Bulletin of the American Physical Society
Spring 2011 Meeting Ohio-Region Section of the APS
Volume 56, Number 3
Friday–Saturday, April 15–16, 2011; University Heights, Ohio
Session P1: Poster Session (4:30-6:00PM) |
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Room: Dolan Science Center A201-202 |
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P1.00001: Construction and optimization of local 3rd order passive shim system for human brain imaging at 4T MRI Mohan Jayatilake, Judd Storrs, Jeff Osterhage, Jing-Huei Lee The optimal MRI quality relies on a homogeneous magnetic field. However, local susceptibility variations within human brain can lead to field inhomogeneity that causes artifacts such as image distortion and signal drop-out, which become worse with increasing magnetic field strength. Many evidences showed that high order shims are required for optimal MRI at field greater than 3T. However, due to limited space, many MRI systems provide only up to second order active shims. In this work, we introduce a 3rd order local passive shimming along with the active 1st and 2nd order shimming to improve field homogeneity within the human brain for a group of subjects. A 3D gradient-echo pulse sequence was used to obtain $B_{0}$ field maps of four subjects' brains at 4T. The field maps for each subject were then decomposed into third-order spherical harmonic coefficients and averaged. The optimized positions, the required susceptibility and dimensions of shim elements for placement of shim elements on a cylindrical shim tube that fits over the RF coil were evaluated on a cylindrical surface to generate the desired magnetic field that can optimize the field variation over the entire human brain.When combined with first- and second-order active shimming, the passive shim tube significantly improved $B_{0}$ homogeneity within the brain. [Preview Abstract] |
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P1.00002: Potential Use of Lime as Nitric Acid Source for Alternative Electrolyte Fuel-Cell Method V. Christianto, Florentin Smarandache Despite growing popularity for the use of biofuel and other similar methods to generate renewable energy sources from natural plantation in recent years, there is also growing concern over its disadvantage, i.e. that the energy use of edible plants may cause unwanted effects, because the plantation price tends to increase following the oil price. Therefore an alternative solution to this problem is to find `natural plantation' which have no direct link to `food chain' (for basic foods, such as palm oil etc.). [Preview Abstract] |
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P1.00003: Simulated Ten Pin Bowling Collisions Jacob Bills, Craig Howald This work investigates the results of the dynamics in the collisions that occur in ten pin bowling. A finite element modeling system (LS-Dyna) was used to construct simplified but approximately physically realistic models and simulate collisions involving the twelve body system composed of a ball, ten pins, and a floor. The investigation focuses on the qualitative features of the map of final pin configuration as a function of the initial conditions. To appropriately limit the breadth of the initial configuration space investigated, the only variables adjusted were the position of the ball upon entering the pins and the initial angle of velocity relative to the long axis of the lane. Results concerning the size and shape of the sets of initial conditions that lead to similar final configurations, in particular those leading to none of the pins remaining standing (aka ``strikes''), are shown. [Preview Abstract] |
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P1.00004: Convergence of a particle swarm optimization algorithm David Hickman, Cavendish McKay In recent years particle swarm optimization (PSO) has been successfully applied to many research and engineering optimization problems. PSO has shown superior performance over other global optimization algorithms for problems with a large number of dimensions, or when the response surface is highly multimodal. We investigate the effects of dimensionality and internal PSO parameters on the rate of convergence. [Preview Abstract] |
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P1.00005: Dynamics of the two process model of human sleep regulation Max Kenngott, Cavendish McKay We examine the dynamics of the two process model of human sleep regulation. In this model, sleep propensity is governed by the interaction between a periodic threshold (process C) and a saturating growth/decay (process S). We find that the parameter space of this model admits sleep cycles with a wide variety of characteristics, many of which are not observed in normal human sleepers. We also examine the effects of phase dependent feedback on this model. [Preview Abstract] |
