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Department of Physics & Astronomy

REU Project Descriptions

Click on the project name for a more detailed description of the project.

NOTE: Additional projects may be listed in early January 2008

Chaotic Mixing Chemical Pattern Formation
Project Mentor: Tom Solomon
Project Code: (THS-1)

Particles moving in well-ordered, smooth flows can follow extremely complicated, unpredictable trajectories. This process, called chaotic advection, has profound implications for the mixing of impurities in simple flows. We are currently studying how chaotic mixing affects the behavior of reacting systems. Specifically, we are studying the movement of reaction fronts (similar to flame fronts) and the formation of self-sustaining spiral and target patterns in the well-known Belousov-Zhabotinsky chemical reaction. The work is predominately experimental, although some numerical simulations might also be used to complement the experiments.

The experimental and numerical work will all involve a substantial amount of computer analysis (predominately image analysis), almost exclusively on Linux workstations running a program called IDL.

Project Name: Star Formation from Turbulent Molecular Clouds
Project Mentors: Ned Ladd and Ray Chastain
Project Code: (EFL-1)

Molecular clouds are dusty, turbulent concentrations of gas that live between and among our galaxy's stars. These clouds are the reservoirs out of which the next generation of stars will form, but making them collapse into stars is harder than it might seem. Turbulent motions within these clouds, fed by energy injected from larger size scales, can provide support against gravity, and in some cases, may even blow a cloud apart.

The battle between gravity and turbulence can be traced with radio wavelength observations of the emission from molecules in the cloud. These observations provide information on both the spatial distribution and dynamical state of the gas. The purpose of this REU program is to make use of radio observations to better understand how these clouds of raw materials organize themselves to form stars and/or groups of stars.

The project is observational in nature, and will involve analysis and interpretation of radio observations. Candidates for this project should be comfortable in a computer environment and have good organizational skills. Some experience developing scripts and/or algorithms for manipulating datasets would be a plus.

Project Name: Radio--X-ray observations of Nearby Active Galactic Nuclei
Project Mentor: Jack Gallimore
Project Code: (JFG-1)

Active galactic nuclei are thought to be powered by the accretion of interstellar gas onto a supermassive black hole. The extreme conditions manifest in a range of observed phenomena, including luminous thermal X-ray emission and the the production of relativistic, non-thermal plasma. The light from an active nucleus is however affected by dilution from surrounding starlight and obscuration by interstellar dust, both of which modify the radiation spectrum before it leaves the host galaxy. We are compiling new and archival observations across the electromagnetic spectrum in an attempt to disentangle the true spectrum of the active nucleus. Our goals include investigations into the role of star-formation on the occurrence and evolution of the active nucleus and the impact of relativistic plasma on the evolution of the host galaxy.

Project Name: Development of an Evanescent Wave Imaging System
Project Mentor: Margot Vigeant
Project Code: (MAV-1)

The goal of this project is two-fold, containing both experimental and theoretical elements. The experimental goal is to optimize the operation of a multiple angle total internal reflection aqueous fluorescence (MA-TIRAF) microscope, a unique laser-powered light microscope capable of imaging nanometer-scale distances between cells and surfaces. Currently, the data generated from this microscope may only be analyzed if the laser light is polarized in a certain way. The theoretical goal is therefore to develop the mathematical description of the light needed to analyze data with alternate polarization, thus making data interpretation from the microscope significantly easier. Interest and/or experience in optics preferred!

Project Name: Nonlinear Modeling of Neural Activity
Project Mentors: Joe Tranquillo and Mark Stecker, M.D.
Project Code: (JVT-1)

The brain is made up of billions of neurons, each with their own complex and diverse range of functions. Currently modeling the brain, neuron-by-neuron is far from a reality and so some researchers have created simplified models. These simplified computer models may be either of a single neuron, or of the aggregate behavior of a group of neurons. Previous simulations identified a parameter range of one such simplified model that yielded an unexpected and new type of behavior. The proposed project will attempt to uncover the nature of this finding. A secondary project goal is to determine how the simulated neurons behave when coupled to other simulated neurons. Prior knowledge of MATLAB or Mathematica and Unix is desirable but not required.

NOTE: Dr. Stecker is based at Geisinger Medical Center in Danville, PA, which is about 20 minutes from the Bucknell campus. Applicants for this project should be aware that a significant fraction of the work will be done off-campus at the Medical Center. Although the successful applicant will live on-campus and be able to participate in all group activities associated with the REU program, the conditions of this project require someone with a demonstrated ability to work independently.

Project Name: Adsorption and Desorption Phenomena in Polymer Thin Film Formulations.
Project Mentor: Erin Jablonski
Project Code: (EJL-1)

The project will involve using atomic force microscopy and other characterization techniques to study the effects of specific small molecule additives in polymer thin film formulations that mimic those used in photolithography for integrated circuit manufacture. Small molecules can be desorbed or "leached" from the surface of polymer thin film formulations by an immersion fluid, but it is also possible for these desorbed species to re-deposit back onto the polymer thin film surface. For polymers with a sensitivity to certain small molecule additives, re-adsorption may be observed as a change in topography using atomic force microscopy. Many parameters will be considered: the composition of the polymer thin film formulation, the composition of the fluid in contact with the polymer thin film, time of immersion, and relevant surface energy effects.

Project Name: Spin-Exchange Optical Pumping of Noble Gases
Project Mentor: Martin Ligare
Project Code: (MKL-1)

Circularly polarized laser light can be used to polarize gases of alkali atoms via optical pumping. The polarization can be transferred to the nuclei of noble gases, like xenon, in spin-exchange collisions. Once polarized, the well-shielded nuclei of noble gases can remain polarized for very long times (on the order of hours). Such samples with long-lived polarizations have been used in precision measurements, as a medium for MRI imaging of the lungs, and as a tool in diagnostics of surface physics. This experimental work will focus on non-adiabatic spin-flip transitions that have been proposed for use in quantum computing.

Project Name: Theoretical Quantum Optics

Project Mentor: Martin Ligare

Project Code: (MKL-2)

Recent of observations of so-called "superluminal" light that appears to travel faster than the speed of light "c" have attracted a great deal of interest, as have observations of ultraslow light. I have investigated theoretical models in which the electromagnetic field and the medium are both treated in a fully quantum mechanical manner in order to understand these anomalous speeds at the level of a single photon. Topics for investigation in the summer of 2008 might include the following:

• Photon localization in disordered media
• Photon transport in metamedia with negative index of refraction
• Negative group velocities in media with gain.
• Photon propagation in evanescent waves.

This project will involve theoretical calculations and work with a computer algebra system. Applicants for this project should have completed a quantum mechanics course at the junior/senior level.

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