Check it frequently; items are turned in daily.

Items usually remain in the catalog for at least one month before they are offered to other government agencies.

For any questions or for information on item availability, contact Gus Venancio (x2329).

This article is the first of two describing how the SLAC community can re-use and/or recycle excess government property. Stay tuned for part II next week.

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