Bulletin of the American Physical Society
2011 Annual Meeting of the Four Corners Section of the APS
Volume 56, Number 11
Friday–Saturday, October 21–22, 2011; Tuscon, Arizona
Session F1: Poster Session (4:30-6:30PM) |
Hide Abstracts |
Chair: Srin Manne, University of Arizona Room: UA Student Union Tucson and Catalina |
|
F1.00001: Utilizing doubly excited states of barium for quantum information storage John Papaioannou, Chris H. Greene The existence of doubly excited perturbers in the alkaline-earth atoms provides a rich spectrum of states with possible applications for quantum information storage. Using the framework of multichannel quantum defect theory, the bound even-parity J = 2 spectrum of Ba were studied, which have 5d7d doubly excited states embedded in the 6snd $^1D_2$ and 6snd $^3D_2$ Rydberg series. Due to configuration mixing, an external electric field can induce transitions to quasi-degenerate Rydberg states in odd-parity neighboring symmetries. This not only allows the possibility of improved control in exciting to high-l Rydberg states but may also be utilized as possible qubit candidates. [Preview Abstract] |
|
F1.00002: Tunable electronic properties of armchair graphene nanoribbons from first-principles calculations Andrew Copple, Xihong Peng, Selina Velasquez, Fu Tang First principles density-functional theory calculations were carried out to study the effects of strain and edge passivation on electronic properties in armchair graphene nano-ribbons (AGNRs). We studied two types of strains (uniaxial expansion and compression) and five groups of edge passivation (H, F, OH group, bridged-O, and bridged-S). The investigated properties of the AGNRs include lattice constant, band gap, effective masses of charge carriers, and work function. We found strain and edge passivation play significant roles in modifying the electronic properties of AGNRs. Uniaxial strain effect on the energy gap shows a zig-zag pattern. Different edge passivation produces its unique zig-zag pattern due to their different optimized lattice constants. In the cases of bridged-O and bridged-S, a transition from direct to indirect band gap occurs at a sufficient tensile strain. With further increased tensile strain, the gap shrinks to zero. The work function increases with tensile strain and decreases with compression, regardless of the edge passivation. Such kinds of modulations of electronic properties in AGNRs are important for its applications in future electronics technology. [Preview Abstract] |
|
F1.00003: \textit{Ab initio} study of wurtzite InAs and GaAs nanowires Phivu Nguyen, Andrew Copple, Xihong Peng The unique properties of one dimensional semiconductor nanowires have inspired extensive research efforts during the past decade. In particular, group III-V semiconductors are promising building blocks for a wide range of applications such as field-effect transistors, light-emitting diodes, and optical sensors. A clear understanding of the fundamental properties of those materials, especially the electronic properties, and their tunability are critically important toward the applications. In this presentation, we report first principles density-functional theory study on the electronic properties of wurtzite InAs and GaAs nanowires along (0001) direction with the diameter of the wires up to 3 nm. The band gap of the nanowires increases with the reduction of the nanowire diameter, mainly due to quantum confinement effect. In addition, the band gap can be further tuned through uniaxial strain. The effective masses of charge carriers and work function of the nanowires are also reported. [Preview Abstract] |
|
F1.00004: Strain-modulated Fermi velocity of charge carriers in 2D graphene: A first principles study Kason Ashe, Xihong Peng Using first principles density-functional theory calculations, we have shown that the Fermi velocity of charge carriers in two-dimensional graphene is tunable. Three different types of strain were studied. They are uniform biaxial strain, uniaxial strain in the armchair direction, and uniaxial strain in the zig-zag direction. We found by applying strains, particularly uniform biaxial type, the Fermi velocity can be modified by an appreciable amount. The Fermi velocity increases when biaxial compression is applied. For example, the Fermi velocity increases 33{\%} under 12{\%} compression. Conversely, the Fermi velocity was shown to decrease by as much as 19{\%} when the graphene was expanded uniformly by up to 12{\%}. In the case of uniaxial strain in the zig-zag direction, it is shown the Dirac point is no longer located at K but near R from the band structure and with a greater amount of strain the Dirac point moves further away from R toward S. As graphene is stretched in the armchair direction the Dirac point moves away from K towards $\Gamma $. These results suggest an effective way to tune the Fermi velocity of graphene. [Preview Abstract] |
|
F1.00005: Temperature Dependence of the Dielectric Function of Germanium by Spectroscopic Ellipsometry Amber A. Medina, L.S. Abdallah, S. Zollner The complex pseudo-dielectric function $<$e$>$ of a two-side polished bulk germanium wafer was measured from 0.6 to 6.6 eV on a J.A. Woollam variable-angle spectroscopic ellipsometer. To obtain accurate results (especially in the near-transparent region of Ge below 2 eV), we employed a computer-controlled Berek wave plate compensator. The thickness of the native oxide was determined from the maximum of $<$e$_{2}>$ at 4.2 eV. The native oxide thickness of the as-received Ge wafer (3.7 nm) could be reduced to 1.6 nm by submerging the wafer in de-ionized water and allowing it to dry in air. After mounting the wafer in a UHV cryostat, the oxide regrew to 1.9 nm. By annealing the wafer at 700C for one hour under UHV conditions, this could be reduced to 1.7 nm. Finally, we acquired $<$e$>$ as a function of temperature from 77 to 700 K. With increasing temperature, the interband transitions redshift and broaden due to the lattice vibration dampening of the electronic states. Measurements on a single-side polished Ge wafer (prepared by roughening the back surface with a bead blaster) and analysis of the second derivative of e to determine the interband critical-point parameters are in progress. [Preview Abstract] |
