November 9, 2012
Benzodiazepines. Arithmetic dynamics. Matter at the coldest temperatures of the universe. The fundamental underlying symmetries of nature. And parasites that live on tsetse flies.
What do all of these have in common? They all are faculty research topics that have recently received significant grants from the National Science Foundation (NSF) or National Institutes of Health (NIH).
John-Paul Baird, Robert L. Benedetto, David S. Hall ’91, Larry Hunter and Amy Springer will each use their funding to continue their work and, in most cases, collaborate with Amherst undergraduates and/or colleagues at other institutions. What follows are brief descriptions of their programs.
These chemicals are well known to interact with certain GABA receptors in the brain. But because GABA receptors are involved in so many different neurological functions, side effects can occur, especially with high doses.
“Benzodiazepines have complex effects. If you give the rats (or humans) a benzodiazepine, it acts as a muscle relaxant, and we do see, when we use a detailed behavioral analysis technique known as a ‘microstructure analysis,’ that rats’ tongues move slower,” Baird explains. “But we also find that the benzodiazepine has a profound effect on the overall amount that rats drink of a sweet solution: they consume twice as much sugar water even though they have ‘floppier’ tongues. Exploring this in more detail, we find that certain aversive tastes become less aversive; the rats are more willing to tolerate high concentrations of bitters, and they’re even more avid in their consumption of sweets than usual.”
All of this suggests that benzodiazepines affect multiple circuits in the brain. Most studies on this topic so far, Baird says, have involved injecting the benzodiazepines into the bloodstream, such that the chemicals travel through the rat’s entire body, yielding a complicated combination of behavioral effects. Now, with the help of Amherst and Wofford students, Baird and his colleague plan to study what will happen when they introduce the benzodiazepines directly and exclusively into areas of the brain where taste is processed. They hope to isolate the circuits specifically responsible for the taste-enhancement effects of benzodiazepines.
The professor notes that he and Pittman, who have been collaborating for more than five years, have “skills that are complementary” and use “differential approaches to tackling the same question.” A director of the Amherst College Summer Science Research Fellowship Program, Baird hopes that some of the NIH funding can go toward an exchange program, whereby an Amherst “student will have an opportunity to work on the project in my lab one summer, and then he or she can go to Wofford the next summer, perhaps, to follow up on the project—to learn the tools and techniques used in both labs.” Ideally, Wofford student researchers will have reciprocal chances to work in Baird’s Amherst lab.
Robert L. Benedetto
This means he studies problems where number theory (the study of rational numbers, integers and the primes) meets dynamical systems (remember chaos theory?), in a zone of math called non-archimedean dynamics (as opposed to traditional dynamics, the name referencing the ancient Greek mathematician Archimedes of Syracuse).
The NSF awarded Benedetto $147,253 for his project, "RUI: Families, Ramification, and Berkovich Spaces in Non-archimedean Dynamics.” Benedetto plans to study several open questions that have applications to arithmetic dynamics over many fields.
This project draws on, builds on and joins together ancient and modern fields. On the one hand, non-archimedean dynamics looks at understanding the set of rational number solutions to a naturally arising set of polynomial equations; this has been a major theme in number theory dating back to ancient Greece. The study of dynamical systems is a newer field, which, according to Benedetto, “exhibits not only a purely mathematical beauty but also spectacular computer drawings of fractals and related sets.”
“The questions that arise from this setup are notoriously difficult to solve,” he said. “To attack them, I spend most of my time working with more technical machinery: p-adic numbers and p-adic dynamics, Julia sets and Fatou sets, Berkovich spaces, arithmetic height functions and capacity theory.”
Benedetto also plans to supervise some students in an NSF summer research project to aid in their mathematical training, and he is writing a graduate-level textbook on dynamics in one non-archimedean variable.
David S. Hall
One could use the term “cool” in reference to the research of many Amherst faculty members, but in the case of Hall, a physics professor, the word is literally true.
For more than a decade, Hall has been studying the behavior of matter at the most frigid temperatures in the universe. His focus is on Bose-Einstein condensation (BEC), the substance that arises as a gas of largely noninteracting particles is cooled to tens of billionths of a degree above absolute zero. At those temperatures, a substantial portion of the gas condenses into the lowest energy state of the system, and its constituent atoms behave collectively. One manifestation of this behavior is the phenomenon of superfluidity, a zero-viscosity phase of matter where the condensed “fluid” flows without friction.
Hall and other scientists have been intrigued by the fact that when a superfluid rotates, it can form one or a series of topological structures resembling miniature whirlpools. These quantized vortices, as they are called, interact with one other and in response to their changing environmental conditions. In 2010, Hall and several of his students published a paper in the prestigious journal Science describing an experimental technique they developed that yields sequences of images of this motion. This year, the NSF awarded him $475,000 to continue his work studying these and other topological structures in BECs.
“While the immediate goal of this project—as with all fundamental research—is to understand some part of the universe a little better, we also expect that other physicists and engineers will sift through the results of this and other studies to draw more broad-reaching conclusions about nature and apply them to problems of societal interest,” he noted, citing the transistor and laser as two major technologies that arose from this approach. “The ancestries of many significant scientific and technological breakthroughs are extensive and composed of the contributions of many different researchers working on many different research problems. It’s exciting to think that work done at Amherst College could serve as the basis for another such major development in the future. We scientists cast a wide net because nature hides her surprises everywhere.”
