Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session A3: Undergraduate Research - Society of Physics Students I |
Hide Abstracts |
Chair: Toni Sauncy, Society of Physics Students - American Institute of Physics Room: 107 |
Monday, March 3, 2014 8:00AM - 8:12AM |
A3.00001: Macroscopic Quantum Mechanics, Tunnelling, and Classical Gravity Deborah C. Good, Marie A.P. McLain, Lincoln D. Carr Macroscopic quantum mechanics is an active area of experimental research, which could benefit from understanding the effects of gravitational interactions in tunnelling. The Schr\"{o}dinger-Newton equation is one method for describing Newtonian gravitational interactions in quantum mechanics. While the Schr\"{o}dinger-Newton equation has been thoroughly described for the single-particle case, there are still open questions in the many-body case. Therefore, we investigate semi-classical solutions to the Schr\"{o}dinger-Newton equation for the many-body quantum tunnelling case using a variational-WKB method. [Preview Abstract] |
Monday, March 3, 2014 8:12AM - 8:24AM |
A3.00002: Modeling the Expansion and Collapse of Shell-Shaped Bose-Einstein Condensates Lydia Shannon, Courtney Lannert Bose-Einstein condensates, produced when atomic gases are cooled to near absolute zero, offer a macroscopic way to view the quantum mechanical world. In order to measure properties of these condensates, the cooled gas must be released from a potential trap and allowed to expand. We explore the three-dimensional system of a shell shaped BEC by applying a recent numerical method for solving the Gross-Pitaevskii equation, to study the properties of the condensate's expansion and collapse. Upon release of the BEC into a harmonic trap (inner collapse only), we observe self-interference fringes and central mass accumulation within the system, taking into account the interactions of atoms in the condensate. By manipulating the parameters of the trap, we also study spherically symmetric collective modes with properties that are distinct from that of a filled, spherical condensate. [Preview Abstract] |
Monday, March 3, 2014 8:24AM - 8:36AM |
A3.00003: Entanglement in ground and excited states of gapped fermion systems and their relationship with fermi surface and thermodynamic equilibrium properties Michelle Storms, Rajiv Singh We study bipartite entanglement entropies in the ground and excited states of model fermion systems, where a staggered potential, $\mu_s$, induces a gap in the spectrum. Ground state entanglement entropies satisfy the ``area law,'' and the ``area-law'' coefficient is found to diverge as a logarithm of the staggered potential, when the system has an extended Fermi surface at $\mu_s=0$. On the square-lattice, we show that the coefficient of the logarithmic divergence depends on the fermi surface geometry and its orientation with respect to the real-space interface between subsystems and is related to the Widom conjecture as enunciated by Gioev and Klich (Phys. Rev. Lett. 96, 100503 (2006)). For point Fermi surfaces in two-dimension, the ``area-law'' coefficient stays finite as $\mu_s\to 0$. The von Neumann entanglement entropy associated with the excited states follows a ``volume law'' and allows us to calculate an entropy density function $s_{V}(e)$, which is substantially different from the thermodynamic entropy density function $s_{T}(e)$ when the lattice is bipartitioned into two equal subsystems, but approaches the thermodynamic entropy density as the fraction of sites in the larger subsystem, that is integrated out, approaches unity. [Preview Abstract] |
Monday, March 3, 2014 8:36AM - 8:48AM |
A3.00004: Quantum phase transitions in the underscreened pseudogap Kondo model Jaimie Stephens, Kevin Ingersent The Kondo effect is the collective screening of the spin of a magnetic impurity atom by the electrons in a nonmagnetic host metal, a fundamental problem in many-body physics. This work addresses a variant in which an impurity spin-1 can only be partially screened by the spin-1/2 conduction electrons of the host. In particular, we study the pseudogap version of this underscreened Kondo model, where the conduction-electron density of states vanishes like $|E - E_F|^r$ at the Fermi energy $E = E_F$. This problem, of current interest in connection with the behavior of impurities in graphene, features a continuous quantum (zero-absolute-temperature) phase transition between underscreened-Kondo and non-Kondo ground states that occurs at a critical value of the impurity-band exchange coupling. We have used the numerical renormalization- group method to study the critical properties in the vicinity of the transition. Various critical exponents, which have a nontrivial dependence on the density of states exponent r, obey the hyperscaling relations expected at an interacting quantum critical point that cannot be described by any simple (mean-field) theory. [Preview Abstract] |
