Biomedical Engineering Reference
In-Depth Information
then why are we all asked to turn off our mobiles when flying in
planes? A mobile phone is miniscule compared to a Boeing 747.
The reason given by the pilot is that the EMFs can interfere with
the navigation systems of the airplane. Ironically this potential
misalignmentissimilartowhatcanoccurwhencellsareexposedto
su
cientlevelsofEMR.EMRcaninterferewiththenaturallyhigh-Q
systems (Adair's
biological amplification mechanisms
), cells that
have evolved to induce mitosis. If electric and magnetic systems are
perturbed,, for example, unnatural rotation of components, mitosis
cannot proceed. Further, depending on the stage of embryonic
development or tissue and organ mitosis that is taking place,
there
is no totally safe level
on the basis that perturbations to growth
and development should be avoided. This is the same conclusion
found for nuclear radiation. At nuclear energies it is the risk of DNA
damage;forEMRtheDNAisnotbrokenbutitcanbeperturbmitosis
outcomesfromtheirunexposedstateandthis,likenuclearenergies,
may be due to a single quantum of energy. This applies both to
healthymitoticprocessesandunhealthyones.Soitcangobothways.
But living in environmental levels of EMR and nuclear radiation, a
practical basis of technological safety is to make levels as low as
reasonably achievable(ALARA).
The 'leaves on heads' brings up another analogue to EMR. In
WWII both the Allies and the Axis forces had many occasions to
blow up bridges to disrupt tra
c carrying supplies, etc., across the
bridges. We need not destroy every vestige of the bridge just to
stop the tra
c from crossing one side to the other. Looking at this
as a problem in energetics, we can begin by taking a look at the
length of a particular bridge. If we had access to unlimited energy,
for instance, we were able to set the wind shear to a predetermined
frequency and amplitude, then we could calculate the oscillatory
vibrational mode. In the case of the bridge shown in Fig. 1.12 we
could choose the longest span, the one on the left, as this would
be the lowest energy needed. However, any vibrational shear force
would still need to be enormous and at the precise resonance
frequency, probably well beyond natural winds. But this is not the
only way to stop the tra
c on the bridge. We might instead look
to bring down the vertical struts on the main bridge. Now we only
need a small amount of TNT to get the job done. Destroy one or two
