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Idiot's Guide or A People's History: Teaching U.S. History in Mexico (open access)

Idiot's Guide or A People's History: Teaching U.S. History in Mexico

This article discusses how textbooks can influence the classroom as a political space, using the example of the "Consorcio Clavijero" program, which offers Mexican professionals the opportunity to enter bilingual contexts in the U.S. as interns and classroom teachers.
Date: June 2008
Creator: Heiman, Daniel
System: The UNT Digital Library
A Method for the Precision Mass Measurement of the Stop Quark at the International Linear Collider (open access)

A Method for the Precision Mass Measurement of the Stop Quark at the International Linear Collider

Many supersymmetric models predict new particles within the reach of the next generation of colliders. For an understanding of the model structure and the mechanism(s) of symmetry breaking, it is important to know the masses of the new particles precisely. In this article the measurement of the mass of the scalar partner of the top quark (stop) at an e+e- collider is studied. A relatively light stop is motivated by attempts to explain electroweak baryogenesis and can play an important role in dark matter relic density. A method is presented which makes use of cross-section measurements near the pair-production threshold as well as at higher center-of-mass energies. It is shown that this method not only increases the statistical precision, but also greatly reduces the systematic uncertainties, which can be important. Numerical results are presented, based on a realistic event simulation, for two signal selection strategies: using conventional selection cuts, and using an Iterative Discriminant Analysis (IDA). Our studies indicate that a precision of {Delta}m{tilde t}{sub 1} = 0.42 GeV can be achieved, representing a major improvement over previous studies. While the analysis of stops is particularly challenging due to the possibility of stop hadronization, the general procedure could be applied …
Date: June 1, 2008
Creator: Freitas, Ayres; U., /Chicago U. /Argonne /Zurich; Milstene, Caroline; U., /Fermilab /Wayne State; Schmitt, Michael; U., /Northwestern et al.
System: The UNT Digital Library
Inhibition of vimentin or B1 integrin reverts morphology of prostate tumor cells grown in laminin-rich extracellular matrix gels and reduces tumor growth in vivo (open access)

Inhibition of vimentin or B1 integrin reverts morphology of prostate tumor cells grown in laminin-rich extracellular matrix gels and reduces tumor growth in vivo

Prostate epithelial cells grown embedded in laminin-rich extracellular matrix (lrECM) undergo morphologic changes that closely resemble their architecture in vivo. In this study, growth characteristics of three human prostate epithelial sublines derived from the same cellular lineage, but displaying different tumorigenic and metastatic properties in vivo, were assessed in three-dimensional lrECM gels. M12, a highly tumorigenic and metastatic subline, was derived from the immortalized, prostate epithelial P69 cell line by selection in athymic, nude mice and found to contain a deletion of 19p-q13.1. The stable reintroduction of an intact human chromosome 19 into M12 resulted in a poorly tumorigenic subline, designated F6. When embedded in lrECM gels, the parental, nontumorigenic P69 line produced acini with clearly defined lumena. Immunostaining with antibodies to {beta}-catenin, E-cadherin, or {alpha}6 and {beta}1 integrins showed polarization typical of glandular epithelium. In contrast, the metastatic M12 subline produced highly disorganized cells with no evidence of polarization. The F6 subline reverted to acini-like structures exhibiting basal polarity marked with integrins. Reducing either vimentin levels via small interfering RNA interference or the expression of {alpha}6 and {beta}1 integrins by the addition of blocking antibodies, reorganized the M12 subline into forming polarized acini. The loss of vimentin significantly reduced …
Date: June 12, 2008
Creator: Zhang, Xueping; Fournier, Marcia V; Ware, Joy L; Bissell, Mina J; Yacoub, Adly & Zehner, Zendra E
System: The UNT Digital Library
[The Last Word] (open access)

[The Last Word]

