Mean velocity and turbulence data that measure turbulent flow phenomena in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic gas-cooled reactor are presented as a follow-up to summaries presented at the 2006 Annual Meeting and the 2006 Winter Meeting. The experiments were designed to develop benchmark databases to support the first Standard Problem endorsed by the Generation IV International Forum to validate the heat transfer and fluid flow software that will be used to study the behavior of the VHTR system.

Laser ablation has proven to be an effective method for generating nanoparticles; particles are produced in the laser induced vapor plume during the cooling stage. To understand the in-situ condensation process, a series of time resolved light scattering images were recorded and analyzed. Significant changes in the condensation rate and the shape of the condensed aerosol plume were observed in two background gases, helium and argon. The primary particle shape and size distribution were measured using a transmission electron microscope (TEM), a scanning electron microscope (SEM) and a differential mobility analyzer (DMA). The gas dynamics simulation included nucleation and coagulation within the vapor plume, heat and mass transfer from the vapor plume to the background gas, and heat transfer to the sample. The experimental data and the calculated evolution of the shape of the vapor plume showed the same trend for the spatial distribution of the condensed particles in both background gases. The simulated particle size distribution also qualitatively agreed with the experimental data. It was determined that the laser energy, the physical properties of the background gas (conductivity, diffusivity and viscosity), and the shape of the ablation system (ablation chamber and the layout of the sample) have strong effects …

Plutonium and its alloys exhibit complex phase diagrams that imply anomalous lattice dynamics near phase stability boundaries. Specifically, the TA [111] phonon branch in Ga-stabilized {delta}-Pu at room temperature shows a pronounced soft mode at the zone boundary, which suggests a possible connection to the martensitic transformation from the fcc {delta}-phase to the monoclinic {alpha}{prime}-phase at low temperatures. This work is a study of the lattice dynamics of this system by x-ray thermal diffuse scattering. The results reveal little temperature dependence of the phonon frequencies, thus indicating that kinetic phonon softening is not responsible for this phase transition.

Ln{sub 3}LuSe{sub 6} (Ln = La, Ce), {beta}-LnLuSe{sub 3} (Ln = Pr, Nd), and Ln{sub x}Lu{sub 4-x}Se{sub 6} (Ln = Sm, Gd; x = 1.82, 1.87) have been synthesized using a Sb{sub 2}Se{sub 3} flux at 1000 C. Ln{sub 3}LuSe{sub 6} (Ln = La, Ce) adopt the U{sub 3}ScS{sub 6}-type three-dimensional structure, which is constructed from two-dimensional {infinity}{sup 2} [Ln{sub 3}Se{sub 6}]{sup 3-} slabs with the gaps between these slabs filled by octahedrally coordinated Lu{sup 3+} ions. The series of {beta}-LnLuSe{sub 3} (Ln = Pr, Nd) are isotypic with UFeS{sub 3}. Their structures include layers formed from LuSe6 octahedra that are separated by eight-coordinate larger Ln{sup 3+} ions in bicapped trigonal prismatic environments. Sm{sub 1.82}Lu{sub 2.18}Se{sub 6} and Gd{sub 1.87}Lu{sub 2.13}Se{sub 6} crystallize in the disordered F-Ln{sub 2}S{sub 3} type structure with the eight-coordinate bicapped trigonal prismatic Ln(1) ions residing in the one-dimensional channels formed by three different double chains via edge and corner sharing. These double chains are constructed from Ln(2)Se{sub 7} monocapped trigonal prisms, Ln(3)Se{sub 6} octahedra, and Ln(4)S{sub 6} octahedra, respectively. The magnetic susceptibilities of {beta}-PrLuSe{sub 3} and {beta}-NdLuSe{sub 3} follow the Curie-Weiss law. Sm{sub 1.82}Lu{sub 2.18}Se{sub 6} shows van Vleck paramagnetism. Magnetic measurements show that Gd{sub …

To avoid multiple head-on collisions the proton and antiproton beams in the Tevatron move along separate helical orbits created by 7 horizontal and 8 vertical electrostatic separators. Still the residual long-range beam-beam interactions can adversely affect particle motion at all stages from injection to collision. With increased intensity of the beams it became necessary to modify the orbits in order to mitigate the beam-beam effect on both antiprotons and protons. This report summarizes the work done on optimization of the Tevatron helical orbits, outlines the applied criteria and presents the achieved results.

