Bulletin of the American Physical Society
2008 Joint Meeting of the APS Ohio-Region Section, the AAPT Southern Ohio Section, and the ACS Dayton-Section
Volume 53, Number 8
Friday–Saturday, October 10–11, 2008; Dayton, Ohio
Session P1: Poster Session (16:30-18:00) |
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Room: Student Union E 156 |
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P1.00001: Design optimization of passive micromixers with fractal surface patterning Petru Fodor, Matthew Itomlenskis, Miron Kaufman Relief patterning of the surface of microchannels has been actively pursued as a method of promoting mixing in systems with a low Reynold's number ($<<$100). For example, structures such as the staggered herring bone (SHB), which consists of periodic groves and ridges distributed along the channel length, improve mixing by inducing counter -- rotating helical flows in pressure driven systems. In this work, we explore computationally using the COMSOL Multiphysics Package and its Chemical Engineering Module, the possibility of enhancing the mixing quality of two fluids within a microchannel by employing a Weierstrass fractal function with different fractal dimensions to produce a non-periodic pattern of groves and ridges on the channel bottom. The designs are optimized with respect to two geometrical parameters: i.e the distances between the ridges and the position range of their tip along the width of the channels. The quality of the mixing between two fluids is analyzed numerically using an entropic measure for the binary fluid system, and is compared with the performance of SHB designs with similar geometrical parameters. The results show that the mixing efficiency associated with Weierstrass function based designs is consistently better than for the SHB counterparts. [Preview Abstract] |
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P1.00002: Terahertz Radar for Remote Measurement of Vital Signs Carla Benton, Erik Bryan, Douglas T. Petkie A radar system operating at 228 GHz was used for measuring the displacement of a subject's chest wall due to respiration and heartbeat. Using various signal processing techniques, the signal was cleaned and the respiration rate and heart rate were extracted from the signal. The radar has been able to produce accurate results at a variety of distances and recent improvements to the system and the signal processing have increased its operating range and accuracy. [Preview Abstract] |
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P1.00003: Stellar Surface Imaging of LO Pegasi Rachel Decker, Conrad Moore, Robert Harmon We present images of dark starspots on the surface of the K8 main-sequence star LO Pegasi. CCD camera images of the star and surrounding field were acquired through B, V, R and I filters at Perkins Observatory in Delaware, OH on clear nights in June and July, 2008. The images were dark-subtracted and flat-fielded and then aperture photometry was performed to yield light curves through each of the four filters. These light curves were then simultaneously inverted via an algorithm devised by one of us (Harmon) so as to yield images of the spots based on the rotational modulation they produced in the light curves. The use of multiple filters significantly improves the latitude resolution of the reconstructions. Comparison of our results with results from 2006 and 2007 shows that the spot structure was more complex in 2008 than in the prior years. [Preview Abstract] |
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P1.00004: Conditional Bell-state discrimination by direct photodetection of emission from a pair of atoms Richard Wagner, James Clemens We report on the performance of a protocol for conditional Bell-state discrimination by means of direct photodetection of the spontaneous emission from a pair of atoms. The performance is characterized by the fidelity of the teleportation of an unknown quantum state from one of the atoms onto the photon number states of a cavity field mode. We find a fidelity approaching unity for atomic separation much less than an emission wavelength with a success probability of 25\%. The fidelity is reduced from the ideal value when imperfect photodetection efficiency is taken into account but still exceeds the value of 2/3 predicted for a classical teleportation protocol. [Preview Abstract] |
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P1.00005: Activation energy of water desorption from guanosine. Megan Smith, Scott Lee The interactions of the nucleic acids with their water of hydration are of fundamental importance and still imperfectly understood. As an initial effort, we have studied a component of RNA: the nucleoside guanosine (rG), composed of the ribose sugar and the guanine base. The interactions of the water of primary hydration with rG have been studied via thermogravimetric measurements and differential thermal analysis. These data yield the activation energy for the desorption of the water of primary hydration from rG. [Preview Abstract] |
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P1.00006: Investigations into the mechanical properties of fibrinogen using molecular simulations Amit Dongol, Ruxandra Dima Fibrinogen, a hexameric molecule, is the main component of a blood clot [1]. The clots are under the action of large mechanical forces during blood flow or at the site of the wound. Hence it is crucial to study the mechanical properties of fibrinogen, which are likely to be responsible for the force response of the clots [2]. To understand the molecular origins of the mechanical properties of fibrinogen, we performed Langevin simulations of a minimalist polymer model of this molecule. Our model [3] enables us to simulate the force-induced unfolding of fibrinogen at experimental loading rates. Our simulations revealed critical unfolding forces in the range of 100 pN in accord with experimental results. By surveying the structures of the various metastable intermediates, we map features of the complex energy landscape of fibrinogen which are at the origin of clot elasticity. \\[0pt] [1] Weisel J, (2008) Science, 320, 456-457 \\[0pt] [2] Brown A, Litvinov R, Discher D, and Weisel J, (2007) Biophysical Journal, 92, L39-L41 \\[0pt] [3] Hyeon C, Dima R. I and Thirumalai D, (2006) Structure, 14, 1633-1645 [Preview Abstract] |
