Bulletin of the American Physical Society
2005 Joint Spring Meeting Ohio Section of APS and the Southern Ohio Section of AAPT
Friday–Saturday, April 8–9, 2005; Dayton, OH
Session B: Poster Session |
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Room: Kennedy Union W. Ballroom 5:30-6:30pm |
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B.00001: Compact wave function useful in educational physics Odil Yusupov In this abstract we want to submit for consideration compact wave function useful in study quantum mechanic. This is improved classical Guillemin-Zener[1] wave function for primary diatomic molecular system -- molecular hydrogen ion. A study of this ion, where one electron moves in field two immovable nuclei, is important for molecular theory, chemical physics, theory of few particle coulomb systems, etc. Compact electronic wave function for ground state of molecular hydrogen ion is \textbf{$\Psi ={\rm N}*$(exp(-a1$*\xi )$+c*exp(-a2$*\xi )$ )$*$( cosh(-b1*$\eta )$+d*cosh(-b2*$\eta ))$ } where N - normalization factor, $\xi $ and $\eta $ are spheroidal coordinates of electron, a1,a2,b1,b2 -- nonlinear variational parameters, c and d - linear variational parameters. We found optimal values of this parameters for any internuclear distance R. For example, at R=2 a.u.: a1= 1.4345, a2= 1.9753, b1= 0.5399, b2= 1.3001, c= -0.332876, d= 0.592279 . Electronic energy of molecular hydrogen ion with this 4-term wave function equals -1.10263418 a. u. and very close to the ``exact'' value -- 1.10263422 a.u. The calculations was shown that our wave function equivalent to 25- term standard mathematical expansion in spheroidal coordinates. This function can to use as good illustration of variational method in quantum mechanic. \newline \newline [1]V.Guillemin, C.Zener. Proc. Natl.Acad. Sci. U.S., 15, 314, (1929) \newline [2]T.K.Rebane and O.N.Yusupov. Opt. and spectr . 72, ยน6, 1289 (1992) [Preview Abstract] |
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B.00002: Randomness in the scattering of light by sound Tobey Thorn, Enrique Manzano, Juan Correa, John Thompson In our experiments, we study the process of a laser passing through a glass optical fiber and scattering off of high frequency sound waves in the glass. The sound waves are created by random thermal fluctuations of silica molecules, and this randomness is passed onto the scattered light which has a complex intensity profile even though the original laser pulses are quite regular in shape. We study the statistical properties of the scattered waveforms and attempt to find general patterns in the random intensity fluctuations of the scattered light. In our experiments, we use a stable single-mode laser system to ensure that there is no significant source of randomness aside from the thermal fluctuations that generate the sound waves. We use a fast detection system, with a resolution of a few hundred picoseconds, to collect thousands of scattered waveforms. We then analyze the data to determine the size of the fluctuations and the probability distribution of the energy contained in the scattered waveforms. We have learned that the relative noise (standard deviation/mean) varies with the amount of the scattered waveform that is integrated. We also observe extremely narrow intensity spikes at the trailing edge of the depleted laser pulses that differ in frequency from the original laser pulse and the highly irregular scattered waveforms. [Preview Abstract] |
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B.00003: Learning From Where Students Look While Observing Simulated Physical Phenomena Dedra Demaree, Stephen Stonebraker, Lei Bao The Physics Education Research (PER) Group at the Ohio State University (OSU) has developed Virtual Reality (VR) programs for teaching introductory physics concepts. Winter 2005, the PER group worked with OSU's cognitive science eye-tracking lab to probe what features students look at while using our VR programs. We see distinct differences in the features students fixate on depending upon whether or not they have formally studied the related physics. Students who first make predictions seem to fixate more on the relevant features of the simulation than those who do not, regardless of their level of education. It is known that students sometimes perform an experiment and report results consistent with their misconceptions but inconsistent with the experimental outcome. We see direct evidence of one student holding onto misconceptions despite fixating frequently on the information needed to understand the correct answer. Future studies using these technologies may prove valuable for tackling difficult questions regarding student learning. [Preview Abstract] |
