Bulletin of the American Physical Society
2007 New England Section of the APS and AAPT Joint Fall Meeting
Volume 52, Number 17
Friday–Saturday, October 19–20, 2007; Storrs, Connecticut
Session C1: Poster Session |
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Chair: Lawrence Kappers, University of Connecticut Room: MSB Ground Floor Hallway, 5:00pm - 6:00pm |
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C1.00001: Measurement of Majorana background neutron interactions D.V. Perepelitsa, V.E. Guiseppe, S.R. Elliott, A. Hime, R.O. Nelson, N. Fotiades, M.J. Devlin, R.C. Haight, D.-M. Mei, C. Keller, Z. Yin Recent experiments have shown that free neutrons produced by cosmic-ray muons are expected to contribute to background events in double-beta decay and dark matter experiments. Neutron-induced transitions in natural lead were investigated with a broad spectrum neutron beam during Fall 2006 at the Los Alamos Neutron Science Center. Specific measurements of the $\gamma$-ray production cross-section of Pb(n,Xn') reactions allow for improved Monte Carlo simulations of neutron-induced background. We focus on the 2040-keV line (in $^{206}$Pb) and 3062-keV double-escape peak (in $^{207}$Pb) which overlap with the germanium-76 neutrinoless double-beta decay signature. In addition, the integral $\gamma$-ray production cross-sections for the first excited state to ground state in $^{206,207,208}$Pb are calculated as a check on this result. [Preview Abstract] |
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C1.00002: COOL COSMOLOGY: ``WHISPER" better than ``BANG" Paul Carr Cosmologist Fred Hoyle coined ``big bang'' as a term of derision for Belgian priest George Lemaitre's prediction that the universe had originated from the expansion of a ``primeval atom'' in space-time. Hoyle referred to Lamaitre's hypothesis sarcastically as ``this big bang idea'' during a program broadcast on March 28, 1949 on the BBC. Hoyle's continuous creation or steady state theory can not explain the microwave background radiation or cosmic whisper discovered by Penzias and Wilson in 1964. The expansion and subsequent cooling of Lemaitre's hot ``primeval atom'' explains the whisper. ``Big bang'' makes no physical sense, as there was no matter (or space) to carry the sound that Hoyle's term implies. The ``big bang'' is a conjecture. New discoveries may be able to predict the observed ``whispering cosmos'' as well as dark matter and the nature of dark energy. The ``whispering universe'' is cooler cosmology than the big bang. Reference: Carr, Paul H. 2006. ``From the 'Music of the Spheres' to the 'Whispering Cosmos.' '' Chapter 3 of \underline {Beauty in Science and Spirit.} Beech River Books. Center Ossipee, NH, http://www.MirrorOfNature.org. [Preview Abstract] |
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C1.00003: Photophysics of single colloidal quantum dots embedded in organic semiconductor optoelectronic devices August Dorn We investigated individual CdSe/ZnS colloidal nanocrystals embedded in sandwiched optoelectronic devices made of the molecular organic semiconductors aluminum \textit{tris}(8-hydroxyquinoline) (Alq$_{3})$ and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD). Spectral diffusion and blinking from individual quantum dots were observed both in electro- and photoluminescence. In addition we analyze field dependant fluorescence quenching under high bias. Our study helps elucidate the elementary interactions between quantum dots and organics, knowledge needed for designing efficient quantum dot organic optoelectronic devices. [Preview Abstract] |
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C1.00004: Afterglow suppression and non-radiative charge-transfer in CsI:Tl,Sm L.A. Kappers, R.H. Bartram, D.S. Hamilton, A. Lempicki, C. Brecher, V. Gaysinskiy, E.E. Ovechkina, V.V. Nagarkar The feasibility of substantially diminishing afterglow in CsI:Tl scintillator material by co-doping with Sm$^{2+}$ is demonstrated. Rate equations informed by experiment predict that deep samarium electron traps scavenge electrons from shallow thallium traps. In addition, combined radioluminescence and thermoluminescence experiments on a sample of CsI:Tl,Sm with nominal concentrations of 0.11{\%} Tl$^{2+}$ and 0.2{\%} Sm$^{2+}$ suggest that electrons released by samarium recombine non-radiatively with holes trapped as $V_{KA}$(Tl$^{+})$ centers, thus providing a mechanism for suppression of trapped-charge accumulation in repetitive applications. A linear-coupling model in the harmonic approximation, based on quantum chemistry calculations with selective lattice relaxation, supports the conclusion that non-radiative charge-transfer is enabled by low-energy excited states of Sm$^{2+}$. [Preview Abstract] |
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C1.00005: An exact study of charge-spin separation, pairing fluctuations and pseudogaps in four-site Hubbard Nanoclusters Kalum Palandage, Armen Kocharian, Gayanath Fernando, James Davenport An exact study is carried out by using the \textit{analytical
}eigenvalues of the four-site Hubbard Nanoclusters with the grand
canonical and canonical ensemble approaches in a multidimensional
parameter space of temperature (T), magnetic field (h), on-site
