Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 60, Number 11
Friday–Saturday, October 16–17, 2015; Tempe, Arizona
Session F1: Poster Session (4:30 pm - 6:30 pm) |
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Chair: Gary Adams, Arizona State University Room: MU221 |
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F1.00001: Spatially Resolved Spectroscopy of Semiconductor Nanostructure Disorder Matthew Day, Riley Sechrist, Rohan Singh, Chris Smallwood, Steven Cundiff Manufacturing processes unintentionally introduce inhomogeneities, typically on the order of a few monolayers, in the width of semiconductor quantum wells. These fluctuations, known as disorder, modulate optical transition energies of excitons confined within the quantum well layer and are the main cause of inhomogeneous spectral broadening. It is therefore imperative to quantify this disorder so its effect on exciton confinement potentials can be accounted for in ultrafast spectroscopic studies on semiconductor quantum wells. We present the use of micro-photoluminescence spectroscopy to accomplish this goal, and preliminary reults of our study. [Preview Abstract] |
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F1.00002: Efficient Coupling of a Super Continuum Laser to a Double Monochromator Samantha Sword-Fehlberg, Rachel Cunio Hyperspectral imagers are electro-optical sensors capable of producing a spectral characterization of an image. Careful calibration of these instruments is critical to their performance, with an optimal calibration process having low uncertainty. The objective of this project is to create an optical mount that will make use of two electrically tunable lenses to efficiently couple a white light laser to a double monochromator thereby matching f/{\#}'s over the entire range of wavelengths (400-2500 nm). [Preview Abstract] |
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F1.00003: Diode-Pumped Dye Laser Using a Tapered Optical Fiber Brian Patterson, James Stofel, Elliot Myers, Randy Knize We describe efforts to construct a simple dye laser based on a single-mode optical fiber. Light from a diode-pumped solid state laser ($\lambda \quad =$ 532 nm) is launched into the fiber. The fiber is tapered to a diameter of approximately 1 \textmu m and placed in Rhodamine 6G laser dye. The pump light interacts with the gain medium through the evanescent field outside the fiber causing stimulated emission, which couples back into the fiber. Mirrors on each end of the fiber provide the necessary feedback for lasing, and a grating is used to narrow the spectral output. We plan to characterize the lasing threshold and output spectrum of the laser. This has been a good project for undergraduate students to learn about lasers and optics. [Preview Abstract] |
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F1.00004: Comparison of the Dielectric Function of SrTiO$_{3}$ on SrTiO$_{3}$, Si and Ge Substrates Cesar Rodriguez, Nuwanjula Samarasingha, Jaime Moya, Stefan Zollner, Patrick Ponath, Alex Demkov A comprehensive study of the optical properties of SrTiO3 (STO) on three different substrates has been conducted using variable angle spectroscopic ellipsometry. STO is a perovskite and has drawn much attention due to its wide range of applications in microelectronics. The STO thin films were grown by molecular beam epitaxy on top of Ge, Si and STO substrates. Using spectroscopic ellipsometry, we studied the films using a broad energy range of 0.76 - 6.6 eV, and using a range of incident angles from 65-75 degrees. This allowed us to collect the spectroscopic angles $\Psi $ and $\Delta $. We used a parametric oscillator model to fit the data of the STO films and added a Lorentzian term to fit the IR region. This allowed us to determine the thickness of each film from which we then extracted the optical constants. From these results we compared the behavior of the dielectric function of STO on a chosen substrate to that of bulk STO. [Preview Abstract] |
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F1.00005: What is solvation: How many waters does it take to dissociate an acid? Joe Youssef, Scott Sayres Strong acids dissociate completely in liquid water. However, the situation is very different when only a few water molecules are present, such as in gas phase or atmospheric conditions. I will present an update on our progress in exploring how electron dynamics in small clusters depend on the addition or subtraction of a single water molecule. Water molecules are introduced into a vacuum chamber through a home-built supersonic expansion nozzle and passed through a skimmer to prepare a molecular beam. This cluster distribution enters into the extraction region of our newly constructed Wiley-McLaren type time-of-flight mass spectrometer where it encounters an ultrafast laser pulse that serves as the ionization source for characterization. This undergraduate research project explores how the water cluster distribution changes with the addition of various acids [Preview Abstract] |
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F1.00006: Tornado Model C Bruce Johnson A model is presented for how the electrical energy stored in a thundercloud can initiate and sustain high wind velocities in the cloud-to-ground region, and how the resulting intense updrafts can result in a tornado. It is known that tornados 1-are accompanied by intense atmospheric electrical activity, 2-originate in thunderclouds as microtornados that descend toward the earth, 3-become dangerous to life and property when they make contact with the ground, and 4-they dissipate when the atmospheric electrical activity in the thundercloud weakens. The high electric field strength between the thundercloud-and-ground gives rise to high atmospheric ion drift velocities. These ions speed toward the bottom of the thundercloud, and in the process air molecules are also dragged along at high speed. The resulting electronic discharge channel that connects the cloud to the ground carries the ion current that tends to discharge the cloud. The tornado continues to exist as long as the electrical energy in the cloud-to-ground system is sufficient to maintain the electrical discharge channel within the tornado [Preview Abstract] |
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F1.00007: Automating Measurement of Continuing Current in Lightning Flashes Jose Martinez, Richard Sonnenfeld Continuing current (CC) is defined as an ongoing current (duration: 0.01 s – 0.5 s) in the 100 Ampere range following a lightning return stroke. Lightning flashes that also have CC are known for initiating forest fires. Continuing current detection is automated by combining NLDN (National Lightning Detection Network) and LEFA (Langmuir Electric Field Array) datasets. The automating algorithm counts the number of flashes in a single minute of data and the number of return strokes of an individual lightning flash; records the time and location of each return stroke; and uses the time derivatives of the Efield between return strokes to recognize whether a continuing current signal exists within the interval. When detected, the duration and magnitude of continuing current signal is measured. A relationship between the presence of CC, stroke order, interstroke interval and which of the multiple channels to ground is active is sought. The dataset used is a few hundred flashes within 10 km of Langmuir Lab, New Mexico measured during the summer 2013 monsoon season. [Preview Abstract] |
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F1.00008: Spectral Measurements of Geosynchronous Satellites during Glint Season Anita Dunsmore, Joshua Key, Francis Chun, Roger Tippets During certain times of the year, stable geosynchronous (GEO) satellites are known to glint or exhibit a very bright specular reflection, which is easily observed through broadband photometric filters. The glints are typically brighter in the Johnson red filter compared to the Johnson blue filter.~ In previous years, USAFA cadets have developed and refined techniques to take, calibrate and process satellite spectral data using a diffraction grating on the USAFA 16-inch, f/8.2 telescope (i.e. slitless spectroscopy). We present research from an Air Force Academy senior physics capstone project on observing glints off of GEO satellites using slitless spectroscopy. We discuss the calibration of the measurements using solar analog stars, as well as results of the spectra of a glinting GEO satellite. [Preview Abstract] |
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F1.00009: Falcon Solid-State Energetic Electron Detector (FalconSEED) Robert Olesen, Ryan Cress, Geoff McHarg Energetic charged particles create a hazardous environment surrounding satellites in orbit. Shielding methods must be implemented to protect electronics in order to prevent satellite anomalies caused by spacecraft charging. A proper understanding of the space environment is required to forecast these events and improve simulation. Using the computer software MCNP, we have developed a preliminary model of an electron detector called the Falcon Solid-State Energetic Electron Detector (FalconSEED).~ The detector is sensitive to electrons from 10-100 keV, which complements sensors already being considered for implementation on Air Force satellites. FalconSEED utilizes a solid-state detector and implements a geometry of tungsten baffles to reduce the uncertainty in angular distribution of the measurements and prevent backscattering. Initial simulations of the detector are being used to provide assurance of the design specifications for a future prototype of the detector. [Preview Abstract] |
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F1.00010: Prediction of Dissolved Oxygen and Water Quality Modeling Using Computational and Mathematical Simulation Baekjoon Kang, Youn Joong Kim, Richard Kyung For most aquatic life to continue its existence, they require some minimum concentration of dissolved oxygen. Therefore, in order to protect aquatic life, there must be a minimum concentration of dissolved oxygen. In other words, the prediction of the critical saturation deficit is crucial in preventing extinction of aquatic life. In analyzing bio-degradation, Streeter-Phelps Equation of biodegradable material, which is a one-dimensional model of oxygen concentrations in a river, is crucial to understand. The equation assumes waste or wastewater to enter at time, t $=$ 0. After the biodegradable material enters the aquatic environment, the equation predicts the change in dissolved oxygen over a given amount of time. In this paper, DO and BOD were calculated for various water bodies including ponds, sluggish streams, and swift streams. For all the water bodies, this paper shows that DO was depleted faster than it was replenished, and the DO of the stream continued to drop until the rate of deoxygenation equals the rate of re-aearation. Also, depending on the range of reaeration constants, the DO and BOD of the bodies converge to equilibrium in different ways. The DO increases as the reaeration process occurs faster than the deoxygenation process. ~ [Preview Abstract] |
(Author Not Attending)
