Bulletin of the American Physical Society
Joint Fall 2011 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 56, Number 7
Thursday–Saturday, October 6–8, 2011; Commerce, Texas
Session H1: Poster Session (6:10 pm - 7:30 pm) |
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Room: Sam Rayburn Student Center Second Floor |
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H1.00001: Positioning devices based on submicro-textured magnetostrictive alloys (Fe$_{85}$Ga$_{15}$) Gamage Dannangoda, Karen Martirosyan Magnetostrictive materials can convert magnetic energy into kinetic energy. Under the influence of an external magnetic field, the rotation of small magnetic domains causes a change in a magnetostrictive materials shape in the direction of the magnetic field. Applying stronger magnetic field will tend to rotate more domains and makes the material to stretch even more until it reaches its saturation. This property has been used in many applications such as micro acoustic sensors, generators, marine sonar, devices, linear motors, robust actuators, automotive accessories, positioning devices etc. There is increasing interest in magnetostrictive applications after discovering the giant magnetostrictive alloys such as Galfenol and Terfenol-D which is capable of generating strains 100 times greater than traditional magnetostrictive materials at high temperatures. Even though Galfenol doesn't produce as much as magnetostriction as Terfenol-D, it can be constructed mechanically strong with tensile strengths up to 500 MPa and can be rolled, extruded, and welded. The magnetostrictive positioning devices based on submicro-textured magnetostrictive alloys (Fe$_{85}$Ga$_{15})$ and their advantages will be discussed. [Preview Abstract] |
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H1.00002: McDonald Observations of J1118+480 Lorena Monroy, Paul A. Mason, E.L. Robinson Starting in the summer of 2010 and continuing to the summer of 2011, we observed J1118+480 at McDonald Observatory using Argos (a charged-coupled device, CCD, camera) for a total of 13 nights. We present the light curves from the gathered nights that have been reduced using scientific linex operating system and IRAF. The light curve data is converted to Heliocentric Julian Date (HJD) and the delta Magnitude between a comparison star and the target star (J1118+480) is plotted. We performed a period search of our light curves using Phase Dispersion Minimization (PDM) and we discuss the implications of the period search. This research is supported by a National Science Foundation, Partnership in Astronomy and Astrophysics Research and Education (PAARE) grant to the University of Texas at El Paso. [Preview Abstract] |
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H1.00003: Optical Observation of Low Mass X-Ray Binary J1753.4-0126 Aurelio Paez, Paul A. Mason, E.L. Robinson We conducted optical observations of the black hole candidate J1753.4-0126 with the 82 inch (2.1 m) Otto Struve Telescope at the McDonald Observatory. A total of 20 nights of data were collected from May 2010 through June 2011. Data was reduced using the Interactive Reduction and Analysis Facility (IRAF). We present the resulting light curves. We discuss our progress in this analysis, which uses a phase dispersion minimization code in order to find periodicity. This research is supported by a National Science Foundation Partnership in Astronomy and Astrophysics Research and Education (PAARE) grant to the University of Texas at El Paso. [Preview Abstract] |
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H1.00004: Optical Characterization and GIS Mapping of Light Pollution in West Texas Hillary Proffit, Shivakumar Surendranath, Hardin Dunham Images of the night sky have been collected in Tom Green County using two SBIG, all-sky CCD cameras. A process has been developed using various software to extract the CCD count data from the images and create an intensity profile across traces in the sky. By correlating stellar magnitudes with the CCD counts recorded, we are able to create an intensity profile of the night sky. Combining current geographical information through the use of GPS locations, the light pollution distribution can be mapped. This research will present data processing methods, techniques, and preliminary results which will be used to map the distribution of light pollution over several years. The continuation of mapping light intensity distributions in West Texas will provide a foundation for future comparisons of light pollution, and raise public awareness for preserving natural dark-sky resources. [Preview Abstract] |
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H1.00005: Optical Observation of Low Mass X-Ray Binary V1727 Cygni Alex Price, Paul Mason, Edward L. Robinson This research is based upon optical observations of the neutron star V1727 Cygni (=4U 2129+47). A total of 19 nights of data were collected from September 2010 through August 2011 at the McDonald Observatory via the 82 inch (2.1 m) Otto Struve Telescope. The Interactive Reduction and Analysis Facility (IRAF) was used to reduce the data collected. We present the resulting light curves. We will describe our analytical methodology, which makes use of a phase dispersion minimization program in order to identify periodicity. Preliminary results seem to support previous research by Bothwell, Torres, Garcia, and Charles that V1727 Cygni is part of a three-body system. Preliminary results also suggest that this system exhibits ellipsoidal variations. This research is supported by a National Science Foundation Partnership in Astronomy and Astrophysics Research and Education (PAARE) grant to the University of Texas at El Paso. [Preview Abstract] |
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H1.00006: Modeling the White Dwarf Luminosity Function Rick Navarro White dwarfs are the final stage of stellar evolution for the vast majority of stars in the Galaxy. The number of white dwarfs as a function of their luminosity (the white dwarf luminosity function, or WDLF) is the convolution of several pieces of interesting information: the star formation history of the Galaxy, the cooling physics of white dwarfs, and the evolution of white dwarf progenitor stars. We have used the most current white dwarf evolution models available and several simple assumptions regarding the form of star formation rates over time in order to construct model WDLFs, which we test for compatibility with previous model results and historical observed WDLFs. Our goal is to use our models to explore the encoded white dwarf physics and star formation history of our Galaxy in forthcoming new generations of observed WDLFs. [Preview Abstract] |
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H1.00007: Equation of State in a Strongly Interacting Relativistic System Jason Keith, Efrain Ferrer The graphical representation of the equation of state of a fermion system with a four-fermion interaction in the strong coupling regime is shown as a function of the four-fermion coupling constant. The crossover from a superconducting BCS regime to a Bose-Einstein-condensate (BEC) regime is obtained by increasing the coupling constant. We show the characteristic quasi-particle spectra for each phase. We discuss how the BEC regime becomes unstable in the strong coupling limit giving rise to BCS stable bound states. [Preview Abstract] |
