Bulletin of the American Physical Society
75th Annual Meeting of the Southeastern Section of APS
Volume 53, Number 13
Thursday–Saturday, October 30–November 1 2008; Raleigh, North Carolina
Session HA: Poster Session (10:45am - 12:45pm) |
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Room: Holiday Inn Brownstone Caucus |
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HA.00001: Correlations between nuclear and fluorescent Imaging of mammary tumors in mice Robin Carroll, John Stone, Eric Blue, Eric Bradley, Jianguo Qian, Margaret Saha, Robert Welsh Progress with new imaging technologies permits the study of biological processes both \textit{in vivo} and noninvasively. Two systems, a position-sensitive gamma camera and a cooled-CCD camera have been applied in this work. A C3H strain of mouse carrying the Mouse Mammary Tumor Virus (MMTV) was imaged using 800 nm Q-tracker fluorescent dots conjugated to a peptide targeting integrin $\alpha \upsilon \quad \beta$ \c{C} a mammary marker for angiogenesis. We subsequently imaged with the gamma camera to detect low levels of $^{125}$I distribution, and hence, the activity of a trans-membrane protein called the sodium iodide symporter (NIS) responsible for iodine transport. Preliminary results indicate that the biodistribution of the tagged Q-tracker dots and $^{125}$I co-localize very early in seemingly normal mammary glands of infected MMTV mice, while in larger palpable tumors the Q-dot signals are less apparent in comparison with the$^{125}$I signal. [Preview Abstract] |
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HA.00002: Testing local DNA stiffness by nanoconfinement Alena Karpusenka, Robert Riehn The primary intent of this work is the study of DNA movement inside curved nanochannels. In particular, we considered channels with a cross-section smaller then the DNA persistence length, and channel length far beyond the contour length of the molecule. This allows us approximation of the polymer with the model of an elastic rod (Odijk model). We are testing the local DNA stiffness by bending the molecule in curved channels, and a bending energy landscape is constructed by comparing forces due to bending stiffness to known electrophoretic forces. To estimate the limiting radius of nanochannel curvature permeable for DNA molecules at a given driving force, two sets of nanochips were fabricated. The first set of nanochannels is formed by the sequence of semi-circumferences with descending radius (20 $\mu$m to 50 nm) and tests moderate bending of a set of length scales. A second set of nanochannels is shaped as a zigzag of constant steps, and tests local bending stiffness. [Preview Abstract] |
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HA.00003: Multi-Color Single Molecule Fluorescence Resonance Energy Transfer (smFret) Trevor Anderson, Keith Weninger The assembly of multi-protein complexes is a vital part of intracellular biology. High resolution methods for characterizing such multi-protein complexes are required to understand functions of these complexes at the mechanistic level. Single molecule Fluorescence Resonance Energy Transfer is a promising method for both characterizing protein conformations and co-localizing different members of such multi-protein complexes. We present our progress towards developing an instrument for three and four color FRET studies at the single molecule level. This method will be useful for characterizing multi-protien complexes. [Preview Abstract] |
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HA.00004: Conformational fluctuation of Synaptotagmin-1 observed with single molecule fluorescence resonance energy transfer (smFRET) Ucheor Choi, Keith Weninger Calcium dependent neurotransmitter release at the synapses involves a synaptic vesicle protein synaptotagmin-1, a calcium sensor, to regulate exocytosis. It has been known that Synaptotagmin-1 interacts with assembled SNARE complexes, but it is unclear how their molecular mechanisms are coupled. X-ray studies in the absence of calcium revealed a closed conformation of synaptotagmin-1 and with calcium bound to the C2 domains of synaptotagmin-3 found extensive interactions holding the domains open. Suggesting the two conformations can be the key to the two functions of synaptotagmin in regulating neurotransmission. Here we use single molecule fluorescence resonance energy transfer (smFRET) to study synaptotagmin interactions with SNARE complexes and the spontaneous conformational changes of synaptotagmin-1 when calcium is induced. [Preview Abstract] |
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HA.00005: Time-resolved spectroscopy of self-assembly of CCMV protein capsids Jelyn Moore, Dina Aronzon, V.N. Manoharan In order to gain a deeper understanding of the process a virus undergoes to assemble; the purpose of this study to time resolve the self-assembly of a virus. Cowpea Chlorotic Mottle virus (CCMV), an icosahedral type virus, can assemble without its genetic code (RNA) depending on its chemical and physical surroundings. The surface plasmon resonance (SPR) of colloidal gold particles is known to display a shift when the gold interacts with the proteins of a virus. Surface plasmon resonance is the free electron oscillation occurring at the surface of the gold particle resulting in a characteristic peak location at maximal absorbance and peak width. The shift results from the change in the refractive index of the particles as induced by the presence of the proteins. We hope to detect this shift through total internal reflection microscopy (TIRM). The accomplishments of this research are the completion of the TIR setup and the purification of the virus and its proteins. [Preview Abstract] |
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HA.00006: Effects of AC/DC magnetic fields, frequency, and nanoparticle aspect ratio on cellular transfection of gene vectors Kris Ford, Lamar Mair, Mike Fisher, Md. Rowshon Alam, Rudolph Juliano, Richard Superfine In order to make non-viral gene delivery a useful tool in the study and treatment of genetic disorders, it is imperative that these methodologies be further refined to yield optimal results. Transfection of magnetic nanoparticles and nanorods are used as non-viral gene vectors to transfect HeLa EGFP-654 cells that stably express a mutated enhanced green fluorescent protein (EGFP) gene. We deliver antisense oligonucleotides to these cells designed to correct the aberrant splicing caused by the mutation in the EGFP gene. We also transfect human bronchial endothelial cells and immortalized WI-38 lung cells with pEGFP-N1 vectors. To achieve this we bind the genes to magnetic nanoparticles and nanorods and introduce magnetic fields to effect transfection. We wish to examine the effects of magnetic fields on the transfection of these particles and the benefits of using alternating (AC) magnetic fields in improving transfection rates over direct (DC) magnetic fields. We specifically look at the frequency dependence of the AC field and particle aspect ratio as it pertains to influencing transfection rate. We posit that the increase in angular momentum brought about by the AC field and the high aspect ratio of the nanorod particles, is vital to generating the force needed to move the particle through the cell membrane. [Preview Abstract] |
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HA.00007: Single Molecule Fluorescence Resonance Energy Transfer (smFRET) in Live Cells John Sakon, Keith Weninger This research reports progress towards single molecule fluorescence resonance energy transfer (smFRET) in the cytoplasmic environment of live cells. Recombinantly expressed, externally dye-labeled SNARE proteins were microinjected into cultured cells, tracked and imaged to observe real-time conformational dynamics. We discuss the many obstacles lowering signal:noise \textit{in vivo} (cellular and coverslip autofluorescence, dye photobleaching) and our methods for overcoming these obstacles. Initial findings and the implications for this technique will also be discussed. [Preview Abstract] |
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HA.00008: Resonant Soft X-ray Reflectivity (RSoXR) for organic thin films characterrization Cheng Wang, Benjamin Watts, Tohru Araki, Harald Ade, Alexander Hexemer, Andres Garcia, Thuc-Quyen Nguyen, Guillermo Bazan, Karen Sohn, Edward Kramer The performance of organic multilayer PLED devices is strongly affected by the structure, e.g. chemical diffusion or physical roughness, of the interfaces between layers. Resonant soft x-ray reflectivity (RSoXR), a recently developed tool to characterize polymer thin films, is able to achieve greatly enhanced contrast between polymer components by tuning the photon energy to carbon 1s photon absorption resonances near 285eV. The measurement of interfacial width becomes possible without deuteration and the use of neutron reflectivity. The interfacial widths w of model bilayers of poly[9,9-bis(6'-N,N,N,-trimethylammoniumhexyl)fluorene-co-alt-1,4 phenylene bromide] (PFNBr)/poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) on SiO2 substrates manipulated by various sample preparation process were measured by RSoXR, allowing w to be correlated to device performance. In addition, for a real PLED device with a more complicated multilayer structure, but missing the top Al electrode, it was demonstrated that the top four interfaces can be fully characterized using RSoXR by adjusting the material contrast to selectively observe different layers at different photon energies. [Preview Abstract] |
