A simple, tunable, synthetic benchmark with a performance directly related to applications would be of great benefit to the scientific computing community. In this paper, we present a novel approach to develop such a benchmark. The initial focus of this project is on data access performance of scientific applications. First a hardware independent characterization of code performance in terms of address streams is developed. The parameters chosen to characterize a single address stream are related to regularity, size, spatial, and temporal locality. These parameters are then used to implement a synthetic benchmark program that mimics the performance of a corresponding code. To test the validity of our approach we performed experiments using five test kernels on six different platforms. The performance of most of our test kernels can be approximated by a single synthetic address stream. However in some cases overlapping two address streams is necessary to achieve a good approximation.

Cathryn H. Greenberg and George W. Tanner. 2004. Breeding pond selection and movement patterns by eastern spadefoot toads (Scaphiopus holbrookii) in relation to weather and edaphic conditions. J. Herp. 38(4):569-577. Abstract: Eastern Spadefoot Toads (Scaphiopus holbrookii) require fish-free, isolated, ephemeral ponds for breeding but otherwise inhabit the surrounding uplands, commonly xeric longleaf pine (Pinus palustris) –wiregrass (Aristida beyrichiana). Hence both pond and upland conditions can potentially affect their breeding biology, and population persistence. Hardwood invasion due to fire suppression in sandhills could alter upland and pond suitability by higher hardwood density and increased transpiration. In this paper we explore breeding and neonatal emigration movements in relation to weather, hydrological conditions of ponds, and surrounding upland matrices. We use 9 years of data from continuous monitoring with drift fences and pitfall traps at 8 ephemeral ponds in 2 upland matrices: regularly-burned, savanna-like sandhills (n = 4), and hardwood-invaded sandhills (n = 4). Neither adult nor neonate captures differed between ponds within the 2 upland matrices, suggesting that they are tolerant of upland heterogeneity created by fire frequency. Explosive breeding occurred during 9 periods and in all seasons; adults were captured rarely otherwise. At a landscape-level rainfall, maximum change in barometric pressure, …

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A method using liquid scintillation spectral analysis (LSSA) for analyzing mixtures of radionuclides in groundwater samples, which is fast, simple, and inexpensive, was developed and bench-tested. Samples can be measured in a field laboratory with a new commercial portable liquid scintillation instrument that provides advanced analysis, display, and computational features previously found only in large expensive laboratory models. Results can be available within hours from the time samples are collected. The analysis provides a good measure of total sample activity and a spectral index value that may detect changes in radionuclide distributions from previous analyses when counting statistic are adequate. If a sample shows no change, further analytical costs for it may be avoided. A method that rapidly and quantitatively concentrates very low levels of activity from liter-size samples in minutes was also tested. With some modest improvements in this step, this work offers a completely new methodology and approach to groundwater remediation, which can dramatically reduce analytical costs and speed monitored cleanup and closure in many types of radiological work programs.

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A 3-D image correlation system has been used to study the deformation behavior of high purity molybdenum single crystals. This system, in conjunction with a recently developed experimental apparatus, provides the full field displacement and strain data needed to validate dislocation dynamics simulations. The accuracy of the image correlation system was verified by comparing the results with data taken from conventional strain gage rosettes. In addition, a stress analysis has been performed to examine the non-uniformities in stress. The results of the analysis show that after the sample has been strain 2%, the axial stress in the sample varies by {+-} 20%.

The structure of KH{sub 2}PO{sub 4} single crystals (so-called KDP) irradiated with {approx} 3-ns, 355-nm laser pulses with fluences above the laser-induced breakdown threshold is studied by a combination of Raman scattering, photoluminescence, and soft x-ray absorption spectroscopies. We compare spectra from the as-grown material, surface and bulk laser-induced damage sites, as well as from KPO{sub 3} references. Results show that irradiation with fluences above the laser-induced breakdown threshold leads to stoichiometric changes at surface damage sites but not at bulk damage sites. New spectroscopic features are attributed to dehydration products. For the laser irradiation conditions used in this study, the decomposed near-surface layer absorbs photons at {approx} 3.4 eV (364 nm). These results may explain the recently reported fact that surface laser damage sites in KDP crystals tend to grow with subsequent exposure to high-power laser pulses, while bulk damage sites do not.

