Numerical Modeling of CO2 Sequestration in Geologic Formations - Recent Results and Open Challenges (open access)

Numerical Modeling of CO2 Sequestration in Geologic Formations - Recent Results and Open Challenges

Rising atmospheric concentrations of CO2, and their role inglobal warming, have prompted efforts to reduce emissions of CO2 fromburning of fossil fuels. An attractive mitigation option underconsideration in many countries is the injection of CO2 from stationarysources, such as fossil-fueled power plants, into deep, stable geologicformations, where it would be stored and kept out of the atmosphere fortime periods of hundreds to thousands of years or more. Potentialgeologic storage reservoirs include depleted or depleting oil and gasreservoirs, unmineable coal seams, and saline formations. While oil andgas reservoirs may provide some attractive early targets for CO2 storage,estimates for geographic regions worldwide have suggested that onlysaline formations would provide sufficient storage capacity tosubstantially impact atmospheric releases. This paper will focus on CO2storage in saline formations.Injection of CO2 into a saline aquifer willgive rise to immiscible displacement of brine by the advancing CO2. Thelower viscosity of CO2 relative to aqueous fluids provides a potentialfor hydrodynamic instabilities during the displacement process. Attypical subsurface conditions of temperature and pressure, CO2 is lessdense than aqueous fluids and is subject to upward buoyancy force inenvironments where pressures are controlled by an ambient aqueous phase.Thus CO2 would tend to rise towards the top of a permeable formation andaccumulate …
Date: March 8, 2006
Creator: Pruess, Karsten
System: The UNT Digital Library
Laboratory Measurements of 3 --> 2 X-ray Line Ratios of F-like Fe XVIII and Ni XX (open access)

Laboratory Measurements of 3 --> 2 X-ray Line Ratios of F-like Fe XVIII and Ni XX

The intensity ratios of 3 {yields} 2 emission lines of Fe XVIII and Ni XX were measured on the Livermore electron beam ion trap (EBIT-I) with a flat-field grating spectrometer. The results were compared with distorted-wave (DW) calculations obtained with the Flexible Atomic Code and recent close-coupling calculations using the R-matrix code. The measured 3s {yields} 2p/3d {yields} 2p ratios are about 20-40% higher than the theoretical values. When more extended configuration interaction is included in the DW theory, the agreement with the measurements improved slightly. At the beam energies of these measurements, no significant resonance contribution is expected to be present, and the discrepancies represent the uncertainties in the direct excitation cross sections.
Date: March 8, 2007
Creator: Gu, M F; Chen, H; Brown, G V; Beiersdorfer, P & Kahn, S M
System: The UNT Digital Library
Intensity-based signal separation algorithm for accuratequantification of clustered centrosomes in tissue sections (open access)

Intensity-based signal separation algorithm for accuratequantification of clustered centrosomes in tissue sections

Centrosomes are small organelles that organize the mitoticspindle during cell division and are also involved in cell shape andpolarity. Within epithelial tumors, such as breast cancer, and somehematological tumors, centrosome abnormalities (CA) are common, occurearly in disease etiology, and correlate with chromosomal instability anddisease stage. In situ quantification of CA by optical microscopy ishampered by overlap and clustering of these organelles, which appear asfocal structures. CA has been frequently associated with Tp53 status inpremalignant lesions and tumors. Here we describe an approach toaccurately quantify centrosomes in tissue sections and tumors.Considering proliferation and baseline amplification rate the resultingpopulation based ratio of centrosomes per nucleus allow the approximationof the proportion of cells with CA. Using this technique we show that20-30 percent of cells have amplified centrosomes in Tp53 null mammarytumors. Combining fluorescence detection, deconvolution microscopy and amathematical algorithm applied to a maximum intensity projection we showthat this approach is superior to traditional investigator based visualanalysis or threshold-based techniques.
Date: March 8, 2006
Creator: Fleisch, Markus C.; Maxell, Christopher A.; Kuper, Claudia K.; Brown, Erika T.; Parvin, Bahram; Barcellos-Hoff, Mary-Helen et al.
System: The UNT Digital Library
X-ray absorption study of the electronic structure of Mn-doped amorphous Si (open access)

