X-Message-Number: 28560
From: 
Date: Sun, 8 Oct 2006 06:14:50 EDT
Subject: Uploading technology (1.v.3) Magnetics Resonance.

Uploading technology (1.v.3) Magnetics  Resonance.

What I have said before about electron resonance  imaging or ERI could be 
termed "classical" MRI. In classical MRI, a continuous  magnetic field line up 
spin 1/2 states and create, by zeeman effect, an energy  difference between 

spins pointing along the field axis and spins pointing in the  opposite 
direction. 
Spins oriented along the fied are then tilted up to the  plane perpendicular 
to the field using a radio frequency at the Larmor  precessing rate. When the 
spin gets back to the field axis it releases its  energy and produce a radio 
wave. 

One shortcoming of that process  is that it can't work with higher spin 

states. For example, a spin 3/2 has 4  states forming a triangular pyramid. The
four states have spins : +3/2, +1/2,  -1/2 and -3/2. Between each one and the 
next, the difference is 2/2 =1 and one  spin one photon is produced. So, three 
photons are produced. That define six  possibilities : Three for independent 

photons, two for coherent two photons : If  the system jumps from +3/2 to -1/2,
there are two photons produced at the same  time in an entangled way. There is 
the similar case from +1/2 to -3/2. The last  case is for a jump from +3/2 to 
-3/2 with three entangled  photons.

Classical MRI can't use such states and less so select one  process over 

another. One possibility is to look at phase shift in a passing  wave (1, 2). 
This 
process can gauge each spin state in a spin system larger than  1/2. The 
resolving power is limited by the incident wave diffraction, but UV or  X rays 

could be used too. With terahertz radio waves (T waves), squeezed states  could
go beyond the classical diffraction limit.

Another  possibility is to monitor resistivity (3). This parameter is 

influenced by spin  displacement. A current in a sample could be monitored by 
small 
electric captors  at a distance with and without the polarising field. The 
difference in local  current flow would give the resistivity shift produced by 

spin polarisation.  This system too, has a sensitivity extending beyond spin 1/2
states.

The possibility to use spin 3/2 states is particularly  interesting, because 
calcium, a major constituent of the cell membrane is a  nuclear spin 3/2 

system. Using more than one detection process open up the  possibility to fine 
tune 
one for imaging and another for chemical analysis using  the frequency shift 
produced by different atomic environments.

The  brain reader could well need the three process : Classical ERI would 
produce the  fine picture at 10 nm resolution limit, resistivity shift would 
produce a more  coarse picture for larger spin states, mostly Ca 3/2 and phase 
shift T waves  would produce the chemical analysis.

(1) Warren S. Warren (2006);  Nature 442, 990.
(2)I.M. Savukov, S.-K. Lee & M.V. Romalis (2006); Nature  442, 1021-1024.
(3) GoYuza et al.(2005), Nature 434, 1001-1005.
 
Yvan Bozzonetti.


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