Supporting Dynamic Ad hoc Collaboration Capabilities (open access)

Supporting Dynamic Ad hoc Collaboration Capabilities

Modern HENP experiments such as CMS and Atlas involve as many as 2000 collaborators around the world. Collaborations this large will be unable to meet often enough to support working closely together. Many of the tools currently available for collaboration focus on heavy-weight applications such as videoconferencing tools. While these are important, there is a more basic need for tools that support connecting physicists to work together on an ad hoc or continuous basis. Tools that support the day-to-day connectivity and underlying needs of a group of collaborators are important for providing light-weight, non-intrusive, and flexible ways to work collaboratively. Some example tools include messaging, file-sharing, and shared plot viewers. An important component of the environment is a scalable underlying communication framework. In this paper we will describe our current progress on building a dynamic and ad hoc collaboration environment and our vision for its evolution into a HENP collaboration environment.
Date: July 14, 2003
Creator: Agarwal, Deborah A. & Berket, Karlo
Object Type: Article
System: The UNT Digital Library
On the Increasing Fragility of Human Teeth with Age: ADeep-Ultraviolet Resonance Raman Study (open access)

On the Increasing Fragility of Human Teeth with Age: ADeep-Ultraviolet Resonance Raman Study

Ultraviolet resonance Raman spectroscopy (UVRRS) using 244nm excitation was used to investigate the impact of aging on humandentin. The intensity of a spectroscopic feature from the peptide bondsin the collagen increases with tissue age, similar to a finding reportedpreviously for human cortical bone.
Date: July 14, 2006
Creator: Ager, J. W., III; Nalla, R. K.; Balooch, G.; Kim, G.; Pugach, M.; Habelitz, S. et al.
Object Type: Article
System: The UNT Digital Library
Top-of-Rail lubricant (open access)

Top-of-Rail lubricant

Analysis of the volatile and semivolatile fractions collected after use of the TOR lubricant indicated that other than contaminants in the collection laboratory, no compounds on the EPA's Target Compound Lists (Tables 2 and 5) were detected in these fractions. The data of these qualitative analyses, given in the various tables in the text, indicate only the relative amounts of the tentatively identified compounds. The authors recommend that quantitative analysis be performed on the volatile and semivolatile fractions to allow confirmation of the tentatively identified compounds and to obtain absolute amounts of the detected compounds. Additionally, the semivolatile fraction should be analyzed by liquid chromatography/mass spectrometry to identify compounds that are not chromatographable under the temperature program used for determination of semivolatile compounds. Introducing the top-of-rail (TOR) lubricant into the wheel/rail interface results in a reduction of almost 60% of lateral friction force over the forces encountered under dry conditions. This reveals good potential for energy savings, as well as wear reduction, for railroad companies. In TOR lubrication, an increase in the angle of attack and axle load results in increased lateral friction and rate of lubricant consumption. The most efficient TOR lubricant quantity to be used in the wheel/rail …
Date: July 14, 2000
Creator: Alzoubi, M. F.; Fenske, G. R.; Erck, R. A. & Boparai, A. S.
Object Type: Report
System: The UNT Digital Library
Ultrathin ta-C films on heads depositied by twist-filteredcathodic arc carbon plasmas (open access)

Ultrathin ta-C films on heads depositied by twist-filteredcathodic arc carbon plasmas

It is known that filtered cathodic-arc-deposited ta-C films have outstanding properties even within the family of diamondlike materials. However, filtering of macroparticles is usually incomplete or accompanied by significant plasma losses. Ongoing research effort is directed towards the following goals: (1) complete elimination of macro- and nanoparticles from the vacuum arc plasma, (2) increase of plasma utilization in the cathodic-arc and macroparticle-filter system, (3) precise control and reproducibility of film deposition, and (4) synthesis of ultrathin films (< 5 nm) that meet requirements of the magnetic storage industry. The development of new filters, in particular the ''Twist Filter'', enables cathodic arc plasma deposition to synthesize ultrathin ta-C films of 3 nm on heads that pass corrosion and other relevant tests. We describe the Twist Filter system and report about recent ta-C tests results. In light of these results, even thinner films seem to be possible.
Date: July 14, 2000
Creator: Anders, Andre & Ryan, Francis W.
Object Type: Article
System: The UNT Digital Library
Temperature and Water Depth Monitoring Within Chum Salmon Spawning Habitat Below Bonneville Dam : Annual Report October 2007-September 2008 (open access)

