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Structure And Stability Of The Alx And Alx- Species, Gennady L. Gutsev, Puru Jena, Rodney J. Bartlett

Physics Publications

The electronic and geometrical structures of the ground and low-lying excited states of the diatomic AlX and AlX− series (X=H, Li, Be, B, C, N, O, and F) are calculated by the coupled-cluster method with all singles and doubles and noniterative inclusion of triples using a large atomic natural orbital basis. All the ground-state AlX molecules except for AlF can attach an additional electron and form ground-state AlX− anions. The ground-state AlBe−, AlB−, AlC−, AlN−, and AlO− anions possess excited states that are stable toward autodetachment of an extra electron; AlBe− also has a second excited state. Low-lying excited states …

Hands-On Computer Use In Science Classrooms: The Skeptics Are Still Waiting, Alan Runge, Amy N. Spiegel, Lisa M. Pytlikzillig, Steven Dunbar, Robert Fuller, Glenn Sowell, David W. Brooks

Robert G. Fuller Publications

Frank Collea was a friend of Robert Fuller and David Brooks, and a mentor to Brooks. We miss him for his energy, his enthusiasm for teaching science, and his perception about how to improve science education. Frank Collea was not a big fan of using computers in instruction. Frank was neither an advocate of using computers to deliver instruction, nor an advocate of teaching their use as professional tools. Indeed, he thought that most of those of us who advocate computer use make assertions that are unwarranted. A decade ago, desktop computers were beginning to appear in colleges and universities …

Burnett Description For Plane Poiseuille Flow, Alejandro Garcia, F. Uribe

Faculty Publications

Two recent works have shown that at small Knudsen number ~K! the pressure and temperature profiles in plane Poiseuille flow exhibit a different qualitative behavior from the profiles obtained by the Navier-Stokes equations. Tij and Santos [J. Stat. Phys. 76, 1399 (1994)] used the Bhatnagar-Gross-Kook model to show that the temperature profile is bimodal and the pressure profile is nonconstant. Malek-Mansour, Baras, and Garcia [Physica A 240, 255 (1997)] qualitatively confirmed these predictions in computer experiments using the direct simulation Monte Carlo method (DSMC). In this paper we compare the DSMC measurements of hydrodynamic variables and non-equilibrium fluxes with numerical …

Spectroscopy Of Brown Dwarf Candidates In The Ρ Ophiuchi Molecular Core, Bruce Wilking, Thomas Greene, Michael Meyer

Physics Faculty Works

We present an analysis of low-resolution infrared spectra for 20 brown dwarf candidates in the core of the ρ Ophiuchi molecular cloud. Fifteen of the sources display absorption-line spectra characteristic of late-type stars. By comparing the depths of water vapor absorption bands in our candidate objects with a grid of M dwarf standards, we derive spectral types that are independent of reddening. Optical spectroscopy of one brown dwarf candidate confirms the spectral type derived from the water bands. Combining their spectral types with published near-infrared photometry, effective temperatures and bolometric stellar luminosities are derived, enabling us to place our sample …

Search For “Quadrupole-Bound” Anions. I, Gennady L. Gutsev, Puru Jena, Rodney J. Bartlett

Physics Publications

In a classical model, some anions exist due to the attraction between an electron and a molecule’s dipole moment. When the dipole moment is sufficiently large (μcrit>2.5 D), an electron can be trapped. Can a sufficiently large quadrupole moment produce the same effect? To help answer this question, we can search for molecules with a large quadrupole moment and use predictive, ab initio, correlated quantum chemistry methods to assess whether an anion forms and, if it does, to discover its nature. For this purpose, coupled-cluster calculations are reported for the structure and properties of KnClm and KnCl−m (n,m=0–2). …

Constructing A Portable Sundial, Michelle B. Larson

All Physics Faculty Publications

Throughout history people have used shadows and sundials to measure the passage of time. This article describes how to construct a personal sundial that can be worn as a necklace or carried as a key chain. The activity is easily adaptable for grade levels elementary through high school. The instructions can be scaled for a schoolyard project. We’ve found sundial construction to be a terrific project that not only encourages students to investigate movement of the Sun in the sky, but also allows them to practice their math skills.