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B.00004: Tunneling Spectroscopy of Self Assembled Monolayers of 7-Ethynyl-2,4,9-trithia-tricyclo[3.3.1.1$^{3,7}$]decane on Cadmium Sulfide Robert Mallik, Ivan Dolog, Anthony Mozynski, Jun Hu Inelastic Electron Tunneling Spectroscopy (IETS) is used to record the vibrational spectrum of 7-Ethynyl-2,4,9-trithia-tricyclo[3.3.1.1$^{3,7}$]decane (7ETTD) adsorbed on amorphous CdS ultra-thin films. The CdS films are 3 nm thick, and are prepared by RF sputtering in argon. Sub-, to supra-monolayer surface coverage is achieved by repeatedly spin-doping 7ETTD onto the CdS films from a very dilute solution consisting of 9 mg 7ETTD/2 ml Dichloromethane/13 ml Diethylether. The resulting doped CdS films form the barrier layer in thin-film Al/barrier/Pb tunnel diodes. Forward and reverse bias IET spectra, conductance-voltage, temperature-dependent current-voltage, and low bias resistance measurements are presented. These corroborate previous data indicating that the 7ETTD layer significantly lowers the barrier height and increases the conductivity of the tunnel diode. [Preview Abstract] |
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B.00005: Modeling Noisy Light in Optical Fiber Elizabeth Huynh, Anel Medrano, Arthur Zavala, Christopher Goedde Light traveling in optical fiber can scatter off high-frequency sound waves in a process known as Brillouin scattering. The sound waves are randomly generated by thermal fluctuations in the fiber, and the amount of scattered light is strongly affected by these variations. Our model consists of three coupled partial differential equations, one for the input laser pulse, one for the scattered wave, and one for the sound waves. We present simulation results and compare them to experimental measurements of the statistics of light generated by Brillouin scattering in optical fiber. [Preview Abstract] |
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B.00006: Transparent conducting films of sputtered tantalum oxide for solar cell window layers Mark Stockett, John Scofield Tantalum Oxide (Ta$_{2}$O$_{5})$ is commonly used in capacitors for its high dielectric constant and is highly insulating with resistivity on the order of 10$^{8}$ ohm m. Ta$_{2}$O$_{5 }$ is however a semiconductor with a bandgap of 4.2 eV and could be made to conduct if appropriately doped. These films may have useful applications as a window layer for thin film heterojunction solar cells. Transparent films of amorphous tantalum oxide (Ta$_{2}$O$_{5})$ have been prepared by reactive DC magnetron sputtering from a metallic tantalum target in an argon/oxygen gas mixture. These films vary in thickness from 100 nm to 550 nm and have a refractive index of about 1.9. Films were characterized using XRD, UV-Vis-NIR spectroscopy and 4-probe electrical measurements. Optimally transparent films were deposited at a 5:1 argon to oxygen flow ratio and a chamber pressure of 20 mTorr. The sputter current for these films was held constant at 175 mA. We are exploring the fabrication of conducting tantalum oxide films through carbon doping. This can be done by adding carbon dioxide to the plasma. The results of this work will be discussed at the conference. [Preview Abstract] |
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B.00007: Modeling the Extreme-Pressure Lubricating Interface Matey Kaltchev, Feng Gao, Javier Lara-Romero, Wilfred Tysoe Extreme-pressure lubricants are currently widely used in various areas of applications. However, despite of their common use, the fundamental aspects of the mechanism in which these lubricants reduce the friction coefficient are not clear yet. Earlier macrotribological experiments using chlorinated hydrocarbons have shown remarkable effectiveness. It has been proven that thin films that resemble those formed under tribological conditions can also be synthesized in ultrahigh vacuum when beams of chlorinated hydrocarbons are directed onto a clean iron surface. Here results obtained using X-ray photoelectron spectroscopy, temperature programmed desorption, atomic force microscopy and microtribological measurements of these films are presented. Substantial information about the fundamental properties and structure of this model lubricating interface is revealed. A mechanism of the formation of the interface under tribological conditions is also suggested. [Preview Abstract] |
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B.00008: Chaos in a Complex Plasma T.E. Sheridan Chaotic dynamics is found experimentally in a complex (dusty) plasma disk of three particles. A sinusoidal modulation of the plasma density excites both the center-of-mass and breathing modes. Low-dimensional chaos is seen for a 1:2 resonance between these modes. The dimension of the attractor is found to be 2.48 $\pm$ 0.05, while the largest positive Lyapunov exponent is 0.17 $\pm$ 0.04 bits/sample. [Preview Abstract] |