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P1.00007: Substrate protein recognition mechanism of archaeal and eukaryotic chaperonins Pooja Shrestha, George Stan Chaperonins are double ring-shaped biological nanomachines that assist protein folding under non-permissive conditions. Spectacular conformational changes take place within each chaperonin ring using energy derived from ATP hydrolysis. These changes result in transitions from opened to closed chaperonin ring via partially closed state. Substrate proteins bind to the open chaperonin ring and are encapsulated within the closed cavity. We focus on the substrate protein recognition mechanism of group II chaperonins. We predict substrate protein binding sites using structural and bioinformatic analyses of functional states. Based on large changes in solvent accessible surface area and contact maps we glean the functional role of chaperonin amino acids. During the transition between open to closed chaperonin ring, the largest change in accessible surface area is found in two helices located at the cavity opening. Based on these calculations and the bioinformatic prediction of protein interaction regions we suggest that these two helices constitute the substrate protein binding site. [Preview Abstract] |
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P1.00008: Intermolecular interactions of reduced nicotinamide adenine dinucleotide (NADH) in solution Joshua Jasensky, M. Junaid Farooqi, Paul Urayama Nicotinamide adenine dinucleotide (NAD$^{+}$/NADH) is a coenzyme involved in cellular respiration as an electron transporter. In aqueous solution, the molecule exhibits a folding transition characterized by the stacking of its aromatic moieties. A transition to an unfolded conformation is possible using chemical denaturants like methanol. Because the reduced NADH form is fluorescent, the folding transition can be monitored using fluorescence spectroscopy, e.g., via a blue-shift in the UV-excited emission peak upon methanol unfolding. Here we present evidence of interactions between NADH molecules in solution. We measure the excited-state emission from NADH at various concentrations (1-100 $\mu $M in MOPS buffer, pH 7.5; 337-nm wavelength excitation). Unlike for the folded form, the emission peak wavelength of the unfolded form is concentration dependent, exhibiting a red-shift with higher NADH concentration, suggesting the presence of intermolecular interactions. An understanding of NADH spectra in solution would assist in interpreting intercellular NADH measurements used for the \textit{in vivo} monitoring cellular energy metabolism. [Preview Abstract] |
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P1.00009: Long-time Behavior of Surface Electromyography Time Series Brian Vyhnalek, Ulrich Zurcher, Miron Kaufman, Paul Sung We have previously reported that the mean-square displacement from the sEMG time series $x_{i}$ with $i=1,2,..., 2^{16}$ exhibits diffusive behavior for short times, $t \stackrel{<}{\sim} 50 \, \mbox{ms}$, which is followed by a plateau-like behavior for intermediate times, $50 \, \mbox{ms} \stackrel{<}{\sim} t \stackrel{<}{\sim} 500 \, \mbox{ms}$. For long times, $t \stackrel{>}{\sim} 500 \, \mbox{ms}$, the msd increases as time $t$ increases. We show that the long-time behavior reflects non-stationarity of the signal; we find that for a fixed time interval $t=\mbox{const}$, the displacement $X_{s,t} = \sum_{i=0}^{t-1} x_{s+i} \simeq \mu_{1} $ for $s \in [s_{0}, s_{1}]$ and $X_{s,t} = - \mu_{2}$ for $s \notin [s_{0}, s_{1}]$. This property explains the fit of the probability distribution $p_{t} ( X) = \left< \delta ( X - X_{s,t} )\right>_{s}$ as a superposition of two Gaussians that we reported in Physica A {\bf 386}, 698-709 (2007). Supported by a grant from the Research Corporation [UZ]. [Preview Abstract] |
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P1.00010: Effect of Polymer Concentration and Cross-linking Density on Microgel Size and Shrinking Capacity Kiril Streletzky, Imaan Benmerzouga, John McKenna Hydroxypropylcellulose (HPC) is a polysaccharide with temperature dependent water solubility. HPC chains can be chemically cross linked into stable nanoparticles called microgels. The structure and dynamics of microgels depend on polymer and salt concentration, crosslinking density, and solution temperature. HPC has easily accessible lower critical solution temperature. At T$_{c}$=41$^{\circ}$C, HPC in solution undergoes a reversible transition at which chains form metastable clusters that fall apart when temperature is lowered below T$_{c}$. HPC microgels undergo a similar transition in which, however, microgel clusters stay intact below and above T$_{c}$. In this transition microgels shrink/swell on average by a factor of eight, a property with a potential for application in targeted drug delivery. Dynamic Light Scattering was used to study microgels in thermal equilibrium. Due to a complexity of microgel spectra the line shape analysis algorithm was employed. Comparison of differently synthesized HPC microgels revealed that higher polymer concentration results in smaller microgels with lower shrinking capacity. The effective cross-linking density that yields relatively monodisperse microgels was determined. The angular dependence of scattering demonstrated that microgels are largely spherical particles. Finally, studying microgels at different temperatures allowed to monitor the shrinking/swelling behavior. [Preview Abstract] |
