A novel model has been developed to capture size scale and gradient effects within the context of continuum crystal plasticity by explicitly incorporating details of dislocation transport, coupling dislocation transport to slip, evolving spatial distributions of dislocations consistent with the flux, and capturing the interactions among various dislocation populations. Dislocation flux and density are treated as nodal degrees of freedom in the finite element model, and they are determined as part of the global system of equations. The creation, annihilation and flux of dislocations between elements are related by transport equations. Crystallographic slip is coupled to the dislocation flux and the stress state. The resultant gradients in dislocation density and local lattice rotations are analyzed for geometrically necessary and statistically stored dislocation contents that contribute to strength and hardening. Grain boundaries are treated as surfaces where dislocation flux is restricted depending on the relative orientations of the neighboring grains. Numerical results show different behavior near free surfaces and non-deforming surfaces resulting from differing levels of dislocation transmission. Simulations also show development of dislocation pile-ups at grain boundaries and an increase in flow strength reminiscent of the Hall-Petch model. The dislocation patterns have a characteristic size independent of the numerical discretization.

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The objectives of this research project are to significantly extend the theoretical foundation and the modeling of radiation-induced microstructural changes in structural materials used in Generation IV nuclear reactors, and to derive from these microstructure models the constitutive laws for void swelling, irradiation creep and stress-induced swelling, as well as changes in mechanical properties. The need for the proposed research is based on three major developments and advances over the past two decades. First, new experimental discoveries have been made on void swelling and irradiation creep which invalidate previous theoretical models and empirical constitutive laws for swelling and irradiation creep. Second, recent advances in computational methods and power make it now possible to model the complex processes of microstructure evolution over long-term neutron exposures. Third, it is now required that radiation-induced changes in structural materials over extended lifetimes be predicted and incorporated in the design of Generation IV reactors. Our approach to modeling and data analysis is a dual one in accord with both the objectives to simulate the evolution of the microstructure and to develop design equations for macroscopic properties. Validation of the models through data analysis is therefore carried out at both the microscopic and the macroscopic levels. …

The authors are in the re-evaluating of all the actinide cross section evaluations in LLNL's ENDL database, starting with uranium and focusing on inventory changing reactions. This article describes their first serious pass at updating the uranium cross section data, including estimates of cross section uncertainties. Furthermore, they are developing new tools to automate the re-evaluation and this article contains some preliminary results from these codes, namely the {sup 235}U(n, 2n) and {sup 238}U(n, 2n) evaluations.

Gas scrubbers for air-pollution control of volatile organic compounds (VOC) cover a wide range of technologies. In this review, we have attempted to evaluate the single-pass scrubber destruction and removal efficiencies (DREs) for a range of gas-scrubber technologies. We have focused primarily on typical industrial DREs for the various technologies, typical problems, and any DRE-related experiential information available. The very limited literature citations found suggest significant differences between actual versus design performance in some technologies. The potentially significant role of maintenance in maintaining DREs was also investigated for those technologies. An in-depth portrayal of the entire gas scrubbing industry is elusive. Available literature sources suggest significant differences between actual versus design performance in some technologies. Lack of scrubber system maintenance can contribute to even larger variances. ''Typical'' industrial single-pass performance of commonly used VOC gas scrubbers generally ranged from {approx}80 to 99%. Imperfect solid and/or liquid particulates capture (possibly as low as 95% despite design for 99+% capture efficiency) can also lead to VOC releases. Changing the VOC composition in the gas stream without modifying scrubber equipment or operating conditions could also lead to significant deterioration in attainable destruction and removal efficiencies.

WET-ETCH FIGURING (WEF) is an automated method of precisely figuring optical materials by the controlled application of aqueous etchant solution. This technology uses surface-tension-gradient-driven flow to confine and stabilize a wetted zone of an etchant solution or other aqueous processing fluid on the surface of an object. This wetted zone can be translated on the surface in a computer-controlled fashion for precise spatial control of the surface reactions occurring (e.g. chemical etching). WEF is particularly suitable for figuring very thin optical materials because it applies no thermal or mechanical stress to the material. Also, because the process is stress-free the workpiece can be monitored during figuring using interferometric metrology, and the measurements obtained can be used to control the figuring process in real-time--something that cannot be done with traditional figuring methods.