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P1.00006: Enhanced chemical sensing in the visible and near-UV utilizing amorphous, nanostructured photonic waveguides Sonja Abbey, Aarthi Srinivasan, Taraveni Chalasani, Gines Lifante, Krishna Manoharan, Ralph Whaley While extensive research has been conducted on the development and analysis of integrated photonic chemical sensors in the IR and near-IR regions, there has been relatively little work done in the visible and near-UV mostly due to the substantial absorption of group-IV and III-V materials in that wavelength range. This work focuses on the design of novel, nanoscale photonic architectures and materials for the application of enhanced chemical sensing in these wavelength regions. Specifically, this project uses ammonia (NH3) and titanium tetrachloride (TiCl4) as the study analytes and focuses on platforms composed of amorphous zinc oxide (a-ZnO) and amorphous hafnium dioxide (a-HfO2). Having an effective bandgap of 3.37 eV and 5.8 eV, respectively, and grown by rf sputtering on a wide variety of substrates at low temperature, a-ZnO and a-HfO2 are highly compatible with standard photonic device fabrication processes. Utilizing a low optical overlap mode (LOOM) architecture, in which only 1 percent of the optical mode resides in the core region, we predict a markedly higher sensitivity than conventional evanescent wave sensors - between 5X and 50X depending on polarization and host environment. [Preview Abstract] |
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P1.00007: Incident Angle Dependence of Organic Solar Cells Vincent DeGeorge, Brent Valle, Kenneth Singer We have recently been studying the use of interference effects to enhance optical absorption in polymer photovoltaic cells. These interference effects are expected to be angle dependent. We measure here the absorption incident angle dependence and compare it with numerical simulations. The cells used were P3HT/PCBM active layer, organic photovoltaic cells. The angular dependence of the cells' reflection was measured using an Ocean Optics light source and spectrophotometer and a precision rotary stage apparatus. The experimental results were compared to a Matlab simulation of the electrodynamic system. Analysis showed that the absorption peaks predicted by the simulation largely coincided in wavelength to those observed in experiment. Blueshift is minimal for most features of the absorption curves, however the absorption peak exhibited the largest shift, 40nm, due change in incidence angle. No additional cavity resonance can be attributed to incidence angle. [Preview Abstract] |
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P1.00008: Oxide Semiconductor Nanowire Biosensors Stephen Fleming, Xuan Gao Recently, several physics research groups have demonstrated that nanowire field effect transistors (FETs) can function as sensors to detect extremely low concentrations of biological molecules in solution.~ Continued development and improved understanding of these types of sensors is essential for the emergence of new technologies in disease diagnostics, drug screening, and the single molecule study of biomolecular reactions, to name only a few areas.~ Currently, the ability to directly and specifically sense molecules in solution would be groundbreaking for medicine, allowing real-time sensing to be incorporated into biomedical devices, as well as used in research.~ This research aims to contribute to an understanding of the functionality of oxide nanowire FETs, and demonstrate their potential for use as biomolecular sensors, aided in low concentration detection by dielectrophoretic concentration of analyte molecules. [Preview Abstract] |
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P1.00009: North/South Deep Fields Demolish the Copernican Principle Charles Sven ~~ The physics of light restricts the parameters of one's view.~ Recognizing such restrictions limits one's inference.~ Prior to Deep Field South results, one had less restrictions then now.~ With both results in hand, the position of the viewer is greatly limited to that of a central position in our Universe.~~~ -~ As noted by NASA: ``Though the field [deep] is a very small sample of the heavens, it is considered representative of the typical distribution of galaxies in space because the universe, statistically, looks largely the same in all directions.''~ -~~ These isotropic North/South views are only possible with a very slow moving Earth located next to the epicenter of the Big Bang.~~~ -~~~ This is a continuation of my presentations at various APS meetings including the 41st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics~ May 25--29, 2010; Houston, Texas~ Sven's Abstract: E1.00044 [Preview Abstract] |
