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![]() "Jim Lux" wrote in message ... The very last study, on the very last page with the second paragraph offers: "For an effectively transmitted power of 0.25 W, the maximum averaged SAR values in both cubic and arbitrary-shaped volumes are, respectively, about 1.72 and 2.55 W kg-1 for 1g and 0.98 and 1.73 W kg-1 for 10 g of tissue." The last study gives us more exposure data (the discussion of which inevitably scatters in the rhetorical wind of debate). I can only wonder if the reader can draw a conclusion from this quoted sentence that can be expressed in temperature rise. There's enough data to do this, only intelligence remains to perform. that's pretty simple.. Assume that the tissue has the specific heat of water. 1 Joule will raise the temperature of 1 gram of water about 1/4 degree C.. So, dump 2.55W/kg and you get about 0.0006 degree rise per second. Hang on the phone for, say, 10 minutes (600 seconds) and you'll get a temperature rise of a bit less than 1/2 degree C. For comparison: putting your head in sunlight results in an incident flux of about 1kW/square meter (peak). Assuming skin reflectivity of 0.36, the flux being absorbed is about 640W/square meter. Let's assume that the energy is absorbed in the first centimeter of your skin/bone, and that your head is a circle about 10cm in radius (e.g. 314 square centimeters).. That works out to about 20 watts total power being absorbed (compare to the 0.25W RF in the example above). Again, let's say that the density is 1g/cc, so the 20W is being dumped into 0.314 kg, or a SAR of 64 W/kg. That's a rise of 0.015 degree/second, or 10 degrees in 10 minutes. In reality, you won't see that much rise, because bloodflow carries some of the heat away, and so does convection. That was my point restated ever so diligently. After reading 1/4 of the "Biological studies..." it is interesting. But we need to remember that experiments only become valid when repeated numerous times. As these are only summaries, they are hard to compare and we loose that without having the full experiment laid out before us. I have tended to throw away those that didn't describe the frequency and field strength in some way as less than anecdotal. I have seen data from a few of the experiments before and further experimentation would be a good thing particularly the ones that seem to describe low levels with certain modulation specifics. Also we need to differentiate the studies that involved 60 Hz AC fields which do seem to have an effect, but again more experimentation is required to try to figure out why some of these experiments conflict. I have performed an RF evaluation at my station and recommend prudence when operating. I am expected to do this because I am in control of the equipment and can make changes that may result in higher levels of exposure. Those who go out and buy the wireless device are limited by the FCC approval of the whole unit, and battery vs. talk time also limit the potential of exposure and hazard to negligible. Now as for certain people who equate that with hazards that require the defeating of safety interlocks to prove their point? Cars are dangerous, but most of all, people who run off the road into overpasses to prove the point. God help them. Real hazards are people trying to expose themselves to exhaust fumes with the vehicle in reverse or in a closed garage or removing the guards from lawn mowers and putting their hand in the blade or electing someone to public office that makes selections on judges, who also pals around with extremists and radicals, including those who hate the country they live in and make death threats on those they hate. You can judge a book by its cover if it is trying to tell you what is inside. Dropping some friends just because you are running for public office says something too. Also it seems to me that those who promote "change" without positive solutions are really seeking to destroy. |
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