Bulletin of the American Physical Society
2008 Joint Fall Meeting of the Texas and Four Corners Sections of APS, AAPT, and Zones 13 and 16 of SPS, and the Societies of Hispanic & Black Physicists
Volume 53, Number 11
Friday–Saturday, October 17–18, 2008; El Paso, Texas
Session D1: Poster Session (15:00-18-00) |
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Room: Union East, 3rd Floor University |
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D1.00001: ABSTRACT WITHDRAWN |
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D1.00002: Using Single-Particle Flourescence to Detect Bioaerosols Elena Fernandez, Hermes Huang, Yong-Le Pan, Steven Hill, Ronald Pinnick, Richard Chang We have developed and operated an UV Laser-Induced Fluorescence single particle spectrometer which is capable of rapidly measuring the fluorescence emitted from individual aerosol particles, on-the-fly, as they are sampled by our sensor. Fluorescence-based detection methods have the advantage that they can deliver results in real-time and require little human labor in order to operate. We present ambient aerosol data measured in New Haven, CT, Las Cruces, NM, and Adelphi, MD. At the different locations, we find that the fluorescence characteristics of organic aerosols found remain rather similar. We also measured many different known samples in order to build a library of characteristic spectra to which we can compare the ambient data. In addition to measuring spectra from the aerosol particles, we have developed an air puffer technology which allows us to collect specific aerosol particles based on their fluorescence spectral signatures. The detection and collection of these Flourescent Bioaerosols is important as we can detect potentially harmful single airborne particles such as biowarfare agents. The research also extends to soldier health as the regional climate of Iraq is similar to that of the Chihuahuan desert where Las Cruces, NM is located. [Preview Abstract] |
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D1.00003: The Last/Heaviest element of the Periodic table and the neutrons-proton diagram Albert Khazan The raised stability of the atomic nucleus containing 2, 8, 20, 28, 50, 82 and 126 protons and neutrons, is caused by that growth of number of neutrons advances quantity of protons in heavy nucleus. As a result they become energetically steadier. The nucleus we have calculated, including an element 155, is located in the line of a trend whose size of reliability makes 0.9966. The element predicted by some scientists, with nucleus Z=114, N=184, is far distant in the party. Thus it was found out, that with Z=114 the N should be 179, and also N=184 results Z=116. In the field of the numbers 104-114 there are essential fluctuations of the nuclear masses and the numbers of neutrons. It is due to the fact that, in the Periodic Table, the nuclear mass of the most long-living isotopes of an element is a result of that fact that the breaking of the strict law of increase in the mass with the growing up of the charge of a nucleus. Independence of the line of a trend of the position of the last element has been verified by calculation. Therefore it is offered to consider N 155 for diagnosing products of nuclear reactions. (Progr. Physics, 2007, v.1, 38; v.2, 83; v.2, 104; 2008, v.3, 56). [Preview Abstract] |
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D1.00004: Methodology of Synthesis and Optical Analysis of Rare-Earth Ions (RE$^{3+})$ in the Polymeric Host PMMA Sreerenjini Chandra, John B. Gruber, Dhiraj K. Sardar We report the syntheses of RE$^{3+}$:Y$_{2}$O$_{3}$ nanoparticles in the polymeric host, PMMA (Poly-Methyl Methacrylate). Addition of adequate amount of surfactant, named Hexadecyl Trimethyl Ammonium Bromide (CTAB) prevents the aggregation of nanoparticles in PMMA. The hydrophobic tails of CTAB micelles link to the hydrocarbon chains of PMMA, forming aggregates which trap the nanoparticles at those positions, thereby giving rise to a uniform distribution of nanoparticles in the polymer-surfactant matrix. Room temperature and the low temperature absorption spectra of various rare-earth samples have been obtained and included for detailed comparison. The Judd-Ofelt intensity parameters, radiative decay rates, branching ratios, and the corresponding radiative lifetimes of excited states are reported. The detailed analysis emphasizes the relevance of embedding the RE$^{3+}$:Y$_{2}$O$_{3}$ ions in the PMMA host. [Preview Abstract] |
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D1.00005: Optical Characterization of Properties of Split Ring Resonators Roberto De Alba, Kai Wang, KyongWan Kim, Robert Bassett, Cynthia Trendafilova, Andrea Burzo, Igor Lyuksyutov, Alexei Sokolov Negative index materials (NIMs) are artificially made structures with unit cells smaller than the wavelength of incident light. Conceptually, these materials have the potential to revolutionize current technologies -- from allowing us to resolve structures smaller than the wavelength of light, to paving the path towards `invisibility cloaks'. In the past, these structures have been demonstrated to exhibit a negative index of refraction for microwave frequencies. Today, the goal is to develop structures with these properties in the visible wavelength range, and state-of-the-art research has already led to NIMs with resonances near infrared wavelengths. In this work we investigate the influence of different parameters, including size, material, and substrate on the resonant properties of the split ring resonator structures (SRR). In particular, the use of semiconductor substrates could lead to control of the resonant frequencies due to changes in carrier concentration. [Preview Abstract] |
