Physics Commons^™

Book Review Of Alla Yaroshinskaya, Chernobyl: The Forbidden Truth, John M. Gleason

RISK: Health, Safety & Environment (1990-2002)

Review of the book: Alla Yaroshinskaya, Chernobyl: The Forbidden Truth (Michele Kahn & Julia Sallabank, trans. University of Nebraska Press 1995). Introduction, foreword, list of illustrations, photographs. ISBN 0-8032-4912-8. [136 pp. Cloth $25.00; Paper $10.00. 312 N. 14th Street, Lincoln NE 68588-0484.]

Bifurcation Of The Equilibrium States Of A Weightless Liquid Bridge, Lev A. Slobozhanin, J. Iwan D. Alexander, Andrew Resnick

Physics Faculty Publications

The bifurcation of the solutions of the nonlinear equilibrium problem of a weightless liquid bridge with a free surface pinned to the edges of two coaxial equidimensional circular disks is examined. The bifurcation is studied in the neighborhood of the stability boundary for axisymmetric equilibrium states with emphasis on the boundary segment corresponding to nonaxisymmetric critical perturbations. The first approximations for the shapes of the bifurcated equilibrium surfaces are obtained. The stability of the bifurcated states is then determined from the bifurcation structure. Along the maximum volume stability limit, depending on values of the system parameters, loss of stability with …

Three-Body Dispersion Coefficients For Alkali-Metal Atoms, Mircea Marinescu, Anthony F. Starace

Anthony F. Starace Publications

We study the nonadditive part of the long-range interaction among three alkali-metal atoms in their ground states. Using nondegenerate perturbation theory, up to the third order, we have computed the dispersion coefficients C for three alkali-metal atoms interacting via their electric dipole moments. Both heteronuclear and homonuclear cases are considered. The numerical values for the C coefficients suggest that such three-body dipole interaction effects may not be neglected in the description of the long-range surface potential interaction for alkali-metal atoms. Furthermore, we show that approximate formulas for C of Midzuno and Kihara [J. Phys. Soc. Jpn. 11, 1045 (1956)] give …

Study Of The Crystallization Of Zeolite Naa By Quasi-Elastic Light-Scattering Spectroscopy And Electron Microscopy, Leszek Gora, Kiril A. Streletzky, Robert W. Thompson, George D.J. Phillies

Physics Faculty Publications

A study of the crystallization of the molecular sieve zeolite NaA from clear aluminosilicate solutions is reported. It was determined by powder X-ray diffraction that zeolite NaA was the only phase in the solid precipitate. The syntheses were monitored in situ by quasi-elastic light scattering spectroscopy. Characteristics of the products were examined by scanning and transmission electron microscopy. Our data show that nuclei formed from the clear aluminosilicate solution, that crystal growth occurred from the solution, that crystal growth was accelerated at elevated temperatures, and that aging the solution at room temperature before raising the synthesis temperature increased both the …

Thermal Fluctuations In Systems With Continuous Symmetry, Ulrich Zürcher

Physics Faculty Publications

We investigate relaxation and thermal fluctuations in systems with continuous symmetry in arbitrary spatial dimensions. For the scalar order parameter ζ(r, t) with r∈ℛd, the deterministic relaxation is caused by hydrodynamic modes η∂ζ(r, t)/∂t= K∇2ζ(r, t). For a finite volume V, we expand the scalar field in a discrete Fourier series and then we study the behavior in the limit V→∞. We find that the second moment is well defined for dimensions d≥3, while it diverges for d=1, 2. Furthermore, we show that for d<4, the decay of the scalar field does not define an "effective" relaxation time. For dimensions d<4, these two properties suggest scale-invariant properties of the scalar field in the limit V→∞. We show that thermal fluctuations are described by fractional Brownian motion for d ≤ 3 and by ordinary Brownian motion for d ≥ 4. The spectral density of the stochastic force follows 1/f for d=1 and d=2, for d=3, and "white noise," f0 for d≥4. We find explicit representation of the equilibrium distribution of the conserved scalar field. For d≥4 it is a Gaussian distribution, while for d=1 and d=2, it is the Cauchy distribution.

