Bulletin of the American Physical Society
Joint Meeting of the Four Corners and Texas Sections of the American Physical Society
Volume 61, Number 15
Friday–Saturday, October 21–22, 2016; Las Cruces, New Mexico
Session E1: Poster Session |
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Chair: Thomas Hearn, New Mexico State University Room: Exhibit Hall 1 |
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E1.00001: Two-photon photolysis of collagen mimicking peptide Aurelio Paez, Kevin Hatch, Alfredo Ornelas, Katja Michael, Chunqiang Li Two-photon microscopy is a powerful tool for imaging and probing biological and molecular samples. This study proposes to use the fluorescence imaging method of two-photon microscopy on a photoreactive collagen mimicking peptide, using the two-photon absorption to explore the benefits of photolysis of the peptide. Probing the use of these techniques to potentially engineer scaffolding within which vascular vessels could be grown in order to solve the vascularization problems existing in current tissue engineering. [Preview Abstract] |
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E1.00002: Imaging Live Drosophila Brain with Two-Photon Fluorescence Microscopy Syeed Ahmed, Yu Ding, Jose Gutierrez, Kyung-An Han, Chunqiang Li Cyclic adenosine monophosphate (cAMP), a second messenger molecule, is responsible for triggering many physiological changes in neural system. However, the mechanism by which this molecule regulates responses in neuron cells is not yet clearly understood. When cAMP binds to a target protein, it changes the structure of that protein. Therefore, studying this molecular structure change with fluorescence resonance energy transfer (FRET) imaging can shed light on the cAMP functioning mechanism. FRET is a non-radiative dipole-dipole coupling which is sensitive to small distance change in nanometer scale. In this study we use a two-photon fluorescence microscope for imaging mushroom bodies inside live drosophila brain cell. We have genetically encoded green fluorescent protein (GFP) color variants cyan fluorescent protein (CFP)-yellow fluorescent protein (YFP) pair to the host protein as fluorophores. We also develop a quantitative method for analysing both CFP and YFP fluorescence emission level. [Preview Abstract] |
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E1.00003: Using Magnetic Nanoparticles in a Static and Dynamic Magnetic Field to Penetrate Model Mucus Meghan Smith, Austin Routt, Evangelos Economou, Guy Hagen, Vira Kravets, Zbigniew Celinski, Kathrin Spendier Current asthma treatment options are often hindered due to inefficient drug delivery methods through the thick layer of mucus lining the lungs, thus inhibiting inhaled medication from reaching underlying inflamed tissue. This project tested magnetically guided Dextran Sulfate Sodium (DXS) coated iron oxide, Fe$_{\mathrm{3}}$O$_{\mathrm{4}}$, nanoparticles (FeNPs) and Carbomethyl Dextran (CMD) coated barium hexaferrite, BaFe$_{\mathrm{12}}$O$_{\mathrm{19}}$, nanoparticles (BaNPs) as a drug delivery system through model mucus. A high magnetic field gradient was generated using a permanent neodymium magnet with an iron core pole piece to pull the magnetic NPs through a 2.5 cm layer of hydroxyethyl cellulose (HEC) gel. Additionally, Helmholtz coils produced an oscillating magnetic field to physically rotate the magnetic NPs. The penetration time of FeNPs and BaNPs through HEC gel was measured as a function of oscillation frequency. For a frequency range of 0 to 1900 Hz, the data illustrated penetration time of BaNPs is functionally dependent on oscillation frequency whereas penetration time of FeNPs showed no correlation. These BaNPs have large magnetic anisotropy fields allowing them to physically rotate and open holes through the HEC gel contrasting FeNPs which simply change magnetization without rotation. [Preview Abstract] |
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E1.00004: EPR Study of Superparamagnetism in Mn$_{\mathrm{\mathbf{3}}}$\textbf{O}$_{\mathrm{\mathbf{4}}}$\textbf{ Nanoparticle Ensembles} Mahesh Koirala, Alex Price, Ronald Tackett, Cristian Botez The superparamagnetic relaxation of Mn$_{\mathrm{3}}$O$_{\mathrm{4}}$ nanoparticles has been investigated using Electron Paramagnetic Resonance (EPR) measurements carried out at low temperatures, between 20 and 120 K, in an applied sweeping magnetic field of 0 to 6000 G. Two nanoparticle ensembles were used, having average particle sizes of 10 nm and 5 nm as determined from X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). [Preview Abstract] |
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E1.00005: Local absorption for plasmon-induced hot carrier generation Nicholas Huntoon, Alejandro Manjavacas Plasmon-induced hot carrier generation is attracting increasing attention due to its potential impact in photocatalysis and solar energy harvesting applications. Despite the great research effort that has been put into the experimental and theoretical characterization of this process it is usual to correlate the carrier production with the total absorption of the nanostructure calculated from the far-field response of the system. Here, by rigorously solving Maxwell's equations, we calculate the local absorption for metallic nanostructures with different morphologies and made of a variety of plasmonic materials and show that this quantity can greatly differ from the far-field absorption. The results of this work contribute to the basic understanding of plasmon-induced hot carrier generation and provide insight for the optimization of this process. [Preview Abstract] |
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E1.00006: Solar Energy Assisted Water Purification: Incorporation of an Environmentally Benign Porous Graphitized Carbon Nitride Photocatalyst with Graphitized Polyacrylonitrile for Efficient Oxidation of Toxic Arsenite Stephanie Richins, Lara Teich The presence of arsenic in New Mexico water bodies is a concern. It is urgent to develop processes for its removal. Recently, graphitized carbon nitride g-C$_{\mathrm{3}}$N$_{\mathrm{4}}$ with proper bandgap (2.7 eV) has attracted attention. However, the efficiency for g-C$_{\mathrm{3}}$N$_{\mathrm{4\thinspace }}$needs improvement due to its low charge separation efficiency and low surface area. Polyacrylonitrile (PAN) is an inexpensive polymer. When heated, it forms graphitized g-PAN with graphite-like sheet network structure, which should facilitate the charge separation efficiency and increase the surface area of g-C$_{\mathrm{3}}$N$_{\mathrm{4}}$. In this work, we report the synthesis of g-C$_{\mathrm{3}}$N$_{\mathrm{4}}$ and its composites with g-PAN with different compositions. Characterization including BET surface area, morphology, crystal structure, microstructure by N$_{\mathrm{2}}$ adsorption/desorption, electron microscopies, and x-ray diffraction. The photocatalytic oxidation of As(III) under visible light irradiation as a function of the percentage g-PAN in g-C$_{\mathrm{3}}$N$_{\mathrm{4}}$ is evaluated. The correlation between photocatalytic performance with composition, microstructure, and surface area will be discussed. [Preview Abstract] |
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E1.00007: Carbon Nanotubes for Everyone? Michael Boergert, Charles Bruce One might be surprised to hear that carbon nanotubes, among the smallest structures extent can have applications on a macroscale. They are well known to have great strength, and can have high thermal and electrical conductivities. They have various applications on the scale of their size. Our research group recently received a sample composed of nanotubes "wet-spun" into much larger fibers from Rice University that purport to have metal-level electrical conductivities. They first announced the results of wet spun fibers in 2013 (Science). Our examinations using X-ray diffraction affirmed that the fibers were composed of nanotubes rather than graphite or amorphous carbon and, using EDX in an electron microscope, do not contain a significant amount of metal materials. The microscope reveals the threads of nanotubes within the much larger fiber structure. The electrical conductivities of the fibers received were roughly at the level of stainless steel but we do not doubt that Rice has exceeded this. Finally the response of the fibers to electromagnetic radiation was measured and compared with theory. Will we one day see conductors of electrical current composed of woven nanotubes rather than copper? [Preview Abstract] |
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E1.00008: Nanoscale Heterogeneity in Ionic Liquid / Organic Solvent Mixtures Carlos Cuellar, Naresh Osti, Eugene Mamontov, Jose L. Banuelos Room-temperature ionic liquid (RTIL) mixtures, as electrolytes in supercapacitors, have desirable properties including a good combination of wide thermal and electrochemical operation range and high conductivity in comparison to conventional electrolytes. The nanostructural properties of eutectic mixtures of RTILs (e.g., BMIM$^{\mathrm{+}}$[TFSI]$^{\mathrm{-}})$ and RTILs with solvents are currently under investigation. Recently our collaborators have found that BMIM$^{\mathrm{+}}$[TFSI]$^{\mathrm{-}})$ / acetonitrile mixtures exhibit a maximum in the conductivity as a function of RTIL concentration, with the maximum occurring at a 1:1 mass mixing ratio. Furthermore, results from quasi-elastic neutron scattering show the presence of two different translational diffusion coefficients for the RTIL, suggesting the presence of spatially distinct RTIL-rich and RTIL-poor nanodomains. SAXS measurements of BMIM$^{\mathrm{+}}$[TFSI]$^{\mathrm{-\thinspace }}$/ acetonitrile mixtures at with RTIL at 0, 25, 75, and 100 mass{\%} were carried out to determine whether nano-heterogeneity is present and to characterize its structural properties. We find a \textasciitilde 3 fold increase in the scattering signal at low-Q compared to the expected scattering from a simple mixture of two liquids, suggesting long-range composition fluctuations. Results and analysis of this system will be discussed. [Preview Abstract] |