interaction (U), chemical potential ($\mu)$ and number of
electrons (N). The electron charge energy gap, with one hole off
half filling, corresponds to an excitonic particle-hole pair
binding instability with $\Delta^{e-h}>0$ at $U>U_c $ and
vanishes at a critical parameter $U_c =4.584$. For $U |
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C1.00006: Direct evidence for the suppression of charge stripes in epitaxial La$_{5/3}$Sr$_{1/3}$NiO$_4$ thin films Changkun Xie, Joseph Budnick, Barrett Wells, Feizhou He, Arnold Moodenbaugh We have successfully grown epitaxial La$_{5/3}$Sr$_{1/3}$NiO$_4$ films with a small crystalline mosaic using pulsed laser deposition. With synchrotron radiation, the x-ray diffraction peaks associated with charge stripes have been successfully observed for relatively thick films. Anomalies due to the charge-ordering transition have been examined using four-point probe resistivity measurement. We also have produced multilayer films with the same total thickness through the use of thin films La$_{5/3}$Sr$_{1/3}$NiO$_4$ alternating with SrTiO$_3$. A thorough search for the charge stripe peaks in the multilayers has been negative; the stripes appear to be suppressed for epitaxial thin films. This suggests that electron-lattice interactions are critical for the formation of stripe phases. [Preview Abstract] |
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C1.00007: Adsorption and Physical Properties of Ar on carbon nanotubes Jeonggil Lee, Euikwoun Kim, Jae-yong Kim Many interesting research results on carbon nanotubes (CNTs) have been reported focusing on their unique mechanical, electrical, physical properties and potential application for hydrogen storage, purification, and gas separation. Among physical properties, Ar gas adsorption study is known to provide useful information in investigate the surface structure and specific surface area of CNTs. Ar adsorption isotherms data were measured below the triple point (83.78K) by using an automatic isotherm apparatus. The amount of adsorbed Ar gas measured as a function of a final equilibrium vapor pressure enabled us to estimate specific surface area of CNTs, and the results were approximately in an order of 100 m$^{2}$/g. The isotherm adsorption results showed the formation of two atomic layers on the CNT surface at 65 and 70K. The broader shape of the isotherm step for the second isotherm step was observed. This observation suggests the irregular shape of the sample. The existence of the second isotherm step was supported by the calculations of the 2-dimenstional compressibility and the isosteric heat of adsorption values, and the results will be presented. [Preview Abstract] |
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C1.00008: Purification of Carbon Nanotubes by Proton Irradiation Euikwoun Kim, Jeonggil Lee, Younman Lee, Jaekyun Jeon, Jae-yong Kim, Jeongha Kim, Kwanwoo Shin, Sang-pil Youn, Kyeryung Kim Carbon nanotubes (CNTs) exhibit variety of superior physical properties including well-defined nanodimensional structure, high electrical and thermal conductivity, and good mechanical stability against external irradiations. Further, a large specific surface area per unit weight suggests that carbon nanotubes could be excellent candidates for gas storage, purification, and separation. However, the practical application of CNTs is limited mainly due to the metallic impurities that were used as a catalyst during the fabrication process. Here, we irradiated CNTs by using high energy proton beams (35.7 MeV at the Bragg Peak). Interestingly, metallic impurities such as Fe, Ni, Co and chunk of amorphous carbon that were attached on the surface of CNTs were completely removed after the irradiation. The mechanism of such the purification process is not understood. The possible speculation will be demonstrated combined with the changes of physical properties including the appearance of the magnetism after the irradiation. [Preview Abstract] |
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C1.00009: Unified field theory with two dimensions of time John Kulick A unified field theory is established by allowing the expansion of spacetime to occur incrementally, according to a very specific multidimensional geometry. The ``quantum sized'' integration of spacetime upon the existing structure of reality produces a disturbance resulting in the observed probabilistic effects associated with Quantum Mechanics. The geometry of the expansion produces the physical properties associated the Conservation of Energy and Conservation of Momentum Principals as well as the inverse square laws associated with gravity and electrodynamics. All local and spatial based measures of time proportionally increase in duration, resulting in a ``slowing'' of physical processes, when described by a ``fixed'' or ``absolute'' measure of time. Absolute time is a historical measure of time that describes a ``point's'' location relative to the beginning of Time. Special and general relativity are locally preserved. The further in the past an object is observed, the more powerful the effect of gravity would be, due to the increased density of systems in the past. Astronomical predictions conform to observation. No dark energy/matter. [Preview Abstract] |
