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This is the FORMATTED DISPLAY,
which shows numbers in scientific notation in 6 significant figures. (For easier
readibility, numbers between .001 and 1,000 will be displayed in standard form).
Unfortunately, some browsers cannot display this formatting properly and if that is the
case, please go to the STANDARD DISPLAY
The "Time 1" and
"Time 2" input boxes are for
inputting the start and end times of the interval you want to be
calculated. Time 1 subtracted from Time 2 equals a difference
that when divided
by ten, yields the increments into which the interval will be divided. For example, if you enter Time 1 as 50 and Time 2 as 70, your results will be in 2 day increments. (50, 52, 54, ... 70). The "Day 0 Activity" is for inputting the radioactivity on the reference date and NOT for the activity at the start of the chosen interval. (Referring to the above example, this would NOT be the Day 20 activity).
As for the isotope "dropbox", we
have chosen 70 of the most popular isotopes used in chemistry and medicine.
They are listed in increasing mass number order.
Choose the isotope, click
the "Calculate" button and you have your calculations. Notice that the
half-life of the
isotope is displayed beneath the "Calculate" button.
Now, let's suppose you
disagree with our half-life value OR you want calculations for an isotope
we haven't listed. You can't use the boxes beneath the 'Calculate'
button - these
are output only. However, going to the drop-down menu, the last two
choices are 'Other (Days)' and 'Other (Years)'. Make your selection from
these two and then click "Calculate". An input 'prompt box' will appear and
then you can input the half-life. Click the 'OK' on the prompt and your
calculations will appear. DO NOT click the "Calculate" button again.
We hope this calculator will save you the time that you previously
spent on these laborious calculations. If this calculator has
been a help to you, please let your colleagues know and
please send us an E-Mail (see our Home Page).
The National Institute of Standards and Technology Radionuclide Half-Life Measurements M. P. Unterweger, D. D. Hoppes, F. J. Schima, and J. S. Coursey
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