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Effect Of Disorder On The Magnetic Properties Of Smco5, Diandra Leslie-Pelecky, R.L. Schalek Jan 1999

Effect Of Disorder On The Magnetic Properties Of Smco5, Diandra Leslie-Pelecky, R.L. Schalek

Diandra Leslie-Pelecky Publications

Mechanical milling of initially ordered ferromagnetic SmCo5 produces dramatic increases in coercivity after short (15 min to 1 h) milling times, accompanied by remanence ratios on the order of 0.7 and shifted hysteresis loops. X-ray diffraction shows that milling induces both chemical and structural disorder. The hysteresis-loop shift is continuous and nonlinear with temperature over the range 5–300 K. The high coercivities are attributed to the formation of a nanostructure consisting of crystalline SmCo5 regions separated by a disordered interphase.

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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 Jan 1999

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 …

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Effects Of Spacecraft Potential On Secondary Electron Yields In Geosynchronous Orbit, Neal E. Nickles Jan 1999

Effects Of Spacecraft Potential On Secondary Electron Yields In Geosynchronous Orbit, Neal E. Nickles

All Physics Faculty Publications

Surface charging due to interactions with the earth=s plasma is a hazard for orbiting spacecraft. Secondary electron (SE) emission is an important physical process in spacecraft charging. Current spacecraft charging models do not consider the SE energy or angular distributions and their implications for estimating the return of SE to the spacecraft. Comprehensive work on the application of SE energy and angular distributions to spacecraft charging has been published [Nickles et al., 1999] and part of that work is summarized here. The application of SE energy distributions to the case of positive charging in geosynchronous orbit is discussed and shown …

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Functional Evolution Of Free Quantum Fields, Charles G. Torre, Madhavan Varadarajan Jan 1999

Functional Evolution Of Free Quantum Fields, Charles G. Torre, Madhavan Varadarajan

All Physics Faculty Publications

We consider the problem of evolving a quantum field between any two (in general, curved) Cauchy surfaces. Classically, this dynamical evolution is represented by a canonical transformation on the phase space for the field theory. We show that this canonical transformation cannot, in general, be unitarily implemented on the Fock space for free quantum fields on flat spacetimes of dimension greater than 2. We do this by considering time evolution of a free Klein-Gordon field on a flat spacetime (with toroidal Cauchy surfaces) starting from a flat initial surface and ending on a generic final surface. The associated Bogolubov transformation …

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Burnett Description For Plane Poiseuille Flow, Alejandro Garcia, F. Uribe Jan 1999

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 …

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Spectroscopy Of Brown Dwarf Candidates In The Ρ Ophiuchi Molecular Core, Bruce Wilking, Thomas Greene, Michael Meyer Jan 1999

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 …

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Search For “Quadrupole-Bound” Anions. I, Gennady L. Gutsev, Puru Jena, Rodney J. Bartlett Jan 1999

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). …

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Noise Measurement Of Yba2Cu3O7-Χ And Ti2Ba2Ca2Cu2O10-Χ Thin Films, J.P. Zheng, Q.Y. Ying, S.Y. Dong, H.S. Kwok, Sy_Hwang Liou Jan 1999

Noise Measurement Of Yba2Cu3O7-Χ And Ti2Ba2Ca2Cu2O10-Χ Thin Films, J.P. Zheng, Q.Y. Ying, S.Y. Dong, H.S. Kwok, Sy_Hwang Liou

Sy-Hwang Liou Publications

The noise of YBa2Cu3O7-χ and Ti2Ba2Ca2Cu2O10-χ thin films in the frequency range from 0.5 Hz to 100 kHz was studied. In the normal state, it was found that 1/f noise dominated, with a magnitude strongly dependent on temperature. In the superconducting state, the noise was only observable at frequencies below 5 Hz with our present setup. Equilibrium thermal fluctuation noise was not observed in these films.