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D1.00006: Visualization of filament on DCM dye Jinhai Chen, Milan Poudel, Alexandre Kolomenski, Hans Schuessler The filament, which consisted of self-focusing, defocusing, intensity clamping and self-phase modulation has been visualized using two-photon fluorescence. The systematic study of power dependence for DCM dye was compared with that of coumarin-30 dye. The simultaneous measurement of two-photon fluorescence and transmission including white light emission was performed to better [Preview Abstract] |
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D1.00007: Optical Lithography on non-flat surfaces; A Case Study Clayton Moore, Conrad Newton, Wilhelmus Geerts, Daniel Palmer, Dan Tamir Only a few studies of optical lithography on non-flat substrates have been reported. Most of these systems only work on polished very well defined substrates. For example, Ball Semiconductor developed a system for projection lithography on polished spherical balls of 1 mm diameter. We propose a system that works on an arbitrary surface and enables lithography on a wide variety of substrates including the wings of insects or a single crystalline grain of a ceramic sample. The system consists of a computer controlled laser beam that is focused through an optical microscope on an XY-table. The size of the beam can be changed by varying the size of the aperture or the change of the objective. The focus of the microscope can be automatically adjusted enabling to follow the 3D profile of the sample's surface. The laser intensity is automatically adjusted to keep the dose constant as the samples profile and the speed of the xy-table very. A cross-compiler, which utilizes principles of computer graphics to figure the required exposure parameters based on the surface of the object was developed. It accepts a text file, a vector based graphic file, or a raster image and generates a file with instructions for the laser beam writer. [Preview Abstract] |
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D1.00008: Physical Detection of Specific Proteins using Gold Nanoparticles Priyanka Ramachandran, Shawn Christensen, Samir Iqbal Protein function relies on binding to specific target molecules in the context of the proteome, perturbations of the proteome are often coincident with diseases and disorders. The ability to detect proteins at the nano scale can lead to more effective treatments. In this work, we report electrical detection of proteins bound to aptamer DNA. For this, the R2Bm protein-DNA pair is used. The 24 base-pair probe DNA is modified with amino group and attached to silicon chips. The DNA binding region of the R2Bm protein is flowed in to the DNA-chip and allowed to bind. For the electrical detection, modified gold nanoparticles are flowed in. The specific binding of DNA and the protein is confirmed with staining. The binding of the gold nanoparticles to the protein is confirmed by electron microscopy. Our current work with metal nano-electrodes will also be presented. [Preview Abstract] |
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D1.00009: Structural and electronic properties of aluminum nanoclusters Mrudula Raparla, Tunna Baruah, Rajendra R. Zope The electronic properties of Al clusters containing upto 60 atoms are investigated using an all electron density functional theory using large polarized Gaussian basis sets with 39 Gaussians per atom (NRLMOL basis). We have performed an extensive search for the lowest energy isomers for clusters up to Al$_{21}$. We build a database of candidate structures for the ground state using different strategies. First, a few structures are randomly generated and fully relaxed using plane wave pseudo potential method. We also performed simulated annealing runs using ab initio molecular dynamics for clusters upto Al$_{20}$. In three sets of simulated annealing runs the clusters were heated upto 900 and 1000K and were slowly cooled to 50K at different rates. After every half picosecond, the cluster was quenched. Additionally the best basin hopping geometries obtained using empirical embedded atoms potential were also fully optimized. The process generates 40-50 structures for each size. All the structures are relaxed using full-potential PAW method using a large energy cutoff. For larger clusters we used best available geometries from literature obtained from basin hopping and simulated annealing techniques. The electronic properties of Al clusters are subsequently determined for this database at the all-electron level using Gaussian basis set. [Preview Abstract] |
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D1.00010: Where can we make an efficiency breakthrough with CdTe solar cells? Kuo-Jui Hsiao CdTe is a potential candidate for the material of high efficiency thin film solar cells due to its high absorption and theoretical optimal bandgap. However the record efficiency of CdTe solar cells is only about 55{\%} of its theoretical maximum efficiency, primarily because of a voltage well below that expected for its bandgap. A CdTe solar cell with superstrate configuration Glass/TCO/CdS/CdTe/CdZnTe/Metal is proposed. In this configuration, CdZnTe electron reflector, which should improve open circuit voltage, will be added to the standard structure. This proposed configuration can be achieved in the continuous in-line deposition system at Colorado State University. Since the vacuum will not be broken, less interfacial defects are expected. [Preview Abstract] |
