X-Message-Number: 3321
Date: 21 Oct 94 16:58:06 EDT
From: yvan Bozzonetti <>
Subject: SCI.CRYONICS : Uploadind, Re:msg 3290, B. Wowk

	I am happy we agree on the holographic method, at least on small 
samples. Now, how to get to larger objects? The smallest element to look at 
is near 100nm, so to have a "light" able to give a classical refraction 
effect, the wavelength must be at least one order (ten times) smaller: 10 
nm or a photon energy near 100 eV. Any radiation with energy near or above 
100 eV will fits the bill, 1 kev is very good.

	Now Brian, why do you say such waves are absorbed? Because you have 
read about experiments on the subject to be sure! Well, but these 
experiments was done with X rays generated by electrons colliding with a 
metal plate at high energy in a tube. Such rays have a very broad band 
spectrum. What absorb them is a forest of very narrow inner atomic energy 
levels. With a very narrow band generator, it becomes possible to choose a 
transparency window where there is very few absorbtion. Think of a large 
mesh grid: it will stop a lion as surely as a concrete wall, but the lion's 
fleas will no even see the grid if they want to jump to another lion on the 
other side.

	I have spoken about nuclear devices as X rays generators because 
they produce the very long coherence length requested for holography. Now, 
a meter long coherence length for a one nanometer wavelength radiation 
implies a frequency stability of one billionth. (no surprise I was 
constrained to look at exotic X rays generators to get this result!). At a 
frequency near 3 x 10^17 Hz, the corresponding waveband is only 300 MHz 
wide at half maximum (3 dB). This is very narrow indeed, the value is more 
often seen in the radio domain than the X ray one. This is sufficiently 
narrow to take place in any clear window.

	Beyond 100 keV, Compton scattering is indeed important and this is 
a continuous process, without any clear windows. When you first put forward 
the 100 keV value in your preceeding message, the implied  Compton's 
process prompted me to write about quantum nondemolition effects, something 
I was not discussing in the original text. May be you know, the quantum 
nondemolition theory (and the name) has been worked out by Vladimir 
Braginsky of Moscow University in the course of a study on gravitational 
wave detectors. One of the best US specialist today is Kip S. Thorne from 
UCLA. If 100 keV radiations must be exploited for any reason, a quantum 
nondemolition device would be required to suppress any Compton effect.

	Stern-Gerlach experiment was about linear spin polarization in 
electrons undergoing a magnetic field. Today, we would say it was the 
discovery of the spin SU(2) symetry group in Special Relativity generated 
tangent space. That was a big step in the quantum world understanding, but 
with few link to Braginsky's work. Bohm's quantum formalism would be a 
better ancestry. There is indeed a view of quantum mechanics where there is 
time travel and a breakdown of causality, another possibility (rulled out 
now, looked at hidden variables), Evrett multi universes is another school 
and Bohm's interpretation once more. To choose between them is largely a 
philosophical problem, I am not very interested  in, and the physical world 
neither. My concern is to find a workable path to brain reading, if the 
technology rests on a physics domain open to philosophical brainstorming, 
that is another issue.

	About MRI: Yes, it has been proposed to use micro cantilevers to 
get close-by MRI informations. May be ordinary X ray tomography would be 
sufficient to locate them without too much radiations... I don't bet on the 
technology, but only experiments would bring a definite answer. Whatever 
the issue, hyperpolarized helium 3 seems far more powerfull, with its 
strong signal, there would be far less noise problems. The idea has been 
published this summer in Nature ( sorry, not the issue at hand) as an 
advanced form of the tested hyperpolarized Xenon 129.

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