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The goal of the microgravity crystallization experiments in space is to
completely avoid gravity-induced mixing/convection. Theoretical
calculations showed that even very small accellerations due to
vibrations were sufficient to mess up this goal. This was reflected in
the inverse correlation between crystal quality and the level of
vibrations measured during flights. This should be much improved on the
international space station.
On earth in our 1G gravitation field convective mixing is a given in
normal liquid-phase experiments. A bit of additional vibrational
accelleration forces shouldn't matter, at least not for this aspect of
crystallization. My feeling is that a vibration-free environment won't
hurt (most of the time) while significant vibrations may or may not hurt
depending on your sample. However, spending a fortune to eliminate the
last bit of vibration may not be the best investment. I also like to
remind people that crystals have been grown in ultracentrifuges and as
co-editor of Acta Cryst F, I am surprized that I haven't yet come across
a paper where people get better crystals when exposing experiments to a
... --- ... pulse sequence in a sonicator. Perhaps I get one on April 1
next year :)
Bart
James Holton wrote:
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The most carefully monitored connection between crystal growth and
vibration I am aware of was made by Eddie Snell's group with their
experiments on the Space Shuttle:
http://scripts.iucr.org/cgi-bin/paper?gr0718
E. H. Snell, T. J. Boggon, J. R. Helliwell, M. E. Moskowitz and A.
Nadarajah, /Acta Cryst./ (1997). D*53*, 747-755
They saw a very clear conneciton between vibrations and crystal growth
rates and indeed crystal quality. Things like "astronaut exercising"
coincided with increased crystal growth rate a short time later. So, it
would appear that even in the most controlled environments vibration
control can be a challenge, but at least on the Shuttle, where
everything gets logged, you can (could) look for relationships.
Hope this is useful.
-James Holton
MAD Scientist
--
==============================================================================
Bart Hazes (Assistant Professor)
Dept. of Medical Microbiology & Immunology
University of Alberta
1-15 Medical Sciences Building
Edmonton, Alberta
Canada, T6G 2H7
phone: 1-780-492-0042
fax: 1-780-492-7521
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