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E1.00009: Temperature Dependency of Electrostatic Breakdown in LDPE and PEEK Tyler Kippen, Allen Anderson, JR Dennison Electrostatic breakdown is a leading cause of many of the anomalies and failures attributed to spacecraft interactions with the space environment. It is therefore critical to understand how the electrostatic field strength varies due to changing environmental conditions, including temperature and radiation dose. Standard step-up to electrostatic discharge (ESD) tests were performed on two polymers, low density polyethylene (LDPE) and polyetheretherketone (PEEK). Tests were done at room temperature and at other temperatures ranging from 130 K to 350 K. Preliminary analysis found that samples tested at a higher temperature had lower average breakdown field strength and a narrower distribution of breakdown field values. These results are considered with respect to a proposed dual-defect theory for electrostatic breakdown, which incorporates both lower energy recoverable defect modes that can be generated and annihilated through thermal annealing and higher energy irrecoverable defect modes such as those created by radiation damage. The model predicts that at lower electric field strengths, an annealing process occurs due to the higher temperature which limits the density of low energy defects in the material. This means that while the overall breakdown field strength decreases, the minimum field strength required to breakdown the material would increase, thereby narrowing the breakdown distribution. [Preview Abstract] |
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E1.00010: Photochemistry with Diamond Jonathon Barkl, Anna Zaniewski, Robert Nemanich In this project, we are exploring thin films of diamond on various substrates for photochemistry through electron emission induced by light in the visible spectrum. Diamond is unique as a semiconductor due to its large 5.5 eV band gap, and can have a negative electron affinity, meaning the conduction band edge is at a higher energy than the vacuum. This property allows the electrons emitted through photoemission to be used as an energy ``reservoir'' for energy intensive reduction reactions, such as the reduction of nitrogen gas to ammonia. This project will explore the properties of the diamond films in order to determine if photoemission and chemistry are possible with diamond in the visible light spectrum, with lower photon energies than previously demonstrated. This will require the lowering of the effective work function, the energy required to excite electrons from the valence band to the conduction band. The first phase of this project will be to recreate previous experimental results achieved using ultraviolet light on diamond films on molybdenum substrates. In the second phase, we will study the physical properties of the diamond films, various substrates, and other properties in order to achieve the necessary low effective work function. [Preview Abstract] |
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E1.00011: Alkali-metal (M) dihydrogen phosphates MH$_{\mathrm{2}}$PO$_{\mathrm{4~}}$stability at superprotonic behavior temperatures. Israel Martinez, Andrea Montgomery, Juan Leal, Alan Goos, Andres Encerrado, Cristian Botez Alkali-metal (M) dihydrogen phosphates MH$_{\mathrm{2}}$PO$_{\mathrm{4~}}$(solid acids) have a particular behavior, at high temperatures they show a huge proton conductivity increase (1000-fold) (e.g. RbH$_{\mathrm{2}}$PO$_{\mathrm{4}}$~and CsH$_{\mathrm{2}}$PO$_{\mathrm{4~}}$(CDP)) upon heating above a certain temperature TS. The so called~superprotonic~behavior observed in CDP~at temperatures above~TS$=$237C has been previously reported; and this behavior is particularly attractive to use alkali-metal dihydrogen phosphates as a fuel cell electrolytes in the intermediate temperatures range. ~A major drawback is that~the cubic CDP~phase (which have been previously debated to be the main cause to generate the superprotonic behavior in the solid acids) is not stable~under ambient humidity and pressure conditions at TS temperatures, becoming a huge barrier to mass production. Indeed,~CDP dehydrates and decomposes chemically after its polymorphic transition from the room temperature (RT) monoclinic phase to the HT cubic.~ ~In order to treat the CDP and become more stable, dopants (such as SiO$_{\mathrm{2}})$ in combination of different humidity conditions have been tried to delay the dehydration of the CDP after the superprotonic its been achieved. [Preview Abstract] |
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E1.00012: Crystalline structure of Solid Acid under different partial pressures Alexandra Dominguez, Cristian Botez Solids acids (such as Cesium Dihydrogen Phosphate CsH$_{\mathrm{2}}$PO$_{\mathrm{4\thinspace }}$(CDP)) have the particular property to become \textit{superprotonic} at temperatures around 232 C (that is, its proton conductivity suddenly increases around three figures) which makes them attractive to be used as electrolytes for fuel cells. Unfortunately, around the temperature that they become \textit{superprotonic}, they start to dehydrate too. In order to overcome this problem the sample was ran under a humid atmosphere. X-Ray Diffraction technique (XRD) was used to analyze the crystal structure of the CDP sample. This is relevant since the nature of the super protonic behavior of the sample is attributed to a polymorphic change transition from monoclinic (room temperature (RT)) to cubic at 232C. [Preview Abstract] |
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E1.00013: Conductivity of Cs$_{\mathrm{\mathbf{1-x}}}$\textbf{Si}$_{\mathrm{\mathbf{x}}}$\textbf{H}$_{\mathrm{\mathbf{2}}}$\textbf{PO}$_{\mathrm{\mathbf{4}}}$\textbf{ trough Impedance spectroscopy: Partial pressure and temperature dependence study}? Matthew Hilding, Cristian Botez The purpose of this study is to find a correlation of an induced cubic phase in Phosphate solid acids due to applied heat and proton conductivity. In order to calculate the proton conductivity the application of the Nernst--Einstein equation. \newline In this study we used different partial humidity pressures with a combination of Cesium Dihydrogen Phosphate CsH$_{\mathrm{2}}$PO$_{\mathrm{4}}$ (CDP) with SiO$_{\mathrm{2}}$, to provide more stability to the sample. We tested different ratios of CDP/SiO$_{\mathrm{2}}$ under different partial pressures. Electrochemical Impedance Spectroscopy techniques (EIS) techniques were used to determine the impedance of the samples, later used in the Nernst--Einstein equation. [Preview Abstract] |
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E1.00014: Spectroscopic ellipsometry of NiO and Co$_{\mathrm{\mathbf{3}}}$\textbf{O}$_{\mathrm{\mathbf{4}}}$\textbf{ thin films with different orientations grown on SrTiO}$_{\mathrm{\mathbf{3}}}$\textbf{ substrates by polymer-assisted deposition} Qi Zhou, Alexandra P. Hartman, Hongmei Luo, Stefan Zollner NiO and Co$_{\mathrm{3}}$O$_{\mathrm{4}}$ films exhibit various interesting properties, such as excellent chemical stability, antiferromagnetic ordering and low light absorption. These properties have rendered them for potential application in protective coatings, electrochromic windows and nonvolatile resistance random access memory devices. NiO and Co$_{\mathrm{3}}$O$_{\mathrm{4}}$ films have been prepared by a number of techniques, including pulsed laser deposition, sputtering, atomic layer deposition and sol-gel method. We have prepared epitaxial NiO and Co$_{\mathrm{3}}$O$_{\mathrm{4}}$ thin films with different orientations (001), (110), (111) grown on three orientations of single crystal SrTiO$_{\mathrm{3}}$(001), (110), (111) substrates by a solution method, called polymer-assisted deposition. Analyses from x-ray diffraction revealed the epitaxial relationship between the films and the substrates. Atomic force microscope showed that those films have very smooth surface with rms surface roughness less than 1 nm. Their optical properties were investigated by spectroscopic ellipsometry. [Preview Abstract] |
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E1.00015: Indium Doping Induced Lattice Constant Variation in Tin Pyrophosphate Heber Martinez, Cristian Botez, Joshua Morris SnP$_{\mathrm{2}}$O$_{\mathrm{7}}$ and Sn$_{\mathrm{1-x}}$In$_{\mathrm{x}}$P$_{\mathrm{2}}$O$_{\mathrm{7}}$ (x from 0 to 0.2), were synthesized and characterized by X-ray diffraction over a range of temperatures and pressures. XRD confirmed indium solubility limit to be x$=$0.12. LeBail and Rietveld refinements confirmed the room temperature structure of the undoped and doped material to be the Pa-3 space group and that doping induced an increase in the lattice constant a with temperature increase. a reaches its highest value at doping level x$=$0.1, consistent with its highest value of protonic conductivity as measured by Nagao et. al. XRD measurements under an evacuated atmosphere, and under 5 bar of He pressure, inhibited the lattice constant a increment, providing a hint for the mechanism of proton incorporation to the bulk and enhancement in conductivity. [Preview Abstract] |
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E1.00016: Correlations Between Thickness and Nanostructure in Soft-Templated Mesoporous Carbon Membranes Francisco Ayala Rodriguez, Pasquale F. Fulvio, Lawrence M. Anovitz, Jose L. Bañuelos The arrangement of mesopores in soft-templated porous carbon has been studied using small-angle x-ray scattering (SAXS). The highly porous (\textasciitilde 8nm pore size) materials studied herein are promising for energy storage and are good model systems to probe the properties of fluid-solid interfaces. One step during synthesis requires the drying of a thin gelatinous sheet of the material. Variations in the thickness of the membranes are present and it is important to know the extent to which structure changes over large length scales (few mm). SAXS measurements reveal that the signal changes across the sample. Data reduction included, transmission corrections, detector dark noise and empty instrument background subtraction. A correlation between sample thickness and mesoporous structure, in which thin sections exhibit a more ordered porous structure of the cylindrical pores, was observed. Also, a nonmonotonic change in the pore-pore correlation distance as a function of thickness. These results highlight the importance of accounting for thickness-dependent nanostructure variations in experiments requiring large samples. [Preview Abstract] |
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E1.00017: Optical Second Harmonic and Multiferroic Properties in LiNbO$_{\mathrm{\mathbf{3}}}$\textbf{ and LiLaNbO}$_{\mathrm{\mathbf{3}}}$\textbf{ nanoparticles}. Carlos Diaz, Yu Ding, Aurelio Paez, Yongdong wang, Chunqiang Li, Jorge Portelles, Abel Hurtado, Jorge Lopez We present a solid-state synthesis of lithium niobate (\textit{LiNbO}$_{3})$ and lithium lanthanum niobate nanoparticles (\textit{La}$_{0.05}$\textit{Li}$_{0.85}$\textit{NbO}$_{3})$ with their corresponding structural aspects, ferroelectric/ferromagnetic and second harmonic generation properties. \textit{LiNbO}$_{3}$ and \textit{La}$_{0.05}$\textit{Li}$_{0.85}$\textit{NbO}$_{3}$ was prepared using lithium carbonate, niobium oxide and lanthanum oxide as precursors, respectively. X-ray diffraction and Raman spectroscopy indicates the formation of ferroelectric/ferromagnetic phase obtained in hydrogen atmosphere with spherical shape as confirmed by TEM micrographs. Hysteresis loop was determinate with the objective to determinate the behavior ferroelectric Relaxor properties with the influence of the La doped new in this system. Fine structures of the material are revealed by studying the Second Harmonic Generation profiles. [Preview Abstract] |
