Bulletin of the American Physical Society
85th Annual Meeting of the APS Southeastern Section
Volume 63, Number 19
Thursday–Saturday, November 8–10, 2018; Holiday Inn at World’s Fair Park, Knoxville, Tennessee
Session D05: Poster Session (6:00pm-7:30pm) |
Hide Abstracts |
Room: Holiday Inn Knoxville Downtown Atrium |
|
D05.00001: User-Friendly Method to Optimize the Network of a Cyber-Physical System Samantha C Harris, Levi Welch, Matt Bunting When developing a cyber-physical system, designers mainly concentrate on functionality and dynamics. As the system becomes more complex, multiple nodes and connections are needed to run the system safely, which may result in a slower network. This research focused on optimizing the network of the CAT Vehicle, the autonomous vehicle at the University of Arizona. The optimization process started with a model of the CPS's network using a Domain Specific Modeling Language (DSML). The DSML then uses interpreters to verify that the system operates within set values of cost, processing power, bandwidth, and latency. If constraints are violated, technique selectors give suggestions on how to rewire connections or exchange nodes within the network. When all constraints are met, a new interpreter is used to generate template code from the DSML which can tell the car how to operate. The purpose of this project is to present a user-friendly method to optimize the network of the CAT Vehicle, which can be applied to any cyber-physical system. |
|
D05.00002: Study on the Spectral and Acoustical Features of the Clarinet Sound Using Physical and Computational Analysis Joshua Rhee, Richard Kyung Acoustically, the clarinet sound is not closely related to the sound generated by other woodwind instrument. In this paper, acoustics knowledge was used to carry out physical and spectral analysis. The wave forms and spectrums of the clarinet and a few other instruments were calculated to compare their sound properties. The research implemented the sound of a clarinet instrument using harmonic equations and computer programs such as Mixcraft and MATLAB. The sound properties that were investigated were wavelength, fundamental frequency, harmonics, and trigonometric functions used in a Fourier transformation. It was noticed that several instruments had much more energy in the second, and/or third harmonics than in the first frequency. Also, a certain instrument showed the purest tones until a certain frequency. After crossing the frequency threshold, the tone became fuzzy. In the spectra analysis, we determined how the harmonics and power or energy of the clarinet were changed over time, but the pitch did not change. The main objective of this research was to study a musical note of the clarinet sound using digital audio workstation (DAW) and computational simulations. |
|
D05.00003: Role of Phosphorus in the Crystallization of Bi-modified Chalcogenide Glasses Margaret J Seage, Roman Golovchak Chalcogenide glasses possess a variety of unique properties, such as high optical transparency in a wide infrared region of spectrum, large optical nonlinearities, and excellent molding and fiber drawing capabilities, which grant them many useful applications in modern photonics. By modifying Ge-Te-Se glass matrices with other elements such as Bi and P, further interesting properties can be achieved, such as thermoelectric effect, change in the conductivity type, or rapid crystallization at the elevated temperatures or under photoexposure. In this work we report the thermal stability and crystallization kinetics studies for Bi-P-Ga-Ge-Se-Te glasses, with P content up to 10 at.%. Our results show that as the concentration of P increases in the composition, the thermal stability of the glass also increases. Conversely, if Bi concentration increases, thermal stability of the glass decreases and rapid crystallization peaks are observed with differential scanning calorimetry. The latter property can be used for phase-change memory applications. |
|
D05.00004: Calculating White Dwarf Stellar Parameters from Survey Data Charlie Mace, Bart Dunlap, Chris Clemens The effective temperatures and masses of white dwarfs have historically been estimated by fitting spectral lines to theoretical model atmospheres. This method has had problems however, because the resulting parameters depend on which spectral line is used to perform the fit. This suggests there are other factors influencing the spectral lines, which is introducing uncertainty to the temperature and mass calculations. To improve upon the traditional method of calculating stellar parameters, we have estimated them without using spectral line fits. Instead, we combined parallaxes measured in the Gaia survey, with atmospheric model fits to fluxes from the Sloan Digital Sky Survey (SDSS) to find the best fit temperature and radius of each star in a sample of 87 DA (hydrogen atmosphere) white dwarfs. These new temperatures and gravities do not suffer from the same systematic errors as line fits, and may improve the white dwarf ages used in cosmochronology, provide more precise masses for the initial-final mass relation, and calibrate the temperature scale for the DA white dwarfs. This research may also shed light on the other factors influencing the spectral line fits, and provide insight into the physics of how metal lines form. |
|
D05.00005: High Resolution IR/Far-IR Spectra and Molecular Constants for 13C & D Substituted Propane Isotopologues for Astrophysical Studies Stephen J Daunt, Robert K. Grzywacz, Walter J Lafferty, Jean-Marie Flaud, Daniel Gjuraj, Brant Billinghurst This ongoing project is to obtain and analyze high resolution IR and Far-IR spectra of 13C and D isotopologues of propane. Spectra were run on the Bruker IFS 125HR on the Far-IR beamline at the Canadian Light Source synchrotron. Bands corresponding to those detected on Titan by Voyager and Cassini for the normal species of propane are one of our main aims. A region of focus is the unpertubed vibrational mode near 360 cm-1 (THz region). This band has allowed us to obtain accurate rotational constants to 6th order for the different species. We hope to predict rotational lines for use in radio astronomy searches in the ISM and planetary atmospheres. Recently we have extended our studies to other isotopic propanes: D2, D3, D6 and D8. Obtaining inertial constants for all these species can be used to refine the molecular structure and provide data to improve ab initio calculations of hydrocarbons found in problems in chemistry, physics, geochemistry and astrophysics. |
|
D05.00006: The INTEGRAL Spiral Arms Monitoring Program Arash Bodaghee, Anyauna Spikes We present the final results of our 3-Ms program to observe the inner spiral arm regions of the Milky Way with the INTEGRAL space telescope. Besides providing routine monitoring of around 600 known sources of X-rays including active galactic nuclei, accreting neutron stars and black holes, this program's objective was to search for new X-ray transients. Images of the fields and light curves (3--100 keV) for all detected sources are available online at isa.gcsu.edu. |
|
D05.00007: Mining Illustris: Cosmological Histories of Major-Merger Galaxy Pairs Spencer Shortt, Jon Reising, Donovan Domingue The Illustris project is a publicly accessible set of large-scale cosmological simulations. In this work, we improve upon an earlier study in which major-merger galaxies were visually identified and investigated with regards to their star formation rates. Using the same criteria, which includes the potential pairs’ spatial separation (<20 kpc), relative velocity (<500km/s), mass ratio (<2.5), and relative K band (<1), python code was written to optimize the sample size of major-merger pairs. We then classified each pair by morphology and compared them against observations of SDSS-2MASS selected galaxy pairs. We hope that the results of this study will give greater insights into why galaxy morphology affects star formation rate within major-mergers. This study has also laid down the ground-work to use data from the highly anticipated Illustris TNG, which when released will hopefully provide for a much larger sample size. |
|
D05.00008: Producing a Galactic Rotation Curve for the Milky Way Galaxy Madison L Jackson, Emily Hill, Douglas Edmonds A galactic rotation curve is the graph of distance and velocity of intergalactic objects from the center of the galaxy. When plotted, the data resembles a curve that can be used to understand the relationship of velocity and mass in a galaxy. In this study, a galactic rotation curve was produced for the Milky Way galaxy. When neutral hydrogen’s electron has an antiparallel spin the energy level is lower than the hydrogen with a parallel spin, causing radiation on the 21 cm line. This radiation was detected with a small radio telescope (SRT) at a frequency of 1420.42 MHz. The SRT took samples every two degrees from 20°- 90° for a duration of 300 seconds then produced output files. Methods were applied to calculate the distance of the hydrogen cloud from the galactic center. Then, by assessing the doppler shift of the cloud orbital velocity was calculated. The distance and orbital velocity were graphed to result in a low resolution galactic rotation curve. |
|
D05.00009: QCD Color Vector Potential Effects on Color Flavor Locked Quark Stellar Cores Keith Andrew, Eric Steinfelds, Kristopher A Andrew We explore the color vector potential dependence of the equation of state (EoS) for a compact stellar core that has undergone a QCD phase transition into a quark color flavor locked (CFL) state. Compact stellar objects such as the pulsar PSR J1614-2230 have been found to have mass values near two solar masses thereby requiring a stiff EoS for long term stability. Under these pressures two flavor quark matter will deconfine and the chemical potentials for the up, down and strange quarks will exceed all three mass values giving rise to a three-flavor free quark core that is both electric charge neutral and in weak force thermal equilibrium. In the mean field model this mixture has a ground state that will become a color superconductor (CSC) with a fixed quark flavor and diquark color pairing, the CFL state. The appearance of the third quark flavor and the transition to a CSC state both soften the equation of state unless there is a color vector gluon exchange with a repulsive color factor. We explore numerical solutions to the spherically symmetric stellar TOV equations with an EoS that includes a single gluon exchange repulsive color force interaction and find the shift in end state TOV mass and radius values for the CFL color vector potential contribution. |
|
D05.00010: NDVI Analysis of Photosynthetic Activity of Plants Grown in Sulfate Enriched Martian Simulant JSC-1 Keith Andrew, Eric Steinfelds, Kristopher A Andrew We examine the relative health of plants grown in sulfate enriched versions of Martian simulant JSC-1 using modified models of the Normalized Difference Vegetation Index, NDVI, developed for satellite imagery following the Beisel – Anderson model. The NDVI method relies on a differential comparison of the visible and near infrared light reflection from a plant as an indicator of the chlorophyll mediated photosynthetic activity. Extensions of this method allow for adaptations to standard digital CCD cameras. We examined Martian simulant JSC-1 with controlled alkaline earth hydrated sulfate additives, especially magnesium sulfates, to match the Mars ChemCam and lab Raman spectral analysis of soil composition near Pahrump Hills and Gale crater. Using Mathematica based image analysis algorithms we separated images into a wavelength series so that weighted functional composites of red and green based differential comparisons could be made as in the RDVI and GDVI modes. We develop an analytical model using histogram, wavelength, and contrast controls to explore the optimization of the index, wavelength weights, JSC-1 mix and fractional area density coverage for the plants. We find positive correlations for hydrated magnesium sulfates coupled to the weighted RDVI functions. |