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HA.00009: Fusion between a content labelled liposome and an enveloped virus particle Laura Wessels, Keith Weninger Membrane fusion is critical during enveloped virus entry into cells for release of the viral genome to the cell. We have developed a fluorescence assay to observe individual virus particles fusing with immobilized liposomes. Dye encapsulated inside a liposome will be released into the virus particle's interior through a fusion pore that is created between the liposome's bilayer and the viral envelope. We used Total Internal Reflection Microscopy (TIRFM) to observe fusion between a liposome with calcein in the intravescular buffer and an influenza particle. A sudden buffer exchange to acidic pH is used to trigger the fusion event. TIRFM allows a time resolution of $\sim $100ms. We plan to use confocal microscopy to improve the time resolution of our measurements of the opening of the fusion pore. [Preview Abstract] |
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HA.00010: DNA fluctuations under nanoconfinement Junhan Pan, Robert Riehn DNA stretching in quasi one-dimensional nanochannels is an emerging technique for the analysis of genomic-sized DNA molecules. For formulating an optimal measurement strategy, the thermal fluctuations of confined molecules are of crucial importance. While previous measurements have concentrated only on the end-to-end length, we present here an experimental study of density fluctuations within the molecule, and find a good agreement with a model similar to a oscillator chain. [Preview Abstract] |
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HA.00011: Nanoscale Effects on the Optical Performance of Nanofiber-Quantum Dot Nanocomposites Teri Walker, Lynn Davis, Howard Walls, Li Han, Jenia Tufts, David Ensor Photoluminescent nanofibers (PLNs) can be created by combining nanofibers and quantum dots using the process of electrospinning. The physical properties of PLNs are dependent upon many different parameters associated with both the nanofiber and the quantum dot and their interactions. By understanding and manipulating these properties, the performance of the resulting optical structure can be tailored for desired end-use applications. For example, the transmittance and reflectance of nanofiber substrates is controlled by factors such as refractive index, thickness, fiber diameter and density, and surface morphology. Likewise, the quantum efficiency of the quantum dots in PLNs depends upon multiple parameters including quantum dot chemistry, method of forming the PLN nanocomposite, and prevention of quantum dot agglomeration. Methods to optimize the performance of PLNs are discussed along with guidelines for tailoring the performance of nanofibers and quantum dots for application specific requirements.. [Preview Abstract] |
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HA.00012: Detection of residual traces of explosives by Surface Enhanced Raman Scattering using gold coated substrates produced by nanospheres imprint technique Fernando Calzzani, Redahegn Sileshi, Aschalew Kassu, Jean Michel Taguenang, Abdul Chowdhury, Anup Sharma, Paul Ruffin, C. Brantley, E. Edwards Explosives detection for national and aviation security has been an area of concern for many years. In order to improve the security in risk areas, much effort has been focused on direct detection of explosive materials in vapor and bulk form. New techniques and highly sensitive detectors have been extensively investigated and developed to detect and identify residual traces that may indicate an individual's recent contact with explosive materials. This paper reports on the use and results of Surface Enhanced Raman Scattering (SERS) technique, to analyze residual traces of explosives in highly diluted solutions by using low-resolution Raman spectroscopy (LRRS). Detection sensitivity of this technique has been measured by using samples of explosives such as TNT, RDX and HMX evaluated at different concentrations. Additionally, results from homemade SERS substrates have been compared to a commercial gold-coated substrate of nanocavities. Sample concentration, starting from 1000ppm was gradually diluted to the smallest detectable amount. Raman spectrum was obtained using a portable spectrometer operating at a wavelength of 780nm. [Preview Abstract] |
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HA.00013: Nanosphere Templating Through Controlled Evaporation: A High Throughput Method For Building SERS Substrates Kristen Alexander, Rene Lopez, Meredith Hampton, Joseph DeSimone When a pair of noble metal nanoparticles are brought close together, the plasmonic properties of the pair (known as a ``dimer'') give rise to intense electric field enhancements in the interstitial gap. These fields present a simple yet exquisitely sensitive system for performing single molecule surface-enhanced Raman spectroscopy (SM-SERS). Problems associated with current fabrication methods of SERS-active substrates include reproducibility issues, high cost of production and low throughput. In this study, we present a novel method for the high throughput fabrication of high quality SERS substrates. Using a polymer templating technique followed by the placement of thiolated nanoparticles through meniscus force deposition, we are able to fabricate large arrays of identical, uniformly spaced dimers in a quick, reproducible manner. Subsequent theoretical and experimental studies have confirmed the strong dependence of the SERS enhancement on both substrate geometry (e.g. dimer size, shape and gap size) and the polarization of the excitation source. [Preview Abstract] |
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HA.00014: Length scale effects on percolation of geometrically complex nanocomposites T.J. Hoffman, D.R. Stevens, W.A. Roberts, R.E. Gorga, L.I. Clarke With growing interest in materials that include nanostructures the focus on nanocomposites (a polymer-based matrix that is enhanced by a nanometer sized particle) has grown. Electrospun nanocomposites contain a complex geometry including fiber sizes of $\approx $ 200 nm arranged in a random mat with a porosity of $\ge $ 70{\%}. Composites utilize connected paths of particles throughout the sample to enhance the mechanical and electrical properties of the matrix. Previous literature has shown, in the case of continuous films, that this percolation phenomenon is affected by the sample size. This work aims to investigate these length scale effects within a complex morphology, such as a nanofiber mat. For a clear understanding of the change in percolation vs. length scale we fabricated interdigitated electrodes (IDEs) with a finger spacing of 10 to 100 $\mu $m, electrospun mats onto the IDEs, and performed electrical conductance measurements. In addition, computation simulations of the experimental systems were undertaken. I will discuss our results and the role sample size/shape plays on 1) the percolation threshold and 2) the conductivity vs. doping fraction curve. [Preview Abstract] |
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HA.00015: Ultrahigh Vacuum Growth and PEEM Characterization of Patterned Graphene Nanostructures on Si-Polar 6H-SiC Surfaces Zhengang Wang, Andreas Sandin, Joeseph Tedesco, Xianhua Kong, J.E. (Jack) Rowe We report the growth and Photoelectron Emission Microscopy (PEEM) characterization of graphene films on Si-polar surfaces of 6H-SiC by thermal decomposition in an ultrahigh vacuum (UHV) chamber. Following growth, focused ion beam lithography has been used to successfully etch the graphene films and control the lateral dimensions of a number of nanostructures on these graphene layers with etch rates of $\sim $18 nm/s and lateral dimensions of $\sim $250 to 1500 nm. Epitaxial graphene films (1-4 layers thick) have been grown on the Si face. Theoretical reports have recently addressed the bandgap engineering of graphene nanoribbons by altering the physical dimensions, edge structure, and edge atoms of the nanoribbons. However, experimental control of the growth and quality graphene nanostructures is still a challenge. Our PEEM results show that the electronic properties of the graphene are very different near step edges which indicates that some confinement effects expected for graphene nanoribbons may be achieved by selected stepped surfaces. The patterned surfaces show additional sites that are chemically different and may be useful for certain sensor applications. Possible interpretations of the PEEM contrast mechanisms will be discussed. [Preview Abstract] |
