Grid-based methods for diatomic quantum scattering problems II: Time-dependent treatment of single- and two-photon ionization of H2+ (open access)

Grid-based methods for diatomic quantum scattering problems II: Time-dependent treatment of single- and two-photon ionization of H2+

The time-dependent Schr\"odinger equation for H2+ in a time-varying electromagnetic field is solved in the fixed-nuclei approximation using a previously developed finite-element/ discrete variable representation in prolate spheroidal coordinates. Amplitudes for single- and two-photon ionization are obtained using the method of exterior complex scaling to effectively propagate the field-free solutions from the end of the radiation pulse to infinite times. Cross sections are presented for one-and two-photon ionization for both parallel and perpendicular polarization of the photon field, as well as photoelectron angular distributions for two-photon ionization.
Date: April 20, 2009
Creator: Rescigno, Thomas N.; Tao, L. & McCurdy, C.W.
System: The UNT Digital Library
Mineral transformation and biomass accumulation associated with uranium bioremediation at Rifle, Colorado (open access)

Mineral transformation and biomass accumulation associated with uranium bioremediation at Rifle, Colorado

Injection of organic carbon into the subsurface as an electron donor for bioremediation of redox-sensitive contaminants like uranium often leads to mineral transformation and biomass accumulation, both of which can alter the flow field and potentially bioremediation efficacy. This work combines reactive transport modeling with a column experiment and field measurements to understand the biogeochemical processes and to quantify the biomass and mineral transformation/accumulation during a bioremediation experiment at a uranium contaminated site near Rifle, Colorado. We use the reactive transport model CrunchFlow to explicitly simulate microbial community dynamics of iron and sulfate reducers, and their impacts on reaction rates. The column experiment shows clear evidence of mineral precipitation, primarily in the form of calcite and iron monosulfide. At the field scale, reactive transport simulations suggest that the biogeochemical reactions occur mostly close to the injection wells where acetate concentrations are highest, with mineral precipitate and biomass accumulation reaching as high as 1.5% of the pore space. This work shows that reactive transport modeling coupled with field data can be an effective tool for quantitative estimation of mineral transformation and biomass accumulation, thus improving the design of bioremediation strategies.
Date: April 20, 2009
Creator: Li, L.; Steefel, C. I.; Williams, K. H.; Wilkins, M. J. & Hubbard, S. S.
System: The UNT Digital Library
Phenolic Compounds Protect Cultured Hippocampal Neurons against Ethanol-Withdrawal Induced Oxidative Stress (open access)

Phenolic Compounds Protect Cultured Hippocampal Neurons against Ethanol-Withdrawal Induced Oxidative Stress

Paper reports findings on the contribution of phenolic antioxidants (17β-estradiol, p-octyl-phenol and 2,6-di-tert-butyl-4-methylphenol) to counterbalance sudden ethanol withdrawal-initiated oxidative events in hippocampus-derived cultured HT-22 cells.
Date: April 20, 2009
Creator: Prokai-Tatrai, Katalin; Prókai, László, 1958-; Simpkins, James W. & Jung, Marianna E.
System: The UNT Digital Library
Predicted Geology of the Pahute Mesa-Oasis Valley Phase II Drilling Initiative (open access)

Predicted Geology of the Pahute Mesa-Oasis Valley Phase II Drilling Initiative

Pahute Mesa–Oasis Valley (PM-OV) Phase II drilling will occur within an area that encompasses approximately 117 square kilometers (45 square miles) near the center of the Phase I PM-OV hydrostratigraphic framework model area. The majority of the investigation area lies within dissected volcanic terrain between Pahute Mesa on the north and Timber Mountain on the south. This area consists of a complex distribution of volcanic tuff and lava of generally rhyolitic composition erupted from nearby calderas and related vents. Several large buried volcanic structural features control the distribution of volcanic units in the investigation area. The Area 20 caldera, including its structural margin and associated caldera collapse collar, underlies the northeastern portion of the investigation area. The southern half of the investigation area lies within the northwestern portion of the Timber Mountain caldera complex, including portions of the caldera moat and resurgent dome. Another significant structural feature in the area is the west-northwest-trending Northern Timber Mountain moat structural zone, which bisects the northern portion of the investigation area and forms a structural bench. The proposed wells of the UGTA Phase II drilling initiative can be grouped into four generalized volcanic structural domains based on the stratigraphic distribution and structural position …
Date: April 20, 2009
Creator: National Security Technologies, LLC
System: The UNT Digital Library
Self-validated Variance-based Methods for Sensitivity Analysis of Model Outputs (open access)

