January 29, 2001
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Editor: Tom Garritano
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Thirty-five years ago, a University of Florida physics
professor suggested a new way to measure very low
temperatures -- that is, temperatures so cold they
were off the official scale, which at that time stopped
at 0.65 Kelvin.
E. Dwight Adams and graduate student Richard Scribner,
with support from the National Science Foundation
(NSF), created a new type of thermometry by determining
the pressure and temperature needed to freeze helium-3.
As more and more research was performed in exteme
cold, scientists used this method to gauge temperatures
that sometimes approached 0 degree, the theoretical
absolute zero.
Now, the International Commission on Weights and Measures
has officially adopted Adams' "melting pressure thermometry"
gauge as the worldwide standard for measuring the
ultra-cold.
Adams' NSF-funded research in magnetism and ultra-low
temperatures spans more than three decades, dating
to his invention, with graduate student Gerald Straty,
of the pressure gauge that allowed the measurements
to be made. He now serves as director of a user facility
at the NSF National High Magnetic Field Laboratory
at the University of Florida, the nation's premier
facility for research into magnetism. [Amber Jones]
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A new research model uses biological factors to quantify
the processes behind ecological responses to climate
change. The work at Penn State University, funded
by NSF, is moving beyond previous observational limits
and providing a way to analyze factors that can accelerate
spring events, said Penn State researcher Eric Post.
Using data for three species of flowering plants collected
during a 50-year period, Post and his collaborators
applied a mathematical and statistical approach developed
originally for studies of population dynamics. The
model incorporates variables such as competition for
resources and population density, which are factors
likely to change with climate, according to Post.
In each of the three species - wood anemone, hepatica
and colt's foot - the model shows that plants bloomed
earlier after warmer winters because of complex interactions
involving competition, climate and resources.
"We hear with increasing frequency reports about birds
nesting earlier and flowers blooming earlier," said
Post. "Those reports get a lot of attention because
they provide convincing evidence that species are
responding to climate change. But if we really want
to understand what's happening and make predictions
about what will happen with future climate changes,
we need to get at the mechanisms and relationships
behind the changes." [Cheryl Dybas]
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Millimeter deviations from the expected wobble of
the Earth's axis are giving geophysicists clues to
what happens 1,800 miles underground, at the boundary
between Earth's mantle and its iron core. The research
is funded by NSF.
The new theory proposes that iron-rich sediments are
floating to the top of Earth's core and sticking like
gum to the bottom of the mantle, creating drag that
throws Earth's wobble off by a millimeter or two over
a period of about 18.6 years.
"The wobble is explained by metal patches attached
to the core-mantle boundary," says Raymond Jeanloz,
a geologist at the University of California at Berkeley,
who conducted the research with colleagues Bruce Buffett
of the University of British Columbia and Edward Garnero
of Arizona State University. "As the outer core turns,
its magnetic field lines are deflected by the patches
and the core fluid gets slowed down."
Now, with 20 years of data, says Jeanloz, "we can confirm
that the discrepancy is there and is explained very
nicely by the Earth's magnetic field causing friction
at the bottom of the mantle." [Cheryl Dybas]
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