X-ray absorption study of the electronic structure of Mn-doped amorphous Si

The electronic structure of Mn in amorphous Si (a-Mn{sub x}Si{sub 1?x}) is studied by X-ray absorption spectroscopy at the Mn L{sub 3,2} edges for x = 0.005-0.18. Except the x = 0.005 sample, which shows a slight signature of Mn{sup 2+} atomic multiplets associated with a local Mn moment, all samples have broad and featureless L{sub 3,2} absorption peaks, corresponding to an itinerant state for all 3d electrons. The broad X-ray absorption spectra exclude the possibility of a localized 3d moment and explain the unexpectedly quenched Mn moment in this magnetically-doped amorphous semiconductor. Such a fully delocalized d state of Mn dopant in Si has not been previously suggested.
Date: March 8, 2008
Creator: Arenholz, Elke; Zeng, Li; Huegel, A.; Helgren, E.; Hellman, F.; Piamonteze, C. et al.
System: The UNT Digital Library
First principles calculations of the effect of Pt on NiAl surfaceenergy and the site preference of Pt (open access)

First principles calculations of the effect of Pt on NiAl surfaceenergy and the site preference of Pt

Pt-modified NiAl is widely used as a coating material in industry. In this study, the surface energies of NiAl with and without Pt are investigated using first-principles calculations. The presence of Pt in NiAl takes the surface electronic states to higher energies, resulting in an increased surface energy, which explains some of the beneficial effects of Pt on the oxidation resistance of NiAl. The electronic structure of NiAl-Pt alloys is also analyzed in terms of the site preference of Pt in NiAl. Results show that Pt bonds strongly to Al, giving its site preference on the Ni site.
Date: March 8, 2007
Creator: Yu, Rong & Hou, Peggy Y.
System: The UNT Digital Library
Cryogenic Neutron Spectrometer Development (open access)

Cryogenic Neutron Spectrometer Development

Cryogenic microcalorimeter detectors operating at temperatures around {approx}0.1 K have been developed for the last two decades, driven mostly by the need for ultra-high energy resolution (<0.1%) in X-ray astrophysics and dark matter searches [1]. The Advanced Detector Group at Lawrence Livermore National Laboratory has developed different cryogenic detector technologies for applications ranging from X-ray astrophysics to nuclear science and non-proliferation. In particular, we have adapted cryogenic detector technologies for ultra-high energy resolution gamma-spectroscopy [2] and, more recently, fast-neutron spectroscopy [3]. Microcalorimeters are essentially ultra-sensitive thermometers that measure the energy of the radiation from the increase in temperature upon absorption. They consist of a sensitive superconducting thermometer operated at the transition between its superconducting and its normal state, where its resistance changes very rapidly with temperature such that even the minute energies deposited by single radiation quanta are sufficient to be detectable with high precision. The energy resolution of microcalorimeters is fundamentally limited by thermal fluctuations to {Delta}E{sub FWHM} {approx} 2.355 (k{sub B}T{sup 2}C{sub abs}){sup 1/2}, and thus allows an energy below 1 keV for neutron spectrometers for an operating temperature of T {approx} 0.1 K . The {Delta}E{sub FWHM} does not depend on the energy of the incident photon …
Date: March 8, 2006
Creator: Niedermayr, T.; Hau, I. D.; Friedrich, S.; Burger, A.; Roy, U. N. & Bell, Z. W.
System: The UNT Digital Library
Experimental study of radium partitioning between anorthite and melt at 1 atm (open access)

