Resource Type

Language

ACOUSTIC FORMING FOR ENHANCED DEWATERING AND FORMATION (open access)

ACOUSTIC FORMING FOR ENHANCED DEWATERING AND FORMATION

The next generation of forming elements based on acoustic excitation to increase drainage and enhances formation both with on-line control and profiling capabilities has been investigated in this project. The system can be designed and optimized based on the fundamental experimental and computational analysis and investigation of acoustic waves in a fiber suspension flow and interaction with the forming wire.
Date: November 30, 2007
Creator: Aidun, Cyrus K
System: The UNT Digital Library
ACRF Instrumentation Status: New, Current, and Future - October – November 2007 (open access)

ACRF Instrumentation Status: New, Current, and Future - October – November 2007

The purpose of this report is to provide a concise but comprehensive overview of Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) instrumentation status. The report is divided into the following four sections: (1) new instrumentation in the process of being acquired and deployed, (2) existing instrumentation and progress on improvements or upgrades, (3) proposed future instrumentation, and (4) SBIR instrument development.
Date: November 30, 2007
Creator: Voyles, J. W.
System: The UNT Digital Library
L AREA WASTEWATER STORAGE DRUM EVALUATION (open access)

L AREA WASTEWATER STORAGE DRUM EVALUATION

This report documents the determination of the cause of pressurization that led to bulging deformation of a 55 gallon wastewater drum stored in L-Area. Drum samples were sent to SRNL for evaluation. The interior surface of these samples revealed blistering and holes in the epoxy phenolic drum liner and corrosion of the carbon steel drum. It is suspected that osmotic pressure drove permeation of the water through the epoxy phenolic coating which was weakened from exposure to low pH water. The coating failed at locations throughout the drum interior. Subsequent corrosion of the carbon steel released hydrogen which pressurized the drum causing deformation of the drum lid. Additional samples from other wastewater drums on the same pallet were also evaluated and limited corrosion was visible on the interior surfaces. It is suspected that, with time, the corrosion would have advanced to cause pressurization of these sealed drums.
Date: November 30, 2007
Creator: Vormelker, P; Cynthia Foreman, C; Zane Nelson, Z; David Hathcock, D & Dennis Vinson, D
System: The UNT Digital Library
Autonomous Control of Space Reactor Systems (open access)

Autonomous Control of Space Reactor Systems

Autonomous and semi-autonomous control is a key element of space reactor design in order to meet the mission requirements of safety, reliability, survivability, and life expectancy. Interrestrial nuclear power plants, human operators are avilable to perform intelligent control functions that are necessary for both normal and abnormal operational conditions.
Date: November 30, 2007
Creator: Upadhyaya, Belle R.; Zhao, K.; Perillo, S.R.P.; Xu, Xiaojia & Na, M.G.
System: The UNT Digital Library
Baseline Radionuclide and Nonradionuclide Concentrations in Soils, Vegetation, and Small Mammals at the Proposed Expansion Area at TA-54 Area G (open access)

Baseline Radionuclide and Nonradionuclide Concentrations in Soils, Vegetation, and Small Mammals at the Proposed Expansion Area at TA-54 Area G

Area G is a 25.5-hectare (63-acre), fenced, low-level radioactive solid waste processing and disposal area located on the east end of Mesa del Buey at Technical Area 54 at Los Alamos National Laboratory. This disposal area has been in existence since 1957 and is expected to be filled by the year 2015. Thus, a new area, located adjacent to Area G on the west side, has been proposed for the expansion of disposal activities. Since 1994 to the present, baseline levels of several radionuclides and nonradionuclides have been collected in soils, vegetation, and small mammals (field mice and rock squirrels). These data will be used to assess potential impacts, if any, at the expanded site once operations begin. Baseline statistical reference levels (BSRLs) (mean plus three standard deviations = 99% confidence level) of radionuclides and nonradionuclides in these media were calculated and compared with regional statistical reference levels (RSRLs). RSRLs are calculated from regional areas away from the influence of the Laboratory and represent natural and worldwide fallout sources. BSRLs in most media, with the exception of field mice (mostly Peromyscus spp.), compare very well with RSRLs. Field mice, probably because they are mobile and may have spent time within …
Date: November 30, 2007
Creator: D. D. Romero, P. R. Fresquez
System: The UNT Digital Library
Bird Surveys at DARHT Before and During Operations: Comparison of Species Abundance and Composition and Trace Element Uptake (open access)

