Posthearing Questions Related to Proposed DOD Human Capital Reform (open access)

Posthearing Questions Related to Proposed DOD Human Capital Reform

Correspondence issued by the General Accounting Office with an abstract that begins "On June 4, 2003, GAO testified before the Senate Committee on Governmental Affairs at a hearing entitled "Transforming the Department of Defense Personnel System: Finding the Right Approach." This letter responds to a request that we provide answers to posthearing questions from Senator George V. Voinovich and Senator Thomas R. Carper concerning the proposed Department of Defense (DOD) Human Capital Reform."
Date: July 3, 2003
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
Medicare: Covert Testing Exposes Weaknesses in the Durable Medical Equipment Supplier Screening Process (open access)

Medicare: Covert Testing Exposes Weaknesses in the Durable Medical Equipment Supplier Screening Process

A letter report issued by the Government Accountability Office with an abstract that begins "According to the Department of Health and Human Services (HHS), schemes to defraud the Medicare program have grown more elaborate in recent years. In particular, HHS has acknowledged Centers for Medicare & Medicaid Service's (CMS) oversight of suppliers of durable medical equipment, prosthetics, orthotics, and supplies (DMEPOS) is inadequate to prevent fraud and abuse. Specifically, weaknesses in the DMEPOS enrollment and inspection process have allowed sham companies to fraudulently bill Medicare for unnecessary or nonexistent supplies. From April 2006 through March 2007, CMS estimated that Medicare improperly paid $1 billion for DMEPOS supplies--in part due to fraud by suppliers. Due to the committee's concern about vulnerabilities in the enrollment process, GAO used publicly available guidance to attempt to create DMEPOS suppliers, obtain Medicare billing numbers, and complete electronic test billing. GAO also reported on closed cases provided by the HHS Inspector General (IG) to illustrate the techniques used by criminals to fraudulently bill Medicare. On June 18, 2008, we briefed CMS representatives on the results of our investigation. In response, they acknowledged that our covert tests illustrate gaps in oversight that still require improvement and stated …
Date: July 3, 2008
Creator: United States. Government Accountability Office.
Object Type: Report
System: The UNT Digital Library
Hourly Fees Paid by Various Federal Agencies to Private Attorneys for Legal Services (open access)

Hourly Fees Paid by Various Federal Agencies to Private Attorneys for Legal Services

Correspondence issued by the General Accounting Office with an abstract that begins "This report provides information on hourly fees paid by the federal government to private attorneys for legal services in fiscal years 1999, 2000, and 2001. Relevant legal services include federal employee defense, litigative consultation, intellectual property consultation, and asset forfeiture-related services. For these types of services, GAO obtained information on hourly fees paid to private attorneys by the Department of Justice, the Administrative Office of the United States Courts, the National Aeronautics and Space Administration, and the Department of Veterans Affairs. GAO found that the hourly fees paid to private attorneys ranged from $125 to $357, depending on the agency and the type of legal service."
Date: July 3, 2001
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
NNSA: Nuclear Weapon Reports Need to Be More Detailed and Comprehensive (open access)

NNSA: Nuclear Weapon Reports Need to Be More Detailed and Comprehensive

Correspondence issued by the General Accounting Office with an abstract that begins "The National Nuclear Security Administration (NNSA) spends $5.5 billion a year to maintain the safety and reliability of the nation's nuclear weapons stockpile through the Stockpile Stewardship Program. Because the United States is no longer designing and building new nuclear weapons, extending the life of each of the nine weapon types in the current stockpile is a key component of this program. However, the criteria used by NNSA for determining when its reporting should begin may prevent Congress from receiving complete information on life extension costs. The current Nuclear Weapon Acquisition Reports (NWAR) are less detailed and comprehensive than the Department of Defense's Selected Acquisition Reports. Finally, the cost data in the NWARs exclude significant costs that are necessary to successfully complete the life-extension efforts."
Date: July 3, 2002
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
Information Security: Weak Controls Place Interior's Financial and Other Data at Risk (open access)

