Bulletin of the American Physical Society
2007 Ohio Section APS/SOS/AAPT Joint Fall Meeting
Volume 52, Number 15
Friday–Saturday, October 19–20, 2007; Oxford, Ohio
Session P1: Poster Session |
Hide Abstracts |
Chair: Khalid Eid, Miami University Room: Shriver Center Multipurpose Room |
|
P1.00001: Characterization of damping force in a magnetic damping device Willis Agutu, Michael Pechan, Joeng-Hoi Koo Self-powered damping systems are interesting from both application and fundamental perspectives. In order to optimize efficiency in a damping system, it is necessary to effectively model the underlying mechanism of damping. We have constructed a magnetic damping device with a magnet traversing a coil of wire to measure the dynamic damping force directly by a strain gauge attached to the coil. This was compared to a model developed by Saslow [1] which calculates the force on a current carrying loop in a magnetic field gradient. By simultaneously measuring force, induced current and magnetic field intensity, we confirm the applicability of the model to magnetic damping. [Preview Abstract] |
|
P1.00002: Magentic Levitation Zachary Brown The idea of magnetic levitation is an attractive concept for the trains of tomorrow.~ The efficiency of this idea was explored using a rotating array of magnets, and a copper sheet. The array was placed on a rotating disc, with a copper plate placed at varying separation distances from the array. As the magnetic field was rotated, a magnetic force was induced in the copper plate, causing it to repel the array. The force exerted on the plate was then measured as a function of separation distance and power input to determine the maximum ratio of output force to input power. Future plans include varying the material and construction of the plate, as well as possibly trying to determine the effect of eddy currents on the project. [Preview Abstract] |
|
P1.00003: Applications of Inorganic Platinum Complexes for the Production of H2 as an Energy Source Christopher Lemon, Pingwu Du, Richard Eisenberg Due to the world's ever increasing energy demands, alternative energy sources must thoroughly be explored. One method is to harness solar power and cause the dissociation of water into hydrogen and oxygen gas. This is an ideal situation since both sunlight and water are abundant. Through a process of photo- induced charge separation and a series of electron transfer processes, two aqueous protons are reduced to hydrogen gas. Inorganic metal complexes are one approach to collecting solar photons. In this investigation platinum compounds of the form Pt (diimine)(dithiolene) were synthesized. The photochemical and photophysical properties of these molecules were thoroughly examined. Absorbance spectra were obtained as well as an emission spectrum at 77K. Two experiments were executed to test the ability of the complex to produce hydrogen. However, no hydrogen gas was evolved using the present system. Further refinement of reaction conditions is necessary to completely evaluate the potential of these compounds. [Preview Abstract] |
|
P1.00004: Optogalvanic transients in a neon discharge plasma Naveed Piracha, Ryan Feaver, Tariq Gilani Time dependent optogalvanic signals induced by the 1s$_{4}$-2p$_{n}$ laser excitations have been studied in the neon DC plasma. The decay rates related to all the four 1s levels have been derived by fitting the waveforms with a mathematical rate equation model. The temporal signatures of the two transitions namely 638 nm and 650 nm related to the 2p$_{7}$ and 2p$_{8}$ upper levels, respectively, have been found different from the rest of the transitions. [Preview Abstract] |
|
P1.00005: Fiber - Optic Devices as Temperature Sensors for Temperature Measurements in AC Magnetic Fields Corneliu Rablau, Joseph LaFrance, Anca Sala We report on the investigation of several fiber-optic devices as potential sensors for temperature measurements in AC magnetic fields. Common temperature sensors, such as thermocouples, thermistors or diodes, will create random and/or systematic errors when placed in a magnetic field. A DC magnetic field is susceptible to create a systematic offset to the measurement, while in an AC magnetic field of variable frequency random errors which cannot be corrected for can also be introduced. Fiber-Bragg-gratings and thin film filters have an inherent temperature dependence. Detrimental for their primary applications, the same dependence allows one to use such devices as temperature sensors. In an AC magnetic field, they present the advantage of being immune to electromagnetic interference. Moreover, for fiber-Bragg-gratings, the shape factor and small mass of the bare-fiber device make it convenient for temperature measurements on small samples. We studied several thin-film filters and fiber-Bragg-gratings and compared their temperature measurement capabilities in AC magnetic fields of 0 to 150 Gauss, 0 to 20 KHz to the results provided by off-the-shelf thermocouples and thermistor-based temperature measurement systems. [Preview Abstract] |
|
