Biomedical Engineering Reference
In-Depth Information
Fig. 1.42
Curves for
function
F
(
r
,
n
)
A
n
(
r
/
r
0
)
n
D
1
˚
Aand
n
for
r
0
D
D
1, 3, 6,
and
A
n
D
1 (reprinted from
[
132
]. Copyright 2010 Royal
Society of Chemistry)
as well as interferences between branch signals. For example, we note that the signal
transmission along intercellular and intracellular pathways and between the exterior
and the interior of a cell may be mediated by protein allostery [
91
-
93
], which may
lead to the redistribution of the charges and the reorientations of the charge dipoles
in the proteins, but the exact molecular mechanism is still unclear.
As we have known, thermal noises usually hold important interference in
signal transmission, conversion, and multiplication. Particularly at the nanoscale,
thermal noises often significantly reduce the signal strength during the transmission,
conversion, and multiplication.
More critically, it should be noted that the interferences between signals can be
very strong if the signals are transmitted by charges. In terms of Coulomb's law,
the interaction potential between two charges decreases with respect to
r
1
,where
r
is the distance between those two charges. At the nanoscale, this slow decay will
result in strong interaction between two charges (signals). Therefore, within one
nanometer's distance, although the VDW interaction almost decreases to zero with
respect to
r
6
, extremely faster than
r
1
, the interaction cannot be neglected between
two atoms yet. As a comparison in Fig.
1.42
, we show a diagram of the function
F
(
r
,
n
)
D
A
n
(
r
/
r
0
)
n
with respect to
r
for
r
0
D
1
˚
Aand
n
D
1, 3, 6, where
A
n
is set as a
constant 1. Therein, the dipole-dipole interaction potential just has a form of
r
3
,
decaying much faster than the charge-charge interaction (
r
1
) with distance.
It is much worthwhile making an attempt to use the dipole to transmit a signal,
due to the much faster decay of the interaction between different dipole signals.
Several decades ago, one began to study the properties of electric dipoles and the
applications on them. The most notable one is the Ising model [
94
,
95
]. Recently,
the behavior of one-dimensional dipole chains has been discussed, including the
energy transfer in a dipole chain [
96
], the design of a logical AND port using dipole
chains with a junction [
97
], and the initiation of the orientation of one-dimensional
dipole chains by a local field [
98
].
