X-Message-Number: 5093
From: 
Date: Thu, 2 Nov 1995 01:40:02 -0500
Subject: SCI. CRYONICS addendum

My recent previous posts on possible hyperbaric freezing should have been
more explicit about the many considerations omitted, including variation of
heat of fusion with pressure and temperature. These can be addressed if the
notion isn't shot down decisively on other grounds.

And a slightly different illustration of the difference between minimization
of freezing damage and minimization of degradation of information:

Several people have proposed chemical fixation of tissue as a cheap
alternative to freezing. The conventional wisdom is that this should be at
most a last resort of desperation, since no living tissue has ever been
reported to have recovered from chemical fixation, whereas many
specimens--invertebrates and even a few mammalian organs--have recovered
after complete freezing and storage at cryogenic temperatures, which shows
that freezing damage generally is very much less than fixation damage, or at
least much more easily reversible. But that isn't the end of the story.

Tjhe point is that if ALL tissues retain nearly full inferrability of
information about the original structure, then in principle a sufficiently
advanced technology should be able to make complete repairs. But if even SOME
of the crucial tissues are essentially destroyed, then (possibly, depending
on several assumptions) recovery might never be possible. 

Repeating, then, hyperbaric quick freezing might substantially reduce
transport and mixing of materials, conserving information, even if damage (by
most measures) is much GREATER than with current methods of slow freezing,
and thus might offer a better long term probability of revival.


Robert Ettinger


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