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Age-Based Methods to Explore Time-Related Variables in Occupational Epidemiology Studies (open access)

Age-Based Methods to Explore Time-Related Variables in Occupational Epidemiology Studies

Although age is recognized as the strongest predictor of mortality in chronic disease epidemiology, a calendar-based approach is often employed when evaluating time-related variables. An age-based analysis file, created by determining the value of each time-dependent variable for each age that a cohort member is followed, provides a clear definition of age at exposure and allows development of diverse analytic models. To demonstrate methods, the relationship between cancer mortality and external radiation was analyzed with Poisson regression for 14,095 Oak Ridge National Laboratory workers. Based on previous analysis of this cohort, a model with ten-year lagged cumulative radiation doses partitioned by receipt before (dose-young) or after (dose-old) age 45 was examined. Dose-response estimates were similar to calendar-year-based results with elevated risk for dose-old, but not when film badge readings were weekly before 1957. Complementary results showed increasing risk with older hire ages and earlier birth cohorts, since workers hired after age 45 were born before 1915, and dose-young and dose-old were distributed differently by birth cohorts. Risks were generally higher for smokingrelated than non-smoking-related cancers. It was difficult to single out specific variables associated with elevated cancer mortality because of: (1) birth cohort differences in hire age and mortality experience …
Date: August 31, 2005
Creator: Janice P. Watkins, Edward L. Frome, Donna L. Cragle
System: The UNT Digital Library
Laser coupling to reduced-scale targets at NIF Early Light (open access)

Laser coupling to reduced-scale targets at NIF Early Light

Deposition of maximum laser energy into a small, high-Z enclosure in a short laser pulse creates a hot environment. Such targets were recently included in an experimental campaign using the first four of the 192 beams of the National Ignition Facility [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technology 26, 755 (1994)], under construction at the University of California Lawrence Livermore National Laboratory. These targets demonstrate good laser coupling, reaching a radiation temperature of 340 eV. In addition, the Raman backscatter spectrum contains features consistent with Brillouin backscatter of Raman forward scatter [A. B. Langdon and D. E. Hinkel, Physical Review Letters 89, 015003 (2002)]. Also, NIF Early Light diagnostics indicate that 20% of the direct backscatter from these reduced-scale targets is in the polarization orthogonal to that of the incident light.
Date: August 31, 2005
Creator: Hinkel, D. E.; Schneider, M. B.; Young, B. K.; Holder, J. P.; Langdon, A. B.; Baldis, H. A. et al.
System: The UNT Digital Library
Mass streams for spacecraft propulsion and energy generation (open access)

Mass streams for spacecraft propulsion and energy generation

A speculative propulsion concept is presented, based on accelerating a spacecraft by impact of a stream of matter in relative motion with respect to the spacecraft. To accelerate the stream to the needed velocity the stream mass is contained in a transit vehicle, launched at low velocity and hence low energy cost, and then sent on a trajectory with near encounters of the planets for gravitational assist. The mass arrives at Earth or wherever the propellant is needed at much higher velocity and kinetic energy, where it is released into an extended stream suitable for propulsion. The stream, moving at a relative velocity in the range of 10 to 30km/s, should be capable of both high thrust and high specific impulse. Means of limiting the transverse expansion of the stream during release and for the {approx}1000 seconds duration of impact are a critical requirement for practicality of the concept. The scheme could potentially lead to a virtually unlimited energy source. One can imagine using a portion of one stream to launch another, larger payload on a similar trajectory. This creates, in effect, an energy amplifier extracting energy from the orbital motions of the planets. The gain of the energy amplifier …
Date: August 31, 2005
Creator: Hammer, J H
System: The UNT Digital Library
The Mercury Laser System: An Average power, gas-cooled, Yb:S-FAP based system with frequency conversion and wavefront correction (open access)

The Mercury Laser System: An Average power, gas-cooled, Yb:S-FAP based system with frequency conversion and wavefront correction

