bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leaching Behaviour of Zirconolite in 0.001M Citric Acid at 90°C Under Various Flow Regimes
Authors: McGlinn Peter J. , Advocat Thierry , Leturcq Gilles , McLeod Terry I. , Aly Zaynab , Yee Patrick 
Published: April 2011

ABSTRACTNd-bearing zirconolite was leached at 90°C for 157 days in 0.001M citric acid under single-pass-flow-through conditions (modified MCC-4 protocol). Three different flow rates were used, ranging in an order of magnitude from 10 mL per day to 100 mL per day, to determine the effect of the rate of leachant replenishment on the durability of the zirconolite. Results of previous studies on the role of complexing agents on the leaching behaviour of single-phase zirconolite have been included in the discussion.The pH of the citric acid solution was adjusted to 5 using KOH, mimicking that of the water in the parallel tests, to avoid the influence of pH on chemical durability of the zirconolite.Simulated groundwater containing 0.001M citric acid at 90°C led to congruency in elemental releases and a diminution of release rate with time of about an order of magnitude, reaching virtual constancy after about 50 to 60 days to a level of about 10−5 g m−2 day−1. The most significant finding was that the elemental release rates of Nd, Ti and Zr (and Ca and Al where detected) were similar for all flow rates. Clearly, varying flow rate by up to an order of magnitude had no effect on elemental releases i.e. there is no solubility limit control on releases at 0.001M citric acid concentration.An important finding of previous studies using identical leaching protocols with 0.001M citric acid, and inferred in our latest investigations reported here, was that there is no secondary layer development at the surface of the zirconolite to affect leach rates. In contrast, parallel tests carried out in deionised water instead of citric acid showed that hydroxides form in situ on the zirconolite surface, effectively forming hydrolysed zirconolite. This controls further dissolution of the zirconolite matrix due to the solubility limit being reached with respect to the hydrolysed phases rather than with zirconolite. Complexation by citrate ions prevents such control by hydrolysed species on zirconolite solubility.Even under the more aggressive conditions imposed in these studies (0.001M citric acid), and regardless of flow rate of the leachant, elemental releases from zirconolite are very low for a candidate wasteform and demonstrate its attributes as a ceramic-based wasteform for the containment of actinides.
Immobilization and Behavior of Technetium in a Magnesium Titanate Matrix for Final Disposal
Authors: Exter Marcel. J. den , Neumann Signe , Tomasberger Tanja 
Published: April 2011

ABSTRACTTechnetium was immobilized in a Mg2TiO4 matrix by atomic substitution of titanium for 20, 50 and 80mol%. Leach tests, conforming to the ASTM C-1220-92 specifications, were carried out using simulated leachants (granite water, clay pore water and saturated salt solution) in order to determine normalized leach rates (NL) and fractional releases (FR%).FR% for technetium have been measured < 0.1% for all Tc-loadings. Typical NL are1.7 E−2 g/m2d and 1.1 E−1 g/m2d for a 50 mol% and 80 mol% Tc-loading. In comparison to published fractional releases for glass, the matrix proves to be a more suitable host.In addition, inactive pellets were produced and leached for investigation of the behaviour of the matrix material itself and the influence of other phases due to possible incomplete reactions during fabrication. Two types of inactive pellets were produced: Mg2TiO4 and Mg2TiO4/MgTiO3/MgO mixed pellets, the latter by decreasing the temperature during fabrication to 1285°C. Release of titanium from MgTiO3 proves to be higher than for Mg2TiO4.It was found that the leachability of the host matrix increases upon increasing the technetium loading. As a compromise between waste volume reduction and leachability, it is suggested that technetium loadings do not exceed about 50 mol%.
Assessment of the relevance of Coffinite formation within the near-field environment of spent nuclear fuel geological disposals
Authors: Robit-Pointeau V. , Poinssot C. , Vitorge P. , Grambow B. , Cui D. , Spahiu K. , Catalette H. 
Published: April 2011

