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FROM THE ISR TO RHIC - MEASUREMENTS OF HARD-SCATTERING AND JETS USING INCLUSIVE SINGLE PARTICLE PRODUCTION AND 2-PARTICLE CORRELATIONS. (open access)

FROM THE ISR TO RHIC - MEASUREMENTS OF HARD-SCATTERING AND JETS USING INCLUSIVE SINGLE PARTICLE PRODUCTION AND 2-PARTICLE CORRELATIONS.

Hard scattering in p-p collisions, discovered at the CERN ISR in 1972 by the method of leading particles, proved that the partons of Deeply Inelastic Scattering strongly interacted with each other. Further ISR measurements utilizing inclusive single or pairs of hadrons established that high p{sub T} particles are produced from states with two roughly back-to-back jets which are the result of scattering of constituents of the nucleons as described by Quantum Chromodynamics (QCD), which was developed during the course of these measurements. These techniques, which are the only practical method to study hard-scattering and jet phenomena in Au+Au central collisions at RHIC energies, are reviewed, as an introduction to present RHIC measurements.
Date: April 23, 2005
Creator: Tannenbaum, M. J.
Object Type: Article
System: The UNT Digital Library
An Overview of the Target Fabrication Operations at Lawrence Livermore National Laboratory (open access)

An Overview of the Target Fabrication Operations at Lawrence Livermore National Laboratory

The Target Engineering team at Lawrence Livermore National Laboratory (LLNL) builds precision laser targets for the National Ignition Facility (NIF) and the Omega Laser in Rochester, NY, and other experimental facilities. The physics requirements demand precision in these targets, which creates a constant need for innovative manufacturing processes. As experimental diagnostics improve, there is greater demand for precision in fabrication, assembly, metrology, and documentation of as-built targets. The team specializes in meso-scale fabrication with core competencies in diamond turning, assembly, and metrology. Figure 1 shows a typical diamond turning center. The team builds over 200 laser targets per year in batches of five to fifteen targets. Thus, all are small-lot custom builds, and most are novel designs requiring engineering and process development. Component materials are metals, polymers and low density aerogel foams. Custom fixturing is used to locate parts on the Diamond Turning Machines (DTM) and assembly stations. This ensures parts can be repeatably located during manufacturing operations. Most target builds involve a series of fabricating one surface with features and then relocating the components on another fixture to finish the opposite side of the component. These components are then assembled to complete multiple-component targets. These targets are typically built …
Date: March 23, 2005
Creator: Hibbard, R L & Bono, M J
Object Type: Article
System: The UNT Digital Library
Comparing 10 Methods for Solution Verification, and Linking to Model Validation (open access)

Comparing 10 Methods for Solution Verification, and Linking to Model Validation

Grid convergence is often assumed as a given during computational analyses involving discretization of an assumed continuum process. In practical use of finite difference and finite element analyses, perfect grid convergence is rarely achieved or assured, and this fact must be addressed to make statements about model validation or the use of models in risk analysis. We have previously provided a 4-step quantitative implementation for a quantitative V&V process. One of the steps in the 4-step process is that of Solution Verification. Solution Verification is the process of assuring that a model approximating a physical reality with a discretized continuum (e.g. finite element) code converges in each discretized domain to a converged answer on the quantity of subsequent validation interest. The modeling reality is that often we are modeling a problem with a discretized code because it is neither continuous spatially (e.g. contact and impact) nor smooth in relevant physics (e.g. shocks, melting, etc). The typical result is a non-monotonic convergence plot that can lead to spurious conclusions about the order of convergence, and a lack of means to estimate residual solution verification error or uncertainty at confidence. We compare ten techniques for grid convergence assessment, each formulated to enable …
Date: March 23, 2005
Creator: Logan, R W & Nitta, C K
Object Type: Report
System: The UNT Digital Library
Characterizing Network Services through Cluster-Set Variations (open access)

