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Physics

2003

University of Nebraska - Lincoln

Articles 1 - 30 of 86

Full-Text Articles in Physical Sciences and Mathematics

Fundamental And Magnetic-Hardening Studies Of Rare-Earth And Nanocomposite Magnets, David J. Sellmyer, George C. Hadjipanayis Dec 2003

Fundamental And Magnetic-Hardening Studies Of Rare-Earth And Nanocomposite Magnets, David J. Sellmyer, George C. Hadjipanayis

David Sellmyer Publications

In this project we study new nanocrystalline and nanocomposite structures that have high potential for permanent-magnet development. These materials, which can be synthesized to have either very high or intermediate coercivities, have many applications in electric power, transportation, and information-storage industries. There is great interest in further development of understanding and application of these materials. Following are brief discussions of recent research highlights for the present grant.

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Strong Field Detachment Of A Negative Ion With Non-Zero Angular Momentum: Application To F-, M. V. Frolov, N. L. Manakov, E. A. Pronin, Anthony F. Starace Dec 2003

Strong Field Detachment Of A Negative Ion With Non-Zero Angular Momentum: Application To F-, M. V. Frolov, N. L. Manakov, E. A. Pronin, Anthony F. Starace

Anthony F. Starace Publications

We apply our recently developed, model-independent quantum approach for intense laser detachment of a weakly bound electron to interpret a recent experiment on above-threshold detachment (ATD) of the F- ion. We find that the measured electron energies correspond to the “Keldysh part” of the ATD spectrum, just below the onset of our predicted rescattering plateau. Overall, our predicted ATD spectrum (using a scaled peak intensity and focal averaging) is in excellent agreement with the experimental data, except for certain structures observed for electron energies above 12.6 eV that we attribute to known two-electron resonances of F-. A …

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Measurement Of Prompt Charm Meson Production Cross Sections In Pp̅ Collisions At √S=1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 2003

Measurement Of Prompt Charm Meson Production Cross Sections In Pp̅ Collisions At √S=1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on measurements of differential cross sections d /dpT for prompt charm meson production in pp̅ collisions at √s=1.96 TeV using 5.8±0.3 pb-1 of data from the CDF II detector at the Fermilab Tevatron. The data are collected with a new trigger that is sensitive to the long lifetime of hadrons containing heavy flavor. The charm meson cross sections are measured in the central rapidity region |y|≤1 in four fully reconstructed decay modes: D0→K- π+, D*+→D0 π+, D+→K- π+ π+, …

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United States Patent: Application Of High Spin Polarization Materials In Two Terminal Non-Volatile Bistable Memory Devices, Bernard Doudin, Andrei Sokolov, Cheol-Soo Yang, Lu Yuan, Sy-Hwang Liou Dec 2003

United States Patent: Application Of High Spin Polarization Materials In Two Terminal Non-Volatile Bistable Memory Devices, Bernard Doudin, Andrei Sokolov, Cheol-Soo Yang, Lu Yuan, Sy-Hwang Liou

Sy-Hwang Liou Publications

Disclosed are two terminal bistable memory cells having least two high-spin polarization magnetic material junctions which are separated from one another by electron trap site defect containing insulator. The two terminal bistable memory cells demonstrate stable, low current readable, hysteretic resistance states which are set by the flow of a relatively high, (eg. a milliamp or less), plus or minus polarity D.C. current therethrough, which resistance is monitored by lower magnitude A.C. or D.C. current flow therethrough. Preferred cells have at least one Cr02/Cr203/ CrO2 sequence but typically have multiple Cr02/Cr …

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“Don’T Tell Me, I’Ll Find Out”: Robert Karplus—A Science Education Pioneer, Robert Fuller Dec 2003

“Don’T Tell Me, I’Ll Find Out”: Robert Karplus—A Science Education Pioneer, Robert Fuller

