Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session E67: Undergraduate Research IVFocus Undergraduate
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Sponsoring Units: APS/SPS Chair: Crystal Bailey, American Physical Society Room: BCEC 050 |
Tuesday, March 5, 2019 8:00AM - 8:12AM |
E67.00001: Complexity and Fly Swarms Troy Taylor, Joelle L Murray A system is considered complex if it is composed of individual parts that abide by a set of simple rules while the system, as a whole, exhibits more elaborate, unexpected properties. The motivation for studying complexity stems from the fact that it is a feature of many different systems. We are particularly interested in fly swarms and the possible complex properties that swarms exhibit, arising from individual fly interactions. To better understand the nature of complexity exhibited by fly swarms, a simple stochastic fly swarm model was created to investigate the relationship between the average radius of the swarm and the number of individuals within it, as experimental data shows a power-law scaling of the number of flies to the average radius. In addition, the model will be used to explore the difference between swarming and non-swarming behavior. |
Tuesday, March 5, 2019 8:12AM - 8:24AM |
E67.00002: Quasiperiodic Earthquake Events in an Olami-Feder-Christensen Model Jacob Owens, Rachele Dominguez We simulated an earthquake fault system using a variation of the OFC cellular automata model. The fault is represented by a 2D lattice structure wherein each site holds some amount of stress. Our model increases the stress on the system in a more realistic way and allows multiple sites to fail simultaneously. The model generates data that produces Gutenberg-Ricther scaling, which is consistent with real earth data. Additionally, the model incorporates “asperity” sites into the lattice; these asperities have a much higher failure threshold relative to other sites in the lattice. The introduction of asperities to the system generates a characteristic period according to which we observe very large events. These main shocks are preceded by a gradually increasing number of large events (foreshocks) and followed by a gradually decreasing number of large events (aftershocks). By introducing multiple distinct failure thresholds for the asperity sites, we were able to identify characteristic periods related to the respective failure thresholds. In varying these parameters we can control the periodicity of large earthquake events. These results suggest that the spatio-temporal clustering observed in real seismic data is related to the physical structure of the fault system involved. |
Tuesday, March 5, 2019 8:24AM - 8:36AM |
E67.00003: Quantum Coherence Enhanced Phototherapy: A Step Towards Quantum Medicine Zachary Withers, Dmitri Voronine Irradiation and phototherapy involves the application of electromagnetic radiation to infected or tumorous tissues. Historically, radiation dosage, energy, and specificity have been of significant research areas, but with the evolution of quantum optics, plasmonics, and nanotechnology new devices and enhancement schemes are being realized. We propose the use of aluminum SPASERs as an ultraviolet phototherapeutic treatment mechanism and discuss the role quantum coherence plays in treatment enhancement, efficiency, effectiveness, and specificity. We further discuss optimization of temporal nonlinear regimes and potential application of laser pulse shaping. |
Tuesday, March 5, 2019 8:36AM - 8:48AM |
E67.00004: Protein-Based Drug Delivery Nanoparticles Ty Naquin, Kiril Streletzky
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Tuesday, March 5, 2019 8:48AM - 9:00AM |
E67.00005: Biocompatible Exchange-Coupled Magnetic Nanoparticles for Advanced Hyperthermia Elizabeth Fuller, Joshua L Robles, Manh-Huong Phan, Hariharan Srikanth Exchange-coupled bimagnetic nanoparticles describe a potential for advanced hyperthermia treatment of cancer with an increased heating capability. The feasibility of magnetic hyperthermia in humans warrants magnetic nanoparticles (MNPs) with an Fe3O4 shell to meet biocompatibility standards. In our study, we compare the heating efficiency and magnetic properties of CoFe2O4@ Fe3O4 MNPs with the inverse system, Fe3O4@ CoFe2O4. We calculate the Specific Absorption Rate (SAR) values of both nanoparticle systems when dispersed in hexane, water, and agar in addition to proper morphological and magnetic characterization using TEM, XRD, and DC Magnetometry. At 80mT, we report SAR values of our CoFe2O4@ Fe3O4 MNPs to be 62% greater in water and 2% greater in agar than the inverse MNPs. We observe a significant coercive field of the CoFe2O4@ Fe3O4 MNPs when taking DC Magnetometry measurements at 10K, to which we attribute its superior heating power over the inverse system in media that limit Brownian movement. We anticipate an increase in saturation magnetization of the CoFe2O4@ Fe3O4 system with negligible effect on coercive field with increased Fe3O4 shell thickness. |
Tuesday, March 5, 2019 9:00AM - 9:12AM |
