States

Engineering surface functional groups on silica aerogel for enhanced cleanup of organics from produced water (open access)

Engineering surface functional groups on silica aerogel for enhanced cleanup of organics from produced water

None
Date: December 3, 2003
Creator: Love, A; Hanna, M L & Reynolds, J
System: The UNT Digital Library
Tilted Thick-Disk Accretion onto a Kerr Black Hole (open access)

Tilted Thick-Disk Accretion onto a Kerr Black Hole

We present the first results from fully general relativistic numerical studies of thick-disk accretion onto a rapidly-rotating (Kerr) black hole with a spin axis that is tilted (not aligned) with the angular momentum vector of the disk. We initialize the problem with the solution for an aligned, constant angular momentum, accreting thick disk around a black hole with spin a/M = J/M{sup 2} = +0.9 (prograde disk). The black hole is then instantaneously tilted, through a change in the metric, by an angle {beta}{sub 0}. In this Letter we report results with {beta}{sub 0} = 0, 15, and 30{sup o}. The disk is allowed to respond to the Lense-Thirring precession of the tilted black hole. We find that the disk settles into a quasi-static, twisted, warped configuration with Lense-Thirring precession dominating out to a radius analogous to the Bardeen-Petterson transition in tilted Keplerian disks.
Date: December 12, 2003
Creator: Fragile, P C & Anninos, P
System: The UNT Digital Library
Interferometric Studies of Laser-Created Plasmas Using Compact Soft X-Ray Lasers (open access)

Interferometric Studies of Laser-Created Plasmas Using Compact Soft X-Ray Lasers

We summarize results of several successful dense plasma diagnostics experiments realized by combining two different kinds of table-top soft x-ray lasers with an amplitude division interferometer based on diffraction grating beam splitters. In the first set of experiments this robust high throughput diffraction grating interferometer (DGI) was used with a 46.9 nm portable capillary discharge laser to study the dynamics of line focus and point focus laser-created plasmas. The measured electron density profiles, which differ significantly from those expected from a classical expansion, unveil important two-dimensional effects of the dynamics of these plasmas. A second DGI customized to operate in combination with a 14.7 nm Ni-like Pd transient gain laser was used to perform interferometry of line focus laser-created plasmas with picosecond time resolution. These measurements provide valuable new benchmarks for complex hydrodynamic codes and help bring new understanding of the dynamics of dense plasmas. The instrumentation and methodology we describe is scalable to significantly shorter wavelengths, and constitutes a promising scheme for extending interferometry to the study of very dense plasmas such as those investigated for inertial confinement fusion.
Date: December 4, 2003
Creator: Dunn, J.; Nilsen, J.; Moon, S.; Keenan, R.; Jankowska, E.; Maconi, M. C. et al.
System: The UNT Digital Library
Impaired fertility in T-stock female mice after superovulation (open access)

Impaired fertility in T-stock female mice after superovulation

Superovulation of female mice with exogenous gonadotrophins is routinely used for increasing the number of eggs ovulated by each female in reproductive and developmental studies. We report an unusual effect of superovulation on fertilization in mice. In vivo matings of superovulated T-stock females with B6C3F1 males resulted in a 2-fold reduction (P<0.001) in the frequencies of fertilized eggs compared to control B6C3F1 matings. In addition, {approx}22 hr after mating only 15% of fertilized eggs recovered in T-stock females had reached the metaphase stage of the first cleavage division versus 87% in B6C3F1 females (P < 0.0001). Matings with T-stock males did not improve the reproductive performance of T-stock females. To investigate the possible cause(s) for the impaired fertilization and zygotic development, the experiments were repeated using in vitro fertilization. Under these conditions, the frequencies of fertilized eggs were not different in superovulated T-stock and B6C3F1 females (51.7% {+-} 6.0 and 64.5% {+-}3.8, P=0.10). There was a 7-fold increase in the frequencies of fertilized T-stock eggs that completed the first cell cycle of development after in vitro versus in vivo fertilization. These results rule out an intrinsic deficiency of the T-stock oocyte as the main reason for the impaired fertility after …
Date: December 5, 2003
Creator: Wyrobek, A J; Bishop, J B; Marchetti, F & Zudova, D
System: The UNT Digital Library
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
Hyperspectral Imaging of Functional Patterns for Disease Assessment and Treatment Monitoring (open access)

Hyperspectral Imaging of Functional Patterns for Disease Assessment and Treatment Monitoring