Temperature and Water Depth Monitoring Within Chum Salmon Spawning Habitat Below Bonneville Dam : Annual Report October 2007-September 2008

The overall goal of the project described in this report is to provide a sound scientific basis for operation of the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance chum salmon populations - a species listed in March 1999 as threatened under the Endangered Species Act of 1973 (ESA). The study objective during fiscal year 2008 was to provide real-time data on Ives Island area water temperature and water surface elevations from the onset of chum salmon spawning through the end of chum salmon emergence. Sampling locations included areas where riverbed temperatures were elevated, potentially influencing alevin development and emergence timing. In these locations, hydrosystem operation caused large, frequent changes in river discharge that affected salmon habitat by dewatering redds and altering egg pocket temperatures. The 2008 objective was accomplished using temperature and water-level sensors deployed inside piezometers. Sensors were integrated with a radio telemetry system such that real-time data could be downloaded remotely and posted hourly on the Internet. During our overall monitoring period (October 2007 through June 2008), mean temperature in chum spawning areas was nearly 2 C warmer within the riverbed than in the overlying river. During chum salmon spawning (mid-November …
Date: July 14, 2009
Creator: Arntzen, E.V.
Object Type: Report
System: The UNT Digital Library
Temperature and Water Depth Monitoring Within Chum Salmon Spawning Habitat Below Bonneville Dam -- Annual Report -- October 2007-September 2008 (open access)

Temperature and Water Depth Monitoring Within Chum Salmon Spawning Habitat Below Bonneville Dam -- Annual Report -- October 2007-September 2008

The overall goal of the project described in this report is to provide a sound scientific basis for operation of the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance chum salmon populations----a species listed in March 1999 as threatened under the Endangered Species Act of 1973 (ESA). The study objective during fiscal year 2008 was to provide real-time data on Ives Island area water temperature and water surface elevations from the onset of chum salmon spawning through the end of chum salmon emergence. Sampling locations included areas where riverbed temperatures were elevated, potentially influencing alevin development and emergence timing. In these locations, hydrosystem operation caused large, frequent changes in river discharge that affected salmon habitat by dewatering redds and altering egg pocket temperatures. The 2008 objective was accomplished using temperature and water-level sensors deployed inside piezo¬meters. Sensors were integrated with a radio telemetry system such that real-time data could be downloaded remotely and posted hourly on the Internet.
Date: July 14, 2009
Creator: Arntzen, Evan V.
Object Type: Report
System: The UNT Digital Library
Improved Measurement of B^ \to\rho^ \rho^0 and Determination of the Quark-Mixing Phase Angle~\alpha (open access)

Improved Measurement of B^ \to\rho^ \rho^0 and Determination of the Quark-Mixing Phase Angle~\alpha

The authors present improved measurements of the branching fraction {Beta}, the longitudinal polarization fraction f{sub L}, and the direct CP asymmetry A{sub CP} in the B meson decay channel B{sup +} {yields} {rho}{sup +}{rho}{sup 0}. The data sample was collected with the BABAR detector at SLAC. The results are {Beta}(B{sup +} {yields} {rho}{sup +}{rho}{sup 0}) = (23.7 {+-} 1.4 {+-} 1.4) x 10{sup -6}, f{sub L} = 0.950 {+-} 0.015 {+-} 0.006, and A{sub CP} = -0.054 {+-} 0.055 {+-} 0.010, where the uncertainties are statistical and systematic, respectively. Based on these results, they perform an isospin analysis and determine the CKM weak phase angle {alpha} to be (92.4{sub -6.5}{sup +6.0}){sup 0}.
Date: July 14, 2009
Creator: Aubert, B.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E.; Prudent, X. et al.
Object Type: Article
System: The UNT Digital Library
MONOSODIUM TITANATE MULTI-STRIKE TESTING (open access)

