Biomedical Engineering Reference
In-Depth Information
10
−
25
. Such a tiny difference due to the unenhanced LGF is likely
inconsequential in terms of biological effect. However, in certain
localised regions, this ratio may be increased. Biogenic crystalline
magnetite chains (Frankel, 1986a) cause an enhancement of the
LGF near chains of length a where the field depends upon
negative powers of the distance
r
. Frankel used equations for a
dipole appropriate where
r
>>
a
, and also for a chain of current
cylinders, to show that the induced B- field, proportional to 1/
r
3
,
could be as high as 0.5 T, so the relative difference in D is 4.0
×
10
−
17
. It can be estimated that to achieve a 10% reduction in Fick's
diffusion, a B field of strength 2.5
×
10
7
T is required. This estimate
agrees well with other estimates (Kinouchi et al., 1988; Chiabrera
andBianco,1987).Intermsoftheionicfluxandchangestoitdueto
the B field, it is required to know the concentration gradients in the
biologicalenvironmentof interest.
Turning to the orbital effect, we estimate its rate from Eq. (4.15)
for
B
0
=
10
6
rad s
−
1
.For
t
1T.Foracalciumion,
ω
c
=
4.8
×
=
1.4
×
10
−
14
s,
2.4
×
10
4
sin
6.72
×
10
−
8
,
1
x
=
10
4
{
1
−
cos
6.72
×
10
−
8
}
Since
ω
c
t
col
<<
1, we estimate the
x
and
y
offsets after one
collision. Examination of Fig. 4.18b shows we may estimate
θ
as
3.07
×
10
−
7
rad per collision. Where the collision rate is 7.8
×
10
13
collisions per second, the angular velocity of the orbit equals 2.4
×
10
6
rad s
−
1
1
y
=
×
2.4
≈
ω
c
/2. For a weak B field,
B
0
=
60
μ
T and the angular
velocityis192rads
−
1
≈
ω
c
/2again.Theradiusoftheorbitisofthe
order of the mean free path length, about 5% of the atomic radius
for a monatomicstructure.
Dependingonthemass,sizeandviscosityoftheliquid,rotational
mobility may induce biological effects on ions and dipolar proteins,
including the disruption of the ability of tissues to attain and
maintain homeostasis. Hence development may not be able to be
initiated as normal while the nucleus or other biological elements
are rotating. There is experimental evidence to show static ELF H
fieldsandelectromagneticfields(EMFs)inducearangeofbioeffects
both harmful and beneficial. The window effects observed by Adey