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B.00009: Normal modes of small complex plasma disks K.D. Wells, T.E. Sheridan Center-of-mass and breathing oscillations of a complex (dusty) plasma disk are excited for $n=3$ and 5 microspheres ($9.62\mu$m diam) with neutral argon pressures $P\approx1-4$ Pa. The mode frequencies and damping rates are determined directly from measured resonance curves. Millikan's coefficient for the Epstein drag force, the Debye length and the particle charge are determined by comparison with theory. The damping rates are the same for both modes and for $n=3$ and 5 particles, as predicted. Millikan's coefficient is found to be $\delta=1.55\pm0.16$, in agreement with $\delta=1.44$ for diffuse reflection. A consistent value of the Debye length that decreases with pressure is found for $n=3$ and 5 particles. The particle charge for $n=3$ particles is found to be more negative than that for $n=5$ particles for the same conditions, indicating that the effective ion collection area of the particles increases as their separation decreases. [Preview Abstract] |
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B.00010: Intrinsic Compressibility of Sperm Whale Myoglobin Determined from High-Pressure Crystallographic Structures Jeremy Clark, Paul Urayama Myoglobin, considered a paradigm for biocomplexity, may serve as a model system for studying the role of cavities and volume fluctuations in proteins. Volume fluctuations are directly probed by pressure via the compressibility. While the physico-chemical basis for pressure effects is well established, effects in structurally complex systems have yet to be fully explored. Biocomplexity can lead to significant effects at moderate, kilo-atmosphere pressures, and is the reason detailed structural information under pressure is needed to understand pressure effects in proteins and other biological systems. Structural determination of proteins at kilo-atmosphere pressures using x-ray crystallography is a powerful method for investigating the effects of pressure on structure. Here we present results quantifying the spatial distribution of intrinsic compressibility in sperm whale myoglobin calculated from crystallographic structures solved at ambient and at 1500 atm pressures. [Preview Abstract] |
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B.00011: A UV-Visible-NIR, Time-Resolved Spectrofluorimeter for High-Pressure Biophysical Studies Jacob Ajimo, Pedro Calderon, Jonathan Dudley, Bill Schneider, Katherine Binzel, Paul Urayama We present a newly developed UV-visible-NIR, time-resolved spectrofluorimeter for probing biological samples at high pressures. The system is capable of simultaneously collecting emission spectrum and time-resolved emission intensity for both spectral and excited-state lifetime determination. The system uses a sub-nanosecond pulsed, nitrogen-pumped dye laser for excitation between 337 -- 1000 nm wavelenth. Spectral information is collected using a nanosecond-gated, intensified CCD. Time-resolved intensity information is collected using a GHz-bandwidth avalanche photodiode. The high-pressure chamber is a thick-walled quartz capillary capable of holding 800 atm pressures. Implementation of the system as a high-pressure, high-numerical aperture fluorescence microscope imaging system is also described. [Preview Abstract] |
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B.00012: Adaptive Optical Beam Shaping Using Hybrid Acousto-optics Yasser Abdelaziez, Dean Evans, Partha Banerjee We theoretically and experimentally demonstrate optical beam shaping through adaptive feedback in an acousto-optic device with electrical feedback using experimentally determined parameters. Cases of positive and negative feedback from undiffracted and diffracted orders are investigated. In addition, we demonstrate the dependence of the final value of the induced grating strength in the acousto-optic cell on the feedback parameters. Feedback, as used now, helps to generate the additional sound pressure which can give beam shaping. Previous analysis of hybrid acousto-optic devices with feedback have been restricted to plane wave treatments only. We show that over a region of convergence, one can achieve beam shaping by using the detected optical output and feeding it back together with the external electrical input. This is fundamentally different than just increasing the electrical input to the transducer. In general, we can also select a certain range of spatial frequencies at the optical detector and use this for feedback purposes, this way, we are selectively feeding back a range of spatial frequencies of the optical beam. [Preview Abstract] |