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P1.00010: Self-Similar Bumps and Wiggles: Isolating the Evolution of the BAO Peak with Powerlaw Initial Conditions Chris Orban, David Weinberg Future observations of a subtle dark matter clustering feature known as Baryon Acoustic Oscillations (BAO) will play a key role in unraveling the mystery of dark energy. Originally detected in galaxy clustering data from the Sloan Digital Sky Survey and the Two-Degree Field Survey, by observing this feature the cosmological distance to galaxies at a particular redshift can be accurately determined and the expansion history of the universe constrained with high precision. A complication of this analysis, however, is that the clustering feature changes over time -- the ``bump'' feature broadens and is shifted slightly. We investigate a simplified model of Baryon Acoustic Oscillations using cosmological N-body simulations to better understand the underlying physics of how this feature evolves. We model our simulation results both phenomenologically and compare with ab initio predictions from perturbation theory, yielding useful insights for more physically-motivated cosmological models. The simplicity of our setup also allows interesting self-similar numerical tests that indicate that modern simulation methods and resolutions robustly capture the non-linear evolution of the BAO feature. [Preview Abstract] |
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P1.00011: Determining the Cause of Mass Segregation in h Persei Zac Long, Ann Bragg The double cluster h and chi Persei is unusual in that it is a pair of open clusters which are close to the same age and close in proximity to each other. Despite these similarities, however, we see a large difference in the distribution of masses in these clusters. In h Persei we observe that the more massive stars are closer to the core than the less massive stars, while in chi Persei we see a much more uniform distribution of masses. This difference in mass distribution is a puzzle which cannot be solved using information that is currently available. This poster will show the need for more velocity measurements of the stars in these clusters in order to determine cause of the observed difference. The necessary observations will be characterized and their feasibility will be assessed. [Preview Abstract] |
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P1.00012: An investigation of the nuclear black hole mass and global properties of NGC 4552 Peter Kircher, Jason Pinkney In previous papers, we presented the spectroscopic and photometric data needed to estimate the mass of the supermassive black hole in NGC 4552. Now we have a new, refined black hole mass estimate from gas disk kinematics. We plot our galaxy on the key demographic scaling relations of $M_{BH}$ vs. $\sigma$ and $M_{BH}$ vs. Luminosity. Since black hole formation appears to be intertwined with galaxy formation, we also compare the global properties of our galaxy (effective radius, luminosity, effective surface brightness, ellipticity) to other galaxies, including views of the ``fundamental plane.'' Our elliptical is relatively compact, low in ellipticity, with almost no rotational support and with a ``core'' surface brightness profile. We also consider the gas/dust morphology: NGC 4552 appears to be another galaxy with an erratic dust disk morphology which nevertheless produces an (apparently) accurate BH mass using gas kinematics. [Preview Abstract] |
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P1.00013: Relative Transition Probabilities of Rare Gases Daniel Delanis, Katherine Duncan-Chamberlin, Naveed Piracha We have measured relative transition probabilities for emissions from the noble gasses using hollow cathode lamps. Relative transition probabilities are reported for thirty lines from Ne I, twenty-four lines from Ar I, fourteen lines from Kr I, and twenty-one lines from Xe I. All transitions discussed are from the 2p level to 1s levels. Uncertainty has been measured and found to be within 5\%. This data can be applied to calibrate the relative detection efficiency of a spectrometer over a range of 4000 {\AA}--10000 {\AA}. Comparisons between the relative transition probabilities of each species is discussed. [Preview Abstract] |
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P1.00014: Absorption and Ablation for Non-Planar Geometries Benjamin Oh, John Sinko The Bouguer-Lambert-Beer absorption law is a critical component of analytical laser ablation models. This law has been found to be useful for planar applications but it can also have significance in non-planar geometries. To be accurate, these applications must take into consideration the precise physical setup. Certain geometries offer special properties that may be beneficial to laser propulsion methods, specifically those of uniform ablation using focusing nozzles. This paper investigates the special circumstances using modified forms of the absorption law that apply to the considered parabolic, conical and spherical non-planar geometries. [Preview Abstract] |
