Wireless News Means Less Pollution

Summaries of Research and Inventions from Science and Technology Journals

According to a pair of researchers at the University of California, Berkeley, switching from paper newspapers to electronic versions on personal digital assistants (PDAs) leads to less CO 2 , NO x , and SO x emissions. The results are based on the environmental impact of several components of newspaper production, including paper, ink, and delivery trucks. For perspective, a year's worth of The New York Times weighs approximately 225 kilograms and requires approximately 23 000 liters of water to produce. In contrast to this, the researchers show using a PDA requires 24 kilowatthours and less than 390 L of water per year. Based on their findings, the researchers conjecture that if one out of every four newspapers were read online instead of in print, it would reduce CO 2 emissions by 6–10 billion kg.

The researchers also found that wireless conference calls are much more environmentally friendly than business trips. So, if you aren't so eager to take those long business trips, tell your boss or client that a conference call is the environmentally responsible thing to do.

Environmental Implications of Wireless Technologies: News Delivery and Business Meetings , by M. Toffel and A. Horvath, Environmental Science and Technology , 1 June 2004, pp. 2961–2970.

Flesh Tones

Although there are many different skin colors, the entire range of skin appearance can be described using just three parameters. These parameters model the two types of pigments as well as skin's physical properties. Until recently, it has been difficult to extract accurate values for these parameters from digital images, but thanks to two British researchers the job is now easier. The two have developed a method for determining the parameter values with a minimal amount of error by using a special set of filters. But determining the appropriate coefficients for the filter requires a large set of training data. They believe that the technique will be very useful for medical imaging and might even be useful for imaging innards like the colon.

Spectral Filter Optimization for the Recovery of Parameters Which Describe Human Skin , by S. Preece and E. Claridge, IEEE Transactions on Pattern Analysis and Machine Intelligence , July 2004, pp. 913–922.

Chaotic Radar

Adding chaotic behavior to radar signals may seem counterproductive, but radar researchers are doing just that. Radar signals can be made more difficult to detect by modulating them with random waveforms--either noise or chaotic signals. The advantage in chaotic signals is that they are completely deterministic, and the right kind of processing will well separate them from the received signals. In a bid to overcome limitations of earlier attempts at adding chaos, a pair of engineers at the University of California, Los Angeles, used a laser driven to chaotic behavior to mask radar signals. The laser is an improvement because it has a higher bandwidth, approximately 10 gigahertz, than the chaotic signal generators used in previous schemes. The higher bandwidth means better target identification and resolution. In addition the laser-driven radar system proved immune to interference from other similar chaotic signals as well as to random noise. The radar was able to achieve a range resolution of approximately 9 centimeters in the lab, limited only by the antennas and monitoring equipment used.

Chaotic Radar Using Nonlinear Laser Dynamics , by Fan-Yi Lin and Jia-Ming Liu, IEEE Journal of Quantum Electronics , June 2004, pp. 815–820.

DNA Memory

DNA has long been known as life's building block, but its potential as a nanotechnological device has only just come to light. Researchers at the California Institute of Technology, in Pasadena. recently fabricated a three-bit rewritable memory device out of DNA. The device consists of a double-helical strand of DNA with three different protruding single-stranded branches, each seven nanometers apart. Each single stranded branch is the equivalent of a digital zero. Adding a branch's chemical complement, the "write" strand, forms a stable protruding double helix, the equivalent of a digital one. Ones can be erased to zeros by adding an "erase" strand, which rips the branch double helix apart again and neutralizes the write strands. Detecting the ones and zeros of this type of memory is done using standard biochemical assays. Preliminary experiments show each DNA logical bit takes about five minutes to write or erase. The group hopes to incorporate the memory into both DNA nanotechnology devices and into synthetic genetic circuits inserted into cells.

Rewritable Memory by Controllable Nanopatterning of DNA , by J. S. Shin and N. A. Pierce, Nano Letters , May 2004, pp. 905–909.

Light bulbs From Nanotubes

According to engineering lore, Edison tested thousands of materials while searching for the perfect incandescent light bulb filament. Today's engineers have an even larger menagerie of materials to consider. The newest candidates are carbon nanotubes, whose exotic electrical and mechanical properties have intrigued the materials and electronics communities for the past decade. A group of engineers at Tsinghua University in Beijing and Louisiana State University in Baton Rouge recently fabricated household light bulbs using nanotube filaments. Compared to tungsten filaments, the carbon nanotubes showed lower threshold voltage for luminescence and emitted more visible light than tungsten filaments at the same voltage.

Carbon Nanotube Filaments in Household Light Bulbs , by J. Wei et al., Applied Physics Letters , 14 June 2004, pp. 4869–4871.

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