X-Message-Number: 1957
Date: Sun, 14 Mar 93 00:54:25 GMT
From:  (Michael Clive Price)
Subject: CRYONICS TG and all that

Some questions and reactions about this cracking business and storage 
at -130C.  WARNING: I have no background solid state physics/medicine, 
nor have I ever participated in a cryonic suspension.  Answers and 
corrections most welcome.

1)   As far as I understand it the reason for storage at -130C is to be
     close to the glass transition point (TG) where cracking is markedly
     reduced over temperatures some distance below TG (say LN2
     temperatures of -196C).  This seems to suppose that we have the
     capability to vitrify humans *now*.  But we don't, do we?  Aren't
     we in danger of putting the cart before the horse and missing the
     wood for the trees?  Solve the vitrification problem first, then
     worry about maintaining patients in a vitreous state.  I thought
     that the levels of cryoprotective perfusion have been (currently)
     too low to permit vitrification of patients.  This seems to be the
     more pressing problem.

2)   Assuming we do store at -130C in a vitreous state.  According to
     Hugh Hixon's table in Jan 1985 Cryonics 1 sec at 37C is 
     approximately 6 days at -130C.  So storage at -130C for (say) a 
     century is equivalent to over an hour's room-temperature storage.
     Yikes!

3)   If the Arrhenius equation breaks down for non-liquid diffusion then
     I want to know by how much.  I am sceptical that the Arrhenius
     equation would be totally invalid *near* the TG 'point' since my
     nascent understanding is that the transition from liquid to glass
     is not a sudden phase transition (by the definition of a glass) but
     a gradual transformation over an extended temperature range.  So
     I would expect the Arrhenius equation to be largely correct just
     above TG and just *below*.  I welcome clarification.

4)   What is the cause of the cracking.  Is it purely differential
     contraction?  And what is the mechanism producing the blue flashes
     of associated light that Mike Darwin mentioned?  How much energy
     is associated with each flash?  The temperature is obviously very
     high, but the total heat output per flash might be very low and not
     cause damage (like a wielder's spark) eg localised annealing.

Personally, from what I've heard, I would prefer storage at -196C where
1 second >> 24.5 million years.  Cracking damage, as Ralph Merkle says,
doesn't cause information loss.  Notice I am not saying that the 
information necessary for revival is necessarily present in presently 
suspended cryonauts, just that any cracking that happens is not causing 
any *additional* informational degradation.  Clearly more information 
would be preserved in vitrified human brains than in the currently frozen
brains.  The question is: how do we vitrify brains, not how shall we store
them.  First things first.

Or am I completely wrong?

Mike Price                         

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