Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates (open access)

Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates

Replacement of methane with carbon dioxide in hydrate has been proposed as a strategy for geologic sequestration of carbon dioxide (CO{sub 2}) and/or production of methane (CH{sub 4}) from natural hydrate deposits. This replacement strategy requires a better understanding of the thermodynamic characteristics of binary mixtures of CH{sub 4} and CO{sub 2} hydrate (CH{sub 4}-CO{sub 2} mixed hydrates), as well as thermophysical property changes during gas exchange. This study explores the thermal dissociation behavior and dissociation enthalpies of CH{sub 4}-CO{sub 2} mixed hydrates. We prepared CH{sub 4}-CO{sub 2} mixed hydrate samples from two different, well-defined gas mixtures. During thermal dissociation of a CH{sub 4}-CO{sub 2} mixed hydrate sample, gas samples from the head space were periodically collected and analyzed using gas chromatography. The changes in CH{sub 4}-CO{sub 2} compositions in both the vapor phase and hydrate phase during dissociation were estimated based on the gas chromatography measurements. It was found that the CO{sub 2} concentration in the vapor phase became richer during dissociation because the initial hydrate composition contained relatively more CO{sub 2} than the vapor phase. The composition change in the vapor phase during hydrate dissociation affected the dissociation pressure and temperature; the richer CO{sub 2} in the vapor …
Date: February 15, 2011
Creator: Kwon, T.H.; Kneafsey, T.J. & Rees, E.V.L.
Object Type: Article
System: The UNT Digital Library
Ridge-Valley Graphs: Combinatorial Ridge Detection Using Jacobi Sets (open access)

Ridge-Valley Graphs: Combinatorial Ridge Detection Using Jacobi Sets

None
Date: February 4, 2011
Creator: Norgard, G & Bremer, P T
Object Type: Report
System: The UNT Digital Library
Order and disorder in the local and long-range structure of the spin-glass pyrochlore, Tb{sub 2}Mo{sub 2}O{sub 7} (open access)

Order and disorder in the local and long-range structure of the spin-glass pyrochlore, Tb{sub 2}Mo{sub 2}O{sub 7}

To understand the origin of the spin-glass state in molybdate pyrochlores, the structure of Tb{sub 2}Mo{sub 2}O{sub 7} is investigated using two techniques: the long-range lattice structure was measured using neutron powder diffraction (NPD), and local structure information was obtained from the extended x-ray absorption fine structure (EXAFS) technique. While the long-range structure appears generally well ordered, enhanced mean-squared site displacements on the O(1) site and the lack of temperature dependence of the strongly anisotropic displacement parameters for both the Mo and O(1) sites indicate some disorder exists. Likewise, the local structure measurements indicate some Mo-Mo and Tb-O(1) nearest-neighbor disorder exists, similar to that found in the related spin-glass pyrochlore, Y{sub 2}Mo{sub 2}O{sub 7}. Although the freezing temperature in Tb{sub 2}Mo{sub 2}O{sub 7}, 25 K, is slightly higher than in Y{sub 2}Mo{sub 2}O{sub 7}, 22 K, the degree of local pair distance disorder is actually less in Tb{sub 2}Mo{sub 2}O{sub 7}. This apparent contradiction is considered in light of the interactions involved in the freezing process.
Date: February 11, 2011
Creator: Jiang, Yu; Huq, Ashfia; Booth, Corwin H.; Ehlers, Georg; Greedan, John E. & Gardner, Jason S.
Object Type: Article
System: The UNT Digital Library
X-ray imaging of vortex cores in confined magnetic structures (open access)

X-ray imaging of vortex cores in confined magnetic structures

Cores of magnetic vortices in micron-sized NiFe disk structures, with thicknesses between 150 and 50 nm, were imaged and analysed by high resolution magnetic soft X-ray microscopy. A decrease of the vortex core radius was observed, from #24; ~38 to 18 nm with decreasing disk thickness. By comparing with full 3D micromagnetic simulations showing the well-known barrel structure, we obtained excellent agreement taking into account instrumental broadening and a small perpendicular anisotropy. The proven magnetic spatial resolution of better than 25 nm was sufficient to identify a negative dip close to the vortex core, originating from stray fields of the core. Magnetic vortex structures can serve as test objects for evaluating sensitivity and spatial resolution of advanced magnetic microscopy techniques.
Date: February 11, 2011
Creator: Fischer, P.; Im, M.-Y.; Kasai, S.; Yamada, K.; Ono, T. & Thiaville, A.
Object Type: Article
System: The UNT Digital Library
Identification of a haloalkaliphilic and thermostable cellulase with improved ionic liquid tolerance (open access)

