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Articles 1201 - 1230 of 2945

Full-Text Articles in Astrophysics and Astronomy

Photoelectrochemical Cell Including Ga(SbX)N1-X Semiconductor Electrode, Madhu Menon, Michael Sheetz, Mahendra Kumar Sunkara, Chandrashekhar Pendyala, Swathi Sunkara, Jacek B. Jasinksi Sep 2017

Photoelectrochemical Cell Including Ga(SbX)N1-X Semiconductor Electrode, Madhu Menon, Michael Sheetz, Mahendra Kumar Sunkara, Chandrashekhar Pendyala, Swathi Sunkara, Jacek B. Jasinksi

Physics and Astronomy Faculty Patents

The composition of matter comprising Ga(Sbx)N1−x where x=0.01 to 0.06 is characterized by a band gap between 2.4 and 1.7 eV. A semiconductor device includes a semiconductor layer of that composition. A photoelectric cell includes that semiconductor device.

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Holographic Entanglement Entropy Of A 1 + 1 Dimensional P-Wave Superconductor, Sumit R. Das, Mitsutoshi Fujita, Bom Soo Kim Sep 2017

Holographic Entanglement Entropy Of A 1 + 1 Dimensional P-Wave Superconductor, Sumit R. Das, Mitsutoshi Fujita, Bom Soo Kim

Physics and Astronomy Faculty Publications

We examine the behavior of entanglement entropy S A EE of a subsystem A in a fully backreacted holographic model of a 1 + 1 dimensional p wave superconductor across the phase transition. For a given temperature, the system goes to a superconducting phase beyond a critical value of the charge density. The entanglement entropy, considered as a function of the charge density at a given temperature, has a cusp at the critical point. In addition, we find that there are three different behaviors in the condensed phase, depending on the subsystem size. For a subsystem size l smaller than …

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Zr-Doped Tio2 As A Thermostabilizer In Plasmon-Enhanced Dye-Sensitized Solar Cells, Anastasia Pasche, Bernd Grohe, Silvia Mittler, Paul A. Charpentier Sep 2017

Zr-Doped Tio2 As A Thermostabilizer In Plasmon-Enhanced Dye-Sensitized Solar Cells, Anastasia Pasche, Bernd Grohe, Silvia Mittler, Paul A. Charpentier

Physics and Astronomy Publications

Harvesting solar energy is a promising solution toward meeting the world’s evergrowing energy demand. Dye-sensitized solar cells (DSSCs) are hybrid organic–inorganic solar cells with tremendous potential for commercial application, but they are plagued by in efficiency due to their poor sunlight absorption. Plasmonic silver nanoparticles (AgNPs) have been shown to enhance the absorptive properties of DSSCs, but their plasmonic resonance can cause thermal damage resulting in cell deterioration. Hence, the influence of Zr-doped TiO2 on the efficiency of plasmon-enhanced DSSCs was studied, showing that 5 mol.% Zr-doping of the photoactive TiO2 material can improve the photovoltaic performance of DSSCs by …

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Photonic Band Structure Of Diamond Colloidal Crystals In A Cholesteric Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston Sep 2017

Photonic Band Structure Of Diamond Colloidal Crystals In A Cholesteric Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston

Physics and Astronomy Publications

In this paper, we demonstrate the presence of a photonic band gap for a diamond lattice structure made of particles with normal anchoring inside a cholesteric liquid crystal. As is typical for liquid crystals (LCs), there is considerable contrast between the dielectric constant parallel ε∥ and perpendicular ε⊥ to the director, with ε∥/ε⊥∼4 here. It is shown that the size of the photonic band gap is directly related to the size of colloidal particles and the contrast between the dielectric constant in the particles and the extreme values of ε in the LC medium (one needs either ε in the …

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Vacuum Birefringence, The Photon Anomalous Magnetic Moment And The Neutron Star Rx J1856.5−3754, Sree Ram Valluri, J.W. Mielniczuk, Farrukh Chishtie, D. Lamm, S. Auddy Aug 2017

Vacuum Birefringence, The Photon Anomalous Magnetic Moment And The Neutron Star Rx J1856.5−3754, Sree Ram Valluri, J.W. Mielniczuk, Farrukh Chishtie, D. Lamm, S. Auddy

