X-Message-Number: 5711 Date: Tue, 6 Feb 1996 22:29:58 -0500 From: "Keith F. Lynch" <> Subject: Fast freeze In #5704 "Richard Schroeppel" <> writes: > f) Superconductors and LHe have interesting heat-conduction > properties. Can we use make use of them? Many superconductors of electricity are known, but they are never superconductors of heat, and they aren't even superconductors of electricity until they are already close to liquid nitrogen temperatures. Liquid helium *is* sometimes a superconductor of heat. But never at even the lowest temperatures used in cryonics. Liquid nitrogen would itself freeze solid long before helium condenses into a liquid. Liquid helium is only useful for conducting heat between things that are already within a few degrees of absolute zero. What are you trying to accomplish by freezing patients faster? The trend in cryonics appears to be toward freezing them more slowly. If you are trying to prevent ice crystallization without using cryoprotectant, this requires *enormous* cooling rates, which have henceforth only been achieved in microscopic droplets. If you could somehow cool a whole patient from normothermy to liquid nitrogen in one thousandth of a second, this would: * Be far too slow to prevent all the ice from crystallizing. * Be so fast that the differential coefficients of expansion of different tissues would cause a shock wave sufficient to explode the patient like something from a Dave Barry humor column. -- Keith Lynch, http://www.access.digex.net/~kfl/ Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5711