Bulletin of the American Physical Society
2005 Ohio Sections of the APS and AAPT Joint Fall Meeting
Friday–Saturday, October 14–15, 2005; Cleveland, OH
Session P: Poster Session |
Hide Abstracts |
Room: Cleveland State University Cole Center Auditorium 4:00-5:30pm |
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P.00001: Teaching Chaos, Monte Carlo and Magnetism to Undergraduates Gaston Barberis The generation of pseudo-random numbers is one of the interesting problems in Monte Carlo simulations, mostly because the common computer generators produce periodic numbers. The use of simple chaotic systems, as the well known logistic map to generate the pseudo-random numbers, applying the results to the simple 2-D or 3-D Ising models, give the opportunity to teach undergraduates two of the modern and interesting topics in our age. I present the technics to calculate, analyze and obtain the pseudo-random numbers, to show in a desk computer the lack of periodicity up to 10$^{11}$ numbers, and the application to simple physical calculations. [Preview Abstract] |
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P.00002: Perfecting E=mc$^{2}$ and Debunking Quantum Weirdness N. Glenn Gratke By perfecting E=mc$^{2}$ and E=hf, we can unify relativity and quantum mechanics. By exposing the error of Bell's inequality and the misinterpretation of EPR experiments, we can debunk quantum weirdness. Non-Euclidean Gravitational Spacetime and Quantum Waves dwell within our single universe of just three spacial dimensions. [Preview Abstract] |
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P.00003: Theory of Superstrings and Escher's Graphics Ivona Maric, Alla Zilichikhis Sometimes art and literature are more wise and ahead in the exploration of the Universe than science is. One reason we think this is that emotions are obviously much more involved in art and literature than in science. Because of this, we are capable of and should show in teaching relationships between art, literature and science. By the proposed way of teaching we can even present very advanced topics to our students on all levels. Long (more than 40 years) and successful teaching in physics experience of one of us at many different schools and countries, supports ideas of activating and mobilizing intellectual abilities in students. In this article we present a lecture called ``Theory of Superstrings and Escher's Graphics'' that is an example of such ideas in teaching. This lecture is delivered by us to students from middle school up to university level [1,2].\newline \newline [1] ``A Century of Physics'' American Physical Society 11 posters. Credits are also listed on the web at \textbf{www.aps.org/credits/} \newline [2] Alla L. Zilichikhis, ``My Key to Success in Teaching'' in Proceedings of AAPT Meetings Ohio Section, October 1998, V. 16, N.1 [Preview Abstract] |
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P.00004: Using the Open Source Physics library to teach about computer simulations in physics Jan Tobochnik, Harvey Gould, Wolfgang Christian The Open Source Physics (OSP) library provides a flexible and powerful set of Java classes and interfaces for writing computer programs in the context of physics. The third edition of our computer simulation textbook (by H. Gould, J. Tobochnik, and W. Christian) uses the OSP library. I will demonstrate some of the capabilities of the OSP library and how our text can be used to teach students how to learn physics using computer simulations. Partial funding for this work was obtained through NSF grant DUE-0126439. [Preview Abstract] |
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P.00005: Kinematics and black hole mass for the narrow-angle tailed radio galaxy NGC 4061 Jason Pinkney In the quest to pin down the high-mass end of the M$_{BH}$-$\sigma$ correlation for galaxies, NGC 4061 may attract attention. It has the largest velocity dispersion, 459 km s$^{-1}$, in the Hypercat catalogue and, according to M$_{BH}$-$\sigma$, the most massive supermassive blackhole in the nearby universe. Here we present analysis of new spectroscopy and imaging from HST and the ground for NGC 4061. HST imaging reveals an organized dust disk with a radius of 2.5 arcseconds. Our ground-based spectroscopy reveal central H$\alpha$ emission from gas in rapid rotation; the velocity change is 270 km s$^{-1}$ in 0.55 $''$ (250 pc). This suggests a BH mass of about $\sf 2\times 10^9 M_{\odot}$ (similar to M87 with $\bf \sf 3.0\times 10^9 M_{\odot}$). Detailed models predict a 2-3$\times$ greater mass. We also obtain stellar kinematics using the absorption lines in the ground-based spectra (MDM 2.4-m) and in spectra from HST. We fit losvd's and Gauss-Hermite moments using a new, direct-template-fitting code. Isothermal sphere models predict a M$_{BH} \sim 1\times 10^9$. The central velocity dispersion is only about 290 km s$^{\sf -1}$. Thus, the large (459 km s$^{\sf -1}$) dispersion is erroneous. Nevertheless, this galaxy is interesting in that it allows a much-needed comparison between the gas and stellar dynamical techniques for determining BH mass. We acknowledge support for HST proposal 9106 from NASA through a grant from the STScI, which is operated by the AURA under NASA contract NAS 5-26555, and to an LTSA grant NAG5-8238 to D. Richstone. [Preview Abstract] |