We have designed and built a six-band multi-spectral NIR imaging system used in clinical testing on cancer patients. From our layered tissue model, we create blood volume and blood oxygenation images for patient treatment monitoring.
Date: December 5, 2003
Creator: Hassan, Moinuddin; Hattery, David; Vogel, Abby; Chernomorkik, Victor; Demos, Stavros; Aleman, Karen et al.
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
Comparison of Three Afterglow Morphologies (open access)

Comparison of Three Afterglow Morphologies

Herein we compare three functional families for afterglow morphologies: the homogeneous afterglow with constant shock surface energy density, the structured afterglow for which the energy density decays as a power-law as a function of viewer angle, and the gaussian afterglow which has an exponential decay of energy density with viewer angle. We simulate observed lightcurves and polarization curves for each as seen from a variety of observer vantage points. We find that the homogeneous jet is likely inconsistent with observations and suggest that the future debate on the structure of afterglow jets will be between the other two candidates.
Date: December 23, 2003
Creator: Salmonson, J D; Rossi, E & Lazzati, D
System: The UNT Digital Library
Jet-Induced Star Formation (open access)

Jet-Induced Star Formation

Jets from radio galaxies can have dramatic effects on the medium through which they propagate. We review observational evidence for jet-induced star formation in low ('FR-I') and high ('FR-II') luminosity radio galaxies, at low and high redshifts respectively. We then discuss numerical simulations which are aimed to explain a jet-induced starburst ('Minkowski's Object') in the nearby FR-I type radio galaxy NGC 541. We conclude that jets can induce star formation in moderately dense (10 cm{sup -3}), warm (10{sup 4} K) gas; that this may be more common in the dense environments of forming, active galaxies; and that this may provide a mechanism for 'positive' feedback from AGN in the galaxy formation process.
Date: December 16, 2003
Creator: van Breugel, W.; Fragile, C.; Anninos, P. & Murray, S.
System: The UNT Digital Library
Correlated Nitrogen and Carbon Anomalies in an Anhydrous Interplanetary Dust Particle - Implications for Extraterrestrial Organic Matter Accreted by the Prebiotic Earth (open access)

Correlated Nitrogen and Carbon Anomalies in an Anhydrous Interplanetary Dust Particle - Implications for Extraterrestrial Organic Matter Accreted by the Prebiotic Earth

Given the ubiquitous presence of H and N isotopic anomalies in interplanetary dust particles (IDPs) and their probable association with carbonaceous material, the lack of similar isotopic anomalies in C has been a major conundrum. We report here the first observation of correlated N and C isotopic anomalies in organic matter within an anhydrous IDP. The {sup 15}N composition of the anomalous region is the highest seen to date in an IDP and is accompanied by a moderate depletion in {sup 13}C. Our observations establish the presence of hetero-atomic organic compounds of presolar origin among the constant flux of carbonaceous material accreting to the terrestrial planets within IDPs. Theoretical models suggest that low temperature formation of organic compounds in cold interstellar molecular clouds does produce C and N fractionations, but it remains to be seen if these models can reproduce the specific effects we observe here.
Date: December 17, 2003
Creator: Floss, C; Stadermann, F J; Bradley, J P; Dai, Z; Bajt, S & Graham, G
System: The UNT Digital Library
POPULATION KINETICS MODELING FOR NON-LTE AND NON-MAXWELLIAN PLASMAS GENERATED IN FINITE TEMPERATURE DENSE MATTER EXPERIMENTS ARISING FROM SHORT PULSE X-RAY SOURCE (open access)

POPULATION KINETICS MODELING FOR NON-LTE AND NON-MAXWELLIAN PLASMAS GENERATED IN FINITE TEMPERATURE DENSE MATTER EXPERIMENTS ARISING FROM SHORT PULSE X-RAY SOURCE

The short pulse x-ray sources will provide a major advance in dense matter studies important to understand implosion physics for ICF as a generator of warm dense matter or a probe of finite temperature dense matter. The interaction of such a high-energy photon pulse with the initially solid matter creates highly transient states of plasmas initially whose relaxation processes are of interest to the equation of states or spectral properties of these matter. For these plasmas, assumptions such as LTE population distributions or Maxwellian electron energy distributions should be tested by employing a method that does not make these assumption a priori. Our goal is to present a model that can be used to simulate the electron distributions, the ionization balance and the spectral output of transient systems generated in the future ICF experiments. We report on the progress in developing a non-LTE atomic population kinetics code integrated with Boltzmann equation solver to provide a self-consistent time-dependent solution of the level populations and the particle energy distributions.
Date: December 23, 2003
Creator: Chung, H; Lee, R W & Morgan, W L
System: The UNT Digital Library
Comparison of up-scaling methods in poroelasticity and its generalizations (open access)

