Bulletin of the American Physical Society
Joint Spring 2012 Meeting of the Texas Sections of the APS and AAPT and Zone 13 of the SPS
Volume 57, Number 2
Thursday–Saturday, March 22–24, 2012; San Angelo, Texas
Session E1: Contributed Oral Presentations: APS 3 |
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Chair: C.A. Quarles, Texas Christian University Room: Houston Harte University Center UC 203 |
Friday, March 23, 2012 3:30PM - 3:42PM |
E1.00001: Tunneling, Diffusion and Dissociation of Feshbach Molecules in Optical Lattices Taylor Bailey, Carlos Bertulani, Eddy Timmermans We show that tunneling and diffusion of cold Rydberg molecules in optical lattices leads to somewhat unexpected effects. One of these effects is the resilience of the molecules to dissociation as their binding energy decreases. We also quantify the dynamics of molecular diffusion and dissociation of molecules in 1D harmonic optical lattice potential by comparing to analytical models. It is found that after an initial transient, the wave packet for dissociating molecules can be described by a power diffusion pattern of the type $\sigma(t)\propto t^{1/2}$ where $\sigma$ is the dispersion of the packet. Surprisingly, we could not obtain such a simple power law fit for the dispersion of dissociated atoms. [Preview Abstract] |
Friday, March 23, 2012 3:42PM - 3:54PM |
E1.00002: Superfluorescence of ZnO nanoparticles: a three-level model Pooja Singh, Yuri Rostovtsev We have studied fluorescence and second harmonic generation that occur in a three-level system. We have obtained that at approaching to the two-photon resonance, the efficiency of second harmonic is decreasing and intensity of resonant fluorescence is increasing. Under some condition, superfluorescence regime leads to generation of short intense pulses under two-photon excitation (duration of the pulses are shorter than the relaxation times). The obtained results are applied to ZnO nanoparticles to explain the experimentally observed behavior of second harmonic generation and two-photon emission excited by fs-laser pulses. [Preview Abstract] |
Friday, March 23, 2012 3:54PM - 4:06PM |
E1.00003: Studying the Proton Spin Puzzle with PHENIX Michael Daugherity The proton spin puzzle remains one of the biggest mysteries in fundamental particle physics today. This talk will explore how the PHENIX Collaboration's forward W-boson program uses RHIC, the world's only polarized proton-proton collider, to probe the spin structure of the proton. [Preview Abstract] |
Friday, March 23, 2012 4:06PM - 4:18PM |
E1.00004: Optically Controllable Photonic Structures Alexander Waldrop, Chris O'Brien, Olga Kocharovskaya Coherent control of the refractive index with vanishing absorption in multilevel systems was a subject of intense recent theoretical and experimental studies [1-3]. We suggest an attractive possibility to use such coherent control of refractive index for optical production and control of photonic structures in the resonant homogeneously distributed in space atoms. The idea is based on spatial modulation of a populated intermediate level position in three-level atoms in nearly degenerate ladder configuration leading to periodic resonant increase and decrease of the refractive index simultaneously keeping zero absorption/gain. Modulation of an intermediate level position is provided by an external standing wave of a laser field via ac-Stark effect allowing one for both optical production and efficient optical control of the produced photonic structures. Possible implementation of the proposed method in rare-earth doped crystals with excited state absorption is considered. \\[4pt] [1] N. Priote, B. Unks, J. Green, D. Yavuz, PRL 101, 147401(2008).\\[0pt] [2] C.O'Brien and O.Kocharovskaya, Phys. Rev. Lett., 107, 137401 (2011).\\[0pt] [3] C.O.Brien, et al., Phys. Rev. A 84, 063835 (2011). [Preview Abstract] |
Friday, March 23, 2012 4:18PM - 4:30PM |
E1.00005: Sample topography measurements by a novel image processing algorithm Bryant Aaron, Dan Tamir, Javad R. Gatabi, Wilhelmus Geerts, R.K. Pandey An exposure tool for lithography on non-flat samples is being developed. The pattern is directly written in a photoresist plated sample by moving the sample under a focused laser beam. During the writing process the topography of the surface is measured and a parametric model of the 3D surface is generated to allow for corrections of the exposure dose, the focus, and the direction of the light incident upon the sample. The system uses image processing techniques for estimating the distance of points on the surface to the objective. An illumination pattern consisting of four squares is projected on the surface of the sample. Images are taken with a high speed SCMOS camera. The topography of the sample is estimated from the measurements of the contrast around the projected patterns. To determine the contrast the k-means algorithm with k=2 is applied. The algorithm groups pixels into two clusters and the contrast is determined from average pixel values in high (u) and low intensity (v) clusters using (u-v)/Max; where max is the maximum pixel value detected in the image. Slope and focus quality are determined from the measured contrast values. The authors would like to thank NSF for financial support (grant: 0923506). [Preview Abstract] |