|
F1.00006: Optical Properties of Epitaxial Graphene M. Spies, A. Boosalis, T. Hofmann, J.L. Tedesco, D.K. Gaskill, T. Tiwald, J.A. Woollam, M. Schubert Spectroscopic ellipsometry in the range from 0.75 to 9 eV was used to investigate epitaxial graphene grown by Si sublimation on 4H, 6H and 3C SiC single crystal substrates. The graphene on Si- terminated SiC is relatively thin with low sheet charge density and mobility compared to the graphene grown on the C-terminated face which has higher charge density and mobility but is also covered with graphitic layers. The parametrized model dielectric function of graphene is composed of three Lorentz oscillators accounting for Drude-like free-charge carrier excitation and band-band transition in the range from 3.6 to 4.4 eV. The interface between the graphene and the substrate was described in our optical model using a simple Bruggeman effective medium approach. Furthermore, a large area map of 3025pt over a spectral range of 0.75- 5.35eV on a 1.5x1.7 cm graphene on Si-terminated 6H SiC substrate revealed distinct variations in the ellipsometric angles Psi and Delta suggesting a variation in the graphene layer as well as the interface layer thickness. \newline [Preview Abstract] |
|
F1.00007: Photolithography Process using Extreme Ultraviolet LASER Wei Li, Dinesh Patel, Lucasz Urbanski, Mario Marconi We have developed a variety of high-resolution and high-accuracy nanofabrication techniques. They are capable of high resolution nanopatterning on the film of HSQ, which is used as mask later in the pattern transfer. The nanopatterns, which is formed by exposure from 46.9nm table top EUV capillary discharge laser made by CSU, is transferred faithfully down to a gold layer underneath by anisotropic reactive ion etching (RIE) equipment. The equipment has the capability of temperature control and feedback from a thickness monitor. A 10nm error of etching height has been achieved. [Preview Abstract] |
|
F1.00008: EUV Scintillator for Localization and Detection of Laser Beam Nils Monserud, Lukasz Urabanski, Eric Malm, Christopher Brown, Mario Marconi We set out to find a means of detecting and locating an EUV laser beam at the wavelength of 46.9 nm in real time. This will facilitate the alignment of our experiments in nano-patterning, nano-fabrication, and holography, consequently allowing multiple experiments to be aligned simultaneously. Methods of detection are either CCD cameras or prints made with Poly(methyl methacrylate) (PMMA) on a coated wafer, neither of which are efficient to operate. We describe the implementation of an alternative imaging method which combines a phosphor scintillator and a web-cam. Using a phosphor scintillator screen provided by Applied Scintillations Technologies Limited the detection and localization of the EUV laser beam at 46.9 nm was seen consistently through reflection providing a distinct image of the beam in the initial tests. We were able to capture an image of the beam using the webcam through the use of a user interface developed in labview which allowed a snap shot to be taken at the exact moment the beam past through the screen. [Preview Abstract] |
|
F1.00009: Extreme Ultraviolet Fourier Transform Holography Erik Malm, Chris Brown Fourier transform holography has been demonstrated with the use of a 46.9nm table-top plasma discharge laser. A zone plate is used to form the reference and plane wave. The scattered light off the object interferes with the spherical reference wave and recorded on a charge-coupled device. A prefocusing algorithm has been implemented to reconstruct different planes of the object. The resolution is limited by the focal spot size of the zone plate which is approximately 120 nanometers. This particular laser and approach should allow for nanoscale dynamics to be imaged. [Preview Abstract] |
|
F1.00010: M\"{o}ssbauer Spectroscopy in the Undergraduate Laboratory Adam Decaria, Spencer Hatch, Colin Inglefield A M\"{o}ssbauer spectrometer has been built primarily from materials that are already available in the physics department at Weber State University. These materials are either common to undergraduate labs or accessible to a small budget, making reproduction at other establishments very feasible. The spectrometer is designed to illustrate and facilitate understanding of physics principles associated with M\"{o}ssbauer spectroscopy, such as Doppler broadening, isomer shift, recoilless gamma ray emission, and resonant absorption. Ultimately the spectrometer will be incorporated into a junior-level physics laboratory course for physics majors. In practice, the lab work is based around the 14.4 keV gamma ray emitted by Co-57 common to M\"{o}ssbauer spectroscopy. In addition to serving as an undergraduate teaching laboratory, design improvements in the near future will enable meaningful undergraduate research to be carried out. As a proof of principle, we present a preliminary M\"{o}ssbauer spectrum and a measurement of the isomer shift in a stainless steel sample. [Preview Abstract] |
|
F1.00011: Magnetization of the One-Dimensional Antiferromagnetic Ising Model on a Two-sublattice Maximally Even Lattice in the Mean Field Approximation Richard Krantz An antiferromagnetic Ising model on a Maximally Even lattice has been developed. The magnetization per spin versus temperature for various applied magnetic fields has been calculated. The magnetization shows the competition between the aligning effects of the applied magnetic field and the anti-aligning effect of the near-neighbor antiferromagnetic interaction. [Preview Abstract] |
|
