Bulletin of the American Physical Society
16th Annual Meeting of the Northwest Section of the APS
Volume 60, Number 6
Thursday–Saturday, May 14–16, 2015; Pullman, Washington
Session E2: Multidisciplinary and Applied Physics |
Hide Abstracts |
Chair: Michael McNeil Forbes, Washington State University Room: Webster Physical Sciences 11 |
Saturday, May 16, 2015 1:30PM - 2:00PM |
E2.00001: Wavelet analyses of Saturn's rings: Extracting masses and motions from wavelet phases Invited Speaker: Matthew Hedman Wavelets are powerful tools for identifying and quantifying quasi-periodic patterns in data sets. Many analyses focus on the power in the wavelet, which quantifies the strength of any periodic signal as a function of position and frequency. However, it turns out that the phase of the wavelet transform can also be extremely useful for characterizing certain types of signals. This talk will present examples of how we have extracted interesting new information about Saturn's rings from wavelet phase analyses of quasi-periodic patterns known as density waves that are generated at specific ring locations by periodic forces. Many of these waves can be attributed to perturbations from Saturn's various moons, but analyses of the wavelet phases have allowed us to identify the frequency of the perturbing forces involved and demonstrate that certain waves are likely produced by normal-mode oscillations inside the planet itself. Elsewhere in the rings, wavelet phase information enables extremely weak wave signals to be identified in nearly opaque regions, yielding new estimates of the rings' surface mass density. These wavelet techniques are therefore providing new insights into the planet's internal structure and the rings' total mass.\\[4pt] In collaboration with Philip Nicholson and Matthew Tiscareno, Cornell University. [Preview Abstract] |
Saturday, May 16, 2015 2:00PM - 2:12PM |
E2.00002: Imaging and spectral analysis of underwater objects Daniel Plotnick, Philip Marston Coherent sonar provides a versatile tool for the study of underwater objects and environments. High resolution images of the seafloor may be formed through the use of a synthetic aperture. Scattering from objects on the seafloor may be used to identify their position, orientation, shape, and material properties. Fourier based imaging algorithms are used to isolate objects from nearby clutter, and the acoustic spectra of the objects may be used to aid identification. In the work performed at Washington State University, scaled sonar experiments test new sonar algorithms and examine physical scattering mechanisms. Scattering experiments with canonical targets, such as spheres and cylinders, are carried out and mechanisms including surface elastic waves, internal glory rays, and shape modes are observed. Images of the objects formed using a variety of scan geometries are explored. Finally, a full scale collaborative experiment carried out with the University of Washington is discussed. [Preview Abstract] |
Saturday, May 16, 2015 2:12PM - 2:24PM |
E2.00003: Identification of Acoustic Backscattering Mechanisms from Partially Exposed Elastic Spheres at an Air-Water Interface Aaron Gunderson, Philip Marston Backscattered ultrasound in water from a variety of spherically shaped elastic targets breaking through an air-water interface is recorded and analyzed. The acoustic illumination is at grazing incidence. Reflected features are identified and compared to expected models in the time domain and frequency domain, developed through various techniques including ray theory, partial wave series analysis, the Kirchhoff Approximation, and complex root finding methods. Features are identified as direct target reflections, multipath reflections involving the interface, elastic target features, and surface guided waves. Comparisons between experimental and theoretical solutions indicate that Rayleigh waves (surface elastic waves) and Franz waves (diffracted surface waves) contribute greatly to the backscattering signatures of elastic spherical targets. The presence, strength, and timing of various scattering features are shown to depend on target material properties, as well as on incident acoustic frequency, target exposure in the water, and underwater viewing angle. Scattering from objects at a free surface can be used to simulate scattering from objects partially buried in smooth sand, such as the seafloor, due to their similar relative acoustic impedances. [Preview Abstract] |
Saturday, May 16, 2015 2:24PM - 2:36PM |
E2.00004: Cavity Cooling of Positrons for Anti-Hydrogen Production Nathan Evetts, Alex Povilus, Eric Hunter, Isaac Martens, Jonathan Wurtele, Walter Hardy, Joel Fajans Precise spectroscopic measurements of anti-hydrogen at the ALPHA experiment aim to probe the mystery of antimatter asymmetry in our universe. However, these measurements are hindered by small numbers of cold anti-atoms. I will describe a cooling technique for positron plasmas which can be used to increase the number of trappable anti-hydrogen atoms. The technique builds on previous work which allows control of spontaneous emission via the Purcell Effect. Our implementation incorporates a novel microwave resonator into an existing Penning trap to enhance spontaneous emission. Preliminary data suggests that temperatures and cooling rates for these plasmas can be improved by about a factor of 10. Eventually this work could result in an order of magnitude increase in anti-hydrogen production at ALPHA. [Preview Abstract] |
