= R. Fourme
{c}
\b[<R. Fourme>] coauthored the 1984 high-resolution structure of human <deoxyhemoglobin> with <G. Fermi>, <Max Perutz> and <B. Shaanan>. The primary record describes <X-ray diffraction> collected on film at room temperature using <synchrotron radiation>, followed by refinement at $1.74\,\mathrm{\mathring A}$ resolution.<The crystal structure of human deoxyhaemoglobin at 1.74 A resolution by G. Fermi and others>[Primary byline and Abstract, experimental apparatus]{ref} This establishes a contribution to experimental <structural biology>; the byline alone does not assign each instrument or calculation to one coauthor.
The physical chain is illuminating: a <crystal> scatters the incident radiation, a detector records <diffraction intensity>, and a model connects the measurements with an <electron density> distribution. Improving incident flux can help collect weak reflections, but flux and <spatial resolution> remain different quantities.
For an original counting example, suppose an ideal detector records 400 independent photons in one reflection and background is negligible. A <Poisson distribution> then gives <standard uncertainty> $\sqrt{400}=20$ counts, or 5% relative uncertainty. Four times as many recorded photons gives 1,600 counts and $40/1600=2.5\%$ relative uncertainty. The square-root improvement describes the chosen counting model; it is not a measured uncertainty for the historical film detector.
Increasing exposure also need not preserve the specimen unchanged. A comparison should keep track of radiation-induced changes, detector response and background rather than assuming that every additional count is interchangeable. Those experimental controls complement the molecular constraints used in <X-ray crystallography>. Fourme's verified coauthorship connects the biological question to the apparatus needed to obtain its structural evidence.
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