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We present an adaptive importance sampling method for quantifying the statistics of rare-event processes in atomistic simulations. The approach is based on an explicit evaluation of the probability that a sequence of states (or path) initiating in a state A leads to a reactive transition event to final state B. The importance sampling method seeks to bias the sampling of system trajectories such that those that contribute significantly, i.e. those that characterize reactive transitions, are generated more frequently. This is accomplished by means of an importance function, which modifies the transition probabilities among the microstates that comprise a path. For each problem there exists an optimal importance function, which biases that path sampling in such a manner that each path initiating in A leads to a successful event. The fact that the optimal function obeys a variational principle, then leads to an adaptive method in which a trial function form containing a set of adjustable parameters is chosen. The parameters are then adjusted so as to bring the trial function as close as possible to the optimal importance function. We demonstrate the method in two model problems.

The Yucca Mountain Drift Scale Test (DST) is a multiyear, large-scale underground heater test designed to study coupled thermal-hydrological-mechanical-chemical behavior in unsaturated fractured and welded tuff. As part of the international cooperative code-comparison project DECOVALEX, four research teams used four different numerical models to simulate and predict coupled thermal-hydrological-mechanical (THM) processes at the DST. The simulated processes included above-boiling temperature changes, liquid and vapor water movements, rock-mass stress and displacement, and THM-induced changes in fracture permeability. Model predictions were evaluated by comparison to measurements of temperature, water saturation,displacement, and air permeability. The generally good agreement between simulated and measured THM data shows that adopted continuum model approaches are adequate for simulating relevant coupled THM processes at the DST. Moreover, TM-induced rock-mass deformations were reasonably well predicted using elastic models, although some individual displacements appeared to be better captured using an elasto-plastic model. It is concluded that fracture closure/opening caused by change in normal stress across fractures is the dominant mechanism for TM-induced changes in intrinsic fracture permeability at the DST, whereas fracture shear dilation appears to be less significant. This indicates that TM-induced changes in intrinsic permeability at the DST, which are within one order of magnitude, tend to be …

The reaction of [Ta({double_bond}CHtBu)(CH{sub 2}tBu){sub 3}] or [Cp*Ta(CH{sub 3}){sub 4}] with a silica partially dehydroxylated at 700 C gives the corresponding monosiloxy surface complexes [({triple_bond}SiO)Ta({double_bond}CHtBu)(CH{sub 2}tBu){sub 2}] and [({triple_bond}SiO)Ta(CH{sub 3}){sub 3}Cp*] by eliminating a {sigma}-bonded ligand as the corresponding alkane (H-CH{sub 2}tBu or H-CH{sub 3}). EXAFS data show that an adjacent siloxane bridge of the surface plays the role of an extra surface ligand, which most likely stabilizes these complexes as in [({triple_bond}SiO)Ta({double_bond}CHtBu)(CH{sub 2}tBu){sub 2}({triple_bond}SiOSi{triple_bond})] (1a') and [({triple_bond}SiO)Ta(CH{sub 3}){sub 3}Cp*({triple_bond}SiOSi{triple_bond})] (2a'). In the case of [({triple_bond}SiO)Ta({double_bond}CHtBu)(CH{sub 2}tBu){sub 2}({triple_bond}SiOSi{triple_bond})], the structure is further stabilized by an additional interaction: a C-H agostic bond as evidenced by the small J coupling constant for the carbenic C-H (H{sub C-H} = 80 Hz), which was measured by J-resolved 2D solid-state NMR spectroscopy. The product selectivity in propane metathesis in the presence of [({triple_bond}SiO)Ta({double_bond}CHtBu)-(CH{sub 2}tBu){sub 2}({triple_bond}SiOSi{triple_bond})] (1a') as a catalyst precursor and the inactivity of the surface complex [({triple_bond}SiO)Ta-(CH{sub 3}){sub 3}Cp*({triple_bond}SiOSi{triple_bond})] (2a') show that the active site is required to be highly electrophilic and probably involves a metallacyclobutane intermediate.

In order for volume sources to deliver the current (e.g., 0.8 A of Ar{sup +} per module) and brightness necessary for heavy ion fusion (HIF), they must operate at high current density. Conventional extractor designs for 1 to 2 MeV run into voltage breakdown limitations and cannot easily produce the required current rise time (about one microsecond). We discuss two systems that can overcome these volume-extraction problems. Each uses multichannel preaccelerators followed by a single channel main accelerator. Fast beam switching is done in the low energy beamlet stages. A new design, utilizing concentric ring preaccelerators, was recently described for another application [2]. A more conventional design uses a large number of small round beamlets. In either case, the merging beamlets are angled toward the axis, a feature that dominates other focusing. By suitable adjustment of the individual angles, beam aberrations are reduced. Because of the high current density, the overall structure is compact. Emittance growth from merging of beamlets is calculated and scaling is discussed.