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H1.00008: Tunneling, Diffusion and Dissociation of Feshbach Molecules in Optical Lattices Taylor Bailey, Carlos Bertulani, Eddy Timmermans We show that tunneling and diffusion of cold Rydberg molecules in optical lattices leads to a somewhat unexpected effects.One of these effects is the resilience of the molecules to dissociation as their binding energy decreases. We also quantify the dynamics of molecular diffusion and dissociation of molecules in 1D harmonic optical lattice potential by comparing to analytical models. It is found that after an initial transient, the wave packet for dissociating molecules can described by a power diffusion pattern of the type $\sigma(t)\propto t^{1/2}$ where $\sigma$ is the dispersion of the packet. Surprisingly, we could not obtain such a simple power law fit for the dispersion of dissociated atoms. [Preview Abstract] |
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H1.00009: Downstream electron beam exciter diagnostic with energy dependent cross section responses for process tool applications P.L. Stephan Thamban, Gabriel Padron Wells, Jimmy Hosch, Matthew Goeckner Optical emission spectroscopy (OES) still remains as the primary diagnostic in plasma process tools in micro-electronics industry. With newer plasma processes and detection demands in low open area etches, process monitoring with direct optical signals is severely limited. Here we present a diagnostic method that realizes optical signals due to an electron beam from an inductively coupled plasma. Distinct merits such as energy dependent optical emission cross section responses and stable operability in polymerizing / corrosive etch environments will be presented. Electron impact optical cross section responses of transitions in fluorocarbon, oxygen and inert gas chemistries will be shown. Such controllability, in the context of species density measurement will be discussed. [Preview Abstract] |
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H1.00010: Improvements to a Compton Polarimeter Brandon Cavness, Dave Gaskell, Mark Dalton The Jefferson Lab in Newport News, Virginia, uses a polarized beam of electrons to perform research on the substructure of nuclei and nucleons. Jefferson Lab uses a relatively new Compton polarimeter to continuously measure the polarization of the electron beam delivered by the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator. The Compton polarimeter determines beam polarization by colliding a high-power laser with the electron beam and measuring the scattered photons and electrons. The Compton polarimeter utilizes this asymmetry of Compton scattering rates to measure polarization to (+/-)1{\%} every few hours. For an accurate measurement, the laser polarization and the position of the scattered photon cone must be well known. The focus of this project was to expand the instrumentation to monitor and control the Compton polarimeter with the intent of improving the electron beam polarization measurement. The individual components of the system are all working as intended, but the system as a whole will not be tested until beam operations resume. An improved measurement of the electron beam polarization will reduce the uncertainty of future experiments. [Preview Abstract] |
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H1.00011: SPP Excitation Using Extremely Low Intensity Light John Sandy, Daniel Dominguez, Luis Grave De Peralta We present the results of experiments designed to create and detect Surface Plasmon Polaritons (SPP) using low intensity light such that SPP excitation is achieved under extremely low intensity condition. This is accomplished using an experimental apparatus which utilizes a laser-intensity varying system, a PMMA on gold on glass sample, and a Single Photon Counting Module (SPCM). We image the characteristic SPP propagation ring using a typical CCD camera and find the corresponding peak intensities using low intensity pump methods and the SPCM. [Preview Abstract] |
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H1.00012: Excitation of atomic and nuclear coherence by strong optical fields Yuri Rostovtsev, Treena Chatterjee Recent progress in ultrashort, e.g. attosecond, laser technology allows to obtain ultra-strong fields which can be of the same order of magnitude as the electric field created by an atomic nucleus. Interaction of such strong and broadband field with atomic systems even under the action of a far-off resonance strong pulse of laser radiation should be revisited. As we have shown, such pulses can excite remarkable coherence on high frequency transitions. We have perform classical calculations and compare it with results of {\it ab initio} calculations using TDDFT for several atoms and simple molecules interacting with strong optical fields. We compare efficiency generation with the efficiency of high harmonic generation approach, and discuss the CEP effects and possible applications of the results to excitation of nuclear transitions. [Preview Abstract] |
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H1.00013: Analysis of crystals using electron diffraction Robert Nick Lanning, Cristian Bahrim Measurements of diffraction patterns produced by electronic beams incident on crystals reveal their atomic arrangement and allow one to find the length of the chemical bonds with high precision. Using fundamental principles we can understand the formation of electronic wave packets when electron projectiles pass through the crystal. The effective electronic charge of the atoms in the crystal acts as an arrangement of narrow slits which generate the Fourier transform of the sinusoidal waves associated to the electron projectiles incident on the crystal. Our study has applications in electronic microscopy, microbiology, and crystallography. This project was sponsored by the STAIRSTEP program [1] under a NSF-DUE grant. The program is designed to engage STEM undergraduate students in high-quality research in several fields of science including physics, at Lamar University.\\[4pt] [1] Doerschuk P, Bahrim C, Daniel J, Kruger J, Mann J, and Martin Ch, \textit{39th ASEE/IEEE Frontiers in Education Conference,} San Antonio 2009, M3F-1-2. [Preview Abstract] |
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H1.00014: Study of plasmonic crystals by Plasmon Tomography far-field Superlenses Willis Agutu, Charles Regan, Arquimedes Columbie, Robier Rodriguez, Ayrton Bernussi, Luis De-Peralta We explore the use of surface plasmon polariton (SPP) tomography far-field superlenses for quantitative characterization of plasmonic crystals. Useful semi-empirical relations are obtained from the quantitative information extracted from the FP images. In addition, based on the comparison of the FP images corresponding to plasmonic crystals with holes of different sizes, we present a comprehensive discussion about the formation of directional stop-bands in the fabricated plasmonic crystals. [Preview Abstract] |