We report on the operation of the Mercury laser with fourteen 4 x 6 cm{sup 2} Yb:S-FAP amplifier slabs pumped by eight 100 kW peak power diode arrays. The system was continuously run at 55 J and 10 Hz for several hours, (2 x 10{sup 5} cumulative shots) with over 80% of the energy in a 6 times diffraction limited spot at 1.047 um. Improved optical quality was achieved in Yb:S-FAP amplifiers with magneto-rheological finishing, a deterministic polishing method. In addition, average power frequency conversion employing YCOB was demonstrated at 50% conversion efficiency or 22.6 J at 10 Hz.
Date: August 31, 2005
Creator: Bibeau, C.; Bayramian, A.; Armstrong, P.; Ault, E.; Beach, R.; Benapfl, M. et al.
System: The UNT Digital Library
Modeling NIF Experimental Designs with Adaptive Mesh Refinement and Lagrangian Hydrodynamics (open access)

Modeling NIF Experimental Designs with Adaptive Mesh Refinement and Lagrangian Hydrodynamics

Incorporation of adaptive mesh refinement (AMR) into Lagrangian hydrodynamics algorithms allows for the creation of a highly powerful simulation tool effective for complex target designs with three-dimensional structure. We are developing an advanced modeling tool that includes AMR and traditional arbitrary Lagrangian-Eulerian (ALE) techniques. Our goal is the accurate prediction of vaporization, disintegration and fragmentation in National Ignition Facility (NIF) experimental target elements. Although our focus is on minimizing the generation of shrapnel in target designs and protecting the optics, the general techniques are applicable to modern advanced targets that include three-dimensional effects such as those associated with capsule fill tubes. Several essential computations in ordinary radiation hydrodynamics need to be redesigned in order to allow for AMR to work well with ALE, including algorithms associated with radiation transport. Additionally, for our goal of predicting fragmentation, we include elastic/plastic flow into our computations. We discuss the integration of these effects into a new ALE-AMR simulation code. Applications of this newly developed modeling tool as well as traditional ALE simulations in two and three dimensions are applied to NIF early-light target designs.
Date: August 31, 2005
Creator: Koniges, A E; Anderson, R W; Wang, P; Gunney, B N; Becker, R; Eder, D C et al.
System: The UNT Digital Library
OPTIMIZATION OF EXPERIMENTAL DESIGNS BY INCORPORATING NIF FACILITY IMPACTS (open access)

OPTIMIZATION OF EXPERIMENTAL DESIGNS BY INCORPORATING NIF FACILITY IMPACTS

For experimental campaigns on the National Ignition Facility (NIF) to be successful, they must obtain useful data without causing unacceptable impact on the facility. Of particular concern is excessive damage to optics and diagnostic components. There are 192 fused silica main debris shields (MDS) exposed to the potentially hostile target chamber environment on each shot. Damage in these optics results either from the interaction of laser light with contamination and pre-existing imperfections on the optic surface or from the impact of shrapnel fragments. Mitigation of this second damage source is possible by identifying shrapnel sources and shielding optics from them. It was recently demonstrated that the addition of 1.1-mm thick borosilicate disposable debris shields (DDS) block the majority of debris and shrapnel fragments from reaching the relatively expensive MDS's. However, DDS's cannot stop large, faster moving fragments. We have experimentally demonstrated one shrapnel mitigation technique showing that it is possible to direct fast moving fragments by changing the source orientation, in this case a Ta pinhole array. Another mitigation method is to change the source material to one that produces smaller fragments. Simulations and validating experiments are necessary to determine which fragments can penetrate or break 1-3 mm thick DDS's. …
Date: August 31, 2005
Creator: Eder, D. C.; Whitman, P. K.; Koniges, A. E.; Anderson, R. W.; Wang, P.; Gunney, B. T. et al.
System: The UNT Digital Library
Study of Scattered Background Neutron in NIF and Time-of Flight (TOF) to Measure Neutron (open access)

Study of Scattered Background Neutron in NIF and Time-of Flight (TOF) to Measure Neutron