This study was focused on meeting the following objectives concerning the process of methyl tertiary butyl ether (MTBE) biodegradation, with the goal of optimizing this process in situ: 1. Assess whether intrinsic bioattenuation of MTBE is feasible under aerobic conditions across several contaminated sites. 2. Determine the effect of co-contaminants, specifically water-soluble gasoline components (most notably benzene, toluene, ethylbenzene and xylenes [BTEX]) on MTBE biodegradation. 3. Determine whether microbial and/or chemical factors contribute to different MTBE degradative activities. 4. Isolate and characterize MTBE-degrading microorganisms from sediments in which MTBE biodegradation was observed.

This project had two main objectives. The first major goal was to develop new, powerful computational simulation capabilities. It was important that these tools have the combination of the accuracy needed to describe the quantum mechanical nature of nanoscale systems and the efficiency required to be applied to realistic, experimentally derived materials. The second major goal was to apply these computational methods to calculate and predict the properties of quantum dots--initially composed of silicon, but then of other elements--which could be used to build novel nanotechnology devices. The driving factor of our purpose has been that, through the development and successful application of these tools, we would generate a new capability at LLNL that could be used to make nanostructured materials ''smarter'', e.g., by selectively predicting how to engineering specific, desired properties. To carry out the necessary work to successfully complete this project and deliver on our goals, we established a two-pronged effort from the beginning: (1) to work on developing new, more efficient algorithms and quantum simulation tools, and (2) to solve problems and make predictions regarding properties of quantum dots which were being studied experimentally here at Livermore.

Extreme conditions of density and temperature of interest to DNT are similar to conditions of low-altitude atmospheres of neutron stars. Consequently, HED experimental capabilities being developed at LLNL (NIF, petawatt lasers) will open the door to laboratory studies of neutron star atmospheres. This capability will seed a new era in the study of extreme physics generated by strongly radiation dominated flows and laser-plasma interactions for the laboratory study of distant astrophysical phenomena. Indeed as has been noted by the recent Davidsen report on Frontiers of HEDPP (p. 85) ''Accretion disks and atmospheres of neutron stars likely fall in the radiation-dominated regimes, where the radiation pressure dominates the particle pressure. Unique dynamics can ensue in such a radiation dominated plasma, especially in the presence of turbulent flows and magnetic fields. With the next generation of HED facilities such as ZR, NIF, coupled with ultra-intense laser ''heater beams'', it may become possible to create radiation-dominated plasma conditions in the laboratory relevant to neutron star (and black hole) accretion dynamics''. With the recent advent of the Rossi XTE time-resolved x-ray satellite, we have entered a new era in our ability to probe the physics and dynamics of neutron stars and black holes on …

Positron annihilation lifetime spectroscopy is a sensitive probe of vacancies and voids in materials. This non-destructive measurement technique can identify the presence of specific defects in materials at the part-per-million level. Recent experiments by Asoka-Kumar et al. have identified two lifetime components in aged plutonium samples--a dominant lifetime component of around 182 ps and a longer lifetime component of around 350-400ps. This second component appears to increase with the age of the sample, and accounts for only about 5 percent of the total intensity in 35 year-old plutonium samples. First-principles calculations of positron lifetimes are now used extensively to guide the interpretation of positron lifetime data. At Livermore, we have developed a first-principles finite-element-based method for calculating positron lifetimes for defects in metals. This method is capable of treating system cell sizes of several thousand atoms, allowing us to model defects in plutonium ranging in size from a mono-vacancy to helium-filled bubbles of over 1 nm in diameter. In order to identify the defects that account for the observed lifetime values, we have performed positron lifetime calculations for a set of vacancies, vacancy clusters, and helium-filled vacancy clusters in delta-plutonium. The calculations produced values of 143ps for defect-free delta-Pu and …

