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Brigham Young University

2004

Articles 1 - 12 of 12

Full-Text Articles in Physics

Atomic Force Microscope Conductivity Measurements Of Single Ferritin Molecules, Degao Xu Dec 2004

Atomic Force Microscope Conductivity Measurements Of Single Ferritin Molecules, Degao Xu

Theses and Dissertations

Conductive Atomic Force Microscope (c-AFM) was used to measure the conductivity of single horse spleen ferritin (HoSF) and azotobacter vinelandii bacterial ferritin (AvBF) molecules deposited on flat gold surfaces. A 500 micron diameter gold ball was also used as a contact probe to measure the conductivity of a thin film of ferritin molecules. The average current measured for holo HoSF was 13 and 5 times larger than that measured for apo HoSF as measured by c-AFM at 1V and gold ball at 2V and respectively, which indicates that the core of ferritin is more conductive than the protein shell and …

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Geometric Acoustic Modeling Of The Lds Conference Center, Heather Smith Nov 2004

Geometric Acoustic Modeling Of The Lds Conference Center, Heather Smith

Theses and Dissertations

This thesis discusses the process of modeling a 21,000 seat fan-shaped auditorium using methods of geometric acoustics. Two commercial geometric acoustics software packages were used in the research: CATT-Acoustic™ 8.0 and EASE™ 4.1. The process first included creating preliminary models of the hall using published absorption coefficients for its surfaces and approximate scattering coefficients based on current best-known techniques. A detailed analysis determined the minimum numbers of rays needed in both packages to produce reliable results with these coefficient values. It was found that 100,000 rays were needed for CATT™ and 500,000 rays were needed for EASE™. Analysis was also …

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Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer Oct 2004

Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer

Faculty Publications

The m = 1 diocotron mode in non-neutral plasmas has long been thought of as a shifted equilibrium, and its frequency has been approximately calculated in this way by Fine and Driscoll [Phys. Plasmas 5, 601 (1998)]. This article shows that this idea can be coupled with a standard axisymmetric equilibrium calculation on a grid to calculate the frequency of this mode to very high precision including both finite-length and thermal effects, provided that the Debye length is small enough. As the Debye length begins to approach the plasma size not only does the shifted equilibrium calculation fail to predict …

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Optical Properties And Application Of Uranium-Based Thin Films For The Extreme Ultraviolet And Soft X-Ray Region, Richard L. Sandberg, David D. Allred, Shannon Lunt, Marie K. Urry, R. Steven Turley Oct 2004

Optical Properties And Application Of Uranium-Based Thin Films For The Extreme Ultraviolet And Soft X-Ray Region, Richard L. Sandberg, David D. Allred, Shannon Lunt, Marie K. Urry, R. Steven Turley

Faculty Publications

Uranium oxide and uranium nitride thin films reflect significantly more than all previously known/standard reflectors (e.g., nickel, gold, and iridium) for most of the 4-10 nm range at low angles of incidence. This work includes measurements of the EUV/soft x-ray (2-20 nm) reflectance of uranium-based thin films (~20 nm thick) and extraction of their optical constants (d and ?). We report the reflectances at 5, 10, and 15 degrees grazing incidence of air-oxidized sputtered uranium, reactively sputtered (O2) uranium oxide, and reactively sputtered (N2) uranium nitride thin films measured at Beamline 6.3.2 at the Advanced Light Source (ALS) at Lawrence …

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Analysis And Comparison Of Three Acoustic Energy Density Probes, Lance Lester Locey Oct 2004

Analysis And Comparison Of Three Acoustic Energy Density Probes, Lance Lester Locey

Theses and Dissertations

Traditional methods for the investigation of sound fields generally rely on a microphone to convert sound pressure into an electrical signal which can be recorded, displayed, and so forth. The squared sound pressure is directly related to potential energy density. Consequently, the measurement of sound pressure alone does not inherently provide insight into the total energy density of the sound field. Specifically, no information about the kinetic energy density of the sound field is available from this measurement alone. However, it is possible to use two microphones to estimate particle velocity. The squared particle velocity magnitude is directly related to …

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On The Variability Of The Fine Structure Constant, Jason Lott Evans Jul 2004

On The Variability Of The Fine Structure Constant, Jason Lott Evans

Theses and Dissertations

This thesis addresses the issue of the time variability of the fine structure constant, alpha. Recent claims of a varying alpha are set against the established standards of quantum electrodynamical theory and experiments. A study of the feasibility of extracting data on the time dependence of alpha using particles in Penning traps is compared to the results obtained by existing methods, including those using astrophysical data and those obtained in atomic clock experiments. Suggestions are made on the nature of trapped particles and the trapping fields.