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P1.00011: The Law of Hyperboles for Chemical Compounds Albert Khazan The essence of the law of the hyperboles is that the contents of substance of a specific chemical element should take the quantity of one gram-atom. Earlier, there in the equation Y=K/X any element of the Periodic Table was considered at the numerator. Now we expand the law: we enter the groups OH, CO3, SO4 and the others into the numerator. In this case the direct and adjacent hyperboles exchange their places, but their shape remains unchanged. Besides, the position of one gram-mole with the number of the group cannot be more than the unit should be carried out. Then the hyperboles have smooth shape without breaks. It confirms that fact, that the hyperboles with various values K are similar against each other, but they are not congruent. At the same time through a point with the coordinates X, Y it is possible to describe only one hyperbole, for which K=XY [for adjacent K=X (1-y)]. The opportunity of application of groups of elements testifies the universality of the law of the hyperboles, and it expands the mathematical base of chemical research (Progr. Physics, 2007, v.1, 38; v.2, 83; v.2, 104; 2008, v.3, 56). [Preview Abstract] |
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P1.00012: The rotational spectrum of deuterated nitric acid April Heddings, Douglas T. Petkie The terahertz rotational spectrum of many small fundamental gas-phase molecules provides an absolutely specific spectral fingerprint and insight into the intramolecular forces through the fitted rotational and vibrational constants. We are currently assigning and fitting the measured rotational transitions in several of the lowest lying, thermally populated, vibrational states of deuterated nitric acid. We will describe the general characteristics of the spectrum and compare the rotational and centrifugal distortion constants of each state to those of the normal species. [Preview Abstract] |
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P1.00013: The Fractional-Linear Function in the Hyperbolic Law Albert Khazan The maintenance of any element in a chemical compound decreases with increase of the molecular weight under the equipotential hyperbolic law Y=K/X (1). However the size (1-Y) increases according to the equation 1-Y=K/X or Y = (X-K)/X (2). This function refers to as fractional-linear one, and after transformations turns to the equation of an equipotential hyperbola whose center is displaced from the beginning of the coordinates about (0; 0) in a point with (0; 1). Hence, the valid axis on which there tops of new hyperboles are, pass perpendicularly to the axes of the equation (1). We shall enter names for hyperboles: (1) - ``straight one,'' (2) - ``adjacent one.'' Their directions are mutually opposite in the point Y=0.5 of crossing of each pair; this line is an axis of symmetry for all the hyperboles; the abscissa is equal to the double nuclear weight of any element (2K). Coordinates of other crossing points of the hyperboles have following parameters: X~=~(K1+K2), Y1 = [K1/(K1+K2)], Y2 = [K2/(K1+K2)]. At the last element the curves designate the borders of the existence of possible chemical compounds (Progr. Phys., 2007, 1, 38; 2, 83; 2, 104; 2008, 3, 56). [Preview Abstract] |
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P1.00014: Field deployable microcantilever based chemical sensing: discrimination between H$_{2}$O, DMMP and Toluene E.J. Thoreson, T.H. Stievater, W.S. Rabinovich, M.S. Ferraro, N.A. Papanicolaou, R. Bass, J.B. Boos, J.L. Stepnowski, R.A. McGill Low cost passive detection of Chemical Warfare Agents (CWA) and being able to distinguish them from interferents is of great interest in the protection of human capital. If CWA sensors could be made cheaply enough, they could be deployed profusely throughout the environment intended for protection. NRL (Naval Research Labs) has demonstrated a small sensor with potentially very low unit cost and compatible with high volume production which has the ability to distinguish between H$_{2}$O, DMMP, and Toluene. Additionally, they have measured concentrations as low as 17 ppb passively in a package the size of a quarter. Using the latest MEMS technology coupled with advanced chemical identification algorithms we propose a development path for a low cost, highly integrated chemical sensor capable of detecting CWA's, Explosives, VOC's (Volatile Organic Chemicals), and TIC's (Toxic Industrial Chemicals). ITT AES (Advanced Engineering {\&} Sciences) has partnered with NRL (Naval Research Labs) to develop this ``microharp'' technology into a field deployable sensor that will be capable of remote communication with a central server. [Preview Abstract] |
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P1.00015: Introducing Quantum Mechanics into General Chemistry Iwona Popkowski, Hafed Bascal Periodicity has long been recognized as the tool that chemists can use to bring some order to investigating the chemistry of more than one hundred elements. Such studies provide useful tools for understanding a wide array of chemical principles. The advances in computational chemistry make it possible to study and teach such trends with hands on approach. In this study we utilize recently acquired software Spartan Pro to illustrate theoretical measurements of bond length, bond angle and dipole as compared to experimental data. We constructed a matrix of values obtained from the theoretical calculations and obtained trends in bond length, bond angle and dipoles for the several periodic groups. [Preview Abstract] |