E67.00006: Computer simulation of a finite-time Carnot engine working under ecological conditions David A. Rojas-Gamboa, Juan I. Rodríguez, Julian Gonzalez-Ayala, F. Angulo-Brown In the context of finite-time thermodynamics some optimization criteria for heat engines have been proposed, such as the maximum power [1] or the ecological criterion [2], being the later the best compromise between high power output and low entropy production. In order to study these criteria, we present a molecular dynamics simulation of a hard-disk gas performing a finite-time cyclic process that is near to a Carnot one. While previous works analysed the maximum power regime [3], in the present work we discuss the ecological case. When the gas is in contact with an stochastic thermal wall (or heat reservoir), we show that the speeds distribution is well described by a Maxwell-Boltzmann function with an effective temperature that is lower/higher than the source/sink temperature (as in the endoreversible model). By obtaining the power output and total entropy production, the ecological efficiency of such an engine was computed via molecular simulations for the first time, showing good agreement with analytical approaches. Our results were reported in D. A. Rojas-Gamboa et al., Phys. Rev. E 98, 022130 (2018). |
Tuesday, March 5, 2019 9:12AM - 9:24AM |
E67.00007: ABSTRACT WITHDRAWN
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Tuesday, March 5, 2019 9:24AM - 9:36AM |
E67.00008: Synchronization of Mid-Frequency Engines for Energy Harvesting. Seo Young Ahn Thermoacoustic engines convert heat to electricity by producing sound, which generates electricity by a piezo electric device. Multi-device arrays of such mid-frequency (2.5 kHz) thermoacoustic energy converters have been studied in order to raise the power output. Devices with 2 and 3 engines were investigated, eventually leading up to 6 engines. Being self-sustained oscillators with random phase, their synchronizations are crucial in attaining maximum power. Indeed, synchronization was observed; coupling between the engines is attributed to their radiation impedance and reflections from the acoustic cavity supporting them. The observed increased output levels substantiate synchronization through the absence of beats between engines, Fast Fourier Transforms, where a peak due to a common frequency is observed, and resultant common, lowered frequency. A benefit of the array is the reduction of onset temperature such as 50°C for 3 engines, and similarly onset times for oscillations. |
Tuesday, March 5, 2019 9:36AM - 9:48AM |
E67.00009: Wearable textile-based energy harvester designed for human motion. Rebeca Gurrola, Janna Eaves, Cary L Pint While there are many different methods of generating sustainable energy, small quantities of energy otherwise wasted in the pursuit of everyday activities are often overlooked. Recently, electrochemical energy harvesters joined the ranks of piezoelectric and triboelectric harvesters to convert mechanical energy into electrical energy. Here, we use materials with mechanochemical response to seamlessly integrate motion harvesting into textiles for wearable applications. |
Tuesday, March 5, 2019 9:48AM - 10:00AM |
E67.00010: Increasing the Number of Sides of a Luminescent Solar Concentrator can Increase its Power Output Bailey Hopkins, Bruce Paul Wittmershaus Luminescent Solar Concentrators (LSCs) are fluorescent sheets of glass or plastic that absorb sunlight and concentrate their fluorescence using total internal reflection onto a small area of photovoltaic solar cells for energy conversion. LSCs have the potential to generate electricity at a lower cost than standard solar panels. Current LSCs are designed as squares. This shape can cause non-uniform illumination along its edges leading to current mismatch in the solar cells resulting in loss of power output. We present results showing that changing the LSC’s shape closer to that of a circle decreases current mismatch by improving the uniformity of illumination. |
Tuesday, March 5, 2019 10:00AM - 10:12AM |
E67.00011: Pretreatment of rice straw for enhancing fermentable sugar yield using a high-pressure reactor Pratham Gupta, Bahiru Tsegaye, Chandrajit Balomajumder Rice straw has proved to be a potential renewable energy source due to its high polysaccharide contents and abundance availability. Fermentable sugars are easily obtained on hydrolysing rice straw using different pretreatment techniques. In this study, organosolv was used to pretreat rice straw in high-pressure autoclave reactor, under different conditions, for the removal of lignin and release of trapped polysaccharides. The composition of rice straw was analyzed as per National Renewable Energy Laboratory (NREL) guidelines. The temperature was varied as 120, 140 and 160 degree Centigrade and the exposure time was varied as 15, 30 and 60 minutes. The amount of sugar and lignin were greatly affected by temperature and time. It was found that sugar yield was maximum at 140 degree Centigrade and 15 minutes. At this pretreatment condition, it was observed that almost all of the hemicellulose was solubilized and 73% and of lignin was removed and 82% cellulose was released from the biomass. The removal of the high amount of lignin facilitates the release of the cellulose from the biomass matrix. Overall, this study showed the possibility of a high-pressure reactor for effective removal of lignin, which enhances the yield of fermentable sugars. |