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E1.00018: Small angle light scattering as a micron-scale structural probe of porosity Greggory McPherson The ability to characterize and measure changes to the pore structure of materials across multiple length scales as a function of physical or chemical processes is of interest for many energy storage, industrial filtration, and environmental remediation applications. Ultra-small and small-angle x-ray and neutron scattering are effective structural probes for features from roughly 1 nm to 1 $\mu$ m, but as some pore structures can span 7 orders of magnitude, a structural probe for micron length scales is required. Employing longer wavelengths, small-angle light scattering (SALS) is able to probe structural features from one to hundreds of microns, bridging the gap in accessible Q between USANS/USAXS and quantitative analysis of electron micrographs. Though SALS has been well developed for studying polymers and biomolecules, its application to multiphase bulk solids is less established. A SALS instrument was designed and built in collaboration with the Geochemistry and Interfacial Sciences group at ORNL. The calibration of this instrument and its ability to characterize pore structure in thin sections of sandstone will be discussed. The use of this technique in finding changes in water's structure with micron-scale confinement is also assessed. [Preview Abstract] |
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E1.00019: Quantum Mechanical Calculation of Thermodynamic Properties and Infrared Spectra of Zirconium Complexes for Selective Oxidation Catalysis Chao Dong, Thomas Manz Selective oxidation of organic substrates is an important process for producing chemical intermediates used in industry, lab chemicals, and pharmaceutical products. It is still challenging not to produce unwanted co-products. Recently published computations predict efficient molecular oxygen activation and selective oxidation of organic substrates using a newly designed zirconium organometallic complex that does not require any co-reductant (B. Yang and T. A. Manz, Theor. Chem. Acc., 2016, 135, 21:1-19 and RSC Adv., 2016, 6, 88189-88215). Here, quantum mechanical calculations are performed using Density Functional Theory to obtain the enthalpy and Gibbs free energy of this zirconium organometallic complex. These results provide insights for designing an experiment to synthesize this Zr complex and test its reactivity in lab. Infrared and hydrogen NMR spectra are calculated for various reaction intermediates to enable a comparison to experimentally measured spectra in order to elucidate the reaction mechanisms and side reactions. [Preview Abstract] |
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E1.00020: Water Sorption in Nanoporous Carbon Electrode Materials Jose Ali Espitia, Jose L. Banuelos, Volker Presser, David J Wesolowski, Gernot Rother Carbide derived carbon (CDC) has garnered much attention as a supercapacitor electrode material. A unique feature of CDC is it's fine-tuned pore size in the subnanometer range, which depends on the initial carbide (TiC) and annealing conditions. Water can enter TiC-CDC pores and give filling fractions in excess of 0.6 g/g (H$_{\mathrm{2}}$O/C). Recent reports of water's diffusional dynamics dependence on CDC pore size indicate confinement effects similar to observed in pores of 16 Angstroms. Though other studies have gleaned insights into the porous structure of CDC, there is currently no direct structural information on the sorption of water at intermediate stages between completely empty and full. Small-angle neutron scattering (SANS) was used to find to what degree pores are filled with water (D$_{\mathrm{2}}$O) at intermediate stages of loading for four TiC-CDC powders, each with different pore size distributions. We present models being developed to reproduce the SANS data and extract information on 1) the structure of CDC, consisting of subnanometer and meso-pores, 2) the kinetics of water sorption in porous media. Being relevant to fundamental studies of water in confinement for its role in supercapacitors, which is still not fully understood. [Preview Abstract] |
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E1.00021: Characterization of Zinc Oxynitride Thin Films Meagan Parker, Charles Smith, Nicholas Allen, Colin Inglefield, Kristin Rabosky Liquid crystal displays (LCDs) and organic light emitting diodes (OLEDs) use oxide based thin film transistors. Zinc oxynitride (ZnON) is a candidate for next generation electronics in LCDs and OLEDs. Here we investigate the correlations between the composition of ZnON and its calculated band gap energy. The composition of our samples is found using energy dispersive x-ray spectroscopy. For the band gap measurements, we have designed and built our own ultraviolet-visible spectrophotometer (UV-VIS). Using the transmission data from the UV-VIS we calculated the band gap energy of the material. We will discuss the experimental methods used to achieve our results. [Preview Abstract] |
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E1.00022: Spectroscopic and Microscopic Analysis of Graphene for Sensor Applications Tamanna Khan, Chao Qiu, John Ciubuc, Kevin Bennet, William Durrer, Felicia Manciu As a two-dimensional material, graphene shows very good thermal and electrical conductivities, which, with its unique optical properties, makes it suitable for a variety of applications. In this study we present detailed investigations by confocal Raman and Drude model analysis of the material's changes and improvements, as it transitioned from 3D graphite to 2D graphene. Besides Raman spectral recording, which can detect single, a few, and multi-layers of graphene, confocal Raman mapping allows distinction of such domains and direct visualization of material inhomogeneity. Moreover, far-infrared transmittance measurements, which are related to electrical conductivity, demonstrate a distinct increase of conductivity with dimensionality reduction. These measurements are particularly suited to determining important material characteristics, including time constant (the inverse of the average time between two carrier-core collisions), carrier concentration, and conductivity by using a Drude-like model. Such information is valuable for developing bio-medical sensors, which is the main application envisioned for this work. [Preview Abstract] |
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E1.00023: Temperature-dependent dielectric function of nickel Stefan Zollner, T.N. Nunley, D.P. Trujillo, L.G. Pineda, L.S. Abdallah Confirming historical results from Ornstein and Koefoed (1938), we found an anomaly in the optical constants at 1.96 eV for bulk nickel near the Curie temperature through careful high-precision spectroscopic ellipsometry measurements from 80 to 800 K. The anomaly is only seen in sweeps with increasing temperature if the sample carries a net magnetization. In decreasing temperature sweeps or for unmagnetized samples, the anomaly is absent. The sign of the anomaly in the optical conductivity at 1.96 eV is in contrast to the sign of the anomaly in the electrical DC conductivity. The anomaly is rather large and therefore explained with changes in the on-diagonal Drude--Lorentz portion of the dielectric tensor. No sign of anisotropy (polar magneto-optical Kerr effect) is found in the data. [Preview Abstract] |
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E1.00024: Negative Differential Resistance of WSe$_{2}$ and HfSe$_{2}$ Diodes J.A. Cooke, A. Shahrabi, M. Hasan, B. Sensale-Rodriguez Exploration in advanced materials may yield improved tunnel junction size, higher frequency limits, and better efficiency. 2-dementional (2D) layered materials are emerging as possible solid-state materials that could be used for this. Tungsten diselenide (W ) and hafnium diselenide (Hf ) were the 2D materials chosen by our group to make high frequency resonant tunneling diodes (RTD) due to their unique band gaps. Using mechanical exfoliation, thin flakes were transferred onto bulk silicon dioxide to make the devises. An atomic force microscope (AFM) was used to determine the exact height and amount of layers while an electron beam (e-beam) of a scanning electron microscope (SEM) was used to make the leads. The devices were tested on a probe station with a Keithley 2400 source meter unit. Due to the tunneling effect, theses devises should be able to have a negative differential resistance (NDR). If the experimental results are successful, we will have demonstrated smaller devices with higher frequency limits and better efficiency. [Preview Abstract] |
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E1.00025: Experimental Errors in Mueller Matrix Elements of Isotropic Samples F Abadizaman, J Moya, S Zollner Ellipsometry is to study the electronic properties of materials. Using a polarizer-sample-rotating analyzer (PSrA) ellipsometry configuration, polarized incident and reflected beams are described by Jones vectors. The effect the sample has on the incident polarization state is given by the Jones matrix. In general, this type of ellipsometry only works for non-depolarizing samples. To study depolarizing samples, generalized Mueller matrix ellipsometry (MME) is used. In MME, the Stokes vectors represent the polarization state of the incident and reflected beams, and the Mueller matrix describes the effect the sample has on the beam. The configuration used in this study is given by: polarizer-compensator-sample-rotating analyzer (PCSrA), in which 11 of the 16 MM elements can be measured. In the special case that the sample is non-depolarizing, the MM has a simple pattern and can be transformed into the Jones matrix. Four samples representing insulating, metallic, and semi-conducting materials were measured from 1 to 6 eV using MME. The measured MM elements are consistent with the MM for isotropic, non-depolarizing samples. Furthermore, to understand the experimental error in future experiments, straight-through MME measurements were taken. [Preview Abstract] |
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E1.00026: X-Ray Reflectometry Studies of Ti Thin Film on Si (100) Binod Paudel, Heinrich Nakotte, Jarek Majewski, Erik Watkins X-ray reflectometry was used to determine the dimensions and surface/interface features of a titanium thin film deposited on a silicon (100) wafer. Specular X-ray reflectivity studies provide insight into the depth variation of the density, thereby providing insight into the film thickness, the (interfacial or surface) roughness and the homogeneity of the film. While the data analysis of the experimental reflectivity data of our sample is largely consistent with an ~100 nm Ti film on Si(100), there are some features in the data that are indicative of additional surface and/or interface layers, such as oxides. We present our attempts to model such additional features present in the data. [Preview Abstract] |