Saturday, May 16, 2015 2:36PM - 2:48PM |
E2.00005: Soy Protein Nanocapsules Fabricated by Flash Desolvation Approach (FDA) Yu-Chung Chang, Li-Ju Wang, Geng Jian, Lei Li Nanocapsules (NCs) are promising carriers for drug delivery, food enhancement, nutraceuticals, and for self-healing materials. Among numerous candidate materials, soy protein (SP) has enabled a wave of research due to its unique functional structures, biocompatibility, and low cost. In this study, we discovered a new self-assembly mechanism to control the formation of soy protein nanocapsules (SP-NCs). For the first time, our group utilized Flash Desolvation Approach (FDA) to fabricate SP-NCs. In FDA, three jets of desolvating agent are used to impinge the stream of SP suspension inside a micromixer. Desolvating at nanoscale processes only within milliseconds and SP-NCs are self-assembly while solvent shifting. The size of SP-NCs is controllable between 80 $\sim$ 200 nm. The effects of SP concentration, solvent ratio, and impinging speed were systematically studied. The size, surface charge, stability, and morphology of SP-NCs were characterized. It was found that the NC size decreased with increasing the SP concentration. With the increase of desolvating agent ratio by FDA, the NC size decreased. Both results are significant different from conventional desolvation method. It reveals that FDA drives a new self-assembly mechanism to form NCs. [Preview Abstract] |
Saturday, May 16, 2015 2:48PM - 3:30PM |
E2.00006: Break
|
Saturday, May 16, 2015 3:30PM - 4:00PM |
E2.00007: Generalized Gaussian Wave Packet Dynamics for Chaotic Systems Invited Speaker: Steven Tomsovic By developing the connection between the semiclassical method of heteroclinic orbit summations\footnote{S. Tomsovic and E. J. Heller, Phys. Rev. E 47, 282 (1993)} and generalized Gaussian wave packet dynamics (GGWPD),\footnote{D. Huber, E. J. Heller, and R. G. Littlejohn, J. Chem. Phys. 89, 2003 (1988)} we demonstrate how to implement GGWPD for fully chaotic systems where the information about the nonlinearities in the dynamics resides in a sum over multiple saddle points. These complex saddle point trajectories are found using a scheme equivalent to a Newton-Raphson method of root finding using the heteroclinic orbits because each one resides within the domain of convergence of a unique saddle point; there are exceptions which are easy to identify. In this sense, the saddle points thus found correspond to classically allowed transport. The method is applied to the chaotic kicked rotor and comparisons of the accuracy are made between the quantum results and the saddle point and heteroclinic orbit approximations.\\[4pt] In collaboration with Harinder Pal and Manan Vyas, Universidad Nacional Autonoma de Mexico. [Preview Abstract] |
Saturday, May 16, 2015 4:00PM - 4:12PM |
E2.00008: Accurate heteroclinic orbits and phase space areas Jizhou Li, Steven Tomsovic Accurate calculation of heteroclinic and homoclinic orbits can be of significant importance in some classes of dynamical system problems. Yet for very strongly chaotic systems initial deviations from a true orbit will be magnified by a large exponential rate making direct iteration methods fail quickly. In this presentation, a method is developed that avoids direct calculation of the orbit by making use of the structural stability property of the invariant unstable and stable manifolds. Under an area-preserving map, this property assures that any initial deviation from the stable (unstable) manifold will collapse onto them under backward (forward) iterations of the map. Using a set of judiciously chosen auxiliary points on the manifolds, long orbit segments can be calculated using the stable and unstable manifold intersections of the heteroclinic (homoclinic) tangle. Detailed calculations using the example of the kicked rotor are provided along with verification of the relation between action differences and certain areas bounded by the manifolds.\footnote{R. S. MacKay, J. D. Meiss, and I. C. Percival, Physica 13D, 55 (1984)}$^,$\footnote{J. D. Meiss, Rev. Mod. Phys. 64, 795 (1992)} [Preview Abstract] |
Saturday, May 16, 2015 4:12PM - 4:24PM |
