X-Message-Number: 4442 Date: Wed, 24 May 1995 07:55:19 -0700 (PDT) From: "Joseph J. Strout" <> Subject: Re: Cool Flies & Chilled Mice. > A second thought. Metals are known to exist in glass state if cooled > at some billion degrees/s. The equivalent for cerebral tissue would > require extremely fast contact of a tiny tissue specimen with a > cryofluid or a LN2fied metal block. Fluid gases will not do since > they have Leidenfrost and low heat capacity. A supercold fluid > (e.g. carbon tetrachloride or sumpn) is definitely better. I dimly > recall reading in Nature about a fast freezer based on a LN2fied copper > block and a probe guillotine bringing specimen slice into tight > contact of the heat sink. Even if we would reach no much glass state > (xRay diffraction pattern as a probe), this should eliminate freeze > artefacts considerably. Anybody care to investigate that? Actually, techniques such as these are routinely used in cryomicroscopy. "Plunge freezing" involves attaching the sample (brain tissue, for example) to a metal screw, then plunging the screw into liquid propane or liquid freon (LN is not good, since it boils away to quickly -- you can actually stick you hand (briefly) in LN without damage -- but don't try this at home, kids). "Slam freezing" involves slamming the sample into a metal mirror cooled to LN temperature. Both techniques result in a vitreous sample, provided it's not too thick. -- Joe Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4442