bluuebunny/crossref_metadata_2025_split huggingface dataset:
Static dissolution tests of α-doped UO2 under repository relevant conditions: Influence of Boom Clay and α-activity on fuel dissolution rates
Authors: Salah Sonia , Cachoir Christelle , Lemmens Karel , Maes Norbert 
Published: April 2011

ABSTRACTSince reprocessing is no longer the reference policy in Belgium, studies on the direct disposal of spent fuel in a clay formation have gained increased interest in the last years. In order to determine to what extent the clay properties and the α-activity influence the dissolution kinetics of spent fuel for the long term disposal, static dissolution tests have been performed on 5 different types of α-doped UO2, representing a PWR fuel with a burn-up of 45 or 55 GWd · tHM−1 and fuel ages ranging between 150 and 90,000 years, in different Boom Clay (BC) media at room temperature and in an anoxic atmosphere for 90 to 720 days. The uranium activity in the clay fraction over time was found to be much higher than the U-activity in the leachates, which has been mainly ascribed to the high retention capacity of the BC. The average dissolution rate between 0 and 90 days obtained for the 5 types of α-doped UO2 were all found to be high and quite similar at ∼263 µg · m−2· d−1and a “longer-term” rate (181 to 720 days) ranging between zero and 15 µg · m−2· d−1. These results suggest that the activity of the fuels does not seem to have an effect on the UO2 dissolution rates under the considered test conditions. In order to study the partition/redistribution of U during UO2dissolution, sequential extraction experiments were performed. Results of the latter have provided a better mechanistic understanding of BC/spent fuel interaction processes as well as information on the role of the different minerals controlling the U-retention/immobilization.
Modelling of the spent fuel dissolution rate evolution for repository conditions. Matrix Alteration Model results and sensitivity analysis
Authors: Quiñones J. , Iglesias E. , Martínez-Esparza A. , Merino J. , Cera E. , Bruno J. , de Pablo J. , Casas I. , Giménez J. , Clarens F. , Rovira M. 
Published: April 2011

ABSTRACTThis paper focuses on how to extrapolate current knowledge of spent fuel matrix alteration processes from laboratory to repository conditions, i.e., the influence of changes in both the environmental conditions and the range of time scale considered. Therefore, a spent fuel matrix alteration model allowing the alteration rate evolution to be predicted as a function of both the host rock considered and evaluation time scale of interest is described.At present, the model assumes that alteration of the spent fuel will start when the groundwater reaches the solid surface and that only the radiolytic species of the groundwater (oxidants generated by α-radiation of spent fuel) will produce the surface oxidation process and subsequent matrix dissolution; O2, H2O2 and OH· are the species that react with UO2(s) for oxidation of the pellet surface. The dissolution process of the surface sites that are oxidized is modelled in two steps: first, a surface co-ordination of the oxidized layer with aqueous ligands and, second, detachment (dissolution) of the product species. Taking this mechanism into account, the model gives the evolution of the spent fuel matrix alteration rate over periods as long as 1,000,000 years.In this work the matrix alteration rate results obtained for two repository environments, granitic and argillaceous, will be presented. Furthermore, a sensitivity analysis study has been performed on the influence of the following variables: type of spent fuel considered, α-dose rate evolution, α-range in groundwater, carbonate and iron concentration in groundwater, H2 partial pressure, container time failure and specific surface area of the pellet.
Obtaining Solubility Constants to Describe the Incongruent Dissolution of SON68 Waste Glass by an Equilibrium Ideal Solid Solution Model Approach
Authors: Jacques Diederik , Lemmens Karel 
Published: April 2011