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E1.00027: Changes in the Coherent Dynamics of Nanoconfined Room Temperature Ionic Liquids Kevin Vallejo, Melissa Cano, Son Li, Gernot Rother, Antonio Faraone, Jose Bañuelos Confinement and temperature effects on the coherent dynamics of the room temperature ionic liquid (RTIL) [C$_{10}$MPy$^{+}$] [Tf$_{2}$N$^{-}$] were investigated using neutron spin-echo (NSE) in two silica matrices with different pore size. Several intermolecular forces give rise to the bulk molecular structure between anions and cations. NSE provided dynamics (via the coherent intermediate scattering function) in the time range of 0.004 to 10 ns, and at Q-values corresponding to intermediate range ordering and inter- and intra-molecular length scales of the RTIL. Pore wall effects were delineated by comparing bulk RTIL dynamics with those of the confined fluid in 2.8 nm and 8 nm pores. Analytical models were applied to the experimental data to extract decay times and amplitudes of each component. We find a fast relaxation outside the experiment time window, a primary relaxation, and slow, surface-induced dynamics, which all speed up with increased temperature, however, the temperature dependence differs between bulk and confinement. This study sheds light on the structure and dynamics of RTILs and is relevant to the optimization of RTILs for green technologies and applications. [Preview Abstract] |
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E1.00028: Degradation of perovskite samples over time Nazia Sharmin, Jorge Lopez, Deidra Hodges, Saimum Shahriar, Venessa Castaneda, Mishra Aditya In this work 24 perovskite samples prepared in four different process, named 1st step, 2nd step, 3rd step method and hot cast to observe the degradation of the samples over time by XRF gun.. Six out of 18 were prepared under 1st step method in which the PbI2 and MAI solutions are mixed together (creating CH3NH3PbI3 ). Other six (2nd step) in two steps process the PbI2 and MAI solutions were separated..Six samples were prepared in third step process which was a solvent to solvent extraction method (SSE).. Afterwards These 18 samples annealed in 90, 100,130,160,200 temperature. In hot cast process Perovskite precursor solution was made by dissolving PbI2 (0.462g) and MAI (0.1589 g) in DMF solvent (2ml). Six samples were prepared under the hot cast process annealed in 155C, 165C, 175C, 185C 195 C. The samples were subjected to XRF studies for 5 minutes. These 24 files were analyzed with a software called PyMca,format .Each of these files contains peak plots, fit parameters and a table with concentration measurement. Composition of 1st step process and hot cast degraded very slowly compared to other two processes which turned into PbI2 within two week of the preparation [Preview Abstract] |
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E1.00029: Light Scattering from Aerosol Particles in the Presence of Humidity Miguel Cortez, Robert McAfee Light scattering phenomena of particles has played a vital role in the investigation of aerosols in the atmosphere. Many computational methods have been developed to explore light scattering phenomena such as Mie theory, Coated Mie, the T-matrix, and the code created by Quirantes for irregularly shaped particles. In this project we investigate and compare the computational scattering coefficients of coated particles using Mie theory to that of actual data. The Mie theory code is specific to only particles of spherical nature and is proposed to fit scattering data collected at humidity above 40 percent. It is proposed that the particle accumulates a water shell which changes the particle's three dimensional geometry to that of a sphere. Below the 40{\%} humidity line, particles may accumulate a thin shell of water but retain their irregular shape. In this project we also work with the recent Quirantes code to further understand light scattering properties of irregularly shaped particles and compare it to the data collected. Future work will be to find where Quirantes and the Mie codes correlate best with data and confirm the 40{\%} humidity mark where particles are more spherical in geometry and can be approximated to be spheres. [Preview Abstract] |
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E1.00030: Insitu experimental setup to study magneto-electric effects in a single nanoparticle using Bragg coherent diffraction imaging Hannah Rich, Dmitry Karpov, Ross Harder, Edwin Fohtung Phase transitions in multiferroic and ferroelectric materials are important for the development of spintronic devices, solar cells, catalysis, energy and information storage. We report on a recently developed insitu experimental setup to study phase transitions in multiferroic nanostructures by means of Bragg coherent diffraction imaging. By using a system capable of providing variable waveforms of pulsed electric and magnetic field uniformly on sample's crystallographic direction, we were able to map local ferroelectric phase transitions in a single nanoparticle. The system is capable of driving the sample with electric field up to 5MV/cm with a pulse of variable shape and duration while simultaneously applying pulsed magnetic field of up to 0.5mT both synchronously and asynchronously. Hall effect sensors provide real-time feedback for calibration and adjustment of magnetic field. In this poster, we highlight the capabilities of our setup to study hundreds of ps to ms dynamics in a single magneto-electric nanostructure under applied EM-field using Bragg coherent diffraction imaging. Further development will allow to synchronize the pulsed fields and arriving pulses of synchrotron radiation to increase the accessible temporal resolution of the experiment. [Preview Abstract] |
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E1.00031: Towards Using Resonant Ultrasound Spectroscopy (RUS) to Investigate Spin-Lattice Couplings in Magnetic Materials Tyler Dodge, Kate Ross All materials have fundamental frequencies at which they naturally vibrate.~ Resonant ultrasound spectroscopy (RUS) is a measurement technique in which a solid is vibrated at a range of frequencies in search for resonance within the material. A RUS measurement is intended to discover the elastic properties of the material, which are described by an elastic tensor consisting of up to 21 unique elastic constants. These elastic constants are the description of the material's feedback to enforced stress, and they originate from the effective ``stiffness'' of the crystal lattice due to bonding and atomic interactions.~ The samples' elastic properties change depending on properties of the specimen such as crystallinity, symmetries, temperature, and magnetic state (e.g. ferromagnet vs. paramagnet). The goal of our research is to identify the coupling of magnetic moments to the crystal lattice through temperature and magnetic field dependent RUS measurements. To do this we must integrate a RUS probe with the Central Instrument Facility's (CIF's) Physical Property Measurement System (PPMS), which will allow low temperature and high magnetic field scans. By modeling the way crystals elastic constants change with respect to temperature and field, we can better understand magnetoelastic coupling effects and their role in quantum magnetic phenomena. [Preview Abstract] |
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E1.00032: Magnetic Susceptibility of CoNb$_{\mathrm{2}}$O$_{\mathrm{6}}$ Timothy Reeder, Kate Ross The exactly solvable transverse field Ising chain (TFIC) is the canonical model for the study of Quantum Phase Transitions (QPT). Despite the wealth of magnetic materials available, there are surprisingly few material examples of the TFIC. One well-known example is CoNb$_{\mathrm{2}}$O$_{\mathrm{6}}$, which behaves like the TFIC near its field-induced QPT: at low temperatures, a second order quantum phase transition exists near H$_{\mathrm{c\thinspace }}=$ 5.5 T. Geometric frustration between the ferromagnetic Ising chains of cobalt introduces a propensity for defect formation between chains, and these may play a role in allowing the QPT to behave like the TFIC despite 3D magnetic order. In order to study the effect of domain wall defects near the QPT in CoNb$_{\mathrm{2}}$O$_{\mathrm{6}}$, we have synthesized a single crystal using the floating zone method. Here we report ac susceptibility measurements, which are sensitive to the free chains generated by domain walls in this frustrated system. These measurements will form the basis for our future study of non-equilibrium effects in CoNb$_{\mathrm{2}}$O$_{\mathrm{6}}$. [Preview Abstract] |
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E1.00033: Measurement Setup for Resistivity RAM Devices James Talbert, Darrell Adams, Jose Mayorga, Wilhelmus Geerts The market for non-volatile memory is potentially about to hit a brick wall with the flash technology as it might not be scalable beyond the 14nm node. The need for other storage devices is a hot topic in said market, and one possibility is Resistive RAM (RRAM) devices. These devices can store information through a reversible switch from high to low resistance. The material that is being studied consists of NiO sandwiched between Pt electrodes. A shadow mask set consisting of three stainless steel masks was designed. Device test wafers with different oxygen concentration were made by rf magnetron sputtering. Each wafer contained 9 four-point probe devices with different dimensions. To measure the resistivity and switching properties of the device wafers, we created a measuring station. Electrical connections between the test station and the device wafers are made by a 6x6 array of pogo pins that can be lowered onto the sample. Connecting a device to four pogo pins allows for a voltage to be applied across two pins while the other pins can measure an IV curve. In addition to the setup preliminary results on an oxygen series of RRAM devices wafers will be discussed. [Preview Abstract] |
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E1.00034: Synthesis and Characterization of Gold Thin Films Evan Wyatt, Connor Luckett, Andra Petrean, Jesus Avila, Carlos Avila, Manuel Quevedo-Lopez In this study, we investigated the properties of gold thin films. We synthesized samples thinner than 50 nm by physical vapor deposition onto glass substrates. We subsequently characterized the electrical properties of the thin films through Hall effect measurements. The optical properties were determined through spectroscopy measurements between 300 to 1,000 nm by recording transmission spectra and extracting the absorption coefficient of our samples, using the Beer-Lambert law. We consider a method of using the absorption coefficient to determine the thickness of thin films [Preview Abstract] |