ABSTRACTExperiments were performed in anoxic gloves box in an attempt to synthesise Coffinite both in representative near-field conditions, and in conditions which were expected to favour its precipitation according to thermodynamic calculations. The experimental results did not confirm the predictions. However, a new mineral was observed instead of Coffinite. In addition, accurate characterization of various natural samples demonstrate the permanent presence of U(VI) within Coffinite contradictory to its theoretical composition. Our observations raise the question on the validity and applicability of available –actually estimated- thermodynamic data of Coffinite. Based on kinetic hindrance of Coffinite formation, coffinitization of spent nuclear fuel in geological disposal is not anticipated to be a dominant short term process.
Cold Crucible Vitrification of Defense Waste Surrogate and Vitrified Product Characterization
Authors: Kobelev A.P. , Stefanovsky S.V. , Knyazev O.A. , Lashchenova T.N. , Holtzscheiter E.W. , Marra J.C. 
Published: April 2011

ABSTRACTIn the framework of the contract “Advanced Melter Technology Application to the Defense Waste Processing Facility (DWPF) –Cold Crucible Induction Heated Melter (CCIM)”, vitrification tests with Savannah River Site defense waste surrogate were performed at the SIA Radon facility. Cold crucible melters with inner diameter of 216 mm and 418 mm were used in the testing. Commercially available (USA) frits 200 and 320 were used as glass-forming additives. In three different test campaigns, waste additive mixtures were fed as slurries with ∼60 wt.%, ∼30 wt.%, and 45 wt.% water content. Maximum slurry capacity and glass productivity under steady-state conditions were 35.4 kg/h and 16.2 kg/h, respectively. Specific glass productivity reached up to ∼3000 kg/(m2×day). The average melt process temperature was 1250- 1350 °C. Waste loadings in glass were 45 wt.% in tests 1 and 2 and 50 wt.% in test 3. The glasses produced were found to be homogeneous but contained a magnetite-type phase with the spinel structure due to high iron and manganese content in waste. Spinel was observed in the glassy matrix as individual regular crystals and their aggregates. All the waste uranium entered the vitreous phase. Infra-red spectra consist of strong absorption bands due to bridging Si-O-Si and non-bridging Si-O- bonds, some weak bands due to B-O bonds, and a number of narrow bands due to occurrence of the crystalline phase. The glassy products demonstrate high leach resistance. Normalized release of major glass elements (Na, Li, B, Si) is by 10 to 50 times lower than the values required for repository disposition by EPA.
Validation of glass dissolution and Si diffusion parameters with a combined glass dissolution-diffusion experiment in Boom Clay
Authors: Lemmens Karel , Aertsens Marc 
Published: April 2011

ABSTRACTExisting knowledge on glass dissolution and silica diffusion in Boom Clay is validated by experiments where both phenomena could be studied simultaneously. SON68 glass coupons, doped with radioactive 32Si, were sandwiched between two cores of fresh humid Boom Clay and heated to 30°C. At the end of the experiment, the system was dismantled, the mass loss of the glass coupon was measured, and the clay core was sliced to determine the diffusion profile of the 32Si dissolved from the glass. These data were completed with analyses of the clay water and surface analyses for analogous tests with undoped glass. The results are interpreted by assuming congruent glass dissolution at a constant rate, with a glass silica saturation concentration between 14 and 20 mg/l, a forward glass dissolution rate (at zero silica concentration) of 0.028 g.m−2day−1, an apparent silica diffusion coefficient in the clay of 1.4 10−12 m2sec−1, and a distribution coefficient for silica on Boom Clay between 0.010 and 0.075 m3kg−1. These parameter values are close to the range found in literature. It was not necessary to consider diffusion through the gel, precipitation or detailed geochemical reactions. The modeling exercise shows that the existing knowledge about the subsystems glass and clay can succesfully be integrated to describe the coupled processes in the whole system.
A Probabilistic Methodology to Determine Acceptance Criteria and Failure Probabilities for the KBS-3 Ductile Cast Iron Inserts
Authors: Nilsson Karl-Fredrik , Andersson Claes-Göran , Nilsson Fred , Dillström Peter , Andersson Mats , Minnebo Philip 
Published: April 2011