Comparison of up-scaling methods in poroelasticity and its generalizations

Four methods of up-scaling coupled equations at the microscale to equations valid at the mesoscale and/or macroscale for fluid-saturated and partially saturated porous media will be discussed, compared, and contrasted. The four methods are: (1) effective medium theory, (2) mixture theory, (3) two-scale and multiscale homogenization, and (4) volume averaging. All these methods have advantages for some applications and disadvantages for others. For example, effective medium theory, mixture theory, and homogenization methods can all give formulas for coefficients in the up-scaled equations, whereas volume averaging methods give the form of the up-scaled equations but generally must be supplemented with physical arguments and/or data in order to determine the coefficients. Homogenization theory requires a great deal of mathematical insight from the user in order to choose appropriate scalings for use in the resulting power-law expansions, while volume averaging requires more physical insight to motivate the steps needed to find coefficients. Homogenization often is performed on periodic models, while volume averaging does not require any assumption of periodicity and can therefore be related very directly to laboratory and/or field measurements. Validity of the homogenization process is often limited to specific ranges of frequency - in order to justify the scaling hypotheses that …
Date: December 13, 2003
Creator: Berger, E. L.
System: The UNT Digital Library
Externally Dispersed Interferometry for Resolution Boosting and Doppler Velocimetry (open access)

Externally Dispersed Interferometry for Resolution Boosting and Doppler Velocimetry

Externally dispersed interferometry (EDI) is a rapidly advancing technique for wide bandwidth spectroscopy and radial velocimetry. By placing a small angle-independent interferometer near the slit of an existing spectrograph system, periodic fiducials are embedded on the recorded spectrum. The multiplication of the stellar spectrum times the sinusoidal fiducial net creates a moire pattern, which manifests high detailed spectral information heterodyned down to low spatial frequencies. The latter can more accurately survive the blurring, distortions and CCD Nyquist limitations of the spectrograph. Hence lower resolution spectrographs can be used to perform high resolution spectroscopy and radial velocimetry (under a Doppler shift the entire moir{acute e} pattern shifts in phase). A demonstration of {approx}2x resolution boosting (100,000 from 50,000) on the Lick Obs. echelle spectrograph is shown. Preliminary data indicating {approx}8x resolution boost (170,000 from 20,000) using multiple delays has been taken on a linear grating spectrograph.
Date: December 1, 2003
Creator: Erskine, D J
System: The UNT Digital Library
Outlook: The Next Twenty Years (open access)

Outlook: The Next Twenty Years

I present an outlook for the next twenty years in particle physics. I start with the big questions in our field, broken down into four categories: horizontal, vertical, heaven, and hell. Then I discuss how we attack the bigquestions in each category during the next twenty years. I argue for a synergy between many different approaches taken in our field.
Date: December 7, 2003
Creator: Murayama, Hitoshi
System: The UNT Digital Library
Anomalous Flavor U(1)_X for Everything (open access)

Anomalous Flavor U(1)_X for Everything

We present an ambitious model of flavor, based on an anomalous U(1)_X gauge symmetry with one flavon, only two right-handed neutrinos and only two mass scales: M_{grav} and m_{3/2}. In particular, there are no new scales introduced for right-handed neutrino masses. The X-charges of the matter fields are such that R-parity is conserved exactly, higher-dimensional operators are sufficiently suppressed to guarantee a proton lifetime in agreement with experiment, and the phenomenology is viable for quarks, charged leptons, as well as neutrinos. In our model one of the three light neutrinos automatically is massless. The price we have to pay for this very successful model are highly fractional X-charges which can likely be improved with less restrictive phenomenological ansatze for mass matrices.
Date: December 1, 2003
Creator: Dreiner, Herbi K.; Murayama, Hitoshi & Thormeier, Marc
System: The UNT Digital Library
A Hidden Twelve-Dimensional SuperPoincare Symmetry In Eleven Dimensions (open access)