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D1.00011: Gallium Nitride Light-Emitting Diodes Grown on Silicon Substrates Eduardo Parra, Joseph Gilgen, Adam Blake, Derek Caselli, Chris Durot, Jason Mueller, Ignatius Tsong, John Roberts, Edwin Piner, Kevin Linthicum, James Cook, Jr., Daniel Koleske, Mary Crawford Light-emitting diodes (LED) of InGaN-GaN multiple quantum wells (MQW) are grown on Si(111) substrates. The lattice mismatch between GaN and Si is accommodated by a buffer layer of ZrB$_{2}$(0001) while the thermal expansion mismatch is alleviated by a transition layer consisting of AlN, AlGaN, and GaN. The ZrB$_{2}$ buffer layer is grown at Arizona State University (ASU) and the transition layer grown at Nitronex Corporation. The MQW-LED is grown on the resulting composite substrate. The fabrication and the testing of the MQW-LED are conducted at Sandia National Laboratories. The results are compared with an identical InGaN-GaN MQW-LED grown on a conventional sapphire substrate. The three-way collaboration among ASU, Nitronex and Sandia is a project of the National Science Foundation Partnership For Innovation (NSF-PFI) program. [Preview Abstract] |
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D1.00012: Remote Plasma Driven Modifications in Luminescent Properties of ZnO Nanopowders Henry Vallejo, Antonio Paramo, Raul Peters, Pankaj Kumar, Yuri Strzhemechny Photoluminescence (PL) spectra of several commercially available ZnO nanopowders were investigated for as-received and remote-plasma treated samples. Sample-to-sample spectral discrepancies, even for materials from the same vendor, were observed at room temperatures as well as at 8 K. These differences, in both the near-band transitions and defect luminescence, are significant enough to obscure possible spectral dependence on the average nanocrystalline grain size and the grain size distribution (as measured by electron microscopy). Temperature-dependent PL spectra were analyzed in detail for the bound exciton range. Numerical fits of peak intensities and peak positions vs. temperature for a number of excitonic emissions using Arrhenius and Varshni approximations yielded activation energies and Debye temperatures. Significant spectral modifications were observed, at room and low temperatures, after the nanopowders were treated with remote O, N, and H plasmas. Different plasma species produced distinct signatures in the spectra. [Preview Abstract] |
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D1.00013: Raman study of supported molybdenum disulfide single layers William Durrer, Felicia Manciu, Pavel Afanasiev, Gilles Berhault, Russell Chianelli Owing to the increasing demand for clean transportation fuels, highly dispersed single layer transition metal sulfides such as MoS$_{2}$-based catalysts play an important role in catalytic processes for upgrading and removing sulfur from heavy petroleum feed. In its crystalline bulk form, MoS$_{2}$ is chemically rather inactive due to a strong tendency to form highly stacked layers, but, when dispersed as single-layer nanoclusters on a support, the MoS$_{2}$ becomes catalytically active in the hydrogenolysis of sulphur and nitrogen from organic compounds (hydrotreating catalysis). In the present studies alumina-supported MoS$_{2}$ samples were analyzed by confocal Raman spectroscopy. Evidence of peaks at 152 cm$^{-1}$, 234 cm$^{-1}$, and 336 cm$^{-1}$, normally not seen in the Raman spectrum of the standard bulk crystal, confirms the formation of single layers of MoS$_{2}$. Furthermore, the presence of the 383 cm$^{-1}$ Raman line suggests the trigonal prismatic coordination of the formed MoS$_{2}$ single layers. Depending on the sample preparation method, a restacking of MoS$_{2}$ layers is also observed, mainly for ex-thiomolybdate samples sulfided at 550\r{ }C. [Preview Abstract] |
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D1.00014: The Current State of Semiconducting Silicide Research Ryan Cottier, Nader Elmarhoumi, Terry Golding Silicon is still the material of choice for most microelectronic applications although it is not the ideal choice for many optoelectronic applications. The twelve semiconducting silicides may bridge this gap. Fundamental energy gaps of the known semiconducting silicides range from 0.07-0.12 eV (hexagonal MoSi$_{2}$ and WSi$_{2}$, ReSi$_{2}$) to 2.3 eV (Os$_{2}$Si$_{3}$). With further development, they may provide a background for energy-gap engineering similar to that achieved with III-V compounds in their superlattices. The authors will discuss the current state of semiconducting silicides including our own investigation into the growth and characterization of $\beta$-FeSi$_{2}$, $\beta$-Fe(SiGe)$_{2}$, OsSi$_{2}$, and Os$_{2}$Si$_{3}$. [Preview Abstract] |
