Research Notes - Spring 2007

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

This issue features:

Below the surface

A team of Princeton University chemists believes it has created a method that will improve medical implants and possibly prevent follow-up surgeries.
Every year, more than half a million injured Americans are implanted with devices such as artificial joints, according to the American Academy of Orthopedic Surgeons. Most implants have metallic components that may need to be removed with a second trip to the operating table. Researchers are actively working to create implants made entirely from polymers such as nylon, which have the potential to dissolve harmlessly after acting as a scaffold to support healing. That's better than retaining a foreign substance in the body over the long term, according to Jeffrey Schwartz, professor of chemistry and a director of the study.
"There is room for big improvements in the efficacy of all sorts of surgical implants," he said. "Hard metal implants stay in the body forever unless removed with a second, 'revision' surgery, and regrowing tissue often requires a soft surface."

One way to coax ligaments, tendons or other connective tissues to mesh with and eventually take over for an implant is to coat their surfaces with a specific protein fragment, or peptide, that is proven to promote tissue growth. However, finding a way to coat a polymer surface efficiently with a peptide is a major obstacle to making viable medical devices.
Working with a nylon surface that physicians use for burns and recurring wounds, the team used a chemistry-based approach to manipulate the surface on a small scale.  Microscopically, nylon looks like a charm bracelet, with repeating links forming a long chain. In the past, other researchers have clipped peptides onto the ends of the nylon bracelet, or on top of "charms" that were already present, which did not cover enough of the implant's surface to encourage adequate tissue growth.
Chemistry graduate student T. Joseph Dennes developed a more effective solution: a nontoxic way to fasten peptides to every link in the bracelet. With Jean Schwarzbauer, professor of molecular biology, and her graduate student Geoff Hunt, the team showed that connective tissue cells can grow and spread properly on the nylon-coated surface.

Schwartz cautioned that the technique is not yet ready for the clinic, but the team is working with a medical research company, Orthobond of Monmouth Junction, N.J., to address limitations like scar tissue growth. Two patent applications are pending.
The team reported its findings in the Jan. 10 issue of the Journal of the American Chemical Society. Their work was funded by the National Science Foundation and the National Institutes of Health. Schwartz is available for comment at or (609) 258-3926.

-by Carmen Drahl

Breath of life

A medical device that requires nothing more than a single breath to detect diabetes instantaneously is being developed by a Princeton-led engineering research center.

The technology hinges on the use of a special type of laser that emits light in the mid-infrared region of the spectrum. Sensors that rely on these lasers are able to detect substances in the breath, such as acetone and ammonia, which are often indicative of disease or inflammation.

"Medicine needs a screen that’s on-the-spot and gives results immediately," said Claire Gmachl, associate professor of electrical engineering and director of the Center for Mid-Infrared Technologies for Health and the Environment (MIRTHE).

The sensors being developed by MIRTHE will be small and compact, making them a feasible option for use in the doctor's office, Gmachl said. This is in sharp contrast to current breath analysis technologies, which require the collection of breath in a bag that is then sent to a lab for testing by bulky, expensive equipment.

MIRTHE researchers at Rice University currently are building a sensor that detects acetone, a substance that can indicate diabetes when present in the breath. The finished device will include a laser made at Princeton, which was subsequently incorporated into a laser system by Maxion Technologies of Hyattsville, Md. Upon completion, the sensor will be tested in a clinical setting at Johns Hopkins University, Gmachl said.

Other sensors in consideration for development would detect other substances, including ammonia, to identify kidney, liver and lung disease as well as the early stages of oxidative stress, which has been implicated in the development of Alzheimer's and Parkinson's diseases.

Funded by the National Science Foundation, MIRTHE unites scientists and engineers from six universities with partners in industry and government labs. Gmachl is available for comment at or (609) 258-7489.

-by Hilary Parker

Cosmic developments

In a finding that could offer insight into the role of dark matter in the structural development of the early universe, a Princeton-led team of scientists has determined that faraway quasars appear in clusters separated by vast reaches of empty space.

