X-Message-Number: 3547 Date: Fri, 30 Dec 94 08:20:13 EST From: (Perry E. Metzger) Subject: CRYONICS: "Flash Freezing" (J. Coetzee) says: >I know cells can be be flash freezed and then revived. According to M. >Darwin activity should continue in these cells at a slow rate.. >If so, then if it was possible to flash freeze a living human and then >flash thaw him he should have not suffered damage from it. If this >assumption is correct then all research should concentrate on a cooling >method such as those used in computers with metal coolers. When an >electric current is reversed through it the metal cools off.. One wonders if Mr. Coetzee comes up with these incredibly, er, interesting (I suppose thats a polite word) ideas on his own, or if he uses a randomizing process -- he produces so many of them, after all. Mentioning not only the notion of flash freezing big thick objects, but mentioning the Peltier Effect as a way to flash freeze these big thick objects, and also mentioning "flash thawing", certainly deserves some sort of prize. I would suggest that Mr. Coetzee answer his own question. Its very easy to do. Heating and cooling of objects can be modeled with very simple differential equations first developed by Isaac Newton that operate on the trivial principle that the rate of cooling or heating is proportional to the temperature difference. Model a human being as a solid cylinder about thirty or fourty centimeters across and about two meters long -- for simplicity you can just assume an infinitely long cylinder until you get to the thermal stress part of the exercise where it starts to count. Assume the same constants as water -- they should be close enough for this purpose. The simply assume that the outside of this cylinder is held suddenly at some low temperature -- pick your favorite cryogenic liquid's temperature -- with the entire cylinder at some uniform temperature -- something around 35 degrees C should be good enough for purposes of this exercise. You should very quickly see how "flash" flash freezing ends up being. You can figure out on your own the sort of thermal stresses being placed on the body in question by this exercise -- thats part of the fun. Remember that humans are made of widely varying non-uniform materials and will experience far greater thermal stresses. Then, just for fun, although the question would have been moot even before you asked if you'd been thinking, I suggest you call up a manufacturer of Peltier Effect cooling devices. You can figure out from the constants for water how much heat you have to move out of that cylinder of water to get it from 35 degrees C to some low temperature -- and you can ask the manufacturer how much heat their devices can move per unit time. Remember that to "flash" cool things with your theoretical peltier-effect "flash cooler" you are going to have to move all that heat in a flash. Not, of course, that it would make any difference, as you would have calculated above the impossibility of making use even of an infinite store of liquid helium for this purpose. Perry Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3547