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F1.00011: Magnetic nanodrug delivery through the mucus layer of air-liquid interface cultured primary normal human tracheobronchial epithelial cells. Kathrin Spendier, Evangelos Economou, Simon Marinelli, Hong Chu, Zbigniew Celinski In several prominent human lung diseases, such as asthma, patients produce a thickened mucosal fluid, irritating and inflaming the underlying tissue that progresses the condition. Many current drug therapies prove ineffective due to the inability to penetrate this thickened mucosal layer. In this study, superparamagnetic Fe$_{\mathrm{3}}$O$_{\mathrm{4}}$ and highly anisotropic BaFe$_{\mathrm{12}}$O$_{\mathrm{19}}$ nanoparticles were surface-engineered for the purpose of transporting anti-mucin medicine through the mucus layer of air-liquid interface cultured primary normal human tracheobronchial epithelial (NHTE) cells via magnetic field gradient. Using wet planetary ball milling, surfactant-coated BaFe$_{\mathrm{12}}$O$_{\mathrm{19}}$ nanoparticles (BaNPs) of 60 nm in diameter were prepared in water. BaNPs and conventional 30 nm surfactant-coated Fe$_{\mathrm{3}}$O$_{\mathrm{4}}$ nanoparticles (FeNPs) were then encased in a polymer (PLGA) loaded with dexamethasone (Dex) and tagged for imaging. Both PLGA-Dex coated BaNPs and FeNPs were added on top of an approximately 100 micrometer thick mucus layer of air-liquid interface cultured NHTE cells. Within 30 minutes, PLGA-Dex coated FeNPs and BaNPs were pulled successfully through the mucus layer by a permanent neodymium magnet for the first time. The penetration time of the nanomedicine was monitored using confocal microscopy. [Preview Abstract] |
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F1.00012: Molecular origins of Protein-Protein Interactions: Dynamic Flexibility of Interface Tushar Modi, Banu Ozkan Timely orchestrated protein-protein interactions underlie cellular functions. Thus, understanding molecular origins of protein interactions is crucial, particularly estimating changes in binding free energies upon mutations. Current methods rely on 3-D structure of the protein complexes, ignoring conformational dynamics. Here using the SKEMPI data set, containing thermodynamic and kinetic parameters for protein-protein interactions forming complexes and mutants, we develop a novel approach that measures the changes in conformational dynamics at protein interfaces using the dynamic flexibility index (DFI). DFI quantifies flexibility of each position by computing its fluctuation response profile to perturbations exerted on chain, encompassing conformational dynamics. We perform molecular dynamics simulations of wild type and mutant for 21 cases, and then compute change in flexibility of the interface upon mutations using DFI \quad analysis. Strikingly, the total change in DFI \quad shows a strong correlation with change in binding free energies with a correlation coefficient of R$=$-0.72, suggesting that mutations leading to an increase in flexibility result in decrease in binding energies. Overall, this new approach gives insight into functional impact of mutations through chain flexibility. [Preview Abstract] |
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F1.00013: Towards an automated pipeline for solvation free energy calculations Ian Kenney, Oliver Beckstein, Bogdan Iorga Solvation free energies are used to determine solvent effects on molecules of interest, such as the $\log P_{ow}$ of drug-like molecules. We developed MDPOW, an automated pipeline to compute solvation free energies with molecular dynamics simulations using Python and Gromacs. In order to optimize the simulation protocol, we examined the effects of varying parameters on these free energy calculations. We employed benzene as a simple test case with an known experimental hydration free energy. We varied the parameters of the MD free energy perturbation (FEP) calculations, such as temperature and pressure coupling algorithms, sampling time of the FEP windows, dispersion correction, initial conditions. We also employed two different schemes to calculate the free energy, thermodynamic integration (TI) and the Bennett acceptance ratio (BAR) method. The Coulomb component of the hydration free energy was generally insensitive to variations in parameters. The Lennard-Jones component, however, can vary by many kJ/mol and is sensitive to the temperature coupling algorithm and inconsistent initial conditions when simulations are performed in the NVT ensemble. [Preview Abstract] |
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F1.00014: A Frequency Domain Sampling of k-Space in Images Using Physical and Computational Simulations Catherine Seung-Woo Kim, Angel Jung, Sol-ji Choi An ideal low pass filter (LPF) frequency would be able to increase the resolution of the MRI image as well as decrease the Ringing Artifact.~Through the use of physical and computational methods in analyzing human chest MRI images, Inverse Fourier Transformation (IFT) transforms every spatial frequency points to its corresponding points in the final image. Such transformation process, from a physical spatial frequency to image domain, requires an immense amount of time and computational operations in the simulation. This research uses selective k-space to find a new mechanism of an image formation.~Originally, the box filter, N/2-13N/40:N/2$+$13N/40$=$1, is used during the Fourier Transformations. Also, the Gaussian filter, y$=$ exp(-r$^{2}$/p$^{2})$, where r$=$h-L/2, h$=$[0,M], L$=$2*13*N/40, and the size of frequency matrix (M, N) $=$ (360,550) is tested. The variable p, chosen from 20 to 120, is tested in creating the image of an object. This research strives to develop a better physical and computational algorithm that would not only enhance the quality of the final image but also decrease the amount of time taken to produce the image. [Preview Abstract] |
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F1.00015: Biophysical Image Processing of the Mandibular and Maxillary Teeth Seung Hyun Han, Albert S Kwon, Eun Kyo Jung In dentistry, early detections can yield significant outcomes. For instance, early reduction of fractures lead to improved results. Prior to the surgery, CT scanning or MRI inspections can successfully identify the intact tooth or mandibular bone. This research, through the observation of 11 maxillary and mandibular teeth along with~3~molars~and 2 premolars, examines the biophysical and~diagnostic ability of magnetic resonance imaging for mandibular and maxillary teeth.~When working with dental imaging, one must acknowledge the use of imaging passing filter to allow an increased resolution and decreased Ringing Artifact. By using different filters on the full~k-space (frequency domain), this paper shows how the efficient filter~can be applied to the original frequency matrix to get~the better~MRI image of the affected dental region. Based on these findings, we establish the practical MRI diagnostic criteria for the treatment and clinical outcome. This research shows~the improved~biomedical~algorithms that not only enhance the quality of the final dental image, but also reduce the time it takes to produce a~dental~image. ~ [Preview Abstract] |
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F1.00016: Design of New Functions Used in the Biomedical and Computational Analysis on Bioimages Angel Jung, Da In Kim, Gun Ha Seo Magnetic Resonance Imaging is a common medical technique that produces an image of the subject's anatomy through radio waves, magnetism and computers. The main purpose of this research is to develop a better algorithm that would not only decrease image production time but also enhance the quality of the final MRI image by minimizing ringing artifact. In Part A, a nonconventional approach is used in MRI image analysis. The original MRI image domain is transformed into k-space using FT, a crucial step to determine the ideal filter. In order to determine such a filter, various filter functions are tested as low pass filters through MATLAB. Some low pass filters significantly reduce the frequency domain data, but at the cost of reduced image quality. However, the optimal low pass filter would reduce frequency data (thus, decreasing production time) without disrupting the resolution of the image. Taking such factors into account, an efficient new filter is proposed and tested with raw data. Part B discusses image reconstruction using raw frequency data and the proposed filters. The proposed filters are applied to multiple k-spaces of the image, which can then be combined using a mathematical function to produce a final image. ~ [Preview Abstract] |
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F1.00017: Iterative phasing of 2D crystal XFEL data Yun Zhao, Matthias Frank, John Spence The phase problem for Bragg diffraction from two-dimensional (2D) crystalline monolayers in transmission may be solved by imposing a compact support which sets the density to zero outside the monolayer. By iterating between the measured structure factor magnitudes along reciprocal space rods (starting with random phases) and a density of the correct sign, the complex scattered amplitudes may be found (J. Struct Biol 144, 209 (2003)). However this one-dimensional support function fails to link the rod phases correctly unless a low-resolution real-space map is also available. Charge flipping algorithm can be used to solve structure from intensities along while it atomic resolution data are required. Here we wish to determine the minimum resolution required for successful three-dimensional (3D) structure retrieval from a 2D crystal XFEL diffraction dataset, when combining the hybrid input-output(HIO) and charge flipping algorithm. This method provides us an alternative way to phase 2D crystal dataset, with less dependence on the high quality model or high resolution data. [Preview Abstract] |
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F1.00018: Data collection strategies for time-resolved X-ray free electron laser diffraction, and 2-color methods. Chufeng Li, Kevin Schmidt, John Spence We compare three schemes for time-resolved X-ray diffraction from protein nanocrystals using an X-ray free-electron laser. We find expressions for errors in structure factor measurement using Monte Carlo pump-probe method of data analysis with a liquid jet, the fixed sample pump-probe (goniometer) method, and a proposed two-color method. Here, an optical pump pulse arrives between X-ray pulses of slightly different energies which hit the same nanocrystal, using a weak first X-ray pulse which does not damage the sample. (Radiation damage is outrun in the other cases.) This two-color method, in which separated Bragg spots are impressed on the same detector readout, eliminates stochastic fluctuations in crystal size, shape, and orientation and is found to require two orders of magnitude fewer diffraction patterns than the currently used Monte Carlo liquid jet method, for 1{\%} accuracy. Detailed simulations provided for cathepsin B and IC3 crystals. While the error is independent of the number of shots for the dose-limited goniometer method, it falls off inversely as the square root of the number of shots for the two-color and Monte Carlo methods, with a much smaller pre-factor for the two-color mode, when the first shot is below the damage threshold. [Preview Abstract] |
