Radiocarbon-Based Ages and Growth Rates of Bamboo Corals from the Gulf of Alaska (open access)

Radiocarbon-Based Ages and Growth Rates of Bamboo Corals from the Gulf of Alaska

Deep-sea coral communities have long been recognized by fisherman as areas that support large populations of commercial fish. As a consequence, many deep-sea coral communities are threatened by bottom trawling. Successful management and conservation of this widespread deep-sea habitat requires knowledge of the age and growth rates of deep-sea corals. These organisms also contain important archives of intermediate and deep-water variability, and are thus of interest in the context of decadal to century-scale climate dynamics. Here, we present {Delta}{sup 14}C data that suggest that bamboo corals from the Gulf of Alaska are long-lived (75-126 years) and that they acquire skeletal carbon from two distinct sources. Independent verification of our growth rate estimates and coral ages is obtained by counting seasonal Sr/Ca cycles and probable lunar cycle growth bands.
Date: December 12, 2004
Creator: Roark, E. B.; Guilderson, T. P.; Flood-Page, S.; Dunbar, R. B.; Ingram, B. L.; Fallon, S. J. et al.
Object Type: Article
System: The UNT Digital Library
Preparation of Biliquid Foam Compositions (open access)

Preparation of Biliquid Foam Compositions

Technology developed by the late Dr. Felix Sebba of the VPI Chemical Engineering Department by which an oil phase can be broken up into small droplets and encapsulated in a continuous water phase led to research on the possible merits of a fuel prepared by this procedure. The resulting mixture is called a polyaphron. Part 1 of this report describes the testing of polyaphronated gasoline in an automobile engine. Nitrogen oxides (NO{sub x}) emissions, total hydrocarbon (HC) emissions, and exhaust temperature were determined for various load and RPM combinations. Difficulties with viscosity and separation of the water phase have prevented complete testing at road load conditions. Rather than continue with engine testing, some bench tests of polyaphrons were performed to see the effect of various filtering processes on fuel stability as well as measuring viscosity and density. These results are reported in Part 2 of this paper. 6 figs., 4 tabs.
Date: December 12, 1990
Creator: Jaasma, D. R.; Osucha, D. C. & Scheuren, J.
Object Type: Report
System: The UNT Digital Library
Transcriptional Response of Desulfovibrio vulgaris Hildenborough to Oxidative Stress Mimicking Environmental Conditions (open access)

Transcriptional Response of Desulfovibrio vulgaris Hildenborough to Oxidative Stress Mimicking Environmental Conditions

Sulphate-reducing bacteria are anaerobes readily found in oxic-anoxic interfaces. Multiple defence pathways against oxidative conditions were identified in these organisms and proposed to be differentially expressed under different concentrations of oxygen, contributing to their ability to survive oxic conditions. In this study, Desulfovibrio vulgaris Hildenborough cells were exposed to the highest concentration of oxygen that sulphate-reducing bacteria are likely to encounter in natural habitats, and the global transcriptomic response was determined. 307 genes were responsive, with cellular roles in energy metabolism, protein fate, cell envelope and regulatory functions, including multiple genes encoding heat shock proteins, peptidases and proteins with heat shock promoters. Of the oxygen reducing mechanisms of D. vulgaris only the periplasmic hydrogen-dependent mechanism is up-regulated, involving the [NiFeSe]hydrogenase, formate dehydrogenase(s) and the Hmc membrane complex. The oxidative defence response concentrates on damage repair by metal-free enzymes. These data, together with the down regulation of the Fur operon, which restricts the availability of iron, and the lack of response of the PerR operon, suggest that a major effect of this oxygen stress is the inactivation and/or degradation of multiple metalloproteins present in D. vulgaris as a consequence of oxidative damage to their metal clusters.
Date: March 12, 2008
Creator: Pereira, Patricia M.; He, Qiang; Xavier, Antonio V.; Zhou, Jizhong; Pereira, Ines A.C. & Louro, Ricardo O.
Object Type: Article
System: The UNT Digital Library
CROSSCUTTING TECHNOLOGY DEVELOPMENT AT THE CENTER FOR ADVANCED SEPARATION TECHNOLOGIES (open access)