Bird Surveys at DARHT Before and During Operations: Comparison of Species Abundance and Composition and Trace Element Uptake

The Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility Mitigation Action Plan specifies the comparison of baseline conditions in biotic and abiotic media with those collected after operations have started. Operations at DARHT at Los Alamos National Laboratory started in 2000. In this study, the abundance and composition of birds collected near the DARHT facility from 2003 through 2006 were determined and compared to a preoperational period (1999). In addition, the levels of radionuclides and other inorganic chemicals in birds were compared to regional statistical reference levels (RSRLs). The number and diversity of bird species generally increased over preoperational levels with the greatest number of birds (412) and species (46) occurring in 2005. The most common bird species collected regardless of time periods were the chipping sparrow (Spizella passerina), the Virginia's warbler (Vermivora virginiae), the western bluebird (Sialia mexicana), the broad-tailed hummingbird (Selasphorus platycercus), the sage sparrow (Amphispiza belli), and the western tanager (Piranga ludoviciana). Most radionuclides, with the exception of uranium-234 and uranium-238, in (whole body) birds collected after operations began were either not detected or below RSRLs. Uranium-234 and uranium-238 concentrations in a few samples were far below screening levels and do not pose a potential unacceptable dose to the …
Date: November 30, 2007
Creator: P. R. Fresquez, D. C. Keller, C. D. Hathcock
System: The UNT Digital Library
Brownfield Issues in the 110th Congress (open access)

Brownfield Issues in the 110th Congress

The Brownfields Act authorizes the Environmental Protection Agency to award grants for the assessment and cleanup of sites that pose a less serious threat to human health and the environment than sites addressed by the Superfund program. The authorization expired on September 30, 2006. In the 109th Congress, a reauthorization bill, H.B. 5810, was reported from the House Committee on Transportation and Infrastructure on July 28, 2006, but went no further. This report contains information on the EPA's involvement in the program, EPA appropriations, Housing and Urban Development's involvement in the program and appropriations, other federal Brownfield programs, and Congressional actions of the 109th and 110th Congresses as related to the programs.
Date: November 30, 2007
Creator: Reisch, Mark
System: The UNT Digital Library
Characterization of BG28 and KG3 filter glass for Drive Diagnostic Attenuators (open access)

Characterization of BG28 and KG3 filter glass for Drive Diagnostic Attenuators

BG28 and KG3 filter glasses were tested for use as attenuators in the NIF drive diagnostic (DrD) systems. Tests were performed in the Optical Sciences Laser facility with a 351 nm, 2-step, 3-nsec pulse at fluences ranging up to {approx} 1 J/cm{sup 2}. Single-shot measurements showed no solarization when the samples were allowed to relax for a week after exposure. KG3 filters exhibited no luminescence and no transient pulse distortion. BG28 filters luminesced appreciably and imposed a 'droop' (similar to 'square-pulse distortion') on the signals. The droop parameter is estimated at 0.50 {+-} 0.11 cm{sup 2}/J. Droop is explained in terms of known copper-doped-glass spectroscopy and kinetics (buildup of triplet-state populations, with excited-state absorption). Simulation of the distortion ({approx}1.6%) expected on a 1.8 MJ Haan pulse led to a minor redesign of the Drive Diagnostic with reduced fluence on the BG28 filters to reduce the droop distortion to 0.5%.
Date: November 30, 2007
Creator: Page, R. H.; Weiland, T. & Folta, J.
System: The UNT Digital Library
CHLORIDE WASHER PERFORMACE TESTING (open access)

CHLORIDE WASHER PERFORMACE TESTING

Testing was performed to determine the chloride (Cl-) removal capabilities of the Savannah River National Laboratory (SRNL) designed and built Cl- washing equipment intended for HB-Line installation. The equipment to be deployed was tested using a cerium oxide (CeO2) based simulant in place of the 3013 plutonium oxide (PuO2) material. Two different simulant mixtures were included in this testing -- one having higher Cl- content than the other. The higher Cl- simulant was based on K-Area Interim Surveillance Inspection Program (KIS) material with Cl- content approximately equal to 70,000 ppm. The lower Cl- level simulant was comparable to KIS material containing approximately 8,000-ppm Cl- content. The performance testing results indicate that the washer is capable of reducing the Cl- content of both surrogates to below 200 ppm with three 1/2-liter washes of 0.1M sodium hydroxide (NaOH) solution. Larger wash volumes were used with similar results - all of the prescribed test parameters consistently reduced the Cl- content of the surrogate to a value below 200 ppm Cl- in the final washed surrogate material. The washer uses a 20-micron filter to retain the surrogate solids. Tests showed that 0.16-0.41% of the insoluble fraction of the starting mass passed through the 20-micron …
Date: November 30, 2007
Creator: Coughlin, J; David Best, D & Robert Pierce, R
System: The UNT Digital Library
The Davis-Bacon Act: Institutional Evolution and Public Policy (open access)