Physics and Astronomy Publications

We analyse the spectrum of the Hamiltonian of a photon propagating in a strong magnetic field B ∼ Bcr, where Bcr=m2e≃4.4×1013" role="presentation">Bcr=m2e≃4.4×1013 G is the Schwinger critical field. We show that the anomalous magnetic moment of a photon in the one-loop approximation is a non-decreasing function of the magnetic field B in the range 0 ≤ B ≤ 30 Bcr. We provide a numerical representation of the expression for the anomalous magnetic moment in terms of special functions. We find that the anomalous magnetic moment μγ of a photon for B = 30 B …

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Entanglement Entropy With Background Gauge Fields, Bom Soo Kim Aug 2017

Entanglement Entropy With Background Gauge Fields, Bom Soo Kim

Physics and Astronomy Faculty Publications

We study the entanglement entropy, the Rényi entropy, and the mutual (Rényi) information of Dirac fermions on a 2 dimensional torus in the presence of constant gauge fields. We derive their general formulas using the equivalence between twisted boundary conditions and the background gauge fields. Novel and interesting physical consequences have been presented in arXiv:1705.01859. Here we provide detailed computations of the entropies and mutual information in a low temperature limit, a large radius limit, and a high temperature limit. The high temperature limit reveals rather different physical properties compared to those of the low temperature one: there exist …

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Energy Dependence Of J/Ψ Production In Au + Au Collisions At √SNn = 39, 62.4 And 200 Gev, L. Adamczyk, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, J. D. Brandenburg, A. V. Brandin, D. Brown, Renee H. Fatemi, Suvarna Ramachandran Aug 2017

Energy Dependence Of J/Ψ Production In Au + Au Collisions At √SNn = 39, 62.4 And 200 Gev, L. Adamczyk, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, J. D. Brandenburg, A. V. Brandin, D. Brown, Renee H. Fatemi, Suvarna Ramachandran

Physics and Astronomy Faculty Publications

The inclusive J/ψ transverse momentum spectra and nuclear modification factors are reported at midrapidity (|y| < 1.0) in Au + Au collisions at √sNN = 39, 62.4 and 200 GeV taken by the STAR experiment. A suppression of J/ψ production, with respect to the production in p + p scaled by the number of binary nucleon–nucleon collisions, is observed in central Au + Au collisions at these three energies. No significant energy dependence of nuclear modification factors is found within uncertainties. The measured nuclear modification factors can be described by model calculations that take into account both suppression of direct J/ψ production due to …

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The Sdss-Iv Manga Sample: Design, Optimization, And Usage Considerations, David A. Wake, Kevin Bundy, Aleksandar M. Diamond-Stanic, Renbin Yan, Michael R. Blanton, Matthew A. Bershady, José R. Sánchez-Gallego, Niv Drory, Amy Jones, Guinevere Kauffmann, David R. Law, Cheng Li, Nicholas Macdonald, Karen Masters, Daniel Thomas, Jeremy Tinker, Anne-Marie Weijmans, Joel R. Brownstein Aug 2017

The Sdss-Iv Manga Sample: Design, Optimization, And Usage Considerations, David A. Wake, Kevin Bundy, Aleksandar M. Diamond-Stanic, Renbin Yan, Michael R. Blanton, Matthew A. Bershady, José R. Sánchez-Gallego, Niv Drory, Amy Jones, Guinevere Kauffmann, David R. Law, Cheng Li, Nicholas Macdonald, Karen Masters, Daniel Thomas, Jeremy Tinker, Anne-Marie Weijmans, Joel R. Brownstein

Physics and Astronomy Faculty Publications

We describe the sample design for the SDSS-IV MaNGA survey and present the final properties of the main samples along with important considerations for using these samples for science. Our target selection criteria were developed while simultaneously optimizing the size distribution of the MaNGA integral field units (IFUs), the IFU allocation strategy, and the target density to produce a survey defined in terms of maximizing signal-to-noise ratio, spatial resolution, and sample size. Our selection strategy makes use of redshift limits that only depend on i-band absolute magnitude (Mi ), or, for a small subset of our sample, …

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A Vision For Canadian Space Exploration, Ilaria Caiazzo, Sarah C. Gallagher, Jeremy Heyl Aug 2017

A Vision For Canadian Space Exploration, Ilaria Caiazzo, Sarah C. Gallagher, Jeremy Heyl

Physics and Astronomy Publications

We propose a sustained and balanced program in space exploration to fuel innovation in the space sector, support Canada's world-leading space researchers, inspire the next generation of scientists and innovators, and create thousands of highly skilled, well-paying jobs for Canadians. During the next decade we recommend a total investment of approximately $1B, increasing to $1.3B in each decade that follows, including a regular flagship mission that Canada would lead and a constellation of smaller missions, either led by Canada or in collaboration with international partners.

