X-Message-Number: 33048
Date: Tue, 9 Nov 2010 09:15:04 -0800
Subject: Nanotechnological repair references
From: Brian Wowk <>

    To further illuminate recent CryoNet discussions about
nanotechnological repair of cryopatients, let me point on that in the
Scientific Basis section of the Alcor's online Library

http://www.alcor.org/Library/index.html#scientific

there are a variety of articles about this subject, beginning with

http://www.alcor.org/Library/html/MNTscenario.html

which contains a bibliography at the end listing many articles about
repair strategies for cryonics patients.

     The heat dissipation constraints in particular were worked out by
Eric Drexler in a technical monograph that I saw in draft form about
25 years ago, although I'm not sure where or whether it was finally
published.  My recollection is that heat dissipation considerations
limited the speed of comprehensive molecular repair of a brain to
several months.  Not coincidentally, this is the same order of
magnitude as the time animals require to grow tissue masses of
comparable size.

     This 1985 talk by Drexler

http://www.alcor.org/Library/html/moleculartechnologycellrepairmachines.html

in the excerpt below explicitly mentions that heat dissipation was
quantitatively analyzed.  Perhaps others can provide a technical
reference.

---Brian

>>>>>>>>>
Let's return now to the more technical aspects of really thorough
tissue repair. In the paper I've been working on, I go into a lot of
detail regarding a more-or-less worst-case example of total-body cell
repair. The assumption is that you have to rework all the molecular
structures in every cell bit-by-bit, and that you aim to do this with
systems that are entirely inside the cells. (I also discuss how to
relax this second constraint.)

In a cubic micron, you can construct the equivalent of a mainframe
computer with a gigabyte of memory (I already mentioned that this is
about as much information as the cell uses to construct itself in the
first place). It turns out that you have enough computational cycles
within the volume, time, and heat-dissipation constraints to identify
all the macromolecules of the cell (even if they're moderately
damaged), by using certain algorithms that can already be specified in
fairly great detail. Since you can identify all the molecules, you can
map the cell structures: the patterns that you recognize are
type-tagged by the molecules they contain (i.e. if it contains
tubulin, it's a microtubule). Since this tells us the type of
structure, it makes it easier to know how to probe and further
characterize the structure.

You can get the machines into cells: white blood cells demonstrate
that systems of molecular machinery can move through tissues. Viruses
demonstrate that systems of molecular machinery can move through cell
membranes to enter cells. The mobility of organelles inside cells
demonstrates that systems of molecular machinery can move around
inside the cell. The fact that cell biologists can stick needles into
cells and do surgery on chromosomes and sometimes have the cells
survive shows that things can enter cells and do even very crude
manipulations without doing permanent damage in many cases. So you can
get repair machines to the site of the damage.

You can identify, take apart, and put back together molecular
structures. Identification is demonstrated by molecular structures
that can identify each other, as antibodies recognize proteins and so
forth. For the "take apart" function, we have the direct analogy of
digestive enzymes. As for assembling molecular structures -- well,
these things were made by molecular machines in the first place, so
again we have a direct analogy. So, again, and again, and again, you
can go to a biological analogy and say, "We already know a process
like this." If the overall process is orchestrated into a computer
(which you can design to some degree of detail using direct
calculations and scaling relationships) then it seems you have
everything necessary to repair cells. I have, of course, only sketched
the case here, but even these facts are enough to make the idea
plausible.

Eric Drexler, Lake Tahoe, 1985

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