Self-validated Variance-based Methods for Sensitivity Analysis of Model Outputs

Global sensitivity analysis (GSA) has the advantage over local sensitivity analysis in that GSA does not require strong model assumptions such as linearity or monotonicity. As a result, GSA methods such as those based on variance decomposition are well-suited to multi-physics models, which are often plagued by large nonlinearities. However, as with many other sampling-based methods, inadequate sample size can badly pollute the result accuracies. A natural remedy is to adaptively increase the sample size until sufficient accuracy is obtained. This paper proposes an iterative methodology comprising mechanisms for guiding sample size selection and self-assessing result accuracy. The elegant features in the the proposed methodology are the adaptive refinement strategies for stratified designs. We first apply this iterative methodology to the design of a self-validated first-order sensitivity analysis algorithm. We also extend this methodology to design a self-validated second-order sensitivity analysis algorithm based on refining replicated orthogonal array designs. Several numerical experiments are given to demonstrate the effectiveness of these methods.
Date: April 20, 2009
Creator: Tong, C
System: The UNT Digital Library
Statistical Analysis and Geologic Evaluation of Laboratory-Derived Physical Property Data for Selected Nevada Test Site Core Samples of Non-Zeolitized Tuffs (open access)

Statistical Analysis and Geologic Evaluation of Laboratory-Derived Physical Property Data for Selected Nevada Test Site Core Samples of Non-Zeolitized Tuffs

A statistical analysis and geologic evaluation of recently acquired laboratory-derived physical property data are being performed to better understand and more precisely correlate physical properties with specific geologic parameters associated with non-zeolitized tuffs at the Nevada Test Site. Physical property data include wet and dry bulk density, grain density (i.e., specific gravity), total porosity, and effective porosity. Geologic parameters utilized include degree of welding, lithology, stratigraphy, geographic area, and matrix mineralogy (i.e., vitric versus devitrified). Initial results indicate a very good correlation between physical properties and geologic parameters such as degree of welding, lithology, and matrix mineralogy. However, physical properties appear to be independent of stratigraphy and geographic area, suggesting that the data are transferrable with regards to these two geologic parameters. Statistical analyses also indicate that the assumed grain density of 2.65 grams per cubic centimeter used to calculate porosity in some samples is too high. This results in corresponding calculated porosity values approximately 5 percent too high (e.g., 45 percent versus 40 percent), which can be significant in the lower porosity rocks. Similar analyses and evaluations of zeolitic tuffs and carbonate rock physical properties data are ongoing as well as comparisons to geophysical log values.
Date: April 20, 2009
Creator: National Security Technologies, LLC
System: The UNT Digital Library
Stepwise DNA Methylation Changes Are Linked to Escape from Defined Proliferation Barriers and Mammary Epithelial Cell Immortalization (open access)

Stepwise DNA Methylation Changes Are Linked to Escape from Defined Proliferation Barriers and Mammary Epithelial Cell Immortalization

The timing and progression of DNA methylation changes during carcinogenesis are not completely understood. To develop a timeline of aberrant DNA methylation events during malignant transformation, we analyzed genome-wide DNA methylation patterns in an isogenic human mammary epithelial cell (HMEC) culture model of transformation. To acquire immortality and malignancy, the cultured finite lifespan HMEC must overcome two distinct proliferation barriers. The first barrier, stasis, is mediated by the retinoblastoma protein and can be overcome by loss of p16(INK4A) expression. HMEC that escape stasis and continue to proliferate become genomically unstable before encountering a second more stringent proliferation barrier, telomere dysfunction due to telomere attrition. Rare cells that acquire telomerase expression may escape this barrier, become immortal, and develop further malignant properties. Our analysis of HMEC transitioning from finite lifespan to malignantly transformed showed that aberrant DNA methylation changes occur in a stepwise fashion early in the transformation process. The first aberrant DNA methylation step coincides with overcoming stasis, and results in few to hundreds of changes, depending on how stasis was overcome. A second step coincides with immortalization and results in hundreds of additional DNA methylation changes regardless of the immortalization pathway. A majority of these DNA methylation changes are …
Date: April 20, 2009
Creator: Novak, Petr; Jensen, Taylor J.; Garbe, James C.; Stampfer, Martha R. & Futscher, Bernard W.
System: The UNT Digital Library
UGTA Photograph Database (open access)