Experimental study of radium partitioning between anorthite and melt at 1 atm

We present the first experimental radium mineral/melt partitioning data, specifically between anorthite and a CMAS melt at atmospheric pressure. Ion microprobe measurement of coexisting anorthite and glass phases produces a molar D{sub Ra} = 0.040 {+-} 0.006 and D{sub Ra}/D{sub Ba} = 0.23 {+-} 0.05 at 1400 C. Our results indicate that lattice strain partitioning models fit the divalent (Ca, Sr, Ba, Ra) partition coefficient data of this study well, supporting previous work on crustal melting and magma chamber dynamics that has relied on such models to approximate radium partitioning behavior in the absence of experimentally determined values.
Date: March 8, 2007
Creator: Miller, S.; Burnett, D.; Asimow, P.; Phinney, D. & Hutcheon, I.
System: The UNT Digital Library
Defect diffusion during annealing of low-energy ion-implanted silicon (open access)

Defect diffusion during annealing of low-energy ion-implanted silicon

We present a new approach for investigating the kinetics of defect migration during annealing of low-energy, ion-implanted silicon, employing a combination of computer simulations and atomic-resolution tunneling microscopy. Using atomically-clean Si(111)-7x7 as a sink for bulk point defects created by 5 keV Xe and Ar irradiation, we observe distinct, temperature-dependent surface arrival rates for vacancies and interstitials. A combination of simulation tools provides a detailed description of the processes that underly the observed temperature-dependence of defect segregation, and the predictions of the simulations agree closely with the experimental observations.
Date: March 8, 2000
Creator: Bedrossian, P J; Caturla, M-J & Diaz de la Rubia, T
System: The UNT Digital Library
Ni spin switching induced by magnetic frustration in FeMn/Ni/Cu(001) (open access)

Ni spin switching induced by magnetic frustration in FeMn/Ni/Cu(001)

Epitaxially grown FeMn/Ni/Cu(001) films are investigated by Photoemission Electron Microscopy and Magneto-Optic Kerr Effect. We find that as the FeMn overlayer changes from paramagnetic to antiferromagnetic state, it could switch the ferromagnetic Ni spin direction from out-of-plane to in-plane direction of the film. This phenomenon reveals a new mechanism of creating magnetic anisotropy and is attributed to the out-of-plane spin frustration at the FeMn-Ni interface.
Date: March 8, 2009
Creator: Wu, J.; Choi, J.; Scholl, A.; Doran, A.; Arenholz, E.; Hwang, Chanyong et al.
System: The UNT Digital Library
New Capabilities in Mercury: A Modern, Monte Carlo Particle Transport Code (open access)

New Capabilities in Mercury: A Modern, Monte Carlo Particle Transport Code

The new physics, algorithmic and computer science capabilities of the Mercury general-purpose Monte Carlo particle transport code are discussed. The new physics and algorithmic features include in-line energy deposition and isotopic depletion, significant enhancements to the tally and source capabilities, diagnostic ray-traced particles, support for multi-region hybrid (mesh and combinatorial geometry) systems, and a probability of initiation method. Computer science enhancements include a second method of dynamically load-balancing parallel calculations, improved methods for visualizing 3-D combinatorial geometries and initial implementation of an in-line visualization capabilities.
Date: March 8, 2007
Creator: Procassini, R. J.; Cullen, D. E.; Greenman, G. M.; Hagmann, C. A.; Kramer, K. J.; McKinley, M. S. et al.
System: The UNT Digital Library
GENERIC THERMO-MECHANICAL MODEL FOR JOINTED ROCK MASSES (open access)

GENERIC THERMO-MECHANICAL MODEL FOR JOINTED ROCK MASSES

A new nonlinear thermo-mechanical model for heavily jointed rock masses is presented. The model uses correlation functions between the porosity and the basic rock properties such as elastic moduli, tensile and compressive strength. The model assumes that the media is isotropic and is characterized by two variable parameters: insipient porosity and in-situ-to-intact modulus ratio.
Date: March 8, 2007
Creator: Vorobiev, O
System: The UNT Digital Library
Damage and ablation of large band gap dielectrics induced by a 46.9 nm laser beam (open access)

Damage and ablation of large band gap dielectrics induced by a 46.9 nm laser beam

