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 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=1957