Information Security: Weak Controls Place Interior's Financial and Other Data at Risk

A letter report issued by the General Accounting Office with an abstract that begins "This report reviews information system general controls over the financial systems maintained by the Department of the Interior at its National Business Center (NBC) in Denver, Colorado. GAO found that although the Denver center has made progress in correcting previously cited computer security weaknesses, additional weaknesses affect the Denver center's information system control environment. These weaknesses affect the center's ability to prevent and detect unauthorized changes to financial information, control electronic access to sensitive personnel information, and restrict physical access to sensitive computing areas. The Denver center did not adequately limit access granted to authorized users, control all aspects of the system software controls, or secure access to its network. Also, the Denver center had not fully established a comprehensive program to routinely monitor access to its computer facilities and data and to identify and investigate unusual or suspicious access patterns that could indicate unauthorized access. The primary reason for these weaknesses was that the Denver center had not yet fully developed and implemented a comprehensive entitywide program to manage computer security."
Date: July 3, 2001
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Homeland Security: Intergovernmental Coordination and Partnership Will Be Critical to Success (open access)

Homeland Security: Intergovernmental Coordination and Partnership Will Be Critical to Success

Testimony issued by the General Accounting Office with an abstract that begins "The challenges posed by homeland security exceed the capacity and authority of any one level of government. Protecting the nation against these threats calls for a truly integrated approach, bringing together the resources of all levels of government. The proposed Department of Homeland Security will have a central role in efforts to enhance homeland security. The proposed consolidation of homeland security programs has the potential to reduce fragmentation, improve coordination, and clarify roles and responsibilities. However, formation of a department should not be considered a replacement for the timely issuance of a national homeland security strategy to guide implementation of the complex mission of the department. Appropriate roles and responsibilities within and between the government and private sector need to be clarified. New threats are prompting a reassessment and shifting of long-standing roles and responsibilities, but these shifts are being considered on a piecemeal and ad hoc basis without benefit of an overarching framework and criteria. A national strategy could provide guidance by more systematically identifying the unique capacities and resources at each level of government to enhance homeland security and by providing increased accountability within the intergovernmental …
Date: July 3, 2002
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
Workforce Investment Act: States and Localities Increasingly Coordinate Services for TANF Clients, but Better Information Needed on Effective Approaches (open access)

Workforce Investment Act: States and Localities Increasingly Coordinate Services for TANF Clients, but Better Information Needed on Effective Approaches

A letter report issued by the General Accounting Office with an abstract that begins "The 1998 Workforce Investment Act (WIA) required states to provide most federally funded employment-related services through one-stop centers. Two years earlier, welfare reform legislation created the Temporary Assistance for Needy Families (TANF) block grant which provided flexibility to states to focus on helping needy adults with children find and maintain employment. Nearly all states reported some coordination of their TANF and WIA services at the state or local level, and the use of some of these coordination methods increased between 2000 and 2001. Historical relationships, geographic considerations, adequacy of facilities, and different perspectives on how best to serve TANF clients influenced how states and localities choose to coordinate services with one-stop centers. Several challenges, including program differences between TANF and WIA and different information systems used by welfare and workforce agencies, inhibit state and local coordination efforts. Though some states and localities have found creative ways to work around these issues, the differences remain barriers to coordination for many others."
Date: July 3, 2002
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Mass Transit: Many Management Successes at WMATA, but Capital Planning Could Be Enhanced (open access)

Mass Transit: Many Management Successes at WMATA, but Capital Planning Could Be Enhanced