We applied a 0.3 mJ, 1.7 ns, 46.9 nm soft X-ray Argon laser to ablate the surface of large band gap dielectrics: CaF{sub 2} and LiF crystals. The ablation versus the fluence of the soft X-ray beam has been studied varying the fluence in the range of 0.05-3 J/cm{sup 2}. An ablation threshold of 0.06 and 0.1 J/cm{sup 2} and an ablation depth of 14 and 20 nm have been found for CaF{sub 2} and LiF, respectively. These results define new ablation conditions for these large band gap dielectrics, which can be of interest for the fine processing of these materials.
Date: March 8, 2006
Creator: Ritucci, A.; Tomassetti, G.; Reale, A.; Arrizza, L.; Zuppella, P.; Reale, L. et al.
System: The UNT Digital Library
Observation of Dynamical spin shielding in Ce: Why It Matters for Pu Electronic Structure (open access)

Observation of Dynamical spin shielding in Ce: Why It Matters for Pu Electronic Structure

In a series of experiments and linked theoretical modeling, the range of possible solutions for Pu electronic structure has been dramatically reduced. Nevertheless, the key issue of electron correlation remains.
Date: March 8, 2007
Creator: Tobin, J G; Yu, S W; Chung, B W; Morton, S A; Komesua, T & Waddill, G D
System: The UNT Digital Library
The Effects of Male Age on Sperm DNA Damage in Healthy Non-Smokers (open access)

The Effects of Male Age on Sperm DNA Damage in Healthy Non-Smokers

The trend for men to have children at older ages raises concerns that advancing age may increase the production of genetically defective sperm, increasing the risks of transmitting germ-line mutations. We investigated the associations between male age and sperm DNA damage and the influence of several lifestyle factors in a healthy non-clinical group of 80 non-smokers (age: 22-80) with no known fertility problems using the sperm Comet analyses. The average percent of DNA that migrated out of the sperm nucleus under alkaline electrophoresis increased with age (0.18% per year, p=0.006); but there was no age association for damage measured under neutral conditions (p=0.7). Men who consumed >3 cups coffee per day had {approx}20% higher % tail DNA under neutral but not alkaline conditions compared to men who consumed no caffeine (p=0.005). Our findings indicate that (a) older men have increased sperm DNA damage associated with alkali-labile sites or single-strand DNA breaks, and (b) independent of age, men with substantial daily caffeine consumption have increased sperm DNA damage associated with double-strand DNA breaks. DNA damage in sperm can be converted to chromosomal aberrations and gene mutations after fertilization increasing the risks for developmental defects and genetic diseases among offspring.
Date: March 8, 2006
Creator: Schmid, T.; Eskenazi, B.; Baumgartner, A.; Marchetti, F.; Young, S.; Weldon, R. et al.
System: The UNT Digital Library
Thermal Stability of LiPF6 Salt and Li-ion Battery ElectrolytesContaining LiPF6 (open access)

Thermal Stability of LiPF6 Salt and Li-ion Battery ElectrolytesContaining LiPF6

The thermal stability of the neat LiPF6 salt and of 1 molal solutions of LiPF6 in prototypical Li-ion battery solvents was studied with thermogravimetric analysis (TGA) and on-line FTIR. Pure LiPF6 salt is thermally stable up to 380 K in a dry inert atmosphere, and its decomposition path is a simple dissociation producing LiF as solid and PF5 as gaseous products. In the presence of water (300 ppm) in the carrier gas, its decomposition onset temperature is lowered as a result of direct thermal reaction between LiPF6 and water vapor to form POF3 and HF. No new products were observed in 1 molal solutions of LiPF6 in EC, DMC and EMC by on-line TGA-FTIR analysis. The storage of the same solutions in sealed containers at 358 K for 300 420 hrs. did not produce any significant quantity of new products as well. In particular, noalkylflurophosphates were found in the solutions after storage at elevated temperature. In the absence of either an impurity like alcohol or cathode active material that may (or may not) act as a catalyst, there is no evidence of thermally induced reaction between LiPF6 and the prototypical Li-ion battery solvents EC, PC, DMC or EMC.
Date: March 8, 2006
Creator: Yang, Hui; Zhuang, Guorong V. & Ross Jr., Philip N.
System: The UNT Digital Library
SUPPLEMENTAL ON-LINE MATERIAL, INFLUENCE OF pH ON PLUTONIUM DESORPTION/SOLUBILIZATION FROM SEDIMENT (open access)