Robert G. Fuller Publications

Robert Karplus (1927–90), who began his career as a brilliant theoretical physicist, switched to science education in the early 1960s. He made many substantial contributions to this field in addition to developing a complete K–6 hands-on science curriculum. Karplus provided his curriculum with a sound epistemological foundation, based on the work of Piaget. He developed an effective classroom teaching strategy, the learning cycle. He and his team used a scientific approach to curriculum development. They focused on teacher development. Karplus was committed to science for ALL students. Through science activities he sought to share the joy of discovery. A recent …

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Laser-Energy Transfer And Enhancement Of Plasma Waves And Electron Beams By Interfering High-Intensity Laser Pulses, P. Zhang, N. Saleh, Shouyuan Chen, Z.M. Sheng, Donald P. Umstadter Nov 2003

Laser-Energy Transfer And Enhancement Of Plasma Waves And Electron Beams By Interfering High-Intensity Laser Pulses, P. Zhang, N. Saleh, Shouyuan Chen, Z.M. Sheng, Donald P. Umstadter

Donald Umstadter Publications

The effects of interference due to crossed laser beams were studied experimentally in the high-intensity regime. Two ultrashort (400 fs), high-intensity (4×1017 and 1.6×1018 W/cm2) and1µm wavelength laser pulses were crossed in a plasma of density 4×1019 cm3. Energy was observed to be transferred from the higher-power to the lower-power pulse, increasing the amplitude of the plasma wave propagating in the direction of the latter. This results in increased electron self-trapping and plasma-wave acceleration gradient, which led to an increased number of hot electrons (by 300%) and hot-electron temperature (by 70%) and a …

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Criss-Crossing Laser Beams Zoom Electrons Along, P. Zhang, N. Saleh, Shouyuan Chen, Z.M. Sheng, Donald P. Umstadter Nov 2003

Criss-Crossing Laser Beams Zoom Electrons Along, P. Zhang, N. Saleh, Shouyuan Chen, Z.M. Sheng, Donald P. Umstadter

Donald Umstadter Publications

Crossing two high-intensity laser beams in a plasma (a collection of charged particles) can have some interesting effects. In a recent experiment performed by researchers at the University of Michigan and the Institute of Physics in China, energy from a higher-power laser pulse was transferred to a lower-power laser pulse. The lower-power pulse had been accelerating electrons with its "wakefield" (like a wave accelerating a surfer). The extra energy to this lower-power pulse enhanced the electron acceleration and decreased the divergence of the electron beam. These features are desirable for proposed "laser particle accelerators" that would be powered by relatively …

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Giant Metamagnetic Moments In A Granular Fecl2-Fe Heterostructure, Sarbeswar Sahoo, Christian Binek, Wolfgang Kleemann Nov 2003

Giant Metamagnetic Moments In A Granular Fecl2-Fe Heterostructure, Sarbeswar Sahoo, Christian Binek, Wolfgang Kleemann

Christian Binek Publications

Giant moments are observed at low temperatures in a granular FeCl2-Fe heterostructure owing to a local metamagnetic transformation of the antiferromagnetic (AF) FeCl2 matrix due to dipolar interactions. A model of metamagnetically (MM) "dressed" single-domain Fe particles is suggested to explain the observations. These include polydispersive ac susceptibility induced by AF-MM domain configurations and weak exchange bias due to non-spin-flipped AF crystallites.

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Search For The Flavor-Changing Neutral Current Decay D0→Μ +Μ - In Pp̅ Collisions At √S =1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Nov 2003

Search For The Flavor-Changing Neutral Current Decay D0→Μ +Μ - In Pp̅ Collisions At √S =1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on a search for the flavor-changing neutral current decay D0→µ+µ- in pp̅ collisions at √s =1.96 TeV using 65 pb-1 of data collected by the CDF II experiment at the Fermilab Tevatron Collider. A displaced-track trigger selects long-lived D0 candidates in the D0→µ+µ- search channel, the kinematically similar D0→ π+ π- channel used for normalization, the Cabibbo-favored D0→ K-π+ channel used to optimize the selection criteria in an unbiased manner, and their charge conjugates. Finding no signal …