Rapid Single- And Multiple-Scattering Exafs Debye-Waller Factor Calculations On Active Sites Of Metalloproteins, Nicholas Dimakis, M-Ali Al-Akhras, Grant Bunker

Physics & Astronomy Faculty Publications

This paper describes recent results using our approach to calculating self-consistently single (SS) and multiple-scattering (MS) Debye- Waller factors (DWF) on active sites of metalloproteins. The calculation of MS DWF, together with the Feff7 program allows us to simulate ab-initio EXAFS spectra for a given temperature systems with no adjustable parameters. In our latest report (Dimakis N., and Bunker G., 1998) we calculate, using density functional and semiempirical approaches, the SS and MS DWF for small molecules and compared them to Raman, infrared and EXAFS spectra. In this report calculation of DWFs is done for tetrahedral Zn imidazole, a complex …

Critical Adsorption On Curved Objects, Andreas Hanke, S. Dietrich

Physics & Astronomy Faculty Publications

A systematic field-theoretical description of critical adsorption on curved objects such as spherical or rodlike colloidal particles immersed in a fluid near criticality is presented. The temperature dependence of the corresponding order parameter profiles and of the excess adsorption are calculated explicitly. Critical adsorption on elongated rods is substantially more pronounced than on spherical particles. It turns out that, within the context of critical phenomena in confined geometries, critical adsorption on a microscopically thin ‘‘needle’’ represents a distinct universality class of its own. Under favorable conditions the results are relevant for the flocculation of colloidal particles.

The Extended Hybrid Model For Optical Phonon Confinement, C. R. Bennett, B. K. Ridley, N. A. Zakhleniuk, M. Babiker

Turkish Journal of Physics

The theory of optical phonons and their confinement in heterostructures is reviewed with analogies made to the theory of acoustic phonons. The dielectric continuum (DC) model is obtained when bulk dispersion is ignored and the hybrid model is found when dispersion is included. The issue of boundary conditions is investigated and the solutions are shown with comparisons made using electron-phonon scattering.

Black Holes And The Sym Phase Diagram, Miao Li, Emil Martinec, Vatche Sahakian

All HMC Faculty Publications and Research

Making combined use of the matrix and Maldacena conjectures, the relation between various thermodynamic transitions in super Yang-Mills (SYM) theory and supergravity is clarified. The thermodynamic phase diagram of an object in DLCQ M theory in four and five non-compact space dimensions is constructed; matrix strings, matrix black holes, and black p-branes are among the various phases. Critical manifolds are characterized by the principles of correspondence and longitudinal localization, and a triple point is identified. The microscopic dynamics of the matrix string near two of the transitions is studied; we identify a signature of black hole formation from SYM physics.

Numerical Simulations Of Fe Ii Emission Spectra, E. M. Verner, D. A. Verner, K. T. Korista, Jason W. Ferguson, F. Hamann, Gary J. Ferland

Physics and Astronomy Faculty Publications

This paper describes the techniques that we have used to incorporate a large-scale model of the Fe⁺ ion and resulting Fe IIemission into CLOUDY, a spectral synthesis code designed to simulate conditions within a plasma and model the resulting spectrum. We describe the numerical methods we use to determine the level populations, mutual line overlap fluorescence, collisional effects, and the heating-cooling effects of the atom on its environment. As currently implemented, the atom includes the lowest 371 levels (up to 11.6 eV) and predicts intensities of 68,635 lines. We describe our data sources, which include the most recent transition …

Measurement Of Jet Shapes In High-Q2 Deep Inelastic Scattering At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