Article titled, "The Last Word" from Newsweek. The article is addressing a California Supreme Court ruling that legalizes gay marriage.
Date: June 9, 2008
Creator: Quindlan, Anna
System: The UNT Digital Library
Computational studies and optimization of wakefield accelerators (open access)

Computational studies and optimization of wakefield accelerators

Laser- and particle beam-driven plasma wakefield accelerators produce accelerating fields thousands of times higher than radio-frequency accelerators, offering compactness and ultrafast bunches to extend the frontiers of high energy physics and to enable laboratory-scale radiation sources. Large-scale kinetic simulations provide essential understanding of accelerator physics to advance beam performance and stability and show and predict the physics behind recent demonstration of narrow energy spread bunches. Benchmarking between codes is establishing validity of the models used and, by testing new reduced models, is extending the reach of simulations to cover upcoming meter-scale multi-GeV experiments. This includes new models that exploit Lorentz boosted simulation frames to speed calculations. Simulations of experiments showed that recently demonstrated plasma gradient injection of electrons can be used as an injector to increase beam quality by orders of magnitude. Simulations are now also modeling accelerator stages of tens of GeV, staging of modules, and new positron sources to design next-generation experiments and to use in applications in high energy physics and light sources.
Date: June 16, 2008
Creator: Tsung, Frank S.; Bruhwiler, David L.; Cary, John R.; Esarey, Eric H.; Mori, Warren B.; Vay, Jean-Luc et al.
System: The UNT Digital Library
Making Maps from Planck LFI 30GHz Data with Asymmetric Beams and Cooler Noise (open access)

Making Maps from Planck LFI 30GHz Data with Asymmetric Beams and Cooler Noise

The Planck satellite will observe the full sky at nine frequencies from 30 to 857 GHz. Temperature and polarization frequency maps made from these observations are prime deliverables of the Planck mission. The goal of this paper is to examine the effects of four realistic instrument systematics in the 30 GHz frequency maps: non-axially-symmetric beams, sample integration, sorption cooler noise, and pointing errors. They simulated one year long observations of four 30 GHz detectors. The simulated timestreams contained CMB, foreground component (both galactic and extra-galactic), instrument nolise (correlated and white), and the four instrument systematic effects. They made maps from the timelines and examined the magnitudes of the systematics effects in the maps and their angular power spectra. They also compared the maps of different mapmaking codes to see how they performed. They used five mapmaking codes (two destripers and three optimal codes). None of their mapmaking codes makes an attempt to deconvolve the beam from its output map. Therefore all our maps had similar smoothing due to beams and sample integration. This is a complicated smoothing, because every map pixel has its own effective beam. Temperature to polarization cross-coupling due to beam mismatch causes a detectable bias in the …
Date: June 19, 2008
Creator: Group, The Planck CTP Working; Ashdown, M. A. J.; Baccigalupi, C.; Bartlett, J. G.; Borrill, J.; Cantalupo, C. et al.
System: The UNT Digital Library
Experimental Investigation of Material Flows Within FSWs Using 3D Tomography (open access)

Experimental Investigation of Material Flows Within FSWs Using 3D Tomography

There exists significant prior work using tracers or pre-placed hardened markers within friction stir welding (FSWing) to experimentally explore material flow within the FSW process. Our experiments replaced markers with a thin sheet of copper foil placed between the 6061 aluminum lap and butt joints that were then welded. The absorption characteristics of x-rays for copper and aluminum are significantly different allowing for non-destructive evaluation (NDE) methods such as x-ray computed tomography (CT) to be used to demonstrate the material movement within the weldment on a much larger scale than previously shown. 3D CT reconstruction of the copper components of the weldment allows for a unique view into the final turbulent state of the welding process as process parameters are varied. The x-ray CT data of a section of the weld region was collected using a cone-beam x-ray imaging system developed at the INL. Six-hundred projections were collected over 360-degrees using a 160-kVp Bremsstrahlung x-ray generator (25-micrometer focal spot) and amorphoussilicon x-ray detector. The region of the object that was imaged was about 3cm tall and 1.5cm x 1cm in cross section, and was imaged at a magnification of about 3.6x. The data were reconstructed on a 0.5x0.5x0.5 mm3 voxel …
Date: June 1, 2008
Creator: Tolle, Charles R.; White, Timothy A.; Miller, Karen S.; Clark, Denis E. & Smartt, Herschel B.
System: The UNT Digital Library
Final Report US-Japan IEC Workshop on Small Plasma and Accelerator Neutron Sources (open access)