The Ubiquitous Coffee Filter, Norman F. Derby, Robert Fuller, Phil W. Gronseth

Robert G. Fuller Publications

What analyst would have predicted that Mr. Coffee^TM would diversify into the scientific supplies market? Nevertheless, that coffeemaker's filters, with their flat bottoms and fluted sides, have been popular in physics classroom experiments for some time now. Besides being cheap and readily available, coffee filters allow students to work experimentally with non-constant forces and, because the filters can be easily stacked without changing their aerodynamic profile, the variation in drag force with velocity can be studied. Since stacks of a few filters fall at speeds of about a meter per second and even a stack of ten reaches terminal …

Naturalness Lowers The Upper Bound On The Lightest Higgs Boson Mass In Supersymmetry, Greg W. Anderson, Diego Castano, Antonio Riotto

Chemistry and Physics Faculty Articles

We quantify the extent to which naturalness is lost as experimental lower bounds on the Higgs boson mass increase, and we compute the natural upper bound on the lightest supersymmetric Higgs boson mass. We find that it would be unnatural for the mass of the lightest supersymmetric Higgs boson to saturate its maximal upper bound. In the absence of significant fine-tuning, the lightest Higgs boson mass should lie below 120 GeV, and in the most natural cases it should be lighter than 108 GeV. For modest tanβ, these bounds are significantly lower. Our results imply that a failure to observe …

Scattering Of A Diagonally Incident Focused Gaussian Beam By An Infinitely Long Homogeneous Circular Cylinder, James A. Lock

Physics Faculty Publications

I expand the radiation potential of an arbitrary monochromatic electromagnetic wave in the cylindrical coordinate eigenfunctions of the scalar Helmholtz equation. Since the resulting beam shape coefficients are found to be an inverse Fourier transform of the z component of the beam fields, the incident Gaussian beam is parameterized by a Fourier angular spectrum of plane waves. The beam's partial-wave coefficients are then obtained, as well as the scattered fields produced by the interaction of the beam with an infinitely long homogeneous circular cylinder. The fields are evaluated analytically in the far zone by the method of stationary phase, and …

Morphology-Dependent Resonances Of An Infinitely Long Circular Cylinder Illuminated By A Diagonally Incident Plane Wave Or A Focused Gaussian Beam, James A. Lock

Physics Faculty Publications

The S matrix for scattering a diagonally incident focused Gaussian beam by an infinitely long circular cylinder is calculated, and the diagonal and off-diagonal elements of the matrix are physically interpreted. In addition, the TE and TM morphology-dependent resonances of the cylinder for plane-wave incidence are examined, and it is found that the cylinder size parameter at resonance increases as the angle of incidence of the plane wave increases. The size parameter increase is explained in terms of the heuristic model of morphology-dependent resonances. The presence of both TE and TM resonances in each of the epsilon-polarized and mu-polarized partial-wave …

Monte Carlo Simulations Of The Dynamical Behavior Of The Coulomb Glass, Torsten Wappler, Thomas Vojta, Michael Schreiber

Physics Faculty Research & Creative Works

We study the dynamical behavior of disordered many-particle systems with long-range Coulomb interactions by means of damage-spreading simulations. In this type of Monte Carlo simulation one investigates the time evolution of the damage, i.e., the difference of the occupation numbers of two systems, subjected to the same thermal noise. We analyze the dependence of the damage on temperature and disorder strength. For zero disorder the spreading transition coincides with the equilibrium phase transition, whereas for finite disorder we find evidence for a dynamical phase transition well below the transition temperature of the pure system.

Minimal Dynamical Triangulations Of Random Surfaces, Simon Catterall, Mark Bowick, Gudmar Thorleifsson

Physics - All Scholarship

No abstract provided.

Minimal Dynamical Triangulations Of Random Surfaces, Mark Bowick, Simon Catterall, Gudmar Thorleifsson

Physics - All Scholarship

We introduce and investigate numerically a minimal class of dynamical triangulations of two-dimensional gravity on the sphere in which only vertices of order five, six or seven are permitted. We show firstly that this restriction of the local coordination number, or equivalently intrinsic scalar curvature, leaves intact the fractal structure characteristic of generic dynamically triangulated random surfaces. Furthermore the Ising model coupled to minimal two-dimensional gravity still possesses a continuous phase transition. The critical exponents of this transition correspond to the usual KPZ exponents associated with coupling a central charge c=1/2 model to two-dimensional gravity.