|
D05.00011: Exploring the Features of Protoplanetary Disks Taylor Stevenson, Daniel Harsono The circumstellar disks which form around young stars hold the key to understanding star and planet formation. The growth of dust particles within the disk is the first step toward planet formation, and these grains must grow from centimeter-sized aggregates to kilometer-sized bodies over the span of a few Myr. However, the processes that lead to the development of these bodies are under debate. In the sub-mm regime, large millimeter-sized grains can be observed and the emergence of planetesimals and protoplanets can be inferred through dust substructures. Through analyzing sub-mm data from the Atacama Large Millimeter Array (ALMA), we are able to resolve the structure of these disks and determine their properties. The determination of disk masses invites speculation on whether or not the amount of disk material is sufficient to create the exoplanets composing the further-evolved stellar systems we observe. The characteristics of these targets can be catalogued to build a database of targets with information for the James Webb Space Telescope (JWST), which will utilize mid- and near-infrared to observe smaller grains and hot inner-disk material, thus providing another piece of the puzzle in understanding disk evolution and planet formation. |
|
D05.00012: Mining the Sloan Digital Sky Survey Database for Quasar Outflows with Possible Distance Indicators Jacob T Pighini The focus of our project is to identify outflows within quasar spectra from the Sloan Digital Sky Survey (SDSS) that exhibit key characteristics and warrant follow-up observations. Quasars are energetic objects in the universe and are connected with the supermassive black holes in the center of galaxies. These objects emit powerful outflows that influence the formation and evolution of the host galaxy. The research goal is to find outflows with specific characteristics that allow us to calculate number density and determine the distance of the outflow from the source, thus forming implications for quasar feedback. Currently, our project director Dr. Nahum Arav is looking for quasars with discernable S IV, N III and P V absorption troughs. These troughs are identified with software developed using the Interactive Data Language (IDL). The IDL software is used to find the velocity of the outflow relative to the quasar rest frame and its velocity spread. Moreover, it is used to check identifications of excited states and compare outflow troughs. After mining through 2,187 objects we found 55 objects that justified a follow-up. With our total being 10,218 objects over a 1,000 hour period, we expect 245 to qualify as interesting. |
|
D05.00013: DES-gravitational waves: compilation of Pan-STARRS images Julia Hinds The Dark Energy Survey (DES) is a collaborative effort to map out the southern sky in hopes of probing the origin of the accelerating universe as well as defining cosmological constants. The Dark Energy Camera (DECam) images the southern sky and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) images the northern sky. By supplementing the DECam data with data from Pan-STARRS, the DES collaboration hopes to identify the optical counterparts to gravitational wave events. The joint detection of gravitational waves and optical counterpart will be used as a new way to uncover the physics of our universe. In order to accomplish this, the sky coverage needs to be increased from the current DECam coverage. Future work would be making template images from the retrieved Pan-STARRS images, which will be integrated into the DES-GW pipeline. This pipeline will be used for the search and discovery of Laser Interferometer Gravitational Waves (LIGO) O3 data. |
|
D05.00014: Analytical Strategies for Large-Area X-Ray Spectroscopic Imaging Measurements of Cultural Heritage Objects: A Case Study in Illuminated Manuscripts Sarah E Deutsch, Louisa Smieska X-ray fluorescence (XRF) mapping is a noninvasive imaging method that reveals the elemental composition of a material. XRF mapping is valuable for studying cultural heritage materials because detailed composition information about trace elements may provide new information about origins of historic pigments. Frequently, researchers collecting XRF data wish to analyze the relationship between spatial distribution and concentration of multiple elements in the scan. Previously, this analysis has been limited to directly comparing two or three elements at a time. This project focuses on expanding XRF mapping data analysis to include all elements present in the sample at a time, so that the entire sample can be described by a small number of characteristic ratios. New Python code was written to test several methods of pixel classification and we find that generally SVM plus k-means classification is a versatile method. |
|
D05.00015: The Production of Aluminum Nanoparticles via Pulsed Laser Ablation for Application in Bacterial Deactivation Lauren Cooper, Khomidkhodzha Kholikov, Saidjafarzoda Ilhom, Ali Er Antibiotic resistance to a widening range of diseases is one of the problems in current medicine; new antibiotic materials are thus needed. To aid in this issue, metal nanoparticles (NPs) are being investigated for their antibacterial properties due to favorable characteristics such as high tunability. We propose aluminum metal NPs as a novel material for bacterial deactivation. Aluminum metal NPs were fabricated using pulsed laser ablation at different laser powers and wavelengths in both alcohol and DI water. The particles were characterized using UV-Vis spectroscopy, transmission electron microscopy, and photoluminescence spectroscopy. The laser power, wavelength, and type of solvent were found to highly affect the final product. Aluminum NPs in a variety of sizes were formed. Initial results in combination with 9,10-Anthracenediyl-bis(methylene)dimalonic acid (ABMDMA) for light therapy showed that the produced NPs were effective in producing singlet oxygen, a highly reactive species to deactivate bacteria. The amount of singlet oxygen showed size dependency. The results of this work could be used to treat skin diseases, prosthetic joint infections, and cancer. |
|
D05.00016: Effect of Evaporative Cooling on Photodetachment from O- at the 2P3/2 → 3P2 Threshold David Patrick Sisson, John Nicholas Yukich The 2P3/2 → 3P2 photodetachment threshold for ions such as S- and O- has been examined in numerous experiments conducted near the electron affinity. Our most recent experiment explores the effect of evaporative cooling on the spectroscopy of O- at this threshold, as a function of photon energy in the range of 11784 -11788 cm-1. The apparatus used was a Penning ion trap which traps and stores the ions, and a tunable, amplified diode laser. Comparing the photodetachment spectrum with and without cooling shows more distinct structure with lower temperatures. The more defined structure may be due to diminished average kinetic energy which decreases the thermal broadening. |
|
D05.00017: Advanced Scanning Patterns for X-ray Ptychography at ALS COSMIC. Joseph Moscoso Recently, lensless X-ray imaging has developed to probe large volumes of material at high spatial resolution, especially with diffraction-based methods such as ptychography, removing the resolution limit imposed by the characteristics of X-ray optics. At LBNL’s Advanced Light Source (ALS), the Coherent Scattering and Microscopy (COSMIC) beamline uses soft x-ray ptychography for probing nanoscale objects, obtaining the highest-resolution x-ray microscopy achieved by imaging 5 nm structures. Ptychographic imaging at high resolution requires the data redundancy provided by overlapping x-ray probe positions and iterative reconstruction algorithms for precise reconstructions of the sample. Therefore, the scan patterns for ptychography play a critical role in the reconstructions, and the ALS uses the traditional mesh pattern which exhibits artifacts in reconstructions, worsening their quality. I have investigated ptychography scans that follow alternative scan patterns, like the Fermat spiral trajectory, and scans that account for details in the sample to more effectively sample high diffraction areas. These scan patterns show to improve the reconstructed images and reduce overhead in scanning and computation times. |
|
D05.00018: Vacuum compatible 3D printed ion optics Marston Copeland, Steven Bromley, Patrick Johnson, Chad Everett Sosolik, Joan Marler Conductive plastic filaments for use with 3D printers are now commercially available and offer an attractive low cost option to professionally machined metal ion optics. We have tested these new filaments by using them to print an ion beam deflection plate. The plate was then tested for its vacuum suitability and compared to both a metal plate and simulated (SIMION) results for performance. High vacuum was maintained and the conductive plastic plate was effective at deflecting a Rb ion beam. The results are suggestive that conductive materials will provide cheaper and easier to manufacture parts that are still suitable for use in UHV experimental setups. |
|
D05.00019: Optimization of Synthesis Conditions for Complex Se/Te Based Glasses Austin Harnage Selenium and Tellurium-based glasses boast a high refractive index and a wide range of transmission in the infrared region of electromagnetic spectrum, making them ideal for applications such as lenses, optical fibers, and optical circuits. In this work, synthesis conditions of complex Bi-Ga-Ge-Se-Te glasses were investigated and optimized by varying melting temperature, quenching rate, and annealing process. The purpose was not only to create samples of new compositions, but also to refine the process for manufacturing quality samples for further practical applications. As a result, a number of high optical quality samples with different Bi content were successfully prepared and characterized with different experimental techniques. |
|
D05.00020: Platinum Surface Study by Scanning Tunneling Microscopy Shannon T Stirling Platinum (Pt) has numerous applications from catalytic converters to dentistry tools, and a visual aid is essential to further study on Pt. Mapping the atomic structure using the scanning tunneling microscope (STM) reveals the crystal orientation and visualizing a single atom will assist the understanding of the structural material. The project includes the design and assembly of the STM as well as the scanning of the material. Vibration isolation will be a key aspect of the scanning and is inspected for a successful scan. A tungsten tip that is etched to an atomic point is used to scan the surface of the material with a bias current. |
|