UGTA Photograph Database

One of the advantages of the Nevada Test Site (NTS) is that most of the geologic and hydrologic features such as hydrogeologic units (HGUs), hydrostratigraphic units (HSUs), and faults, which are important aspects of flow and transport modeling, are exposed at the surface somewhere in the vicinity of the NTS and thus are available for direct observation. However, due to access restrictions and the remote locations of many of the features, most Underground Test Area (UGTA) participants cannot observe these features directly in the field. Fortunately, National Security Technologies, LLC, geologists and their predecessors have photographed many of these features through the years. During fiscal year 2009, work was done to develop an online photograph database for use by the UGTA community. Photographs were organized, compiled, and imported into Adobe® Photoshop® Elements 7. The photographs were then assigned keyword tags such as alteration type, HGU, HSU, location, rock feature, rock type, and stratigraphic unit. Some fully tagged photographs were then selected and uploaded to the UGTA website. This online photograph database provides easy access for all UGTA participants and can help “ground truth” their analytical and modeling tasks. It also provides new participants a resource to more quickly learn the …
Date: April 20, 2009
Creator: National Security Technologies, LLC
System: The UNT Digital Library
WASTE SAMPLING AND CHARACTERIZATION FACILITY (open access)

WASTE SAMPLING AND CHARACTERIZATION FACILITY

None
Date: April 20, 2009
Creator: TF, DALE
System: The UNT Digital Library
Benchmark Measurements of the Ionization Balance of Non-LTE Gold (open access)

Benchmark Measurements of the Ionization Balance of Non-LTE Gold

The authors present a series of benchmark measurements of the ionization balance of well characterized gold plasmas with and without external radiation fields at electron densities near 10{sup 21} cm{sup -3} and various electron temperatures spanning the range 0.8 to 2.4 keV. They have analyzed time- and space-resolved M-shell gold emission spectra using a sophisticated collisional-radiative model with hybrid level structure, finding average ion changes <Z> ranging from 42 to 50. At the lower temperatures, the spectra exhibit significant sensitivity to external radiation fields and include emission features from complex N-shell ions not previously studied at these densities. The measured spectra and inferred <Z> provide a stringent test for non-local thermodynamic equilibrium (non-LTE) models of complex high-Z ions.
Date: April 20, 2007
Creator: Heeter, R. F.; Hansen, S. B.; Fournier, K. B.; Foord, M. E.; Froula, D. H.; Mackinnon, A. J. et al.
System: The UNT Digital Library
The Energy Diameter Effect (open access)

The Energy Diameter Effect

Various relations for the detonation energy and velocity as they relate to the inverse radius of the cylinder are explored. The detonation rate-inverse slope relation seen in reactive flow models can be used to derive the familiar Eyring equation. Generalized inverse radii can be shown to fit large quantities of cylinder and sphere results. A rough relation between detonation energy and detonation velocity is found from collected JWL values. Cylinder test data for ammonium nitrate mixes down to 6.35 mm radii are presented, and a size energy effect is shown to exist in the Cylinder test data. The relation that detonation energy is roughly proportional to the square of the detonation velocity is shown by data and calculation.
Date: April 20, 2007
Creator: Souers, P; Vitello, P; Garza, R & Hernandez, A
System: The UNT Digital Library
Molecular beam epitaxy of InN dots on nitrided sapphire (open access)

