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Iowa State University

2000

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Articles 1 - 30 of 34

Full-Text Articles in Physics

Chemical And Dynamical Speciation Of Mobile Ions In The Glassy Fast Ionic Conductor Ag2s+B2s3+Sis2: A 109ag Nuclear Magnetic Resonance Study, Tomoko Akai, Steve W. Martin, Ferdinando Borsa Dec 2000

Chemical And Dynamical Speciation Of Mobile Ions In The Glassy Fast Ionic Conductor Ag2s+B2s3+Sis2: A 109ag Nuclear Magnetic Resonance Study, Tomoko Akai, Steve W. Martin, Ferdinando Borsa

Materials Science and Engineering Publications

109Ag NMR in the highly conductive glass 0.525Ag2S+0.475(0.5B2S3+0.5SiS2) was investigated from 230 to 433 K. The 109Ag NMR spectra reveal for the first time three well resolved lines corresponding to three kinds of chemically speciated Ag ions in sites with different chemical shifts in a macroscopically homogeneous glass. This chemical speciation of Ag ions is discussed in relation to the microstructure of the glass. As the temperature is increased, the three lines that originate from three different species of ions are narrowed, but these lines exist independently up to 433 K, the highest ...


Optical And Magneto-Optical Properties And Electronic Structures Of Single-Crystalline Ral2 (R=Y, La, Ce, Pr, And Lu), R. J. Lange, S. J. Lee, K. J. Kim, Paul C. Canfield, David W. Lynch Dec 2000

Optical And Magneto-Optical Properties And Electronic Structures Of Single-Crystalline Ral2 (R=Y, La, Ce, Pr, And Lu), R. J. Lange, S. J. Lee, K. J. Kim, Paul C. Canfield, David W. Lynch

Physics and Astronomy Publications

The diagonal optical conductivity spectra of single crystals of RAl2 (R=Y, La, Ce, Pr, and Lu) were measured at room temperature by spectroscopic ellipsometry in the 1.5–5.6−eV range. All the compounds exhibit two strong interband absorption peaks at about 1.8 and 3.6 eV for YAl2 and LuAl2, and at about 2.0 and 3.0 eV for LaAl2, CeAl2, and PrAl2. Such differences in the second peak position appear in the theoretical optical conductivity spectra calculated from their band structures obtained by the tight-binding linear-muffin-tin-orbitals method. Most of the contributions to the two ...


Surface Diffusion In Mixed Overlayers With Superlattice Ordering: Percolative Transport Around Obstacles And Along Domain Boundaries, Da-Jiang Liu, James W. Evans Dec 2000

Surface Diffusion In Mixed Overlayers With Superlattice Ordering: Percolative Transport Around Obstacles And Along Domain Boundaries, Da-Jiang Liu, James W. Evans

Mathematics Publications

To elucidate surface diffusion in the presence of a coadsorbate with superlattice ordering, we consider particle hopping on a square lattice with some fraction, u B , of quenched blocking sites arranged with checkerboard or c(232) ordering. Behavior for low u B corresponds to diffusion around isolated obstacles, and can be described by exact density expansions. Behavior for high u B corresponds to percolative diffusion along ~or sometimes away from! domain boundaries. The connectivity of these domain boundaries is closely related to the existence of symmetry breaking @i.e., long-range c(232) order# in the distribution of blocking sites. In ...


Electronic Structure Of Quasicrystalline Surfaces: Effects Of Surface Preparation And Bulk Structure, V. Fournée, P. J. Pinhero, J. W. Anderegg, Thomas A. Lograsso, A. R. Ross, Paul C. Canfield, I. R. Fisher, Patricia A. Thiel Dec 2000

Electronic Structure Of Quasicrystalline Surfaces: Effects Of Surface Preparation And Bulk Structure, V. Fournée, P. J. Pinhero, J. W. Anderegg, Thomas A. Lograsso, A. R. Ross, Paul C. Canfield, I. R. Fisher, Patricia A. Thiel

Chemistry Publications

We elucidate the nature of the surface electronic properties of quasicrystalline Al-Pd-Mn. We do this by using photoelectron and Auger electron spectroscopies, and by making a variety of comparisons—across types of bulk samples, and across methods of surface preparation. The main conclusions are these: (i) The narrow Mn 2p3/2core-level line observed in the icosahedral phase is a fingerprint of a suppression in the density of states (a pseudogap) at the Fermi level and is not unique to the quasicrystalline phase. It is also independent of the symmetry of the quasicrystalline surface. The Auger line shape is ...


