Bulletin of the American Physical Society
14th Annual Meeting of the Northwest Section of the APS
Volume 57, Number 7
Thursday–Saturday, October 18–20, 2012; Vancouver, British Columbia, Canada
Session D1: Poster Session (4:30-6:00PM) |
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Chair: Jennifer Heath, Linfield College Room: SFU Harbour Centre Main Concourse |
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D1.00001: Microsphere interaction with non-Newtonian solid-supported films to model respiratory therapies Nathan Lee, Javed Ally, Michael Kappl, Hans-J\"urgen Butt Films used as lubricants and particle filters interact with microspheres. One example of a biological particle filter is the mucus lining the human respiratory system. In the conducting airways of the respiratory tract, a 10 $\mu $m thick layer of mucus sits on top of a periciliary layer. These cilia sweep the mucus towards the nose and mouth whereby debris, such as dust and bacteria that are trapped by the mucus layer, may be expelled from the body. Mucus, like other biofluids, can be modeled after a non-Newtonian fluid due to their viscoelastic properties. Interactions between particles and non-Newtonian thin films have not been widely characterized. Atomic force microscopy (AFM) is an ideal technique due to its ability to measure in the microNewtown and micrometer scale. The AFM setup also allows for calculation of the force from direct contact of the particle with the film. Data from these experiments may further the development aerosol-based respiratory therapies. Factors such as particle size and approach speed are necessary to determine improved parameters for drug deposition and retention. It is the goal of this study to analyze interaction forces between particles and non-Newtonian solid-supported films. [Preview Abstract] |
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D1.00002: Characterization of a chiral nematic mesoporous organosilica using NMR Alan Manning, Kevin Shopsowitz, Michael Giese, Mark MacLachlan, Ronald Dong, Carl Michal Using templation with nanocrystalline cellulose, a mesoporous organosilica film with a chiral nematic pore structure has recently been developed. [1] We have used a variety of Nuclear Magnetic Resonance (NMR) techniques to characterize the pore structure. The pore size distribution has been found by analyzing the freezing point depression of absorbed water via NMR cryoporometry. The effective longitudinal and transverse pore diameters for diffusing water were investigated with Pulsed-Field Gradient (PFG) NMR and compared to a 1-D connected-pore model. Preliminary data on testing imposed chiral ordering in absorbed liquid crystals is also presented. \\[4pt] [1] K.E. Shopsowitz et al. JACS 134(2), 867 (2012) [Preview Abstract] |
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D1.00003: Optimization of holographic optical tweezers for multiplexed fluorescence spectroscopy Matthew Cibula, David McIntyre We are developing a multiplexed spectroscopy technique that employs holographic optical tweezers to trap and excite multiple sensor particles. Our goal is to develop a lab-on-a-chip measurement platform for monitoring pH and other ion concentrations with high spatial resolution in a microfluidic device or within biological cells. To ensure efficient use of the available laser power required to trap multiple particles, we address three aspects of the spatial light modulator (SLM) used in the holographic technique. We measure and optimize the input and output polarizations used before and after the birefringent SLM. We reduce optical aberrations by adding appropriate Zernike polynomials to the computed hologram. We optimize the diffraction efficiency of the SLM by adjusting the gray scale input-to-output table to account for the nonlinear phase response of the SLM. [Preview Abstract] |
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D1.00004: Waveguide characterization with multi-photon photoemission electron microscopy J.P.S. Fitzgerald, Robert C. Word, Sebastian Saliba, Rolf Koenenkamp Multi-photon photoemission electron microscopy (PEEM) images surface interactions of visible light with matter, showing electromagnetic (EM) waves that propagate at or near the surface. Images are interferometric, showing where incident and surface waves are in-phase (bright) and out-of-phase (dark), with strong contrast between regions of high and low rates of photoelectron emission. Interferogram analysis can determine the amplitude, wavelength, phase evolution, and propagation decay length of the surface waves. Most multi-photon PEEM studies focus on surface plasmon polaritons. We show that this technique can also be applied to conducting thin-film waveguides, measuring the properties of confined EM waves in a two-mode slab waveguide made of indium tin oxide on glass, which are consistent with waveguide theory. This research was funded by the US Department of Energy Basic Science Office under contract DE-FG02-10ER46406. [Preview Abstract] |