ABSTRACTThe Swedish KBS-3 copper-cast iron canisters for geological disposal are in an advanced stage of its development. This reports deals with the cast iron insert that provides the mechanical strength of the canister. The ductility of manufactured inserts often fall below the initial requirements [1]. An issue then was what consequences low tensile properties and scatter may have on the long-term failure probability of the canisters. This paper describes an approach to assess the failure probabilities for given actual material data and how to derive acceptance criteria for manufactured canisters. A statistical test programme was implemented using three inserts to determine the tensile, compression and fracture properties. Tested specimens were investigated by micro-structural analysis to determine the microstructure and categorize and size defects. It was found that the material scatter and low ductility was caused by many defect types, but with slag defects as the most important ones. These data were then used to compute defect distributions and as direct input to FE-calculations of KBS-3 canisters. A large number of FE- analyses were performed at the maximum design load (44 MPa) covering distributions of material parameters and geometrical features of the canisters. The computed probabilities were very low for both failure modes even for material data with poor ductility.
HR-TEM Studies of FePt Nanoparticles by Exit Wave Reconstruction
Authors: Sudfeld Daniela , Dmitrieva Olga , Friedenberger Nina , Dumpich Guenter , Farle Michael , Song ChengYu , Kisielowski Christian , Gruner Markus E. , Entel Peter 
Published: April 2011

ABSTRACTFePt nanoparticles are promising materials for high-density magnetic data storage media [1] and bio-medical applications such as drug-targeting and hyperthermia [2]. To understand their magnetic properties [3] it is essential to get insights into the lattice structure of isolated nanoparticles which influence the magnetic behavior.Typically, lattice fringes are observed with high-resolution transmission electron microscopy (HR-TEM). In this case delocalization effects disturb imaging of the lattice structure in particular if 2 to 6 nm small nanoparticles are involved. Therefore, FePt nanocrystals were investigated by reconstructing amplitude and phase of the scattered electron wave from a focal series of HRTEM images, which can produce delocalization free and direct images of the crystal structure [4]. The formation of 5-fold twinned structures of 3 to 7 nm face-centered cubic FePt nanocrystals is investigated that were grown from a colloidal solution [1]. The results are compared with abinitio density functional (DFT) calculations of FePt particles with a diameter of larger than 2 nm. Image simulations were performed with the Accelrys Cerius2 software package (Version 4.6). Good agreement between the ab-initio calculations and the experimental data is found.
Intrinsic Phase Shift and Novel Dynamic Magnetization States of a Spin Torque Oscillator under ac Current Injection
Authors: Zhou Yan , Persson Johan , Akerman Johan 
Published: April 2011

ABSTRACTWe report on a preferred phase shift ΔΦ0 between a spin torque oscillator (STO) and an ac current (Iac) injected at the intrinsic frequency (fSTO) of the STO. In the in-plane precession mode (IP) the STO adjusts to a state where its resistance (or voltage) lags Iac about a quarter of a wave length (ΔΦ0 = 87°−94°). In the IP mode ΔΦ0 increases somewhat with the dc current. As the precession changes into the Out-Of-Plane (OOP) mode, ΔΦ0 jumps by about 180°, i.e. the STO resistance now precedes Iac by about a quarter of a wave length (|ΔΦ0| = 86°). At the IP/OOP boundary, the ac current mixes the two oscillation modes and both periodic and chaotic oscillations are observed. As a consequence of mixing, subharmonic terms appear in the STO signal. ΔΦ0 can furthermore be tuned by changing one or more of the anisotropy field, the demagnetizing field or the applied field. At the IP/OOP boundary, Iac mixes the two oscillation modes. The intrinsic ΔΦ0 will impact any circuit design based on STO technology and will e.g. have direct consequences for phase locking in networks of serially connected STOs.
Positive Magnetisation in Carbon Nanoclusters Produced by High-Repetition-Rate Laser Ablation
Authors: Rode Andrei V. , Arcon Denis , Zorko Andrej , Jaglicic Zvonko , Christy Andrew G. , Madsen Nathan R. , Luther-Davies Barry , Lau Desmond W. M. , McCulloch Dougal G. 
Published: April 2011

ABSTRACTCarbon nanoclusters produced by high-repetition-rate laser ablation of graphite and glassy carbon in Ar exhibits para- and ferromagnetic behaviour at low temperature. The results show that the degree of remanent order is strongly dependent on the magnetic history, i.e. whether the samples were cooled under zero-field or field conditions. Such behaviour is typical for a spin glass structure where the system can exist in many different roughly equivalent spin configurations. The spin-freezing temperature is unusually high (50–300 K) compared with ≤ 15 K for typical spin glasses. The maximum in the zero-field magnetic susceptibility experiments and their field dependence indicate that there is competition between ferromagnetic and antiferromagnetic exchange pathways, accounting for the spin glass behavior and/or a low-dimensionality of the system.
Effects of Ta on the Microstructure and Magnetic Properties of FePt Thin Films
Authors: Jin Sangho , Jang Sung Uk , Kwon Soon-Ju 
Published: April 2011

