We present the results of x-ray scattering studies of the charge and orbital ordering in the manganite series Pr{sub 1{minus}z}, Ca{sub x}, MnO{sub 3} with x = 0.25, 0.4 and 0.5. The polarization and azimuthal dependence of the charge and orbital ordering in these compounds is characterized both in the resonant and nonresonant limits, and compared with the predictions of current theories. The results are qualitatively consistent with both cluster and LDA+U calculations of the electronic structure.

Atoms and molecules adsorbed on metals affect each other even over considerable distances. In a tour-de-force of density-functional methods, the authors establish the nature and strength of such indirect interactions, and explain for what adsorbate systems they can critically affect important materials properties. These perceptions are verified in kinetic Monte Carlo simulations of epitaxial growth, and help rationalize a cascade of recent experimental reports on anomalously low diffusion prefactors. The authors focus their study on two metal systems: Al/Al(111) and Cu/Cu(111).

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Chinguetti is a 4.5 kg mesosiderite find recovered from the Adra region of Mauretania. In this paper the authors analyse a portion of the recovered sample for cosmogenic radionuclides to determine its terrestrial age, and to determine its pre-atmospheric radius. They determined the terrestrial age of Chinguetti to be < 30 ky. They constrain the pre-atmospheric radius to 50--80 cm and the shielding depths of 15--25 cm. These data indicate that Chinguetti is a comparatively recent fall.

Trialkoxysilyl-containing monomers of the type (RO){sub 3}Si(CH{sub 2}){sub 3}C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyl esters CH{sub 3}CHCH{sub 2}C(O)OtBu. Acid- or base-catalyzed polymerization of the monomers leads to very high molecular weight polymers with relatively narrow polydispersities. The polymerization results in complete condensation of the alkoxy groups while the tert-butyl ester functionality remains fully intact. Partial or full deprotection of the tert-butyl group can easily be achieved to yield the corresponding carboxylic acid polymers. The ester and carboxylic acid functionalities of these new materials allow for their potential use in a variety of applications such as scavenging of heavy metals.

The structure of Na{sub 16}Nb{sub 12.8}Ti{sub 3.2}O{sub 44.8}(OH){sub 3.2} {center_dot} 8H{sub 2}O, a member of a new family of Sandia Octahedral Molecular Sieves (SOMS) having a Nb/Na/M{sup IV} (M= Ti, Zr) oxide framework and exchangeable Na and water in open channels, was determined from Synchrotron X-ray data. The SOMS phases are isostructural with variable M{sup IV}:Nb(1:50--1:4) ratios. The SOMS are extremely selective for sorption of divalent cations, particularly Sr{sup 2+}. The ion-exchanged SOMS undergo direct thermal conversion to a perovskite-type phase, indicating this is a promising new method for removal and sequestration of radioactive Sr-90 from mixed nuclear wastes.

The miscibility of polypropylene (PP) melts in which the chains differ only in stereochemical composition has been investigated by two different procedures. One approach used detailed local information from a Monte Carlo simulation of a single chain, and the other approach takes this information from a rotational isomeric state model devised decades ago, for another purpose. The first approach uses PRISM theory to deduce the intermolecular packing in the polymer blend, while the second approach uses a Monte Carlo simulation of a coarse-grained representation of independent chains, expressed on a high-coordination lattice. Both approaches find a positive energy change upon mixing isotactic PP (iPP) and syndiotactic polypropylene (sPP) chains in the melt. This conclusion is qualitatively consistent with observations published recently by Muelhaupt and coworkers. The size of the energy chain on mixing is smaller in the MC/PRISM approach than in the RIS/MC simulation, with the smaller energy change being in better agreement with the experiment. The RIS/MC simulation finds no demixing for iPP and atactic polypropylene (aPP) in the melt, consistent with several experimental observations in the literature. The demixing of the iPP/sPP blend may arise from attractive interactions in the sPP melt that are disrupted when the sPP …

The objectives of this presentation are two-fold: first, to demonstrate the connection between the attainable coefficients and transition to turbulent flow by using the transition-based corresponding states method to generalize results obtained with smooth tubes and enhanced tubes, and second, to provide guidelines on the calculation of heat transfer coefficients from pressure-drop data and vice versa by using the transition concept or the functional law of corresponding states.