Tuesday, March 5, 2019 10:12AM - 10:24AM |
E67.00012: Thermal Expansion in 3D Printing Materials for Interferometric Devices Theodore Morin, Luisa Velasco, Catherine Hand, Michael Ewnetu 3D printed optomechanics offers a cheaper alternative to conventional machined parts with the potential for customization. Examples include the kinetic mounts, precise linear movement, and integrating sphere described by Salazar-Serrano et al (2017). When considering the use of 3D printed parts to make high precision interferometric instruments, thermal expansion becomes an important consideration. We present an inexpensive interferometric measurement of thermal expansion in 3D printed materials. Tests are performed with ABS and PLA plastics. We also explore variation with different colors of the plastics and different printing conditions. Finally, we present a design for a low-cost, 3D printed scanning Fabry-Perot interferometer with minimal thermal sensitivity and an anticipated finesse of about 50. |
Tuesday, March 5, 2019 10:24AM - 10:36AM |
E67.00013: Electrode Coatings for Neurostimulation and Cardiac Pacing Applications Sierra Dutko, Anthony Valenti, Natalie Page, Robert Lowe, Rhandy Paladines, Jeffrey Hettinger Neurostimulation and cardiac pacing electrodes have many applications each requiring biocompatibility and the ability to exchange charge between the underlying metallic electrode and the ionic fluid surrounding it. The trend toward smaller electrodes as well as higher current applications has resulted in the need for improved charge transfer. With this goal, cubic nitride coatings with columnar microstructure have been added to the electrodes using reactive magnetron sputtering in a nitrogen rich atmosphere. These coatings which provide capacitive coupling between the electrode and the biological solutions increase the surface area improving the required charge transfer. Coating performance is measured electrochemically using cyclic voltammetry with the coated metal as the working electrode, a platinum coiled wire as the counter electrode, and phosphate buffered saline as the electrolyte. We report on the thickness dependence of the coating performance and delineate important parameters influencing this performance. |
Tuesday, March 5, 2019 10:36AM - 10:48AM |
E67.00014: Hygroscopic Nature of Solution Processed Al2O3 Thin Film Dielectric and Impact on Electrical Characteristics James Tran, Trey B Daunis, Julia Wan-Ping Hsu Metal oxides are a good candidate for gate dielectrics because of their high dielectric constant and low leakage current. Solution deposition is a favorable method for thin film fabrication due to its low cost and high throughput. Here, we compare the property and stability of solution-processed Al2O3 and ZrO2 films. Fourier transform infrared spectroscopy (FTIR) and electrical characterization reveal that Al2O3 absorbs moisture from air, while ZrO2 remains stable with no moisture gain. This conclusion is established by comparing Al2O3, ZrO2, and bilayers of Al2O3/ZrO2 and ZrO2/Al2O3. FTIR spectra show increased intensity in the water -OH region (3700-2500 cm-1) when Al2O3 is exposed to air or purposely soaked in water. The change in surface contact potential indicates that the adsorbed water molecules’ dipoles point away from the surface. Effects of the moisture gain on electrical characteristics are studied with metal-insulator-metal capacitors and field effect transistors. Absorption of water in Al2O3 results in higher capacitance and dissipation at low frequencies and show a counter-clockwise hysteresis in transistor drain current vs. gate voltage curves. |
Tuesday, March 5, 2019 10:48AM - 11:00AM |
E67.00015: Seebeck Coefficient Measurement Probe by Using a Differential Thermocouple Andrea Capa Salinas, Jesus Velasquez, Pei-Chun Ho When a temperature gradient is imposed at the ends of a conducting material, a voltage will be generated on this material. This phenomenon is known as the Seebeck effect and is characterized by the Seebeck coefficient. Thermopower, or Seebeck coefficient measurements, can provide a deeper understanding of the properties of a sample, its normal state behavior, and help progress on applications, such as thermoelectric generators, cooling systems, and temperature measurement devices. The samples of interest for thermopower measurements in our lab are filled-skutterudite compounds, for they exhibit thermoelectric effects. For this purpose, a thermopower measurement probe was designed and its resolution tested using Nickel 201 alloy and platinum samples. It was concluded that the device provides measurements within 3% error in the 100K-300K range. However, measurements bellow 100K must be improved, since current data indicates measurements are limited by the operating range of the type-T thermocouple used. Thus, future improvement will consist of adding a Cernox thermometer on the hot platform to account for a more accurate temperature difference at low temperatures. |
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