SUPPLEMENTAL ON-LINE MATERIAL, INFLUENCE OF pH ON PLUTONIUM DESORPTION/SOLUBILIZATION FROM SEDIMENT

The oxidation state distribution of Pu in each sample for each reaction time was measured using a combined ultrafiltration and solvent extraction technique (1-4). First the oxidation state distribution of aqueous Pu is measured. Then the total system (solid and aqueous phase combined) Pu oxidation state distribution is measured by lowering the pH to leach Pu from the solid phase. For each reaction time, a 2.5-mL aliquot of the aqueous phase was removed and passed through a 12-nm filter (Microsep 30K MWCO Centrifugal Device; Pall Corporation, East Hills, NY). An aliquot of the filtrate was removed to determine the aqueous phase Pu concentration, and oxidation state distribution in the remaining filtrate was measured using the parallel solvent extraction technique discussed.
Date: March 8, 2006
Creator: Kaplan, D
System: The UNT Digital Library
Studies of N{sub 2}0 adsorption and decomposition on Fe-ZSM-5 (open access)

Studies of N{sub 2}0 adsorption and decomposition on Fe-ZSM-5

The interactions of N2O with H-ZSM-5 and Fe-ZSM-5 have been investigated using infrared spectroscopy and temperature-programmed reaction. Fe-ZSM-5 samples with Fe/Al ratios of 0.17 and 0.33 were prepared by solid-state exchange. It was determined that most of the iron in the samples of Fe-ZSM-5 is in the form of isolated cations, which have exchanged with Bronsted acid H+ in H-ZSM-5. The infrared spectrum of N2O adsorbed on H-ZSM-5 at 298 K exhibits bands at 2226 and 1308 cm-1 associated with vibrations of the N-N and N-O bonds, respectively. The positions of these bands relative to those seen in the gas phase suggest that N2O adsorbs through the nitrogen end of the molecule. The heat of N2O adsorption in H-ZSM-5 is estimated to be 5 kcal/mol. In the case of Fe-ZSM-5, additional infrared bands are observed at 2282 and 1344 cm-1 due to the interactions of N2O with the iron cations. Here too, the directions of the shifts in the vibrational features relative to those for gas-phase N2O suggest that the molecule adsorbs through its nitrogen end. The heat of adsorption of N2O on the Fe sites is estimated to be 16 kcal/mol. The extent of N2O adsorption on Fe depends …
Date: March 8, 2002
Creator: Wood, Benjamin R.; Reimer, Jeffrey A. & Bell, Alexis T.
System: The UNT Digital Library
Tuning the SP to FM transition of cobalt nanoparticles in view of biomedical applications (open access)

Tuning the SP to FM transition of cobalt nanoparticles in view of biomedical applications

None
Date: March 8, 2002
Creator: Puntes, Victor F.; Parak, Wolfgang J. & Alivisatos, A. Paul
System: The UNT Digital Library
Ti K-alpha radiography of Cu-doped plastic microshell implosions via spherically bent crystal imaging (open access)

Ti K-alpha radiography of Cu-doped plastic microshell implosions via spherically bent crystal imaging

None
Date: March 8, 2005
Creator: King, J A; Freeman, R R; Key, M H; Akli, K; Borghesi, M; Chen, C D et al.
System: The UNT Digital Library
Leakage analysis of the evolve first wall. (open access)

Leakage analysis of the evolve first wall.