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B.00013: Dual Laser Beam ``Jitter'' Analysis Gregg Anderson, Mark Walker This work involves recording, analyzing and characterizing the fringe pattern resulting from overlapping two pulsed laser beams. A stationary fringe pattern is essential in order for our laboratory's experimental work to succeed. The resulting fringe pattern, however, is seen to move erratically and hence introduces experimental complications that we would rather avoid. The work proposes isolating the beams from air currents or from sources of vibration external to the beams as a means of reducing, if not eliminating this fringe movement or ``jitter.'' This work explores those solutions and provides data analysis techniques through a plotting, graphing and analysis software package called IGOR{\textregistered}. [Preview Abstract] |
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B.00014: Determination of the electric field and its gradient in the plasma sheath using floating microspheres M.R. Katschke, K.D. Wells, T.E. Sheridan The electric field and its gradient in an rf plasma sheath are determined experimentally. Either two or three uniform, dielectric microspheres are suspended in the plasma near the sheath edge. The center-of-mass and breathing frequencies for the particle clusters are found by measuring the resonance curves for horizontal oscillations driven by amplitude modulating the rf power. The particle charge and plasma Debye length are inferred from the ratio of these resonance frequencies. Knowledge of the particle mass then allows the electric field at the position of the particles to be found, while the electric field gradient is determined by measuring the vertical resonance frequency. [Preview Abstract] |
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B.00015: The Rotational Spectrum of H$^{15}$NO$_{3}$ Mark Kipling, Ashley Jones, Douglas Petkie, Ivan Medvedev, Atsuko Maeda, Brian Drouin, Paul Helminger The millimeter and submillimeter rotational spectrum of the isotopic species of nitric acid, H$^{15}$NO$_{3}$, is currently being analyzed. Many transitions in the ground and first four lowest vibrational states, \textit{$\upsilon $}$_{9}$, \textit{$\upsilon $}$_{7}$, \textit{$\upsilon $}$_{6}$, and \textit{$\upsilon $}$_{8}$, have been assigned and fit using a Watson-type Hamiltonian. We will describe the general characteristics of the nitric acid spectrum and compare the rotational and centrifugal distortion constants of each state with those of the normal species. [Preview Abstract] |
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B.00016: Synthesis and Frequency Dependent Properties of Ferromagnetic Nanoparticles/Polyurethane Nanocomposites Christy Vestal, Max Alexander The development of materials with high permeability, high permittivity and with low loss is of interest due to their application in microelectronics and microwave communication systems. Although ferromagnetic materials display high permeabilities, they have limited applications in microwave applications due to their large conductivities that limit the ability of microwaves to penetrate into bulk materials. One approach commonly taken to overcome the limitations of bulk ferromagnetic materials is to disperse ferromagnetic inclusions in an insulating matrix (i.e. a dielectric material). Although polymeric nanocomposites with magnetic inclusions of different dimensionality and chemistry are possible, efforts to understand and evaluate the effects of nano-sized inclusions have been limited and a general understanding is necessary to establish structure-property relationships of these materials. Here we report the frequency dependent properties of ferromagnetic nanoparticle/polyurethane nanocomposites as a function of nanoinlcusoin loading and nanoparticle size. Novel magnetic core/shell nanoparticles will also be synthesized and evaluated. [Preview Abstract] |
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B.00017: Polarization spectrum of the atomic Cs on the $6s^{2}S_{1/2}\rightarrow6p^{2}P_{3/2}\rightarrow10s^{2}S_{1/2}$ transition Seda Kin, Morgan J. Welsh, Jacob D. Hinkle, S. Burcin Bayram An experimental investigation of collisional depolarization of the atomic cesium $6s^{2}S_{1/2}\rightarrow 10s^{2}S_{1/2}$ two- color two-photon polarization spectrum with Ar buffer gas has been made. In the vicinity of the $6s^{2}S_{1/2} \rightarrow6p^{2}P_{3/2}\rightarrow10s^{2}S_{1/2}$~stepwise resonances the dependence of the Ar pressure revealed strong depolarization on the polarization spectrum. Measurements of the linear polarization degree were made with the first laser tuned to resonance and the second laser tuned within a $\pm~11$ cm$^{- 1}$ range over the final state. In the absence of collisions, the measurements of the polarization spectrum is in agreement with calculations. The polarization measurement on the $6s^{2}S_{1/2} \rightarrow6p^{2}P_{3/2}\rightarrow10s^{2}S_{1/2}$ transition and an overview of the experimental techniques of our results are also presented. [Preview Abstract] |