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E1.00035: Imaging of twinning defects in Au nanoparticles with Bragg Coherent Diffraction Imaging Dmitry Karpov, Douglas Brown, Edwin Fohtung In condensed matter physics and material sciences phase transitions are usually accompanied by creation, annihilation and propagation of topological defects. For transition-metal nanoparticles the presence of such defects can mediate structure-property relation, leading to strain engineering of plasmonic, electronic and magnetic functionality. Here we use Bragg Coherent Diffraction Imaging (BCDI) to map 3D distribution of defect in gold nanoparticle. BCDI is a technique capable of imaging 3D electron density distribution along with atomic and ionic displacement fields at nanoscale resolution through recording and iterative reconstruction of far-field patterns of the sample. In the current work we used improved reconstruction technique to refine for solving for highly strained nanocrystals. [Preview Abstract] |
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E1.00036: Ion Sheath Creation in the Inductively Coupled Plasma Mass Spectrometer Joseph Chandler Between the skimmer cone and the mass analyzer of an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) lies an electrostatic ion lens. This lens uses a large negative potential to remove the electrons from the weakly ionized plasma and to collimate the ions in the plasma, forming a plasma sheath. This interaction can be modeled computationally by using Boltzmann electrons and collisionless ions. Their combined effects can be used to calculate the potential and the ion density within this region. For simplification, this calculation is carried out on a cylindrically symmetric grid. This version of Poisson's equation is a second order nonlinear partial differential equation which is solved using a banded-matrix direct solver. The solution is found by iterating until self-consistent values for the potential as a function of position are obtained. This is a plasma sheath calculation, but no ion pre-sheath is needed due to the supersonic velocities of the ions. By calculating the position of the plasma sheath as a function of the ion lens potential we can better describe how the ion lens directs the ions into the mass spectrometer. [Preview Abstract] |
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E1.00037: Order in Chaos: an Algorithmic Approach to Holistic Flocking Behavior Garett Brown, Manuel Berrondo The emergent behavior of certain collective systems such as starling murmurations reveals coherent behavior arising from the simple, individual interactions of its entities. Using a two-dimensional algorithmic model, we can show that self-driven particles (boids) group together and display emergent flocking characteristics. The model is based on the ideas of consensus and frustration as well as the dynamic interplay between global and local phase transitions. The frustration is a perturbation that drives the boids beyond the simple phase transitions and towards chaotic behavior while the consensus is a topological averaging, that balances the frustration. The results are interpreted in terms of global and local order parameters, and correlation functions. [Preview Abstract] |
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E1.00038: Electron Collisions and Ionization of Argon Gas in the Inductively Coupled Plasma Mass Spectrometer Carson Evans, Ross Spencer The plasma torch of the Inductively Coupled Plasma Mass Spectrometer (ICP) is powered by a 3-turn coil attached to a radio-frequency generator running at 40 MHz. The discharge is started by a Tesla coil that briefly ionizes a small fraction of the argon gas flowing through the coil. After the initial ionization pulse, the RF field produces the electric field that gives the electrons enough energy to either exciting or ionizing the argon atoms. We are modeling the effect of the RF field on the electrons, as well as the effect of collisions between electrons with neutral, excited, and ionized argon and with other electrons. We eventually will also include the possibility of de-excitation and recombination of the argon. Our goal is to see an electron avalanche, a chain reaction as electrons accelerate away from the argon ions and collide with neutral argon atoms, causing them to ionize also, and then to see the resulting plasma come to steady state. We find that normal operating condition of the RF coil does not produce a strong-enough electric field to ionize argon; an initial high-field transient is needed. The details of how the electrons evolve during startup will be presented. [Preview Abstract] |
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E1.00039: Recent Developments in Computing the Properties of Atoms in Materials Nidia Gabaldon Limas, Taoyi Chen, Thomas Manz Recent advances in computing power are making it ever more practical to use quantum chemistry methods to study complex materials. A key challenge is to extract meaningful insights from the results of these computations. Although net atomic charges (NACs), bond orders, and magnetic moments are widespread chemical concepts, their computation requires specialized methods. The Density Derived Electrostatic and Chemical (DDEC) method optimizes atomistic descriptors to accurately reproduce both the chemical states of atoms in materials and the force fields surrounding the material. This makes them ideally suited both for studying the chemical properties of materials and for constructing force-fields used in classical molecular dynamics or Monte Carlo simulations. The latest generation of this method, called DDEC6, offers substantial improvements in accuracy and computational cost compared to prior generations. The DDEC6 method assigns NACs, atomic spin moments, effective bond orders, atomic multipole moments, polarizabilities, and dispersion coefficients using only the total electron and spin distributions of the material as inputs. To assess the accuracy of this approach, comparisons of computed to experimental results will be presented for a broad range of periodic and non-periodic materials. [Preview Abstract] |
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E1.00040: Investigation of Shock Induced Amorphization in Metallic Single Crystals Celia Garcia Amparan, Ramon Ravelo Recent large-scale non-equilibrium molecular dynamics simulations of shock propagation in metals (Cu, Al, Ta) have shown melting at the shock front for temperatures much lower than the equilibrium melt temperature of the material, at the corresponding shock pressure. The nature of this phenomenon can be associated with amorphization of the material brought about by the loss of shear rigidity at the very high elastic deformations reached in the pressure range where this phenomena is observed. In this work amorphization is examined by evaluating phonon dispersion and sound velocities in single crystal Copper as a function of compressive strain along the (110) direction. Phonon instabilities were characterized by eigenmodes which describe the behavior of the system in a coordinate space. We show that above a critical strain, the shear modes become imaginary, indicating a dynamical instability in the wave propagation of shear waves in the sample. [Preview Abstract] |
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E1.00041: Fish Switching Schools: Emergence of Consensus in a Boolean Belief Network Jake Christensen, David Griffin, David Peak Many natural (e.g., insect swarming) and engineered (e.g., cloud computing) networks consist of locally connected units with no central processing unit (CPU). Optimal task-performance by such networks depends on the units achieving consensus, via self-organized dynamics, of what their internal states should be. Experiments using fish that are trained to school toward colored targets yield hints for understanding and designing functional CPU-less networks. One experiment involves two targets of different color and two populations each trained on one of the colors. If one population is in a small majority, the two schools are stable: each member holds an unshakable ``Boolean belief'' of the correct color. Introducing a few untrained fish can cause all of the fish to school toward the color of the initial majority. The undecided fish apparently enable the whole network to perform the ``initial majority task.'' Directed, local, three-fish interactions that harbor ``residual synergy'' somehow make this consensus possible. To investigate the essential aspects of such collective dynamics, we study a binary cellular automaton on a square lattice with nearest neighbor interactions. The update rule is ``if the current state of a cell is 1, then adopt in the next instant the majority state of that cell plus its north and east neighbors, otherwise use the south and west neighbors.'' This rule accurately senses the majority over a wide range of randomly distributed initial states and shows precisely how checkerboard (i.e., undecided) patches propagate through the network switching the Boolean beliefs of cells in their paths. [Preview Abstract] |
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E1.00042: The Structure of the N-terminal end (1-961 aa) of Txo2: an important player in the synthesis of the antibiotic teixobactin Raul Higuera, Dominka Borek, Zbyszek Otwinowski Every year, 2 million people are infected with~drug resistant~bacteria and many die from~infections. Understanding the sources of antibiotics is one important step to finding solutions to combat drug-resistant bacteria. E. terrae is a gram negative bacteria that produces the antibiotic~teixobactin. A fragment (1-961 aa) of the Txo2 gene in E. terrae encodes the production of an important enzyme involved in the synthesis of teixcobactin. We are interested in the sites of the fragment that help synthesize necessary enzymes. Thus, we solved the 2.8{\AA} crystal structure of the fragment at Argonne National Laboratory. The structure was processed using~WinCoot~and REFMAC and analyzed using programs and servers: -BLAST, Consurf, and DALI. We found that Txo2 contains three domains: a condensation domain,~an HxxPF~domain, and canonical fold of non-ribosomal peptide~synthetases, or NRPS, domain. We analyzed several properties, e.g. the evolutionary conservation, to find molecular level components responsible for important actions.We found that the structure of the N-terminal end of Txo2 is responsible for adding the Ser residue to~teixobactin. [Preview Abstract] |