Characterizing Network Services through Cluster-Set Variations

Common Internet services can be reliably distinguished based solely upon the locations of clusters in traffic-based features (ratios of inbound to outbound packets, ratios of packets to payloads, etc.) This capability has value in revealing the nature of ''hidden'' (tunneled) services and in detecting anomalous changes to known services. We provide measures of session capture volumes sufficient to make confidence-level assertions regarding ''unknown'' services, and outline a throughput system for providing alarms for service anomalies.
Date: March 23, 2005
Creator: Bartoletti, A & Tang, N
Object Type: Report
System: The UNT Digital Library
Scalable Parallel Algebraic Multigrid Solvers (open access)

Scalable Parallel Algebraic Multigrid Solvers

The authors propose a parallel algebraic multilevel algorithm (AMG), which has the novel feature that the subproblem residing in each processor is defined over the entire partition domain, although the vast majority of unknowns for each subproblem are associated with the partition owned by the corresponding processor. This feature ensures that a global coarse description of the problem is contained within each of the subproblems. The advantages of this approach are that interprocessor communication is minimized in the solution process while an optimal order of convergence rate is preserved; and the speed of local subproblem solvers can be maximized using the best existing sequential algebraic solvers.
Date: March 23, 2005
Creator: Bank, R; Lu, S; Tong, C & Vassilevski, P
Object Type: Report
System: The UNT Digital Library
Protein Model Database (open access)

Protein Model Database

The phenomenal success of the genome sequencing projects reveals the power of completeness in revolutionizing biological science. Currently it is possible to sequence entire organisms at a time, allowing for a systemic rather than fractional view of their organization and the various genome-encoded functions. There is an international plan to move towards a similar goal in the area of protein structure. This will not be achieved by experiment alone, but rather by a combination of efforts in crystallography, NMR spectroscopy, and computational modeling. Only a small fraction of structures are expected to be identified experimentally, the remainder to be modeled. Presently there is no organized infrastructure to critically evaluate and present these data to the biological community. The goal of the Protein Model Database project is to create such infrastructure, including (1) public database of theoretically derived protein structures; (2) reliable annotation of protein model quality, (3) novel structure analysis tools, and (4) access to the highest quality modeling techniques available.
Date: February 23, 2005
Creator: Fidelis, K; Adzhubej, A; Kryshtafovych, A & Daniluk, P
Object Type: Report
System: The UNT Digital Library
Oxidation Resistance of Ru-Capped EUV Multilayers (open access)

Oxidation Resistance of Ru-Capped EUV Multilayers

Differently prepared Ru-capping layers, deposited on Mo/Si EUV multilayers, have been characterized using a suite of metrologies to establish their baseline structural, optical, and surface properties in as-deposited state. Same capping layer structures were tested for their thermal stability and oxidation resistance. Post-mortem characterization identified changes due to accelerated tests. The best performing Ru-capping layer structure was studied in detail with transmission electron microscopy to identify the grain microstructure and texture. This information is essential for modeling and performance optimization of EUVL multilayers.
Date: February 23, 2005
Creator: Bajt, S.; Dai, Z.; Nelson, E. J.; Wall, M. A.; Alameda, J.; Nguyen, N. et al.
Object Type: Article
System: The UNT Digital Library
The Spin Structure of the Nucleon. (open access)

The Spin Structure of the Nucleon.

For many years now, spin has played a very prominent role in QCD. The field of QCD spin physics has been carried by the hugely successful experimental program of polarized deeply-inelastic lepton-nucleon scattering (DIS), and by a simultaneous tremendous progress in theory. A new milestone has now been reached with the advent of RHIC, the world's first polarized proton-proton collider. RHIC is poised to help answer many of the important question pertaining to the spin structure of the nucleon. Recently, it has also been proposed to study spin phenomena in transversely polarized {bar p}p collisions at the planned GSI-FAIR facility. This talk describes some of the opportunities provided by RHIC and the proposed GSI experiments.
Date: May 23, 2005
Creator: Vogelsang, W.
Object Type: Article
System: The UNT Digital Library
Foaming of E-Glass II (Report for G Plus Project for PPG) (open access)

Foaming of E-Glass II (Report for G Plus Project for PPG)

