Welcome to Research Notes, an online publication highlighting recent Princeton University research in the physical and social sciences, engineering, and the humanities. Research summarized here for which full online articles are available is listed in the Web stories section, along with links to the full text.
News on research in the fields of engineering and applied science is also distributed through the University's engineering school Web site, and most research conducted by faculty in the Woodrow Wilson School of Public and International Affairs is highlighted on the Wilson School Web site. For more information about Research Notes, contact Chad Boutin at (609) 268-5729 or cboutin@princeton.edu.
This issue features:
- Climate stability: Oceanic nitrogen cycle may not contribute to climate change
- Bat bearings: Bats fly by compass as well as by echo
- Funhouse telescope?: Deformable mirrors may bring distant Earthlike planets into sharper focus
- Data disguise: Beyond encryption, new stealth technique hides messages
- Making waves: Laser experiments reveal strange properties of superfluids
- Lifting her lamp: Life of Emma Lazarus provides inspiration for Princeton's Schor
- A better barrier: Living coral reefs provide better protection from tsunami waves
- Following the money: McCarty explores economic roots of today's political strife
- Rocking the vote: Researchers reveal vulnerabilities in e-voting machines
- Reading the street: Researchers seek to incorporate street psychology into economics
- Deactivating viruses: Scientists find potential 'off-switch' for HIV
- Scanning the sky: Sloan survey team on a quest for the universe's 'rare birds'
- CEO pay: Stock options may cost shareholders much less than previously thought
- Alzheimer's hints: Tangled fibers prove inspiring for Princeton chemists
- Going deep: Two miles underground, strange bacteria found thriving
Climate stability
A tight link between two naturally occurring processes in the ocean
prevents them from influencing the planet’s climate as much as
previously thought, according to Princeton geoscientists.
These
two biochemical processes are nitrogen fixation and denitrification,
which respectively increase and decrease the level of biologically
available nitrogen in the ocean. In a healthy ocean, the two processes
keep each other in balance, and this stability has significance as a
regulator of the amount of carbon dioxide that is stored in the ocean,
away from the atmosphere.
The conventional wisdom among
scientists is that imbalances may occur between nitrogen fixation and
denitrification because of the ocean's routinely fluctuating levels of
oxygen and iron, which are used in the chemical processes that
determine nitrogen levels. Because carbon dioxide is a greenhouse gas,
a long-term nitrogen discrepancy in the oceans that would result from
an imbalance between the two processes could have an impact on the
world’s climate, contributing to an ice age at one extreme or global
warming at the other. Recent studies by other scientists have suggested
that nitrogen fixation is currently outpaced by denitrification, and
that significant climate change could occur in the 1,000 years it would
take for balance to be re-established.
However,
using computer models, the Princeton team has obtained a better
estimate than was previously available for nitrogen fixation. In
addition, the team has found that fixation and denitrification are so
closely associated that they may have the ability to rebound from a
disturbance within 40 to 50 years, which would be fast enough to keep
any noticeable climate changes from happening.
“In short, an
imbalance would indeed cause a ‘bump in the road,’ but a bump too small
to cause concern in and of itself,” said team member Jorge Sarmiento, a
professor of geosciences
and director of Princeton's Program in Atmospheric and Oceanic
Sciences. "The findings turn the conventional wisdom about nitrogen
fixation on its head."
Sarmiento cautioned
that more tests will be necessary to confirm these initially
encouraging results. He next plans to analyze the ocean’s
denitrification rates.
The lead author of the study, published
in the Jan. 11 issue of Nature, is Curtis Deutsch, a former graduate
student in Sarmiento’s group currently conducting postdoctoral research
at the University of Washington. Sarmiento is available for comment at jls@princeton.edu or (609) 258-6585.
-by Carmen Drahl
Bat bearings
Bats have another extraordinary way of navigating, in addition to their
well-known (and misnamed) "radar." Princeton University researchers
have found that the animals also navigate over longer distances using
an internal compass that senses the Earth's magnetic field.
Both
to locate prey and to avoid nearby obstacles in the dark, bats bounce
sound waves from objects and perceive the echoes in a manner roughly
comparable to sonar aboard a submarine. However, this form of
navigation, called echolocation, is less helpful over long distances,
and scientists have wondered how the animals keep their bearings so
they can return to their homes after flying all night.
Bats
have long been suspected of keeping their general bearings by sensing
the planet's magnetic field, which has a general north-south
orientation. However, testing this theory has presented a problem
because of the difficulty of tracking the flying mammals during their
nightly search for food.
To overcome this
difficulty, the research team attached tiny lightweight radio
transmitters to big brown bats and prepared to follow them with a small
aircraft at nightfall. Before releasing them, the team disoriented the
bats by exposing them to artificial magnetic fields that pointed away
from the Earth's field for a 90-minute period at dusk, in order to
determine whether bats were using the sunset or stars as additional
cues to calibrate the magnetic compass. The team divided the bats into
two groups, exposing one to a field whose "north pole" faced eastward,
and the other westward.
The bats were transported 20
kilometers north of home and released. After following the bats
individually for 5 kilometers, the team found that each group had flown
substantially in the direction its respective magnetic field had
pointed. According to lead author Richard Holland, the finding suggests
that big brown bats navigate using a magnetic compass that is
calibrated around sunset.