P1.00006: The Long-term Rotational Behavior of Ceres and Vesta Tiandan Wu, S.G. Alexander, N.P. Abel The DAWN mission which was launched in September of 2007 will visit both the dwarf planet Ceres and the asteroid Vesta. We have calculated the long-term (10 My) evolution of the obliquity of these two objects using a gravitational N-body simulation. For each object, we calculate the obliquity fluctuations for three cases: the first is with the entire solar system present; the second includes just Jupiter and the Sun; and the final is just the Sun. Our results indicate that Jupiter is the dominant perturber for both Ceres and Vesta. In the full solar system case, we find that both Ceres and Vesta show fluctuations in their obliquities with a range of approximately twenty degrees and periods of about 20 ky for Ceres and about 50 ky for Vesta. We show that these fluctuations are not due to inclination variations, but are due to changes in the orientation of the spin axis. Large variations in the obliquity of Ceres and Vesta may have a significant impact on the evolution of their surface characteristics. [Preview Abstract] |
|
P1.00007: General Relativity Effects for Close In Gas Giants Sandipan Basu, Stephen Alexander Tests of Einstein's general theory of relativity (GR) did not provide an experimental foundation for the theory until well after it was introduced in 1915. Physicists accepted the theory because it correctly accounted for the precession of the perihelion of Mercury which is about 43 arc seconds per century. To date almost all of the extrasolar planets that have been discovered are Jupiter sized gas giants in orbits very close to their parent stars. There has been much work on the orbital stability and somewhat less work on the rotational stability of possible terrestrial planets in systems with close in Gas giants. In this research project we are testing the N-body code by calculating the precession of the perihelion of Mercury. We are ultimately concerned with the GR effects on extrasolar systems. We propose to include the effects of GR to the lowest order on the orbits of extrasolar systems to see if this has important effects on the orbital and/or rotational stability of any terrestrial planets in the system [Preview Abstract] |
|
P1.00008: Transits of Extrasolar Planets and Analysis Methods Joseph Fritchman Using Wittenberg's 10-inch refracting telescope housed in Elgar Weaver Observatory, and an ST-8XE CCD camera, the egress of the transit of planet HD209458 `b' was observed on the night of December 18$^{th}$, 2006. This transit occurs when the planet passes directly between its host star and the telescope on Earth, and the brightness of the star decreases by about 1.5{\%}. The brightness of the stars is measured by the number of counts in pixels in images taken as 30 second exposures over a period of 64 minutes. Data analysis techniques using Diffraction Limited's MaxImDL$^{TM}$ yield a standard deviation of less than .004 magnitudes using a sliding box averaging method. This means that a change in brightness can be measured of about .4{\%} and much dimmer transits of other planets may be recorded from this telescope. Analysis methods using MathWork's MATLAB$^{\mbox{{\textregistered}}}$ are being developed to gain more control over how pixels are combined to determine the brightness of stars and more effective modes of combining images. [Preview Abstract] |
|
P1.00009: The Dynamics of Extragalactic Jets Nicholas Geitner, Daniel Homan We present a preliminary analysis of the motion of extragalactic jets, taken from the 2 cm/MOJAVE survey with NRAO's Very Long Baseline Array, to find and analyze jet accelerations. Most of the reliable jets we examined exhibited superluminal motion with at most small accelerations. We then examined statistical limits on these accelerations. To do so, several accelerations models were examined, including a mass loading model. It was found that mass loading has the greatest effect on fast jets directed close to our line of sight. We concluded that the levels of mass loading for all of the reliable sources were roughly 1\% mass increase or less per year. We also examined data from an expanded data set with observations up through 2006; a few jets were found with interesting and significant bends in their trajectories. One such case shows possible evidence of collimation. [Preview Abstract] |
|
P1.00010: Optical Variability of Stars in the LMC Adam Gray The majority of stars in the galaxy have constant properties for most of their lives; however, some stars vary constantly over a period of days, weeks, months, or even up to a year. Understanding how these variable stars are changing over time can help enhance the understanding of how stars in the universe evolve throughout their lifespan. By using both the infrared data collected from the nearby Large Magellanic Cloud by the SAGE survey, with two separate data epochs taken three months apart, and the optical data from the MACHO survey, with data taken from over eight years, more may be able to be understood about these varying stars. [Preview Abstract] |
|
P1.00011: Measuring Galaxy Properties in the Cluster Abell 160 Craig Koontz, Jason Pinkney We develop a procedure for building a large catalog of cluster galaxies and their photometric properties, as measured with CCDs. Our first case, Abell 160, is relatively nearby and we have already obtained spectroscopic redshifts for its brightest galaxies. We have mosaiced this cluster in R and V filters using a CCD imager on the 1.3-meter McGraw-Hill telescope. We fit a world coordinate system to the images using the software ``WCStools.'' We use ``SExtractor'' to extract sources from the images. We create software for merging catalogs in such a way as to avoid double counting, to reject cosmic rays, and to combine redundant measurements. The measured properties include magnitude, ellipticity, position angle, size, and color (V-R). We investigate the efficacy of our separation of galaxies and stars and find that it begins breaking down around R=19.0. We attempt to separate cluster members from foreground and background galaxies using the color-magnitude relation. In future work, we will investigate substructure (clumping) within clusters and its correlation with galaxy properties (especially color, size and morphology). [Preview Abstract] |
