Biological Effects - RF/Microwave Interaction with Biological Tissues - page 120

a consequence, thermal effects might drown microthermal effects. This is
particularly to be expected when the signal of the considered effect in the
nonthermal region is opposite to that of the thermal ones.
It might be tempting to link frequency-dependent biological effects of res-
onance type to absorption bands in certain biomolecules. Fröhlich has demon-
strated, however, that such resonances are properties of the whole system and
may depend on the biological activity. Biological systems have to be consid-
ered in terms of their activities, which require a high degree of organization.
Such organization may be of a complex nature, but it does require considera-
tion of the system as a whole. This section is largely based on his contributions
[98].
It is important to realize that in some instances biosystems can exhibit prop-
erties similar to those of the most refined electronic instruments, achieving this
in a way that is not well understood. For instance, at low intensities, the human
visual system has a sensitivity that is close to the theoretical limit. Comparing
the energy of a light quantum with that of a nerve impulse, there is a gain of
more than 10 6 . Clearly the light quantum acts as a trigger for a nerve impulse,
the energy of which is provided by the biological system.
Control of activities represents another important set of in vivo biological
properties. It must be well understood that, for instance, the absence of control
of cell division consists in cancer. Of particular interest among materials are
enzymes, which through their catalytic action regulate most biological chemi-
cal processes. Of particular interest also is the maintenance of the electric
potential difference across biological membranes, with a thickness of about
10 nm, described in Section 3.3. In this section we discuss how this might be
involved in the interaction with microwaves.
Macroscopic organization is, of course, uniquely correlated to details of
microscopic structure. This does not mean, however, that knowing all micro-
scopic details will reveal the interesting macroscopic properties. The number
of microstates is so enormous that it cannot be handled. Furthermore, the rel-
evant macroscopic properties are expressed in terms of concepts that do not
exist in microphysics: They are collective properties. In these circumstances,
the use of the concept of information , which is negative entropy, cannot be
useful. For instance, the enormous number of microstates may lead to a cor-
responding information content of the order of 200 log 20.
It is a general feature of active biological systems that energy is always
available, through metabolic processes, and that this causes nonlinear changes
in molecules or large subsystems. Hence, from the point of view of physics,
there are nonlinear effects that change with time and are maintained through
constant energy supply. It is dangerous, therefore, to extrapolate from prop-
erties of biological molecules obtained by extracting them from the living
system to their behavior in vivo, although in some cases this can be done. Still,
from the point of view of physics, biological systems are relatively stable from
a microscopic point of view: The thermal vibrations of single atoms are prac-
tically the same as in a corresponding nonbiological system. In some respect,