The Davis-Bacon Act: Institutional Evolution and Public Policy

This report examines policy issues the Davis-Bacon Act has sparked through the years and which remain a part of the Davis-Bacon debate of the 1990s. These include such questions as: wage rate determination procedures, reporting requirements under the Copeland Act, an appropriate threshold for activation of the statute, interagency relationships with respect to Davis-Bacon enforcement and compliance activity, administrative or judicial appeals procedures, the use of "helpers" and other low-skilled workers on covered projects, and the right of a President to suspend the statute as well as the conditions under which such a suspension may occur. That the fundamental premise of the Act remains in contention after 60 years may be, itself, part of the public policy debate.
Date: November 30, 2007
Creator: Whittaker, William G.
System: The UNT Digital Library
Defense Trade: State Department Needs to Conduct Assessments to Identify and Address Inefficiencies and Challenges in the Arms Export Process (open access)

Defense Trade: State Department Needs to Conduct Assessments to Identify and Address Inefficiencies and Challenges in the Arms Export Process

A letter report issued by the Government Accountability Office with an abstract that begins "To regulate the export of billions of dollars worth of arms to foreign governments and companies, the Department of State's (State) Directorate of Defense Trade Controls (DDTC) reviews and authorizes export licenses and other arms export cases. While such reviews require time to consider national security and foreign policy interests, the U.S. defense industry and some foreign government purchasers have expressed concern that the U.S. export control process is unnecessarily time-consuming. In 2005, GAO reported that processing times for arms export cases had increased despite State efforts to streamline its process. GAO was asked to (1) describe recent trends in the processing of arms export cases and (2) identify factors that have contributed to these trends. To conduct its work, GAO obtained and analyzed State arms export case data for fiscal year 2003 through April 30, 2007; reviewed relevant laws, regulations, and guidelines, as well as DDTC funding and staffing information; and interviewed State and Department of Defense officials and selected arms exporters."
Date: November 30, 2007
Creator: United States. Government Accountability Office.
System: The UNT Digital Library
Economic Sanctions: Agencies Face Competing Priorities in Enforcing the U.S. Embargo on Cuba (open access)

Economic Sanctions: Agencies Face Competing Priorities in Enforcing the U.S. Embargo on Cuba

A letter report issued by the Government Accountability Office with an abstract that begins "The 48-year U.S. embargo on Cuba aims to deny resources to the Castro regime by prohibiting most trade, travel, and financial transactions with Cuba. The departments of Commerce, Homeland Security (DHS), Justice, and the Treasury are responsible for enforcing the embargo as well as protecting homeland and national security. Since 2001, U.S. agencies have changed the embargo's rules in response to new laws and policies. GAO was asked to examine (1) the rule changes in 2001-2005 and their impact on U.S. exports, travel, cash transfers, and gifts to Cuba; (2) U.S. agencies' embargo-related activities and workloads; and (3) factors affecting the embargo's enforcement. GAO analyzed laws, regulations, and agency data, interviewed agency officials, and observed agency activities at Port Everglades and Miami International Airport, Florida."
Date: November 30, 2007
Creator: United States. Government Accountability Office.
System: The UNT Digital Library
Extension of 4-8 Texture Hierarchies to Large Video Processing and Visualization (open access)