We construct a sigma model in two dimensions with Galilean symmetry in flat target space similar to the sigma model of the critical string theory with Lorentz symmetry in 10 flat spacetime dimensions. This is motivated by the works of Gomis and Ooguri[1] and Danielsson et. al.[2, 3]. Our theory is much simpler than their theory and does not assume a compact coordinate. This non-relativistic string theory has a bosonic matter {beta}{gamma} CFT with the conformal weight of {beta} as 1. It is natural to identify time as a linear combination of {gamma} and {bar {gamma}} through an explicit realization of the Galilean boost symmetry. The angle between {gamma} and {bar {gamma}} parametrizes one parameter family of selection sectors. These selection sectors are responsible for having a non-relativistic dispersion relation without a nontrivial topology in the non-relativistic setup, which is one of the major differences from the previous works[1, 2, 3]. This simple theory is the non-relativistic analogue of the critical string theory, and there are many different avenues ahead to be investigated. We mention a possible consistent generalization of this theory with different conformal weights for the {beta}{gamma} CFT. We also mention supersymmetric generalizations of these theories.

The measured physical parameters of a superconducting cavity differ from those of the designed ideal cavity. This is due to shape deviations caused by both loose machine tolerances during fabrication and by the tuning process for the accelerating mode. We present a shape determination algorithm to solve for the unknown deviations from the ideal cavity using experimentally measured cavity data. The objective is to match the results of the deformed cavity model to experimental data through least-squares minimization. The inversion variables are unknown shape deformation parameters that describe perturbations of the ideal cavity. The constraint is the Maxwell eigenvalue problem. We solve the nonlinear optimization problem using a line-search based reduced space Gauss-Newton method where we compute shape sensitivities with a discrete adjoint approach. We present two shape determination examples, one from synthetic and the other from experimental data. The results demonstrate that the proposed algorithm is very effective in determining the deformed cavity shape.

An array of Neutral-Current Detectors (NCDs) has been builtin order to make a unique measurement of the total active ux of solarneutrinos in the Sudbury Neutrino Observatory (SNO). Data in the thirdphase of the SNO experiment were collected between November 2004 andNovember 2006, after the NCD array was added to improve theneutral-current sensitivity of the SNO detector. This array consisted of36 strings of proportional counters lled with a mixture of 3He and CF4gas capable of detecting the neutrons liberated by the neutrino-deuteronneutral current reaction in the D2O, and four strings lled with a mixtureof 4He and CF4 gas for background measurements. The proportional counterdiameter is 5 cm. The total deployed array length was 398 m. The SNO NCDarray is the lowest-radioactivity large array of proportional countersever produced. This article describes the design, construction,deployment, and characterization of the NCD array, discusses theelectronics and data acquisition system, and considers event signaturesand backgrounds.

This study combines a variably-saturated groundwater flow model and a mesoscale atmospheric model to examine the effects of soil moisture heterogeneity on atmospheric boundary layer processes. This parallel, integrated model can represent spatial variations in land-surface forcing driven by three-dimensional (3D) atmospheric and subsurface components. The development of atmospheric flow is studied in a series of idealized test cases with different initial soil moisture distributions generated by an offline spin-up procedure or interpolated from a coarse-resolution dataset. These test cases are performed with both the fully-coupled model (which includes 3D groundwater flow and surface water routing) and the uncoupled atmospheric model. The effects of the different soil moisture initializations and lateral subsurface and surface water flow are seen in the differences in atmospheric evolution over a 36-hour period. The fully-coupled model maintains a realistic topographically-driven soil moisture distribution, while the uncoupled atmospheric model does not. Furthermore, the coupled model shows spatial and temporal correlations between surface and lower atmospheric variables and water table depth. These correlations are particularly strong during times when the land surface temperatures trigger shifts in wind behavior, such as during early morning surface heating.

The author discusses results from the Tevatron experiments on mixing and CP-violation in B{sub s} mesons, including the observation of B{sub s} oscillations and the first precision measurement of the mixing frequency, as well as a measurement of the lifetime difference {Delta}{Lambda}{sub s} and the first measurement of the CP-violating phase {delta}{sub s}. The author also briefly reports on the observation of four new bottom baryons at CDF.