Molecular beam epitaxy of InN dots on nitrided sapphire

A series of self-assembled InN dots are grown by radio frequency (RF) plasma-assisted molecular beam epitaxy (MBE) directly on nitrided sapphire. Initial nitridation of the sapphire substrates at 900 C results in the formation of a rough AlN surface layer, which acts as a very thin buffer layer and facilitates the nucleation of the InN dots according to the Stranski-Krastanow growth mode, with a wetting layer of {approx}0.9 nm. Atomic force microscopy (AFM) reveals that well-confined InN nanoislands with the greatest height/width at half-height ratio of 0.64 can be grown at 460 C. Lower substrate temperatures result in a reduced aspect ratio due to a lower diffusion rate of the In adatoms, whereas the thermal decomposition of InN truncates the growth at T>500 C. The densities of separated dots vary between 1.0 x 10{sup 10} cm{sup -2} and 2.5 x 10{sup 10} cm{sup -2} depending on the growth time. Optical response of the InN dots under laser excitation is studied with apertureless near-field scanning optical microscopy and photoluminescence spectroscopy, although no photoluminescence is observed from these samples. In view of the desirable implementation of InN nanostructures into photonic devices, the results indicate that nitrided sapphire is a suitable substrate for …
Date: April 20, 2007
Creator: Romanyuk, Yaroslav E.; Dengel, Radu-Gabriel; Stebounova, LarissaV. & Leone, Stephen R.
System: The UNT Digital Library
A monolithic time stretcher for precision time recording (open access)

A monolithic time stretcher for precision time recording

Identifying light mesons which contain only up/down quarks (pions) from those containing a strange quark (kaons) over the typical meter length scales of a particle physics detector requires instrumentation capable of measuring flight times with a resolution on the order of 20ps. In the last few years a large number of inexpensive, multi-channel Time-to-Digital Converter (TDC) chips have become available. These devices typically have timing resolution performance in the hundreds of ps regime. A technique is presented that is a monolithic version of ``time stretcher'' solution adopted for the Belle Time-Of-Flight system to address this gap between resolution need and intrinsic multi-hit TDC performance.
Date: April 20, 2007
Creator: Varner, Gary S.
System: The UNT Digital Library
On-Chip Real-Time Single-Copy Polymerase Chain Reaction in Picoliter Droplets (open access)

On-Chip Real-Time Single-Copy Polymerase Chain Reaction in Picoliter Droplets

The first lab-on-chip system for picoliter droplet generation and PCR amplification with real-time fluorescence detection has performed PCR in isolated droplets at volumes 10{sup 6} smaller than commercial real-time PCR systems. The system utilized a shearing T-junction in a silicon device to generate a stream of monodisperse picoliter droplets that were isolated from the microfluidic channel walls and each other by the oil phase carrier. An off-chip valving system stopped the droplets on-chip, allowing them to be thermal cycled through the PCR protocol without droplet motion. With this system a 10-pL droplet, encapsulating less than one copy of viral genomic DNA through Poisson statistics, showed real-time PCR amplification curves with a cycle threshold of {approx}18, twenty cycles earlier than commercial instruments. This combination of the established real-time PCR assay with digital microfluidics is ideal for isolating single-copy nucleic acids in a complex environment.
Date: April 20, 2007
Creator: Beer, N. Reginald; Hindson, Benjamin J.; Wheeler, Elizabeth K.; Hall, Sara B.; Rose, Klint A.; Kennedy, Ian M. et al.
System: The UNT Digital Library
Speech recognition systems on the Cell Broadband Engine (open access)

Speech recognition systems on the Cell Broadband Engine

In this paper we describe our design, implementation, and first results of a prototype connected-phoneme-based speech recognition system on the Cell Broadband Engine{trademark} (Cell/B.E.). Automatic speech recognition decodes speech samples into plain text (other representations are possible) and must process samples at real-time rates. Fortunately, the computational tasks involved in this pipeline are highly data-parallel and can receive significant hardware acceleration from vector-streaming architectures such as the Cell/B.E. Identifying and exploiting these parallelism opportunities is challenging, but also critical to improving system performance. We observed, from our initial performance timings, that a single Cell/B.E. processor can recognize speech from thousands of simultaneous voice channels in real time--a channel density that is orders-of-magnitude greater than the capacity of existing software speech recognizers based on CPUs (central processing units). This result emphasizes the potential for Cell/B.E.-based speech recognition and will likely lead to the future development of production speech systems using Cell/B.E. clusters.
Date: April 20, 2007
Creator: Liu, Y.; Jones, H.; Vaidya, S.; Perrone, M.; Tydlitat, B. & Nanda, A.
System: The UNT Digital Library
Spin Spectrometer at the ALS and APS (open access)

