Optical, UV, and EUV Oscillations of SS Cygni in Outburst (open access)

Optical, UV, and EUV Oscillations of SS Cygni in Outburst

I provide a review of observations in the optical, UV (HST), and EUV (EUVE and Chandra LETG) of the rapid periodic oscillations of nonmagnetic, disk-accreting, high mass-accretion rate cataclysmic variables (CVs), with particular emphasis on the dwarf nova SS Cyg in outburst. In addition, I drawn attention to a correlation, valid over nearly six orders of magnitude in frequency, between the frequencies of the quasi-periodic oscillations (QPOs) of white dwarf, neutron star, and black hole binaries. This correlation identifies the high frequency quasi-coherent oscillations (so-called ''dwarf nova oscillations'') of CVs with the kilohertz QPOs of low mass X-ray binaries (LMXBs), and the low frequency and low coherence QPOs of CVs with the horizontal branch oscillations (or the broad noise component identified as such) of LMXBs. Assuming that the same mechanisms produce the QPOs of white dwarf, neutron star, and black hole binaries, this correlation has important implications for QPO models.
Date: December 19, 2003
Creator: Mauche, C W
System: The UNT Digital Library
Flame Inhibition by Phosphorus-Containing Compounds in Lean and Rich Propane Flames (open access)

Flame Inhibition by Phosphorus-Containing Compounds in Lean and Rich Propane Flames

Chemical inhibition of laminar propane flames by organophosphorus compounds has been studied experimentally, using a laboratory Mache Hebra nozzle burner and a flat flame burner with molecular beam mass spectrometry (MBMS), and with a computational flame model using a detailed chemical kinetic reaction mechanism. Both fuel-lean and fuel-rich propane flames were studied to examine the role of equivalence ratio in flame inhibition. The experiments examined a wide variety of organophosphorus compounds. We report on the experimental species flame profiles for tri-methyl phosphate (TMP) and compare them with the species flame profile results from modeling of TMP and di-methyl methyl phosphonate (DMMP). Both the experiments and kinetic modeling support and illustrate previous experimental studies in both premixed and non-premixed flames that inhibition efficiency is effectively the same for all of the organophosphorus compounds examined, independent of the molecular structure of the initial inhibitor molecule. The chemical inhibition is due to reactions involving the small P-bearing species HOPO{sub 2} and HOPO that are produced by the organophosphorus compounds (OPCs). The ratios of the HOPO{sub 2} and HOPO concentrations differ between the lean and rich flames, with HOPO{sub 2} dominant in lean flames while HOPO dominates in rich flames. The resulting HOPO{sub 2} …
Date: December 19, 2003
Creator: Curran, H; Korobeinichev, O P; Shvartsberg, V M; Shmakov, A G; Bolshova, T A; Jayaweera, T M et al.
System: The UNT Digital Library
NEUTRINO SCATTERING IN PERTURBATIVE QCD AND IMPLICATIONS FOR THE WEINBERG ANGLE. (open access)

NEUTRINO SCATTERING IN PERTURBATIVE QCD AND IMPLICATIONS FOR THE WEINBERG ANGLE.

We summarize a recent calculation of perturbative neutrino cross sections that includes NLO and mass corrections. We provide numerical results for quantities that are related to the extraction of the weak mixing angle from neutrino deep inelastic scattering.
Date: May 19, 2003
Creator: KRETZER,S. HALL-RENO,M.
System: The UNT Digital Library
Experimental limits on the width of the reportedTheta(1540)+ (open access)

Experimental limits on the width of the reportedTheta(1540)+

None
Date: November 19, 2003
Creator: Cahn, Robert N. & Trilling, George H.
System: The UNT Digital Library
Modeling of recent volcanic episodes at Phlegrean Fields (Italy): Geochemical variations and ground deformation (open access)

Modeling of recent volcanic episodes at Phlegrean Fields (Italy): Geochemical variations and ground deformation