Final Report US-Japan IEC Workshop on Small Plasma and Accelerator Neutron Sources

Abstract The history of IEC development will be briefly described, and some speculation about future directions will be offered. The origin of IEC is due to the brilliance of Phil Farnsworth, inventor of electronic TV in the US. Early experiments were pioneered in the late 1960s by Robert Hirsch who later became head of the DOE fusion program. At that time studies of IEC physics quickly followed at the University of Illinois and at Penn State University. However, despite many successes in this early work, IEC research died as DOE funding stopped in the mid 1980s. In the early 90’s, R. W. Bussard of EMC revived work with a new major project based on a magnetic assisted IEC. While doing supportive studies for that project, G. Miley proposed a grided “STAR mode” IEC as a neutron source for NAA. This concept was later used commercially by Daimler- Benz in Germany to analysis impurities in incoming ores. This represented a first practical application of the IEC. During this period other research groups at LANL, U of Wisconsin and Kyoto University entered IEC research with innovative new concepts and approaches to IEC physics and applications. Much of this work is documented in …
Date: June 4, 2008
Creator: Miley, George, H.
System: The UNT Digital Library
Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections (open access)

Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections

We report re-optimization of a recently proposed long-range corrected (LC) hybrid density functionals [J.-D. Chai and M. Head-Gordon, J. Chem. Phys. 128, 084106 (2008)] to include empirical atom-atom dispersion corrections. The resulting functional, {omega}B97X-D yields satisfactory accuracy for thermochemistry, kinetics, and non-covalent interactions. Tests show that for non-covalent systems, {omega}B97X-D shows slight improvement over other empirical dispersion-corrected density functionals, while for covalent systems and kinetics, it performs noticeably better. Relative to our previous functionals, such as {omega}B97X, the new functional is significantly superior for non-bonded interactions, and very similar in performance for bonded interactions.
Date: June 14, 2008
Creator: Chai, Jeng-Da & Head-Gordon, Martin
System: The UNT Digital Library
Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach (open access)

Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach

Techniques to study the electronic structure of liquids are rare. Most recently, resonant x-ray emission spectroscopy (XES) has been shown to be an extremely versatile spectroscopy to study both occupied and unoccupied electronic states for liquids in thermodynamic equilibrium. However, XES requires high-brilliance soft x-ray synchrotron radiation and poses significant technical challenges to maintain a liquid sample in an ultra-high vacuum environment. Our group has therefore developed and constructed a novel experimental setup for the study of liquids, with the long-term goal of investigating the electronic structure of biological systems in aqueous environments. We have developed a flow-through liquid cell in which the liquid is separated from vacuum by a thin Si3N4 or SiC window and which allows a precise control of temperature. This approach has significant advantages compared to static liquids cells used in the past. Furthermore, we have designed a dedicated high-transmission, high-resolution soft x-ray spectrometer. The high transmission makes it possible to measure complete resonant XES"maps" in less than an hour, giving unprecedented detailed insight into the electronic structure of the investigated sample. Using this new equipment we have investigated the electronic structure of liquid water. Furthermore, our XES spectra and maps give information about ultra-fast dissociation …
Date: June 17, 2008
Creator: Weinhardt, L.; Fuchs, O.; Blum, M.; Bär, M.; Weigand, M.; Denlinger, J.D. et al.
System: The UNT Digital Library
Indoor Thermal Factors and Symptoms in Office Workers: Findings from the U.S. EPA BASE Study (open access)

