Craig L. Zirbel
= Craig L. Zirbel
{c}
\b[Craig L. Zirbel] is a mathematician whose research connects <probability theory> with applications including <RNA> geometry and stochastic fluid motion. Bowling Green State University's faculty page identifies him as professor emeritus in mathematics and statistics and lists <random measures>, mass transport, and <RNA> structure and sequence variability among his interests.<Craig Zirbel faculty profile at Bowling Green State University>[Research Interests and Professional Experience]{ref}
\Image[https://www.bgsu.edu/content/dam/BGSU/college-of-arts-and-sciences/mathematics-and-statistics/images/zirbel.jpg]
{title=Craig L. Zirbel, portrait supplied on his university faculty page}
{width=240}
With <Jesse Stombaugh>, <Eric Westhof> and <Neocles B. Leontis>, he coauthored the 2009 study <Frequency and isostericity of RNA base pairs by Jesse Stombaugh and others>. It introduces the <RNA IsoDiscrepancy Index> and uses structural comparisons to investigate which base-pair substitutions preserve local geometry. This connects geometric annotation with comparisons of sequence variation, rather than treating nucleotide identities alone as a complete structural description.<Frequency and isostericity of RNA base pairs by Jesse Stombaugh and others>[Abstract; definition and validation of the index]{ref}
One mathematical task in that study is choosing an observed representative from several instances of a base-pair type. The authors compare instances and select the row with the smallest sum of discrepancies. An original miniature example uses the symmetric comparison-cost matrix
$$
D=\begin{pmatrix}0&1&4\\1&0&3\\4&3&0\end{pmatrix}.
$$
Its row sums are 5, 4 and 7, so the second instance is the representative minimizing total comparison cost. These are chosen teaching values, not reported measurements of an RNA structure. The rule selects an observed instance; it does not require constructing an average set of atomic coordinates.<Frequency and isostericity of RNA base pairs by Jesse Stombaugh and others>[Methods, selection of base-pair exemplars using the minimum row sum]{ref}
Such a geometric representative is not necessarily the lowest-<free energy> structure, nor does a small discrepancy prove identical biological function. The example shows how an explicit comparison rule turns structural data into a reproducible choice, while leaving the physical interpretation to the measurement and molecular context.