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2014

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Articles 1 - 30 of 922

Full-Text Articles in Physics

Statistics Of The Island-Around-Island Hierarchy In Hamiltonian Phase Space, Or Alus, Shmuel Fishman, James Meiss Dec 2014

Statistics Of The Island-Around-Island Hierarchy In Hamiltonian Phase Space, Or Alus, Shmuel Fishman, James Meiss

Applied Mathematics Faculty Contributions

The phase space of a typical Hamiltonian system contains both chaotic and regular orbits, mixed in a complex, fractal pattern. One oft-studied phenomenon is the algebraic decay of correlations and recurrence time distributions. For area-preserving maps, this has been attributed to the stickiness of boundary circles, which separate chaotic and regular components. Though such dynamics has been extensively studied, a full understanding depends on many fine details that typically are beyond experimental and numerical resolution. This calls for a statistical approach, the subject of the present work. We calculate the statistics of the boundary circle winding numbers, contrasting the distribution ...


Gauge Transformations Of The Biconformal Connection, James Thomas Wheeler Dec 2014

Gauge Transformations Of The Biconformal Connection, James Thomas Wheeler

All Physics Faculty Publications

We study the changes of the biconformal gauge fields under the local rotational and dilatational gauge transformations.


Measurement Of Compton Scattering From The Deuteron And An Improved Extraction Of The Neutron Electromagnetic Polarizabilities, L. S. Myers, J. R. M. Annand, J. Brudvik, G. Feldman, H. W. Grießhammer, K. Hansen, S. S. Henshaw, L. Isaksson, R. Jebali, Michael A. Kovash, M. Lundin, J. A. Mcgovern, D. G. Middleton, A. M. Nathan, D. R. Phillips, B. Schröder, S. C. Stave Dec 2014

Measurement Of Compton Scattering From The Deuteron And An Improved Extraction Of The Neutron Electromagnetic Polarizabilities, L. S. Myers, J. R. M. Annand, J. Brudvik, G. Feldman, H. W. Grießhammer, K. Hansen, S. S. Henshaw, L. Isaksson, R. Jebali, Michael A. Kovash, M. Lundin, J. A. Mcgovern, D. G. Middleton, A. M. Nathan, D. R. Phillips, B. Schröder, S. C. Stave

Physics and Astronomy Faculty Publications

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data—and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and ...


Inductive Measurement Of Optically Hyperpolarized Phosphorous Donor Nuclei In An Isotopically Enriched Silicon-28 Crystal, P. Gumann, O. Patange, C. Ramanathan, H. Haas Dec 2014

Inductive Measurement Of Optically Hyperpolarized Phosphorous Donor Nuclei In An Isotopically Enriched Silicon-28 Crystal, P. Gumann, O. Patange, C. Ramanathan, H. Haas

Open Dartmouth: Faculty Open Access Scholarship

We experimentally demonstrate the first inductive readout of optically hyperpolarized phosphorus-31 donor nuclear spins in an isotopically enriched silicon-28 crystal. The concentration of phosphorus donors in the crystal was 1.5×1015  cm−3, 3 orders of magnitude lower than has previously been detected via direct inductive detection. The signal-to-noise ratio measured in a single free induction decay from a 1  cm3 sample (≈1015 spins) was 113. By transferring the sample to an X-band ESR spectrometer, we were able to obtain a lower bound for the nuclear spin polarization at 1.7 K of ∼64%. The 31P-T2 measured with a ...