Monday, March 3, 2014 8:48AM - 9:00AM |
A3.00005: Quantum Theoretical Study of KCl and LiCl Clusters Ted Koetter, Ajit Hira, Justin Salazar, Danelle Jaramillo This research focuses on the theoretical study of molecular clusters to examine the chemical properties of small K$_{\mathrm{n}}$Cl$_{\mathrm{n}}$ and Li$_{\mathrm{n}}$Cl$_{\mathrm{n}}$ clusters (n $=$ 2 - 20). The potentially important role of these molecular species in biochemical and medicinal processes is well known. This work applies the hybrid ab initio methods of quantum chemistry to derive the different alkali-halide (M$_{\mathrm{n}}$H$_{\mathrm{n}})$ geometries. Of particular interest is the competition between hexagonal ring geometries and rock salt structures. Electronic energies, rotational constants, dipole moments, and vibrational frequencies for these geometries are calculated. Magic numbers for cluster stability are identified and are related to the property of cluster compactness. Mapping of the singlet, triplet, and quintet, potential energy surfaces is performed. Calculations were performed to examine the interactions of these clusters with some atoms and molecules of biological interest, including O, O2, and Fe. Potential design of new medicinal drugs is explored. [Preview Abstract] |
Monday, March 3, 2014 9:00AM - 9:12AM |
A3.00006: Density functional calculation of superatomic molecular orbitals in C60: First truly converged results on a real grid mesh Kyle Drake, Jason Bonacum, Guo-ping Zhang The molecular structure of Buckminster fullerene (C60) allows for electron delocalization in all of the pi-bonding electrons of the molecule. This coupled with the symmetry of the molecule allows for the formation of super-atomic molecular orbitals (SAMOs) similar to those observed in aluminum clusters. The SAMOs behave as if the molecule that they belong to is a single atom. We compute the eigenstates of C60 compulationally using density functional theory (DFT) and a grid mesh. Using larger radii also allows us to accurately describe SAMOs and test the convergence of our data. The results are interesting because for the first time, we can show the true converged super atomic orbitals in C60. [Preview Abstract] |
Monday, March 3, 2014 9:12AM - 9:24AM |
A3.00007: DFT Calculations of Carbon Monoxide Adsorbed on Pt and Ru Surfaces Nestor Navarro, Andres Salgado, Julian Velazquez, Nicholas Dimakis, Eugene Smotkin The effect of carbon monoxide surface coverage on Platinum and Ruthenium surfaces has been studied using density functional theory (DFT) on periodic structures. DFT shows that as CO coverage increases the adsorbate internal bond strengthens as verified by the corresponding stretching frequency upshifts. Moreover, increased surface coverage reduces the CO adsorption energy in agreement with prior repots. These results are correlated with changes in the hybrid adsorbate-substrate orbitals, their polarizations within the CO molecule unit, and changes in the CO dipole moment. Here, we establish a theoretical framework based on the $\pi $-attraction and $\sigma $-repulsion mechanism to explain the behavior of the CO on these surfaces at different coverages. [Preview Abstract] |
Monday, March 3, 2014 9:24AM - 9:36AM |
A3.00008: Studying the Toroidal Dipole Moment within Metamaterials Aaron Mohammed, Khagendra Bhattari, Jiangfeng Zhou Recently, a toroidal dipole moment was demonstrated by using metamaterials in the classical electrodynamic system, which behaves with a number of unusual electromagnetic properties. In this project, we are particularly interested in optimizing metamaterial design for enhancing the toroidal moment, which could be used in potential applications like low-threshold plasmonic lasing or biosensing. Through numerical simulations, a number of toroidal metamaterial designs, which are made up of planar split ring resonators (SRRs), are studied and the toroidal moment of each design is calculated. [Preview Abstract] |
Monday, March 3, 2014 9:36AM - 9:48AM |