D05.00021: Ion Effect of Apolipoprotein A1 Stabilization Benjamin R Smith, Luis Sanchez-Diaz Our research furthered work on APOA1 protein and how its confirmation and stability is affected by ionic solutions. APOA1 was of particular interest to us due to it being a high density lipoprotein which plays a significant role in cholesterol efflux and therefore effect rates of heart disease. To study this protein we used GROMACS which is a Molecular Dynamic Simulation Program in which we can control the environment around APOA1. Protein confirmation and stabilization is key in the functionality of APOA1. From GROMACS we can create systems to compare the different ionic solutions and their effect on the stability and folding of the protein. We calculate Radius of Gyration as well as root mean squared distribution to analyze the affect the ionic concentrations on our system. These values will be measured over 100 ns in order to show the protein progression over time in the various ionic solutions. We will also view the protein in VMD to visually back up GROMACS data. |
|
D05.00022: A computational modeling approach to investigate energy-costs of linearly-summed synaptic activation in single neurons Danielle Morel Linear additivity of synaptic input is a pervasive assumption for computations performed by individual neurons. Bernander et al. (1994) first pointed out that, in a passive neuronal model, the inherent sublinear additivity of excitatory synaptic input could be linearized with the inclusion of voltage-dependent currents. However, the biophysical mechanisms needed to produce linear summation in such a manner may add to the overall metabolic cost of neural processing. The benefits may therefore be outweighed by the energy-costs. Based on in-vivo intracellular recordings, three dendritic voltage-dependent conductances seem to be of interest: a persistent sodium conductance with associated current INaP; a hyperpolarization-activated mixed-ion conductance with current Ih; and a potassium conductance with current IA. Each of these voltage-dependent currents linearizes a particular range of synaptic excitation. Using a multi-compartment leaky single neuron model, combinations of these conductances were also examined, and many are found to produce linearization over extended ranges. Regarding the energy-costs, comparison to a purely passive model reveals that some models display minimal or even no additional costs. Work performed in primary collaboration with Dr. W.B Levy at UVA. |
|
D05.00023: Tissue Spreading Rate Dependence on Extracellular Matrix Concentration Riley E Reynolds, George Ridgeway, Holley E Lynch The collective migration of tissues is an essential part of development. In order to understand this process, we must understand the physical mechanisms that drive these movements. In order for tissue to self-propagate, they must form adhesions to their substrate. To study the rate of tissue spreading, I varied the number of adhesion sites. I began by cutting the tissue explants from gastrulation-stage Axolotl (Ambystoma mexicanum) embryos, removing a tissue that spreads across the surface of the embryo. These tissue explants spread in a similar manner when placed onto a fibronectin-coated substrate. By varying the concentration of fibronectin, an extracellular matrix protein, I tested the effect of the number of adhesion sites on the rate of tissue spreading. Initial analysis showed that over a concentration of 25 µg/ml, changes in fibronectin concentration no longer had an effect on the spreading rate of tissue. These results will allow us to conduct future experiments on tissue spreading in a regime where slight variations in fibronectin-coating are unlikely to affect spreading rate. |
|
D05.00024: Myoelectric control of prosthetics and robotics Katherine A Crosby, Preston K Robinette, Eli T Owens Prosthetic limbs improve mobility and give people the power to perform tasks that would otherwise be arduous to undertake. In our research, we have developed a functional, 3D printed prosthetic hand. This hand detects and interprets the myoelectric signal from healthy muscles to control motors that move the prosthetic fingers and wrist, mimicking the functionality of a true hand. In order to detect a myoelectric signal, we use two electrodes placed across the muscle of interest. The signal from these two electrodes is measured differentially using an instrumentation amplifier. The signal from the instrumentation amplifier is then sent into a twin t-notch filter to remove the parasitic 60 Hz noise; this filtering increases the signal to noise ratio to approximately 10:1. We also send the signal through a high pass RC filter to remove any DC offset. Finally, the signal is sent to an additional amplification stage before being interpreted by a microcontroller. The microcontroller uses a simple threshold algorithm to decide if the hand should be opened or closed. In conclusion, we were able to create a functional 3D printed prosthetic hand controlled via myoelectric sensing and interpretation. |
|
D05.00025: Molecular Dynamics Simulation of the Extracellular Matrix Bailey L Canter, Britta Gorman, Laurie E McNeil During metastasis, a cancer cell invades the extracellular matrix (ECM) by secreting an enzyme that cleaves collagen molecules. A better understanding at the molecular level of the elastic behavior of the ECM will provide significant insight into the mechanisms involved in cell migration, cell adhesion and during cell communication. We model the ECM in a molecular dynamics simulation using LAMMPS, Large-scale Atomic/Molecular Massively Parallel Simulator. Since collagen is the most abundant protein in the ECM, we create an environment containing collagen and water molecules at a density equivalent to the composition of the MatrigelTM ECM samples used in our experiments. We deform the simulation box to calculate the stress tensor and elastic constants of the system. We mimic the enzymatic effect on the ECM by cleaving a peptide bond in the collagen molecules and recalculating the elastic constant. The results are compared to the experimental results which show the elastic constant decreases as more collagen molecules are scissioned by the enzyme. The findings will provide molecular-level insight to interpret measurements made at the cellular level. |
|
D05.00026: Bio-mechanical Modeling and Analysis of Knee Joints Affected by Kyphosis Using Computational and Physical Calculations Minseo Lee, Amanda Kyung The physical and computational analysis can be used in cases where determining the clinical condition of patients is not easy. Kyphosis is one of the most well known disorders that elders suffer from the deformed thoracic vertebra causing incorrect postures and changing the center of mass of the body forward. In this paper, the effect of aging kyphosis on the patient 's use of stairs was experimentally investigated, and the most comfortable physical factors for kyphosis patients were suggested. Also, the effect of kyphosis on kinematics of knee joints and legs has been computationally performed. Using the free body of diagram of forces acting on the knee during loading and walking, bio-mechanical model depicting knee joint kinematics has been studied. Moment equilibrium and force equilibrium are also considered. Based on the fact that magnitude of the joint reaction force on knee joints can reach several times the body weight, the stability analysis of the knee and lower leg bone has been studied. This research includes two procedures: Study of mathematical modeling of the lower leg using bio-mechanics, and the development of mechanical analysis of the tibial bone.
|
|
D05.00027: Ab initio molecular dynamics of fully solvated biomolecules with periodic boundary conditions using the Oak Ridge Leadership Computing Facility (OLCF) supercomputers Ada Sedova, Micholas Dean Smith We present the first nanosecond-scale molecular dynamics simulations of small ribonucleic acids with a full solvation shell of explicit water and ions at the density functional theory (DFT) level, using high performance ab initio molecular dynamics programs and the OLCF supercomputers. Comparison of the trajectories to classical molecular dynamics performed, including effects of polarization, changes in molecular conformations, and dynamics of the system in metastable states and with respect to barrier crossing. We find important differences in the conformational dynamics that can be attributed to effects of dynamic changes to polarization and which may be essential to a correct description of conformational ensembles of these difficult to model molecules. |
|
D05.00028: How initial explant size affects spreading rate of tissue explants from Axolotl embryos George EA Ridgeway, Riley E Reynolds, Holley E Lynch Large scale tissue movements are an integral part of early development. In order to understand the forces that drive this motion, I investigated the initial size-dependence of the spreading rate of tissues explanted from Axolotl (Ambystoma Mexicanum) embryos. We did this by cutting a tissue explant and then plating it on glass, the tissue spreads similarly to how it would in an intact embryo. Testing variously sized explants allows us to determine the effect of the initial amount of total material on how fast tissues spread. Our preliminary analysis shows that explants with a larger initial size spread faster than explants with a smaller initial size, suggesting that limits in available material may reduce the rate that tissues can spread. |
(Author Not Attending)
|
D05.00029: pH sensitive properties of ionizable residues in a hydrophobic protein interior Ankita Sarkar, Adrian E Roitberg Internal ionizable residues in proteins display anomalous pKa values. An atomistic understanding of factors determining the shifted pKa values is important in obtaining insights into the mechanisms driving important biological processes such as enzyme catalysis and energy transduction. We study the diversity of the pH dependent conformational changes undergone by several mutants of staphylococcal nuclease (SNase), driven by the presence of a single internal ionizable residue, using pH Replica Exchange molecular dynamics simulations (pH-REMD). We present thermodynamic models to calculate the ‘conformation-specific pKa’ of the water-exposed and buried conformations of the internal ionizable residues and explain it in association with the observed anomalous ‘apparent pKa’. We further investigate the pH sensitive structural and thermodynamic properties driven by the presence of two ionizable residues within the hydrophobic interiors. |
|
D05.00030: Biophysical Analysis of the Dental Radiograph Image Using Computational and Physical Method Won Jun Lee, Sun Lee In this paper, an alternative fast algorithm for dental diseases detection was computationally and physically studied. Generally, digital image subtraction method and filtering method such as LPF (Low Pass Filter) and HP (High Pass Filter) are used to reduce the structure noise of normal anatomic detail. The main purpose of this research was to develop a better algorithm that would enhance the quality of the final digital radiograph image of dental structures. An ideal low pass filter would be able to increase the resolution of image as well as decrease the Ringing Artifact. In this paper, a few trigonometric functions and specific algebraic function were tested to reduce Ringing Artifact. Compared to those produced by using a box function, the presented method improved the resolution of the resulting image.