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P.00006: Analysis of the Mars Global Surveyor Radio Occultation Data Katherine Yeager The Mars Global Surveyor which was launched on November 7, 1996 was designed to orbit Mars over a two year period and collect data on the surface morphology, topography, composition, gravity, atmospheric dynamics, and magnetic field. The surveyor was equipped with several different types of instruments but the one that we were most interested in was the radio transmission relay. With the data obtained from this instrument we have been able to study different aspects of the Martian atmosphere and relate it to the Chapman function. We have been able to show several ways as to how the Chapman function relates to the Martian atmosphere based on several different forms of data. [Preview Abstract] |
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P.00007: Mapping the Surface of Pluto via Light-curve Inversion Annie Schneider, Robert Harmon, Brad Trees Ever since its discovery in 1930, Pluto has presented scientists with a great challenge: in ground-based images it is completely unresolved, while even the Hubble Space Telescope produces an image which is only a few pixels across. However, as Pluto orbits the Sun and rotates, its brightness varies as surface features move in and out of view from Earth. We present albedo maps of the surface based on these variations. We utilize light curves spanning many decades, because the changing inclination of the rotation axis to the line of sight allows us to better constrain the latitudes of surface features that would be possible for a fixed inclination. [Preview Abstract] |
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P.00008: Simple Model for the Critical Mass of a Fissile Nuclide Cameron Reed A straightforward time-independent model for determining the critical mass of a spherical sample of a fissile nuclide is developed. Only elementary scattering theory and probability concepts are used. This model is suitable for presentation to students at a sophomore level and gives results in excellent accord with published values. [Preview Abstract] |
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P.00009: Nano-mechanical-resonator induced synchronization in Josephson junction arrays Stefan Natu, Brad Trees We show that a serial array of $N$ disordered, underdamped, Josephson junctions coupled piezoelectrically to a nanomechanical (NEM) oscillator results in phase locking (synchronization) of the junctions. Our approach is based on a semiclassical solution to a set of coupled differential equations generated by the Heisenberg operator equations, which in turn are based on a model Hamiltonian that includes the following effects: the charging and Josephson energies of the junctions, dissipation in the junctions, the effect of a dc bias current, and an underdamped simple harmonic oscillator representing the NEM. Resonance between the array and NEM is signaled by a step in the voltage-current curve. Synchronization is also measured by the value of the phase and frequency order parameters on the step. The stability analysis of the synchronized junctions reveals that the phase-locked junctions are neutrally stable at the bottom and top of the step but not for bias currents in the middle of the step. Using harmonic balance, we are able to calculate an analytic expression for the voltage locating the resonance step in the I-V curve. [Preview Abstract] |
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P.00010: Doubly-Excited States of the Be Atom in the MCRRPA Lin-Ru Wang, Keh-Ning Huang Photoionization parameters for double-excitation autoionization resonances in neutral beryllium are calculated in the multiconfiguration relativistic random-phase approximation (MCRRPA). Precise energies and widths of all five Rydberg series of low-lying doubly-excited states are given. [Preview Abstract] |
