SMALL-SCALE IMPACT SENSITIVITY TESTING ON EDC37 (open access)

SMALL-SCALE IMPACT SENSITIVITY TESTING ON EDC37

EDC37 was tested at LLNL to determine its impact sensitivity in the LLNL's drop hammer system. The results showed that impact sensitivities of the samples were between 86 cm and 156 cm, depending on test methods. EDC37 is a plastic bonded explosive consisting of 90% HMX, 1% nitrocellulose and binder. We recently conducted impact sensitivity testing in our drop hammer system and the results are presented in this report.
Date: April 28, 2008
Creator: HSU, P C; HUST, G & MAIENSCHEIN, J L
Object Type: Report
System: The UNT Digital Library
Flat Field Anomalies in an X-ray CCD Camera Measured Using a Manson X-ray Source (HTPD 08 paper) (open access)

Flat Field Anomalies in an X-ray CCD Camera Measured Using a Manson X-ray Source (HTPD 08 paper)

The Static X-ray Imager (SXI) is a diagnostic used at the National Ignition Facility (NIF) to measure the position of the X-rays produced by lasers hitting a gold foil target. The intensity distribution taken by the SXI camera during a NIF shot is used to determine how accurately NIF can aim laser beams. This is critical to proper NIF operation. Imagers are located at the top and the bottom of the NIF target chamber. The CCD chip is an X-ray sensitive silicon sensor, with a large format array (2k x 2k), 24 {micro}m square pixels, and 15 {micro}m thick. A multi-anode Manson X-ray source, operating up to 10kV and 10W, was used to characterize and calibrate the imagers. The output beam is heavily filtered to narrow the spectral beam width, giving a typical resolution E/{Delta}E {approx} 10. The X-ray beam intensity was measured using an absolute photodiode that has accuracy better than 1% up to the Si K edge and better than 5% at higher energies. The X-ray beam provides full CCD illumination and is flat, within {+-}1% maximum to minimum. The spectral efficiency was measured at 10 energy bands ranging from 930 eV to 8470 eV. We observed an …
Date: April 28, 2008
Creator: Haugh, M & Schneider, M B
Object Type: Article
System: The UNT Digital Library
Enhanced Functionality for Materials Analysis in the DTEM (open access)

Enhanced Functionality for Materials Analysis in the DTEM

The recent explosion in the use of pump–probe studies on the picosecond timescale to investigate structural and electronic phase transitions and the dynamics of chemical reactions has been based largely on laser–induced reactions coupled with laser interrogation techniques, or on laser induced reactions coupled with synchrotron radiation interrogation techniques. Much less attention has been given to approaches based on laser–induced (or electron–beam–induced) reactions coupled with electron interrogation methods, despite the fact that electron sources are brighter, and their interactions with matter stronger (thereby giving higher signal levels). The use of electrons as probes has great potential to study complex transient events not only because of the possible high temporal resolution using ultrafast electron diffraction (UED) but also the potential for high spatial resolution using dynamic transmission electron microscopy (DTEM). Taking this potential of electron interrogation methods and turning it into a routine nanoscale characterization technique requires several key aspects of the instrumentation used for electron microscopy/diffraction to be optimized. In this proposal, several approaches to instrument optimization for DTEM and UED (to be performed in the same instrument) will be addressed. The new instrumentation developments will be used to study the dynamics of strongly driven materials, aging and corrosion in …
Date: April 28, 2008
Creator: Browning, Nigel D.
Object Type: Report
System: The UNT Digital Library
CO2 Capture by Absorption with Potassium Carbonate (open access)

CO2 Capture by Absorption with Potassium Carbonate

The objective of this work is to improve the process for CO{sub 2} capture by alkanolamine absorption/stripping by developing an alternative solvent, aqueous K{sub 2}CO{sub 3} promoted by piperazine. The final campaign of the pilot plant was completed in February 2006 with 5m K{sup +}/2.5m PZ and 6.4m K{sup +}/1.6m PZ using Flexipac AQ Style 20. The new cross-exchanger reduced the approach temperature to less than 9 C. Stripper modeling has demonstrated that a configuration with a ''Flashing Feed'' requires 6% less work that a simple stripper. The oxidative degradation of piperazine proceeds more slowly than that of monoethanolamine and produces ethylenediamine and other products. Uninhibited 5 m KHCO{sub 3}/2.5 m PZ corrodes 5 to 6 times faster that 30% MEA with 0.2 mol CO{sub 2}/mol MEA.
Date: April 28, 2006
Creator: Rochelle, Gary T.; Chen, Eric; Oyenekan, Babatunde; Sexton, Andrew & Veawab, Amorvadee
Object Type: Report
System: The UNT Digital Library
Revised Master Plan for the Hood River Production Program, Technical Report 2008. (open access)

