Digital Commons Network^™

Light Curve Changes In The Eclipsing Binary V719 Her, Edward G. Schmidt

Department of Physics and Astronomy: Faculty Publications

The General Catalogue of Variable Stars (Kholopov 1985) lists V719 Her as a probable type c RR Lyrae star with a period of 0.336 days. In the remarks, it is noted that another possibility is that V719 Her is a W UMa eclipsing binary with a period of .67 days. Schmidt (1991; 1993) obtained 15 light curve points in 1989-91 and concluded that V719 Her is indeed a W UMa star but with a period of .400995 days. Goderya, Leung and Schmidt (1996; 1997) subsequently obtained extensive photometry in 1993 which pro¬vided timings for five minima over an interval of …

Erratum: Equilibrium Polymerization Of Chains And Rings: A Bicritical Phenomenon, Rolfe G. Petschek

Faculty Scholarship

[No abstract available]

In Situ Measurement Of Radiation Induced Conductivity In Oxide Insulators During Neutron Irradiation, D. P. White, L. L. Snead, S. J. Zinkle, W. S. Earthley

Physics Faculty Publications

No abstract provided.

The Surface Plasmon Enhancement Effect On Adsorbed Molecules At Elevated Temperatures, P.T. Leung, Hai-Pang Chiang, W. S. Tse

Physics Faculty Publications and Presentations

The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure is idealized to be a monodisperse spherical particle with its nonlocal dielectric response accounted for. The temperature effects are modeled using a temperature-dependent collision frequency in the Drude model. Numerical results show that only a small decrease in the SERS enhancement ratio occurs for temperatures up to the melting point of the substrate, even for scattering close to the surface plasmon resonance frequency of the metal. More definitive results are subjected to more …

Thermal Equilibrium Of Warm Clouds Of Charge With Small Aspect Ratio, Deborah L. Paulson, Ross L. Spencer

Faculty Publications

Global thermal equilibrium computations are presented for non-neutral plasmas whose radial size is much larger than their axial thickness. Axial and radial density profiles are computed for both ideal and nonideal Penning trap fields. Simple results are obtained in the limits of both low and high central density. Comparison is made to the grid calculations of Mason et al. [Phys. Plasmas 3 (5), 1502 (1996)].

Measurement Of The Total Cross Section For E+E-→Hadrons At √S=10.52 Gev, R. Ammar, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using the CLEO detector at the Cornell Electron Storage Ring, we have made a measurement of R≡ σ(e⁺e^- → hadrons)/σ(e⁺e^-→μ⁺μ^-)=3.56± 0.01± 0.07 at √s= 10.52 GeV. This implies a value for the strong coupling constant of α_s(10.52 GeV) =0.20±0.01±0.06, or α_s (M_Z)=0.13±0.005±0.03.

Specific Heat And Critical Fields Of The Organic Superconductor Β″–(Bedt-Ttf)2sf5ch2cf2so3, S. Wanka, J. Hagel, D. Beckmanm, J. Wosnitza, J. A. Schlueter, Jack M. Williams, P. G. Nixon, Rolf Walter Winter, Gary L. Gard

Chemistry Faculty Publications and Presentations

We report on specific-heat, magnetization, and ac-susceptibility measurements of β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, an organic superconductor with Tc=4.5 K, where BEDT-TTF stands for bis(ethylenedithio)-tetrathiafulvalene. The jump of the specific heat C at Tc and the exact form of the specific heat difference between C in the superconducting (B=0 T) and in the normal (B=3.5 T) state can be well described by BCS theory with strong coupling. We estimate an electron-phonon coupling parameter λ≈1.1. From measurements of C in magnetic fields we extract the upper critical field Bc₂(T). Low-field dc-magnetization measurements were used to determine the temperature dependence of the lower critical field Bc₁. …

Electron-Irradiation-Induced Deep Level In N-Type Gan, Z-Q. Fang, Joseph W. Hemsky, David C. Look, M. P. Mack

Physics Faculty Publications

Deep-level transient spectroscopy measurements of n-type GaN epitaxial layers irradiated with 1-MeV electrons reveal an irradiation-induced electron trap at E_C−0.18 eV. The production rate is approximately 0.2 cm⁻¹, lower than the rate of 1 cm⁻¹ found for the N vacancy by Hall-effect studies. The defect trap cannot be firmly identified at this time. ©1998 American Institute of Physics.

