Biomedical Engineering Reference
In-Depth Information
(a)
Time (ns)
(b)
Time (ns)
Figure 4.18
(a)Orbitaldiffusionvs.time,where
B
z
=
0Tand
E
x
=
1Vm
−
1
.
(b)Orbital diffusion vs. time, where
B
z
=
1Tand
E
x
=
0Vm
−
1
.
agitation (Adair, 1991a). Mobility studies show, however, that
tiny, non-random microscopic drift velocities are observable at
the macroscopic level. Barnes (1986) reported drift velocities for
sodiumionsinsolution10
−
10
timesthatofitsmeanthermalvelocity,
whileCiccottiandJacucci(1975)reportedsimilarfindingsforliquid
argon at low temperatures.
Calcium ions may be examined using a hard-sphere model.
Figure 4.11a,b shows that the E field induces an acceleration
between collisions, which results in a small drift velocity and
associated positional offset to the thermal walk. The final velocity
offsetafteronecollisionperiodis
qEt
/
m
,where
m
isthemass,
q
the