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B.00018: Using the iCARE for monitoring cognitive conflicts and anxiety in PBI classes Yeounsoo Kim, Lei Bao Cognitive conflicts can cause some students to have high levels of anxiety during their learning, which, when not properly addressed, can have negative effects to students' motivations and performance. Based on the large amount of literatures on studies of cognitive conflicts and student anxiety, we developed an easy-to-use instrument, the In-class Conflict and Anxiety Recognition Evaluation (iCARE), for monitoring the status of students' cognitive conflicts and anxiety in the context of Physics by Inquiry (PbI) classes. In this poster, we present examples to show the types of information that can be obtained with iCARE in a PBI class and discuss how instructors can use such an instrument in instruction. [Preview Abstract] |
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B.00019: Adaptive Fourier Bessel and Wavelet transform methods for tracking optical pulses in (D+1)-dimensions Georges Nehmetallah, Partha Banerjee Traditional numerical techniques such as finite-difference, function approximation and pseudo-spectral methods are used to solve the NLS equation, which models pulse, beam or optical bullet propagation in fiber and unbounded media respectively. However, in all the above techniques tracking the solution is either time consuming or inaccurate because the problem in hand might be (D+1) dimensional. In this work we present two novel techniques which we call adaptive Fourier Bessel split-step (ASFBSS) and adaptive wavelet transform (AWT) methods, to numerically solve (D+1) optical pulse propagation in fiber and bulk Kerr type nonlinear media based on the scalar nonlinear Schr\"{o}dinger (NLS) equation in (D+1) dimensions with cylindrical or spherical symmetry in 2 and 3 dimensions respectively. Using fast algorithms for cylindrical/spherical Fourier Bessel or wavelet transforms along with adaptive longitudinal stepping and transverse grid management in a symmetrized split-step technique, it is possible to accurately study many nonlinear effects, including the possibility of self-focusing, self-steepening, spatio-temporal collapse, collapse-arresting mechanism due to saturable non-linearity or beam nonparaxiality, variable Kerr nonlinearity, and variable dispersion managed systems. [Preview Abstract] |
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B.00020: Fabrication and Characterization of Waterborne Multi-wall Carbon Nanotube Paints Heather Dowty, Max Alexander, Chyi-Shan Wang, William Click, Marlene Houtz, Jacque Henes, Hilmar Koerner The fabrication of water-borne polyurethane nanocomposites containing multi-wall nanotubes has presented a significant technological challenge to those in the polymer community. Such conductive polyurethanes are of great interest to the paint and coatings industry for use in electrical grounding and shielding. Currently, these materials are formed by strong acidic reflux of the nanotubes and subsequent dispersal in the polymer matrix. This treatment can result in significant shortening of the tubes and degradation of the resulting mechanical and electrical transport properties. Here we present an alternate technique in which various conductive and non-conductive water-soluble polymers are physi-adsorbed to the surface of the nanotube. These interactions with the nanotubes result in highly uniform suspensions of water-based urethane coatings and bulk materials. We will examine the polymer chemistry and morphologies of these nanostructured materials and the resulting thermal, electrical and mechanical properties. [Preview Abstract] |
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B.00021: Investigation of Electrospun Nanocomposite Polymer Nanofibers Max Alexander, Brandon Black, Jennifer Stuckey, Chyi-Shan Wang, Jacque Henes, Hao Fong Electrospinning of polymers offers the ability to reproducibly manufacture sub-micron diameter fibers with desired morphologies. Conductive electrospun fibers offer new avenues to producing high surface area electrodes and membranes for a variety of applications. The goal of this work was to produce controlled nanostructured morphologies by the electrospinning of intrinsically conductive polymers, nanocomposites containing carbon nanotubes, and Nylon 6/layered silicate nanocomposites (NLS). Additionally, intentionally phase separated polymer nanofiber structures of intrinsically conductive polymer / polyurethane blends were also produced. The extremely high interfacial area of these fiber materials is of great interest for reinforced composites, chemical/biological filtration, protective clothing, and biomedical applications such as wound dressing. Of particular significance is for use in high surface area electrodes for hybrid organic-inorganic photovoltaic devices. [Preview Abstract] |