F1.00012: Quasi-Quantum Dynamics of Collinear Reactive Collisions using Operator methods Tim Wendler, Manuel Berrondo We calculate transition probabilities between discrete states of a diatomic molecule induced by an incoming atom. Our prototype Hamiltonian is constructed treating the translation classically and the internal variables quantum mechanically. The corresponding equations of motion are coupled quasi-classically. We present applications to a canonical ensemble of initial conditions as well as results for the time dependence of transition probabilities for different initial and final states. In the reactive case we are driven to using natural coordinates i.e. the reaction coordinate and the transverse vibrational coordinate. [Preview Abstract] |
|
F1.00013: Imaging the 3D structure of vortex cores in Bose-Einstein Condensates Kali Wilson, E. Carlo Samson, Zachary Newman, Brian P. Anderson We describe an absorption imaging technique that enables the determination of the three-dimensional structure of vortex cores in Bose-Einstein condensates. In our procedure, spherical or oblate BECs are created in a magnetic trap, and various excitation techniques can be used to generate vortices in the condensate. The condensate is then released from the trap, and multiple absorption images are taken of the ballistically expanding condensate. These images are stitched together to form a single 3D image. This technique allows for studies of vortex structure and dynamics in experiments where the vortex cores are not aligned with a single imaging axis. [Preview Abstract] |
|
F1.00014: Atom Interferometry Measurements of Static and Dynamic Polarizability Raisa Trubko, Will Holmgren, Ivan Hromada, Joe Ronan, Alex Cronin We report progress towards new measurements of static and dynamic polarizabilities for several atomic species. We use a nanograting Mach-Zehnder atom interferometer with an electric field gradient to observe atomic de Broglie wave phase shifts that are proportional to the electric polarizability. These measurements provide tests of atomic structure calculations that are needed to improve the precision of atomic clocks. We explain the progress and challenges of measuring the dynamic polarizability of potassium, the static polarizability of strontium and ytterbium, and several polarizability ratios (e.g. $\alpha _{Na}$/$\alpha _{Li})$ with one part per thousand accuracy. [Preview Abstract] |
|
F1.00015: Laser cooling and trapping of atomic mercury Justin Paul, Christian Lytle, Jason Jones The level structure of the Hg atom is similar to other alkaline earth-like atoms, offering the possibility to realize an extremely high quality resonance factor (Q) on the ``clock'' transition ($^{1}S_{0}- ^{3}P_{0}$) when confined in an optical lattice at the Stark-shift free wavelength. A key feature of the Hg system is the reduced uncertainty due to black-body induced Stark shifts, making it an interesting candidate as an optical frequency standard. For cooling on the $^{1}S_{0}- ^{3}P_{1}$ transition at 253.7 nm, we employ an optically pumped semiconductor laser (OPSEL) operating at 1015 nm. The OPSEL frequency is quadrupled, generating over 120 mW at 253.7 nm. With this laser source we have trapped $Hg^{199}$ from a background vapor in a standard MOT. We trap up to $2 x 10^{6}$ atoms with a $1/e^{2}$ radius of our MOT of $\sim$310 microns, corresponding to a density of $1.28 \times 10^{11}$ atoms/cm$^{3}$. Using the time- of-flight method, we have measured a doppler-limited temperature of 46$\mu$K for the MOT. We have also generated 10 mW at the 266 nm clock transition using a frequency-quadrupled fiber laser. This light will be referenced to an iodine standard for assisting in high-precision spectroscopy of the $^{1}S_{0}- ^{3}P_{0}$ transition. We present updated results on the MOT and the probe laser system. [Preview Abstract] |
|
F1.00016: High intensity pulse formation and plasma dynamics in passive femtosecond enhancement cavities for high harmonic generation David Carlson, John Mongelli, Ewan Wright, R.J. Jones The use of passive femtosecond enhancement cavities to create frequency combs in the vacuum ultraviolet spectral region is complicated by the ionization of the dilute gas target required for high harmonic generation. We numerically simulate the intracavity pulse formation in the presence of the gas and report time resolved experimental results measuring the persistent background plasma level. [Preview Abstract] |
|
F1.00017: Atomic 2F Rydberg States Calculations Using Explicitly Correlated Gaussian Basis Functions Nikita Kirnosov, Keeper Sharkey, Ludwik Adamowicz Very accurate variational non-relativistic calculations are performed for Rydberg (2)F states of the lithium atom ((7)Li). The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions and finite nuclear mass is used. The exponential parameters of the Gaussians are optimized using the variational method with the aid of the analytical energy gradient determined with respect to those parameters. The results of the calculations allow for refining the experimental energy levels determined with respect to the (2)S 1s(2)2s(1) ground state. [Preview Abstract] |
|
F1.00018: Phase-Space Trajectories and Transition Probabilities of Driven Anharmonic Oscillators Ryan Sayer, Jean-Francois Van Huele We model the interaction of diatomic molecules with radiation by studying the time evolution of Morse oscillators subjected to a dipole electric field. A Lie algebra method allows us to find expectation values of position and momentum as well as transition probabilities as a function of time. We study the molecular response as a function of the shape, frequency, and duration of the pulse and evaluate the method based on internal consistency and practicality. [Preview Abstract] |
|
