7th Annual Fall Meeting
A Joint Meeting of the NCS-AAPT, SACS-AAPT, and SPS
UNC Asheville
November 1-2, 2002
Zone 5 SPS Councilor, Host: Michael J. Ruiz, UNC-Asheville, NC
Zone 5 SPS Associate Councilor, Host: Kwayera Davis, College of Charleston, SC
Local SPS Advisor, Host: Randy A. Booker, UNC-Asheville, NC
Local AAPT Host: Chuck Bennett, UNC-Asheville, NC
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1:00 p.m. The Electronic Structure of Chlorophyll a Cation Radicals as Determined from ESEEM Spectroscopy [Best Undergraduate Student Paper, Awarded by the NCS-AAPT]
Jean Rockford* and Michelle Mac** (Advisor), College of Charleston, *Department of Physics and Astronomy, **Department of Chemistry and Biochemistry, 66 George Street, Charleston. SC. 29424, (843) 953-1405, Fax: (843) 953-1404, jrockfor@edisto.cofc.edu, macm@cofc.edu
Chlorophyll a, ubiquitous in the photosynthetic systems of higher plants and cyanobacteria, provides a system that can be studied experimentally both in vivo and in vitro, but whose information rich ESEEM (Electron Spin Echo Envelope Modulation) spectra are not well understood on a theoretical level. Through experimental trials and computer simulation of the ESEEM spectra of the chlorophyll a cation radical in vitro and in vivo, the structure-function relationship of this molecule can be discovered. Multiple simulations of experimental spectra of the radical species in vitro, methodically varying the paramagnetic parameters, provide the breadth of information necessary to unravel the complexities observed and ultimately understand the electronic structure of these radicals in the proteins. Information garnered from these studies can be used as a template for analogous experiments on the cofactors in vivo and ultimately as a starting point for the development of human designed photosynthetic systems.
1:15 p.m. The Internal Luminosity function of Gamma-Ray Bursts
Andrew Stallworth, Dept. of Physics & Astronomy, College of Charleston, 66 George Street, Charleston. SC 29424, wastintime@comcast.net
Gamma-ray bursts (GRBs) are the most energetic phenomena in the universe. Although the observed properties of GRBs have provided valuable insights into the physics driving them, much about them is still shrouded in mystery. One GRB property that appears to be potentially useful in exposing underlying burst physics is the Internal Luminosity Function. The Internal Luminosity Function (ILF) is defined as the differential distribution of luminosity measured within a gamma-ray burst (Horack & Hakkila, Astrophysical Journal 479, 371, 1997). The procedures used to measure this distribution from BATSE (the Burst And Transient Source Experiment on NASAs Compton Gamma Ray Observatory) data are discussed. Also discussed is a current effort to compile a database of GRB ILFs and to search for correlations between the ILF and other measured GRB properties.
1:30 p.m. Light Dosimetry for Esophageal Photodynamic Therapy
Brooke D. Bivens*, Linda R. Jones Ph.D* and Michael B.Wallace M.D. MPH** (advisors), *College of Charleston, Department of Physics and Astronomy, 66, George Street Charleston, SC 29424, (843) 953-4985, **Digestive Disease Center, Medical University of South Carolina 96 Jonathan Lucas Street Suite 210 CSB PO Box 250327 Charleston, SC, 29425 brookedbivens@hotmail.com, jonesl@cofc.edu, WallaceM@musc.edu
Photodynamic therapy (PDT) is a cancer treatment that combines visible light and a photosensitizing dye, neither of which have any effect alone. PDT with Photofrin is used clinically for the treatment of esophageal dysplasia, a pre-cancerous condition that often accompanies Barrett's Esophagus. The objective of this project was to develop a clinical method to quantify the concentration of sensitizer in vivo for optimization of the light dose. Endoscopic spectroscopy can be utilized to measure the fluorescence emission of the tissues to be treated. Photofrin has characteristic fluorescence emission peaks throughout the visible region; however endogenous fluorophores interfere with the analysis. A previously developed tissue phantom was modified to simulate the fluorescence of normal as well as dysplastic tissues. After placing different concentrations of Photofrin into the tissue phantom, the peaks in the various emission spectra were normalized with the reflectance measurements. Unique Photofrin-induced excitation and emission values were identified.
1:45 p.m. Evaporative Cooling in a Penning Ion Trap
Anders K. Langworthy, John N. Yukich, Davidson College, Physics Department, PO Box 7133, Davidson, NC 28035-7133, (704) 892-9003, anlangworthy@davidson.edu
Resolution of spectroscopic structure in photodetachment from negative ions has in the past been limited by thermal broadening effects. Recently we have developed an evaporative cooling technique to reduce the average temperature in an ensemble of ions created in a Penning trap. We describe the current state of the project as well as future directions.