|
P1.00012: Gas and Stellar Kinematics in the Galaxy NGC 1961 Brian Sacash, Jason Pinkney Long-slit spectroscopy and CCD imaging from the Hubble Space Telescope and the MDM Observatory is presented for the massive spiral galaxy NGC 1961. We intend to measure the mass of the central supermassive black hole (SMBH). We developed our own software for spectral extraction, and for the fitting of absorption and emission lines. The program subtracts the absorption-line (stellar) portion from the emission-line spectra using a shifted template star. This improves the measurements of the residual emission lines. We present our measurements of the line centroids (velocities), widths (velocity dispersions), and strengths for the most prominent emission lines (H$\alpha $, [NII], and [SII]). The rotation curve from the ground-based data is in good agreement with previous work by Rubin (1979); its asymmetric appearance suggests a possible merger. The emission lines near the nucleus broaden indicating some intrinsic dispersion. The central gas rotation curve at HST resolution is more complex than that expected for a cold, gas disk, confounding the measurement of a central black hole. [Preview Abstract] |
|
P1.00013: Imaging Starspots on II Pegasi via Light-curve Inversion Nalin Vutisalchavakul, Ryan Deskins, Robert Harmon Starspots on the star II Pegasi were mapped via the method of Light-curve Inversion, which infers the appearance of the dark spots based on the brightness variations they produce as the star rotates. Our data were obtained with the 0.4-meter Vanderbilt/Tennessee State University Automated Photometric Telescope from September 1995 to January 1996 and from November 1988 to September 1992 (Henry, et al. 1995, ApJSS, 97, 513). For the first data set our results suggest that II Peg has opposite differential rotation to that of the Sun, with higher latitude spots having shorter rotation periods. We analyzed the second data set in an attempt to confirm this, but found that no definite conclusion could be drawn, though differential rotation is clearly present. The difficulty arises in part because the data were obtained through only two photometric filters (B and V), which limits the resolution in latitude. Future observations of the star through a larger set of filters might resolve this ambiguity. [Preview Abstract] |
|
P1.00014: A calibration approach for the rapid estimation of fluorophore excited-state lifetimes with applications in biomedicine Scott B. Keller, Joshua A. Jasensky, Hector Michael De Pedro, Eric W. Frey, Paul Urayama Nanosecond-pulse-width lasers, such as nitrogen lasers, are relatively inexpensive and are commonly used for biological and biomedical applications. Because the laser pulse width is comparable to fluorophore excited-state lifetimes ($\sim $1 -- 10 ns), deconvolution of the temporal system response is needed for accurate lifetime determination. Such deconvolution analysis can be time consuming, and so we report a method for rapid lifetime estimation based on geometric features of the time-resolved emission signal. We find that the time-integrated signal, normalized to the peak intensity, is linear with the lifetime, and can be used for calibration of the measured emission signal to the excited-state lifetime. The approach is accurate to $\sim $15{\%} despite using emission signals with low signal-to-noise ratios ($\sim $10). The approach has applications ranging from flow cytometry to fluorescence lifetime imaging microscopy. Results from fluorescence-based pH sensing are presented. [Preview Abstract] |
|
P1.00015: Entropy measures of back muscles EMG for subjects with and without pain Ulrich Zurcher, Miron Kaufman, Bryan Vyhnalek, Paul Sung We have previously reported that the time-dependent entropy $S(t) $ calculated from electromyography time series of low back muscles exhibit plateau-like behavior for intermediate times [$50 \, \mbox{ms} < t < 0.5 \, \mbox{s}$]. We proposed that the plateau value can be used to characterize the sEMG signal of subjects with low back pain [J. Rehab. Res. Dev. {\bf 44}, 599 (2007)]. We report results of a larger study, and compare the entropies for the left -and right thoracic and left- and right lumbar muscles. We also compare entropies from muscles before and after physical therapy intervention. [Preview Abstract] |
|
P1.00016: Magnetic Properties of Nanostructures John Ciraldo The recent development of the superlattice nanowire pattern transfer (SNAP) technique has enabled the fabrication of complex molecular-electronic circuits at unprecedented densities. In this project, we explore the possibility of extending this technique to generate comparably dense arrays of nanoscale giant magnetoresistive (GMR) and tunneling magnetoresistive (TMR) devices. My primary contribution to this project has focused on using a vibrating sample magnetometer (VSM), as well as a superconducting interference device (SQUID) magnetometer to monitor the magnetic properties of the devices as they are processed from thin 2D films into nanostructure arrays. This investigation allows us to investigate both fundamental and technological aspects of the nanopatterning process. For example, the effects of changing surface to volume ratios on the ferromagnetic exchange interaction and the role of various patterning techniques in determining surface chemistry and oxidation of the final nanostructures, respectively. Additionally I have worked on simulations of the materials using NIST's OOMF program, allowing me to compare actual results with theoretical expectations. I am also designing a magneto-optical Kerr effect (MOKE) detector, which will allow faster approximations of magnetic behavior. [Preview Abstract] |
