Biomedical Engineering Reference
In-Depth Information
A
Fig. 1.18
The water probability density distributions along the nanotube axis for ı D
0
(reprinted from [
129
]. Copyright 2008 American Physical Society)
water molecules located in the middle part of the nanotube increases. The distance
between water molecules is not a constant in this case. But in the above model,
d
isassumedtobefixed.Ası further increases from ı
c
, the error of the theoretical
prediction increases very quickly (see Fig.
1.19
).
From the theoretical model, we can understand the origin of the wavelike pattern
of water density distribution inside the CNT. The wavelike pattern mainly results
from the potential barriers at both ends of the nanotube together with the tight
hydrogen-bonding chain inside the tube that fixes the distance between neighboring
water molecules approximately.
We know, for molecular biological systems, that the external and internal
fluctuations are usually nonnegligible. In this section, we will discuss the effect of
the external fluctuation on water molecule transportation. Different from the above
where the forced-atom is fixed, if the forced carbon atom vibrates periodically,
the behavior of the single-filed water chain inside the CNT still keeps stable. The
simulation framework is similar to the simulation system in Fig.
1.3
. In this system,
the forced-atom is forced to move according to the equation
x
D
x
0
C
A cos.!t
C
/;
