Be Fruitful and Symmetrize - HONORABLE MENTION

-Dan Anderson

Description of Image:

I used some props to explain my work to my non-crystallographer collaborators in the vaults project. Although my props are stone-age relative to those shown by Wally Cordes at the San Antonio ACA meeting, they seem to have worked for communication.

This photograph served as low-tech introduction to the goals and problems of non-crystallographic symmetry averaging. The foreground object is a “Kiwano Melon,” a fruit that seems to have evolved specifically for this figure. I found it in the grocery store. In the background is a Navajo pot in my apartment. The structure in the crystal has concentric 24- and 48-fold non-crystallographic rotational symmetry, as exemplified by the patterns of varying periodicity incised into the pot. The averaged electron density (as of the Difficult Structures session last July) was mostly patterned, but had spikes, bumps and holes. The Kiwano Melon looks like it’s almost patterned. To try to improve the phases, I put atoms into the patterned density while avoiding the un-patterned features. I will try to present all this low-throughput work (without pointing at a melon) in the next Difficult Structures session.

The light came from a studio flash to camera right. A 32 inch white reflector just left of the fruit eliminated almost all black pixels from the eventual image histogram. I used a flash meter and macro lens. Compensating for divergence of the T-stop away from the F-stop, I arrived at a flash energy of 308 Joules radiating into my favorite 36x48 inch diffuser. The image file came from a film scan.

The collaborators were amused. The fruit was almost tasteless.