|
P1.00017: Suppression of Quantum Fluctuations in a Josephson Junction Coupled to a Nanomechanical Resonator Yaser Helal, Joshua Schiffrin, Brad Trees The behavior of a Josephson junction (JJ) in parallel with a nanomechanical resonator was studied. The JJ was treated as a particle trapped in a quadratic potential well, and the problem could thus be characterized as two coupled harmonic oscillators. The Feynman path integral technique was used to find the density matrix and partition function for the system. When coupled to the resonator, the square of the uncertainty in the position of the JJ particle was suppressed, i.e. quantum fluctuations of the JJ were reduced by the resonator. The uncertainty principle was obeyed in that the square of the uncertainty in the JJ's momentum was enhanced with resonator coupling. We also included the effects of environmental damping. Damping the junction enhanced the suppression of quantum fluctuations beyond that due to resonator coupling alone. Damping the resonator, however, weakened the effect of JJ-resonator coupling and thus resulted in less suppression of quantum fluctuations. Preliminary results for the effects on quantum fluctuations of a weak nonlinear term in the JJ's potential energy have also been obtained. [Preview Abstract] |
|
P1.00018: Investigating the Diffusive Behavior of HPC with DLS and FPR Ryan McDonough, Paul Russo, Kiril Streletzky The study of the dynamic properties of HPC (Hydroxy-propyl-cellulose) in aqueous solution through the experimental techniques of FPR (Fluorescence Photo-bleaching Recovery) and DLS (Dynamic Light Scattering) has shown empirical inconsistencies in observed polymer dynamics. The approach to analyzing the inconsistencies consisted of preparing fluorescently labeled and unlabeled HPC solutions at a range of concentrations from the same stock solution. Results from DLS have indicated the reliable presence of a slow mode of diffusion. The slow mode appeared in FPR experiments, but not reproducibly. In addition, results from DLS on labeled and unlabeled HPC have found startling differences in line shape of correlation function indicating signal detection from an unknown mechanism. Future directions for this study include an investigation into the reasons behind the before mentioned inconsistencies and an analysis of HPC solutions with different fluorescent labels to further explore the nature of the slow diffusion mode if it is determined to not be an artifact. [Preview Abstract] |
|
P1.00019: Monte Carlo Simulation Characteristics of Tracer Diffusion for Concentrated Lattice Gases Trevor J. Torpin, Christopher D. Wentworth Monte Carlo simulations of tracer diffusion for a concentrated lattice gas are presented for one, two, and three dimensional lattices. The model considered involves particles that can hop to nearest-neighbors only and that do not interact except that double occupancy of a lattice site is not allowed. We explore the time-dependence of the mean-square displacement of a tagged particle (the tracer) as characteristics of the model vary, including lattice dimensionality, lattice size, boundary conditions, and concentration of the lattice gas. The lattices considered include the one-dimensional chain, the square lattice, and the simple cubic lattice. For conditions that yield normal diffusion, the equilibrium value of the correlation factor is calculated as a function of concentration. [Preview Abstract] |
|
P1.00020: Study of Brij Micelles Using Dynamic Light Scattering Spectroscopy Karen Wilson, Mike Lekan, Kiril Streletzky We studied properties of Brij-35 surfactant micelles using Dynamic Light Scattering (DLS) and Optical Probe Diffusion method. Aqueous solutions of Brij-35 with concentrations ranging from 2 to 100g/L were prepared, both with and without polystyrene latex probes of diameters 24, 50, 282, and 792nm. Solutions were studied at four temperatures of 10, 25, 40, and 70$^{o}$C with DLS to obtain micelle and probe diffusion coefficients (D$_{m}$, D$_{p})$. Using both diffusion coefficients we deduced micelle radius (a$_{m})$, micelle water content ($\delta )$, and number of surfactant molecules per micelle (N) using two different models. First, we used the hard sphere model of micelle/probe interaction to analyze the data by two methods. In this model, a$_{m}$ is obtained from Stokes-Einstein equation using the intercept of D$_{m}$(c). The first method of the model uses the slope of D$_{m}$(c) and the size of probes to determine N and $\delta $. The second method of the model uses the linear least-squares fit of D$_{p}$(c) for different probe sizes to determine N and $\delta $. Both methods reveal that with solution temperature increase, a$_{m}$ increases by 10{\%}, N increases and $\delta $ decreases by a factor of 2. Two hard sphere methods yield somewhat different trends, but overall agree with published data on Brij micelles. The second model treats micelles as core-shell particles and uses D$_{m}$(c) to determine not only a$_{m}$, $\delta $, and N, but also micelle corona radius a$_{c}$. [Preview Abstract] |
|