Spin Spectrometer at the ALS and APS

A spin-resolving photoelectron spectrometer, the"Spin Spectrometer," has been designed and built. It has been utilized at both the Advanced Light Source in Berkeley, CA, and the Advanced Photon Source in Argonne, IL. Technical details and an example of experimental results are presented here.
Date: April 20, 2007
Creator: Laboratory, Lawrence Livermore National; Missouri-Rolla, University of; Technologies, Boyd; Morton, Simon A; Morton, Simon A; Tobin, James G et al.
System: The UNT Digital Library
Air to Muscle and Blood/Plasma to Muscle Distribution of Volatile Organic Compounds and Drugs: Linear Free Energy Analyses (open access)

Air to Muscle and Blood/Plasma to Muscle Distribution of Volatile Organic Compounds and Drugs: Linear Free Energy Analyses

Article on air to muscle and blood/plasma to muscle distribution of volatile organic compounds and drugs and linear free energy analyses.
Date: April 20, 2006
Creator: Abraham, M. H. (Michael H.); Ibrahim, Adam & Acree, William E. (William Eugene)
System: The UNT Digital Library
Defining an end state for CO2 sequestration and EOR in North America (open access)

Defining an end state for CO2 sequestration and EOR in North America

CO{sub 2} capture and storage (CCS) presents a challenge to long-range planners, economic interests, regulators, law-makers, and other stakeholders and decision makers. To improve and optimize the use of limited resources and finances, it is important to define an end state for CCS. This ends state should be defined around desired goals and reasonable timelines for execution. While this definition may have substantial technology, policy or economic implications, it need not be prescriptive in terms of technology pathway, policy mechanism, or economic targets. To illustrate these concerns, this paper will present a credible vision of what an end state for North American might look like. From that, examples of key investment and planning decisions are provided to illustrate the value of end-state characterization.
Date: April 20, 2006
Creator: Friedmann, S J
System: The UNT Digital Library
The effect of solvent dynamics on the low frequency collectivemotions of DNA in solution and unoriented films (open access)

The effect of solvent dynamics on the low frequency collectivemotions of DNA in solution and unoriented films

Infrared spectroscopy is used to probe the dynamics of invitro samples of DNA prepared as solutions and as solid unoriented films.The lowest frequency DNA mode identified in the far-infrared spectra ofthe DNA samples is found to shift in frequency when the solvent influencein the hydration shell is altered. The lowest frequency mode also hascharacteristics that are similar to beta - relaxations identified inother glass forming polymers.
Date: April 20, 2006
Creator: Woods, K.N.; Lee, S.A.; Holman, H.-Y.N. & Wiedemann, H.
System: The UNT Digital Library
Electron Impact Excitation Cross Section Measurement for n=3 to n=2 Line Emission in Fe17+ to Fe23+ (open access)

Electron Impact Excitation Cross Section Measurement for n=3 to n=2 Line Emission in Fe17+ to Fe23+

We have measured the electron impact excitation cross sections for the strong iron L-shell 3 {yields} 2 lines of Fe XVIII to Fe XXIV at the EBIT-I electron beam ion trap using a crystal spectrometer and NASA-Goddard Space Flight Centers 6 x 6 pixel array microcalorimeter. The cross sections were determined by direct normalization to the well established cross section of radiative electron capture through a sophisticated model analysis which results in the excitation cross section for the strong Fe L-shell lines at multiple electron energies. This measurement is part of a laboratory X-ray astrophysics program utilizing the Livermore electron beam ion traps EBIT-I and EBIT-II.
Date: April 20, 2006
Creator: Chen, H; Beiersdorfer, P; Brown, G V; Scofield, J; Gu, M F; Kahn, S M et al.
System: The UNT Digital Library
Formation of Pillars at the Boundaries between HII Regions and Molecular Clouds (open access)