Temperature-Induced Configurational Excitations For Predicting Thermodynamic And Mechanical Properties Of Alloys, Duane D. Johnson, Andrei V. Smirnov, J. B. Staunton, F. J. Pinski, W. A. Shelton Nov 2000

Temperature-Induced Configurational Excitations For Predicting Thermodynamic And Mechanical Properties Of Alloys, Duane D. Johnson, Andrei V. Smirnov, J. B. Staunton, F. J. Pinski, W. A. Shelton

Duane D. Johnson

We show that a structural energy difference, ΔE, must include explicit symmetry-breaking changes of the electronic structure due to temperature-induced configurational excitations, and why ΔE at T=0 K is not necessarily relevant to thermodynamic and mechanical modeling. In Ni3V, we calculate a tenfold decrease of ΔE between D022 and L12 structures from T=0 K to states of order relevant to experiment. ΔE calculated directly from states with short-range order (8 meV) or with low partial order (7–12 meV) agree with high-T experiment (10 meV).


Observation Of A Metamagnetic Phase Transition In An Itinerant 4f System Via The Magneto-Optic Kerr Effect: Ce(Fe1−Xcox)2, R. J. Lange, I. R. Fisher, Paul C. Canfield, Vladimir P. Antropov, S. J. Lee, Bruce N. Harmon, David W. Lynch Sep 2000

Observation Of A Metamagnetic Phase Transition In An Itinerant 4f System Via The Magneto-Optic Kerr Effect: Ce(Fe1−Xcox)2, R. J. Lange, I. R. Fisher, Paul C. Canfield, Vladimir P. Antropov, S. J. Lee, Bruce N. Harmon, David W. Lynch

Physics and Astronomy Publications

The optical and magneto-optical properties of single crystals of YFe2, CeFe2, and Ce(Fe1−xCox)2 (x≃0.1) were measured between 1.4 and 5.0 eV using a rotating-analyzer ellipsometer and a normal-incidence polar Kerr spectrometer. The electronic structures and optical properties of YFe2 and CeFe2 were calculated using the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation. For YFe2 the calculations reproduce the experimental spectra. Alloying CeFe2 with small amounts of Co leads to an electronic instability which is evidenced by a low-temperature antiferromagnetic (AF) phase. The Kerr effect was measured in the AF and field-induced ...


Superparamagnetic Magnetization Equation In Two Dimensions, David C. Jiles, S. J. Lee, J. M. Kenkel, K. L. Metlov Aug 2000

Superparamagnetic Magnetization Equation In Two Dimensions, David C. Jiles, S. J. Lee, J. M. Kenkel, K. L. Metlov

Ames Laboratory Publications

An equation for the dependence of magnetization on magnetic field in the case of two-dimensional (base plane) anisotropy has been derived. The resulting equation is expressed as an infinite series of modified Bessel functions, unlike the elementary function expressions that are applicable to the one-dimensional (axially anisotropic) and three-dimensional (isotropic) cases. Nevertheless, in the low-field limit, the series can be effectively truncated to give an approximate solution, while, in the high-field limit, an alternative expression has been derived which represents the limiting function as the field strength tends to infinity. The resulting expressions can be used to describe the superparamagnetic ...


6% Magnetic-Field-Induced Strain By Twin-Boundary Motion In Ferromagnetic Ni–Mn–Ga, S. J. Murray, M. Marioni, S. M. Allen, R. C. O'Handley, Thomas A. Lograsso Aug 2000

6% Magnetic-Field-Induced Strain By Twin-Boundary Motion In Ferromagnetic Ni–Mn–Ga, S. J. Murray, M. Marioni, S. M. Allen, R. C. O'Handley, Thomas A. Lograsso

Ames Laboratory Publications

Field-induced strains of 6% are reported in ferromagnetic Ni–Mn–Ga martensites at room temperature. The strains are the result of twin boundary motion driven largely by the Zeeman energy difference across the twin boundary. The strain measured parallel to the applied magnetic field is negative in the sample/field geometry used here. The strain saturates in fields of order 400 kA/m and is blocked by a compressive stress of order 2 MPa applied orthogonal to the magnetic field. The strain versus field curves exhibit appreciable hysteresis associated with the motion of the twin boundaries. A simple model accounts ...