Extension of 4-8 Texture Hierarchies to Large Video Processing and Visualization

The purpose of this Techbase was to reduce to practice the tiled 4-8 texture hierarchy for the display of video imagery (i.e. sequences of frames). The immediate intent was to demonstrate its use in the analysis and display of sensor imagery. As sensors are increasing in resolution the physical amount of imagery that needs to be displayed can quickly overwhelm most display systems. For example, a sensor with a horizontal resolution of over 8000 pixels would generate an image over 10 feet wide on a standard 72 DPI display. Breaking an image into tiles, and then decomposing each tile into a multiresolution hierarchy, allows a user (or software) to efficiently select and display only those parts of the image that are of interest to the user. The originator of the idea of 4-8 Texture Hierarchies was Dr. Mark Duchaineau, and we consulted with him in much of our work. We also consulted with Dan Knight, from SequoiaTek Corp., who is a contractor responsible for implementing the viewers for our applications. Most of the code for actual 4-8 Texture Hierarchy generation already existed; a large focus of the Techbase was to determine how to best use what was available for video …
Date: November 30, 2007
Creator: Senecal, J G & Wegner, A E
System: The UNT Digital Library
Final Report for DOE Grant DE-FG02-03ER54712, Experimental Studies of Collisionless Reconnection Processes in Plasmas (open access)

Final Report for DOE Grant DE-FG02-03ER54712, Experimental Studies of Collisionless Reconnection Processes in Plasmas

The Grant DE-FG-02-00ER54712, ?Experimental Studies of Collisionless Reconnection Processes in Plasmas?, financed within the DoE/NSF, spanned a period from September , 2003 to August, 2007. It partly supported an MIT Research scientist, two graduate students and material expenses. The grant enabled the operation of a basic plasma physics experiment (on magnetic reconnection) at the MIT Plasma Science and Fusion Center and the MIT Physics Department. A strong educational component characterized this work throughout, with the participation of a large number of graduate and undergraduate students and interns to the experimental activities. The study of the collisionless magnetic reconnection constituted the primary work carried out under this grant. The investigations utilized two magnetic configurations with distinct boundary conditions. Both configurations were based upon the Versatile Toroidal Facility (VTF). The first configuration is characterized by open boundary conditions where the magnetic field lines interface directly with the vacuum vessel walls. The reconnection dynamics for this configuration has been methodically characterized and it has been shown that kinetic effects related to trapped electron trajectories are responsible for the high rates of reconnection observed [7]. This type of reconnection has not been investigated before. Nevertheless, the results are directly relevant to observations by the …
Date: November 30, 2007
Creator: Porkolab, Miklos & Egedal, Jan
System: The UNT Digital Library
Final Technical Report: Effects of Changing Water and Nitrogen Inputs on a Mojave Desert Ecosystem (open access)

Final Technical Report: Effects of Changing Water and Nitrogen Inputs on a Mojave Desert Ecosystem

In order to anticipate the effects of global change on ecosystem function, it is essential that predictive relationships be established linking ecosystem function to global change scenarios. The Mojave Desert is of considerable interest with respect to global change. It contains the driest habitats in North America, and thus most closely approximates the world’s great arid deserts. In order to examine the effects of climate and land use changes, in 2001 we established a long-term manipulative global change experiment, called the Mojave Global Change Facility. Manipulations in this study include the potential effects of (1) increased summer rainfall (75 mm over three discrete 25 mm events), (2) increased nitrogen deposition (10 and 40 kg ha-1), and (3) the disturbance of biological N-fixing crusts . Questions addressed under this grant shared the common hypothesis that plant and ecosystem performance will positively respond to the augmentation of the most limiting resources to plant growth in the Mojave Desert, e.g., water and nitrogen. Specific hypotheses include (1) increased summer rainfall will significantly increase plant production through an alleviation of moisture stress in the dry summer months, (2) N-deposition will increase plant production in this N-limited system, particularly in wet years or in concert …
Date: November 30, 2007
Creator: Smith, Stanley, D.; Nowak, Robert S.; Fenstermaker, Lynn, F. & Young, Michael,H.
System: The UNT Digital Library
Final Technical Report: Effects of Changing Water and Nitrogen Inputs on a Mojave Desert Ecosystem (open access)

Final Technical Report: Effects of Changing Water and Nitrogen Inputs on a Mojave Desert Ecosystem

