Bulletin of the American Physical Society
2014 Annual Fall Meeting of the APS Ohio-Region Section
Volume 59, Number 13
Friday–Saturday, October 24–25, 2014; Portsmouth, Ohio
Session C1: Poster Session |
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Chair: Tim Hamilton, Shawnee State University Room: University Center Ballroom |
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C1.00001: The black hole mass in NGC 4258 from gas kinematics David DeColibus, Jason Pinkney NGC 4258 (or M106) is an important galaxy for the demographics of supermassive black holes (SMBH). Radio (VLBA) observations of its nuclear disk of water masers has allowed a very precise estimate of the mass of the central SMBH ($3.82\pm.01\times 10^7 M_\odot$), and the distance to the galaxy (7.2 Mpc). Hubble Space Telescope (HST) archival data allow the measurement of the BH mass in two additional, independent ways: stellar and gas kinematics, thus providing a crucial test of these more widely-used methods. Here we report on progress in a re-analysis of the archival data allowing gas kinematics. These data consist of HST long-slit spectroscopy from two programs, a total of 6 slit positions. We have fitted the H$\alpha$ + [NII] and [SII] lines in order to determine radial velocities and velocity dispersions as a function of distance from the BH. The gas only shows organized rotation out to $\sim$0.4$''$. The H$\alpha$ emission shows a broad-line (BL) component from the central AGN, and regions outside of the BL region show greater line widths than expected for a kinematically ``cold'' gas disk. We report initial results of modeling the kinematics as resulting from a thin, inclined disk of line-emitting gas orbiting under the influence of gravity only. [Preview Abstract] |
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C1.00002: Investigation of Use of Calcein Dye for the Purpose of Studying Membrane Fusion Matthew Tenorio, Laura Wessels Calcein dye was to be used as the detection fluorphor while fusing an enveloped virus particle with a liposome. Dye was encapsulated into the liposome and membrane dye was incorporated into a virion. Calcein dye is quenched and water soluble making it easy to encapsulate into liposomes. There are several lipid dyes that will incorporate directly into a lipid bilayer that are also quenched. The properties, specifically the osmolality, of calcein dye was studied in order to determine the feasibility of this dye for membrane fusion experiments that require different signals to distinguish between a hemifusion state and fusion pore creation. Attempts to balance the osmolality of calcien dye incluced using high salt and high sucrose buffers, as well as trying different lipid compositions. [Preview Abstract] |
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C1.00003: Solution Processed SERS Substrates Narayan Sharma Surface enhanced Raman spectroscopy (SERS) is a great analytical tool to obtain information on molecular composition. This technique has gained a reputation as one of the most sensitive spectroscopic methods available for the detection of a wide range of adsorbate molecules down to a single molecule detection limit. The most investigated metals for SERS substrates are gold (Au) and silver (Ag). Unfortunately, the fabrication of such devises poses a significant challenge due to an expensive deposition technology including, vapor deposition, electron-beam lithography, focused ion-beam lithography, and nano-transfer printing. Herein, we introduce a simple and low-cost approach to fabricate SERS substrates using roll-to-roll printing of matrix encapsulated gold nanoparticle arrays. The enhancement of Raman signals obtained using these materials was found to be comparable to commercially available SERS substrates. We expect that an on-going optimization of the film morphology should yield further enhancement of the demonstrated SERS architecture. [Preview Abstract] |
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C1.00004: Exciton Generation in Semiconductor Nanocrystals \textit{via} Near-Field Plasmon Coupling Amit Acharya We demonstrate that contrary to the classical electrodynamics standpoint, the phonon-driven decay of surface plasmons (SP) in small-diameter metal nanoparticles can be suppressed through efficient coupling of SP modes to excitons in the external environment. Such near-field energy exchange was manifested here through the generation of excitons in CdSe nanocrystals (NCs) that were coupled to 5-nm Au nanoparticles. A unique signature of the energy transfer process was observed in photoexcitation measurements that unambiguously correlate the increase in the CdSe exciton population with the excitation of SP modes in Au. To enhance the efficiency of plasmon to exciton energy transfer, the backwards flow of photoinduced charges into metal was suppressed by embedding Au and CdSe nanoparticles into insulating matrices. The observed generation of semiconductor excitons through near-field energy transfer from small-diameter Au nanoparticles presents an excellent opportunity for converting the energy of strongly confined (near field) radiation into long-lived excitations, which could be utilized by photovoltaic or photocatalytic applications. [Preview Abstract] |
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C1.00005: Shreedhar Raj Kandel, Zhoufeng Jiang, Simeen Khan, Sailendra Chiluwal, Liangfeng Sun Shreedhar Kandel, Zhoufeng Jiang, Simeen Khan, Sailendra Chiluwal, Liangfeng Sun Colloidal nanostructured materials are promising for applications in optoelectronic devices. Beyond size-tuning as in quantum dots, shape-tuning of the material at the nanometer scale also results in novel optical and electronic properties. For instance, the multiple exciton generation (which is critical for high-efficient photovoltaic devices) is significantly enhanced in one-dimensional PbSe nanorods as contrast to the zero-dimensional quantum dots. The applications demand high quality and structure-well-controlled materials, which are still greatly underdeveloped. We report a method of catalyst-free, one-pot synthesis of colloidal PbSe nanorods with a well-controlled structure. This method is based on a typical synthesis of PbSe quantum-dot, but a chloroalkane cosolvent is added during the synthesis to drive the one-dimensional growth of the crystal. The synthesized nanorods have a uniform diameter of 6 nm and a length of 40 to 50 nm. Photoluminescence from these nanorods shows a peak at around 2000 nm, exhibiting a strong quantum confinement on the excitons in the nanorods. [Preview Abstract] |
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C1.00006: Synchronization of Huygens' clocks: An elementary treatment Ulrich Zurcher, Laura Karle, Andrew Slifkin We discuss a Huygens' model in the ``language'' for someone with a background in algebra-based physics. The system consists of two pendulums mounted on a cart. We show how the movement of the cart removes the degeneracy of the two bobs, and use the conservation of linear momentum to describe the necessary escapement mechanism. We present results from an Excel calculation for the decay of the symmetric and antisymmetric modes. [Preview Abstract] |