Fine-Scale Comparison Of Toms Total Ozone Data With Model Analysis Of An Intense Midwestern Cyclone, Mark A. Olsen, William A. Gallus Jr., John L. Stanford, John M. Brown Aug 2000

Fine-Scale Comparison Of Toms Total Ozone Data With Model Analysis Of An Intense Midwestern Cyclone, Mark A. Olsen, William A. Gallus Jr., John L. Stanford, John M. Brown

Geological and Atmospheric Sciences Publications

High-resolution (∼40 km) along-track total column ozone data from the Total Ozone Mapping Spectrometer (TOMS) instrument are compared with a high-resolution mesoscale numerical model analysis of an intense cyclone in the Midwestern United States. Total ozone increased by ∼100 DU (nearly 38%) as the TOMS instrument passed over the associated tropopause fold region. Complex structure is seen in the meteorological fields and compares well with the total ozone observations. Ozone data support the meteorological analysis showing that stratospheric descent was confined to levels above ∼600 hPa; significant positive potential vorticity at lower levels is attributable to diabatic processes. Likewise, meteorological ...


Spin Fluctuations In Nearly Magnetic Metals From Ab Initio Dynamical Spin Susceptibility Calculations: Application To Pd And Cr95v5, J. B. Staunton, J. Poulter, B. Ginatempo, E. Bruno, Duane D. Johnson Jul 2000

Spin Fluctuations In Nearly Magnetic Metals From Ab Initio Dynamical Spin Susceptibility Calculations: Application To Pd And Cr95v5, J. B. Staunton, J. Poulter, B. Ginatempo, E. Bruno, Duane D. Johnson

Duane D. Johnson

We describe our theoretical formalism and computational scheme for making ab initio calculations of the dynamic paramagnetic spin susceptibilities of metals and alloys at finite temperatures. Its basis is time-dependent density functional theory within an electronic multiple scattering, imaginary time Green function formalism. Results receive a natural interpretation in terms of overdamped oscillator systems making them suitable for incorporation into spin fluctuation theories. For illustration we apply our method to the nearly ferromagnetic metal Pd and the nearly antiferromagnetic chromium alloy Cr95V5. We compare and contrast the spin dynamics of these two metals and in each case identify those fluctuations ...


Ordering And Percolation Transitions For Hard Squares: Equilibrium Versus Nonequilibrium Models For Adsorbed Layers With C(2x2) Superlattice Ordering, Da-Jiang Liu, James W. Evans Jul 2000

Ordering And Percolation Transitions For Hard Squares: Equilibrium Versus Nonequilibrium Models For Adsorbed Layers With C(2x2) Superlattice Ordering, Da-Jiang Liu, James W. Evans

Mathematics Publications

We study the critical behavior of models for adsorbed layers in which particles reside on a square lattice and have infinite nearest-neighbor repulsions. Such particles are often described as “hard squares.” We consider both the equilibrium hard-square model and a nonequilibrium model. The latter involves dimer adsorption onto diagonally adjacent sites, and the desorption and possible hopping of adsorbed monomer particles (where neither adsorption nor hopping can create adjacent pairs of occupied sites). In the limit of high monomer mobility, one recovers the equilibrium model. Both models exhibit a continuous symmetry breaking transition in the Ising universality class, and also ...


Evidence For A Strong Impact Of The Electron-Photon Matrix Element On Angle-Resolved Photoelectron Spectra Of Layered Cuprate Compounds, S. Haffner, C. G. Olson, L. L. Miller, David W. Lynch Jun 2000

Evidence For A Strong Impact Of The Electron-Photon Matrix Element On Angle-Resolved Photoelectron Spectra Of Layered Cuprate Compounds, S. Haffner, C. G. Olson, L. L. Miller, David W. Lynch

Physics and Astronomy Publications

Little is known about the impact of the electron-photon matrix element on angle-resolved photoelectron spectra of layered cuprate compounds. Using the example of the model layered cuprate Sr2CuO2Cl2, we demonstrate that the electron-photon matrix element has a significant influence on energy distribution curves, rendering their interpretation as images of the spectral function nontrivial.