In a previous study, the effect of the furnace atmosphere on E glass foaming was investigated with the specific goal to understand the impact of increased water content on foaming in oxy-fired furnaces. The present study extended the previous study and focused on the effect of glass batch chemical composition on E-glass foaming. The present study also included reruns of foam tests performed in a previous study, which resulted in the same trend: the foaming extent increased nearly linearly with the heating rate and no foam was produced when CO2 + 55% H2O atmosphere was introduced at 300°C. It was shown that the lack of foaming in the test with CO2 + 55% H2O atmosphere introduced at 300°C was caused by a loss of sulfate at T <1250°C because of higher water content at the early stages of melting. The tests with new batches in the present study showed that replacing quicklime with limestone tend to decrease foaming, possibly caused by increased sulfate loss during early stages of melting in the batch with limestone. The batches where Na2SO4 was replaced with NaNO3, NaNO3 + CeO2, or CeO2, produced only very limited foaming regardless of the replacing components. As expected, the …
Date: September 23, 2005
Creator: Kim, Dong-Sang; Portch, Matthew P.; Matyas, Josef; Hrma, Pavel R. & Pilon, Laurent
Object Type: Report
System: The UNT Digital Library
Nanometer-scale imaging and pore-scale fluid flow modeling inchalk (open access)

Nanometer-scale imaging and pore-scale fluid flow modeling inchalk

For many rocks of high economic interest such as chalk,diatomite, tight gas sands or coal, nanometer scale resolution is neededto resolve the 3D-pore structure, which controls the flow and trapping offluids in the rocks. Such resolutions cannot be achieved with existingtomographic technologies. A new 3D imaging method, based on serialsectioning and using the Focused Ion Beam (FIB) technology has beendeveloped. FIB allows for the milling of layers as thin as 10 nanometersby using accelerated Ga+ ions to sputter atoms from the sample surface.After each milling step, as a new surface is exposed, a 2D image of thissurface is generated. Next, the 2D images are stacked to reconstruct the3D pore or grain structure. Resolutions as high as 10 nm are achievableusing this technique. A new image processing method uses directmorphological analysis of the pore space to characterize thepetrophysical properties of diverse formations. In addition to estimationof the petrophysical properties (porosity, permeability, relativepermeability and capillary pressures), the method is used for simulationof fluid displacement processes, such as those encountered in variousimproved oil recovery (IOR) approaches. Computed with the new methodcapillary pressure curves are in good agreement with laboratory data. Themethod has also been applied for visualization of the fluid distributionat various saturations …
Date: August 23, 2005
Creator: Tomutsa, Liviu; Silin, Dmitriy & Radmilovich, Velimir
Object Type: Article
System: The UNT Digital Library
Reconstructing Past Ocean Salinity ((delta)18Owater) (open access)

Reconstructing Past Ocean Salinity ((delta)18Owater)

Temperature and salinity are two of the key properties of ocean water masses. The distribution of these two independent but related characteristics reflects the interplay of incoming solar radiation (insolation) and the uneven distribution of heat loss and gain by the ocean, with that of precipitation, evaporation, and the freezing and melting of ice. Temperature and salinity to a large extent, determine the density of a parcel of water. Small differences in temperature and salinity can increase or decrease the density of a water parcel, which can lead to convection. Once removed from the surface of the ocean where 'local' changes in temperature and salinity can occur, the water parcel retains its distinct relationship between (potential) temperature and salinity. We can take advantage of this 'conservative' behavior where changes only occur as a result of mixing processes, to track the movement of water in the deep ocean (Figure 1). The distribution of density in the ocean is directly related to horizontal pressure gradients and thus (geostrophic) ocean currents. During the Quaternary when we have had systematic growth and decay of large land based ice sheets, salinity has had to change. A quick scaling argument following that of Broecker and Peng …
Date: November 23, 2005
Creator: Guilderson, T. P. & Pak, D. K.
Object Type: Book
System: The UNT Digital Library
Development of the Table of Initial Isolation Distances and Protective Action Distances for the 2004 Emergency Response Guidebook. (open access)

Development of the Table of Initial Isolation Distances and Protective Action Distances for the 2004 Emergency Response Guidebook.