CROSSCUTTING TECHNOLOGY DEVELOPMENT AT THE CENTER FOR ADVANCED SEPARATION TECHNOLOGIES

This Technical Progress Report describes progress made on the seventeen subprojects awarded in the first year of Cooperative Agreement DE-FC26-02NT41607: Crosscutting Technology Development at the Center for Advanced Separation Technologies. This work is summarized in the body of the main report: the individual sub-project Technical Progress Reports are attached as Appendices. Due to the time taken up by the solicitation/selection process, these cover the initial 6-month period of project activity only. The U.S. is the largest producer of mining products in the world. In 1999, U.S. mining operations produced $66.7 billion worth of raw materials that contributed a total of $533 billion to the nation's wealth. Despite these contributions, the mining industry has not been well supported with research and development funds as compared to mining industries in other countries. To overcome this problem, the Center for Advanced Separation Technologies (CAST) was established to develop technologies that can be used by the U.S. mining industry to create new products, reduce production costs, and meet environmental regulations. Originally set up by Virginia Tech and West Virginia University, this endeavor has been expanded into a seven-university consortium--Virginia Tech, West Virginia University, University of Kentucky, University of Utah, Montana Tech, New Mexico Tech …
Date: May 12, 2004
Creator: Rimmer, Hugh W.
Object Type: Report
System: The UNT Digital Library
Experiments with the Dragon Machine (open access)

Experiments with the Dragon Machine

The basic characteristics of a self-sustaining chain reaction were demonstrated with the Chicago Pile in 1943, but it was not until early 1945 that sufficient enriched material became available to experimentally verify fast-neutron cross-sections and the kinetic characteristics of a nuclear chain reaction sustained with prompt neutrons alone. However, the demands of wartime and the rapid decline in effort following the cessation of hostilities often resulted in the failure to fully document the experiments or in the loss of documentation as personnel returned to civilian pursuits. When documented, the results were often highly classified. Even when eventually declassified, the data were often not approved for public release until years later.2 Even after declassification and approval for public release, the records are sometimes difficult to find. Through a fortuitous discovery, a set of handwritten notes by ''ORF July 1945'' entitled ''Dragon - Research with a Pulsed Fission Reactor'' was found by William L. Myers in an old storage safe at Pajarito Site of the Los Alamos National Laboratory3. Of course, ORF was identified as Otto R. Frisch. The document was attached to a page in a nondescript spiral bound notebook labeled ''494 Book'' that bore the signatures of Louis Slotin and …
Date: August 12, 2005
Creator: Malenfant, R.E.
Object Type: Report
System: The UNT Digital Library
Engineering Development of Advanced Physical Fine Coal Cleaning Technologies: Froth Flotation (open access)

Engineering Development of Advanced Physical Fine Coal Cleaning Technologies: Froth Flotation

The Department of Energy (DOE) awarded a contract entitled Engineering Development of Advanced Physical Fine Coal Cleaning Technology - Froth Flotation'', to ICF Kaiser Engineers with the following team members, Ohio Coal Development Office, Babcock and Wilcox, Consolidation Coal Company, Eimco Process Equipment Company, Illinois State Geological Survey, Virginia Polytechnic Institute and State University, Process Technology, Inc. This document a quarterly report prepared in accordance with the project reporting requirements covering the period from July 1, 1992 to September 30, 1992. This report provides a summary of the technical work undertaken during this period, highlighting the major results. A brief description of the work done prior to this quarter is provided in this report under the task headings.
Date: February 12, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Engineering Development of Advanced Physical Fine Coal Cleaning Technologies: Froth Flotation (open access)

