Category Archives: Body

I Don't Like Cell Phones

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But it has nothing to do with radiation safety concerns.

Fraud Charges Cast Doubt on Claims of DNA Damage From Cell Phone Fields

The only two peer-reviewed scientific papers showing that electromagnetic fields (EMFs) from cell phones can cause DNA breakage are at the center of a misconduct controversy at the Medical University of Vienna (MUV). Critics had argued that the data looked too good to be real, and in May a university investigation agreed, concluding that data in both studies had been fabricated and that the papers should be retracted.

Do Not Fear the Banana

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Zapperz has a short post on an article that appeared in the NY Times, chumming the waters of fear about radiation from granite countertops. I see that Chad has promised and delivered a bit of a rant, pointing out that popular media could and should do science. The problem is that they don’t — not in the living section, and sometimes not in the science section, and almost certainly not on the op-ed page.

But that’s not actually what piqued my interest here. It’s mediocre reporting, to be sure; the author makes sure to give “both sides” of the story, even though science boils down there being experimentally verified claims or not, so reporting knee-jerk reactions to the ticking of a geiger counter isn’t particularly responsible. But there was a snippet that reminded me of a conversation I was having last week.

Indeed, health physicists and radiation experts agree that most granite countertops emit radiation and radon at extremely low levels. They say these emissions are insignificant compared with so-called background radiation that is constantly raining down from outer space or seeping up from the earth’s crust, not to mention emanating from manmade sources like X-rays, luminous watches and smoke detectors.

And not to mention — because they don’t — people. That’s right: YOU are radioactive. An adult contains something like 140 g of potassium, of which about 16.5 mg will be K-40, which is radioactive with a 1.26 billion year half-life, yielding about 4400 decays per second. You also have C-14 in you, adding in another 3000 decays per second. The C-14 decay, and 89% of the K decays give betas, which will be deposited in your body. The other 11% of the K-40 decays have a 1.46 MeV gamma, and about half of them will be deposited in your body as well. This ends up being tens of millirem of dose per year.

The rest of the gammas escape, which means that you are a 6.5 nanoCurie gamma source. (Sleep with someone else 8 hours a night, all cuddled up? That’s around a millirem of dose each year. Not a cuddler? Here’s your excuse — your exposure decreases as you move away.) Do you use potassium in your water softener or as an alternative to table salt? What about bananas? That’s a 300 picoCurie source there, and you’re eating it. If you leave it alone, it’s only about 20 picoCuries of gamma.

The point here isn’t to make anyone afraid of bananas. You need potassium, and K-40 is along for the ride. But reporting like this gives no context, and paints a very simplistic “all radiation is bad” picture, when some dose is simply inescapable. It accentuates and panders to our inability to properly assess risk for unusual circumstances, especially with the mention of radon testing kits at the close of the article.

Looking for Energy in all the Right Places

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Bionic bra: Victoria’s circuit

An attempt to harness, as it were, the kinetic energy stored in the ones that bounce.

It turns out that the physics of breast motion has been studied closely for the last two decades by a gamut of researchers – most of them women.

Formally, perhaps.

Lawson explains that breasts move on three different axes: from side to side, front to back, and up and down. The most motion is generated on the vertical axis. Naturally, the bigger the breast, the more momentum it generates. “Let’s face it – if you’re a double-A marathoner, you’re probably not going to get that iPod up and running,” Lawson says. Measurements compiled by Lawson and her colleagues show that a D-cup in a low-support bra can travel as much as 35 inches (89cm) up and down (35 inches!) during exercise, while a B-cup in a high-support bra barely moves an inch.

Again, something that a motivated amateur scientist might have also observed.

via O, Teh Interwebz!

The Other Kind of Seven-Year Itch

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THE ITCH by Atul Gawande from the New Yorker

Fascinating article, albeit with occasionally disturbing imagery, on itching and phantom pain.

Now various phenomena became clear. Itch, it turns out, is indeed inseparable from the desire to scratch. It can be triggered chemically (by the saliva injected when a mosquito bites, say) or mechanically (from the mosquito’s legs, even before it bites). The itch-scratch reflex activates higher levels of your brain than the spinal-cord-level reflex that makes you pull your hand away from a flame. Brain scans also show that scratching diminishes activity in brain areas associated with unpleasant sensations.
But some basic features of itch remained unexplained—features that make itch a uniquely revealing case study. On the one hand, our bodies are studded with receptors for itch, as they are with receptors for touch, pain, and other sensations; this provides an alarm system for harm and allows us to safely navigate the world. But why does a feather brushed across the skin sometimes itch and at other times tickle? (Tickling has a social component: you can make yourself itch, but only another person can tickle you.) And, even more puzzling, how is it that you can make yourself itchy just by thinking about it?

Random Thought

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I was out sick a few days last week (you may have noticed a fever-induced tinge to my ramblings) and was reassured today (back at work) to find out that others had been ill last week as well. Being sick when all around you are well raises the question of what, exactly, is wrong with you, but if others have it then it’s whatever’s going around and probably nothing serious.

OTOH, I can’t really imagine how reassuring “Oh, it’s just something that’s going around” was circa 1350.

Crime Scene Investigation Investigated

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I stumbled across a dead body couple of posts over at Quantum Moxie on the thermodynamics of post-mortem cooling of a body: Mistakes were made . . . and the followup, Post-mortem body cooling in variable environments.