Identification of a haloalkaliphilic and thermostable cellulase with improved ionic liquid tolerance

Some ionic liquids (ILs) have been shown to be very effective solvents for biomass pretreatment. It is known that some ILs can have a strong inhibitory effect on fungal cellulases, making the digestion of cellulose inefficient in the presence of ILs. The identification of IL-tolerant enzymes that could be produced as a cellulase cocktail would reduce the costs and water use requirements of the IL pretreatment process. Due to their adaptation to high salinity environments, halophilic enzymes are hypothesized to be good candidates for screening and identifying IL-resistant cellulases. Using a genome-based approach, we have identified and characterized a halophilic cellulase (Hu-CBH1) from the halophilic archaeon, Halorhabdus utahensis. Hu-CBH1 is present in a gene cluster containing multiple putative cellulolytic enzymes. Sequence and theoretical structure analysis indicate that Hu-CBH1 is highly enriched with negatively charged acidic amino acids on the surface, which may form a solvation shell that may stabilize the enzyme, through interaction with salt ions and/or water molecules. Hu-CBH1 is a heat tolerant haloalkaliphilic cellulase and is active in salt concentrations up to 5 M NaCl. In high salt buffer, Hu-CBH1 can tolerate alkali (pH 11.5) conditions and, more importantly, is tolerant to high levels (20percent w/w) of ILs, …
Date: February 17, 2011
Creator: Zhang, Tao; Datta, Supratim; Eichler, Jerry; Ivanova, Natalia; Axen, Seth D.; Kerfeld, Cheryl A. et al.
Object Type: Article
System: The UNT Digital Library
Mask roughness induced LER: geometric model at long correlation lengths (open access)

Mask roughness induced LER: geometric model at long correlation lengths

Collective understanding of how both the resist and line-edge roughness (LER) on the mask affect the final printed LER has made significant advances. What is poorly understood, however, is the extent to which mask surface roughness couples to image plane LER as a function of illumination conditions, NA, and defocus. Recently, progress has been made in formulating a simplified solution for mask roughness induced LER. Here, we investigate the LER behavior at long correlation lengths of surface roughness on the mask. We find that for correlation lengths greater than 3/NA in wafer dimensions and CDs greater than approximately 0.75/NA, the previously described simplified model, which remains based on physical optics, converges to a 'geometric regime' which is based on ray optics and is independent of partial coherence. In this 'geometric regime', the LER is proportional to the mask slope error as it propagates through focus, and provides a faster alternative to calculating LER in contrast to either full 2D aerial image simulation modeling or the newly proposed physical optics model. Data is presented for both an NA = 0.32 and an NA = 0.5 imaging system for CDs of 22-nm and 50-nm horizontal-line-dense structures.
Date: February 11, 2011
Creator: McClinton, Brittany M. & Naulleau, Patrick P.
Object Type: Article
System: The UNT Digital Library
Coal/Biomass Gasification at the Colorado School of Mines (open access)

Coal/Biomass Gasification at the Colorado School of Mines

This program was a 2.5 year effort focused on technologies that support coal and biomass gasification. Two primary tasks were included in the effort: 1) Coal/Biomass gasification and system optimization and 2) development of high temperature microchannel ceramic heat exchangers.
Date: February 28, 2011
Creator: Parker, Terry; Braun, Robert; Dreyer, Chris; Dean, Anthony; Eberhart, Mark; Kee, Robert et al.
Object Type: Report
System: The UNT Digital Library
NUCLEAR FORENSICS ANALYSIS CENTER FORENSIC ANALYSIS TO DATA INTERPRETATION (open access)

NUCLEAR FORENSICS ANALYSIS CENTER FORENSIC ANALYSIS TO DATA INTERPRETATION

The Nuclear Forensics Analysis Center (NFAC) is part of Savannah River National Laboratory (SRNL) and is one of only two USG National Laboratories accredited to perform nuclear forensic analyses to the requirements of ISO 17025. SRNL NFAC is capable of analyzing nuclear and radiological samples from bulk material to ultra-trace samples. NFAC provides analytical support to the FBI's Radiological Evidence Examination Facility (REEF), which is located within SRNL. REEF gives the FBI the capability to perform traditional forensics on material that is radiological and/or is contaminated. SRNL is engaged in research and development efforts to improve the USG technical nuclear forensics capabilities. Research includes improving predictive signatures and developing a database containing comparative samples.
Date: February 7, 2011
Creator: Nichols, T.
Object Type: Book
System: The UNT Digital Library
Aspen Winter Conferences on High Energy (open access)

