Bulletin of the American Physical Society
Joint Fall 2009 Meeting of the New England Section of the APS and AAPT
Volume 54, Number 11
Friday–Saturday, October 16–17, 2009; Durham, New Hampshire
Session C1: Poster Session: APS/AAPT (5:40-7:00PM) |
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Chair: Mark McConnell, University of New Hampshire |
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C1.00001: Synergistic Ag (111) and Cu (111) texture evolution in phase segregated Cu$_{1-x}$Ag$_{x}$ magnetron sputtered composite thin films Dana I. Filoti, Andrea R. Bedell, James M.E. Harper We have investigated the evolution of texture and microstructure of Cu$_{1-x}$Ag$_{x}$ composite thin films through X-ray diffraction pole figures as a function of composition for x $\le $ 0.5. The texture evolution of Cu (111) and Ag (111) in phase-segregated Cu-Ag thin films proves to be synergistically enhanced when compared to pure copper or silver thin films. As-codeposited at room temperature, the fcc composite Cu$_{1-x}$Ag$_{x}$ grows as a phase-segregated thin film, when the Ag volume fraction represents more than 15 at. {\%} up to 50 at. {\%}, or as a single phase thin film when Ag volume fraction represents less than 15 at. {\%}. Not only is a stronger perpendicular (111) fiber texture obtained, but also an in-plane alignment of Ag (200) develops related to deposition direction and composition. By the use of transmission electron microscopy we observed a decrease in grain size in Cu-Ag composite films as compared with pure copper and silver films. [Preview Abstract] |
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C1.00002: Modeling the Self-Assembly of Carboxylic Acid Substituted Fullerenes on Au(111) Gregory Bubnis, Howard Mayne Self-assembled surface architectures incorporating functionalized fullerenes have been studied extensively; However, the prediction and rational design of molecular scale patterns remain challenging. For small organic molecules, hydrogen bonding functional groups are often used as the dominant intermolecular interaction to drive self-assembly. We focus on a family of fullerenes with carboxylic acid terminated phenyl, biphenyl, and (linear) polyphenylene substituents to study their monolayer pattern formation on Au(111). All-atom modeling efforts for such systems are often limited to small clusters and the most accurate \textit{ab initio} calculations can require experimental guidance because exhaustive explorations of configuration space are intractable. We develop simplified potential energy functions for the relevant physical interactions and constrain the molecules and surface to be rigid. This ``coarse-grained'' approach permits studies of 25 to 50 molecules -- using unbiased Metropolis Monte Carlo simulations to thoroughly explore the configuration space -- at a modest computational expense. Fullerene moieties are found to form hexagonal monolayers and substituent groups dictate additional orientational order. The largest substituents hinder pattern formation while parallel, one-dimensional hydrogen bonded chains as well as herringbone patterns are observed in other cases. [Preview Abstract] |
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C1.00003: Molecular Self-assembly for Organic Electronics Jun Wang, Irvinder Kaur, Bogdan Diaconescu, Mikael Jazdzyk, Glen P. Miller, Karsten Pohl Self-assembled thin films of novel organic molecules hold the promise of emerging technologies and applications ranging from sensors for biological applications to organic electronics and more efficient organic photovoltaics. Self-assembled monolayers (SAMs) form as a result of a delicate balance between competing molecule-substrate and intermolecular interactions. To control such self-assembly processes, it is mandatory to understand how this balance reflects onto the SAM's final structure. Here we present an ultra-high vacuum scanning tunneling microscopy (STM) study of the self-assembly of novel pentacene derivatives and functionalized fullerenes (F-C60) on metal surfaces. Pentacene is known to exhibit large carrier mobility and has been studied extensively as a semiconductor in organic thin film devices. However, it is subject to facile photo-oxidation that limits device lifetime. We recently synthesized novel pentacene derivatives that show a dramatically increased resistance to photo-oxidation. We identified 6,13-dichloropentacene as a promising candidate for organic electronics. On the compact surface of gold, 6,13-dichloropentacene forms self-assembled domains with various high symmetry orientations. The quality of the SAM is seem to dramatically improve when the 6,13-dichloropentacene are deposited on the (788) vicinal surface of gold where the presence of parallel atomic steps will select only one of the possible SAM orientations due to the molecule-step interaction. Thus we observe the formation of very large self-assembled 6,13-dichloropentacene monolayers with perfect single domain orientation. We have also studied the self-assembly of C60 functionalized with alkyl chains of various lengths (F-C60) on Ag(111). We find that as a function of the alkyl chain length various structures are forming, ranging from zigzag like to linear arrays of C60 fullerene cages. The symmetry and unit cell size of the F-C60 SAMs is dictated by the alkyl-surface and the intermolecular interactions. These results show that C60 molecules can be assembled in 2D and non-compact molecular arrays with a surface density controllable via appropriate chemical functionalization. Those structures show promise as candidates for selfassembled molecular junctions. [Preview Abstract] |
