Lecture 19 March 5,2015

Static Magnetic FieldsChapter 8

Magnetic Field Forces • 1• density • 2. Torque• moment

• Χ is the magnetic susceptibility

For two plates and o

ABF

2

2

d

FB om

Biological Effects of Magnetic Fields

Biological Changes with Magnetic Fields

• 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