Presentation on theme: "ECEN5341/4341Bioelectromagnetics Spring 2015 Frank S. Barnes Contact Info: (303)492-8225 ECOT 250"— Presentation transcript:
ECEN5341/4341Bioelectromagnetics Spring 2015 Frank S. Barnes Contact Info: (303)492-8225 firstname.lastname@example.org ECOT 250 http://ecee.colorado.edu/~ecen4341/5341 index.html
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 into 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
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
INTRODUCTION COURSE OPERATIONS : Assigned reading: "Handbook of Biological Effects of Electromagnetic Fields", 3rd Edition, Edited by Frank Barnes and Ben Greenebaum Also of interest will be “ The Physiology of Bioelectricity in Development, Tissue Regeneration, and Cancer Edited” Christine Pullar and other literature depending on your interests. Requirements. Work through a large part of the material in the Handbook Biological Effects of Electromagnetic Fields. Review at least two new papers a week and bring in at least a one or two page review of them to class. Also be prepared to present your review to the class. For example 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 15 people, 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. It is likely that with 15 students you will be asked to make presentation every week. 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.
Research topics that we might include: Can we treat 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. What are the effects of DC Magnets on pain? How do we calculate the EMFs at the location of interest in the interior of the body? How do electric forces on molecules compare with mechanical stresses at membranes in different directions?
Definitions of Electric Fields Define the electric field E by The force between two point charges is given by Coulomb’s Law Where F is the force and q is the charge on the particle Where ε is the dielectric constant and r is the separation between charges.
Magnetic Flux Density 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 Static Case N S N S
Magnetic Field The magnetic field is defined from Maxwell’s equations and is related to the magnetic flux density by Where µ is the magnetic permeability 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
Radiation. The difference between induced fields and radiation depends on the dimensions of the device and the wave length. At 60Hz 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 The power radiated from a charged q is given by Where a is the acceleration and c is the velocity of light For a short wire power radiated is given by ηIs the impedance of free space
Electromagnetic Fields Near a Dipole Near E Fields Near H 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 Radiated field Induced E Field
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.
1 At DC the Parallel Components Tangential components For AirFor tissue So that for a wave from air to tissue And θ 2 is nearly 0 so that E 1 is nearly perpendicular and E 2 is nearly parallel to the surface. The perpendicular Components The penetration of DC Electric Fields from Air to Tissue
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 E field inside the body is very small for reasonable external E fields!!
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.