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C1.00004: Analyzing Interstellar Gas Flow Distributions Observed with IBEX Using a Maximum Likelihood Method Trevor Leonard The Interstellar Boundary Explorer (IBEX) observes interstellar neutral gas flow distributions of species that remain neutral to a large part in the interstellar gas, such as He and O. In order to fit model distributions to the data a maximum likelihood method is used to extract more information even with low counting statistics, compared with using a least chi square fit. Parameters, such as peak position, distribution height, width, and skewness may be obtained with the maximum likelihood method to characterize, for example, flow velocity, density, and temperature of the interstellar source as well as ionization rates. We will give an introduction to the application of the maximum likelihood method to the IBEX observations. [Preview Abstract] |
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C1.00005: Using IBEX-Lo to Determine the He Component of the Interstellar Flow Lee Petersen IBEX-Lo is a powerful, large aperture camera that detects neutral atoms (ENA) from Earth orbit by converting an incoming ENA to a negative ion on a diamond-like carbon conversion surface. The energy of the ENAs is restricted by an electrostatic analyzer and then boosted by post-acceleration before they are analyzed for their energy/mass in a time-of-flight (TOF) spectrometer. The efficiency of the TOF spectrometer and the conditions for the generation of negative ions on the conversion surface limit direct detection to only three species (hydrogen, carbon, and oxygen). However, on the conversion surface two other effects occur: sputtering and knock-off of secondary ions. These effects are both species and energy dependent. Through analyzing the species ratios of ions emerging from the conversion surface and comparing them to calibration measurements with known species and energy, the distribution of He (and possibly Ne) from the interstellar flow can be determined. [Preview Abstract] |
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C1.00006: Study on cusp/cleft O+ transport path inside the magnetosphere Jing Liao, Lynn Kistler, Christopher Mouikis The plasma in the magnetosphere comes from both the solar wind and the ionosphere. Energy from the solar wind can heat and accelerate the ionospheric ions, causing them to flow out from the cusp and be transported across the polar cap, into the magnetotail. The polar orbit of the CLUSTER satellite is ideal for observing the transport path. Using the instrument CODIF/CIS, which measures ion composition from 40 eV to 40 keV, these ions can be identified as tailward streaming O+, with a narrow energy range. We have developed an automated procedure to identify this population. The database gives the occurrence frequency of the streaming O+ as a function of position for geomagnetically quiet and storm times and how it depends on IMF magnitude and orientation, solar wind pressure, and geomagnetic activity. We find that while the beams can be observed for all geomagntic conditions, their occurrence frequency is much higher during geomagnetic storms. In addition. we find that there is a strong asymmetry in the transport that depends on the y-component of the interplanetary magnetic field. [Preview Abstract] |
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C1.00007: GRAPE: A Compton Polarimetry Experiment Taylor Connor, Peter Bloser, Jason Legere, Mark McConnell, James Ryan We review the design, calibration and data analysis of the Gamma Ray Polarimetry Experiment (GRAPE), a Compton polarimeter device for measuring the polarization of photons in the 50-500 keV energy range. In Compton scattering, X-ray and gamma-ray photons tend to scatter at right angles with respect to their polarization vector. We exploit this fact to measure the polarization of the incident radiation by looking at the azimuthal distribution of the scattered photons. This distribution gives us a measure of both the level of polarization and the orientation of the polarization vector. These measurements will allow us to probe the particle acceleration regions of astronomical sources. GRAPE will be flown in the fall of 2011 on as a high altitude balloon payload. The primary target of that flight will be the Crab Nebula, with the Sun (solar flares) and Cygnus X-1 as secondary targets. Our observations of the Crab will be compared to the findings of the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), which provided constraints on the location of the particle acceleration region within the Crab Nenbula. Following the initial flight in 2011, we hope to fly GRAPE on a long duration balloon flight from Antarctica to study gamma-ray bursts. [Preview Abstract] |