The INCCA (Integrated Climate and Carbon) strategic initiative developed and applied the ability to simulate the fate and climate impact of fossil fuel-derived carbon dioxide (CO{sub 2}) on a global scale. Coupled climate and carbon cycle modeling like that of INCCA is required to understand and predict the future environmental impacts of fossil fuel burning. At present, atmospheric CO{sub 2} concentrations are prescribed, not simulated, in large climate models. Credible simulations of the entire climate system, however, need to predict time-evolving climate forcing using anthropogenic emissions as the fundamental input. Predicting atmospheric CO{sub 2} concentrations represents a substantial scientific advance because there are large natural sources and sinks of carbon that are likely to change as a result of climate change. Both terrestrial (e.g., vegetation on land) and oceanic components of the carbon cycle are known to be sensitive to climate change. Estimates of the amount of man-made CO{sub 2} that will accumulate in the atmosphere depend on understanding the carbon cycle. For this reason, models that use CO{sub 2} emissions, not prescribed atmospheric concentrations, as fundamental inputs are required to directly address greenhouse-related questions of interest to policymakers.

The goal of the project was to understand the effect of shocks on the subsequent mechanical response of metals. The framework revolves around the sequence and timing of events during shock loading. A shock will transmit through a solid at speed of several mm per {micro}s. The result of the shock passage is a step change in the velocity of the material. This subsequent velocity will cause deformation in the material that could extend in time to several 10s or 100s of {micro}s after the passage of the shock. How the material responds in this timeframe after shock passage is intimately related to its mechanical properties. The mechanical properties of interest are the stress-strain response, the susceptibility to localization, and the failure process. In short, the shock passes through a material first before it has time to move, however it does send the material into motion that causes mechanical deformation and usually some sort of failure.

This workshop was the first major activity in developing a strategic plan for high-performance networking in the Office of Science. Held August 13 through 15, 2002, it brought together a selection of end users, especially representing the emerging, high-visibility initiatives, and network visionaries to identify opportunities and begin defining the path forward.

This paper examines the explicit communication characteristics of several sophisticated scientific applications; which, by themselves, constitute a representative suite of publicly available benchmarks for large cluster architectures. By focusing on the Message Passing Interface (MPI) and by using hardware counters on the microprocessor, we observe each application's inherent behavioral characteristics: point-to-point and collective communication, and floating-point operations. Furthermore, we explore the sensitivities of these characteristics to both problem size and number of processors. Our analysis reveals several striking similarities across, our diverse set of applications including the use of collective operations, especially those collectives with very small data payloads. We also highlight a trend of novel applications parting with regimented, static communication patterns in favor of dynamically evolving patterns, as evidenced by our experiments on applications that use implicit linear solvers and adaptive mesh refinement. Overall, our study contributes a better understanding of the requirements of current and emerging paradigms of scientific computing in terms of their computation and communication demands.

Most optical pulses, even at the 10-femtosecond timescale, consist of several oscillations of the electric field. By producing and amplifying an ultra-broadband continuum, single cycle (e 3 fs) or shorter optical pulses may be generated. This requires a very challenging pulse-compression with sub-femtosecond accuracy. Production of these single-cycle pulses will lead to new generations of experiments in the areas of coherent control of chemical excitations and reactions, 0.1-fs high-order harmonic (XUV) generation for probing of materials and fast processes, and selective 3-D micron-scale material removal and modification. We activated the first stage of a planned three-stage optical parametric amplifier (OPA) that would ultimately produce sub-3 fs pulses. Active control with a learning algorithm was implemented to optimize the continuum generated in an argon-filled capillary and to control and optimize the final compressed pulse temporal shape. A collaboration was initiated to coherently control the population of different states upon dissociation of Rb{sub 2}. Except for one final optic, a pulse compressor and diagnostics were constructed to produce and characterize pulses in the 5-fs range from the first OPA stage.