ABSTRACTOne of the waste forms resulting from the Belgian programme for nuclear energy is the R7T7 high level waste glass, simulated by the SON68 glass. When exposed to distilled water or synthetic interstitial clay water, SON68 glass dissolves incongruently, releasing some elements (B, Li, Na) faster to the solution than others (Si, Al, Ca). The objective of this study is to describe the composition of the leachate in contact with inactive SON68 glass by assuming congruent glass dissolution followed by the precipitation of a secondary solid phase represented as an ideal solid solution in equilibrium with the leachate. Experimental SON68 dissolution data in distilled water was available at three temperatures. The solubility of the different end members in the solid solution is optimized using the available data for each temperature. The temperature dependence of the different end members was then obtained by Van 't Hoff equation. The calibrated model can describe the composition of the leachate and the altered glass phase during glass dissolution at different temperatures. The model, calibrated for the distilled water system, could successfully describe the composition of the leachate during glass dissolution experiments in a synthetic clay water system.
Temperature Dependence of Long-Term Alteration Rate for Aqueous Alteration of P0798 Simulated Waste Glass under Smectite Forming Conditions
Authors: Inagaki Y. , Saruwatari T. , Idemitsu K. , Arima T. , Shinkai A. , Yoshikawa H. , Yui M. 
Published: April 2011

ABSTRACTSeveral kinetic models have been proposed to evaluate the aqueous dissolution/alteration rate of nuclear waste glass for long-term. However, reaction processes controlling the long-term rate are much more subjected to controversy. Temperature dependence of the long-term alteration rate is an essential issue to understand the rate controlling processes. In the present study, the static aqueous alteration tests were performed with a Japanese simulated waste glass P0798 as a function of temperature from 60°C to120°C, and the temperature dependence of the long-term alteration rate was evaluated to understand the rate controlling processes. The tests were performed in 0.001M NaOH solution to maintain a constant solution pH of around 10 during the test period and to provide smectite forming conditions where smectite forms as the major secondary phase without zeolite formation. From the test results on dissolution of boron, the alteration rate at each temperature was analyzed by use of a water-diffusion model. The water-diffusion model used is based on a simple assumption; the glass alteration is controlled by water diffusion with ion-exchange between water (hydronium ion: H3O+) and soluble elements (B, Na, Li, etc) at the glass surface layer with the apparent diffusion coefficient Di. A good agreement was observed between the model analysis and the test results, and the value of Di was evaluated to be 1.2 × 10−22 m2/s at 60°C to 1.8 × 10−21 m2/s at 120°C. The Arrhenius plot of Di showed a good linearity to give the activation energy of 49 kJ/mol, which value is close to that for the residual dissolution rate of French waste glass (53 kJ/mol) by Gin [1], and is very close to that for ion-exchange in sodium aluminosilicate glass (49 kJ/mol) by McGrail [2]. These results suggest that water diffusion with ion-exchange can be the dominant process controlling the alteration rate under smectite forming conditions. At elevated temperatures (100°C and 120°C), however, the model-predicted boron releases deviated from the experimental data at the later stage beyond 50-80 days, which suggests that the alteration layer developing at the glass surface may evolve to be protective against the water diffusion to depress the alteration rate as the alteration proceeds.
Modelling of transport in fractures with complex matrix properties
Authors: Moreno Luis , Crawford James , Neretnieks Ivars 
Published: April 2011

ABSTRACTIn the ongoing Swedish site investigations it has been found that the rock matrix adjacent to many open fractures has been altered. The alteration can extend from mm to several cm. The altered rock can have different sorption and diffusion properties compared to the undisturbed rock and this may influence the retardation of the nuclides. The paper presents how the Channel Network model has been adapted to handle diffusion into a matrix composed of several layers with different properties in addition to the infinite undisturbed matrix. For one channel, the solution for the Residence Time Distribution, RTD, may be found in the Laplace-plane. For the transport in the Channel Network, a particle tracking technique is used to determine the paths followed by solute particles. The RTD for this path is obtained using convolution, which in the Laplace-plane means multiplication of the transfer functions for each channel. The inversion to the time-plane is made by numerical inversion of the Laplace transforms for each path. The method has been tested with data from the TRUE (Tracer Retention Understanding Experiments) project, Task 6F, fluid flow and solute transport in two features in 100 m scale where a complex matrix was modelled. The model was used to predict the transport of the tracers (I-129), Cs-137, and Am-241) over some 20 m. The paper also addresses how the RTD is influenced by the different retardation mechanisms under Site Characterisation (SC) as well as Performance Assessment (PA) conditions.
Impact of Device Variability and Circuit Phase Shift in Synchronized Spin Torque Oscillators
Authors: Persson Johan , Zhou Yan , Akerman Johan 
Published: April 2011