A letter report issued by the General Accounting Office with an abstract that begins "In recent years, the Washington Metropolitan Area Transit Authority's (WMATA) public transit system has experienced problems with the safety and reliability of its transit services, including equipment breakdowns, delays in scheduled service, unprecedented crowding on trains, and some accidents and tunnel fires. At the same time, WMATA's ridership is at an all time high and WMATA managers expect the number of passengers to double during the next 25 years. This report reviews (1) the challenges WMATA faces in operating and maintaining its Metrorail system; (2) efforts WMATA has made to establish and monitor safety and security within its transit system; and (3) the extent to which WMATA follows established best practices in planning, selecting, and budgeting for its capital investments. GAO found that WMATA is addressing significant challenges brought about by the agency's aging equipment and infrastructure and its ever-increasing ridership. WMATA has established programs to identify, evaluate, and minimize safety and security risks throughout its rail and bus systems. WMATA has also adopted several best capital practices used by leading public and private sector organizations, but it could benefit by establishing a more formal, disciplined …
Date: July 3, 2001
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Non-Income Tax Revenue Systems Requirements (Exposure Draft) (open access)

Non-Income Tax Revenue Systems Requirements (Exposure Draft)

Other written product issued by the General Accounting Office with an abstract that begins "The Joint Financial Management Improvement Program Non-Income Tax Revenue System Requirements documents is intended to provide a common set of non-income tax revenue financial information requirements with which each agency's integrated financial management system must be consistent. This document delineates those interface requirements between non-income tax revenue and other systems that are critical to the performance of both functions. These requirements are intended to be available to all users who rely on the information to carry out their responsibilities. This document does not address system requirements associated solely with the non-income tax revenue process."
Date: July 3, 2002
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
2000 Census: Refinements to Full Count Review Program Could Improve Future Data Quality (open access)

2000 Census: Refinements to Full Count Review Program Could Improve Future Data Quality

A letter report issued by the General Accounting Office with an abstract that begins "To ensure the completeness and accuracy of the 2000 census data, Bureau of the Census analysts were to identify, investigate, and document suspected data discrepancies or issues to clear census data files and products for subsequent processing or public release. They were to determine whether and how to correct the data by weighing quality improvements against time and budget constraints. Because the bureau lacked sufficient staff to conduct a full count review on its own, it contracted out some of the work to members of the Federal-State Cooperative Program for Population Estimates (FSCPE). FSCPE documented 1,402 data issues, 29 percent of the 4,809 issues identified by both FSCPE and bureau analysts during the full count review. Of the 4,809 issues, 1,599 dealt with "group quarters," where counts for prisons, nursing homes, dormitories, and other group living facilities differed from what analysts expected. Of the 1,599 group quarters issues, FSCPE identified 567. Discrepancies relating to housing unit counts, population data, and demographic characteristics accounted for 1,150 issues, 375 of which were identified by FSCPE. Overall, of the 4,809 issues identified during review, 4,267 were not subjected to …
Date: July 3, 2002
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
300 Area Building Retention Evaluation Mitigation Plan (open access)

300 Area Building Retention Evaluation Mitigation Plan

Evaluate the long-term retention of several facilities associated with the PNNL Capability Replacement Laboratory and other Hanfor mission needs. WCH prepared a mitigation plan for three scenarios with different release dates for specific buildings. The evaluations present a proposed plan for providing utility services to retained facilities in support of a long-term (+20 year) lifespan in addition to temporary services to buildings with specified delayed release dates.
Date: July 3, 2007
Creator: McBride, D. J.
Object Type: Report
System: The UNT Digital Library
Microwave Transmission Measurements of the Electron Cloud Density In The Positron Ring of PEP-II (open access)

Microwave Transmission Measurements of the Electron Cloud Density In The Positron Ring of PEP-II