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The Conductor-Dielectric Junctions In A Low Density Plasma, B. V. Vayner, J. T. Galofaro, D. C. Ferguson, Win De Groot, Clint Thomson, John R. Dennison, Robert Davies Jan 1999

The Conductor-Dielectric Junctions In A Low Density Plasma, B. V. Vayner, J. T. Galofaro, D. C. Ferguson, Win De Groot, Clint Thomson, John R. Dennison, Robert Davies

All Physics Faculty Publications

A conductor-dielectric junction exposed to the space environment is a frequent spacecraft design feature. Due to spacecraft charging and/or solar array operation, the conductor can acquire a high potential with respect to the surrounding plasma. If this potential is positive the insulators adjacent to exposed conductors can collect current as if they were conductors themselves. This phenomenon, called snapover, results in a substantial increase in current collection, and may even result in a glow discharge if the potential is high enough. If a conductor has a negative potential, arcing can occur at the site of a junction. Both of these …

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Rapid Optical Variability In Radio-Quiet Quasars, Meenakshi Uppal Jan 1999

Rapid Optical Variability In Radio-Quiet Quasars, Meenakshi Uppal

Theses

Results from imaging and spectral surveys at radio wavelengths indicate that radio quiet quasars (RQQs) may have accretion-fuelled Super Massive Black Holes (SMBH) as their so-called central engines, similar to those hypothesised for radio loud quasars (RLQs). Recent evidence suggests that some RQQs may also harbour weak jets. Rapid optical variability is a common property of most RLQs with compact radio cores, flat radio spectra, and extended linear features emanating from the core and is linked to the presence of a powerful relativistically boosted jet. We present the results of a 3 year monitoring campaign of sixteen RQQs displaying evidence …

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Effects Of Magnetospheric Precipitation And Ionospheric Conductivity On The Ground Magnetic Signatures Of Traveling Convection Vortices, Lie Zhu, Robert W. Schunk, Jan Josef Sojka Jan 1999

Effects Of Magnetospheric Precipitation And Ionospheric Conductivity On The Ground Magnetic Signatures Of Traveling Convection Vortices, Lie Zhu, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

By using an improved TCV model (Zhu et al., 1997), a quantitative study of the effects of magnetospheric precipitation and ionospheric background conductivity on the ground magnetic signatures of traveling convection vortices (TCVs) has been conducted. In this study the localized conductivity enhancement associated with the TCVs is present and the ratio of the Hall and Pedersen conductances vary both spatially and temporally according to the hardness of the TCV precipitation. It is found that a strong conductivity enhancement associated with hard TCV precipitation can significantly distort the TCV current closure in the ionosphere and lead to ground magnetic disturbance …

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Null Geodesics In The Alcubierre Warp Drive Spacetime: The View From The Bridge, Chad Clark, William A. Hiscock, Shane L. Larson Jan 1999

Null Geodesics In The Alcubierre Warp Drive Spacetime: The View From The Bridge, Chad Clark, William A. Hiscock, Shane L. Larson

All Physics Faculty Publications

The null geodesic equations in the Alcubierre warp-drive spacetime are numerically integrated to determine the angular deflection and redshift of photons which propagate through the distortion of the `warp-drive' bubble to reach an observer at the origin of the warp effect. We find that for a starship with an effective warp speed exceeding the speed of light, stars in the forward hemisphere will appear closer to the direction of motion than they would to an observer at rest. This aberration is qualitatively similar to that caused by special relativity. Behind the starship, a conical region forms from within which no …

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Constructing A Portable Sundial, Michelle B. Larson Jan 1999

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.

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The Extended Hybrid Model For Optical Phonon Confinement, C. R. Bennett, B. K. Ridley, N. A. Zakhleniuk, M. Babiker Jan 1999

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.

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Black Holes And The Sym Phase Diagram, Miao Li, Emil Martinec, Vatche Sahakian Jan 1999

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.

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Synchrotron X-Ray Diffraction Of Layering Transitions Of Multilayer Nitrogen Physisorbed On Graphite, T. E. Burns, John R. Dennison, S. N. Ehrlich Jan 1999

Synchrotron X-Ray Diffraction Of Layering Transitions Of Multilayer Nitrogen Physisorbed On Graphite, T. E. Burns, John R. Dennison, S. N. Ehrlich

All Physics Faculty Publications

We use synchrotron x-ray diffraction for structural analysis of the behavior of multilayer nitrogen films physisorbed on graphite foam. We provide structural information and concentrations of 2D and 3D solid phases at a coverage of Θ = 8 ML (Θ / 1 ML for a %3 x %3 structure) for temperatures from below the bulk α-ß transition temperature [Tα-ß = 34 " 0.5 K] to above the bulk triple point [Ttp = 63 K]. Our data indicate layering begins near Tα-ß, with subsequent layering occurring as the temperature is raised; all bulk nitrogen forms disordered film …

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Numerical Simulations Of Fe Ii Emission Spectra, E. M. Verner, D. A. Verner, K. T. Korista, Jason W. Ferguson, F. Hamann, Gary J. Ferland Jan 1999

