Article discussing linear free energy relationship correlations for room temperature ionic liquids and revised cation-specific and anion-specific equation coefficients for predictive applications covering a much larger area of chemical space.

We have extracted polarized nucleon distributions from recent data at CERN, SLAC and DESY. The flavor-dependent valence and sea quark spin distributions are determined for each experiment. We take into account possible differences in the up and down sea distributions, and assume that the strange sea contribution is suppressed by mass effects. Physics results determined from different experiments are compared, including higher order corrections.

The (La{sub 1{minus}} x Sr{sub x}){sub 3}Mn{sub 2}O{sub 7} compounds are layered materials that exhibit higher magneto-resistance than the corresponding 3D manganite perovskites. Quasi-elastic neutron scattering on a polycrystalline sample of La{sub 1.4}Sr{sub 1.6}Mn{sub 2}O{sub 7} shows that the spin fluctuation spectrum of the these layered CMR materials is qualitatively similar to those found in the perovskite manganites (La,Ca)MnO{sub 3}; their concentration, lifetime, and coherence length increase as T decreases to T{sub c}. Unlike the perovskites we find a lower spin-diffusion constant above T{sub c} of {approximately}5 meV {angstrom}{sup 2}.

This paper briefly summarizes requirements of site characterization for Natural Phenomena Hazards (NPH) at DOE sites. In order to comply with DOE Order 5480.28, site characterization criteria has been developed to provide site-specific information needed for development of NPH assessment criteria. Appropriate approaches are outlined to ensure that the current state-of-the-art methodologies and procedures are used in the site characterization. General and detailed site characterization requirements are provided in the areas of meteorology, hydrology, geology, seismology and geotechnical studies.

This paper focuses on the lessons learned during the decontamination and decommissioning (D and D) of two reactors at Argonne National Laboratory-East (ANL-E). The Experimental Boiling Water Reactor (EBWR) was a 100 MW(t), 5 MSV(e) proof-of-concept facility. The Janus Reactor was a 200 kW(t) reactor located at the Biological Irradiation Facility and was used to study the effects of neutron radiation on animals.

Neutron diffuse scattering in the form of rod-like features are observed in single crystals of the layered CMR material La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} (x=0.4,0.36), consistent with the presence of 2D ferromagnetic spin correlations. These diffuse features are observed over a wide temperature region, however, their coherence length does not appear to diverge at T{sub c}, although there is evidence of the development of three-dimensional correlations around ferromagnetic reflections of the 3D-ordered magnetic structure close to T{sub c}. Quasi-elastic neutron scattering on a ceramic sample of x = 0.3 shows that the lifetime of these ferromagnetic correlations increases at T {r_arrow} T{sub c}. They exhibit a spin-diffusion constant above T{sub c} of {approximately}5 meV {angstrom}{sup 2}, much lower than that reported for La{sub 2/3}Ca{sub 1/3}MnO{sub 3}. We discuss the relationship of these magnetic correlations to models of the ferromagnetic transition in CMR compounds.

Electronic absorption and resonance Raman (RR) spectra of the ferric form of barley grain peroxidase (BP 1) at various pH values both at room temperature and 20 K are . reported, together with EPR spectra at 10 K. The ferrous forms and the ferric complex with fluoride have also been studied. A quantum mechanically mixed-spin (QS) state has been identified. The QS heme species co-exists with 6- and 5-cHS heroes; the relative populations of these three spin states are found to be dependent on pH and temperature. However, the QS species remains in all cases the dominant heme spin species. Barley peroxidase appears to be further characterized by a splitting of the two vinyl stretching modes, indicating that the vinyl groups are differently conjugated with the porphyrin. An analysis of the presently available spectroscopic data for proteins from all three peroxidase classes suggests that the simultaneous occurrence of the QS heme state as well as the splitting of the two vinyl stretching modes is confined to class III enzymes. The former point is discussed in terms of the possible influences of heme deformations on heme spin state. It is found that moderate saddling alone is probably not enough to cause …

The effect of excluded volume on the coil size of dilute linear polymers was investigated by off-lattice Monte Carlo simulations. The radius of gyration R{sub g} was evaluated for a wide range of chain lengths at several temperatures and at the athermal condition. The theta temperature and the corresponding theta chain dimensions were established for the system, and the dependence of the size expansion factor, a{sub s} = R{sub g} /(R{sub g}){sub {theta}}, on chain length N and temperature T was examined. For long chains and at high temperatures, a{sub s} is a function of N/N{sub s}{sup 2} alone, where the length scale N{sub s}{sup 2} depends only on T. The form of this simulations-based master function compares favorably with {alpha}{sub s}(M/M{sub s}{sup 2}), an experimental master curve for linear polymers in good solvents, where M{sub s}{sup 2} depends only on polymer-solvent system. Comparisons when N{sub s}{sup 2}(T) and M{sub s}{sup 2}(system) are reduced to common units, numbers of Kuhn steps, strongly indicate that coil expansion in even the best of good solvents is small relative to that expected for truly athermal solutions. An explanation for this behavior is proposed, based on what would appear to be an inherent difference …

In two recent publications relativistic electron flow in cylindrical magnetically-insulated transmission lines (MITL) was analyzed and modeled under the assumption of negligible electron pressure. Cylindrical MITLs were used because of their common occurrence, and because they are the simplest case of finite width. The authors show in this report that the models apply equally to MITLs of any cross section.