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B.00022: Phase conjugation, isotropic and anisotropic higher order diffraction generation, and image correlation using photorefractive barium titanate Prathan Buranasiri, Partha Banerjee Using barium titanate as the photorefractive material, we demonstrate phase conjugation, beam coupling, higher diffraction order generation. At small incident angles less than 0.015 radian, both codirectional isotropic self-diffraction (CODIS) and contradirectional isotropic self-diffraction (CONDIS) are generated simultaneously. At bigger incident angles approximately more than 0.2094 radian, only codirectional anisotropic-self diffraction (CODAS) are generated. On going imaging correlation is also showing. [Preview Abstract] |
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B.00023: Wavelength tuning by means of a temperature gradient in periodically poled lithium niobate Jason Kramb, Peter Powers Nonlinear frequency conversion in periodically poled lithium niobate (PPLN) is controlled by the periodicity of the poled structure and by the crystal temperature. Crystals with multiple poled regions and crystals with a continuous periodicity change (fan-out design) can achieve rapid tuning. Changing the crystal temperature also results in tuning, however this is relatively slow for large temperature changes. Another approach, which has not yet been demonstrated, is tuning by means of a temperature gradient. This talk will show the results of such a temperature-gradient tuned PPLN device. In particular we will discuss the change in efficiency of the PPLN device and changes in the output beam profile when a temperature gradient is applied to the crystal. [Preview Abstract] |
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B.00024: Single-mode and narrow-linewidth operation of high power broad-area laser diodes using a passively stabilized variable external cavity design Brian Sands, S. Burcin Bayram Many applications in atomic spectroscopy require the use of lasers with a narrow linewidth and high beam quality. External cavities have long been used with low-cost laser diodes to achieve this and to continuously tune the wavelength. Recently, broad-area laser diodes and laser diode arrays have been fabricated to produce many watts of cw output power. These are necessary in applications requiring high powers, such as spin-exchange polarization of $^{129}Xe$, and as affordable alternatives to solid-state lasers in high-resolution spectroscopy. Coupling these lasers to external cavities becomes increasingly difficult, as the beam quality goes down with increasing power. We describe an external cavity based on the Littman-Metcalf design that can be easily aligned in a wide range of cavity lengths to adapt to different types of high power laser diodes and different applications. The cavity utilizes passive stabilization techniques to maintain a stable mode structure over long periods of time. We have narrowed the linewidth of a Coherent 2W single-stripe cw laser diode ($\sim$ 780) from about 550GHz to $<$ 200MHz with a coupling efficiency greater than 60$\%$. We also describe the single mode, continuous tunable range of the cavity and its applications to high-resolution spectroscopy. [Preview Abstract] |
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B.00025: Magnetodynamics of Multi-Scale Magnetic Dots in the Vortex State Dane Owen, Chengtao Yu, Michael Pechan, Jordan Katine, Liesl Folks, Matthew Carey A definite exchange energy is associated with the boundary between domains in ferromagnetic materials. For this reason, submicron dot samples do not energetically favor domain formation. Vortex structures have been predicted and experimentally shown to exist in these small samples. Four permalloy dot arrays (40nm thick circular dots in a square lattice with 100nm/150nm, 200nm/400nm, 500nm/550nm, and 1000nm/1100nm dot diameters/periodicities) were fabricated with e-beam lithography. Magneto-Optical Kerr Effect measurements were used to show when the vortex state was supported in the dots and to determine the anisotropy as a function of the angle between the magnetic field and dot lattice sides. Spin dynamics of the permalloy dots were also measured by ferromagnetic resonance, and additional modes besides the main resonance were shown to exist under certain conditions. [Preview Abstract] |