Indoor Thermal Factors and Symptoms in Office Workers: Findings from the U.S. EPA BASE Study

Some prior research in office buildings has associated higher indoor temperatures even within the recommended thermal comfort range with increased worker symptoms. We reexamined this relationship in data from 95 office buildings in the U.S. Environmental Protection Agency's Building Assessment Survey and Evaluation (BASE) Study. We investigated relationships between building-related symptoms and thermal metrics constructed from real-time measurements. We estimated odds ratios (ORs) and 95percent confidence intervals in adjusted logistic regression models with general estimating equations, overall and by season. Winter indoor temperatures spanned the recommended winter comfort range; summer temperatures were mostly colder than the recommended summer range. Increasing indoor temperatures, overall, were associated with increases in few symptoms. Higher winter indoor temperatures, however, were associated with increases in all symptoms analyzed. Higher summer temperatures, above 23oC, were associated with decreases in most symptoms. Humidity ratio, a metric of absolute humidity, showed few clear associations. Thus, increased symptoms with higher temperatures within the thermal comfort range were found only in winter. In summer, buildings were overcooled, and only the higher observed temperatures were within the comfort range; these were associated with decreased symptoms. Confirmation of these findings would suggest that thermal management guidelines consider health effects as well as …
Date: June 1, 2008
Creator: Mendell, Mark & Mirer, Anna
System: The UNT Digital Library
Establishing an IEZ at the K-25 Site With Realism - ANS 2008 Annual Meeting - June 8-12, 2008 Anaheim, CA (open access)

Establishing an IEZ at the K-25 Site With Realism - ANS 2008 Annual Meeting - June 8-12, 2008 Anaheim, CA

The requirement from ANSI/ANS-8.3 states: (1) a criticality alarm system meeting the requirements of this standard shall be installed in areas where personnel would be subject to an excessive radiation dose; and (2) excessive dose = any dose to personnel corresponding to an absorbed dose from neutrons and gamma rays equal to or greater than 0.12 Gy (12 rad) in free air. The requirement was misconstrued to imply that the Immediate Evaluation Zone (IEZ) had to cover out to 12 Rad of dose. This mis-interpretation prompted the following official clarification: The standard does not attempt to define the area that is to be evacuated, which is considered a management responsibility and outside the scope of this Standard. What we wanted was an IEZ that: (1) depended on the facility characteristics and hazards; (2) departed from the one 'Size' fits all mentality; (3) balanced the risk of a criticality with the risk of evacuating; and (4) was consistent with the emergency planning process. What they have is a facility that is a mile long; a facility that was falling down around them; a facility where workers are routinely in fall protection; and a facility where high noise is the normal condition. …
Date: June 8, 2008
Creator: Kimball, K.D.
System: The UNT Digital Library
Investigation of key parameters influencing the efficient photocatalytic oxidation of indoor volatile organic compounds (VOCs) (open access)

Investigation of key parameters influencing the efficient photocatalytic oxidation of indoor volatile organic compounds (VOCs)

Photocatalytic oxidation of indoor VOCs has the potential to eliminate pollutants from indoor environments, thus effectively improving and/or maintaining indoor air quality while reducing ventilation energy costs. Design and operation of UV photocatalytic oxidation (UVPCO) air cleaners requires optimization of various parameters to achieve highest pollutant removal efficiencies while avoiding the formation of harmful secondary byproducts and maximizing catalyst lifetime.
Date: June 1, 2008
Creator: Quici, Natalia; Kibanova, Daria; Vera, Maria Laura; Choi, Hyeok; Dionysiou, Dionysios D.; Litter, Marta I. et al.
System: The UNT Digital Library
The Effects of Oxygen Plasma on the Chemical Composition and Morphology of the Ru Capping Layer of the Extreme Ultraviolet (EUV) Mask Blanks (open access)