Aspen Winter Conferences on High Energy

The 2011 Aspen Winter Conference on Particle Physics was held at the Aspen Center for Physics from February 12 to February 18, 2011. Ninety-four participants from ten countries, and several universities and national labs attended the workshop titled, �New Data From the Energy Frontier.� There were 54 formal talks, and a considerable number of informal discussions held during the week. The week�s events included a public lecture (�The Hunt for the Elusive Higgs Boson� given by Ben Kilminster from Ohio State University) and attended by 119 members of the public, and a physics caf� geared for high schoolers that is a discussion with physicists. The 2011 Aspen Winter Conference on Astroparticle physics held at the Aspen Center for Physics was �Indirect and Direct Detection of Dark Matter.� It was held from February 6 to February 12, 2011. The 70 participants came from 7 countries and attended 53 talks over five days. Late mornings through the afternoon are reserved for informal discussions. In feedback received from participants, it is often these unplanned chats that produce the most excitement due to working through problems with fellow physicists from other institutions and countries or due to incipient collaborations. In addition, Blas Cabrera of …
Date: February 12, 2011
Creator: multiple speakers, presenters listed on link below
Object Type: Article
System: The UNT Digital Library
Report of On-Site Inspection Workshop-18 (open access)

Report of On-Site Inspection Workshop-18

None
Date: February 1, 2011
Creator: Sweeney, J. J.
Object Type: Report
System: The UNT Digital Library
Design and Construction of a Gas Jet Target for RIB Experiements (open access)

Design and Construction of a Gas Jet Target for RIB Experiements

PNNL is now part of the JENSA collaboration to produce a gas jet system for the Facility for Rare Isotope Beams (FRIB). This document is a status report for the gas jet working group to be delivered to the FRIB scientific advisory council (SAC). It briefly describes PNNL’s capability at constructing cost efficient and high detection efficiency HPGe arrays.
Date: February 4, 2011
Creator: Greife, Uwe; Chipps, Kelly A.; Smith, Michael; Bardayan, Dan W.; Pain, Steven D.; Schmitt, Kyle et al.
Object Type: Report
System: The UNT Digital Library
Nanocoatings for High-Efficiency Industrial and Tooling Systems (open access)

Nanocoatings for High-Efficiency Industrial and Tooling Systems

None
Date: February 1, 2011
Creator: Blau, Peter Julian; Qu, Jun & Higdon, Clifton
Object Type: Report
System: The UNT Digital Library
Electrostatically Self-assembled Amphiplexes (open access)

Electrostatically Self-assembled Amphiplexes

This research will focus on characterizing the phase behavior of polyelectrolyte-surfactant microemulsions (PSM) that were recently discovered in our lab and indentifing possible uses of their long-range ordered nanostructures towards bioseparation, oil-recovery and drug delivery systems. In addition, we are proposing strategies for synthesizing solid and long-range ordered materials with unit cells on the nanometer scale using polymerization and/or cross-linking to solidify the soft template.
Date: February 15, 2011
Creator: Strey, Helmut H.
Object Type: Report
System: The UNT Digital Library
Analysis of Axial Growth of Gold Indide by Indium Diffusing away from Solder Mounds and Creating the Gold to Gold-Indide Interface Angle Inside the Solder Mounds (open access)

Analysis of Axial Growth of Gold Indide by Indium Diffusing away from Solder Mounds and Creating the Gold to Gold-Indide Interface Angle Inside the Solder Mounds

None
Date: February 3, 2011
Creator: Siekhaus, W J & Hrousis, C A
Object Type: Report
System: The UNT Digital Library
Proceedings of RIKEN BNL Research Center Workshop: Initial State Fluctuations and Final-State Particle Correlations (open access)

Proceedings of RIKEN BNL Research Center Workshop: Initial State Fluctuations and Final-State Particle Correlations

N/A
Date: February 2, 2011
Creator: A., Dumitru; Molnar, D. & Wang, F.
Object Type: Report
System: The UNT Digital Library
Silicon Carbide Derived Carbons: Experiments and Modeling (open access)

Silicon Carbide Derived Carbons: Experiments and Modeling

The main results of the computational modeling was: 1. Development of a new genealogical algorithm to generate vacancy clusters in diamond starting from monovacancies combined with energy criteria based on TBDFT energetics. The method revealed that for smaller vacancy clusters the energetically optimal shapes are compact but for larger sizes they tend to show graphitized regions. In fact smaller clusters of the size as small as 12 already show signatures of this ‘graphitization’. The modeling gives firm basis for the ‘slit-pore’ modeling of porous carbon materials and explains some of their properties. 2. We discovered small vacancy clusters and their physical characteristics that can be used to spectroscopically identify them. 3. We found low barrier pathways for vacancy migration in diamond-like materials by obtaining for the first time optimized reaction pathways.
Date: February 28, 2011
Creator: Kertesz, Miklos
Object Type: Report
System: The UNT Digital Library
Battery-free Wireless Sensor Network For Advanced Fossil-Fuel Based Power Generation (open access)