The National Ignition Facility (NIF) requires diagnostics to analyze high-energy density physics experiments. A VISAR (Velocity Interferometry System for Any Reflector) diagnostic has been designed to measure shock velocities, shock breakout times, and shock emission of targets with sizes from 1 to 5 mm. An 8-inch-diameter fused silica triplet lens collects light at f/3 inside the 30-foot-diameter vacuum chamber. The optical relay sends the image out an equatorial port, through a 2-inch-thick vacuum window, and into two interferometers. A 60-kW VISAR probe laser operates at 659.5 nm with variable pulse width. Special coatings on the mirrors and cutoff filters are used to reject the NIF drive laser wavelengths and to pass a band of wavelengths for VISAR, passive shock breakout light, or thermal imaging light (bypassing the interferometers). The first triplet can be no closer than 500 mm from the target chamber center and is protected from debris by a blast window that is replaced after every event. The front end of the optical relay can be temporarily removed from the equatorial port, allowing other experimenters to use that port. A unique resolution pattern has been designed to validate the VISAR diagnostic before each use. All optical lenses are on …

Ion-beam-synthesized {sup 74}Ge nanocrystals embedded in an amorphous silica matrix exhibit large compressive stresses in the as-grown state. The compressive stress is determined quantitatively by evaluating the Raman line shift referenced to the line position of free-standing nanocrystals. Post-growth thermal treatments lead to stress reduction. The stress relief process is shown to be governed by the diffusive flux of matrix atoms away from the local nanocrystal growth region. A theoretical model that quantitatively describes this process is presented.

Although it is well known that the rate of sintering is governed by deceleratory kinetics, it is often difficult to fit power-law and nth-order reaction models over broad time-temperature ranges. This work shows that a phenomenological model combining a reaction order with an activation energy distribution can correlate surface area as a function of sintering time and temperature over a greater range of those variables. Qualitatively, the activation energy distribution accounts the dependence of free energy on particle size and material defects, while the reaction order accounts for geometric factors such as a distribution of diffusion lengths. The model is demonstrated for sintering of hydroxyapatite using data of Bailliez and Nzihou (Chem. Eng. J. 98 (2004), 141-152).

We review the relationship between energy efficiency improvement measures and productivity in industry. We review over 70 industrial case studies from widely available published databases, followed by an analysis of the representation of productivity benefits in energy modeling. We propose a method to include productivity benefits in the economic assessment of the potential for energy efficiency improvement. The case-study review suggests that energy efficiency investments can provide a significant boost to overall productivity within industry. If this relationship holds, the description of energy-efficient technologies as opportunities for larger productivity improvements has significant implications for conventional economic assessments. The paper explores the implications this change in perspective on the evaluation of energy-efficient technologies for a study of the iron and steel industry in the US. This examination shows that including productivity benefits explicitly in the modeling parameters would double the cost-effective potential for energy efficiency improvement, compared to an analysis excluding those benefits. We provide suggestions for future research in this important area.

The proof-of-principle HGHG experiment at 5 {mu} [1, 2] and recent HGHG experiment at DUVFEL [3] have generated significant interests in the FEL community. The more relaxed requirement on electron beam current and emittance to generate coherent deep UV output with much narrower bandwidth and high pulse energy stability, as exhibited by the recent experiment, and its potential to be generalized to soft-x-ray FEL, have attracted much attention. Several labs, including BESSY, ELETRRA, LBL, MIT, and SSRF proposed the development of UVFEL based on HGHG principle or soft-x-ray FEL based on the cascaded HGHG principle [4, 5]. Among them SSRF has already started the construction of an FEL system based on the HGHG principle [6]. Hence it would be a contribution to be able to carry out a first proof-of-principle experiment of cascaded HGHG at DUVFEL. In this paper, we discuss this experiment and several associated experiments that can be carried out at BNL before this experiment and may also have important impact on the development of multi-stage cascaded HGHG FELs.

In an effort to build seismic models that are most consistent with multiple data sets, we have applied a new probabilistic inverse technique. This method uses a Markov Chain Monte Carlo (MCMC) algorithm to sample models from a prior distribution and test them against multiple data types to generate a posterior distribution. While computationally expensive, this approach has several advantages over a single deterministic model, notably the reconciliation of different data types that constrain the model, the proper handling of uncertainties, and the ability to include prior information. We also benefit from the advantage of forward modeling rather than inverting the data. Here, we use this method to determine the crust and upper mantle structure of the Yellow Sea and Korean Peninsula (YSKP) region. We discuss the data sets, parameterization and starting model, outline the technique and its implementation, observe the behavior of the inversion, and demonstrate some of the advantages of this approach.