The Effects of Oxygen Plasma on the Chemical Composition and Morphology of the Ru Capping Layer of the Extreme Ultraviolet (EUV) Mask Blanks

Contamination removal from extreme ultraviolet (EUV) mask surfaces is one of the most important aspects to improve reliability for the next generation of EUV lithography. We report chemical and morphological changes of the ruthenium (Ru) mask surface after oxygen plasma treatment using surface sensitive analytical methods: X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). Chemical analysis of the EUV masks shows an increase in the subsurface oxygen concentration, Ru oxidation and surface roughness. XPS spectra at various photoelectron takeoff angles suggest that the EUV mask surface was covered with chemisorbed oxygen after oxygen plasma treatment. It is proposed that the Kirkendall effect is the most plausible mechanism that explains the Ru surface oxidation. The etching rate of the Ru capping layer by oxygen plasma was estimated to be 1.5 {+-} 0.2 {angstrom}/min, based on TEM cross sectional analysis.
Date: June 7, 2008
Creator: Belau, Leonid; Park, Jeong Y.; Liang, Ted & Somorjai, Gabor A.
System: The UNT Digital Library
Optical Reflectance Measurements for Commonly Used Reflectors (open access)

Optical Reflectance Measurements for Commonly Used Reflectors

When simulating light collection in scintillators, modeling the angular distribution of optical light reflectance from surfaces is very important. Since light reflectance is poorly understood, either purely specular or purely diffuse reflectance is generally assumed. In this paper we measure the optical reflectance distribution for eleven commonly used reflectors. A 440 nm, output power stabilized, un-polarized laser is shone onto a reflector at a fixed angle of incidence. The reflected light's angular distribution is measured by an array of silicon photodiodes. The photodiodes are movable to cover 2 pi of solid angle. The light-induced current is, through a multiplexer, read out with a digital multimeter. A LabVIEW program controls the motion of the laser and the photodiode array, the multiplexer, and the data collection. The laser can be positioned at any angle with a position accuracy of 10 arc minutes. Each photodiode subtends 6.3o, and the photodiode array can be positioned at any angle with up to 10 arc minute angular resolution. The dynamic range for the current measurements is 105:1. The measured light reflectance distribution was measured to be specular for several ESR films as well as for aluminum foil, mostly diffuse for polytetrafluoroethylene (PTFE) tape and titanium dioxide …
Date: June 11, 2008
Creator: Janecek, Petr Martin & Moses, William
System: The UNT Digital Library
Guiding of an electromagnetic pulse in a plasma immersed in combined wiggler and axial magnetic fields (open access)

Guiding of an electromagnetic pulse in a plasma immersed in combined wiggler and axial magnetic fields

None
Date: June 1, 2008
Creator: Hur, Min Sup; Wurtele, Jonathan S. & Penn, Gregory
System: The UNT Digital Library
Spectrophotometric and Calorimetric Studies of Np(V) Complexation with Sulfate at 10-70oC (open access)

Spectrophotometric and Calorimetric Studies of Np(V) Complexation with Sulfate at 10-70oC

Sulfate, one of the inorganic constituents in the groundwater of nuclear waste repository, could affect the migration of radioactive materials by forming complexes. Spectrophotometric and microcalorimetric titrations were performed to identify the Np(V)/sulfate complex and determine the equilibrium constants and enthalpy of complexation at 10-70 C. Results show that the complexation of Np(V) with sulfate is weak but slightly enhanced by the increase in temperature. The complexation is endothermic and becomes more endothermic with the increase in temperature. The enhanced complexation at elevated temperatures is due to the increasingly larger entropy of complexation that exceeds the increase in enthalpy, suggesting that the complexation of Np(V) with sulfate is entropy-driven.
Date: June 16, 2008
Creator: Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian & Friese, Judah I.
System: The UNT Digital Library
Influence of base and PAG on deprotection blur in EUV photoresists and some thoughts on shot noise (open access)