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D1.00015: Synchrotron-Based X-Ray Absorption Spectroscopy of Iron Silicon Germanide and Osmium Silicide Grown by Molecular Beam Epitaxy Nader Elmarhoumi, R. Cottier, F. Amir, G. Merchan, A. Roy, H. Geisler, C.A. Ventrice, T.D. Golding Some of the iron- and osmium-based metal silicide and germanide phases have been predicted to be direct band gap semiconductors. Therefore, they show promise for use as optoelectronic materials. We have used synchrotron-based x-ray absorption spectroscopy to study the structure of iron silicon germanide and osmium silicide films grown by molecular beam epitaxy. Osmium silicide films which are primarily in the Os$_{2}$Si$_{3}$ phase and a series of Fe(Si$_{1-x}$Ge$_{x})_{2}$ films with a nominal Ge concentration of up to x = 0.04 have been grown. X-ray absorption near edge structure (XANES) measurements on both the iron silicon germanide and osmium silicide films has been performed. An absorption edge shift of 0.9 eV is observed for the osmium silicide films; however, no shift was observed for the iron silicon germinide films. Extended x-ray absorption fine structure (EXAFS) measurements have also been performed on the iron silicon germanide films. The nearest neighbor co-ordination corresponding to the $\beta $-FeSi$_{2}$ phase of iron silicide provides the best fit with the EXAFS data. [Preview Abstract] |
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D1.00016: MaRIE: Matter-Radiation Interactions in Extremes, a Signature Facility Providing Experimental Resources for Transformational Materials Discovery Cris W. Barnes, R.D. Fulton, David J. Funk, Carter P. Munson, Andrea Palounek, John L. Sarrao, Kurt F. Schoenberg Materials-centric national security science is vital for addressing 21st Century missions of energy security, stockpile stewardship, homeland security, and providing discovery science. Relevant grand challenges of the next two decades include: closing the 10~TW gap between the energy we have and the energy we need; transforming the enterprise of the nuclear weapons complex; and detecting threats with unprecedented sensitivity and efficiency. MaRIE is a proposed signature facility for Los Alamos National Laboratory that is centered on creating and exploiting radiation-matter interactions and providing transformational materials performance through validated predictive multi-scale understanding. Building on the capabilities of the Los Alamos Neutron Science Center, components of MaRIE will provide extreme irradiation fluxes, multiple diagnostic probes to bridge the ``micron gap'' between atomic scale/molecular dynamics and continuum model/integrated tests, and synthesis and characterization labs to make, measure, and model materials. This presentation will describe the challenges, approaches, and implementation timescale being developed for MaRIE, and engender input and interest by the scientific user community. [Preview Abstract] |
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D1.00017: The Effect of Plastic deformation on the Magnetic Properties of thin Iron and Permalloy Films Amanda Gregory, Kyle Smith, Clayton Moore, Anup Bandyopadhyay, Dan Palmer, Wim Geerts, Martin Sablik Understanding the influence of stress on the magnetic properties of thin films is vital if one wishes to apply them in devices. Although extensive work has been done on the magneto-elastic properties, little research has been done on the magneto-plastic properties of thin films. In order to investigate these effects, we deposited thin Fe and NiFe films on polished and non-polished superelastic nitinol sheet metal by ion beam sputtering. The magnetic properties before and after plastic deformation of the thin films were determined by VSM. The films were plastically deformed either by linear extension using an Materials Tester, or by bending the samples over a cylinder. The linear stretching experiments resulted in an inhomogeneous strain throughout the sample showing the pseudo-elastic properties of the superelastic nitinol. In the large strain areas the thin film would be removed from the nitinol substrates while in the low strain areas the thin film appeared to be unaffected. The bending experiments, on the contrary, yielded an apparently homogeneous strain through the thin film. The magnetic properties of these strained samples will be discussed. [Preview Abstract] |
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D1.00018: SCD installed at LANSCE Joe Peterson, Karunakar Kothapalli, Heinrich Nakotte, Arthur Schultz Flight path 6 at Los Alamos Neutron Science Center (LANSCE) was equipped with a single crystal diffractometer (SCD). Imported from Argon's recently terminated Intense Pulsed Neutron Source (IPNS), the SCD features two positions-sensitive neutron scintillator area detectors based on the Anger camera design. Each detector has an active area of 15 x 15 cm$^2$ and boasts achieve spatial resolution finer then 2 mm. Some of our initial studies indicate that useful measurements can be preformed on single crystals less then 1 mm$^3$. [Preview Abstract] |
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D1.00019: Conductivity in disordered graphene systems by the recursion method Shangduan Wu Conductivity in disordered graphene systems are calculated based on the recursion method. With the real-space method, we calculate diagonal Kubo conductivity with a binary alloy disorder. Our results are in good agreement with recent experiments and provide a way for detecting the concentration of gas molecules absorbed on graphene in numerical studies. Diffusion coefficient, Charge mobility and mean free path in these systems will also be discussed. A new method which allows one to evaluate hall conductivity of independent electrons in a static potential also has been developed. [Preview Abstract] |
