Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session B11: Society of Physics Students I |
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Chair: Gary White, AIP/SPS Room: Marriott Tampa Waterside Room 7 |
Saturday, April 16, 2005 10:45AM - 10:57AM |
B11.00001: Inverse Scattering/ Inversion of Gamows Formula Sohang Gandhi Classically it is impossible for a particle to penetrate a potential barrier exceeding its energy. In quantum mechanics, however, there is always a finite probability for such an occurrence. The transmission probability is given by Gamow's formula: \begin{equation} T(E)=e^{-{2\over \hbar}\int_{x_1(E)}^{x_2(E)}{\sqrt{2m(V(x)-E)}\,\mathrm{d}x}}, \end{equation} where $V(x)$ is the potential, $E$ the particles energy, and $x_1$ and $x_2$ are the classical reflection points. $T(E)$ can typically be easily obtained through experiment. However, the task of determining $V(x)$ is often more difficult. Hence, the inversion of Gamow's formula would provide a tool for probing physical structure. Procedures for doing so and results obtained shall be discussed. [Preview Abstract] |
Saturday, April 16, 2005 10:57AM - 11:09AM |
B11.00002: Applying Quantum Mechanics on Simple Graphs Samson J. Alva Simple graphs with links (edges) of weights either one (existent) or zero (non-existent) are considered as a model of discrete structure of ordinary space at very small scales. The links are not a part of the space but rather determine the relationships between the nodes, which constitute the physical space. The quantum mechanical propagator, intimately related to the graph Laplacian, is used to define the relative distances between nodes (vertices). Analytical methods are applied to obtain results for very small graphs (four or fewer nodes) and for certain highly symmetric graphs. Numerical methods are used for larger graphs containing clusters (cliques) of nodes to define effective inter-cluster distances. [Preview Abstract] |
Saturday, April 16, 2005 11:09AM - 11:21AM |
B11.00003: Molecular Dynamics and Monte Carlo William Holmes Molecular Dynamics (MD) and Monte Carlo simulations were constructed and compared. The basis of the MD simulation was the classical Lennard Jones potential. Due to computational constraints, simulations were limited to a thirty-eight particle hexagonal close packed shell with outlier configuration in 2-dimensions. The MD simulations were used to observe factors such as types of transitions made and the probabilities with which they were made. Two types of Monte Carlo methods were considered. The first utilized a coarse time step model. The probabilities observed in the MD simulations were used in conjunction with a random number generator in order to determine whether or not an event would occur in the given time step. The second method used the exponential distribution to give probabilistic times for an event to occur and forced the one with the minimum time to occur. Both methods were compared to the MD simulations and exhibited similar agreement but the second was significantly faster. Current work is being done to deal with the complexity of allowing for multiple outlier particles along with interactions with the stable magic shell. [Preview Abstract] |
Saturday, April 16, 2005 11:21AM - 11:45AM |
B11.00004: Negative Ions of Bucky-dumbbells Olga Ovchinnikov, Robert Compton A photochemical route to the formation of two C$_{60}$ molecules which are bridged by one and up to ten carbon atoms to form a bucky-dumbbell shaped molecule, i.e., C$_{60}$=C=C$_{60 }$to$_{ }$C$_{60}$=C=C=C=C=C=C=C=C=C=C=C$_{60}$, will be described. Irradiation of C$_{60}$ in solutions of chloroform and iodine (magenta color) with pulsed laser light from the frequency tripled (355 nm) Nd:YAG laser produced a dark crimson color. Matrix assisted laser desorption ionization (MALDI) mass spectroscopy using negative ions was used to examine the irradiated fullerenes. Irradiation of solutions under low laser power for short periods of time ($\sim $ 1 hr) gave exclusively C$_{60}$=C=C$_{60}$ negative ions. Higher power and longer irradiation times ($\sim $ 3 hrs) produced C$_{60}$=C$_{n}$=C$_{60}$ negative ions with n = 1 to 10. All values of n are equally abundant. High performance liquid chromatography was used to separate the bucky-dumbbells from the dominant C$_{60}$ molecules, confirming the production of the dumbbells in the solution and not in the MALDI. Experiments are underway to examine the multiply charged negative ion properties of these molecules. These studies include electron attachment to the singly charged negative ion, electrospray mass spectroscopy and charge transfer collisions between singly-charged anions and molecules. [Preview Abstract] |
Saturday, April 16, 2005 11:45AM - 11:57AM |
B11.00005: Spatial Resolution of CT/PET Images Daniel Mitchell There are many considerations to make when addressing issues in Computational Tomography/Positron Emission Tomography (CT/PET) image resolution. Through a combination of gating techniques, dosage adjustments, and dwell time optimization, the inherent ``blur'' of PET images con be reduced greatly. This correction must be more exact for patients carrying an excess amount of adipose tissue; and can be shown as a direct relation to increasing weight. [Preview Abstract] |
Saturday, April 16, 2005 11:57AM - 12:09PM |
B11.00006: Video-Based Motion Analysis Paul French, Joel Peterson, Julie Arrighi Video-based motion analysis has recently become very popular in introductory physics classes. This paper outlines general recommendations regarding equipment and software; videography issues such as scaling, shutter speed, lighting, background, and camera distance; as well as other methodological aspects. Also described are the measurement and modeling of the gravitational, drag, and Magnus forces on 1) a spherical projectile undergoing one-dimensional motion and 2) a spinning spherical projectile undergoing motion within a plane. Measurement and correction methods are devised for four common, major sources of error: parallax, lens distortion, discretization, and improper scaling. [Preview Abstract] |
Saturday, April 16, 2005 12:09PM - 12:21PM |
B11.00007: Resonant-cavity tests of Lorentz invariance Alexander Petroff, Matthew Mewes Highly suppressed violations of Lorentz invariance are candidate signals for new physics with Planck-scale origins. We examine a class of experiments based on the resonances of electromagnetic cavities that are sensitive to possible violations. In particular, we study potential increases in sensitivity that might be obtained by utilizing cavities with different geometries. [Preview Abstract] |
Saturday, April 16, 2005 12:21PM - 12:33PM |
B11.00008: Studying Flame Structures in Free Fall. Dmitriy Plaks, James Espinosa, Elizabeth Nelson, Zade Coley, Cathy Tran, Nesha Hyatt, Ben de Mayo We are studying the effects of acoustics on a flame in microgravity. Our research is meant to provide a new approach to reducing and extinguishing a combustion reaction in space (where a conventional fire extinguisher is hazardous). Our setup includes an interior cage, inside of which is a candle; four speakers surround the cage, which are used to manipulate the flame. A video camera, infrared camera, light sensor, and microphone are placed in various locations throughout the setup to collect data. The master computer records all data and is later used for data analysis. We will describe the experimental apparatus in more detail, which will be flown aboard a NASA DC-9 Aircraft. We will show 1g data collected with the apparatus and briefly describe NASA's Reduced Gravity Student Flight Opportunities Program (RGSFOP). [Preview Abstract] |
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