Influence of base and PAG on deprotection blur in EUV photoresists and some thoughts on shot noise

A contact-hole deprotection blur metric has been used to monitor the deprotection blur of an experimental open platform resist (EH27) as the weight percent of base and photo acid generator (PAG) were varied. A 6x increase in base weight percent is shown to reduce the size of successfully patterned 1:1 line-space features from 52 nm to 39 nm without changing deprotection blur. Corresponding isolated line-edge-roughness is reduced from 6.9 nm to 4.1 nm. A 2x increase in PAG weight percent is shown to improve 1:1 line-space patterning from 47 nm to 40 nm without changing deprotection blur or isolated LER. A discussion of improved patterning performance as related to shot noise and deprotection blur concludes with a speculation that the spatial distribution of PAG molecules has been playing some role, perhaps a dominant one, in determining the uniformity of photo generated acids in the resists that have been studied.
Date: June 1, 2008
Creator: Anderson, Christopher N.; Naulleau, Patrick P.; Niakoula, Dimitra; Hassanein, Elsayed; Brainard, Robert; Gallatin, Gregg et al.
System: The UNT Digital Library
Use of Yb(III) Centered Near Infra-Red (NIR) Luminescence to Determine the Hydration State of a 3,2-HOPO based MRI-Contrast Agent (open access)

Use of Yb(III) Centered Near Infra-Red (NIR) Luminescence to Determine the Hydration State of a 3,2-HOPO based MRI-Contrast Agent

It has been more than a decade since the first reports of [Gd(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] as a potential new class of magnetic resonance imaging contrast agent (MRI-CA). The defining feature of these 1-methyl-3-hydroxypyridin-2-one (Me-3,2-HOPO) based compounds has been the use of a hexadentate ligand design, and hence an increase in the number of metal bound water molecules, without sacrificing complex stability compared to the typically octadentate contrast agents used commercially. Since that time, significant advances in the properties of these chelates have been steadily reported, including improvements in relaxivity, incorporation into macromolecular architectures and, recently, the first direct verification of solution structure using the discovery of Eu(III) centered luminescence with the isomeric 1-hydroxypyridin-2-one (1,2-HOPO) chelate as a sensitizing chromophore. Nonetheless, it has remained frustrating that direct measurements of the inner sphere hydration state, q, using luminescence techniques with the parent Me-3,2-HOPO compounds have remained elusive, even when direct laser excitation of weakly absorbing f-f transitions were employed (eg. for Eu(III) complexes). This failing can likely be traced to the presence of a low lying LMCT state which efficiently quenches metal based emission. Instead, estimates of the q and hence solution structure have relied on the fitting of relaxivity data to …
Date: June 9, 2008
Creator: Moore, Evan G.; Seitz, Michael & Raymond, Kenneth N.
System: The UNT Digital Library
Robotic Welding and Inspection System (open access)

Robotic Welding and Inspection System

This paper presents a robotic system for GTA welding of lids on cylindrical vessels. The system consists of an articulated robot arm, a rotating positioner, end effectors for welding, grinding, ultrasonic and eddy current inspection. Features include weld viewing cameras, modular software, and text-based procedural files for process and motion trajectories.
Date: June 1, 2008
Creator: Smartt, H. B.; Pace, D. P.; Larsen, E. D.; McJunkin, T. R.; Nichol, C. I.; Clark, D. E. et al.
System: The UNT Digital Library
Intermixing and chemical structure at the interface between n-GaN and V-based contacts (open access)

Intermixing and chemical structure at the interface between n-GaN and V-based contacts