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H1.00015: Determining Favorable Binding Configurations of the Anti-Cancer Drug Ellipticine to the KV11.1 Potassium Channel V-VI Transmembrane Domain Through Autodock Simulations Dawn Lipscomb, Saverio Gentile, Lorenzo Brancaleon Ellipticines such as 9-methoxy-N-2-methylellipticinium acetate (MMEA) and 9-hydroxy-N-2-methylellipticinium acetate (NMEA, Celiptium {\textregistered}) are antineoplastic drugs that exert their selective cytotoxicity against leukemia and endometrial carcinoma. Ellipticine's action is also related to severe physical side effects, but the link between undesired effects and pharmacological application is not well understood. We investigated the binding of Ellipticine derivatives with the Kv11.1 potassium ion channel using Autodock and revealed that hydroxyellipticinium derivatives provide binding configurations with Kv11.1, but the energy, location and estimated dissociation constant varied. The binding energy is as follows: Chloroceliptium (-6.60 kcal/mol) $>$ Celiptium (- 6.37 kcal/mol) $>$ Methoxyceliptium (- 6.20 kcal/mol) $>$ Datelliptium (-6.08 kcal/mol). Autodock simulations demonstrate that binding affinity is high at opposing ends of the channel and low within the channel interior. These favorable binding configurations suggest that Ellipticine derivatives may bridge among end subunits of the channel and potentially inhibit the flow of ions. [Preview Abstract] |
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H1.00016: Nanostructured thermites based on iodine pentoxide for bio agent defeat systems. Mkhitar Hobosyan, Alexander Kazansky, Karen Martirosyan The risk for bioterrorist events involving the intentional airborne release of contagious agents has led to development of new approaches for bio agent defeat technologies both indoors and outdoors. Novel approaches to defeat harmful biological agents have generated a strong demand for new active materials. The preferred solutions are to neutralize the biological agents within the immediate target area by using aerosolized biocidal substances released in situ by high energetic reactions. By using nano-thermite reactions, with energy release up to 25 kJ/cc, based on I2O5/Al nanoparticles we intend to generate high quantity of vaporized iodine for spatial deposition onto harmful bacteria for their destruction. In this report, the effect of reaction product on growth and survival of Escherichia coli (E-coli) expressing GFP (Green Fluorescent Protein) was investigated. Moreover, we developed an approach to increase sensitivity of the detection. The study has shown that I2O5/Al nanosystem is extremely effective to disinfect harmful biological agents such (E-coli) bacteria in seconds. [Preview Abstract] |
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H1.00017: Thermophoresis in microfluidic devices: Lattice-Boltzmann simulations Jennifer Pearce, David Wilson, Seth Norman Thermophoresis, or mass accumulation due to a temperature gradient, has been shown to occur in microfluidic channels with fluid flow. It has separately, without flow, to lead to separation of different sizes of polymers. Here we report on simulations that combine these effects, fluid flow and size segregation. The simulation is based on the lattice-Boltzmann method for the fluid and a bead spring model for the polymer and has reproduced quantitatively thermophoresis of DNA. We investigate if thermophoresis can be used to separate polymers of different sizes using thermal flow field fractionation in microfluidic devices. [Preview Abstract] |
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H1.00018: Electromagnetism of Bacterial Growth Ailiyasi Ainiwaer There has been increasing concern from the public about personal health due to the significant rise in the daily use of electrical devices such as cell phones, radios, computers, GPS, video games and television. All of these devices create electromagnetic (EM) fields, which are simply magnetic and electric fields surrounding the appliances that simultaneously affect the human bio-system. Although these can affect the human system, obstacles can easily shield or weaken the electrical fields; however, magnetic fields cannot be weakened and can pass through walls, human bodies and most other objects. The present study was conducted to examine the possible effects of bacteria when exposed to magnetic fields. The results indicate that a strong causal relationship is not clear, since different magnetic fields affect the bacteria differently, with some causing an increase in bacterial cells, and others causing a decrease in the same cells. This phenomenon has yet to be explained, but the current study attempts to offer a mathematical explanation for this occurrence. The researchers added cultures to the magnetic fields to examine any effects to ion transportation. Researchers discovered ions such as potassium and sodium are affected by the magnetic field. A formula is presented in the analysis section to explain this effect. [Preview Abstract] |
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H1.00019: Temperature Dependence of DNA Charge Transport Chris Wohlgamuth, Marc McWilliams, Jason Slinker Charge transport (CT) through DNA has been extensively studied, and yet the mechanism of this process is still not yet fully understood. DNA CT has been utilized in sensing proteins and DNA fragments, and it has been postulated that it may assist DNA damage prevention and repair. Besides the benefits of understanding charge transport through this fundamental molecule, further understanding of this process will elucidate the biological implications of DNA CT and advance sensing technology. Therefore, we have investigated the temperature dependence of DNA CT by measuring the electrochemistry of DNA monolayers modified with a redox-active probe. By using multiplexed electrodes on silicon chips, we compare the cyclic and square wave voltammetry of distinct DNA sequences under identical experimental conditions. Accordingly, we compare well matched DNA duplexes to those containing a single base pair mismatch, which has been shown to attenuate CT. The yield of CT is shown to follow Arrhenius behavior, with increased activation energies for mismatches that structurally distort the duplex. These observations suggest that charge transport is thermally activated and highly dependent upon DNA conformation. [Preview Abstract] |