The role of hydrogen in enhancing the photoluminescence (PL) yield observed from Si nanocrystals embedded in SiO{sub 2} has been studied. SiO{sub 2} thermal oxides and bulk fused silica samples have been implanted with Si and subsequently annealed in various ambients including hydrogen or deuterium forming gases (Ar+4%H{sub 2} or Ar+4%D{sub 2}) or pure Ar. Results are presented for annealing at temperatures between 200 and 1100 C. Depth and concentration profiles of H and D at various stages of processing have been measured using elastic recoil detection. Hydrogen or deuterium is observed in the bulk after annealing in forming gas but not after high temperature (1100 C) anneals in Ar. The presence of hydrogen dramatically increases the broad PL band centered in the near-infrared after annealing at 1100 C but has almost no effect on the PL spectral distribution. Hydrogen is found to selectively trap in the region where Si nanocrystals are formed, consistent with a model of H passivating surface states at the Si/SiO{sub 2} interface that leads to enhanced PL. The thermal stability of the trapped H and the PL yield observed after a high temperature anneal have been studied. The hydrogen concentration and PL yield are unchanged …

Nanostructured particles exhibiting well-defined pore sizes and pore connectivities (1-, 2-, or 3-dimensional) are of interest for catalysis, chromatography, controlled release, low dielectric constant fillers, and custom-designed pigments and optical hosts. During the last several years considerable progress has been made on controlling the macroscopic forms of mesoporous silicas prepared by surfactant and block copolymer liquid crystalline templating procedures. Typically interfacial phenomena are used to control the macroscopic form (particles, fibers, or films), while self-assembly of amphiphilic surfactants or polymers is used to control the mesostructure. To date, although a variety of spherical or nearly-spherical particles have been prepared, their extent of order is limited as is the range of attainable mesostructures. They report a rapid, aerosol process that results in solid, completely ordered spherical particles with stable hexagonal, cubic, or vesicular mesostructures. The process relies on evaporation-induced interfacial self-assembly (EISA) confined to a spherical aerosol droplet. The process is simple and generalizable to a variety of materials combinations. Additionally, it can be modified to provide the first aerosol route to the formation of ordered mesostructured films.

Detailed materials evaluations have been performed for MC2969 Intent Stronglink switch monitor circuit parts returned from the field out of retired weapon systems. Evaluations of local contact resistance, surface chemical composition and surface roughness and wear have been determined as a function of component level contact loop resistance testing position. Several degradation mechanisms have been identified and correlated with the component level measurements. Operational degradation produces surface smoothing and wear with each actuation of the monitor circuit, while aging degradation is observed in the segregation of contaminant species and alloy constituent elements to the surface in the stressed wear regions.

Nanosatellite space launches could significantly benefit from an electrically powered launch complex, based on an electromagnetic coil launcher. This paper presents results of studies to estimate the required launcher parameters and some fixed facility issues. This study is based on electromagnetic launch, or electromagnetic gun technology, which is constrained to a coaxial geometry to take advantage of the efficiency of closely-coupled coils. A baseline configuration for analysis considers a payload mass of 10 kg, launch velocity of 6 km/s, a second stage solid booster for orbital insertion, and a payload fraction of about 0.1. The launch facility is envisioned as an inclined track, 1-2 km in length, mounted on a hillside at 25 degrees aimed in the orbital inclination of interest. The launcher energy and power requirements fall in the range of 2000 MJ and 2 MW electric. This energy would be supplied by 400 modules of energy storage and magnetic coils. With a prime power generator of 2 MW, a launch rate of some 200 satellites per day is possible. The launch requires high acceleration, so the satellite package must be hardened to launch acceleration on the order of 1000 gee. Parametric evaluations compare performance parameters for a launcher …

Savannah River Site (SRS) in South Carolina is dissolving Pu239 scrap, which is a legacy from the production of nuclear weapons materials, and will later convert it into oxide form to stabilize it. An eductor has been used to both dilute and transfer a plutonium containing solution between tanks. Eductors have the advantages of simplicity and no moving parts. Reliable control of dilution is important because the geometry of the receiving tank could potentially allow a nuclear criticality. Dilution factor was to have been controlled by the appropriate choice of flow restrictor in the line between the plutonium solution tank and the eductor. However, dilution factors measured for liquid transfers with different flow restrictors showed unexpected trends, causing concern that the process was not well understood. As a result, the performance of the eductor and associated piping were analyzed using a mathematical model. The one dimensional, two phase model accounted for eductor performance and for air and vapor coming out of solution at low pressures. The unexpected trends were shown to be the result of variations in viscosities and densities of both the plutonium solution and the nitric acid solution used as both the motive fluid and diluent. The model …