[T]he standard post-mortem body cooling method used to estimate time of death (TOD) does not take into account a varying environmental temperature (i.e. it assumes a constant ambient temperature when applying Newton’s Law of Cooling).

And since were on the subject of physics and dead bodies, Zapperz notes a brouhaha about a physics exam question involving a gunshot victim and bullet trajectories.

Not Pretty

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A doctor tells a man, “You’re fat. Lose some weight.”
The man says, “I want a second opinion.”
“OK, you’re ugly, too.”

According to the International Journal of Obesity, we’re fat because we’re stuffing our faces, and not so much because we’re sitting on our duffs (Ha! Speak for yourself. I’m a double-threat.)

(from the journal)

Conclusion: As physical activity expenditure has not declined over the same period that obesity rates have increased dramatically, and daily energy expenditure of modern man is in line with energy expenditure in wild mammals, it is unlikely that decreased expenditure has fuelled the obesity epidemic.

So if you’re burning just as many (or more) Calories, gaining weight must be from increased intake. Basic physics.

And as for the International Journal of Obesity? From this angle it looks to be a few extra pages thick, if you take my meaning.

Magnets Gone Bad

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Why is striking woo so easy on the internet?

My knee has been bothering me, and the knee brace I have used in the past (which AFAICT stabilizes against some lateral movement) wasn’t helping me. The problem appears to be consistent with patellar tendinitis, aka jumper’s knee (and yes, mister fancy-pants word-check software, thatisthe correct spelling for tendinitis). It’s not bad enough to send me to the doctor’s office — that event has a fairly high activation potential — so I bought a patellar knee strap, and it seems to be helping thus far.

But when you go out on the web and search on things like “knee pain brace,” you end up hitting a lot of sites selling magnetic therapy bracelets. And, of course, these are bunk — total crap. Now it’s not insane to wonder if magnetic fields will affect the body, but the explanations of the way the bracelets are supposed to work are just clearly bogus. The fields of these bracelets/wraps/jockstraps are weak, and hemoglobin isn’t ferromagnetic. Depending its the oxygenation state, you can get diamagnetic or paramagnetic behavior in the hemoglobin, which allows you to do functional MRI, but this uses fields several orders of magnitudes stronger to see effects. People have done tests that show that these devices don’t work, but it’s also true that these suffer from some problems, namely, that you can’t have a magnetic “placebo” device, since it isn’t difficult to tell if a bracelet is magnetic.

But there’s actually a deeper level to some of the shenanigans, and this is where the basic physics breaks down – badly. Continue reading →

The Physics of Weight Loss

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The physics of weight loss is quite simple. It’s the first law of thermodynamics: Energy is conserved. Our body stores energy as fat, which has mass and thus weight, when we’re in the presence of gravity, as I assume we all are. Burning more calories as you consume results in an overall trend of less weight, if the two are equal the weight stays the same, and more calories in adds to the weight. Now, this discounts fluctuations you may have, due to things such as how much water (zero calories, but still has mass) or food is currently being processed by your body, so this is something that needs to be measured over a longer time frame than a day or two.

That’s all there is to it. Eat less and/or exercise more and you’ll tip the balance, as it were, toward losing weight.

But it’s never quite that simple in practice, now is it? There was a recent article in the NY Times, “In the Fatosphere, Big Is In, or at Least Accepted” in which the author states (about some overweight people): “And they reject a core belief that many Americans, including overweight ones, hold dear: that all a fat person needs to do to be thin is exercise more and eat less.” Well, they key here is a subtle distinction — “be thin” rather than “lose weight.” I agree that not everyone is going to be thin — hell, I’m never going to be thin, but that’s a separate issue. “Thin” is an ideal that doesn’t necessarily equate with “not overweight;” it’s a comparison of a physical dimension, a size and shape, compared with a mass. But the “core belief” is not a belief, it’s science. Eat less and exercise more, and you will lose weight. The barriers to that are largely psychological, it seems to me (what motivates you eat, or eat too much, and what prevents you from prioritizing exercise, and there’s a lot that can be written about that. And I’m sure a lot has been).

But there’s a little more physics, or at least math, that confounds the issue. Continue reading →

No Sweat

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Or, the myth of “working up a good sweat”

On occasion my “private” workouts get interrupted by someone with the audacity to want to use the exercise room at the same time I do. That’s no biggie. But what bugs me is when the offendor will turn on the heat, or turn off the AC or close the window. I prefer to not be sweating just by walking in the room. It shortens my workout, and here’s why.

Your body is about a 100-watt heat source. That is, you you are shedding heat at level of about 100 watts, give or take, just by sitting around. There’s an overview here. Most of that is radiation, and takes into account that we would normally be shedding more heat if not clothed. Long sleeves and pants insulate more, and reduce the heat loss, or compensate for larger heat loss when it’s cooler. Imagine that.

Radiation heat transfer is covered by the Stefan-Boltzmann law, which tells us that heat transfer depends on the difference of the fourth power of temperature of our body vs. the ambient room. Your body is a heat engine, and once you start exercising that engine needs to reject more heat. So you hop on the treadmill or bike or stairmaster and start your workout. The little display tells you that the output is about 100 Watts, but your body isn’t 100% efficient — no engine can be. You’re actually burning carbs at about 400 Watts, and that extra 300 Watts needs to leave your body, so your temperature goes up. If radiation were to take the whole load, your body would need to rise about 30 degrees C, and obviously it can’t do that. So, you start sweating.

Continue reading →