Rotational Tuning Of Hc2 Anomalies In Erni2b2c: Angular-Dependent Superzone Gap Formation And Its Effect On The Superconducting Ground State, Sergey L. Bud'ko, Paul C. Canfield Jun 2000

Rotational Tuning Of Hc2 Anomalies In Erni2b2c: Angular-Dependent Superzone Gap Formation And Its Effect On The Superconducting Ground State, Sergey L. Bud'ko, Paul C. Canfield

Ames Laboratory Publications

ErNi2B2C is a member of the RNi2B2C family of magnetic superconductors, with Tc≈11 K and TN≈6 K. For magnetic fields applied along the magnetically hard c axis, the upper critical field Hc2 manifests a clear, sharp local maximum at TN. For magnetic fields applied within the basal plane, features in Hc2 are less distinct and there are field induced changes in the local magnetic ordering. In order to address the relationship between Hc2 and local moment order, anisotropic magnetic and transport measurements on single crystals of ErNi2B2C will be presented. In particular, detailed H−T phase diagrams for ...


An Extended Model Of The Barkhausen Effect Based On The Abbm Model, D. M. Clatterbuck, V. J. Garcia, M. J. Johnson, David C. Jiles May 2000

An Extended Model Of The Barkhausen Effect Based On The Abbm Model, D. M. Clatterbuck, V. J. Garcia, M. J. Johnson, David C. Jiles

Ames Laboratory Publications

The Barkhausen model of Alessandro et al. [J. Appl. Phys. 68, 2901 (1990)] has been extended to nonstationary domain walldynamics. The assumptions of the original model limit, its use to situations where the differential permeability, and time derivative of applied field are constant. The later model of Jiles et al. assumes that the Barkhausen activity in a given time interval is proportional to the rate of change of irreversible magnetization which can be calculated from hysteresis models. The extended model presented here incorporates ideas from both of these. It assumes that the pinning field and domain wall velocity behave according ...


Interwoven Magnetic And Flux Line Structures In Single Crystal (Tm,Er)Ni2b2c, P. L. Gammel, D. Lopez, D. J. Bishop, M. R. Eskildsen, N. H. Andersen, K. Mortensen, I. R. Fisher, K. O. Cheon, Paul C. Canfield May 2000

Interwoven Magnetic And Flux Line Structures In Single Crystal (Tm,Er)Ni2b2c, P. L. Gammel, D. Lopez, D. J. Bishop, M. R. Eskildsen, N. H. Andersen, K. Mortensen, I. R. Fisher, K. O. Cheon, Paul C. Canfield

Ames Laboratory Publications

We review studies of the interactions between magnetic order and the flux line lattice (FLL) in the (RE)Ni2B2Cintermetallic borocarbides for (RE)=Tm and Er using small angle neutron scattering (SANS) and magneto-transport. For (RE)=Tm the magnetic order and the FLL assume a common symmetry, sharing a phase transition at ∼2 kOe, despite an order of magnitude difference in periodicity. For (RE)=Er, the penetration depth λ and the coherence length ξ, both of which are derived from the FLL form factor, are modified near TN=6 K by a theoretically predicted weakly divergent pairbreaking. Finally, below 2.3 ...


Viability Of Competing Field Theories For The Driven Lattice Gas, Beate Schmittmann, H. K. Janssen, U. C. Tauber, R. K. P. Zia, K.-T. Leung, J. L. Cardy May 2000

Viability Of Competing Field Theories For The Driven Lattice Gas, Beate Schmittmann, H. K. Janssen, U. C. Tauber, R. K. P. Zia, K.-T. Leung, J. L. Cardy

Beate Schmittmann

It has recently been suggested that the driven lattice gas should be described by an alternate field theory in the limit of infinite drive. We review the original and the alternate field theory, invoking several well-documented key features of the microscopics. Since the alternate field theory fails to reproduce these characteristics, we argue that it cannot serve as a viable description of the driven lattice gas. Recent results, for the critical exponents associated with this theory, are reanalyzed and shown to be incorrect.