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Accelerator Based Fusion Reactor, Keh-Fei Liu, Alexander Wu Chao Aug 2017

Accelerator Based Fusion Reactor, Keh-Fei Liu, Alexander Wu Chao

Physics and Astronomy Faculty Publications

A feasibility study of fusion reactors based on accelerators is carried out. We consider a novel scheme where a beam from the accelerator hits the target plasma on the resonance of the fusion reaction and establish characteristic criteria for a workable reactor. We consider the reactions d+t→n+α, d+3He→p+α and p+11B→3α in this study. The critical temperature of the plasma is determined from overcoming the stopping power of the beam with the fusion energy gain. The needed plasma lifetime is determined …

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The Formation And Dynamics Of Clouds In The Environment Of Active Galactic Nuclei, Timothy Waters Aug 2017

The Formation And Dynamics Of Clouds In The Environment Of Active Galactic Nuclei, Timothy Waters

UNLV Theses, Dissertations, Professional Papers, and Capstones

Active galactic nuclei (AGN) are among the most luminous objects in the universe and are known to be powered by accretion onto supermassive black holes in the centers of galaxies. AGN clouds are prominent components of successful models that attempt to unify the diversity of AGN. These clouds are often hypothesized to be the source of the broad and narrow line emission features seen in AGN spectra. Moreover, the high column densities of gas needed to account for broad absorption lines has been attributed to the same population of clouds, while the motion of AGN clouds has been invoked to …

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The Validity Of 21 Cm Spin Temperature As A Kinetic Temperature Indicator In Atomic And Molecular Gas, Gargi Shaw, Gary J. Ferland, I. Hubeny Jul 2017

The Validity Of 21 Cm Spin Temperature As A Kinetic Temperature Indicator In Atomic And Molecular Gas, Gargi Shaw, Gary J. Ferland, I. Hubeny

Physics and Astronomy Faculty Publications

The gas kinetic temperature (TK) of various interstellar environments is often inferred from observations that can deduce level populations of atoms, ions, or molecules using spectral line observations; H I 21 cm is perhaps the most widely used, and has a long history. Usually the H I 21 cm line is assumed to be in thermal equilibrium and the populations are given by the Boltzmann distribution. A variety of processes, many involving Lyα, can affect the 21 cm line. Here we show how this is treated in the spectral simulation code Cloudy, and present numerical …

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Direct Virtual Photon Production In Au+Au Collisions At √SNn = 200 Gev, L. Adamczyk, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, J. D. Brandenburg, A. V. Brandin, D. Brown, Renee H. Fatemi, Suvarna Ramachandran Jul 2017

Direct Virtual Photon Production In Au+Au Collisions At √SNn = 200 Gev, L. Adamczyk, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, J. D. Brandenburg, A. V. Brandin, D. Brown, Renee H. Fatemi, Suvarna Ramachandran

Physics and Astronomy Faculty Publications

We report the direct virtual photon invariant yields in the transverse momentum ranges 1 < pT < 3 GeV/c and 5 < pT < 10 GeV/c at mid-rapidity derived from the dielectron invariant mass continuum region 0.10 < Mee < 0.28 GeV/c2 for 0–80% minimum-bias Au+Au collisions at √sNN = 200 GeV. A clear excess in the invariant yield compared to the nuclear overlap function TAA scaled p + p reference is observed in the pT range 1 < pT < 3 GeV/c. For pT > 6 GeV/c the production follows TAA scaling. Model calculations with contributions from thermal radiation …

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Ionic Thermoelectric Paper, Fei Jiao, Ali Naderi, Dan Zhao, Joshua Schlueter, Maryam Shahi, Jonas Sundström, Hjalmar Granberg, Jesper Edberg, Ujwala Ail, Joseph W. Brill, Tom Lindström, Magnus Berggren, Xavier Crispin Jun 2017

Ionic Thermoelectric Paper, Fei Jiao, Ali Naderi, Dan Zhao, Joshua Schlueter, Maryam Shahi, Jonas Sundström, Hjalmar Granberg, Jesper Edberg, Ujwala Ail, Joseph W. Brill, Tom Lindström, Magnus Berggren, Xavier Crispin