This report provides technical documentation for values in the Table of Initial Isolation and Protective Action Distances (PADs) in the 2004 Emergency Response Guidebook (ERG2004). The objective for choosing the PADs specified in the ERG2004 is to balance the need to adequately protect the public from exposure to potentially harmful substances against the risks and expenses that could result from overreacting to a spill. To quantify this balance, a statistical approach is adopted, whereby the best available information is used to conduct an accident scenario analysis and develop a set of up to 1,000,000 hypothetical incidents. The set accounts for differences in containers types, incident types, accident severity (i.e., amounts released), locations, times of day, times of year, and meteorological conditions. Each scenario is analyzed using detailed emission rate and atmospheric dispersion models to calculate the downwind chemical concentrations from which a 'safe distance' is determined. The safe distance is defined as the distance downwind from the source at which the chemical concentration falls below health protection criteria. The American Industrial Hygiene Association's Emergency Response Planning Guideline Level 2 (ERPG-2) or equivalent is the health criteria used. The statistical sample of safe distance values for all incidents considered in the …
Date: September 23, 2005
Creator: Brown, D. F.; Freeman, W. A.; Carhart, R. A.; Krumpolc, M.; Sciences, Decision and Information & Chicago, Univ. of Illinois at
Object Type: Report
System: The UNT Digital Library
National Register Eligibility Evaluation of the East Area, Argonne National Laaboratory-East Dupage County, Illinois. (open access)

National Register Eligibility Evaluation of the East Area, Argonne National Laaboratory-East Dupage County, Illinois.

Pursuant to Sections 106 and 110 of the National Historic Preservation Act Argonne National Laboratory-East (ANL-E) has completed an evaluation of buildings located within the East Area to determine whether any of these buildings meet the eligibility criteria for listing on the National Register of Historic Places (NRHP). Several buildings within the East Area are scheduled for demolition during fiscal years 1999-2000 (Buildings 4, 5, and 6 and possibly Buildings 26, 27, and 28).
Date: September 23, 2005
Creator: Wescott, K. L.; O'Rourke, D. J. & Assessment, Environmental
Object Type: Report
System: The UNT Digital Library
Effect of Shock Compression Method on the Defect Substructure in Monocrystalline Copper (open access)

Effect of Shock Compression Method on the Defect Substructure in Monocrystalline Copper

Monocrystalline copper samples with orientations of [001] and [221] were shocked at pressures ranging from 20 GPa to 60 GPa using two techniques: direct drive lasers and explosively driven flyer plates. The pulse duration for these techniques differed substantially: 40 ns for the laser experiments at 0.5 mm into the sample and 1.1 {approx} 1.4 {micro}s for the flyer-plate experiments at 5 mm into the sample. The residual microstructures were dependent on orientation, pressure, and shocking method. The much shorter pulse duration in the laser driven shock yielded microstructures closer to the ones generated at the shock front. For the flyer-plate experiments, the longer pulse duration allows shock-generated defects to reorganize into lower energy configurations. Calculations show that the post-shock cooling for the laser driven shock is 10{sup 3} {approx} 10{sup 4} faster than that for plate-impact shock, propitiating recovery and recrystallization conditions for the latter. At the higher pressure level, extensive recrystallization was observed in the plate-impact samples, while it was absent in the laser driven shock. An effect that is proposed to contribute significantly to the formation of recrystallized regions is the existence of micro-shear-bands, which increase the local temperature beyond the prediction from adiabatic compression.
Date: September 23, 2005
Creator: Cao, B. Y.; Lassila, D. H.; Schneider, M. S.; Kad, B. K.; Huang, C. X.; Xu, Y. B. et al.
Object Type: Article
System: The UNT Digital Library
PIMC Simulation of Ps Annihilation: From Micro to Mesopores (open access)

