Question
Incomplete measurements from CCDs in this technique can lead to a loss of information called the “phase problem.” For 10 points each:
[10e] Name this technique that uses low-wavelength light to probe lattice structures. Rosalind Franklin used this technique to determine the structure of DNA.
ANSWER: X-ray crystallography [or X-ray diffraction or XRD]
[10m] X-ray crystallography is limited in scale by the diffraction limit for this quantity usually measured in angstroms. A coefficient of 1.22 appears in the Rayleigh criterion for this quantity.
ANSWER: resolution [accept angular resolution; accept resolving power; prompt on angle]
[10h] Molecular modelling using X-ray crystallography uses this quantity defined by summing differences in structure factors over all reflections. A “free” form of this quantity is usually one tenth the resolution.
ANSWER: R-factor [or R-value; accept R-free; accept discrepancy index]
<Ohio State A, Chemistry>
Summary
| California | 2025-02-01 | Y | 3 | 13.33 | 100% | 33% | 0% |
| Florida | 2025-02-01 | Y | 2 | 25.00 | 100% | 100% | 50% |
| Lower Mid-Atlantic | 2025-02-01 | Y | 6 | 10.00 | 83% | 0% | 17% |
| Midwest | 2025-02-01 | Y | 6 | 10.00 | 100% | 0% | 0% |
| North | 2025-02-01 | Y | 3 | 13.33 | 67% | 33% | 33% |
| Northeast | 2025-02-01 | Y | 5 | 14.00 | 100% | 20% | 20% |
| Overflow | 2025-02-01 | Y | 5 | 20.00 | 100% | 40% | 60% |
| South Central | 2025-02-01 | Y | 2 | 20.00 | 100% | 100% | 0% |
| Southeast | 2025-02-01 | Y | 4 | 12.50 | 100% | 0% | 25% |
| UK | 2025-02-01 | Y | 10 | 13.00 | 100% | 30% | 0% |
| Upper Mid-Atlantic | 2025-02-01 | Y | 8 | 16.25 | 88% | 63% | 13% |
| Upstate NY | 2025-02-01 | Y | 3 | 10.00 | 100% | 0% | 0% |
Data
| Columbia B | NYU A | 10 | 10 | 0 | 20 |
| Haverford A | Columbia C | 10 | 10 | 0 | 20 |
| John Jay College | Maryland A | 10 | 0 | 0 | 10 |
| Johns Hopkins A | Vassar A | 10 | 10 | 10 | 30 |
| Maryland B | Penn A | 10 | 0 | 0 | 10 |
| Yale A | NYU B | 10 | 10 | 0 | 20 |
| George Washington B | Penn B | 0 | 10 | 0 | 10 |
| Rutgers A | George Washington A | 10 | 0 | 0 | 10 |