Physics faculty and students are very involved in research. At any given time there are three or four active programs in the Department. Several students typically work with faculty on their research over the summer months and can even be co-authors of published papers. Also, as part of the curriculum, students must complete some original research for their Senior Comprehensive project (the Comp). Frequently they choose to work with faculty in their field of study and can even end up publishing the results. But students can also branch out and do work in an area outside the existing programs, depending on their interests.
Below you will find brief descriptions of the active research programs in the Physics Department. Also included is a list of recent Comp projects in each group. You can even browse the entire Comp archive.
Biophysics (Petasis Group)
My research is focused on the study of the active centers of metalloproteins using Electron Paramagnetic Resonance (EPR) and related spectroscopic techniques. Metalloproteins are important biological species with vital functions in many living systems, such as oxygen transport and storage in humans, photosynthesis in plants, and nitrogen fixation in bacteria. EPR is particularly suited for this kind of research since it can single out the paramagnetic species at the active site of a metalloprotein and tell us what it is, what valence state it is at, and how it interacts with the surrounding ligands and with other ions. With this information, the structure of the active site can be determined, enabling us to understand how the protein works.
One of our major projects is the development of a rare earth crystalline thermometer for frozen EPR metalloprotein samples. The need for such a thermometer arose from the fact that precise knowledge of the temperature of such samples studied in commercially available EPR spectrometers is not possible. This is due to the inherent limitations of the liquid helium continuous-flow cryostats employed. Single crystals of cerium trifluoromethane sulfonate can be incorporated within protein samples and give us accurate information on the temperature of the protein sample. We are attempting to grow such crystals, characterize them and find ways of incorporating them within the protein samples.
Other projects currently underway are: EPR measurements of the enzyme Cytochrome c554, a protein with a new type of a tetra-heme cluster that has important functions in metabolic pathways (collaboration with the Hendrich group, Department of Chemistry, Carnegie Mellon University); Development of an electron-nuclear double resonance (ENDOR) accessory for the Q-band (34 GHz) EPR spectrometer at Carnegie Mellon University; EPR studies of color centers in mineral single crystals (collaboration with the Carnegie Mellon Research Institute).
Recent Senior Projects:
- Synthesis of Rare Earth Crystalline Thermometers for Low Temperature Metalloprotein EPR Measurements (Michael Spilatro, 2007)
- Synthesis of Ce:YES Crystalline Thermometers from Alcohol Solutions to Determine the Temperature of EPR Metalloprotein Samples (Hikmat Daghestani, 2006)
- Electron Paramagnetic Resonance of Color Centers in Precious Gems (Adam Duncan, 2006)
- Analysis of an Unknown Purple Protein using Electrochemical Electron Paramagnetic Resonance Techniques (Jonathan Schmitt, 2006)
- Synthesis of Rare Earth Crystalline Thermometers for Low Temperature Metalloprotein EPR Measurements (Colby Mangini, 2004)
Nonlinear Optics (Statman Group)
We (my students, collaborators and I) have been looking at the interaction of light with matter to see how that interaction affects the properties of the light signal. One type of interaction of interest to us is the nonlinear optical interaction. This is where the light actually changes the optical properties of the material. Two classic examples include (1) frequency doubling, where the light/matter interaction is such that the matter doubles the frequency, halves the wavelength, of the light, and (2) self focusing, where the light turns the material into a lens and starts to focus in on itself.
For most materials, the intensity of the light must be very high to observe any nonlinear effects. Two exceptions, however, are photorefractive ceramics and liquid crystals, both of which exhibit third order effects at low light intensities. These materials have demonstrated the nonlinear optical process referred to as four-wave mixing, where three beams of laser light interact with one another to produce a fourth beam whose properties are determined by the original three. Four-wave mixing is useful to such technologies as dynamic holography. In our lab, we have, in fact, demonstrated dynamic reconstruction of a distorted image (where the distrotion was thereby removed) using four-wave mixing.
By studying the dynamics of four-wave mixing processes, we have been able to begin to develop an understanding of the processes that allow theses materials to demonstrate nonlinear optical properties at low intensities. In particular, we are looking at the effect of different dopants on the material system, and how those dopants change the nonlinear optical dynamics. We are also exploring areas of application for these nonlinear optical systems.
Recent Senior Projects:
- Intensity and Polymer Dependence of Photoinduced Azimuthal Gliding in Azo Dye-Doped Nematic Liquid Crystals (Valerie Basore, 2007)
- Spatial Solitons in Azo Dye-Doped Nematic Liquid Crystals (David Barnes, 2006)
- LCPCF Bandgaps And Their Properties in the Visual Range (Matthew Geiger, 2006)
- Director Gliding in the Reorientation of Dye-Doped Nematic Liquid Crystals (Vincent Werner, 2006)
- Surface Effects in Azo Dye-Doped 5CB Nematic Liquid Crystal Cells (Zachary Cataldi, 2005)
Low-Temp Microwave Spectroscopy (Willey Group)
The research which we perform is focused towards understanding the dynamics of collisions between molecules in a low temperature gas. Using liquid helium (4.2 K) and a special technique called collisional cooling, we can cool molecules down to temperatures of 5 K, five degrees above absolute zero. We then use microwaves to probe the molecules and gain information regarding the forces which mediate collisions in the gas. The molecules we choose to study are ones which are present in the interstellar medium, the clouds of dust and gas between stars. Many of these clouds are also very cold (10 - 100 K) and the data we gather can be used to gain insight into the collisional process occurring in these cold molecular clouds and help to determine their density, temperature and age.