Some of the planned core diagnostics for National Ignition Facility (NIF) will use neutron time-of-flight (TOF) spectroscopy techniques to gather information for primary neutron yield measurement or neutron imaging. This technique has been widely and routinely used at other laser facilities including Nova and Omega. TOF methods will also be used to observe target fuel areal density <{rho}R> (radial integral of density) via measuring the number of primary 14.1 MeV neutrons that are down-scattered to lower energies by nuclear collisions inside the compressed target core. The substantially larger target chamber size and higher neutron yield for NIF raises issues related to the large number of scattered neutrons produced by high yield deuterium-tritium (D-T) shots at NIF. The effect of primary neutrons scattered by the walls of the massive target chamber and structures both inside and outside the chamber will contribute a significant scattered background signal when trying to determine the number of neutrons down-scattered from the target core. The optimum detector locations outside the target chamber or target bay wall will be proposed. Appropriate collimators at the chamber port and the bay wall (between the neutron source at target chamber center (TCC) and detector) that maximize detection of signal neutrons …
Date: August 31, 2005
Creator: Song, P.; Moran, M.; Phillips, T.; Lerche, R.; Koch, J. & Eder, D.
System: The UNT Digital Library
Tenascin-X, Collagen, Elastin and the Ehlers-Danlos Syndrome (open access)

Tenascin-X, Collagen, Elastin and the Ehlers-Danlos Syndrome

Tenascin-X is an extracellular matrix protein initially identified because of its overlap with the human CYP21B gene. Because studies of gene and protein function of other tenascins had been poorly predictive of essential functions in vivo, we used a genetic approach that critically relied on an understanding of the genomic locus to uncover an association between inactivating tenascin-X mutations and novel recessive and dominant forms of Ehlers-Danlos syndrome. Tenascin-X provides the first example of a gene outside of the fibrillar collagens and their processing enzymes that causes Ehlers-Danlos syndrome. Tenascin-X null mice recapitulate the skin findings of the human disease, confirming a causative role for this gene in Ehlers-Danlos syndrome. Further evaluation of these mice showed that tenascin-X is an important regulator of collagen deposition in vivo, suggesting a novel mechanism of disease in this form of Ehlers-Danlos syndrome. Further studies suggest that tenascin-X may do this through both direct and indirect interactions with the collagen fibril. Recent studies show that TNX effects on matrix extend beyond the collagen to the elastogenic pathway and matrix remodeling enzymes. Tenascin-X serves as a compelling example of how human experiments of nature can guide us to an understanding of genes whose function may …
Date: August 31, 2005
Creator: Bristow, James; Carey, William & Schalkwijk, Joost
System: The UNT Digital Library
Using Groundwater Age and Other Isotopic Signatures to Delineate Groundwater Flow and Stratification (open access)

Using Groundwater Age and Other Isotopic Signatures to Delineate Groundwater Flow and Stratification

Isotopic tracers, such as stable isotopes of the water molecule and tritium, have been used in investigations of groundwater flow and transport and recharge water source for several decades. While these data can place hard constraints on groundwater flow rates, the degree of vertical flow between aquifers and across aquitards, and recharge source area(s), they are rarely used, even for validation, in conceptual or numerical models of groundwater flow. The Groundwater Ambient Monitoring and Assessment Program, sponsored by the California State Water Resources Control Board, and carried out in collaboration with the U.S. Geological Survey, has provided the means to gather an unprecedented number of tritium-helium groundwater ages in the basins of California. As the examples below illustrate, a collection of groundwater ages in a basin allows delineation of recharge areas (youngest ages), bulk flow rates and flowpaths, as well as a means of assessing susceptibility to anthropogenic contaminants.
Date: August 31, 2005
Creator: Moran, J. E. & Hudson, G. B.
System: The UNT Digital Library
Active Control for Statistically Stationary Turbulent PremixedFlame Simulations (open access)

Active Control for Statistically Stationary Turbulent PremixedFlame Simulations

The speed of propagation of a premixed turbulent flame correlates with the intensity of the turbulence encountered by the flame. One consequence of this property is that premixed flames in both laboratory experiments and practical combustors require some type of stabilization mechanism to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. Furthermore, the stabilization introduces additional fluid mechanical complexity into the overall combustion process that can complicate the analysis of fundamental flame properties. To circumvent these difficulties we introduce a feedback control algorithm that allows us to computationally stabilize a turbulent premixed flame in a simple geometric configuration. For the simulations, we specify turbulent inflow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm on methane flames at various equivalence ratios in two dimensions. The simulation data are used to study the local variation in the speed of propagation due to flame surface curvature.
Date: August 30, 2005
Creator: Bell, J. B.; Day, M. S.; Grcar, J. F. & Lijewski, M. J.
System: The UNT Digital Library
CP Violation in B Meson Decays: Experimental Results (open access)