None
Date: August 19, 2003
Creator: Todesco, Micol; Rutqvist, Jonny; Chiodini, Giovanni; Pruess, Karsten & Oldenburg, Curtis M.
System: The UNT Digital Library
Speciation of technetium in borosilicate glasses prepared in air (open access)

Speciation of technetium in borosilicate glasses prepared in air

A series of glass samples were prepared analogous to high level waste glass using either glass frit or glass precursors combined with a high level waste surrogate containing NaTcO{sub 4}. Three different technetium species were observed in these glasses depending upon the synthesis conditions. If the glasses were prepared by reducing NaTcO{sub 4} to TcO{sub 2} {center_dot} 2H{sub 2}O with hydrazine or if a large amount of organic material was present, inclusions of TcO{sub 2} were observed. If no organic material was present, technetium was incorporated as TcO{sub 4}{sup -}. If only a small amount of organic material was present, isolated Tc(IV) sites were observed in the glass. The relative technetium retention of these glasses was estimated from the Tc K-edge height, and had no correlation with the oxidation state of the technetium. Pertechnetate was well retained in these glasses.
Date: December 19, 2003
Creator: Lukens, Wayne W.; Shuh, David K.; Muller, Isabelle S. & McKeown, David A.
System: The UNT Digital Library
Failure by fracture and fatigue in 'NANO' and 'BIO'materials (open access)

Failure by fracture and fatigue in 'NANO' and 'BIO'materials

The behavior of nanostructured materials/small-volumestructures and biologi-cal/bio-implantable materials, so-called "nano"and "bio" materials, is currently much in vogue in materials science. Oneaspect of this field, which to date has received only limited attention,is their fracture and fatigue properties. In this paper, we examine twotopics in this area, namely the premature fatigue failure ofsilicon-based micron-scale structures for microelectromechanical systems(MEMS), and the fracture properties of mineralized tissue, specificallyhuman bone.
Date: December 19, 2003
Creator: Ritchie, R. O.; Muhlstein, C. L. & Nalla, R. K.
System: The UNT Digital Library
Recent improvements to the ASTRA particle tracking code (open access)

Recent improvements to the ASTRA particle tracking code

The Astra simulation code has been successfully used in the design of linac and rf photoinjector systems utilizing beams with azimuthal symmetry. We present recently implemented changes to Astra that allow tracking of beams in beamlines without the assumption of any symmetry. The changes especially include a 3D mesh space charge algorithm and the possibility to import 3D electromagnetic fieldmaps from eigensolver programs.
Date: May 19, 2003
Creator: Flottmann, Klaus; Lidia, Steven & Piot, Philippe
System: The UNT Digital Library
D0 silicon trackers (open access)

D0 silicon trackers

The present Fermilab D0 silicon microstrip tracker, the silicon microstrip tracker which was designed to replace it, and plans for upgrading the present silicon tracker are described.
Date: December 19, 2003
Creator: Cooper, W. E.
System: The UNT Digital Library
Emittance compensation studies of photoinjector beams with angular momentum (open access)

Emittance compensation studies of photoinjector beams with angular momentum

Beam dynamics studies on the FNPL photo injector that seek to optimize the transport of intense electron beams with large values of canonical angular momentum have been performed. These studies investigate the effect of solenoid emittance compensation on beams that evolve under the combined influence of intense space charge forces and large angular momentum. We present details of experimental measurements and supporting simulations of beam envelope evolution.
Date: May 19, 2003
Creator: Lidia, Steven
System: The UNT Digital Library
The CDF Run IIa Silicon Detector and Its Upgrade RunIIb (open access)

The CDF Run IIa Silicon Detector and Its Upgrade RunIIb

The CDF RunIIa silicon detector made the transition from commissioning to data taking. CDF's online and offline tracking algorithms, the performance of Layer 00 and the RunIIb silicon upgrade project are covered in this article.
Date: December 19, 2003
Creator: Issever, Cigdem
System: The UNT Digital Library
Hera Beam Tail Shaping by Tune Modulation. (open access)

Hera Beam Tail Shaping by Tune Modulation.