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P1.00016: Measuring dn/dc of HPC polymer and microgel solutions Krista Freeman, Kiril Streletzky The refraction process is the basis of light scattering experiments on transparent solutions where light refraction depends on spontaneous concentration fluctuations in solution caused by molecular Brownian motion. The specific refractive index increment (dn/dc), the change in index of refraction with concentration, is essential for static light scattering (SLS) experiments on polymer solutions. With a reliable value for dn/dc, SLS yields radius of gyration and molecular weight of the polymer, and second virial coefficient. This study focuses on determining dn/dc values of hydroxypropylcellulose (HPC) polymer and microgel solutions. Precise calibration of the Brice-Phoenix differential refractometer (BP) was necessary to attain accurate values for dn/dc. Using the BP, HPC solutions were analyzed at a range of concentrations, molecular weights, wavelengths, temperatures, and filtration protocols. Through the course of the study it was determined that dn/dc of HPC polymer is independent of temperature in good solvents, slightly dependent on molecular weight, inversely proportional to wavelength squared, and sensitive to polymer solution's filtration protocol. HPC microgel testing produced dn/dc values one order of magnitude larger than the dn/dc of HPC polymer solutions and did not support the expected wavelength dependence. [Preview Abstract] |
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P1.00017: Monte Carlo Simulation Study of Lattice Gas Diffusion in a Box Fractal Daniel P. Knowlton, James L. Johnson, Christopher D. Wentworth In this investigation we study a simple model of diffusion of a concentrated lattice gas in a box fractal structure. The model involves a fixed concentration of particles that undergo random hopping to nearest-neighbor sites with equal probability. The particles do not interact except that double-occupancy of a lattice site is not allowed. The particles move in a lattice of box fractal structure, which has a fractal dimension of 1.465. The mean-square displacement of a tracer particle as a function of time is calculated from the simulation. The simulation suggests anomalous diffusion occurs in this lattice structure. [Preview Abstract] |
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P1.00018: Diffusion of a Concentrated Lattice Gas in a Regular Comb Structure Paul Garcia, Christopher Wentworth Understanding diffusion in constrained geometries is of interest in a variety of contexts as varied as mass transport in disordered solids, such as a percolation cluster, or intercellular transport of water molecules in biological tissue. In this investigation we explore diffusion in a very simple constrained geometry: a comb-like structure involving a one-dimensional backbone of lattice sites with regularly spaced teeth of fixed length. The model considered assumes a fixed concentration of diffusing particles can hop to nearest-neighbor sites only, and they do not interact with each other except that double occupancy is not allowed. The system is simulated using a Monte Carlo simulation procedure. The mean-square displacement of a tagged particle is calculated from the simulation as a function of time. The simulation shows normal diffusive behavior after a period of anomalous diffusion that increases as the tooth size increases. [Preview Abstract] |
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P1.00019: Transport Properties of Nanostructures Amir Maharjan, H.E. Jackson, L.M. Smith, A. Kogan, J.Y. Rice, C. Jagadish The current-voltage (I-V) properties of an InP nanowire and a CdS nanosheet are studied. Back to back metal semiconductor metal contacts are modeled based on thermionic emission theory and field emission theory. These are used to explain the I-V characteristics of these nanostructures which enables measurement of the important intrinsic properties including donor density and electrical conductivity of nanostructures. Photolithography followed by lift-off is used to fabricate the Al/Ti contact pads across these nanostructures for transport measurements. Scanning photocurrent microscopy (SPCM) is used to see the variation of photocurrent along the nanostructure. The SPCM image shows that the peak photocurrent always appears at the reverse biased metal-semiconductor contact edge indicating strong localization of electric field which is also confirmed by numerical simulation. [Preview Abstract] |
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P1.00020: Chemical C-V Measurements on ZnO Sarah Jane Gabig, Gary Farlow When metal/semiconductor schotky barriers are not practical, an electrolyte/semiconductor interface can be used to make capacitance-voltage (C-V) measurements. The physics of such electrochemical C-V measurements will be described. Electrical properties of ZnO were measured by electrochemical C-V techniques and photovoltage spectroscopy using an Accent 4400 Electrochemical CV system. Specifically, the electrical behavior of a 0.1 M ZnCl$_{2}$ electrolyte-ZnO interface has been investigated with attention to the electrolyte-ZnO interface's C-V dependence on carrier frequency. [Preview Abstract] |