F1.00019: MOKE: Magneto Optical Kerr Effect Erik Wildforster, Kristen Buchanan The magneto-optical Kerr effect (MOKE) is a powerful tool for studying the magnetization reversal process of ferromagnetic materials. It works by measuring changes in the polarization of reflected light that are proportional to the magnetization of the sample, an effect discovered in the 1800's. This effect, known as the magneto-optical Kerr effect, provides a non-destructive means to measure the magnetization of thin film or patterned ferromagnetic materials. Furthermore, the light can be focused down to a diffraction-limited spot, allowing one to measure much smaller samples than conventional magnetometers. This poster will give an overview of the MOKE technique and we will show a comparison of magnetic hysteresis loops of ferromagnetic thin film samples measured using the longitudinal MOKE effect and with a conventional vibrating sample magnetometer. We acknowledge support from NIST award number 60NANB10D011 and the NSF, award 0907706. [Preview Abstract] |
|
F1.00020: 3- and 5- Minute Oscillatory Behavior in the Solar Corona Brandon Calabro, James McAteer, Alexander Pevtsov We study the spatially- and temporally-localized oscillatory behavior of the solar corona using a 6-hour sequence of narrowband 171A (extreme ultraviolet) image from the SWAP instrument onboard Proba2. We use a Morlet wavelet transform to extract oscillation parameters from the temporal evolution of emission in each pixel and study the variation in space and time of oscillatory power in the 3- and 5-minute band. We extract and compare these parameters between active Sun, quiet Sun and coronal hole regions. In each region of the corona studied the 5-minute periodicity is more prevalent than the 3-minute periodicity by a factor of 2--3. All areas of the corona exhibit a similar temporal behavior in the 5-minute band, suggesting a global driving mechanism. However, the dominance of the 5-minute periodicity is stronger in active regions than in other areas of the Sun. The 3-minute periodicity in active regions tends to be localized in the sunspot umbra, whereas the 5-minute is more prevalent in the penumbra. [Preview Abstract] |
|
F1.00021: Coronal Loop detection and seismology Alexander Pevtsov, R.T.J. McAteer, Jason Jackiewicz, Brandon Calabro, Bernie McNamara Using a TRACE image with a bipolar active region and over one hundred distinguishable loops, we examine several current methods for automated coronal loop detection. Using the same TRACE image, several new approaches are also taken in an attempt to increase accuracy and completeness rates for the automated detection process. These new methods are applied to AIA data from the Solar Dynamic Observatory with the expectation to achieve a higher degree of completeness while maintaining a high level of accuracy in the detection process. To increase completeness, an automated attempt for the reconnection between orphaned loop segments will also be tested. In the future, an approach to reconstruction of three-dimensional images from several two-dimensional images can be devised by using the detected coronal loops and a known 3D offset of each image. However this process heavily depends on the ability to accurately and completely detect the coronal loops. [Preview Abstract] |
|
F1.00022: Observational Bias as an Explanation for Distributions of Galaxy Inclination Angles Jordan Rozum, Matt Garlock, Shane L. Larson, Bradley W. Carroll The distribution of spiral and bar galaxy inclination angles is expected to be uniform. However, analysis of several major galaxy catalogs shows this is not the case; the frequency of inclination angles for galaxies classified as spirals or bars peaks between 80 and 90 degrees from edge-on. In an attempt to explain this discrepancy, we examine the dependence of observed brightness upon inclination angle by using luminous mass density as an analog for light intensity. If this dependence strongly corresponds to the observed distribution of inclination angles, we can attribute much of the discrepancy to a geometrical selection effect. [Preview Abstract] |
|
F1.00023: Magnetohydrodynamic Fluid Stability in the Presence of Streaming Cosmic Rays Eric Greenfield, J.R. Jokipii, Joe Giacalone We examine the effects of streaming cosmic rays upstream of a strong, parallel collisionless shock. We include explicitly the inertia of the cosmic rays in our analysis, which was neglected in previous work. For parameters relevant to the acceleration of cosmic rays at a supernova blast wave, we find {\it no} MHD fluid instability that would lead to the amplification of the magnetic field above that given by the compression at the shock. We show how to recover, from our own analysis, the cosmic-ray-driven MHD fluid instability found by previous authors. We conclude that including the inertia of the cosmic rays keeps the system stable. More over, the cosmic ray current leads to an additional Hall-like term in the magnetic evolution equation. The implications of this paper for acceleration of galactic cosmic rays at supernova remnants are briefly discussed. [Preview Abstract] |
|
F1.00024: Using Chemical Compositions of Kinematically Selected Stars to Trace Galactic Mergers Dylan Gregersen The chemical characteristic of low alpha element abundances distinguishes a few rare stars from their place among the halo population of our Milky Way. Encouraging the search for these stars, the unusual chemical nature is thought to distinguish them as remnants of a now merged extragalactic system. Until now, these stars have only been found serendipitously, on the order of a few in a thousand. In this talk, we report stars with low enhancements of alpha elements found within two kinematically distinct candidate moving clusters. Stars within these candidate moving clusters were distinguished from common halo stars by shared stellar characteristics: orbital energy, angular momentum, and overall chemical enrichment (Allen et al, 2007, Proc. IAU, 2: 405-413). We collected high-resolution spectra of these stars and employed multi-line analysis code with stellar models to determine their chemical compositions. This current research is part of a larger chemical composition investigation of these and other stars to search for other low alpha star tracers of the dynamic formation of our Galaxy. [Preview Abstract] |