PIMC Simulation of Ps Annihilation: From Micro to Mesopores

Path Integral Monte Carlo (PIMC) can reproduce the results of simple analytical calculations in which a single quantum particle is used to represent positronium within an idealized, spherical pore. Our calculations improve on this approach by explicitly treating the positronium as a two-particle e{sup -}, e{sup +} system interacting via the Coulomb interaction. We study the lifetime and the internal contact density, {kappa}, which controls the self-annihilation behavior, for positronium in model spherical pores, as a function of temperature and pore size. We compare the results with both PIMC and analytical calculations for a single-particle model.
Date: August 23, 2005
Creator: Bug, A. R. & Sterne, P. A.
Object Type: Article
System: The UNT Digital Library
A QSAR for the Mutagenic Potencies of Twelve 2-Amino-trimethylimidazopyridine Isomers: Structural, Quantum Chemical,and Hydropathic Factors (open access)

A QSAR for the Mutagenic Potencies of Twelve 2-Amino-trimethylimidazopyridine Isomers: Structural, Quantum Chemical,and Hydropathic Factors

An isomeric series of heterocyclic amines related to one found in heated muscle meats was investigated for properties that predict their measured mutagenic potency. Eleven of the 12 possible 2-amino-trimethylimidazopyridine (TMIP) isomers were tested for mutagenic potency in the Ames/Salmonella test with bacterial strain TA98, and resulted in a 600-fold range in potency. Structural, quantum chemical and hydropathic data were calculated on the parent molecules and the corresponding nitrenium ions of all of the tested isomers to establish models for predicting the potency of the unknown isomer. The regression model accounting for the largest fraction of the total variance in mutagenic potency contains four predictor variables: dipole moment, a measure of the gap between amine LUMO and HOMO energies, percent hydrophilic surface, and energy of amine LUMO. The most important determinants of high mutagenic potency in these amines are: (1) a small dipole moment, (2) the combination of b-face ring fusion and N3-methyl group, and (3) a lower calculated energy of the {pi} electron system. Based on predicted potency from the average of five models, the isomer not yet synthesized and tested is expected to have a mutagenic potency of 0.84 revertants/{micro}g in test strain TA98.
Date: April 23, 2005
Creator: Knize, M G; Hatch, F T; Tanga, M J; Lau, E V & Colvin, M E
Object Type: Article
System: The UNT Digital Library
Hydrogen Production via a Commercially Ready Inorganic membrane Reactor (open access)

Hydrogen Production via a Commercially Ready Inorganic membrane Reactor

Single stage low-temperature-shift water-gas-shift (WGS-LTS) via a membrane reactor (MR) process was studied through both mathematical simulation and experimental verification in this quarter. Our proposed MR yields a reactor size that is 10 to &gt;55% smaller than the comparable conventional reactor for a CO conversion of 80 to 90%. In addition, the CO contaminant level in the hydrogen produced via MR ranges from 1,000 to 4,000 ppm vs 40,000 to &gt;70,000 ppm via the conventional reactor. The advantages of the reduced WGS reactor size and the reduced CO contaminant level provide an excellent opportunity for intensification of the hydrogen production process by the proposed MR. To prepare for the field test planned in Yr III, a significant number (i.e., 98) of full-scale membrane tubes have been produced with an on-spec ratio of &gt;76% during this first production trial. In addition, an innovative full-scale membrane module has been designed, which can potentially deliver &gt;20 to 30 m{sup 2}/module making it suitable for large-scale applications, such as power generation. Finally, we have verified our membrane performance and stability in a refinery pilot testing facility on a hydrocracker purge gas. No change in membrane performance was noted over the &gt;100 hrs of testing …
Date: August 23, 2005
Creator: Liu, Paul K.T.
Object Type: Report
System: The UNT Digital Library
DIRECT OBSERVATION OF THE ALPHA-EPSILON TRANSITION IN SHOCKED SINGLE CRYSTAL IRON (open access)

DIRECT OBSERVATION OF THE ALPHA-EPSILON TRANSITION IN SHOCKED SINGLE CRYSTAL IRON

In-situ x-ray diffraction was used to study the response of single crystal iron under shock conditions. Measurements of the response of [001] iron showed a uniaxial compression of the initially bcc lattice along the shock direction by up to 6% at 13 GPa. Above this pressure, the lattice responded with a further collapse of the lattice by 15-18% and a transformation to a hcp structure. The in-situ measurements are discussed and results summarized.
Date: August 23, 2005
Creator: Kalantar, D H; Collins, G W; Colvin, J D; Davies, H M; Eggert, J H; Hawreliak, J et al.
Object Type: Article
System: The UNT Digital Library
Muon G-2 and Electric Dipole Moments in Storage Rings: Powerful Probes of Physics Beyond the Standard Model. (open access)

Muon G-2 and Electric Dipole Moments in Storage Rings: Powerful Probes of Physics Beyond the Standard Model.