Battery-free Wireless Sensor Network For Advanced Fossil-Fuel Based Power Generation

This report summarizes technical progress achieved during the project supported by the Department of Energy under Award Number DE-FG26-07NT4306. The aim of the project was to conduct basic research into battery-free wireless sensing mechanism in order to develop novel wireless sensors and sensor network for physical and chemical parameter monitoring in a harsh environment. Passive wireless sensing platform and five wireless sensors including temperature sensor, pressure sensor, humidity sensor, crack sensor and networked sensors developed and demonstrated in our laboratory setup have achieved the objective for the monitoring of various physical and chemical parameters in a harsh environment through remote power and wireless sensor communication, which is critical to intelligent control of advanced power generation system. This report is organized by the sensors developed as detailed in each progress report.
Date: February 28, 2011
Creator: Jia, Yi
Object Type: Report
System: The UNT Digital Library
Detailed Chemical Kinetic Model for H2 and H2/CO (Syngas) Mixtures at Elevated Pressure (open access)

Detailed Chemical Kinetic Model for H2 and H2/CO (Syngas) Mixtures at Elevated Pressure

None
Date: February 4, 2011
Creator: Keromnes, A; Metcalfe, W K; Donohoe, N; Curran, H J & Pitz, W J
Object Type: Article
System: The UNT Digital Library
In situ optimization of co-implantation and substrate temperature conditions for Nv-center formation in single crystal diamonds (open access)

In situ optimization of co-implantation and substrate temperature conditions for Nv-center formation in single crystal diamonds

We present first results from in situ characterization of NV-formation in single crystal diamonds following implantation of low energy nitrogen ions (7.7 keV), co-implantation of hydrogen, helium and carbon ions and in situ annealing. Diamond samples were implanted at room temperature or at a temperature of 780{degree} C during the implantation steps. We find that dynamic annealing during co-implantation enhances NV-center formation by up to 25%.
Date: February 1, 2011
Creator: Schwartz, Julian; Michaelides, Philip; Weis, Christoph D. & Schenkel, Thomas
Object Type: Article
System: The UNT Digital Library
In situ optimization of co-implantation and substrate temperature conditions for Nitrogen-Vacancy center formation in single crystal diamonds (open access)

In situ optimization of co-implantation and substrate temperature conditions for Nitrogen-Vacancy center formation in single crystal diamonds

None
Date: February 11, 2011
Creator: Schwartz, J.; Michaelides, P.; Weis, C. D. & Schenkel, T.
Object Type: Article
System: The UNT Digital Library
Welcome to Greenhouse Gases: Science and Technology: Editorial (open access)

Welcome to Greenhouse Gases: Science and Technology: Editorial

This editorial introduces readers and contributors to a new online journal. Through the publication of articles ranging from peer-reviewed research papers and short communications, to editorials and interviews on greenhouse gas emissions science and technology, this journal will disseminate research results and information that address the global crisis of anthropogenic climate change. The scope of the journal includes the full spectrum of research areas from capture and separation of greenhouse gases from flue gases and ambient air, to beneficial utilization, and to sequestration in deep geologic formations and terrestrial (plant and soil) systems, as well as policy and technoeconomic analyses of these approaches.
Date: February 1, 2011
Creator: Oldenburg, C. M. & Maroto-Valer, M. M.
Object Type: Article
System: The UNT Digital Library
Directed Relation Graph with Expert Knowledge for Skeletal Mechanism Reduction (open access)

Directed Relation Graph with Expert Knowledge for Skeletal Mechanism Reduction

None
Date: February 7, 2011
Creator: Lu, T; Plomer, M; Luo, Z; Sarathy, S M; Pitz, W J; Som, S et al.
Object Type: Article
System: The UNT Digital Library
OpenADR Open Source Toolkit: Developing Open Source Software for the Smart Grid (open access)

OpenADR Open Source Toolkit: Developing Open Source Software for the Smart Grid

Demand response (DR) is becoming an increasingly important part of power grid planning and operation. The advent of the Smart Grid, which mandates its use, further motivates selection and development of suitable software protocols to enable DR functionality. The OpenADR protocol has been developed and is being standardized to serve this goal. We believe that the development of a distributable, open source implementation of OpenADR will benefit this effort and motivate critical evaluation of its capabilities, by the wider community, for providing wide-scale DR services
Date: February 1, 2011
Creator: McParland, Charles
Object Type: Article
System: The UNT Digital Library