Physics and Astronomy Faculty Publications

Ionic thermoelectric materials, for example, polyelectrolytes such as polystyrene sulfonate sodium (PSSNa), constitute a new class of materials which are attracting interest because of their large Seebeck coefficient and the possibility that they could be used in ionic thermoelectric SCs (ITESCs) and field effect transistors. However, pure polyelectrolyte membranes are not robust or flexible. In this paper, the preparation of ionic thermoelectric paper using a simple, scalable and cost-effective method is described. After a composite was fabricated with nanofibrillated cellulose (NFC), the resulting NFC–PSSNa paper is flexible and mechanically robust, which is desirable if it is to be used in …

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Sloan Digital Sky Survey Iv: Mapping The Milky Way, Nearby Galaxies, And The Distant Universe, Michael R. Blanton, Matthew A. Bershady, Bela Abolfathi, Franco D. Albareti, Carlos Allende Prieto, Andres Almeida, Javier Alonso-García, Friedrich Anders, Scott F. Anderson, Brett Andrews, Erik Aquino-Ortíz, Alfonso Aragón-Salamanca, Maria Argudo-Fernández, Eric Armengaud, Eric Aubourg, Vladimir Avila-Reese, Carles Badenes, Stephen Bailey, Kathleen A. Barger, Jorge Barrera-Ballesteros, Curtis Bartosz, Dominic Bates, Falk Baumgarten, Julian Bautista, Rachael Beaton, Francesco Belfiore, Chad F. Bender, Andreas A. Berlind, Mariangela Bernardi, Florian Beutler, Renbin Yan, Daniel Lazarz, Kai Zhang Jun 2017

Sloan Digital Sky Survey Iv: Mapping The Milky Way, Nearby Galaxies, And The Distant Universe, Michael R. Blanton, Matthew A. Bershady, Bela Abolfathi, Franco D. Albareti, Carlos Allende Prieto, Andres Almeida, Javier Alonso-García, Friedrich Anders, Scott F. Anderson, Brett Andrews, Erik Aquino-Ortíz, Alfonso Aragón-Salamanca, Maria Argudo-Fernández, Eric Armengaud, Eric Aubourg, Vladimir Avila-Reese, Carles Badenes, Stephen Bailey, Kathleen A. Barger, Jorge Barrera-Ballesteros, Curtis Bartosz, Dominic Bates, Falk Baumgarten, Julian Bautista, Rachael Beaton, Francesco Belfiore, Chad F. Bender, Andreas A. Berlind, Mariangela Bernardi, Florian Beutler, Renbin Yan, Daniel Lazarz, Kai Zhang

Physics and Astronomy Faculty Publications

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median z ~ 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between z ~ 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, …

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Dissipationless Hall Current In Dense Quark Matter In A Magnetic Field, Efrain J. Ferrer, Vivian De La Incera Jun 2017

Dissipationless Hall Current In Dense Quark Matter In A Magnetic Field, Efrain J. Ferrer, Vivian De La Incera

Physics & Astronomy Faculty Publications

We show the realization of axion electrodynamics within the Dual Chiral Density Wave phase of dense quark matter in the presence of a magnetic field. The system exhibits an anomalous dissipationless Hall current perpendicular to the magnetic field and an anomalous electric charge density. Connection to topological insulators and 3D optical lattices, as well as possible implications for heavy-ion collisions and neutron stars are outlined.

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Searching For Signals Of Dark Matter Decay, Gardner R. Marshall, William Hester Jun 2017

Searching For Signals Of Dark Matter Decay, Gardner R. Marshall, William Hester

Journal of the South Carolina Academy of Science

Dark matter is believed to make up approximately eighty-three percent of the matter in the universe. Despite its apparent abundance, it has not yet been directly detected, and it is not known what types of particles it is composed of. Efforts to understand what dark matter is made of and how it fits into the Standard Model of particle physics is currently an important and active area of research. In this paper we investigate a method of studying dark matter indirectly by using terrestrial neutrino telescopes to search for signs of dark matter decay. In particular, we study leptonically decaying …

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Atomic Data Revisions For Transitions Relevant To Observations Of Interstellar, Circumgalactic, And Intergalactic Matter, Frances H. Cashman, Varsha P. Kulkarni, Romas Kisielius, Gary J. Ferland, Pavel Bogdanovich May 2017

