An instrument combining an array of Cadmium-Zinc-Telluride (CZT) detectors, a NaI scintillator, and two {sup 3}He neutron detectors has been constructed. The instrument uses the CZT array to identify radioactive materials. As an example of this application, the 3 {sigma} Minimum Detectable Activity for the 375 keV peak of {sup 238}Pu is less than 1 gram at a distance of 20 cm for a 100-second counting time. The 2 x 2 NaI scintillator has a dual purpose. First, it is used to supplement the CZT array for identification of high-energy gammas, such as those from {sup 60}Co. Second, the principle use of the NaI scintillator is to help search for radioactive material and to find a suitable measurement location on a suspect package for the CZT-based isotope-identification measurement. This detector also produces energy-corrected exposure-rate data. The {sup 3}He neutron detectors provide an additional confirmation of the presence of some plutonium isotopes. The neutron sensitivity is 90 counts per second at 20 cm from a moderated {sup 252}Cf neutron source.

Large distributed systems such as Computational/Data Grids require large amounts of data to be co-located with the computing facilities for processing. Ensuring that the data is there in time for the computation in today's Internet is a massive problem. From our work developing a scalable distributed network cache, we have gained experience with techniques necessary to achieve high data throughput over high bandwidth Wide Area Networks (WAN). In this paper, we discuss several hardware and software design techniques and issues, and then describe their application to an implementation of an enhanced FTP protocol called GridFTP. We also describe results from two applications using these techniques, which were obtained at the Supercomputing 2000 conference.

Artifacts can result when reconstructing a dynamic image sequence from inconsistent single photon emission computed tomography (SPECT) projections acquired by a slowly rotating gantry. The artifacts can lead to biases in kinetic parameters estimated from time-activity curves generated by overlaying volumes of interest on the images. To overcome these biases in conventional image based dynamic data analysis, we have been investigating the estimation of time-activity curves and kinetic model parameters directly from dynamic SPECT projection data by modeling the spatial and temporal distribution of the radiopharmaceutical throughout the projected field of view. In previous work we developed computationally efficient methods for fully four-dimensional (4-D) direct estimation of spatiotemporal distributions [1] and their statistical uncertainties [2] from dynamic SPECT projection data, using a spatial segmentation and temporal B-splines. In addition, we studied the bias that results from modeling various orders of temporal continuity and using various time samplings [1]. In the present work, we use the methods developed in [1, 2] and Monte Carlo simulations to study the effects of the temporal modeling on the statistical variability of the reconstructed distributions.

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Despite a number of published studies on the effectiveness of lighting controls in buildings, only one US study examines the occupancy patterns of building occupants. Occupancy profiles allow one to determine, for example, the probability that an office is occupied for each hour of the workday. Occupancy profiles are useful for many purposes including: (1) predicting the effectiveness of occupancy sensors for reducing peak demand, (2) evaluating the impact of human activity on building lighting and other electric loads and (3) providing lighting equipment manufacturers with detailed lighting operation data to help evaluate the impact of advanced lighting controls on equipment life. In this paper, we examine the occupancy profiles for 35 single person offices at a large office building in San Francisco and analyze the data to obtain average occupancy as a function of time of day. In addition, we analyzed the data to identify how the use of occupancy sensors may affect switching cycles and lamp life.

The D0 experiment is recording physics quality data. Both the detector and the accelerator performance are continually improving. We are studying issues such as the b{bar b} mass resolution, b-jet tagging efficiency, missing E{sub T} resolution, and backgrounds to Higgs processes. We look forward to seeing exciting results. The status of the Higgs search at the upgraded D0 detector is discussed.

The effects of electron-hole interaction on the optical properties of a variety of materials have been calculated using an ab initio method based on solving the Bethe-Salpeter equation. Results on selected semiconductors, insulators, and semiconducting polymers are presented. In the cases of alpha-quartz (SiO2) and poly-phenylene-vinylene, resonant excitonic states qualitatively alter the absorption spectra.

The photosynthetic water oxidation complex consists of a cluster of 4 Mn atoms bridged by O atoms, associated with Ca2+ and Cl- and incorporated into protein. The structure is similar in higher plants and algae, as well as in cyanobacteria of more ancient lineage, dating back more than 2.5 Ga on Earth. It has been proposed that the proto-enzyme derived from a component of a natural early marine manganese precipitate that contained a CaMn4O9 cluster. A variety of MnO2 minerals is found in nature. Three major classes are spinels, sheet-like layered structures and 3-dimensional networks that contain parallel tunnels. These relatively open structures readily incorporate cations (Na+, Li+, Mg2+, Ca2+, Ba2+, H+ and even Mn2+) and water. The minerals have different ratios of Mn(III) and Mn(IV) octahedrally coordinated to oxygens. Using X-ray spectroscopy we compare the chemical structures of Mn in the minerals with what is known about the arrangement in the water-oxidation complex to define the parameters of a structural model for the photosynthetic catalytic site. This comparison provides for the structural model a set of candidate Mn4 clusters -- some previously proposed and considered and others entirely novel.