Engineering Development of Advanced Physical Fine Coal Cleaning Technologies: Froth Flotation

Work completed produced the criteria for additional engineering analysis, computation and detailed experimental benchscale testing for areas of uncertainty. The engineering analysis, computation, bench-scale testing and component development was formulated to produce necessary design information to define a commercially operating system. In order to produce the required information by means of bench-scale testing and component development, a uniform coal sample was procured. After agreement with DOE, a selected sample of coal from those previously listed was secured. The test plan was developed in two parts. The first part listed procedures for engineering and computational analyses of those deficiencies previously identified that could be solved without bench scale testing. Likewise, the second part prepared procedures for bench-scale testing and component development for those deficiencies previously identified in Task 3.
Date: February 12, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Engineering Development of Advanced Physical Fine Coal Cleaning Technologies: Froth Flotation. Quarterly Technical Progress Report No. 15, April 1, 1992--June 30, 1992 (open access)

Engineering Development of Advanced Physical Fine Coal Cleaning Technologies: Froth Flotation. Quarterly Technical Progress Report No. 15, April 1, 1992--June 30, 1992

The Department of Energy (DOE) awarded a contract entitled ``Engineering Development of Advanced Physical Fine Coal Cleaning Technology - Froth Flotation``, to ICF Kaiser Engineers with the following team members, Ohio Coal Development Office, Babcock and Wilcox, Consolidation Coal Company, Eimco Process Equipment Company, Illinois State Geological Survey, Virginia Polytechnic Institute and State University, Process Technology, Inc. This document a quarterly report prepared in accordance with the project reporting requirements covering the period from July 1, 1992 to September 30, 1992. This report provides a summary of the technical work undertaken during this period, highlighting the major results. A brief description of the work done prior to this quarter is provided in this report under the task headings.
Date: February 12, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Engineering Development of Advanced Physical Fine Coal Cleaning Technologies: Froth Flotation. Quarterly Technical Progress Report No. 13, October 1, 1991--December 31, 1991 (open access)

Engineering Development of Advanced Physical Fine Coal Cleaning Technologies: Froth Flotation. Quarterly Technical Progress Report No. 13, October 1, 1991--December 31, 1991

Work completed produced the criteria for additional engineering analysis, computation and detailed experimental benchscale testing for areas of uncertainty. The engineering analysis, computation, bench-scale testing and component development was formulated to produce necessary design information to define a commercially operating system. In order to produce the required information by means of bench-scale testing and component development, a uniform coal sample was procured. After agreement with DOE, a selected sample of coal from those previously listed was secured. The test plan was developed in two parts. The first part listed procedures for engineering and computational analyses of those deficiencies previously identified that could be solved without bench scale testing. Likewise, the second part prepared procedures for bench-scale testing and component development for those deficiencies previously identified in Task 3.
Date: February 12, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Study of Multi-Scale Cloud Processes Over the Tropical Western Pacific Using Cloud-Resolving Models Constrained by Satellite Data (open access)

Study of Multi-Scale Cloud Processes Over the Tropical Western Pacific Using Cloud-Resolving Models Constrained by Satellite Data

Clouds in the tropical western Pacific are an integral part of the large scale environment. An improved understanding of the multi-scale structure of clouds and their interactions with the environment is critical to the ARM (Atmospheric Radiation Measurement) program for developing and evaluating cloud parameterizations, understanding the consequences of model biases, and providing a context for interpreting the observational data collected over the ARM Tropical Western Pacific (TWP) sites. Three-dimensional cloud resolving models (CRMs) are powerful tools for developing and evaluating cloud parameterizations. However, a significant challenge in using CRMs in the TWP is that the region lacks conventional data, so large uncertainty exists in defining the large-scale environment for clouds. This project links several aspects of the ARM program, from measurements to providing improved analyses, and from cloud-resolving modeling to climate-scale modeling and parameterization development, with the overall objective to improve the representations of clouds in climate models and to simulate and quantify resolved cloud effects on the large-scale environment. Our objectives will be achieved through a series of tasks focusing on the use of the Weather Research and Forecasting (WRF) model and ARM data. Our approach includes: -- Perform assimilation of COSMIC GPS radio occultation and other satellites …
Date: March 12, 2013
Creator: Dudhia, Jimy
Object Type: Report
System: The UNT Digital Library
Hanford site transuranic waste certification plan (open access)

