It seems to me that this ingenious setup should minimize the
thickness of the cold gas layer, but NOT eliminate it. Effectively,
it should keep the vessel filled up to (or close to) the brim; but
Warkentin et al. show that even when the vessel is filled to the
brim, a significant cold gas layer remains.
On Feb 1, 2007, at 6:06 AM, James Stroud wrote:
I propose a simple contraption to minimize the vapor layer in
cryocrystallography, using freezing in the liquid phase. This idea
is based on the findings in the citation below. It is modified from
designs used in the pet feeding industry. The novel aspect is that
liquid nitrogen is used rather than water or nutritional liquids
and that this particular contraption can be used for the freezing
of crystals rather than the satiation of animals.
The idea is to invert a dewar over a dish. The dewar sits on a
block to raise its opening while the block has a gap to allow
liquid N2 to escape from the dewar. The block is adjusted so that
the opening to the dewar is just below the brim of the dish,
minimizing the vapor head space. The cold vapor should either rise
or fall depending on its density relative to the atmosphere,
minimizing the thickness of the trapped vapor phase.
The dish should be deep enough to allow one to plunge a crystal in
the liquid N2 without easily hitting the bottom of the dish.
I call this invention "James's Petfeeder Contraption for
Cryocrystallography". A diagram is at:
http://www.jamesstroud.com/Contraptions/Petfeeder.pdf
James
O
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---------------
Patrick J. Loll, Ph. D. (215) 762-7706
Associate Professor FAX: (215) 762-4452
Department of Biochemistry & Molecular Biology
Director, Biochemistry Graduate Program
Drexel University College of Medicine
Room 10-102 New College Building
245 N. 15th St., Mailstop 497
Philadelphia, PA 19102-1192 USA
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