To study CP violation, the HEM-B experiment uses an internal wire target in the transverse halo of the stored HERA proton beam. Operational experience shows that the resulting interaction rates are extremely sensitive to tiny orbit jitter amplitudes. Various methods have been studied to stabilize these interaction rates by increasing diffusion in the transverse proton beam tails without affecting the luminosity at the electron-proton collider experiments ZEUS and H1. Tune modulation was found to be a promising method for this task. Experiments performed in recent years will be reported.
Date: May 19, 2003
Creator: Montag, C.
System: The UNT Digital Library
Rheology Modifiers for Radioactive Waste Slurries (open access)

Rheology Modifiers for Radioactive Waste Slurries

The goals of this study were to determine if trace levels of chemical additives could be used to reduce the rheological characteristics of radioactive waste slurries, identify potential chemical additives for this work and future testing, test a limited set of chemical additive candidates on simulated radioactive wastes, and develop advanced techniques to visualize the internal slurry structure and particle-particle interaction within the slurry.
Date: February 19, 2003
Creator: Calloway, T.B. Jr.
System: The UNT Digital Library
Lithium-Based Electrochromic Mirrors (open access)

Lithium-Based Electrochromic Mirrors

Antimony, antimony-copper, and antimony-silver thin films were prepared by DC magnetron sputtering on glass substrates. Their reflectance and transmittance in the visible range were measured before and after electrochemical lithiation. The mixed metal films exhibited larger changes in reflectance and small shifts in the optical absorption edge compared with pure antimony films. Electrochromic cycling speed and stability of the Sb-Li system were improved by the addition of copper and silver.
Date: May 19, 2003
Creator: Richardson, Thomas J. & Slack, Jonathan L.
System: The UNT Digital Library
Effective theory approach to unstable particles (open access)

Effective theory approach to unstable particles

The authors present a novel treatment of resonant massive particles appearing as intermediate states in high energy collisions. The approach uses effective field theory methods to treat consistently the instability of the intermediate resonant state. As a result gauge invariance is respected in every step and calculations can in principle be extended to all orders in perturbation theory, the only practical limitation in going to higher orders being the standard difficulties related to multi-loop integrals. The authors believe that the longstanding problem related to the treatment of instability of particles is now solved.
Date: May 19, 2003
Creator: Zanderighi, Giulia
System: The UNT Digital Library
Effect of surface carbon structure on the electrochemical performance of LiFePO{sub 4} (open access)

Effect of surface carbon structure on the electrochemical performance of LiFePO{sub 4}

None
Date: February 19, 2003
Creator: Doeff, Marca M.; Hu, Yaoqin; McLarnon, Frank & Kostecki, Robert
System: The UNT Digital Library
Scattering of slow electrons by polar molecules: Application of effective-range potential theory to HC1 (open access)

Scattering of slow electrons by polar molecules: Application of effective-range potential theory to HC1

We present a non-empirical potential model for studying threshold vibrational excitation of polar molecules by electron impact. This work builds on the zero-range potential virtual state model of Gauyacq and Herzenberg (J.P. Gauyacq and A. Herzenberg, Phys. Rev. A 25, 2959 (1982)), using known analytic properties of the S-matrix for a dipole potential to predict the analytic continuation of the negative ion potential curve into the continuum. We derive an equation that determines the nuclear dynamics which can be solved without the need for an expansion in target vibrational states. The model is applied to e{sup -} - HCl and is found to capture the essential features of the observed excitation cross sections, including both the threshold peaks as well as oscillatory structures at energies above threshold.
Date: June 19, 2003
Creator: Vanroose, Wim; McCurdy, C. W. & Rescigno, T. N.
System: The UNT Digital Library
Cold asymmetrical fermion superfluids (open access)