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C1.00010: Production of ultracold molecules via photoassociation through a Feshbach resonance Philippe Pellegrini, Marko Gacesa, Robin C\^ot\'e We present a theoretical investigation of photoassociation in the vicinity of a Feshbach resonance for the production of ultracold molecules in their lowest vibrational levels. The formation of ultracold molecules is of particular interest for the realization of quantum computing systems or the development of a cold physical chemistry which proposes to control elementary chemical reactions with or without electro-magnetic fields. Photoassociation, which occurs when two colliding atoms absorb a photon to form a molecule in a bound rovibrational level, has been widely used to produce ultracold dimers but the use of a magnetically induced Feshbach resonance enhances dramatically the probability density at short range allowing efficient transitions even for deeply bound levels. We illustrate this effect in both heteronuclear and homonuclear systems. [Preview Abstract] |
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C1.00011: NMR Study of $\varepsilon $-Co Nanoparticles David Perry, Joseph Budnick, William Hines, Madhur Sachan, Sara Majetich $^{59}$Co spin-echo nuclear magnetic resonance (NMR) spectra were obtained at 4.2 K and 1.3 K for a 6.5 nm $\varepsilon $-Co nanoparticle system. The powder sample was synthesized using an air-free high boiling point solution procedure and sealed in glass ampules without exposure to air. No NMR signal is observed at either 4.2 K or 1.3 K over the frequency range 150 MHz $<$= $\nu \quad <$= 250 MHz for H = 0; however, the application of a magnetic field 1.5 kOe $<$= H $<$= 7.5 kOe results in the appearance of a very strong echo. The NMR spectra are characterized by two components: (1) a distinct peak at 232 MHz whose intensity increases but does not shift with increasing field and (2) a very broad distribution between 150 MHz and 210 MHz whose intensity both increases and shifts to higher frequency with increasing field. There is no trace of the peaks which characterize either the multidomain or single domain fcc or hcp phases. Furthermore, a dramatic time evolution of the echo (observed at both 205 MHz and 232 MHz) is observed when the field is suddenly increased or decreased. An attempt to understand the spectra in the light of a core-shell picture for the $\varepsilon $-Co nanoparticles, superparamagnetism, and the interparticle and intraparticle interactions is made. [Preview Abstract] |
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C1.00012: Ultracold collisions of Li + Na atoms in variable magnetic field Marko Gacesa, Philippe Pellegrini, Robin C\^ot\'e We are studying collisional properties of $^{6,7}$Li + $^{23}$Na in the presence of a magnetic field at ultracold temperatures. Our main goal is an accurate characterization of Feshbach resonances using coupled-channel calculation. Feshbach resonances can be used for production of ultracold heteronuclear molecules in the low vibrational levels. Depending on the Li isotope, formed polar molecules are either fermionic or bosonic, which, in turn allows the study of degenerate Bose-Fermi mixtures with adjustable interactions, or the Bose-Einstein condensate of polar molecules. [Preview Abstract] |
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C1.00013: Magnetization and Resistivity Study of FCC $\gamma $-Fe Precipitates in Cu Joseph Budnick, William Hines, Robert Miller, Douglas Pease, David Perry, Poorani Shanthakumar Magnetization and resistivity measurements on two samples of Cu + 2.0 at.{\%} Fe are reported here. The first sample, prepared by annealing at 950 $^{o}$C for 2 days followed by rapid quenching, consists of a random solid solution of Fe in Cu. The magnetization follows the Curie-Weiss law 10 K $<$= T $<$= 300 K yielding an effective Fe moment of 1.9 $\mu _{B }$+/- 0.1 $\mu _{B}$ and Curie temperature of -- 2.0 K +/- 2.0 K. The second sample, prepared using the heat treatment above followed by a second annealing at 620 $^{o}$C for 2 hours, consists of face-centered-cubic $\gamma $-Fe precipitates in the Cu matrix. Evidence is given for an antiferromagnetic ordering occurring in this sample with a Neel temperature $\approx $ 55 K. The magnetization follows the Curie-Weiss law 100 K $<$= T $<$= 300 K yielding an effective Fe moment of 1.8 $\mu _{B}$ +/- 0.2 $\mu _{B}$ and a Curie temperature of -- 58 K +/--10 K. Resistivity measurements are also presented which assist in describing the structural nature and relevant magnetic interactions for these two samples. [Preview Abstract] |