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H1.00020: Real-Time Interaction between Antimicrobial Peptide and Lipid Membrane Using Atomic Force Microscopy and Confocal Microscopy Jie Hu, Vernita Gordon, Ahmed Touhami Peptidyl-glycylleucine-carboxyamide (PGLa) is a helical cationic amphiphilic antimicrobial peptide known to interact with bacterial membranes. The electrostatic interaction is the major determinant that triggers the affinity of the PGLa towards bacterial membranes. Here, Atomic Force Microscopy (AFM) and Confocal Microscopy (CM) were used to investigate this interaction. Giant Unilamellar Vesicles (GUV) mimicking E. coli membranes were prepared by the natural swelling method that allows the fluorescence dye to be capsulated in the GUVs. After GUVs were incubated with PGLa in medium with low ionic strength, excessive leakage of the internal contents of GUVs was detected. Our results demonstrate that AFM and CM, as well as appropriate sample preparation protocols, are needed to obtain detailed mechanistic insights into antimicrobial function. [Preview Abstract] |
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H1.00021: Porphyrin-Mediated Photoinduced Conformational Changes to Albumin Sarah Rozinek, Lorenzo Brancaleon Many biological and nonbiological uses of protoporphyrin-IX (PPIX) depend on its ability to bind large macromolecules such as human serum albumin (HSA). HSA is both biomedically and technologically relevant to PPIX (free base and metal), and its binding site for PPIX-derivatives is well established. The irradiation of PPIX noncovalently bound to BetaLactoglobulin (BLG) is known to cause protein conformational changes that are pH-dependent due to BLG's intrinsic conformational transitions. These processes have not been extensively studied in nonphysiological pH conditions for FePPIX or PPIX bound to HSA. This study implemented a combination of optical and computational methods to compare binding characteristics of hemin and PPIX to HSA as well as structural effects of lowdose irradiation of the ligand on the protein. Spectroscopic data suggests that irradiation of the Soret band of PPIX bound to HSA is capable of modifying the globular protein structure by direct charge transfer between the porphyrin and the binding site at both physiological and acidic pH confirmations. Computational docking simulations predict lower free energy of binding for PPIX than for heme. [Preview Abstract] |
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H1.00022: Titrated fluorescent binding of Thioflavin-T with bovine serum albumin Jacob Friday, Jeremiah Babcock, Lorenzo Brancaleon Thioflavin-T (ThT) can be used as a bio-marker to detect protein aggregation. ThT can be applied towards detecting protein structural changes, and possibly, protein structure. Spectroscopic analysis was used to investigate the interaction of bovine serum albumin (BSA), a globular $\alpha $-helix structured protein, with Thioflavin-T in titrated phosphate buffer solutions from pH 2 -- 10. The objective for this study was to analyze the binding characteristics of BSA, with the fluorescent marker, ThT. Under constant concentrations of 40 $\mu $M ThT and 10 $\mu $M BSA, absorbance spectra and florescence spectroscopy was used to~determine the binding characteristics of Thioflavin-T to BSA. Evidence is not certain on whether binding occurred or not, and future plans are to investigate the protein folding dynamics of partial $\beta $-sheet proteins such as lactoglobulin. [Preview Abstract] |
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H1.00023: Polarized Reflectance Measurement of Burned Skin Tissues Hector Michael de Pedro, Chuan-I. Chang, Faranak Zarnani, Robert Glosser, D. Maas, A. Idris In the US, there are over 400,000 burn victims with 3,500 deaths in 2010. Recent evidence suggests that early removal of burn tissues can significantly increase the success of their recovery, since burns continue to spread and damage surrounding tissues after hours of injury. The rationale behind this procedure is that burns trigger the body's immune system to overreact, causing additional damage. Therefore, it is important to distinguish burn areas so that it can be removed. The problem with this is that it is difficult to recognize the margins of the burn area. In our project, we use polarized reflectance as a tool to identify the burned tissues from unburned ones. [Preview Abstract] |
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H1.00024: Investigating the Mechanical Properties of Plasma von Willebrand Factor Using Atomic Force Microscopy Sitara Wijeratne, Eric Botello, Hui-Chun Yeh, Zhou Zhou, Angela Bergeron, Eric Frey, Joel Moake, Jing-Fei Dong, Ching-Hwa Kiang Single-molecule manipulation allows us to study the real-time kinetics of complex cellular processes. The mechanochemistry of different forms of von Willebrand factor (VWF) and their receptor-ligand binding kinetics can be probed by atomic force microscopy (AFM). Since plasma VWF can be activated upon shear, the structural and functional properties of VWF that are critical in mediating thrombus formation become important. Here we characterized the mechanical resistance to domain unfolding of VWF to determine its conformational states. We found the shear-induced conformational changes, hence the mechanical property, can be detected by the change in unfolding forces. The relaxation rate of such effect is much longer than expected. Our results offer an insight in establishing strategies for regulating VWF adhesion activity, increasing our understanding of surface-induced thrombosis as mediated by VWF. [Preview Abstract] |
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H1.00025: Raman Micro-spectroscopy Study of Healthy and Burned Biological Tissue Faranak Zarnani, Robert Glosser, Ahamed Idris Burn injuries are a significant medical problem, and need to be treated quickly and precisely. Burned skin needs to be removed early, within hours (less than 24 hrs) of injury, when the margins of the burn are still hard to define. Studies show that treating and excising burn wounds soon after the injury prevents the wound from becoming deeper, reduces the release of proinflammatory mediators, and reduces or prevents the systemic inflammatory reaction syndrome. Also, removing burned skin prepares the affected region for skin grafting. Raman micro-spectroscopy could be used as an objective diagnostic method that will assist burn surgeons in distinguishing unburned from burned areas. As a first step in developing a diagnostic tool, we present Raman micro-spectroscopy information from normal and burned ex vivo rat skin. [Preview Abstract] |
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H1.00026: Photoinduced Charge Transfer Process Luis Basurto, Tunna Baruah, Rajendra Zope, Jose Rodriguez The photoinduced charge transfer process is the fundamental process in a photovoltaic system. Organic photovoltaics contain a donor-acceptor molecular system which undergoes photoinduced charge transfer leading to a large dipole moment. Often the charge transfer properties of such donor-acceptor systems are measured in solution. The dipole moments on the solvent molecules creates a reaction field. To simulate this reaction field we adopt an approach similar to the explicit solvent model proposed by Washel and co-workers. We use Monte Carlo simulations to determine various possible solvent structures. We use a carotenoid-porphyrin-C60 molecular triad as the light-harvesting system. This molecular triad has a very large dipole moment (153 Debye) in the charge separated state. The resulting solvent structures and the reaction field as a function of temperature will be presented. [Preview Abstract] |