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C1.00008: Simulations of an X-Ray Detector Using Geant4 Camden Ertley, Mark McConnell, Peter Bloser, Jason Legere, Taylor Connor, James Ryan NASA's Black Hole Finder Probe mission has two proposed concepts. CASTER, one of the proposed concepts, is a scintillator based Coded Aperture Survey Telescope for Energetic Radiation. This paper focuses on the development of a simulation that accurately models the proposed CASTER detector. The current detector design consists of a Lanthanum Bromide (LaBr$_{3})$ scintillator directly coupled to a multianode photomultiplier tube (MAPMT). This detector should be optimized to give the best energy and position resolution. The simulation is based on the Geant4 toolkit, a set of detector simulation tools developed at CERN. Geant4 was chosen because it accurately models radiation devices and detectors, while allowing the simulation of transport and boundary conditions of optical photons. The results of the simulation were compared with data taken in the lab with a $^{57}$Co and an $^{241}$Am source. Once validated, the simulations will be used to optimize the final detector design. [Preview Abstract] |
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C1.00009: A Note on Geometric and Information Fusion Interpretation of Bell's Theorem and Quantum Measurement Florentin Smarandache, Vic Christianto In this paper we present four possible extensions of Bell's Theorem: Bayesian and Fuzzy Bayesian interpretation, Information Fusion interpretation, Geometric interpretation, and the viewpoint of photon fluid as medium for quantum interaction. [Preview Abstract] |
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C1.00010: Galileo's Courage to Create New Cosmology Paul H. Carr The trial of Galileo was a confrontation between the creativity of new science and the traditions of ``the religious establishment.''Galileo challenged ancient cosmology, where heavenly bodies were thoughtto be perfect spheres made of ``ether.'' His trail might have been avoided if Galileo had been more diplomatic. Paradoxically, the Roman Catholic Church was \textit{scientifically} correct: Galileo had no proof the earth rotated about its axis as it orbited around the sun. His assertion that the tides arise from the earth's rotation later turned out to be correct, but at that time no one knew enough about gravitational and centrifugal forces. Galileo courageously argued, ``The Bible tells us how to go to heaven, not how the heavens go [1].'' He was nevertheless convicted at age 69, Galileo, although deeply hurt, did not withdraw from the Church. He believed himself to be a good Catholic who had sought to keep his church, for its own good, from making a mistake. In 1992, Pope John Paul said the Church had erred in condemning Galileo. \\[4pt] [1] Carr, P. H. (2006). ``The Courage to Create Beauty,'' Chap 10 of ``Beauty in Science {\&} Spirit,'' Beech River Books, Center Ossipee, NH. [Preview Abstract] |
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C1.00011: What do Seniors Remember from Freshman Physics? Analia Barrantes, Andrew Pawl, David E. Pritchard We have given a group of 56 MIT seniors who took mechanics as freshmen a written test similar to the final exam they took in their freshman course, plus the MBT and C-LASS standard instruments. Students in majors unrelated to physics scored 60\% lower on the written analytic part of the final than they did as freshmen. The mean score of all students on conceptual multiple choice questions included on the final declined by approximately 50\% relative to the scores of freshmen. The mean score of all participants on the MBT was insignificantly changed from the posttest taken as freshmen. More specifically, however, the students' performance on 9 of the 26 MBT items (with 6 of the 9 involving graphical kinematics) represents a gain over their freshman pretest score (a normalized gain of about 70\%, double the gain achieved in the freshman course alone), while their performance on the remaining 17 questions is best characterized as a loss of approximately 50\% of the material learned in the freshman course. Attitudinal survey results indicate that almost half the seniors feel the specific mechanics course content is unlikely to be useful to them, a significant majority (75-85\%) feel that physics does teach valuable skills, and an overwhelming majority believe that mechanics should remain a required course at MIT. [Preview Abstract] |