Leakage of lithium through cracks in the first wall of EVOLVE was analyzed for two limiting cases, which are simplified versions of the real case, where the lithium enters the cracks as liquid and flashes to vapor phase within the first wall. Leakage rates were calculated for the cases of liquid lithium flow and lithium vapor flow. Inasmuch as the coolant pressure is close to the saturation pressure, the limiting case of lithium vapor flow should be closer to reality. The impact of lithium leakage on first-wall cooling and plasma contamination is discussed.
Date: March 8, 2002
Creator: Majumdar, S.
System: The UNT Digital Library
Web technology to support work processes in energy policy research - A case study with energy efficiency standards (open access)

Web technology to support work processes in energy policy research - A case study with energy efficiency standards

This paper focuses on a process to design and build a web-based system to assist staff in day-to-day management and contemporaneous documentation of their work. Other groups that want to use web technology to support their work could apply the approach presented here, but the design itself pertains to a particular set of issues in a unique context. Each user must apply the approach to identify their objectives and design a site to meet them. The main question that the Energy Efficiency Standards Group addressed was: ''How can we facilitate documentation of interim results and final products while conducting a complex, interdependent set of analyses by multiple authors under time pressures for delivering a final product?'' The approach to address this question includes categorization of the components of the work, discussions with staff, development of infrastructure support for documentation, implementation of the documentation process and integration with the workflow, and follow- up with staff. The search for a solution raised a number of issues such as the need for a thorough understanding of the work, consensus building by inclusion of key staff, and deliverable scheduling to allow for contemporaneous documentation. Documentation results vary among the product analyses, from extensive internal …
Date: March 8, 2002
Creator: Benenson, Peter; McMahon, James E. & Brown, Stephen R.
System: The UNT Digital Library
["A Falling Out Among Friends" article, March 8, 2004] (open access)

["A Falling Out Among Friends" article, March 8, 2004]

An article, written by Debra Rosenberg and Mark Miller for Newsweek, about President George W. Bush's support of the marriage amendment that would ban gay and lesbian marriages at the federal level. It includes the response of Charles C. Francis and other gay and lesbian Republicans. An advertisement follows the article.
Date: March 8, 2004
Creator: Rosenberg, Debra & Miller, Mark
System: The UNT Digital Library
Natural attenuation assessment of multiple VOCs in a deep vadose zone (open access)

Natural attenuation assessment of multiple VOCs in a deep vadose zone

The fate of six volatile organic compounds (VOC) in a 150-meter deep vadose zone was examined in support of a RCRA Corrective Measures Study of the Chemical Waste Landfill at Sandia National Laboratories, Albuquerque, New Mexico. The study focused on the modeling of potential future transport of the VOCs to exposure media upon the completion of two separate voluntary corrective measures--soil vapor extraction and landfill excavation--designed to significantly reduce contaminant levels in subsurface soils. modeling was performed with R-UNSAT, a finite-difference simulator that was developed by the U.S. Geological Survey. R-UNSAT facilitated a relatively unique and comprehensive assessment of vapor transport because it (1) simulated the simultaneous movement of all six VOCs, taking into account each constituent's diffusion coefficient as affected by its mole fraction within a mixture of chemicals, and (2) permitted simultaneous assessment of risk to human health via volatilization (air) and drinking water (groundwater) pathways. Modeling results suggested that monitored natural attenuation would represent a viable remedial alternative at the landfill after both voluntary corrective measures were completed.
Date: March 8, 2000
Creator: Peterson, David M.; Singletary, Michael A.; Studer, James E. & Miller, David R.
System: The UNT Digital Library
Hot isostatic pressing of ceramic waste from spent nuclear fuel. (open access)

Hot isostatic pressing of ceramic waste from spent nuclear fuel.

Argonne National Laboratory has developed a process to immobilize waste salt containing fission products, uranium, and transuranic elements as chlorides in a glass-bonded ceramic waste form. This salt was generated in the electrorefining operation used in electrometallurgical treatment of spent Experimental Breeder Reactor-II fuel. The ceramic waste process culminated with a hot isostatic pressing operation. This paper reviews the installation and operation of a hot isostatic press in a radioactive environment. Processing conditions for the hot isostatic press are presented for non-irradiated material and irradiated material. Sufficient testing was performed to demonstrate that a hot isostatic press could be used as the final step of the processing of ceramic waste for the electrometallurgical spent fuel treatment process.
Date: March 8, 2002
Creator: Bateman, Kenneth J.; Rigg, Richard H. & Wiest, James D.
System: The UNT Digital Library