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D1.00020: Micromachined thermal isolation devices for measuring in-plane thermal conductivity of thin films from 77 to 325 K Azure Avery, Rubina Sultan, Barry Zink Thin films and nanostructures are some of the potential materials being studied for improved thermoelectric properties. Thermal properties of these thin films can often differ from those of bulk materials. Although there are several well established techniques for measuring cross plane thermal conductivity $k_{\perp}$, measuring in plane thermal conductivity $k_{\parallel}$ is often difficult. We describe our technique to measure $k_{\parallel}$ of thin films from 77 K to 325 K using micromachined thermal isolation structures. The geometry of the structures dramatically reduces the contribution of radiation heating to thermal conductance which often complicates steady state measurements at temperatures above 100 K. We will present our $k_{\parallel}$ measurements for 500 nm thick amorphous silicon nitride (a-Si-N) and 200 nm thick Molybdenum (Mo) thin film samples. We will compare the Mo measurements to those calculated for Mo using the Wiedemann-Franz law to establish the validity of our measurement technique. Finally, we will discuss how our technique can be applied to measurements of thermal transport in ferromagnetic thin films. [Preview Abstract] |
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D1.00021: Structures and spin states of small Rhodium clusters Olga Ruiz, Tunna Baruah We use density functional theory to investigate the geometrical structures and spin ordering in small clusters of Rh in the size range 7-10. The calculations are performed at the all-electron level using a linear combination of atomic orbital approach. The exchange-correlation effects are treated using the generalized gradient approximation. The Gaussian basis set contains 56 basis functions per atom. For each cluster size, several isomers were studied and for each isomer all the possible ferromagnetic and anti-ferromagnetic spin orderings were studied. We find that in several isomers, the anti-ferromagnetic spin orders are competitive in energy to the ferromagnetic one.The structures, binding energies, spin magnetic moments and spin orderings of the ground and low-lying states will be presented. [Preview Abstract] |
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D1.00022: Direct measurements of thermoelectric properties of thin films and nanostructures Rubina Sultan, Azure Avery, Barry Zink Dwindling energy reserves have created an urgent need for alternative energy sources. Measurement and development of new thermoelectric materials offer an opportunity to recycle the waste heat from energy consumption, transforming it into a viable energy source. Efforts to maximize the dimensionless figure-of-merit $ZT$ rely on accurate and effective measurement techniques. The aim of this poster is to present the design of thermal isolation structures and the thermopower measurements made using these structures on thermoelectric thin films. The unique design of the micromachined structures allows us to make simultaneous measurements of thermopower $\alpha$ and thermal conductivity $k_{\parallel}$ to calculate $ZT$. We will present the measurement platform design and results from our first measurements on devices with established thermoelectric properties. Finally we will discuss the growth of our first doped amorphous silicon thin films and their potential as an efficient new class of thermoelectric materials. [Preview Abstract] |
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D1.00023: Chaotic Backward Volume Spin Waves A. Hagerstrom, W. Tong, M. Wu, B. Kalinikos, R. Eykholt Chaotic backward volume spin waves, excited by three-wave interactions, have been investigated. The waves were produced in an yttrium-iron-garnet film in an active feedback ring. Previous experiments have focused on the three-wave interaction of surface waves and backward volume waves produced in a similar system. In contrast to the previous work, this experiment focused on the detailed study of the three-wave processes of backward volume spin waves only. Measurements on the three-wave process threshold were first carried out for different magnetic fields and frequencies. After that, measurements were made for a set of ring gain levels in order to study the development of chaotic behavior in the feedback ring in a systematic way. Time profiles and frequency spectra of the generated signals were recorded. It was observed that in the formation of the chaotic signals, the ring eigen-modes played an important role. It was these modes that were becoming parametrically unstable against three-wave decay processes as the ring gain increased. Chaotic behavior existed over a range of ring gain levels. With a ring gain between 1.5 and 3 dB, it was possible to calculate the correlation dimension of the chaotic signal. As the ring gain increased from 1.5 dB to 3 dB, the correlation dimension increased from 4.7 to 12.5. This experiment demonstrates a new approach to construct a microwave chaotic oscillator as well as a possible microwave power limiter. [Preview Abstract] |
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D1.00024: Explorations into the Schrodinger Uncertainty Relation Nathan Steiger, Jean-Francois Van Huele Are there situations that find the Heisenberg Uncertainty Relation lacking? We use harmonic oscillators, free particle wave packets, square wells, and spin to demonstrate the need for the unsung Schr\"{o}dinger Uncertainty Relation. Schr\"{o}dinger expanded upon Heisenberg's original informal relation $ \Delta x\Delta p \approx h $ and Robertson's formal derivation of $\Delta A \Delta B\geq \frac{1}{2}|\langle[\hat{A},\hat{B}]\rangle|$ to find $\Delta A \Delta B \geq \sqrt{\Big(\frac{1}{2}\langle\{\hat{A},\hat{B}\}\rangle - \langle \hat{A} \rangle\langle \hat{B}\rangle\Big)^{2}+ \Big|\frac{1}{2}\langle[\hat{A},\hat{B}]\rangle\Big|^{2}}$. We will highlight the importance of the contributions that eluded Heisenberg. These contributions have both classical and quantum realizations. [Preview Abstract] |