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E1.00043: Protein solution-state structure, intermolecular interactions, and tracking aggregation using small-angle x-ray scattering Crystal Rodriguez, Raul Higuera, Jacquelyn Kim, Emmanuel Zubia, Mahesh Narayan, Jose Banuelos Investigating the structural properties of proteins during their folding/unfolding may elucidate the reasons why debilitating protein mis-folding diseases occur. In solution, protein concentration, solvent properties, and the presence of other molecular species impact protein intermolecular interactions including binding events and aggregation. Small-angle x-ray scattering experiments over a Q-range of 0.01 -- 0.6 {\AA}\textasciicircum -1 are being used to investigate the nanoscale shape and interactions of the proteins hen egg-white lysozyme and human serum albumin at concentrations of 0.01, 0.1, 1 and 10 mg/ml. As concentration increases, interactions increase and this approach allows us to distinguish protein shape from interactions. The ATSAS analysis software suite allow us to apply models to the SAXS data and obtain the structure of the proteins, including their size, as well as generating solution-state SAXS profiles from protein data base (PDB) files. This preliminary work will set the stage for structural studies of temperature induced aggregation, fibril formation of amyloid fragments (amyloid-beta fibrils are prevalent in Alzheimer's disease), and the possibility of fibril disruption by tanshinone compounds. [Preview Abstract] |
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E1.00044: Surfactant Free Aqueous Emulsions Jacob Urquidi, Joshua Amburgey, Greggory McPhearson The stabilization of hydrophobic colloids, such as oil droplets, in water has attracted scientist for a long time for a variety of scientific, pharmaceutical and industrial applications. Several studies have been done to understand the stability of oil-in-water emulsions. Pashley and coworkers have proven that the removal of dissolved gasses from water enhances the dispersion of hydrophobic oil in water and these surfactant free emulsions do not lose their stability when the previously removed gasses are reintroduced. This work has demonstrated the formation of a stable emulsion of Silicone Oil in degassed ultra-pure water alone. The emulsion droplets were on the order of 50 nm in diameter and stable over a period of 8 hours. Stable emulsions of hydrocarbon oils in ultra-pure, degassed water were also prepared successfully, showing no oil/water separations after several freeze-pump-thaw cycles. Emulsions prepared in this manner were cloudy in appearance. However, after a day or two became completely clear with no oil/water separation. The formation of a stable emulsion in the complete absence of a surfactant could provide an alternative approach to a physiologically safe drug carrier. The emulsion's structure and stability were characterized using small angle x-ray scattering. [Preview Abstract] |
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E1.00045: Development of Label-free Raman Assessment of Metastatic Bone Matthew Alonzo, Chao Qiu, Avudaiappan Maran, Michael Yaszemski, John Ciubuc, Marian Manciu, Felicia Manciu Bone metastasis has a significant pathological impact in the form of bone fracture risks that are caused by chronic bone loss and degeneration. The goal of this study is to evaluate bone quality by Raman spectroscopy, which enables assessment and differentiation between non-cancerous and cancerous specimens. Besides spectral analysis of bone constituents and of the key biomarker in cancer identification, namely, the phosphate constituent, we also present representative confocal Raman maps of their distributions. The statistically significant number of spectra considered in this study validates the accuracy of our analysis from both perspectives: that of spectroscopic measurements and that of a statistical approach. [Preview Abstract] |
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E1.00046: Toward ab initio calculations of polymer structure and properties Marian Manciu, Sorour Hosseini In the absence of special symmetries (such as the translational symmetry of a crystal), ab initio calculations are limited to molecules of small sizes, much smaller than a typical polymer. We showed that the energetic and entropic contributions to the partition function of a long polymer can be separated via a variational procedure. This procedure allows the partition function of the polymer to be written as a sum over simpler (and shorter) configurations, such as trains, loops, tails and bridges, occurring with known probabilities, which depend on both their entropy and configuration energy (the later one taking into account the interactions with the rest of the system via a mean field Flory-Huggins approach). Because these configurations are much smaller than the original polymer, the procedure reduces drastically the number of molecules for which the\textit{ ab initio} calculations have to be performed. [Preview Abstract] |
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E1.00047: Automatic Studies 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 interstroke interval (ISI) E-field data fits to recognize whether continuing current (CC) exists within the interval. When detected, its duration and magnitude is measured. A relationship between the presence of CC, stroke order, stroke peak current, location relative to station, CC duration (when present),and ISI duration is studied. Datasets used are a few thousand flashes within 40 km of Langmuir Lab, New Mexico measured during the summer 2013 monsoon season. [Preview Abstract] |
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E1.00048: A high stability frequency standard using narrow linewidth atoms in an optical cavity Matthew Winchester, Matthew Norcia, James Thompson In this work we study a spectroscopic feature suitable for use as a frequency reference for laser stabilization that could offer an appealing compromise between frequency stability and experimental complexity. A cold ensemble of $^{88}$Sr atoms interacts with a single mode of a high-finesse optical cavity via the 7.5kHz linewidth, dipole forbidden $^1$S$_0$ to $^3$P$_1$ transition. The strong collective coupling between the atoms and cavity places the system in the vacuum Rabi splitting regime. By applying a magnetic field to split out the Zeeman sublevels of the $^3$P$_1$ state, we observe a small additional feature as a result of interference between the two dressed states. We demonstrate that this spectroscopic feature approaches the atomic transition linewidth and is highly immune to the type of reference cavity length fluctuations that limit current state-of-the-art lasers. [Preview Abstract] |
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E1.00049: Fine Structure Excitation Transfer in Rb-Buffer Gas Mixtures Jeremiah Wells, Alina Gearba, Randy Knize, Jerry Sell The purpose of this experiment is to measure the collisional excitation transfer rates between Rb 5P states in the presence of buffer gas mixtures. Rubidium is excited to the 5P$_{\mathrm{3/2}}$ state with a 780 nm photon and then collision with a buffer gas results in excitation transfer to the 5P$_{\mathrm{1/2\thinspace }}$state followed by emission of a 795 nm photon. Previous studies showed a nonlinear dependence of the excitation transfer rate with the He pressure. We interpreted this increase in terms of three body collisions and developed a theoretical model based on interatomic potentials to explain our experimental results. To better understand the three body collision process and further test our model, we are investigating the excitation transfer process in buffer gas mixtures of He-Ar and He-Xe. We expect to see an increase in excitation transfer in the presence of Ar or Xe even though their excitation rates are much lower than those of He. We will present our experimental results at the conference. [Preview Abstract] |
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E1.00050: Laser damage threshold measurement of optical coatings with picosecond pulses from a 1030nm diode-pumped Laser. Hanchen Wang, Travis Day, Elzbieta Jankowska, Brendan Reagan, Jorge Rocca, Carmen Menoni The damage characteristics and quality control methods of optical coating are of significant interest for all high power laser applications. Of interest is also the study of damage mechanisms for different laser pulse duration. We have developed a set-up to measure damage threshold of optical coatings at a wavelength of 1030nm with 220ps pulse duration. We have measured various samples including single layer HfO2, SiO2 coating, multilayers stacks and the reference fused silica substrate with a single laser shot on each damage site. A high energy diode-pumped, chirped pulse amplification laser was used for the measurement. The laser combines both room temperature and cryogenically cooled Yb:YAG amplifiers with a total of 80mJ, 220ps pulsed output at 20Hz repetition rate. The chirped pulse amplification system also offers control over the pulse duration. Fluence versus damage probability curves for each sample were obtained. [Preview Abstract] |
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E1.00051: An Empirical Three-Body Potential for Tetrahedral Liquids Joshua Amburgey, Jacob Urquidi, Greggory McPherson A simple three-body empirical potential function is proposed for computational studies of liquid water and other liquids possessing tetrahedral coordination. The potential is derived from a linear combination of nearly degenerate structural forms. The potential presented has three types of minima associated with the structure of liquid water; one nearest neighbor and two next-nearest-neighbor minima. The inner minima corresponds to the hydrogen bonded distance of 2.78{\AA} present in liquid water whilst the other two minima represent the non-hydrogen bonded neighbor normally present at a tetrahedral distance of 4.5{\AA} but which begins to occupy an interstitial distance of 3.4{\AA} with increased pressure, increased temperature, increased confinement, and changes in pH. The 3.4{\AA} distance is populated at the expense of the 4.5{\AA} distance and it is these two explicit bonding distances in the liquid which gives rise to the anomalous behavior of liquid water. [Preview Abstract] |
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E1.00052: Time-resolved Studies of 1,3,6-Substituted Fulvenes Anne Werkley, Nick Godman, Scott Iacono, Kimberly de La Harpe Fulvene-based compounds are of interest as accepting moieties in donor-acceptor organic molecules for molecular electronic materials. The photophysical and electrochemical properties of these compounds have been shown to be highly tunable depending on the fulvene ring substitution$^{\mathrm{1,2}}$. We report steady-state absorption and emission measurements along with emission lifetimes for a series of 1,3,6-substitued fulvene compounds. A better understanding of the excited-state dynamics of these compounds can guide the development of compounds optimized for use in donor-acceptor organic molecules and other applications. $^{\mathrm{1}}$A.J. Peloquin, R.L. Stone, S.E. Avila, E.R. Rudico, C.B. Horn, K.A. Gardner, D.W. Ball, J.E.B. Johnson, S.T. Iacono, G.J. Balaich, \textit{J. Org. Chem}. 2012, 77, 6371-6376. $^{\mathrm{2}}$E. Shurdha, B.K. Repasy, H.A. Miller, K. Dees, S.T. Iacono, D.W. Ball, G.J. Balaich. \textit{RSC Adv}., 2014, 4, 41989-41992. [Preview Abstract] |
