ECEN5341/4341Bioelectromagnetics

1. ECEN5341/4341Bioelectromagnetics Spring 2014 Frank S. Barnes Contact Info:            (303)492-8225      frank.barnes@colorado.eduECOT 250 http://ecee.colorado.edu/~ecen4341/index.html

2. INTRODUCTION • OBJECTIVES: • To explore the field of bioelectromagnetics and maybe to push the frontier a little bit. • To have you become acquainted with the complexity of going from the physics through the chemistry to the biology and possible health effects to public policy for risk. • To have you gain some experience in acquiring information from the literature and putting it into a useful form. • OUTLINE OF THE COURSE • A review of some of the electrical properties of biological materials and the problems of coupling electric and magnetic fields in to them. • A review of the physics of the effects of electric fields on biological systems at low frequencies. • A review of the physics of the effects of magnetic fields on biological systems • A discussion of some possible health effects of these fields

3. INTRODUCTION • A review of radio and microwaves • The coupling of radio waves into a biological system • Some physics of the interactions of RF on biological systems and some effects. • A review of lasers and laser safety if time • APPROACH TO THE SUBJECT • Start with the physics at the simplest levels and work up through the layers of biological complexity. The scope of the problem is from:10-12 seconds to generations. • From electrons and atoms to the whole body. • From DC to gamma rays • The major part of the problem is our lack of understanding of the biology

4. INTRODUCTION • COURSE OPERATIONS: • Assigned reading:"Handbook of Biological Effects of Electromagnetic Fields", 3rd Edition, Edited by Frank Barnes and Ben Greenebaum... and other literature much of which will be handed out. . Requirements. Work through a large part of  the material in the Handbook Biological effects of Electromagnetic fields. • Bring at least two new reprints on the subject of the class discussion to class each week and be prepared to present it to the class. For example the first assignment will be to read the preface in the hand book for Wednesday. The second will be to find papers on the measurement of the electrical properties of biological materials and related it to the material in the Handbook. As the class is about 30 you will need to write up each paper you read at the level of about one page per paper. I want critical comments on the papers like what are the strengths and weakness of the papers as well as brief review of the important results it contains. Also you should be prepared to present some of the most interesting result in class. • Two term papers. These papers may be presented to the class and discussed. They may also be handed back for farther development. • Two  one hour tests and a final. • The course will be flexible in the choice of material to be covered to match the interests of the class.

5. Research topics that we might include: • The treatment of electromagnetic fields as a source of biological stress. What do we mean by stress? • What are the effects of small periodic temperature variations on biological systems? In particular what might they do to the brain and nerve cells? • What are the differences between cancer and normal tissues that can be observed with electromagnetic fields from DC to light? Can we build an optical fiber system that will detect cancer that will fit in a needle? • Can we change growth patterns with magnetic fields? • Are there some ways to use electric or magnetic fields in therapy? • What are the effects of electric and magnetic fields on the immune system? • How are Type-B Cytochromes and Free Radicals effected by electric and magnetic fields. • The effects of DC Magnets on pain

6. Definitions of Electric and Magnetic Fields Define the electric field E by where F is the force and q is the charge on the particle The force between two charges is given by Coulomb’s Law Where ε0 is the dielectric constant and r is the separation between charges. We can define the magnetic flux density B in terms of the time rate of change of Charge or in terms of the velocity of the charge by the Lorentz force law. Where The magnetic field is defined from Maxwell’s equations and is related to the The magnetic flux density by

7. Magnetic Fields The magnetic field around a current carrying wire is given by The induced voltage V is given by The magnetic field from a short wire is given By : Ampere’s Law

8. Radiation . The power radiated from a charged q is given by Where a is the acceleration and c is the velocity of light η Is the impedance of free space The difference between induced fields and radiation depends on the dimensions of the device and the wave length where the wavelength is given by The radiation resistance for short linear dipoles of length l <<λ is given by The radiated power is given by

9. Electromagnetic Fields Near a Dipole Radiated field Near H Field Near E Fields Induced E Field Radiated field H is the height of the dipole, k is the propagation constant k=2π/λ, is the angular frequency is the wave impedance r is the distance from the radiating element

10. Results for Low Frequencies • 1 Almost all the fields are static or induced. • 2. At 60Hz fields with in a few km the radiated fields are orders of magnitude smaller than the static or induced fields . • 3. Heating from radiated fields is very small at low frequencies but not at RF.

11. 1 The penetration of DC Electric Fields from Air to Tissue At DC the Parallel Components The perpendicular Components Tangential components For Air For tissue So that for a wave from air to tissue And θ2 is nearly 0 so that E1 is nearly perpendicular and E2 is nearly parallel to the surface.

12. Low Frequency Field Penetration from Air to Tissue Boundary conditions for incident wave with the E field Where is the surface charge density For tissue at very low frequencies At 60Hz this gives So the induced field inside the body is very small for reasonable external fields!!

13. Low Frequency Field Penetration from Air to Tissue • For DC • For 60 Hz This says that the high conductivity and dielectric constants of tissue basically shield the body from external low frequency electric fields. However you need to be more careful if you look at skin and the sensory nerves near the surface.

14. A Membrane and Cell Model

15. Endothelial Cell Growth 45T static field Low level fields