The last major development effort for nuclear power and propulsion systems ended in 1993. Currently, there is not an initiative at either the National Aeronautical and Space Administration (NASA) or the U.S. Department of Energy (DOE) that requires the development of new nuclear power and propulsion systems. Studies continue to show nuclear technology as a strong technical candidate to lead the way toward human exploration of adjacent planets or provide power for deep space missions, particularly a 15,000 lbf bimodal nuclear system with 115 kW power capability. The development of nuclear technology for space applications would require technology development in some areas and a major flight qualification program. The last major ground test facility considered for nuclear propulsion qualification was the U.S. Air Force/DOE Space Nuclear Thermal Propulsion Project. Seven years have passed since that effort, and the questions remain the same, how to qualify nuclear power and propulsion systems for future space flight. It can be reasonably assumed that much of the nuclear testing required to qualify a nuclear system for space application will be performed at DOE facilities as demonstrated by the Nuclear Rocket Engine Reactor Experiment (NERVA) and Space Nuclear Thermal Propulsion (SNTP) programs. The nuclear infrastructure …

This work characterizes the interfaces resulting from exposing oxide and non-oxide ceramic substrates to zirconium metal and stainless steel-zirconium containing alloys. The ceramic/metal systems together were preheated at about 600 C and then the temperatures were increased to the test maximum temperature, which exceeded 1800 C, in an atmosphere of high purity argon. Metal samples were placed onto ceramic substrates, and the system was heated to elevated temperatures past the melting point of the metallic specimen. After a short stay at the peak temperature, the system was cooled to room temperature and examined. The chemical changes across the interface and other microstructural developments were analyzed with energy dispersive spectroscopy (EDS). This paper reports on the condition of the interfaces in the different systems studied and describes possible mechanisms influencing the microstructure.

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A glass-bonded ceramic waste form is being developed to immobilize radioactively contaminated chloride waste salts generated during the conditioning of spent sodium-bonded nuclear fuel for disposal. The waste salt is first mixed with zeolite A to occlude the salt into cavities in the zeolite structure. The salt-loaded zeolite is then mixed with a borosilicate glass and consolidated by hot isostatic pressing. During this process, the zeolite converts to the mineral sodalite, which retains most of the waste salt, and small amounts of halite are generated. Halite inclusions have been observed within micron- to submicron-sized pores that form within the glass phase in the vicinity of the sodalite/glass interface. These inclusions are important because they may contain small amounts of radionuclide contaminants (eg {sup 135}Cs and {sup 129}I),and may affect the corrosion behavior of the waste form. Optical microscopy, scanning electron microscopy, and transmission electron microscopy were used to characterize the chemical nature and distribution of halite inclusions in the waste form.

The analytical figure of merit of a laser-induced breakdown (LIBS) system was evaluated for technetium measurements in liquid. LIBS data of elements that have similar properties to Tc such as Cr, Mn, and Re were studied. Various optical geometries which produce the laser spark in and at the liquid sample were tested. The calibration curve for Mn, Cr, and Re were obtained at the optimized experimental conditions with bulk liquid and liquid jet. We found that measurements using a liquid jet provide better detection limits than the bulk liquid measurements. The detection limits of Mg, Cr, Mn, and Re in a liquid jet measurement are found to be 0.1, 0.4, 0.7, and 10 ppm, respectively.

Ge(mnn) surfaces between (100) and (111) were annealed under either arsine or phosphine in a metal-organic chemical vapor deposition chamber, then imaged with a scanning tunneling microscope. In general, arsine-exposed Ge surfaces are facetted, while phosphine-exposed surfaces remain flat. For the arsine-exposed Ge surfaces, four stable facetting directions have been identified: (100), (11,3,3), (955), and (111).

The most recent results on CP violation and mixing in the charm system are reviewed as a guide to the future. While no surprising results are reported so far, charm provides a unique window to physics beyond the Standard Model. The results reported here come from four sources, ALEPH at LEP, E791 and FOCUS/E831 at Fermilab, and CLEO II.V at CESR. Results beyond these sources may be expected as a byproduct of B-motivated experiments.