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HA.00016: Ultra low temperature high magnetic field materials' characterization tool Dmitri Ponarin, Alex Smirnov, William Holton Development of a Cross-disciplinary Quantum Engineering Laboratory at NCSU for characterization of a wide range of materials for next generation of information devices operating on spin principles is being reported. The tool provides electrical and magnetic resonance measurements for samples subjected to mK temperatures and high magnetic fields to achieve the highest polarization of electronic or nuclear spins. This first-of-its kind instrument operates in cryogen-free mode and comprises of a high homogeneity (10 ppm over 1 cm$^{3})$ 9 T superconducting magnet with a wide (89 mm) room-temperature bore to accommodate an independent dilution refrigerator (DR). The tested DR base temperature is below 20 mK and the cooling power exceeds 350 $\mu $W a 100 mK. The magnet and the DR are cooled from room temperature by independent pulse-tube cryocoolers in less than 48 hours. The magnet is equipped with an uncoupled +/-600 G sweep coil and a persistent switch. Magnetic field drift of $<$1ppm/hr is acceptable for high resolution ESR experiments. Flexible design and the short turnaround time makes the tool convenient for conducting a wide range of experiments. [Preview Abstract] |
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HA.00017: Analysis of gel heterogeneities on a local level Philip Boyne, Frederic Lechenault, Karen Daniels We study the heterogeneity of gels near the sol-gel transition through measurements of the spatial variations in gel strength. The correlated motion of fluorescent polystyrene microspheres suspended in gels is measured via two-point microrheology. Analysis of this correlated motion provides a local measure of gel heterogeneity. Additionally, we divide the images into micron-wide squares and determine how rheological properties spatially vary as a function of gel concentration. Our results imply that weaker gels exhibit more heterogeneity than stronger gels. [Preview Abstract] |
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HA.00018: Shear segregation of granular materials as a function of particle size and confining pressure Laura Golick, Karen Daniels We experimentally investigate the dependence of granular shear segregation rates on particle size ratio and confining pressure. Within a cylindrical annulus, we shear two monodisperse layers of spherical glass beads, with an equal volume of small beads initially placed in a layer above the large. From changes in the height of the sample, we compute the mixing and segregation rates of six different particle size ratios. We observe that contrasting as well as similar particle size ratios segregate and mix more slowly than intermediate particle sizes, in disagreement with kinetic sieving theory. Additional pressure reduces the segregation and mixing rates. [Preview Abstract] |
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HA.00019: Spreading of a Fluorescent Surfactant on a Glycerine Layer David Fallest, Christopher Fox, Karen Daniels We study the spreading of a fluorescent surfactant on a thin layer of glycerine. Measurements of the height profile of the capillary ridge are conducted as the surfactant travels outward from the point of deposition. We examine the dynamics of the ridge as a function of the volume of surfactant released, and find that for the largest volumes the shape and speed of the spreading ridge are influenced by the outer edge of the underlying glycerine layer. The intensity of the fluorescence is also used to visualize the position and the concentration of surfactant as it spreads. The location of the surfactant is compared to the location of the capillary ridge. [Preview Abstract] |
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HA.00020: Magnetic Properties of Dihydrate and Monohydrate Forms of Nickel Dibromide G.C. DeFotis, C.L. DeSanto, C.M. Davis, J.M. Pothen, A.S. Hampton As with transition metal bromides generally, especially hydrates, the title materials are either little studied previously or not at all (monohydrate). Curie-Weiss analysis of paramagnetic region susceptibilities yields Weiss theta values of 8.0 and 27.3 K for dihydrate and monohydrate respectively, indicating predominant ferromagnetic interactions but less so in the dihydrate. Peculiar behavior appears in the susceptibility of the monohydrate in the 40-100 K range. A large zero field splitting of the triplet ground state emerges from fits to dihydrate data especially. Susceptibility maxima occur just below and, unexpectedly, just above 6.0 K for dihydrate and monohydrate respectively. Fits to the data suggest more lower dimensional magnetic character in the monohydrate. While magnetization isotherms in the two systems are without hysteresis, a remarkable contrast in their temperature evolution distinguishes the two materials. [Preview Abstract] |
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HA.00021: Jamming in Microfluidic Devices Carlos Ortiz, Karen Daniels, Robert Riehn Systems of grains, colloids, and foams cease to flow, or jam, under poorly understood conditions. The phase transition common to these jamming phenomena depends on imposed load, temperature, and packing fraction. We study microfluidic jamming by flowing aqueous suspensions of sub-micron fluorescent polystyrene spheres through a microfluidic device. The device consists of a single wide channel followed by parallel rows of varying-size posts. These posts focus the bead flow into micron-sized channels, allowing us to control the particle volume fraction. Varying the particle size and the flow rate of the suspension allows us to indirectly control the importance of thermal effects and the applied load on the particles. Preliminary results show that bidisperse suspensions jam more readily at a lower flow rate, whereas monodisperse suspensions require ten times higher flow rates to jam. These results suggest that jamming transitions depend strongly on polydispersity. [Preview Abstract] |
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HA.00022: Magnetic Behavior in Dihydrate and Monohydrate Forms of Manganese Dibromide G.C. DeFotis, A.S. Hampton, J.M. Pothen Transition metal bromides, especially hydrates, are much less examined than chlorides, and the title materials are believed to be previously unstudied. Curie-Weiss analysis of paramagnetic region susceptibilities yields Weiss theta values of -13.1 and -3.9 K for dihydrate and monohydrate respectively. A susceptibility maximum appears at 6.34 and 3.20 K in the same order, with the maximum broader in the monohydrate. Ordering temperatures are suggested by susceptibility anomalies at 5.91 and 2.63 K in the same order. The ratio T(ordering)/T(maximum) is 0.93 and 0.82 for dihydrate and monohydrate respectively. These results are consistent in suggesting three-dimensional magnetic character in the dihydrate but lower dimensional in the monohydrate. A similar relation was found previously for corresponding chloride systems, with which further comparison can be made. The results can also be considered in the broader context of other metal dihalide dihydrate and monohydrate pairs of materials. [Preview Abstract] |
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HA.00023: Energetics, coherent transport and work fluctuations of a Brownian particle driven by time dependent temperature Ronald Benjamin We study the efficiency and transport coherence of a Brownian particle in an asymmetric potential and driven by time dependent temperature, also known as a diffusion ratchet. Effect of coupling between many different Bownian particles is also discussed. Work fluctuations of the Brownian particle in a bistable potential and subject to time dependent temperature is studied and the Jarzynski equality is confirmed from numerical solution of the Langevin equation. Analytical results obtained for a harmonic potential are also presnted. [Preview Abstract] |
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HA.00024: Atomic Force Microscopy and Low Energy Electron Diffraction of Epitaxial Zinc Oxide Films Mark Learner, Y. Zhang, Andreas Sandin, Dong Wu, J.E. (Jack) Rowe The purpose of the current thin-film Zinc Oxide (ZnO) research is to characterize OMCVD- grown heteroepitaxial thin films of ZnO, which are thought to be single crystal. These ZnO films have many interesting technological applications, including LCD screens and solar cells. We use We also use Atomic Force Microscopy (AFM) and Low Energy Electron Diffraction (LEED) to measure the topography and investigate the periodicity of the ZnO samples produced. The topography data shows nanoscale domains that appear to range in length from 300-700nm, width from 180-270nm, and height from 20-50 nm depending on growth conditions. Optical microscopy has been used to gain additional qualitative understanding of surface topography features on different areas of the samples. We observe single crystal patterns with LEED and thus confirm the expected epitaxial nature of the growth process. Analysis of the energy dependent LEED data has shown that the diffraction patterns are always single crystal orientation in good registry with the substrate orientation. However, we have also found that there are sample charging effects (which shift the apparent energy by 26 to 43 eV) occur during LEED measurements due to the high resistance of the samples on insulating substrates and Al$_{2}$O$_{3}$. [Preview Abstract] |