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We summarize structural properties of thick HVPE GaN templates from the point of view of their application as substrates for growth of nitride layers. This is followed by the results of optical and structural studies, mostly transmission electron microscopy, of nitride layers grown by MOCVD on top of the HVPE substrates. The results indicate high structural quality of these layers with a low density of threading dislocations (in the range of 10{sup 6} cm{sup -2}). Convergent beam electron diffraction studies showed that the MOCVD GaN films have Ga-polarity, the same polarity as the HVPE GaN substrates. Structural studies of an InGaN layer grown on top of the MOCVD GaN film showed the presence of two layers, which differed in lattice parameter and composition. The upper layer, on the top of the structure had a c-lattice parameter about 2% larger than that of GaN and contained 10.3 {+-} 0.8% of In. Values measured for the thinner, intermediate layer adjacent to the GaN layer were about 2 .5 times lower.

We have created an elastic version of the IFF Marmousi model for use in AVO analysis in the presence of complex structure. The model is larger, includes larger offsets, lies in deeper water, includes surface streamer, multicomponent OBC and VSP acquisition, and contains more hydrocarbons than its predecessor. In addition to AVO analysis, we believe these data will be suitable for calibrating emerging technologies including converted wave tomography and vector seismic processing.

Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) studies of GaAs/GaN interfaces, obtained by direct wafer bonding, are presented. TEM observations show that most of the interface area was well bonded. A thin oxide layer, confirmed by EDX, was present at the interface in the well-bonded regions. Plan-view TEM studies showed the presence of two dislocation networks in such regions. They formed to accommodate: (1) tilt between bonded crystals and (2) strain, which appeared during sample cooling due to mismatch in thermal expansion coefficients. Asymmetrical, often elongated, cavities, formed on the GaAs side, were present at the interface between the well-bonded regions. It was shown by EDX that the walls of these cavities are covered with native oxide.

The Control System for the Advanced Light Source (ALS) at Lawrence Berkeley National Lab (LBNL) uses in-house designed IndustryPack(registered trademark) (IP) modules contained in compact PCI (cPCI) crates with 16-bit analog I/O to control instrumentation. To make the IP modules interchangeable, each module is calibrated for gain and offset compensation. We initially developed a method of verifying and calibrating the IP modules in a lab bench test environment using a PC with LabVIEW. The subsequent discovery that the ADCs have significant drift characteristics over periods of days of installed operation prompted development of an ''in-situ'' calibration process--one in which the IP modules can be calibrated without removing them from the cPCI crates in the storage ring. This paper discusses the original LabVIEW PC calibration and the migration to the proposed in-situ EPICS control system calibration.

Several elastic models, both 2-D and 3-D, are being built for use in calculating synthetic elastic seismic data. The models will be made available to the research community, along with the synthetic data that are being calculated from them. These shared models have been proposed or contributed by participants in a collaborative industry, national laboratory, and university research project. The purpose of the modeling is to provide synthetic data to better understand elastic wave propagation and the effects of structural and stratigraphic complexities. The 2-D models are easier to design and change and synthetic calculations can be run relatively quickly in them. It will be possible to alter their layer properties and calculate time-lapse data sets from them. Field data will be available to accompany many of the 2-D models. 3-D models are more realistic, but more difficult to design and change. They also require considerably more computing resources to calculate synthetic data from them. A new 3-D model is being designed, and will be used for computing synthetic elastic data.

In this talk, I discuss a universal form of matter, the Color Glass Condensate. It is this matter which composes the low x part of all hadronic wavefunctions. The experimental programs at RHIC and HERA, and future programs at LHC and eRHIC may allow us to probe and study the properties of this matter.

The increasingly common practice of (1) replicating datasets and (2) using resources as distributed data stores in Grid environments has lead to the problem of determining which replica can be accessed most efficiently. Due to diverse performance characteristics and load variations of several components in the end-to-end path linking these various locations, selecting a replica location from among many requires accurate prediction information of end-to-end data transfer times between the sources and sinks. In this paper, we present a prediction system that is based on combining end-to-end application throughput observations and network load variations, drawing from their merits of capturing whole system performance and variations in load patterns respectively. We develop a set of regression models to derive predictions that characterize the effect of network load variations on file transfer times. We apply these techniques to the GridFTP data movement tool, part of the Globus Toolkit{sup TM}, and observe performance gains of up to 10% in prediction accuracy when compared to approaches based on past system behavior in isolation.