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B.00026: Stirling Engine for Classroom Demonstration Purposes Andrew Miller, Rex Berney In the study of Thermodynamics, the Carnot cycle is representative of an ideal engine. Such an engine has the maximum efficiency possible for a given temperature difference. The Stirling Cycle engine closely resembles the Carnot cycle in terms of efficiency. In order to demonstrate the Stirling Cycle in a classroom setting, a Stirling engine was built. Robert Stirling first patented the Stirling engine in 1816. The Stirling engine runs on the temperature differential between hot and cold air. As the air is cycled through the engine, the expansion and contraction of the air drives the piston. The work on the piston is transferred into mechanical work via a walking beam. There are no exhaust values that vent gases, because the gases inside the engine never leave. The power for the Stirling engine does not come from explosions like a combustion engine. Rather, the engine is powered by an external heat source. These engines also have practical purposes. They are used in very specialized applications where quiet operation is important. Examples of such uses are in submarines and auxiliary power generators. [Preview Abstract] |
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B.00027: Comparing teacher attitudes and student perceptions of various physics laboratory classes at Ohio State University using a Q-type assessment instrument Gordon Aubrecht, Dedra Demaree, Yuhfen Lin A modified version of the Laboratory Program Variables Inventory (LPVI),[1] a Q-type instrument originally developed to assess chemistry laboratories, has been used at Ohio State University to study the correlation between instructor expectations and student descriptions in out physics by inquiry classes and in the various types of introductory university physics (enginnering physics) classes. Our study of the correlation among different classes shows that Q-type assessment is an effective tool for describing course type. Here we examine correlations between instructor expectations and student perceptions among different sections of the same course, as well as differences in student perceptions among the sections taught by the same instructor. This Q-type assessment tool may be used to diagnose problems in curriculum development and instructor education. [1] M. R. Abraham, ``A descriptive instrument for use in investigating science laboratories,'' Journal of Research in Science Teaching 19, 155-165 (1982). [Preview Abstract] |
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B.00028: Adaptive Materials from Carbon Nanotube - Polyurethane Nanocomposites Daniel Powers, Michael Arlen, Richard Vaia, Max Alexander, Hilmar Koerner Adaptive materials undergo large-scale shape or property change in response to an external stimulus such as stress, temperature, light, or pH. Technological uses range from durable, shape recovery eye-glass frames, to temperature sensitive switches, to the generation of stress to induced mechanical motion. Here in, we demonstrate that the uniform dispersion of 1-5vol{\%} of carbon nanotubes in a thermoplastic elastomer yields nanocomposites that can store and subsequently release, through remote means, up to 50{\%} more recovery stress than the pristine resin. The anisotropic nanotubes increase the rubbery modulus by a factor of 2 to 5 (for 1-5vol{\%}) and improve shape fixity by enhancing strain-induced crystallization. Non-radiative decay of infrared photons absorbed by the nanotubes raises the internal temperature, melting the polymer crystallites (which act as physical cross-links that secure the deformed shape) and remotely triggering the release of the stored strain energy. Comparable effects occur for electrically-induced actuation associated with Joule heating of the matrix when a current is passed through the conductive percolative network of the nanotubes within the resin. [Preview Abstract] |
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B.00029: Sensitive Investigation of Radiation Trapping in an Atomic Vapor using the Hanle Effect John McHugh, Rench David, Burch Peter, Michael McClimans, Ronald Stites, Samir Bali Radiation Trapping refers to the re-absorption of spontaneously emitted photons in an atomic vapor. The decoherence introduced by reabsorbed spontaneous emission significantly affects a vast variety of important experiments that rely on the preparation of coherent atomic media, such as in the field of quantum computing. Recently interest has focused on devising experimental techniques that are capable of detecting extremely small amounts of radiation trapping in atomic samples. Here, we investigate the possibility of sensitively detecting the presence of radiation trapping in an atomic vapor by using the Hanle effect which measures the coherence of atomic energy levels at zero magnetic field. It is expected that the slight decoherence caused by small amounts of radiation trapping should lead to a measurable loss of coherence in the Hanle signal. We report our experimental progress on this problem. [Preview Abstract] |