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F1.00019: Label-free Silicon nanowire field effect transistor for impedance-based sensing of molecules Yuan Wang, Quan Qing Impedance biosensors are promising electrical biosensors due to low cost, ease of miniaturization and label-free operation. Recent investigations on impedance measurement yield a wealth of information about different molecular motion and relaxation process, utilizing a wide frequency range from 10uHz to 1THz, which typically measure the impedance between two large chemically modified electrodes as target molecules bind to the surface. Our question is: can we scale this method down to single molecule level by matching the size of the whole device with that of the target molecules, which falls in the 10-100 nm length scale, and integrating the amplifier directly within such nano-electrodes? Here we will show our prototype devices based on silicon nanowire field-effect transistors (SiNW FETs) with a paired-gate structure. We will discuss the basic characteristics of these devices and demonstrate proof-of-concept results of pH sensing with high-frequency gate modulation. Our results will be further developed to a new platform for the enrichment and detection of low-copy biomolecules in physiological environments. [Preview Abstract] |
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F1.00020: Sub-10 nm fluidic system with self-aligned nanogap electrodes for biomolecule characterization Joshua Sadar, Quan Qing Nanopore sensors, an emerging third-generation DNA sequencing technique with rapid speed, single-base sensitivity and long read lengths, exemplify a new strategy in biomolecule characterization. In such designs, the dimension of the sensor matches precisely with a single target molecule, so that the presence and/or motion of the molecule inside the sensor can generate time-dependent electrical read-out signals containing significant local structural information. The capability of single-molecule level and label-free detection of sequence of DNA and protein molecules promise a new paradigm in both fundamental studies and biomedical applications. However, existing techniques face great challenges such as the scalability and reproducibility of fabrication, translocation control, and read-out signal specificity. Here we propose a new framework of preparing a sub-10 nm fluidic system with the additional integration of a pair of embedded nanogap electrodes in a self-aligned manner. We will introduce our impedance-based feedback control system for the electrochemical deposition of metal on pre-defined nanoscale electrodes within a confined space to construct sub-10 nm nanopores with gate electrodes. Our design can be developed into a promising platform for the scalable preparation of single-molecule characterization devices with active translocation control and additional readout mechanisms, including recognition tunneling signals and surface enhanced Raman spectrum. [Preview Abstract] |
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F1.00021: Magnetic Field Optimization of an Augmented Rail Gun Matthew Crader, Andy Dills, Gabriel Font Linear magnetic motors or rail guns are currently under study for high velocity projectile acceleration and lower velocity orbital launch applications. These systems frequently encounter problems with rail damage from the large currents required to accelerate the armature. An alternative which may be able to lower the required currents is to utilize magnetic augmentation. Multiple rail pairs are used to increase the magnetic field and diminish the current to less damaging levels. One or more pairs of rails are used to impart force to the armature while auxiliary rails are used to augment the magnetic field and increase the force. This study details an undergraduate research project to experimentally and theoretically determine the optimal combination of augmenting and accelerating rails. [Preview Abstract] |
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F1.00022: A Study on the Optimization of~Wheelchair~Geometry Using Mathematical and Mechanical Analysis Joo Hyun Kim, Andy Kim, Richard Kyung Although wheelchairs in the twenty-first century are lighter and easier to use than those made in earlier years, there are over 40,000 wheelchair related accidents in the United States each year. Tipping and falling from wheelchairs make up approximately seventy-five percent of the total wheelchair related injuries.~ While the technology of these wheelchairs include anti-tipping and automatic brakes, injuries often occur when the user of the wheelchair leans, which decreases the~mechanical~static stability in the direction of the lean, and increases the stability of the opposite direction. This study examines the~mathematical and physical~relationship between the body position (center of gravity)~and the~dimensions (geometry) of~wheelchair~to assess the~stability~by using the force equilibrium equations and moment equilibrium equations. The study provides mathematical explanations by calculating the force required to climb on increasing curb heights and varied radii of wheels. To test for the~optimized geometry and~stability of the wheelchair, we loaded varying weights and placed them on a tilted landscape. We used commercial post processing tools to display the static forward, rear, and lateral stability on tilted platforms. ~ [Preview Abstract] |
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F1.00023: In situ Observation of Ag Nanoparticles Catalyzed Oxidation of Carbon Nanotubes in an Aberration-corrected Environmental TEM Datong Yuchi, Yonghai Yue, Jingyue Liu The emission of soot or particulate matter formed during combustion of carbonaceous fuels is the major source of air pollution. Catalytic oxidation of soot in the exhaust gas is critical to reducing the negative environmental impact of power sources. The fundamental understanding of metal nanoparticle catalyzed oxidation processes of carbon materials is of interest. We report here the \textit{in situ} investigation of Ag nanoparticle catalyzed oxidation of multi-wall carbon nanotubes (MW-CNTs) inside an aberration-corrected environmental TEM with the goal of probing the nature of the active sites, the catalytic processes and the atomic scale structural evolutions of the Ag nanoparticles and the MW-CNTs. It was found that the Ag nanoparticles initiated the oxidation of MW-CNTs at a temperature of about 250 \textdegree C while without the use of Ag nanoparticle the MW-CNTs did not oxidize until well above 500 \textdegree C. Atomic scale information on the Ag nanoparticle catalyzed oxidation processes of MW-CNTs has been obtained and a model for the catalytic oxidation process was proposed. [Preview Abstract] |
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F1.00024: \begin{center} Predictive Formula for Electron Range over a Large Span of Energies \end{center} Anne Starley, Gergory Wilson, John Dennison, Lisa Phillipps A model has been developed to predict the approximate penetration depth into diverse classes of materials for a broad range of energetic incident electrons (\textless 10 eV to \textgreater 10 MeV, with better than 20{\%} accuracy). The penetration depth---or range---of a material describes the maximum distance electrons can travel through a material, before losing all of its incident kinetic energy. This model leads to a predictive formula that estimates the penetration depth for materials without the need for supporting data, but rather using only basic material properties and a single fitting parameter ($N_{v}$, described as the effective number of valence electrons). $N_{v}$ was first empirically calculated for 247 materials which have tabulated range and inelastic mean free path data in the NIST ESTAR and IMFP databases. Correlations of $N_{v}$ with key material constants (atomic number, atomic weight, density, and band gap) were established for this set of materials. These correlations allow prediction of the range for additional materials which have no supporting data. Estimates for both simple compounds ($e.g.$, BnN and AlN) and complex biological materials ($e.g.,$ brain tissue and cortical bone tissue) are presented, along with tests of the validity and accuracy of the predictive formula. These calculations are of great value for studies involving high electron bombardment, such as electron spectroscopy, spacecraft charging or electron beam therapy. [Preview Abstract] |
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F1.00025: Spatial resolution in vibrational-loss electron energy-loss spectroscopy Christian Dwyer Arizona State University is home to the first transmission electron microscope in the world that can perform vibrational-loss spectroscopy. This new experimental capability, whereby we distinguish those transmitted electrons that have imparted some of their energy to excite the atomic vibrational modes of the specimen, has sparked significant interest in the underlying scattering physics. In particular, the question of whether or not it is possible to perform vibrational spectroscopy at, or near, atomic spatial resolution is the subject of ongoing debate. Such a capacity would offer substantial advantages in several technologically-important fields, such as catalysis and nanostructured device materials. The experimental data obtained thus far indicates that the vibrational-loss signals contain a significant degree of so-called "inelastic delocalization", which would imply that high spatial resolution is not achievable. Here, we present part of our ongoing theoretical investigations which show that, despite the presence of delocalization, high spatial resolution may be achieved in some circumstances. The relevance for advanced materials characterization and the ongoing experimental efforts at ASU will be discussed. [Preview Abstract] |
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F1.00026: Invisible Sorites Paradox Florentin Smarandache There is not a clear frontier between visible matter and invisible matter. An invisible particle does not form a visible object, nor do two invisible particles, three invisible particles, etc. However, at some point, the collection of invisible particles becomes large enough to form a visible object, but there is apparently no definite point where this occurs. A similar paradox is developed in an opposite direction. It is always possible to remove a particle from an object in such a way that what is left is still a visible object. However, repeating and repeating this process, at some point, the visible object is decomposed so that the left part becomes invisible, but there is no definite point where this occurs. [Preview Abstract] |
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F1.00027: Learning from the Dolphins: How Anterior Motion Affects the Dolphin Kick Thomas Choi In this study, an observational analysis of the underwater human dolphin kick was conducted in order to investigate the hypothesis that large anterior movements increase the velocity of the kick. Two female and four male adolescents participated in the study. The subjects’ heights were recorded, along with data about their swimming speed and kick velocities and amplitudes at the toes, chest, and arms. From these data, kick frequency, normalized kick amplitude, and Strouhal numbers at the toes, chest, and arms were calculated. This analysis confirmed the initial hypothesis, but further research with additional study subjects is needed to verify these results. [Preview Abstract] |