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H1.00027: Calix[6]arene electron beam sensitivity and contrast dependence on functionalization and molecular weight Gregory Spencer, Daniel Ralls, Stephan Wolfe, Michael Blanda, Anup Bandyopadhyay Calixarenes are macrocyclic molecules that have shown high resolution as electron beam resists. Earlier work has demonstrated that the sensitivity can be increased by adding functional groups to the molecular rim of these ring-shaped molecules. However, these earlier studies used either unfunctionalized resists or ones that were fully functionalized. In this study, the number of functional groups added to a calix[6]arene structure was deliberately varied from zero to the maximum possible number of groups. This allowed direct observation of the effect of the number of attached groups on the sensitivity. Two different conformers were used; a cone conformer and the 1,2,3-alternate conformer. Both used xylenyl groups as bridging units, giving conformationally-locked monomers. The number of added allyl groups was varied from 0 to 8. The resulting nine resists were exposed and contrast curves were measured by AFM. This allowed measurement of both resist sensitivity and contrast. The sensitivity was found to be a strong function of the number of pendant groups. Also the effect of molecular weight on sensitivity was found for the heaviest resist, after the functional group effect saturated between four and six groups. These results and comparison with others will be discussed. [Preview Abstract] |
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H1.00028: Spectroscopic analysis of temperature dependent growth of WO3 and W0.95Ti0.05O3 thin films Young Yun, Felicia Manciu, Durrer William, James Howard, Chintalapalle Ramana We present a comparative spectroscopic study of the morphology and composition of tungsten oxide WO$_{3}$ and W$_{0.95}$Ti$_{0.05}$O$_{3}$ thin films, grown by radio frequency magnetron reactive sputtering at substrate temperatures varied from room temperature (RT) to 500~$^{\circ}$C, using Raman and X-ray photoelectron spectroscopy (XPS). The Raman results demonstrate the occurrence of a phase transformation from a monoclinic WO$_{3}$ structure to an orthorhombic or tetragonal configuration in the W$_{0.95}$Ti$_{0.05}$O$_{3}$ thin films. This remark is based on the observed shifting, with Ti doping, to lower frequencies of the Raman peaks corresponding to W-O-W stretching modes of WO$_{3}$ at 806 and 711 cm$^{-1}$, to 793 and 690 cm$^{-1}$, respectively. Also, higher growth temperatures are required to obtain crystalline microstructure for Ti-doped WO$_{3}$ films than for WO$_{3}$ films. XPS data indicate that the doped material has a reduced WO$_{3-x}$ stoichiometry at the surface, with the presence of W$^{+6}$ and W$^{+5}$ tungsten oxidation states; this observation could also be related to the existence of a different structural phase of this material, corroborating with the Raman measurements. [Preview Abstract] |
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H1.00029: Morphology and chemical composition of Zn-Co alloy electrodeposits from alkaline solutions Meysam Heydari Gharahcheshmeh, Ahmed Touhami Zn-Co alloy electrodeposits were obtained from weakly alkaline glycine solutions by using direct current. The influence of current density, electrolyte temperature, electrolyte's Co$^{2+}$ concentration on the surface morphology and chemical composition were investigated by using scanning electron microscope (SEM) and energy dispersive spectroscopy (EDX), respectively. The results showed that increasing temperature, electrolyte's Co$^{2+}$ concentration and current density, increases cobalt content of the coatings. It was also shown that increasing current density, up to 15 mA cm$^{-2}$, decreases the grain size and further increase in current density increases the grain size of the deposit. [Preview Abstract] |
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H1.00030: Effects of electronic correlations on the mechanical properties of Gallium Phosphide using density functional theory (DFT+U) Prashant Khatri, Brandon Butler, John A. Turner, Muhammad N. Huda Developing an efficient material for solar energy conversion and storage has been an important task for many scientists working on renewable energy technology. Gallium phosphide (GaP) alloys are among the materials that have potential to be used in the solar technology. Hence, we investigate the elastic property, mainly the bulk modulus, and electronic properties of GaP. The goal of this work is to study the effect of electron correlation on the mechanical stability of GaP. The calculation of energy as a function of cell volume has been performed using density functional theory with U-parameter (DFT+U) The Birch-Murnaghan equation of state is used to calculate equilibrium cell volume, total energy, bulk modulus, B$_0$, and its first pressure derivative, B$_0^{\prime}$. The bulk modulus obtained using different U-parameter was compared with published experimental values. The use of U-parameter in Gallium d-orbital has increased the theoretical value of bulk modulus, making it closer to the experimental value. On the other hand, increasing values of U on Phosphorus p-orbital decreases the bulk modulus further. The physical consequences of these results will be discussed. [Preview Abstract] |
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H1.00031: Positron Doppler Broadening of Pure Elemental Metals Desmond Fernandez, C.A. Quarles Positron Doppler Broadening experiments using either a Sodium 22 or a Germanium 68 source were run on a range of pure elemental metals. The results are presented as ratios of the 511 keV annihilation line spectra to selected standard metals as a function of momentum of the atomic electron. The data are compared with theoretical calculations and with previous experimental results using the Coincidence Doppler Broadening method. Additionally, systematic investigations were done to determine the best techniques for optimization of the data. The factors that have an effect on the data include counting rate, detector resolution, amplifier shaping time, source backing material, background and total number of counts in the 511 keV annihilation peak. Furthermore, we were able to extend our results using the Germanium 68 source to a quality close to that of the more expensive and complex Coincidence Doppler Broadening practice. [Preview Abstract] |