Effects Of Fatigue-Induced Changes In Microstructure And Stress On Domain Structure And Magnetic Properties Of Fe–C Alloys, Chester C.H. Lo, F. Tang, S. B. Biner, David C. Jiles May 2000

Effects Of Fatigue-Induced Changes In Microstructure And Stress On Domain Structure And Magnetic Properties Of Fe–C Alloys, Chester C.H. Lo, F. Tang, S. B. Biner, David C. Jiles

Ames Laboratory Publications

A study of the effects of microstructural changes on domain structure and magnetic properties as a result of fatigue has been made on Fe–C alloys subjected to either cold work, stress-relief annealing, or heat treatment that produced a ferritic/pearlitic structure. The magnetic properties varied with stress cycling depending on the initial condition of the samples. Variations in coercivity in the initial stage of fatigue were closely related to the changes in dislocation structure. In the intermediate stage of fatigue the observed refinement of domain structures was related to the development of dislocation cell structures and formation of slip ...


Temperature Dependence Of The Magnetomechanical Effect In Metal-Bonded Cobalt Ferrite Composites Under Torsional Strain, Y. Chen, John E. Snyder, Kevin W. Dennis, R. William Mccallum, David C. Jiles May 2000

Temperature Dependence Of The Magnetomechanical Effect In Metal-Bonded Cobalt Ferrite Composites Under Torsional Strain, Y. Chen, John E. Snyder, Kevin W. Dennis, R. William Mccallum, David C. Jiles

Materials Science and Engineering Publications

Metal-bonded cobaltferrite composites are promising candidates for torquesensors and other magnetostrictive sensing and actuating applications. In the present study, the temperature dependence of the magnetomechanical effect in a ring-shape cobaltferrite composite under torsional strain has been investigated in the temperature range of −37 to 90 °C. The changes of external axial magnetic field were measured as a function of applied torque. Magnetomechanical sensitivity of ΔHext/Δτ=65 A N−1 m−2 was observed with a magnetomechanical hysteresis of Δτ=±0.62 N m at room temperature (22 °C). These were then measured as a function of temperature. Both decreased ...


Optical And Magneto-Optical Properties Of Rfe2 (R=Gd,Tb,Ho,Lu) And Gdco2, S. J. Lee, R. J. Lange, Paul C. Canfield, Bruce N. Harmon, David W. Lynch Apr 2000

Optical And Magneto-Optical Properties Of Rfe2 (R=Gd,Tb,Ho,Lu) And Gdco2, S. J. Lee, R. J. Lange, Paul C. Canfield, Bruce N. Harmon, David W. Lynch

Physics and Astronomy Publications

The conductivity tensors of single crystals and polycrystals of RFe2 (R=Gd,Tb,Ho,Lu) and GdCo2 were determined in the visible and near UV ranges. The magneto-optical Kerr effect (MOKE) was studied at different temperatures and magnetic fields. The single-crystal data show more features and larger magnitudes in the MOKE spectrum than the polycrystalline data under the same experimental conditions. The theoretical optical conductivity tensors for these compounds were calculated using the tight-binding linear-muffin-tin orbital (TB-LMTO) method in the local spin-density approximation. The agreement between theory and experiment was poor except for LuFe2, in which the 4f shell is ...


Optical Properties And Electronic Structure Of Single Crystals Of Lual2 And Ybal2, S. J. Lee, S. Y. Hong, I. R. Fisher, Paul C. Canfield, Bruce N. Harmon, David W. Lynch Apr 2000

Optical Properties And Electronic Structure Of Single Crystals Of Lual2 And Ybal2, S. J. Lee, S. Y. Hong, I. R. Fisher, Paul C. Canfield, Bruce N. Harmon, David W. Lynch

Physics and Astronomy Publications

The optical conductivities of single crystals of LuAl2 and YbAl2 were measured by spectroscopic ellipsometry in the energy range of 1.4–5.5eV for LuAl2 and 1.4–5.2eV for YbAl2. The optical conductivity spectra of LuAl2 and YbAl2 show similar features except for a difference in magnitude. Both have peaks near 1.8–2.1eV and broad shoulders between 3.0 and 4.0eV. The shoulder is weaker in YbAl2. The band structure, density of states, and optical conductivity were calculated with the tight-binding linear muffin-tin orbital method in the atomic sphere approximation. The calculated optical conductivity ...


