= Denis E. Bergeron
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\b[Denis E. Bergeron] is a NIST research chemist in its Radioactivity Group whose work concerns physical <radioactive activity> measurements and standards. His official profile identifies his work in that group; an author account in the Journal of Research of NIST documents the comparison of primary activity standards over several decades.<Denis E. Bergeron profile at NIST>[Official staff profile, Radioactivity Group and employment]{ref}<A Review of NIST Primary Activity Standards for 18F: 1982 to 2013 by Denis E. Bergeron and others>[First-page author affiliation and Abstract]{ref}
\Image[https://www.nist.gov/sites/default/files/styles/480_x_480_limit/public/images/2020/11/05/Bergeron_ARI.jpg?itok=eZ8W84w4]
{title=Denis E. Bergeron, from his labeled NIST staff portrait}
{height=200}
{source=https://www.nist.gov/people/denis-e-bergeron}
In the 2014 coauthored review, Bergeron and colleagues examined ten <fluorine-18> standardizations from 1982 to 2013. A new standard differed by about 4 percent from results obtained in1998–2008. The authors compared multiple primary measurement methods and possible sources of bias, while explicitly reporting that the older discrepancy was not fully explained.<A Review of NIST Primary Activity Standards for 18F: 1982 to 2013 by Denis E. Bergeron and others>[Abstract; §4 Discussion, comparison of techniques and unresolved bias]{ref}
A simple <ionization chamber> example shows why a calibration difference matters. Suppose measured <electric current> is $I=10\,\mathrm{pA}$ and the response model is $I=kA$. A hypothetical factor $k=2\,\mathrm{pA/MBq}$ gives activity $A=5\,\mathrm{MBq}$. Replacing it by $1.92\,\mathrm{pA/MBq}$ gives approximately $5.2083\,\mathrm{MBq}$ for the same current, an increase of about $4.17\%$.
These numbers are invented, not the review's calibration table. They separate the detector observation from the inferred <radioactive activity>. Bergeron's standards work demonstrates why cross-method comparisons and an explicit <measurement uncertainty> budget matter even when repeated readings are consistent.
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