[RASMB] Thoughts about convection, Identifying convection and preventing convection

[Tom Laue]

Just a quick thought to add to David's musings-
If you accelerate quickly, a ~1 C temperature gradient will develop in 
the cell from top to bottom. The temperature gradient disappears pretty 
quickly, but may be the cause of some of the early scans having "odd" 
residuals, especially towards the meniscus.
Jon Kingsbury did a series of experiments in my lab looking at the 
thermal conductivity of epoxy, aluminum filled epoxy, carbon filled 
epoxy and diamond dust filled epoxy. The aluminum, carbon and diamond 
filled epoxies all had the same thermal conductivity (within 
experimental error), and all were much better than plain epoxy. He also 
looked at using carbon fiber filled epoxy, which had good thermal 
characteristics but which weakened the epoxy (contrary to what we had 
hoped for).
Our conclusion is: choice of carbon or aluminum filled epoxies should be 
based on chemical compatibility, they do not differ in thermal 
conductivity. In general, the carbon filled epoxy tends to be more inert 
with biological samples. There is no passivation step for the carbon 
filled centerpieces, whereas the aluminum-filled centerpieces require an 
NaOH soak to remove any residual Al. The carbon and aluminum filled 
centerpieces exhibit nearly equal strength, which is close to that for 
the pure epoxy (the strongest).
Best wishes to all-
Tom

-- 
Department of Biochemistry and Molecular Biology
University of New Hampshire
Durham, NH 03824-3544
Phone: 603-862-2459
FAX:   603-862-0031
E-mail: Tom.Laue at unh.edu
www.bitc.unh.edu
www.camis.unh.edu