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P1.00015: The construction and characterization of optical traps for manipulating microscopic particles Tiffany Thompson, Ernest Behringer Optical traps use tightly focused laser light to manipulate microscopic particles and have applications in nanofabrication, characterizing DNA, and \textit{in vitro} fertilization [1]. We will describe the design, construction, and characterization of an optical trap that is capable of trapping and imaging 3 $\mu $m polystyrene spheres using a 12 mW HeNe laser. The design was based on previous work [2,3] describing how to build affordable optical traps. We will discuss trapping forces and their calibration. \\[4pt] [1] D.G. Grier, ``A Revolution in Optical Manipulation,'' Nature \textbf{424}, 810-816 (2003). \\[0pt] [2] S.P. Smith et al., ``Inexpensive optical tweezers for undergraduate laboratories,'' Am. J. Phys. \textbf{67} (1), 26-35 (1999).\\[0pt] [3] J. Bechhoefer \textit{et al.}, ``Faster, cheaper, safer optical tweezers for the undergraduate laboratory,'' Am. J. Phys. \textbf{70} (4), 393-400 (2001). [Preview Abstract] |
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P1.00016: Low frequency Raman study of the nucleosides Craig Koontz, Scott Lee In both transcription and replication, the two helices of the DNA molecule move apart. Consequently, vibrations involving the relative motions of large portions of the molecule with respect to one another are of intrinsic interest. Such vibrations have relatively low frequencies because they involve weak bonds and large masses. Low frequency modes are difficult to observe in Raman spectroscopy because they are very close to the signal from the Rayleigh scattered light (which is very intense). In this poster, we will describe our results for the eight nucleosides: adenosine, deoxyadenosine, guanosine, deoxyguanosine, cytidine, deoxycytidine, uracil and deoxythymidine. [Preview Abstract] |
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P1.00017: Investigation of the feasibility of a wide-field depth resolved optical imaging method Ben Curatolo, Peifang Tian Since the extraordinary capabilities of the brain are tied to the interactions of large groups of neurons, it is crucial to visualize how neuronal groups work together to represent and process sensory information. Wide-field optical imaging can achieve this by mapping a large cortical area with good spatial and temporal resolution. The main drawback is that it cannot resolve depth information. Since light at longer wavelength experiences less scattering than light at shorter wavelength, thus, can penetrate deeper into the brain, we may access different depths of the brain by using multiple wavelengths of light. As a first step to build such a wide-field depth resolved optical imaging system, we have performed a numeric feasibility study using Monte Carlo simulation and evaluated the performance of the proposed system using two light sources at 455nm and 590nm, respectively. We have found that these two wavelengths can indeed access different depths of the brain tissue, thus, our proposed method is feasible. [Preview Abstract] |
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P1.00018: Achieving collimated illumination for wide-field depth-resolved optical imaging John Kaminsky, Martin Glose, Stephen Neil V. Tacastacas, Peifang Tian Camera based wide field optical imaging allows for in vivo functional imaging of the brain. The benefits of this method include a larger sampling area, faster data acquisition and higher spatial resolution; however it is unable to resolve depth information. This issue may be resolved by employing multiple wavelengths in the imaging system. As a demonstration of principle, we are building an imaging system with two different wavelengths at 455 nm and 585 nm, respectively by employing light emitting diodes (LEDs). The beam of an LED diverges quickly, therefore the objective of my research was to attach a collimating lens to modify the beam and minimize the divergence. In order to achieve this, we investigated different types of collimating lens and found the optimal one that can collimate the beam. We will present radiation patterns of beams with and without collimating lens. [Preview Abstract] |
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P1.00019: Computer Simulation Study of the Stability Mechanism of Thermophile, MJ0305 Hyundeok Song, Thomas Beck Methanococcus jannaschii (MJ) is a methane-producing thermophile, which was discovered in a 2600m-deep Pacific Ocean vent in 1983. It has the ability to thrive at high temperatures and high pressures, which are unfavorable for most life forms. There have been some experiments to study its stability under extreme conditions, but still the origin of the stability of MJ is not exactly known. MJ0305 is MJ's chloride channel protein. The structure of MJ0305 was built by homology modeling. We compared the stability of MJ0305 with mesophilic Ecoli at 300K, 330K, and 360K by computer simulation to test the effects of temperature. Our results show that high temperatures significantly affect the number of salt bridges and hydrogen bonds. High temperatures decreased the average number of hydrogen bonds for Ecoli and MJ0305. Increased salt bridges at 330K make MJ0305 more stable. Network analysis of MJ0305 showed an increase in the number of hubs at high temperatures. In contrast, the number of hubs of Ecoli was decreased at high temperatures. Calculated network entropy is proportional to the number of hubs. Increased network entropy of MJ0305 at 330K implies increased robustness. [Preview Abstract] |