Investigation Of Emic Wave Scattering As The Cause For The Barrel 17 January 2013 Relativistic Electron Precipitation Event: A Quantitative Comparison Of Simulation With Observations, Zan Li, Robyn M. Millan, Mary K. Hudson, Leslie A. Woodger, David M. Smith, Yue Chen, R. Friedel, J. V. Rodriguez, Mark J. Engebretson, J. Goldstein, Joseph F. Fennell, Harlan E. Spence Dec 2014

Investigation Of Emic Wave Scattering As The Cause For The Barrel 17 January 2013 Relativistic Electron Precipitation Event: A Quantitative Comparison Of Simulation With Observations, Zan Li, Robyn M. Millan, Mary K. Hudson, Leslie A. Woodger, David M. Smith, Yue Chen, R. Friedel, J. V. Rodriguez, Mark J. Engebretson, J. Goldstein, Joseph F. Fennell, Harlan E. Spence

Physics Scholarship

Abstract

Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) balloons and was magnetically mapped close to Geostationary Operational Environmental Satellite (GOES) 13. We simulate the relativistic electron pitch angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES 13 and the Van Allen Probes. We show that the count rate, the energy ...


Rainich-Type Conditions For Perfect Fluid Spacetimes, Dionisios Krongos, Charles G. Torre Dec 2014

Rainich-Type Conditions For Perfect Fluid Spacetimes, Dionisios Krongos, Charles G. Torre

Research Vignettes

In this worksheet we describe and illustrate a relatively simple set of new Rainich-type conditions on an n-dimensional spacetime which are necessary and sufficient for it to define a perfect fluid solution of the Einstein field equations. Procedures are provided which implement these Rainich-type conditions and which reconstruct the perfect fluid from the metric. These results provide an example of the idea of geometrization of matter fields in general relativity, which is a purely geometrical characterization of matter fields via the Einstein field equations.


Shape-Memory Transformations Of Niti: Minimum-Energy Pathways Between Austenite, Martensites, And Kinetically Limited Intermediate States, Nikolai A. Zarkevich, Duane D. Johnson Dec 2014

Shape-Memory Transformations Of Niti: Minimum-Energy Pathways Between Austenite, Martensites, And Kinetically Limited Intermediate States, Nikolai A. Zarkevich, Duane D. Johnson

Ames Laboratory Publications

NiTi is the most used shape-memory alloy; nonetheless, a lack of understanding remains regarding the associated structures and transitions, including their barriers. Using a generalized solid-state nudged elastic band method implemented via density-functional theory, we detail the structural transformations in NiTi relevant to shape memory: those between a body-centered orthorhombic (bco) ground state and a newly identified stable austenite (“glassy” B2-like) structure, including energy barriers (hysteresis) and intermediate structures (observed as a kinetically limited Rphase), and between martensite variants (bco orientations). All results are in good agreement with available experiment. We contrast the austenite results to those from the often-assumed ...


Strain-Driven Growth Of Gaas(111) Quantum Dots With Low Fine Structure Splitting, Paul J. Simmonds Dec 2014

Strain-Driven Growth Of Gaas(111) Quantum Dots With Low Fine Structure Splitting, Paul J. Simmonds

Physics Faculty Publications and Presentations

Symmetric quantum dots (QDs) on (111)-oriented surfaces are promising candidates for generating polarization-entangled photons due to their low excitonic fine structure splitting(FSS). However, (111) QDs are difficult to grow. The conventional use of compressive strain to drive QD self-assembly fails to form 3D nanostructures on (111) surfaces. Instead, we demonstrate that (111) QDs self-assemble under tensile strain by growing GaAs QDs on an InP(111)A substrate. Tensile GaAs self-assembly produces a low density of QDs with a symmetric triangular morphology. Coherent, tensile QDs are observed without dislocations, and the QDs luminescence at room temperature. Single QD measurements ...


Nuclear Structure Aspects Of Neutrinoless Double Beta Decay, B. Alex Brown, Mihai Horoi, Roman A. Sen′Kov Dec 2014

Nuclear Structure Aspects Of Neutrinoless Double Beta Decay, B. Alex Brown, Mihai Horoi, Roman A. Sen′Kov

Publications and Research

We decompose the neutrinoless double-beta decay matrix elements into sums of products over the intermediate nucleus with two less nucleons. We find that the sum is dominated by the J^pi=0^+ ground state of this intermediate nucleus for both the light and heavy neutrino decay processes. This provides a new theoretical tool for comparing and improving nuclear structure models. It also provides the connection to two-nucleon transfer experiments.