In a world with water resources severely impacted bytechnology, science must actively contribute to water law. To this end,this paper is an earth scientist s attempt to comprehend essentialelements of water law, and to examine their connections to science.Science and law share a common logical framework of starting with apriori prescribed tenets, and drawing consistent inferences. In science,observationally established physical laws constitute the tenets, while inlaw, they stem from social values. The foundations of modern water law inEurope and the New World were formulated nearly two thousand years ago byRoman jurists who were inspired by Greek philosophy of reason.Recognizing that vital natural elements such as water, air, and the seawere governed by immutable natural laws, they reasoned that theseelements belonged to all humans, and therefore cannot be owned as privateproperty. Legally, such public property was to be governed by jusgentium, the law of all people or the law of all nations. In contrast,jus civile or civil law governed private property. Remarkably, jusgentium continues to be relevant in our contemporary society in whichscience plays a pivotal role in exploiting vital resources common to all.This paper examines the historical roots of modern water law, followstheir evolution through the centuries, and examines how …

In the 1949 Report of the Atomic Weights Commission, a series of new elements were added to the Atomic Weights Table. Since these elements had been produced in the laboratory and were not discovered in nature, the atomic weight value of these artificial products would depend upon the production method. Since atomic weight is a property of an element as it occurs in nature, it would be incorrect to assign an atomic weight value to that element. As a result of that discussion, the Commission decided to provide only the mass number of the most stable (or longest-lived) known isotope as the number to be associated with these entries in the Atomic Weights Table. As a function of time, the mass number associated with various elements has changed as longer-lived isotopes of a particular element has been found in nature, or as improved half-life values of an element's isotopes might cause a shift in the longest-lived isotope from one mass to another. In the 1957 Report of the Atomic Weights Commission, it was decided to discontinue the listing of the mass number in the Atomic Weights Table on the grounds that the kind of information supplied by the mass number …

Long-term phase drifts of less than a femtosecond per hour have been demonstrated in a 2 km length of single-mode optical fiber, stabilized interferometrically at 1530 nm. Recent improvements include a wide-band phase detector that reduces the possibility of fringe jumping due to fast external perturbations of the fiber and locking of the master CW laser wavelength to an atomic absorption line. Mode-locked lasers may be synchronized using two wavelengths of the comb, multiplexed over one fiber, each wavelength individually interferometrically stabilized.

The {tau}{sup -} {yields} {pi}{sup -}{pi}{sup +}{pi}{sup -}{nu}{sub {tau}} and {tau}{sup -} {yields} {pi}{sup -}{pi}{sup -}{pi}{sup +}{eta}{nu}{sub {tau}} decays have been studied with the BABAR detector. Preliminary branching fractions on the two modes are presented. The {tau}{sup -} {yields} {pi}{sup -}{pi}{sup -}{pi}{sup +}{eta}{nu}{sub {tau}} mode is found to have a large contribution from the {tau}{sup -} {yields} {omega}{pi}{sup -}{nu}{sub {tau}} decay. The {tau}{sup -} {yields} {pi}{sup -}{pi}{sup -}{pi}{sup +}{eta}{nu}{sub {tau}} decay is studied using the {eta} {yields} {gamma}{gamma} mode and the {tau}{sup -} f{sub 1}(1285){pi}{sup -}{nu}{sub {tau}} decay is seen to be the primary source of these decays. A 90% confidence level upper limit is placed on the {tau}{sup -} {yields} {eta}{prime}(958){pi}{sup -}{nu}{sub {tau}} decay which proceeds through a second-class current and is expected to be forbidden in the limit of perfect isospin symmetry.

Chemical and thermal performance of crystalline silicotitanate (CST) and resorcinol-formaldehyde (RF) ion exchange media were predicted for column configurations designed for installation in high level waste tanks and intended for cesium removal from radioactive waste supernates. Modeling predictions for the processing of a known Savannah River Site tank waste composition were generated. In a two column configuration under presumed nominal operating conditions (432 gallon packed bed, 10 gpm liquid flow, 25 C, 45 nCi/g average breakthrough limit) with lead/lag column rotation between processing cycles, approximately two cycles were predicted to treat 1,000,000 gallons of radioactive waste with CST as compared to three cycles predicted for RF. However, this processing mode was shown to be highly unfavorable for RF due to the fact that the lead column is unnecessarily exposed to large radiation doses during movement of the cesium mass transfer zone into the lag column. Thermal modeling calculations indicated that maximum temperatures within stagnant, packed CST and RF columns containing the highest anticipated cesium loading and no active cooling will reach 128 and 78 C, respectively, within 6 days. Active cooling maintains the cesium-saturated CST and RF columns below 88 and 41 C, respectively, under stagnant flow conditions.