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P1.00020: The Llifetime of Quenched and Unquenched Fluorescent Processes Andrew Hout, Debra Egolf, Dennis Kuhl Properties of both quenched and unquenched fluorescence excited states of 9-cyanoanthracene and 9,10-dicyanoanthracene were measured to investigate if upon interaction with a quencher the cyanoanthracenes are quenched by an electron transfer process. The overall quenching rate constant, k$_{q}$, was determined through laser-based kinetic measurements of the lifetime of quenched and unquenched fluorescent processes. Values of k$_{q}$ were calculated from this data using a deconvolution method. Instrumentation and calculation methods were investigated and improved. [Preview Abstract] |
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P1.00021: The Effects of Atmospheric pH on the Transport Properties of Gallium Nitride Andrew McElroy, Jeffrey S. Dyck, Kathleen Kash It has been theorized that there exists a thin layer of water molecules on the surface of many materials when in air. This layer is predicted to have an effect on the electrochemical properties of the material. GaN is one of these materials. It has been demonstrated that the optical properties of GaN are affected by the pH of the atmosphere around the sample. In this study the effects of pH on transport properties are tested. A system was developed to test the Hall coefficient and resistivity of samples under different ambients to discover the effects of pH on carrier concentration and Hall mobility of GaN. Thus far, the results show that the pH of the ambient water vapor does not have an effect on the transport properties. This project was funded through the National Science Foundation (DMR-1006132) and the Huntington and Codrington Foundations. [Preview Abstract] |
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P1.00022: Electrical and electrochemical characterization of nano-sized LiFePO4 cathode materials synthesized by a lauric acid-based sol--gel method Khadije Bazzi, Ambesh Dixit, Ratna Naik, Vaman Naik, Prem Vaishnava, Abbas Nazri, Mariam Nazri We synthesized pure LiFePO$_{4}$ and C-LiFePO$_{4}$ nanoparticles by sol-gel technique. Carbon coating was accomplished by including Lauric acid in the sol-gel precursor solution. Three C-LiFePO$_{4}$ samples of particle sizes 29, 27, 23 nm, were prepared by varying lauric acid concentration in the precursor solution. All the samples were characterized by X-ray diffraction, Raman, conductivity, and electrochemical measurements. The micro-Raman measurements showed two major bands at 1350 and 1590 cm$^{-1}$ respectively (I$_{D}$/I$_{G})$ and the electronic conductivity were found to depend strongly on the amount of surfactant coverage. The 23 nm particle size sample showed minimum (D/G) band ratio and the maximum electrical conductivity among the three samples. The measured value of the capacity for 23 nm sized sample, $\sim $ 170 mAh/g, approached the theoretical capacity limit value for LiFePO$_{4}$ [Preview Abstract] |
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P1.00023: Synthesis and characterization of multiferroic Bismuth Ferrite nanoparticles Maheshika Palihawadana Arachchige, Rajesh Regmi, Gavin Lawes In recent years, there has been considerable research in multiferroics, materials that exhibit more than one of ferroelectric, ferromagnetic and ferroelastic properties simultaneously. BiFeO$_{3}$, as one of the very few mutiferroics with a simultaneous coexistence of ferroelectric and antiferromagnetic at room temperature, is among the most intensely studied and promising multiferroics. It has a rhombohedrally distorted pervokite structure and exhibits antiferromagnetic ordering with Neel temperature of about 643 K and ferroelectric properties below approximately 1123 K. We synthesized BiFeO$_{3}$ nanoparticles having a diameter of roughly 14 nm using a ferrioxalate precursor method and characterized their structure using X-ray diffraction and Raman spectroscopy. Using room temperature magnetization data, we find that the saturation magnetization is close to 0.5 emu/cm$^{3}$. We also measured the temperature dependent magnetization, both zero field cooled and field cooled, and found that the blocking temperature is 116 K, which is slightly higher than the value reported for similar BiFeO3 nanoparticles. Dielectric measurements show a broad anomaly near 275 K, which consistent with observations on bulk BiFeO$_{3}$, although a second anomaly found in bulk samples near 25 K is not present in our data. [Preview Abstract] |