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H1.00032: Calculating the Phonon Dispersion From First Principles Frank Ceballos, Andy O'Hara, Alexander Slepko, Alexander Demkov The goal of this project was to construct a user-friendly tool that can compute the phonon dispersion for any solid with a periodic crystal structure. The phonon dispersion describes the crystal's vibrational properties and thermodynamic properties of the solid. Using the Vienna Ab-initio Simulation Package (VASP) we compute the forces between the atoms. Assuming harmonic approximation we numerically evaluate force constant matrix. The lattice Fourier transform of the force constants yields the dynamical matrix, whose eigenvalues and eigenvectors represent the allowed phonon frequencies and displacement patterns for specific k-vectors. Our code then plots the frequencies along high symmetry lines in the Brillouin zone. We will present our results for silicon, GaAs and ZrO$_{2}$. [Preview Abstract] |
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H1.00033: Investigation of a strain generated internal field in an InGaAs/GaAs quantum well heterostructure Kaleb Gilbert, James Matthews, Sauncy Toni Piezoelectrically active InGaAs/GaAs quantum wells grown along the $<$111$>$ crystal axis have been investigated using temperature dependent photoluminescence spectroscopy. The goal of this work is to determine the temperature dependence of the internal electric field generated by strain within the quantum well layer as a function of temperature. Data was collected ove a temperature range of 8-150 K; Excitation intensity was varied at each temperature using neutral density filters. By examination of the emission energy as a function of incident excitation power density, we have determined the electric field within the well at each temperature. An automated custom MATLAB code was developed to correct each data plot for system response. The temperature dependence of the internal field based on preliminary analysis is discussed [Preview Abstract] |
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H1.00034: Electronic Structure of Semiconductor Random Alloys Kevin Kendall, Byounghak Lee, Xavier Cartoixa We present a theoretical investigation of the evolution of the electronic properties of the random alloys as they undergo a transition from one pure crystal to another. For random substitutional alloys the Bloch wavevector is not a good quantum number due to the lack of translational invariance. In spite of this obvious fact the conventional methods used for random alloys calculations, e.g., Virtual Crystal Approximation and Coherent Potential Approximation, assume a medium that pertains the same symmetries of the parent compounds. The question we ask is how well the band structures from such effective medium theories agree with the real electronic structures. We address this issue using direct simulations of randomly distributed (Al,Ga)As and Ga(P,As) atom structures. [Preview Abstract] |
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H1.00035: Remote plasma-assisted deposition of metals onto the surface of nanocrystalline ZnO Sergio A. Leal, Anastasiia Nemashkalo, Puskar Chapagain, Shreedhar Pant, Phillip Alarcon, Yuri M. Strzhemechny Controllable surface modification of nanoscale ZnO is crucial for many existing and future applications. We investigated the effectiveness of metal deposition using remote O$_{2}$/He plasma passing through a metal mesh electrode onto the surface of ZnO nanopowders with an average grain size of 25 nm. Surface stoichiometry was monitored in situ with Auger electron spectroscopy, whereas surface optoelectronic properties were probed; also in situ, using surface photovoltage (SPV) spectroscopy. We observed a strong dependence of surface modification on the distance from the metal electrode. At short distances the metal coverage was reaching tens of percent of one monolayer. Simultaneously we observed a significant improvement of the SPV response pointing to metal-enhanced surface charge dynamics. [Preview Abstract] |
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H1.00036: Evidence for evanescent waves at interfaces in a high-index prism/liquid-crystal-Au-NPs/glass/air structure and effects of relative concentration of gold nanoparticles, wavelength, polarization, and incident angle of the laser beam Kunal Tiwari, Ankit Singh, Suresh Sharma Incorporation of relatively small concentrations of gold nanoparticles (Au NPs) in a polymer-dispersed liquid crystal (PDLC) is known to lower the operating threshold voltage and increase optical transmission through the device.\footnote{A. Hinojosa and S. C. Sharma, Applied Physics Letters, \textbf{97}, 081114 (2010)} In order to understand whether there is an interplay between the localized surface plasmon resonance at Au-NPs-dielectric interfaces and the electro-optical properties of PDLC devices, we have investigated propagation of light through a high-index prism/liquid-crystal-Au-NPs/glass/air structure by using Kretschmann geometry as functions of concentration of Au NPs in the liquid crystal, and the wavelength, polarization, and angle of incidence of the laser beam. We will discuss to what extent the results of these experiments support an interplay between the localized surface plasmon resonance at NPs/dielectric interfaces and optical propagation through the above-described structure. [Preview Abstract] |
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H1.00037: Comparison of Low Energy CVV Auger transitions in Cu and Au (100) using Measured and estimated values K. Shastry, S.F. Mukherjee, S. Satyal, P.V. Joglekar, A.H. Weiss Low energy Auger lineshapes are difficult to measure because they sit on a large background due to secondary electrons arising from loss processes unrelated to the Auger mechanism. In this poster we discuss the implications of our PAES measurements of the ratio of the integrated Auger Peak and integrated low energy tail (LET) intensities for comparisons between theoretical and measured values of the Auger intensities. The experiments were carried out at university of Texas at Arlington on Cu (100) and Au (100) crystals. Our conclusions regarding the importance of the LET in determining the ratio of electrons in the Auger peak to the number of initial core holes are discussed in light of the electron stimulated Auger results obtained by Seah et.al using monte carlo simulations on various elements. [Preview Abstract] |
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H1.00038: Characterization of Si and C implantation induced defects in 4H-SiC Venkata Kummari, Mangal Dhoubhadel, Bibhudutta Rout, Tilo Reinert, Daniel Spemann, Weilin Jiang, Floyd McDaniel Silicon Carbide is considered to be a promising material for dilute magnetic semiconductors (DMSs). Past experimental studies reveal that ferromagnetism can be observed in SiC diluted with 3d transition metals. Recent studies, based on first principle calculations, show that for SiC monolayers, the presence of silicon vacancies (V$_{Si})$ may induce local magnetization. However, no spin polarization occurs for carbon vacancies (V$_{C})$, Si+C divacancies, and Si-C antisite defects. Ion implantation is an excellent technique to create vacancies for defect induced magnetism. We have implanted Si and C into 4H-SiC at low energy 60 keV to study the implantation defects for different fluences which corresponds to different percentages of simulated damages (e.g. 10 -- 60 {\%}) obtained using Monte-Carlo simulations code SRIM/TRIM-2008. Defect disorder after ion implantation has been investigated using Rutherford Backscattering Spectrometry/Channeling (RBS/C) and Raman spectroscopy. [Preview Abstract] |
