The Federal Communications Commission limits cell phone radio frequency energy emissions, called the specific absorption rate (SAR), at 1.6 watts per kilogram, as measured over one gram of tissue.

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By changing the composition of the dye, G24's engineers ensure that the maximum sensitivity of the cell coincides with whatever frequency mix is appropriate for the artificial light concerned.

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Using millimeter wave technology, which the TSA says emits 10, 000 times less radio frequency than a cell phone, the machine scans a traveler and a robotic image is generated that allows security personnel to detect potential threats -- and, some fear, more -- beneath a person's clothes.

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Agarwal is in the early stages of further research that can model the human body's role in protecting from radio-frequency electromagnetic waves emitted from cell phones.

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The other, which faces a specialised type of solar cell made of a material called indium gallium arsenide, is sculpted into a structure called a photonic crystal that causes it to emit infra-red radiation selectively at the frequency best absorbed by the cell.

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Another goal: to make Songdo the largest so-called ubiquitous city, where wireless networks and radio-frequency identification will link all information systems--every laptop, stoplight, cell phone, TV and toaster.

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Higher frequency spectrum is the winner in this battle when combined with lots of pico and nano cell sites.

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