MONOSODIUM TITANATE MULTI-STRIKE TESTING

Research over the past decade has studied the adsorption of plutonium and uranium onto monosodium titanate (MST) in alkaline solutions. Tests showed that MST would remove the targeted radionuclides from simulated alkaline waste. Testing also indicated that Pu removal kinetics and Np capacity of the MST material impacts the size of equipment and waste blending plans for the Salt Waste Processing Facility (SWPF). Additionally, calculations suggested the baseline MST process may not achieve the desired decontamination in wastes containing elevated concentrations of Pu and Np. In this task, the authors investigated the performance of non-baseline process parameters and their effectiveness for treating waste feed in the Salt Waste Processing Facility. The work addresses a DOE request in support of technical needs expressed, in part, by the Engineering, Procurement, and Construction Contractors for the Salt Waste Processing Facility. The work investigated the effect of increased MST addition (up to 1.2 g/L) and the benefit of extra filtration steps with multiple additions of MST to salt waste containing actinides and strontium. Both simulant and actual waste testing occurred. Actual waste tests used a Tank 39H composite waste solution. In addition, testing to determine desorption of actinides from residual MST occurred. The release …
Date: July 14, 2004
Creator: BARNES, MARKJ
Object Type: Report
System: The UNT Digital Library
Production Improvement From Increased Permeability Using Engineered Biochemical Secondary Recovery Methodology in Marginal Wells of the East Texas Field (open access)

Production Improvement From Increased Permeability Using Engineered Biochemical Secondary Recovery Methodology in Marginal Wells of the East Texas Field

A regenerating biochemical mixture and organic surfactant has been applied to wells in the East Texas Field with the goal of restoring permeability, reversing formation damage, mobilizing hydrocarbons, and ultimately increasing production. Initial work in task 1 was designed to open the perforations and remove blockages of scale, asphaltene, and other corrosion debris. This was accomplished on three wells that produce from the Woodbine, and was necessary to prepare the wells for more substantial future treatments. Secondly, in task 2, two wells were treated with much larger quantities of the biochemical mixture, e.g. 25 gallons, followed by approximately 140 barrels of a 2% KCl solution that carried the active biochemical solution into the near wellbore area and into the producing reservoir. After a 7 to 10 day acclamation and reaction period, the wells were put back into production. The biochemical solution successfully broke down the scale, paraffin and other binders blocking permeability and released significant debris which was immediately produced into the flowlines and separators. Oil production was clearly improved and the removed debris was a maintenance issue until the surface equipment could be modified. Next steps include larger treatments and tracer tests to better understand the fluid flow dynamics.
Date: July 14, 2004
Creator: Bassett, R. L. & Botto, William S.
Object Type: Report
System: The UNT Digital Library
Visual Data Exploration and Analysis - Report on the Visualization Breakout Session of the SCaLeS Workshop (open access)

Visual Data Exploration and Analysis - Report on the Visualization Breakout Session of the SCaLeS Workshop

Scientific visualization is the transformation of abstract information into images, and it plays an integral role in the scientific process by facilitating insight into observed or simulated phenomena. Visualization as a discipline spans many research areas from computer science, cognitive psychology and even art. Yet the most successful visualization applications are created when close synergistic interactions with domain scientists are part of the algorithmic design and implementation process, leading to visual representations with clear scientific meaning. Visualization is used to explore, to debug, to gain understanding, and as an analysis tool. Visualization is literally everywhere--images are present in this report, on television, on the web, in books and magazines--the common theme is the ability to present information visually that is rapidly assimilated by human observers, and transformed into understanding or insight. As an indispensable part a modern science laboratory, visualization is akin to the biologist's microscope or the electrical engineer's oscilloscope. Whereas the microscope is limited to small specimens or use of optics to focus light, the power of scientific visualization is virtually limitless: visualization provides the means to examine data that can be at galactic or atomic scales, or at any size in between. Unlike the traditional scientific tools …
Date: July 14, 2003
Creator: Bethel, E. Wes; Frank, Randy; Fulcomer, Sam; Hansen, Chuck; Joy, Ken; Kohl, J et al.
Object Type: Report
System: The UNT Digital Library
LLNL's Regional Model Calibration and Body-Wave Discrimination Research in the Former Soviet Union using Peaceful Nuclear Explosions (PNEs) (open access)

