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All Fall Down
October 31, 1998 | Volume 154 | Number 18
Cover: The flutter of falling leaves has
intrigued—and puzzled—generations of scientists. Inspired anew by chaos
theory, physicists in a recent spate of studies find the hallmarks of chaotic behavior as
well as surprising regularities in the tumble of leaflike objects. |
 Click on this icon listed by each article to get full r
eferences and
sources. |
News of the Week:
Adult Human Brains Add New Cells
Scientists presented the
first solid evidence that nerve cells in the human brain continue to be born throughout
life.
Cancer drug helps paralyzed mice walk
A bacterial toxin enables
a mouse's injured spinal cord to heal.
Studies support an accelerating universe
New findings support the
notion that the universe will expand forever at an increasing rate.
Time proves not reversible at deepest level
Certain subatomic
physical processes, such as the interconversion of complementary particles called kaons
and antikaons, appear to take a different course if time runs in reverse.
At peace with itself, an ant triumphs
Argentine ants are
succeeding in their march around the globe in part because they’ve stopped scrapping
among themselves.
Geologists anticipate an oil crisis soon
Several forecasts
indicate that the supply of oil will start drying up in the near future.
Blood, semen harbor distinct HIV mutations
Different, drug-resistant
populations of HIV can arise in different locations in the same infected man.
Big shocks push volcanoes over the edge
Some of Earth’s
mightiest earthquakes have triggered volcanic explosions.
Physics
Blue eyes, big earplugs: Bad hearing?
Light eye color and large ear-canal size may be linked to greater
vulnerability to hearing loss.
Cooking up bubbles to make tiny pumps
Swelling and shrinking bubbles may eventually act as tiny pumps to driv
e
micromachines.
Sound was secret weapon in Civil War
Because Civil War commanders relied on the sounds of battles to make
judgments, unexpected acoustical effects may have altered the course of the war.
African dialect uses unexpected sound
A sound that linguists said was absent from human language turns up in
a
southern African dialect.
Better seal for see-through sound wall
Researchers have arranged rods into a new kind of sound filter that for
bids a
selected frequency band from passing through from any angle.
Biomedicine
A sugar averts some ear infections
A natural sweetener called birch sugar helps to prevent some ear infect
ions
in preschoolers by thwarting Streptococcus pneumoniae bacteria.
Survival improving in organ recipients
Among organ transplant recipients in the United States, survival rates
improved between 1988 and 1994, especially for those receiving liver, lung, and heart-lung
transplants.
The Leonids are Coming! The Leonids are Coming!
A memorable light show or just a bracing shower?
This Nov. 17, Earth makes its closest approach in 33 years to Comet
55P/Tempel-Tuttle, but it isn't clear how dramatic the annual light show put on by its
trail of dusty debris — the Leonid meteoroids — will prove to be.
The Puzzle of Flutter and Tumble
Physicists reconsider the fall of leaves
Computer simulations and chaos theory come to the fore in attempts to ex
plain
the motions of falling leaves and paper sheets.
Letters: A
Selection from Letters to the Editor