Formation of Pillars at the Boundaries between HII Regions and Molecular Clouds

We investigate numerically the hydrodynamic instability of an ionization front (IF) accelerating into a molecular cloud, with imposed initial perturbations of different amplitudes. When the initial amplitude is small, the imposed perturbation is completely stabilized and does not grow. When the initial perturbation amplitude is large enough, roughly the ratio of the initial amplitude to wavelength is greater than 0.02, portions of the IF temporarily separate from the molecular cloud surface, locally decreasing the ablation pressure. This causes the appearance of a large, warm HI region and triggers nonlinear dynamics of the IF. The local difference of the ablation pressure and acceleration enhances the appearance and growth of a multimode perturbation. The stabilization usually seen at the IF in the linear regimes does not work due to the mismatch of the modes of the perturbations at the cloud surface and in density in HII region above the cloud surface. Molecular pillars are observed in the late stages of the large amplitude perturbation case. The velocity gradient in the pillars is in reasonably good agreement with that observed in the Eagle Nebula. The initial perturbation is imposed in three different ways: in density, in incident photon number flux, and in the …
Date: April 20, 2006
Creator: Mizuta, A.; Kane, J. O.; Pound, M. W.; Remington, B. A.; Ryutov, D. D. & Takabe, H.
System: The UNT Digital Library
Implications of the measurement of the B0s Bbar0s massdifference (open access)

Implications of the measurement of the B0s Bbar0s massdifference

We analyze the significant new model independent constraints on extensions of the standard model (SM) that follow from the recent measurements of the B{sup 0}{sub s} {bar B}{sup 0}{sub s} mass difference. The time-dependent CP asymmetry in B{sub s} {yields} {psi}{phi}, S{sub {psi}{phi}}, will be measured with good precision in the first year of LHC data taking, which will further constrain the parameter space of many extensions of the SM, in particular, next-to-minimal flavor violation. The CP asymmetry in semileptonic B{sub s} decay, A{sup s}{sub SL}, is also important to constrain these frameworks, and could give further clues to our understanding the flavor sector in the LHC era. We point out a strong correlation between S{sub {psi}{phi}} and A{sup s}{sub SL} in a very broad class of new physics models.
Date: April 20, 2006
Creator: Ligeti, Zoltan; Papucci, Michele & Perez, Gilad
System: The UNT Digital Library
Laboratory observation of secondary shock formation ahead of a strongly radiative blast wave (open access)

Laboratory observation of secondary shock formation ahead of a strongly radiative blast wave

We have previously reported the experimental discovery of a second shock forming ahead of a radiative shock propagating in Xe. The initial shock is spherical, radiative, with a high Mach number, and it sends a supersonic radiative heat far ahead of itself. The heat wave rapidly slows to a transonic regime and when its Mach number drops to two with respect to the downstream plasma, the heat wave drives a second shock ahead of itself to satisfy mass and momentum conservation in the heat wave reference frame. We now show experimental data from a range of mixtures of Xe and N{sub 2}, gradually changing the properties of the initial shock and the environment into which the shock moves and radiates (the radiative conductivity and the heat capacity). We have successfully observed second shock formation over the entire range from 100% Xe mass fraction to 100% N{sub 2}. The formation radius of the second shock as a function of Xe mass fraction is consistent with an analytical estimate.
Date: April 20, 2006
Creator: Hansen, J. F.; Edwards, M. J.; Froula, D. H.; Edens, A. D.; Gregori, G. & Ditmire, T. R.
System: The UNT Digital Library
Mass-stripping analysis of an interstellar cloud by a supernova shock (open access)

Mass-stripping analysis of an interstellar cloud by a supernova shock

The interaction of supernova shocks and interstellar clouds is an important astrophysical phenomenon since it can result in stellar and planetary formation. Our experiments attempt to simulate this mass-loading as it occurs when a shock passes through interstellar clouds. We drive a strong shock using the Omega laser ({approx} 5 kJ) into a foam-filled cylinder with an embedded Al sphere (diameter D = 120 {micro}m) simulating an interstellar cloud. The density ratio between Al and foam is {approx}9. We have previously reported on the interaction between shock and cloud, the ensuing Kelvin-Helmholtz and Widnall instabilities, and the rapid stripping of all mass from the cloud. We now present a theory that explains the rapid mass-stripping. The theory combines (1) the integral momentum equations for a viscous boundary layer, (2) the equations for a potential flow past a sphere, (3) Spalding's law of the wall for turbulent boundary layers, and (4) the skin friction coefficient for a turbulent boundary layer on a flat plate. The theory gives as its final result the mass stripped from a sphere in a turbulent high Reynolds number flow, and it agrees very well with our experimental observations.
Date: April 20, 2006
Creator: Hansen, J. F.; Robey, H. F.; Miles, A. R.; Klein, R. I. & McKee, C. F.
System: The UNT Digital Library