Effects of fission product accumulation in cubic zirconia

Yttria stabilized cubic-zirconia (YSZ) is a promising candidate material for both inert matrix fuel and waste form based on its high solubility for actinides, high chemical durability and its reported exceptional stability under radiation. Because the incorporation of fission and other transmutation products during burnup may significantly affect the radiation response and the chemical durability of cubic zirconia, the solubility and mobility of the fission product nuclides in the inert matrix fuel at high temperatures (reactor fuel conditions) and low temperatures (repository conditions) are important. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87572/2/95_1.pd

Nanodomains of pyrochlore formed by Ti ion implantation in yttria-stabilized zirconia

The microstructural evolution of a single crystal of yttria-stabilized zirconia (YSZ) implanted with Ti has been studied by cross-sectional transmission electron microscopy (TEM). The implantation of 180 keV Ti ions to a dose of 1×1017 ions/cm21×1017ions/cm2 was completed at room temperature. After annealing at 1100 °C in an Ar atmosphere for 2 h, a phase transition from the fluorite structure of ZrO2ZrO2 to an isometric pyrochlore structure-type, A2B2O7,A2B2O7, occurred due to cation ordering. High-resolution TEM revealed nanodomains of pyrochlore, Y2(TixZr1−x)2O7,Y2(TixZr1−x)2O7, with a ≅ 10.24±0.05 Å.a≅10.24±0.05Å. The nanodomains of the pyrochlore phase, embedded within the YSZ fluorite substrate, occurred in a depth range from 45 to 105 nm below the surface, which corresponds to Ti concentrations from ∼10 to ∼15 at. %. The nanoscale pyrochlore precipitates and the YSZ matrix have a completely coherent orientation. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70072/2/APPLAB-80-23-4327-1.pd

Radiation effects in uranium-niobium titanates

Pyrochlore is an important actinide host phase proposed for the immobilization of high level nuclear wastes and excess weapon plutonium.[1] Synthetic pyrochlore has a great variety of chemical compositions due to the possibility of extensive substitutions in the pyrochlore structure.[2] During the synthesis of pyrochlore, additional complex titanate phases may form in small quantities. The response of these phases to radiation damage must be evaluated because volume expansion of minor phases may cause micro-fracturing. In this work, two complex uranium-niobium titanates, U3NbO9.8U3NbO9.8 (U-rich titanate) and Nb3UO10Nb3UO10 (Nb-rich titanate) were synthesized by the alkoxide/nitrate route at 1300 °C under an argon atmosphere. The phase composition and structure were analyzed by EDS, BSE, XRD, EMPA and TEM techniques. An 800 KeVKr2+800KeVKr2+ irradiation was performed using the IVEM-Tandem Facility at Argonne National Laboratory in a temperature range from 30 K to 973 K. The radiation effects were observed by in situ TEM. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87573/2/403_1.pd

Nano-porosity in GaSb induced by swift heavy ion irradiation

Nano-porous structures form in GaSb after ion irradiation with 185 MeV Au ions. The porous layer formation is governed by the dominant electronic energy loss at this energy regime. The porous layer morphology differs significantly from that previously reported for low-energy, ion-irradiated GaSb. Prior to the onset of porosity, positron annihilation lifetime spectroscopy indicates the formation of small vacancy clusters in single ion impacts, while transmission electron microscopy reveals fragmentation of the GaSb into nanocrystallites embedded in an amorphous matrix. Following this fragmentation process, macroscopic porosity forms, presumably within the amorphous phase.The authors thank the Australian Research Council for support and the staff at the ANU Heavy Ion Accelerator Facility for their continued technical assistance. R.C.E. acknowledges the support from the Office of Basic Energy Sciences of the U.S. DOE (Grant No. DE-FG02-97ER45656)

Multi-time delay, multi-point Linear Stochastic Estimation of a cavity shear layer velocity from wall-pressure measurements

Multi-time-delay Linear Stochastic Estimation (MTD-LSE) technique is thoroughly described, focusing on its fundamental properties and potentialities. In the multi-time-delay ap- proach, the estimate of the temporal evolution of the velocity at a given location in the flow field is obtained from multiple past samples of the unconditional sources. The technique is applied to estimate the velocity in a cavity shear layer flow, based on wall-pressure measurements from multiple sensor

Super-Group Field Cosmology

In this paper we construct a model for group field cosmology. The classical equations of motion for the non-interactive part of this model generate the Hamiltonian constraint of loop quantum gravity for a homogeneous isotropic universe filled with a scalar matter field. The interactions represent topology changing processes that occurs due to joining and splitting of universes. These universes in the multiverse are assumed to obey both bosonic and fermionic statistics, and so a supersymmetric multiverse is constructed using superspace formalism. We also introduce gauge symmetry in this model. The supersymmetry and gauge symmetry are introduced at the level of third quantized fields, and not the second quantized ones. This is the first time that supersymmetry has been discussed at the level of third quantized fields.Comment: 14 pages, 0 figures, accepted for publication in Class. Quant. Gra

A New Perennial Legume to Combat Dryland Salinity in South-Western Australia

Dryland salinity has devastated large tracts of productive land in Australia. This has resulted from the clearing of native perennial vegetation and its replacement with annual crops and pastures. As annual plants are shallow rooted and only use water during their winter-spring growing season, unutilised rainwater leaks into groundwater tables which rise and bring stored salt to the soil surface. The adoption of deep rooted perennial pasture plants that increase the water use can help to manage dryland salinity whilst maintaining productivity. However, new plants are needed as few perennial pasture options currently exist. Preliminary research into the potential of hairy canary clover (Dorycnium hirsutum (L.) Ser.) to increase water use is presented

Qualitative study in Loop Quantum Cosmology

This work contains a detailed qualitative analysis, in General Relativity and in Loop Quantum Cosmology, of the dynamics in the associated phase space of a scalar field minimally coupled with gravity, whose potential mimics the dynamics of a perfect fluid with a linear Equation of State (EoS). Dealing with the orbits (solutions) of the system, we will see that there are analytic ones, which lead to the same dynamics as the perfect fluid, and our goal is to check their stability, depending on the value of the EoS parameter, i.e., to show whether the other orbits converge or diverge to these analytic solutions at early and late times.Comment: 12 pages, 7 figures. Version accepted for publication in CQ

Naturally occurring Ehrlichia chaffeensis infection in coyotes from Oklahoma.

A nested polymerase chain reaction assay was used to determine the presence of Ehrlichia chaffeensis, E. canis, and E. ewingii DNA in blood samples of free-ranging coyotes from central and northcentral Oklahoma. Of the 21 coyotes examined, 15 (71%) were positive for E. chaffeensis DNA; none was positive for E. canis or E. ewingii. Results suggest that E. chaffeensis infections are common in free-ranging coyotes in Oklahoma and that these wild canids could play a role in the epidemiology of human monocytotropic ehrlichiosis