|
F1.00025: BYU Radio Astronomy System for Imaging Galactic H1 and OH MASERs Daniel Blakley, Victor Migenes We have built a radio astronomy system initially designed to image galactic H1 (Hydrogen Spin-Flip) [at 1.42 GHz] and OH MASERS [ 1.66 GHz ] in star forming regions. Initial system architecture includes one 4-meter dish antenna, 0.38dB noise figure LNA and conventional super-heterodyne block down-conversion. Enhancements underway include baseline extensions for these wavelengths, CASPER based digital correlation / spectrometer design activity including Linux server, additional imaging wavelengths, rubidium clocks, and lock-in amplifiers. [Preview Abstract] |
|
F1.00026: Afterglow photometry and Modeling GRB 091018 Apurva Oza We focus on continuing the modeling of GRB (Gamma-ray Burst) 091018. Our data is mostly collected across 4 bands (BVRI) from PROMPT (Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes) approximately 4.1 hours after the trigger. We have added NIR, UVOT, X-ray, and more optical points to our datasets. After rejecting the orginal assertion of dust evolution by linking extinction parameters with Galapagos (a software that employs genetic algorithms to output the best fit model with our circum-burst GRB parameters (we have settled on a model with the circumburst density index k, at -1.75 which is close to the wind-blown medium of k=-2). In addition to k, the results of our baseline fit indicate that the cooling break is above the data, and may be crossing the synchrotron peak during the early UVOT data. This cross-over will yield interesting results about the circumburst medium of a GRB at early times. Photometring GRBs live was also conducted along with instrumentation techniques. [Preview Abstract] |
|
F1.00027: Seasonal Variability and Dynamics of Mesospheric Gravity Waves Over the Andes Neal Criddle, Michael Taylor, Dominique Pautet, Yucheng Zhao The ALO is a new facility developed for atmospheric research, located at the foot of the Andes in Cerro Pachon, Chile (30.2 S, 70.7 W). As part of a collaborative program, Utah State has a mesospheric temperature mapper (MTM) on site, which is used to study short period gravity wave dynamics and temperature variations in the mesosphere-lower thermosphere region. The MTM began taking measurements of the OH(6,2) and O2(0,1) spectral bands in August 2009 and a complete profile of seasonal variation in gravity wave characteristics has been created for August 2009 through August 2010 using the OH(6,2) Band. The primary goal of this program is to Quantify seasonal variability of gravity wave structures. Compare and contrast seasonal directionality with results from the Maui-MALT site. Quantify mountain wave observations, their frequency, characteristics and seasonal variability. Seasonal variability for gravity wave structures at this site is shown. Mountain waves have been exclusively observed to appear in the winter months. Future work includes verifying yearly repeatability, which is seen at other sites, and continued investigation of unique events occurring over the Andes mountain range. [Preview Abstract] |
|
F1.00028: Comparison of Polar Mesospheric Clouds in Northern 2007 and Southern 2007-2008 Seasons Rachel Ward In April 2007, the Aeronomy of Ice in the Mesosphere (AIM) satellite was launched into polar orbit to photograph the phenomenon of PMCs (Polar Mesospheric Clouds), which form from ice particles at high latitudes and about 80 km. On the AIM satellite is a highly sensitive Cloud Imaging and Particle Size (CIPS) UV imager, which measures the radiance and morphology of PMCs. Since the launch of the AIM satellite, tens of thousands of images of PMCs have been recorded, which provide key information to understanding the relationship between the temperature, upper mesospheric water chemistry, location, and span of these clouds. While PMCs have been recorded from the ground for many years, the AIM satellite has some unique advantages which are not shared by its ground-based counterparts. Namely, it can record images at a broader range of latitudes than is possible from the ground, at it allows images to be taken during the summer months of the Northern and Southern hemispheres. Comparison of Northern and Southern Hemispheric CIPS data from the 2007-2008 seasons has yielded some interesting results and gives a baseline for study of future years. [Preview Abstract] |
|
F1.00029: LEISA: Low-Earth Orbit Ionospheric Spectrum Analyzer Mario Ortega, Anastasia Ierides, Michael Thomas, Steve Suddarth The Configurable Space Microsystems Innovations and Applications Center (COSMIAC) at the University of New Mexico (UNM) has been awarded the Research Experience for Undergraduates (REU) grant by the National Science Foundation (NSF) to design, prototype, and launch a space borne ionospheric spectrum analyzer 1-U (1000cm3) CubeSat. The LEISA (Low Earth Orbit Ionospheric Spectrum Analyzer) satellite constellation will measure intracloud lightning via the production of radio wave distortions as a means to measure total electron content (TEC) in the ionosphere. The satellite constellation and various ground stations will digitize, record, and timestamp RF signals emitted by lightning. This allows for clientele to download data easily and rapidly for use in ionospheric modeling and real time GPS correction. The LEISA constellation is currently being developed by various graduate and undergraduate students at UNM and has introduced students to orbital mechanics, plasma physics, and signal propagation. In addition, lightning interaction with the atmosphere, provides students with a solid foundation in research, integration, and design techniques. [Preview Abstract] |
|