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P.00011: Mesoscopic fluctuation of off-diagonal matrix elements of the angular momentum and orbital magnetism of free electrons in a rectangular box Ming Lou, J.M.A.S.P. Wickramasinghe, R.A. Serota We study, analytically and numerically, mesocsopic fluctuation of the off-diagonal matrix elements of the ortbital angular momentum between the nearest energy levels $i=(n_x ,n_y )$ and $f=(k_x ,k_y )$ in a rectangular box with incommensurate sides. In the semiclassical regime, where the level number $N>>1$, our derivation gives $\left\langle {\left| {\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}}\over {L}} _{if} } \right|^2} \right\rangle \sim \sqrt N $. Numerical simulations, using simultaneous ensemble averaging (over the aspect ratios of rectangles) and spectral averaging (over the energy interval), are in excellent agreement with this analytical prediction. Physically, the mean is dominated by the level pairs $k_x =n_x \pm 1,k_y =n_y \pm 1$ .Also in a rectangular box, we investigate the mean orbital susceptibility of a free electron gas and argue that it reduces, up to a coefficient, to the two-level van Vleck susceptibility that involves the last occupied (Fermi) level and the first unoccupied level. This result is confirmed numerically as well, though the effect of fluctuations is much more pronounced for the susceptibility since it is due both to large fluctuations in $\left\langle {\left| {\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}}\over {L}} _{if} } \right|^2} \right\rangle $ and in level separations $\varepsilon _f -\varepsilon _i $. [Preview Abstract] |
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P.00012: A Monte Carlo Model for Luminescent Solar Concentrators Alex Mooney, Paul Fontecchio, Bruce Wittmershaus Luminescent Solar Concentrators (LSCs) offer an inexpensive alternative for solar power generation. A LSC is a flat, translucent plate that absorbs sunlight through embedded, highly fluorescent chromophores. The emitted light is concentrated via total internal reflection at the edges of the LSC, where photovoltaic cells covert it into electricity. We've developed a Monte Carlo model that predicts the properties of LSCs by tracing individual light rays. The user controls the plate's geometry and spectral properties, along with the spectral profile of the excitation source. The user can include a specular or diffuse reflective background under the LSC. We've demonstrated the ability to predict the output of a LSC as a function of its optical density. Reabsorption distorts the profile of fluorescence as light propagates through a LSC, and the program can accurately reproduce the effect. The goal is to use the model as a predictive tool for improving the design of LSCs. [Preview Abstract] |
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P.00013: Elasticity of a Rubber Band Model Ulrich Zurcher, Lorin Woodford We study the two-state model proposed for the stretching of DNA. We study the stretching at low force. We consider the case of long-range interactions between spins. We show results for long chains obtained using the Ohio Supercomputer [OSC]. We discuss the elastic modulus of the chains in the presence of long-range interactions. [Preview Abstract] |
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P.00014: Nuclear Lifetimes in $^{79}$Sr S.R. Arora, R.A. Kaye, S.L. Tabor, J. D\"{o}ring Lifetimes of eight discrete energy states in the $^{79}$Sr nucleus were measured using the Doppler-shift attenuation method. These states were populated at high angular momentum using the $^{28}$Si + $^{54}$Fe fusion-evaporation reaction at 90 MeV, with a thick 14 mg/cm$^{2}$ $^{54}$Fe target used to stop all recoiling nuclei. The de-exciting $\gamma$ rays were measured in prompt coincidence using a Compton-suppressed Ge array consisting of three Clover detectors and seven single-crystal detectors. Lifetimes were determined from experimental line shapes measured at 145$^\circ$ relative to the beam direction. Quadrupole deformations $\beta_2$ inferred from the lifetimes in the two lowest-energy positive-parity state sequences indicate highly deformed structures, in agreement with theoretical predictions from total Routhian surface calculations. Of these two sequences, the one built upon a higher intrinsic energy may have a larger average deformation, in agreement with the theoretical calculations. [Preview Abstract] |
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P.00015: The Feasibility of Developing an X-Ray Based Quality Assurance Tool for Patient Proton Range Compensators Courtney Buckey, Anthony Mascia, Jonathan Farr There exists the need to develop a stronger quality assurance regimen in order to crosscheck the physically manufactured compensator with the treatment planning prescribed compensator. Currently, the compensator QA protocol involves manually measuring a representative group of drill points and if that group coincides with what is expected, the compensator passes the QA procedure. However, in the clinic, the case when a compensator passes the QA protocol but is actually flawed (i.e. the false-positive) must be reduced or eliminated. It may be possible to develop a radiographic tool and accompanying computer analysis program to measure every manufactured drill point and compare them to the treatment planning compensator request within minutes. [Preview Abstract] |