ABSTRACTCurrent-induced magnetization dynamics in a system composed of two electrically coupled spin torque oscillators (STOs) is examined. The dynamics of the STOs is modeled by the Landau–Lifshitz–Gilbert equations modified with a Slonczewski spin-transfer torque term. To study the impact of realistic process variations on STO synchronization we let the two STOs have different in-plane anisotropy fields (Hk). The simulation also provides for a time delay τ. We construct a phase diagram of the STO synchronization as a function of Hk and direct current (Idc) at different τ. The phase diagram turns out to be quite rich with different types of synchronized precession modes. While the synchronized state is originally very sensitive to STO process variations and can only sustain up to 4% Hk variation, the addition of a small time delay dramatically improves its robustness and allows as much as 145% Hk variation in the entire out-of-plane precession regime. It is also shown that the two STOs can not only be locked in frequency, but also in phase at a given τ and the phase difference between the two STOs can be tuned by varying the dc current.
Comparative Study in Magnetic Properties of Ni/Co/Pt(111) and Co/Ni/Pt(111)
Authors: Chen Yao-Jung , Ho H. Y. , Shern C. S. 
Published: April 2011

ABSTRACTMagneto-optical Kerr effect (MOKE), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES) were used to study the magnetic properties and the growth modes of thin Ni films on 1ML Co/Pt(111) and Co /1 ML Ni/Pt(111) at room temperature (RT). Because the lattice constants of Co and Ni are only slightly different, both growth modes have similar behavior. They grow 2 ML in layer-by-layer mode then turn to 3-D island growth. On the contrary, the magnetic properties have great difference. For Ni/1 ML Co/Pt(111), the easy axis of magnetization changed from the canted state to the out-of-plane direction when the Co buffer layer was inserted into Ni/Pt(111). The perpendicular magnetization persisted to 24 ML of Co thin films. This spin reorientation transition can be understood by the change of effective interface magnetic anisotropy. For Co/1 ML Ni/Pt(111), Kerr signal was not observed when the thickness of Co film was below 3 ML, and the easy axis of the magnetization was in-plane when the thickness of Co was greater than 3 ML at RT. The polar Kerr signal appeared after the sample was annealed at 450 K for 1 ML of Co. Further studies in the magnetic properties and surface composition of 3 ML Co/1 ML Ni/Pt(111) during an annealing process showed that the out-of-plane magnetization enhanced significantly when Co and Ni atoms diffused into the Pt substrate.The Curie temperature (TC) of both systems can be adjusted by changing the annealing temperature. Measuring at RT, TC decreased when the annealing temperature rose. However, the change rates were different in these two mirror systems. The possible mechanism of the evolution in the magnetic property with the interface structure was comparatively discussed.
Focused ion beam structured Co/Pt multilayers for field-coupled magnetic computing
Authors: Becherer Markus , Csaba Gyorgy , Emling Rainer , Ji Lili , Porod Wolfgang , Lugli Paolo , Schmitt-Landsiedel Doris 
Published: April 2011

ABSTRACTWe fabricated and patterned magnetic dots from Co/Pt multilayers and optimized the structure for strong inter-dot magnetic coupling. SQUID measurements show strong perpendicular anisotropy with characteristic sheared hysteresis loops. The films are fabricated by RF-magnetron sputtering and then patterned with a 50 keV Ga+ focused ion beam (FIB) tool. This keeps surface roughness low and feature sizes in the hundred-nanometer-regime are achievable by a single processing step. Simulations with the well established SRIM (Stopping and Range of Ions in Matter) code give an estimation of the beam diameter and help to estimate the FIB patterning potential. In order to show antiferromagnetic ordering large 48×48 dot arrays of (200×200) nm2 single domain dots were fabricated. The samples were demagnetized and scanned by magnetic force microscopy (MFM) in the remanent state. The demagnetized checkerboard patterns show no frustration over hundreds of dots. The fabricated single domain magnets are prospective building blocks for field-coupled magnetic logic devices.
Preparation and Magnetic Properties of Monodisperse Nanocomposite Hollow Spheres
Authors: Lin Chun-Rong , Wang Cheng-Chien , Chen I-Han 
Published: April 2011