F1.00030: Reentry Experiment SAT-X Maurice Woods, Casey Kuhns, Motoaki Honda, Robert Shiely, Aaron Adamson, Jordan Aken, Robert Walch, Cynthia Galovich, Matthew Semak The challenge of \textit{re}entering the Earth's atmosphere is not new. For years, NASA has successfully designed vessels that have endured the harsh process of reentry. However, in most cases, this is made possible only through the act of over-engineering; designing to withstand conditions far beyond what is expected to be encountered. Though this method has been effective, there would be benefit in knowing more precisely what to expect upon atmospheric reentry. The University of Northern Colorado Reentry Experiment SAT-X project, launched from Wallops Island, Virginia on July 21, 2011, was designed to shed light on the reentry process by collecting motion data for a capsule ejected from a rocket. Moreover, a secondary objective was to test the capability of the prototype capsule to serve as a platform for future reentry experiments. The mission and preliminary results from the launch will be described. [Preview Abstract] |
|
F1.00031: Comparing Theory and Experiment for Analyte Transport in the First Vacuum Stage of the ICP-MS Matthew Zachreson, Ross Spencer The Direct Simulation Monte Carlo algorithm as coded in FENIX has been used to model the transport of trace ions in the first vacuum stage of the inductively coupled plasma mass spectrometer. Haibin Ma collected two radial trace density profiles: one .5 mm upstream of the sampling cone and the other 10 mm downstream. We will compare the simulation results from FENIX with the experimental results. To better understand the simulation results, two fluid codes have been written. One uses ideal convection and the other uses both convection and diffusion. This enables us to compare convection, convection and diffusion, and full long-mean-free-path simulation with each other and with the experimental data in order to see the importance of each of these effects. Results of these comparisons will be presented. [Preview Abstract] |
|
F1.00032: The Tucson Electric Power Solar Test Yard Vincent Lonij, Sean Orsburn, Anas Salhab, Emily Kopp, Adria Brooks, Vijai Jayadevan, James Greenberg, Michael St. Germaine, Nate Allen, Sarah Jones, Garrett Hardesty, Alex Cronin In collaboration with Tucson Electric Power we studied the performance of twenty different grid-tied photovoltaic systems, consisting of over 600 PV modules in all. We added data acquisition hardware to monitor DC power from the modules, AC power from the inverters, PV module temperatures, and meteorological data such as the irradiance incident on the PV systems. We report measurements of PV system yields and efficiencies over periods of minutes, days, and years. We also report temperature and irradiance coefficients of efficiency and measurements of long-term degradation. We also use our data to validate models that predict the output from PV systems. [Preview Abstract] |
|
F1.00033: Performance of Scanning Ladar Imaging through Atmospheric Turbulence Mazen Nairat, David Voelz The imaging performance of long range laser scanning system through atmospheric turbulence is examined using the concept of Modulus Transfer Function (MTF). The target is assumed to be within the Fresnel zone with considering long time and short time exposures. The effect of beam wander is described in terms of MTF. Our analysis indicates wave front tilt is a dominant factor for recovering high spatial frequencies. A physical optics simulation is employed to demonstrate the utility of the MTF approach and verify the theoretical model. [Preview Abstract] |
|
F1.00034: Studying the Upper Atmosphere Using a Sodium LIDAR Zachary Butterfield, Brett Bostrom, Titus Yuan Studying the mesopause region of the atmosphere (between 80 km and 105 km) is important when trying to understand atmospheric turbulence and global temperature change in the upper atmosphere. A Sodium LIDAR system can be used to generate laser induced fluorescence by Na atoms that are naturally present in this region of the atmosphere. The LIDAR system at Utah State University was designed in such a way that its laser pulses are not only narrow band (120MHz FWHM) but also strictly frequency controlled ($\pm $ $\sim $ 1MHz), and therefore can measure the profiles of temperature and horizontal wind velocity, as well as sodium density. The mesopause seems to have two distinct levels in its thermal structure and, opposite from intuition, is cold during summer months and warm in the winter.\footnote{C. Y. She and D. A. Krueger, Optics and Photonics News \textbf{18} (9), 35-41 (2007).} Through the observations of Sodium LIDAR over the past few decades, a much better understanding of this area of the atmosphere has been gained. However, in order to better understand certain phenomena that occur or to make any reliable inference on climate change more data are needed. [Preview Abstract] |
|
F1.00035: Hamiltonian Dynamics of a Forced Two-Degree-of-Freedom Arm with Viscoelastic Muscles Executing Planned Motions Sayan Patra, Greg Ojakangas, Andrew Chase, Anish Chakrabarti, Dalton Sivils, Evan Johnson, Kiefer Barrett, Mason North, Preston Julian In order to improve our understanding of how the brain controls the human arm both in the presence and absence of gravity, we have developed a two-degree-of-freedom robotic arm which is driven by six servo-actuated viscoelastic muscles. The computer-controlled servos mimic the contractive action of the sarcomeres in actual muscles, sections of elastic tubing represent the elastic behavior of actual muscles, while the behavior of tendons is represented by inelastic strings.~The servos receive instructions to move from the visual C++ platform in the computer and the actual motion of the arm is recorded with optical encoders built into each joint axis. This experiment is a purely feed-forward system, and our goal is to determine whether our equations of motion, formulated using Hamiltonian dynamics, when numerically integrated, will predict the observed motion of the arm within experimental uncertainties. [Preview Abstract] |