Hanford site transuranic waste certification plan

As a generator of transuranic (TRU) and TRU mixed waste destined for disposal at the Waste Isolation Pilot Plant (WIPP), the Hanford Site must ensure that its TRU waste meets the requirements of U.S. Department of Energy (DOE) Order 5820.2A, ''Radioactive Waste Management, and the Waste Acceptance Criteria for the Waste Isolation Pilot Plant' (DOE 1996d) (WIPP WAC). The WIPP WAC establishes the specific physical, chemical, radiological, and packaging criteria for acceptance of defense TRU waste shipments at WIPP. The WIPP WAC also requires that participating DOE TRU waste generator/treatment/storage sites produce site-specific documents, including a certification plan, that describe their management of TRU waste and TRU waste shipments before transferring waste to WIPP. The Hanford Site must also ensure that its TRU waste destined for disposal at WIPP meets requirements for transport in the Transuranic Package Transporter41 (TRUPACT-11). The U.S. Nuclear Regulatory Commission (NRC) establishes the TRUPACT-I1 requirements in the ''Safety Analysis Report for the TRUPACT-II Shipping Package'' (NRC 1997) (TRUPACT-I1 SARP).
Date: May 12, 1999
Creator: Greager, T. M.
Object Type: Report
System: The UNT Digital Library
Development of an automated guided vehicle system for large scale materials handling of optics in the National Ignition Facility (open access)

Development of an automated guided vehicle system for large scale materials handling of optics in the National Ignition Facility

None
Date: February 12, 1999
Creator: McMahon, D H; Tiszauer, D & Yakuma, S
Object Type: Article
System: The UNT Digital Library
Corrective Action Investigation Plan for Corrective Action Unit 143: Area 25 Contaminated Waste Dumps, Nevada Test Site, Nevada (open access)

Corrective Action Investigation Plan for Corrective Action Unit 143: Area 25 Contaminated Waste Dumps, Nevada Test Site, Nevada

None
Date: July 12, 1999
Creator: /NV, USDOE
Object Type: Report
System: The UNT Digital Library
Waste Isolation Pilot Plant Environmental Monitoring Plan (open access)

Waste Isolation Pilot Plant Environmental Monitoring Plan

U.S. Department of Energy (DOE) Order 450.1, Environmental Protection Program, requires each DOE site to conduct environmental monitoring. Environmental monitoring at the Waste Isolation Pilot Plant (WIPP) is conducted in order to: (a) Verify and support compliance with applicable federal, state, and local environmental laws, regulations, permits, and orders; (b) Establish baselines and characterize trends in the physical, chemical, and biological condition of effluent and environmental media; (c) Identify potential environmental problems and evaluate the need for remedial actions or measures to mitigate the problems; (d) Detect, characterize, and report unplanned releases; (e) Evaluate the effectiveness of effluent treatment and control, and pollution abatement programs; and (f) Determine compliance with commitments made in environmental impact statements, environmental assessments, safety analysis reports, or other official DOE documents. This Environmental Monitoring Plan (EMP) explains the rationale and design criteria for the environmental monitoring program, extent and frequency of monitoring and measurements, procedures for laboratory analyses, quality assurance (QA) requirements, program implementation procedures, and direction for the preparation and disposition of reports. Changes to the environmental monitoring program may be necessary to allow the use of advanced technology and new data collection techniques. This EMP will document changes in the environmental monitoring program. …
Date: March 12, 2008
Creator: Washington Regulatory and Environmental Services
Object Type: Report
System: The UNT Digital Library
Final Technical Report: Hydrogen Codes and Standards Outreach (open access)