Clouds of electrons in the vacuum chambers of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We applied a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave which is independently excited and transmitted over a straight section of the accelerator. The modulation in the wave transmission which appear to increase in depth when the clearing solenoids are switched off, seem to be directly correlated to the electron cloud density in the section. Furthermore, we expect a larger phase shift of a wave transmitted through magnetic dipole field regions if the transmitted wave couples with the gyration motion of the electrons. We have used this technique to measure the average electron cloud density (ECD) specifically for the first time in magnetic field regions of a new 4-dipole chicane in the positron ring of the PEP-II collider at SLAC. In this paper we present and discuss the measurements taken in the Low Energy Ring (LER) between 2006 and …
Date: July 3, 2008
Creator: Pivi, M. T. F.; Krasnykh, A. K; Byrd, J.; Santis, S.De; Sonnad, K. G.; Caspers, F. et al.
Object Type: Article
System: The UNT Digital Library
Confirmatory Survey Results for the Emergency Operations Facility (EOF) at the Connecticut Yankee Haddam Neck Plant, Haddam, Connecticut (open access)

Confirmatory Survey Results for the Emergency Operations Facility (EOF) at the Connecticut Yankee Haddam Neck Plant, Haddam, Connecticut

The U.S. Nuclear Regulatory Commission (NRC) requested that the Oak Ridge Institute for Science and Education (ORISE) perform a confirmatory survey on the Emergency Operations Facility (EOF) at the Connecticut Yankee Haddam Neck Plant (HNP) in Haddam, Connecticut
Date: July 3, 2007
Creator: Adams, W. C.
Object Type: Report
System: The UNT Digital Library
A New Chicane Experiment In PEP-II to Test Mitigations of the Electron Cloud Effect for Linear Colliders (open access)

A New Chicane Experiment In PEP-II to Test Mitigations of the Electron Cloud Effect for Linear Colliders

Beam instability caused by the electron cloud has been observed in positron and proton storage rings, and it is expected to be a limiting factor in the performance of future colliders [1-3]. The effect is expected to be particularly severe in magnetic field regions. To test possible mitigation methods in magnetic fields, we have installed a new 4-dipole chicane experiment in the PEP-II Low Energy Ring (LER) at SLAC with both bare and TiN-coated aluminum chambers. In particular, we have observed a large variation of the electron flux at the chamber wall as a function of the chicane dipole field. We infer this is a new high order resonance effect where the energy gained by the electrons in the positron beam depends on the phase of the electron cyclotron motion with respect to the bunch crossing, leading to a modulation of the secondary electron production. Presumably the cloud density is modulated as well and this resonance effect could be used to reduce its magnitude in future colliders. We present the experimental results obtained during January 2008 until the April final shut-down of the PEP-II machine.
Date: July 3, 2008
Creator: Pivi, M. T. F.; Ng, J. S. T.; Arnett, D.; Cooper, F.; Kharakh, D.; King, F. K. et al.
Object Type: Article
System: The UNT Digital Library
Quantum Phase Transitions and New Scales in QCD-Like Theories (open access)

Quantum Phase Transitions and New Scales in QCD-Like Theories

It is commonly believed that in confining vector-like gauge theories the center and chiral symmetry realizations are parametrically entangled, and if phase transitions occur, they must take place around the strong scale {Lambda}{sup -1} of the gauge theory. We demonstrate that (non-thermal) vector-like theories formulated on R{sup 3} x S{sup 1} where S{sup 1} is a spatial circle exhibit new dynamical scales and new phenomena. There are chiral phase transitions taking place at {Lambda}{sup -1}/N{sub c} in the absence of any change in center symmetry. {Lambda}{sup -1}/N{sub c}, invisible in (planar) perturbation theory, is also the scale where abelian versus non-abelian confinement regimes meet. Large N{sub c} volume independence (a working Eguchi-Kawai reduction) provides new insights and independently confirms the existence of these scales. We show that certain phases and scales are outside the reach of holographic (supergravity) modeling of QCD.
Date: July 3, 2008
Creator: Unsal, Mithat
Object Type: Report
System: The UNT Digital Library
Local Area Signal-to-Noise Ratio (LASNR) algorithm for Image Segmentation (open access)

