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Archive for November 24, 2010

Do Cell Phones Cause Cancer? See What a Real Expert Says

November 24, 2010 6 comments

I’ve written about the issue of cell phones and Wi-Fi and the supposed health risks associated with their use. The resounding scientific evidence shows they are perfectly safe, but the media continues to stoke fear in the public with unbalanced coverage.

When reading a news story about this sort of thing, I always wonder why they don’t ask an actual expert. The answer is that an expert would say how implausible the story is, and that they are silly for reporting it.

That doesn’t sell newspapers.

Instead, they find the one person on the fringe who maintains that there is a magical mechanism by which non-ionizing radiation can harm us. But thankfully, Phil Plait posted on his blog today something I have been looking for a long time.

I’m not a researcher (anymore). I don’t have a Ph.D, so I can tell you what I think, and I can tell you I know what I’m talking about, but I will never have as much credibility as a real university professor in physics or electrical engineering.

Enter this talk by Professor Christopher Davis from the University of Maryland’s Department of Electrical and Computer Engineering. It was given at a National Capitol Area Skeptics meeting, and posted on YouTube. It’s in 5 parts and each part is about 13 minutes long.

It is a fascinating talk and not too technical, so you don’t need a science background to understand the main points. He even touches on backscatter x-ray scanners which have been in the news quite a bit lately. Enjoy!

The Physics of Coffee Rings

November 24, 2010 Leave a comment

In keeping with the abstract on the physics of jump rope, the 63rd meeting of the American Physical Society has yielded yet another fascinating study.

63rd Annual Meeting of the APS Division of Fluid Dynamics

Volume 55, Number 16 

Abstract: RU.00007 : Coffee ring deposition in bands

Authors:

  Shreyas Mandre
    (Brown University)

  Ning Wu
    (Colorado School of Mines)

  Joanna Aizenberg
    (Harvard University)

  Lakshminarayanan Mahadevan
    (Harvard University)

Microscopic particles suspended in a liquid are transported and deposited at a contact line, as the contact line recedes due to evaporation. A particle layer of uniform thickness is deposited if the particle concentration is above a threshold; below this threshold the deposit forms periodic bands oriented parallel to the contact line. We present a model for the formation of these bands based on evaporation leading to the breakup of the thin liquid film near the contact line. The threshold results from a competition between evaporation speed and deposition speed. Using this model, we predict the thickness and length of the bands, making the control of patterned deposition possible.

[My comments: The authors used glass particles in a liquid to mathematically model how rings form. They can make these predictions using parameters such as evaporation rate and surface tension of the liquid. Aside from just being interesting, this study may have some practical implications for working at small scales.

Controlling the ring deposition process would be useful for creating such things as new microphysics tools operating at a scale where pliers or other traditional tools for moving particles cannot operate,” notes Mandre. (From Physorg.com)]