|
|
D05.00031: Biophysical Study on the Leber Congenital Amaurosis (LCA) Using Computational Analysis Namju Kim, Andrew Kyung Gene therapy aims to deliver a healthy, functional copy of a gene to the patient’s cells via engineered viral vectors. A point mutation or silent mutation can have detrimental effects on one’s health. In the case of retinal diseases, a mutation in the RPE65 gene, such as Arg91Trp, can lead to Retinitis Pigmentosa or Leber Congeital Amaruosis. The onset of these conditions can heavily affect visual function, with symptoms that range from light sensitivity to poor peripheral vision. This paper identifies and analyzes abnormalities in the genetic sequence that lead to mutations in patients with genetic eye disorders. A computational and biophysical study were performed with genetic mutations identified in RP patients, then a computational study was also performed with pathogenic mutations identified in LCA patients, examining sequence abnormalities in their DNA. |
|
D05.00032: Stereochemical and Biophysical Analysis of Targeted Nanoparticles for the Treatment of Alzheimer's Disease Mia Moon, Amanda Kyung In this paper, the theoretical and stereochemical structures of targeted nanoparticles for the treatment of Alzheimer's Disease was studied. Using quantum chemical calculations, it can be determined which compound can be used more efficiently to achieve thermodynamic stability. Based on the calculated optimized energy which is used to assess the stability of each molecule, it is possible to determine whether the targeted nanoparticle molecules can be formed in a stable manner. Optimization configuration energies were collected in order to compare each chemical compound's safety and stability. Also, electro-potential maps were obtained in order to figure out each chemical compound's activities. Calculations show that some compounds easily converge to lowest value of energy they can have, which makes them suitable to use in biochemical compound or drugs for the treatment of Alzheimer's Disease. This research examined the chemical and electric properties including potential energy and dipole moments of nanoparticles as contrast agents as well. Molecular editing chemical softwares were used to model and optimize the nanoscale molecular compounds. |
|
D05.00033: Probing Photocurrent Response in 2D Materials Using Scanning Photocurrent Microscopy Alex Strasser, Christopher Rouleau, Akinola Oyedele, Kai Xiao, David Geohegan Understanding the photoresponse of 2D materials and their heterostructures is important for applications in optoelectronic devices, including photovoltaics, photodetectors, etc. Scanning photocurrent microscopy is a useful photoresponsivity mapping technique for characterizing the optoelectronic properties of nanomaterials including carrier diffusion lengths, internal electric field distribution, band bending effects at heterojunctions, photothermal properties, and information about recombination mechanisms. Results contained are the exploration of 2D material heterojunctions of InSe/WSe2 and MoSe2/black phosphorous as well as the recently discovered PdSe2. This tool, operating as part of a user facility, can be used to investigate optoelectronic properties and applications of a wide range of nanomaterials, as is demonstrated in several use cases. |
|
D05.00034: Engineered Nanocomposite Materials Properties through Embedding of Smaller Nanoparticles in a Polymer Matrix Sanju Gupta, Alex Henson Polymer nanocomposites are significant for modern and future technologies due to their tailored properties, lightweight and low-cost. However, ‘forward’ engineered polymer (host matrix) composites with smaller size nanoparticles (guest) providing desired properties targeting specific applications remains a challenging task as they depend on nanoparticles size, shape and loading. This study investigates polymer nanocomposites impregnated with ‘organic-inorganic’ silsesquioxane nanoparticles (diameter ~2-5nm) and graphene nanoribbons (lateral dimension ~5-10 nm) in poly(2-vinylpyridine) (P2VP) matrix (segment ~5nm) and investigates microscopic structure and interfacial dynamics to predict macroscale properties. This approach reinforces the role of molecular parameters controlling the structure and interfacial layer dynamics. The atomic force spectroscopy will reveal morphology and the lattice bonding, interfacial stress transfer and conjugation length are determined from Raman spectroscopy. Temperature dependent broadband dielectric spectroscopy provided fundamental insights into the interfacial and diffusion dynamics above and below glass transition temperature and to establish microstructure-property correlations. |
|
D05.00035: Thermoelectric Properties of Graphene-Carbon Nanotube Aerogels as ‘Organic’ Energy Harvesters Sanju Gupta, Romney Meek In this work, we prepared graphene-carbon nanotube (Gr-CNT, hereon) and nitrogenated analogs three dimensional scaffolds using facile hydrothermal technique as thermal and thermo-electrochemical energy harvesters. The resulting aerogels are structurally ordered with ultralow densities and tunable mesoscopic pore sizes by means of organic wet chemistry used to cross-link the component nanomaterials yielding multiplex hierarchical topologies. In contrast to methods that utilize physical cross-links between GO nanosheets, this approach with polymeric linkers and organic functionalization provides covalent carbon bonding among the graphene nanosheets and molecular attachment with carbon nanotubes, facilitating rapid and facile electron and ion transport. They exhibit large internal surface area thus promote enhanced surface ion adsorption viable for use in thermal energy harvesting technologies. They have shown improved electrical conductivities (> 5 S.cm-1), higher Seebeck coefficient (> 0.5 V.K-1), and moderate thermal conductivity (~0.028 W.m-1.K-1). Complementary characterization techniques such as electron microscopy, Raman spectroscopy and scanning electrochemical microscopy established structural property-activity-performance correlations. |
|
D05.00036: Graphene-mediated Surface Enhanced Raman Spectroscopy for Detection of Biomolecules and DNA Hybridization Sanju Gupta, Alexander Banaszak In this work, we prepared graphene-mediated surface-enhanced Raman scattering (G-SERS) substrates comprising few-layer graphene nanosheets decorated gold and silver nanoparticles for bio-nanotechnology. Raman scattering and particularly, SERS is a surface-sensitive spectroscopy technique useful for rapid and precise identification of biological molecules, industrially relevant chemical dyes at ultralow concentration and DNA hybridization due to the enhanced signal by several orders of magnitude on SERS-active surfaces. While SERS technology is based on metal nanoparticles, which generates localized surface plasmon resonances, diameter and interparticle gap on graphene supports offer an advance toward sensitive G-SERS substrates via localized hybridization at the interface. We used thermal reduction to produce few-layer functionalized graphene and wet chemistry for size tunable gold and silver nanoparticles for strategic G-SERS platforms. High-throughput arrays (or ‘biochips’) are developed as well as sandwiching gold and silver nanoparticles and few-layer graphene for cascaded signal amplification to differentiate among nucleotide bases (adenine; A, thymine; T, cytosine; C, guanine; G), DNA hybridization and to detect beta-carotene and malachite green chemical dye. |
|
D05.00037: Hydrothermally Synthesis and Properties of Mesoporous Molybdenum Disulfide (MoS2) - Reduced Graphene Oxide Composites for Hydrogen production Sanju Gupta, Jacob Dobler, Taylor Robinson Graphene and related two-dimensional layered materials are attracting attention due to inherent advantages as potential game changers at the grand challenges of energy-water nexus. These technologies require delicate control over geometric and electronic structures affecting physical-electrochemical properties. In this study, we prepared three-dimensional aerogels consisting of varying graphene oxide-MoS2 (molybdenum disulfide) ratio under hydrothermal conditions (P < 20 bar, T <200 oC) and synergy of PVP and components. We systematically characterized designed heterostructure interfaces, understand interaction through optical absorption and Raman spectroscopy (RS), to correlate between number defect density (via RS) and electrocatalytic activity. We demonstrate that controlled defects density (desulfurization), edges plane sites, hierarchical porosity and topological interconnectedness (monolithic aerogels) invoked can finely tune morphological structure and enhance activity towards electrocatalytic hydrogen production with a low Tafel slope ~77 mV·dec−1. Additionally, Raman spectral bands are analyzed and the pore size distribution and mesoporosity are determined from electron microscopy and tomography.
|
|
D05.00038: Electrochemical Desulfurization and Electroactivity of Molybdenum Disulfide (MoS2) Nanocatalysts Supported on Reduced Graphene Oxide for Efficient Hydrogen Evolution Sanju Gupta, Taylor Robinson, Jacob Dobler Electrocatalytic water splitting resulting in hydrogen production using platinum (Pt) and palladium catalysts has high impact in energy generation. However, high cost hinders their widespread applications. Recent developments in graphene and related materials including molybdenum disulfide (MoS2) are gaining popularity as efficient and cost-effective catalysts. In this work, we prepared few-layer molybdenum disulfide (MoS2) and aerogels with reduced graphene oxide (rGO) hydrothermally as nanocatalysts and electrochemically desulfurize for accelerated hydrogen evolution reaction (HER) activity via point defects (S-vacancy) in basal plane and exposed edge sites. Moreover, the interaction between rGO and MoS2 create emergent hetero-interfaces with desirable physicochemical properties (specific surface area, mechanical strength, faster diffusion, facile electron and ion transport). The applied desulfurization potential and operating duration is varied for controlled HER activity. This unique method of tuning the properties of MoS2 is promising for creating noble metal-free catalysts. We also performed electrochemical stability tests to confirm long-term operation of the catalysts and established structure-catalytic activity correlations. |
|
D05.00039: Graphene-Polymer Thin Film Composite Membranes as Efficient and Anti-fouling Membranes for Water Purification Sanju Gupta, Brendan Evans, Alex Henson Water is our planet’s most precious resources and life’s most basic indispensable component. Reverse osmosis (RO) filtration is highly adopted, growing technologies to produce clean water by removing undesired (charged or uncharged) solute species. However, polymer and ceramic membranes suffer from low permeability, structural breakdown and fouling. Graphene, a form of carbon, provides the foundation for the production of highly permeable membranes as an emerging technology for RO desalination. Adding oxygen to few-layer graphene nanosheets, i.e. graphene oxide (GO), opens allows efficient adsorption of charged ionic species (selectivity) and augmented flow of water molecules (ultrafast permeability). This works reports on the development of novel graphene oxide thin film nanocomposite (G-TFNC) membranes embedded with a thinner active polymer layer via interfacial polymerization to tackle the trade-offs among water flux transport and salt ionic species rejection, robustness and anti-fouling characteristics. This study overcomes the gap between drinkable freshwater demand and supply through nanotechnology-enabled high performance graphene composite membranes. |
|
D05.00040: Toward strain control of magnetism in few-layer CrI3 Salem Clay Wright, Arash Fereidouni, Jin Hu, Hugh Churchill CrI3 is a van der Waals material and known monolayer ferromagnet that can be cleaved into |
|
D05.00041: Transverse Voltage in Superconducting Films: Patterns in Current, Amplitude and Peak Width Anna C Spencer, Phillip R Broussard While others have observed transverse voltage in superconducting films, no study has compared these signals in a variety of systems. Our goal was to see if any universal patterns exist between films of different materials (Nb, NbZr, NbCN, NbN) and thicknesses (40 nm - 3160 nm). To investigate this, we swept current through superconducting films and compared the amplitudes of the transverse voltage signals, the widths of the peaks, and the currents at which these peaks occurred for multiple temperatures near T$_c$. Although we saw universal behavior in the current, we did not see any scaling in the peak widths or amplitudes. We hope to continue to compare to various models of transverse voltage. |
|
D05.00042: Design and Preparation Of Positron Source For Non-Destructiive Positron Annihilation Lifetime Spectroscopy Jared K Averitt, Roman Golovchak Positron annihilation lifetime (PAL) spectroscopy uses positrons to characterize void content in materials at the sub-nm scale. The time a positron survives in a defect corresponds to the free volume of the defect and its associated charge. Radioactive sodium (22Na) salt prepared from aqua solution is mostly used as a positron source in laboratory PAL systems, which is sandwiched between two identical glass samples. Encapsulating the source between two layers of Kapton film allows successive use of the same source for nondestructive PAL measurements of different samples, reducing measurement uncertainties, cost of experimentation and raising reproducibility of the results. Quality of the obtained data and precision of further analysis depends significantly on the condition of the encapsulated positron source, which in turn, depends on the uniformity of 22Na salt layer deposited on Kapton films. Our work reports our first results on the design of an apparatus for positron source preparation and encapsulation. Uniformity of the source layer is achieved by adjusting water evaporation rate and solution supply rate. In this way a positron sources of ~5 mm in diameter are obtained. |
|
D05.00043: Upper Limit Transverse Voltage Calculations Matthew E Broussard, Phillip R Broussard L. I. Glazman's paper(1) on transverse voltage in thin films near their superconducting transition temperature predicted that for wide films (w $\gg$ $\lambda$), the upper limit for current at which transverse voltage would appear is temperature independent. Using a Runge-Kutta algorithim and the complete equations for vortex/anti-vortex interactions the upper limit for the thin niobium films were calculated for several temperatures, and how these compare to Glazman's model and experimental results on the same films will be discussed. (1)L. I. Glazman, "Vortex Induced Transverse Voltage in a Film," \textit{Soviet J. Low Temp. Phys.}, \textbf{12,} 389-392, (1986).