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Labview Interface For School-Network Daq Card, Hans Berns, T. H. Burnett, Richard Gran, Graham Wheel, R. Jeffrey Wilkes, Daniel R. Claes, Jared Kite, Gregory R. Snow Nov 2003

Labview Interface For School-Network Daq Card, Hans Berns, T. H. Burnett, Richard Gran, Graham Wheel, R. Jeffrey Wilkes, Daniel R. Claes, Jared Kite, Gregory R. Snow

Gregory Snow Publications

A low-cost DAQ card has been developed for school-network cosmic ray detector projects, providing digitized data from photomultiplier tubes via a standard serial interface. To facilitate analysis of these data and to provide students with a starting point for custom readout systems, a model interface has been developed using the National Instruments LabVIEW(R) system. This user-friendly interface allows one to initialize the trigger coincidence conditions for data-taking runs and to monitor incoming or pre-recorded data sets with updating singles- and coincidence-rate plots and other user-selectable histograms.

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Low-Cost Data Acquisition Card For School-Network Cosmic Ray Detectors, Sten Hansen, Thomas Jordan, Daniel R. Claes, Gregory R. Snow, Hans Berns, T. H. Burnett, Richard Gran, R. Jeffrey Wilkes Nov 2003

Low-Cost Data Acquisition Card For School-Network Cosmic Ray Detectors, Sten Hansen, Thomas Jordan, Daniel R. Claes, Gregory R. Snow, Hans Berns, T. H. Burnett, Richard Gran, R. Jeffrey Wilkes

Gregory Snow Publications

The Cosmic Ray Observatory Project (CROP) at University of Nebraska/Lincoln and the Washington Area Large-scale Time coincidence Array (WALTA) at University of Washington/Seattle are among several outreach projects siting cosmic-ray detectors at local high schools in cities around North America, to study the origins and interactions of highenergy cosmic rays. In a collaboration between QuarkNet, the outreach program based at Fermilab, CROP, and WALTA, a low-cost data acquisition electronics card has been developed to collect and synchronize the data from each detector site. The cost for each card is under US$500 for parts, functionally replacing much more expensive electronics crates …

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Magnetoresistance In Boron Carbide Junctions, L. Bernard, J. Monson, Andrei Sokolov, Zong-Yuan Liu, C.S. Yang, Peter A. Dowben, Bermard Doudin, A. Harken, P. Welsch, B. W. Robertson Nov 2003

Magnetoresistance In Boron Carbide Junctions, L. Bernard, J. Monson, Andrei Sokolov, Zong-Yuan Liu, C.S. Yang, Peter A. Dowben, Bermard Doudin, A. Harken, P. Welsch, B. W. Robertson

Peter Dowben Publications

Photoemission and electric transport properties of ferromagnet–insulator–ferromagnet junctions with boron carbide (C2B10) dielectric barrier are presented. Using a non-oxide barrier confidence avoids oxidation of the interfaces with the ferromagnetic layers. Photoemission confirms chemical abruptness of the interface. Magnetoresistance ratios reaching 50% are observed at low temperatures, and large nonlinearity in the current–voltage curves show that impurities in the junctions play a key role. © 2003 American Institute of Physics.

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The Spectra Of Type Ii Cepheids. Ii. The Hα Line In Intermediate-Period Stars, Edward G. Schmidt, Shawn Langan, Kevin M. Lee, Dale Johnston, Peter R. Newman, Stephanie A. Snedden Nov 2003

The Spectra Of Type Ii Cepheids. Ii. The Hα Line In Intermediate-Period Stars, Edward G. Schmidt, Shawn Langan, Kevin M. Lee, Dale Johnston, Peter R. Newman, Stephanie A. Snedden

Edward Schmidt Publications

We present 98 Hα profiles for 21 pulsating variable stars with periods from 3 to 8 days. The strength, depth, and shape of Hα vary throughout the cycles of the stars in a way consistent with the temperature changes. Otherwise, they are quite uniform among all the stars, with a single exception. In FM Del, Hα is weaker and has a smaller central depth than in the other stars. This and the wavelength shifts of the core are attributed to incipient emission. The differential velocity of Hα relative to the metal lines is less than 25 km s-1 for …