Galaxy Zoo: Candels Barred Discs And Bar Fractions, B. D. Simmons, Thomas Melvin, Chris Lintott, Karen L. Masters, Kyle W. Willett, William C. Keel, R. J. Smethurst, Edmond Cheung, Robert C. Nichol, Kevin Schawinski, Michael Rutkowski, Jeyhan S. Kartaltepe, Eric F. Bell, Kevin R. V. Casteels, Christopher J. Conselice, Omar Almaini, Henry C. Ferguson, Lucy Fortson, William Hartley, Dale D. Kocevski, Anton M. Koekemoer, Daniel H. Mcintosh, Alice Mortlock, Jeffrey A. Newman, Jamie Owensworth, Steven Bamford, Tomas Dahlen, Sandra M. Faber, Steven L. Finkelstein, Adriano Fontana, Audrey Galametz, N. A. Grogin, Ruth Grützbauch, Yicheng Guo, Boris Häußler, Kian J. Jek, Sugata Kaviraj, Ray A. Lucas, Michael Peth, Mara Salvato, Tommy Wiklind, Stijn Wuyts Dec 2014

Galaxy Zoo: Candels Barred Discs And Bar Fractions, B. D. Simmons, Thomas Melvin, Chris Lintott, Karen L. Masters, Kyle W. Willett, William C. Keel, R. J. Smethurst, Edmond Cheung, Robert C. Nichol, Kevin Schawinski, Michael Rutkowski, Jeyhan S. Kartaltepe, Eric F. Bell, Kevin R. V. Casteels, Christopher J. Conselice, Omar Almaini, Henry C. Ferguson, Lucy Fortson, William Hartley, Dale D. Kocevski, Anton M. Koekemoer, Daniel H. Mcintosh, Alice Mortlock, Jeffrey A. Newman, Jamie Owensworth, Steven Bamford, Tomas Dahlen, Sandra M. Faber, Steven L. Finkelstein, Adriano Fontana, Audrey Galametz, N. A. Grogin, Ruth Grützbauch, Yicheng Guo, Boris Häußler, Kian J. Jek, Sugata Kaviraj, Ray A. Lucas, Michael Peth, Mara Salvato, Tommy Wiklind, Stijn Wuyts

Physics and Astronomy Faculty Publications

The formation of bars in disc galaxies is a tracer of the dynamical maturity of the population.

The remainder of the abstract is available at:

http://dx.doi.org/10.1093/mnras/stu1817


Deriving The Dyer-Roeder Equation From The Geodesic Deviation Equation Via The Newman Penrose Null Tetrad, Aly Aly Dec 2014

Deriving The Dyer-Roeder Equation From The Geodesic Deviation Equation Via The Newman Penrose Null Tetrad, Aly Aly

Honors Program Theses and Projects

In this paper we examine the geodesic deviation equation using the Newman-Penrose (N-P) formalism for a flat Friedmann-Lemaitre-Robertson-Walker (FLRW) metric (Carroll, S. (2004); Ryden, B. (2003); Newman & Penrose (1962)). We solved the geodesic deviation equation for angular diameter distance, using the relevant N-P components, and the resulting expression was the Dyer-Roeder equation of cosmology (Ryden, B. (2003)) (Schneider et al. (1992)). This leads us to believe that we can apply the N-P formalism to a perturbed FLRW metric and find a solvable equation for angular diameter distance (Kling & Campbell (2008)). The perturbed FLRW metric incorporates clumps of matter into a ...