Physical Coupling Schemes And Qcd Exclusive Processes, David G. Robertson

Physics Faculty Scholarship

I discuss application of the BLM method to obtain commensurate scale relations connecting QCD exclusive amplitudes to other observables, in particular the heavy quark potential.

The Poisson Ratio Of Crystalline Surfaces, Marco Falcioni, Mark Bowick, Emmanuel Guitter, Gudmar Thorleifsson

Physics - All Scholarship

A remarkable theoretical prediction for a crystalline (polymerized) surface is that its Poisson ratio (\sigma) is negative. Using a large scale Monte Carlo simulation of a simple model of such surfaces we show that this is indeed true. The precise numerical value we find is (\sigma \simeq -0.32) on a (128^2) lattice at bending rigidity (kappa = 1.1). This is in excellent agreement with the prediction (\sigma = -1/3) following from the self-consistent screening approximation of Le Doussal and Radzihovsky.

A Telescopic Approach To Modeling Leachate Dynamics And Migration At The St. Johns Landfill, Portland, Oregon, Thomas Stephen Lowry

Dissertations and Theses

The St. Johns Landfill is a 225-acre site that lies near the confluence of the Columbia and Willamette Rivers, in the North Portland Industrial District of Portland, Oregon. A slough system surrounds the landfill on three sides with the fourth side adjacent to a shallow lake. The landfill first opened in 1930 when it was operated as an open dump. It operated as an open dump until 1969 when it was converted to a sanitary landfill, employing daily cover and compaction. The landfill was closed in 1991.

The landfill sits directly on top of a thick layer of silty overbank …

Photoluminescence Properties Of Silicon Quantum-Well Layers, Peter N. Saeta, A. C. Gallagher

All HMC Faculty Publications and Research

Nanometer-scale crystal silicon films surrounded by SiO₂ were prepared by oxidizing silicon-on-insulator substrates prepared from SIMOX (separation by implantation of oxygen) and crystallized hydrogenated amorphous silicon films. Average silicon layer thickness was determined from reflection spectra. When sufficiently thin (<2 >nm), all layers emitted red photoluminescence under blue and UV cw excitation, with a spectrum that did not depend on the mean layer thickness. The spectrum was roughly Gaussian with a peak energy of 1.65 eV, which is lower than for most porous silicon spectra. The time scale for the luminescence decay was ~35 μs at room temperature and …

Centimeter-Wave Reflection In The Nitrates And Nitrites Of Sodium And Potassium: Experiment And Theory, Steven G. Cornelison, Arthur Guass, Jr., J. Krane, John R. Hardy

John R. Hardy Papers

Temperature-dependent centimeter-wave reflection is studied in powdered samples of potassium nitrate (KNO₃), potassium nitrite (KNO₂), sodium nitrate (NaNO₃), and sodium nitrite (NaNO₂). Temperature-dependent reflection measurements at centimeter-wave frequencies were performed on an HP8510B Network analyzer based reflectometer. These measurements are compared to calculations utilizing a Debye relaxation model. Reflection losses seen in KNO₂ and NaNO₂ are expected to be due to the presence of permanent dipoles that are excited to ‘‘hopping’’ modes as the temperature is raised. Although NaNO₃ shows little reflection losses, KNO₃ shows significant losses as …

Thermoconvective Instability Of Paramagnetic Fluids In A Uniform Magnetic Field, J. Huang, Boyd F. Edwards, D. D. Gray

All Physics Faculty Publications

The effect of a uniform oblique magnetic field on a laterally unbounded insulating paramagnetic fluid layer heated from below is studied using a linear stability analysis of the Navier–Stokes equations supplemented by Maxwell’s equations and the appropriate magnetic body force. Two-dimensional rolls in an arbitrary vertical plane are considered. Longitudinal rolls with axes parallel to the horizontal component of the field are the rolls most unstable to convection. The corresponding critical Rayleigh number and critical wavelength for the onset of such rolls are less than the well-known Rayleigh–Bénard values in the absence of magnetic fields. Vertical fields maximize these deviations, …

Optical And Magneto-Optical Constants Of Mnpt3, K. W. Wierman, J. N. Hilfiker, R. F. Sabiryanov, Sitaram S. Jaswal, Roger D. Kirby, John A. Woollam