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P1.00021: The Heat Bath Monte Carlo Algorithm for the Ising Model of Ferromagnetism Christopher Lemon, Ronald Johns The mathematical theory of Markov chains is placed in the context of the Ising model of ferromagnetism, an important problem in statistical physics. Although not a Markov chain itself, the two-dimensional Ising model can be simulated with the heat bath algorithm, which treats the Ising model as a Markov Chain. A Matlab program and variations were written that use Monte Carlo simulation and the heat bath algorithm to compute quantities arising in the Ising model. Results from this method were then compared to those derived from the mathematical definition of the Ising Model. Based on the agreement of results, it can be concluded that the heat bath Markov Chain method is a convenient and valid method to simulate the two-dimensional Ising model. [Preview Abstract] |
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P1.00022: Preparation and Characterization of Electrospun Alumina Nanofibers Marie J. Pinti, Stephen N. Tacastacas, Nenad Stojilovic, John P. O'Brien, Anna Pischera, Matthew P. Espe Alumina nanofibers are promising materials for use in high- temperature applications since they are chemically inert up to very high temperatures. Applications include use as catalyst support in high-temperature chemical reactions, fire protection materials, and as a high-temperature insulator. Electrospinning is a relatively simple and inexpensive method for obtaining nanometer-size fibers and has become a popular technique for producing metal-oxide nanofibers in recent years. The electrospinning mixture for the production of alumina nanofibers typically contains aluminum acetate stabilized with boric acid as the alumina precursor; but the observed presence of boron and sodium on the surface of these nanofibers may affect their use as catalytic supports. We have produced alumina nanofibers from an aluminum reagent devoid of the boric acid stabilizer and calcined the fibers at different temperatures to produce nanofibers with different phases of alumina. Characterization of the fibers by TGA, FE-SEM equipped with the XEDS, powder XRD, DRIFTS, and SSNMR methods to determine the fate of the precursors, fiber morphology and the composition and structure of the calcined alumina nanofibers. [Preview Abstract] |
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P1.00023: XRD and DRIFTS study of Titania/Zinc Oxide Nanofibers Stephen N. Tacastacas, Marie J. Pinti, Nenad Stojilovic, Adria F. Lotus, George G. Chase Titania nanofibers are very promising materials for high- temperature applications, and in recent years, electrospinning has been typically used for their production. With the objective of controlling the properties of the formed nanofibers, titania nanofibers doped with zinc oxide were annealed at different temperatures. Characterization of these fibers involved the use of TGA, powder XRD, SEM and DRIFTS methods; allowing a better understand of formation of these materials, and determination of their structure and composition. [Preview Abstract] |
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P1.00024: Evidence for Multiple Negative-Parity Band Structure in $^{71}$Se N.R. Baker, R.A. Kaye, S.R. Arora, J. Bruckman, S.L. Tabor, T.A. Hinners, C.R. Hoffman, S. Lee, J. Doring The negative-parity bands of $^{69}$Se and $^{73}$Se indicate a stark contrast between strong single-particle ($^{69}$Se) and collective ($^{73}$Se) behavior over a wide range of spins. However, only one negative-parity band has been observed so far in $^{71}$Se, making it difficult to see where it lies between these two very different cases. Thus, the goal of the present work was to extend the level scheme of $^{71}$Se as much as possible, with an emphasis on finding new negative-parity states. $^{71}$Se nuclei were produced at high spin following the 80-MeV $^{54}$Fe ($^{23}$Na, $\alpha pn$) reaction at Florida State University. $\gamma-\gamma$ coincidences were measured using an array of 10 Compton-suppressed Ge detectors which included three Clover detectors. From the coincidence relationships, new states were found that formed candidates for perhaps two new negative-parity bands. Cranked-shell model calculations indicate that one new band is associated with rigid-body rotation at high spin. [Preview Abstract] |
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P1.00025: Power-scalable, polarization-stable, dual-colour DFB fibre laser system for CW terahertz imaging Finn Eichhorn, Jens Engholm Pedersen, Peter Uhd Jepsen Imaging with electromagnetic radiation in the terahertz (THz) range has received a large amount of attention during recent years. THz imaging systems have diverse potential application areas such as security screening, medical diagnostics and non-destructive testing. We will discuss a power-scalable, dual-colour, polarization-maintaining distributed feedback (DFB) fibre laser system with an inherent narrow linewidth from the DFB fibre laser oscillators. The laser system can be used as source in CW THz systems employing photomixing (optical heterodyning) for generation and detection and is an alternative to pulsed THz systems using femtosecond lasers. The laser system generates output powers up to several hundred mW, has a 25 kHz linewidth and a polarization extinction ratio of better than 20 dB. Since the output power reaches the Watt-level, the laser system is a suitable candidate for future multi-channel THz imaging systems. [Preview Abstract] |
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P1.00026: Improving Corrosion Diagnostics with Terahertz Sensors. Stanley Smith, Lindsay Owens, Douglas Petkie, Jason Deibel The objective of this project is to characterize metal samples using terahertz imaging to determine whether terahertz frequency radiation can detect the difference between corroded and clean metal including samples obscured with coatings of paint. A terahertz imaging system was used at incident angles of 45 and 90 degree to characterize the metal samples. Multiple imaging techniques were utilized such as time-domain amplitude imaging, single frequency amplitude imaging, and time-domain reflectometry. The images indicate that terahertz imaging does detect a noticeable difference between corroded and clean metal including measurements performed on painted samples. [Preview Abstract] |