Revised Master Plan for the Hood River Production Program, Technical Report 2008.

The Hood River Production Program (HRPP) is a Bonneville Power Administration (BPA) funded program initiated as a mitigation measure for Columbia River hydrosystem effects on anadromous fish. The HRPP began in the early 1990s with the release of spring Chinook and winter steelhead smolts into the basin. Prior to implementation, co-managers, including the Confederated Tribes of the Warm Springs Reservation and the Oregon Department of Fish and Wildlife drafted the Hood River Production Master Plan (O'Toole and ODFW 1991a; O'Toole and ODFW 1991b) and the Pelton Ladder Master Plan (Smith and CTWSR 1991). Both documents were completed in 1991 and subsequently approved by the Council in 1992 and authorized through a BPA-led Environmental Impact Statement in 1996. In 2003, a 10-year programmatic review was conducted for BPA-funded programs in the Hood River (Underwood et al. 2003). The primary objective of the HRPP Review (Review) was to determine if program goals were being met, and if modifications to program activities would be necessary in order to meet or revise program goals. In 2003, an agreement was signed between PacifiCorp and resource managers to remove the Powerdale Dam (RM 10) and associated adult trapping facility by 2010. The HRPP program has been …
Date: April 28, 2008
Creator: Wildlife, Oregon Department of Fish and & Reservation, Confederated Tribes of the Warm Springs
Object Type: Report
System: The UNT Digital Library
Request for Naval Reactors Comment on Proposed Prometheus Space Flight Nuclear Reactor High Tier Reactor Safety Requirements and for Naval Reactors Approval to Transmit These Requirements to JPL (open access)

Request for Naval Reactors Comment on Proposed Prometheus Space Flight Nuclear Reactor High Tier Reactor Safety Requirements and for Naval Reactors Approval to Transmit These Requirements to JPL

The purpose of this letter is to request Naval Reactors comments on the nuclear reactor high tier requirements for the PROMETHEUS space flight reactor design, pre-launch operations, launch, ascent, operation, and disposal, and to request Naval Reactors approval to transmit these requirements to Jet Propulsion Laboratory to ensure consistency between the reactor safety requirements and the spacecraft safety requirements. The proposed PROMETHEUS nuclear reactor high tier safety requirements are consistent with the long standing safety culture of the Naval Reactors Program and its commitment to protecting the health and safety of the public and the environment. In addition, the philosophy on which these requirements are based is consistent with the Nuclear Safety Policy Working Group recommendations on space nuclear propulsion safety (Reference 1), DOE Nuclear Safety Criteria and Specifications for Space Nuclear Reactors (Reference 2), the Nuclear Space Power Safety and Facility Guidelines Study of the Applied Physics Laboratory.
Date: April 28, 2005
Creator: Kokkinos, D.
Object Type: Report
System: The UNT Digital Library
WASHING AND DEMONSTRATION OF THE DWPF FLOWSHEET IN THE SRNL SHIELDED CELLS USING POST ALUMINUM DISSOLUTION TANK 51 SLUDGE SLURRY (open access)

WASHING AND DEMONSTRATION OF THE DWPF FLOWSHEET IN THE SRNL SHIELDED CELLS USING POST ALUMINUM DISSOLUTION TANK 51 SLUDGE SLURRY