LLNL's Regional Model Calibration and Body-Wave Discrimination Research in the Former Soviet Union using Peaceful Nuclear Explosions (PNEs)

Long-range seismic profiles from Peaceful Nuclear Explosions (PNE) in the Former Soviet Union (FSU) provide a unique data set to investigate several important issues in regional Comprehensive Nuclear-Test-Ban Treaty (CTBT) monitoring. The recording station spacing ({approx}15 km) allows for extremely dense sampling of the propagation from the source to {approx} 3300 km. This allows us to analyze the waveforms at local, near- and far-regional and teleseismic distances. These data are used to: (1) study the evolution of regional phases and phase amplitude ratios along the profile; (2) infer one-dimensional velocity structure along the profile; and (3) evaluate the spatial correlation of regional and teleseismic travel times and regional phase amplitude ratios. We analyzed waveform data from four PNE's (m{sub b} = 5.1-5.6) recorded along profile KRATON, which is an east-west trending profile located in northern Sibertil. Short-period regional discriminants, such as P/S amplitude ratios, will be essential for seismic monitoring of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) at small magnitudes (m{sub b} < 4.0). However, P/S amplitude ratios in the short-period band, 0.5-5.0 Hz, show some scatter. This scatter is primarily due to propagation and site effects, which arise from variability in the elastic and anelastic structure of the crustal waveguide. …
Date: July 14, 2000
Creator: Bhattacharyya, J.; Rodgers, A.; Swenson, J.; Schultz, C.; Walter, W.; Mooney, W. et al.
Object Type: Article
System: The UNT Digital Library

YMP Site Activity Update

None
Date: July 14, 2005
Creator: Bishop, L.
Object Type: Presentation
System: The UNT Digital Library
Direct Measurement of the Combined Effects of Lichen, Rainfall, and Temperature On silicate Weathering (open access)

Direct Measurement of the Combined Effects of Lichen, Rainfall, and Temperature On silicate Weathering

A key uncertainty in models of the global carbonate-silicate cycle and long-term climate is the way that silicates weather under different climatologic conditions, and in the presence or absence of organic activity. Digital imaging of basalts in Hawaii resolves the coupling between temperature, rainfall, and weathering in the presence and absence of lichens. Activation energies for abiotic dissolution of plagioclase (23.1{+-} 2.5 kcal/mol) and olivine (21.3 {+-} 2.7 kcal/mol) are similar to those measured in the laboratory, and are roughly double those measured from samples taken underneath lichen. Abiotic weathering rates appear to be proportional to rainfall. Dissolution of plagioclase and olivine underneath lichen is far more sensitive to rainfall.
Date: July 14, 2000
Creator: Brady, Patrick V.; Dorn, Ronald I.; Brazel, Anthony J.; Clark, James; Moore, Richard B. & Glidewell, Tiffany
Object Type: Article
System: The UNT Digital Library
X-Ray Digital Radiography and Computed Tomography of High Energy Density Physics (HEDP) Material, Subassemblies and Targets (open access)

X-Ray Digital Radiography and Computed Tomography of High Energy Density Physics (HEDP) Material, Subassemblies and Targets

None
Date: July 14, 2006
Creator: Brown, W. D. & Martz, H. E., Jr.
Object Type: Article
System: The UNT Digital Library
Totally Integrated Munitions Enterprise ''Affordable Munitions Production for the 21st Century'' (open access)

Totally Integrated Munitions Enterprise ''Affordable Munitions Production for the 21st Century''