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Removing Surface Contaminants From Silicon Wafers To Facilitate Euv Optical Characterization, Richard L. Sandberg, David D. Allred, A. L. Jackson, J. E. Johnson, W. Evans, T. Doughty, A. E. Baker, K. Adamson, A. Jacquier, R. E. Robinson Apr 2004

Removing Surface Contaminants From Silicon Wafers To Facilitate Euv Optical Characterization, Richard L. Sandberg, David D. Allred, A. L. Jackson, J. E. Johnson, W. Evans, T. Doughty, A. E. Baker, K. Adamson, A. Jacquier, R. E. Robinson

Faculty Publications

The extreme ultraviolet (EUV) is becoming increasingly important. Principal applications include orbital space-based astronomy and lithography for integrated circuit computer chips. A main impediment to further development of efficient mirrors is the lack of reliable optical constants for various materials in this region of the electromagnetic spectrum. One reason for the unreliability of the optical constants is that the sample surfaces are often contaminated with foreign material, especially organic compounds, when exposed to laboratory air. Several cleaning techniques were evaluated, namely: 1) strippable solid optical cleaner (Opticlean®); 2) oxygen plasma etch; 3) high energy UV light/ozone; 4) strippable coating followed …

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Microsecond Spin-Flip Times In N-Gaas Measured By Time-Resolved Polarization Of Photoluminescence, John S. Colton, T. A. Kennedy, A. S. Bracker, D. Gammon Mar 2004

Microsecond Spin-Flip Times In N-Gaas Measured By Time-Resolved Polarization Of Photoluminescence, John S. Colton, T. A. Kennedy, A. S. Bracker, D. Gammon

Faculty Publications

We have observed microsecond spin-flip times in lightly doped n-GaAs, by measuring the photoluminescence polarization in the time domain with pump and probe pulses. Times up to 1.4 μs have been measured. Our results as a function of magnetic field indicated three regions governing the spin relaxation: a low field region, where spin-flip times increase due to suppression of the nuclear hyperfine interaction for localized electrons, a medium field region where spin-flip times increase due to narrowing of the hyperfine relaxation for interacting electrons, and a high field region where spin-flip times begin to level off due to the increasing …

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Active Minimization Of Acoustic Energy Density In A Mock Tractor Cab, Benjamin Mahonri Faber Mar 2004

Active Minimization Of Acoustic Energy Density In A Mock Tractor Cab, Benjamin Mahonri Faber

Theses and Dissertations

An active noise control (ANC) system has been applied to the problem of attenuating low-frequency tonal noise inside small enclosures. The intended target application of the system was the reduction of the engine firing frequency inside heavy equipment cabins. The ANC system was based on a version of the filtered-x LMS adaptive algorithm, modified for the minimization of acoustic energy density (ED), rather than the more traditional minimization of squared acoustic pressure (SP). Three loudspeakers produced control signals within a mock cabin composed of a steel frame with plywood sides and a Plexiglas® front. An energy density sensor, capable of …

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Boron Alloying In Gan, Gus L. W. Hart, Laurian Escalanti Feb 2004

Boron Alloying In Gan, Gus L. W. Hart, Laurian Escalanti

Faculty Publications

Using first-principles calculations in the local density approximation, we studied effects of adding up to 6% boron to zinc-blende GaN. We found that the band gap increases monotonically with boron incorporation, in agreement with experiment. A composition-independent band-gap bowing parameter of 4.30 eV was determined, and proved to be large compared to bowing for other mixed cation systems. The formation enthalpy of mixing, ΔH, was determined for BxGa1-xN, BxGa1-xAs, and GaAs1-xNx. A comparison of enthalpies indicates that the production of BxGa1-xN films with boron concentrations of at least 5% may be possible.

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Derivation Of Moving-Coil Loudspeaker Parameters Using Plane Wave Tube Techniques, Brian Eric Anderson Jan 2004

Derivation Of Moving-Coil Loudspeaker Parameters Using Plane Wave Tube Techniques, Brian Eric Anderson

Theses and Dissertations

Small-signal moving-coil loudspeaker driver parameters are traditionally derived through electrical impedance measurement techniques. These parameters are commonly called Thiele/Small parameters, after Neville Thiele and Richard Small who are credited with developing industry-standard loudspeaker modeling techniques. However, because loudspeaker drivers are electro-mechano-acoustical transducers, it should be possible to measure their parameters in physical domains other than the electrical domain. A method of measuring loudspeaker parameters from the acoustical domain will be developed. The technique uses a plane wave tube to measure acoustical properties of a baffled driver under test. Quantities such as the transmission loss through the driver are measured for …

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Uranium Oxide As A Highly Reflective Coating From 100-400 Ev, Richard L. Sandberg, David D. Allred, Luke J. Bissell, Jed E. Johnson, R. Steven Turley Jan 2004

Uranium Oxide As A Highly Reflective Coating From 100-400 Ev, Richard L. Sandberg, David D. Allred, Luke J. Bissell, Jed E. Johnson, R. Steven Turley

Faculty Publications

We present the measured reflectances (Beamline 6.3.2, ALS and LBNL) of naturally oxidized uranium and naturally oxidized nickel thin films from 100-460 eV (2.7 to 11.6 nm) at 5 and 15 degrees grazing incidence. These show that uranium as UO2, can fulfill its promise as the highest known single surface reflector for this portion of the soft x-ray region, being nearly twice as reflective as nickel in the 124-250 eV (5-10 nm) region. This is due to its large index of refraction coupled with low absorption. Nickel is commonly used in soft x-ray applications in astronomy and synchrotrons. (Its reflectance …

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