CP Violation in B Meson Decays: Experimental Results

CP violation is intimately connected with the puzzle of matter-antimatter asymmetry and baryogenesis. In the Standard Model of particle physics, the observed CP violation phenomena are accounted for by the Cabibbo-Kobayashi-Maskawa mechanism involving a phase in the quark mixing matrix. This paper is devoted to a review of the experimental status of CP violation in the decays of B mesons.
Date: August 30, 2005
Creator: Lanceri, Livio & /Trieste U. /INFN, Trieste
System: The UNT Digital Library
Fabrication of Planar Laser Targets with Sub-Micrometer Thickness Uniformity (open access)

Fabrication of Planar Laser Targets with Sub-Micrometer Thickness Uniformity

None
Date: August 30, 2005
Creator: Bono, M.; Castro, C.; Griffith, L.; Hibbard, R.; Kass, J. & Satcher, J.
System: The UNT Digital Library
Level densities of iron isotopes and lower-energy enhancement of y-strength function (open access)

Level densities of iron isotopes and lower-energy enhancement of y-strength function

The neutron spectrum from the {sup 55}Mn(d,n){sup 56}Fe reaction has been measured at E{sub d} = 7 MeV. The level density of {sup 56}Fe obtained from neutron evaporation spectrum has been compared to the level density from Oslo-type {sup 57}Fe({sup 3}He, a{gamma}){sup 56}Fe experiment [1]. The good agreement supports the recent results [1, 8] including an availability of a low-energy enhancement in the {gamma}-strength function for iron isotopes. The new level density function allowed us to investigate an excitation energy dependence of this enhancement, which is shown to increase with increasing excitation energy.
Date: August 30, 2005
Creator: Voinov, A. V.; Grimes, S. M.; Agvaanluvsan, U.; Algin, E.; Belgya, T.; Brune, C. R. et al.
System: The UNT Digital Library
Moving Overlapping Grids with Adaptive Mesh Refinement for High-Speed Reactive and Non-reactive Flow (open access)

Moving Overlapping Grids with Adaptive Mesh Refinement for High-Speed Reactive and Non-reactive Flow

We consider the solution of the reactive and non-reactive Euler equations on two-dimensional domains that evolve in time. The domains are discretized using moving overlapping grids. In a typical grid construction, boundary-fitted grids are used to represent moving boundaries, and these grids overlap with stationary background Cartesian grids. Block-structured adaptive mesh refinement (AMR) is used to resolve fine-scale features in the flow such as shocks and detonations. Refinement grids are added to base-level grids according to an estimate of the error, and these refinement grids move with their corresponding base-level grids. The numerical approximation of the governing equations takes place in the parameter space of each component grid which is defined by a mapping from (fixed) parameter space to (moving) physical space. The mapped equations are solved numerically using a second-order extension of Godunov's method. The stiff source term in the reactive case is handled using a Runge-Kutta error-control scheme. We consider cases when the boundaries move according to a prescribed function of time and when the boundaries of embedded bodies move according to the surface stress exerted by the fluid. In the latter case, the Newton-Euler equations describe the motion of the center of mass of the each body …
Date: August 30, 2005
Creator: Henshaw, W D & Schwendeman, D W
System: The UNT Digital Library
The National Ignition Facility Performance Status (open access)