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C1.00012: Modeling Applied to Problem Solving Andrew Pawl, Analia Barrantes, David E. Pritchard Modeling Applied to Problem Solving (MAPS) is a pedagogy that helps students transfer instruction to problem solving in an expert-like manner. Declarative and Procedural syllabus content is organized and learned (not discovered) as a hierarchy of General Models. Students solve problems using an explicit Problem Modeling Rubric that begins with System, Interactions and Model (S.I.M.). System and Interactions are emphasized as the key to a strategic description of the system and the identification of the appropriate General Model to apply to the problem. We have employed the pedagogy in a three-week review course for students who received a D in mechanics. The course was assessed by a final exam retest as well as pre and post C-LASS surveys, yielding a one standard deviation improvement in the students' ability to solve final exam problems and a statistically significant positive shift in 7 of the 9 categories in the C-LASS. [Preview Abstract] |
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C1.00013: Toward an Inventory Assessing Expert Problem Solving Skills Andrew Pawl, Analia Barrantes, David E. Pritchard We describe some of the challenges inherent in constructing a standardized instrument assessing problem solving skills, and suggest ways to overcome these challenges. We present items from a conceptual multiple choice instrument assessing problem solving skills relevant to freshman mechanics that we are developing. This instrument is inspired in part by Lawson's Classroom Test of Scientific Reasoning and Van Domelen's Problem Decomposition Diagnostic. We seek teachers who are interested in testing the preliminary version! [Preview Abstract] |
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C1.00014: Solar Observations During Solar Minimum Using a Small Radio Telescope Gary Forrester, Martina Arndt The Sun is currently in a quiescent phase called solar minimum. We used B.S.C.'s Small Radio Telescope (SRT) to observe solar radio emission during this quiet phase and correlate our data to solar X-ray data readily available through the National Oceanic and Atmospheric Administration (NOAA). Previous observations made during a period of high solar activity (solar maximum) using one of M.I.T.'s SRTs showed that some solar radio and X-ray emission were correlated, while others were not. We made observations during solar minimum and found one instance where there was a correlation between radio and X-ray emission. [Preview Abstract] |
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C1.00015: Throw Away Your Mathematical Handbook! Undergraduate Physics with Wolfram|Alpha, a FREE(!) Internet-Based Mathematical Engine Craig W. Looney Wolfram|Alpha (http://www.wolframalpha.com/), a free internet-based mathematical engine released earlier this year, represents an orders-of magnitude advance in mathematical power freely available - without money, passwords, or downloads - on the web. Wolfram|Alpha is based on Mathematica, so it can plot functions, take derivatives, solve systems of equations, perform symbolic and numerical integration, and more. These capabilities (especially plotting and integration) will be explored in the context of topics covered in upper level undergraduate physics courses. [Preview Abstract] |
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C1.00016: Describing Student Epistemologies in Reformed Laboratories: Developing valid descriptions of student treatment of lab experience using a mixed methodology Christopher Shubert Traditional introductory physics laboratories serve as validation of material presented in lectures, however, reformed laboratory activities stress the active construction of understanding through a student's lab experience. Our question probes the buy-in of students to reformed labs: How are students approaching knowledge construction in reformed lab activities? We seek a description of student epistemology achieved through a mixed methodology that utilizes group video from reformed student lab activities, individual interviews, and an analysis that stresses validity of developed codes. In individual interviews clips of group video are presented and discussed further. Validity of codes are assessed as they correspond to both individual learners and material design. Our labs are informed by the underpinnings of Modeling Instruction and are adapted to our lecture course which covers biologically motivated algebra based content. We will present key aspects of our methodology and initial descriptions of individual student epistemologies. [Preview Abstract] |
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