The Nature Of The Continuum Limit In The 2d Rp^2 Gauge Model, Simon Catterall, M. Hasenbusch, R. R. Horgan, R. Renken

Physics - All Scholarship

The RP(2) gauge model is studied in 2D. We use Monte-Carlo renormalization techniques for blocking the mean spin-spin interaction, , and the mean gauge field plaquette. The presence of the O(3) renormalized trajectory is verified and is consistent with the known three-loop beta-function. The first-order `vorticity' transition observed by Solomon et al. is confirmed, and the location of the terminating critical point is established. New scaling flows in (,) are observed associated with a large exponent kappa in the range 4~5. The scaling flows give rise to a strong cross-over effect between regions of high and low vorticity …

Novel Doubly Excited States Produced In Negative Ion Photodetachment, Anthony F. Starace

Anthony F. Starace Publications

Eigenchannel R-matrix calculations for photodetachment partial cross sections of H^–, Li^–, Na^–, and Aℓ^– provide results that are dominated by high doubly-excited states and that are in excellent agreement with available measurements. Propensity rules for doubly-excited states developed for H^– apply also for heavier targets. However, states not observed in H^– may be observed in the heavier target spectra owing to the non-Coulomb core. Finally the signature of particular doubly excited states changes drastically from one partial cross section to another.

Fluctuation Properties Of Precipitation. Part Ii: Reconsideration Of The Meaning And Measurement Of Raindrop Size Distributions, A. R. Jameson, Alexander Kostinski

Department of Physics Publications

For M drop size categories, rain is frequently viewed simply as the superposition of M,statistically independent Poisson-distributed drop fluxes each described by its own mean concentration. Implicit in such a Poissonian model is the assumption of uncorrelated counts among the drops. However, it is well known that drop size distributions are the result of the processes of collision, coalescence, and breakup, which should lead to correlations.

This inconsistency is resolved in this work. Using 1-min disdrometer measurements, two-point cross-correlation functions are used to show that drop counts at different sizes are correlated rather than independent. Moreover, it is argued …

Optimal Renormalization Scale And Scheme For Exclusive Processes, Stanley J. Brodsky, Chueng-Ryong Ji, Alex Pang, David G. Robertson

Physics Faculty Scholarship

We use the Brodsky-Lepage-Mackenzie (BLM) method to fix the renormalization scale of the QCD coupling in exclusive hadronic amplitudes such as the pion form factor and the photon-to-pion transition form factor at large momentum transfer. Renormalization-scheme-independent commensurate scale relations are established which connect the hard scattering subprocess amplitudes that control exclusive processes to other QCD observables such as the heavy quark potential and the electron-positron annihilation cross section. The commensurate scale relation connecting the heavy quark potential, as determined from lattice gauge theory, to the photon-to-pion transition form factor is in excellent agreement with γe⃗ π0e data assuming that the …

Dynamics And Instabilities Near The Glass Transition: From Clusters To Crystals, Saroj K. Nayak, Puru Jena, Keith D. Ball, R. Stephen Berry

Physics Publications

Molecular dynamics simulation has been used to explore the evolution, kinetics, and dynamics of a liquid–glass transition in clusters and bulk matter. We demonstrate a dynamical indicator that characterizes the onset of the glass transition in clusters and is consistent with other indicators of glass transitions in bulk systems. This criterion, based on changes in chaotic behavior as measured by the largest Liapunov exponent, reveals aspects of the microscopic processes associated with the phase change from liquid to glass, and provides a connection between the thermodynamic and dynamical behavior of systems and their multidimensional potential surfaces.

Atomic And Electronic Structure Of Neutral And Charged Sinom Clusters, Saroj K. Nayak, B. K. Rao, S. N. Khanna, P. Jena

Physics Publications

Using molecular orbital approach and the generalized gradient approximation in the density functional theory, we have calculated the equilibrium geometries, binding energies, ionization potentials, and vertical and adiabatic electron affinities of SinOm clusters (n⩽6,m⩽12). The calculations were carried out using both Gaussian and numerical form for the atomic basis functions. Both procedures yield very similar results. The bonding in SinOm clusters is characterized by a significant charge transfer between the Si and O atoms and is stronger than in conventional semiconductor clusters. The bond distances are much less sensitive to cluster size than seen for metallic clusters. Similarly, calculated energy …

Geodetic Vlbi Observations Of Egret Blazars, B. Glenn Piner, Kerry A. Kingham

Physics

We present VLBI observations of the EGRET quasars 0202+149, CTA 26, and 1606+106, as well as additional analysis of VLBI observations of 1156+295 presented in a previous letter. We have produced 8 and 2 GHz VLBI images at 11 epochs, 8 epochs, and 12 epochs, spanning the years 1989-1996, of 0202+149, CTA 26, and 1606+106, respectively. The VLBI data have been taken from the Washington VLBI correlator's geodetic database. We have measured the apparent velocities of the jet components and find that CTA 26 and 1606+106 are superluminal sources, with average apparent speeds of 8.9 and 2.9 h-1c …