The National Ignition Facility Performance Status

The National Ignition Facility (NIF) laser has been designed to support high energy density science (HEDS), including the demonstration of fusion ignition through Inertial Confinement. NIF operated a single ''quad'' of 4 beams from December 2002 through October 2004 in order to gain laser operations experience, support target experiments, and demonstrate laser performance consistent with NIF's design requirement. During this two-year period, over 400 Main Laser shots were delivered at 1{omega} to calorimeters for diagnostic calibration purposes, at 3{omega} to the Target Chamber, and at 1{omega}, 2{omega}, and 3{omega} to the Precision Diagnostics System (PDS). The PDS includes its own independent single beam transport system, NIF design frequency conversion hardware and optics, and laser sampling optics that deliver light to a broad range of laser diagnostics. Highlights of NIF laser performance will be discussed including the results of high energy 2{omega} and 3{omega} experiments, the use of multiple focal spot beam conditioning techniques, the reproducibility of laser performance on multiple shots, the generation on a single beam of a 3{omega} temporally shaped ignition pulse at full energy and power, and recent results on full bundle (8 beamline) performance. NIF's first quad laser performance meets or exceeds NIF's design requirements.
Date: August 30, 2005
Creator: Haynam, C.; Auerbach, J.; Nicola, J. D.; Dixit, S.; Heestand, G.; Henesian, M. et al.
System: The UNT Digital Library
A novel method to synthesize high purity, nanostructured copper (open access)

A novel method to synthesize high purity, nanostructured copper

Nanostructured high purity (99.999%) copper foils, 10 cm in diameter and 22-25 microns thick were produced using nanoscale multilayer technology. The foils were produced using five different layer thicknesses ranging from 1.25 to 43.6 nm (18,000 to 520 layers). This process delivers the ability to produce multiple large-scale samples during a single deposition run with very small residual stresses. Tensile and indentation tests demonstrate that the material produced is a high strength copper ({sigma}{sub y} {approx} 540-690 MPa).
Date: August 30, 2005
Creator: Hodge, A M; Wang, Y M & Barbee, T W
System: The UNT Digital Library
Thermal Neutron Capture Cross Sections of The Palladium Isotopes (open access)

Thermal Neutron Capture Cross Sections of The Palladium Isotopes

We have measured precise thermal neutron capture {gamma}-ray cross sections {sigma}{sub {gamma}} for all stable Palladium isotopes with the guided thermal neutron beam from the Budapest Reactor. The data were compared with other data from the literature and have been evaluated into the Evaluated Gamma-ray Activation File (EGAF)[1]. Total radiative neutron capture cross-sections {sigma}{sub 0} can be deduced from the sum of transition cross sections feeding the ground state of each isotope if the decay scheme is complete. The Palladium isotope decay schemes are incomplete, although transitions deexciting low-lying levels are known for each isotope. We have performed Monte Carlo simulations of the Palladium thermal neutron capture de-excitation schemes using the computer code DICEBOX [2]. This program generates a level scheme where levels below a critical energy E{sub crit} are taken from experiment, and those above E{sub crit} are calculated by a random discretization of an a priori known level density formula {rho}(E, J{sup {pi}}). Level de-excitation branching intensities are taken from experiment for levels below E{sub crit} and the capture state, or calculated for levels above E{sub crit} assuming an a priori photon strength function and applying allowed selection rules and a Porter-Thomas distribution of widths. The calculated feeding …
Date: August 30, 2005
Creator: Firestone, R. B.; Krticka, M.; McNabb, D. P.; Sleaford, B.; Agvaanluvsan, U.; Belgya, T. et al.
System: The UNT Digital Library
XRM2005 Conference Summary (open access)

XRM2005 Conference Summary

X-ray microscopy is at a state of rapid development. The presentations at the Conference covered the latest developments in the field.
Date: August 30, 2005
Creator: Kirz, Janos
System: The UNT Digital Library
Application of Sequence-based Methods in Human MicrobialEcology (open access)

Application of Sequence-based Methods in Human MicrobialEcology

Ecologists studying microbial life in the environment have recognized the enormous complexity of microbial diversity for many years, and the development of a variety of culture-independent methods, many of them coupled with high-throughput DNA sequencing, has allowed this diversity to be explored in ever greater detail. Despite the widespread application of these new techniques to the characterization of uncultivated microbes and microbial communities in the environment, their application to human health and disease has lagged behind. Because DNA based-techniques for defining uncultured microbes allow not only cataloging of microbial diversity, but also insight into microbial functions, investigators are beginning to apply these tools to the microbial communities that abound on and within us, in what has aptly been called the second Human Genome Project. In this review we discuss the sequence-based methods for microbial analysis that are currently available and their application to identify novel human pathogens, improve diagnosis of known infectious diseases, and to advance understanding of our relationship with microbial communities that normally reside in and on the human body.
Date: August 29, 2005
Creator: Weng, Li; Rubin, Edward M. & Bristow, James
System: The UNT Digital Library
CONFERENCE PROPOSAL: “Time-Resolved Vibrational Spectroscopy XII” (open access)