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F1.00028: From Spintronics To CFD/ContractForDifferences W.H. Maksoed Involves the CFD/ComputationalFluidDynamics \& HCCI/Homogeneous Charge Compression Ignition -Marcine Frackowiak, Dissertation, 2009, for CFD/ContractForDifferences, spintronics theirselves include active control \& manipulation of spin d.o.f ever quotes, the nano-obelisk of SEM/scanning electron microscopy of galliumnitride/GaN nanostructures-Yong-Hoon Cho, et.al:``Novel photonic device using Core-Shell Nanostructures, SPIE, newsroom, 10.1117/2.1201503.005864. Herewith commercial activated carbon/C can be imaged directly using abberation-corrected transmission electron microscopy[PJF Harris, et.al: ``Imaging the atomic structures of activated C,'' J.Phys.:Condens.Matt, 20 ( 2008) in fig (b \& c) images networks of hexagonal rings can be clearly be seen depict equal etchings of 340px\_Akhenaten\_and\_their-children-Windows Picture \& fax Viewer reminds between Isaac Asimov \& Yithzak HERZOG candidacies. [Preview Abstract] |
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F1.00029: From Vortex Motion of Zn Dust to Charles WEBB through MagnetoHydroDynamics/MHD W.H. Maksoed, Fatahillah Hidajatullah-Maksoed Refers to BJ Lee, F Najmabadi \& L Schimtz:"Modelling of a High Pressure Gas Target Divertor", July 8 1994, to a given investigations aimed at developing the physical principles of a current source for those nuclear-to-electric energy conversion[AV Filippov,et.al-2005] further retrieved Tony Arber:"Fundamental of MHD", 2013 stated:"Plasma effects enter the Maxwell equations through the charge density \& current 'source' producer by the response of a plasma to electric\&magnetic fields". "A plasma-neutral model is developed in which,essentially, a single-fluid MHD plasma reacts\&interacts with gasdynamic neutral fluid derived from the ion, electron \& neutral species Boltzmann equations accounts for electron impact ionization, radiative recombination \& resonant charge exchange/CX-Meier\&Shumlak,Phys ofPlasmas,2012.Configuratively, vortex motion of Zn dust particles at U=187V, additional electrode potential of 442V, neon pressure of 0.4x100000 Pa (d),(e)\&(f)-variation of the additional electrode potential i the 8',400-500V[Filippov, 141] depict similar to phase portraits (b)asymptotically stable from Lyapunov criterion,at last show web/Charles WEBB implied featurette-Murray,Li\&Sastry:"Mathematical Introduction to RoboticManipulations" [Preview Abstract] |
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F1.00030: From Vortex Motion of Zn Dust to Charles Webb W.H. Maksoed Refers to BJ Lee,et.al:''Modelling of a High Pressure Gas Target Divertor'', July 8, 1994 to a given, investigations aimed at developing the physical principles of a current source for the nuclear-to-electric energy conversion[AV Filippov,et.al-2005] further retrieved Tny ARBER:''Fundamental of MHD'', 2013 states:''plasma effects enter the Maxwell equations through the charge density {\&} current `source' produced by the response of a plasma to electric{\&}magnetic fields''. ``A plasma-neutral model developed in which, essentially, a single-fluid MHD plasma reacts{\&}interacts with gasdynamic neutral fluid derived from ion, electron {\&}neutral species Boltzmann equations accounts for electron impact ionization, radiative recombination {\&} resonant chrge exchange/CX''- Meier {\&} Shumlak,Phys ofPlasmas,2012. Configuratively vortex motion of Zn dust particles at U$=$187V, additional electrode potential of 442V, neon pressure of 0.4x100000 Pa (d),(e){\&}(f)- variation of the additional electrode potential in the 8',400-500V [Filippov,141] depict similar to phase portraits for (b) asymptotically stable from Lyapunov criterion,at last show web/Charles Webb implied featurette-Murray,Li {\&} Sastry:''Mathematical Introduction to RoboticManipulations''. [Preview Abstract] |
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F1.00031: The Effect of Preparation Uncertainty on Error-Disturbance Relations AJ Rasmusson, Jacob "J" Collings, Jean-Francois S. Van Huele Heisenberg's work on quantum uncertainty has developed into two distinct concepts. (1) Preparation uncertainty puts a limit on the joint precision with which two incompatible physical variables can be described in a given quantum state. (2) Measurement uncertainty puts a joint lower limit on the error in the measurement of one physical variable and the disturbance in another physical variable as a result of that same measurement. Specific measurement uncertainty relations are affected by state preparation. We explore these connections and extend previous work done on coherent states to squeezed and less-intelligent states. [Preview Abstract] |
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F1.00032: The Equivalence Problem: Einstein-Maxwell Solutions Rebecca Whitney, Charles Torre The ``Equivalence Problem'' is part of the Digital Einstein Project. The goal of this project is to create a digital and interactive library of all known solutions to the Einstein field equations in general relativity. The ``Equivalence Problem'' involves determining when two solutions are physically equivalent. This requires calculating physical and geometric features to characterize each solution independently of any coordinate system. One of the principal features used to characterize the solutions is the degree of symmetry or the isometry group of the space-time metric. We have focused on the solutions to the Einstein-Maxwell field equations and compared the isometry group of the space-time metric to the symmetry group of the electromagnetic fields for all known solutions. To further characterize these solutions, we have determined whether the electromagnetic fields are null. These characterizations have been added to the library of solutions of the Einstein field equations. ~~ [Preview Abstract] |
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F1.00033: $\backslash $Analytic theory for the switch from Bloch to N\'{e}el domain wall in rectangular nanowires with perpendicular anisotropy$\backslash $ Miriam DeJong, Karen Livesey h $pardabstract-$\backslash $Domain walls in rectangular magnetic nanowires have been proposed for a variety of important applications, including use in logic schemes, data storage and bio-sensing. It is known that at the precise geometry where the switch between Bloch and N\'{e}el domain walls occurs, the walls can be moved through a nanowire with the least amount of energy. For a constant wire thickness, reducing the wire width leads to a switch from the lowest energy domain wall being of Bloch-type to it being of N\'{e}el-type. This switch occurs due to competing energy contributions in the domain wall types, with the demagnetizing energy being the most influential. Through an iterative process we have found analytic energies that can easily be plotted to determine the precise geometry where the switch from one wall type to another occurs. Our results agree well with micromagnetic simulations and experiment and it is therefore expected that the analytic expressions provided here will be useful to experimentalists aiming to make nanowires for low-power applications.$\backslash $-/abstract-$\backslash $pard$\ [Preview Abstract] |
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F1.00034: Lightcurve Analysis of 3366 Godel, 5685 Sanenobufukui, 6438 Suarez, and 15224 Penttila Karl Madden, Samuel Montgomery Over 690,000 minor planets have been discovered within the solar system, only one percent of which have well-defined rotational periods. The purpose of this project was to construct a visual magnitude versus time plot, called a lightcurve, for four main-belt asteroids in order to determine their rotational periods. In general, all asteroids spin as they orbit the sun, allowing observers from earth to view an asteroid from multiple perspectives. The area of the asteroid's visible surface will change as it rotates, which proportionally affects the amount of light reflected towards the earth. The variation in reflected light alters the asteroid's brightness over a measurable synodic period correlating to its rotational period. The C-14 telescopes at the Etscorn Campus Observatory were used to image the asteroids 3366 Godel, 5685 Sanenobufukui, 6438 Suarez, and 15224 Penttila over several weeks. Corrections for vignetting and artifacts were made with flat-field techniques. The software package \textit{MPOCanopus} was then used to construct the plots based on the apparent magnitude of the asteroid in each image. The periods determined were 4.687 hours, 3.388 hours, 2.941 hours, and 4.377 hours respectively. [Preview Abstract] |
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F1.00035: Characterizing the Stellar Halo of M83 Michael Busch, Eric Bell, Sarah Loebman, Ian Roederer Cosmological simulations of $\Lambda $CDM predict a hierarchical Galactic formation by the accretion of smaller satellite galaxies onto the main galactic plane. We observe far fewer satellite galaxies (\textasciitilde 20) in the stellar halo in the Local Group than predicted by $\Lambda $CDM (\textasciitilde 500). The GHOSTS (Galaxy Halos, Outer disks, Substructure, Thick disks and Star clusters) survey is the largest study of stellar populations in the stellar halos of 16 nearby disk galaxies using the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST). Additionally, the Subaru Telescope on Mauna Kea is a ground-based telescope capable of providing a wide-field survey of the stellar halo. This work characterizes the stellar halo of M83, a Milky Way type galaxy at a distance of \textasciitilde 5 Mpc. We present early results on a method to use GHOSTS as a targeting survey to calibrate Subaru data, using Stellar Locus Regression to calculate color-color cuts and star-galaxy separation in Subaru data. This allows for a deep imaging survey to probe most of the stellar halo of M83. The goal is to characterize the stellar populations, specifically Red Giant Branch (RGB) stars, as they are tracers of the underlying galactic formation. [Preview Abstract] |
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F1.00036: Use of Plasma Enhanced ALD to Construct Efficient Interference Filters for Astronomy in the FUV Paul Scowen Over the past few years the advent of atomic layer deposition (ALD) technology has opened new capabilities to the field of coatings deposition for use in optical elements. At the same time, there have been major advances in both optical designs and detector technologies that can provide orders of magnitude improvement in throughput in the far ultraviolet (FUV) and near ultraviolet (NUV) passbands for use in observational astronomy. Recent review work has shown that a veritable revolution is about to happen in astronomical diagnostic work for targets ranging from protostellar and protoplanetary systems, to the intergalactic medium that feeds gas supplies for galactic star formation, and supernovae and hot gas from star forming regions that determine galaxy formation feedback, to the most distant of objects in the early universe. These diagnostics are rooted in access to a forest of emission and absorption lines in the ultraviolet (UV), and all that prevents this advance is the lack of throughput in such systems, even in space-based conditions. We describe our program that has been designed to use a range of materials to implement stable optical layers suitable for protective overcoats with high UV reflectivity and unprecedented uniformity, and use that capability to leverage innovative ultraviolet/optical filter construction to enable the type of science described above. [Preview Abstract] |