The U.S. Army faces several munitions manufacturing issues: downsizing of the organic production base, timely fielding of affordable smart munitions, and munitions replenishment during national emergencies. TIME is addressing these complex issues via the development and demonstration of an integrated enterprise. The enterprise will include the tools, network, and open modular architecture controller to enable accelerated acquisition, shortened concept to volume production, lower life cycle costs, capture of critical manufacturing processes, and communication of process parameters between remote sites to rapidly spin-off production for replenishment by commercial sources. TIME addresses the enterprise as a system, integrating design, engineering, manufacturing, administration, and logistics.
Date: July 14, 2000
Creator: Burleson, R. R.; Poggio, M. E.; Rosenberg, S. J. & McWilliams, T.
Object Type: Report
System: The UNT Digital Library
Pepper-pot scraper parameters and data processing (open access)

Pepper-pot scraper parameters and data processing

Parameters required for the pepperpot scraper are described, and its data processing is proposed.
Date: July 14, 2004
Creator: Burov, Alexey & Shemyakin, Alexander
Object Type: Report
System: The UNT Digital Library
Field Test Program for Long-Term Operation of a COHPAC System for Removing Mercury from Coal-Fired Flue Gas (open access)

Field Test Program for Long-Term Operation of a COHPAC System for Removing Mercury from Coal-Fired Flue Gas

With the Nation's coal-burning utilities facing the possibility of tighter controls on mercury pollutants, the U.S. Department of Energy is funding projects that could offer power plant operators better ways to reduce these emissions at much lower costs. Sorbent injection technology represents one of the simplest and most mature approaches to controlling mercury emissions from coal-fired boilers. It involves injecting a solid material such as powdered activated carbon into the flue gas. The gas-phase mercury in the flue gas contacts the sorbent and attaches to its surface. The sorbent with the mercury attached is then collected by the existing particle control device along with the other solid material, primarily fly ash. During 2001, ADA Environmental Solutions (ADA-ES) conducted a full-scale demonstration of sorbent-based mercury control technology at the Alabama Power E.C. Gaston Station (Wilsonville, Alabama). This unit burns a low-sulfur bituminous coal and uses a hot-side electrostatic precipitator (ESP) in combination with a Compact Hybrid Particulate Collector (COHPAC{reg_sign}) baghouse to collect fly ash. The majority of the fly ash is collected in the ESP with the residual being collected in the COHPAC{reg_sign} baghouse. Activated carbon was injected between the ESP and COHPAC{reg_sign} units to collect the mercury. Short-term mercury removal …
Date: July 14, 2005
Creator: Bustard, Jean; Lindsey, Charles; Brignac, Paul; Starns, Travis; Sjostrom, Sharon & Larson, Cindy
Object Type: Report
System: The UNT Digital Library
Mixing of Isotactic and Syndiotactic Polypropylenes in the Melt (open access)

Mixing of Isotactic and Syndiotactic Polypropylenes in the Melt

The miscibility of polypropylene (PP) melts in which the chains differ only in stereochemical composition has been investigated by two different procedures. One approach used detailed local information from a Monte Carlo simulation of a single chain, and the other approach takes this information from a rotational isomeric state model devised decades ago, for another purpose. The first approach uses PRISM theory to deduce the intermolecular packing in the polymer blend, while the second approach uses a Monte Carlo simulation of a coarse-grained representation of independent chains, expressed on a high-coordination lattice. Both approaches find a positive energy change upon mixing isotactic PP (iPP) and syndiotactic polypropylene (sPP) chains in the melt. This conclusion is qualitatively consistent with observations published recently by Muelhaupt and coworkers. The size of the energy chain on mixing is smaller in the MC/PRISM approach than in the RIS/MC simulation, with the smaller energy change being in better agreement with the experiment. The RIS/MC simulation finds no demixing for iPP and atactic polypropylene (aPP) in the melt, consistent with several experimental observations in the literature. The demixing of the iPP/sPP blend may arise from attractive interactions in the sPP melt that are disrupted when the sPP …
Date: July 14, 2000
Creator: CLANCY,THOMAS C.; PUTZ,MATHIAS; WEINHOLD,JEFFREY D.; CURRO,JOHN G. & MATTICE,WAYNE L.
Object Type: Article
System: The UNT Digital Library
Whole-genome analyses of the speciation events in the pathogenic Brucellae (open access)