The interface between n-type GaN and V-based contacts was characterized by soft x-ray spectroscopy. We have investigated the chemical interface structure before and after a rapid thermal annealing (RTA) step, which is crucial for the formation of an Ohmic contact. X-ray photoelectron and x-ray excited Auger electron spectra suggestthat RTA induces an accumulation of metallic Ga at the surface. Using x-ray emission spectroscopy, we find that the probed nitrogen atoms are in a VN-like environment, indicating that vanadium interacts with nitrogen atoms from the GaN to form VN.
Date: June 30, 2008
Creator: Pookpanratana, S.; France, R.; Bar, M.; Weinhardt, L.; Fuchs, O.; Blum, M. et al.
System: The UNT Digital Library
Coarse Grained Modeling of The Interface BetweenWater and Heterogeneous Surfaces (open access)

Coarse Grained Modeling of The Interface BetweenWater and Heterogeneous Surfaces

Using coarse grained models we investigate the behavior of water adjacent to an extended hydrophobic surface peppered with various fractions of hydrophilic patches of different sizes. We study the spatial dependence of the mean interface height, the solvent density fluctuations related to drying the patchy substrate, and the spatial dependence of interfacial fluctuations. We find that adding small uniform attractive interactions between the substrate and solvent cause the mean position of the interface to be very close to the substrate. Nevertheless, the interfacial fluctuations are large and spatially heterogeneous in response to the underlying patchy substrate. We discuss the implications of these findings to the assembly of heterogeneous surfaces.
Date: June 23, 2008
Creator: Willard, Adam & Chandler, David
System: The UNT Digital Library
Co-Firing Oil Shale with Coal and Other Fuels for Improved Efficiency and Multi-Pollutant Control (open access)

Co-Firing Oil Shale with Coal and Other Fuels for Improved Efficiency and Multi-Pollutant Control

Oil shale is an abundant, undeveloped natural resource which has natural sorbent properties, and its ash has natural cementitious properties. Oil shale may be blended with coal, biomass, municipal wastes, waste tires, or other waste feedstock materials to provide the joint benefit of adding energy content while adsorbing and removing sulfur, halides, and volatile metal pollutants, and while also reducing nitrogen oxide pollutants. Oil shale depolymerization-pyrolysis-devolatilization and sorption scoping studies indicate oil shale particle sorption rates and sorption capacity can be comparable to limestone sorbents for capture of SO2 and SO3. Additionally, kerogen released from the shale was shown to have the potential to reduce NOx emissions through the well established “reburning” chemistry similar to natural gas, fuel oil, and micronized coal. Productive mercury adsorption is also possible by the oil shale particles as a result of residual fixed-carbon and other observed mercury capture sorbent properties. Sorption properties were found to be a function particle heating rate, peak particle temperature, residence time, and gas-phase stoichmetry. High surface area sorbents with high calcium reactivity and with some adsorbent fixed/activated carbon can be produced in the corresponding reaction zones that exist in a standard pulverized-coal or in a fluidized-bed combustor.
Date: June 1, 2008
Creator: Carrington, Robert A.; Hecker, William C. & Clayson, Reed
System: The UNT Digital Library
Complexation of Neptunium(V) with Fluoride at Elevated Temperatures (open access)

Complexation of Neptunium(V) with Fluoride at Elevated Temperatures

Complexation of neptunium(V) with fluoride at elevated temperatures was studied by spectrophotometry and microcalorimetry. Two successive complexes, NpO{sub 2}F(aq) and NpO{sub 2}F{sub 2}{sup -}, were identified by spectrophotometry in the temperature range of 10-70 C. Thermodynamic parameters, including the equilibrium constants and enthalpy of complexation between Np(V) and fluoride at 10-70 C were determined. Results show that the complexation of Np(V) with fluoride is endothermic and that the complexation is enhanced by the increase in temperature - a two-fold increase in the stability constants of NpO{sub 2}F(aq) and more than five-fold increase in the stability constants of NpO{sub 2}F{sub 2}{sup -} as the temperature is increased from 10 to 70 C.
Date: June 16, 2008
Creator: Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian & Friese, Judah I.
System: The UNT Digital Library