Cusp Energetic Particle Events: Implications For A Major Acceleration Region Of The Magnetosphere, J. Chen, T. A. Fritz, R. B. Sheldon, Harlan E. Spence, W. N. Spjeldvik, J. F. Fennell, S. Livi, C. T. Russell, J. S. Pickett, D. A. Gurnett

Physics & Astronomy

The Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE) on board the Polar spacecraft observed 75 energetic particle events in 1996 while the satellite was at apogee. All of these events were associated with a decrease in the magnitude of the local magnetic field measured by the Magnetic Field Experiment (MFE) on Polar. These new events showed several unusual features: (1) They were detected in the dayside polar cusp near the apogee of Polar with about 79% of the total events in the afternoonside and 21% in the morningside; (2) an individual event could last for hours; (3) the measured …

Nanosecond Duration Broadband Luminescence Of Quartz Glasses, Maruf A. Kasymdzhanov, Pulat K. Khabibullaev, Saidislam S. Kurbanov

Turkish Journal of Physics

The results of investigations of luminescence, excited by radiations of $N_2$- and $Nd^{3+}$: YAG-lasers ($\lambda = 337 nm, \lambda = 532 nm$) in high purity quartz glasses are reported. The luminescence has broad spectrum (350-850 nm) and very short duration (1-20 ns).

Production Of Susy Particles In Polarized \Gammap Collisions, A. Kandemi̇r

Turkish Journal of Physics

We discuss the production of several SUSY particles in the high energy collisions of the real photons off the protons within the MSSM. The polarizations of the colliding beams are also considered. The discovery mass limits for the squark and gluinos are presented and we conclude that the capacity of the future TeV scale $\gamma p$ colliders is quite promising in the search for SUSY particles.

Resummation Of Ir Renormalons In A Single Meson Photoproduction, Shahin S. Agaev

Turkish Journal of Physics

Single pseudoscalar and vector mesons hard semi-inclusive photoproduction $\gamma h\rightarrow MX $ via higher twist mechanism is calculated using the QCD running coupling constant method. It is proved that in the context of this method a higher twist contribution to the photoproduction cross section cannot be normalized in terms of the meson electromagnetic form factor. The structure of infrared renormalon singularities of the higher twist subprocess cross section and the resummed expression (the Borel sum) for it are found. Comparisons are made with earlier results, as well as with leading twist cross section. Phenomenological effects of studied contributions for $\pi, …

Interdisciplinary Scientists Gather For Plasma Structure Workshop, Jan Josef Sojka

All Physics Faculty Publications

Two of the most exciting papers presented at the Third Peaceful Valley Workshop were on the nature of plasma structure found in the nighttime midlatitude E and F regions. The first was from a coordinated rocket campaign called Sporadic E Experiment over Kyushu (SEEK) dedicated to the understanding of puzzling quasi-periodic radar echoes that have been detected in association with sporadic E layers. In-situ probes on two rockets measured localized electric fields as large as 20 mV/m, confirming theoretical predictions of strong polarization processes that may result from wavelike distortions imposed on normally stratified sporadic E layers. An unexpected result …

Heavy Quark Production At \Gammap Colliders, O. Çakir, M. Yilmaz

Turkish Journal of Physics

Heavy quark pair production at $\gamma p$ colliders is discussed. It is shown that the numbers of $t\bar{t}$ pairs are sufficiently large for investigation of the top quark properties in detail.

Generalized Multiphoton-Ionization Cross Sections Of The Rare Gases For 500-Fs, 248.6-Nm Pulses, Cornelis J. Uiterwaal, D. Xenakis, D. Charalambidis, P. Maragakis, H. Schröder, P. Lambropoulus

C.J.G.J. Uiterwaal Publications

Absolute values for the generalized multiphoton-ionization cross sections and saturation intensities of rare gases are reported for 500-fs, 248.6-nm pulses. For He, Ar, and Kr these values are experimentally determined from the intensity dependence of the ponderomotive shift for intensities comparable to and above the saturation intensity. The measured experimental cross sections [σ₍₅₎^He=(0.9₊₉^-o.4)×10^-152 cm¹⁰ s⁴, σ₍₄₎^Ar=(1.3₊₁^-0.5)×10^-116 cm⁸ s³, σ₍₅₎^Kr=(1.2_+1.7^-0.6)×10^-82 cm⁶ s², σ₍₃₎^Xe=(50_-45⁺³⁵⁰)×10^-82 cm …

Nature Of The Blue-Phase-Iii-Isotropic Critical Point: An Analogy With The Liquid-Gas Transition, M. A. Anisimov, V. A. Agayan, Peter J. Collings