Stratified Turbulence In The Nearshore Coastal Ocean: Dynamics And Evolution In The Presence Of Internal Bores, Ryan K. Walter, Michael E. Squibb, C. Brock Woodson, Jeffrey R. Koseff, Stephen G. Monismith Dec 2014

Stratified Turbulence In The Nearshore Coastal Ocean: Dynamics And Evolution In The Presence Of Internal Bores, Ryan K. Walter, Michael E. Squibb, C. Brock Woodson, Jeffrey R. Koseff, Stephen G. Monismith

Physics

High-frequency measurements of stratified turbulence throughout the water column were collected over a 2 week period in the nearshore environment of southern Monterey Bay, CA, using a cabled observatory system and an underwater turbulence flux tower. The tower contained a vertical array of acoustic Doppler velocimeters and fast-response conductivity-temperature sensors, providing a nearly continuous data set of turbulent velocity and density fluctuations and a unique look into the stratified turbulence field. The evolution of various turbulence quantities and direct measurements of the vertical turbulent diffusivity is examined in the presence of nearshore internal bores, both in the near-bed region and ...


Nuclear Matter Effects On J/Psi Production In Asymmetric Cu Plus Au Collisions At Root S-Nn=200 Gev, Andrew Adare, Nicole J. Apadula, Sarah C. Campbell, Lei Ding, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Milap R. Patel, Joshua Perry, Marzia Rosati, Alex Shaver, M. Shimomura, Arbin Timilsina, Shawn Whitaker, Et Al., Phenix Collaboration Dec 2014

Nuclear Matter Effects On J/Psi Production In Asymmetric Cu Plus Au Collisions At Root S-Nn=200 Gev, Andrew Adare, Nicole J. Apadula, Sarah C. Campbell, Lei Ding, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Milap R. Patel, Joshua Perry, Marzia Rosati, Alex Shaver, M. Shimomura, Arbin Timilsina, Shawn Whitaker, Et Al., Phenix Collaboration

Physics and Astronomy Publications

We report on J/psi production from asymmetric Cu + Au heavy-ion collisions at root S-NN = 200 GeV at the Relativistic Heavy Ion Collider at both forward (Cu-going direction) and backward (Au-going direction) rapidities. The nuclear modification of J/psi yields in Cu + Au collisions in the Au-going direction is found to be comparable to that in Au + Au collisions when plotted as a function of the number of participating nucleons. In the Cu-going direction, J/psi production shows a stronger suppression. This difference is comparable in magnitude and has the same sign as the difference expected from shadowing effects due ...


Carbon Nanotube Sensors And Field Emitters, Ben Pound Dec 2014

Carbon Nanotube Sensors And Field Emitters, Ben Pound

Physics Capstone Project

Carbon nanotube (CNT) forests are arrays of free-standing CNTs, as seen in Fig. 1a. The goal of this project was to deposit 1,5-diaminonaphthalene (DAN) evenly on each CNT. The motivation is that CNTs cannot effectively participate in chemical reactions by themselves. However, DAN can bind to the CNT surface in such a way that it can participate in chemical reactions while staying on the CNT side wall1. If DAN could be coated evenly on the CNTs throughout the forest, it could make a very sensitive biological sensor. A sensor is only as good as the number of detection ...


Electrostatic Force Microscopy And Electrical Isolation Of Etched Few-Layer Graphene Nano-Domains, D. Patrick Hunley, Abhishek Sundararajan, Mathias J. Boland, Douglas R. Strachan Dec 2014

Electrostatic Force Microscopy And Electrical Isolation Of Etched Few-Layer Graphene Nano-Domains, D. Patrick Hunley, Abhishek Sundararajan, Mathias J. Boland, Douglas R. Strachan

Physics and Astronomy Faculty Publications

Nanostructured bi-layer graphene samples formed through catalytic etching are investigated with electrostatic force microscopy. The measurements and supporting computations show a variation in the microscopy signal for different nano-domains that are indicative of changes in capacitive coupling related to their small sizes. Abrupt capacitance variations detected across etch tracks indicates that the nano-domains have strong electrical isolation between them. Comparison of the measurements to a resistor-capacitor model indicates that the resistance between two bi-layer graphene regions separated by an approximately 10 nm wide etch track is greater than about 1×1012 Ω with a corresponding gap resistivity greater than ...


