X-Message-Number: 3356 Date: 26 Oct 94 14:05:52 EDT From: yvan Bozzonetti <> Subject: SCI.CRYONICS Brain scanning, answer msg 3344, 3348 About Msg 3344 Brian Wowk: I fear we will never agree on anything or near so. I answer you at two levels: one broad, another point by point. On the first I suggest we continue our exchange directly and send a copy at any interested person but let free cryonet of arguments on detail points. Second, I suggest any reader looking my answer adds directly your next message in the form: Not so, I disagree, wrong, and so on. I conclude from your position than you'll never use your knowledge for working on nonlinear electromagnetic devices, the next generation tools of biological research, sad... Now, for the general reader, not for you (I am not in a position to give you any lesson and don't want to) I try to give some brief informations on a point by point basis. QED:(Quantum ElectroDynamics) No, that theory is not used in this full blown version in everyday problems, it is not used for computing the interaction of a photon in a solid with very many electrons in an energy band. Its main use is to test on special cases the validity of simplification done in reduced but more manageable theories. Nobody compute big molecule interactions from first principles. Bragg: Yes, your knowledge is based on polychomatic rays as seen at the scale of monochromaticity needed for bulk holography. What limit X ray holography today is not radiation destruction or opacity, but short coherence length, thiat is to say, polychromaticity of the beam. Mossbauer: The experiment is about detecting gravitational redshift in gamma rays produced by radioactive nuclei. It is essential to have zero recoil in the radiating nucleus, so that there is no Doppler shift. This is indeed the case: The nucleus remains coupled to the whole crystal throughout its electron cloud, the link from atom to atom is produced by peripheral electrons (valence electrons), this is a proof of the collective action of these soft bound particles and the impossibility to work on them independently. This is well known and any textbook on solid state physics speaks about larger mass electrons in solide: The collective action looks as a mass extension on each particle. I come to the number of photon estimate: I take as an example a one dm^3 cube scanned with a 0.1 micrometer resolution. On one cube face there will be 10^12 squares .1 micron on a side. The information is encoded in tiny phase shifts on each wave, there must be one wave (one photon) for each square. Doing that on three perpendicular sides produces both, all the informations requested to define the content of each .1 micrometer cell and a redundant data for result checking. 3 x 10^12 have been used, even if one in ten only was not absorbed (this is plainly wrong), 3 x 10^13 photons would travel in the brain. If each one has a 1 keV energy, the total deposited energy is at most: 1 000 eV x 3 x 10^13 photons x 1.6 x 10^-19 joule/eV = 5 x 10^-3 joule or near 0.001 calory or a 10^-6 degre heating of the full 1 kg brain. And this is ultra pessimistic with absorbtion coefficient out of all reason (if they where true, no classical radiography would be possible). Even with data collected by absorbtion (without holography) and 10^18 absorbed photons, the temperature rise would be only some degres, to get the boilling water point would ask for 100 kev radiations. And in this case, why deliver it in a single pulse? A scanning extended to some hours would produce only some supplementary bubbles in liquid nitrogen. On the other hand radiation damages would be a far more worying problem than mere heat, that is why I am not interested in classical radiography even if it is plain evidence than nothing forbid it to take the picture with the useful sharpness. ( the problem is at the detector level, but I not extends myself here). If that talk forum must be see as a scientific communication place, then I apologize: Every statement must indeed be subtended by a calculation, a mathematical demonstration or a reference (at the scientific litterature or an experiment laboratory log). When dealing with absorbtion by matter of very narrow waveband X rays, we hit a domain very useful for building mirror used in thermonuclear devices. Knowing simply what wavebands have been explored would give very precise information on the nuke technology, this is not the kind of data published in academic journals. So, I am sorry, I know there must be some windows with low absorbtion but I don't know where they are, nor where to find the information (outside making anew the experiments). If anybody can get such data without strings, I would be interested. ------------ Answer to msg 3348. Dear Keith F. Lynch, Thank you for your informations, but I fear I am not the author of your citation. Whatever the system used, vaporization is a false problem: It suffice to do the job on some hours so that there is time for thermal dissipation. The real concern is radiation damage, even if there is less problems in solids with x rays. I think the first systems will use MRI with hyperpolarized xenon 129 or helium 3. This is slow, so if there is a mass market, it will be necessary to find a faster system, there x rays enter into play with holography, unbunching, squeezed states or quantum nondemolition. The common feature of all these efficient x ray systems is to rest on a source whose technology is today monopolysed by nuclear military activities. It is sad to see that expertise lost when it would be so useful in some years. I think data collection must be envisionned in a nondestructive perspective. My objective is to alows uploading of brains before biological repair is at hand. Yvan Bozzonetti. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3356