A Hidden Twelve-Dimensional SuperPoincare Symmetry In Eleven Dimensions

First, we review a result in our previous paper, of how a ten-dimensional superparticle, taken off-shell, has a hidden eleven-dimensional superPoincare symmetry. Then, we show that the physical sector is defined by three first-class constraints which preserve the full eleven-dimensional symmetry. Applying the same concepts to the eleven dimensional superparticle, taken off-shell, we discover a hidden twelve dimensional superPoincare symmetry that governs the theory.
Date: December 13, 2003
Creator: Bars, Itzhak; Deliduman, Cemsinan; Pasqua, Andrea & Zumino, Bruno
System: The UNT Digital Library
The Status of Beryllium Research for Fusion in the United States (open access)

The Status of Beryllium Research for Fusion in the United States

Use of beryllium in fusion reactors has been considered for neutron multiplication in breeding blankets and as an oxygen getter for plasma-facing surfaces. Previous beryllium research for fusion in the United States included issues of interest to fission (swelling and changes in mechanical and thermal properties) as well as interactions with plasmas and hydrogen isotopes and methods of fabrication. When the United States formally withdrew its participation in the International Thermonuclear Experimental Reactor (ITER) program, much of this effort was terminated. The focus in the U.S. has been mainly on toxic effects of beryllium and on industrial hygiene and health-related issues. Work continued at the INEEL and elsewhere on beryllium-containing molten salts. This activity is part of the JUPITER II Agreement. Plasma spray of ITER first wall samples at Los Alamos National Laboratory has been performed under the European Fusion Development Agreement. Effects of irradiation on beryllium structure are being studied at Oak Ridge National Laboratory. Numerical and phenomenological models are being developed and applied to better understand important processes and to assist with design. Presently, studies are underway at the University of California Los Angeles to investigate thermo-mechanical characteristics of beryllium pebble beds, similar to research being carried out …
Date: December 1, 2003
Creator: Longhurst, Glen R.
System: The UNT Digital Library
PLEIADES: High Peak Brightness, Subpicosecond Thomson Hard-X-ray source (open access)

PLEIADES: High Peak Brightness, Subpicosecond Thomson Hard-X-ray source

The Picosecond Laser-Electron Inter-Action for the Dynamic Evaluation of Structures (PLEIADES) facility, is a unique, novel, tunable (10-200 keV), ultrafast (ps-fs), hard x-ray source that greatly extends the parameter range reached by existing 3rd generation sources, both in terms of x-ray energy range, pulse duration, and peak brightness at high energies. First light was observed at 70 keV early in 2003, and the experimental data agrees with 3D codes developed at LLNL. The x-rays are generated by the interaction of a 50 fs Fourier-transform-limited laser pulse produced by the TW-class FALCON CPA laser and a highly focused, relativistic (20-100 MeV), high brightness (1 nC, 0.3-5 ps, 5 mm.mrad, 0.2% energy spread) photo-electron bunch. The resulting x-ray brightness is expected to exceed 10{sup 20} ph/mm{sup 2}/s/mrad{sup 2}/0.1% BW. The beam is well-collimated (10 mrad divergence over the full spectrum, 1 mrad for a single color), and the source is a unique tool for time-resolved dynamic measurements in matter, including high-Z materials.
Date: December 15, 2003
Creator: Kuba, J.; Anderson, S. G.; Barty, C. J.; Betts, S. M.; Booth, R.; Brown, W. J. et al.
System: The UNT Digital Library
Analytical and Numerical Ray Tracing of X-Ray Lasers (open access)

Analytical and Numerical Ray Tracing of X-Ray Lasers

Soft x-ray lasers in 10-30nm range are now routinely produced in hot plasmas generated either by a laser from a solid target or by an electrical discharge in a capillary. Such an x-ray laser is a convenient tool for future applications, such as probing dense plasmas of interest for fusion experiments. Their short wavelength enables plasma diagnosis beyond the capabilities of optical lasers, because the high critical plasma density ({approx}{lambda}{sup 2}) limits the optical beam propagation. In our paper, we present analytical and numerical ray tracing of an x-ray laser in dense amplifying plasmas. A general analytical formula for a beam propagation has been developed for a gradient plasma. The simplified analytical formulaes enable better understanding of processes involved. They also simplify optimization of the beam propagation and ''mapping'' the parameter space for further studies by numerical codes. We discuss implications for a transient x-ray laser that is produced from a slab target by a (sub-)picosecond laser pulse.
Date: December 22, 2003
Creator: Kuba, J; Shlyaptsev, V N; Benredjem, D & Moller, C
System: The UNT Digital Library
Sub-picosecond streak camera measurements at LLNL: From IR to x-rays (open access)