The remaining contents of Tank 51 from Sludge Batch 4 will be blended with Purex sludge from Tank 7 to constitute Sludge Batch 5 (SB5). The Savannah River Site (SRS) Liquid Waste Organization (LWO) has completed caustic addition to Tank 51 to perform low temperature Al dissolution on the H-Modified (HM) sludge material to reduce the total mass of sludge solids and Al being fed to the Defense Waste Processing Facility (DWPF). The Savannah River National Lab (SRNL) has also completed aluminum dissolution tests using a 3-L sample of Tank 51 sludge slurry through funding by DOE EM-21. This report documents assessment of downstream impacts of the aluminum dissolved sludge, which were investigated so technical issues could be identified before the start of SB5 processing. This assessment included washing the aluminum dissolved sludge to a Tank Farm projected sodium concentration and weight percent insoluble solids content and DWPF Chemical Process Cell (CPC) processing using the washed sludge. Based on the limited testing, the impact of aluminum dissolution on sludge settling is not clear. Settling was not predictable for the 3-L sample. Compared to the post aluminum dissolution sample, settling after the first wash was slower, but settling after the second …
Date: April 28, 2008
Creator: Pareizs, J; Cj Bannochie, C; Damon Click, D; Erich Hansen, E; Dan Lambert, D & Michael Stone, M
Object Type: Report
System: The UNT Digital Library
The Hyperion Project: Partnership for an Advaned Technology Cluster Testbed (open access)

The Hyperion Project: Partnership for an Advaned Technology Cluster Testbed

The Hyperion project offers a unique opportunity to participate in a community-driven testing and development resource at a scale beyond what can be accomplished by one entity alone. Hyperion is a new strategic technology partnership intended to support the member-driven development and testing at scale. This partnership will allow commodity clusters to scale up to meet the growing demands of customers multi-core petascale simulation environments. Hyperion will tightly couple together the outstanding research and development capabilities of Lawrence Livermore National Laboratory with leading technology companies, including Cisco, Data Direct Networks, Dell, Intel, LSI, Mellanox, Qlogic, RedHat, SuperMicro and Sun. The end goal of this project is to revolutionize cluster computing in fundamental ways by providing the critical software and hardware components for a highly scalable simulation environment. This environment will include support for high performance networking, parallel file systems, operating system, and cluster management. This goal will be achieved by building a scalable technology cluster testbed that will be fully dedicated to the partners and provide: (1) A scalable development testing and benchmarking environment for critical enabling Linux cluster technologies; (2) An evaluation testbed for new hardware and software technologies; and (3) A vehicle for forming long term collaborations.
Date: April 28, 2008
Creator: Seager, M & Leininger, M
Object Type: Report
System: The UNT Digital Library
Cleanup Summary Report for the Defense Threat Reduction Agency Fiscal Year 2007, Task 6.7, U12u-Tunnel (Legacy Site), Nevada Test Site, Nevada (open access)

Cleanup Summary Report for the Defense Threat Reduction Agency Fiscal Year 2007, Task 6.7, U12u-Tunnel (Legacy Site), Nevada Test Site, Nevada

This letter serves as notice of completion for cleanup of the U12u-Tunnel (Legacy Site) as specified in the Defense Threat Reduction Agency (DTRA) Fiscal Year 2007 Statement of Work, Task 6.7. The U12u-Tunnel Legacy Site is located near the intersection of the U12u-Tunnel access road and the U12n-Tunnel access road in Area 12 of the Nevada Test Site (see Figure 1). The site encompasses 1.2 acres and was used to store miscellaneous mining equipment and materials that were used to support DTRA testing in Area 12. Field activities commenced February 11, 2008, and were completed February 20, 2008. Radiological surveys were performed on a drill jumbo and all material stored at the site. The drill jumbo was relocated to U12p-Tunnel portal and consolidated with other critical mining equipment for future use or storage. Ten truck loads of solid waste (53 tons) were shipped to the Nevada Test Site, Area 9 U10c Sanitary Landfill for disposal. No hazardous or radiological waste was generated at this site.
Date: April 28, 2008
Creator: National Security Technologies, LLC
Object Type: Report
System: The UNT Digital Library
Asphalt Roofing Shingles Into Energy Project Summary Report (open access)