"Some of the bats were able to
reorient themselves as the night went on, which shows that they
eventually may recognize that their compass is faulty and switch to
some other, as yet unknown mechanism," said Holland, a Marie Curie
Research Fellow at Princeton, who is visiting Princeton's Department of
Ecology and Evolutionary Biology
from the University of Leeds in England. “This research demonstrates
that it is possible to study the orientation behavior of small, wide
ranging, wild animals in the field. Given that it is possible to
receive the signals of the transmitters used in our experiments from a
low-orbit satellite, it will hopefully soon be possible to track small
animals such as bats, birds and insects globally with significant
consequences for disease, agriculture and conservation."
The team reported its findings in the Dec. 7 issue of Nature. Holland is available for comment at rahollan@princeton.edu or (609) 258-9722.
-by Chad Boutin
Funhouse telescope?
In an effort to reveal distant Earth-like planets far more clearly, a
Princeton University group is using deformable mirrors to eliminate the
visual noise that often masks planets in telescope images of faraway
star systems.
Through the most powerful of telescopes, any
terrestrial planet located even a few dozen light-years away would look
like no more than a tiny dot, just another flicker in the random
speckles found in all telescope images. These extraneous spots of
light, which are generated by minute imperfections in the mirrors that
direct and focus light, are particularly troublesome to planet finders
because they may hide the exceptionally faint light of Earth-like
planets.
But the Princeton Terrestrial Planet Finder Group,
which is part of NASA’s Terrestrial Planet Finder (TPF) mission to find
habitable planets orbiting the 200 stars closest to the Earth, may have
found a way to eliminate some of these visual distractions.
The
University’s two new 11-mm-by-11-mm deformable mirrors each feature
1,024 actuators, or movable parts, that can reshape the surfaces of the
mirrors with great precision. In the lab, the team is designing a
computer interface that can detect speckle-generating errors in
telescopes and adjust the deformable mirrors to compensate for them.
“Telescope optics aren’t perfect,” said Jeremy Kasdin, associate professor of mechanical and aerospace engineering and the director of the Princeton planet finding lab. “We are correcting for errors in the mirrors themselves.”
Though
funding for NASA’s TPF mission is uncertain, the Princeton researchers
hope their system will one day control deformable mirrors in a
space-based telescope launched to search for other planets similar to
Earth. Regardless, their work has applications in existing ground and
space-based telescopes, and long-distance laser-based communications.
The
researchers also are continuing to work on a telescope design that
could block starlight while allowing light reflected off nearby planets
to shine through. The design is based on an idea from team member David
Spergel, chair of the astrophysical sciences department.
The
Princeton TPF group also includes mechanical and aerospace engineering
professor Michael Littman, operations research and financial
engineering chair Robert Vanderbei, astrophysical sciences professor Ed
Turner, scientific instrumentation engineer Michael Carr and
postdoctoral research associate Ruslan Belikov. Kasdin is available for
comment at jkasdin@princeton.edu or (609) 258-5673.
-by Hilary Parker
WEB STORIES
Beyond encryption, new stealth technique hides messages
Princeton engineers have invented a method of stealth communication that disguises not only the information contained in a message, but also the existence of the message itself. Full text.
Laser experiments reveal strange properties of superfluids
Princeton engineers are using lasers to shed light on the behavior of superfluids -- strange, frictionless liquids that are hard to create and study. Their technique allows them to simulate experiments that are otherwise difficult or impossible to conduct. Full text.
Life of Emma Lazarus provides inspiration for Princeton’s Schor
Well known as the author of the sonnet at the Statue of Liberty's base,
Lazarus reveals in her writings a complex woman who defied the female
roles of her time in her career as a poet, critic and public figure. Full text.
Living coral reefs provide better protection from tsunami waves
Healthy coral reefs provide their adjacent coasts with substantially more protection from destructive tsunami waves than do unhealthy or dead reefs, a Princeton study suggests. Full text.
McCarty explores economic roots of today’s political strife
Why America is so politically polarized lies in the widening gulf between its richest and poorest citizens, according to a book by a Princeton political expert that has been cited as a breakthrough in the study of the country's bitterly divided political environment. Full text.
Researchers reveal vulnerabilities in e-voting machines
A group of Princeton computer scientists says it has created demonstration vote-stealing software that can be installed within a minute on a common electronic voting machine. The software can fraudulently change vote counts without being detected. Full text.
Researchers seek to incorporate street psychology into economics
Some economic policies, argues a Princeton psychologist, fail to consider important psychological factors that come into play when people handle their finances. Full text.
Scientists find potential 'off-switch' for HIV
While there is no cure for lingering infections such as HIV and herpes, it may be possible to deactivate such viruses indefinitely with the flick of a genetic switch. Full text.
Sloan survey team on a quest for the universe’s ‘rare birds’
Expanding their original research goal, Sloan astrophysicists now have the freedom to explore the Milky Way’s newly discovered entourage of satellite galaxies, as well as search for two rare types of stars. Full text.
Stock options may cost shareholders much less than previously thought
A Princeton researcher has demonstrated that, in many scenarios, stock options are worth far less than they would be valued if their worth were calculated using conventional methods. Full text.
Tangled fibers prove inspiring for Princeton chemists
An apparent setback in the effort to custom design proteins could provide answers to larger questions regarding how proteins fold, and even begin to shed light on how to treat illnesses such as Alzheimer’s disease. Full text.
Two miles underground, strange bacteria are found thriving
A Princeton-led research group has discovered an isolated community of bacteria nearly two miles underground that derives all of its energy from the decay of radioactive rocks rather than from sunlight. Full text.