Cold asymmetrical fermion superfluids

The recent experimental advances in cold atomic traps have induced a great amount of interest in fields from condensed matter to particle physics, including approaches and prospects from the theoretical point of view. In this work we investigate the general properties and the ground state of an asymmetrical dilute gas of cold fermionic atoms, formed by two particle species having different densities. We have show in a recent paper, that a mixed phase composed of normal and superfluid components is the energetically favored ground state of such a cold fermionic system. Here we extend the analysis and verify that in fact, the mixed phase is the preferred ground state of an asymmetrical superfluid in various situations. We predict that the mixed phase can serve as a way of detecting superfluidity and estimating the magnitude of the gap parameter in asymmetrical fermionic systems.
Date: December 19, 2003
Creator: Caldas, Heron
System: The UNT Digital Library
An injector for the proposed Berkeley Ultrafast X-Ray Light Source (open access)

An injector for the proposed Berkeley Ultrafast X-Ray Light Source

Berkeley Lab has proposed to build a recirculating linac based X-ray source for ultra-fast dynamic studies [1]. This machine requires a flat electron beam with a small vertical emittance and large x/y emittance ratio to allow for compression of spontaneous undulator emission of soft and hard x-ray pulses, and a low-emittance, round electron beam for coherent emission of soft x-rays via the FEL process based on cascaded harmonic generation [2]. We propose an injector system consisting of two high gradient high repetition rate photo cathode guns [3] (one for each application), an {approx}120 MeV super conducting linear accelerator, a 3rd harmonic cavity for linearization of the longitudinal phase space, and a bunch compressor. We present details of the design and the results of particle tracking studies using several computer codes.
Date: May 19, 2003
Creator: Lidia, Steven; Corlett, John; Pusina, Jan; Staples, John & Zholents, Alexander
System: The UNT Digital Library
Visual Sample Plan (VSP) - FIELDS Integration (open access)

Visual Sample Plan (VSP) - FIELDS Integration

Two software packages, VSP 2.1 and FIELDS 3.5, are being used by environmental scientists to plan the number and type of samples required to meet project objectives, display those samples on maps, query a database of past sample results, produce spatial models of the data, and analyze the data in order to arrive at defensible decisions. VSP 2.0 is an interactive tool to calculate optimal sample size and optimal sample location based on user goals, risk tolerance, and variability in the environment and in lab methods. FIELDS 3.0 is a set of tools to explore the sample results in a variety of ways to make defensible decisions with quantified levels of risk and uncertainty. However, FIELDS 3.0 has a small sample design module. VSP 2.0, on the other hand, has over 20 sampling goals, allowing the user to input site-specific assumptions such as non-normality of sample results, separate variability between field and laboratory measurements, make two-sample comparisons, perform confidence interval estimation, use sequential search sampling methods, and much more. Over 1,000 copies of VSP are in use today. FIELDS is used in nine of the ten U.S. EPA regions, by state regulatory agencies, and most recently by several international countries. …
Date: April 19, 2003
Creator: Pulsipher, Brent A.; Wilson, John E.; Gilbert, Richard O.; Hassig, Nancy L.; Carlson, Deborah K.; Bing-Canar, John et al.
System: The UNT Digital Library
COLLIMATION EXPERIENCE AT RHIC. (open access)

COLLIMATION EXPERIENCE AT RHIC.

In the Relativistic Heavy Ion Collider (RHIC) the abort kicker magnets are the limiting aperture. Continuous losses at this location could deteriorate the kicker performance. In addition, losses especially in the triplet area cause backgrounds in the experimental detectors. The RHIC one-stage collimation system was used to reduce these backgrounds as well as losses at the abort kickers. Collimation performance and results from various runs with even and uneven species (Au-Au, pp and d-Au) are presented and compared. Upgrades of the system for the upcoming high luminosity runs are outlined.
Date: May 19, 2003
Creator: DREES,K. A. FLILLER,R. TRBOJEVIC,D. KAIN,V.
System: The UNT Digital Library
Defect Based Spin Mediation in Delta-Phase Plutonium (open access)