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P.00016: Nonlinear waves in two-dimensional crystalline plasma T.E. Sheridan, V. Nosenko, J. Goree Complex (dusty) plasma consists of negatively-charged microscopic particles suspended in normal electron--ion plasma. Under appropriate circumstances, monodisperse particles will form a two-dimensional crystal at the lower sheath edge of an rf discharge. The particles repel each other via a shielded Coulomb force (a Yukawa potential) and are confined by a radial parabolic well. A crystal with $\approx 5000$ particles ($8~\mu\rm m$ diam.) was created for a neutral argon pressure of 3 mtorr. The Debye shielding parameter was $\kappa \sim 4$. Highly-nonlinear, planar compressive waves were launched by pushing all the particles in a rectangular region at the center of the crystal in the same direction using an 18 W green laser. Solitary waves were found to propagate in the forward direction at Mach numbers up to 1.5. Oscillatory shocks were seen to propagate in the backward direction after the laser was turned off. Rarefactive pulses, which are predicted theoretically, were not seen. [Preview Abstract] |
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P.00017: Charge and Debye length measurements in two-dimensional Debye clusters using thermal fluctuations W.L. Theisen, T.E. Sheridan A two-dimensional Debye cluster is a system of $n$ identical particles confined in a two-dimensional parabolic well and interacting through a screened Coulomb force (i.e., a Debye-H\"uckel or Yukawa potential) with a Debye length $\lambda$. In the strong-coupling regime, the particles exhibit small-amplitude motions about their equilibrium positions. These thermal oscillations are projected onto the center-of-mass and breathing modes to determine resonance curves from which the natural mode frequencies are found. The ratio of the breathing frequency to the center-of-mass frequency is then compared with theory to determine the Debye length and the average particle charge. Experiments were performed for $n=3$ to 63 particles with $9~\mu\rm m$-diameter particles at a neutral argon pressure of 13.6 mtorr and for $\approx9$ W of rf power. The Debye length increases slightly and the absolute value of the charge decreases slightly as the number of particles increases. [Preview Abstract] |
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P.00018: Magnetic fluctuations close to an antiferromagnetic quantum critical point in heavy fermion alloys Almut Schroeder, Bilal Zoghbi, Collin Broholm Neutron scattering spectra of the heavy fermion compounds Ce(Cu,Au)$_6$ and CeNi$_2$Ge$_2$ will be compared to characterize the magnetic correlations and dynamics close to an antiferromagnetic quantum critical point. While the magnetic response in Ce(Cu,Au)$_6$ reveals quantum critical fluctuations which can be consistently described in a simple although unconventional picture, the scenario in CeNi$_2$Ge$_2$ is more complex, both defying the ``ideal'' conventional scenario expected for a three dimensional antiferromagnetic quantum critical point. (Work in collaboration with G. Aeppli, D.F. McMorrow, N. Christensen, M. Adams, O. Tegus, J. Mydosh, Y. Qiu.) [Preview Abstract] |
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P.00019: Influence of hydrostatic pressure on the diluted magnetic semiconductor Sb$_{2-x}$Cr$_{x}$Te$_{3}$ Andrew J. Luciana, Cestmir Drasar, Petr Lostak, Jeffrey S. Dyck Currently, there is a great deal research activity on the incorporation of magnetic ions into semiconductors to produce ferromagnetism. These diluted magnetic semiconductors (DMSs) are of interest both to theorists, because of their unusual mechanisms of magnetic behavior, and to experimentalists, because the manipulation of spin in addition to charge promises devices based on spin polarized transport. We have investigated electrical transport properties of bulk single crystals of the ferromagnetic DMS Sb$_{2-x}$Cr$_{x}$Te$_{3}$ under varying pressure (0 GPa to 1.2 GPa), temperature (2 K to 300 K), and magnetic fields (0 T to 6 T). High pressure measurements afford a reversible way to tune both the electronic structure and magnetic interactions of these materials. Assuming a Curie temperature T$_{C}$ model based on RKKY indirect spin exchange we seek to observe how pressure and carrier concentration relate to the T$_{C}$ in this material. We show that both T$_{C}$ and carrier concentration exhibit increasing trends as hydrostatic pressure is increased. This work was supported by the Research Corporation. [Preview Abstract] |