Atomic Data Revisions For Transitions Relevant To Observations Of Interstellar, Circumgalactic, And Intergalactic Matter, Frances H. Cashman, Varsha P. Kulkarni, Romas Kisielius, Gary J. Ferland, Pavel Bogdanovich

Physics and Astronomy Faculty Publications

Measurements of element abundances in galaxies from astrophysical spectroscopy depend sensitively on the atomic data used. With the goal of making the latest atomic data accessible to the community, we present a compilation of selected atomic data for resonant absorption lines at wavelengths longward of 911.753 Å (the H I Lyman limit), for key heavy elements (heavier than atomic number 5) of astrophysical interest. In particular, we focus on the transitions of those ions that have been observed in the Milky Way interstellar medium (ISM), the circumgalactic medium (CGM) of the Milky Way and/or other galaxies, and the intergalactic medium …

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Emission Line Ratios Of Fe Iii As Astrophysical Plasma Diagnostics, Sibasish Laha, Niall B. Tyndall, Francis P. Keenan, Connor P. Ballance, Catherine A. Ramsbottom, Gary J. Ferland, Alan Hibbert May 2017

Emission Line Ratios Of Fe Iii As Astrophysical Plasma Diagnostics, Sibasish Laha, Niall B. Tyndall, Francis P. Keenan, Connor P. Ballance, Catherine A. Ramsbottom, Gary J. Ferland, Alan Hibbert

Physics and Astronomy Faculty Publications

Recent, state-of-the-art calculations of A-values and electron impact excitation rates for Fe III are used in conjunction with the Cloudy modeling code to derive emission-line intensity ratios for optical transitions among the fine-structure levels of the 3d6 configuration. A comparison of these with high-resolution, high signal-to-noise spectra of gaseous nebulae reveals that previous discrepancies found between theory and observation are not fully resolved by the latest atomic data. Blending is ruled out as a likely cause of the discrepancies, because temperature- and density-independent ratios (arising from lines with common upper levels) match well with those predicted by theory. For …

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Universal Disorder In Organic Semiconductors Due To Fluctuations In Space Charge, Tzucheng Wu May 2017

Universal Disorder In Organic Semiconductors Due To Fluctuations In Space Charge, Tzucheng Wu

Physics & Astronomy ETDs

This thesis concerns the study of charge transport in organic semiconductors. These materials are widely used as thin-film photoconductors in copiers and laser printers, and for their electroluminescent properties in organic light-emitting diodes. Much contemporary research is directed towards improving the efficiency of organic photovoltaic devices, which is limited to a large extent by the spatial and energetic disorder that hinders the charge mobility. One contribution to energetic disorder arises from the strong Coulomb interactions between injected charges with one another, but to date this has been largely ignored. We present a mean-field model for the effect of mutual interactions …

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Almost Dark Galaxies: The Search For Optical Counterparts, Quinton O. Singer May 2017

Almost Dark Galaxies: The Search For Optical Counterparts, Quinton O. Singer

Macalester Journal of Physics and Astronomy

Presented in this paper are results from neutral hydrogen (HI) imaging and analysis of the "Almost Dark" galaxies AGC 219533, AGC 227982, and AGC 268363 using new, higher resolution observations from the Very Large Array (VLA). Selected from the ALFALFA survey, "Almost Dark" galaxies possess significant HI reservoirs but, when the HI data is compared to survey-depth ground-based optical imaging, their optical stellar counterparts have extremely low surface brightnesses. AGC 219533 is one such object. The other two sources, AGC 227982 and AGC 26833, were candidate dark galaxies, as no stellar counterpart was identified in initial ALFALFA optical matching, and …

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Intervalley Scattering Rates In Tellurium Observed Via Time-Resolved Terahertz Spectroscopy, Joshua R. Rollag May 2017

Intervalley Scattering Rates In Tellurium Observed Via Time-Resolved Terahertz Spectroscopy, Joshua R. Rollag

Macalester Journal of Physics and Astronomy

We conducted time-resolved terahertz spectroscopy measurements on the elemental semiconductor tellurium. Pump-probe measurements were used to find the conductivity as a function of time in single crystalline tellurium samples. It was found that the excitation dynamics in tellurium changes for photon energies of 1.03 eV and 1.55 eV. The change in these excitation dynamics was attributed to intervalley scattering effects. A model using intervalley scattering and Auger recombination was fit to the data, giving a value of 2.28 ps for the intervalley scattering time constant in tellurium.