Urban areas are likely locations for release of toxic material into the atmosphere, whether by accident or terrorist act. Both the Department of Energy, through the Chemical and Biological National Security Program, and the Department of Defense, through the Defense Threat Reduction Agency, are supporting simulation and experimental efforts to develop urban modeling capabilities. These developed tools would be used in response to the release of toxic material in populated urban centers. We are developing a capability to predict the detailed flow and dispersion in and around population centers, to address issues of response to release of toxic agents into the atmosphere. Due to the complexity of these problems and their great demand on computing power, the scientific community has not had the ability to address the urban problem previously. LLNL's unique combination of modeling capability and access to terascale computing resources allows us to address such problems. However, in regions with such small scale features and with heterogeneous building configurations and complex terrain, classical approaches with simplifying assumptions are no longer valid. Turbulence closure approximations that are employed in models with 5km resolution are inappropriate when the resolution is 3 orders of magnitude finer. Also, closure assumptions based on …

Achieving public acceptance has become a central issue in discussions regarding the future of nuclear power and associated nuclear activities. Effective public communication and public participation are often put forward as the key building blocks in garnering public acceptance. A recent international workshop in Finland provided insights into other features that might also be important to building and sustaining public confidence in nuclear activities. The workshop was held in Finland in close cooperation with Finnish stakeholders. This was most appropriate because of the recent successes in achieving positive decisions at the municipal, governmental, and Parliamentary levels, allowing the Finnish high-level radioactive waste repository program to proceed, including the identification and approval of a proposed candidate repository site Much of the workshop discussion appropriately focused on the roles of public participation and public communications in building public confidence. It was clear that well constructed and implemented programs of public involvement and communication and a sense of fairness were essential in building the extent of public confidence needed to allow the repository program in Finland to proceed. It was also clear that there were a number of other elements beyond public involvement that contributed substantially to the success in Finland to date. …

A Fresnel zone plate lens made with solar sail material could be used as the primary optic for a very large aperture telescope on deep space probes propelled by solar sails. The large aperture telescope capability could enable significant science on fly-by missions to the asteroids, Pluto, Kuiper belt or the tort cloud and could also enable meaningful interstellar fly-by missions for laser propelled sails. This type of lens may also have some potential for laser communications and as a solar concentrator. The techniques for fabrication of meter size and larger Fresnel phase plate optics are under development at LLNL, and we are extending this technology to amplitude zone plates made from sail materials. Corrector optics to greatly extend the bandwidth of these Fresnel optics will be demonstrated in the future. This novel telescope concept will require new understanding of the fabrication, deployment and control of gossamer space structures. It will also require new materials technology for fabricating these optics and understanding their long term stability in a space environment.

This report is the second in a series detailing the procedures used and the results obtained from studies designed to determine the impacts of erosion control structures on fish habitat at Willapa Bay, Washington. The erosion control structure, consisting of a 1600-ft rock groin and an attached 930-ft underwater dike was placed on Washaway Beach in 1998 to protect State Route (SR) 105 from erosion. The objectives of the study are to develop an understanding about whether groin-type structures on the outer coast can alter migratory movement or predation pressure on juvenile and adult salmon. Field surveys in this report were conducted from October 14-21, 2001, and consisted of gillnetting, passive drifter surveys, diver surveys, interviews with fishers and Washington Department of Fish and Wildlife (WDFW) personnel, bird and mammal surveys, and split beam hydroacoustic surveys. Field sampling activities were begun on October 14 and were suspended during the commercial gillnet season from October 16-18. Interviews with fishers and WDFW were conducted during that period, and field sampling recommenced on October 19. The hydroacoustic surveys were conducted from October 19-21. The migration pattern of fish, presumed to be salmon, was documented relative to the tidal phase. Fish were observed to …

