X-Message-Number: 33242
Date: Sat, 15 Jan 2011 23:50:27 EST
Subject: Response to Metzger & Base Part II

> In other words, the ice that makes the solution milky which   is
> most of the ice that will form in a 7.5 M glycerol solution -  is
> ice  that formed in a deeply supercooled state.This happens even  in
> the absence of  ice blockers because this is how  concentrated
> cryoprotectant solutions behave  when cooled slowly to  below their
> freezing point. Thus, ice formation in  supercooled  solutions in
> cryonics patients is not a new phenomenon that began   with
> vitrification.

Yes, that last sentence (which is one of the  punchlines in your note)
is almost certainly true.

> As Brian  points out: "It should also be clear from
> this that idea of nucleating  high molarity glycerol solutions
> externally would not have achieved  anything because such nucleated
> ice, like those ice balls in the flask  formed near Tm, could only
> have  grown a few millimeters into the  solution before cooling was
> complete. The  same goes for any ice  that nculeated at higher
> temepratures inside the patients  in poor  perfused areas.

Well, this sounds plausible, but I don't have a well  validated model
here of what's going on in a uniform solution, and biological  tissues
are very different from a uniform solution, so it is hard to know  how
well that applies in tissues. It is, I think, a mistake to believe  you
understand something simply because you have a plausible  but
unvalidated model. Experiments would probably be needed to  determine
the answers for real.  

MD: I too would be happier if there were more robust experiments and I  
suspect they are done or are being done at 21CM, but have no way of knowing.  
I've not been there in ~10 years, and maybe longer.>>

> In parts  of the brain that experienced good equilibration with the
> high  concentration solution, the penetration of ice from other areas
> would be  minimal, and most of the ice that formed in well-perfused
> areas would be  formed under conditions of deep supercooling.

Presuming that the  explanation of the opacity in the cooled solutions
is indeed homogenous  nucleation of some sort, this is again
potentially plausible. Of course,  tissues are very different from a
uniform solution -- some components of the  tissues might promote
nucleation at much higher temperatures, might impede  nucleation, etc.,
and in any case, the contents of cells and tissues are  very
MD: Yes, and in any event, I am very unhappy with cryonics organizations  
calling what they are currently offering 'vitrification.' In most patients,  
vitrification will be inhomogeneous due to perfusion defects and I think 
that  some other, more accurate and more descriptive term should be employed, 
possibly  something like, Inhomogeneous Vitrification (IHV) or Very Low Ice  
Cryopreservation (VLIC). That would also be an incentive for the COs to  
develop a method of determining both WHERE and HOW MUCH ice is forming in  
patients and both correlate that with the patient's medical history  and 
Transport and CPA perfusion care.>>

> You
> can  bet whatever "blasted areas" or ice holes were seen  in your
> 7.5  Molar 1995 canine brains were areas hit by ice that started
>  growing  in a very supercooled state." What I take away from this
>  is that ice will still form and grow extracellularly under
> conditions  where the colligative CPA concentration is very  high
> and the  solution is very viscous. Where nucleation and ice growth
> occur close to  the melting point of the solution (Tm), the ice
> formed will be 'large  mass' ice, and likely mechanically
> disruptive. Where ice forms well  below Tm, it will likely be in
> microscopic domains that still begin  forming (nucleate)  outside of
> cells and consequently do little  damage.

Again, extremely plausible, but this is a question which  actual
experiments could answer, and in fact very quickly.

Now, going  beyond all that we've discussed up to here, this whole
topic brings to mind a  very basic question: has anyone in the cryonics
world or cryobiology world  done a deep exploration of the physical
chemistry literature on the formation  of glasses at low temperatures?
MD: You can probably bet next to your bottom dollar that 21CM has a  

veritable digital mountain of data on this. In fact, while Brian got his Ph.D.  
Medical Physics (imaging) he is now more properly a physical chemist  
specializing in the behavior of water at low temperatures in the presence of  
CPAs. His medical physics Ph.D. is probably nearly useless now, - judging by 
the  stunning advances in both imaging and treatment I'm seeing emerging in 
research  and medicine. For instance, direction diffusion tensor imagine now 
allows  sub-millimeter resolution of the brain in humans, and considerably 
better in  rats. Thus, it is now possible to map the general pathways of the 
white matter  circuitry - and a consequence we are getting our first picture 
of just how  devastating so called normal aging is to the human brain. I 
won't digress  further here beyond saying that by the time you are 40 you are 
already  f#%&@, big time.>>

I have to admit that until a few years ago I  wouldn't have even
thought to ask if such a literature existed, but I'm now  no longer so
ignorant. My suspicion is that the pchem guys know a whole lot  more
about this topic than most of us, and have a lot of  understanding
about the competition between crystal and glass formation and  what
shifts the equilibrium one way or the other.

I'm unsure as to  whether we would learn anything valuable by exploring
that topic in depth,  but there is a good chance we would. Knowing what
things are like in most of  science, I suspect that the pchem guys and
even conventional cryobiology  types have never really talked, though
of course I could be entirely wrong on  this.

Anyway, it doesn't hurt to ask...
MD: There is an exploding literature on these topics with entire books  
coming out just on the subject of Tg. In fairness, so much data is being  
generated that it would take a team of specialized cryobiological physical  
chemists to stay on top of it. But then, this is the case in so many areas of  
science - even cerebral ischemia and the related area of neuroprotection, the  
literature is simply impossible to track and  absorb.>> 

Message  #33232
From: "Eisab" <>
References:  <>
Subject:   latent  heat of fusion
Date: Fri, 14 Jan 2011 21:34:58 -0500

"Despite the  control applied to the cooling of cells, most of
the water present will  freeze at approximately -2 C to -5 C. The
change in state from liquid to  crystalline form results in the
release of energy in the form of heat; this  is known as the latent
heat of fusion. Warming of the sample occurs until the  equilibrium 
point is reached, at which temperature ice
continues  to form. To minimize the detrimental effects of this
phenomenon, undercooling  must be minimized by artificially
inducing the formation of ice. This can be  accomplished by
seeding the suspension with ice or some other  nucleating
agent, or by rapidly dropping the temperature of the  external
environment to encourage ice crystal  formation."


I   wonder if the latent heat of fusion is a big problem in cryonics.


MD: It used to be a proverbial pain the fanny, when we were freezing with  
low molarity concentrations of colligative agent. But with the advent of 
high  molarity cryoprotection, and much more aggressive cooling, the amount of 
ice  formed is so small that it is not much of a problem, if any. And of 
course, in  vitrification there is no latent heat of fusion and any energy 

released in  moving through Tg is both smeared out (rather than abrupt) and VERY
small,  compared to that seen with ice formation.
Mike Darwin

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