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P1.00027: Spicing up Science: Mini Undergraduate Research Projects in Physics and Chemistry George Devendorf Individual student research projects are often small pieces of a larger research program and may or may not provide an interesting and satisfying research experience for a student researcher who only is engaged in the project for a limited time. This researcher describes a variety of research activities conducted with advanced high school students in a high school setting. These research projects are limited by the academic experience of the student, facilities and resources and available time. Such limitations however, have shaped some of the research projects into ``mini-projects'' that form interesting scientific questions which can be addressed within a semester or yearlong project. Several of these research ideas have been inspired from teaching introductory courses and though they may not further a continuing research program or spawn significant publications, they do provide an avenue for teaching and inspiring scientific inquiry in the minds of young potential scientists. [Preview Abstract] |
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P1.00028: Kinematics from footprints: Analysis of a possible dinosaur predation event in the Cretaceous Era Scott Lee Motivation is enhanced by challenging students with interesting and open-ended questions. In this talk, a methodology for studying the locomotion of extinct animals based on their footprint trackways is developed and applied to a possible predation event recorded in a Cretaceous Era deposit.\footnote{J.O. Farlow, ``Lower Cretaceous Dinosaur Tracks, Paluxy River Valley, Texas,'' South Central Geological Society of America, Baylor University, 1987.} Students usually love learning about dinosaurs, an unexpected treat in a physics class. This example can be used in the classroom to help build critical thinking skills as the students decide whether the evidence supports a predation scenario or not. [Preview Abstract] |
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P1.00029: Discovering and Understanding Misconceptions in Fifth grade Academic Content Standards Adam Hicks, Jennifer Blue Misconceptions are known to be prevalent among students, especially younger students. However, misconceptions can become engrained in the scientific thought process and linger throughout a person's life. This study examines the results on test questions regarding the physical and space science from the fifth grade Ohio Academic Content Standards (Ohio Department of Education, 2003). Tests have been developed to evaluate the Southwest Ohio Science Institutes (http://www.units.muohio.edu/sosi), which teach content knowledge to teachers. These tests have been given to fifth grade teachers who participated in the institutes and to their students. The same questions were also given to university students. Eventually, the results from all three groups will be compared to find the persistence of misconceptions. This presentation will focus on the results from the university students. [Preview Abstract] |
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P1.00030: Observation of quasi-periodic route to chaos in driven dusty plasma W.L. Theisen, T.E. Sheridan Chaotic dynamics have previously been observed in a driven dusty plasma with three particles [T. E. Sheridan, Phys. Plasma {\bf 12}, 080701 (2005)] due to a resonance overlap between the center-of-mass and breathing modes. In the present work, the transition to chaos in this system is characterized as a function of driving amplitude for two different driving frequencies. In the first case, the driving frequency is matched to the frequency minimum of the Arnold tongue, while in the second case, the driving frequency is slightly above this value. Dynamics are characterized by the power spectrum, Lyapunov exponent, and correlation dimension, as a function of driving amplitude. For the higher driving frequency we observe asymmetric spectral sidebands at intermediate driving amplitudes, a clear indication of quasi-periodic dynamics. For large driving amplitudes the dynamics become chaotic. [Preview Abstract] |
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P1.00031: Sheath area for large planar Langmuir probes T.E. Sheridan Electrostatic (i.e., Langmuir) probes made of thin, circular disks are often used to determine plasma parameters (e.g., electron temperature and density) by analyzing the probe's current-voltage characteristic. A probe biased below the plasma potential (i.e., the ion saturation regime) attracts positive ions and repels electrons, leading to the formation of a cathodic sheath around the probe. The probe's effective collecting area is determined by the sheath area, which, for a given probe radius, depends on the probe's bias. The structure of this sheath is calculated using a particle-in-cell (PIC) code with kinetic ions and Boltzmann electrons by allowing a pulsed sheath to relax to a steady-state configuration. The Bohm criterion is used to define the sheath edge, which is taken to be the surface on which the average ion velocity equals the ion acoustic speed. The sheath area is calculated for probe radii from 50 to 200 times the electron Debye length biased from -5 to -50 times the electron temperature. The sheath area is found to have a power law dependence on both probe bias and probe radius. [Preview Abstract] |