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HA.00025: Optical Properties and Aging of Gasochromic WO$_{3}$ Rudresh Ghosh, Matthew B. Baker, Rene Lopez WO$_{3}$ as a possible optical gas sensor has gained increasing importance with H$_{2}$ becoming a major fuel of the future. This has led to efforts to understand the theoretical and practical aspects of the gasochromic behavior of WO$_{3}$. WO$_{3}$ films were fabricated using pulsed laser deposition (PLD). Morphological and stoichiometric ratios of films obtained were observed as functions of deposition parameters. We present the optical constants induced by 2{\%} H$_{2}$:Ar in WO$_{3}$ films. This allows us to obtain the limits of the gasochromic change in comparison to ion injection. It was found using Langmuir's adsorption equation that at low H$_{2}$ concentrations a high sensitivity is predicted but the coloration could saturate at 57.9 {\%} of the material's maximum ion adsorption. Poisoning of the films was also addressed by coating with a permeable polydimethylsiloxane layer. It is shown that gasochromic degradation is prevented thus eliminating common atmospheric gases as possible contaminants. Our studies suggest WO$_{3}$ thin films as highly sensitive and stable optical hydrogen sensors. [Preview Abstract] |
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HA.00026: A novel nanoglue and whole wafer self-alignment based upon self-assembled monolayers Ako Emanuel, Ernest Walker, Hans Hallen New methodologies for fabrication of multilevel packaging, particularly for RF signal analysis, are investigated. A new method for ``gluing'' silicon wafers together with a Self Assembled Monolayers (SAMs) based nanoglue are discussed, as are methods to enable its use with nonconforming wafers. Results of bond strength measurements as a function of temperature and process will be presented. Surface area bonded is characterized by infrared (IR) imaging. We will also present a method of inducing self-alignment between whole silicon wafers with micrometer precision. This represents a qualitative departure from alignment of millimeter-sized object as has been previously demonstrated. Self-alignment is induced by creating hydrophilic and hydrophobic regions on the wafers and using capillary forces of water in these regions to force the wafers to align with little to no outside influence. Results are characterized by IR imaging. Physical ideas that enable the whole-wafer alignment such as flow channels, elimination of secondary minima, large central capture areas and small edge features are discussed. The possibility of aligning with the nanoglue materials as the alignment drivers is discussed. [Preview Abstract] |
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HA.00027: Infrared Laser-Induced Breakdown Spectroscopy of Alkali Metal Halides Ei Brown, Uwe Hommerich, Clayton Yang, Sudhir Trivedi, Alan Samuels, Peter Snyder Laser-induced breakdown spectroscopy (LIBS) is a powerful diagnostic tool for detection of trace elements by monitoring the atomic and ionic emission from laser-induced plasmas. LIBS is a relatively simple technique and has been successfully employed in applications such as environmental monitoring, materials analysis, medical diagnostics, industrial process control, and homeland security. Most LIBS applications are limited to emission features in the ultraviolet-visible-near infrared (UV-VIS-NIR) region arising from atoms and simple molecular fragments. In the present work, we report on the observation of mid- infrared emission lines from alkali metal halides due to laser-induced breakdown processes. The studied alkali metal halides included LiCl, NaCl, NaBr, KCl, KBr, KF, RbCl, and RbBr. The laser-induced plasma was produced by focusing a 16 mJ pulsed Nd:YAG laser (1064 nm) on the target. The LIBS infrared emission from alkali halides showed intense and narrow bands located in the region from 2-8 $\mu $m. The observed emission features were assigned to atomic transitions between higher-lying Rydberg states of neutral alkali atoms. More detailed results of the performed IR LIBS studies on alkali metal halides will be discussed at the conference. [Preview Abstract] |
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HA.00028: Ion Molecule Collisions at Low Energies Dwayne Joseph, Robert Buenker, Bidhan Saha Charge transfer is a fundamental phenomenon in nature, playing a crucial role in many chemical and biological processes. The capture of electron (also known as charge transfer or charge exchange) is well known to be an important collision process in nearly all types of plasma environments from terrestrial laboratories [1] to solar system atmospheres [2] to astrophysical sources. Ion-molecule collisions have received less attention both theoretically and experimentally than its atomic counterpart due to extra degree of freedom. Using \textit{ab initio} calculations we report the potential surfaces and coupling matrix elements. Our results will be compared with other theoretical and experimental results, if available. [1] R. K. Janev, in ``Atomic and Molecular Processes in Fusion Edge Plasmas'' (Plenum Press, NY, 1995), p1. [2] T. E. Cravens, Science 296, 1042 (2002). [Preview Abstract] |
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HA.00029: Near-field photoemission microscopy A. Fisher, C.T. Chadwick, H.D. Hallen Near-field scanning optical microscopy (NSOM) with UV illumination can be used to provide high resolution images of photoelectron production as well as optical and electrical data. A tunable ultraviolet laser can be used to create photoelectrons, which can be collected with the metal coating on the NSOM tapered optical fiber tip. The collection geometry does not permit energy analysis so the source energy must be varied for spectroscopy, but the close proximity of the tip to the sample allows the creation of an extremely high electric field with only a modest (few volt) bias between the tip and sample. These high fields can change the local work function of the material and thus aid the removal of the electrons. This NSOM configuration permits variations of laser wavelength, tip-sample distance, collection voltage, and lateral position on a sample, enabling robust model testing of voltage-assisted photoemission. [Preview Abstract] |
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HA.00030: ABSTRACT WITHDRAWN |
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HA.00031: Rate Coefficients for H$_{3}^{+}$ Production Measured in an RF Ion Trap Sam Ronald, Emily Mount, Nick Pope, Adrian Daw, Anthony Calamai The reaction H$_{2}^{+}$ + H$_{2} \rightarrow$ H$_{3}^{+}$ + H is studied using a quadrupole radio frequency ion trap coupled with a time of flight mass spectrometer. Protonated molecular hydrogen is one of the most abundant ions in the universe, and is believed to be responsible for the formation of many molecular ions in, for example, the interstellar medium and the aurorae of Jupiter. Also, since this ion is the simplest polyatomic molecule, it can be used as a basis for comparison with other polyatomic molecules. H$_{2}^{+}$ is created in a RF ion trap by electron bombardment of H$_{2}$, and then allowed to react with H$_{2}$ for varying time intervals before the H$_{2}^{+}$ and H$_{3}^{+}$ populations are ejected from the trap and detected with an active-film electron multiplier. A number of different experimental parameters (H$_{2}$ pressure, trapping parameters and electron bombardment conditions) are explored and preliminary rate coefficients for the H$_{2}^{+}$ + H$_{2} \rightarrow$ H$_{3}^{+}$ + H reaction are presented. [Preview Abstract] |
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HA.00032: Optical Filtering with Phase Singularities William Ames, Irina Novikova It is a common situation in nonlinear optics for strong and weak light fields to propagate nearly collinearly inside an interaction region, but for detection the strong field must be completely removed without attenuating the weak field. To solve this problem we have adopted the idea of the optical vortex coronagraph [G. Foo et al., Opt. Lett. 30, 3308 (2005)]. This optical filtering device converts the strong field into a ``doughnut'' intensity profile by introducing an optical vortex using a step phase mask, and then filters it out by blocking everything but the dark central part. The weak field, on the other hand, propagating at small angle, is not affected by the mask and can be detected. We demonstrate the effectiveness of the technique, discuss its limitations, and propose improvements to the design. [Preview Abstract] |