The shapes of jets with transverse energies, EjetT, up to 45 GeV produced in neutral- and charged-current deep inelastic e+p scattering (DIS) at Q2 > 100 GeV2 have been measured with the ZEUS detector at HERA. Jets are identified using a cone algorithm in the η-φ plane with a cone radius of one unit. The jets become narrower as EjetT increases. The jet shapes in neutral- and charged-current DIS are found to be very similar. The jets in neutral-current DIS are narrower than those in resolved processes in photoproduction and closer to those in direct-photon processes for the same ranges in …

Exclusive Electroproduction Of Ρ0 And J/Ψ Mesons At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci

Faculty Publications

Exclusive production of ρ0 and J/ψ mesons in e+p collisions has been studied with the ZEUS detector in the kinematic range 0.25 < Q2 < 50 GeV2, 20 < W < 167 GeV for the ρ0 data and 2 < Q2 < 40 GeV2, 50 < W < 150 GeV for the J/ψ data. Cross sections for exclusive ρ0 and J/ψ production have been measured as a function of Q2, W and t. The spin-density matrix elements r0400, r11-1i and Re r510 have been determined for exclusive ρ0 production as well as r0400 and r041-1 for exclusive J/ψ production. The results are discussed in the context of theoretical models invoking soft and hard phenomena.

Measurement Of Inclusive D*± And Associated Dijet Cross Sections In Photoproduction At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

Inclusive photoproduction of D*± mesons has been measured for photon-proton centre-of-mass energies in the range 130 < W < 28OGeV and photon virtuality Q2 < IGeV2. The data sample used corresponds to an integrated luminosity of 37 pb-1. Total and differential cross sections as functions of the D* transverse momentum and pseudorapidity are presented in restricted kinematical regions and the data are compared with next-to-leading order (NLO) perturbative QCD calculations using the "massive charm" and "massless charm" schemes. The measured cross sections are generally above the NLO calculations, in particular in the forward (proton) direction. The large data sample also allows the study of dijet production associated with charm. A significant resolved as well as a direct photon component contribute to the cross section. Leading order QCD Monte Carlo calculations indicate that the resolved contribution arises from a significant charm component in the photon. A massive charm NLO parton level calculation yields lower cross sections compared to the measured results in a kinematic region where the resolved photon contribution is significant.

Forward Jet Production In Deep Inelastic Scattering At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

The inclusive forward jet cross section in deep inelastic e+p scattering has been measured in the region of cursive Greek chi-Bjorken, 4.5 · 10-4 to 4.5 · 10-2. This measurement is motivated by the search for effects of BFKL-like parton shower evolution. The cross section at hadron level as a function of cursive Greek chi is compared to cross sections predicted by various Monte Carlo models. An excess of forward jet production at small cursive Greek chi is observed, which is not reproduced by models based on DGLAP parton shower evolution. The Colour Dipole model describes the data reasonably well. …

Measurement Of Dijet Photoproduction At High Transverse Energies At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

The cross section for dijet photoproduction at high transverse energies is presented as a function of the transverse energies and the pseudorapidities of the jets. The measurement is performed using a sample of ep-interactions corresponding to an integrated luminosity of 6.3 pb-1, recorded by the ZEUS detector. Jets are defined by applying a kT-clustering algorithm to the hadrons observed in the final state. The measured cross sections are compared to next-to-leading order QCD calculations. In a kinematic regime where theoretical uncertainties are expected to be small, the measured cross sections are higher than these calculations.

Measurement Of Multiplicity And Momentum Spectra In The Current And Target Regions Of The Breit Frame In Deep Inelastic Scattering At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi

Faculty Publications

Charged particle production in neutral current deep inelastic scattering (DIS) has been studied using the ZEUS detector. The evolution of the mean multiplicities, scaled momenta and transverse momenta in Q2 and cursive Greek chi for 10 < Q2 < 5120 GeV2 and cursive Greek chi > 6 × 10-4 has been investigated in the current and target fragmentation regions of the Breit frame. Distributions in the target region, using HERA data for the first time, are compared to distributions in the current region. Predictions based on MLLA and LPHD are inconsistent with the data.