Evidence For (And Against) Progenitor Bias In The Size Growth Of Compact Red Galaxies, Stephanie K. Keating, Roberto G. Abraham, Ricardo Schiavon, Genevieve Graves, Ivana Damjanov, Renbin Yan, Jeffrey Newman, Luc Simard Dec 2014

Evidence For (And Against) Progenitor Bias In The Size Growth Of Compact Red Galaxies, Stephanie K. Keating, Roberto G. Abraham, Ricardo Schiavon, Genevieve Graves, Ivana Damjanov, Renbin Yan, Jeffrey Newman, Luc Simard

Physics and Astronomy Faculty Publications

Most massive, passive galaxies are compact at high redshifts, but similarly compact massive galaxies are rare in the local universe. The most common interpretation of this phenomenon is that massive galaxies have grown in size by a factor of about five since redshift z = 2. An alternative explanation is that recently quenched massive galaxies are larger (a "progenitor bias"). In this paper, we explore the importance of progenitor bias by looking for systematic differences in the stellar populations of compact early-type galaxies in the DEEP2 survey as a function of size. Our analysis is based on applying the statistical technique ...


Neutral Density Behavior From 45-90 Km Based On Rayleigh Lidar Observations Above Usu, David Barton Dec 2014

Neutral Density Behavior From 45-90 Km Based On Rayleigh Lidar Observations Above Usu, David Barton

Physics Capstone Project

There are over 900 nights of observations taken by the Rayleigh lidar above Utah State University from 1993 to 2004. The data have been reduced to give absolute temperatures and relative densities in the mesosphere, from 45-90 km (Herron, 2004, 2007). From the 11 years of relative density data an 11-year climatology of mesospheric densities above Logan, Utah has been created. From this climatology I have been able to normalize the 11 years of density data to the following models: the MSISe00 empirical model, the CPC (Climate Prediction Center) reanalysis model, the ERA Interim reanalysis model, and the NASA MERRA ...


Thermophonon, Nikolai A. Zarkevich Dec 2014

Thermophonon, Nikolai A. Zarkevich

Ames Laboratory Software

ThermoPhonon is a stand-alone code, which can be integrated into other software packages. Typically, it is used together with a density functional theory (DFT) code (such as VASP, Wien2k, AbInit, SIESTA) and a phonon code (such as Phonopy or Phon). The workflow is the following.

  • Molecular dynamics (MD) in a supercell at a given temperature T is performed using another code. After sufficient equilibration, the output in the form of atomic positions and forces for a large number of selected MD steps is recorded into a file. If needed, one can modify this file by applying additional constraints, such as ...


J/Ψ Polarization In P + P Collisions At √S=200 Gev In Star, James K. Adkins, Renee H. Fatemi, Wolfgang Korsch, Suvarna Ramachandran, G. Webb, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer Dec 2014

J/Ψ Polarization In P + P Collisions At √S=200 Gev In Star, James K. Adkins, Renee H. Fatemi, Wolfgang Korsch, Suvarna Ramachandran, G. Webb, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer

Physics and Astronomy Faculty Publications

We report on a polarization measurement of inclusive J/ψ mesons in the di-electron decay channel at mid-rapidity at 2T/c in p+p collisions at √s=200 GeV. Data were taken with the STAR detector at RHIC. The J/ψ polarization measurement should help to distinguish between different models of the J/ψ production mechanism since they predict different pT dependences of the J/ψ polarization. In this analysis, J/ψ polarization is studied in the helicity frame. The polarization parameter λθ measured at RHIC becomes smaller towards high pT, indicating more longitudinal J/ψ polarization ...