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HA.00033: Dye Assisted-Optical Lithography of Polymers from Liquid-Phase Redahegn Sileshi, Jean-Mishel Taguenang, Fernando Calzzani, Aschalew Kassu, Anup Sharma There has been much recent interest in polymeric materials for holographic gratings in the field of information storage, wave guide coupling, and non linear optoelectronics. Polybutadiene which is synthetic rubber is biologically benign and used in making it attractive as a platform for biomolecular applications. NBD dye assisted optical Lithography of polybutadiene polymers from liquid phase is our main interest here .aqueous solution of NBD (NBD dissolved in distilled water having various concentration) is confined between two polybutadiene coated glass substrate. The aqueous solution is contact with the coated surface. The two glass substrates are separated by a spacer which provide enough space for the molecules to move and rearrange themselves. Interferometery of two coherent beams derived from the 488 nm Argon-ion laser excites the dye. Formation of the grating is due to the laser excited dye with a polymer on the substrate. Dependency of light diffraction efficiency on the concentration of the aqueous solutions as well as intensity of the laser will be investigated. The interesting phenomenon in this technique is following a short initial exposure the grating continues to grow for several time after the beam is blocked. [Preview Abstract] |
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HA.00034: Electron Impact K-shell Ionization Cross Sections at high energies A.K.F. Haque, M.S.I. Sarker, M.A.R. Patoary, M. Shahjahan, M. Ismail Hossain, M. Alfaz Uddin, A.K. Basak, Bidhan Saha A simple modification of the empirical model of Deutsh \textit{et. al}. [1] by incorporating both the ionic [2] and relativistic corrections [3] is proposed for evaluating the electron impact K -shell ionization cross sections of neutral atomic targets. Present results for 30 atomic targets with atomic number Z=1 -- 92 for incident energies up to E=2 GeV, agree well with available experimental cross sections. Comparisons with other theoretical findings will also be presented at the conference. [1] H. Deutsh, K. Becker, T. D. Mark, Int. J. Mass Spect. \textbf{177}, 47 (1998). [2] M. A. Uddin, A. K. F. Haque, M. M. Billah, A. K. Basak, K. R. Karim, B. C. Saha, Phys. Rev. A \textbf{71}, 032715 (2005).; Phys. Rev. A \textbf{73}, 012708 (2006). [3] M. Gryzinski, Phys. Rev \textbf{138}, 336 (1965). [Preview Abstract] |
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HA.00035: Optical Fluorescence of Long Lived States in NO$^+$ Emily Mount, Sam Ronald, Nick Pope, Adrian Daw, Anthony Calamai By examining the UV and VUV photons emitted from a population of NO$^+$ ions stored in a radio-frequency ion trap, we have observed the optical fluorescence of at least two long-lived excited states of NO$^+$. These states lie above the NO$^+$ \emph{a}$^3\Sigma^+$ metastable state and have significantly shorter apparent lifetimes, Calamai and Yoshino J. Chem. Phys. 101 (1994) 9480, than the \emph{a}$^3\Sigma^+$ state. The measurements we present in this work were obtained as part of a systematic plan to study reaction rate coefficients, decay rates, and cross sections for metastable states of molecules containing nitrogen and/or oxygen. Small atomic and molecular ions, such as O$^+$, O$^{2+}$, O$_2^+$, O$_2^{2+}$, N$^+$, N$_2^+$, N$_2^{2+}$, and NO$^+$, are particularly relevant to the Earth's ionosphere. By improving our knowledge of radiative and collisional parameters associated with metastable states of these ions, significant uncertainties in current ionospheric models will be minimized, and our understanding of the ionosphere will be improved. Data and tentative assignments of the radiative decay signals are presented and discussed. [Preview Abstract] |
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HA.00036: Mid-infrared Emission and Energy Transfer Properties of Sensitized Nd$^{3+}$ Ions in Low Phonon-Energy Hosts Althea Bluiett, Natasha Jacobitz, Natasha Stokes, EiEi Brown, Uwe Hommerich, Sudhir Trivedi, John Zavada Mid-infrared emission (4-6 $\mu $m) stemming from the first excited state of Nd$^{3+}$ can be generated in KPb$_{2}$Cl$_{5}$ by pumping its $^{4}$F$_{5/2}$ absorption band at $\sim $800 nm. It has been proposed that 4-6 $\mu $m emission of Nd$^{3+}$ could be enhanced by directly pumping the $^{4}$I$_{15/2}$ absorption band centered at $\sim $1650 nm. This pumping scheme could initiate a 3-for-1 cross relaxation, which ultimately increases the population in the first excited state of Nd$^{3+}$. Unfortunately, the $^{4}$I$_{15/2}$ absorption band of Nd$^{3+}$ is weak and diode laser pumping of this level is not practical. To more efficiently populate the $^{4}$I$_{15/2}$ level in Nd: KPb$_{2}$Cl$_{5}$, Tm sensitization of Nd$^{3+}$ via $\sim $1700 nm excitation is under exploration. Experimental results show that the Tm$\diamondsuit $Nd energy transfer was successful with energy transfer efficiencies ranging from 46{\%} - 98{\%}. The energy transfer was followed by strong 4-6 $\mu $m emission from co-doped Tm, Nd: KPb$_{2}$Cl$_{5}$ samples. Preliminary results on Tm, Nd: KPb$_{2}$Br$_{5}$ will also be discussed. [Preview Abstract] |
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HA.00037: Pulsed Proton Beam from an ECR Ion Source Matthew Q. Buckner, Bret P. Carlin, John M. Cesaratto, Thomas B. Clegg A remote, LabView-controlled circuit producing variable beam pulse widths and periods has been implemented for an electron-cyclotron-resonance (ECR) ion source at TUNL's Laboratory for Experimental Nuclear Astrophysics. The pulsed signal programs high voltage power supplies of the ECR source's beam extraction system. Because the Coulomb barrier lowers the rate for very-low-energy nuclear reactions of astrophysical significance, and environmental and cosmic-ray backgrounds often dominate the signal, pulsed beam can reduce these backgrounds. Increasing the beam intensity by a factor of 10 and pulsing the beam with a 10{\%} duty factor (i.e. 100 ms on and 900 ms off), leaves the average target current unchanged. By gating detector electronics on only during the pulse, 90{\%} of environmental and cosmic-ray backgrounds are suppressed. The pulsing circuit utilizes a 555 timer to produce a pulse, and digital potentiometers to adjust the pulse width and period remotely. Relays allow the ECR source operator to switch between a constant DC beam and a pulsed beam. [Preview Abstract] |
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HA.00038: Search for fractionally-charged particles in Super-Kamiokande Alexander Tuna In this study, the search for a fractionally-charged particle (FCP) is extended to the Super-Kamiokande water-Cherenkov particle detector. Monte Carlo techniques are used to simulate FCPs in Super-K and establish cuts to differentiate FCPs from their normally-charged counterparts. The size of this data set will make this study the most sensitive search for FCPs in the cosmic rays to date. [Preview Abstract] |
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HA.00039: Study of Dark Noise in Super-K Outer Detector Ashley Jones Super-Kamiokande is a large water Cherenkov neutrino detector in Japan. New algorithms were written to determine the dark noise rates in the photomultiplier tubes of Super-K's outer detector. They were determined over a period of several years in order to track variations. The sensitivity of neutrino selection routines to the dark noise rates was monitored to improve simulations for the detector. [Preview Abstract] |
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HA.00040: Method to Investigate the Charging Characteristics of Lunar Dust Particles Stacy Irwin, Samuel Durrance, Charles Buhler, Carlos Calle We have designed an experiment to investigate the induction charging and charge decay characteristics of lunar dust particles. The induction and charge decay characteristics of granular materials depend on their surface resistivity. Since the surface resistivity properties of hydrophilic materials can be easily controlled with humidity, we have conducted initial experiments with borosilicate glass beads in a 10-20 kV constant electric field at various humidities in a controlled environmental chamber. We report on the results of these initial experiments. [Preview Abstract] |
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HA.00041: Effects of fluid instabilities in three-dimensional SNR structure Don Warren, John Blondin The Chandra X-Ray Observatory has provided spectacular high-resolution views of the shocked ejecta in young supernova remnants like Tycho. We use large-scale three-dimensional simulations to investigate the hypothesis that the spatial structure seen in these images is attributable to the fluid instabilities at the interface between shocked ejecta and shocked circumstellar gas. Simulations were run on the University of Texas' Ranger supercomputing cluster, over many expansion times, on grids of $\sim $500-1000 zones on a side. [Preview Abstract] |