We have shown that the study of dipole moments, both magnetic and electric, in storage rings offer unique opportunities in probing physics beyond the Standard Model (SM). Both methods use similar techniques (particle and spin precession in magnetic storage rings). We are currently investigating the systematic errors associated with the resonance electric dipole moment (EDM) method. So far it looks very promising.
Date: May 23, 2005
Creator: Semertzidis, Y. K.
Object Type: Article
System: The UNT Digital Library
Picosecond X-Ray Diffraction From Laser-Shocked Copper and Iron (open access)

Picosecond X-Ray Diffraction From Laser-Shocked Copper and Iron

In situ X-ray diffraction allows the determination of the structure of transient states of matter. We have used laser-plasma generated X-rays to study how single crystals of metals (copper and iron) react to uniaxial shock compression. We find that copper, as a face-centered-cubic material, allows rapid generation and motion of dislocations, allowing close to hydrostatic conditions to be achieved on sub-nanosecond timescales. Detailed molecular dynamics calculations provide novel information about the process, and point towards methods whereby the dislocation density might be measured during the passage of the shock wave itself. We also report on recent experiments where we have obtained diffraction images from shock-compressed single-crystal iron. The single crystal sample transforms to the hcp phase above a critical pressure, below which it appears to be uniaxially compressed bcc, with no evidence of plasticity. Above the transition threshold, clear evidence for the hcp phase can be seen in the diffraction images, and via a mechanism that is also consistent with recent multi-million atom molecular dynamics simulations that use the Voter-Chen potential. We believe these data to be of import, in that they constitute the first conclusive in situ evidence of the transformed structure of iron during the passage of a …
Date: August 23, 2005
Creator: Wark, J. S.; Belak, J. F.; Collins, G. W.; Colvin, J. D.; Davies, H. M.; Duchaineau, M. et al.
Object Type: Article
System: The UNT Digital Library
Exploratory Simulation Studies of Caprock Alteration Induced byStorage of CO2 in Depleted Gas Reservoirs (open access)

Exploratory Simulation Studies of Caprock Alteration Induced byStorage of CO2 in Depleted Gas Reservoirs

This report presents numerical simulations of isothermalreactive flows which might be induced in the caprock of an Italiandepleted gas reservoir by the geological sequestration of carbon dioxide.Our objective is to verify that CO2 geological disposal activitiesalready planned for the study area are safe and do not induce anyundesired environmental impact.Gas-water-rock interactions have beenmodelled under two different intial conditions, i.e., assuming that i)caprock is perfectly sealed, or ii) partially fractured. Field conditionsare better approximated in terms of the "sealed caprock model". Thefractured caprock model has been implemented because it permits toexplore the geochemical beahvior of the system under particularly severeconditions which are not currently encountered in the field, and then todelineate a sort of hypothetical maximum risk scenario.Major evidencessupporting the assumption of a sealed caprock stem from the fact that nogas leakages have been detected during the exploitation phase, subsequentreservoir repressurization due to the ingression of a lateral aquifer,and during several cycles of gas storage in the latest life of reservoirmanagement.An extensive program of multidisciplinary laboratory tests onrock properties, geochemical and microseismic monitoring, and reservoirsimulation studies is underway to better characterize the reservoir andcap-rock behavior before the performance of a planned CO2 sequestrationpilot test.In our models, fluid flow and mineral alteration …
Date: November 23, 2005
Creator: Gherardi, Fabrizio; Xu, Tianfu & Pruess, Karsten
Object Type: Report
System: The UNT Digital Library
Contaminant Uptake and Demography of the Loggerhead Shrike (Lanius ludovicianus) at the Lawrence Livermore National Laboratory, Site 300 (open access)

Contaminant Uptake and Demography of the Loggerhead Shrike (Lanius ludovicianus) at the Lawrence Livermore National Laboratory, Site 300

