X-Message-Number: 25345 Date: Thu, 16 Dec 2004 13:16:05 -0500 From: Henry R Hirsch <> Subject: Cryonic cooling by adiabatic demagnetization The magnetic resonance method discussed by Leo in message #25294 appears to work by adiabatic demagnetization of a paramagnetic substance. I agree with Leo that it is very promising and should be studied by CI, Alcor, and others doing cryonic research. I too discussed this topic two years ago in message #18924. Because of its importance, I would like to expand a bit on the comments I made at that time. The most difficult part of cooling a cryonic patient is that the surface-to-volume ratio is small. If the patient, or in the case of a neuro suspension, the brain, is submerged in a cold fluid, heat is removed slowly because the surface through which the heat passes is small relative to the volume which must be cooled. If the interior could be cooled directly, the process would be much more rapid, perhaps fast enough to achieve vitrification and avoid freezing. In principle, interior cooling can be achieved by adiabatic demagnetization of a paramagnetic substance. The molecules of such a substance are, in effect, minute magnets - "nanomagnets" in today's terminology. When an external magnetic field is applied, the nanomagents are aligned parallel to the field. When the external field is switched off, the nanomagnets become disoriented, with the use of heat drawn from their surroundings. They cool their environment. This is the process of adiabatic demagnetization. There are practical problems in using this process for cryonic cooling. The molecules of the body, for the most part, are not paramagnetic, although the iron atoms in hemoglobin in the blood and myoglobin in muscle, are strongly so. It would probably be necessary to perfuse the blood vessels with a water solution of a paramagnetic salt or a slurry of a paramagnetic substance in a liquid fluorocarbon carrier. It might even be necessary to drain the perfusate, cool it, remagnetize it, and repeat the process one or more times. Initial experiments need not be expensive, since small tissue samples, such as the brain of a rat, could be used. I am not in a position to do such experiments myself, but I urge those who are to do so. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=25345