Questions addressed under this grant shared the common hypothesis that plant and ecosystem performance will positively respond to the augmentation of the most limiting resources to plant growth in the Mojave Desert, e.g., water and nitrogen. Specific hypothesis include (1) increased summer rainfall will significantly increase plant production thorugh an alleviation of moisture stress in the dry summer months, (2) N-deposition will increase plan production in this N-limited system, particularly in wet years or in concert with added summer rain, and (3) biological crust disturbance will gradually decrease bio-available N, with concomitant long-term reductions in photosynthesis and ANPP. Individual plan and ecosystem responses to global change may be regulated by biogeochemical processes and natural weather variability, and changes in plant and ecosystem processes may occur rapidly, may occur only after a time lag, or may not occur at all. During the first PER grant period, we observed changes in plant and ecosystem processes that would fall under each of these time-response intervals: plant and ecosystem processes responded rapidly to added summer rain, whereas most processes responded slowly or in a lag fashion to N-deposition and with no significant response to crust disturbance. Therefore, the primary objectives of this renewal grant …
Date: November 30, 2007
Creator: Smith, Stanley D. & Nowak, Robert S.
System: The UNT Digital Library
Improved Soybean Oil for Biodiesel Fuel (open access)

Improved Soybean Oil for Biodiesel Fuel

The goal of this program was to generate information on the utility of soybean germplasm that produces oil, high in oleic acid and low in saturated fatty acids, for its use as a biodiesel. Moreover, data was ascertained on the quality of the derived soybean meal (protein component), and the agronomic performance of this novel soybean germplasm. Gathering data on these later two areas is critical, with respect to the first, soybean meal (protein) component is a major driver for commodity soybean, which is utilized as feed supplements in cattle, swine, poultry and more recently aquaculture production. Hence, it is imperative that the resultant modulation in the fatty acid profile of the oil does not compromise the quality of the derived meal, for if it does, the net value of the novel soybean will be drastically reduced. Similarly, if the improved oil trait negative impacts the agronomics (i.e. yield) of the soybean, this in turn will reduce the value of the trait. Over the course of this program oil was extruded from approximately 350 bushels of soybean designated 335-13, which produces oil high in oleic acid (>85%) and low in saturated fatty acid (<6%). As predicted improvement in cold flow …
Date: November 30, 2007
Creator: Clemente, Tom & Gerpen, Jon Van
System: The UNT Digital Library
Industrial Assessment Center Program (open access)

Industrial Assessment Center Program

The work described in this report was performed under the direction of the Industrial Assessment Center (IAC) at University of Texas at Arlington. The IAC at The University of Texas at Arlington is managed by Rutgers University under agreement with the United States Department of Energy Office of Industrial Technology, which financially supports the program. The objective of the IAC is to identify, evaluate, and recommend, through analysis of an industrial plant’s operations, opportunities to conserve energy and prevent pollution, thereby reducing the associated costs. IAC team members visit and survey the plant. Based upon observations made in the plant, preventive/corrective actions are recommended. At all times we try to offer specific and quantitative recommendations of cost savings, energy conservation, and pollution prevention to the plants we serve.
Date: November 30, 2007
Creator: Agonafer, Dr. Dereje
System: The UNT Digital Library
LITERATURE REVIEWS TO SUPPORT ION EXCHANGE TECHNOLOGY SELECTION FOR MODULAR SALT PROCESSING (open access)

LITERATURE REVIEWS TO SUPPORT ION EXCHANGE TECHNOLOGY SELECTION FOR MODULAR SALT PROCESSING

This report summarizes the results of literature reviews conducted to support the selection of a cesium removal technology for application in a small column ion exchange (SCIX) unit supported within a high level waste tank. SCIX is being considered as a technology for the treatment of radioactive salt solutions in order to accelerate closure of waste tanks at the Savannah River Site (SRS) as part of the Modular Salt Processing (MSP) technology development program. Two ion exchange materials, spherical Resorcinol-Formaldehyde (RF) and engineered Crystalline Silicotitanate (CST), are being considered for use within the SCIX unit. Both ion exchange materials have been studied extensively and are known to have high affinities for cesium ions in caustic tank waste supernates. RF is an elutable organic resin and CST is a non-elutable inorganic material. Waste treatment processes developed for the two technologies will differ with regard to solutions processed, secondary waste streams generated, optimum column size, and waste throughput. Pertinent references, anticipated processing sequences for utilization in waste treatment, gaps in the available data, and technical comparisons will be provided for the two ion exchange materials to assist in technology selection for SCIX. The engineered, granular form of CST (UOP IE-911) was the …
Date: November 30, 2007
Creator: King, W
System: The UNT Digital Library
Load Monitoring CEC/LMTF Load Research Program (open access)