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HA.00042: GRB 080319b: Modeling the Naked Eye Burst Mark Schubel Modeling Gamma-Ray Bursts (GRBs) requires both rapid response and attention to detail. GRBs often only last several seconds, and in that time, one needs to be able to image the field, and then begin to quickly reduce and analyze the data to determine if the burst can be found, and then to begin to determine its brightness. This is especially true when a truly unique burst occurs, such as GRB 080319b. This burst, often referred to as the ``Naked-Eye'' burst since it was so bright ($\sim$5 magnitude in R at peak) it could have been seen by the naked eye. We will discuss the process of getting this burst ready for modeling, including the prompt-response by the PROMPT telescopes (which responded 32 seconds after the burst and had detections in UVRI), reduction in IRAF, field-calibration and finally modeling the burst using Galapagos, a genetic-algorithm powered modeling suite that can efficiently maneuver the multi-dimensional parameter space to determine some of the environmental conditions of the burst, and shed some light on conditions of the early universe. [Preview Abstract] |
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HA.00043: The GRB Afterglow Modeling Project: Extinction of Extragalactic Point Sources Adam Trotter, Daniel Reichart The Afterglow Modeling Project (AMP) will determine, in a statistically self-consistent way, parameters that describe the time- and frequency-dependent emission and absorption of every gamma-ray burst (GRB) afterglow observed since the first detection in 1997. The result will be an ever-growing catalog of GRB afterglow models that can itself be analyzed to better describe the range of and relationships among the physical properties of GRBs and their environments. We present the model for GRB afterglow extinction. Approximately 40 parameters describe line-of-sight extinction due to: dust, neutral Hydrogen and molecular Hydrogen in the GRB host galaxy; neutral Hydrogen in the intergalactic medium (the Lyman-alpha forest); and dust in our own Galaxy. This very large parameter space is significantly reduced by priors, which we determined by analyzing previously published extinction measurements of stars in our Galaxy, and flux deficits due to Lyman-alpha absorption in the spectra of quasars at redshifts in the range 1$<$ z$<$5 (which includes the Gunn-Peterson trough). The AMP project aside, these parameters and priors can be used to model extinction towards any extragalactic point source, including supernovae. [Preview Abstract] |
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HA.00044: Origin of the Ring Fingers in Supernova 1987A John Blondin, Clint Gibson We demonstrate that the fingers of dense gas protruding inwards from the equatorial ring of SN 1987A is a natural consequence of the interacting winds model invoked to explain the circumstellar rings. At early times in the formation of the circumstellar shell, the wind shocks must have been strongly radiative, leading to a thin, dense, shock-bounded shell. Such a shell is subject to the non-linear thin shell instability, albeit in a more complex geometry than the early planar studies of the NTSI. Using three-dimensional hydrodynamic simulations, we show that the observed characteristics of the ``string of pearls'' around SN 1987A are consistent with the canonical interacting winds model subject to the NTSI. [Preview Abstract] |
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HA.00045: Mechanics in Early Solar System Formation Junichiro Fukai The generally accepted model for the early stage of the evolution of the solar system is the solar nebula, where a protostar, in this case our sun, at the origin is surrounded by a rotating material disk. The material in the disk collides, coalesces, and gradually forms aggregated objects. This coalescence of objects increases the total angular momentum of the resulting aggregate and the aggregating objects consequently experience an effective force of the form A/r$^{2}$ (where A is a constant) in the radial direction (Bacon 1959). Taking into account the gravitational force exerted by the sun, the force acting on such an aggregating object is A/r$^{2}$-- B/r$^{2}$, leading to logarithmic spiral orbits with a periodic feature of 2$\pi $ in the azimuthal angle. This paper treats the interactions of these small spiraling objects with larger protoplanets as perturbations to the Kepler problem of the planets (Gryzinski 1980). When stability conditions are imposed, the periods of the planetary orbits are found to be discrete; T$_{n}$ = (34)exp(0.815n) with n = 0, 1, 2, 3, . . . measured in days, which is in good agreement with observations (Graner and Dubrulle 1994). \newline Reference \newline Bacon, R.H. 1959. Am. J. Phys., 27, 164. \newline Graner, E. and Dubrulle, B. 1994. A{\&}A,282,262. \newline Gryzinski, M. 1980, Phys. Letters, 76A, 28. [Preview Abstract] |
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HA.00046: Acoustic Wave Dynamics in the Post-Bounce Phase of Core Collapse Supernovae Keith Heyward How a core collapse supernova successfully ``explodes'' is only partially understood. Computer models indicate that the accretion shock wave stalls around 200 km from the newly formed proto-neutron star. Despite the abundance of energy from the gravitational collapse and theories predicting how this energy might reenergize the accretion shock, simulations still fail to produce a robust explosion. Hydrodynamic models play an important role in this analysis. Using hydrodynamic modeling, I will describe the nature of acoustic waves driven by the proto-neutron star and the dissipation of thermal energy by these waves into the critical ``Gain Region.'' Using the criteria for a successful explosion laid out by Janka in 2001, I will then describe the impact that this energy has on a successful restart of the stalled accretion shock. [Preview Abstract] |
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HA.00047: Supernova neutrino sensitivity of a water Cherenkov detector Mark Steadman One of the most interesting recent discoveries is that of neutrino oscillations. Even with recent progress some of the parameters of the mixing matrix, such at Theta 13, are not well-known. A galactic supernova provides the possibility to measure these parameters, as well as to determine the nature of the mass hierarchy. I will present a poster on the potential to measure these parameters using current water Cherenkov detectors such as the Super-Kamiokande detector. [Preview Abstract] |
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HA.00048: The Earthly Origin of the Penzias-Wilson Microwave Background According to General Relativity Dmitri Rabounski, Larissa Borissova According to General Relativity, an observer on board of a satellite fixed to the Earth should register a Doppler-like anisotropy in the field of photons, emitted on the Earth, due to the rotation of the Earth's space and its motion relative to the resting stars (Rabounski, Borissova: Fall 2008 Meeting of the New England Sect. of APS). Thus the Doppler anisotropy of temperature in the Penzias-Wilson microwave background, obtained from photons by the COBE satellite (Rabounski: Fall 2008 Meeting of the Ohio Sect. of APS; Prog. Phys., 2007, v.1, 24), indicates the earthly origin of the background. This is the complete theoretical proof to the experimental analysis by Robitaille (Prog. Phys., 2007, v.1, 3, 19), according to which the Penzias-Wilson microwave background is of the Earth, and is generated by the oceans. The monopole component of the Earth's microwave background decreases with altitude, while its dipole anisotropy remains the same (Rabounski, Borissova: 2008 APS March Meeting; Prog. Phys., 2008, v.2, 3). Thus the PLANCK satellite targeting the monopole at the L2 point (1.5 mln km from the Earth), will give the final answer to the problem. [Preview Abstract] |
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HA.00049: Search for Diffuse Astrophysical Neutrino Flux Using Ultra-High-Energy Upward-Going Muons in Super-Kamiokande II Ariana Minot Several leading astrophysical models associate a diffuse flux of high-energy neutrinos from active galatic nuclei and other extra-galactic sources. It is expected that ,for muon energies about 1 TeV, the upward-going muon flux induced by neutrinos from astrophysical sources should exceed the flux of muons induced by atmospheric neutrinos. A search for high energy neutrinos of the $\stackrel{>}{=} 1$ TeV range in Super-Kamiokande II's data was performed by looking in the data for ultra-high energy upward-going muons induced by the high energy neutrinos interacting in the rock beneath the detector. One UHE-upmu candidate was found in the 860.37 days of live-time. The method used to fit the track of the muons' path in the detector has been improved, so the search is now less dependent on human classification and more automated than the previous search. This search will be used to place a $90 \%$ classical confidence level limit on the diffuse flux of upward-going muons due to neutrinos from astrophysical sources in the muon energy range 3.16-100 TeV. [Preview Abstract] |