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D1.00025: Magnetic Nano Films and Devices for Millimeter Wave Communications Mitchell Knaub Magnetic devices that operate in the microwave regime have revolutionized the wireless communications industry. Devices such as phase shifters and circulators are vital components in wireless phones, satellites, and radar; however, there is focus on these devices to push the operating frequencies to the millimeter wave regime. The push to millimeter wave devices entails wireless communication to easily penetrate thick clouds and dust, where microwaves could not. The strategy to push millimeter wave devices begins with ferromagnetic thin films. Metallic films are a prime candidate because of their high magnetization, and thus, higher ferromagnetic resonance (FMR) frequencies. The FMR frequency is what ultimately determines a devices operating frequency. Another strategy to produce high FMR frequencies in films without a large static field is to induce surface spin-wave pinning. By pinning the spin waves, it is possible to induce secondary FMR modes (at the same high frequency as un-pinned modes) which require a lower static magnetic field. This would allow millimeter wave devices to operate at higher frequencies as well as meeting size and weight requirements. [Preview Abstract] |
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D1.00026: Evidence of Glauber Dynamics in a Metamagnetically Ordered Nanowire Andrey Prosvirin, Hanhua Zhao, Kim Dunbar In this work, we describe an unusual type of nanowire obtained from a decomposition of Mn$_{12}$-Ac. The structure of {\{}[Mn(OH)(CH$_{3}$CO$_{2})_{2}$]CH$_{3}$CO$_{2}$HH$_{2}$O{\}}$_{\infty }$, consists of neutral 1-D chains based on the six coordinate Mn(III) centers [1]. AC magnetic susceptibility measurements reveal to the appearance of an out-of-phase signal, \textit{$\chi $"}$_{m}$ in the range of 1.8-2.6 K. The signal is clearly frequency dependent, which is an indication of a slow relaxation process. The magnitude of the \textit{$\chi $''}$_{m}$ signal is approximately one-third that of \textit{$\chi $'}$_{m}$, as is generally observed for such systems. The frequency dependence of the position of the peak in \textit{$\chi $"}$_{m}$ follows an Arrhenius law with an activation energy $\Delta E$/$k_{B}$ = 27.1 cm$^{-1}$ and \textit{$\tau $}$_{0}$ = 1.2 10$^{-10}$ s. The Cole-Cole plot shows the expected semicircle shape for a single relaxation process, confirming single-chain magnet behavior. The compound constitutes a new member of the single chain magnet family, being an homometallic antiferromagnetic chain [2]. Since antiferromagnetic exchange interactions are typically much stronger than those of the ferromagnetic type, higher blocking temperatures can be expected in such examples of single chain magnet, with the only requirement being the presence of spin canting. [1] D. J. Price, S. R. Batten, B. Moubaraki, K. S. Murray Polyhedron 22, 2003, 2161 [2] Z.-M. Sun, A. V. Prosvirin, H. Zhao, J.-G. Mao, K. R. Dunbar, J. Appl. Phys. 2005, 97 (10, Pt. 2), 10B305/1 [Preview Abstract] |
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D1.00027: Gas sensing response of nanostructured CoSb$_{2}$O$_{6}$ prepared by non-aqueous solution methods Carlos Michel, Juan Moran, Hector Guillen, Alma Martinez Nanostructured CoSb$_{2}$O$_{6}$, with trirutile type structure, was prepared by a non-aqueous solution-polymerization method, using antimony chloride, cobalt nitrate, polyvinyl pyrrolidone and ethyl alcohol. The evaporation, by microwave radiation, of the precipitate obtained in the initial stage of the synthesis, produced an amorphous solid precursor. Further calcination at 700$^{\circ}$C yielded the target composition. X-ray powder diffraction was used to identify the crystal structure, which corresponds to tetragonal with cell parameters a = 4.6544 {\AA} and c = 9.2823 {\AA}, and space group P42/nmn. SEM and TEM were used to analyze particle size and shape; by TEM, nanostructured particles with shape of filaments with 20 nm diameter and length up to 600 nm were observed. Their local crystallinity was confirmed by selected area electron diffraction. To test CoSb$_{2}$O$_{6}$ as a gas sensor material, the powder was deposited on alumina substrates using the screen-printing technique. DC electrical characterization was performed in air, O$_{2}$ and CO$_{2}$ from room temperature to 600$^{\circ}$C. The dynamic response of resistance characterization displayed a variation of about 1k$\Omega$ when detecting CO$_{2}$; whereas for O$_{2}$ a change in the order of 10$^{2} \Omega$ was measured. [Preview Abstract] |