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P1.00024: Infrared and magneto-optical studies of topological insulators Bi$_2$Te$_3$, Sb$_2$Te$_3$ and Bi$_2$Se$_3$ M.S. Wolf, G.M. Foster, S.V. Dordevic, N. Stojilovic, H. Lei, C. Petrovic, L.C. Tung Topological insulators are a main focus in condensed matter physics due to their classification as a new state of matter. They have a unique property in which the bulk of the material is insulating, while the surface states have metallic behavior. We have studied 3D topological insulators Bi2Se3, Bi2Te3 and Sb2Te3 using infrared spectroscopy at vary temperatures to understand their optical properties. Furthermore, we have investigated these materials at vary magnetic fields up to 18 Tesla. Our results reveal strong temperature and magnetic field dependence of optical functions, which indicates unconventional charge dynamics. [Preview Abstract] |
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P1.00025: Optical Modeling of Organic Photovoltaic Solar Cells Maithili Ghamande, Jutta Luettmer-Strathmann Organic photovoltaic devices consist of several thin layers of material with different optical properties. Since the conversion of incident photons to charge carriers occurs only in the active layer, the intensity distribution of light within the device has an important effect on the efficiency of a solar cell. The intensity in turn depends upon properties of the layers, such as refractive index, absorption coefficient, and thickness, as well as on properties of the incident light, such as angle of incidence, spectral distribution, and polarization. In this work, we investigate the absorption of light in thin-film organic solar cells with computational methods. Since interference effects play an important role in thin films, we employ a transfer matrix method to calculate the complex amplitude of the electric field at the interfaces and propagate the electromagnetic wave within the layers. Intensity profiles are then calculated from the time averaged Poynting vector. We apply the method to conjugated polymer/fullerene bulk heterojunction solar cells and investigate devices with a range of geometrical parameters. We present results for plane geometries and explore how layer curvature may affect the efficiency of a solar cell. [Preview Abstract] |
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P1.00026: Study of the dielectric and magnetic properties of Multiferroic Ca$_{3}$Mn$_{2}$O$_{7}$ Ehab Abdelhamid, Ambesh Dixit, Gavin Lawes Materials exhibiting simultaneous magnetic and ferroelectric order are widely studied because of the strong spin-charge coupling that can arise in these systems together with their applications to novel magnetoelectric devices. While it has long been recognized that Ca$_{3}$Mn$_{2}$O$_{7}$ develops magnetic order below 120K, recent theoretical calculations suggest that this system may undergo a structural transition to a ferroelectric state above this temperature. Ca$_{3}$Mn$_{2}$O$_{7}$ is a member of the Ruddlesden Popper series A$_{n+1}$B$_{n}$C$_{3n+1}$ with n=2, which has a tetragonal crystal structure at high temperatures but undergoes a transition to an orthorhombic structure at lower temperatures. We prepared a powder sample of Ca$_{3}$Mn$_{2}$O$_{7}$ using a conventional ceramic technique and investigated the structure using X-ray diffraction and temperature dependent Raman spectroscopy. We measured the temperature dependent magnetization, which shows the development of weak ferromagnetism near 120K, together with evidence for some Mn3O4 impurity phase. We find marked shifts in the Raman peaks near the magnetic ordering temperature, suggesting significant spin-lattice coupling in Ca$_{3}$Mn$_{2}$O$_{7}$. Finally, measurements of the temperature dependent dielectric response and pyroelectric current find anomalies consistent with a ferroelectric transition just below room temperature showing a polarization of 1$\mu $C cm$^{-2}$ developing below 280K. [Preview Abstract] |
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P1.00027: Low-Energy Electron Diffraction Study of Clean, Unreconstructed Au(111) Stephanie Ash, Mellita Caragiu, James Thompson, Renee Diehl, Heekeun Shin, Garry McGuirk The present study investigates the surface of clean gold, cut along the (111) crystallographic plane. Computational Low-Energy Electron Diffraction (LEED) analysis of experimental data reveals an unreconstructed Au(111) surface with the main feature being the relaxation of the top- most atomic layers, i.e. a variation in the interatomic distance between consecutive layers within the surface, as compared to the bulk interatomic distance. Understanding of the clean Au surface precedes future studies of the gold surface on which different species of atoms are adsorbed and expected to induce a reconstruction of the substrate. [Preview Abstract] |