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Elucidating The Mechanisms Of Double Ionization Using Intense Half-Cycle, Single-Cycle, And Double Half-Cycle Pulses, G. Lagmago Kamta, Anthony F. Starace Oct 2003

Elucidating The Mechanisms Of Double Ionization Using Intense Half-Cycle, Single-Cycle, And Double Half-Cycle Pulses, G. Lagmago Kamta, Anthony F. Starace

Department of Physics and Astronomy: Faculty Publications

We investigate the interaction of a two-active electron system (Li-) with intense single-cycle and double half-cycle pulses. The ‘‘intensity’’ and ‘‘frequency’’ considered correspond to the ‘‘multiphoton above-barrier regime.’’ For the single-cycle pulse (SCP), the electric field changes sign once, allowing electron wave packets created during the first half cycle to recollide with the parent ion when driven back by the field. For the double half-cycle pulse (DHP), however, the electric field does not change sign, and electron wave packets created during the first half cycle are not driven back to the parent ion. We find that both single …

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Measurement Of The Mass Difference M(DS+)–M (D+) At Cdf Ii, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Oct 2003

Measurement Of The Mass Difference M(DS+)–M (D+) At Cdf Ii, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a measurement of the mass difference m(Ds+)– m (D+), where both the Ds+ and D+ are reconstructed in the Φπ+ decay channel. This measurement uses 11.6 pb-1 of data collected by CDF II using the new displaced-track trigger. The mass difference is found to be m(Ds+)–m (D+)=99.41±0.38(stat)±0.21(syst) MeV/c2.

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Search For Lepton Flavor Violating Decays Of A Heavy Neutral Particle In Pp̅ Collisions At √S =1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Oct 2003

Search For Lepton Flavor Violating Decays Of A Heavy Neutral Particle In Pp̅ Collisions At √S =1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on a search for a high mass, narrow width particle that decays directly to eµ, eτ, or µτ. We use approximately 110 pb-1 of data collected with the Collider Detector at Fermilab from 1992 to 1995. No evidence of lepton flavor violating decays is found. Limits are set on the production and decay of sneutrinos with R-parity violating interactions.

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Fabrication Of Nonepitaxially Grown Double-Layered Fept:C/Feconi Thin Films For Perpendicular Recording, M.L. Yan, Xingzhong Li, L. Gao, Sy_Hwang Liou, David J. Sellmyer, R.J.M Van De Veerdonk, K.W. Wierman Oct 2003

Fabrication Of Nonepitaxially Grown Double-Layered Fept:C/Feconi Thin Films For Perpendicular Recording, M.L. Yan, Xingzhong Li, L. Gao, Sy_Hwang Liou, David J. Sellmyer, R.J.M Van De Veerdonk, K.W. Wierman

Sy-Hwang Liou Publications

A noneptaxially grown double-layered thin-film medium of nanocompsite FePt:C with a FeCoNi soft underlayer for high-density perpendicular magnetic recording was fabricated and investigated. Square-shaped perpendicular loops with a remanance ratio nearly equal to one and a coercivity as large as 8.5 kOe were obtained for this ordered FePt:C double-layered medium. The formation of the ordered L10 phase is confirmed by electron diffraction experiments. Transmission electron microscope observations reveal that FePt grains with a uniform size less than 5 nm are embedded in the C matrix and appear to be well isolated. Our results show that nonepitaxially grown (001) textured …

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Controlling H- Detachment With Few-Cycle Pulses, S. X. Hu, Anthony F. Starace Oct 2003

Controlling H- Detachment With Few-Cycle Pulses, S. X. Hu, Anthony F. Starace

Department of Physics and Astronomy: Faculty Publications

We present a detailed analysis of short-pulse detachment processes using few-cycle pulses with the aim of demonstrating means for controlling such processes. We first generalize the standard Keldysh-type formalism for laser-target interactions (in which final-state interaction between the detached electron and the core is ignored) to include the possibility that the vector potential is nonzero at the end of the interaction between a short laser pulse and the target. With this formalism in hand, we examine the effects of half-cycle pulses (HCPs) on detachment of the prototypical negative ion H–, and show that detachment by pairs of oppositely-directed (i.e., "bidirectional") …