|
|
D05.00044: Synthesis of Cobalt-doped MoS2 Monolayers for an Efficient Nanocatalyst in Hydrogen Fuel Cells Nicolas Muecke The current best materials for catalysts in hydrogen fuel cells are noble-metal based which makes them too scarce and cost-prohibitive for widespread commercial use. Transition Metal Dichalcogenide (TMD) nanomaterials in the form of repeatable MX2 units, like MoS2, have significant potential to outperform these metals based on extensive density functional theory (DFT) calculations. To achieve the highest surface area for the catalyst, nanomaterials in the form of 2D film are desirable for their superior electron control in the vertical direction. Despite all of these reasons, MoS2 in any form has yet to reach the current best standard of platinum. However, multiple studies have shown that introducing strain in some form or exposing MoS2 edge sites can greatly improve its catalytic efficiency. In this experiment, we synthesize a cobalt-doped variant of MoS2 to benefit from the synergistic properties of metal doping with superior electron control. |
|
D05.00045: Experimental Studies of Transport Properties of Novel Amorphous Fe-Dy-O Thin Films. Sara Bey, Tatiana Allen, Krishna Koirala, Ramki Kalyanaraman, Phillip Broussard, William L. Roes This work focuses on the transport properties of Fe-Dy oxides. The material is related to the recently discovered Fe-Tb-Dy oxides that show remarkable optical and galvanomagnetic properties with potential for electronics, photonics, and spintronics applications. By eliminating Tb, we hope to gain a better understanding of the individual ways the two lanthanides, Tb and Dy, affect the properties of the Fe-Tb-Dy oxides. In addition, Fe-Dy-O, the material that has not been studied yet, may exhibit interesting properties and potential for applications on its own. Fe-Dy-O films were grown by the ion beam evaporation on different substrates. The amorphous nature of the films was confirmed by the EBSD. The chemical composition of the films was studied by the EDS. Galvanomagnetic measurements were performed in the Van-der Pauw geometry in the temperature range between 6K and 700K. Then samples were repeatedly heated from 300K to 700K in the low vacuum environment, while resistivity and Hall Effect were monitored in-situ. We will discuss the effect of the initial annealing on the sample properties as well as the evolution of the transport properties of as-deposited samples as a result of the thermal cycling. |
|
D05.00046: Abstract Withdrawn
|
|
D05.00047: Antiferromagnetic ordering in spinel GeV4Se8 Hasitha Suriya Arachchige, Ganesh Pokharel, Stuart Calder, Andrew May, Andrew Christianson, David Mandrus In the search for topologically non-trivial spin textures, the spinel family of materials stands out as a host of such phenomena. Lacunar spinels (AM4X8) are a subset of spinels, where there is an ordered vacancy on the A-site, which results a breathing pyrochlore structure. In these compounds, there are two major molecular units, namely, (AX4)n- cubane, and (M4X4)n+ tetrahedral units. Because of those weakly coupled molecular units, lacunar spinels demonstrate exotic behavior, where some members host a Néel-type skyrmion lattice. We have synthesized powder samples of GeV4Se8. The physical properties were investigated with x-ray diffraction, magnetometry, and neutron diffraction measurements. The room temperature x-ray diffraction data confirm that GeV4Se8 crystallizes in the space group 216 (F-43m). The magnetometry data shows anomalies 12, and 34 K. The neutron diffraction data shows that the 12 K transition corresponds to the onset of long-range antiferromagnetic order in GeV4Se8. |
|
D05.00048: Synthesis of the Kagome Spin Ice Ho3Mg2Sb3O14 Emily M Hollingworth A geometrically frustrated magnet is a system in which the material’s crystal structure prevents its magnetic spins from each anti-aligning in the most energetically favorable way. In particular, there is no single lowest energy state, resulting in a high ground state degeneracy. This can lead to exotic states of matter that may behave non-classically even at ultra-low temperatures. The kagome spin ice is an example of such a material, wherein Ising spins are frustrated due to the triangular 2D kagome lattice structure. We have synthesized powder of such a material: Ho3Mg2Sb3O14, as well as holmium doped La3Mg2Sb3O14. With this doped material, we are able to isolate the effects of the magnetic Holmium ions from those of the surrounding environment. We have also found preliminary results on the synthesis of single crystals of this kagome lattice. Additionally, we have measured neutron scattering data on powder samples of these materials, which has allowed us to separate out the contributions of the magnetic ions from the environment and nearby interactions. Resources Dun, Zhiling, et al. "Quantum Spin Fragmentation in Kagome Ice Ho3Mg2Sb3O14." arXiv preprint arXiv:1806.04081 (2018). |
|
D05.00049: Pressure-induced valance change in Ytterbium intermetallic YbCuGa Tyler Brett Helton, Keely Jane Sage, Farzana Nasreen, Daniel Antonio, Andrew Cornelius, Corwin H Booth, Milton Torikachvili, Yuming Xiao, Karunakar Kothapalli Ytterbium (Yb) intermetallic systems are known to exhibit intermediate valence (IV) behavior due to the hybridization of two energetically close localized configurations, the non-magnetic Yb2+ (4f14) and the magnetic Yb3+ (4f13), with the conduction electrons. The IV behavior plays a crucial role in the exhibition of anomalous properties of several rare-earth compounds. Pressure and temperature variation can tune the valency of these types of compounds and increase in pressure tends to delocalize these systems and they show tendency to move towards trivalent state Yb3+ (4f13). YbCuGa is one such compound which shows very intriguing electronic properties owing to its IV. Previous experimental work on YbCuGa at ambient pressure showed IV nature of Yb ions. We report on high pressure, 0-14 GPa, x-ray absorption measurements in partial fluorescence yield mode on YbCuGa system at ambient temperature. Increase in pressure delocalizes the system and pushes it from a valency of ~ 2.58 at ambient pressure to ~ 2.9 at 14.0 GPa. Our results indicate that application of pressure pushes the Yb ion to a magnetic state and therefore magnetic interactions can be expected to dominate as the unit cell volume is decreased. |
|
D05.00050: Monte Carlo Simulations of Spin Liquids Hannah K Price, Xiaojian Bai, Martin P Mourigal Using Monte Carlo, we simulate the ground state spin configurations of spin liquids at low temperatures. The program requires only basic unit cell and coupling energy information to be run. Thus, most materials can be easily simulated. We have modeled the frustrated diamond lattice for a range of J2/J1 energies. As well as the frustrated pyrochlore lattice for a select J2/J1 energies. In particular, we compare the modeled critical temperature and structure factor with that from previous models and experiments. |
|
D05.00051: Implementation of D.R. Heat Capacity Data Processing, and Measurement of 1D Spin Chain Heat Capacity in Cu Elpasolite Liam J Ritchie, Luwei Ge, Martin P Mourigal We recreate the P.P.M.S. D.R. heat capacity measurement system's data processing chain to produce heat capacity over temperature data, and we investigate the heat capacity of materials which support 1D spin chains when saturated at high magnetic field. The recreation of the data processing method for the D.R. heat capacity measurements allows not only greater transparency in how the experimental data is handled, but also allows different data processing methods and experimental techniques to be used with the P.P.M.S. D.R., such as the long H.C. pulse method. This refactoring required creating ways of reading and using temperature calibration files and raw data files, along with fitting the experimental data to heating curves based on one-tau and two-tau models to extract heat capacity. The Cu Elpasolite material supports 1D spin chains, which are a 1-dimensional quantum system having the characteristic of bosons and fermions having no difference. We measure the low temperature heat capacity at high magnetic field, and discern whether this material supports this kind of excitation characteristic. |
|
D05.00052: High Dynamic Gas Pressure Single Crystal Growth: My PARADIM REU Experience Zachary A Kennedy, Martin P Mourigal, W. Adam Phelan, Tyrel McQueen The growth of single crystals is crucial to the advancement of Solid State Physics. With these crystals, neutron scattering that accounts for the directionality of the crystal can be performed, allowing for a much deeper exploration of a material’s low temperature magnetic phases. This summer I had the fantastic opportunity to study single crystal growth on one of the world’s premier floating zone furnaces, the 300 bar optical floating zone furnace at Johns Hopkins University. This furnace opens up an entirely new area of phase space where crystal growth can occur, allowing for large single crystals to be grown in materials where this is impossible at lower pressures. This machine is available for users through the Platform for the Accelerated Realization, Analysis, & Discovery of Interface Materials (PARADIM). It is important for potential users to know the benefits this machine offers, the different techniques that can be used with it, and what potential challenges will arise when operating this furnace. This presentation will be a summary of my experience with the 300 bar optical floating zone furnace that will provide potential users with the information they need to know to successfully grow large single crystals of their material. |
|
D05.00053: Phase Field Simulations of Magnetic Domain Stability in Anisotropic Polycrystals Will T Bowers, Tiannan Yang, Fei Xue, Long-Qing Chen Scaling effect in finite-size magnetic materials is manifested as a transition of domain structures upon increasing size of the magnet, typically from a flower-like domain structure to a vortex-type multi-domain structure within a magnetic cube with cubic or uniaxial magnetocrystalline anisotropy. In finite-size magnetic bicrystals or polycrystals, the thermal stability of these domain structures is further dependent on the size and orientation of the grains. We explore the stability of these states in ferromagnetic crystals using phenomenological phase-field simulations, using the critical size of a system as a metric of the stability of the magnetic particle. Our system parameters for the simulations included the anisotropy strength, grain size, and grain orientation of the system, all of which contributed to the shape and behavior of the magnetic domain. We find that grain size and anisotropy strength have a relatively weak effect on the stability of the magnetic phase of a polycrystal. |
|
D05.00054: Numerical Modelling of Tandem Solar Cells Spencer Shortt, Aidan Burleson, Hasitha Mahabaduge In this work, Solar Cell Capacitance Simulator (SCAPS-1D), a software primarily developed to analyze single-junction devices, was used to effectively model photovoltaic thin-film multi-junction solar cells. The tandem configuration in this study consists of a modified cadmium telluride based top cell which uses n-MZO (magnesium doped zinc oxide) as an emitter layer (as opposed to n type cadmium sulfide) and a silicon-based bottom cell with n type silicon as an emitter layer. Parameters including the thickness of the emitter and absorber layers were varied to improve the open circuit voltage to 1.4 V, short circuit current to 24.5 mA/cm2, fill-factor to 85.9%, and overall efficiency of the device to 28.8%. This numerical work supports the study of tandem-devices and their potential to optimize efficiency by making use of the entire spectrum of solar irradiation. |
|