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HA.00050: Searching for Gravitational Waves in LIGO Data:Using Tools in Multivariate Analysis Ariana Minot Evidence of gravitational waves associated with gamma ray bursts(GRBs), in addition to perhaps revealing new physics, may explain the cause of these highly energetic events. In order to detect the presence of gravitational waves in association with GRB events, it is necessary to separate signal and background effectively. Different multivariate analysis algorithms using Boosted Decision Trees(BDTs) and Artificial Neural Networks(ANNs) were implemented to achieve better separation during this project. Using simulated events of gravitational wave signal and real LIGO data not associated with GRBs, trees and networks were trained and tested under many different configurations. Currently, the best classifier is a BDT that achieves a signal efficiency of $89.5\pm 0.2 \%$ at $1 \%$ background contamination. [Preview Abstract] |
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HA.00051: Comparison of Water Vapor Measurements from GPS Atmospheric Remote Sensing Techniques Ian C. Colon-Pagan, Bill Kuo In this study, we compare precipitable water vapor (PWV) values from two different observing techniques over the Caribbean Sea, Gulf of Mexico, and U.S. regions, including ground-based GPS water vapor sensing and COSMIC radio occultation (RO) measurements, as well as global analyses from NCEP and ECMWF models. The PWV values estimated by ground-based GPS receivers tend to have a slight dry bias for low PWV values and a slight wet bias for higher PWV values, when compared with space-based techniques. This may be a consequence of missing low altitude data from RO in areas where the water vapor is concentrated, locations of the RO soundings with respect to ground-based stations, or simply the difference of these two measurement techniques. A student T-test application gives a retrieved t-value of 2.35, which is larger than the sample's critical value, 1.96. This means there is a significant difference between both GPS techniques datasets with a 0.01{\%} chance of observing a difference as large as it was observed in other random samples. [Preview Abstract] |
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HA.00052: The Topology of Chaotic Transport and Escape Jaison Novick, Kevin Mitchell, John Delos Chaotic transport and escape appears in many different systems such as the escape of an asteroid from a planet's gravitational field to the escape of ionizing electrons from hydrogen in parallel electric and magnetic fields. Numerical simulations have shown that the times to escape some region without return possess a complicated fractal structure. These fractals result from the intersection of a line of initial conditions and a homoclinic tangle, which is formed from the intersections of infinitely long stable and unstable manifolds emanating from an unstable fixed point. Our group has developed Homotopic Lobe Dynamics, a topological theory that allows one to predict subsets of the fractals seen in numerical simulations. We first show how to apply homotopy to a homoclinic tangle to obtain a set of symbols and a dynamical mapping on the symbols. A symbol and its mappings encode the evolution of an entire family of trajectories. Given a symbol and its mappings, we show how to construct a theoretical fractal. Finally, we compare a predicted fractal to one obtained from a numerical simulation of trajectories propagating in an open chaotic vase-shaped billiard. [Preview Abstract] |
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HA.00053: Chaotic Escape of Particles from a Vase-shaped Cavity: Theory and Experiment Jaison Novick, Len Keeler, John Delos We study the escape of particles from a two dimensional, specularly-reflecting open vase-shaped cavity. The narrowest point of the vase's neck defines a dividing surface between particles that escape without return and those turned back into the vase. We find trajectories whose path displays a sensitive dependence on launch angle. For our analysis, we consider a point burst of particles emitted in all directions and record the time to reach the vase's neck. We find that this escape time versus the launch angle displays a complex fractal structure. First, we outline a topological theory that predicts a subset of the fractals seen in numerical simulations. We perform a simulation of classical trajectories and compare the simulated fractal to the theoretical prediction. Through a collaborative effort we have experimentally verified the early fractal structure in the escape time using ultrasound. A microphone was placed along the vase's neck to record escaping pulses. We find that classical trajectories arriving at the microphone positions arrive very near the times at which the experimental signal is strongest. [Preview Abstract] |
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HA.00054: Why So Many Calories? H.L. Neal It is observed that there are at least four definitions of the calorie, including the one used in nutrition. In this note a detailed review of each of these definitions is presented. This is followed by a discussion of why and how multiple definitions were developed. [Preview Abstract] |
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HA.00055: QMC Goes BOINC: Using Public Resource Computing to Perform Quantum Monte Carlo Calculations Cameron Rainey, Larry Engelhardt, Christian Schr{\"o}der, Thomas Hilbig Theoretical modeling of magnetic molecules traditionally involves the diagonalization of quantum Hamiltonian matrices. However, as the complexity of these molecules increases, the matrices become so large that this process becomes unusable. An additional challenge to this modeling is that many repetitive calculations must be performed, further increasing the need for computing power.\footnote{See, e.g., L.~Engelhardt, et.~al., Angew.~Chem.~Int.~Ed. 47, 924 (2008).} Both of these obstacles can be overcome by using a quantum Monte Carlo (QMC) method and a distributed computing project. We have recently implemented a QMC method within the Spinhenge@home\footnote{C.~Schr{\"o}der, in \emph{Distributed \& Grid Computing - Science Made Transparent for Everyone. Principles, Applications and Supporting Communities}. (Weber, M.H.W., ed., 2008).}$^,$\footnote{Project URL: http://spin.fh-bielefeld.de} project, which is a Public Resource Computing (PRC) project where private citizens allow part-time usage of their PCs for scientific computing. The use of PRC for scientific computing will be described in detail, as well as how you can contribute to the project. [Preview Abstract] |
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HA.00056: What is Fine-structure Constant? Shantilal Goradia Equation in [1] $\alpha \quad \ge $ 1/ ln $\surd \lambda $, linking fine-structure constant and cosmological constant derived by using S = k ln W, the total number of microstates used (W) is 10$^{60}$, justified based on a unique age tag attached to each Planck time. The OPEN and CLOSED states of the particle's mouth illustrated in [1] could be two different types of entropic repositioning pulses, say attractive and repulsive. They need not be confused as affecting the number of microstates. The characteristics of a microstate need not change the number of microstates. Mathematically then, W = N! / n!(N-n)!; where N = 10$^{60}$ and n =1; giving W = 10$^{60}$, used in [1]. There are reasons to consider each Planck time as unique microstate based on its unique age. While investigating the proposal in terms of other theories, one has to be to keep in mind that the knowledge that created one problem cannot solve another. Refer to [1] Goradia, Shantilal, ``What is Fine-structure Constant?'' http://www.arXiv.org/pdf/physics/0210040v3. [Preview Abstract] |
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HA.00057: The Hyperbolic Law in the Periodic Table Albert Khazan My recent presentations at the APS Meetings gave a theory which gave the heaviest (last) element of the Periodic Table of Elements. The basis of the theory is the equilateral hyperbolae Y=K/X. These arcs taken in the logarithm coordinates (Ln Xo, Ln Yo) draw straight lines in the 4th quadrant right of Hydrogen, and parallel to it. The real axis (ln Yo=ln Xo-6.0202) transects them at the points which present the tops of the elements of the Periodic Table. The number of the heaviest (last) element was calculated through the exponential function of the atomic mass on the element's number and a logarithm of it. A new hyperbolic fundamental law of the Periodic Table has been conducted: the element content Y per gram-atom in any chemical composition of the molecular mass X can be given by the equations of the positive branches of the equilateral hyperbolae Y=K/X (Y$\le $ 1, K$\le $ X), which are located according to the increase of the nuclear change, and are a real axis common with their tops: with distance from the origin of the coordinates they approach to the positions Y=1 or K=X where the atomic mass is ultimate high - the last element of the Table (Progr. Phys., 1/2007, 38; 2/2007, 83, 104; 3/2008, 56). [Preview Abstract] |