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 …

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History Of The Forum On Physics And Society, David W. Hafemeister Jan 1999

History Of The Forum On Physics And Society, David W. Hafemeister

Physics

Physics is a major component of many of society's difficult issues: nuclear arms and their proliferation, energy shortages and energy impacts, climate change and technical innovation. Because physics principles underlie so many of these societal issues and because physics offers a way to quantify some aspects of them, members of the American Physical Society (APS) should be encouraged to understand, analyze and debate them. That's precisely why APS members formed the Forum on Physics and Society (FPS). To those of us who have been long involved in FPS affairs, it seems but yesterday that we attended the organizing meeting at …

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Speed Range For Breakdown Waves, Mostafa Hemmati, Eric L. George, Frances Terry Jan 1999

Speed Range For Breakdown Waves, Mostafa Hemmati, Eric L. George, Frances Terry

Journal of the Arkansas Academy of Science

Considering the electrons as the main element in breakdown wave propagation and using a one-dimensional, steady-state, three-fluid, hydrodynamical model, previous investigations have resulted in the completion of a set of equations for conservation of mass, momentum, and energy. We will use the terms proforce and antiforce waves, depending on whether the applied electric field force on electrons is with or against the direction of wave propagation. In the case of antiforce waves, the electron gas temperature and therefore the electron fluid pressure is assumed to be large enough to sustain the wave propagation down the discharge tube. For strong discontinuity …

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Direct Current Glow Discharges In Atmospheric Air, Robert H. Stark, Karl H. Schoenbach Jan 1999

Direct Current Glow Discharges In Atmospheric Air, Robert H. Stark, Karl H. Schoenbach

Bioelectrics Publications

Direct current glow discharges have been operated in atmospheric air by using 100 μm microhollow cathode discharges as plasma cathodes. The glow discharges were operated at currents of up to 22 mA, corresponding to current densities of 3.8 A/cm2 and at average electric fields of 1.2 kV/cm. Electron densities in the glow are in the range from 1012 to 1013  cm−3. Varying the current of the microhollow cathode discharge allows us to control the current in the atmospheric pressure glow discharge. Large volume atmospheric pressure air plasmas can be generated by operating microhollow cathode discharges …

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Approaching Critical Thinking Through Science, Linda A. George, Jack C. Straton Jan 1999

Approaching Critical Thinking Through Science, Linda A. George, Jack C. Straton

Physics Faculty Publications and Presentations

One unanticipated development of University Studies is the degree to which it rapidly became seen not just as general education, but as the replacement for all generally re quired courses. Because the natural sciences had com prised one of the distribution areas of the old program, expectations that the new program would teach science quickly flowered, although exactly what faculty mean by that term has yet to be established. In fact, discussions of what we intend by science education have brought in creased attention to these expectations as we continually revisit the goals of University Studies. The matter is far …

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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 Jan 1999

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 …

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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 Jan 1999

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.

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Measurement Of The Diffractive Cross Section In Deep Inelastic Scattering Using Zeus 1994 Data, 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 Jan 1999

Measurement Of The Diffractive Cross Section In Deep Inelastic Scattering Using Zeus 1994 Data, 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 DIS diffractive cross section, dσdiffγ*p→XN/dMx, has been measured in the mass range Mx < 15 GeV for γ*p c.m. energies 60 < W < 200 GeV and photon virtualities Q2 = 7 to 140 GeV2. For fixed Q2 and Mx, the diffractive cross section rises rapidly with W, dσdiffγ*p→X N (Mx, W, Q2)/dMx ∝ Wadiff with adiff = 0.507 ± 0.034 (stat) +0.155-0.046 (syst) corresponding to a t-averaged pomeron trajectory of ̄αℙ = 1.127 ± 0.009 (stat) +0.039-0.012 (syst) which is larger than ̄αℙ observed in hadron-hadron scattering. The W dependence of the diffractive cross section is found to be the same as that of the total cross section for scattering of virtual photons on protons. The data are consistent with the assumption that the diffractive structure function FD(3)2 factorizes according to cursive greek chiℙFD(3)2(cursive greek chiℙ, β, Q2) = (cursive greek chi0//cursive greek chiℙ)nFD(2)2(β, Q2). They are also consistent with QCD based models which incorporate factorization breaking. The rise of cursive greek chiℙFD(3)2 with decreasing cursive greek chiℙ and the weak dependence of FD(2)2 on Q2 suggest a substantial contribution from partonic interactions.