P1.00021: Measuring the absolute {\boldmath $D^{0} \to K_{s} \pi^{0}$} branching fraction Thomas Maloney We describe an algorithm for measuring the absolute branching fraction of the $D^{0}\to K_{s}\pi^{0}$ decay using Monte Carlo data from the BaBar experiment at SLAC. The power of this algorithm comes from identifying and counting the number of slow pions, $\pi_{s}$, from charged $D^{*}$ decay in $c\overline{c}$ events in which the flavor of the $D^{*}$ is consistent with the flavor of a fully reconstructed second charm decay, referred to as the tag, in the same event. The analysis uses three tagging samples: $D^{+}\to K^{*}\pi^{+}\pi^{+}$, $D^{*}\to D^{0}\pi^{+}$ with $D^{0}\to K^{-}\pi^{+}\pi^{0}$ and $D^{0}\to K^{-}\pi^{+}$ with an additional tag created by requiring the $D^{0}$ to come from a $D^{*+}$ along with a $\pi^{+}$. With 400 fb${}^{-1}$ of data, the branching fraction can be measured with 5\% precision, accounting for both the statistical and systematic uncertainties. [Preview Abstract] |
|
P1.00022: Characterizing Atom-Thick Carbon via Electron Diffraction Eric Mandell Electron scattering models for various carbon nanostructures can be compared in order to gauge how diffraction effects due to crystal shape manifest in diffraction. Model diffraction profiles for specific molecules are calculated using the formula described by Debye, which averages the molecule over all orientations relative to an incident electron beam. This creates an azimuthally-averaged powder profile, as if from an infinite collection of identical crystals. Due to the atom-thick nature of graphene, interesting changes in diffraction peak shape arise from small changes in crystal shape. Particularly, differences are measured between Debye profiles for triangular and hexagonal graphene sheets. Also, it is shown here that diffraction peak shapes are altered due to curvature or faceting around pentagonal defects (i.e. nanocones), including the development of satellite peaks near the graphene periodicities. These satellite peaks manifest due to the coherence between lattice fringes resulting from in-plane defects that warp the 2D graphene crystal into a 3D structure. Improving the ability to characterize the structure of graphene and other molecular carbon forms will provide a better understanding of formation mechanisms, or the role of growth conditions present during the fabrication of carbonaceous materials. [Preview Abstract] |
|
P1.00023: Recent Results on the Branching Ratio in the Beta Decay of Oxygen-14 Matthew Kowalski, Elizabeth George, Paul Voytas, Lynn Knutson, Gregory Severin, Sean Cotter As one of the most allowed beta decays, and as a member of the A=14 isospin triplet, the 0+ to 0+ beta decay of oxygen-14 plays an important role in tests of the weak interaction. We have been involved in high precision measurements of the spectral shape and of the branching ratio, which are important for such tests. Preliminary analysis of the latest branching ratio data will be presented. [Preview Abstract] |
|
P1.00024: Parity Measurements in $^{80}$Sr C.S. Myers, R.A. Kaye, S.L. Tabor, T.D. Baldwin, D.B. Campbell, C. Chandler, M.W. Cooper, C.R. Hoffman, J. Pavan, M. Wiedeking, J. D\"{o}ring, S.M. Gerbick, L.A. Riley Until recently, $^{80}$Sr was thought to possess only positive-parity states, in contrast to many other neighboring nuclei which are known to have negative-parity states. Now there is indirect experimental evidence for negative-parity states, but the parities have not been measured directly. The goal of this study was to finally resolve this long-standing mystery by measuring conclusively the parities of as many excited states in $^{80}$Sr as possible. $^{80}$Sr nuclei were produced at Florida State University following the $^{54}$Fe($^{28}$Si, 2$p$) and the $^{54}$Fe($^{28}$Si, $\alpha$2$p$) reactions at 90 and 110 MeV, respectively. Following the reactions, high-spin states in $^{80}$Sr were populated and data were collected on the resulting cascades of emitted $\gamma$ rays using an array of 10 Ge detectors. The linear polarizations of 31 $\gamma$ rays were measured and many times allowed for the determination of the parity of the parent state that released the $\gamma$ ray. The results have conclusively verified negative parity for one sequence of states, and positive parity for the yrast states. [Preview Abstract] |
|
P1.00025: Using spatial deconvolution to improve image contrast in a capillary-based high-pressure chamber for fluorescence microscopy Thomas Haver, Erica C. Raber, Paul Urayama A quartz capillary is used as a simple-to-construct high-pressure chamber for fluorescence microscopy imaging, with capillary walls acting as both the mechanical support and optical window. Because wall curvature introduces image aberrations, the effectiveness of spatial deconvolution as an image restoration technique is investigated. The point-spread-function is measured in both a capillary and a flat-slide control, then applied in the imaging of sub-cellular dimension microspheres. Results demonstrate that sub-cellular dimension objects can be spatially resolved in a capillary capable of pressurization to several hundred atmospheres, the range of interest when studying pressure effects in cellular systems. Contrast improvement is observed for both high- and low-numerical-aperture objectives. [Preview Abstract] |
|