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P1.00032: Laue X-Ray spectrograph for the 200-TW Trident Laser Nalin Vutisalchavakul, James Cobble, Jonathan Workman, Kirk Flippo, David Montgomery, Sandrine Gaillard With the 200-TW laser at the Trident Laser Facility, experiments on x-ray backlighting were performed. The sub-ps short pulse laser with energy up to 100 J can be shot on targets with different atomic number. The focused laser beam has intensities up to 10$^{21}$ W/cm$^{2}$. The high energy laser interacted with the targets, producing X rays due to K-shell emission. Among other diagnostic devices, a Laue X-ray spectrograph was used to record the x-ray spectrum, which showed emission lines and bremsstrahlung radiation. The Laue spectrograph uses a LiF(200) crystal to disperse the x-ray spectra with a bandpass of 17-70 keV. The spectra were recorded using Fuji image plates. The Laue instrument was designed to include a tungsten shield in the front, a magnetic trap, and a light trap to reduce background noise. K$\alpha$ lines of Mo, Ag, and Sn were observed. [Preview Abstract] |
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P1.00033: Measurements of the Non-Linear Coupling of Plasma Waves E.K. Snipes, J. McClenaghan, A.J. Noble, A.A. Kabantsev, C.F. Driscoll A separatrix is created in a pure electron plasma column by applying a $\theta$-symmetric wall voltage. This ``squeeze'' voltage traps less energetic electrons in either end and allows more energetic electrons to pass through. These trapped particles enable the novel Trapped Particle Diocotron Mode (TPDM). We excite an ordinary $m=2$ diocotron mode at frequency $f_2$ to amplitude $A_2$ and observe the decay into the $m=1$ TPDM at $f_1 \approx f_2 / 2$. The exponential growth rate, $\Gamma$, of the TPDM is obtained as a function of the amplitude $A_2$ as well as a function of the ``squeeze'' voltage which determines the frequency mismatch $\delta f = f_2 / 2 - f_1$. We calibrate the amplitudes of the modes in terms of the received wall voltages, and obtain a quantitative value of the non-linear coupling coefficient, $V$. These results at $B = 280$~G will be compared to recent results\footnote{A.A. Kabantsev, T.M. O'Neil, Yu.A. Tsidulko, and C.F. Driscoll, Phys.~Rev.~Lett. {\bf 101}, 065002 (2008).} from a separate apparatus at $B > 2000$~G. [Preview Abstract] |
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P1.00034: Modeling Rotation of H in Cu-H Defect Complex in ZnO Andrew Magyar The rotational motion of the bond-centered H or D atom in an isolated Cu-H defect complex in the ZnO crystal lattice is modeled under uniaxial stress. The uniaxial stress is applied along the c-axis of the crystal and causes an absorption line at 3229 cm$^{-1}$ to appear and then increase in intensity under increased stress. The behavior of this line, and the characteristic line of the defect at 3192 cm$^{-1}$, are studied. Our model assumes that stressing the crystal breaks the rotational symmetry of the H atom, causing the rotational states to mix together. Under these assumptions, the model is able to match experimental data collected by Lavrov and Weber. Methods for selecting parameters of the model are discussed, along with the behavior of the probability function of the H or D atom. [Preview Abstract] |
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P1.00035: Capacitance-Voltage Properties of AlGaN Schottky Devices A. Di Mascio, M. Ahoujja, S. Elhamri, R. Berney Electrical properties of Si doped AlGaN films, grown by radio-frequency plasma assisted molecular beam epitaxy, are investigated using variable frequency capacitance-voltage as a function of temperature. In particular, a comprehensive investigation of the properties of Ni/Au Schottky contacts as a function of temperature and frequency will be reported. [Preview Abstract] |
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P1.00036: On the Doppler Deviation between the Temperatures of the Microwave Background Obtained by COBE. Dmitri Rabounski The COBE satellite, located in a 900 km orbit, gives two temperatures of the Penzias-Wilson microwave background: 2.730$\pm $0.001 K measured by the absolute spectrophotometer and 2.717$\pm $0.003 K calculated from the temperature of the dipole component (the 1st derivative of the monopole) measured by the differential radiometer. This deviation, 0.013 K, is 10 times exceeding the measurement precision. If, according to the experimental analysis by Robitaille (Prog. Phys., 2007, v.1, 3, 19), the microwave background is generated by the oceans of the Earth, this deviation meets a clear theoretical explanation by Rabounski (Prog. Phys., 2007, v.1, 24) as the Doppler effect of the dipole anisotropy due to the motion of the monopole in common with the source, the Earth, relative to the intergalactic foreground at 365 km/sec. According to this theory, there is no the monopole component at the L2 point (1.5 mln km from the Earth, the position of the WMAP and PLANCK satellites) due to its decrease with altitude. In contrast to WMAP, whose differential instruments target the dipole anisotropy, PLANCK will have on board absolute instruments and be able to give a proof to this theory. [Preview Abstract] |
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P1.00037: Building New Dynamic Light Scattering Spectroscopy System Maxwell Orseno, Kiril Streletzky Our goal is to construct a high resolution, versatile Light Scattering Spectroscopy Setup. When complete, this system will allow measurements with Dynamic Light Scattering and Static Light Scattering techniques, with polarized and depolarized light, several different laser wavelengths, and a wide range of scattering angles and temperatures. The first task was to get the Ar+ laser operational. A water cooling system for the laser was developed and installed. Laser bases for the Ar+ laser as well as a He-Ne laser were designed and machined. A system of mirrors that allows for a quick change from one laser to the other was added. The Ar+ laser itself was tuned for optimal output. The light scattering spectroscopy system was aligned and test experiments were run on it. The data, after collected and analyzed, was compared with the data on existing Dynamic Light Scattering setup. The new results demonstrate that both polarized and depolarized Dynamic Light Scattering experiments of high accuracy can be successfully performed at several different laser wavelengths and a range of scattering angles using the new Light Scattering Setup. Careful tests of Static Light Scattering on the new system are still needed to be performed. [Preview Abstract] |