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P1.00028: Investigating photocurrent generation and transport in organic photovoltaics with event driven Monte Carlo simulations Vincent Robbiano, Jutta Luettmer-Strathmann The generation of photocurrent in organic solar cells starts with a photon being absorbed in the active layer and creating an excited electron/hole pair (exciton). The exciton is mobile and dissociates into electron and hole at an interface between donor and acceptor material, unless it decays before it reaches the interface. If they do not recombine, the charge carriers migrate toward the appropriate electrode and contribute to the photocurrent. Thus, the efficiency of organic solar cells depends strongly on the morphology and electronic properties of the donor/acceptor materials. Simulating in detail the processes described above is of interest since it enables the modeling of devices with different architectures and materials properties. Since processes such as exciton absorption, electron hopping, and recombination take place on vastly different time scales, we employ an event-driven Monte Carlo algorithm to simulate a coarse grained lattice model of the active layer of organic solar cells. [Preview Abstract] |
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P1.00029: Statistical evidence of predation by theropods -- using physics to understand the lives of dinosaurs Scott Lee Dinosaurs hold a great fascination for everyone and provide an interesting venue for teaching many elementary concepts of kinematics. Dinosaur trackways provide interesting information about the locomotion of these extinct animals. A statistical analysis of the known trackways made by theropods (carnivorous dinosaurs) shows that they usually moved by walking with an average speed of 2.4 $\pm $ 1.5 m/s. Fast running, determined by a relative stride length of 3 or greater, is observed in about 4{\%} of the trackways, corresponding to running speeds of 6 m/s or higher. These trackways are believed to have been formed during predation. [Preview Abstract] |
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P1.00030: Excitation and Characterization of Chladni Plate Patterns Shannon Bourke, Ernest Behringer When a thin metal plate with a small amount of sand on it is made to vibrate, aesthetically pleasing sand patterns can form along the nodal lines of the plate. These symmetric patterns are called Chladni Patterns. Students taking PHY 101 Physical Science in the Arts at Eastern Michigan University create these patterns by pulling a violin bow across the edge of a plate, or by using a mechanical oscillator to drive the center of a plate. These two methods only allow a small subset of all possible points on the plate to be excited. We designed and built an electronic device that allows its user to excite the plate at \textit{any} point. We present patterns created with this electronic device and other methods, and describe ways to model the observed patterns. [Preview Abstract] |
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P1.00031: A Search for Correlations Between Teaching Style, Academic Gain, and Epistemology of Introductory Physics Students Abigail Bogdan, Dennis Kuhl Ideally, a physics class would improve both students' academic abilities and their attitudes towards physics. This study was designed both to investigate any correlation between academic ability and epistemology, and to examine the effects of teaching style on academic and epistemological growth. Over four hundred students in high school and college introductory physics courses were given two pre- and post-instruction surveys: the Force and Motion Conceptual Evaluation (FMCE) to measure knowledge of physics and the Epistemological Beliefs Assessment for Physical Science (EBAPS) to quantify epistemological beliefs about physics. The average normalized gains from each class were then compared to teaching style. It was found that, though different teaching styles produced drastically different academic gains, student epistemologies remained fairly constant. [Preview Abstract] |
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P1.00032: Using PER ideas at middle and high school Gordon Aubrecht Project IMPACT2 has used ideas from PER and the nationally-available FOSS and Materials World Modules to help middle-school and ninth-grade teachers involve students more in science. The program is now in its third year and is in several transitions. A progress report will be given. [Preview Abstract] |
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P1.00033: Preliminary results on two-dimensional diffusion in dusty plasma Donald Pleshinger, W.L. Theisen, T.E. Sheridan We investigate self diffusion of particles in two dimensions (2D) using a dusty (complex) plasma. A 2D liquid containing $\sim 100$ particles is formed at the center of, and heated by, a toroidal gas of dust particles. The motions of individual dust particles are capturing using a video camera, allowing diffusion to be directly observed. This system will be characterized and the diffusion constant determined. [Preview Abstract] |