The purpose of the Workshop 'Excellence Empowered by a Diverse Academic Workforce: Achieving Racial & Ethnic Equity in Chemistry' was to promote the development of a cadre of academic leaders who create, implement and promote programs and strategies for increasing the number of racial and ethnic minorities to equitable proportions on the faculties of departments throughout the academic chemistry community. An important objective of the workshop was to assist in creating an informed and committed community of chemistry leaders who will create, implement and promote programs and strategies to advance racial and ethnic equity in both the faculty and the student body with the goal of increasing the number of U.S. citizen underrepresented minorities (URM) participating in academic chemistry at all levels, with particular focus on the pipeline to chemistry faculty. This objective was met by (1) presentations of detailed data describing current levels of racial and ethnic minorities on the faculties of chemistry departments; (2) frank discussion of the obstacles to and benefits of racial/ethnic diversity in the chemistry professoriate; (3) summary of possible effective interventions and actions; and (4) promotion of the dissemination and adoption of initiatives designed to achieve racial/ethnic equity. Federal programs over the past thirty …

We show that backward-forward elliptic asymmetry correlations provide an experimentally accessible observable which distinguishes between collective and non-collective contributions to the observed elliptic asymmetry v2 in relativistic heavy ion collisions. The measurement of this observable will reveal the momentum scale at which collective expansion seizes and where the elliptic asymmetry is dominated by (semi)-hard processes. In addition, the knowledge of the actual magnitude of the collective component of the elliptic asymmetry will be essential for the extraction of the viscosity of the matter created in these collisions.

A testing program evaluating actual tank waste was developed in response to Task 4 from the M-12 External Flowsheet Review Team (EFRT) issue response plan.(a) The testing program was subdivided into logical increments. The bulk water-insoluble solid wastes that are anticipated to be delivered to the Waste Treatment and Immobilization Plant (WTP) were identified according to type such that the actual waste testing could be targeted to the relevant categories. Eight broad waste groupings were defined. Samples available from the 222S archive were identified and obtained for testing. The actual wastetesting program included homogenizing the samples by group, characterizing the solids and aqueous phases, and performing parametric leaching tests. Two of the eight defined groups—plutonium-uranium extraction (PUREX) cladding waste sludge (Group 3, or CWP) and reduction-oxidation (REDOX) cladding waste sludge (Group 4, or CWR)—are the subjects of this report. Both the Group 3 and 4 waste composites were anticipated to be high in gibbsite, requiring caustic leaching. Characterization of the composite Group 3 and Group 4 waste samples confirmed them to be high in gibbsite. The focus of the Group 3 and 4 testing was on determining the behavior of gibbsite during caustic leaching. The waste-type definition, archived sample conditions, …

The CTMC method is used to calculate emission cross sections following charge exchange collisions involving highly charged ions of astrophysical interest and typical cometary targets. Comparison is made to experimental data obtained on the EBIT machine at Lawrence Livermore National Laboratory (LLNL) for O{sup 8+} projectiles impinging on different targets at a collision energy of 10 eV/amu. The theoretical cross sections are used together with ion abundances measured by the Advanced Composition Explorer as well as those obtained by a fitting procedure using laboratory emission cross sections in order to reproduce the x-ray spectrum of comet C/LINEAR S4 measured on July 14th 2001.

Line-edge roughness (LER) and the related effect of contact size variation remain as significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. LER is typically viewed as a resist problem; however, recent simulation results have shown that the mask can indeed be an important contributor. Problems arise from both mask absorber LER as well as mask multilayer roughness leading to random phase variations in the reflected beam (see Fig. 1). The latter effect is especially important as higher coherence off-axis illumination conditions are used and defocus is considered. Here we describe these effect in detail and explore how they will impact EUV mask requirements for the 22-nm half-pitch node and beyond. Figure 2 shows modeling results for 22-nm lines printed in a 0.32-numerical aperture system with 100-nm defocus assuming a mask with 0.24-nm rms multilayer roughness and no absorber edge roughness (unlike the example in Fig. 1). The impact of the phase roughness on the printed line-edge roughness is clearly evident and demonstrates the basic problem with mask roughness. The more detailed modeling-based analysis to be presented will account for performance throughout the process window as well as non-stochastic resist effects. We note that the mean-field resist effect is …