None

None

In this article the authors concisely present several modern strategies that are applicable to drift-dominated carrier transport in higher-order deterministic models such as the drift-diffusion, hydrodynamic, and quantum hydrodynamic systems. The approaches include extensions of upwind and artificial dissipation schemes, generalization of the traditional Scharfetter-Gummel approach, Petrov-Galerkin and streamline-upwind Petrov Galerkin (SUPG), entropy variables, transformations, least-squares mixed methods and other stabilized Galerkin schemes such as Galerkin least squares and discontinuous Galerkin schemes. The treatment is representative rather than an exhaustive review and several schemes are mentioned only briefly with appropriate reference to the literature. Some of the methods have been applied to the semiconductor device problem while others are still in the early stages of development for this class of applications. They have included numerical examples from the recent research tests with some of the methods. A second aspect of the work deals with algorithms that employ unstructured grids in conjunction with adaptive refinement strategies. The full benefits of such approaches have not yet been developed in this application area and they emphasize the need for further work on analysis, data structures and software to support adaptivity. Finally, they briefly consider some aspects of software frameworks. These include dial-an-operator approaches …

A source of instability in the western Pacific warm pool is shown to be due to sea surface elevation variations caused by changes in the zonal sea-surface temperature (SST) gradient and the changes in the Pacific Ocean basin length in relation to the warm pool latitudinal location. The variation of the sea-surface elevation is measured by using the thermocline depth response calculated from a two-layer ocean. The warm pool is shown to be barely at equilibrium during the boreal late winter and early spring by comparing the measured thermocline at 110{degree}W, 0{degree}E with the calculated thermocline depth. Based on this analysis, a failure or reversal of the climatological zonal winds are apparently not a necessary precursor for the instability of the warm pool and initiation of a warm event. A warm event can be initiated by an increase in the size of the warm pool and/or an increase in zonal SST differences during the boreal/winter spring. This mechanism could be an alternate mechanism for El-Nino Southern Oscillation (ENSO) dynamics to that postulated by Bjeknes (1969).

None

For highly crosslinked, polymer networks bonded to a solid surface, the effect of interfacial bond density as well as system size on interfacial fracture is studied molecular dynamics simulations. The correspondence between the stress-strain curve and the sequence of molecular deformations is obtained. The failure strain for a fully bonded surface is equal to the strain necessary to make taut the average minimal path through the network from the bottom solid surface to the top surface. At bond coverages less than full, nanometer scale cavities form at the surface yielding an inhomogeneous strain profile. The failure strain and stress are linearly proportional to the number of bonds at the interface unless the number of bonds is so few that van der Waals interactions dominate. The failure is always interfacial due to fewer bonds at the interface than in the bulk.

A single column model (SCM) is, in essence, an isolated grid column of a general circulation model (GCM). Hence, SCMs have rather demanding input data requirements, but do not suffer from problems associated with balance of a GCM. Among the initial conditions that must be used to describe the initial state of the SCM column are the vertical profile of the horizontal wind components and the vertical profiles of cloud water and ice. In addition, the large-scale divergence and advective tendencies of cloud water and ice must be supplied as external parameters. Finally, the liquid and ice cloud amount as a function of height within the SCM column are required for model evaluation. The scale of the SCM column over which the initial conditions, external parameters, and model evaluation fields must apply is relatively large ({approximately}300 km). To quantify atmospheric structure on this scale, the ARM SGP CART site is located within the NOAA wind profiler network and has boundary and extended measurement facilities in an area compatible with the scale requirements of SCMs. Over an area this size, however, there is often rich mesoscale structure. This mesoscale variability creates a sampling problem that can thwart even the most sophisticated …

One of the primary objectives of the Fall 1997 IOP was to intercompare Ka-band (35GHz) and W-band (95GHz) cloud radar observations and verify system calibrations. During September 1997, several cloud radars were deployed at the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site, including the full time operation 35 GHz CART Millimeter-wave Cloud Radar (MMCR), (Moran, 1997), the University of Massachusetts (UMass) single antenna 33GHz/95 GHz Cloud Profiling Radar System (CPRS), (Sekelsky, 1996), the 95 GHz Wyoming Cloud Radar (WCR) flown on the University of Wyoming King Air (Galloway, 1996), the University of Utah 95 GHz radar and the dual-antenna Pennsylvania State University 94 GHz radar (Clothiaux, 1995). In this paper the authors discuss several issues relevant to comparison of ground-based radars, including the detection and filtering of insect returns. Preliminary comparisons of ground-based Ka-band radar reflectivity data and comparisons with airborne radar reflectivity measurements are also presented.

Growth of InAs/AlAs short-period superlattices on appropriately miscut (001) InP substrates is shown to alter the microstructure of composition modulation from a 2D organization of short compositionally enriched wires to a single dominant modulation direction and wire lengths up to {approximately}1 {micro}m. The effects of miscut are interpreted in terms of surface step orientation and character. The material is strongly modulated and exhibits intense optical emission. The 1D modulations appear potentially useful for new devices that take advantage of the preferred direction formed in the growth plane.

The atomic process, kinetics, and equilibrium thermodynamics underlying the gettering of transition-metal impurities in Si are reviewed from a mechanistic perspective. Methods for mathematical modeling of gettering are reviewed and illustrated. Needs for further research are discussed.