On Thu, Jul 25, 2024 at 3:53 PM Keith Henson <[email protected]> wrote:
>> >> *I also agree with Hanson chemical fixation is a very promising >> alternative to liquid nitrogen that deserves much more emphasis:* >> > > * > **I don't think it makes a lot of difference. The difference between > zero and what it costs to keep a neuro patient stored is about $200/year. * > *Being cheaper is nice but that's not chemical fixation's primary virtue. Electron microscopic pictures of brains preserved by chemical fixation are clearer, have fewer artifacts, and give us much more information about brain structure than brains preserved with liquid nitrogen .* *> Being recovered from suspension probably takes nanotechnology. * > *Yes absolutely, if it wasn't for nanotechnology I wouldn't be interested in Cryonics. Back in 2013 on the Extropian List I responded to an article that was in cryonics magazine by Aschwin de Wolf trying to make the point that cryonic suspension was better than Chemical fixation, * * http://www.alcor.org/Library/html/chemopreservation.html <http://www.alcor.org/Library/html/chemopreservation.html> . This is what I said: * * > For example, the expensive and extremely toxic chemical osmium > tetroxide is routinely used for stabilization of lipids in preparation for > electron microscopy.* > *If something as dangerous to handle and expensive as osmium tetroxide were needed then that could be a show stopper for chemical fixation being an alternative to cryonics, but I don't see why it would be needed. Osmium tetroxide is primarily not a stabilizer but a stain, it works well as a contrast agent in electron microscopes because heavy metals like Osmium scatter lots of electrons. However, how information is extracted from my 3 pounds of frozen or chemically fixed brain is not my problem, it is the problem of beings who live in an age of advanced Nanotechnology. My only concern is that the information remains intact inside that 3 pounds of grey goo, I don't know exactly how it will be extracted but I doubt it will be by electron microscopes. * * > Unlike the cryobiologist, the chemical fixation researcher cannot > reverse fixation and test for viability.* > *I don't understand what is meant by that. or what edge Cryonics has over fixation because of it. Viability just means it works, and so far neither Cryonics nor fixation has brought anybody back and I don't think anybody will until advanced nanotechnology is developed. It almost sounds like there is supposed to be some advantage in using the same atoms in the reawakened being as in the old one, but I can't imagine what that advantage could be.* *> The cryobiologist does not have to confine himself to this fate because > he can attempt to measure viability in the brain* > *Obviously during revival at every step you'd like to know if you're doing it right and are on the right track, but again I don't see why cryonics would be better at this than fixation.* *> or even the whole organism.* > *Preserving any part of the body with either method except for the brain seems completely pointless to me.* *> Let us assume, for the sake of the argument, that the chemopreservation > advocate has identified a number of fixatives (and other treatments) that > are sufficient for complete ultrastructural preservation of the brain. The > next question is going to be: how stable will chemopreservation be over > time? This is a very important point for the technical feasibility of > chemopreservation.* > *Yes, that is an important point. With Cryonics, unless we're talking about millions of years and as long as things remain cold (but will it?), pretty much all the damage that is going to be done has been done by the time the brain reaches liquid nitrogen temperatures. And I'm not worried about damage caused during thawing because that won't be done with existing technology, assuming it's even thawed at all and it probably won't be; the information will probably be read out by disassembling the brain from the outside in while it remains in solid form.* *I don't know if chemical fixation would remain as stable over the centuries as freezing, my hunch is that cryonics has a small edge over fixation in this regard but I could be dead wrong, maybe it's a big edge. And I don't want to be dead. * > * > It is not only necessary to demonstrate that all chemicals can be > introduced by perfusion fixation without perfusion artifacts* *Both methods are imperfect so it is only necessary to demonstrate that fixation produces fewer artifacts than Cryonics or that the artifacts produced are easier to identify as artifacts to make it the superior technology. * *> In my opinion, the prospect of autolysis is much worse because when > biomolecules break up into their constitutive parts, and go into solution,* > *True, but if fixation is done correctly there won't be any fluid for things to move in.* *> there is a risk that essential parts of the brain will not be fixed, as > a result of inadequacies of the protocol, perfusion artifacts, or long term > degradation. It is at this point where classic cryopreservation really > shines. Even tissue that is not protected from ice formation as a > consequence of perfusion impairment will still be "fixed" through low > temperatures.[...]* > *That is another very good point. If the cryo-preservative doesn't reach a certain part of the brain things might not be hopeless because at least it still gets frozen so you still might be able to get information out of it if your technology is good enough, but if the chemical fixative doesn't reach part of the brain things are far far more serious.* *But the smaller the biological sample you're trying to infuse with cryo-preservative or chemical fixative the easier it is, so both methods might be improved if before any chemical was infused or any freezing done a dozen or so thin cuts were made to slice the brain into smaller pieces. The cuts could be made very thin indeed, 30 nanometers or about 100 atoms thick. Yes you would be destroying some tissue but if the technology is good enough to repair all the damage caused by freezing or chemical fixation then I don't think they'd have much trouble figuring out what is supposed to be in that very narrow gap.* > > *[...] there is little hope of inferring the original structure of the > brain.* *Yes, the important thing is that things stay put, or at least if they must move the flow should not be turbulent so you can figure out where the parts were before they moved. If things are turbulent then a small change in initial conditions will lead to a huge change in outcome and you'll never figure out where things are supposed to go. I don't see why turbulence would occur in chemical fixation and fortunately (see below) it doesn't look like it would happen during the freezing of a brain either (I'm not interested in what happens during unfreezing, that's a problem for advanced nanotechnology, I just want to be sure the information is still inside that frozen lump of tissue). That's why I think Cryonics has a pretty good chance of working at least from a technical viewpoint, whether the brain will actually remain at liquid nitrogen temperatures until the age of nanotechnology and whether anybody will think we're worth the bother of reviving is an entirely different question. * *Fluid flow stops being smoothly Laminar and starts to become chaotically turbulent when a system has a Reynolds number between 2300 and 4000, although you might get some non chaotic vortices if it is bigger than 30. We can find the approximate Reynolds number by using the formula LDV/N. L is the characteristic size we're interested in, we're interested in cells so L is about 10^-6 meter. D is the density of water, 10^3 kilograms/cubic meter. V is the velocity of the flow, during freezing it's probably less than 10^-3 meters per second but let's be conservative, I'll give you 3 orders of magnitude and call V 1 meter per second. N is the viscosity of water, at room temperature N is 0.001 newton-second/meter^2, it would be less than that when things get cold and even less when water is mixed with glycerol as it is in cryonics but let's be conservative again and ignore those factors. If you plug these numbers into the formula you get a Reynolds number of about 1. 1 is a lot less than 2300 so it looks like any mixing caused by freezing would probably be laminar not turbulent, so you can still deduce the position where things are supposed to be. John K Clark* -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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