Local Area Signal-to-Noise Ratio (LASNR) algorithm for Image Segmentation

Many automated image-based applications have need of finding small spots in a variably noisy image. For humans, it is relatively easy to distinguish objects from local surroundings no matter what else may be in the image. We attempt to capture this distinguishing capability computationally by calculating a measurement that estimates the strength of signal within an object versus the noise in its local neighborhood. First, we hypothesize various sizes for the object and corresponding background areas. Then, we compute the Local Area Signal to Noise Ratio (LASNR) at every pixel in the image, resulting in a new image with LASNR values for each pixel. All pixels exceeding a pre-selected LASNR value become seed pixels, or initiation points, and are grown to include the full area extent of the object. Since growing the seed is a separate operation from finding the seed, each object can be any size and shape. Thus, the overall process is a 2-stage segmentation method that first finds object seeds and then grows them to find the full extent of the object. This algorithm was designed, optimized and is in daily use for the accurate and rapid inspection of optics from a large laser system (National Ignition …
Date: July 3, 2007
Creator: Kegelmeyer, L; Fong, P; Glenn, S & Liebman, J
Object Type: Article
System: The UNT Digital Library
(2,2-Bipyridyl)bis(eta5-1,2,3,4,5-pentamethylcyclopentadienyl)Strontium(II) (open access)

(2,2-Bipyridyl)bis(eta5-1,2,3,4,5-pentamethylcyclopentadienyl)Strontium(II)

In the title compound, the Sr-N distances are 2.624 (3) and 2.676 (3) Angstroms. The Sr-centroid distances are 2.571 and 2.561 Angstroms. The N-C-C-N torsion angle in the bipyridine ligand is 2.2 (4){sup o}. Interestingly, the bipyridine ligand is tilted. The angle between the plane defined by Sr1, N1 and N2 and the plane defined by the 12 atoms of the bipyridine ligand is 10.7{sup o}.
Date: July 3, 2008
Creator: Kazhdan, Daniel; Kazhdan, Daniel; Hu, Yung-Jin; Kokai, Akos; Levi, Zerubba & Rozenel, Sergio
Object Type: Article
System: The UNT Digital Library
DE-FG02-06ER15364: Final Technical Report Nanoscale Reactivity of Clays, Clay Analogues (Micas), and Clay Minerals (open access)

DE-FG02-06ER15364: Final Technical Report Nanoscale Reactivity of Clays, Clay Analogues (Micas), and Clay Minerals

The project objectives were to determine the nanoscale to molecular scale structure of the interface between muscovite mica and aqueous solutions containing various sorbates and to explore systematics that control the incorporation of inorganic and organic chemical components during aging of nanoparticles of iron-oxides and aluminosilicate clays. The basal surface of phyllosilicates is a primary sorbent of environmental contaminants, natural organic matter, and nutrients. Micas are also superb atomically-flat substrates used in materials science and surface physics applications. We applied X-ray scattering techniques using high brilliance synchrotron radiation to investigate molecular-scale details of mica’s interface structure in solutions containing common and toxic cations, anions, and natural organic molecules. Nanoparticles are ubiquitous in the environment and have a high capacity for sorbing contaminants through the combined effects of their high surface areas and pH-dependent surface charge. Aging of nanoparticles from metastable to stable phases can be inhibited by sorption of nonstructural components, but exact mechanisms are unknown. We synthesized Fe-oxides and aluminosilicate clay minerals from aqueous solutions in the presence of selected anions, and organic molecules, and quantified the uptake of these additives during aging and some implications for nanoparticle formation.
Date: July 3, 2008
Creator: Nagy, Kathryn L.
Object Type: Report
System: The UNT Digital Library
Automated analysis for detecting beams in laser wakefield simulations (open access)