P1.00026: Residential solar energy: one family's experience with installation, performance, and cost David Carpenter, Gordon Aubrecht, Michelle Aubrecht ``Meet the Carpenters'' is Michelle Aubrecht's submission to Al Gore's global warming awareness contest. The 60-second ad focuses on the Carpenter family's efforts to reduce their personal carbon footprint. One major way is a solar panel installation David Carpenter installed on his family's south-facing roof. This poster will present the contest ad and give highlights of David Carpenter's energy and monetary savings from the solar roof as well as details about how net metering works in Ohio. [Preview Abstract] |
|
P1.00027: Acceleration: Physical experience creates a better understanding M.T. Dougherty, S.A. Lee Many concepts of mechanics are familiar to students because of their everyday experiences. Though students have an intuitive idea about acceleration, their impressions are often misguided or poorly defined. Specifically, these students find difficulties in distinguishing between velocity and acceleration. In this project, we report physical activities in which students have the opportunity to measure their accelerations in an easy and straight-forward manner. Students then compare their data to the acceleration due to gravity. The pairing of these quantitative results with the qualitative experience of the student draws a connection which is essential to internalizing the concept of acceleration. [Preview Abstract] |
|
P1.00028: Cognitive Work Analysis: Preliminary Data for a Model of Problem Solving Strategies Mark Rothmayer, Jennifer Blue Investigations into problem solving strategies are part of the field of physics education research where investigators seek to improve physics instruction by conducting basic research of problem solving abilities among students, differences in knowledge representations between experts and novices, and how to transfer knowledge structures more effectively onto novices. We developed a new conceptual research tool in our laboratory, where we could potentially map the step by step flow of problem solving strategies among experts and novices. This model is derived from the theory of Cognitive Work Analysis, which is grounded in ecological psychology, and as far as we know it has never been applied to a knowledge domain like physics. We collected survey data from 140 undergraduates enrolled in an algebra based introductory physics course at Miami University as part of a larger study aimed to test the validity of the model. Preliminary data will be presented and discussed. [Preview Abstract] |
|
P1.00029: Mathematical Modeling of a non-linear oscillator Ed Timko, Mo Ahoujja, Rex Berney We discuss a simple experiment developed to show non-linear oscillations. The Data shows amplitude jumps as the frequency of the periodic driving force is slowly varied on the way up as well as on the way down past the resonance frequency for the linear system. A theoretical description using modified Duffing's Equation with damping is used to model the non-linear phenomenon. [Preview Abstract] |
|
P1.00030: A Transport Study of AlGaN/GaN Heterostructures Grown on an AlN Substrate Mo Ahoujja, S. Elhamri, R. Berney, J.D. Daniel, W.C. Mitchel, G. Landis AlGaN/GaN heterostructures grown on AlN substrates by MOCVD/MEMOCVD technique were investigated using Hall and magnetoresistance measurements. The results indicate the presence of well defined Shubnikov-de Haas (SdH) oscillations which confirm the presence of a good quality two-dimensional electron gas in this structure. The carrier density and mobility were roughly 1.19x10$^{13}$ cm$^{-2}$ and 1100 cm$^{2}$/Vs at room temperature and 1.02x10$^{13}$ cm$^{-2}$ and 5279 cm$^{2}$/Vs at 10 K, respectively. Following illumination, a persistent photocurrent and an increase in the SdH amplitude were observed. Both of these effects are indicative of an increase in the quantum scattering time. The value of the ratio of the classical to the quantum scattering times is within the expected values for the AlGaN/GaN grown on other substrates. [Preview Abstract] |
|
P1.00031: A Method to Optimize Transport Properties of AlGaN/GaN on Silicon J.D. Daniel, S. Elhamri, R. Berney, M. Ahoujja, W.C. Mitchel, J.C. Roberts, P. Rajagopal, J.W. Cook, Jr., E.L. Piner, K.J. Linthicum We report on a study to investigate the impact of a thin AlN interlayer on the transport properties of AlGaN/GaN heterostructures grown by MOCVD on silicon substrates. Hall and Shubnikov-de Haas (SdH) measurements were used to compare the transport parameters of the conventional, AlGaN/GaN, structure to those of an AlGaN/AlN/GaN. The results clearly indicate that the interlayer leads to an enhancement of both the mobility and the carrier density. At 300 K, the carrier density and mobility for the conventional structure were roughly 8.57x10$^{12}$ cm$^{-2}$ and 1523 cm$^{2}$/Vs, respectively. For the structure containing the AlN interlayer these numbers were 10.03 x 10$^{12}$ cm$^{-2}$ and 1937 cm$^{2}$/Vs respectively. While the carrier density remained relatively unchanged down to 10 K, the mobility for the modified structure increased substantially. Shubnikov-de Haas measurements confirmed the presence of a high quality 2DEG in both structures. However, the amplitudes of the SdH oscillations in the conventional structure were higher. [Preview Abstract] |
|