Whole-genome analyses of the speciation events in the pathogenic Brucellae

Despite their high DNA identity and a proposal to group classical Brucella species as biovars of B. melitensis, the commonly recognized Brucella species can be distinguished by distinct biochemical and fatty acid characters as well as by a marked host range (e.g. B. suis for swine, B. melitensis for sheep and goats, B. abortus for cattle). Here we present the genome of B. abortus 2308, the virulent prototype biovar 1 strain, and its comparison to the two other human pathogenic Brucellae species and to the B. abortus field isolate 9-941. The global distribution of pseudogenes, deletions and insertions support previous indications that B. abortus and B. melitensis share a common ancestor that diverged from B. suis. With the exception of a dozen genes, the genetic complement of both B. abortus strains is identical, whereas the three species differ in gene content and pseudogenes. The pattern of species-specific gene inactivations affecting transcriptional regulators and outer membrane proteins suggest that these inactivations may play an important role in the establishment of host-specificity and may have been a primary driver of speciation in the Brucellae. Despite being non-motile, the Brucellae contain flagellum gene clusters and display species-specific flagellar gene inactivations, which lead to …
Date: July 14, 2005
Creator: Chain, P,; Comerci, D.; Tolmasky, M.; Larimer, F.; Malfatti, S.; Vergez, L. et al.
Object Type: Article
System: The UNT Digital Library
Implications of structural genomics target selection strategies: Pfam5000, whole genome, and random approaches (open access)

Implications of structural genomics target selection strategies: Pfam5000, whole genome, and random approaches

The structural genomics project is an international effort to determine the three-dimensional shapes of all important biological macromolecules, with a primary focus on proteins. Target proteins should be selected according to a strategy which is medically and biologically relevant, of good value, and tractable. As an option to consider, we present the Pfam5000 strategy, which involves selecting the 5000 most important families from the Pfam database as sources for targets. We compare the Pfam5000 strategy to several other proposed strategies that would require similar numbers of targets. These include including complete solution of several small to moderately sized bacterial proteomes, partial coverage of the human proteome, and random selection of approximately 5000 targets from sequenced genomes. We measure the impact that successful implementation of these strategies would have upon structural interpretation of the proteins in Swiss-Prot, TrEMBL, and 131 complete proteomes (including 10 of eukaryotes) from the Proteome Analysis database at EBI. Solving the structures of proteins from the 5000 largest Pfam families would allow accurate fold assignment for approximately 68 percent of all prokaryotic proteins (covering 59 percent of residues) and 61 percent of eukaryotic proteins (40 percent of residues). More fine-grained coverage which would allow accurate modeling of …
Date: July 14, 2004
Creator: Chandonia, John-Marc & Brenner, Steven E.
Object Type: Article
System: The UNT Digital Library
Probing Structure Property Relationships in Complex Engineering Silicones by 1H NMR (open access)

Probing Structure Property Relationships in Complex Engineering Silicones by 1H NMR

It is generally accepted that the properties of polymeric materials are controlled by the network structure and the reactions by which they have been constructed. These properties include the bulk moduli at creation, but also the properties as a function of age during use. In order to interpret mechanical properties and predict the time dependent changes in these properties, detailed knowledge of the effect of structural changes must be obtained. The degree and type of crosslinking, the molecular weight between crosslinks, the number of elastically ineffective chains (loops, dangling chain ends, sol-fraction) must be characterized. A number of theoretical and experimental efforts have been reported in the last few years on model networks prepared by endlinking reactions and the relationships of those structures with the ultimate mechanical properties. A range of experimental methods have been used to investigate structure including rheometric, scattering, infrared, {sup 29}Si MAS and CPMAS, {sup 1}H relaxation measurements, and recently {sup 1}H multiple quantum methods. Characterization of the growth of multiple quantum coherences have recently been shown to provide detailed insight into silicone network structure by the ability to selective probe the individual components of the polymer network, such as the polymer-filler interface or network chains. …
Date: July 14, 2006
Creator: Chinn, S. C.; Gjersing, E. L.; Maxwell, R. S.; Eastwood, E.; Bowen, D. & Stephens, T.
Object Type: Article
System: The UNT Digital Library
Comparative Plutonium-239 Dose Assessment for Three Desert Sites: Maralinga, Australia; Palomares, Spain; and the Nevada Test Site, USA - Before and After Remedial Action (open access)