Asphalt Roofing Shingles Into Energy Project Summary Report

Based on a widely cited September, 1999 report by the Vermont Agency of Natural Resources, nearly 11 million tons of asphalt roofing shingle wastes are produced in the United States each year. Recent data suggests that the total is made up of about 9.4 million tons from roofing tear-offs and about 1.6 million tons from manufacturing scrap. Developing beneficial uses for these materials would conserve natural resources, promote protection of the environment and strengthen the economy. This project explored the feasibility of using chipped asphalt shingle materials in cement manufacturing kilns and circulating fluidized bed (CFB) boilers. A method of enhancing the value of chipped shingle materials for use as fuel by removing certain fractions for use as substitute raw materials for the manufacture of new shingles was also explored. Procedures were developed to prevent asbestos containing materials from being processed at the chipping facilities, and the frequency of the occurrence of asbestos in residential roofing tear-off materials was evaluated. The economic feasibility of each potential use was evaluated based on experience gained during the project and on a review of the well established use of shingle materials in hot mix asphalt. This project demonstrated that chipped asphalt shingle materials …
Date: April 28, 2008
Creator: Jameson, Rex, PE
Object Type: Report
System: The UNT Digital Library
NIF HEPW 2D Radiography Option Survey (open access)

NIF HEPW 2D Radiography Option Survey

None
Date: April 28, 2004
Creator: Koch, J
Object Type: Report
System: The UNT Digital Library
Thick Liquid-Walled Spheromak Magnetic Fusion Power Plant (open access)

Thick Liquid-Walled Spheromak Magnetic Fusion Power Plant

We assume a spheromak configuration can be made and sustained by a steady plasma gun current, which injects particles, current and magnetic field, i.e., helicity injection. The magnetic configuration is evaluated with an axisymmetric free-boundary equilibrium code, where the current profile is tailored to support an average beta of 10%. An injection current of 100 kA (125 MW of gun power) sustains the toroidal current of 40 MA. The flux linking the gun is 1/1000th of the flux in the spheromak. The geometry allows a flow of liquid, either molten salt (flibe-Li{sub 2}BeF{sub 4} or flinabe-LiNaBeF{sub 4}) or liquid metal, such as SnLi, which protects most of the walls and structures from neutron damage. The free surface between the liquid and the burning plasma is heated by bremsstrahlung and optical radiation and neutrons from the plasma. The temperature of the free surface of the liquid is calculated and then the evaporation rate is estimated. The impurity concentration in the burning plasma is estimated and limited to a 20% reduction in the fusion power ({approx}0.8% fluorine impurity). The divertor power density of 620 MW/m{sup 2} is handled by high-speed (100 m/s) liquid jets. Calculations show that the tritium breeding is adequate …
Date: April 28, 2003
Creator: Moir, R W; Bulmer, R H; Fowler, T K; Rognlien, T D & Youssef, M Z
Object Type: Report
System: The UNT Digital Library
MANHATTAN PROJECT B REACTOR HANFORD WASHINGTON [HANFORD'S HISTORIC B REACTOR (12-PAGE BOOKLET)] (open access)

MANHATTAN PROJECT B REACTOR HANFORD WASHINGTON [HANFORD'S HISTORIC B REACTOR (12-PAGE BOOKLET)]

The Hanford Site began as part of the United States Manhattan Project to research, test and build atomic weapons during World War II. The original 670-square mile Hanford Site, then known as the Hanford Engineer Works, was the last of three top-secret sites constructed in order to produce enriched uranium and plutonium for the world's first nuclear weapons. B Reactor, located about 45 miles northwest of Richland, Washington, is the world's first full-scale nuclear reactor. Not only was B Reactor a first-of-a-kind engineering structure, it was built and fully functional in just 11 months. Eventually, the shoreline of the Columbia River in southeastern Washington State held nine nuclear reactors at the height of Hanford's nuclear defense production during the Cold War era. The B Reactor was shut down in 1968. During the 1980's, the U.S. Department of Energy began removing B Reactor's support facilities. The reactor building, the river pumphouse and the reactor stack are the only facilities that remain. Today, the U.S. Department of Energy (DOE) Richland Operations Office offers escorted public access to B Reactor along a designated tour route. The National Park Service (NPS) is studying preservation and interpretation options for sites associated with the Manhattan Project. …
Date: April 28, 2009
Creator: MS, GERBER
Object Type: Book
System: The UNT Digital Library
Probing the Planck Scale with Proton Decay (open access)