D05.00055: Effects of general relativity on nonradial stellar pulsations of compact stars Abhijit Gupta, S. Reece Boston, Charles R. Evans, Jonathan Bennett In the present age of space-based photometry, telescopes such as K2 and TESS are providing pulsation frequencies of stellar objects to unprecedented accuracy, requiring equally precise theoretical models correlating these observations to mass- and composition-dependent characteristics of stars. At this precision, relativistic models are required for compact objects such as white dwarfs and neutron stars. We model these stars as polytropes using the Tolman-Oppenheimer-Volkoff equation, and compute relativistic nonradial stellar pulsations around this equilibrium state. Outside the stellar surface, we integrate the Zerilli equation to locate resonant quasinormal modes, where ingoing gravitational radiation vanishes. We compare the frequencies of a subset of these modes to their corresponding pressure-modes in the Newtonian limit, as a function of the strength of relativity inside the star. Our results contribute to our understanding of the impact of general relativity on stellar oscillations, and can be used to determine the conditions under which the Newtonian approximation is justified. |
|
D05.00056: A Mirror World? Detector Background Measurements for a Mirror Neutron Regeneration Experiment Alexander Blose, Leah J Broussard, Christopher B Crawford There may exist a hidden mirror gauge sector with a complete copy of our normal gauge sector, standard model matter. This so-called mirror world would interact only weakly through the gravitational force, making it a candidate for dark matter, and may allow neutrons to oscillate. An experiment to search for neutron oscillations will take place at Oak Ridge National Laboratory’s High Flux Isotope Reactor (HFIR) using the General Purpose-Small Angle Neutron Scattering (GP-SANS) instrument and its low background Linear Position Sensitive Detectors (LPSD). We used a separate LPSD to characterize the sources of neutron backgrounds in the vicinity to determine the necessary shielding requirements for the GP-SANS detectors from backgrounds from cosmogenic sources or other instruments. We will present results of the detector characterization, comparison to the GP-SANS detector performance, and background studies at GP-SANS. |
|
D05.00057: Simulating a UCN “PPM Depolarization” Experiment to Verify the Integrity of an Analysis Mode Sanjay K Chakrabarty, Adam Holley The depolarization probability per bounce (DPB) is used to understand systematic and statistical effects in experiments requiring polarized ~100 neV 'ultracold' neutrons (UCN). To predict this effect, experiments were performed at Los Alamos National Laboratory to determine the DPB of UCN upon interaction with material guides as a function of the ambient holding field. To account for systematic effects in the experiment, the analysis model must be verified through a Monte Carlo computer simulation. In such simulations, a high-fidelity model of the UCN production source and the experimental geometry are used to simulate the effects of UCN angular and energy distributions. Other variables, such as loss per bounce and specularity, must be calibrated to match the simulation to data. After the simulation is verified to be consistent with the experiment, simulated data that is representative of experimental data can be created by varying DPB. If the analysis model fails to correctly predict the programmed DPB, the simulation can guide changes to the analysis model. The simulation method and a comparison to the experimental data will be presented, along with results from tests of one possible analysis model. |
|
D05.00058: Studies of the Gain of Small-Pore Size Microchannel Plate Photomultipliers in High Magnetic Fields Alan M Rowland Microchannel plate photomultipliers (MCP PMTs) are small devices that convert light into an electric signal. These devices have many applications, but most notably in physics they are used to readout Cherenkov detectors. In the current designs of the central detector of a future Electron Ion Collider MCP PMTs will readout several Cherenkov detectors located in a magnetic field. Because of this, tests need to be conducted to determine whether the photomultipliers can retain their functionality in the magnetic field of the detector, which can go as high as 3 T. In this work we study two MCP PMTs, with pore sizes of 6 µm and 10 µm, inside a variable magnetic field. We determined that the gain of both devices would slightly increase as the magnetic field increased, until about 0.8T and 0.3T, respectively. While the gain would decrease afterwards, the photomultipliers are able to produce a signal until about 2 T. The orientation of the devices also has an effect, as the gain decreases faster for some orientations. This effect was more noticeable when the magnetic field was above 1 T. Our results suggest that photomultipliers with a small pore size are a viable option to use in the upcoming Collider in a limited range of magnetic-field magnitude. |
|
D05.00059: Tracking Radon Deposition as a Function of Charge Andrew C Dunton In our universe, there is a preponderance of matter over antimatter. Neutrinoless double-beta decay would serve as a potential mechanism by which this asymmetry of matter and antimatter occurs. In a single beta decay, a proton decays into a neutron and releases a beta particle (electron) and an electron neutrino. In a theoretical double-beta decay, two protons would decay, two electrons would be released, but no neutrinos would be detected. This would mean the electron neutrino is its own antiparticle, a Majorana particle. To observe this phenomenon, one requires a large collection of nucleons prone to beta decay far away from any potential sources of interference. One such potential interference source is alpha radiation from radon gas, which permeates the earth and air around us. Its interference levels in the first trial runs of the experiment were higher than expected, and so reducing radon's presence has become a priority. In order to do this, we must understand how it attaches itself to various materials and in various conditions, and how best to remove it. Developments in this research have indicated that radon deposition may be affected by charge, and this project seeks to quantify that relationship. |
|
D05.00060: Experimental Study of the Dual Radiation Rotating Scattering Mask to Localize Neutron and Gamma Sources with CLYC Detector Alexander Barzilov, Devon Alexander Loomis, Lawrence Madriaga, Ivan Novikov A Dual Radiation Rotating Scattering (DRRS) Mask was developed at the Applied Physics Institute at Western Kentucky University to simultaneously locate gamma and neutron radiation sources. The DRRS mask surrounds a radiation detector and rotates around to modulate detector signal. The DRRS mask consists of neutron scattering material (UHMW) and gamma rays scattering materials (lead). The source location is determined based on signal dependence as a function of angle of rotation. We present the progress in the DRRS construction, development of rotating platform and its control modules, and the first experimental results obtained with Cs2LiYCl6:Ce (CLYC) scintillating detector. |
|
D05.00061: Abstract Withdrawn
|
|
D05.00062: Non-equilibrium Thermodynamics in the Driven Ising Model Joaquín Drut, Yasmine A Zefri The goal of this study is to observe the non-equilibrium behavior of simple quantum mechanical models, specifically the driven Ising model. Most systems in nature spend most of their time away from thermodynamic equilibrium. Understanding their collective dynamics in these conditions is one of the most relevant problems in condensed-matter physics today. However, the problem poses a formidable challenge from the theoretical and computational standpoints, as the number of particles (or degrees of freedom) involved is extremely large. In an attempt to address this problem, python code can be written simulating the 3D and 2D Ising models with a constant magnetic field, H, imposed on the system. The energy, magnetization, specific heat, and susceptibility are calculated for each value of H. Each time this process is completed, H is increased and the calculations are performed again. The above defines the equilibrium properties of the system. To study the non-equilibrium counterparts, we will study two kinds of problems: introducing random magnetic fields and introducing spin dynamics in the Monte Carlo process. |
|
D05.00063: Performance of Scintillation Counters for the Mu2e Cosmic Ray Veto Ningshun Chen Photoelectron yields of extruded scintillation counters with titanium dioxide coating and embedded wavelength shifting fibers read out by silicon photomultipliers have been measured at the Fermilab Test Beam Facility using 120 GeV protons. The yields were measured as a function of transverse, longitudinal, and angular positions for a variety of scintillator compositions, reflective coating mixtures, and fiber diameters. Timing performance was also studied. These studies were carried out by the Cosmic Ray Veto Group of the Mu2e collaboration as part of their R&D program. |
|
D05.00064: Precision Top Mass Determination at the LHC Henry McElroy Sanders, Seth David Iwan The Standard Model (SM) is the established theory of particle physics down to distance scales as small as a thousandth of a femtometer. The frontier of high energy physics is the search for new physics beyond the SM through direct searches at the Large Hadron Collider (LHC), complimented by high precision measurements of key SM parameters. One such parameter is the mass of the top quark, the heaviest known elementary particle, about 170 times more massive than the hydrogen atom. The uncertainty in its value affects precision fits, limiting the ability to test the SM and constrain new physics. At the LHC, the most precise experimental top mass measurements are based on the method of kinematic reconstruction, which yields enhanced sensitivity to the top quark mass. We perform Pythia Monte Carlo simulations of a related observable, the boosted top jet mass spectrum, based on a newly developed factorization-based theoretical framework. We study the sensitivity of this observable to the top quark mass with over 18 million simulation events. Good agreement is found with the theoretical predictions. |
|
D05.00065: Kinetics of Tin Whisker Growth Emily K Mitchell, Chad L Rodekohr Tin whiskers are single-crystalline structures that grow out of tin-rich surfaces. Whiskers are found to grow most notably on thin surfaces, such as those deposited via electroplating or sputtering [2]. Tin whiskers are highly conductive and pose a threat to many systems via their ability to cause short circuits, bringing about malfunctions in products from satellites to pacemakers [3]. Little is known about the growth mechanisms of whiskers, but many agree that stress is a necessary factor. This research aims to evaluate the necessary components of tin whisker growth. We hypothesize that stress and nucleation points are the critical features for whiskers to form. Uniting nucleation points and stress through etching and bending respectively, we hope to find an increased whisker growth, showing that these components are necessary for whisker growth. Through the understanding of why whiskers grow, we hope to control the location, orientation, and occasion of whisker growth. These abilities will enable us to stop harmful whisker growth and use whiskers for beneficial use, such as in the MEMS field. |
|
D05.00066: Cosmic Ray Telescope Measurements of Muon Flux at Mu2e Kristen E Schumacher The Cosmic Ray Veto group at the University of Virginia is designing and constructing the Cosmic Ray Veto, to reject background events in the Mu2e experiment which were caused by cosmic rays. In order to confirm previous simulations and to add to our understanding of flux at angles close to the horizon we needed to measure the cosmic ray muon flux at the experiment site. Therefore a cosmic ray telescope large enough to collect a substantial amount of data in a short time, yet with sufficient resolution to distinguish between angles close to the horizon was constructed. Measurements were taken at the Mu2e detector hall and compared to expected rates. |
|
D05.00067: Down-conversion and Demodulation of AM Radio Waves Using a Stanford Research Systems SR770 Chace Covington, James Morris, R. Seth Smith This experiment utilized a Stanford Research Systems SR770 instrument and a TeachSpin ‘Electronic Modules’ instrument box to study the down-conversion and demodulation of AM radio waves. In this experiment, local AM radio stations were located by finding their frequencies, and different methods of demodulation (envelope detection, heterodyne to ‘zero beat,’ and product detection) were used to observe effects such as motorboating, unwanted cyclic variation of output voltage that produces a sound similar to an idling motorboat engine. |
|
