X-Message-Number: 4574
From:  (Brian Wowk)
Newsgroups: sci.cryonics
Subject: Re: why is deep freezing necessary?
Date: 26 Jun 1995 21:09:45 GMT
Message-ID: <3sn7mp$>
References: <3sep83$>

In <3sep83$>  (Adam Dingle) writes:

>I read the Cryonics FAQ with curiosity.  However one question remains quite
>unclear to me: why is it necessary to store
>the suspended individuals at a sub-freezing temperature?  Given that dogs
>and even a baboon have been revived after
>being at cool, but above-freezing temperatures, for a number of hours, it
>would seem to me that a suspended person
>could be kept indefinitely at a temperature of, say, 1 degree Celsius,
>without freezing damage.  Is the fundamental
>problem that bacterial decomposition would occur at such a temperature?
>Or is there some other problem?

	Chemistry proceeds *furiously* at 1'C.  Worst of all, it does so in an
imbalanced manner (with some reactions suppressed by the cold, while others
continue unabated).  This problem has been faced by organ transplant surgeons
for years as they race organs around the country on ice before they lose
viability.  The best preservative solutions around today will keep hearts
good for about 12 hours, and kidneys for 36 hours, then that's it.

	This problem can be viewed in more familiar terms.  Foods do not
stay fresh indefinitely in refrigerators or even deep freezers.  Traces
of liquid water within which diffusion can occur remain inside cells 
all the way down to -120'C.  Below this temperature the last traces
of liquid water will vitrify (become as viscous as glass), and only then
will all molecules be locked in place and unable to react.  Long-term
storage of biological materials therefore requires temperatures of
-130'C or lower.  Liquid nitrogen (cheap and convenient) is -196'C.

---Brian Wowk

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4574