X-Message-Number: 1623
Date: Fri, 15 Jan 93 20:30:56 EST
From: 
Subject: CRYONICS glass transition point

A few questions about problems around the glass transition temperature:

1) This may be entirely off the wall, but has anyone tried to add
water soluble long chain polymers like polyoxyethylene or polyvinyl
alcohol to water/glycerol glasses to try to improve their strength?
I realize that this may cause viscosity problems, and sufficiently
large viscosity increases would preclude using polymers in perfusion.
>From the description of the microfractures in even very carefully cooled
water/glycerol ice it sounded like the forces doing the fracturing must
be quite small, so even a small absolute increase (but hopefully a
substantial fractional) increase in strength could be a help.  Any
comments?  At least it could be a cheap, non-animal experiment.  Just
cooling a beaker of the mix could be informative.

2) Is there any published information on rates of loss of viability of
cells at various temperatures above 77K?  As has been noted in this
group, going below the glass transition temperature may effectively
stop molecular diffusion, perhaps with a much sharper temperature
dependence (since it is a collective phase transition, albeit a rather
peculiar one which has caused physicists a lot of work) than the
Arrhenius rate law.  If there is a regime just a few degrees below
the glass transition temperature where cracking is suppressed but so is
loss of viability, it might considerably brighten the prospects for
pre-nanotech reversible cryosuspension.  Any comments?

                                              -Jeffrey Soreff

standard disclaimer: I do not speak for my employer.

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