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Origin And Implications Of The Observed Rhombohedral Phase In Nominally Tetragonal Pb(Zr0.35Ti0.65)O3 Thin Films, Paul C. Mcintyre, Alexei Gruverman, Bryan C. Hendrix, Steven M. Bilodeau, Jeffrey F. Roeder Oct 2003

Origin And Implications Of The Observed Rhombohedral Phase In Nominally Tetragonal Pb(Zr0.35Ti0.65)O3 Thin Films, Paul C. Mcintyre, Alexei Gruverman, Bryan C. Hendrix, Steven M. Bilodeau, Jeffrey F. Roeder

Alexei Gruverman Publications

The structural and electrical properties of Pb(Zr0.35Ti0.65)O3 (PZT) thin films ranging in thickness from 700 to 4000 Å have been investigated. These (001)/(100)-textured films were grown by metalorganic chemical vapor deposition on (111)-textured Ir bottom electrodes. It was observed that, in the as-deposited state, the thinnest PZT films are rhombohedral even though bulk PZT of this composition should be tetragonal. Thicker films have a layered structure with tetragonal PZT at the surface and rhombohedral PZT at the bottom electrode interface. In this article we investigate the origin of this structure and its effect of the …

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Plasma Density Gratings Induced By Intersecting Laser Pulses In Underdense Plasmas, Z.-M. Sheng, Jiandi Zhang, Donald Umstadter Oct 2003

Plasma Density Gratings Induced By Intersecting Laser Pulses In Underdense Plasmas, Z.-M. Sheng, Jiandi Zhang, Donald Umstadter

Donald Umstadter Publications

Electron and ion density gratings induced by two intersecting ultrashort laser pulses at intensities of 1016 W/cm2 or lower are investigated. The ponderomotive force generated by the inhomogeneous intensity distribution in the intersecting region of the interfering pulses produces deep electron and ion density modulations at a wavelength less than a laser wavelength in vacuum. Dependence of the density modulation on the plasma densities, temperatures, and the ion mass, as well as the laser pulse parameters are studied analytically and by particle-in-cell simulations. It is found that the density peaks of such gratings can be a few times …

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Kinetics Of Ferroelectric Switching In Ultrathin Films, G. Vizdrik, Stephen Ducharme, V.M. Fridkin, S.G. Yudin Sep 2003

Kinetics Of Ferroelectric Switching In Ultrathin Films, G. Vizdrik, Stephen Ducharme, V.M. Fridkin, S.G. Yudin

Stephen Ducharme Publications

The kinetics of polarization switching in ultrathin ferroelectric polymer films exhibit a critical behavior; there is a pronounced slowing just above the coercive field and just below the critical temperature. The critical slowing is observed in the switching kinetics of ferroelectric Langmuir-Blodgett films of 70% vinylidene-fluoride and 30% trifluoroethylene copolymer with thickness up to 30 ML. Thicker films exhibit an exponential dependence on the field and temperature that is normally associated with extrinsic switching by domain nucleation and growth. We show that the critical behavior arises naturally from the dynamics of homogeneous intrinsic switching in the context of mean-field theory. …

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Nanocomposite (Nd,Dy)(Fe,Co,Nb,B) 5.5/Α-Fe Multilayer Magnets With High Performance, W. Liu, Z.D. Zhang, J. Ping Liu Sep 2003

Nanocomposite (Nd,Dy)(Fe,Co,Nb,B) 5.5/Α-Fe Multilayer Magnets With High Performance, W. Liu, Z.D. Zhang, J. Ping Liu