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F1.00037: Using Brigham Young University's Orson Pratt Observatory 16" telescope to identify possible transiting planets discovered by the Kilodegree Extremely Little Telescope Kyle Matt, Denise Stephens, Clement Gaillard, Mary Thea Dumont We use a 16" telescope on the Brigham Young University (BYU) campus to follow-up on the Kilodegree Extremely Little Telescope (KELT) survey to identify possible transiting planets. KELT is an all sky survey that monitors the same area of the sky throughout the year to identify stars that exhibit a change in brightness. Objects found to exhibit a variation in brightness similar to predicted models of transiting planets are sent to the ground-based follow-up team where we get high precision differential photometry to determine whether or not a transit is occurring and if the transiting object is a planet or companion star. If a planetary transit is found, the object is forwarded for radial velocity follow-up and could eventually be published as a KELT planet. In this poster we present light curves from possible planets we have identified as well as eclipsing binary systems and non-detections. We will highlight features of our telescope and camera and the basic steps for data reduction and analysis. [Preview Abstract] |
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F1.00038: External Calibrator for HI Observatories (ECHO) Jacob Burba, Daniel C. Jacobs, Judd Bowman, Michael Busch, Marc Leatham, Abraham Neben, Benjamin Stinnett, Lauren Turner A new generation of radio arrays is being developed that use large numbers of low-cost elements, such as phased tiles of dipole antennas, to map Hydrogen at very high redshift. These maps are three dimensional tracers of matter and energy when the universe was only 400,000 years old and covers scales much larger than previously possible. Calibration of the primary beams of phased dipole arrays has been found to be crucial to analysis of observations from the the Murchison Widefield Array (MWA), the Precision Array for Probing the Epoch of Reionization (PAPER), and the upcoming Hydrogen Epoch of Reionization Array (HERA). The goal of the Experimental Calibrator for HI Observatories (ECHO) is to map the primary beam response using a drone-mounted transmitter which is flown along a pre-programmed flight path designed to cover the entire sky. As a test of this method, beams of calibrated reference dipoles were mapped and compared with measurements by an alternate method. Here we present the results of these tests. [Preview Abstract] |
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F1.00039: The evolution of massive galaxies over cosmic time Bhavin Joshi Massive elliptical galaxies are characterized by older stellar populations, redder colors, and relatively steep light profiles. Although a lot of progress has been made in understanding their properties we still have to understand how these galaxies were formed and how they have grown over the last 12 billion years or so. The spectra for these massive galaxies tend to show broad absorption lines and also typically show a sharp discontinuity in the flux at wavelengths shorter than 4000 A - a feature called the 4000 A break. This feature is caused by multiple absorption lines largely from ionized metals that fall within the wavelength range of 3600-4200 A. It provides information about the star formation history and the stellar content of a galaxy. I will present work that studies massive galaxies using data from the Faint Infrared Grism Survey (FIGS) as well as data from the Probing Reionization And Evolution Survey (PEARS) that are large Hubble Space Telescope (HST) programs with 160 orbits and 200 orbits respectively. I will introduce the methods used to select galaxies for analyzing them through the strength of their 4000 A break and I will present and discuss the results that have been obtained thus far. [Preview Abstract] |
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F1.00040: Designing an all-sky Camera to observe the weather conditions at the Murchison Widefield Array Kali Johson, Lauren Turner, Judd Bowman The All-Sky Camera was created as a means to observe the weather conditions at the Murchison Widefield Array for the EDGES (Experiment to Detect the Global EoR Signature) project, under supervision of Professor Judd Bowman. The system was constructed using two cameras, one of which was is fairly standard color webcam, and another which was a more sophisticated, monochrome camera with a fisheye lens used for night sky imaging which was modified with a filter to take images both during the day and night. The two cameras are housed inside a Faraday cage-like enclosure to block out any radio wave emissions that may disturb the EDGES data. The webcam looks out over the horizon, while the fish eye camera is pointed towards the sky to record images throughout the day to give insight to the weather conditions over the array. The images provide the EDGES project with more insight to possible weather conditions and their effects on the recorded data and general operation of the hardware. The camera has been fully operational at the MWA and included in the public data archives since April 19th, 2015. [Preview Abstract] |
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F1.00041: Spin-Polarized Current Induced by a Magnetic Insulator Bochao Li, Gejian Zhao, Dongrin Kim, Miguel Bueno, Ji Zhang, Jessica Gifford, Tingyong Chen Spintronics takes advantage of both charge and spin of conduction electrons but a spin source is often required to generate a spin polarized current for a spintronic device. Conventionally a magnetic metal is utilized as a spin source but in many cases spin cannot be efficiently injected from a magnetic metal into another material because of complexities such as lattice and conductivity mismatch. In this work, we experimentally demonstrate that a spin-polarized current can be generated in a nonmagnetic metal using a magnetic insulator through the proximity effect. A Pt layer of a few nanometers grown on a magnetic insulator Yttrium iron garnet, Y3Fe2(FeO4)3, (YIG) shows anisotropic magnetoresistance and substantial spin polarization. [Preview Abstract] |
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F1.00042: Temperature Effect on Intramolecular Electron Transfer Morteza Moghimi Waskasi, Gerdenis Kodis, Dmitry Matyushov A deeper understanding of the electron transfer process in Porphyrin-Fullerene (P-C60) dyad can be helpful in the development of chemical systems with high efficiency in the conversion of light to electricity. The rate of charge recombination in the P-C60 dyad can be described in the frame of the Marcus approach. Based on this approach, the kinetics of electron transfer depend on (i) driving force, (ii) reorganization energy, (iii) electronic coupling, and (iv) temperature. The temperature dependence can be complicated since reorganization energy and free energy are functions of temperature through the polarization of the solvent. The density functional theory is employed to obtain charge and optimized structures of ground, excited and charge separated states of the dyad. The free energy and reorganization energy at various temperatures are calculated using SolvMol code in 2-mTHF, and THF solvents. We found a good agreement between the temperature dependence of the recombination rate in experimental and computational approaches. It has a very pronounced bell shape and provides a critical test of the theory. The appropriate choice of solvent and temperature can provide a powerful tool for tuning the dynamics of electron transfer. [Preview Abstract] |
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F1.00043: Ultrafast Pump-Probe Measurement of Media Dependent Exciton Lifetimes in Lead Sulfide Quantum Dots. John Maurer, Mark Siemens, Brian Green We present exciton lifetime measurements of Lead Sulfide (PbS) quantum dots (QDs) in solution versus a dried film. In our experiments, we use ultrafast laser pulses from a Ti:Sapphire oscillator in a pump-probe experiment. The laser pulses resonantly generate excitons (pump) and probe the remaining exciton population (probe) to measure the exciton lifetime. The pronounced differences in environmental conditions between a solution and solid film could have drastic effects on the mean lifetime of excitons confined to QDs, due to the differing electrostatic and mechanical properties of the media. In particular, contributions of the surface morphology on exciton dephasing and depopulation, including direct exciton-surface interactions and surface-mediated phonon states that can scatter excitons. By investigating samples of PbS QDs in solution versus dried film, the effects of media dependent exciton lifetimes can be probed and exciton lifetimes tuned to a desirable time scale, allowing for utilization of the excited state energy. [Preview Abstract] |
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F1.00044: Nanoscale Interface Interaction with Magneto-Optical Kerr Effect (MOKE) Cameron Hickert, Bradley Becker, Mark Siemens, Xin Fan While much effort has been dedicated to studying the interplay between magnetism and light, the role of nanoscale effects is only now being recognized. Our lab recently measured a surprising phenomenon in which the magneto-optical response of a magnetic material is reversed when a nonmagnetic film is added above it. This effect cannot be explained by basic theories of magnetism, suggesting an uncharacterized role of the interface in affecting bulk magnetization. The specific phenomenon we study is the Magneto-Optic Kerr Effect (MOKE), which describes the polarization rotation of light reflecting off a magnetized surface. The developed surface MOKE setup allows us to study how electricity can affect magnetism via interface spin-orbit interaction. In this study, we utilize a nonmagnetic platinum nanofilm layered above a permalloy ferromagnetic nanofilm. By varying the current passing through the nanofilms, and measuring the MOKE with perpendicular light incidence, we are able to detect how electricity can manipulate magnetism. Preliminary data from other experiments suggests this rigorous quantification will allow us to improve scientific conceptions of magnetization and spin-orbit interaction, with potential technological applications in magnetic memory and computer hard drives. [Preview Abstract] |