Probing the Planck Scale with Proton Decay

We advocate the idea that proton decay may probe physics at the Planck scale instead of the GUT scale. This is possible because supersymmetric theories have dimension-5 operators that can induce proton decay at dangerous rates, even with R-parity conservation. These operators are expected to be suppressed by the same physics that explains the fermion masses and mixings. We present a thorough analysis of nucleon partial lifetimes in models with a string-inspired anomalous U(1)_X family symmetry which is responsible for the fermionic mass spectrum as well as forbidding R-parity violating interactions. Protons and neutrons can decay via R-parity conserving non-renormalizable superpotential terms that are suppressed by the Planck scale and powers of the Cabibbo angle. Many of the models naturally lead to nucleon decay near present limits without any reference to grand unification.
Date: April 28, 2004
Creator: Harnik, Roni; Larson, Daniel T.; Murayama, Hitoshi & Thormeier, Marc
Object Type: Article
System: The UNT Digital Library
Designing Neutralized Drift Compression for Focusing of Intense Ion Beam Pulses in a Background Plasma (open access)

Designing Neutralized Drift Compression for Focusing of Intense Ion Beam Pulses in a Background Plasma

Neutralized drift compression offers an effective method for particle beam focusing and current amplification. In neutralized drift compression, a linear radial and longitudinal velocity drift is applied to a beam pulse, so that the beam pulse compresses as it drifts in the drift-compression section. The beam intensity can increase more than a factor of 100 in both the radial and longitudinal directions, resulting in more than 10,000 times increase in the beam number density during this process. The self-electric and self-magnetic fields can prevent tight ballistic focusing and have to be neutralized by supplying neutralizing electrons. This paper presents a survey of the present theoretical understanding of the drift compression process and plasma neutralization of intense particle beams. The optimal configuration of focusing and neutralizing elements is discussed in this paper.
Date: April 28, 2009
Creator: Kaganovich, I. D.; Davidson, R. C.; Dorf, M.; Startsev, E. A.; Barnard, J. J.; Friedman, A. et al.
Object Type: Article
System: The UNT Digital Library
Ultrasonic Examination of Double-Shell Tank 241-AP-107 Examination Completed February 2008. (open access)

Ultrasonic Examination of Double-Shell Tank 241-AP-107 Examination Completed February 2008.

AREVA NC Inc. (AREVA), under a contract from CH2M Hill Hanford Group (CH2M Hill), has performed an ultrasonic examination of selected portions of Double-Shell Tank 241-AP-107. PNNL is responsible for preparing a report(s) that describes the results of the AREVA ultrasonic examinations.
Date: April 28, 2008
Creator: Pardini, Allan F.; Weier, Dennis R. & Anderson, Kevin K.
Object Type: Report
System: The UNT Digital Library
ALTERNATE APPROACH TO HAZARD CATEGORIZATION FOR SALTSTONE FACILITY AT SRS (open access)

ALTERNATE APPROACH TO HAZARD CATEGORIZATION FOR SALTSTONE FACILITY AT SRS

The Saltstone Facility at Savannah River Site (SRS) was originally segmented into two segments: the Saltstone Production Facility (SPF) and the Saltstone Disposal Facility (SDF). Based on the inventory of radionuclides available for release the SPF and SDF were categorized as Nonreactor Hazard Category (HC)-3. The hazard categorization recognized the SDF will contain contributions of radionuclides which would exceed the HC-2 Threshold Quantity (TQ) in the form of grout. However it was determined not to impact the facility hazard categorization based on the grout being in a solid, monolithic form which was not easily dispersible. But, the impact of a quantity of unset grout expected to be present at the vault following operation of the process was not addressed. A Potential Inadequacy in Safety Analysis (PISA) was later issued based on the hazard categorization determination for the facility not addressing unset grout. This initiated a re-evaluation of the accident scenarios within the hazards analysis. During this re-evaluation, the segmentation of the facility was challenged based on the potential interaction between facility segments; specifically, the leachate return line and the grout transfer line, which were considered separate segments, are located in close proximity at one point. such that for certain events …
Date: April 28, 2009
Creator: Roy, B.
Object Type: Article
System: The UNT Digital Library
E10 Orbifolds (open access)