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P1.00038: Experimental progress toward creating optical crystals of ultracold atoms Nathan Souther, Richard Wagner, Matthew Briel, Samir Bali We propose an experiment to form an optical crystal using atoms that have been laser-cooled to temperatures of a few microKelvin. First we create an optical lattice -- an array of periodic potential wells, half an optical wavelength apart, formed by intersecting laser beams, with about one well out of hundred occupied by an atom. Next, we use another beam to superpose a long-range periodicity on the lattice -- causing wells located every few wavelengths apart to be deepest. This creates what is called a superlattice, where the atoms eventually collect in the lowest wells thus creating a long-range ``crystal.'' This is called a crystal, not a lattice, because the probability of an atom occupying the periodic array of deepest wells is unity. Such optical crystals may have far-reaching implications for nanolithography and quantum computing. [Preview Abstract] |
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P1.00039: Detection and Characterization of a Laser Induced Plasma Michael Dexter, Matthew Bohn A plasma is generated and detected in ambient air using a 50 femtosecond, amplified Ti:sapphire laser at 800 nm and its second-harmonic at 400 nm. The plasma is monitored as a function of laser polarization and amplitude using an ultrasound detector. The second harmonic is generated in a BBO crystal located in a 1:1 telescope. The group delay of the second harmonic through the collimating lens of the telescope will be calculated and the resulting experimental complication requiring the separation of the fundamental and second-harmonic will be discussed. The goal of the experiment is to generate terahertz via the mixing of the second-harmonic and the fundamental in the plasma. The mechanism for terahertz generation in a plasma will be introduced as resulting from either a transient current or via four-wave mixing. The terahertz radiation can be detected using either the electro-optic method or a liquid He cooled silicon bolometer. The prospects of using this terahertz generation method in a two color femtosecond enhancement cavity will be discussed. [Preview Abstract] |
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P1.00040: Solvent Effect on Linear Photophysical Properties of a Two Photon Absorbing Dye Jennifer Monahan, Joy Rogers-Haley, Jonathan Slagle, Ramamurthi Kannan, Loon-Seng Tan, Augustine Urbas The nonlinear photophysical properties of two-photon absorbing materials have been of great interest but have not been well understood. The Air Force Research Laboratory has developed a two-photon absorbing dye termed AF240 which consists of an electron donating group linked to a $\pi $-conjugated center then to an electron withdrawing group. A solvent study was undertaken in which AF240 was investigated in order to determine the effect of solvent on the linear photophysical properties. These properties include the ground state molar absorption coefficient, steady-state emission, time resolved emission utilizing time correlated single photon counting, and triplet absorbance spectra. The ground state and triplet absorbance spectra indicate a slight red shift due to an increase of polarity of the solvent. Dramatic red shifts in the steady state emission also have been observed which result from an increase in the polarity of the solvent. The formation of an intramolecular charge transfer (ICT) state has been observed and determined to be the origin of these changes with solvent. [Preview Abstract] |
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P1.00041: Laser-Excited Fluorescence Spectroscopy of Br$_{2}$: NIR Transitions to High Vibrational Levels in the $X(^{1}$\textit{$\Sigma $}$_{g}^{+})$ State David Dolson, David Postell, Glen Perram The B($^{3}\Pi _{0u}^{+})$ -- X($^{1}\Sigma _{g}^{+})$ laser-excited fluorescence spectrum of Br$_{2}$ was recorded with rotational resolution in the visible and near infrared (NIR) spectral regions to 1400 nm. The line-narrowed (0.2 cm$^{-1})$ output of a 532nm pulsed Nd:YAG laser was used to excite eight fluorescence progressions in a natural abundance sample. Six of the excitation transitions occur in the $^{79,81}$Br$_{2}$ isotopomer and one each in the $^{79}$Br$_{2}$ and $^{81}$Br$_{2}$ isotopomers. NIR fluorescence transitions from the 25 $\le $ v$^{\prime}$ $\le$ 33 laser-excited levels to the 28 $\le $ v$^{\prime \prime} \le$ 44 vibrational levels in the ground state were observed between 950 nm and 1400 nm. The 97 lines from this NIR data set were combined with 6300 lines calculated with the data of Focsa et al [\textit{J. Mol. Spectrosc.} \textbf{200}, 104-119 (2000)] to derive a set of Dunham coefficients for the ground state. An X($^{1}\Sigma _{g}^{+})$ state RKR potential curve also was constructed for vibrational levels, v$^{\prime \prime }$ = 0 -- 44, which extends three quarters of the way to the dissociation limit. [Preview Abstract] |
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