X-Message-Number: 3595 Date: Wed, 4 Jan 1995 22:20:27 -0500 From: "Keith F. Lynch" <> Subject: Re: SCI.CRYONICS: Low Temperature Cryonics > Molecules in an ice crystal may have vibrational rather than > translational motion, but there is no reason for this to be true > of a vitrified solid. But it is true. > Try looking at a window pane that is decades old -- the slow flow > has visible effects. No. The reason why old windows tend to be thicker on the bottom than the top is because the pane of glass was inadvertantly made that way, due to poor quality control procedures in those days, and it was then installed thick-side-down for stability. > The very most conservative approach is the lowest possible > temperature. I don't agree. The chemistry, evaporation, and translational motion going on at liquid nitrogen temperatures is utterly negligible. The only thing lower temperatures gain you are additional cracking and additional expense. Cracking releases lots of heat over a small area, possibly enough to scramble the clues that would otherwise allow reconstruction of the "jigsaw puzzle". Ignoring political and economic issues, and natural disasters, the limiting factor in suspension time is radiation damage, which lower temperatures won't prevent. This limit is somewhere between a thousand and a million years, depending on how repairable radiation damage turns out to be, how radioactive the patient is, and how much radiation there is from the surroundings. (Patients can be made considerably less radioactive by feeding them non-radioactive potassium for several weeks before death, if anyone thinks it's worth it, and if the death isn't without advance notice.) > Only 3 elements have boiling points below that of liquid nitrogen > (which boils at 77 degrees Kelvin) -- namely Neon (27 Kelvin), > Hydrogen (20 Kelvin) and Helium (4.2 Kelvin). True. I checked for compounds with lower boiling points, and found to my surprise that there aren't any (though carbon monoxide comes close). It would also be possible to use the melting of a solid instead of the boiling of a liquid, in the unlikely event that lower temperatures are desired. Another approach is to lower the pressure to get nitrogen to boil at a lower temperature. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3595