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D1.00028: Magnetic Speckle Images: A Cross-Correlation Study Joseph Nelson, Karine Chesnel Ferromagnetism has intrigued scientists since ancient times, and within the last few years, new methods have been developed to study the properties and behavior of thin ferromagnetic films. Soft X-Ray Resonant Magnetic Scattering (SXRMS) has been used to detect spatial and temporal variations in the microscopic magnetic domain of such films on the scale of $\sim$100nm. Coherent X-ray beams are projected through (or reflected off of) a sample, creating an interference speckle pattern in the reciprocal space, analogous to a Fourier Transform of the microscopic domain pattern. Speckles, or areas of high and low local intensity within these images are unique to the microscopic configuration of the magnetic domains. Thus, the magnetic memory, or extent to which a material will return to its original magnetic configuration, can be measured using quantitative cross-correlation of SXRMS images. In our analysis, we used Matlab to perform such cross-correlation procedures. We will discuss the methods of calculating the correlation coefficient ? between pairs of images (represented in matrix form), our optimization procedure, as well as data representing the cross-correlation of a Cobalt-Platinum sample measured at 20K. Inferences will be drawn regarding the magnetic memory of the sample. [Preview Abstract] |
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D1.00029: Thickness Dependency of Ferromagnetic Domains in CoPt Multilayers Nathan Gay, Karine Chesnel, Olav Hellwig Ferromagnetic materials have been providing and still provide large potential technological interests, especially in the data storage industry. As first evidenced by L. Neel and F. Bloch, when the material is formed as a thin layer and exhibits a perpendicular easy magnetization axis, magnetic domains form in the nanometric scale with magnetic moments pointing alternatively in and out perpendicularly to the layer. In this work, we study the influence of the film thickness on the domain size and morphology in Co/Pt multilayers. We performed this study by using Magnetic Force Microscopy (MFM), a tool allowing the imaging of magnetic domains morphology through the interaction between a sharp magnetic probe and the stray field emanating form the surface of the sample. [Preview Abstract] |
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D1.00030: The bouncing ball through a geometrical series Sergio Flores, Luis L. Alfaro, Juan E. Chavez, Aztlan Bastarrachea, Jazmin Hurtado The mathematical representation of the physical situation related to a bouncing ball on the floor is an important understanding difficulty for most of the students during the introductory mechanics and mathematics courses. The research group named \textit{Physics and mathematics in context} from the University of Ciudad Juarez is concerned about the versatility in the change from a mathematical representation to the own physical context of any problem under a traditional instruction. In this case, the main idea is the association of the physical properties of the bouncing ball situation to the nearest mathematical model based on a geometrical series. The proposal of the cognitive development is based on a geometrical series that shows the time the ball takes to stop. In addition, we show the behavior of the ratio of the consecutive heights during the motion. [Preview Abstract] |
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D1.00031: A visualization of the charging and discharging processes of a capacitor Karla Carmona, Sergio Flores, L. Alfaro, Angel Hernandez, Juan E. Chavez Many instructors try students understand physical concepts through mathematical representations. In most of the cases, these representations are: the analytical and the graphical representations. These instructors believe that the approach based on equations and two-dimension graphics is enough didactic elements to develop a meaningful understanding in the students. This time, we have developed a learning proposal based on computer animations of the charging a discharging processes of a capacitor. The design is achieved through the use of Power Point and the geometry software Cabri. We hope students understand somehow the parallel plates of a capacitor get electric charge. [Preview Abstract] |
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D1.00032: EUV Spectrometers for Source Development, Characterization and Optimization Bryce Allred, Jeff Kemp, Jershon Lopez, Larry Knight, Scott Bergeson, Alexander Shevelko We report on the development of EUV transmission grating spectrometers. These compact instruments cover an extremely wide spectral range, from 2 to 250 nm, with 0.2 nm resolution and can be absolutely calibrated. They are ideal for characterizing spectral emission from EUV sources. The wide spectral range allows simultaneous measurements of both in-band and out-of-band emission. Spectral measurements from LPP sources on Li and Sn will be presented. [Preview Abstract] |
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D1.00033: Comparison of Synchronization in Small World and Random Networks Tess Bernard, Bruce Miller There are many models that simulate neuron firing in the brain. These range from the basic integrate-and-fire method to the complex Hodgkin-Huxley model. Eugene Izhikevich (2003) employed the principles of nonlinear dynamics, specifically bifurcation theory, to develop a model that is both simple and powerful, which can be described as an integrate-and-reset model. By changing only a few parameters, this model can simulate all the known types of cortical neuron firing patterns. Using it, we studied the properties of two different types of neural networks. In the first, originally used by Izhikevich, the synaptic connection strengths between the neurons are determined randomly, and each neuron is connected to all of the other neurons in the network. The second is a small world network modeled after the one employed by Alex Roxin, et al. (2004), but expanded to include inhibition. This geometry is an idealized representation of the nervous system. In our investigation we compared the onset of synchronization in each network, as well as its stability in the presence of external currents. We also considered the relevance of these results to real world phenomena such as seizures. [Preview Abstract] |