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Zeus Results On The Measurement And Phenomenology Of F2 At Low Cursive Greek Chi And Low Q2, 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, 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 Jan 1999

Zeus Results On The Measurement And Phenomenology Of F2 At Low Cursive Greek Chi And Low Q2, 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, 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

Faculty Publications

Measurements of the proton structure function F2 for 0.6 < Q2 < 17 GeV2 and 1.2 × 10-5 < cursive Greek chi < 1.9 × 10 -3 from ZEUS 1995 shifted vertex data are presented. From ZEUS F2 data the slopes dF2/d ln Q2 at fixed cursive Greek chi and din F2/d ln(1/cursive Greek chi) for cursive Greek chi < 0.01 at fixed Q2 are derived. For the latter, E665 data are also used. The transition region in Q2 is explored using the simplest non-perturbative models and NLO QCD. The data at very low Q2 ≤ 0.65 GeV2 are described successfully by a combination of generalised vector meson dominance and Regge theory. From a NLO QCD fit to ZEUS data the gluon density in the proton is extracted in the range 3 × 10-5 < cursive Greek chi < 0.7. Data from NMC and BCDMS constrain the fit at large cursive Greek chi. Assuming the NLO QCD description to be valid down to Q2 ∼ 1 GeV2, it is found that the qq̄ sea distribution is still rising at small cursive Greek chi and the lowest Q2 values whereas the gluon distribution is strongly suppressed.

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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 Jan 1999

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.

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Experimental Determination Of \Beta And \Gamma Critical Exponents In The Sol-Gel Phase Transition By Using Steady-State Fluorescence Technique, Y. Yilmaz, Ö. Pekcan Jan 1999

Experimental Determination Of \Beta And \Gamma Critical Exponents In The Sol-Gel Phase Transition By Using Steady-State Fluorescence Technique, Y. Yilmaz, Ö. Pekcan

Turkish Journal of Physics

The gelation of methyl methacrylate and ethylene glycol dimethacrylate was studied using the steady-state fluorescence technique. Samples with various crosslinker densities were prepared and sol-gel phase transitions were observed at various temperatures. Percolation theory was employed to interpret the results. For all samples the gel fraction and the average cluster size exponents, \beta and \gamma, were measured and found to be around 0.42 and 1.7 respectively. These values show excellent agreement with theoretical and simulation results.

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Studies On Extremal Segments In Random Sequences, Deniz Ertaş, Yacov Kantor Jan 1999

Studies On Extremal Segments In Random Sequences, Deniz Ertaş, Yacov Kantor

Turkish Journal of Physics

We review our main findings on the size distribution of the largest neutral segments in a sequence of N randomly charged monomers. Upon mapping to one--dimensional random walks (RWs), this corresponds to finding the probability distribution for the size L of the largest segment that returns to its starting position in an N--step RW. Using analytical, exact enumeration, and Monte Carlo methods, we reveal the complex structure of the probability distribution in the large N limit. In particular, the size of the longest neutral segment has a distribution with a square-root singularity at \ell\equiv L/N = 1, an essential singularity …

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Orbital Period Modulation In Chromospherically Active Close Binaries, Cafer İbanoğlu Jan 1999

Orbital Period Modulation In Chromospherically Active Close Binaries, Cafer İbanoğlu

Turkish Journal of Physics

The orbital period changes in some chromospherically active close binaries have been interpreted as a consequence of magnetic activity. At least in two active close binaries a possible relationship between the orbital period modulation and activity cycle was suggested. The existence of a third companion in these binaries has also been proposed. The light-time effect which arises from orbiting around a third-body has been subtracted from all the O-C values and a cyclic change of the orbital period has been obtained. These cyclic changes seem to be connected with the total brightness variations at least in two samples, namely, V471 …

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Natural Terrestrial Electromagnetic Fields Of Extremely Low Frequencies And Detection Of Periodic Gravitational Radiation, L. V. Grunskaya, D. V. Vinogradov Jan 1999

Natural Terrestrial Electromagnetic Fields Of Extremely Low Frequencies And Detection Of Periodic Gravitational Radiation, L. V. Grunskaya, D. V. Vinogradov

Turkish Journal of Physics

The present research is connected with nontraditional ways of detecting periodic gravitational radiation. Some records of extremely low frequency variations of electromagnetic fields of Earth with extracting periodicities are realized corresponding to the source of gravitational radiation of geophysical and astrophysical origin.

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