Physics & Astronomy Faculty Works

The analogy with the liquid-gas critical point is analyzed to clarify the nature of the pretransitional behavior of physical properties in the vicinity of the Blue-Phase-m-isotropic transition in chiral liquid crystalline systems. The analogy is unusual: temperature serves as the ordering field and entropy plays the role of the order parameter. Both mean field and parametric equations of state are formulated in terms of scaling fields. The scaling fields are linear combinations of the physical fields, which are temperature and chirality. It is shown that mixing of the physical field variables naturally leads to a strong asymmetry with respect to …

Co Physisorbed On Ionic Crystals: An Extended Beg Spin-Lattice Model Of Absorbed Dipolar Molecules, T. E. Burns, John R. Dennison

All Physics Faculty Publications

The 2D dielectric phases and phase transitions of adsorbed dipolar molecules are studied using a dilute spin-one Ising model. The spin-one formulation assigns a spin S_i=±1 to a (up/down) dipole occupying a lattice site I adsorbed perpendicular to the substrate surface and S_i=0 to unoccupied sites. We relate the mean field expression for the spin-model interaction energy to a more detailed microscopic model involving dipolar, quadrupolar and repulsive interactions beyond nearest neighbor. Analytic solutions in the mean field approximation are discussed for dipole-orientation order–disorder transitions and ferroelectric-to-antiferroelectric transitions as a function of temperature and coverage. The …

Quantum Fields At Any Time, Charles G. Torre, Madhavan Varadarajan

All Physics Faculty Publications

The canonical quantum theory of a free field using arbitrary foliations of a flat two-dimensional spacetime is investigated. It is shown that dynamical evolution along arbitrary spacelike foliations is unitarily implemented on the same Fock space as that associated with inertial foliations. It follows that the Schrodinger picture exists for arbitrary foliations as a unitary image of the Heisenberg picture for the theory. An explicit construction of the Schrodinger picture image of the Heisenberg Fock space states is provided. The results presented here can be interpreted in terms of a Dirac constraint quantization of parametrized field theory. In particular, it …

Single Magnetic Domains In Magnetotactic Bacteria, Richard B. Frankel, Jin-Ping Zhang, Dennis A. Bazylinski

Physics

Magnetotactic bacteria construct an internal, permanent magnetic dipole based on single magnetic domain particles of magnetite or greigite. The organisms exert a high degree of control over the size and morphology of the particles. This may be relevant in distinguishing biogenic from nonbiogenic iron mineral particles.

Magnetic Control Of Convection In Nonconducting Paramagnetic Fluids, J. Huang, Boyd F. Edwards, D. D. Gray

All Physics Faculty Publications

An inhomogeneous magnetic field exerts a magnetic body force on magnetically permeable fluids. A recent experiment [D. Braithwaite, E. Beaugnon, and R. Tournier, Nature (London) 354, 134 (1991)] demonstrates that this force can be used to compensate for gravity and to control convection in a paramagnetic solution of gadolinium nitrate. We provide the theory of magnetically controlled convection in a horizontal paramagnetic fluid layer heated from either above or below. Our theoretical predictions agree with the experiments.

Suppression Of Switchable Polarization In Kdp By Ionizing Radiation, Timothy D. Usher

Physics Faculty Publications

Switching curves were obtained from KH₂PO₄ single crystals exposed to x-ray radiation for various time intervals, up to 8 h. The applied electric field was varied between 370 and 740 V/cm, as well. The temperature was held constant at 99 K. The switching curves were fit to a three-parameter nucleation and growth model based on the original works by Johnson and Mehl, and independently by Avrami. The two dynamic parameters, characteristic time t_c, and effective domain wall dimensionality n, produced values consistent with unirradiated studies, however, they did not show any clear dependancy on …

Hard Diffractive Photoproduction With Rapidity Gap, Ilya F. Ginzburg

Turkish Journal of Physics

Hard diffractive photoproduction with rapidity gap is the best place for study of perturbative Pomeron. Some predictions of pQCD and the range of their applicability are described.

Theoretical Analysis Of The Crystallography For Do_3 --> M18r Martensitic Transformation, Seyfettin Çakmak, Ekrem Artunç

Turkish Journal of Physics

A mathematical approach of the phenomenological theory has been applied to the martensitic transformation of DO$_3 \rightarrow$ M18R close-packed structure. The crystallography of DO$_3 \rightarrow$ M18R martensitic transformation in Fe-25.8 wt\%Mn-7.4wt\%Al-0.11wt\%C alloy was studied using single crystals. Martensitic crystallographic parameters such as habit plane, magnitude of lattice invariant shear, shape deformation direction and orientation relationships are calculated with new mathematical approach. Phenomenological theoretical calculations were compared with predictions of the phenomenological crystallographic CRAB theory and with experimental observations.