P1.00032: Evaluating the Karhunen-Loeve Transform for SETI Yuru Niu, Daniel Fleisch One of the significant challenges in the Search for Extraterrestrial Intelligence (SETI) is the detection and identification of unusual signals. Traditional signal-processing techniques employing the Fast Fourier Transform (FFT) are very effective for extracting sinusoidal signals from noise and interference, but are less effective for non-sinusoidal signals. Some SETI researchers have suggested that the Karhunen-Loeve Transform (KLT) is well-suited to detecting signals with unknown characteristics. To evaluate this possibility, we have built a MATLAB simulation that allows us to synthesize a variety of signals and then apply both FFT and KLT processing. Initial results indicate that the KLT is more effective than the FFT for detecting signals with low signal-to-noise ratio and significantly outperforms the FFT for non-sinusoidal signals. [Preview Abstract] |
|
P1.00033: Next Generation High Power Dual-Frequency Transmitter For Space Borne and/or Air Borne Doppler Radar Precipitation Measurements Stephanie Vasicek, Edwin Wintucky Data analysis was performed using a Tektronix RSA 3303A Real-Time Spectrum Analyzer with the objective of demonstrating that an approach using Ka-band Differential Frequency Precipitation Radar (DFPR) works when operating a single Boeing Traveling Wave Tube (TWT) Model 999H to amplify two pulses. This approach is being studied to replace a current model using two separate TWTs at two separate frequencies. Applicability of MATLAB, Tektronix, and Agilent software was explored to investigate and refine pulse analysis techniques. Vector Signal Analysis software used with an Agilent Performance Spectrum Analyzer observed modulated signals at Ka-band in the time domain and is being further investigated to enable more detailed quantitative comparisons. MATLAB Signal Processing Toolbox is being explored as a possible analysis tool. A staggered pulse method of study was determined to be more advantageous than a simultaneous pulse study in that full peak power at each frequency can be viewed and intermodulation products can be avoided. [Preview Abstract] |
|
P1.00034: Effects of Depolarizing Noise on the Precision of an Atomic Clock Using GHZ States Matthew Briel, Andrew Jacobs, James Clemens We consider an atomic clock utilizing a sample of $N$ atoms prepared in a Greenberger-Horne-Zeilinger (GHZ) state. We studied the effects of depolarizing gate noise (caused by the preparation of the GHZ state), on the uncertainty of the detuning from the resonant transition atomic transition. We also studied the uncertainty's functional dependence on the number of atoms $N$ that the GHZ state is prepared with. Having then families of curves for the uncertainty of the detuning as a function of error probability, across different $N$ values, we contrasted these results with the classical limits, finding a lower boundary for the error probability that one must operate under to beat out the classical system. [Preview Abstract] |
|
P1.00035: Photodetachment Spectroscopy of As$^{\_}$ R.L. Field III, A.P. Snedden, J.Z. Shapiro, C.M. Janczak, C.W. Walter, N.D. Gibson Tunable infrared laser photodetachment spectroscopy has been performed on As$^{\_ }$ using a crossed laser-ion beam apparatus. The relative photodetachment cross section for neutral production was measured, revealing a threshold near 804.8 meV, interpreted as the opening of the As$^{\_}$ (4$p^{4} \quad ^{3}P_{2})$ to As (4$p^{3} \quad ^{4}S_{3/2})$ ground state to ground state transition. The $\Delta $E ($^{3}$P$_{1}$ -- $^{3}$P$_{2})$ fine structure splitting is also measured. The values of the present work are consistent with, and reduce the uncertainty of, previous measurements [1,2]. [1] Lippa, T. P., \textit{et al}, Journal of Chemical Physics \textbf{109}, 10727 (1998). [2] Haeffler, G., \textit{et. al}. Zeitshrift f\"{u}r Physik D \textbf{42}, 263 (1997). [Preview Abstract] |
|
P1.00036: Computational study of nonlinear waves in 2d complex plasma M.J. Garee, T.E. Sheridan We have developed a one-dimensional, nonlinear model for dust- acoustic waves in a two-dimensional complex plasma. In this model, dust particles with identical charge and mass reside on a periodic triangular lattice. Particles interact through a shielded Coulomb force and are allowed to move only in one direction. This model is solved computationally. The dispersion relation found by solving the model for small-amplitude waves is in good agreement with the theoretical dispersion relation. Simulations of large- amplitude unipolar pulses are currently being undertaken with the goal of comparing our model to the predictions of Korteweg-de Vries (KdV) soliton theory. This comparison focuses on two main attributes of KdV solitons: proportionality between wave speed, amplitude, and width; and conservation of waveform during soliton collisions. Recent results will be discussed. [Preview Abstract] |
|
P1.00037: Synchronization of Coupled Mechanical Oscillators Linda Kennedy, Barbara Andereck The Kuramoto model is used to describe synchronization of non-linear oscillators in biological, chemical, and physics systems. Using identical metronomes with similar frequencies on a movable platform, as per J. Pantaleone \textit{Am. J. Phys.} \textbf{70}, 992 (2002), we hope to realize a mechanical example of this model. A variety of materials were used for the movable platforms that coupled the metronomes. Platforms were either allowed to roll on cylindrical supports or suspended in pendulum fashion from the ceiling. Metronomes were started out of phase and allowed to synchronize. Measurements by PASCO photogates monitored by a LabView program were used to determine the phase difference between the two metronomes as a function of time. The dynamics of the metronome coupling was described by two second-order differential equations involving four key parameters: platform coupling, oscillation angle, damping/driving strength, and intrinsic frequency difference. Outstanding agreement between theory and experiment was achieved when the vertical motion of the platform and metronomes was included in the governing equations. [Preview Abstract] |