Load Monitoring CEC/LMTF Load Research Program

This white paper addresses the needs, options, current practices of load monitoring. Recommendations on load monitoring applications and future directions are also presented.
Date: November 30, 2007
Creator: Huang, Zhenyu; Lesieutre, B.; Yang, Steve; Ellis, A.; Meklin, A.; Wong, B. et al.
System: The UNT Digital Library
Nonlinear System Identification for Damage Detection (open access)

Nonlinear System Identification for Damage Detection

None
Date: November 30, 2007
Creator: Charles R. Farrar, Keith Worden, Michael D. Todd, Gyuhae Park, Jonathon Nichols, Douglas E. Adams, Matthew T. Bement, Kevin Farinholt
System: The UNT Digital Library
Potential impacts of nanotechnology on energy transmission applications and needs. (open access)

Potential impacts of nanotechnology on energy transmission applications and needs.

The application of nanotechnologies to energy transmission has the potential to significantly impact both the deployed transmission technologies and the need for additional development. This could be a factor in assessing environmental impacts of right-of-way (ROW) development and use. For example, some nanotechnology applications may produce materials (e.g., cables) that are much stronger per unit volume than existing materials, enabling reduced footprints for construction and maintenance of electricity transmission lines. Other applications, such as more efficient lighting, lighter-weight materials for vehicle construction, and smaller batteries having greater storage capacities may reduce the need for long-distance transport of energy, and possibly reduce the need for extensive future ROW development and many attendant environmental impacts. This report introduces the field of nanotechnology, describes some of the ways in which processes and products developed with or incorporating nanomaterials differ from traditional processes and products, and identifies some examples of how nanotechnology may be used to reduce potential ROW impacts. Potential environmental, safety, and health impacts are also discussed.
Date: November 30, 2007
Creator: Elcock, D. & Division, Environmental Science
System: The UNT Digital Library
Protable Analyzer Based on Microfluidic/Nanoengineered electrochemical Sensors for in Situ Characterization of Mixed Wastes (open access)

Protable Analyzer Based on Microfluidic/Nanoengineered electrochemical Sensors for in Situ Characterization of Mixed Wastes

This project aimed on the development of compact microchip sensing devices for on-site monitoring of pollutants in contaminated DOE sites. As described in this report, we have made a substantial progress, and introduced effective routes for improving the on-site detection of toxic metals and for interfacing microfluidic (Lab-on-Chip) sensing devices with the real world. This activity has been very productive and has already been described in 12 research papers (published in major international journals). The resulting microchip sensor technology should allow testing for toxic metals and other major pollutants to be performed more rapidly, inexpensively, and reliably in a field setting. These new analytical capabilities resulted from the generous DOE support will facilitate the characterization and remediation of mixed waste contaminated sites.
Date: November 30, 2007
Creator: Joseph Wang, PhD
System: The UNT Digital Library
Release of Methane from Bering Sea Sediments During the Last Glacial Period (open access)

Release of Methane from Bering Sea Sediments During the Last Glacial Period

Several lines of evidence suggest that during times of elevated methane flux the sulfate-methane transition zone (SMTZ) was positioned near the sediment-water interface. We studied two cores (from 700 m and 1457 m water depth) from the Umnak Plateau region. Anomalously low d13C and high d18O in benthic and planktonic foraminifera in these cores are the consequence of diagenetic overgrowths of authigenic carbonates. There are multiple layers of authigenic-carbonate-rich sediment in these cores, and the stable isotope compositions of the carbonates are consistent with those formed during anaerobic oxidation of methane (AOM). The carbonate-rich layers are associated with biomarkers produced by methane-oxidizing archaea, archaeol and glyceryl dibiphytanyl glyceryl tetraether (GDGT). The d13C of the archaeol and certain GDGTs are isotopically depleted. These carbonate- and AOM-biomarker-rich layers were emplaced in the SMTZ during episodes when there was a high flux of methane or methane-rich fluids upward in the sediment column. The sediment methane in the Umnak Plateau region appears to have been very dynamic during the glacial period, and interacted with the ocean-atmosphere system at millennial time scales. The upper-most carbonate-rich layers are in radiocarbon-dated sediment deposited during interstitials 2 and 3, 28-20 ka, and may be associated with the climate …
Date: November 30, 2007
Creator: Cook, Mea & Keigwin, Lloyd
System: The UNT Digital Library