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H1.00039: Synthesis and Characterization of Transitional Metal Nanosystems in Semiconductor Mangal Dhoubhadel, Bibhu Rout, Venkata Kummari, Jerom Duggan, Tilo Reinert, Floyd McDaniel Low energy (less than 80 keV) transition metal ions (Ag, Cu) were implanted into Si(100) to create buried metal-silicon layers. The physical structure of the defects due to the various ion energies and fluencies has been studied. The evolution of defects clusters in the Si due to the implanted ion as well as the morphology of formed nanostructures was observed for various annealing parameters. The annealing temperature ($\sim $500 $^{\circ}$C) was kept moderately low to study the diffusion of the implanted metal ions. The samples were characterized using Rutherford Back Scattering Spectrometry (RBS), Ion Channeling (RBS/C), Raman Spectroscopy and Transmission Electron Microscopy (TEM). [Preview Abstract] |
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H1.00040: Synthesis and Characterization of Au@Cu Core-Shell Nanoparticles Subarna Khanal, Jesus Velazquez-Salazar, Miguel Jose Yacaman The synthesis of bimetallic nanoparticles has become so important in present times due to its diverse applications of nanotechnology. Particularly most of the bimetallic nanoparticles are focused to use in catalysis, plasmonic, magnetic, sensors, and many other applications. In Au/Cu case, the bulk Au and Cu are soluble at all compositions. But the structure of Au/Cu nanoparticles depends on the preparation methods. The structure might be the core shell, alloys or other morphology. Au- Cu core-shell nanocrystals were prepared using a two-step polyol reduction method. First, Au core seeds were prepared by reducing HAuCl$_{4}$. 4H$_{2}$O in ethylene glycol (EG) using oil-bath heating in the presence of polyvinylpyrrolidone (PVP) as a polymer surfactant. Then Cu shells were overgrown on Au core seeds by reducing Cu$_{2}$(OAc)$_{4}$ in EG with PVP again using oil-bath heating. The morphology is studied by STEM HITACHI S-5500.The resultant crystal structures were characterized using TEM, high-resolution (HR)-TEM and the STEM were using for the study of micro analysis. [Preview Abstract] |
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H1.00041: Synthesis and characterization of Au/Pd core/shell bimetallic nanoparticles Nabraj Bhattarai, Jesus Velazquez-Salazar , Gilberto Casillas Garcia, Miguel J. Yacaman The structure of nanoparticles plays an important role in many applications of nanotechnology like plasmonics, catalysis, electronic, optical, sensing and others. Using the bimetallic nano particles the properties will be changed. The particles shape is equally important as the size of the particles. The production of high index facet nanoparticles changes the shape by increasing the kinks and density of atomic steps there by increasing the catalytic activity of the reactions. The structure of Au/Pd nanoparticles depends on the preparation methods. The structure might be the core shell, alloys or others. We synthesized Au-Pd core-shell cubic nanoparticle of size 30nm. The morphology is studied by STEM HITACHI S-5500. The HRTEM image, diffraction pattern, weak beam dark field image is obtained by JEOL 2010-F transmission electron microscope equipped with field emission gun and an ultra-high-resolution pole piece with STEM attachment. The micro analysis EELS and EDS spectra is obtained by ARM 200F. The distribution of nanoparticles is observed by EDS mapping. The strains from weak beam dark field image and the reconstructed image from tomography confirmed the nanocube structure. Also the EDS mapping and EELS spectrum confirmed the Au core and Pd shell structure. [Preview Abstract] |
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H1.00042: Structural and Magnetic Properties of Multifunctional Gold, Silica, and C225 antibody triply coated Superparamagnetic Iron Oxide nanoparticles Gan Liang, Marites Melancon, Chun Li In this study, extensive structural and magnetic characterizations have been carried out on the silica, gold, and C225 antibody triply coated iron oxide nanoparticles for image-guided laser ablation of head and neck tumors. X-ray absorption and x-ray diffraction results show the phase of the uncoated and coated nanoparticles to be in the $\gamma $-Fe$_{2}$O$_{3}$ structure. The nanoparticles are studied by transmission electron microscopy and it is found that these nanoparticles have an average diameter of 82 nm and contain 142 antibodies per nanoshell. The magnetization measured at 500 Oe indicates that coating of the iron oxide nanoparticles by silica/gold/C225 decreases blocking temperature from 160 K to about 55 K, which can be explained by the spin-disorder induced change in the effective volume of the $\gamma $-Fe$_{2}$O$_{3}$ core. The blocking temperature decreases from 95 K to 55 K with an increase of magnetic field from 100 Oe to 500 Oe. It is found that the coercivity of the triply coated nanoparticles decreases from 195 to 25 Oe with an increase of temperature from 5 K to 300 K. [Preview Abstract] |
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H1.00043: Of intent, citation game, and scale-free networks in science: A heuristic argument Victor Christianto, Florentin Smarandache A heuristic argument was presented in favor of hypothesis that scientific communication corresponds to a process known as scale-free network. As a result, it is argued that scientific referencing through citation follows the same process, therefore it could be expected that this shall also exhibit fractality as observed in various phenomena associated with scale-free networks. This argument appears conceivable because the process of citation involves a decision-making, coined here as ``citation game.'' [Preview Abstract] |
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H1.00044: Pilot Study on Alternative Pictorial Representations and Supporting Text of Sound Standing Waves of Air Columns in a Pipe Liang Zeng, Chris Smith, Jennifer Rodriguez, Edgar Corpuz Alternative pictorial representations of sound standing waves of air columns in a pipe were drawn for the first three harmonics in an open-open pipe as well as in an open-closed pipe. Supporting text describing air molecule motion over time was also provided. These pictorial representations and supporting text were designed to reveal the main characteristics of the physical mechanisms of sound standing waves of air columns in pipes. Through a pilot study utilizing surveys and interviews, we validated our design and investigated the differences in the effects on student learning of underlying physics concepts between the new design and the existing one in an introductory physics textbook. The implications of our results for teaching were discussed. [Preview Abstract] |