During the past few decades great numbers of meteorites have been recovered from the ice accumulation zones of Antarctica and from the vast Sahara. Although these two great deserts are the two most productive areas, the Southern High Plains in USA (New Mexico and Texas) and Nullarbor Plain, Western Australia have great potential for meteorite recovery. The number of meteorite finds from Roosevelt County, New Mexico alone exceeds 100 in only approximately 11 km{sup 2} area. Most meteorites from this area have been found on the floors of active deflation basins (blowouts) that have been excavated from a mantle of sand dunes. This area has no apparent fluvial or permafrost activity within the last 50,000 years, suggesting that only prevailing winds and natural aridity aid in the concentration and preservation of meteorites. The authors investigated these deflation surfaces in Lea County (the SE corner of New Mexico) and neighboring Winkler County, Texas following a prior search in this area which found two chondrites. They found a tiny H4 chondrite in this search and here they report its mineralogy and petrology along with preliminary data on its exposure history.

Two carrier/shipping cask options are being developed to transport bottles of EBR-II fuel elements stored at INTEC. Some fuel bottles are intact, but some have developed leaks. Reactivity control requirements to maintain subcriticality during the hypothetical transport accident have been examined for both transport options for intact and leaking bottles. Poison rods, poison sleeves, and dummy filler bottles were considered; several possible poison materials and several possible dummy filler materials were studied. The minimum number of poison rods or dummy filler bottles has been determined for each carrier for transport of intact and leaking bottles.

The finite element method is being used today to model component assemblies in a wide variety of application areas, including structural mechanics, fluid simulations, and others. Generating hexahedral meshes for these assemblies usually requires the use of geometry decomposition, with different meshing algorithms applied to different regions. While the primary motivation for this approach remains the lack of an automatic, reliable all-hexahedral meshing algorithm, requirements in mesh quality and mesh configuration for typical analyses are also factors. For these reasons, this approach is also sometimes required when producing other types of unstructured meshes. This paper will review progress to date in automating many parts of the hex meshing process, which has halved the time to produce all-hex meshes for large assemblies. Particular issues which have been exposed due to this progress will also be discussed, along with their applicability to the general unstructured meshing problem.

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The use of plasma spray to deposit thin metal-sulfide cathode films is described in this paper. Conventional electroactive stack components in thermal batteries are constructed from pressed-powder parts that are difficult to fabricate in large diameters in thicknesses <0.010. Plasma-sprayed electrodes do not steer from this difficulty, allowing greater energy densities and specific energies to be realized. Various co-spraying agents have been found suitable for improving the mechanical as well as electrochemical properties of plasma-sprayed cathodes for thermal batteries. These electrodes generally show equal or improved performance over conventional pressed-powder electrodes. A number of areas for future growth and development of plasma-spray technology is discussed.

The angle correlation in e{sup +}e{sup {minus}} pair production by linear polarized photon was proposed for photon polarization measurements by Yang and Berlin and Madansky. An accurate QED calculation with analysis of the possible experimental setup was done by L Maximon and H. Olsen. The effect was used successfully for measurement of the beam polarization. The limitation of the method at photon energies above 100 MeV arises from the small value of an angle between pair components. They propose a new polarimeter for high energy photons based on the well known correlation in electron-positron pair production from an amorphous converter. The detector design utilizes silicon micro-strip detectors that allow the construction of a compact device useful in the few GeV photon energy range. The most important features of these detectors are the capability to detect two tracks separated by a very small distance ({approximately} 100 microns) and very good position resolution, ({approximately} a few microns). Because the typical opening angle in e{sup +}e{sup {minus}} pair is about 1/{gamma} and available space for a polarimeter is about 1 meter, the distance e{sup +}e{sup {minus}} is about a fraction of mm. It means that at the photon energies of interest, most of …

Argonne National Laboratory (ANL) has worked closely with Western Area Power Administration (Western) over many years to develop a variety of electric power marketing and transmission system models that are being used for ongoing system planning and operation as well as analytic studies. Western markets and delivers reliable, cost-based electric power from 56 power plants to millions of consumers in 15 states. The Spot Market Agent Research Tool Version 2.0 (SMART II) is an investigative system that partially implements some important components of several existing ANL linear programming models, including some used by Western. SMART II does not implement a complete model of the Western utility system but it does include several salient features of this network for exploratory purposes. SMART II uses a Swarm agent-based framework. SMART II agents model bulk electric power transaction dynamics with recognition for marginal costs as well as transmission and generation constraints. SMART II uses a sparse graph of nodes and links to model the electric power spot market. The nodes represent power generators and consumers with distinct marginal decision curves and varying investment capital as well individual learning parameters. The links represent transmission lines with individual capacities taken from a range of central …

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