Bulletin of the American Physical Society
Joint Fall 2017 Meeting of the Texas Section of the APS, Texas Section of the AAPT, and Zone 13 of the Society of Physics Students
Volume 62, Number 16
Friday–Saturday, October 20–21, 2017; The University of Texas at Dallas, Richardson, Texas
Session N4: Biophysics II/Atomic Molecular & Optical Physics I |
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Chair: Kuei Sun, University of Texas at Dallas Room: DGAC 1.128 |
Saturday, October 21, 2017 2:30PM - 2:42PM |
N4.00001: Decoupling Entropy and Energy in the Partition Function of Grafted Polymers: some Mean-Field Results Marian Manciu The partition function of a polymer can be, in general, written as a sum over shorter configurations (loops, trains and tails), whose probability of occurrence can be easily calculated in the limit of infinite dilution (corresponding to a non-interacting polymer). In the presence of interactions (between monomers and monomers, monomers and solvent and monomers and surfaces), the minimum mean field energy corresponding to a configuration can also be straightforwardly estimated. Consequently, a constrained minimization allows the calculation of the probability of occurrence of the configurations in the polymer brush and therefore the determination of the physical properties of the polymer brush. The model predicts the range in which the well-known Alexander' scaling laws are valid and allows to calculate the transitions from a collapsed brush to a parabolic brush (predicted by the self-consistent field theory of Milner, Witten and Cates) and successively to a step-like brush (suggested by the Alexander-De Gennes model). For two interacting surfaces, it is shown that the adsorbed polymer can induce either long range repulsions or long-range attractions, depending on the interaction parameters. [Preview Abstract] |
Saturday, October 21, 2017 2:42PM - 2:54PM |
N4.00002: Analysis of Serotonin Molecules on Silver Nanocolloids -- a Raman Computational and Experimental Study Emma Sundin, John Ciubuc, Kevin Bennet, Felicia Manciu The neurotransmitter serotonin is found throughout the human body and serves numerous functions, but is found physiologically in very low concentrations. To better understand issues surrounding detection and monitoring of serotonin at such levels, this study combines quantum chemical density functional modeling and surface-enhanced Raman spectroscopy. The ultrasensitive experimental analyte detection at 10$^{\mathrm{-11}}$ molar concentrations is in relatively good agreement with the modeled results. The simulation results indicate the presence of all serotonin molecular forms, including neutral, ionic, and redox-reaction oxidized forms. Furthermore, ionic and oxidized forms were found to exhibit molecular deformations such as bending of amine chains. Serotonin is thus revealed, by this combined approach, to absorb with greater probability onto the silver surface at its hydroxyl/oxygen sites than through NH/nitrogen sites, and to absorb more readily in its neutral (reduced) form than in its ionic forms. By investigating the vibrational signatures of this important neurotransmitter, this study furnishes some necessary background for future advancements in opto-voltammetric biosensors. [Preview Abstract] |
Saturday, October 21, 2017 2:54PM - 3:06PM |
N4.00003: Improving Performance of an Analog Electronic Device Using Quantum Error Correction Corey Ostrove, Brian La Cour, S. Andrew Lanham, Granville Ott The use of analog classical systems for computation is generally thought to be a difficult proposition due to the susceptibility of these devices to noise and the lack of a clear framework for achieving fault-tolerance. We present results for the application of quantum error correction techniques to a prototype analog computational device called a quantum emulation device (QED). It is shown that for the gates tested (Z, X and SH) there is a marked improvement in the performance characteristics of the gate operations. Gate performance after QEC, as measured by the average log-fidelity ($-\log_{10}(1-F)$), increases by 2.15. This corresponds to a reduction in the infidelity of the gate operation by more than two orders of magnitude on average. Comparison to numerical modeling of device errors shows that the errors in the device are well modeled by a combination of small random perturbations in the gate coefficients and by a baseline degradation from additive white gaussian noise (AWGN). [Preview Abstract] |
Saturday, October 21, 2017 3:06PM - 3:18PM |
N4.00004: Super-quasicrystal stripe phases in optical superlattices with Raman-assisted tunneling Junpeng Hou, Haiping Hu, Kuei Sun, Chuanwei Zhang Quasicrystal is a class of ordered structures defying conventional classification of solid crystals and may carry classically forbidden (e.g. 5-fold) rotational symmetries. In view of long-sought supersolids, a nature question is whether the quasicrystal order can also coexist with superfluidity, forming "super-quasicrystals", which spontaneously break $U(1)$ symmetry due to superfluidity and forms quasicrystalline order that is not possessed by the underlying Hamiltonian. Here we show that a super-quasicrystal stripe state with the minimum 5-fold rotational symmetry can be realized as the ground state of a Bose-Einstein condensate in an optical superlattice with Raman-assisted tunneling. There exists a rich phase diagram consisting of various super-quasicrystal, supersolid, plane-wave phases, and their phase transitions. Our scheme can be generalized for generating other higher-order (e.g., 7-fold) quasicrystal states, and provides a platform for investigating such new exotic quantum matter. [Preview Abstract] |
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