Universal Aspects Of Vacancy-Mediated Disordering Dynamics: The Effect Of External Fields, Wannapong Triampo, Timo Aspelmeier, Beate Schmittmann Mar 2000

Universal Aspects Of Vacancy-Mediated Disordering Dynamics: The Effect Of External Fields, Wannapong Triampo, Timo Aspelmeier, Beate Schmittmann

Beate Schmittmann

We investigate the disordering of an initially phase-segregated binary alloy, due to a highly mobile defect which couples to an electric or gravitational field. Using both mean-field and Monte Carlo methods, we show that the late stages of this process exhibit dynamic scaling, characterized by a set of exponents and scaling functions. A new scaling variable emerges, associated with the field. While the scaling functions carry information about the field and the boundary conditions, the exponents are universal. They can be computed analytically, in excellent agreement with simulation results.


Shadowing Corrections And Diffractive Production In Dis On Nuclei, E. Gotsman, E Levin, M. Lublinsky, U. Maor, Kirill Tuchin Jan 2000

Shadowing Corrections And Diffractive Production In Dis On Nuclei, E. Gotsman, E Levin, M. Lublinsky, U. Maor, Kirill Tuchin

Kirill Tuchin

We calculate, in the Glauber–Mueller approach, the ratio of the diffractive dissociation cross section to the total cross section for nuclei. We observe that shadowing corrections (SC) in the calculated ratio are significant, but they do not lead to a smooth energy dependence of the ratio for a proton target as was observed at HERA.


Field-Induced Vacancy Localization In A Driven Lattice Gas: Scaling Of Steady States, M. Thies, Beate Schmittmann Jan 2000

Field-Induced Vacancy Localization In A Driven Lattice Gas: Scaling Of Steady States, M. Thies, Beate Schmittmann

Beate Schmittmann

With the help of Monte Carlo simulations and a mean-field theory, we investigate the ordered steady-state structures resulting from the motion of a single vacancy on a periodic lattice which is filled with two species of oppositely “charged” particles. An external field biases particle-vacancy exchanges according to the particle’s charge, subject to an excluded volume constraint. The steady state exhibits charge segregation, and the vacancy is localized at one of the two characteristic interfaces. Charge and hole density profiles, an appropriate order parameter, and the interfacial regions themselves exhibit characteristic scaling properties with system size and field strength. The ...


Behavior Of Grain Boundary Resistivity In Metals Predicted By A Two-Dimensional Model, Rand Dannenberg, Alexander H. King Jan 2000

Behavior Of Grain Boundary Resistivity In Metals Predicted By A Two-Dimensional Model, Rand Dannenberg, Alexander H. King

Alexander H. King

The behavior of a model for the specific grain boundary resistivity in metallic bamboo conductor lines is developed and compared to other theoretical treatments, and to experiment. The grain boundary is modeled as an array of scatterers on a plane. The scatterers are called “vacancy-ion” complexes, in which the vacancy represents the boundary free volume, and the ion is an atom adjacent to the vacancy. Three cases are investigated, that of noninterfering scatterers, a continuum of interfering scatterers, and discrete interfering scatterers. The approximations used lead to a specific grain boundary resistivity ∼10−16 Ω m2 for aluminum, in agreement ...


The Influence Of Growth Rate On Porosity In Al-Pd-Mn Icosahedral Quasicrystals, Amy R. Ross, Ian R. Fisher, Paul C. Canfield, Thomas A. Lograsso Jan 2000

The Influence Of Growth Rate On Porosity In Al-Pd-Mn Icosahedral Quasicrystals, Amy R. Ross, Ian R. Fisher, Paul C. Canfield, Thomas A. Lograsso

Ames Laboratory Conference Papers, Posters, and Presentations

Growth experiments have been carried out to characterize the occurrence and development of porosity in Bridgman and flux grown Al-Pd-Mn icosahedral quasicrystals. The porosity level has been observed to fluctuate between values of 0.0 and 3.75 percent along the length of Bridgman single crystals implying that the development of porosity is affected by the local growth conditions. Experiments were conducted to evaluate the influence of the rate of solidification on the occurrence of porosity. Alloys were solidified with different growth rates, 1mm/hr and >10 mm/hr, using the Bridgman configuration and at different cooling rates, ranging from ...