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D1.00005: Evaluation of Low-Thrust Propulsion Options for Cargo Missions to Near-Earth Objects Christopher Grochowski, Jonathan Hoff This study evaluated the ability of eight existing ion and Hall thrusters to meet some of the key requirements of the OSIRIS-REx mission -- to carry a dry mass of 750 kg to the asteroid 1999RQ36, land on it in 2019, stay for 219 days, and return it with a 10 kg sample to Earth. The thrusters were chosen based on demonstrated performance and lifetime characteristics at power levels higher than 5 kW, and were evaluated for this mission at their measured performance levels. It was shown that all the evaluated thrusters could complete the mission in a significantly less time ($<$ 4 years) then the current 7-year round-trip plan of the OSIRIS-REx mission, and still remain within the mass requirements of conventional launchers considered for the mission (10000 kg at 500-km LEO). This study was conducted with a fixed landing date, and did not specifically estimate the shortest trip possible. Because it was assumed that the thrusters always operated at full power, and did not consider throttling to reduce fuel requirement, there could be other options to save even more time and fuel with these thrusters than what has been discussed here. [Preview Abstract] |
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D1.00006: Solar Wind - Mars Interactions: Energetic Neutral Atom Production Erena Friedrich, Andrew Yau, Jerry Brackbill We study the energetic neutral atoms (ENAs) that are formed by charge exchange between solar wind ions and neutral particles in the Martian atmosphere. Mars Global Surveyor has shown that Mars has no notable global intrinsic magnetic field. Consequently, the neutral particles in the Martian atmosphere are unshielded from the flow of energetic solar wind protons. There results extensive production of energetic neutral hydrogen atoms (H-ENAs). In our study, we use a 3D hybrid (kinetic ions, fluid electrons), quasi-neutral, particle-in-cell (PIC) plasma simulation to investigate the production of H-ENAs due to collisions with neutral oxygen (O, O) and nitrogen (N) molecules in the near-space environment of Mars. A detailed chemical model that comprises multi-species reactions, such as ionization by photons, electron recombination, particle collisions, and charge exchange, is self-consistently included in the simulation. These chemical interactions, which take place between ions, atoms, and molecules in the martian exosphere and ionosphere, control the production of the H-ENAs. What is presented is a ``work in progress'' highlighting the ionospheric chemical and physical model as we work towards our goal of computing the flux of escaping H-ENAs due to charge exchange. [Preview Abstract] |
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D1.00007: Using Graphene as Gas Detector Christina Bibler, Kyel Lambert, Michael Crosser The resistivity of graphene is sensitive to the presence of gas molecules adsorbed on it. Since graphene is one atom thick, a gas detector made from it might be sensitive to the presence of even single molecules of gas. We report on progress in making devices for this purpose and on future directions of research. [Preview Abstract] |
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D1.00008: Photoemission electron microscopy of graphene Sebastian Saliba, Jenna Wardini, J.P.S. Fitzgerald, Robert C. Word, Josh Kevek, Ethan Minot, Rolf Koenenkamp A study of chemical vapor deposited graphene on copper foil is conducted using an aberration-corrected photoemission electron microscope (PEEM). We demonstrate the efficacy such a PEEM has in identifying multi-layer graphene, defects and cracking. A model is developed to describe the observed reduction in photoemission rate where electrons originate from the copper foil and scatter through the graphene. A survey of several multi-layer feature line profiles demonstrates the reduced photoemission rate as the number of graphene layers increases. A mean-free-path length of $l=3.8\pm0.8$ nm is inferred assuming the layer spacing in graphene is $\Delta z=0.35$ nm. The PEEM's high spatial resolution and surface sensitivity combined with no electron beam damage are promising for characterizing biosensors and other nanoscale graphene devices. [Preview Abstract] |
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D1.00009: Effect of Pair Annihilation and Neutrino Decoupling on Cosmological Perturbations Elham Alipour, Kris Sigurdson The origin and evolution of the primordial perturbations is the key to understanding structure formation. Through their evolution, these primordial fluctuations have generated first the observed Cosmic Microwave Background (CMB) anisotropies and later the distribution of galaxies and dark matter in the Universe. One possibility for the origin of the primordial perturbations is that the fluctuations were generated during a period of inflation. As inflation ended the fluctuations would have been imprinted as initial conditions for the cosmological perturbations on scales far beyond the horizon. Assuming a growing adiabatic mode as the initial condition, we investigated the impact of electron-positron annihilation and neutrino decoupling on the evolution of primordial perturbations and in particular on the gravitational potential transfer function. [Preview Abstract] |