2:00 p.m. Global Heat and Momentum fluxes related to the North Atlantic Oscillation
Nathan Woodward* and Varavut Limpasuvan** (Advisor), Department of Marine Science, **Department of Chemistry and Physics, Coastal Carolina University, P.O. Box 261954, Conway, SC 29528-6054, (843) 349-2826, Woodm4457@aol.com, var@coastal.ed
The North Atlantic Oscillation (NAO) is a dominant mode of wintertime climate variability in the Northern Hemisphere. While previous studies have documented strong correlations between the NAO and various weather phenomena over the Eurasian continent and eastern North America, the driving mechanisms of the NAO have been in question. The divergence of the heat and momentum fluxes by atmospheric waves can force changes in the atmospheric circulation. Based on composite techniques using 42-year data set from the National Center for Environmental Prediction (NCEP), the potential influences of these wave fluxes on the NAO are investigated in this research. Knowledge of the wave influences may provide further insights into the NAO characteristics and its recent trend.
2:15 p.m. Java 3D Simulations of Rigid Body Dynamics
Adam Abele and Wolfgang Christian, Physics Department, Davidson College, Box 7133, Davidson 28035, adabele@davidson.edu.
Programming 3D physics simulations presents two challenges. The first challenge is the physics and the mathematics since the modeling of interesting three-dimensional phenomena is often difficult. Euler angles, for example, cannot be used to numerically solve the rigid body problem due to singularities in the differential equations. The second challenge is the visualization itself. This paper presents a new Java library that utilizes Java 3D to create, organize and manipulate 3D worlds for physics simulations. This library has been used to simulate rigid body dynamics using Hamiltons quaternions as an alternative to the Euler angle solution. A generalized solution for the rigid body rotation problem will be presented.
Programs will be available on the Open Source Physics website, http://www.opensourcephysics.org/.
This work is generously supported by the National Science Foundation (DUE-0126439).
2:30 p.m. Break
3:00 p.m. Finding Variable Stars in Globular Clusters Observed by Hubble Space Telescope
Kwayera Davis, College of Charleston, Department of Physics & Astronomy, 101 Science Center, 58 Coming St., Charleston, SC, 29403, (843)953-5593, kwayera_d@hotmail.com
An image of the globular cluster M54 from the Hubble Space Telescopes WFPC2 (Wide Field Planetary Camera 2) has been analyzed for the presence of variable stars. The QDPHOT (Quick & Dirty CCD Stellar PHOTometry) software package for the IRAF (Image Reduction and Analysis Facility) astronomy program was used to create a color-magnitude diagram for the cluster. The presence of many stars in the RR Lyrae segment of the instability strip motivated us to statistically analyze the photometry yielded for the presence of these variables. Out of some 13,000 stars visible in the cluster approximately 1000 variable candidates were identified. We believe that with further work we will be able to definitively identify these stars as variables. This research was conducted as part of the Kitt Peak National Observatory: Research Experiences for Undergraduates Program at the National Optical Astronomy Observatory in Tucson Arizona.
3:15 p.m. Design, Development, and Testing of a Transient Capacitance Spectroscopy System
Kiril Simov and Tim Gfroerer, Davidson College, Physics Department, PO Box 7133, Davidson, NC 28035, phone: (704) 894-2319, fax: (704) 894-2894, kisimov@davidson.edu and tigfroerer@davidson.edu
Defect-related trapping and recombination limit the performance of a wide variety of semiconductor devices. Hence, it is important to determine how the concentration and energetic position of defect levels depend on alloy composition and device structure. Photoluminescence spectroscopy is a very sensitive probe of radiative levels but it cannot detect states that couple weakly with light. Transient capacitance spectroscopy (TCS) is a complementary electrical transport technique that can be used to study these nonradiative centers. In TCS, one monitors the transient capacitance of a nonequilibrium p-n junction to probe changes in trap occupation. The measurement is performed over a range of temperatures so that thermal activation can be used to gauge the depth of the traps. We report on the development and testing of a versatile TCS system that uses the LabVIEW development environment to acquire and analyze temperature-dependent transient capacitance data.
3:30 p.m. Forced Oscillations with Nonlinear Friction
Chris Schmitt and Xiaojun Wang (advisor), Department of Physics, Georgia Southern University, Statesboro, GA 30460, Tel: (912) 681-5292, E-mail: Mobius64_99@yahoo.com
Experiments of forced oscillation with a constant frictional force are commonly discussed in general and classical mechanics texts, though the dominating friction involves a nonlinear dependence on the velocity. In this presentation, the constant sliding friction was reduced to become negligible, allowing the air friction to become dominant. A slider car was positioned between two stretched springs on an air track where a sinusoidally driven arm provides the forced oscillations. A sail was attached to the car, providing a quadratic damping due to the air friction. By varying the area of the sail it will vary the degree of dominance to the quadratic damping as well as the broadness of the resonance curve. An analytical solution for the differential equation of motion is obtained after several approximations. The experimental results agree very well with the theoretical prediction.