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P.00020: Electronic Conduction Mechanisms 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 Four-terminal current-voltage (I-V) data are recorded for tunnel junctions of the type Al/barrier/Pb at temperatures ranging from 4K to room temperature. Conductance voltage (G-V) data are then derived numerically. The tunnel barrier is comprised of 7-Ethynyl-2,4,9-trithia-tricyclo[3.3.1.1$^{3,7}$]decane adsorbed on amorphous CdS ultra-thin films. The CdS films are of the order of 1-4 nm thick, and are prepared by RF sputtering in argon. 7ETTD is then spin-doped onto the CdS films from a dilute ($\sim $1.4 mg.ml$^{-1})$ solution in dimethylether which produces a self-assembled monolayer of the compound. Analysis of I-V, G-V and other data indicates that a combination of conduction mechanisms come into play depending on the current, voltage, and temperature. These mechanisms are primarily temperature activated hopping, direct tunneling, and, possibly, frontier-orbital coupling. The results show that the addition of a 7ETTD layer dramatically changes the electronic properties of the tunnel barrier. These changes are reflected in corresponding inelastic electron tunneling spectroscopy data. [Preview Abstract] |
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P.00021: Resistivity and Anomalous Hall Effect of Ga$_{1-x}$Mn$_{x}$As Kimberly L. Adams, Xinyu Liu, Jacek K. Furdyna, Jeffrey S. Dyck Diluted magnetic semiconductors (DMS) are compounds in which there is a non magnetic semiconductor host doped with a small concentration of a magnetic element. DMS thin films are being investigated for their potential as spintronic devices that would utilize both the spin and charge properties of the electrons in a single material. Resistivity and Hall effect measurements were made on varying thicknesses of Ga$_{1-x}$Mn$_{x}$As thin film samples through a temperature range of 10K-300K. The influence of the spin of the manganese ions is clearly evident in the electrical transport properties. The obtained data was compared to a model for the anomalous Hall Effect in these materials in an attempt to extract the free hole concentration. Funded by the Henry Luce Foundation and Research Corporation. [Preview Abstract] |
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P.00022: Building Optical Tweezers to Study a Dusty Plasma Robert Merrill, John Goree Research was conducted to determine the feasibility of using optical tweezers to study particles in a dusty (complex) plasma. We will describe a method for building optical tweezers intended to manipulate plastic microspheres in a complex plasma. The apparatus for trapping dielectric microspheres is presented. Preliminary measurements of beam profiles will be presented and future work will be discussed. [Preview Abstract] |
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P.00023: Development of a Negative Ion Beam Apparatus C.M. Janczak, K.A. Starr, D.A. Richardson, C.H. Mosier, C.W. Walter, N.D. Gibson, P. Andersson Primary design and construction tasks have been completed for a new negative ion beam apparatus for laser photodetachment experiments. A cesium sputtered negative ion source produces 10-20 keV ions which are formed into a beam and mass selected. Projects included installation of a new ultrahigh vacuum chamber, tuning of a 90$^{^{\circ}}$ mass separating magnet and associated beam optics, and construction of a photon-ion interaction region with neutral particle separation and detection. Working pressures of 1.0x10$^{-9}$ torr have been achieved in the analysis chamber, and successful detection of photodetached neutrals from multiple ion species has been demonstrated. Isotopic identification of Pt$^{-}$ has been used to determine the mass resolution to be $\sim $1 in 330 amu. Use of a limited sputter angle CeO$_{2}$ cathode in the source permitted production of $^{140}$Ce$^{-}$ beams of $\sim $70 pA with a cathode life up to 76 hours without deterioration of ion source performance. [Preview Abstract] |
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P.00024: Photodetachment of Ce$^{-}$ K.A. Starr, C.M. Janczak, D.A. Richardson, N.D. Gibson, C.W. Walter, P. Andersson Infrared laser photodetachment spectroscopy has been performed on Ce$^{-}$ using a crossed ion-laser beam apparatus. Negative ions were created in a Cs sputtered negative ion source, mass selected with a 90$^{o}$ mass analyzing magnet, and then sent into a UHV interaction region. The relative photodetachment cross section was measured by counting the number of photodetached neutrals as a function of photon energy after the ion beam was intersected with a tunable pulsed OPPO infrared/visible laser. The relative cross section was measured from 0.5eV to 2.6eV. The results will be compared to recent theoretical[1] and experimental[2] results which are in significant disagreement on fundamental physical quantities such as the electron affinity of Ce and the ground state configuration of Ce$^{-}$. [1]X. Cao and M. Dolg, Phys. Rev. A \textbf{69}, 042508 (2004). [2]V.T. Davis and J.S. Thompson, Phys. Rev. Lett. \textbf{88}, 073003 (2002). [Preview Abstract] |