Ferroelectric Polarization Dependent Interface Effects, Xiaohui Liu Dec 2014

Ferroelectric Polarization Dependent Interface Effects, Xiaohui Liu

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

Utilization of the switchable spontaneous polarization of nanometer scale ferroelectric materials offers a promising avenue for future nanoelectronic devices. In this dissertation, we use density-functional calculations and phenomenological modeling to explore the effects of interface termination on thin-film heterostructures, the effects of electron doping in bulk ferroelectric materials on ferroelectric stability, and the effects of ferroelectric polarization switching on the electronic and transport properties of interfaces.

For SrRuO3/BaTiO3/SrRuO3 epitaxial heterostructures grown on SrTiO3, we find that the built-in dipole at the BaO/RuO2 terminated interface leads to a strong preference for one polarization ...


Diffractive Optical Elements With A Large Angle Of Operation Recorded In Acrylamide Based Photopolymer On Flexible Substrates, Hoda Akbari, Izabela Naydenova, Lina Persechini, Sean Garner, Pat Cimo, Suzanne Martin Dec 2014

Diffractive Optical Elements With A Large Angle Of Operation Recorded In Acrylamide Based Photopolymer On Flexible Substrates, Hoda Akbari, Izabela Naydenova, Lina Persechini, Sean Garner, Pat Cimo, Suzanne Martin

Articles

A holographic device characterised by a large angular range of operation is under development. The aim of this study is to increase the angular working range of the diffractive lens by stacking three layers of high efficiency optical elements on top of each other so that light is collected (and focussed) from a broader range of angles. The angular range of each individual lens element is important, and work has already been done in an acrylamide-based photosensitive polymer to broaden the angular range of individual elements using holographic recording at a low spatial frequency.This paper reports new results on ...


Iranian Nuclear Proliferation And Sanctions, Bailey Nicole Burlingame Dec 2014

Iranian Nuclear Proliferation And Sanctions, Bailey Nicole Burlingame

Student Scholar Symposium Abstracts and Posters

This project will involve the current problem of nuclear development in the nation of Iran. The question involved in the election studies was, “Should we try to stop Iranian Nuclear Development by increasing sanctions, yes or no?” According to the US Department of State website, they are attempting to increase these sanctions against individuals or cooperations who can be proven to have provided aid, information, or mechanical aspects to assist the goal of Iranian nuclear proliferation. The website provides identifying information for the individuals involved. The answer to this question I believe will be determined the amount of news information ...


Overview Of The Sdss-Iv Manga Survey: Mapping Nearby Galaxies At Apache Point Observatory, Kevin Bundy, Matthew A. Bershady, David R. Law, Renbin Yan, Niv Drory, Nicholas Macdonald, David A. Wake, Brian Cherinka, José R. Sánchez-Gallego, Anne-Marie Weijmans, Daniel Thomas, Christy Tremonti, Karen Masters, Lodovico Coccato, Aleksandar M. Diamond-Stanic, Alfonso Aragón-Salamanca, Vladimir Avila-Reese, Carles Badenes, Jésus Falcón-Barroso, Francesco Belfiore, Dmitry Bizyaev, Guillermo A. Blanc, Joss Bland-Hawthorn, Michael R. Blanton, Joel R. Brownstein, Nell Byler, Michele Cappellari, Charlie Conroy, Aaron A. Dutton, Eric Emsellem, Kai Zhang Dec 2014

Overview Of The Sdss-Iv Manga Survey: Mapping Nearby Galaxies At Apache Point Observatory, Kevin Bundy, Matthew A. Bershady, David R. Law, Renbin Yan, Niv Drory, Nicholas Macdonald, David A. Wake, Brian Cherinka, José R. Sánchez-Gallego, Anne-Marie Weijmans, Daniel Thomas, Christy Tremonti, Karen Masters, Lodovico Coccato, Aleksandar M. Diamond-Stanic, Alfonso Aragón-Salamanca, Vladimir Avila-Reese, Carles Badenes, Jésus Falcón-Barroso, Francesco Belfiore, Dmitry Bizyaev, Guillermo A. Blanc, Joss Bland-Hawthorn, Michael R. Blanton, Joel R. Brownstein, Nell Byler, Michele Cappellari, Charlie Conroy, Aaron A. Dutton, Eric Emsellem, Kai Zhang