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B.00030: Temperature Dependent Conductivity of Metallized and NonMetallized Multiwall Carbon Nanotubes and Corresponding Nanocomposites Max Alexander, Hilmar Koerner, Chyi-Shan Wang, Heather Dowty The availability of multi-wall carbon nanotubes (MWCNT) has lead to realization of low cost, highly conductive, bulk nanocomposites. Bulk nanocomposites of MWCNTs and metallized MWCNTs have been produced at loadings ranging from 0.1 to 20 vol {\%} in select thermoplastics. The corresponding DC, room temperature conductivity of these nanocomposites ranged from a few uS/cm to 400S/cm. The DC electrical conductivity of the nanocomposites and of the pure nanotubes were characterized over a broad temperature range (5K to 500K) to elucidate the electron transport properties of these materials. Significant changes in the electrical conductivity were observed and will be reported. The understanding of the temperature dependent behavior of these materials is critical to determining the appropriate use temperatures for end products made from these multi-wall carbon nanotubes. [Preview Abstract] |
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B.00031: Electrical Percolation in Polymer Nanocomposites of Nickel and Iron Nanostrands George Hansen, Matt Pettit, Max Alexander, Brandon Black, Heather Dowty Nickel and Iron nanostrands are elemental nickel nanoparticles on the same length scale of multiwall carbon nanotubes with diameters ranging from 50nm to 500nm typically depending on growth conditions; with an aspect ratio greater than forty. We present data on the fabrication of the nickel and iron nanostrands via thermal decomposition and the corresponding electrical behavior of polymer nanocomposites made from these materials. The concentration of the nanostrands in the polymer was varied as was the method of loading into the polymer to determine the effect on the percolation threshold. The electrical properties of the nanocomposites were characterized by four probe dc conductivity as well as microwave spectroscopy. The Electromagnetic Interference Shielding Effectiveness (EMI SE) is also reported for these materials and can be correlated to the morphology in these systems based on mixing technique. [Preview Abstract] |
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B.00032: CVD Metallized Nanotubes and Crystals Matt Pettit, George Hansen, Max Alexander We examine a new method to produce metallized nanostructures with controlled thickness and crystal morphology. The substrate materials are placed in a flow of metal carbonyl which is photo-thermally reduced. The reduced metal species deposit on the heated nanomaterial substrate (typically multiwall carbon nanotubes or salt crystals) and form a ductile polycrystalline lattice. This process has been shown to dramatically effect the electrical and optical properties of the resulting materials. The materials were characterized by optical spectroscopy, x-ray diffraction, scanning electron microscopy, and energy disperse x-ray spectroscopy to elucidate the interactions of the metal layer with the substrate. Charge transport at the interface between particles has also been examined. When loaded into a nanocomposite there was a significant reduction in the contact resistance from nanoelement to nanoelement compared to the uncoated materials. [Preview Abstract] |
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B.00033: Laser Interaction, Micromachining and Precision Joining of Carbon Nanocomposites Larry Dosser, Ken Hix, Kevin Hartke, Max Alexander, Brandon Black Carbon nanocomposites consist of thermoset and thermoplastic materials filled with carbon nano-particles such as nanofibers, nanotubes, and Bucky Balls. This new and innovative group of materials offers many advantages over standard polymers such as electrical/thermal conductivity and improved structural properties. The presence of carbon nano-particles introduces unique advantages to the laser micromachining and microjoining processes. These advantageous include strong optical absorption at the laser wavelengths of interest and improved thermal stability during the laser processing. As a result, carbon nanocomposites exhibit superior laser processing properties when compared to conventional unfilled thermoset and thermoplastic materials. In the current study, Nd:YAG and Nd:YVO4 solid-state lasers were used to micromachine several carbon nanocomposite, thermoplastic, and thermoset materials. In addition, direct diode and Nd:YAG solid-state lasers were used to transmission weld carbon nanocomposites and carbon black filled polymers. The effects of nano-particle type, nano-particle fill percentage, and polymer type on the laser micromachining and laser welding processes are discussed. [Preview Abstract] |
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