We present a measurement of the correlated b{bar b} production cross section. The data used in this analysis were taken with the upgraded CDF detector (CDF II) at the Fermilab Tevatron collider, and correspond to an integrated luminosity of 742 pb{sup -1}. We utilize muon pairs with invariant mass 5 {le} m{sub {mu}{mu}} {le} 80 GeV/c{sup 2} produced by b{bar b} double semileptonic decays. For muons with p{sub T} {ge} 3 GeV/c and |{eta}| {le} 0.7, that are produced by b and {bar b} quarks with p{sub T} {ge} 2 GeV/c and |y| {le} 1.3, we measure {sigma}{sub b{yields}{mu},{bar b}{yields}{mu}} = 1549 {+-} 133 pb. We compare this result with theoretical predictions and previous measurements. We also report the measurement of {sigma}{sub c{yields}{mu},{bar c}{yields}{mu}}, a by-product of the study of the background to b{bar b} production.

Nanoparticles of certain materials can respond structurally to changes in their surface environments. We have previously shown that methanol, water adsorption, and aggregation-disaggregation can change the structure of 3 nm diameter zinc sulfide (ZnS). However, in prior observations of water-driven structure change, aggregation may also have taken place. Therefore, we investigated the structural consequences of water adsorption alone on anhydrous nanoparticles that were dried to minimize changes in aggregation. Using simultaneously collected small- and wide-angle x-ray scattering (SAXS/WAXS) data, we show that water vapor adsorption alone drives a structural transformation in ZnS nanoparticles in the temperature range 22-40 C. The transition kinetics are strongly temperature dependent, with an activation energy of 58.1 {+-} 9.8 kJ/mol, consistent with atom displacement rather than bond breaking. At 50 C, aggregate restructuring occurred, increasing the transition kinetics beyond the rate expected for water adsorption alone. The observation of isosbestic points in the WAXS data suggests that the particles do not transform continuously between the initial and final structural state but rather undergo an abrupt change from a less ordered to a more ordered state.

A high-order finite volume algorithm is developed for the Fokker-Planck Operator (FPO) describing Coulomb collisions in strongly magnetized plasmas. The algorithm is based on a general fourth-order reconstruction scheme for an unstructured grid in the velocity space spanned by parallel velocity and magnetic moment. The method provides density conservation and high-order-accurate evaluation of the FPO independent of the choice of the velocity coordinates. As an example, a linearized FPO in constant-of-motion coordinates, i.e. the total energy and the magnetic moment, is developed using the present algorithm combined with a cut-cell merging procedure. Numerical tests include the Spitzer thermalization problem and the return to isotropy for distributions initialized with velocity space loss cones. Utilization of the method for a nonlinear FPO is straightforward but requires evaluation of the Rosenbluth potentials.

Adaptive optics (AO) and optical coherence tomography (OCT) are powerful imaging modalities that, when combined, can provide high-volumetric-resolution, images of the retina. The AO-OCT system at UC Davis has been under development for 2 years and has demonstrated the utility of this technology for microscopic, volumetric, in vivo retinal imaging [1]. The current system uses an AOptix bimorph deformable mirror (DM) for low-order, high-stroke correction [2] and a 140-actuator Boston Micromachines DM for high-order correction [3]. We are beginning to investigate the potential for increasing the image contrast in this system using higher-order wavefront correction. The first step in this analysis is to quantify the residual wavefront error (WFE) in the current system. Developing an error budget is a common tool for improved performance and system design in astronomical AO systems [4, 5]. The process for vision science systems is also discussed in several texts e.g. [6], but results from this type of analysis have rarely been included in journal articles on AO for vision science. Careful characterization of the AO system will lead to improved performance and inform the design of a future high-contrast system. In general, an AO system error budget must include an analysis of three categories …

A few observable distributions in min-bias (inelastic, non-diffractive) events which could be well constrained with early LHC data are presented, with some comments on their significance for placing constraints on theoretical models. The effects of fiducial cuts (p{perpendicular} > 0.5 GeV, |{eta}| < 2.5) and extrapolation from the Tevatron are illustrated.