An important aspect of Hall’s work is that undergraduates play most of the central roles in the research program. It’s a component of which he, as an alumnus and former young researcher, is especially proud. “These students, selected from increasingly diverse backgrounds as a result of the college’s admission policy, participate in cutting-edge research early in their careers,” he explained. “No matter how they later employ these skills, their educational opportunities through this program help enhance our overall scientific literacy. That, to me, is inherently a good thing.”
Nearly 20 years ago, Hunter, Stone Professor of Natural Science in the physics department, began his studies of Local Lorentz Invariance (LLI), a long-held scientific principle that the laws of physics are identical for all observers, independent of each observer’s speed, direction of motion or orientation in space. He recently received his fifth NSF grant to continue his explorations of LLI and the associated principle of CPT invariance—this time, for more than $500,000. Hunter will use a portion of the funding to pursue his work on LLI; the remainder will be used for a new project involving the laser cooling of thallium fluoride (TlF). What he finds may one day have profound implications on particle theory and could drastically change scientists’ thinking about the fundamental underlying symmetries of nature.
Hunter explained that every particle in a nucleus (every neutron and proton, to be specific) has the intrinsic atomic property of “spin.” Spin can be thought of as an arrow—or “a pseudo-vector,” he said—that points in a particular direction. He and his team are trying to ascertain whether the energy of the nucleus depends on the direction that the spin points in space. “For example, it might be that the nucleus has a higher energy when the spin points towards the constellation Virgo than when it points away from it,” he said. “Such an observation would indicate a ‘preferred direction’ in space and would violate LLI.” And since no violation of LLI has ever been observed, “much of our understanding of fundamental physics would be radically altered if a violation is observed,” he added.
In the past, Hunter had conducted his research on LLI using two pieces of equipment: one of the world’s most sensitive nuclear magnetometers using mercury atoms and one of the world’s most sensitive electron magnetometers using cesium atoms. Those devices already provided what Hunter had previously described as “an exquisitely sensitive measurement of the energy associated with the nuclear spin.” He will replace the equipment with devices of a new design that should be more sensitive by at least a factor of 20. “At this level, the experiment will provide the most stringent heavy-atom test of several possible mechanisms for violating LLI and CPT invariance,” he said.
The second project aims to determine if it is possible to laser cool the diatomic molecule TlF. If laser cooling TlF is possible, he noted, it would open up the possibility of performing a high-precision search for a nuclear electric dipole moment (EDM). An EDM, Hunter explained, is a charge distribution characterized by the distance that separates positive and negative charges.
“Even though both of these projects are relatively modest table-top experiments, they have important possible implications for particle physics,” he noted. “The LLI experiment can provide limits on String Theory, and a future TlF EDM experiment would test time-reversal symmetry in the proton and in the nuclear interaction.” The experiments will also use the precision techniques of atomic and laser physics, exposing his Amherst undergraduate assistants to the emerging field of the laser-cooling molecules and providing them with broad and flexible training in physics research.
What’s more, the projects dovetail nicely with Hall’s work involving BECs and the studies of David Hanneke, a new assistant professor of physics, who focuses on precision ion measurements that also require ultraviolet lasers. “Our fundamental symmetries experiments have drawn many talented undergraduates into careers in physics over the last 29 years,” said Hunter. “This project will build on that tradition of pursuing state-of-the-art experiments while providing exciting research opportunities and valuable training for undergraduates, so I’m delighted that the NSF has enabled us to continue.”
Tsetse flies are notorious as the biting pests responsible for spreading diseases such as elephantiasis and sleeping sickness in Africa. Springer, adjunct visiting assistant professor of biology, has been making it her job to get to know the less familiar culprits: the microorganisms that ride aboard the flies.
Her research plan, which netted a $401,582 grant from the NIH, involves Trypanosoma brucei, a protozoan parasite prevalent in sub-Saharan Africa. T. brucei is a subspecies of the parasite that causes sleeping sickness, which effects some 30,000 people annually. If untreated, the disease can cause mental deterioration, coma and death. It is often misdiagnosed, and the currently available drugs are themselves quite toxic.
“In rural areas where many people have limited access to health care, it is important to develop disease treatments that are low-cost, easy to administer and nonperishable. Elucidating the biology of these pathogens is critical for developing new treatments,” Springer said.
Her project, “Flagellar Regulatory Protein IC138 in Trypanosomes,” focuses on understanding how the organisms adapt and survive in an infected host. In particular, she is looking at how they control their movements with their lashlike flagella. For the grant project, she is studying one specific gene, IC138, which is believed to control a large protein complex called inner arm dynein, which in turn is believed to control the shape of the flagella movements.
Springer said she made a point of enlisting the aid of four undergraduates (two from Amherst, one from Mount Holyoke and one from UMass). She credits her current and past student research assistants with helping her earn the grant.
“Undergraduates in my lab have helped to produce two publications and 15 honors theses, all of which gave the grant reviewers confidence that my research was worth funding,” she said.