E10 Orbifolds

We study Z2 orbifolds of M-theory in terms of E10. We find a simple relation between the Z2 action on E10 and the imaginary root that corresponds [hep-th/0401053]to the"twisted sector" branes. We discuss the connection between the Kac-Moody algebra DE10 and the"untwisted" sector, and we demonstrate how DE18 can describe both the untwisted and twisted sectors simultaneously.
Date: April 28, 2005
Creator: Brown, Jeffrey; Ganguli, Surya; Ganor, Ori J. & Helfgott, Craig
Object Type: Article
System: The UNT Digital Library
Limits on a muon flux from neutralino annihilations in the Sun with the IceCube 22-string detector (open access)

Limits on a muon flux from neutralino annihilations in the Sun with the IceCube 22-string detector

A search for muon neutrinos from neutralino annihilations in the Sun has been performed with the IceCube 22-string neutrino detector using data collected in 104.3 days of live-time in 2007. No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured neutralinos in the Sun and converted to limits on the WIMP-proton cross-sections for WIMP masses in the range 250-5000 GeV. These results are the most stringent limits to date on neutralino annihilation in the Sun.
Date: April 28, 2009
Creator: Collaboration, IceCube & Klein, Spencer
Object Type: Article
System: The UNT Digital Library
Urinary Metabolites of the Dietary Carcinogen PhIP are Predictive of Colon DNA Adducts After a Low Dose Exposure in Humans (open access)

Urinary Metabolites of the Dietary Carcinogen PhIP are Predictive of Colon DNA Adducts After a Low Dose Exposure in Humans

Epidemiologic evidence indicates that exposure to heterocyclic amines (HAs) in the diet is an important risk factor for the development of colon cancer. Well-done cooked meats contain significant levels of HAs which have been shown to cause cancer in laboratory animals. To better understand the mechanisms of HA bioactivation in humans, the most mass abundant HA, 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), was used to assess the relationship between PhIP metabolism and DNA adduct formation. Ten human volunteers were administered a dietary relevant dose of [{sup 14}C]PhIP 48-72 h prior to surgery to remove colon tumors. Urine was collected for 24 h after dosing for metabolite analysis, and DNA was extracted from colon tissue and analyzed by accelerator mass spectrometry for DNA adducts. All ten subjects were phenotyped for CYP1A2, NAT2, and SULT1A1 enzyme activity. Twelve PhIP metabolites were detected in the urine samples. The most abundant metabolite in all volunteers was N-hydroxy-PhIP-N{sup 2}-glucuronide. Metabolite levels varied significantly between the volunteers. Interindividual differences in colon DNA adducts levels were observed between each individual. The data showed that individuals with a rapid CYP1A2 phenotype and high levels of urinary N-hydroxy-PhIP-N{sup 2}-glucuronide, had the lowest level of colon PhIP-DNA adducts. This suggests that glucuronidation plays a …
Date: April 28, 2006
Creator: Malfatti, M.; Dingley, K.; Nowell, S.; Ubick, E.; Mulakken, N.; Nelson, D. et al.
Object Type: Article
System: The UNT Digital Library
Time Dependent Hartree Fock Equation: Gateway to Nonequilibrium Plasmas (open access)

Time Dependent Hartree Fock Equation: Gateway to Nonequilibrium Plasmas

This is the Final Technical Report for DE-FG02-2ER54677 award “Time Dependent Hartree Fock Equation - Gateway to Nonequilibrium Plasmas”. Research has focused on the nonequilibrium dynamics of electrons in the presence of ions, both via basic quantum theory and via semi-classical molecular dynamics (MD) simulation. In addition, fundamental notions of dissipative dynamics have been explored for models of grains and dust, and for scalar fields (temperature) in turbulent edge plasmas. The specific topics addressed were Quantum Kinetic Theory for Metallic Clusters, Semi-classical MD Simulation of Plasmas , and Effects of Dissipative Dynamics.
Date: April 28, 2007
Creator: Dufty, James W.
Object Type: Report
System: The UNT Digital Library
Generalized in situ adaptive tabulation for constitutive model evaluation in plasticity (open access)