We also operate a small radio telescope located on top of Carr Hall. This telescope is sensitive to the radio emissions of hydrogen atoms present in the Sun, planetary atmospheres and the interstellar medium. The wavelength of the hydrogen emission we observe, 21 cm, is also the wavelength which many believe an extraterrestrial intelligence would use to communicate with other civilizations in our galaxy, so perhaps one day we may hear E. T.!
Recent Senior Projects:
- An Investigation of Low Temperature Ammonia-Helium Collisions: State-to-State Cross Sections (Mark Delaney, 2006)
- An Investigation into Low Temperature Collisions: Carbonyl Sulfide-Helium (Bryan Lyssy, 2006)
- Experimental Investigation of Collision Induced Rotational Intra-Doublet Energy Transfer Rate of NH3 by He at 8 K (Michael Dean, 2005)
- An Investigation into Low Temperature Collisions: Ammonia - Helium (Joseph Ribaudo, 2005)
- Low Temperature Energy Transfer Studies of Ammonia-Helium Collisions (Ibrahim Sulai, 2004)
Soft Materials and Surfaces (Poynor Group)
Currently, my research is focused on how water interacts with hydrophobic surfaces. By definition, hydrophobic surfaces hate water. When large, rigid hydrophobic surfaces are forced into contact with water, the water will pull back leaving a low density region with a thickness of a few Angstroms. What happens when water meets smaller or more flexible hydrophobic regions is still unknown.
To investigate these questions, I use highly sensitive surface techniques such as Surface Plasmon Resonance (SPR) and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR).
Astrophysics (Lombardi Group)
My research students and I work in computational astrophysics. We use Smoothed Particle Hydrodynamics (SPH) calculations to study stellar interactions, and, in particular, stellar collisions and mergers. One environment where stellar interactions occur frequently is a so-called globular cluster. Globular clusters are collections of many hundreds of thousands of stars found in galactic halos, the sparse region outside of the disk of a galaxy, and are thought to have formed early in the evolution of the universe.
One exciting aspect of dense stellar systems such as globular clusters is the simultaneous importance of three principal areas of stellar astrophysics: dynamics, evolution, and hydrodynamics. Many simulation codes focus on one of these areas and have often been lifelong works in progress. The first attempts at unifying these treatments into a coherent model to describe clusters have begun only recently (see the MODEST home page). Attempting to integrate stellar dynamics, evolution, and hydrodynamics codes into one fully functional package will be challenging, largely because each area treats stellar properties that evolve on different time-scales. However, by combining these areas, we will be able to better model the origins, dynamics, evolution, and death of globular clusters, galactic nuclei, and other dense stellar systems.
At Allegheny, our focus is on modelling hydrodynamic interactions between stars. There are many types of exotic stellar objects that may be formed from stellar mergers and collisions, including blue stragglers, binary neutron stars, ultracompact X-ray binaries, catacylsmic variables, helium stars, and rapidly rotating horizontal branch stars. One of our goals is to develop a software module for quickly generating collision product models, ultimately for any type of stellar collision, that could be incorporated into simulations of dense star clusters.
Recent Senior Projects:
- Formation of Massive Stellar Objects and Intermediate Mass Black Holes Due to Runaway Collisions in Young Dense Star Clusters (Valerie McVay, 2007)
Theoretical Research (Rahman Group)
Prof. Rahman's research deals with phase transitions in anti-ferromagnetic systems, in particular, with Monte-Carlo simulation of anti-ferromagnetic Potts model.
A perfect magnet (ferromagnet) derives its properties from the fact that all the electrons in the system have their spins pointing in the same direction. In an anti-ferromagnet, on the other hand, neighboring spins point in opposite directions. Many materials show anti-ferromagnetic behavior. The problem gets considerably more complex when the number of possibilities at each location is not just two (spin up and spin down as for an electron), but more. An alloy made of more than two materials can be thought of as an example of such a system. "Potts model" deals with this latter situation. One designates the number of possibilities at each atomic location with q (for example, q=3). These are complicated problems that can only be handled by computer simulation.
With the advent of cluster flip methods that combine ideas from Percolation theory and Monte-Carlo simulation, these problems can now be handled in a way such that one can be reasonably confident about the validity of the results. Over the past several years, students have systematically worked with the anti-ferromagnetic Potts model on a cubic lattice for various q-values (q=3,4,5,6).
Recent Senior Projects:
- Ising Model Simulation of a Two-Dimensional Antiferromagnetic Triangular Lattice (Sean Laird, 2006)
- Computational Solution of the Antiferromagnetic Potts Model (Brandon Redding, 2005)
- Five State Antiferromagnetic Potts Model: Monte Carlo Simulation (Joshua Monk, 2003)
- Efficient Use of Monte Carlo Simulation Data Through the Use of the Single Histogram Method (Charles Ruggiero, 2002)
- Using the Monte Carlo and Single Histogram Methods to Study the Energy and Magnetization of Complex Systems (Robyn Nelson, 2001)
Other Student Research
Here are some of the recent student projects that have been conducted that lie outside existing areas of faculty research:
- Radio Waves from the Heavens: The Study of Radio Signals from Space (Michael Fisher, 2007)
- Solar at Allegheny: Model for the Future (Maggie Surface, 2007)
- A Study of Secondary Rays and the Construction of a Secondary Cosmic Ray Detector (Justen Altemus, 2006)
- Underground Exploration through Resistivity Surveying (Joshua Oidick, 2006)
- An Investigation Into Phenomena: Sunspots (Aaron Rape, 2006)