Physics and Astronomy Faculty Publications

We present an overview of a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), one of three core programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV) that began on 2014 July 1. MaNGA will investigate the internal kinematic structure and composition of gas and stars in an unprecedented sample of 10,000 nearby galaxies. We summarize essential characteristics of the instrument and survey design in the context of MaNGA's key science goals and present prototype observations to demonstrate MaNGA's scientific potential. MaNGA employs dithered observations with 17 fiber-bundle integral field units ...


Collective Edge Modes Near The Onset Of A Graphene Quantum Spin Hall State, Gunpathy Murthy, Efrat Shimshoni, H. A. Fertig Dec 2014

Collective Edge Modes Near The Onset Of A Graphene Quantum Spin Hall State, Gunpathy Murthy, Efrat Shimshoni, H. A. Fertig

Physics and Astronomy Faculty Publications

Graphene subject to a strong, tilted magnetic field exhibits an insulator-metal transition tunable by tilt angle, attributed to the transition from a canted antiferromagnetic (CAF) to a ferromagnetic (FM) bulk state at filling factor ν=0. We develop a theoretical description for the spin and valley edge textures in the two phases, and the implied evolution in the nature of edge modes through the transition. In particular, we show that the CAF has gapless neutral modes in the bulk, but supports gapped charged edge modes. At the transition to the FM state the charged edge modes become gapless and are ...


Antimicrobial Properties Of Nano-Silver: A Cautionary Approach To Ionic Interference, Kate Sheehy, Alan Casey, Anna Murphy, Gordon Chambers Dec 2014

Antimicrobial Properties Of Nano-Silver: A Cautionary Approach To Ionic Interference, Kate Sheehy, Alan Casey, Anna Murphy, Gordon Chambers

Articles

Hypothesis: Metallic nanoparticles such as nano-silver have found many applications as alternative antimicrobials in recent years. However methods for determining their proposed antimicrobial activity have received little attention to date. The disk diffusion assay is commonly used as a demonstration of antimicrobial properties and is a regular feature in synthetic nanoparticle papers. The aim of this study was to assess its effectiveness in demonstrating the ‘‘nanoparticle specific’’ antimicrobial properties in the absence of ionic contributions from unreacted reducing agents and or impurities. Experiments: The disk diffusion assay was carried out on a range of silver nanoparticles, both in-house synthesised and ...


Vibrational And Structural Signatures Of The Crossover Between Dense Glassy And Sparse Gel-Like Attractive Colloidal Packings, Matthew A. Lohr, Tim Still, Raman Ganti, Matthew D. Gratale, Zoey S. Davidson, Kevin B. Aptowicz, Carl P. Goodrich, Daniel M. Sussman, A. G. Yodh Dec 2014

Vibrational And Structural Signatures Of The Crossover Between Dense Glassy And Sparse Gel-Like Attractive Colloidal Packings, Matthew A. Lohr, Tim Still, Raman Ganti, Matthew D. Gratale, Zoey S. Davidson, Kevin B. Aptowicz, Carl P. Goodrich, Daniel M. Sussman, A. G. Yodh

Physics

We investigate the vibrational modes of quasi-two-dimensional disordered colloidal packings of hard colloidal spheres with short-range attractions as a function of packing fraction. Certain properties of the vibrational density of states (vDOS) are shown to correlate with the density and structure of the samples (i.e., in sparsely versus densely packed samples). Specifically, a crossover from dense glassy to sparse gel-like states is suggested by an excess of phonon modes at low frequency and by a variation in the slope of the vDOS with frequency at low frequency. This change in phonon mode distribution is demonstrated to arise largely from ...