Digital Signal Propagation In Dispersive Media., P. M. Jordan, Ashok Puri

Physics Faculty Publications

In this article, the propagation of digital and analog signals through media which, in general, are both dissipative and dispersive is modeled using the one-dimensional telegraph equation. Input signals are represented using impulsive, Heaviside unit step, Gaussian, rectangular pulse, and both unmodulated and modulated sinusoidal pulse type boundary data. Applications to coaxial transmission lines and freshwater signal propagation, for both digital and analog signals, are included. The analysis presented here supports the finding that digital transmission in dispersive media is generally superior to that of analog. The boundary data (input signals) give rise to solutions of the telegraph equation which …

Weak Localization In Disordered Two-Dimensional Crystals With Half-Filled Band, E.P. Nakhmedov, T. Kaya

Turkish Journal of Physics

Effect of subtitutional impurities on electron localization in two dimensional (2D) lattice near the middle of the band is studied. Calculation of density of the electronic states, \rho (\varepsilon ), increases logaritmically in the middle of the band. This singularity in the density of states of noninteracting electron gas on lattice gives rise to anomalous dependencies of thermodynamic quantities on the temperature. The quantum correction to the conductivity of a nonintreracting electron gas due to Umklapp electron--impurity scattering is calculated. This correction to the conductivity is shown to compete with that from the localization corrrection for a Normal scattering process. …

Efficient Dynamic Unstructured Methods And Applications For Transonic Flows And Hypersonic Stage Separation, Xiaobing Luo

Mechanical & Aerospace Engineering Theses & Dissertations

Relative-moving boundary problems have a wide variety of applications. They appear in staging during a launch process, store separation from a military aircraft, rotor-stator interaction in turbomachinery, and dynamic aeroelasticity.

The dynamic unstructured technology (DUT) is potentially a strong approach to simulate unsteady flows around relative-moving bodies, by solving time-dependent governing equations. The dual-time stepping scheme is implemented to improve its efficiency while not compromising the accuracy of solutions. The validation of the implicit scheme is performed on a pitching NACA0012 airfoil and a rectangular wing with low reduced frequencies in transonic flows. All the matured accelerating techniques, including the …

Ordering Due To Disorder In Frustrated Quantum Magnetic Systems, Taner Yildirim

Turkish Journal of Physics

The phenomenon of order by disorder in frustrated magnetic systems is reviewed. Disorder (thermal or quantum fluctuations) may sometimes give rise to long range ordering in systems with frustration, where one must often consider the selection among classically degenerate ground states which are not equivalent by any symmetry. The lowest order effects of quantum fluctuations in such frustrated systems usually resolves the continues degeneracy of the ground state manifold into discrete Ising--type degeneracy. A unique ground state selection out of this Ising degenerate manifold then occurs due to higher order effects of quantum fluctuations. For systems such as face-centered cubic …

Diverging Strains Near Threshold: Breakdown Of The Elastic Description Of A Charge Density Wave Model, Muhittin Mungan, Susan N. Coppersmith, Valeri M. Vinokur

Turkish Journal of Physics

We analyze the strains near threshold in 1-d charge density wave models at zero temperature and strong pinning. We show that in these models local strains diverge near the depinning threshold and characterize the scaling behavior of the phenomenon. This helps quantify when the underlying elastic description breaks down and plastic effects have to be included.

Photon Counting In Astrophotometry. Fundamentals And Some Advices For Beginners, Romualdas Kalytis

Turkish Journal of Physics

The beginners in astrophotometry are reminded of fundamentals of photon counting. Several advices for new users of electrophotometric technics are given.