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P1.00034: Structural transitions in an anisotropic dusty plasma T.E. Sheridan Dusty (complex) plasma is a system of charged dust particles floating in an electron-ion plasma. Under appropriate circumstances, the particles can be confined in a two-dimensional potential well. For a biharmonic well, dust particle configurations range from straight lines, to ellipses, to circles. For highly anisotropic wells, the particles form a straight line, which becomes unstable to the zigzag as the well anisotropy is reduced. The zigzag configuration corresponds to a 2-chain in long systems. It is predicted that the 2-chain next makes a transition to a 4-chain. We have experimentally investigated this transition in a dusty plasma cluster with $n=14$ monodisperse particles confined in a variable biharmonic potential well. For high well anisotropies the configuration is a ``capped'' zigzag. As the well anisotropy is reduced the zigzag units tilt until the local lattice is rectangular and then transition to the finite equivalent of a 4-chain. Other structural transitions are also observed, and will be discussed. [Preview Abstract] |
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P1.00035: Local Structure in Short Chain Molecule Fluids Sambid Wasti, Subrat Khanal, Mark Taylor The macroscopic properties of materials comprised of polymeric components depend on the underlying local structure or conformation of the constituent polymers. Thus, the viscosity and optical birefringence of a polymeric liquid depend on the degree of entanglement and alignment of the individual polymer chains. Similarly, the functionality of biopolymers is strongly dependent on local chain conformation. Chain conformation itself is determined by both intramolecular interactions and the local solvent environment. Here we use Monte Carlo computer simulation techniques to study local structure in liquids comprised of short flexible chain molecules. We work with a simple pearl-necklace polymer chain model in which the monomers are hard- spheres. We have computed both single chain and chain-chain average structure in pure $N$-mer liquids with $N \leq 5$ across a range of fluid densities. We have also investigated the conformation of a flexible $M$-mer chain in a $N$-mer solvent. Our primary interest in this study has been how solvent architecture (i.e., chain length in this case) affects the conformation of a polymer solute. We are currently developing a solvation potential representation of these molecular solvents which will allow us to map the chain-in-solvent problem to a single chain problem. [Preview Abstract] |
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P1.00036: Conformation of a Lennard-Jones Chain in Explicit Solvent: A Solvation Potential Approach Shishir Adhikari, Mark Taylor The conformation of a polymer chain in solution is intrinsically coupled to the chain's local solvent environment. In much of the theoretical work on polymers in solution the effects of solvent are treated implicitly and explicit chain-solvent coupling is ignored. Although a formally exact treatment of chain-solvent coupling can be constructed, the required many-body solvation potential is not practical to compute. Following on our work with hard-sphere and square-well chain-in-solvent systems [1] here we show that for Lennard-Jones (LJ) systems this many-body solvation potential can be made tractable via an ``exact'' decomposition into a set of two-site potentials. We use these exact short chain results, combined with the pure solvent potential of mean force, to construct approximate two-site solvation potentials for long LJ-chains. Monte Carlo simulations for full chain-in-solvent systems verify the accuracy of our solvation potential mapping across the full LJ-solvent phase diagram.\\[4pt] [1] J. Chem. Phys. 127, 184901 (2007); J. Polym. Sci., Part B: Polym. Phys. 45, 3319 (2007). [Preview Abstract] |
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P1.00037: Non-equilibrium Thermodynamics of Glassy Systems Pyie Aung, Gujrati Puru When a linear amorphous polymer is in the glassy state, equilibrium thermodynamics theory is no longer consistent, for, a glass cannot be described by equilibrium statistical mechanics. Therefore, a non-equilibrium thermodynamics approach has been developed, which we intend to apply to glasses. The approach starts from the most general law of nature, the second law of thermodynamics, and shows correction terms that are missing in the conventional non-equilibrium thermodynamics of de Donder and Prigogine. We have applied this new approach and have discovered the generalization of (equilibrium) Maxwell's relations to non-equilibrium states. The generalization replaces simple partial derivatives by Jacobians' Matrices. The non-equilibrium Maxwell's relations lead to one the most paradoxical equations, the Prigogine-Defay ratio. The goal of this research is to understand non-equilibrium states with an emphasis on glasses and to solve the Prigogine-Defay ratio paradox with deeper definitions. [Preview Abstract] |
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