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Transient Photoconductivity Of A Thermoelectric Nanomaterial Pedot:Pss With Tecu Nanowires, Gunnar J. Footh, Michaela S. Koller, James Heyman May 2017

Transient Photoconductivity Of A Thermoelectric Nanomaterial Pedot:Pss With Tecu Nanowires, Gunnar J. Footh, Michaela S. Koller, James Heyman

Macalester Journal of Physics and Astronomy

Thermoelectric materials are able to transfer heat energy into electrical energy. They have many important applications, and an increased understanding of them would allow the scientific community to develop more efficient thermoelectrics. We provide here transient photoconductivity measurements of a thermoelectric nanomaterial - PEDOT:PSS with TeCu nanowires on quartz substrate. Increased copper concentration in nanowires decreases photoconductivity in both transmission and reflectance measurements. Fermi blocking provides a reasonable explanation for this decrease in photoconductivity, which occurs when total nanowire mass approaches ~15% copper concentration.

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A Direct Comparison Of Lyman-Alpha And Neutral Hydrogen Morphologies, Kathleen Fitzgibbon, John M. Cannon May 2017

A Direct Comparison Of Lyman-Alpha And Neutral Hydrogen Morphologies, Kathleen Fitzgibbon, John M. Cannon

Macalester Journal of Physics and Astronomy

The Lyman-Alpha Reference Sample (LARS) and its extension (eLARS) represent an exhaustive campaign to reverse-engineer galaxies. The main goal is to understand how \lya radiation is transported within galaxies: what fraction of it escapes, and what physical properties affect the \lya morphology and radiative transport (e.g., dust and gas content, metallicity, kinematics, properties of the producing and underlying stellar populations). Two galaxies from the sample, LARS02 and LARS09, were observed using the B and C configurations of the Very Large Array to examine the neutral hydrogen emission, which can be used to determine a galaxy's neutral hydrogen (HI) structure and …

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Beyond 3 Au From The Sun: The Hypervolatiles Ch4, C2h6, And Co In The Distant Comet C/2006 W3 (Christensen), Boncho Bonev, Geronimo Villanueva, Michael Disanti, Hermann Boehnhardt, Manuela Lippi, Erika Gibb, Lucas Paganini, Michael Mumma May 2017

Beyond 3 Au From The Sun: The Hypervolatiles Ch4, C2h6, And Co In The Distant Comet C/2006 W3 (Christensen), Boncho Bonev, Geronimo Villanueva, Michael Disanti, Hermann Boehnhardt, Manuela Lippi, Erika Gibb, Lucas Paganini, Michael Mumma

Physics Faculty Works

Comet C/2006 W3 (Christensen) remained outside a heliocentric distance (R h) of 3.1 au throughout its apparition, but it presented an exceptional opportunity to directly sense a suite of molecules released from its nucleus. The Cryogenic Infrared Echelle Spectrograph at ESO-VLT detected infrared emissions from the three "hypervolatiles" (CO, CH4, and C2H6) that have the lowest sublimation temperatures among species that are commonly studied in comets by remote sensing. Even at R h = 3.25 au, the production rate of each molecule exceeded those measured for the same species in a number of other comets, although these comets were observed …

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Swift Monitoring Of Ngc 4151: Evidence For A Second X-Ray/Uv Reprocessing, R. Edelson, J. Gelbord, E. Cackett, S. Connolly, C. Done, M. Fausnaugh, E. Gardner, N. Gehrels, M. Goad, K. Horne, I. Mchardy, B. M. Peterson, S. Vaughan, M. Vestergaard, A. Breeveld, A. J. Barth, M. Bentz, M. Bottorff, W. N. Brandt, S. M. Crawford, E. Dalla Bontà, D. Emmanoulopoulos, P. Evans, R. Figuera Jaimes, A. V. Filippenko, Gary J. Ferland, D. Grupe, M. Joner, J. Kennea, K. T. Korista May 2017