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P.00025: Laser Optogalvanic Spectroscopy in Hollow Cathode Discharges Kurt Nesbett, James Farrant, Donald Moore, Naveed Piracha An efficient dye laser pumped by an Nd: YAG laser has been developed for laser optogalvanic spectroscopic studies of rare gases. Using this tunable laser system, we have recorded neon and krypton time resolved optogalvanic spectra under different discharge conditions. Such a work will lead to investigate the temporal mechanism of the optogalvanic effect in rare gases. [Preview Abstract] |
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P.00026: Laser Diagnostics of Energized Atmospheric Air Andrea Herrick, Steven Adams The time dependent behavior of molecular nitrogen ions, following pulsed photoionization of near atmospheric pressure N2, has been investigated using multi-photon laser techniques and kinetic modeling. Measured time dependent fluorescence~spectra, during and after pulsedlaser resonance-enhanced multi-photon ionization of N2, together with a coupled rate equation model, allowed for the determination of the absolute densities of N2+ and N4+ as these species evolved. [Preview Abstract] |
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P.00027: Atmospheric Effects On Laser Light Debra Cox, Steven Fiorino HELEEOS (High Energy Laser End-to-End Operational Simulation) was developed by the Air Force Institute of Technology's Center for Directed Energy. HELEEOS simulates how the presence of aerosols affects a beam of laser light propagating though the atmosphere. We worked to improve HELEEOS by giving it the additional capability to simulate how clouds, fog, and rain affect the propagation of laser light. HELEEOS simulates how these disturbances affect laser light by using Mie scattering theory to calculate the extinction, scattering, and absorption coefficients. The cloud, fog, and rain calculations have been successfully incorporated into HELEEOS. We also endeavored to calculate how much laser light is scattered in a particular direction. This work has not been incorporated into HELEEOS, but it will be used as a starting point for further research. [Preview Abstract] |
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P.00028: Multifractal Analysis of Mixing in Microchannels Marco Camesasca, Miron Kaufman, Ica Manas-Zloczower Mixing in microfluidic systems is important for many technological applications, as for example in biotechnolology when sensing trace amounts of chemicals or detecting the bases in a small DNA segment. In such systems, the flow is laminar and driven by pressure gradients with no moving parts to drag the fluid. We develop rigorous measures for assessing the quality of mixing in microchannels by employing Renyi entropies and multifractal dimensions. We apply these measures to asses mixing in microchannels of different surface geometries. We find enhanced mixing efficiency for the geometry similar to the staggered herringbone mixer by comparison with a mixer with straight diagonal ridges. We also analyze the multifractal dimensions for a sequence of pictures obtained at various cross-sections of a staggered herringbone mixer in an experiment where a fluorescent fluid is mixed into a non-fluorescent one*. This multifractal analysis of the generated structures during mixing is used as another measure of quality of mixing. * Stroock A D, Dertinger S K W, Ajdari A, Mezic I, Stone H A, Whitesides G M 2002 Science 295 647--651 [Preview Abstract] |
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P.00029: Novel monomer-liquid crystal mixtures for homeotropically aligned, PSLC films with high optical contrast and fast response times Luana Tortora, Sabrina Manfredi, Roberta Cassano, Nevio Picci, Giuseppe Chidichimo Composite systems consisting of polymers and low-molecular-weight liquid crystals have attracted increasing interest over the last years, opening a new field of liquid crystal science and technology research\textbf{. }Liquid crystal-polymer composites include standard polymer-dispersed liquid crystals (PDLCs) and polymer stabilized liquid crystals (PSLCs); macroscopically oriented PSLCs films, also defined as anisotropic gels, are of great interest for electro-optical applications [1-6]. They are prepared by in situ photo-polymerization of a liquid crystal monomer with reactive end groups in an oriented state, in the presence of a non reactive nematic liquid crystal. The orientation is induced by orientational layers applied to the cell surfaces, due to the presence of an electric or a magnetic field. In this work we present results on new liquid crystal-acrylate monomers mixtures used to realize homeotropically aligned polymer-stabilized liquid crystal films (PSLCs) with high transparency and fast electro-optical response times. A detailed investigation of the electro-optical performance and a morphological analysis were performed to explain the correlation between the polymerization condition, the matrix composition and the film properties. \textbf{References} [1] GAUTIER, P., BRUNET, M., GRUPP, J., NOIREZ, L., and ANGLARET, E., 2003, \textit{Phys. Rew. E}, \textbf{68}, 011709. [2] KOSSYREV, P.A., QUI, J., PRIEZJEV, N.V., PELCOVITS, R.A., and CRAWFORD, G.P., 2002, \textit{Appl. Phys. Lett.}, \textbf{81}, 2986. [3] Liquid Crystals in Complex Geometries, edited by G.P. Crawford and S. Zumer (Taylor and Francis, London, (1996) [4] HIKMET, R.A.M., and BOOTS, H.M.J., 1995, \textit{Phys. Rew. E}, \textbf{51}, 5824. [5] HIKMET, R.A.M., and HOWARD, R., 1993, \textit{Phys. Rew. E}, \textbf{48}, 2752. [6] HIKMET, R.A.M., 1992, \textit{Mol. Cryst. Liq. Cryst}, \textbf{213}, 117. [Preview Abstract] |