The United States is considering the development of a domestic hydrogen-based energy economy. Hydrogen is of particular interest as a secondary energy carrier because it has the potential to be storable, transportable, environmentally benign, and useful in many chemical processes. Obviously, before a hydrogen economy can be implemented, an efficient and environmentally friendly means for large scale hydrogen production must be identified, proven, and developed. Hydrogen is now produced primarily via steam reforming of methane. However, from a long-term perspective, methane reforming is not a viable process for large-scale production of hydrogen since such fossil fuel conversion processes consume non-renewable resources and emit greenhouse gases. The U. S. National Research Council has recommended the use of water-splitting technologies to produce hydrogen using energy derived from a nuclear reactor. For the past several years, the Idaho National Laboratory has been actively studying the use of solid oxide fuel cells in conjunction with nuclear power for large-scale, high-temperature, electrolytic hydrogen production.

A novel compact CT-guided intensity modulated proton radiotherapy (IMPT) system is described. The system is being designed to deliver fast IMPT so that larger target volumes and motion management can be accomplished. The system will be ideal for large and complex target volumes in young patients. The basis of the design is the dielectric wall accelerator (DWA) system being developed at the Lawrence Livermore National Laboratory (LLNL). The DWA uses fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. High electric field gradients are achieved by the use of alternating insulators and conductors and short pulse times. The system will produce individual pulses that can be varied in intensity, energy and spot width. The IMPT planning system will optimize delivery characteristics. The system will be capable of being sited in a conventional linac vault and provide intensity modulated rotational therapy. Feasibility tests of an optimization system for selecting the position, energy, intensity and spot size for a collection of spots comprising the treatment are underway. A prototype is being designed and concept designs of the envelope and environmental needs of the unit are beginning. The status of …

RF electron guns are capable of producing electron bunches with high brightness, which outperform DC electron guns and may even be able to provide electron beams for the ILC without the need for a damping ring. However, all successful existing guns for polarized electrons are DC guns because the environment inside an RF gun is hostile to the GaAs cathode material necessary for polarization. While the typical vacuum pressure in a DC gun is better than 10{sup -11} torr the vacuum in an RF gun is in the order of 10{sup -9} torr. Experiments at BINP Novosibirsk show that this leads to strong ion back-bombardment and generation of dark currents, which destroy the GaAs cathode in a short time. The situation might be much more favorable in a (super-conducting) SRF gun. The cryogenic pumping of the gun cavity walls may make it possible to maintain a vacuum close to 10{sup -12} torr, solving the problem of ion bombardment and dark currents. Of concern would be contamination of the gun cavity by evaporating cathode material. This report describes an experiment that Brookhaven National Laboratory (BNL) in collaboration with Advanced Energy Systems (AES) is conducting to answer these questions.

This paper presents numerical simulations of reactive transport which may be induced in the caprock of an on-shore depleted gas reservoir by the geological sequestration of carbon dioxide. The objective is to verify that CO{sub 2} geological disposal activities currently being planned for the study area are safe and do not induce any undesired environmental impact. In our model, fluid flow and mineral alteration are induced in the caprock by penetration of high CO{sub 2} concentrations from the underlying reservoir, where it was assumed that large amounts of CO{sub 2} have already been injected at depth. The main focus is on the potential effect of precipitation and dissolution processes on the sealing efficiency of caprock formations. Concerns that some leakage may occur in the investigated system arise because the seal is made up of potentially highly-reactive rocks, consisting of carbonate-rich shales (calcite+dolomite averaging up to more than 30% of solid volume fraction). Batch simulations and multi-dimensional 1D and 2D modeling have been used to investigate multicomponent geochemical processes. Numerical simulations account for fracture-matrix interactions, gas phase participation in multiphase fluid flow and geochemical reactions, and kinetics of fluid-rock interactions. The geochemical processes and parameters to which the occurrence of high …