A3.00009: Optimal Vaccination For A Probabilistic Epidemic Edwin Yuan, Sean Stromberg, Jean Carlson In epidemiology, herd immunity is the well-known idea that by vaccinating a sufficient fraction of a susceptible population, one lowers the basic reproduction number of the pathogen below one, and thereby prevents an epidemic. A natural conclusion from this is that given two identical populations, and enough vaccine to induce herd immunity in only one, we can prevent the greatest number of people from infection by inequitably distributing vaccine to completely protect one population while leaving the other much more relatively susceptible. This heuristic has been verified by simulation of the standard deterministic SIR epidemic. We show, however, that when stochasticity is introduced to the system, or more specifically when there is now a significant probability that an epidemic will not develop independently, it is counter-intuitively optimal to distribute vaccine more equally and not induce herd immunity in either population. There is thus a regime where the purely deterministic SIR model is a poor predictor of the optimal vaccination scheme. [Preview Abstract] |
Monday, March 3, 2014 9:48AM - 10:00AM |
A3.00010: Effects of Memantine and Oleocanthal on Alzheimer's Disease Mariyam Houston, Jason Bonacum, Guoping Zhang Alzheimer's Disease (AD) is a neurodegenerative disorder characterized by accumulation of neuritic plaques composed of amyloid-$\beta $ (A$\beta )$ proteins and neurofibrillary tangles composed of tau proteins. Although there is no known cure for AD, the symptoms can be treated with a drug called memantine. Memantine acts an NMDAR antagonist by inhibiting the action of the NMDA receptor. Recently, Oleocanthal, a phenolic molecule that is found in extra virgin olive oil, has been linked to reduced risk of AD. Though the mechanism by which Oleocanthal plays in reducing the risk of AD is not completely understood, recent studies have shown that Oleocanthal somehow inhibits the formation of the neurofibrillary tangles and reduces the formation of A$\beta $ senile plaques. Our first-principles calculation, based on Gaussian03 program, shows that in the M2 segment, memantine binds to serine, but ketamine binds to glycine. This may explain their different effects, despite the fact that they are both NMDAR antagonists. Using the same method, we also investigate how Oleocanthal binds to the peptides by comparing the relative energies of each of the structures. Our results may help better understand the mechanism by which Oleocanthal decreases the chances of developing AD. [Preview Abstract] |
Monday, March 3, 2014 10:00AM - 10:12AM |
A3.00011: Self-organized criticality of protein folding simulations using AMBER parameters Yura Sim, Joelle Murray Self-organized criticality is a framework that can be used to describe many natural processes, ranging from avalanches to forest fires. These processes exhibit power-law characteristics and scale invariance. Self-organized critical systems have yet to be applied to protein folding and its identification as such may be useful to understanding protein behavior. A dynamical simulation was constructed using AMBER energy parameters and evidence of self-organized criticality was investigated. Furthermore, the features of self-organized criticality were used to explore the development of protein structures within the simulation. [Preview Abstract] |
Monday, March 3, 2014 10:12AM - 10:24AM |
A3.00012: How They (Should Have) Built the Pyramids Gregory Gallagher, Joseph West, Kevin Waters A novel ``polygon method'' is proposed for moving large stone blocks. The method is implemented by the attachment of rods of analytically chosen radii to the block by means of rope. The chosen rods are placed on each side of the square-prism block in order to transform the square prism into a prism of higher order polygon, i.e. octagon, dodecagon etc. Experimental results are presented and compared to other methods proposed by the authors, including a dragging method and a rail method which includes the idea of dragging the block on rails made from arbitrarily chosen rod-shaped ``tracks,'' and to independent work by another group which utilized wooden attachments providing a cylindrical shape. It is found that the polygon method when used on small scale stone blocks across level open ground has an equivalent of a coefficient of friction order of 0.1. For full scale pyramid blocks, the wooden ``rods'' would need to be of order 30 cm in diameter, certainly within reason, given the diameter of wooden masts used on ships in that region during the relevant time period in Egypt. This project also inspired a ``spin-off'' project in which the behavior or rolling polygons is investigated and preliminary data is presented. [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