Differential Cross Section Measurements For The Production Of Awboson In Association With Jets In Proton–Proton Collisions At √S=7tev, Cms Collaboration, Cern, Switzerland, V. Gaultney, Samantha Hewamanage, Stephan Linn, Pete E. Markowitz, German Martinez, Jorge Luis Rodriguez Dec 2014

Differential Cross Section Measurements For The Production Of Awboson In Association With Jets In Proton–Proton Collisions At √S=7tev, Cms Collaboration, Cern, Switzerland, V. Gaultney, Samantha Hewamanage, Stephan Linn, Pete E. Markowitz, German Martinez, Jorge Luis Rodriguez

Department of Physics

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0fb−1. The measured ...


Measurement Of The Pp→Zzproduction Cross Section And Constraints On Anomalous Triple Gauge Couplings In Four-Lepton Final States At √S=8tev, Cms Collaboration, Cern, Switzerland, V. Gaultney, Samantha Hewamanage, Stephan Linn, Pete E. Markowitz, German Martinez, Jorge Luis Rodriguez Dec 2014

Measurement Of The Pp→Zzproduction Cross Section And Constraints On Anomalous Triple Gauge Couplings In Four-Lepton Final States At √S=8tev, Cms Collaboration, Cern, Switzerland, V. Gaultney, Samantha Hewamanage, Stephan Linn, Pete E. Markowitz, German Martinez, Jorge Luis Rodriguez

Department of Physics

A measurement of the inclusive ZZproduction cross section and constraints on anomalous triple gauge couplings in proton–proton collisions at √s=8TeVare presented. The analysis is based on a data sample, corresponding to an integrated luminosity of 19.6fb−1, collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes ZZ →, where=e, μand =e, μ, τ. The measured total cross section σ(pp →ZZ) =7.7 ±0.5(stat)+0.5−0.4(syst)±0.4 (theo) ±0.2(lumi)pb, for both Zbosons produced in the mass range 60


Hf Accelerated Electron Fluxes, Spectra, And Ionization, Herbert C. Carlson, Joseph B. Jensen Dec 2014

Hf Accelerated Electron Fluxes, Spectra, And Ionization, Herbert C. Carlson, Joseph B. Jensen

All Physics Faculty Publications

Wave particle interactions, an essential aspect of laboratory, terrestrial,and astrophysical plasmas, have been studied for decades by transmitting high power HF radio waves into Earth’s weakly ionized space plasma, to use it as a laboratory without walls. Application to HF electron acceleration remains an active area of research (Gurevich, 2007) today. HF electron acceleration studies began when plasma line observations proved (Carlson et al, 1982) that high power HF radio wave-excited processes accelerated electrons not to ~ eV, but instead to - 100 times thermal energy (10s of eV), as a consequence of inelastic collision effects on electron transport. Gurevich ...


Nucleation At The Contact Line Observed On Nanotextured Surfaces, C W. Gurganus, J. C. Charnawskas, A. B. Kostinski, R. A. Shaw Dec 2014

Nucleation At The Contact Line Observed On Nanotextured Surfaces, C W. Gurganus, J. C. Charnawskas, A. B. Kostinski, R. A. Shaw

Department of Physics Publications

It has been conjectured that roughness plays a role in surface nucleation, the tendency for freezing to begin preferentially at the liquid-gas interface. Using high speed imaging, we sought evidence for freezing at the contact line on catalyst substrates with imposed characteristic length scales (texture). Length scales consistent with the critical nucleus size and with δ∼τ/σ, where τ is a relevant line tension and σ is the surface tension, range from nanometers to micrometers. It is found that nanoscale texture causes a shift in the nucleation of ice in supercooled water to the three-phase contact line, while microscale ...