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HA.00058: Photoactivity of Chemically Deposited Rutile Thin Films on Si(111) John F. Anderson, Erie Morales, Kenneth Harris, Ulrike Diebold Chemical Bath Deposition from acidic (pH $<$ 2) solutions at low temperature (35$^{\circ}$C -- 55$^{\circ}$C) produced thin titanium dioxide films with rutile crystalline structure on clean Si(111) wafers. The films were characterized by X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD). Their thicknesses varied from 300 nm up to $\sim $ 1$\mu $m, and annealing was required to ensure adherence to the Si(111) substrate. SEM images show a rough TiO$_{2}$ surface, and XRD indicates the rutile structure of TiO$_{2}$. The rutile films exhibit photoactivity as evidenced by the decomposition of methyl orange when exposed to a 254 nm (4.88 eV) lamp. [Preview Abstract] |
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HA.00059: \textit{In vitro} Electroporation on a microchip with heart valve cells HongBae Kim, JungHan Yi, HungSik Kim, Youn-Suk Choi, SaeYoung Ahn Electroporation in biological cells involves rapid structural rearrangement and formation of pores in the lipid bilayer, in response to an externally applied electric field. To investigate electroporation, we fabricated a chip with two electrodes that is 1mm in distance between them, having six electroporation sites of the same geometry that mounted on a Pyrex glass substrate. The electroporation was performed using a sequence of nine dc pulses of having a pulse width 100 \textit{$\mu $}s each varying the applied amplitudes (375, 750, 1k, 1.3kV/cm), at a frequency of two and five pulses per second so that we may investigate how the applied voltages and pulse number may exert on efficacy of the chip. We used PI and Calcein-AM to measure the efficacy of the electroporation. Cell viability was also measured after electroporation. The analysis have showed that the sample applied 1kV/cm gated at a rate 15.9{\%} and 88.9{\%} than the control along with pulse number 2 and 5 respectively, revealing the increasing exponentially. The cell viability was over 91{\%} as all the applied electrical conditions. [Preview Abstract] |
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HA.00060: Controlled Deposition of SWNTs for Fabrication of Flexible Structural Health Monitoring Strain Sensors Phillip Williams, Buzz Wincheski, David Browne Single-wall carbon nanotubes (SWNTs) are currently investigated for a host of aerospace applications due to their remarkable strength-to-weight ratio and electromagnetic properties. Based on the predicted strength-to-weight advantages and inherent multifunctionality, single-wall carbon nanotube (SWNT)-based materials represent an ideal candidate for the construction of sensors capable of measuring several parameters related to an aerospace vehicle's structural health (e.g., strain, pressure, temperature, etc.), i.e. structural health monitors (SHMs). Specifically, individual SWNTs can exhibit electrical conductivity changes due to strain. Here we report on progress in utilizing this phenomenon to produce SWNT strain-sensing SHMs. Prototype device geometries are fabricated via lithographic techniques to pattern contact electrodes on substrates and controlled depositions of SWNTs between the electrodes using electric fields via dielectrophoresis. After deposition, conductivity measurements and scanning electron and probe microscopy characterize the degree of SWNT alignment and the physical and electrical properties of the devices. Optimization of the carbon nanotube deposition parameters and transfer of the patterned SWNT devices to flexible, polymer-based substrates are discussed as a basis for flexible, SHM strain sensors. [Preview Abstract] |
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HA.00061: Single Molecule Measurements of Protelomerase TelK-DNA Complexes Markita Landry, Rustem Khafizov, Wai Mun Huang, Yann Chemla Protein-DNA interactions lie at the heart of many essential cellular processes such as replication, recombination, and repair. Recent advances in optical ``tweezers'' have made it possible to resolve motions on the scale of a single base pair of DNA, 3.4{\AA}. High-resolution optical traps have the potential to reveal these interactions at their fundamental length scales and should reveal how certain proteins bind to DNA or recognize target sequences. Telomerases are enzymes that have been actively studied in various organisms because of their fundamental involvement with both cancer and aging$^{1}$. Protelomerase TelK is an enzyme responsible for forming closed DNA hairpin ends in linear DNA. TelK is not an ATP dependant enzyme, which is surprising given the degree of DNA distortion accomplished by the enzyme, and the large energy barrier intrinsic in DNA hairpin formation. Therefore, our focus is on TelK mutants lacking their c-terminal domain, and TelK YF mutants lacking their tyrosine active site amino acid. Preliminary data have shown remarkable differences in protein binding and unbinding forces caused by the removal of a single oxygen atom from a 73 kDa protein. Further measurements using high-resolution optical tweezers should provide fundamental insights into the nature and importance of the electrostatic interactions between TelK and its DNA substrate. 1. Shay, J. et al. \textit{Rad. Res.} \textbf{155}, 188 (2001) [1] Huang, W. et al. \textit{Mol. Cell}. \textbf{27}, 901 (2007). [Preview Abstract] |
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HA.00062: Is there Significant Evidence for a Sterile Neutrino? Aaron Allen, Nathaniel Moore, David Ernst Throughout the history of neutrino physics and neutrino experiments, there have been significant hints in the data that seemingly give rise to new implications for neutrino physics. Neutrino oscillations are the only experimentally verified particle phenomenon not accounted for in the Standard Model of particle physics. Evidence for a new type of neutrino has been proposed. In this project, we seek to re-analyze and reproduce key results from LSND and MiniBoone. Combining with existing analysis programs, we look to achieve a consistent data approach fitting into a 3+1 (sterile) neutrino scheme. Finding a neutrino such as this would have major effect on existing cosmological models as a new candidate for dark matter and the early development of the universe. [Preview Abstract] |
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HA.00063: Quasiguided optical modes in nanophotonic organic solar cells John Tumbleston, Doo-Hyun Ko, Edward Samulski, Rene Lopez Organic photovoltaics with highly ordered, nanopatterned photoactive layers offer an alternative to conventional planar devices that suffer from a competition between absorption and free carrier transport. Our recent studies have shown that nanopatterned devices exhibit enhanced absorption and exciton creation profiles as compared to planar cells. Improved absorption results in part from the excitation of quasiguided optical modes where certain photon energies near the semiconducting band edge are enhanced 20-fold. Prerequisites for their excitation include an index of refraction contrast of 0.3 for the two nanopatterned materials and a periodicity comparable to the band edge wavelength. Quasiguided mode dispersion determined via photonic band calculations and variable angle absorption measurements indicate that both fast and slow modes exist in nanopatterned devices. Quantum efficiency measurements also confirm that quasiguided mode excitation occurs in the photoactive material leading to improved electrical performance. [Preview Abstract] |
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HA.00064: Visible Far-Field Superlens for Two-Dimensional Imaging Below the Diffraction Limit Emily Ray, Rene Lopez Retaining the information carried by evanescent waves scattered from an object could allow for imaging features below the diffraction limit without time consuming scanning procedures. We show experimental results of sub-diffraction-limited imaging with visible light using a metal and dielectric multilayer structure with a 2-D diffraction grating. The multilayer structure has an effective negative index of refraction that enhances evanescent waves. Interaction with the diffraction grating converts waves from evanescent into propagating, enabling collection with conventional optics. We are able to tune this far-field superlens (FSL) to our choice of operating wavelengths by modulating the thickness of the metal and dielectric layers. For a wavelength of 532 nm, we used thicknesses of 20 and 100 nm for the Ag and Al$_{2}$O$_{3}$ layers, respectively, and simulated the evanescent waves by launching from beyond the critical angle of a 1.5 refractive index material. This data supports that a FSL of this type can be used in the visible to amplify evanescent waves in spite of the metal absorption. [Preview Abstract] |
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