Concentrations of eleven potential environmental contaminants (metals) in the blood and retrice feathers of fledged-Hatch Year and adult loggerhead shrikes (Lanius ludovicianus) were examined at Lawrence Livermore National Laboratory's Site 300 and a control site, in San Joaquin and Contra Costa Counties, California. The purpose of this pilot study was to determine, through non-lethal means, if loggerhead shrikes are exposed to metals at Site 300 and whether specific demographic variables (i.e., clutch size, fledgling success, etc.) are affected. Loggerhead shrikes at Site 300 had higher blood concentrations of metals, especially birds on the west side of the site, when compared to control site birds. Metal concentrations in the feathers of control site birds tended to be higher than Site 300 shrikes. Blood concentrations of metals in loggerhead shrikes from both Site 300 and the control site were well below the Most Tolerant Dietary Level (MTDL) for domestic birds for all metals except selenium. Clutch size was similar to other populations but one deformed embryo was discovered in a failed egg. The results of this pilot study suggest further work is needed to understand possible synergistic effects related to other contaminants of concern found at Site 300 and overall population variability.
Date: February 23, 2005
Creator: van Hattem, M G & Santolo, G
Object Type: Report
System: The UNT Digital Library
Evidence for the Spectroscopic Signature of Aging in (delta)-Pu(Ga) (open access)

Evidence for the Spectroscopic Signature of Aging in (delta)-Pu(Ga)

Plutonium, because of its radioactive nature, ages from the 'inside out' by means of self-irradiation damage and thus produces nanoscale internal defects. The self-irradiation induced defects come in the form of Frenkel-type defects (vacancies and self-interstitial atoms), helium in-growth, and defect clusters. At present there are neither experimental nor theoretical models describing the changes in the electronic structure caused by the aging in Pu. This fact appears to be associated primarily with the absence of reasonably convincing spectroscopic evidence of the changes. This paper demonstrates that Resonant Photoemission, a variant of Photoelectron Spectroscopy, has strong sensitivity to aging of Pu samples. The spectroscopic results are correlated with an extra-atomic screening model [1], and are shown to be the fingerprint of mesoscopic or nanoscale internal damage in the Pu physical structure. This means that a spectroscopic signature of internal damage due to aging in Pu has been established.
Date: November 23, 2005
Creator: Chung, B. W.; Schwartz, A. J.; Ebbinghaus, B. B.; Fluss, M. J.; Haslam, J. J.; Blobaum, K. M. et al.
Object Type: Article
System: The UNT Digital Library
Reference Material for Radionuclides in Sediment, IAEA-384 (Fangataufa Lagoon Sediment) (open access)

Reference Material for Radionuclides in Sediment, IAEA-384 (Fangataufa Lagoon Sediment)

The IAEA Marine Environment Laboratory (IAEA-MEL) in Monaco has conducted intercomparison exercises on radionuclides in marine samples for many years as part of its contribution to the IAEA's program of Analytical Quality Control Services (AQCS). An important part of the AQCS program has been a production of Reference Materials (RMs) and their provision to radioanalytical laboratories. The RMs have been developed for different marine matrices (sediment, water, biota), with accuracy and precision required for the present state of the art of radiometrics and mass spectrometry methods. The RMs have been produced as the final products of world-wide intercomparison exercises organized during last 30 years. A total of 44 intercomparison exercises were undertaken and 39 RMs were produced for radionuclides in the marine environment. All required matrices (seawater, biota, sediment) have been covered with radionuclide concentrations ranging from typical environmental levels to elevated levels affected by discharges from nuclear reprocessing plants. The long-term availability of RMs (over 10 years) requires the use of very specific techniques to collect and pretreat large quantities of material (e.g., in excess of 100 kg) in order to ensure sample stability and homogenization of any analytes of interest. The production of a RM is therefore a …
Date: September 23, 2005
Creator: Povinec, P. P.; Pham, M. K.; Barci-Funel, G.; Bojanawski, R.; Boshkova, T.; Burnett, W. et al.
Object Type: Article
System: The UNT Digital Library