Final Technical Report: Hydrogen Codes and Standards Outreach

This project contributed significantly to the development of new codes and standards, both domestically and internationally. The NHA collaborated with codes and standards development organizations to identify technical areas of expertise that would be required to produce the codes and standards that industry and DOE felt were required to facilitate commercialization of hydrogen and fuel cell technologies and infrastructure. NHA staff participated directly in technical committees and working groups where issues could be discussed with the appropriate industry groups. In other cases, the NHA recommended specific industry experts to serve on technical committees and working groups where the need for this specific industry expertise would be on-going, and where this approach was likely to contribute to timely completion of the effort. The project also facilitated dialog between codes and standards development organizations, hydrogen and fuel cell experts, the government and national labs, researchers, code officials, industry associations, as well as the public regarding the timeframes for needed codes and standards, industry consensus on technical issues, procedures for implementing changes, and general principles of hydrogen safety. The project facilitated hands-on learning, as participants in several NHA workshops and technical meetings were able to experience hydrogen vehicles, witness hydrogen refueling demonstrations, see …
Date: May 12, 2007
Creator: Hall, Karen I.
Object Type: Report
System: The UNT Digital Library
Wavelet/scalar quantization compression standard for fingerprint images (open access)

Wavelet/scalar quantization compression standard for fingerprint images

US Federal Bureau of Investigation (FBI) has recently formulated a national standard for digitization and compression of gray-scale fingerprint images. Fingerprints are scanned at a spatial resolution of 500 dots per inch, with 8 bits of gray-scale resolution. The compression algorithm for the resulting digital images is based on adaptive uniform scalar quantization of a discrete wavelet transform subband decomposition (wavelet/scalar quantization method). The FBI standard produces archival-quality images at compression ratios of around 15 to 1 and will allow the current database of paper fingerprint cards to be replaced by digital imagery. The compression standard specifies a class of potential encoders and a universal decoder with sufficient generality to reconstruct compressed images produced by any compliant encoder, allowing flexibility for future improvements in encoder technology. A compliance testing program is also being implemented to ensure high standards of image quality and interchangeability of data between different implementations.
Date: June 12, 1996
Creator: Brislawn, C.M.
Object Type: Article
System: The UNT Digital Library
Overview of MFTF supervisory control and diagnostics system software (open access)

Overview of MFTF supervisory control and diagnostics system software

The Mirror Fusion Test Facility (MFTF) at the Lawrence Livermore Laboratory (LLL) is currently the largest mirror fusion research project in the world. Its Control and Diagnostics System is handled by a distributed computer network consisting of nine Interdata minicomputer systems and about 65 microprocessors. One of the design requirements is tolerance of single-point failure. If one of the computer systems becomes inoperative, the experiment can still be carried out, although the system responsiveness to operator command may be degraded. In a normal experiment cycle, the researcher can examine the result of the previous experiment, change any control parameter, fire a shot, collect four million bytes of diagnostics data, perform intershot analysis, and have the result presented - all within five minutes. The software approach adopted for the Supervisory Control and Diagnostics System features chief programmer teams and structured programming. Pascal is the standard programming language in this project.
Date: November 12, 1979
Creator: Ng, W.C.
Object Type: Article
System: The UNT Digital Library
The Holdup Measurement System II (HMSII) (open access)

The Holdup Measurement System II (HMSII)