Department of Physics and Astronomy: Faculty Publications

Optically thick films of MnPt₃ were deposited on quartz using dc magnetron sputtering. The films were covered with an SiO_x protective overcoat and annealed in vacuum at 850 °C for 1 h to form the crystalline L1₂ (Cu₃Au) cubic structure. These films have a high degree of long-range order and are highly textured with the (111) axis along the film normal. Variable angle spectroscopic ellipsometry measurements were taken over the spectral range of 1.2–4.2 eV to determine the optical constants of both MnPt₃ and the SiO_x overcoat. Spectroscopic magneto-optic Kerr rotation and …

Improving Flavor Symmetry In The Kogut-Susskind Hadron Spectrum, James E. Hetrick, T. Blum

All Faculty Articles - School of Engineering and Computer Science

We study the effect of modifying the coupling of Kogut-Susskind quarks to the gauge field by replacing the link matrix in the quark action by a “fat link,” or sum of link plus three-link paths. Flavor symmetry breaking, determined by the mass difference between the Goldstone and non-Goldstone local pions, is reduced by approximately a factor of 2 by this modification.

Epr Studies On The Mono- And Dicobalt(Ii)-Substituted Forms Of The Aminopeptidase From Aeromonas Proteolytica. Insight Into The Catalytic Mechanism Of Dinuclear Hydrolases, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The structure and function of the prototypical dinuclear hydrolase, namely, the aminopeptidase from Aeromonas proteolytica (AAP), was probed by EPR spectroscopy of the mono- and dicobalt(II)-substituted derivatives. A new systematic protocol for the interpretation of Co(II) EPR spectra is described and the S = ³/₂ spin states of the Co(II)-substituted forms of the enzyme have been characterized. This protocol allows the simulation of line shape using theoretically allowed g_eff values corresponding to an isotropic g_real value. In addition, the gross distortion of EPR spectra of high-spin S = ³/₂ Co(II) ions has been investigated, …

An Atlas Of Computed Equivalent Widths Of Quasar Broad Emission Lines, Kirk Korista, Jack Baldwin, Gary J. Ferland, Dima Verner

Physics and Astronomy Faculty Publications

We present graphically the results of several thousand photoionization calculations of broad emission-line clouds in quasars, spanning 7 orders of magnitude in hydrogen ionizing flux and particle density. The equivalent widths of 42 quasar emission lines are presented as contours in the particle density-ionizing flux plane for a typical incident continuum shape, solar chemical abundances, and cloud column density of N(H) = 10²³ cm^-2. Results are similarly given for a small subset of emission lines for two other column densities (10²² and 10²⁴ cm^-2), five other incident continuum shapes, and a gas …

Optical Properties Of Gan Grown On Zno By Reactive Molecular Beam Epitaxy, F. Hamdani, A. Botchkarev, W. Kim, H. Morkoç, M. Yeadon, J. M. Gibson, S.-C. Y. Tsen, David J. Smith, Donald C. Reynolds, David C. Look, K. R. Evans, Cole W. Litton, William C. Mitchel, P. Hemenger

Physics Faculty Publications

High quality wurtzite GaN epilayers have been grown on ZnO(0001) substrates by reactive molecular beam epitaxy. Photoluminescence and reflectivity measurements point to high quality presumably due to the near match of both the crystal lattice parameter and the stacking order between GaN and ZnO. In addition, the good films lack the characteristic yellow photoluminescence band. Any misorientation of the GaN epilayer planes with respect to the ZnO substrate is not detectable with polarized reflectivity. The x-ray double crystal diffraction measurements indicate this misorientation is much smaller than those for GaN epilayers on SiC and Al₂O₃ . © …

Application Of A Picosecond Soft X-Ray Source To Time-Resolved Plasma Dynamics, J. Workman, M. Nantel, Anatoly Maksimchuk, Donald P. Umstadter

Donald Umstadter Publications

We demonstrate the application of an ultrashort x-ray source as an external probe to measure plasma dynamics. The plasma is generated by a 100-fs Ti: sapphire laser focused onto thin metallic films. Time-resolved spectroscopy of the gold x-ray probe transmission through a perturbed 1000 Å aluminum film reveals redshifts of the L-shell photoabsorption edge. We show that the dynamic behavior of this shift is consistent with the relaxation of the aluminum following the compression generated by a shock wave traveling through the film. An analytic plasma model, with comparison to a numerical hydrodynamics model, indicates compression up to 1.4 …