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D1.00010: 2D Bose gases near resonance Dmitry Borzov, Mohammad Mashayekhi, Jean-Sebastien Bernier, Jun-Liang Song, Fei Zhou We explore 2D Bose gases at large scattering lengths near resonance by analyzing contributions of 3-body scattering events that are universal in 2D unlike the 3D case of Efimov physics dependable upon ultraviolet limit energy scale. Within our approach, we study competition between 2-body and 3-body forces for varying scattering length parameter beyond the dilute limit, and find that, as the role of 3-body processes becomes significant, chemical potential saturates and reaches maximum at the first critical value beyond which we get region of negative compressibility. For even larger scattering lengths the 3-body forces become dominant and eventually lead to the onset of instability at the second critical value. [Preview Abstract] |
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D1.00011: Measuring the Magnetic Induction of Isolated CoFeB Nanowires by Off-Axis Electron Holography Azadeh Akhtari-Zavareh, T. Kasama, L.P Carignan, A. Yelon, D. M\'enard, R. Herring, R.E. Dunin-Borkowski, M.R. McCartney, K.L. Kavanagh Soft, and high saturation magnetization CoFeB Ferromagnetic Nanowires with diameters of 40 nm and 170 nm, were studied by \textit{Selected Area Electron Diffraction (SAED)} and Electron Holography (EH). Diffraction patterns obtained from the nanowires suggest that the wires are nanocrystalline rather than amorphous. Holograms Show the magnetization inside the wire is uniform over most of the wire length, except at the edge. Since the wires consist of soft magnetic nanocrystals, the magnetic anisotropy is likely dominated by the shape anisotropy. Numerical simulations suggest that the stray fields at the top of the wire are well reproduced by a truncated cone model, rather than a cylinder. The measured magnetic induction for wires with diameters near 170 nm is 1.45 T, which is somewhat smaller than the saturation magnetization extracted from static magnetometry measurements of thin films of CoFeB (about 1.67 T). For the 40 nm diameter wires the magnetic induction is ranging from an average of 0.5 T near the tip of the wires to 1.5 T in the middle of the wires. The smaller induction near the end of the wires is attributed to the presence of a significant \textit{out-of-plane} magnetic component since their tips are generally pointed out of the plane of the sample holder. [Preview Abstract] |
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D1.00012: Optical Trapping in Silicon-Based Photonic Crystal Microcavities Seyed Hamed Mirsadeghi, Jeff F. Young A Si-based photonic integrated circuit has been designed to optically trap gold nano-particles at precise, lithographically defined positions on a silicon wafer. The circuit consists of input/output grating couplers, waveguides and a photonic crystal resonant cavity, all designed to operate at wavelengths near 1.5 microns. The objective is to use this as a means of bringing together metal and semiconductor (tethered to the metal) nanoparticles with plasmonic and excitonic resonances coincident with the microcavity resonance, for cavity quantum electrodynamic experiments and applications. The optical trapping potential achievable at the main antinode of the resonant cavity was calculated using 3D FDTD simulations, assuming 10 mW of CW optical power is available to excite the input grating coupler. These calculations suggest that the optical trap depth is 40 kT at room temperature, for a 30 nm diameter gold sphere. Experimental characterization of test samples fabricated based on this design agrees well with simulations. [Preview Abstract] |
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D1.00013: Nanoscale diffraction gratings and electron vortex beams in a scanning electron microscope Alexander Schachtner, Carly Wright, Benjamin McMorran, Tyler Harvey, Tyler Yahn, Jordan Pierce We use focused ion beam nanofabrication to manufacture forked diffraction gratings capable of producing electron beams with helical wavefronts and orbital angular momentum (OAM). A vast number of unique beam modes carrying OAM can be produced through manipulation of grating fork number or position. Generally these gratings are milled such that they produce a phase shift in the beam and are used with high energy electrons (300keV) in a TEM to investigate the quantum or magnetic properties of the electron or image magnetic materials. Our latest work focuses on manufacturing sub-100-nm pitch binary transmission gratings that produce only an amplitude modulation, which opens up imaging capability to lower energy electrons (5-30 keV) and thus expands their use to a wider range of commercially available SEMs. We use these amplitude gratings to show the relationship between the number/position of forks and OAM inherited by the beam. This work could lead to advances in imaging capability, and also creates a widely accessible and scalable demonstration of the quantum properties of the electron which can be leveraged by any science program with SEM access. [Preview Abstract] |