3:45 p.m. Swimming in 3d Optical Lattices
Lisa M. DeBeer, Georgia Southern University, 8031 Georgia Ave., Statesboro, GA 30460, 912-681-5292, ldebeer@gasou.edu
The goal of this project was to create a set of tools that aid both theorists and experimentalists in visualizing the optical potentials created by lasers applied to Bose-Einstein condensates and the energy spectra of these potentials. An important step along the road to the realization of a neutral-atom as quantum- computational device is the ability to manipulate atoms in an ultra-precise way. One method to accomplish this is by trapping a Bose-Einstein condensate (BEC) in a space-periodic optical potential created by counter-propagating laser beams called an "optical lattice." A Bose-Einstein condensate is a collection of atoms that all share the same quantum-mechanical wave function. Understanding the behavior of BEC's in optical lattices should be key to the design of future quantum- computing devices. Optical lattice potentials created by more than two laser beams can vary in space in a complex way so that the ability to visualize them is useful for both theorists and experimentalists. I have created a tool to perform such visualizations, it is a stand-alone program that can execute on a windows PC.
4:00 p.m. The Great Pumpkin Drop! Communicating Science to Kids
Michelle Walker, Steven Overby, Department of Physics, North Carolina A&T State University, 1601 East Market Street, Greensboro, NC 27411, (336) 334-7646, mw003447@ncat.edu , sco96@yahoo.com
Science is notorious for being dull and boring, but that does not mean it has to be taught that way! This Halloween, undergraduate physics students at North Carolina A&T State University presented a lively, one-hour long on-campus physics show called Communicating Science to Kids. This program introduced 400 third grade students to many of the magical wonders of science, with explanations tailored to their level of understanding. Musical sounds, a laser-light show, interactive demonstrations, and hands-on activities captured young hearts and imaginations. After the main event, the A&T bulldog mascot led the students in an outdoor parade to watch Aristotle and Galileo debate their contrasting views on The Motion of Falling Bodies. To help settle this dispute, we culminated our day with a giant pumpkin drop. This presentation will discuss the planning, preparation, and success of this endeavor that we hope to make an annual event.
4:15 p.m. Teaching the Quark Model of Matter Using an Activity
Sasha Salters and Joanne Yallum (Don Franklin, advisor), Battery Creek High School Blue Dolphin Drive, Burton, SC 29906, 1-800-763-1875
Teaching students difficult material needs to have a different approach. This activity is from the C3P manual and has the students competing for the Nobel prize by assembling Mesons and Baryons using various combinations of quarks. This activity also comes in handy if you are running out of time for the year, and want to assign the activity for out of class experience.
4:30 p.m. Mapping Kinetic Energy Flow Through an Organic Crystal
Christopher Garrick and Kristen Krantzman (Advisor)*, College of Charleston, Department of Physics and Astronomy, Department of Chemistry and Biochemistry *, 66 George St. Charleston SC 29424, Ph.: (843)953-5593, ctgarric@edisto.cofc.edu
Secondary Ion Mass Spectrometry (SIMS) is am analytical technique used to identify organic molecules that are in a solid state. This technique involves hitting an organic solid with an ionic projectile in order to eject molecules from the solid and into the gas phase so that the molecules can be analyzed by spectroscopy. I am studying the transfer of kinetic energy through an organic crystal of benzene during SIMS. This model uses classical mechanics to find the position, velocity, and energy of each atom in the crystal at 10fs time intervals. I am using Mathematica and Microsoft Excel to plot the energy of each atom of the crystal with respect to its initial position in the crystal. This research is important to help understand the types of collisions that take place during SIMS and to find a suitable and predictable technique for producing these molecules in a stable form.
4:45 p.m. Preliminary Tests of a Low-Cost Solar Infrared Adaptive Optics System
S. M. Ammons (Duke University Physics Dept.) and C. U. Keller (National Solar Observatory)
Images produced by the National Solar Observatory's McMath-Pierce telescope on Kitt Peak, the largest solar telescope in the world, have been at the mercy of atmospheric turbulence for decades. Work is currently underway to install a low-cost adaptive optics (AO) system with the goal of correction in the infrared region of the spectrum for a total hardware cost of $25k. As a preliminary step a slow AO system was constructed in the lab to demonstrate the feasibility of the low-cost approach. The design is a simple feedback loop that reads the wavefront shape with a Hartmann wavefront sensor and makes corrections through a micromachined membrane deformable mirror. A computer calculates the voltages to adjust the 37-actuator mirror based on the wavefront information. The system operates at 1 Hz and is able to correct a distorted laser wavefronts within several cycles. This test paves the way to deploy a faster version of this system that runs at 500 Hz. This work is carried out through the National Solar Observatory Research Experience for Undergraduates (REU) program, supported by the National Science Foundation.