E2.00009: Ultrafast Carrier Dynamics in Single-Crystal Two-Dimensional CuInSe$_{2}$ Nanosheets Xin Tao, Elham Mafi, Yi Gu Recently, two-dimensional (2D) layered materials beyond graphene are being extensively studied. In particular, the excitonic effects due to the decreased dielectric screening in 2D materials contributes significantly to the enhanced optical absorptions, which motivates the explorations of more ``conventional'' semiconductors in the 2D form for solar cell applications. One material of interest is CuInSe$_{2}$, with CuInSe$_{2}$-based solar cells among the most efficient thin-film technologies. Here, we report, for the first time, the synthesis of single-crystal CuInSe$_{2}$ nanosheets with the thickness on the nanoscale by solid-state chemical reaction. Carrier dynamics was studied via the measurements of the transient optical reflectivity using an optical pump-probe technique. Hot carrier cooling was suggested to dominate the carrier dynamics within a few ps following the optical excitation. The hot carrier diffusion coefficient was obtained by spatially resolved pump-probe measurements. The dependence of the hot carrier diffusion coefficient on the nanosheet thickness provides insight into the limiting mechanisms of hot carrier transport, and can be used to gauge the possibility of efficient hot carrier collection in nanostructured CuInSe$_{2}$ solar cells. [Preview Abstract] |
Saturday, May 16, 2015 4:24PM - 4:36PM |
E2.00010: Removal of Actinides and Lanthanides from Aqueous Solution by DTPA-Functionalized Magnetic Nanosorbents Huijin Zhang, Rocklan McDowell, Leigh Martin, You Qiang Diethylenetriamine pentaacetic acid (DTPA) functionalized magnetic nanosorbents have been synthesized and investigated for the removal of actinides and lanthanides from aqueous solutions in our laboratory. Various factors influencing metal sorption efficiency such as contact time, solution pH, and ionic radius of metal ions were studied. The sorption process reached saturation within 30 min of contact. For actinides, the oxidation states of metal ions had great effect on the chelating efficiency, which can be utilized to improve the separation selectivity. Displacement phenomena were observed between the heavier and lighter trivalent lanthanides (Ln(III)) that were co-existing in solution. The Ln(III) interaction with DTPA-functionalized magnetic nanosorbent followed the pseudo-second-order kinetics with a correlation coefficient extremely high and close to unity. The order of affinity of Ln(III) to DTPA functionalized magnetic nanosorbents perfectly followed the corresponding stability constants between Ln(III) and non-immbolizied DTPA. [Preview Abstract] |
Saturday, May 16, 2015 4:36PM - 4:48PM |
E2.00011: Using Lasers to Achieve Extreme Material States on Ultra-fast Timescales James Hawreliak The vast majority of observable matter in our galaxy is much hotter and denser than the solids, liquids and gases we have on earth. Studying these extreme material states is complex and exciting. Exciting, because it tests the limits of scientific understanding of the phenomena by which atoms, ions and electrons interact and organize over a range of extreme conditions. Complex, because the study of materials in these conditions is multi-disciplinary. Dynamic compression provides a form of inertial confinement, where the pressure is applied as an impulse and the state is maintained while the pressure traverse the sample. Through dynamic compression some of the most extreme states of matter can be achieved. Recent experimental developments have coupled x-ray probes to shock wave pumps have started to build the bridge between the continuum level response of a material and the atomic phenomena that cause it. This talk will cover experiments where in situ probing with x-rays has looked at shock induced phase transitions in iron and defect formation in copper as well as material studies in the extreme states relevant to the cores of gas giants. [Preview Abstract] |
Saturday, May 16, 2015 4:48PM - 5:00PM |
E2.00012: Zinc Oxide Random Lasers: Threshold Enhancement and Operational Stability Zachariah Peterson, Robert Word, Rolf K\"onenkamp Both incoherent and coherent laser emission have been observed from a number of zinc oxide (ZnO) nanostructures. Our initial results show enhanced optical feedback in optically pumped ZnO nanoparticle films with the addition of scattering magnesium oxide (MgO) nanoparticles. The emission intensity, as well as the thresholds for line narrowing and amplification, all improve significantly. The effect of laser annealing on the lasing threshold was also investigated, as laser annealing has previously been shown to improve the optical properties of ZnO films. Laser annealing initially improves the lasing threshold and emission intensity. However, after some critical exposure the threshold deteriorates. The damage threshold is initially comparable to the lasing threshold, which brings into question the operating stability of these devices. Morphology changes are also observed to accumulate due to laser annealing. In order to resolve spectra from our random lasers, we show that certain modes can be excluded from emission spectra using a microscope objective with an adjustable internal aperture. Further work will focus on more methods for enhancing the lasing threshold and establishing highly stable operating conditions in ZnO random lasers. [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