Using a map of the universe's 4,000 most distant known quasars -- massive galaxies that are among the most luminous objects known -- graduate student Yue Shen and professor Michael Strauss have not only found that quasars form widely separated clusters, but have also deduced from the findings that the quasars are surrounded by massive dark matter halos, which prevailing theories say should be quite rare in the early universe. This discovery, made with the Sloan Digital Sky Survey telescope at New Mexico's Apache Point Observatory, supports the currently predominant theory regarding dark matter, the still-mysterious substance thought to constitute most of the universe's mass.

"These findings have no implications on what dark matter consists of, but they do have implications on its behavior," said Shen. "They confirm our suspicions that quasars formed in very special and unusual dense concentrations of dark matter in the early universe."

The early universe had an almost perfectly smooth distribution of matter, but during the approximately 14 billion years since the cosmos formed, gravity has pulled it into the highly structured collection of galaxies scientists see through telescopes today. To find clues as to how the universe ordered itself, Shen and Strauss decided to look at an intermediate step in its evolution by examining quasars that lie more than 11 billion light years from Earth. Because the light from these distant beacons started traveling toward Earth long ago, images of them provide a snapshot of the cosmos as it appeared in its youth.

Though most visible matter was distributed more evenly billions of years ago, Strauss said he was both "delighted and surprised" to find the quasars even more strongly clustered than they are today. This does not mean that scientists' theories about universal structure are wrong, he said, but that the massive halos of dark matter -- which cannot be seen directly -- are revealing their influence.

"Quasars can be envisioned as little glowing bits of foam floating on an invisible pervasive sea of dark matter," said Strauss, a professor of astrophysical sciences. "Just as foam on the ocean tends to form on the peaks of the biggest waves, so too we expect that quasars should lie in the highest and rarest peaks in the 'sea' of dark matter that fills the universe."

Shen and Strauss will publish a paper on their findings in the May issue of The Astronomical Journal. Strauss is available for comment at or (609) 258-3808, and Shen at or (609) 258-8057.

-by Chad Boutin



New laser technique promises swift detection of bioterrorism agents

A new laser technique allows for instant detection of bioterrorism agents, permitting tests that previously were cumbersome or impossible. Full text.

Research removes major obstacle from production of tiny circuits

By eliminating the tiny air bubbles that form when liquid droplets are molded into intricate circuits, a Princeton-led team is dissolving a sizable obstacle to the mass production of smaller, cheaper microchips. Full text.

Study yields surprising findings, arresting images

Two of the world’s worst recent natural disasters actually had much in common, according to Yin Lu "Julie" Young, who has been studying both the Indian Ocean tsunami of 2004 and the United States' Hurricane Katrina. Full text.

Flexible electronics aid brain injury research

Flexible electronic membranes may overcome a longstanding dilemma faced by brain researchers: how to replicate injuries in the lab without destroying the electrodes that monitor how brain cells respond to physical trauma. Full text.

Sloan team on a quest for the universe's 'rare birds'

Astrophysicists working with the Sloan Digital Sky Survey now have more freedom to explore our cosmic neighborhood in greater detail and continue their search for two unusual kinds of stars. Full text.

Investigating clues to a life, Biehl discovers larger reality

Anthropologist João Biehl explores a Brazilian "zone of social abandonment" populated by the sick, mentally ill and poor who have passed beyond the care of families and social institutions. Full text.

Nanoparticles improve delivery of medicines and diagnostics

Tiny, biodegradable particles filled with medicine may also contain answers to some of the biggest human health problems, including cancer and tuberculosis. The secret is the size of the package. Full text.

New chemistry approach promises less expensive drugs

With a newly discovered method of assembling organic molecules, a team of chemists may have found a way to sidestep many of the expensive and hazardous barriers that stand in the way of drug development. Full text.

New fuel cell design adds control, reduces complexity

When engineers want to increase the power output of their new fuel cell, they just give it a little more gas -- hydrogen gas, to be exact. Though the control mechanism was once thought impossible, two Princetonians showed it can work. Full text.

Scientists build a world in a grain of silicon

Physicists have fashioned a living, changeable ecosystem out of a tiny chip of silicon. Their creation could help researchers better understand how organisms survive in the natural world. Full text.

Historian's work helps community 'look itself in the eye'

A new book by Jan Gross describes how Jews who returned home after surviving the Holocaust were scorned and in some cases murdered by the Polish neighbors they had lived alongside before the war. Full text.