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F1.00045: A New Spin on Barium Cobalt Phosphate Jesse Brown We have successfully synthesized a metastable phase of Barium Cobalt Phosphate Ba2Co2(PO4)2 (i.e. BCPO) via hydrothermal reactions. BCPO hosts magnetic cobalt ions arranged in a quasi 2-D honeycomb lattice. In the past this material has been suggested as an example of a 2-D XY Universality class, which theoretically exhibits a spin vortex binding transition, called the Kosterlitz-Thouless transition. By measuring the magnetization and heat capacity of BCPO as a function of temperature we are investigating this transition in detail. In the future we plan to use neutron scattering to investigate any anisotropic magnetic interactions on this honeycomb lattice. Our work may reveal that BCPO hosts a new phase of matter called a "quantum spin liquid". [Preview Abstract] |
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F1.00046: Noise of 1/f type in a constrained Heisenberg spin model Bryce Davis, Ralph Chamberlin A variety of systems and materials have been seen to undergo fluctuations with a power spectral density that depends upon frequency as approximately 1/f: electronic and magnetic devices, graphene and carbon nanotubes, and biological molecules. However, there is no agreed upon mechanism for this 1/f noise. Many explanations depend upon heterogeneity in the dynamics of the system yielding a distribution of relaxation times. Presented here is a Heisenberg spin model with dipolar anisotropy, simulated with the Metropolis algorithm using the standard Boltzmann factor as well as an entropic constraint to impose heterogeneity. The constraint simulates heterogeneity by determining transition probabilities not just by the availability of heat from the bath through the standard Boltzmann factor, but by the availability of entropy in the local environment such that the larger system becomes an ensemble of local regions with their own dynamics and time constants, consistent with the dynamic heterogeneity observed in many materials. The noise spectra of magnetization in these simulations is found to depend on frequency as 1/f$^{\mathrm{\alpha (T)}}$ over a range of frequencies, where $\alpha $(T) is an exponent depending upon temperature. [Preview Abstract] |
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F1.00047: Measuring Surface Energy and Reactivity for Wet NanoBonding$^\mathrm{TM}$ via Three Liquid Contact Angle Analysis Ender W. Davis, Nicole Herbots, Robert J. Culbertson, Alex L. Brimhall, Ashley A. Mascareno, Clarizza F. Watson, Nithin Kannan, Abijith Krishnan, Matthew T. Bade Silicon-based surfaces, such as thermally-grown amorphous a-SiO$_2$ and Si(100), are hermetically bonded using wet NanoBonding$^\mathrm{TM}$. Initial surfaces are modified to favor electron exchange and cross-bonding. a-SiO$_2$ is etched with hydrofluoric acid (HF), while $\beta$-cSiO$_2$ is grown on Si(100). Next, both are NanoBonded under steam pressurization. NanoBonding can bond medical, marine, and air sensors to their electronics, and be used in night vision goggles and solar cells. To optimize cross-bonding, surface energy $\gamma^T$ is studied via 3 liquid contact angle analysis (3LCAA) and the Van Oss theory. This models $\gamma^T$ via 3 components: $\gamma^{LW}$ for dipole interactions, $\gamma^+$ for electron donors, and $\gamma^-$ for acceptors. 3LCAA extracts contact angles from 3 liquids with known surface energies: water, glycerin, and $\alpha$-bromonaphthalene. We use several droplets of each liquid on the surface to improve accuracy. $\gamma^+$ accounts for little to none of the surface energy of all surfaces, but the annealing in Wet NanoBonding significantly increases $\gamma^+$ in $\beta$-cSiO$_2$. Conversely, HF etching significantly increases $\gamma^-$ for a-SiO$_2$. This donor/acceptor imbalance enhances reactivity and NanoBonding between the surfaces. [Preview Abstract] |
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F1.00048: Plasma Enhanced Atomic Layer Deposition Nucleation Performance on Atomically Smooth Graphene Surfaces Trevor Van Engelhoven, Anna Zaniewski, Manpuneet Kaur, Christie Trimble, Will Gannett, Mark Keller, Robert Nemanich Electronics using graphene may lead to the next generation of computation and innovative devices. Layering dielectrics with graphene is key to realizing many of these functional devices. Plasma enhanced atomic layer deposition (PEALD) is a novel way to introduce dielectrics to graphene, however graphene is susceptible to etching by PEALD. This motivates us to explore the role of graphene quality on film nucleation and graphene robustness. In this experiment we will use spectroscopy and atomic force microscopy to quantify film and graphene quality. Here we will present the experimental design, initial findings and theory behind this upcoming research. At the current stage of experimentation sample holders have been designed and machined, control C-AFM data has shown smoothness of 4-6 nm with strong conductivity. We discuss how graphene quality, plasma conditions, and ample geometry may play a role in post-PEALD graphene quality and film nucleation. [Preview Abstract] |
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F1.00049: A simple, solution-based technique to pattern copper nanowires Brandon E. Palafox, Veronica S. Meeks, Anna M. Zaniewski, Robert J. Nemanich Metal nanowires have a range of optoelectronic applications, including solar cells, photonic circuits, and nanoscale lasers. In this work, we present a technique to grow copper nanowires on a ferroelectric surface via a photochemical reaction. Copper acetylacetonate in a solution is placed on top of periodically poled lithium niobate and exposed to a UV source for 3 hours. The copper reduction is most favorable at the boundary between positively and negatively charged domain surfaces, resulting in copper nanowire formation. We find that the pattern of copper deposition on the surface is affected by the concentration of the solution, with optimal nanowire formation at a concentration of 1E-4 M. The wires vary in height from 50-65nm. [Preview Abstract] |
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F1.00050: Comparison of LiF and NiO crystallographic structure using XRD Jaime Moya, Nuwanjula Samarasingha, Stefan Zollner Using x-ray diffraction (XRD), the crystallographic structures of LiF and NiO powders and single crystals were compared. Two types of scans were taken: $\omega $-2$\theta $ scans were taken for both the powders and single crystals, and $\omega $ (rocking) scans were taken for the single crystals. LiF is of the face-centered cubic rock salt structure, whereas NiO contracts along the [111] direction producing a rhombohedral (hexagonal) crystal structure. Therefore, the cubic (222) peak splits in bulk NiO into hexagonal (006) and (202) peaks. From the $\omega $-2$\theta $ NiO powder scans, no splitting of the c(222) peak is observed because the NiO is a nano-powder, preferring high symmetry orientations. The $\omega $-2$\theta $ peaks are broader in NiO because the grain size is smaller in the NiO than in LiF powders. The rocking curve scans of the c(222) peaks show that the crystals have multiple domains. [Preview Abstract] |
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F1.00051: Electronic states of plasma-enhanced atomic layer deposited SiO2 on GaN Brianna Eller, Wenwen Li, Sarah Rupprecht, Srabanti Chowdhury, Robert Nemanich Silicon dioxide is a stable dielectric with a large bandgap that leads to effective band offsets suitable for wide bandgap semiconductor electronics. This research is focused on band offsets and bending for plasma-enhanced atomic layer deposited (PEALD) SiO2 on in-situ cleaned GaN. We have investigated low-temperature SiO2 using tris(dimethylamino)silane (TDMAS) and oxygen plasma on GaN substrates. Thin film thicknesses, compositions, and band offsets were determined with \textit{in-situ} x-ray photoelectron spectroscopy (XPS). Results showed the growth rate for TDMAS and oxygen plasma process increased as temperature decreased within the ALD regime. The growth rate was higher at 550 \textdegree C, which was likely the result of thermal decomposition of TDMAS. Results also demonstrated temperature does not greatly affect the stoichiometry of the films. A more detailed analysis showed increasing deposition temperature resulted in a secondary O1s peak; however, this peak was not present for thick films. This secondary peak likely suggests the high temperature may relate to the oxidization of the GaN substrates. This effect may also explain the variation in observed valence band offsets (VBO), where the measurement technique does not account for the potential drop across the interfacial Ga-O layer. The next stage of this work will employ electrical measurements to ascertain the quality of this interface on SiO2/Si. [Preview Abstract] |
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F1.00052: Aberration-corrected STEM of Cross-sectional View of Core-shell Nanowires Jia Xu, Jingyue Liu Aberration-corrected scanning transmission electron microscopy (AC-STEM) technique was used to investigate the interfacial structures of core-shell nanowires (NWs). The ultramicrotome technique was used to prepare cross-sectional samples of ZnO-Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ core-shell NWs. Thin layers Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ epitaxially grew onto the six \textbraceleft 11-20\textbraceright but not the six \textbraceleft 10-10\textbraceright nanoscale facets. Such selective growth can be explained by the differences in the interfacial energy between the two oxide phases. AC-STEM further revealed the interfacial reconstruction of the Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ layers, a consequence of minimizing the interfacial energy and to make the epilayer growth of the Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ possible. A model was proposed to understand the growth processes of Bi-containing phases onto ZnO NWs. [Preview Abstract] |
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F1.00053: Dependence of Electrostatic Field Strength on Voltage Ramp Rates for Spacecraft Materials Krysta Moser, Allen Andersen, JR Dennison Previous tests done by the USU Materials Physics Group (MPG) using our electrostatic discharge (ESD) custom vacuum chamber have found that, for the polymeric materials polyimide and low density polyethylene (LDPE), the electrostatic field strength at breakdown depends on the voltage ramp rate applied across the materials. At ramp rates an order of magnitude lower than the maximum recommended rate of 500 V/s, the breakdown electrostatic field strength was also found to be significantly lower. The data from these tests were compared to a microscopic mean field theory for dielectric breakdown in highly disordered insulating materials. We present new ramp rate testing data on a third polymeric material, polypropylene. The voltage was incrementally increased at a constant rate across the samples until breakdown occurred. Breakdown is marked by the current increasing significantly and continuing to rise linearly according to Ohm's law. Different ramp rates were used in order to compare the dependence of electrostatic field strength on ramp rate for polypropylene to the theory applied to past experiments for polyimide and LDPE. Understanding these relationships between electrostatic field strength and voltage ramp rates will aid in the understanding and mitigation of ESD related anomalies and failures due to spacecraft interactions with the plasma space environment. [Preview Abstract] |
