lsparrish comments on Cryonics Wants To Be Big - Less Wrong

28 Post author: lsparrish 05 July 2010 07:50AM

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Comment author: ciphergoth 06 July 2010 07:55:35AM 4 points [-]

I haven't directly applied the formula, but How Cold is Cold Enough? suggests that 500 years at -140 is equivalent to slightly over an hour at body temperature.

Comment author: lsparrish 06 July 2010 05:58:28PM 3 points [-]

Thanks for linking to that. I was having a hard time remembering where I had read about all this stuff. From the same article:

There is one bright spot. Below -100°C, the water in biological systems is finally all frozen, and molecules can't move to react. We use cryoprotectants that have the effect of preventing freezing, but somewhere around -135°C they all have glass transition points, becoming so viscous that molecules can't move and undergo chemical change. While the table indicates that staying below -150°C is safe from a rate of reaction standpoint, in fact any temperature below -130°C to -135°C is probably safe due to elimination of translational molecular movement as a result of vitrification.

In other words, the effect at -135C in terms of molecules being locked in place is better than before the glass transition is occurred. I assume he means in addition to the Arrhenius effect. The main reason for cooling in a cryogen like LN2 directly is the fact that its boiling point keeps the system at a constant temperature easily at a small scale. Scaled up, keeping the temperature constant should prove less of a challenge, or at least cheaper (per unit volume) to solve.