ABSTRACTWe have studied the effect of Ta on the structure, magnetic properties and the ordering temperature of FePt(Ta) thin films. The samples are prepared by the dc and rf magnetron cosputtering method with 3 single element targets. After a deposition, the samples are annealed in a vacuum at various temperatures. The XRD patterns show strong (111) peaks at all annealing temperatures, but the change in the d-spacings reveals a disorder-order transformation. The more Ta is added to the FePt, the larger the coercivity becomes. The coercivity of the FePtTa40W film annealed at 700°C reaches about two times as large as the value of the pure FePt film. The delta m curves imply that Ta atoms diffuse into the grain boundary to reduce inter-granular exchange coupling, which leads the enhancement of coercivity
Spin Wave Based Logic Circuits
Authors: Khitun Alexander , Bao Mingqiang , Lee Joo-Young , Wang Kang , Lee Dok Won , Wang Shan 
Published: April 2011

ABSTRACTWe investigate spin wave propagation and interference in conducting ferromagnetic nanostructures for potential application in spin wave based logic circuits. The novelty of this approach is that information transmission is accomplished without charge transfer. A bit of information is encoded into the phase of spin wave propagating in a nanometer thick ferromagnetic film. A set of “AND”, “NOR”, and “NOT” logic gates can be realized in one device structure by utilizing the effect of spin wave superposition. We present experimental data on spin wave transport in 100nm CoFe films at room temperature obtained by the propagation spin wave spectroscopy technique. Spin wave transport has been studied in the frequency range from 0.5 GHz to 6.0 GHz under different configurations of the external magnetic field. Both phase and amplitude of the spin wave signal are sensitive to the external magnetic field showing 60Deg/10G and 4dB/20G modulation rates, respectively. Potentially, spin wave based logic circuits may compete with traditional electron-based ones in terms of logic functionality and power consumption. The shortcomings of the spin wave based circuits are discussed.
Phytotoxicity and Potential Allelopathy in Pale (Cynanchum rossicum) and Black swallowwort (C. nigrum)
Authors: Douglass Cameron H. , Weston Leslie A. , Wolfe David 
Published: April 2011

AbstractThe introduced exotic vines pale and black swallowwort rapidly have become invasive throughout regions of the northeastern United States and adjoining areas of Canada. Preliminary studies have reported that the species are allelopathic, possibly contributing to their competitive ability and invasiveness. Results from our laboratory assays indicated that swallowwort root exudates caused significant root length reductions (e.g., 40% for butterfly milkweed and 20% for large crabgrass) and reduced germination (e.g., 25% for lettuce) of indicator species. Additional bioassays with dried swallowwort tissues demonstrated that tissue leachates caused varied responses in indicators, with both significant stimulatory and inhibitory effects. In particular, significant congeneric interactions were noted between the two swallowwort species. Evidence from this study of swallowwort tissue phytotoxicity has important implications for developing effective management and habitat restoration strategies for the two invasive species.
Suitability of a New Plant Invader as a Target for Biological Control in Florida
Authors: Manrique Veronica , Diaz Rodrigo , Cuda James P. , Overholt William A. 
Published: April 2011

AbstractThe suitability of a target weed for classical biological control should be considered early in the process of plant invasion. Concerns have been raised about the recent arrival ofMikania micranthaKunth in south Florida and its potential to spread and invade natural and managed ecosystems. This weed is native to the neotropics, and has been introduced into many Asian countries and, more recently, into Australia. In Asia,M. micranthais particularly problematic in plantation crops, but also threatens natural areas and disturbed ecosystems. Several aspects of the biology and ecology ofM. micranthaare discussed in this review to evaluate its suitability as a target of biological control in Florida. Based on an ecological niche model, the climate in southern and central Florida is highly favorable for the invasion of this weed. Previous biological control programs provide valuable information for Florida scientists about the availability of natural enemies and potential areas for future foreign surveys. Genetic comparison of the Florida population and native range populations, in addition to climate matching, should be considered when selecting areas for foreign exploration. Finally, the authors used a scoring system and risk-benefit–cost analysis to evaluateM. micranthaas a potential target for biological control in Florida. We suggest that similar feasibility evaluations should be conducted not only for well-established problematic weeds but also for new invaders with a known history of invasiveness.
Empirical Evidence of Long-Distance Dispersal inMiscanthus sinensisandMiscanthus×giganteus
Authors: Quinn Lauren D. , Matlaga David P. , Stewart J. Ryan , Davis Adam S. 
Published: April 2011