Friday, March 23, 2012 4:30PM - 4:42PM |
E1.00006: Three Dimensional Surface Topography Using LCD Pattern Transfer Method Javad R. Gatabi, Wilhelmus Geerts, Bryant Aaron, Dan Tamir, R.K. Pandey Laser lithography on curved surfaces has recently been researched due to its applicability in production processes for devices that combine integrated optical, mechanical, magnetic, and/or electronic technologies. Several laser lithography methods have been reported for pattern transfer to convex and cylindrical surfaces, but there is not a general methodology for arbitrary 3D surface lithography. This project implements an optical method for laser lithography on arbitrary 3D surfaces. An illumination pattern generated by a transparent LCD is projected through an optical microscope on top of a 3D surface and recorded by a camera. The focus quality and the distortion of the observed image depend on the local topography of the sample. The effect of the local sample topography on the projected pattern is theoretically investigated using Zemax ray-tracing software. Analysis are made for amplitude and phase modulation LCDs with different resolutions and compared with preliminary experimental results. The authors acknowledge financial support from NSF through an MRI-grant (grant: 0923506). [Preview Abstract] |
Friday, March 23, 2012 4:42PM - 4:54PM |
E1.00007: Onset of Marangoni convection of a liquid layer with insoluble surfactant in modulated thermal field Alexander Mikishev A horizontal layer of an incompressible liquid layer bounded by rigid lower plane and free non-deformable flat upper surface is considered. The layer is heated from below and the heat flux is varying with time around fixed mean value. On the free surface the liquid adsorbs an insoluble surfactant, whose local concentration changes with time due to the advection and diffusion. The linear stability analysis with respect to disturbances of arbitrary finite wave-numbers is performed. Two response modes of the convective system to an external periodic stimulation have been found, the first one with a period of oscillation twice as the period of heat flux modulation (subharmonic mode) and the second one with the same period (synchronous mode). The neutral stability curves are presented for a variety of external conditions. The cellular and long-wave instability thresholds are compared. [Preview Abstract] |
Friday, March 23, 2012 4:54PM - 5:06PM |
E1.00008: A Cable Equation Model of Electrical Signal Transmission in Non-uniformly Deformed Nerve Cells Emily Hendryx In order for the human body to function, neurons must be able to properly transmit electrical signals. One method of modeling this voltage flow is through the cable equation. Assuming that an aneurysm or tumor is present, we modify the cable equation to account for radially asymmetric deformation of a dendrite. Through this modification, we hope to improve our current understanding of overall brain function in the presence of neuronal deformation. [Preview Abstract] |
Friday, March 23, 2012 5:06PM - 5:18PM |
E1.00009: Utilizing Functionalized Nano-Paterned Surfaces as a clue to Cell Metastasis in Prostate and Breast Cancer James Matthews, Lyndon Bastatas There is a direct relation between the survival of a patient diagnosed with prostate or breast cancer and the metastatic potential of the patient's cancer. It is therefore extremely important to prognose metastatic potentials. In this study we investigated whether the behaviors of cancer cells responding to our state of the art nano-patterns differ by the metastatic potential of the cancer cells. We have used lowly (LNCaP) and highly (CL-1) metastatic human prostate cancer cells and lowly (MCF-7) and highly (MB231) metastatic breast cancer cells. A surface functionalization study was then performed first on uniform gold and glass surfaces, then on gold nano-patterned surfaces made by nano-sphere lithography using nano-spheres in diameter of 200nm to 800nm. The gold surfaces were functionalized with fibronectin (FN) and confirmed through XPS analysis. The CL-1, MCF-7, and MB231 cells show similar proliferation on all surfaces regardless of the presence of FN, whereas LNCaP show a clear preference for FN coated surfaces. The proliferation of the LNCaP was reduced when grown on finer nano-scaffolds, but the more aggressive CL-1, MB231, and MCF-7 cells show an abnormal proliferation regardless of pattern size. The difference in adhesion is intrinsic and was verified through dual fluorescent imaging. Clear co-localization of actin-vinculin were found on CL-1, MCF-7, and MB231. However LNCaP cells showed the co-localization only on the tips of the cells. These results provide vital clues to the bio-mechanical differences between the cancer cells with different metastatic potential. [Preview Abstract] |
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