David Sellmyer Publications

The structural and magnetic properties of rare-earth nanocomposite magnets of a (Nd,Dy)(Fe,Co,Nb,B) 5.5 single layer and a (Nd,Dy)(Fe,Co,Nb,B) 5.5/α-Fe multilayer prepared by sputtering and heat treatment have been investigated. Incomplete exchange coupling behaviour is observed in the Ti-buffered NdDyFeCoNbB + 40 wt%Fe single layer magnet. After annealing, the laminated nanostructure consisting of mutually dispersed soft and hard phases results in remanence enhancement. The optimum magnetic properties of Jr= 1.11 T, μ0i Hc = 0.88 T and (BH)max = 192 kJ m-3 are achieved in the multilayer magnet annealed at 550°C for 30 min. …

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Observation Of A Narrow Resonance Of Mass 2.46 Gev/C2 Decaying To DS*+ Π0 And Confirmation Of The D*SJ (2317) State, Dave Z. Besson, Kenneth A. Bloom, Cornell Electronic Storage Ring Aug 2003

Observation Of A Narrow Resonance Of Mass 2.46 Gev/C2 Decaying To DS*+ Π0 And Confirmation Of The D*SJ (2317) State, Dave Z. Besson, Kenneth A. Bloom, Cornell Electronic Storage Ring

Kenneth Bloom Publications

Using 13.5 fb-1 of e+e- annihilation data collected with the CLEO II detector, we have observed a narrow resonance decaying to Ds*+π0 with a mass near 2.46 GeV/c2. The search for such a state was motivated by the recent discovery by the BaBar Collaboration of a narrow state at 2.32 GeV/c2, the DsJ*(2317) +, that decays to Ds+ π0. Reconstructing the Ds+ π0 and Ds*+ π0 final states in CLEO data, we …

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Dielectric Permittivity And Electric Modulus In Bi2Ti4O11, Jianjun Liu, Chun-Gang Duan, Wai-Ning Mei, R. W. Smith, John R. Hardy Aug 2003

Dielectric Permittivity And Electric Modulus In Bi2Ti4O11, Jianjun Liu, Chun-Gang Duan, Wai-Ning Mei, R. W. Smith, John R. Hardy

John R. Hardy Papers

Frequency and temperature dependences of dielectric permittivity and electric modulus of pure and Ba-doped Bi2Ti4O11 were studied in the ranges of 10-1–106 Hz and -150–350 °C, respectively. We found that the antiferroelectric phase transition temperature of Bi2Ti4O11 decreases with Ba doping. In the permittivity studies, we also observed dielectric relaxation peaks shift to higher temperature with increasing frequency. Furthermore, in the electric modulus formalism, conducting peaks were uncovered above 150 °C in addition to the dielectric relaxation peak. We discussed the mechanisms for the dielectric relaxation and …

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The Spectra Of Type Ii Cepheids. I. The Hα Line In Short-Period Stars, Edward G. Schmidt, Kevin M. Lee, Dale Johnston, Peter R. Newman, Stephanie A. Snedden Aug 2003

The Spectra Of Type Ii Cepheids. I. The Hα Line In Short-Period Stars, Edward G. Schmidt, Kevin M. Lee, Dale Johnston, Peter R. Newman, Stephanie A. Snedden

Edward Schmidt Publications

We present 88 Hα profiles for 24 pulsating variable stars with periods between 1 and 3 days in order to explore the behavior of this line in type II as compared with classical Cepheids. Surprisingly, large velocity differences were found between Hα and the metal lines in some type II Cepheids. Strong emission was observed in three stars, VZ Aql, NW Lyr, and V439 Oph, while line filling by incipient emission is present in seven others. All of the stars with emission and most with incipient emission belong to Diethelm's AHB2 class, and the emission is associated with the secondary …

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Model-Independent Quantum Approach For Intense Laser Detachment Of A Weakly Bound Electron, M.V. Frolov, N. L. Manakov, E.A. Pronin, Anthony F. Starace Aug 2003

Model-Independent Quantum Approach For Intense Laser Detachment Of A Weakly Bound Electron, M.V. Frolov, N. L. Manakov, E.A. Pronin, Anthony F. Starace

Anthony F. Starace Publications

We present a model-independent theory for laser detachment of a weakly bound electron having a nonzero angular momentum. Our treatment reduces to the well-known Keldysh result for tunnel ionization upon neglecting rescattering effects. Numerical results for the above-threshold detachment spectrum of a negative ion having an outer p electron show significant modification of the rescattering plateau as compared to that for an ion having an outer s electron.