Automated analysis for detecting beams in laser wakefield simulations

Laser wakefield particle accelerators have shown the potential to generate electric fields thousands of times higher than those of conventional accelerators. The resulting extremely short particle acceleration distance could yield a potential new compact source of energetic electrons and radiation, with wide applications from medicine to physics. Physicists investigate laser-plasma internal dynamics by running particle-in-cell simulations; however, this generates a large dataset that requires time-consuming, manual inspection by experts in order to detect key features such as beam formation. This paper describes a framework to automate the data analysis and classification of simulation data. First, we propose a new method to identify locations with high density of particles in the space-time domain, based on maximum extremum point detection on the particle distribution. We analyze high density electron regions using a lifetime diagram by organizing and pruning the maximum extrema as nodes in a minimum spanning tree. Second, we partition the multivariate data using fuzzy clustering to detect time steps in a experiment that may contain a high quality electron beam. Finally, we combine results from fuzzy clustering and bunch lifetime analysis to estimate spatially confined beams. We demonstrate our algorithms successfully on four different simulation datasets.
Date: July 3, 2008
Creator: Ushizima, Daniela M.; Rubel, Oliver; Prabhat, Mr.; Weber, Gunther H.; Bethel, E. Wes; Aragon, Cecilia R. et al.
Object Type: Article
System: The UNT Digital Library
Algorithm refinement for fluctuating hydrodynamics (open access)

Algorithm refinement for fluctuating hydrodynamics

This paper introduces an adaptive mesh and algorithmrefinement method for fluctuating hydrodynamics. This particle-continuumhybrid simulates the dynamics of a compressible fluid with thermalfluctuations. The particle algorithm is direct simulation Monte Carlo(DSMC), a molecular-level scheme based on the Boltzmann equation. Thecontinuum algorithm is based on the Landau-Lifshitz Navier-Stokes (LLNS)equations, which incorporate thermal fluctuations into macroscopichydrodynamics by using stochastic fluxes. It uses a recently-developedsolver for LLNS, based on third-order Runge-Kutta. We present numericaltests of systems in and out of equilibrium, including time-dependentsystems, and demonstrate dynamic adaptive refinement by the computationof a moving shock wave. Mean system behavior and second moment statisticsof our simulations match theoretical values and benchmarks well. We findthat particular attention should be paid to the spectrum of the flux atthe interface between the particle and continuum methods, specificallyfor the non-hydrodynamic (kinetic) time scales.
Date: July 3, 2007
Creator: Williams, Sarah A.; Bell, John B. & Garcia, Alejandro L.
Object Type: Article
System: The UNT Digital Library
Lattice Design of PEP-X as a Light Source Machine at SLAC (open access)

Lattice Design of PEP-X as a Light Source Machine at SLAC

SLAC is studying an option of building a high brightness synchrotron light source machine, PEP-X, in the existing PEP-II tunnel [1]. The new machine will replace the PEPII High Energy Ring (HER) with the goal of achieving an ultra low emittance of {approx} 0.1 nm-rad at 4.5 GeV. The PEPX will utilize the same layout as in the PEP-II with 6 arcs and 6 long straight sections. The existing RF and injection systems will be re-used. The two HER FODO arcs will be replaced with the DBA arcs providing 30 dispersion free 4.26 m sections for magnetic undulators. The other four arcs will be replaced with the TME lattice for attaining the low emittance. Finally, a 89.3 m long damping wiggler with 10 cm period and 1.5 T maximum magnetic field will be installed in a long straight section to reduce the natural emittance to 0.094 nm-rad. The PEP-X dynamic aperture was studied and found sufficient for a vertical injection.
Date: July 3, 2008
Creator: Wang, Min-Huey; Cai, Yunhai; Hettel, Robert & Nosochkov, Yuri
Object Type: Article
System: The UNT Digital Library
Secondary Electron Yield Measurements and Groove Chambers Tests in the PEP-II Beam Line Straights Sections (open access)

Secondary Electron Yield Measurements and Groove Chambers Tests in the PEP-II Beam Line Straights Sections

Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron Damping Ring (DR) of future Linear Colliders such as ILC and CLIC [1, 2]. In the Positron Low Energy Ring (LER) of the PEP-II accelerator, we have installed vacuum chambers with rectangular grooves in a straight magnetic-free section to test this promising possible electron cloud mitigation technique. We have also installed a special chamber to monitor the secondary electron yield of TiN and TiZrV (NEG) coating, Copper, Stainless Steel and Aluminum under the effect of electron and photon conditioning in situ in the beam line. In this paper, we describe the ongoing R&D effort to mitigate the electron cloud effect for the ILC damping ring, the latest results on in situ secondary electron yield conditioning and recent update on the groove tests in PEP-II.
Date: July 3, 2008
Creator: Pivi, M. T. F.; King, F.; Kirby, R. E.; Markiewicz, T; Raubenheimer, T. O.; Seeman, J. et al.
Object Type: Article
System: The UNT Digital Library
Search for Oscillation of the Electron-Capture Decay Probability of Pm-142 (open access)

Search for Oscillation of the Electron-Capture Decay Probability of Pm-142

We have searched for time modulation of the electron capture decay probability of 142Pm in an attempt to confirm a recent claim from a group at the Gesellschaft fur Schwerionenforschung (GSI). We produced 142Pm via the 124Sn(23Na, 5n)142Pm reaction at the Berkeley 88-Inch Cyclotron with a bombardment time short compared to the reported modulation period. Isotope selection by the Berkeley Gas-filled Separator is followed by implantation and a long period of monitoring the 142Nd K alpha x-rays from the daughter. The decay time spectrum of the x-rays is well-described by a simple exponential and the measured half-life of 40.68(53) seconds is consistent with the accepted value. We observed no oscillatory modulation at the proposed frequency at a level 31 times smaller than that reported by Litvinov (Phys. Lett. B 664 (2008) 162). A literature search for previous experiments that might have been sensitive to the reported modulation uncovered another example in 142Eu electron-capture decay. A reanalysis of the published data shows no oscillatory behavior.
Date: July 3, 2008
Creator: Vetter, Paul A; Vetter, Paul; Clark, Roderick; Dvorak, Jan; Freedman, Stuart; Gregorich, Kenneth et al.
Object Type: Article
System: The UNT Digital Library
Neutron-Absorbing Coatings for Safe Storage of Fissile Materials with Enhanced Shielding & Criticality Safety (open access)

Neutron-Absorbing Coatings for Safe Storage of Fissile Materials with Enhanced Shielding & Criticality Safety

Neutron-absorbing Fe-based amorphous-metal coatings have been developed that are more corrosion resistant than other criticality-control materials, including Al-B{sub 4}C composites, borated stainless steels, and Ni-Cr-Mo-Gd alloys. The presence of relatively high concentration of boron in these coatings not only enhances its neutron-absorption capability, but also enables these coatings to exist in the amorphous state. Exceptional corrosion resistance has been achieved with these Fe-based amorphous-metal alloys through additions of chromium, molybdenum, and tungsten. The addition of rare earth elements such as yttrium has lowered the critical cooling rate of these materials, thereby rendering them more easily processed. Containers used for the storage of nuclear materials, and protected from corrosion through the application of amorphous metal coatings, would have greatly enhanced service lives, and would therefore provide greater long-term safety. Amorphous alloy powders have been successfully produced in multi-ton quantities with gas atomization, and applied to several half-scale spent fuel storage containers and criticality control structures with the high-velocity oxy-fuel (HVOF) thermal spray process. Salt fog testing and neutron radiography of these prototypes indicates that such an approach is viable for the production of large-scale industrial-scale facilities and containers. The use of these durable neutron-absorbing materials to coat stainless steel containers and …
Date: July 3, 2007
Creator: Choi, J.; Farmer, J.; Lee, C.; Fischer, L.; Boussoufi, M.; Liu, B. et al.
Object Type: Article
System: The UNT Digital Library