Lecture 19 March 4,2016
Static Magnetic Fields
Chapter 8
Magnetic Field Forces
• 1
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• 2. Torque
•
density
moment
• Χ is the magnetic susceptibility
For two plates
B2 A
F
and
2 o
B
Fm o
d
Biological Effects of Magnetic Fields
Biological Changes with Magnetic
Fields
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•
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4. Changes in H2O vaporization rate
5. Decrease in skin temperature
6. Changes in O2 concentration
7. Changes In radical pair lifetimes.
8. Change in cell culture growth at low fields.
In Vivo Studies
• 1. Animal Navigation , Birds , bees, salmon
• 2. Rat cognitive function modified by magnetic
fields of 14µT horizontal 116µT vertical also
55µT and 240µT vs. normal of 14µT and 34µT
• 3. 5T field suppressed eating and drinking
• 4. Analgesia, pain reduction, by reducing the
magnetic field to < 1µT. Also to fields of 79µT
• Foot on hot plate. Also 60hz at 299µT
In Vivo Studies
• 5. Changes in Heart rate at 100mT in rats.
80% of the time
• 6. Some effects observed in trout embryos
• 7. Ohkubo, Changes in micro circulation ,
modulated vessel size at 1mT up to 180mT for
10minutes. Reduced or expanded vessel size
dependent on animal stress. Moved toward
normal. Normal capillaries showed no change.
• 8. This is backed up by other studies.
Reproductive and Development
• 1. High fields MRI, at 0.7T +RF Minimal effects of
sperm motility etc. for 24hour exposures up to 35
days on mice.
• 2. Also on fetus.
• 3. Some reduction in weight for long exposures of
embryos to MRI fields
• 4. Exposures of chick embryos to 29mT for 6 days
could induce irreversible effects on cell migration
and differentiation. Measured at day 13.
Development Changes
• 1 Prolonged transportation of fertilized
salmonid eggs and trout at 4mT, lower
mortality rates. Effects on orientation in fields
from 0.5 to 1mT
• 2. Effects on carp muscle at 50 to 70mT
• 3. Lots of other effects in this range.
Cell Changes
• 1. Reduction in Cell growth, ecoli, at B< 1µT
• 2. Changes to antibiotic resistance for several
different cases.
• 3. Other studies show not effects at field of
0.35mT and 2.45mT for different types of cells
and also O.2T,1T and 1.5T on fetal human lung
fibroblast cells
• 4. We see changes in growth rates for
fibrocarcoma cells but not fbroblast cells at
100µT
•
Medical Applications
• 1. MRI, FMRI imaging
• 2. Bone growth and repair
• 3. Transcranial Stimulations . Can get 5mm
resolution with figure eight coils. τ = 0.1ms to
0.2ms Bmax= 1T for motor cortex
• 4. MEG, use squids to measure 10-15T
• 5. MCG