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Boron-Carbide And Boron Rich Rhobohedral Based Transistors And Tunnel Diodes, Peter A. Dowben Jul 2003

Boron-Carbide And Boron Rich Rhobohedral Based Transistors And Tunnel Diodes, Peter A. Dowben

Peter Dowben Publications

The present invention relates to the fabrication of a boron carbide/boron semiconductor devices. The results suggest that with respect to the approximately 2 eV band gap pure boron material, 0.9 eV band gap boron carbide (B5C) acts as a p-type material. Both boron and boron carbide (B5C) thin films were fabricated from single source borane cage molecules using plasma enhanced chemical vapor deposition (PECVD). Epitaxial growth does not appear to be a requirement. We have doped boron carbide grown by plasma enhanced chemical vapor deposition. The source gas close- 1,2-dicarbadecaborane (orthocarborane) was used to grow the …

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Mechanical Stress Effect On Imprint Behavior Of Integrated Ferroelectric Capacitors, Alexei Gruverman, B. J. Rodriguez, A. I. Kingon, R. J. Nemanich, A. K. Tagantsev, J. S. Cross, M. Tsukada Jul 2003

Mechanical Stress Effect On Imprint Behavior Of Integrated Ferroelectric Capacitors, Alexei Gruverman, B. J. Rodriguez, A. I. Kingon, R. J. Nemanich, A. K. Tagantsev, J. S. Cross, M. Tsukada

Alexei Gruverman Publications

Stress-induced changes in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3 (PZT)-based capacitors have been studied using piezoresponse force microscopy. Visualization of polarization distribution and d33-loop measurements in individual 1x1.5-μm2 capacitors before and after stress application, generated by substrate bending, provided direct experimental evidence of stress-induced switching. Mechanical stress caused elastic switching in capacitors with the direction of the resulting polarization determined by the sign of the applied stress. In addition, stress application turned capacitors into a heavily imprinted state characterized by strongly shifted hysteresis loops and almost complete backswitching after application of the poling voltage. …

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Static And Dynamic Dipole Polarizability Of The Helium Atom Using Wave Functions Involving Logarithmic Terms, Mauro Masili, Anthony F. Starace Jul 2003

Static And Dynamic Dipole Polarizability Of The Helium Atom Using Wave Functions Involving Logarithmic Terms, Mauro Masili, Anthony F. Starace

Department of Physics and Astronomy: Faculty Publications

We present a calculation of the static and dynamic dipole polarizability of the helium atom using a variationally stable treatment that incorporates the coupled-channel hyperspherical representation of the wave functions. Inclusion of logarithmic terms in intermediate functions as well as the effect of an optimization procedure for the variational parameter are analyzed. When available, our coupled-channel results are compared with other values in the literature.

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Central Pseudorapidity Gaps In Events With A Leading Antiproton At The Fermilab Tevatron P̅P Collider, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Jul 2003

Central Pseudorapidity Gaps In Events With A Leading Antiproton At The Fermilab Tevatron P̅P Collider, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report a measurement of the fraction of events with a large pseudorapidity gap Δη within the pseudorapidity region available to the proton dissociation products X in p̅+p→p̅+X. For a final state p̅of fractional momentum loss ξp̅ and 4-momentum transfer squared tp̅ within 0.06<ξp̅tp̅|2 at √s=1800 [630] GeV, the fraction of events with Δη>3 is found to be 0.246±0.001 (stat)±0.042 (syst) [0.184±0.001 (stat)±0.043 (syst)]. Our results are compared with gap fractions measured in minimum bias p̅p collisions and with theoretical expectations.

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