Blue Light Second Harmonic Generation In The Organic Crystal Ortho-Dicyanovinyl-Anisole, Carl H. Grossman, Samuel Aryeh Schulhofer-Wohl , '98, Erik Robert Thoen , '95

Physics & Astronomy Faculty Works

Type I phase matched second harmonic generation (SHG) in the organic crystal ortho-Dicyanovinyl-anisole (DIVA) has been measured for a range of near infrared fundamental wavelengths (855-960 nm). Turning curves for type I phase matched SHG were derived from measured refractive index values and show noncritical phase matching at 860. Measured type I phase matched SHG is in close agreement with the calculated results and gives effective SHG coefficients ranging from 1.9 to 5.9 times as large as d(32) Of potassium niobate. (C) 1997 American Institute of Physics.

On Protostellar Disks In Herbig Ae/Be Stars, Anatoly Miroshnichenko, Željko Ivezić, Moshe Elitzur

Physics and Astronomy Faculty Publications

The spectral shape of IR emission from Herbig Ae/Be stars has been invoked as evidence for accretion disks around high-mass protostars. Instead, we present here models based on spherical envelopes with an r^-1.5 dust density profile that successfully explain the observed spectral shapes. The spectral energy distributions of eight primary candidates for protostellar disks are fitted in detail for all wavelengths available, from visual to far-IR. The only envelope property adjusted in individual sources is the overall visual optical depth, and it ranges from 0.3 to 3. In each case, our models properly reproduce the data for IR excess, …

Roughening And Preroughening Of Diamond-Cubic {111} Surfaces, Donald L. Woodraska, John A. Jaszczak

Department of Physics Publications

A solid-on-solid model for {111} surfaces of diamond-cubic materials that correctly takes into account the diamond-cubic crystal structure has been developed for Monte Carlo simulation. In addition to a roughening transition at temperature T_R, a distinct preroughening transition at T_PR≈0.43T_R is indicated by divergences in the surface specific heat and order-parameter susceptibility. Preroughening appears to arise naturally in our nearest-neighbor bond model from the entropic freedom available in the nontrivial crystal structure. Preroughening is shown to dramatically lower the nucleation barrier for growth and etching at low driving forces.

[Fe Iv] In The Orion Nebula, R. H. Rubin, R. J. Dufour, Gary J. Ferland, P. G. Martin, C. R. O'Dell, J. A. Baldwin, J. J. Hester, D. K. Walter, Z. Wen

Physics and Astronomy Faculty Publications

Using the Goddard High-Resolution Spectrograph on the Hubble Space Telescope, we measured the flux of [Fe IV] (3d^{5 4}P_5/2 --> 3d^{5 6}S_5/2) λ_vac = 2836.56 Å in the Orion Nebula, the first detection of an [Fe IV] line in an H II region. A useful upper limit is set on the sum of fluxes of [Fe IV] (3d^{5 4}D_{5/2, 3/2} --> 3d^{5 6}S_5/2) λ_vac = 2568.4, 2568.2 Å. By comparing these observations with predicted fluxes from simply ``retrofitting'' our two previous photoionization models, …

High Resolution Imaging Of Thin-Film Recording Heads By Superparamagnetic Magnetic Force Microscopy Tips, Sy_Hwang Liou, S.S. Malhotra, John Moreland, P.F. Hopkins

Sy-Hwang Liou Publications

We have used superparamagnetic magnetic force microscopy (MFM) tips to obtain high spatial resolution MFM images of recording heads. Profiles of the magnetic field gradient above a thin-film recording head under 3 mA bias current to the head and various tip-head distance conditions are presented. At a low tip-head distance, the gap width, gap location, and gap-field structure can be well resolved in these MFM images. Superparamagnetic tips show promise for the magnetic imaging of recording heads with gap widths below 200 nm.

Raman-Scattering Study Of The Order-Disorder Phase Transition In Kscn, R. Li, John R. Hardy

John R. Hardy Papers

Raman measurements were performed from room temperature to above the phase transition at 413 K on KSCN crystals. The internal mode spectra reveal a sideband above the internal CN stretching vibration which shows softening in frequency approaching the phase transition, while the CN mode shifts toward higher frequencies. Given that the sideband is a two-phonon process, involving an off-zone-center CN stretching mode and a lattice phonon, the substantial softening in its frequency shift indicates the possibility of an off-zone-center lattice instability related to the order-disorder phase transition. An anomalous temperature dependence was also found for the intensity of both the …