X-Message-Number: 13661
Date: Fri, 28 Apr 2000 21:19:06 -0700 (PDT)
From: Driven FromThePack <>
Subject: Radiation damage to frozen brains

Last time this subject was discussed on Cryonet, I
believe Brian Wowk calculated that storage time was
limited to perhaps 5000 or 10000 years because of
radiation damage. However,  a poster on the Extropian
mailing list has stated that 500 years is a likely
limit due to radiation damage from C-14 isotopes from
*within* the patient himself. Any comment?

 Here are the relevant posts:


The limits on cryonic storage are much less than those
discussed (quoted below). Robert Freitas has done a
paper on this and the draft version placed limits of
500-1000 years cryonic suspension before endoradiation
would become a significant factor. Currently the paper
is being reworked to take into account radiation from
the carbon in the histones, so those limits may be
revised downward. Counter to that is the possibility
of syn-genome replacement based on the methods of
genome fragment reassembly (pioneered by TIGR). 

As I've stated before, and I'll state again, the
limits on cryonic reanimation would appear to be
fundamentally based on the question of whether or not
the freezing process causes loss of positional
information that could prevent 3D-reassembly. Given
the size of synaptic and cellular structures, I
strongly doubt that to be the case. These are hundreds
of thousands to tens-of-millions of atoms in size.
They are only going to match up in unique places. Only
if you unfreeze the brain and let it decay away into a
molecular soup have you lost that 


>From: "Robert J. Bradbury" <>
>Reply-To: 
>To: 
>Subject: CRYONICS: Limits to storage [was: Where to
look for the 
>answers...]
>Date: Thu, 27 Apr 2000 14:21:27 -0700 (PDT)
>
>
>The limits on cryonic storage are much less than
those discussed
>(quoted below). Robert Freitas has done a paper on
this and
>the draft version placed limits of 500-1000 years
cryonic
>suspension before endoradiation would become a
significant
>factor
As I've stated before, and I'll state again, the
limits on
cryonic reanimation would appear to be fundamentally
based
on the question of whether or not the freezing process
causes
loss of positional information that could prevent
3D-reassembly.
Given the size of synaptic and cellular structures, I
strongly
doubt that to be the case.  These are hundreds of
thousands to
tens-of-millions of atoms in size.  They are only
going to match
up in unique places.  Only if you unfreeze the brain
and let it
decay away into a molecular soup have you lost that
information.

Mike:
Thanks, Robert. I had not considered the fact that
unstable isotopes within
the frozen body would slowly damage surrounding cells.
Is carbon-14 believed
to be the main culprit?
  Regarding loss of positional information, you
indicate that ice damage
should not be an insurrmountable problem because of
the small size of
synaptic and cellular structures which should match up
uniquely. But are
these truly unique? Or are there merely very many
permutations? Perhaps like
snowflakes, there are huge numbers of different
configurations, but there is
still some duplication because of the still larger
number of instances.




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