D05.00068: Ohm’s law and I-V characteristics with current and voltage sensors Ponn Maheswaranathan Ohm’s law is a fundamental law of electricity which describes how electrical circuits behave. It is introduced with electric circuits in introductory physics courses. In the laboratory it is verified and unknown constant resistances are determined by measuring the voltage across and the current through them. In the past, it is customary to use a voltmeter and an ammeter to measure the voltage and current with limited accuracy and eaze. Current-Voltage (I-V) characteristics of diodes are introduced as an extension but seldom in the laboratory due to its complexities in measuring small currents and voltages, simultaneously. Observing and studying the I-V characteristics is much easier and straightforward with currently available interfaces and current & voltage sensors in an introductory physics laboratory. We use PASCO’s 850 interface with its current and voltage sensors to observe the I-V characteristics of various circuit elements with ease and elegant results are obtained. The “Keep Mode” feature of the Capstone software is used to control the data. Data and curves are displayed instantly as the current and voltage are changed using a variable power supply. Current-Voltage characteristics of a resistor, an incandescent light bulb, and a silicon diode will be presented. |
|
D05.00069: Community-based Engaged Learning: An Application of Renewable Energy Technology Nicholas S Palmer, Hasitha Mahabaduge Traditional development methods like energy generation and transportation have been the main drivers of environmental degradation since the industrial revolution. Remediating these effects with global scale efforts can disregard local environment characteristics, requiring local development strategies to define the gestalt of global climate action. However, garnering grassroots support can be difficult. Reaching a communal understanding of base scientific mechanisms starts at a young age and is difficult to develop without hands-on experiences. Community-based engaged learning (C-bEL) programs provide a platform for exposing community members to interactive experiences while providing teaching opportunities for college students. We developed a stand-alone workshop for local schools comprised of hands-on, renewable energy demonstrations adhering to the C-bEL guidelines. With the variety of activities, demonstrations, and a foundational presentation, students interacted with these new concepts and worked with renewable energy technologies. Students showed an increased understanding with concepts such as renewable energy and efficiency. Further research is being conducted to quantify the understanding of students using pre/post tests. |
|
D05.00070: Enhancing the Ruby Phosphorescence Senior Lab: the Cr3+ 2E Lifetimes and 4T Absorption Studies. Zack Jones, Julia Hinds, Sophia Woznichak, William Dulaney, Christer R Akouala, Anthony G Calamai Many existing advanced laboratory experiences associated with the metastable 2E term of Cr3+ in ruby, which gives rise to the R-lines at 692.7 and 694.3 nm, focus on a room-temperature measurement of the radiative lifetime of the 2E term. In our local work developing a laboratory experience in atomic phosphorescence, we noted a lack of consistency in the literature for the lifetime of the Cr3+ 2E term. These projects typically use commercially available ruby spheres for which the manufacturer(s) only state about a 2% Cr3+ concentration. The uncertainty in Cr concentration represents one source of systematic error for this laboratory experience. We present our measured lifetime with corrections for systematic issues that make this project a more rewarding experience for students. Our result for the room-temperature radiative-lifetime for the 2E term is 3.3 ± 0.1 ms; which, unlike some more recent reports (e.g. [1]), compares favorably with that of Nelson and Sturge [2]. In order to address the uncertainty in sample Cr concentration, our laboratory has recently begun a detailed study of the Cr3+ 4T absorption using commonly available advanced-physics lab equipment. We also provide a status report on that aspect of our work to enhance this laboratory activity. |
|
D05.00071: Assessing the Efficiency of Night Interruption Light Therapy on the Growth of Short-Day Plants in Virginia. 1Department of Physics, Emory & Henry College, Emory, VA, 2Kelly Ridge Farms, Meadowview, VA. Anisha Dawadi The per plant production of Humulus Lupulus, commonly known as a hop plant, in the northwest of the United States far exceeds that of Virginia. Hops are short-day plants dependent on night length to reach maturity before flowering. Lower latitude regions have longer nights during the growing season which influences the flowering process. Night Interruption is the use of artificial light to mislead the plants, causing them to register night as day-time. This process targets two different forms of phytochrome photoreceptors: the active form (Pfr - phytochrome far-red) which controls flowering, leaf and chloroplast development; and the inactive form (Pr - phytochrome red). At night, only the Pr form is synthesized. When red light with peak wavelength of 657 nanometers is applied, Pr phytochromes convert to Pfr. As part of a larger project, we propose to study night interruption light therapy in hops and biological equivalents. This experiment will include field testing with delivery of red light over different time intervals throughout the night on hop plants. The goal is to compare the growth of hops under varying conditions to provide information on the most efficient application of night interruption in this region. |
|
D05.00072: Our Magnetic Moon Dany Waller, Dhananjay Ravat Lunar swirls are complex optical structures on the Moon with distinct albedo signatures. They occur in both mare and highland terrain, and are strongly correlated with crustal magnetic anomalies. Recent research has suggested the formation of lunar swirls is related to the shielding of solar wind from these magnetic anomalies, through a shift in certain electromagnetic wavelength peaks relative to the surrounding regolith. We have combined current models and methods to investigate how diffuse patterns could form, exploring the effect of field superposition from several weak, permanently magnetized crustal sources. We are working on a model of diffuse swirl formation using dipole and electric field modeling, with current emphasis on Reiner Gamma. |
|
D05.00073: Controlling probability distributions in a noise-driven dynamical system with correlated noise sources Niall Mullane, Stephen W Teitsworth, Jonathan Bennett The analysis of probability distributions in the phase space of a noise-driven dynamical system provides important insights into its variability and predictability. Here we analyze the probability density ellipse in the two dimensional phase space of a noise-driven electrical circuit that is composed of two identical RC circuits coupled together with a capacitor. The elliptical shape results from the two RC circuits having different input noise intensities. The voltages across the coupling capacitor are the phase space coordinates that we analyzed. Each RC circuit is driven by a variable linear combination of two independent noise sources.We find that with certain linear combinations the probability density ellipse will narrow, equalizing the voltages on either side of our coupling capacitor and thus removing a large portion of noise in the phase diagram of our system. We quantify the narrowing of the probability density ellipse using two methods: 1) We graph the aspect ratio of the ellipse for many different linear combinations and 2) We analyze the area enclosed within the most probable escape and relaxation path to a target point. Our method illustrates a way to reduce output noise in a system by simply adding a new noise source. |
|
D05.00074: Measuring the Granular Density of Modes in 3D Sydney Blue, Eli T Owens Sand covering the earth, snow on a mountainside, and even plastic balls in a ball pit are all considered granular materials. These athermal materials, while ubiquitous, behave in a unique manner. For instance, granular materials have the ability to behave like all three phases of matter; sand in a sandstorm behaves like a gas, whereas sand flowing in an hourglass behaves like a liquid, and packed sand on a beach behaves like a solid. The solid/liquid transition is known as the jamming transition. This study will experimentally measure the granular density of modes, which is analogous to the density of states in a thermal system. In order to measure the granular density of modes, we need to mimic the randomized motion of thermal particles. We accomplish this using a white noise acoustic wave to vibrate the particles of the granular material allowing us to measure the density of modes using methods from thermal physics. From our measurement of the granular density of modes, we are able to study the jamming transition in a 3D granular material; since, as the jamming transition is approached, there is an excess number of low frequency modes in the density of modes. |
|
D05.00075: Detecting a Small LED Signal in a Noisy Environment with a Lock-in Amplifier Thomas Dixon, Nicholas Tomlinson, R. Seth Smith A light emitting diode (LED) was placed at various distances away from a photodiode detector. |
|
D05.00076: Modular Multiwire Proportional Chambers: Design, Construction, Electronics, and Simulation Michael Z Reynolds, Jacob Barron, Emma Pearson, Shu Cui The Society of Physics Students (SPS) at Kennesaw State University is building a series of multi-wire proportional chambers as a tool to detect cosmic ray muons with the goal of doing muography on large structures. The chamber consists of two cathode plates that enclose an array of wires under high voltage and is filled with an ArCO2 mixture. High energy muons that pass through the chamber will trigger an electron avalanche that induces a current in the anode wires. In designing the chamber Paschen theory was considered to determine wire spacing and operating voltage. The avalanche formation region is where the electric field strength exceeds about 3 million volts per meter. The signal generated by the chamber is on the order of microvolts, so amplifier electronics are needed to boost the signal to a readable level. We are using AD8099 operational amplifiers for their high speed and low noise. Chamber construction is cheap and efficient, utilizing CAD programs to design custom circuit boards and 3D printed frames. Wires are tensioned and soldered by hand. Sealing the chamber will require an o-ring to be incorporated into the frame design. Simulations of the electric field were created using ComSol to visualize the avalanche region and electric field over the entire chamber. |
|
D05.00077: 3D Printing for Scientists and Engineers Andrew P Rhodes, Eli T Owens 3D printing is an often-misunderstood subject; the main reason being the large pay and skill floors that are thought to exist between the average person and a 3D printer. 3D printing Is thought to be a semi-exclusive resource accessible only to specialists in businesses and large educational institutions, however in actuality 3D printing is very easy and beneficial to get in to. 3D printers can be used in several applications including prototyping, custom parts for an experimental apparatus, and demonstration aids. For example, we used our printer to prototype a low-cost, functional, 3D printed prosthetic hand. For all of these applications 3D printers provide a low-cost solution with rapid turnaround time. This presentation will give a brief overview of the fundamentals of 3D printing and how anyone can take an inexpensive 3D printer and modify it to produce professional quality prints. The goal of this presentation is to give an understanding of the intricacies of 3D printing and dispel concerns about elements of 3D printing such as how it works, price points, filament types and uses, and applications, as well as discuss how to turn an idea into a tangible 3D model from scratch. |
|