|
F1.00036: Cell-based Adaptive Mesh Refinement on the GPU with Applications to Exascale Supercomputing Dennis Trujillo, Robert Robey, Neal Davis, David Nicholaeff We present an OpenCL implementation of a cell-based adaptive mesh refinement (AMR) scheme for the shallow water equations. The challenges associated with ensuring the locality of algorithm architecture to fully exploit the massive number of parallel threads on the GPU is discussed. This includes a proof of concept that a cell-based AMR code can be effectively implemented, even on a small scale, in the memory and threading model provided by OpenCL. Additionally, the program requires dynamic memory in order to properly implement the mesh; as this is not supported in the OpenCL 1.1 standard, a combination of CPU memory management and GPU computation effectively implements a dynamic memory allocation scheme. Load balancing is achieved through a new stencil-based implementation of a space-filling curve, eliminating the need for a complete recalculation of the indexing on the mesh. A cartesian grid hash table scheme to allow fast parallel neighbor accesses is also discussed. Finally, the relative speedup of the GPU-enabled AMR code is compared to the original serial version. We conclude that parallelization using the GPU provides significant speedup for typical numerical applications and is feasible for scientific applications in the next generation of supercomputing. [Preview Abstract] |
|
F1.00037: Neutrosophic Degree of Paradoxicity of a Scientific Statement Florentin Smarandache Let $<$S$>$ be a scientific statement (in physics, mathematics, etc.). Let's also consider the implication $(C_{1})$ ``If $<$S$>$ is true it may result that $<$S$>$ is false'', and the reciprocal implication $(C_{2}) $``If $<$S$>$ is false it may result that $<$S$>$ is true''. Both implications (conditionals) depend on other factors in order to occur or not, or they are partially true (T), partially indeterminate (I), and partially false (F) [as in neutrosophic logic]. If the implication $(C_{1})$ has the neutrosopihc truth value $(T_{1}, I_{1}, F_{1}), $and the reciprocal implication $(C_{2}) $has the neutrosophic truth value $(T_{2}, I_{2}, F_{2})$, then the \textbf{neutrosophic degree of paradoxicity }of the statement $<$S$>$ is the average of the component triplets: $((T_{1}+T_{2})/2, (I_{1}+I_{2})/2, (F_{1}+F_{2})/2),$ where the addition of two sets A and B (in the case when T, I, or F are sets) is simply defined as: A + B = {\{}x $\vert $ x = a + b, with a$\in $A and b$\in $B{\}}. [Preview Abstract] |
|
F1.00038: Final Results from a Large-Scale National Study of General Education Astronomy Students' Learning Difficulties with Cosmology Colin Wallace, Edward Prather, Douglas Duncan We recently completed a large-scale, systematic study of general education introductory astronomy students' conceptual and reasoning difficulties related to cosmology. As part of this study, we analyzed a total of 4359 surveys (pre- and post-instruction) containing students' responses to questions about the Big Bang, the evolution and expansion of the universe, using Hubble plots to reason about the age and expansion rate of the universe, and using galaxy rotation curves to infer the presence of dark matter. We also designed, piloted, and validated a new suite of five cosmology Lecture-Tutorials. We found that students who use the new Lecture-Tutorials can achieve larger learning gains than their peers who did not. This material is based in part upon work supported by the National Science Foundation under Grant Nos. 0833364 and 0715517, a CCLI Phase III Grant for the Collaboration of Astronomy Teaching Scholars (CATS). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. [Preview Abstract] |
|
F1.00039: Outreach and Education on Photovoltaic Systems Deanna Lewis, Adria Brooks, Vincent Lonij, Alex Cronin Our photovoltaic (PV) outreach and education project is designed to promote understanding of PV technology through tours of PV facilities, experiential education, public lectures, and volunteer opportunities. In collaboration with Tucson Electric Power we give tours of an outdoor solar test yard. We organized Girl Scout camps thematic to solar power education, taught grade-school teachers about solar power curricula, started a non-profit organization for volunteer PV system installers, and served as mentors for the Tucson public schools' solar go-cart program. Examples of these outreach activities will be described. [Preview Abstract] |
|
F1.00040: Quantum Information and Nepal Adam Brady, Nirdosh Chapagain, Prashanna Simkhada Quantum Information (QI) is a relatively young science with exciting research opportunities. Nepal has an untapped reserve of motivated students with scientific research potential. Based on our educational experience in Nepal and in the US and based on our exposure to QI, we explore the possibility of developing QI research in Nepal. In this poster we lay out basic facts on physics and physics education in Nepal, report on an introductory QI class experiment at BYU, and use what we have learned to envision a QI future in Nepal. [Preview Abstract] |
|
F1.00041: Chemical Physics Program at the University of Arizona Charles A. Stafford, Michael F. Brown The Chemical Physics Program at The University of Arizona provides an interdisciplinary track for cutting-edge research at the forefront of the interface of Physics and Chemistry. Research is highly collaborative and interdisciplinary in nature and geared towards preparing students for a career in research in fields including: nanotechnology, spectroscopy, and organic electronics. Successful applicants will be able to perform research in participating groups in both Chemistry and Physics, all of whom share a broad multidisciplinary outlook. Students in the Chemical Physics Program have the opportunity for a very flexible graduate course track. The course sequence is chosen to optimally meet the student's interests. [Preview Abstract] |