Kinematics Of Rs Cvn And W Uma Binaries In The Hipparcos Catalogue, Zeki̇ Aslan, Tuncay Özdemi̇r, Cahi̇t Yeşi̇lyaprak, Ahmet İskender

Turkish Journal of Physics

Space motions of RS CVn and W UMa binaries have been calculated using parallaxes and proper motions from Hipparcos catalogue and radial velocities from the literature. We have calculating the mean motions and velocity dispersions. We have excluded those binaries with relative parallax errors \geq 0.5. The comparison of the asymmetric drift, velocity ellipsoids and vertex deviation with those of main sequence stars given by Dehnen and Binney indicates that both RS CVn and W UMa binaries have kinematics similar to main sequence stars slightly bluer than the Parenago's discontinuity and B-V \simeq 0.62. Implication of this has been discussed.

Factorization And High-Energy Effective Action, Ian Balitsky

Physics Faculty Publications

I demonstrate that the amplitude for high-energy scattering can be factorized as a convolution of the contributions due to fast and slow fields. The fast and slow fields interact by means of Wilson-line operators—infinite gauge factors ordered along the straight line. The resulting factorization formula gives a starting point for a new approach to the effective action for high-energy scattering in QCD.

Soliton Stability In A Z (2) Field Theory, J. J. P. Veerman, D. Bazeia, Fernando Moraes

Mathematics and Statistics Faculty Publications and Presentations

We investigate the stability of the coupled soliton solutions of a two-component Z(2) vector fieldmodel, in contraposition to similar solutions of a Z(2)×Z(2)model recently introduced. We demonstrate that the coupled soliton solutions of the Z(2) model are classically unstable.

Electron Liquid Beyond The Random Phase Approximation, Mehmet Tomak, Ceyhun Bulutay

Turkish Journal of Physics

A deeper understanding of low-dimensional and small-scale electronic systems requires an accurate characterization of the many-electron effects. Based on the electron liquid (EL) model, these many-body effects in the three-dimensional (3D) and two-dimensional (2D) electronic systems are dealt going beyond the random phase approximation within the zero-temperature framework. The dielectric formulation of the many-body problem is recapitulated and the longitudinal dielectric function of the EL is obtained using the self-consistent local-field correction scheme, known as STLS, under a general spin-valley degeneracy. Extensive explicit expressions are provided for the use of other researchers. The performance of this formalism is compared in …

Magnetic Excitations In Random Anisotropic Magnets, İbrahim Avgin

Turkish Journal of Physics

A study is made for the magnetic excitations and their Anderson localization properties for a Heisenberg ferromagnet with random anisotropic fields. The system is assumed to be in a strong applied field so that complete spin alignment is established. The magnetic excitations, i.e., the harmonic spin waves, are computed using coherent-field-anisotropy approximation (a version of coherent potential approximation of the electronic problem). The spin wave shift and damping are calculated using the computed coherent field which is a complex function of energy approximating the random medium as a mean field level. The localizaton of the excitations are calculated by adopting …

Three-Channel General-Purpose Astrophotometer, Romualdas Kalytis

Turkish Journal of Physics

The high-speed three-channel photometer suitable for the time-series observations of the "Whole Earth Telescope" (WET) project as well as for multicolor photometry is described. The photometer, designed for the Capodimonte Astronomical Observatory, Italy, is the latest version of the WET photometers developed by the WET group of Vilnius University since 1992. The main optical and mechanical layouts of the optico-mechanical module as well as the block-diagram of electronics are presented. The main specifications of the photometer expected after its completion are given.

Photometric Imaging With Distributive Solar Analogy, Zeki̇ Eker

Turkish Journal of Physics

The importance of DSA (Distributive Solar Analogy) when modeling starspots from a photometric data is discussed. It's advantage over the other modeling techniques to confine the solution parameters, especially the spot latitudes are described. Unlike the other photometric techniques which tries to locate limited number of cool surface spots, DSA aims to model global distribution of all virtually existing spots.