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E1.00053: Isospin-symmetry dependent properties of nuclear matter Alan Salcedo, Jorge Lopez, Enrique Ramirez-Homs In this study, infinite nuclear matter is simulated employing Classical Molecular Dynamics for settings of 2000 nucleons. These simulations were done for configurations of isospin content X$=$Z/A$=$ 0.3, 0.4, 0.5 (where Z is the number of protons and A the number of nucleons) at temperatures of 10, 12, and 14 MeV with densities from 0.02 fm$^{-3}$ to 0.18 fm$^{-3}$. Results of previous investigations performed at temperatures of 1 to 5 MeV indicated that symmetric and asymmetric matter showed transitions of phase for subsaturation densities for all temperatures. Moreover, asymmetric matter showed reduced compressibility softened for increasing temperatures and a reduction of equilibrium densities. Now we performed 81 simulations of nuclear matter at higher temperatures at the High Performance Computing Center of the University of Texas at El Paso and numerical data was stored for immediate analysis. Our aim is to study the isospin dependence of bulk properties of nuclear matter such as the energy per nucleon, pressure, saturation density, and symmetry energy. [Preview Abstract] |
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E1.00054: Neutrino Oscillations: the RENO experiment Karla Tellez Giron Flores, Jesus Escamilla Roa, Jorge A. Lopez Gallardo Neutrinos are the Universe's second most common particles after the photons. The three flavor eigenstates are the mixture of the three mass eigenstates. This mixture of neutrinos can generally be parameterized by the three so-called mixing angles ($\theta_{12}$, $\theta_{23}$, $\theta_{13}$) and a CP phase. A non-zero value for $\theta_{13}$ has opened up a window to eventually be able to measure the above-mentioned CP phase, which provide information about the existing matter-antimatter asymmetry in the Universe. RENO (Reactor Experiment for Neutrino Oscillation) is a South-Korean experiment which studies electron antineutrinos from nuclear power plants to directly determine the value of $\theta_{13}$. In this work, we present an overview of the experiment as well as the results of the statistical analysis using the most updated data. [Preview Abstract] |
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E1.00055: High Altitude Dependence of Ionizing Radiation from Cosmic Rays Zachary Gibson, Akihiro Nagata, Midori Morikawa, Takuyuki Sakai, Takahiro Shimizu, Yuta Takahashi, Shusuke Okita, Raul Ramirez, Alexandra Hughlett, Toshihiro Kameda, JR Dennison Cosmic radiation was measured as a function of altitude using a compact Geiger counter aboard a high altitude balloon. Researchers from University of Tsukuba developed and flew the payload with the Utah State Get-Away-Special team. Dose rate, temperature, pressure, humidity, altitude and position data were acquired during a \textasciitilde 4 hour flight up to an altitude of 32 km in August 2016. The balloon reached an altitude more than 5 times the height of that reached by Victor Hess' experiment in 1912 and the dose rate increased by a factor of \textasciitilde 300. Data from a second flight in October 2016 will be corrected for the temperature and pressure dependence of the efficiency of the Geiger counter. The magnitude and non-monotonically increasing profile of the dose curve with altitude were found to agree well with previous measurements and with theoretical predictions based on the production of showers of daughter products generated by interactions with the atmosphere of cosmic rays. [Preview Abstract] |
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E1.00056: Building a Self-Consistent Magnetosphere Model Keith McElroy, Paul Arendt The magnetospheres of rotating magnetized astrophysical objects such as neutron stars and white dwarfs are still poorly understood, with basic tenets guiding their modeling often differing markedly between various authors. In this poster, we present preliminary results from a program designed to address this issue by assembling a rotating magnetosphere self-consistently, letting effects follow causes without preconception. A rotating reference frame is employed which has no singularities at the light cylinder, which allows us to correlate our results with pulsar profiles and to study the breakdown of corotation near the light cylinder. Charged particle trajectories are modeled using a simplified form of the dynamics applicable to strong magnetic fields, allowing us to define position-dependent effective EMFs on the stellar surface with minimal computation time. This quantifies each object's ability to act as a unipolar generator, and serves as a seed for magnetospheric currents in refinements to the model and as initial conditions for a future full MHD model. [Preview Abstract] |
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E1.00057: Comparison of Geosynchronous Satellites Spectral Signatures During Glint Season Daniel Weisz Cadets in the Department of Physics at the United States Air Force Academy are using the technique of slitless spectroscopy to analyze the spectra from geostationary satellites during glint season. The equinox periods of the year are particularly favorable for earth-based observers to detect specular reflections off satellites (glints), which have been observed in the past using broadband photometry techniques. Three seasons of glints were observed and analyzed for multiple satellites, as measured across the visible spectrum using a diffraction grating on the Academy's 16-inch, f/8.2 telescope. It is clear from the results that the glint maximum wavelength decreases relative to the time periods before and after the glint, and that the spectral reflectance during the glint is less like a blackbody. The glint spectra are also quantitatively compared to different blackbody curves and the solar spectrum by means of absolute differences. Our initial analysis appears to indicate a potential method of determining relative power capacity. These results are consistent with the presumption that solar panels are the predominant source of specular reflection. [Preview Abstract] |
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E1.00058: Identifying Binary Brown Dwarf Systems Using Model Point Spread Functions Kyle Matt, Denise Stephens A Brown Dwarf (BD) is a celestial object that is not massive enough to undergo hydrogen fusion in its core. BDs can form in pairs called binaries. Due to the great distances between Earth and these BDs, they act as point sources of light and the angular separation between binary BDs can be small enough to appear as a single, unresolved object in images. Due to limitations in modern technology, it is not currently possible to resolve some of these objects into separate light sources. Stephens and Noll (2006) developed a method that used model point spread functions (PSFs) to identify binary Trans-Neptunian Objects, we will use this method to identify binary BD systems in the Hubble Space Telescope archive. This method works by comparing model PSFs of single and binary sources to the observed PSFs. We describe the method, its challenges and possible uses in this poster. [Preview Abstract] |
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E1.00059: Monitoring 192 of the Brightest Northern Blazars for Variability Lauren Hindman, Joseph Moody Blazars, a subclass of Active Galactic Nuclei (AGN), are characterized by a jet of particles which originate from the torus of a supermassive black hole and point along our line of sight. On occasion these objects are known to flare, or greatly increase in intensity. Little is understood about the exact flaring mechanism. Using our Remote Observatory for Variable Object Research (ROVOR), we monitored 192 of these objects using both V and R Johnson broadband spectral filters from July 2015 to August 2016. We present the results of this program. By comparing the data we gathered to previously found data on each object, we can estimate how often these flares happen. [Preview Abstract] |
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E1.00060: Luminosity Curve Calculations and Applications in Radiation Hydrodynamics Codes JC Canright, Wesley Even, Joshua Dolence An algorithm is described by which calculations of the escaping luminosity from a laser-ionized plasma, supernova, atmospheric blast, or similar scenario may be performed using LANL’s OPLIB database. This algorithm exists in the SPECTRUM code for computing supernova light curves; jaytrace, a robust, lightweight toolkit suitable for plasma experiments, atmospheric blast simulations, and similar scenarios is described herein. LANL’s radiation hydrodynamics code xRAGE is often used for stellar and atmospheric blast simulations, wherein observed spectra are of paramount importance; due to the often exponential dependence of opacity on temperature and density, small numerical artifacts can significantly alter the observed spectra. jaytrace is used to determine the effects of numerical artifacts in the code, notably shock front dispersion, and inform methods by which to correct them. Further examples are examined in the area of laser-induced high-energydensity plasmas. [Preview Abstract] |
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E1.00061: Design Considerations: Falcon M Dwarf Habitable Exoplanet Survey Matthew Miller, Evan Hatfield, Zack Wilcox, Devin Della-Rose, Francis Chun, Steven Novotny, Kimberlee Gresham, Roger Tippets, Daniel Polsgrove M-dwarf stars are attractive targets for exoplanet discoveries because of the deep light curve transits for Earth-sized exoplanets. However, they also present specific challenges in acquiring the uncertainty and photometric stability needed to make statistically significant observations of Earth-sized exoplanet transits. In this study, we showed that a large source of uncertainty in photometric stability is the SNR of dim check stars, used in differential photometry. Additionally, we have demonstrated that we can achieve an uncertainty as low as 1.2mmag using the Falcon Telescope Network. [Preview Abstract] |
