Biomimicry -- the practice of mining nature's billions of years
worth of evolutionary experience for solutions to technological challenges
-- is increasingly popular and fruitful. In many cases nature has already
solved problems that humans are just beginning to tackle.
Researchers from Exeter University in England have found
that the nanoscale structure of the wings of certain African butterflies
closely matches the most advanced photonic materials under development
in laboratories around the world.
The wings of the African swallowtail butterflies Princeps nireus
are black with fluorescent blue patches formed from two-dimensional photonic
crystal positioned above distributed Bragg reflectors. Fluorescent pigment
in the photonic crystal structure of the butterfly wing absorbs light
from blue skies and emits darker blue light.
Photonic crystal has regularly spaced nanoscale air holes or plugs
of other material that block specific wavelengths of light. Distributed
Bragg reflectors are highly efficient mirrors made from extremely thin
alternating layers of material.
The basic design is the same as experimental ultra-high-efficiency
light-emitting diodes. Light-emitting diodes use semiconductor material
that converts electrical current to light of a particular wavelength.
The photonic crystal-distributed Bragg reflector combination concentrates
light and directs it outward. Such light-emitting diodes would be much
more efficient than today's models, which scatter light in all directions,
causing much of the light they produce to be reabsorbed by the devices'
(Directionally Controlled Fluorescence Emission in Butterflies,
Science, November 18, 2005)
Search engines share the wealth
Search engines have a tremendous influence over what information
is accessed on the Web. Some researchers have been concerned that the
way search engines rank pages could lead to a vicious cycle that benefits
popular sites at the expense of new and less popular sites -- a rich-get-richer
Researchers from Indiana University and the University of Bielefeld
in Germany have found
that the combination of the way search engines return results and the
way people use those results counterbalances the rich-get-richer phenomenon
to send more traffic to less popular sites than they would receive from
It turns out that the number of hits a search engine returns and
the wording of the query introduces a bias toward less popular sites,
and this bias more than offsets the bias toward popular sites introduced
by search engine page ranking algorithms.
The research could be useful for optimizing Web sites for search
engines, forecasting Web traffic and designing search engines.
Separately, researchers from Indiana University, the University
of Barcelona in Spain and the University of Bielefeld in Germany have
uncovered sampling biases
in studies of the underlying structure of the Web. The work shows that
scientists do not yet have a clear picture of the Web's structure, which
is important for developing effective ways of indexing, searching and
surfing the Web.
(The Egalitarian Effect of Search Engines; Decoding the Structure
of the WWW: Facts Verses Sampling Biases, posted on the Computing Research
Finger tap interface detailed
The acoustics research that is helping law enforcement officials
locate gunshot sources could also be used to turn everyday objects into
virtual keyboards and command consoles.
Scientists from Sensitive Object S.A. and the French National
Center for Scientific Research (CNRS) have detailed the
physics behind their invention -- unveiled last year -- of an acoustics
sensor and analyzer that localizes finger impacts on a surface and maps
them to computer commands. The system taps time-reversal acoustics to
analyze reverberations within a solid object in order to trace a sound
back to its point of origin.
The system works with rigid materials like glass, metal, hard
plastics and ceramics, and can work with irregularly-shaped objects. The
system is made up of a single acoustic receiver and a personal computer,
and can identify contact points as small as a square centimeter.
The system can be used to turn a desk top into a computer keyboard,
a coffee table into a remote control, and a spot on a wall into a light
(In Solid Localization of Finger Impacts Using Acoustic Time-Reversal
Process, Applied Physics Letters, November 14, 2005)
Hologram stats ID microbes
Rapidly identifying microorganisms is important for medicine,
security and biological research. While using tiny biochips to ID pathogens
is an exciting emerging method, the trusty microscope is getting a makeover
that promises to keep it in the game.
University of Connecticut researchers are using
statistics to improve their digital holographic technique for identifying
The system uses a type of digital holography that captures three-dimensional
microscope images in a single exposure, which makes it possible to image
moving and growing microorganisms. The system uses statistical analysis
to identify features within the images that allow the bugs to be classified.
The statistical analysis method makes classification possible even though
many microorganisms have similar shapes.
In the researchers' tests, the system correctly identified 87
of 100 positive test images, and misidentified 2 of 100 false test images.
The method could eventually be used to diagnose bacterial infections,
detect biological weapons, track microorganisms in wastewater treatment,
and monitor plankton in the ocean.
(Shaped Tolerant Three-dimensional Recognition of Biological Microorganisms
Using Digital Holography, Optics Express, November 14, 2005)
Bits and pieces
crystals promise lightweight hydrogen storage; a silver
superlens could boost optical storage capacities; a six-legged
molecule picks up and deposits sets of individual atoms for nanofabrication;
interconnects speed parallel processing supercomputers; a new way
of electrifying carbon nanotubes produces very
bright infrared light; a laser beam shot through ultracold atoms guides
slow light from another laser.