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D1.00014: Electrodeposition of CoS on ITO substrates for the counter electrode of dye-sensitized solar cells Tamiko Masuda, Hafeez Anwar, Ian Hill Dye-sensitized solar cells (DSSCs) provide a relatively low-cost option for harvesting solar energy. The counter electrode (CE) of a DSSC incorporates a catalyst layer, which plays a vital role in the cell cycle by reducing the triiodide ions in the electrolyte. In this study, CoS is studied as a possible replacement for platinum, the standard catalyst [1]. This is relevant because replacing Pt with CoS would reduce production barriers that are associated with cost and supply. Using a two-electrode ``dummy'' flow cell setup the effects of delay times, scan rates and bias voltages in electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements were studied. Preliminary results on CoS samples are taken and indicate charge transfer resistance values an order of magnitude higher than the Pt reference. Future steps to improve the CoS deposition process to optimize charge transfer will be discussed.\\[4pt] [1] Wang, M.; Anghel, A.M.; Marsan, B.; Ha, N.C.; Pootrakulchote, N.; Zakeeruddin, S.M.; Graetzel, M. J. Am. Chem. Soc. 2009, 131, 15976. [Preview Abstract] |
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D1.00015: Geometric Optimization of Spin Current Josh Melander, Sergei Urazhdin Spintronics is the study of spin transport electronics. Already employed in data storage technologies, spintronics offers the opportunity to continue to shrink electronic devices past what traditional electronics are capable of. The application of spintronics requires highly optimized devices; more so than what is available currently. In this experiment we aim to optimize spin transport properties through the geometry of the device. More specifically, we investigate how the thickness of the sample affects the diffusion length of the spin current (SC). The sample device is a multilayer made up of FeMn(0.5)Pt($x)$Py(5), where $x$ is the thickness in nm, sputtered onto an oxidized silicon chip. SC is then induced by the Spin Hall Effect (SHE) which occurs when a current is passed through the Pt layer. The effect of SC on Py is measured by Brillouin light scattering (BLS) spectroscopy. Our data shows that spin diffusion length is dependent on the thickness of the sample and we are currently working to formulate a working model for it. [Preview Abstract] |
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D1.00016: Probing interactions between collagen proteins via microrheology Marjan Shayegan, Nancy R. Forde Collagen is the major structural protein of our connective tissues. It provides integrity and mechanical strength through its hierarchical organization. Defects in collagen can lead to serious connective tissue diseases. Collagen is also widely used as a biomaterial. Given that mechanical properties are related to the structure of materials, the main goal of our research is to understand how molecular structure correlates with microscale mechanical properties of collagen solutions and networks. We use optical tweezers to trap and monitor thermal fluctuations of an embedded probe particle, from which viscoelastic properties of the solution are extracted. We find that elasticity becomes comparable to viscous behavior at collagen concentrations of 5mg/ml. Furthermore, by simultaneously neutralizing pH and adding salt, we observe changes in viscosity and elasticity of the solution over time. We attribute this to the self-assembly process of collagen molecules into fibrils with different mechanical properties. Self-assembly of collagen under these conditions is verified by turbidity measurements as well as electron microscopy. By comparing results from these local studies of viscoelasticity, we can detect spatial heterogeneity of fibril formation throughout the solution. [Preview Abstract] |
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D1.00017: Undergraduate Construction of Optical Tweezers Lawrence Hubbell I will present a poster on the construction of optical tweezers. This will demonstrate the full process one must go through when working on a research project. First I sifted through the internet for papers and information pertaining to the tweezers. Afterwards I discussed the budget with the lab manager. Next I made purchases, however some items, such as the sample mount, needed to be custom made. These I built in the machine shop. Once the tweezers were operational I spent some time ensuring that the mirrors and lenses were adjusted just right, so that the trap performed at full strength. Finally, I used video data of the Brownian motion of trapped silica microspheres to get a reasonable estimate of the trapping stiffness with such particles. As a general note, all of this was done with the intent of leaving the tweezers for future use by other undergraduates. Because of this extra effort was taken to ensure the tweezers were as safe to use as possible. For this reason a visible LASER was chosen over an infrared LASER, in addition, the LASER was oriented parallel to the surface of the table in order to avoid stray upwards beams. [Preview Abstract] |