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C1.00014: Molecular Probe for Electroweak Physics E.F. Deveney, R. Paolino, S.B. Cahn, D. Murphree, D.A. Rahmlow, D. DeMille, M.G. Kozlov Parity nonconservation (PNC) arises in atoms and molecules due to neutral current electroweak (EW) interactions. Our experiment is sensitive to nuclear spin-dependent (NSD)-PNC including electron-vector times nucleon-axial (VeAn) interaction due to $Z^0$exchange. VeAn terms are suppressed in the Standard Model (SM) making NSD radiative corrections from weak interactions within the nucleus, known as nuclear anapole moments, significant to the overall NSD-PNC signal. We report on our experiment using rotational hyperfine (HF) levels of well understood diatomic molecules to study NSD-PNC. Initially, one state, B, of a pair of opposite parity HF ground states, A and B, of the molecule is depleted. In the interaction region (IR), A and B are Zeeman shifted to near degeneracy in order to amplify perturbative state mixing caused by NSD-PNC interactions. Interference with Stark-induced mixing is revealed using laser-induced fluorescence from B emerging from the IR. This technique is applicable to a wide class of molecules and the variety of nuclei within so that VeAn and anapole contributions to NSD-PNC can be deciphered. This will yield new anapole results and constrain VeAn coupling constants to up and down quarks which are at present poorly characterized SM parameters. [Preview Abstract] |
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C1.00015: ABSTRACT WITHDRAWN |
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C1.00016: Isolated impurities in graphene Ling Yang, Nuno M.R. Peresp, Shan-Wen Tsai We study different types of isolated impurities in graphene. We employ a T-matrix formalism and find the exact electronic Green's functions. From the Green's functions, we calculate the local density of states and electron density distribution, getting exact analytical and numerical results for the electronic spectra and the Friedel oscillations around a localized impurity in a graphene lattice. We are studying the problem of an Anderson impurity in graphene. [Preview Abstract] |
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C1.00017: Calibration and Performance of the UConn-Yale-PTB-Weizmann-UCL-TUNL O-TPC Alexander Young, Moshe Gai, Tristan Kading, Mohammad Ahmed, Henry Weller, Volker Dangendorf, Kai Tittelmeier An Optical Readout Time Projection Chamber (O-TPC) will be used in an experiment at the HigS facility at Duke University for studying oxygen formation during stellar helium burning. The calibration of the O-TPC was carried out at the LNS at Avery Point prior to installation at TUNL in August 2007. A variety of pre-amplifers and high voltage power supplies were tested and under stable conditions an energy resolution as good as 3.5 {\%} was found in the charge signal. Charge and light gain curves were obtained using a Gd-148 source and a 75 mm diameter PMT placed at approximately 85 cm. These determined the optimal conditions for operating the O-TPC. Under the optimized conditions a CCD camera was used to capture images of single and double tracks of alpha particles from a Gd-148 source. The 3.18 MeV alpha particles yielded tracks containing only 40-50 photo electrons due to the small lens currently in use. [Preview Abstract] |
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C1.00018: Expectations of Science from Bilingual and Bicultural Students and Their Parents Carol Artacho Guerra This abstract has not been submitted yet. [Preview Abstract] |
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C1.00019: Engaging Students in a Physics Course through Use of Digital Video Capture and Analysis Zenobia Lojewska Use of digital video motion analysis as a teaching tool in an introductory physics course is presented. The focus of the presentation is the application of digital video technology in a \textit{Physics for Movement Science} course geared towards Physical Education, Athletic Training and Exercise Science majors. \textit{The Dickinson movie set} was found to be the most applicable for in-class activities, homework assignments, and projects. Some of the movie clips chosen for analysis are focused on human motion and sports. Additionally, students are starting to capture and analyze their own movie clips. [Preview Abstract] |
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C1.00020: Evaluating the Effectiveness of an Inquiry Curriculum using FCI and CLASS as Assessment Tools J. Russell Harkay The Force Concept Inventory [1] and Colorado Learning Attitudes about Science Survey [2] have been administered to students enrolled in the inquiry courses at Keene State College both before and after completion of courses using the Phenomenal Physics [3] curriculum as well as students in algebra physics. Results are used to interpret course effectiveness in the areas of retention of concepts, knowledge of basic physics, and student beliefs about physics and about learning physics. Information from CLASS is used to probe how student beliefs and attitudes are impacted by their educational experience. Data from both are used every semester to fine-tune the curriculum to ensure that it is as robust and effective as possible. Both of the instruments are well-established and validated using reliability studies and extensive statistical analysis of responses. Remarkable gains are consistently exhibited by students enrolled in the inquiry curriculum while those in the traditional algebra physics follow national norms. \newline \newline [1] D. Hestenes, Arizona State University, modified by E. Mosca and others\newline [2] W. K. Adams, N. S Podolefsky, N. D. Finkelstein, Univ. of Colorado \newline [3] J. R. Harkay, ``Phenomenal Physics-A Guided Inquiry Approach'' [Preview Abstract] |
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