Sub-picosecond streak camera measurements at LLNL: From IR to x-rays

An ultra fast, sub-picosecond resolution streak camera has been recently developed at the LLNL. The camera is a versatile instrument with a wide operating wavelength range. The temporal resolution of up to 300 fs can be achieved, with routine operation at 500 fs. The streak camera has been operated in a wide wavelength range from IR to x-rays up to 2 keV. In this paper we briefly review the main design features that result in the unique properties of the streak camera and present its several scientific applications: (1) Streak camera characterization using a Michelson interferometer in visible range, (2) temporally resolved study of a transient x-ray laser at 14.7 nm, which enabled us to vary the x-ray laser pulse duration from {approx}2-6 ps by changing the pump laser parameters, and (3) an example of a time-resolved spectroscopy experiment with the streak camera.
Date: December 21, 2003
Creator: Kuba, J; Shepherd, R; Booth, R; Steward, R; Lee, E W; Cross, R R et al.
System: The UNT Digital Library
Structural disorder produced in KH2PO4 by light-ion bombardment (open access)

Structural disorder produced in KH2PO4 by light-ion bombardment

We study structural disorder produced in tetragonal KDP (KH{sub 2}PO{sub 4}) single crystals at room temperature by irradiation with MeV light ions. Results show that electronic energy loss plays a major role in the production of lattice defects in KDP. The effective diameters of ion tracks depend superlinearly on the electronic stopping power of energetic light ions. Structural lattice disorder is also accompanied by the formation of a network of cracks and blisters on the sample surface. Such irradiation-induced cracking and blistering typically evolves over extended periods of time (e.g., days) after bombardment, strongly affected by ion irradiation and sample storage conditions.
Date: December 16, 2003
Creator: Kucheyev, S O & Felter, T E
System: The UNT Digital Library
Mitigating Systems Performance Index Baselines (open access)

Mitigating Systems Performance Index Baselines

This paper discusses the technical assessment of recommended train unavailability and component unreliability baselines for the US Nuclear Regulatory Commission Mitigating Systems Performance Index. To perform this evaluation, recent data were compared with the recommended baselines. Comparisons indicate that the recommended baselines appear to accurately represent recent (1999 – 2001) industry experience.
Date: December 1, 2003
Creator: Eide, S. A.; Zeek, D. P. & Dube, D. A.
System: The UNT Digital Library
Quantum Monte Carlo study of the reaction: C1 + CH3OH -->CH2OH+ HCl (open access)

Quantum Monte Carlo study of the reaction: C1 + CH3OH -->CH2OH+ HCl

A theoretical study is reported of the Cl + CH{sub 3}OH {yields} CH{sub 2}OH + HCl reaction based on the diffusion Monte Carlo (DMC) variant of the quantum Monte Carlo method. Using a DMC trial function constructed as a product of Hartree-Fock and correlation functions, we have computed the barrier height, heat of reaction, atomization energies and heats of formation of reagents and products. The DMC heat of reaction, atomization energies, and heats of formation are found to agree with experiment to within the error bounds of computation and experiment. Moller-Plesset second order perturbation theory (MP2) and density functional theory, the latter in the B3LYP generalized gradient approximation, are found to overestimate the experimental heat of reaction. Intrinsic reaction coordinate calculations at the MP2 level of theory demonstrate that the reaction is predominantly direct, i.e., proceeds without formation of intermediates, which is consistent with a recent molecular beam experiment. The reaction barrier as determined from MP2 calculations is found to be 2.24 kcal/mol and by DMC it is computed to be 2.39(49) kcal/mol.
Date: December 1, 2003
Creator: Kollias, A. C.; Couronne, O. & Lester, W. A. Jr.
System: The UNT Digital Library
Approximating spheroid inductive responses using spheres (open access)

Approximating spheroid inductive responses using spheres

The response of high permeability ({mu}{sub r} {ge} 50) conductive spheroids of moderate aspect ratios (0.25 to 4) to excitation by uniform magnetic fields in the axial or transverse directions is approximated by the response of spheres of appropriate diameters, of the same conductivity and permeability, with magnitude rescaled based on the differing volumes, D.C. magnetizations, and high frequency limit responses of the spheres and modeled spheroids.
Date: December 12, 2003
Creator: Smith, J. Torquil & Morrison, H. Frank
System: The UNT Digital Library