A project is in progress that addresses two of the problems with existing holdup measurement technology: the need for compact instrumentation and a more efficient means of reducing the massive amounts of data to quantities of Special Nuclear Materials (SNM). The approach taken by the project utilizes the Miniature Modular MultiChannel Analyzer (M{sup 3}CA), a complete and truly portable gamma-ray spectroscopy system, under development at Los Alamos National Laboratory. The hardware is then integrated and automated by the Holdup Measurement System II (HMSII) software being developed by the Oak Ridge Y-12 Plant. Together they provide the hardware components, measurement control in the field, automated data acquisition, data storage and manipulation which simplify holdup measurements.
Date: July 12, 1993
Creator: Smith, S. E.; Gibson, J. S.; Halbig, J. K.; Klosterbuer, S. F.; Russo, P. A. & Sprinkle, J. K. Jr.
Object Type: Article
System: The UNT Digital Library
Ionizing Radiation-Induced DNA Damage and Its Repair in Human Cells (open access)

Ionizing Radiation-Induced DNA Damage and Its Repair in Human Cells

DNA damage in mammalian chromatin in vitro and in cultured mammalian cells including human cells was studied. In the first phase of these studies, a cell culture laboratory was established. Necessary equipment including an incubator, a sterile laminar flow hood and several centrifuges was purchased. We have successfully grown several cell lines such as murine hybridoma cells, V79 cells and human K562 leukemia cells. This was followed by the establishment of a methodology for the isolation of chromatin from cells. This was a very important step, because a routine and successful isolation of chromatin was a prerequisite for the success of the further studies in this project, the aim of which was the measurement of DNA darnage in mammalian chromatin in vitro and in cultured cells. Chromatin isolation was accomplished using a slightly modified procedure of the one described by Mee & Adelstein (1981). For identification and quantitation of DNA damage in cells, analysis of chromatin was preferred over the analysis of "naked DNA" for the following reasons: i. DNA may not be extracted efficiently from nucleoprotein in exposed cells, due to formation of DNA-protein cross-links, ii. the extractability of DNA is well known to decrease with increasing doses of …
Date: May 12, 1999
Creator: Dizdaroglu, Miral
Object Type: Report
System: The UNT Digital Library
Empowering Minority Communities with Health Information - ASU (open access)

Empowering Minority Communities with Health Information - ASU

Training Manual updated for United Negro College Fund Special Programs Corporation/National Library of Medicine - HBCU ACCESS Project for Alcorn State University, Natchez, Mississippi, November 12, 2010
Date: November 12, 2010
Creator: McMurray, L. and W. Templin-Branner
Object Type: Book
System: The UNT Digital Library
Evolution of Long-Term Stewardship at Hanford - 14189 (open access)

Evolution of Long-Term Stewardship at Hanford - 14189

Hanford�s Long-Term Stewardship (LTS) Program has evolved from a small, informal process, with minimal support, to a robust program that provides comprehensive transitions from cleanup contractors to long-term stewardship for post-cleanup requirements specified in the associated cleanup decision documents. The LTS Program has the responsibility for almost 100,000 acres of land, along with over 200 waste sites and will soon have six cocooned reactors. Close to 2,600 documents have been identified and tagged for storage in the LTS document library. The program has successfully completed six consecutive transitions over the last two years in support of the U.S. DOE Richland Operations Office�s (DOE-RL) near-term cleanup objectives of significantly reducing the footprint of active cleanup operations for the River Corridor. The program has evolved from one that was initially responsible for defining and measuring Institutional Controls for the Hanford Site, to a comprehensive, post remediation surveillance and maintenance program that begins early in the transition process. In 2013, the first reactor area―the cocooned 105-F Reactor and its surrounding 1,100 acres, called the F Area was transitioned. In another �first,� the program is expected to transition the five remaining cocooned reactors into the program through using a Transition and Turnover Package (TTP). …
Date: November 12, 2013
Creator: Moren, Richard J. & Grindstaff, Keith D.
Object Type: Article
System: The UNT Digital Library
Borehole Data Package for Four CY 2003 RCRA Wells 299-E27-4, 299-E27-21, 299-E27-22, and 299-E27-23 at Single-Shell Tank, Waste Management Area C, Hanford Site, Washington (open access)