Solution To The Evolution Equation For High Parton Density Qcd, E. Levin, Kirill Tuchin Jan 2000

Solution To The Evolution Equation For High Parton Density Qcd, E. Levin, Kirill Tuchin

Kirill Tuchin

In this paper a solution is given to the non-linear equation which describes the evolution of the parton cascade in the case of the high parton density. The related physics is discussed as well as some applications to heavy ion - ion collisions.


Metallic Compounds Of Scandium-Tellurium And Related Systems , Paul Anthony Maggard Jr. Jan 2000

Metallic Compounds Of Scandium-Tellurium And Related Systems , Paul Anthony Maggard Jr.

Retrospective Theses and Dissertations

Research contributions from our group have evinced significant progress in the solid-state chemistry of the rare-earth metal halides. This thesis presents results of the first extension of this progress into the scandium-tellurium and related ternary systems. The first evidence for the existence of metal-rich compounds in this system was the synthesis of Sc2Te. The internal metal-bonded features of the structure are double quasi-infinite chains of trans-edge-sharing metal octahedra, further augmented on each end by square-pyramids down the chain. These scandium chains have a blade-like shape and are spaced apart by tellurium atoms and a scandium zigzag chain. A second metal-rich ...


Optically Detected Magnetic Resonance Studies On Small [Pi]-Conjugated Molecules , Brian Leigh Uhlhorn Jan 2000

Optically Detected Magnetic Resonance Studies On Small [Pi]-Conjugated Molecules , Brian Leigh Uhlhorn

Retrospective Theses and Dissertations

This work describes and discusses the X-band Photoluminescence (PL) Detected Magnetic Resonance (PLDMR) of three small pi-conjugated molecules as powders, films, and solutions: 5,6,11,12-tetraphenyl tetracene (rubrene), Tris (8-hydroxyquinoline) Aluminum (Alq3), and 4,4'-Bis (9-carbazolyl) biphenyl (CBP);Rubrene exhibited both quenching and enhancing triplet resonances but lacked a detectable spin ½ polaron resonance. These triplet resonances changed over the course of time in both the powder and film samples. These changes appeared to be correlated with changes in their morphology or microstructure. In the powder, the relatively narrow quenching pattern weakened after the first measurement leaving the ...


Studies Of The Inclusive Semileptonic Decays Of The B-Hadrons , Jong Il Yi Jan 2000

Studies Of The Inclusive Semileptonic Decays Of The B-Hadrons , Jong Il Yi

Retrospective Theses and Dissertations

A detailed description of a new analysis, in which the correlation of the electric charge of the b-quark to that of the lepton is utilized to isolate different decay modes of the b-hadrons, is presented. Using the data collected by the DELPHI detector during the 1994 and 1995 data-taking periods, the inclusive b-hadron semileptonic branching fraction is measured to be B R b→ℓ % =10.75+/-0.15stat +/-0.28syst -0.24+0.43model . Along with the semileptonic branching fraction, the branching fractions for the cascade mode, b→c→ℓ , and the upper-vertex mode, b→c&d1;→ℓ , are also measured: BR b→c ...


Photonic Bandgap Materials: Design, Fabrication, And Characterization , Ganapathi S. Subramania Jan 2000

Photonic Bandgap Materials: Design, Fabrication, And Characterization , Ganapathi S. Subramania

Retrospective Theses and Dissertations

The last few decades have seen a tremendous explosion in the area of new synthetic materials. As we begin to better understand the nature of the atomic and molecular bonds it has been possible to systematically search for materials with specific properties thanks to the availability of powerful supercomputers. Due to significant advances in materials synthesis a rich variety of artificial materials whose mechanical, chemical, electronic and optical properties can be suitably tailored can now be produced. Some of the materials (plastics, synthetic fibers, ceramics, alloys etc.) can replace or substitute traditional materials; some others have managed to create new ...