AbstractMany perennial bioenergy grasses have the potential to escape cultivation and invade natural areas. We quantify dispersal, a key component in invasion, for two bioenergy candidates:Miscanthus sinensisandM.×giganteus. For each species, approximately 1 × 106caryopses dispersed anemochorously from a point source into traps placed in annuli near the source (0.5 to 5 m; 1.6 to 16.4 ft) and in arcs (10 to 400 m) in the prevailing wind direction. For both species, most caryopses (95% forM. sinensisand 77% forM.×giganteus) were captured within 50 m of the source, but a small percentage (0.2 to 3%) were captured at 300 m and 400 m. Using a maximum-likelihood approach, we evaluated the degree of support in our empirical dispersal data for competing functions to describe seed-dispersal kernels. Fat-tailed functions (lognormal, Weibull, and gamma (Γ)) fit dispersal patterns best for both species overall, but becauseM. sinensisdispersal distances were significantly affected by wind speed, curves were also fit separately for dispersal distances in low, moderate, and high wind events. Wind speeds shifted theM. sinensisdispersal curve from a thin-tailed exponential function at low speeds to fat-tailed lognormal functions at moderate and high wind speeds.M. sinensiscaryopses traveled farther in higher wind speeds (low, 30 m; moderate, 150 m; high, 400 m). Our results demonstrate the ability ofMiscanthuscaryopses to travel long distances and raise important implications for potential escape and invasion of fertileMiscanthusvarieties from bioenergy cultivation.
Genetic Ablation of cGMP-Dependent Protein Kinase Type I Causes Liver Inflammation and Fasting Hyperglycemia
Authors: Lutz Stefan Z. , Hennige Anita M. , Feil Susanne , Peter Andreas , Gerling Andrea , Machann Jürgen , Kröber Stefan M. , Rath Michaela , Schürmann Annette , Weigert Cora , Häring Hans-Ulrich , Feil Robert 
Published: April 2011

OBJECTIVE
The nitric oxide/cGMP/cGMP-dependent protein kinase type I (cGKI) signaling pathway regulates cell functions that play a pivotal role in the pathogenesis of type 2 diabetes. However, the impact of a dysfunction of this pathway for glucose metabolism in vivo is unknown.

RESEARCH DESIGN AND METHODS
The expression of cGKI in tissues relevant to insulin action was analyzed by immunohistochemistry. The metabolic consequences of a genetic deletion of cGKI were studied in mice that express cGKI selectively in smooth muscle but not in other cell types (cGKI-SM mice).

RESULTS
In wild-type mice, cGKI protein was detected in hepatic stellate cells, but not in hepatocytes, skeletal muscle, fat cells, or pancreatic β-cells. Compared with control animals, cGKI-SM mice had higher energy expenditure in the light phase associated with lower body weight and fat mass and increased insulin sensitivity. Mutant mice also showed higher fasting glucose levels, whereas insulin levels and intraperitoneal glucose tolerance test results were similar to those in control animals. Interleukin (IL)-6 signaling was strongly activated in the liver of cGKI-SM mice as demonstrated by increased levels of IL-6, phospho-signal transducer and activator of transcription 3 (Tyr 705), suppressor of cytokine signaling-3, and serum amyloid A2. Insulin-stimulated tyrosine phosphorylation of the insulin receptor in the liver was impaired in cGKI-SM mice. The fraction of Mac-2–positive macrophages in the liver was significantly higher in cGKI-SM mice than in control mice. In contrast with cGKI-SM mice, conditional knockout mice lacking cGKI only in the nervous system were normal with respect to body weight, energy expenditure, fasting glucose, IL-6, and insulin action in the liver.

CONCLUSIONS
Genetic deletion of cGKI in non-neuronal cells results in a complex metabolic phenotype, including liver inflammation and fasting hyperglycemia. Loss of cGKI in hepatic stellate cells may affect liver metabolism via a paracrine mechanism that involves enhanced macrophage infiltration and IL-6 signaling.