As-fabricated EN82H welds are susceptible to low temperature embrittlements in 54 degree C hydrogenated water. Values of J[sub]IC in water are typically 90% to 98% lower than those in air due to a fracture mechanism transition from microvoid coalescence to hydrogen-included intergranular fracture. Environmental J[sub]IC testing demonstrated that a high temperature (1093 degree C) anneal and furnace-cool alleviates the material's susceptibility to hydrogen-induced intergranular cracking. To identify metallurgical and compositional features that are responsible for the material's environment-sensitive behavior, detailed characterization of the microstructure and grain boundary chemistry for the as-fabricated and as-annealed materials was performed. Results from light optical microscopy, analytical electron microscopy, electron probe microanalysis, Auger electron spectroscopy and mechanical property characterization are used to provide insight into the observed low temperature embrittlement phenomenon. The key microstructural feature responsible for low temperature cracking in as-fabricated welds appears to be fine niobium and titanium-rich carbonitrides that cover most grain boundaries. These precipitates are effective hydrogen traps that promote hydrogen-induced intergranular cracking. Dissolution the fine carbonitrides during the 1093 degree C anneal reduces grain boundary trapping sites, which accounts for the improved fracture resistance displayed by the annealed weld. The role of strength level in promoting low temperature embrittlement is …

Gold Basin is a large L4 chondrite shower, that was recently discovered in the Mojave Desert, Arizona [1]. Based on {sup 109}Be and {sup 14}C concentrations in several fragments, the pre-atmospheric radius of this shower was estimated to be 3-4 meters [2]. Among chondrites, Gold Basin is one of the largest, thus providing a unique opportunity for comparing measured cosmogenic nuclide concentrations with model calculations for large objects. Noble gas measurements combined with {sup 10}Be data of most Gold Basin samples suggest a single-stage exposure of 15-30 Myr, although a few samples may require a complex exposure history [3]. We selected eight samples of the Gold Basin shower that were analyzed for noble gases; these samples represent a wide range of shielding depths.

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Cold bubbling springs in the Separation Creek area, the locus of current uplift at South Sister volcano show strong mantle signatures in helium and carbon isotopes and CO{sub 2}/{sup 3}He. This suggests the presence of fresh basaltic magma in the volcanic plumbing system. Currently there is no evidence to link this system directly to the uplift, which started in 1998. To the contrary, all geochemical evidence suggests that there is a long-lived geothermal system in the Separation Creek area, which has not significantly changed since the early 1990s. There was no archived helium and carbon data, so a definite conclusion regarding the strong mantle signature observed in these tracers cannot yet be drawn. There is a distinct discrepancy between the yearly magma supply required to explain the current uplift (0.006 km{sup 3}/yr) and that required to explain the discharge of CO{sub 2} from the system (0.0005 km{sup 3}/yr). This discrepancy may imply that the chemical signal associated with the increase in magma supply has not reached the surface yet. With respect to this the small changes observed at upper Mesa Creek require further attention, due to the recent volcanic vent in that area it may be the location were the …

We investigate the stress-dependent permeability issue in fractured rock masses considering the effects of nonlinear normal deformation and shear dilation of fractures using a two-dimensional distinct element method program, UDEC, based on a realistic discrete fracture network realization. A series of ''numerical'' experiments were conducted to calculate changes in the permeability of simulated fractured rock masses under various loading conditions. Numerical experiments were conducted in two ways: (1) increasing the overall stresses with a fixed ratio of horizontal to vertical stresses components; and (2) increasing the differential stresses (i.e., the difference between the horizontal and vertical stresses) while keeping the magnitude of vertical stress constant. These numerical experiments show that the permeability of fractured rocks decreases with increased stress magnitudes when the stress ratio is not large enough to cause shear dilation of fractures, whereas permeability increases with increased stress when the stress ratio is large enough. Permeability changes at low stress levels are more sensitive than at high stress levels due to the nonlinear fracture normal stress-displacement relation. Significant stress-induced channeling is observed as the shear dilation causes the concentration of fluid flow along connected shear fractures. Anisotropy of permeability emerges with the increase of differential stresses, and this …

The existence of the top quark, discovered by CDF and D0 in 1995, has been re-established in the burgeoning dataset being collected in Run 2 of the Tevatron at Fermilab. Results from CDF on the top quark production cross section and top quark mass are consistent with the Standard Model expectations. The well-characterized top data samples will make it possible in the future to probe further for new physics in the top quark sector. This report summarizes recent CDF top quark physics results.

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This paper presents preliminary findings from DOEs pilot program. The results show how a web-based monitoring system can form the basis for aggregation of data and correlation and benchmarking across broad geographical lines. A longer report describes additional findings from the pilot, including impacts of power quality and reliability on customers operations [Divan, Brumsickle, Eto 2003].