Defect Based Spin Mediation in Delta-Phase Plutonium

We earlier reported the measured decrease of electrical resistivity during isochronal-annealing of ion irradiation damage that was accumulated at low-temperature (10 or 20K), and the temperature dependence of the resistance of defect-populations produced by low-temperature damage-accumulation and annealing in a stabilized {delta}-phase plutonium alloy, Pu(3.3 at%Ga)[1]. We noted that the temperature dependence of the resistance of defects resulting from low-temperature damage accumulation and subsequent annealing exhibits a -ln(T) temperature dependence suggestive of a Kondo impurity. A discussion of a possible ''structure-property'' effect, as it might relate to the nature of the {delta}-phase of Pu, is presented.
Date: November 19, 2003
Creator: Fluss, M J; Wirth, B D; Wall, M; Felter, T E; Caturla, M J; Kubota, A et al.
System: The UNT Digital Library
Experimental and Computational Study of Nonpremixed Ignition of Dimethyl Ether in Counterflow (open access)

Experimental and Computational Study of Nonpremixed Ignition of Dimethyl Ether in Counterflow

The ignition temperature of nitrogen-diluted dimethyl ether (DME) by heated air in counterflow was experimentally determined for DME concentration from 5.9 to 30%, system pressure from 1.5 to 3.0 atmospheres, and pressure-weighted strain rate from 110 to 170/s. These experimental data were compared with two mechanisms that were respectively available in 1998 and 2003, with the latter being a substantially updated version of the former. The comparison showed that while the 1998-mechanism uniformly over-predicted the ignition temperature, the 2003-mechanism yielded surprisingly close agreement for all experimental data. Sensitivity analysis for the near-ignition state based on both mechanisms identified the deficiencies of the 1998-mechanism, particularly the specifics of the low-temperature cool flame chemistry in effecting ignition at higher temperatures, as the fuel stream is being progressively heated from its cold boundary to the high-temperature ignition region around the hot-stream boundary. The 2003-mechanism, consisting of 79 species and 398 elementary reactions, was then systematically simplified by using the directed relation graph method to a skeletal mechanism of 49 species and 251 elementary reactions, which in turn was further simplified by using computational singular perturbation method and quasi-steady-state species assumption to a reduced mechanism consisting of 33 species and 28 lumped reactions. It …
Date: December 19, 2003
Creator: Zheng, X L; Lu, T F; Law, C K & Westbrook, C K
System: The UNT Digital Library
Massively Parallel Combined Monte Carlo and Molecular Dynamics Methods to Study the Long-Time-Scale Evolution of Particulate Matter and Molecular Structures Under Reactive Flow Conditions (open access)

Massively Parallel Combined Monte Carlo and Molecular Dynamics Methods to Study the Long-Time-Scale Evolution of Particulate Matter and Molecular Structures Under Reactive Flow Conditions

An important challenge in computational modeling is the development of new computational methods and capabilities for studying molecular-scale structures over very large time-scales. In particular, there is great interest in understanding the nucleation and growth of carbon soot particles as well as their fate in the atmosphere. We have recently developed and implemented a new computational tool to time-integrate the detailed structure of atomistically resolved surfaces and nanostructures driven by chemical and physical kinetic rule-based rate expressions. Fundamental chemical and physical processes such as chemical reactions, surface adsorption and surface diffusion are performed using a non-lattice real-space kinetic Monte Carlo scheme and driven by user-defined rule-based kinetic rate expressions, while atomic structure relaxation is approached using molecular dynamics. We demonstrate the sensitivity of particle evolution to chemical and physical kinetic mechanism using a parallel implementation of the combined Monte Carlo and molecular dynamics code.
Date: December 19, 2003
Creator: Kubota, A; Mundy, C J; Pitz, W J; Melius, C; Westbrook, C K & Caturla, M
System: The UNT Digital Library