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D1.00018: Measurements of adsorbate binding on individual suspended carbon nanotubes Hao-Chun Lee, Boris Dzyubenko, David Cobden, Oscar Vilches By measuring the resonance frequency shift of vibrating suspended single-walled nanotubes at controlled temperature and pressure we can accurately detect the adsorption of gases including He, Ar, Kr, Xe, O2, and N2. The binding energy can then be determined from the low-coverage part of the adsorption isotherms. We find that the adsorption isotherms generally resemble those on graphite but with weaker binding energies, allowing access to behavior at lower two-dimensional (2D) chemical potential than on graphite. For He-4 the binding energy is reduced by as much as a factor of two. For Ar the binding energy on all nanotubes measured is in the range 800 - 900 K, about three quarters of that on graphite. This enables us to investigate the 2D critical and triple points of Ar. Puzzlingly, we find that the devices fall into two classes: one with monolayer condensation at lower pressures and sudden 2D liquid-vapor transitions, the other with condensation at higher pressures and lacking sharp transitions even well below the 2D critical point. [Preview Abstract] |
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D1.00019: Strain control and the triple point of the metal-insulator transition in vanadium dioxide nanobeams Jae-Hyung Park, Jim Coy, Serkan Kasirga, Zaiyao Fei, Chunming Wang, Brad Smith, Eli Bingham, David Cobden We have developed an apparatus for applying controlled strain to suspended nanostructures while carrying out optical measurements. This platform enables us to study phenomena which are very sensitive to strain, such as the metal-insulator transition (MIT) occuring in vanadium dioxide nanobeams. The relationship between the metallic (R) phase and the two insulating (M1 and M2) phases involved in the MIT in vanadium dioxide remains unclear. Due to the different lattice constants of these phases, control of the strain along the nanobeam allows us to study the transitions between them methodically as a function of temperature and nanobeam length. One of our findings is that the triple point of the three phases occurs at zero strain. [Preview Abstract] |
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D1.00020: NO$\nu $A Far Detector Module Fiber QA Test Analyses Amanda Bowers In an effort to better understand the fiber-optic technology used to read out information regarding neutrino interactions in the NOvA far detector, various tests are performed at multiple stages of the detector module production. These fiber tests are used to check for and find sources of damaged fibers that may yield faulty readings. Analyses were performed specifically on the Stringing Fiber Test, closed fiber test, and visual inspection test both with and without a card. Cross-analyses were also performed to consolidate the data from these various tests and draw conclusions regarding the location and source of damaged fiber. The goal is to minimize the number of future tests that need be performed on a module while maintaining a high confidence level in the acceptance and rejection of modules to be installed at the detector site. [Preview Abstract] |
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D1.00021: Charmonium Hybrid Masses From QCD Sum-Rules Timothy Richards, Jason Ho, Brendan Bulthuis, Derek Harnett, Robin Kleiv, Tom Steele Over the past decade or so, more than a dozen new charmonium-like resonances, the so-called XYZ resonances, have been discovered due largely to work done by the Belle and BaBar collaborations. Few of these resonances fit neatly into a conventional charmonium interpretation as there are significant discrepancies between predicted and observed masses and widths. As such, there has been considerable speculation that some of these new states may lie outside of the constituent quark model. Hybrids, hadrons with explicit quark and gluon degrees of freedom, represent one such possibility. Using QCD sum-rules, we predict charmoniun hybrid masses for a variety of $J^{PC}$ quantum numbers, and comment on possible phenomenological implications. [Preview Abstract] |