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P.00030: Synthesis, Structure, and Dynamics of a promising drug delivery system: HPC microgel nanoparticles Rami Mohieddine, Kiril Streletzky Recent advances of macromolecular and medical sciences created a lot of interest in processes of self-association of amphiphilic molecules into stable nanoparticles with ability to solubilize hydrophobic drugs and serve as reservoirs for controlled drug delivery/release. Microgel nanoparticles formed in water solutions of neutral polymer Hydroxypropylcellulose (HPC) is a promising drug carrier system with an important advantage of being non-toxic (HPC is FDA-approved food additive). We synthesized HPC microgel at room temperature by crosslinking and dialysis after lowering HPC phase transition with salt addition. Using Dynamic Light Scattering (DLS) we studied structure and dynamics of microgel nanoparticles at different polymer concentrations and at a range of temperatures and scattering angles. Contrary to the literature, the size distribution of microgels is found to be multimodal leading to failure of conventional cumulant analysis. We present the initial steps of alternative analysis of microgel structure and dynamics and outline a few possible future directions of our study. [Preview Abstract] |
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P.00031: Aggregation and Transport Properties of Spherical Brij-35 Micelles Kiril Streletzky, Mike Lekan Dynamic light scattering (DLS) spectroscopy was used to measure the mutual diffusion coefficient of Brij-35 micelles in water and probe diffusion of polystyrene latex spheres with diameter of 50, 186, 282nm in aqueous solution of Brij-35. We studied the both mutual and probe diffusion over the surfactant concentration range of 3 to 100g/l and a temperature range of 10 to 70C. Assuming a simple hard sphere model for micelles and probes we found micelle hydrodynamic radius (am), aggregation number of surfactant molecule per micelle ($N$), and hydration number ($\delta$) as a function of solution temperature. We found am increasing from 4.4 to 4.8 nm, $N$ increasing from 33 to 67 molecules per micelle, and $\delta$ decreasing from 4.5 to 2.4 g H20/g Brij-35. These results agree with the literature. While in all of our probe diffusion experiments probes were the dominating scatterers, the spectra of our largest 780nm probes in water solutions of Brij-35 showed unusual bimodality. One mode is reminiscent of probe diffusion and the other of mutual micelle diffusion. Both observed simultaneously. A possible explanation for this finding is discussed. [Preview Abstract] |
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P.00032: Computational studies of model polymers in solution Sayuri Ichida, Tyson Papay, Gregory Petersen, Mark Taylor The conformation of a polymer molecule in solution is strongly dependent on the ``quality'' of the solvent. In a good solvent a chain is expanded or swollen relative to an isolated chain while in a poor solvent a chain is in a compact or collapsed state. In this work we present a series of Monte Carlo simulation studies of a single interaction-site polymer in an explicit monomeric solvent. In particular, we have studied both a hard-sphere chain and a hard-sphere ring in a hard-sphere solvent, a hard-sphere chain tethered to a surface in a hard-sphere solvent, and a square-well chain in a square-well solvent. In all cases, the hard sphere solvent is found to compress the hard sphere polymer thus acting as a poor solvent. For the square-well system both chain expansion and chain compression are observed as the solvent quality changes from poor to good with decreasing temperature. Application of these results to developing accurate solvation potentials for polymer-in- solvent systems will be discussed. [Preview Abstract] |
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P.00033: Statistical Instability of Barrier Micro-Discharges in Townsend Regime V.P. Nagorny, V.N. Khudik This abstract was not submitted electronically. [Preview Abstract] |
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P.00034: Ultrasensitive Real-time Refractometry without Interferometry Michael McClimans, Charles LaPlante, David Bonner, Samir Bali This abstract was not submitted electronically. [Preview Abstract] |
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