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H1.00045: Conductance Control Iris for the K150 Cyclotron H- Ion Source Armando Maldanado, Henry Clark, Gabriel Tabacaru A multi-cusp H- ion source has been installed on the K150 cyclotron for the production of high intensity proton beams. These beams will be used to create secondary radioactive ions for the Upgrade Project [1]. One of the limiting factors in creating an intense beam comes from poor vacuum along the injection line caused by the ion source itself. A large flow of hydrogen gas is required to make the Hydrogen negative (H-) ions in the ion source. As a result, many of the hydrogen molecules exit the ion source and migrate into the injection line and deteriorate the vacuum. To reduce the flow of these molecules into the injection line, a computer controlled iris will be installed between the ion source and the injection line. With the iris set at the correct diameter, the vacuum in the injection line should improve the transport efficiency of the H- ions to the cyclotron inflector should increase. For the project we used an 8" OD Conflat DVM brand iris with an MDrive 17 Plus motor which will be controlled by a Labview software interface. [Preview Abstract] |
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H1.00046: Electron screening and its effects on Big-Bang nucleosynthesis John Fuqua, Carlos Bertulani We study the effects of electron screening on nuclear reaction rates occurring during the Big Bang nucleosynthesis epoch. The sensitivity of the predicted elemental abundances on electron screening is studied in details. It is shown that electron screening does not produce noticeable results in the abundances unless the traditional Debye-H\"uckel model for the treatment of electron screening in stellar environments is enhanced by several orders of magnitude. The present work rules out electron screening as a relevant ingredient to Big Bang nucleosynthesis and other exotic possibilities for the treatment of screening, beyond the mean-field theoretical approach. [Preview Abstract] |
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H1.00047: Testing Scintillators for Homeland Security James Bourbeau, Andrew Brandt, Rasool Kenarangui, Alex Weiss, Wei Chen Scintillating nanoparticles have a bright future in radiation detection, especially in the area of detecting nuclear devices. As part of a UTA nanoparticle scintillator development team funded by the Department of Homeland Security, I have been developing a scintillator test stand using various radioactive sources and a Hamamatsu S3590 photodiode. I will present initial test results. [Preview Abstract] |
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H1.00048: Angelo State Society of Physics Students Peer Pressure Team Public Engagement Efforts -- Do we make a difference? Jeremy Johnson, Toni Sauncy The Angelo State Society of Physics Students Peer Pressure Team travels throughout West-CentralTexas for a week following the spring semester. The goals of this activity are two-fold. First the group seeks to engage undergraduate presenters in public servive; the second goal is to enhance attitudes about science and encourage students in K-12 public schools to study science. Many of the schools we choose for our outreach visits are geographically isolated and populated with socioeconomically disadvantaged students, and/or groups underrepresented in physics. Over the week, the Peer Pressure Team visited over 1300 students, teachers and administrators. At each visit, surveys were collected to gauge the program's effectiveness. Student responses indicate a strong desire to study more science in their regular school curriculum. In addition, results are used to determine which demonstrations leave the most lasting impression on the audience participants. The 2011 Road Tour was dedicated to the 100$^{th}$ anniversary of the discovery of the nucleus by Rutherford. [Preview Abstract] |
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H1.00049: Construction of a Single Beam Optical Trap with a Modified Design David To, Tanya Dax, Toni Sauncy We have constructed an apparatus known as an optical tweezers using off the shelf, fairly inexpensive components. These include a 20 mw HeNe laser, a standard student lab optical microscope, and an inexpensive CCD firewire camera. The trap is designed to work with polystyrene spheres of various diameters, but to be robust enough for more advanced research. The goal of the work is to use the device for undergraduate research projects but also for use in the advanced labs at Angelo State. Trapping is achieved in the device by focusing the collimated laser beam using a 100x oil immersion objective on the microscope. At the position of the beam waist, the light produces gradient forces that trap the micron-sized spheres. Images are collected and processed using LabVIEW$^{TM}$ software. Measurement of particle size is accomplished through software tools for use with unknown-sized samples in the future. [Preview Abstract] |
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H1.00050: Developing a procedure for the fabrication of PLED structures for an advanced undergraduate lab Jordan Perez, Toni Sauncy Using polymer materials in thin layers to fabricate Light Emitting Diode (LED) structures is a topic of much current research.Because the structures are composed of commercially available polymers, they have become accessible as tools for teaching at the undergraduate level for advanced labs. At Angelo State, the fabrication of polymer-based LED structures is being pursued in order to develop a procedure that can be reproduced easily by undergraduate students. The structure consists polymer layers: PEDOT:PSS--MEH-PPV sandwiched between Indium Tin Oxide (ITO) coated glass slides. An Indium Gallium Eutectic metal layer on the ITO serves as the cathode, while the bottom ITO layer serves as the anode. Devices have been fabricated which emit light in response to an external voltage as low as 7V. The results have been inconsistent primarily due to the difficulties in layering the polymers uniformly on the ITO substrates. An inexpensive spin coater is used to deposit polymer layers; determining the proper spin rate and controlling the spin rate are thought to be the primary issues in producing uniform layers. [Preview Abstract] |
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H1.00051: By emotion, no atomic bomb and no blackhole Philip Shin As to be, we glory to God and that is basic theology for christian. And I want to say that BE means just thinking. There is no clue of nature and no proposition to prove it. I just believe by feeling and emotion. I trust that it can be the physic really. As for me, I believe when there is atomic bomb, than anytime it has to blow out the world each time of we are living. So the atomic bomb we thinking is just accident and not by the atomic theory. Also when there is blackhole, than there must be the wall to block me forever and never to walk again. So there are no blackhole. And these two subject is the best two subject for the physic. [Preview Abstract] |
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