|
F1.00042: Biological Physics Program at the University of Arizona Koen Visscher, Michael F. Brown Biological Physics studies the physics of life processes by applying the quantitative physical sciences approach to outstanding problems in Biology while also feeding crucial insights back into Physics. The Biological Physics Program is a graduate program with a broad scope, involving Physics, Chemistry and Biochemistry, and Molecular and Cellular Biology faculty members. Graduate work in involves teamwork and collaboration that cuts across the traditional boundaries of academic departments and includes the areas of single molecule biophysics, molecular simulations, and membrane biophysics. The Biological Physics Program offers laboratory rotations and research opportunities in multiple departments and opportunities for research fellowships and awards. [Preview Abstract] |
|
F1.00043: Using Chemical Compositions of Kinematically Selected Stars to Trace Galactic Mergers Dylan Gregersen, Inese Ivans, Claire Lackner, Christine Allen Low \textit{$\alpha $}-element chemical abundances discriminate rare stars from their place among the rest of the halo population of our Milky Way. The unusual chemical nature is thought to distinguish them as remnants of a now merged extragalactic system. Until now, these stars have only been found serendipitously, on the order of a few in a thousand. In this talk, we report stars with low enhancements of \textit{$\alpha $}-elements found within two kinematically distinct candidate moving clusters. Stars within these candidate moving clusters were distinguished from common halo stars by shared stellar characteristics in orbital energy, angular momentum, and overall chemical enrichment (Allen et al, 2007, Proc. IAU, 2: 405-413). Using high-resolution spectra, we employed multi-line analysis code with stellar models to determine their chemical compositions. This study is part of a larger chemical composition investigation of these and other stars to search for other low-\textit{$\alpha $} star tracers of the dynamic formation of our Galaxy. [Preview Abstract] |
|
F1.00044: Scanning Probe Microscopy of Graphene Pamela Tautz Scanning tunneling microscopy has been used to study the unusual electronic properties of graphene. In an effort to support the graphene with minimal interaction with the substrate, we used a hexagonal boron nitride (hBN) substrate. To minimize contaminants between the CVD graphene and boron nitride, the graphene samples were cleaned with distilled water and isopropanol prior to transfer to hBN substrate. We have also examined the growth of graphene flakes by chemical vapor deposition. In particular, we examined the relationship between the orientations of the first and second layer of CVD grown graphene. We found the growth mechanism preferentially resulted in rotations of 9$^{\circ}$ or less indicating flakes with first and second layers aligned. [Preview Abstract] |
|
F1.00045: What model describes a Brownian particle? Scott Hottovy For a small particle in fluid, the dynamics of the system in the limit where friction effects dominate the inertial (i.e. the mass of the particle goes to zero) are important for diffusion approximations. The approximation will have differing drift fields which are dependent on the relationship between friction and diffusion that lead to interesting and physically relevant results. [Preview Abstract] |
|
F1.00046: A Stochastic Model of RNA Translation with Frameshifting Brenae Bailey Many viruses can produce different proteins from the same RNA sequence by encoding them in overlapping genes. One mechanism that causes the ribosomes of infected cells to decode both genes is called programmed ribosomal frameshifting (PRF). Although PRF has been recognized for 25 years, the mechanism is not well understood. We have developed a model that treats RNA translation as a stochastic process in which the transition probabilities are based on the free energies of local molecular interactions. The model reproduces observed translation rates and frameshift efficiencies, and can be used to predict the effects of mutations in the viral RNA sequence on both the mean translation rate and the frameshift efficiency. [Preview Abstract] |
|
F1.00047: Truncation and Extrapolation of Ab initio Calculations in a Finite Model Space Matthew Ishkhan Avetian, S.A. Coon, M.K.G. Kruse, U. Van Kolck, P. Maris, J.P. Vary Estimating the errors due to the truncation to a model space is crucial for ab initio calculations which require an extrapolation scheme to obtain a converged result in the full space. Of the calculations done in a harmonic oscillator (HO) basis, the model space is assumed to be characterized by Nmax which counts the maximum number of shells, above the minimum configuration, kept in the total energy. In the spirit of effective field theory (EFT) we have examined the dependence of the truncated results on two regulators of the model space. The HO ultraviolet (UV) regulator $\Lambda$ is associated with the maximum momentum included in the calculation. The infrared (IR) regulator $\lambda$ is associated with the minimum momentum variation allowed. Our investigations are made with different ``realistic'' NN interactions smooth enough that these calculations, performed with a technology developed for the shell model, are variational in nature. Our energy spectra show a significant tendency towards simple scaling in these two regulators as the calculation approaches separately the IR and UV limits. We have established a novel extrapolation parameter composed of the two UV and IR regulators which appears universal (and NN interaction and nucleus independent) and is useful even for modest model spaces. [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