Transmission measurements of niobium and zirconium at both extreme-ultraviolet (EUV) and ultraviolet, visible, and near infrared (UV/Vis/NIR) wavelengths are presented. Thin foils of various thicknesses mounted on nickel mesh substrates were measured, and these data were used to calculate the optical constants {delta} and {beta} of the complex refractive index n = 1- {delta} +i{beta}. {beta} values were calculated directly from the measured transmittance of the foils after normalizing for the nickel mesh. The average {beta} values for each set of foils are presented as a function of wavelength. The real (dispersive) part of the refractive index, {delta} was then calculated from Kramers-Kronig analysis by combining these {beta} values with those from previous experimental data and the atomic tables.

Tunability is one of the key aspects of any laser system. In High-Gain Harmonic Generation Free Electron Laser (HGHG FEL) the seed laser determines the output wavelength. Conventional scheme of tunable HGHG FEL requires tunable seed laser. The alternative scheme [1] is based on compression of the electron bunch with energy-time correlation (chirped bunch) in the FEL dispersive section. The chirped energy modulation, induced by the seed laser with constant wavelength, compressed as the whole bunch undergoes compression. In this paper we discuss experimental verification of the proposed approach at the DUV FEL [2,3] and compare experimental results with analytical estimates.

We present preliminary experimental results on evolution of properties of the DUV FEL [1,2] radiation along the radiator. Intercepting the electron beam at the different locations inside the undulator we recorded and analyzed transverse profiles, spectra and intensity of the FEL output. Shot-to-shot fluctuations of the FEL radiation may significantly affect the accuracy of measurement. In the paper we present and discuss a single-shot measurement technique, based on a special imaging system.

Atmospheric CO{sub 2} concentration ([CO{sub 2}]) is expected to rise from a current level of 372 {micro}mol mol{sup -1} to about 550 {micro}mol mol{sup -1} by the middle of the century (Prentice 2001). Accumulation of foliar carbohydrates is one of the most pronounced and universal changes observed in the leaves of C{sub 3} plants grown at elevated [CO{sub 2}] (Drake et al 1997). Carbohydrates are the product of photosynthetic cells and the substrate for sink metabolism. However, carbohydrates are not just substrates, changes in the composition and pool size of foliar carbohydrates have the potential to communicate source-sink balance and a role for carbohydrates in the regulation of the expression of many plant genes is well established (Koch 1996). Importantly, carbohydrate feedback is thought to be the mechanism through which long-term exposure to elevated [CO{sub 2}] leads to a reduction in carboxylation capacity (Rogers et a1 199S, Long et al 2004). Foliar sugar content has recently been linked to an increased susceptibility of soybeans to insect herbivory (Hamilton et al submitted). In addition increases in the C:N ratio of leaf litter of plants grown at elevated [CO{sub 2}] has been implicated in negative feedbacks on ecosystem productivity (Oechel et al …

Atomic structure codes have a difficult time accurately calculating the wavelengths of many-electron ions without the benefit of laboratory measurements. This is especially true for wavelengths of lines in the extreme ultraviolet and soft x-ray regions. We are using the low-energy capability of the Livermore electron beam ion traps to compile a comprehensive catalog of astrophysically relevant emission lines in support of satellite x-ray observations. Our database includes wavelength measurements, relative intensities, and line assignments, and is compared to a full set of calculations using the Hebrew University - Lawrence Livermore Atomic Code (HULLAC). Mean deviation of HULLAC calculations from our measured wavelength values is highest for L-shell transitions of neon-like ions and lowest for lithium-like ions, ranging from a mean deviation of over 0.5 {angstrom} for Si V to 12 m{angstrom} in Ar XVI.

The working group on computational accelerator physics at the 11th Advanced Accelerator Concepts Workshop held a series of meetings during the Workshop. Verification, i.e., showing that a computational application correctly solves the assumed model, and validation, i.e., showing that the model correctly describes the modeled system, were discussed for a number of systems. In particular, the predictions of the massively parallel codes, OSIRIS and VORPAL, used for modeling advanced accelerator concepts, were compared and shown to agree, thereby establishing some verification of both codes. In addition, a number of talks on the status and frontiers of computational accelerator physics were presented, to include the modeling of ultrahigh-brightness electron photoinjectors and the physics of beam halo production. Finally, talks discussing computational needs were presented.