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D1.00022: On the Formation of Luminescent MgZnO Ceramics with the Hexagonal and the Cubic Phase Leah Bergman, John Morrison, Jesse Huso, Michelle Huso, Hui Che, Dinesh Thapa Mg(x)Zn(1-x)O is a promising alloy family with UV-tuneable bandgaps, which can have the hexagonal or cubic structure depending on the composition x. ZnO has the hexagonal wurtzite structure and a bandgap of $\sim 3.4$ eV, while MgO has the NaCl cubic structure and a bandgap of $\sim 7.4$ eV. Mg(x)Zn(1-x)O can yield bandgaps spanning the range $3.4$ eV to $7.4$ eV that are achieved via the choice of composition x. We present studies of the optical and material properties of sintered ceramics with two alloy compositions, $x=0.1$ and $x=0.6$, to investigate both the wurtzite and the cubic phases. To study the alloying dynamics, the properties as a function of annealing temperature in the range of 600-1100C were investigated. For the low Mg composition ceramic sample it was found that a threshold temperature around 900C is required in order to initiate the formation of the solid solution of MgZnO with the wurtzite structure. The formation of the high Mg composition ceramic sample was found to have a sequence of phases: initially the alloy formed with the wurtzite structure at around 900C, then a transition into the NaCl cubic structure took place at the high temperature regime. Due to such formation, the cubic phase ceramics inherently include defects within the wurtzite structure. [Preview Abstract] |
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D1.00023: Measuring the spin relaxation time of donor-bound electrons in InP Pasqual Rivera, Emma Lorenzen, Todd Karin, Russell Barbour, Kai-Mei Fu Neutral donor-bound electrons and excitons in bulk semiconductors provide a system that may have interesting prospects for quantum information processing (QIP). In GaAs, the donor-bound exciton system exhibits extremely high optical homogeneity with spin relaxation times similar to that of negatively charged quantum dots. The complex excited state structure, however, makes full coherent optical control of the spin state challenging. In this work we investigate the spin relaxation properties of donor-bound electrons in InP, a material which exhibits a simpler excited-state structure and a higher exciton binding energy than GaAs. Current progress towards measuring the T1 via polarization-induced optical pumping will be presented. [Preview Abstract] |
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D1.00024: Electrical Conductivity of Sr$_{x}$VMoO$_{6-y }$(x=0.0, 0.1, 0.2) Double Perovskite Solid Oxide Fuel Cell Anode Nicholas Childs, Adam Weisenstein, Camas Key, Stephen Sofie, Richard Smith Solid Oxide Fuel Cells (SOFCs) are suited for high efficiency power generation, fuel flexibility, high temperature electrolysis, closed loop regenerative systems, oxygen generation, and carbon dioxide reduction. These capabilities make the SOFC highly versatile for: primary/secondary power systems, advanced life support, and in-situ resource utilization which may all be desired for a forthcoming lunar return and Mars Exploration. A promising anode material for a SOFCs is the double perovskite Sr$_{2-x}$VMoO$_{6-y}$(x=0.0-0.2), due to its stability, electronic, and ionic conduction. Anodes of this material were prepared via a tape casting technique. Electrical conductivity was studied in reducing atmospheres at temperatures up to 800 $^{\circ}$C. V and Mo valence states were indentified before and after annealing in a hydrogen environment. Samples exhibited metallic conduction with electrical conductivity of $\sim $10$^{4}$S/cm in a reducing atmosphere at 25 $^{\circ}$C. A highly insulating SrMoO$_{4}$ phase forms upon room temperature exposure to air. The SrMoO$_{4}$ phase can be reduced above 400 $^{\circ}$C resulting in an increase in conductivity. [Preview Abstract] |
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D1.00025: Fabrication of hybrid GaP/diamond resonators for quantum information processing Nicole Thomas Long spin coherence time and coupling of spin to optical transitions make nitrogen vacancy centers in diamond promising candidates for stationary qubits for quantum information processing. Their integration into photonic networks may allow for the measurement-induced entanglement of different spins through photon interference. One possible chip-based photonic entanglement network could consist of ring resonators for the enhancement of light emitted by the nitrogen vacancy centers, optical switches and waveguides. GaP is an ideal material choice for the fabrication of photonic networks in that it is transparent at the wavelength range of interest, provides a high refractive index for efficient waveguiding and electro-optic tuning capabilities for switching. We present two approaches to the fabrication and testing of hybrid GaP/diamond nanophotonic structures: (1) direct growth of GaP on diamond by molecular beam epitaxy and (2) transfer for a 200 nm thick GaP sheet from a bulk GaP/AlGaP/GaP sample to diamond. Disk resonators were fabricated via electron beam lithography and an anisotropic dry etch, and the resonator quality factor is measured. [Preview Abstract] |