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D1.00034: Escape in the Strong Quantum Regime Alejandro Puga, Bruce Miller Physicists have used billiards to understand and explore both classical and quantum chaos. Recently, in 2001, a group at the University of Texas introduced an experimental set up for modeling the wedge billiard geometry called optical billiard in two dimensions. It is worth mentioning that this experiment is more closely related with classical rather than quantum chaos. The motivation for the present work was born from the idea of laying the foundations of a quantum treatment for optical billiards, named ``The Escape Problem'', by presenting the concept of a Transparent Boundary Condition (TBC). Since a four-dimensional phase space is computationally very difficult to investigate, we will explore a pair of one-dimensional examples. First we will consider a classical perspective by analyzing a ``gas of particles'' limited to stay inside a one dimensional box of length L, and finishing with the resolution of a Quantum Initial Value Problem (QIVP) using a numerical method developed and entirely checked with an exact, analytic theoretical method. The numerical method introduces a novel way to solve a Diffusion Type Equation by implementing Discrete Transparent Boundaries Conditions (DTBCs) recently developed by mathematicians. [Preview Abstract] |
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D1.00035: Improvements to a Michelson interferometer based wavemeter for precision laser wavelength measurement Bryce McClurg, John Sohl The Michelson wavemeter developed by Fox, \textit{et. al.}, is basically a solid design but has problems with speed and single pass accuracy. The main problem is associated with the speed of the fringe detection and the fringe contrast. Electronic noise can also be an issue if the design is not carefully laid out. We are designing a high speed counting circuit and small area photodetector that should solve these problems. Standard op amps and counting circuits are not fast enough to keep up with the fringe counting which needs to be at least 5 MHz. The quality of the fringes is not reliably high and a way to increase the fringe contrast is critical to allow for a reliable fringe count. We have created the high speed counting circuit and a possible fringe detection system. Our current status and results will be reported. P. J. Fox, R. E. Scholten, M. R. Walkiewicz, and R. E. Drullinger, Am. J. Phys. \textbf{67} (7), July 1999. [Preview Abstract] |
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D1.00036: Multi-sensor Array for High Altitude Balloon Missions to the Stratosphere Tim Davis, Bryce McClurg, John Sohl We have designed and built a microprocessor controlled and expandable multi-sensor array for data collection on near space missions. Weber State University has started a high altitude research balloon program called HARBOR. This array has been designed to data log a base set of measurements for every flight and has room for six guest instruments. The base measurements are absolute pressure, on-board temperature, 3-axis accelerometer for attitude measurement, and 2-axis compensated magnetic compass. The system also contains a real time clock and circuitry for logging data directly to a USB memory stick. In typical operation the measurements will be cycled through in sequence and saved to the memory stick along with the clock's time stamp. The microprocessor can be reprogrammed to adapt to guest experiments with either analog or digital interfacing. This system will fly with every mission and will provide backup data collection for other instrumentation for which the primary task is measuring atmospheric pressure and temperature. The attitude data will be used to determine the orientation of the onboard camera systems to aid in identifying features in the images. This will make these images easier to use for any future GIS (geographic information system) remote sensing missions. [Preview Abstract] |
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D1.00037: High Altitude Ballooning and Site Selection John Metcalf High altitude ballooning provides a near-space platform for amateur research projects in science and engineering. This venue allows new experiments, otherwise not conducted from costs or lack of transportation, from WSU and surrounding areas to be flown into the upper atmosphere. A highly skilled and motivated group of scientist and engineering students from WSU have contrived its own high altitude balloon to lift payload capsules filled with experiments and tracking equipment up to 120,000 feet where it then bursts and payload capsules are parachuted into a landing zone. Launch site selection is based upon the safety of those that come within the balloons projected flight path and terrain accessibility from the launch and landing zones. Restricted ground and airspace, mountainous regions, lakes and rivers, and densely populated or high air traffic areas were obstacles to be avoided. Computer flight simulations and region analysis show that there are several viable launch and recovery sites in Utah as well as SE Idaho, SW Wyoming, and NW Colorado. [Preview Abstract] |
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