Swift Monitoring Of Ngc 4151: Evidence For A Second X-Ray/Uv Reprocessing, R. Edelson, J. Gelbord, E. Cackett, S. Connolly, C. Done, M. Fausnaugh, E. Gardner, N. Gehrels, M. Goad, K. Horne, I. Mchardy, B. M. Peterson, S. Vaughan, M. Vestergaard, A. Breeveld, A. J. Barth, M. Bentz, M. Bottorff, W. N. Brandt, S. M. Crawford, E. Dalla Bontà, D. Emmanoulopoulos, P. Evans, R. Figuera Jaimes, A. V. Filippenko, Gary J. Ferland, D. Grupe, M. Joner, J. Kennea, K. T. Korista

Physics and Astronomy Faculty Publications

Swift monitoring of NGC 4151 with an ~6 hr sampling over a total of 69 days in early 2016 is used to construct light curves covering five bands in the X-rays (0.3–50 keV) and six in the ultraviolet (UV)/optical (1900–5500 Å). The three hardest X-ray bands (> 2.5 keV) are all strongly correlated with no measurable interband lag, while the two softer bands show lower variability and weaker correlations. The UV/optical bands are significantly correlated with the X-rays, lagging ~3–4 days behind the hard X-rays. The variability within the UV/optical bands is also strongly correlated, with the UV appearing to …

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Heterogeneous Colloidal Particles Immersed In A Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston May 2017

Heterogeneous Colloidal Particles Immersed In A Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston

Physics and Astronomy Publications

In this paper, we explore anisotropic interactions between particles with heterogeneous boundary conditions inside both nematic and cholesteric liquid crystals. The results show that when particles are put at different distances and angles with respect to each other, new types of defect structures are produced, depending on the relative distances and directions. In a cholesteric liquid crystal, the value of the pitch affects the defect structures and induced forces. Moreover, it was observed that it is energetically favorable for the particles to remain in a plane parallel to the far-field director in a nematic liquid crystal, while for particles immersed …

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What Are The Low-Q And Large-X Boundaries Of Collinear Qcd Factorization Theorems?, E. Moffat, W. Melnitchouk, T. C. Rogers, N. Sato May 2017

What Are The Low-Q And Large-X Boundaries Of Collinear Qcd Factorization Theorems?, E. Moffat, W. Melnitchouk, T. C. Rogers, N. Sato

Physics Faculty Publications

Familiar factorized descriptions of classic QCD processes such as deeply inelastic scattering (DIS) apply in the limit of very large hard scales, much larger than nonperturbative mass scales and other nonperturbative physical properties like intrinsic transverse momentum. Since many interesting DIS studies occur at kinematic regions where the hard scale, Q ∼ 1-2 GeV, is not very much greater than the hadron masses involved, and the Bjorken scaling variable xbj is large, xbj ≳ 0.5, it is important to examine the boundaries of the most basic factorization assumptions and assess whether improved starting points are needed. Using an …

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Target And Double Spin Asymmetries Of Deeply Virtual Π0 Production With A Longitudinally Polarized Proton Target And Clas, A. Kim, H. Avakian, V. Burkert, K. Joo, W. Kim, K. P. Adhikari, Z. Akbar, S. Anefalos Pereira, R. A. Badui, M. Battaglieri, S. Bültmann, A. Klein, S E. Kuhn, Y. Prok, B. Torayev, L. B. Weinstein, J. Zhang May 2017

Target And Double Spin Asymmetries Of Deeply Virtual Π0 Production With A Longitudinally Polarized Proton Target And Clas, A. Kim, H. Avakian, V. Burkert, K. Joo, W. Kim, K. P. Adhikari, Z. Akbar, S. Anefalos Pereira, R. A. Badui, M. Battaglieri, S. Bültmann, A. Klein, S E. Kuhn, Y. Prok, B. Torayev, L. B. Weinstein, J. Zhang

Physics Faculty Publications

The target and double spin asymmetries of the exclusive pseudoscalar channel e→p→→epπ0 were measured for the first time in the deep-inelastic regime using a longitudinally polarized 5.9 GeV electron beam and a longitudinally polarized proton target at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS). The data were collected over a large kinematic phase space and divided into 110 four-dimensional bins of Q2, xB, −t and ϕ. Large values of asymmetry moments clearly indicate a substantial contribution to the polarized structure functions from transverse virtual photon amplitudes. The interpretation of experimental data in terms of …

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Epoch, Latitude And Star Positions From Hipparchus’ Commentary, Irene Vargas-Salazar May 2017

Epoch, Latitude And Star Positions From Hipparchus’ Commentary, Irene Vargas-Salazar

Honors Capstones

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