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E1.00062: Stable and unstable rotational dynamics of a smartphone Chad Gibbons, Matthew Loth, Sami Belaiter, James Clarage One of the canonical, and memorable, classroom demonstrations from an upper division Mechanics course is to toss a rigid body with three distinct principal moments of inertia into the air, giving it a spin along one of its three principal axes. A student's Mechanics textbook itself works great for the body, secured rigidly shut with a rubber band. The book will spin stably about its longest and shortest dimensions, just like a top or gyroscope. What is surprising is that any attempt to spin the book about its intermediate axis (the axis parallel to the book's lines of text) will result in a wildly unstable and chaotic tumbling, which most students find curious enough to warrant staying awake for a subsequent derivation of Euler's equations. However, now that most students read text "books" off a tablet or phone, this demonstration may seem outdated. Or is it? Like a textbook, a phone or tablet also has three distinct principal moments. Better still, not only do these solid state devices require no rubber band, but these bodies can collect detailed data on their dynamical state, turning a demonstration into an actual experiment. This article reports the results of this modern version of the classical "book toss" demonstration using a cell phone tossed off a five story building. [Preview Abstract] |
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E1.00063: High Pressure Processing of Hyper-doped Silicon John Testerman, Daniel Weisz, Kimberly de La Harpe, Rajani Ayachitula We demonstrate the successful processing of sulfur-hyperdoped silicon using a nanosecond-pulsed laser in the presence of sulfur hexafluoride at pressures greater than one atmosphere. Processing at these pressures resulted in surface microstructures with sulfur content comparable to samples processed traditionally at atmospheric pressure. These structures were verified to have enhanced absorption into the infrared spectrum, characteristic of black silicon and of interest for solar and infrared detection technologies. [Preview Abstract] |
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E1.00064: Thermal Properties of Flashed Aircraft Skin Eric Nagamine The Air Force's Nuclear Hardness Database System (NHDBS) contains information on safe escape distances and vulnerability of aircraft exposed to nuclear detonations gathered from testing in the 1980s and 1990s. Since the 1990s, the Air Force has introduced new airframes and has made upgrades to existing airframes, so updating the NHDBS is of great importance. Funded by the Air Force Nuclear Weapons Center research has been done at the Air Force Institute of Technology (AFIT) since 2012 testing thermal effects on simulate aircraft skin samples beginning with aluminum coated with F16 paint. Research has shifted from simply gathering data in the testing apparatus to creating a model that can predict the survivability of aircraft exposed to nuclear flashes. Preliminary attempts at creating a model have given mixed results, mainly due to the physical properties of the samples being unknown. Our current research is exploring some of those physical properties, namely thermal conductivity and emissivity. Unflashed and flashed samples will be tested and thermal conductivity and emissivity will be measured at varying temperatures by utilizing a setup containing an IR camera, thermistor and thermocouple probes. [Preview Abstract] |
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E1.00065: Relaxation of Radiation Effects on the Optical Transmission of Polymers Alexandra Hughlett, Tyler Kippen, JR Dennison Changes in optical transmission of polymers over time were studied to determine the factors contributing to relaxation of defect states induced by intense radiation doses. Samples of low density polyethylene (LDPE), polyether ether ketone (PEEK), polypropylene (PP), and polyimide (PI) received doses up to 500 MGy. These doses were intended to simulate long-term exposure of common spacecraft materials in geosynchronous orbit. Features and absorption edges can be related to energies associated with various defects previously observed in these highly disordered materials. Recent work has suggested that such radiation-induced defect states are sensitive to atmospheric exposure and that the radiation-induced effects would begin to relax. Upon prolonged exposure, the material would return to its original state. These findings have called in to questions the usefulness of many previous studies of radiation effects on spacecraft materials. After irradiation, transmission spectra were collected as soon as the samples were exposed to oxygen and water vapor in the atmosphere. Between irradiation and the time data collection began, the samples were stored in anaerobic environments. The spectra were collected periodically over several weeks in order to allow for accurate comparisons and to determine the relation rates and final equilibrium states. [Preview Abstract] |
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E1.00066: Optimization of downstream processing for plasmid DNA using ion-exchange chromatography Camille Baird, Stacey Floyd, Robert Davis, Kenneth Christensen, Jordan Finnell, Tsz Tsang Increasing interest in gene therapy and DNA vaccines has sparked an industry-wide focus on producing large quantities of plasmid DNA, while still maintaining quality requirements from regulatory agencies. Optimization of the downstream processing of pDNA has shown promising results for high quality, high quantity batches of plasmids. A protocol was developed and optimized for ion-exchange capture and purification of 5kpb pDNA extracted from E. Coli lysate using commercial borosilicate membrane filters. When compared to similar published processes using varying mediums, our protocol was as effective or more effective in maintaining quality, purity and yield. Principles and procedures developed in this protocol will help aid further research in adapting this process to a newly developed filter medium that offers extremely high surface area for increased binding capacity. [Preview Abstract] |
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E1.00067: Correlation Between Underground Radon Gas and Dormant Geological Faults Israel Chavarria, Jorge Lopez, Oscar Dena, Laszlo Sajo-Bohus, German Rodriguez This work studies the concentration of radon in soil around a fault in the East Franklin Mountains in the El Paso area in West Texas. It is found that the in-soil production of radon is correlated to the existence of a fault even if it has not had any recorded activity in recent geological times. This adds to previous observations that link the production of radon to seismic activity, and seems to indicate that in non-active faults the radon production is due mainly to the radioactivity of the top soil and to the transport properties of the medium and not to deeper seismic activity. These results open the possibility of using in-soil radon gas concentrations as an examination tool of dormant faults. [Preview Abstract] |
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E1.00068: Programming of the Universe from its Fifth Dimension (Information) by Fundamental Sub-particles (substrings) Hassan Gholibeigian, Abdolazim Amirshahkarami, Ghasem Gholibeigian, Kazem Gholibeigian In our vision there is dimension of information in addition of space-time. This dimension including packages of exact positions of quantum states of the fundamental particles (strings) and laws (governing equations and standard ethics). These five dimensions are nested inside each other but with different quality and softness. On the other hand, there are four nested fundamental sub-particles (potentials) as: 1-matter, 2- plant, 3- animal and 4- human sub-particles which are inside each fundamental particle. They have no dimension. They act as the origin of the life and generator of momentum in fundamental particles (strings) [Gholibeigian, APS 2015, abstract {\#}L1.027]. These are softer than the space-time, and themselves are in spectrum of softness. 2 is softer than 1, 3 is softer than 2, and 4 is softer than 3. Dimension of information is softer than sub-particles (substrings) too. Its quality is like knowledge. Sub-particles get (communicate) the packages of information from the fifth dimension of the universe and process it. Then their fundamental particles go to their next situation. This process is programming of the universe and its evolution for a Planck time. [Preview Abstract] |
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E1.00069: Computational identification of a new form of Li2MnSiO4 for battery applications Maxim Arsentev, Marina Kalinina The BMW laboratory identified 12 cathode materials, which offer concrete chances of being used in electric vehicles applications. Amongst them Li2MnSiO4 offer some advantages like high theoretical capacities, environmental friendliness, thermal stability, and inexpensiveness. But Li2MnSiO4 easily undergoes amorphization and shows a poor cyclability due to layer exfoliation and/or need for octahedral coordination for Mn. In this presentation we analyzed the properties of 132 structures of the lithium manganese silicate compounds provided by Materials Project, a core program of the Materials Genome Initiative, to meet the requirements imposed on the cathode material in the long term for 2025. The main selection criteria were stability, specific gravimetric and volumetric capacity, and presence of channels for Li ion migration. Among the 14 selected compounds, only cubic Li2MnSiO4 (P213, space group number 198) was found to have stable analogue -- Na2CaSiO4 with the same structure. Using this information, we present the results of the structure stabilization obtained using the ABINIT software. [Preview Abstract] |
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E1.00070: Changes of an Atom's Lifetime in Speed of near Light Speed Due to Changes of its Properties and Geometry Hassan Gholibeigian, Abdolazim Amirshahkarami, Kazem Gholibeigian, Ghasem Gholibeigian The matter moves permanently in its entity and the magnitude of this motion (fundamental particles' momentum) is its relative time, Sadra (1571/2-1640) [Gholibeigian, APS 2015]. When an atom moves in speed of near light speed two coupling phenomena occur. Firstly, the speed of fundamental particles of involved nucleons become slowly and they occupy a smaller space (nucleus volume squeezing) for their activities. It means that the interaction boundary layer between coupled quarks' momentum and gluons' fields of nucleus and electromagnetic-momentum fields of electrons' cloud, as the radius boundary of nucleons is changed. Secondly, the external boundary of interaction zone of spins and orbital angular momentum of electrons and electromagnetic fields generation by them as the boundary of atom is deformed. As a result, the momentum (time flux) of each fundamental particle is decreased while its lifetime is increased. Changes of particle's lifetime is a key factor in variability of species in creation and evolution in nature. Here, the four animated sub-particles (substrings) of the matter, plants, animals and human, play the vital roles in this process. [Preview Abstract] |
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