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F1.00054: Measurement of Thermal Effects by Thermoelectric Coolers Ji Zhang, Jessica Gifford, Charles Snider, Nathaniel Vargas, Tingyong Chen In pure spin current, electrons of opposite spins flow in opposite directions,to convey information only by spin current without any charge current. This process causes little power consumption, which has the potential to realize ultra-low-power-consumption electronics. Recently, thermal effects, such as the spin Seebeck effect in magnetic materials have been proposed to generate pure spin currents using a thermal gradient ($\nabla T$). However, unlike electric potential, direction of $\nabla T$ is difficult to control, which has already caused misinterpretation of thermal effects in Py and Py/Pt films. In this poster, we show that a well-defined $\nabla T$ can be created by two thermoelectric coolers (TECs) based on Peltier effect. $\nabla T$ can be accurately controlled by the driven voltage on the TECs. Using a square-wave driven potential, $\mu V$ scale signal is measured. With this technique, we have measured the thermal effects in bulk Bi, thin film Py and Co samples. In Bi both the Nernst and the Seebeck effects are present if $\nabla T$ is not along the appropriate direction.With a well-defined $\nabla T$,we show that thermal effect in polycrystalline Py/Pt and Co/Pt films are mostly anomalous Nernst effect, with the same angular symmetry as the anomalous Hall effect. [Preview Abstract] |
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F1.00055: Novel Carbon Nanoscale Architectures for Supercapcitors Guanhua Zhang, Huigao Duan, Jingyue Liu Supercapacitors have received considerable attention because of their high power density, fast recharge capability and long cycle life. Hierarchically structured carbons are highly desirable because of their potential to provide high capacitance and good rate capability. To fabricate such structures, however, is complicated, expensive, and time-consuming. We recently developed a novel synthesis approach to fabricate three-dimensionally patterned growth of hollow carbon arrays (CNTAs) on a flexible carbon fibers (CFs) substrate. The facile synthesis protocol is repeatable, scalable and easy to process. The CNTAs@CFs were directly used as integrated electrodes for supercapacitors and exhibited a high specific capacitance of 200 F/g at 20 A/g in 6 M KOH aqueous solution, and an excellent cycling ability with a 98{\%} of the initial capacitance remained after 4000 cycles. Moreover, the capacitance still maintained 182 F/g even when the current density increased to 40 A/g. The CNTAs@CFs electrodes without the use of any auxiliary materials are expected to open up new opportunities for carbon-based materials to power flexible electronic devices. [Preview Abstract] |
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F1.00056: Density of State Models of Steady-State Temperature Dependent Radiation Induced Conductivity Jodie Gillespie, JR Dennison, Alec Sim Radiation induced conductivity (RIC) occurs when incident radiation deposits energy and excites electrons into the conduction band of insulators. The magnitude of the enhanced conductivity is dependent on a number of factors including temperature and the spatial- and energy-dependence and occupation of the material’s distribution of localized trap states within the band gap—or density of states (DOS). Expressions are developed for steady-state RIC over an extended temperature range, based on DOS models for highly disordered insulating materials. A general discussion of the DOS of disordered materials can be given using two simple distributions: one that monotonically decreases below the band edge and one that shows a peak in the distribution within the band gap. Three monotonically decreasing models (exponential, power law, and linear), and two peaked models (Gaussian and delta function) are developed, plus limiting cases with a uniform DOS for each type. Variations using the peaked models are considered, with an effective Fermi level between the conduction mobility edge and the trap DOS, within the peaked trap DOS, and between the trap DOS and the valence band. Explicit solutions, limiting cases, and applications of the models to RIC measurements are presented. [Preview Abstract] |
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F1.00057: Interference coatings for 1-2 $\mu $m high energy lasers by reactive ion beam sputtering Travis Day, Drew Schiltz, Cory Baumgarten, Brendan Reagan, Dinesh Patel, Jorge Rocca, Carmen Menoni The development of Joule-level chirped pulse amplification solid state diode pumped laser systems with numerous scientific and technological applications motivates our work in interference coatings for operation in the 1-2 \textmu m wavelength range. Interference coatings were designed using a combination of metal-oxides, and were grown by ion beam sputtering. Results will be presented on 1 \textmu m coatings based on Ta2O5/SiO2 in which by modifying the top few layers it is possible to achieve a laser damage fluence 2x that of a quarter wave Ta2O5/SiO2. Results will also be presented on interference coatings designed with metal oxides for 1.6-2 \textmu m operation. At-wavelength testing of the laser damage resistance of these coatings showed they can withstand fluences similar to that of the high quality infrared fused silica substrates when tested with a train of pulses of 2 picosecond duration. Work supported by the DoD Office of Naval Research, the Army Research Office and the High Energy Laser Program of the DoD Joint Technology Office. [Preview Abstract] |
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F1.00058: High-pressure Processing of Hyper-doped Silicon Dan Weisz, John Testerman, Kimberly de La Harpe, Reni Ayachitula We report the successful processing and characterization of silicon hyper-doped with sulfur using a nanosecond-pulsed laser in the presence of sulfur hexafluoride at pressures greater than one atmosphere. Microstructures on the surface formed during the high-pressure processing require less energy to form yet contain comparable sulfur content as samples processed at one atmosphere. These structures exhibit enhanced short-infrared absorption, a property of interest for solar cell and infrared detection applications. [Preview Abstract] |
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F1.00059: The Space Survivability Test Chamber. Katie Gamaunt, Heather Tippets, Alex Souvall, Ben Russon, JR Dennison The Space Survivability Test chamber is a new ground-based research instrument being used for accelerated testing of environment-induced modifications of diverse samples. The chamber simulates space environment conditions, including neutral gas atmospheres and vacuum (\textless 10$^{\mathrm{-5}}$ Pa) environments, temperature (\textasciitilde 100 K to \textgreater 450 K), ionizing radiation, electron fluxes (\textless 10 eV to \textasciitilde 2\textonehalf MeV), and vacuum ultraviolet through mid-infrared photon fluxes. This versatile test chamber is well-suited for cost-effective testing of complete systems up to the size (\textless 20 cm dia.) of a 1U CubeSat, smaller components or electronics, and individual material samples. Multiple \textit{in-flux} or \textit{in-situ} space survivability and radiation exposure tests can be performed simultaneously, as well as extensive before and after\textit{ ex-situ} tests. Currently the chamber is performing a series of radiation experiments using a Sr$^{\mathrm{90}}$ beta radiation source which approximately mimics the geostationary high energy electron spectra at \textasciitilde 4-10X accelerated rates. These measurements will serve to forecast sample radiation damage, predict lifetimes of electronics, and substantiate the ability of the chamber to mimic space environments. Specific tests include: modified efficiency of solar arrays; single event upsets and failure of commercial off-the shelf microcontrollers, memory, and sensors; structural damage and modifications of mechanical and electrical properties; changes in electron transport and arcing of materials; and modification of optical properties of glasses and polymeric materials. [Preview Abstract] |
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F1.00060: Properties of Spacecraft Materials Exposed to Ionizing Radiation Alexander Souvall, Gergory Wilson, Heather Tippets, Ben Russon, Katie Gamaunt, John Dennison The effects of ionizing radiation damage on the various properties of spacecraft materials resulting from exposure in the Space Survivability Testing chamber (SST) are being studied with both\textit{ ex situ} and \textit{in situ} tests. The SST is a ground based test facility designed to mimic low earth orbit (LEO), and geosynchronous orbit to test potential environmental-induced modifications to small satellites , and materials. Tests described here expose spacecraft materials to a Sr$^{\mathrm{90}}$ ionizing beta radiation source at room temperature and in high vacuum. \textit{Ex situ} optical transmission/reflectivity measurements glass samples will monitor optical darkening. Properties of polymeric samples will be measured before and after SST exposure as well as a comparative study of SST ground-based tests to space flown samples. These include materials from the MISSE and PrintSat missions. The MISSE mission studied the effects of prolonged exposure to the LEO space environment properties of common spacecraft materials. PrintSat is a 3D printed CubeSat built by students at Montana State University constructed of WindForm, a nano-carbon-impregnated plastic; it will use on-board sensors to observe mechanical and electrical space-induced changes of WindForm. By comparison of ground-based tests in the SST to the results of these in-flight tests, the ability of the chamber to mimic the space environment and predict potential radiation damage effects will be quantified. [Preview Abstract] |
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F1.00061: Measurement of Effects of Long Term Ionizing Radiation on High Efficiency Solar Arrays Ben Russon, Heather Tippets, Alex Souvall, Katie Gamaunt, JR Dennison Degradation of power output efficiency for high-efficiency multilayer solar arrays due to ionizing radiation is measured using the Space Survivability Test chamber. Exposure to ionizing radiation disrupts the crystalline structure and can reduce solar array power output to the point that it no longer provides adequate output capacity. This can be a significant concern, particularly in the harsh environment of space where radiation dose rate is significantly higher and replacing components is often impossible. Ionizing radiation is simulated in a controlled environment to allow measurement and characterization of the power output of solar arrays, using a 100 mCi encapsulated Sr$^{\mathrm{90}}$ beta radiation source which produces a high energy spectrum similar to the geosynchronous space environment at more than 10X intensity for accelerated testing. The total ionizing dose is measured by a radiation sensitive diode and can be controlled by varying both the exposure time and distance to the source. Controlled temperature conditions are monitored with thermocouples. The critical measurement of power output is made through IV curves, using a standard solar light source (Class AAA Solar Simulator). IV curves can be monitored \textit{in situ,} allowing for characterization with respect to total ionizing dose. More extensive IV response curves as a function of temperature and incident UV flux can be completed \textit{ex situ} before and after SST exposure. [Preview Abstract] |