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D1.00026: Generation of coherent blue light in rubidium vapor: An advanced undergraduate laboratory Shannon Mayer, Marcus Kienlen, Noah Holte, Hunter Dassonville, Kurt Iversen, Ryan McLaughlin, Andrew Dawes We describe an experiment for generating and characterizing coherent blue light in a rubidium vapor using two grating-feedback diode lasers. The lasers, operating at 780.2 nm and 776.0 nm respectively, provide step-wise excitation from the 5S ground state to the 5D excited state in rubidium. Cascade decay through the 6P state can produce a coherent beam of light at 420 nm. In this experiment, carried out in two different laboratories with different equipment, we investigate the spatial coherence and spectral characteristics of the blue beam under a variety of experimental conditions. This experiment provides advanced undergraduate physics students with a unique opportunity to investigate nonlinear optical phenomena in the laboratory. The equipment is similar to that used for saturated absorption spectroscopy in rubidium and can therefore be easily performed in laboratories with apparatus for that experiment. [Preview Abstract] |
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D1.00027: Investigating and manipulating color centers in yttrium aluminum garnets Chris Varney, Autumn Pratt, Farida Selim Rare-earth-doped yttrium aluminum garnets (YAG) are important photonic materials with numerous applications in many fields such as lasers, phosphors, and scintillators. Color centers forming from point defects and impurities play a significant role on the optical properties of YAG crystals. In this work, color centers in undoped and RE doped YAG crystals were identified by absorption measurements in the UV-VIS- NIR range. Photo- and radio-luminescence measurements were carried out to study their emission. Growth atmosphere, annealing and UV excitation were utilized to alter the charge state of color centers and manipulate their absorption and luminescence characteristics. [Preview Abstract] |
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D1.00028: Women in Physics in Canada Janis McKenna Here we are in the 21st century in Canada, where most of us would say that young girls and boys have equal access to education, opportunities, and careers of their own choice. In Canada, women currently outnumber men in full-time university enrollment, in Medical Schools and in Law Schools. 48\% of the Canadian work force is female, yet women make up only 21\% of working professionals in science, engineering and technology. Canada-wide in Physics, the situation is such that only 20\% of our BSc graduates are women, and 19\% of our PhD graduates are women. It is evident that the ``leaky pipeline'' in Physics leaks most at a young age, before BSc graduation. High school physics statistics in BC indicate that while most of the grade 12 science and math disciplines have roughly equal numbers of young men and women enrolled, this is not the case for high school physics, where province-wide, only 30\% of Physics 12 students are women. (Biology is also skewed, but in the other direction: 62\% of Biology 12 students are women) This poster will present current statistics and will hopefully be a wake-up call for us all to consider participating in more outreach in science, and especially physics, in our high schools. [Preview Abstract] |
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D1.00029: Developing a Research Tool to Gauge Student Metacognition Alistair McInerny, Andrew Boudreaux, Sepideh Rishal, Kelci Clare Metacognition refers to the family of thought processes and skills used to evaluate and manage learning. A research and curriculum development project underway at Western Washington University uses introductory physics labs as a context to promote students' abilities to learn and apply metacognitive skills. A required ``narrative reflection'' has been incorporated as a weekly end-of-lab assignment. The goal of the narrative reflection is to encourage and support student metacognition while generating written artifacts that can be used by researchers to study metacognition in action. We have developed a Reflective Thinking Rubric (RTR) to analyze scanned narrative reflections. The RTR codes student writing for Metacognitive Elements, identifiable steps or aspects of metacognitive thinking at a variety of levels of sophistication. We hope to use the RTR to monitor the effect of weekly reflection on metacognitive ability and to search for correlations between metacognitive ability and conceptual understanding. [Preview Abstract] |
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D1.00030: Proportional reasoning competence among different student populations King Wong A collaborative project between Western Washington University, Rutgers University, and New Mexico State University seeks to understand student's competence level on proportional reasoning. We have been collecting and analyzing data from introductory physics and science education courses using a set of assessment tasks. We utilize the notion of constructs to categorize student thinking according to repetitive patterns. Results suggest that, when students confront ratio and proportion problems, they often experience a gap between the mechanics of the mathematical operations and the conscious understanding of what they are doing. In this poster we will share results of our findings from different courses, institutions, and student populations. Supported by NSF grants DUE-1045227, DUE-1045231, DUE-1045250.. [Preview Abstract] |
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