Comparative Plutonium-239 Dose Assessment for Three Desert Sites: Maralinga, Australia; Palomares, Spain; and the Nevada Test Site, USA - Before and After Remedial Action

As a result of nuclear weapons testing and accidents, plutonium has been distributed into the environment. The areas close to the sites of these tests and accidental dispersions contain plutonium deposition of such a magnitude that health authorities and responsible officials have mandated that the contaminated areas be protected, generally through isolation or removal of the contaminated areas. In recent years remedial actions have taken place at all these sites. For reasons not entirely clear, the public perceives radiation exposure risk to be much greater than the evidence would suggest [1]. This perception seems to be particularly true for plutonium, which has often been ''demonized'' in various publications as the ''most hazardous substance known to man'' [2]. As the position statement adapted by the Health Physics Society explains, ''Plutonium's demonization is an example of how the public has been misled about radiation's environmental and health threats generally, and in cases like plutonium, how it has developed a warped ''risk perception'' that does not reflect reality'' [3]. As a result of this risk perception and ongoing debate surrounding environmental plutonium contamination, remedial action criteria are difficult to establish. By examining the data available before and after remedial actions taken at the …
Date: July 14, 2000
Creator: Church, B. W.; Shinn, J.; Williams, G. A.; Martin, L. J.; O'Brien, R. S. & Adams, S. R.
Object Type: Article
System: The UNT Digital Library
Determining neutron capture cross sections with the Surrogate Reaction Technique: Measuring decay probabilities with STARS (open access)

Determining neutron capture cross sections with the Surrogate Reaction Technique: Measuring decay probabilities with STARS

Neutron-induced reaction cross sections are sometimes difficult to measure due to target or beam limitations. For two-step reactions proceeding through an equilibrated intermediate state, an alternate ''surrogate reaction'' technique can be applicable, and is currently undergoing investigation at LLNL. Measured decay probabilities for the intermediate nucleus formed in a light-ion reaction can be combined with optical-model calculations for the formation of the same intermediate nucleus via the neutron-induced reaction. The result is an estimation for overall (n,{gamma}/n/2n) cross sections. As a benchmark, the reaction {sup 92}Zr({alpha},{alpha}'), surrogate, for n+{sup 91}Zr, was studied at the A.W. Wright Nuclear Structure Laboratory at Yale. Particles were detected in the silicon telescope STARS (Silicon Telescope Array for Reaction Studies) and {gamma}-ray energies measured with germanium clover detectors from the YRAST (Yale Rochester Array for SpecTroscopy) ball. The experiment and preliminary observations will be discussed.
Date: July 14, 2004
Creator: Church, J. A.; Ahle, L.; Bernstein, L. A.; Cooper, J.; Dietrich, F. S.; Escher, J. et al.
Object Type: Article
System: The UNT Digital Library
HST imaging of MEGA Microlensing Candidates in M31 (open access)

HST imaging of MEGA Microlensing Candidates in M31

We investigate HST/ACS and WFPC2 images at the positions of five candidate microlensing events from a large survey of variability in M31 (MEGA). Three closely match unresolved sources, and two produce only flux upper limits. All are confined to regions of the color-magnitude diagram where stellar variability is unlikely to be easily confused with microlensing. Red variable stars cannot explain these events (although background supernova are possible for two). If these lenses arise in M31's halo, they are due to masses 0.08 < m/M{sub {circle_dot}} < 0.85 (95% certainty, for a {delta}-function mass distribution), brown dwarfs for disk/disk, and stellar masses for disk/bulge ''self-lensing''.
Date: July 14, 2005
Creator: Cseresnjes, Patrick; Crotts, Arlin P.S.; de Jong, Jelte T.A.; Bergier, Alex; Baltz, Edward A.; Gyuk, Geza et al.
Object Type: Article
System: The UNT Digital Library