D05.00078: Thermoelectric Modeling and Effective Analysis of the Peltier Module Using Numerical and Computational Method Sawoong Min, Richard Kyung Thermoelectric cooling uses the Peltier effect to generate a heat flux caused by temperature difference between two ceramic substrates which provide the platform for pellets.In this paper, variables such as semiconductor dimensions, material properties and initial temperatures are used as input data to find heat flux, temperature distributions, and electric properties in the thermoelectric cooling system. Computer simulations and numerical analysis are employed to find out the effect of the various factors on the electric field distribution in the Peltier system. Also, a calculator program which calculates the efficiency of the thermoelectric Peltier module that can be used in cooling systems. As a result, electric and thermodynamic properties such as the energy flux density and temperature distribution along the semiconductor pellets as functions of time are found. The objective of this study is to understand the mechanism of the thermoelectric coolers and to formulate equations of the electric and heat flux through P-type and N-type semiconductor pellets in the thermoelectric modules. Heat transfer by conduction is applied to the partitioned and non-partitioned modules by introducing mathematical and thermodynamic modeling. |
|
D05.00079: Designing a Bluetooth Communication Network for High-Altitude Balloons Zachary Hill To comply with FAA regulations, High-Altitude Balloons sometimes need to be split into multiple payloads. When running an experiment that requires input from several different devices, this can become troublesome. To remedy this, we have developed a Bluetooth communication system on the Raspberry Pi platform to allow different payloads on the same flight to share their data with a master Raspberry Pi. Source code, parts list, and schematics will be presented as well as results from a test flight running an experiment across different payloads. |
|
D05.00080: The Effects of a Helmholtz Coil on a Magnetic Dipole Rachael Kerr, R. Seth Smith, Charles Griggs The goal of this project was to study the behavior of a magnetic dipole (due to a permanent magnet) in the presence of an external magnetic field and an external magnetic field gradient. A Helmholtz Coil pair was used produce the external magnetic field and the external magnetic field gradient. Three situations were investigated: (1) currents flowing in the same direction in the coils, (2) currents flowing in opposite directions in the coils, and (3) current flowing in only one coil. In addition, the magnetic moment of the magnetic dipole was measured. The experimental setup and results will be described |
|
D05.00081: Gravimetric Study For Detecting Subsurface Density Structures Beneath Volcanoes Rachel Willis, Katherine Cosburn, Mousumi Roy, Brady Spears We created an accurate model of subsurface density structure beneath a volcano, which is crucial for observing time dependent processes such as magma flow and transport. Accuracy in this research has been restricted by the underdetermined and non-unique nature of surface gravity measurements. In an effort to increase the accuracy of surface gravity measurements, we performed a redundant absolute gravity survey to improve the calibration our gravimeter. We then performed corrections on gravity data taken at station locations in our target region, Redondo Mountain. In these corrections we utilized Tsoft Earth Tide data, regional LIDAR data, and the NAD83 reference ellipsoid to improve precision. We created a discretization of the target region from the LIDAR data. After we use the corrected gravity measurements to optimize the discretization this research will be used to calculate the gravity effect, represent the varying density estimations of the mountain, and track time dependent changes such as magma motion. |
|
D05.00082: Using a Hybrid Machine Learning Approach for Test Cost Optimization in Scan Chain Testing Luke Duan, Arjun Chaudhuri Continual technological advances have led to more complex microchip designs, which in turn, have led to the need for more complex fault testing. As a result, higher testing costs (increased test time and data volume) have emerged as well. This work examines one application of hybrid machine learning (ML) to optimize the costs of scan chain testing. We used fifty-one benchmark circuits to train the models and analyze their performances. Results produced with these circuits may not have any industrial significance, but the methods described may be useful for future work. We generated training data through MentorGraphics’s DFTAdvisor and FastScan and compiled them into files readable by the ML framework Weka. We then trained three individual ML models and evaluated their accuracies by comparing them against a test set. Finally, we created a hybrid model by combining these individual models, with different weights allotted to each model based on individual accuracy. Initial findings showed that there was a slight increase in performance by using a hybrid approach. We concluded that this method can be improved by using larger training sets and better heuristic algorithms when assigning weights. This research could be useful for the microchip industry by reducing time-to-market. |
|
D05.00083: Error mitigation for generative models deployed on noisy intermediate-scale quantum (NISQ) devices Holly G Stemp, Kathleen E Hamilton, Eugene F Dumitrescu, Raphael C Pooser Generative modeling is a method for learning arbitrary distributions. A promising generative model scheme involves the use of a quantum circuit Born machine (QCBM) 1. This model involves a classical optimizer to perform gradient-based training of QCBM, which utilizes the hardware efficient ansatz to encode the probability distribution in the QCBM’s quantum state. In this work we model the 2x2 BAS dataset on IBM’s superconducting quantum computer, accessed via cloud interface. We map the generative model ansatz circuit directly to the IBM hardware. After training the circuits on a noiseless simulator for 100 steps of ADAM, the Kullback Leiber (KL) divergence and a metric known as the qBAS score, introduced by Benedetti et al.2, were used to determine how well the QCBM modeled the distribution. Using the results of these metrics, and assuming a uniform error rate for two qubit gates, we used the error extrapolation method of Li and Benjamin3 to estimate the distribution encoding ability of error-resilient QCBM schemes. [1] Liu, J. et al. (2018) preprint arXiv:1804.04168v1 [2] Benedetti, M. et al. (2014). arXiv preprint arXiv:1801.07686 [3] Li, Y. and Benjamin, S. (2017). Physical Review X, 7(2) |
|
D05.00084: Ultrasonic Acoustic Probing Based on Gaussian Beam Analysis Emily J LaPrime, Kyohei Miyasaka, David Feldbaum Acoustic contrast describes the relationship between a material’s density and the speed of sound through it. Analyzing the difference in phase and amplitude, information about the differing acoustic contrast between materials can be quantified. Prior methods used a scanning acoustic microscope (SAM) which allowed for phase shifts to be identified by reflections but could not actually quantify phase shifts besides 0° or 180°. The new method uses a continuous signal and Gaussian beam analysis to identify more precisely the change in phase and amplitude to analyze the transmitted signal. By keeping the transmitter stationary and probing the receiver, we examine how the phase and amplitude change as the distance between transducers varies (transverse profiles). This approach is believed to have a potential biological application. Because cells are made mostly of water, the acoustic contrast between healthy cells and cancerous cells is difficult to identify using current ultrasonic methods. This testing method could potentially gather more precise data with respect to the slightly differing contrasts between the cells and help better identify the presence and location of unhealthy cells. |
|
D05.00085: Glass formation in Bi-doped Ga-Ge-Se-Te system Cord R Beck Bismuth is a unique dopant in chalcogenide glasses for novel optical applications. However, its solubility in chalcogenide matrixes is relatively low. This work is focused on glass formation within Bi-modified Ga-(GeSe4)-(GeTe4) system, which is considered as perspective chalcogenide matrix to host Bi functionality. The materials were synthesized using standard melt-quenching technique. According to the performed IR spectroscopy, differential scanning calorimetry and X-ray diffraction analysis, the samples with Bi content up to 5 at.% were obtained in a vitreous state, while those with greater amount of Bi (up to 10 at.%) crystallized to a different degree. By varying diameter of the ampoule, melting temperature and quenching rate, the glass forming region can be extended, and the quality of the glass can be further improved. |
|
D05.00086: Development of a Night Interruption Light Therapy Delivery Apparatus for Field Treatment of Hop Plants Carlos E Andrade, Anisha Dawadi, Madison L Jackson, Jacob T Pighini, Charles W Fay, Danielle Morel The short-day plant Humulus Lupulus, or hops, relies on night length to control growth. During relatively long nights, as is the case in Virginia in summer, hop plants do not grow as tall as they do in the northwestern US. Growth triggers in hop plants are partially controlled by photoreceptors called phytochromes, which respond to light. Of particular interest are those phytochromes sensitive to the red and far-red wavelengths of light. When exposed to red light, the inactive form of phytochrome (Pr - red) is converted to the active form (Pfr - far-red), the latter regulating growth processes. Whereas far-red light triggers Pfr conversion back to Pr. In order to counter the effect of longer nights on phytochromes, three types of LED-based, Arduino-controlled, light delivery structures are under development. With the use of spectrometers, measurements of intensity as a function of wavelength give a profile of the illumination delivered by each array. The most efficient type of LED light for hop plants can be determined by comparing spectral data with the desired peak wavelength of red light for conversion of Pr to Pfr. Further measurements can verify calculations of the effective intensity of the light at various distances from the source, suggesting treatment regimens. |
|
D05.00087: NEXT: New Neutron Detector Design Cole Howell, Mustafa M Rajabali, Robert Grzywacz, Joe Heideman, David Perez-Loureiro, Joseph Owens In recent years, neutron detection has become more important in studying nuclear structure and processes. In beta delayed neutron emission, neutron energies provide important information about the parent nucleus and the decay process. Neutron energies are calculated by measuring neutron time of flight (ToF) between two detectors. The energy resolution is therefore dependent upon the ToF resolution and the position resolution within the detector. The Neutron dEtector with Tracking (NEXT) is a segmented neutron detector based on pulse shape discriminating (PSD) plastic coupled to segmented photomultipliers. The NEXT design will improve energy resolution by increasing particle localization and ToF resolution. Current research focuses on determining PSD and timing capabilities of different detector designs. Results of timing and PSD dependence on scintillator type and geometry will be shown. |
|
D05.00088: Albedo Protons and Neutrons Emitted from Hydrated Layers of Lunar Regolith Fahad Zaman, Wouter deWet, Lawrence Townsend In 2009, NASA launched the Lunar Reconnaissance Orbiter mission to Earth's moon carrying several instruments including the Cosmic Ray Telescope for the Effects of Radiation (CRaTER). CRaTER measures Linear Energy Transfer spectra of charged particles in the lunar radiation environment, which consists of incident galactic cosmic rays, incident solar energetic particles, and albedo particles from the lunar surface. Measurements of albedo protons show an increase in proton fluxes when observing the lunar limb rather than the nadir direction. The albedo proton flux also exhibits diurnal variations, and several other anomalies in proton yields. To better understand these unexpected phenomena, the angular yields of the albedo neutrons and protons emitted from different hydrogenated layer thicknesses, due to incident galactic cosmic rays, are modeled using the MCNP Monte Carlo transport code. Establishing the presence of a hydrogen layer might also aid in developing maps of the lunar surface regions with increased water content. |
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