activity (redirected from natural process)

activity

1. the number of disintegrations of a radioactive substance in a given unit of time, usually expressed in curies or disintegrations per second

2. 

a. the capacity of a substance to undergo chemical change

b. the effective concentration of a substance in a chemical system. The absolute activity of a substance B, λ_B, is defined as exp (μ_BRT) where μ_B is the chemical potential

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activity [‚ak′tiv·əd·ē]

(computer science)

The use or modification of information contained in a file.

(nuclear physics)

The intensity of a radioactive source. Also known as radioactivity.

(physical chemistry)

A thermodynamic function that correlates changes in the chemical potential with changes in experimentally measurable quantities, such as concentrations or partial pressures, through relations formally equivalent to those for ideal systems.

(systems engineering)

The representation in a PERT or critical-path-method network of a task that takes up both time and resources and whose performance is necessary for the system to move from one event to the next.