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C1.00007: An introductory physics laboratory that uses magnetic interactions to aid student understanding of the Coulomb and gravitational interactions Anthony Roy Day Introductory physics students often have difficulty interpreting energy curves and force curves for the 1/r potentials of the Coulomb and the gravitational interaction. It has not been possible to give students direct experience with these potentials in the laboratory but the with the ready availability of powerful rare earth magnets laboratory studies of a dynamical system where the force increases rapidly with decreasing separation and tends to zero at large separation, qualitatively similar to the Coulomb and the gravitational interaction, are now possible. We present a series of experiments that allow students to infer the existence of magnetic potential energy from changes in the kinetic energy of the system, plot the potential energy as a function of separation, and confirm the relationship between the gradient of the magnetic potential energy and the magnetic force. Additional activities allow students to include the effect of kinetic friction and velocity dependent dissipative forces. [Preview Abstract] |
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C1.00008: Using CFAs and observations to measure growth in inquiry-based middle school science teaching Gordon Aubrecht, Bill Schmitt, Jennifer Esswein, Jessica Creamer We work with inservice middle-school and high-school teachers in two high-needs urban school districts in Ohio. We estimate that new teachers who attend the summer institutes received at least 188 hours of professional development involvement. We expect to see changes in teacher practice as a result. We first look at publicly available information to observe changes. In addition, we analyzed common formative assessments (CFAs) administered to middle and high school students across a broad range of science subjects including biology, geology, physics, etc. For the analysis of CFAs, we established a rubric with four defining parameters: reasoning, clarity, analysis, and correctness. Teachers worked with PER faculty to improve their teaching methodology and CFAs were used to analyze and quantify changes in student learning across the four rubric parameters that resulted from the intervention. We also explain our attempt to quantify changes in teacher practice by using staff observations and self-reported measures such as RTOP and other self-assessments to quantify changes in teachers and teaching practice. [Preview Abstract] |
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C1.00009: Dealing with more climate myths Gordon Aubrecht Many scientists understand that climate change has a sociopolitical aspect, but some scientists are unwilling to address the issue lest they be perceived as political themselves. Nevertheless, when we scientists find climate myths, I think it is our duty as scientists to be willing to debunk them. A poster at YSU on this topic was well received (Myths 1---7). This poster exhibits some more climate myths and contrasts them with the science. [Preview Abstract] |
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C1.00010: Preliminary study of relaxation mechanisms for dusty plasma clusters Andrew Kurtz, William Theisen, Terrance Sheridan Dusty plasma particles in a confining potential well regularly form into single layer plasma clusters under certain experimental conditions. The time evolution of these particles from random thermal motion to regular lattice structures is being investigated. The strongly coupled particles shift and rotate in a two-dimensional plane in order to achieve an equilibrium position. Each slip stick adjustment in the structure results in less overall systemic energy. In the process of shifting, changes in the height and width of the clusters were found and are seen to be inversely proportional. [Preview Abstract] |
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C1.00011: Some results on metastable states of two-dimensional dusty plasma Austin R. Howell, T.E. Sheridan In dusty (complex) plasma, charged microscopic dust particles are confined inside a regular electron-ion plasma. Small clusters of identical dust particles can be confined to two dimensions at the edge of the plasma sheath, and will take the overall shape of the confining potential well. For strongly-coupled systems, clusters with more than a few particles may be trapped in metastable arrangements due to potential barriers that block rearrangement. We have experimentally characterized the arrangements of clusters with $n = 14$ to 30 dust particles confined in a two-dimensional biharmonic potential well. Ensembles of particle arrangements are created by applying a step increase to the plasma density, which briefly melts the cluster to create a new arrangement state. For $n = 14$ dust particles we find a single arrangement state without interior particles. When $n$ is increased to 15, we observe a number of different arrangement states with interior particles. Most of these states must be metastable. We suggest that particles in the interior of the cluster cannot easily move, thereby preventing rearrangement into the minimum energy state. [Preview Abstract] |
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C1.00012: Effect of ion collisions on the plasma presheath T.E. Sheridan We investigate solutions of a collisional Tonks-Langmuir model for a bounded plasma discharge using a particle-in-cell simulation. This is a one-dimensional model where ions are created uniformly throughout the volume and experience constant mean-free-time collisions. Results for the time-averaged potential as a function of collisionality will be presented. [Preview Abstract] |
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C1.00013: Plasma sheath measurement using two dust particles Nicholas R. Weiner, T.E. Sheridan Plasma is a gas of charged particles that interact through electromagnetic forces. Because of the long-range particle-particle interaction, plasma displays collective behavior such as the sheath. The plasma sheath is the boundary layer that separates plasma from a material wall. The large sheath electric field confines high-speed electrons and accelerates positive ions out of the plasma. Charged, microscopic dust particles may float near the sheath-plasma interface. As a consequence, dust particle motions can be used to characterize the sheath. A conducting rectangular confining well was placed on a negative electrode, and two dust particles were trapped in resulting plasma sheath. Natural frequencies of the oscillation modes of the two-particle clusters have been measured, allowing us to determine the ellipticity of the potential energy well parallel to the electrode, the dust particle charge, and the plasma Debye length. [Preview Abstract] |
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