|
P1.00038: Using genetic algorithms to search for an optimal investment strategy Edward Mandere, Haowen Xi In this experiment we used genetic algorithms to search for an investment strategy by dividing capital among different stocks with varying returns. The algorithm involves having a ``manager'' who divides his capital among various ``experts'' each of whom has a simple investment strategy. The expert strategies act like genes, experiencing mutation and crossover, in a selection process using previous returns as the fitness function. When algorithm was run with test data where the optimal strategy favored non-uniform investment in one stock it consistently beat a simple buy hold. However when the algorithm was run on actual stock data the system overwhelmingly stabilized at a population that closely resembled a simple buy hold portfolio, that is, evenly distribute the capital among all stocks. [Preview Abstract] |
|
P1.00039: Analysis of the 1$^{3}\Delta $ Potential Curve of NaK Rachael Roettenbacher, A. Peet Hickman The process of determining energy levels from a given potential is relatively straightforward; however, the inverse process, given certain energy levels how to determine the potential is more difficult. In this study, a potential curve of the 1$^{3}\Delta $ state of NaK was created based on experimentally determined energy levels. The goal in this research was to suppress the unphysical wiggles at high internuclear separations found in a previous analysis by using a different method that would better determine the physical shape of the potential of the 1$^{3}\Delta $ state of NaK. The potential fitting program \textit{DPotFit 1.1} by Robert J. Le Roy was used with a modified expanded Morse oscillator (EMO) potential. The modification made to the EMO potential was that a dispersion term, $V_{dispersion}$, was added to account for the behavior of the well at high internuclear separations. The modified EMO potential did not eliminate the wiggles, but it did reduce them. The rms deviation between the calculated and experimental energy levels was 0.021 cm$^{-1}$ for the new fit, compared to 0.026 cm$^{-1}$ for the previous fit. The use of parameters in fitting energy levels is essential; here, the number of fitting parameters was reduced from the previous study. The employment of the modified EMO potential allowed for a better fit to the experimental energy levels and a more realistic potential function for the 1$^{3}\Delta $ state of NaK. [Preview Abstract] |
|
P1.00040: Experimental study of solitary waves in a two-dimensional complex plasma T.E. Sheridan The propagation of large-amplitude non-linear waves has been studied in a two-dimensional strongly-coupled complex (dusty) plasma. A system with $\approx5000$ particles (8 $\mu{\rm m}$ diam.) was created for a neutral argon pressure of 3.0 mtorr. The Debye shielding parameter was found to be $\kappa\approx1.6$. Highly-nonlinear, planar compressive waves were launched by pushing all the particles in a rectangular region at the center of the crystal in the same direction using a high-power green laser. Solitary waves were found to propagate in the forward direction at Mach numbers up to 1.4. Oscillatory shocks were seen to propagate in the backward direction after the laser was turned off. Coherent rarefactive pulses were not observed. [Preview Abstract] |
|
P1.00041: Photodetachment Spectroscopy of Ce$^{\_}$ A.P. Snedden, R.L. Field III, C.M. Janczak, K.A. Star, N.D. Gibson, C.W. Walter, P. Andersson Tunable infrared laser photodetachment spectroscopy has been performed on Ce$^{\_ }$ using a crossed laser-ion beam apparatus. The relative photodetachment cross section for neutral production was measured over the photon energy range 0.61 eV -- 0.75 eV. The spectrum reveals a threshold near 0.65 eV, which is interpreted as the opening of Ce$^{\_}$ the (4$f$5$d^{2}$6$s^{2} \quad ^{4}H_{7/2})$ to Ce (4$f$5$d$6$s^{2} \quad ^{1}G_{4})$ ground state to ground state transition. At least five narrow peaks associated with negative ion resonances are observed over the range 0.62 -- 0.70 eV, and their energies and widths are measured. The present measurements are compared to recent theoretical [1] and experimental [2] results, which are in significant disagreement on fundamental physical quantities such as the electron affinity of Ce and the ground state configuration of Ce$^{\_}$. [1] S.M. O'Malley and D.R. Beck, Phys. Rev. A \textbf{61}, 034501 (2000); X. Cao and M. Dolg, Phys. Rev. A \textbf{69}, 042508 (2004). [2] V.T. Davis and J.S. Thompson, Phys. Rev. Lett. \textbf{88}, 073003 (2002). [Preview Abstract] |
|
P1.00042: Supersonic Particles Trapped below a Plasma Crystal William Theisen Supersonic dust particles traveling below a two dimensional Coulomb crystal were studied. The strongly-coupled dusty plasma Coulomb crystal forms a hexagonal lattice in a horizontal plane and levitates in a parabolic potential well. During the formation of a crystal occasionally, one to several of the electrically charged microspheres becomes trapped below the crystal exhibiting supersonic stochastic flight characteristics. Trajectory plots, speed distribution charts and position time histories of the particles were generated and analyzed. A decomposition of particle position into x -- y coordinates shows oscillatory motion at a frequency of 2 Hz. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700