Borehole Data Package for Four CY 2003 RCRA Wells 299-E27-4, 299-E27-21, 299-E27-22, and 299-E27-23 at Single-Shell Tank, Waste Management Area C, Hanford Site, Washington

Four new Resource Conservation and Recovery Act (RCRA) groundwater monitoring wells were installed at the single-shell tank farm Waste Management Area (WMA) C in fiscal year 2003 to fulfill commitments for well installations proposed in the draft Hanford Federal Facility Agreement and Consent Order milestone M-24-00. Well 299-E27-22, installed upgradient, was drilled through the entire uppermost unconfined aquifer to the basalt and wells 299-E27-4, 299-E27-21 and 299-E27-23 were drilled approximately 40 feet into the uppermost unconfined aquifer and installed downgradient of the WMA. Specific objectives for these wells include monitoring the impact, if any, that potential releases from inside the WMA may have on current groundwater conditions (i.e., improved network coverage) and differentiating upgradient groundwater contamination from contaminants released at the WMA. This report supplies the information obtained during drilling, characterization, and installation of the four new groundwater monitoring wells. This document also provides a compilation of hydrogeologic and well construction information obtained during drilling, well development, aquifer testing, and sample collection/analysis activities.
Date: May 12, 2004
Creator: Williams, Bruce A. & Narbutovskih, Susan M.
Object Type: Report
System: The UNT Digital Library
Condensed draft action description memorandum for the decontamination and decommissioning of Battelle Columbus facilities (open access)

Condensed draft action description memorandum for the decontamination and decommissioning of Battelle Columbus facilities

Under provisions of the Surplus Facilities Management Program (SFMP), the US Department of Energy, Chicago Operations Office, proposes to provide funding for Surveillance and Maintenance (S & M) and subsequent Decontamination and Decommissioning (D & D) of fifteen facilities and associated premises belonging to Battelle Columbus Division. The fifteen facilities are contaminated as a result of nuclear research and development activities conducted over a period of approximately 43 years for DOE and its predecessor agencies--the Energy Research and Development Administration (ERDA), the Atomic Energy Commission (AEC) and the Manhattan Engineer District (MED). The proposed action includes continuation of ongoing S & M as well as a D & D of the facilities. The S & M activities include a continued environmental monitoring program to maintain assurance that radioactive contamination has not escaped to the surrounding environment; regularly scheduled inspection and maintenance of health, safety, and radiation protection equipment and instrumentation; a program of health physics surveillance monitoring, personnel dosimetry, and equipment and instrumentation maintenance and calibration; and emergency planning, training, and drills. The so- called dismantlement D & D mode is the proposed alternative for D & D of these facilities. For the facilities in question this will generally involve …
Date: July 12, 1988
Creator: unknown
Object Type: Report
System: The UNT Digital Library
The Redshift Dependence of Gamma-Ray Absorption in the Environments of Strong-Line AGNs (open access)

The Redshift Dependence of Gamma-Ray Absorption in the Environments of Strong-Line AGNs

The case of {gamma}-ray absorption due to photon-photon pair production of jet photons in the external photon environments, such as the accretion disk and the broad-line region radiation fields, of {gamma}-ray--loud active galactic nuclei (AGNs) that exhibit strong emission lines is considered. I demonstrate that this 'local opacity,' if detected, will almost unavoidably be redshift-dependent in the sub-TeV range. This introduces nonnegligible biases and complicates approaches for studying the evolution of the extragalactic background light with contemporary GeV instruments such as the Gamma-Ray Large Area Space Telescope (GLAST ), where the {gamma}-ray horizon is probed by means of statistical analysis of absorption features (e.g., the Fazio-Stecker relation) in AGN spectra at various redshifts. It particularly applies to strong-line quasars, where external photon fields are potentially involved in {gamma}-ray production.
Date: November 12, 2007
Creator: Reimer, A. & /Stanford U., HEPL /KIPAC, Menlo Park
Object Type: Article
System: The UNT Digital Library