CONFERENCE PROPOSAL: “Time-Resolved Vibrational Spectroscopy XII”

None
Date: August 29, 2005
Creator: Heilweil, Edwin J. & Gustafson, Terry L.
System: The UNT Digital Library
Current Status of Deep Geological Repository Development (open access)

Current Status of Deep Geological Repository Development

This talk provided an overview of the current status of deep-geological-repository development worldwide. Its principal observation is that a broad consensus exists internationally that deep-geological disposal is the only long-term solution for disposition of highly radioactive nuclear waste. Also, it is now clear that the institutional and political aspects are as important as the technical aspects in achieving overall progress. Different nations have taken different approaches to overall management of their highly radioactive wastes. Some have begun active programs to develop a deep repository for permanent disposal: the most active such programs are in the United States, Sweden, and Finland. Other countries (including France and Russia) are still deciding on whether to proceed quickly to develop such a repository, while still others (including the UK, China, Japan) have affirmatively decided to delay repository development for a long time, typically for a generation of two. In recent years, a major conclusion has been reached around the world that there is very high confidence that deep repositories can be built, operated, and closed safely and can meet whatever safety requirements are imposed by the regulatory agencies. This confidence, which has emerged in the last few years, is based on extensive work around …
Date: August 29, 2005
Creator: Budnitz, R. J.
System: The UNT Digital Library
Establishing Ergonomics in Industrially Developing Countries (open access)

Establishing Ergonomics in Industrially Developing Countries

The introduction of ergonomics is an ongoing effort in industrially developing countries and will ultimately require an organized, programmatic approach spanning several countries and organizations. Our preliminary efforts with our partner countries of Viet Nam, Thailand, and Nicaragua have demonstrated that a one-time course is just the first step in a series of necessary events to provide skills and create an infrastructure that will have lasting impact for the host country. To facilitate that any sort of training has a lasting impact, it is recommended that host countries establish a 'contract' with class participants and the guest instructors for at least one follow-up visit so instructors can see the progress and support the participants in current and future efforts. With repeated exchanges, the class participants can become the 'in country experts' and the next generation of ergonomic trainers. Additionally, providing participants with an easy to use hazard assessment tool and methods for evaluating the financial impact of the project (cost/benefit analysis) will assist increase the likelihood of success and establish a foundation for future projects. In the future, developing trade and regionally/culturally specific 'ergonomics toolkits' can help promote broader implementation, especially where training resources may be limited.
Date: August 29, 2005
Creator: Stewart, K.; Silverstein, B. & Kiefer, M.
System: The UNT Digital Library
Hadron Physics in BaBar (open access)

Hadron Physics in BaBar

Some recent results in hadron physics from the BaBar experiment are discussed. In particular, the observation of two new charmed states, the D*{sub sJ}{sup +}(2317) and the D*{sub sJ}{sup +}(2457), is described, and results are presented on the first measurement of the rare decay mode of the B meson, B{sup 0} {pi}{sup 0}{pi}{sup 0}.
Date: August 29, 2005
Creator: Lafferty, G.D.
System: The UNT Digital Library
A Hybrid approach to molecular continuum processes combining Gaussian basis functions and the discrete variable representation (open access)

A Hybrid approach to molecular continuum processes combining Gaussian basis functions and the discrete variable representation

Gaussian basis functions, routinely employed in molecular electronic structure calculations, can be combined with numerical grid-based functions in a discrete variable representation to provide an efficient method for computing molecular continuum wave functions. This approach, combined with exterior complex scaling, obviates the need for slowly convergent single-center expansions, and allows one to study a variety of electron-molecule collision problems. The method is illustrated by computation of various bound and continuum properties of H2+.
Date: August 29, 2005
Creator: Rescigno, Thomas N.; Horner, Daniel A.; Yip, Frank L. & McCurdy, C. William
System: The UNT Digital Library