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F1.00062: Strain relaxation in InAs quantum dots and its suppression by indium flushing Hongen Xie, Fernando Ponce The intermediate band opens new absorption paths enhancing light harvesting and its conversion into electricity. We present direct evidence that InAs quantum dots (QDs) embedded in Al0.3Ga0.7As, designed for optimized intermediateband solar cells, are strongly affected by plastic relaxation. A transition from relaxed to strained QDs has been observed when reducing the thickness of the dots using partial capping of GaAs followed by indium flushing. Fully capped QDs exhibit moir\'{e} fringes in the transmission electron microscope, indicating significant misfit strain relaxation. QDs produced by indium flushing are found to be fully strained, and exhibit luminescent characteristics consistent with the desired intermediate band values. Critical thickness calculations, based on the equilibrium of the lattice misfit force and the dislocation line tension acting on misfit dislocation loops, are used to understand these experimental observations. [Preview Abstract] |
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F1.00063: Band alignment of hydrogen-plasma cleaned MBE CdTe on InSb (001) Xingye Wang, Calli Campbell, Yonghang Zhang, Robert Nemanich CdTe is a II-VI semiconductor with promising potential in many applications, in particular for optoelectronics. It has a bandgap of 1.5 eV. InSb is a III-V semiconductor with a reported narrow bandgap of 0.17 eV. A close lattice match exists between these two semiconductors. Thus, it is interesting to investigate the band offset between a CdTe-InSb heterojunction, which could be applied to quantum well structures. In this research, the substrates is commercially obtained single crystal InSb (001). A dual-chamber II-VI and III-V molecular beam epitaxy (MBE) system was used to thermally desorb native oxides, then deposit an InSb (001) buffer layer followed by 7 nm of epitaxial CdTe (001). After film deposition the sample was transferred to a multichamber system for photoemission analysis. A remote hydrogen plasma process was used to clean the surfaces, which were exposed to atmosphere during the transition process. Monochromatic x-ray photoemission spectroscopy (XPS) and ultra-violet photoemission spectroscopy (UPS) were used to characterize the electrical properties of the samples. The result of this research indicates a valence band offset of 0.9 eV, which is between the value predicted by the Anderson electron affinity rule (0.96 eV) and that calculated by Tersoff (0.84 eV). [Preview Abstract] |
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F1.00064: Structural and Optical Properties of AlGaN MQWs Grown by MOCVD Using One and Two TMG Sources Shuo Wang, Yong Wei, Hongen Xie, Alec Fischer, Fernando Ponce, Michael Moseley, Brendan Gunning, Alan Doolittle Multiple quantum wells (MQWs) are grown by metal-organic chemical vapor deposition (MOCVD) at a temperature of 1155 $^{\mathrm{o}}$C. The quantum well (QW) and the quantum barrier (QB) are designed to be Al$_{\mathrm{0.6}}$Ga$_{\mathrm{0.4}}$N and Al$_{\mathrm{0.75}}$Ga$_{\mathrm{0.25}}$N, respectively. One sample is grown by the traditional method with one Trimethylgallium (TMG) source. The other is grown with two TMG sources. In the one TMG configuration, the TMG flow rate needs to be changed for QW and QB. During this change, there is no Ga injecting onto the wafer surface, resulting Al-rich dark layers at the interfaces between QWs and QBs seen in the high-angle annular dark-field (HAADF) image. In two TMG configuration, QW and QB are grown by two TMG sources with different flow rates, allowing instantaneous switch between QW and QB. In the HAADF image, the interfaces exhibit no dark layer with better contrast between QW and QB. In the cathodoluminescence (CL) spectra, the two TMG sample shows a higher efficiency than the other by a factor of 7. In the one TMG sample, the Al atoms are mostly gathered at the interfaces, which leads to an ineffective quantum confinement as the width of the barriers is actually smaller than designed. The CL peak of the one TMG sample has shorter wavelength (257 nm) than the two TMG sample (263 nm), because the QW has an actual Ga content lower than 40{\%} and the Al-rich dark layers squeeze up the ground state in QW. [Preview Abstract] |
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F1.00065: Ultra-small implantable probes with bend-up micro-electrodes Xiangbing Jiao, Quan Qing Implantable electrodes have been widely used for biomedical research and therapy. The biocompatibility of existing probe techniques is heavily hindered due to their big sizes and stiff mechanical properties that do not match with live cells and tissues. Different materials, geometry and strategies have been proposed to solve these challenges, but it is still a difficult task to reconcile the request for scaling down the size of probe, maintaining the mechanical strength for implantation surgery, while having the core structure flexible for bettering interfacing with cells. Here we propose a new strategy to address this challenge by integrating flexible micro-electrodes on a supporting ultra-small silicon shaft, which features the formation of a bend-up micro-electrode structure in situ only after the surgery. Keywords: bend-up micro-electrodes, biocompatibility, implantable probe [Preview Abstract] |
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F1.00066: Unmatter as a Consequence of the Law of Included Multiple-Middles Florentin Smarandache Similarly as between \textless A\textgreater and \textless antiA\textgreater there is a multitude of \textless neutA\textgreater 's, between matter and antimatter there is a multitude of unmatter types, according to the Law of Included Multiple-Middles (F. Smarandache, 2014, \textit{Law of Included Multiple-Middle {\&} Principle of Dynamic Neutrosophic Opposition, }EuropaNova, Brussels, Belgium, 136 p.). [Preview Abstract] |
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F1.00067: Testing New Liquid Scintillators Jacob Glasby At Colorado State University, we are developing neutrino detectors using water soluble liquid scintillators. These liquids are contained in an acrylic test cell containing a wavelength shifting fiber that captures scintillation light to a Multi-Pixel-Photon-Counter (MPPC). We have cosmic ray sensors on top and bottom of the plastic scintillator test cell, which triggers when a cosmic ray passes through both sensors and through the cell. The sensors and MPPC are connected to a Tektronix Oscilloscope that reads out the MPPC signal. Using software from National Instruments called Signal Express we are able to analyze the data by each individual waveform, determine each peak-to-peak value, and form a histogram of the peak-to-peak values. After we have calibrated the software and equipment for our plastic scintillator, we will swap in a conventional liquid scintillator with other types of scintillator. Using the test cell, we plan to study a new water-soluble liquid scintillator Linear Alkylbenzene from Brookhaven National Laboratory. [Preview Abstract] |
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F1.00068: Test of Gravitational Time Dilation Jonathan Schiller, Patrick O'Shea, Robert Olesen, David Emanuel, Brian Patterson, Jerry Sell, Alina Gearba, Mario Serna, Shane Burns, Jeff Steele Colorado College and USAFA have collaborated on a demonstration of gravitational time warping\textellipsis the same effect highlighted in the movie \textit{Interstellar}. Time flows more slowly in a region of stronger gravity. In the movie, one hour on the surface of an alien planet near a black hole equated to seven years of time on earth. We have demonstrated this effect (on a much smaller scale!) by comparing the difference between the time at sea-level versus 7000 feet. Because GPS reports sea-level time, we compare an atomic clock to GPS time to measure the time difference. We observed that, at 7000 feet, our days are 20 nanoseconds longer than at sea level, consistent with the predictions of general relativity. Both USAF Academy and Colorado College have demonstrated the extra 20 nanoseconds per day. We also report recent measurements taken at the summit of Pikes Peak, at an altitude of 14,115 feet above sea level. [Preview Abstract] |
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F1.00069: Testing and Optimization of a Wireless Handheld Gamma Camera Brianna Thorpe, Jack McKisson, John McKisson Gamma cameras can help in mapping the distribution of a radioactive substance called a tracer in a patient's body. Many of these devices use a photomultiplier detector array. Due to the material of the photomultiplier, these devices are large and not easily portable. The data processing module and radio module of a wireless handheld gamma camera containing a new photomultiplier material have been tested to determine the most efficient rate of receiving data for these components. In this device, the data processing module sends streams of information into an RF (Radio Frequency) Module. For testing purposes, the data processing module will be replaced by a microprocessing board which will send simulated data to the RF Module board via radio. The most efficient rate of receiving data will be determined by measuring the desktop CPU (Central Processing Unit) event rate, the FPGA (Field-Programmable Gate Array) event rate, the packet loss rate, and the data channel availability. With this information, we will optimize the performance of the data channel. These results will show the most efficient rate of receiving data. [Preview Abstract] |
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F1.00070: Using femtosecond laser pulses to explore the catalytic processing of biomass molecules Nancy Fujikado, Scott Sayres Hydrothermal liquefaction (HTL) is an emerging process for converting biomass into a renewable fuel source. While the composition of biomass may be complex, our focus is to gain a molecular level understanding of the breakdown of carbohydrates, which have been identified as a main component. I will present recent progress on the design and construction of a time-of-flight mass spectrometer that is used to explore chemical reactions important to biomass conversion. In this experimental setup, a femtosecond laser pulse removes electrons faster than the molecule can respond, and therefore is used to identify the parent molecule. By increasing the laser intensity, the target molecule is destroyed and the relative peak ratios between the generated fragmentation products reveals details about the chemical structure and breakdown mechanisms. By exposing the carbohydrate to different molecular catalysts, the mass spectra peak ratios are modified and therefore suggest reaction conditions to improve biomass to biofuel conversion efficiency. [Preview Abstract] |
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