Generalized in situ adaptive tabulation for constitutive model evaluation in plasticity

A database storage, search and retrieval method of constitutive model responses for use in plasticity simulations is developed to increase the computational efficiency of finite element simulations employing complex non-linear material models. The method is based in the in situ adaptive tabulation method that has been successfully applied in the field of combustion chemistry, but is significantly modified to better handle the system of equations in plasticity. When using the database, the material response is estimated by a linear extrapolation from an appropriate database entry. This is shown to provide a response with an acceptable error tolerance. Two different example problems are chosen to demonstrate the behavior of the constitutive model estimation technique: a dynamic shock simulation, and a quasi-static inhomogeneous deformation simulation. This generalized in situ adaptive tabulation method shows promise for enabling simulations with complex multi-physics and multi-length scale constitutive descriptions.
Date: April 28, 2005
Creator: Arsenlis, A.; Barton, N.; Becker, R. & Rudd, R.
Object Type: Article
System: The UNT Digital Library
On the Putative Detection of Z>0 X-Ray Absorption Features in the Spectrum of Mrk 421 (open access)

On the Putative Detection of Z>0 X-Ray Absorption Features in the Spectrum of Mrk 421

In a series of papers, Nicastro et al. have claimed the detection of z > 0 O VII absorption features in the spectrum of Mrk 421 obtained with the Chandra Low Energy Transmission Grating Spectrometer (LETGS). We evaluate those claims in the context of a high quality spectrum of the same source obtained with the Reflection Grating Spectrometer (RGS) on XMM-Newton. The data comprise over 955 ksec of usable exposure time and more than 2.6 x 10{sup 4} counts per 50 m{angstrom} at 21.6 {angstrom}. We concentrate on the spectrally clean region (21.3 < {lambda} < 22.5 {angstrom}) where sharp features due to the astrophysically abundant O VII may reveal an intervening, warm-hot intergalactic medium (WHIM). In spite of the fact that the sensitivity of the RGS data is higher than that of the original LETGS data presented by Nicastro et al., we do not confirm detection of any of the intervening systems claimed to date. Rather, we detect only three unsurprising, astrophysically expected features down to the log (N{sub i}) {approx} 14.6 (3{sigma}) sensitivity level. Each of the two purported WHIM features is rejected with a statistical confidence that exceeds that reported for its initial detection. While we can …
Date: April 28, 2006
Creator: Rasmussen, Andrew P.; /SLAC /KIPAC, Menlo Park; Kahn, Steven M.; /SLAC /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Paerels, Frits; /Columbia U., Astron. Astrophys. et al.
Object Type: Report
System: The UNT Digital Library
The O VII X-Ray Forest Toward Markarian 421: Consistency between XMM-Newton and Chandra (open access)

The O VII X-Ray Forest Toward Markarian 421: Consistency between XMM-Newton and Chandra

Recently the first detections of highly ionized gas associated with two Warm-Hot Intergalactic Medium (WHIM) filaments have been reported. The evidence is based on X-ray absorption lines due to O VII and other ions observed by Chandra towards the bright blazar Mrk 421. We investigate the robustness of this detection by a re-analysis of the original Chandra LETGS spectra, the analysis of a large set of XMM-Newton RGS spectra of Mrk 421, and additional Chandra observations. We address the reliability of individual spectral features belonging to the absorption components, and assess the significance of the detection of these components. We also use Monte Carlo simulations of spectra. We confirm the apparent strength of several features in the Chandra spectra, but demonstrate that they are statistically not significant. This decreased significance is due to the number of redshift trials that are made and that are not taken into account in the original discovery paper. Therefore these features must be attributed to statistical fluctuations. This is confirmed by the RGS spectra, which have a higher signal to noise ratio than the Chandra spectra, but do not show features at the same wavelengths. Finally, we show that the possible association with a Ly{alpha} …
Date: April 28, 2006
Creator: Kaastra, J. S.; Werner, N.; den Herder, J. W. A.; /SRON, Utrecht; Paerels, F. B. S.; /Columbia U., Astron. Astrophys. et al.
Object Type: Report
System: The UNT Digital Library