The Association of Digital Forensics, Security and Law (ADFSL)
In nuclear physics, the phrase decay rate is used to denote the rate that atoms and other particles spontaneously decompose. Uranium-235 famously decays into a variety of daughter isotopes including Thorium and Neptunium, which themselves decay to others. Decay rates are widely observed and wildly different depending on many factors, both internal and external. U-235 has a half-life of 703,800,000 years, for example, while free neutrons have a half-life of 611 seconds and neutrons in an atomic nucleus are stable.
Fairbanks, Kevin and Garfinkel, Simson
"Column: Factors Affecting Data Decay,"
Journal of Digital Forensics, Security and Law: Vol. 7
, Article 1.
Available at: http://commons.erau.edu/jdfsl/vol7/iss2/1