ABSTRACTWe present a simple process to prepare the hollow ceramic (CoFe2O4/SiO2) composite nanospheres and hollow alloy (Co33Fe67/SiO2) composite nanospheres. The hollow CoFe2O4/SiO2 composite nanospheres were prepared by calcining polymer/CoFe2O4/SiO2 core/shell composite spheres which were synthesized by the sol-gel method following the chemical co-precipitation. In a typical process, the monodisperse polymer poly(MMA-co-MAA) latex (450 nm) was used as a core template. To create hollow CoFe2O4/SiO2 spherical structures with various sizes of CoFe2O4 nanoparticles, the hybrid PMMA/CoFe2O4/SiO2
core-shell spheres were subsequently calcined in the temperature range from 450 to 900°C for 4h. On the other hand, the hollow Co33Fe67/SiO2 composite nanospheres were formed by reduction of hollow CoFe2O4/SiO2 nanospheres in a stream of H2/Ar mixed gas at 900°C for 8 hrs. X-ray diffraction pattern shows that the coated phase of the hollow CoFe2O4/SiO2 composite nanospheres has a cubic spinel ferrite structure. Based on the thermogravimetric analysis (TGA), we found that the content of CoFe2O4 is 73 wt% in the hollow CoFe2O4/SiO2 composite shell. The scanning electron microscope and transmission electron microscope photographs show that the hollow spheres are uniform. According to the line scanning EDX analysis of the cross section of hollow spheres, the SiO2 is not only coated on the surface of sphere but also distributed over the shell of hollow sphere. The thickness of shell of hollow spheres is about 40 nm. Magnetic measurements show that the saturation magnetization is clearly decreases as the magnetic particle size decreased. This phenomenon can be interpreted as the effect of surface spin canting when the particle size is reduced. As for the hollow alloy (Co33Fe67/SiO2) composite nanospheres, the magnetic phase has a body-centered cubic structure and an average crystallite size of 28.7 nm. This alloy nanospheres exhibit a ferromagnetic behavior with saturation magnetization of 170 emu/g, coercivity of 250 Oe, and Curie temperature of 968 °C. Due to metallic and ferromagnetic behavior of Co33Fe67 nanoparticles, these hollow spheres can be used as a lightweight electromagnetic wave absorber.
Broom Snakeweed (Gutierrezia sarothrae): Toxicology, Ecology, Control, and Management
Authors: Ralphs Michael H. , McDaniel Kirk C. 
Published: April 2011

AbstractBroom snakeweed is a native weed widely distributed on rangelands of western North America. It often increases to near monocultures following disturbance from overgrazing, fire, or drought. This paper presents an up-to-date review of broom snakeweed toxicology, seed ecology, population cycles, succession, and management. The greatest ecological concern is that broom snakeweed displaces desirable forage for livestock or wildlife and greatly reduces biodiversity. It also is toxic and can cause abortions in all species of livestock. Propagation usually is pulse-driven in wet years, allowing large expanses of even-aged stands to establish and dominate plant communities. Snakeweed can be controlled by prescribed burning or spraying with herbicides. A weed-resistant plant community dominated by competitive grasses can prevent or minimize its reinvasion.
Cutleaf Teasel (Dipsacus laciniatus): Seed Development and Persistence
Authors: Bentivegna Diego J. , Smeda Reid J. 
Published: April 2011

AbstractCutleaf teasel (Dipsacus laciniatus) is an exotic, invasive plant that infests roadsides and other minimally disturbed areas. Plants in established stands appear to be a mixture of rapidly growing rosettes and rosettes with developing reproductive structures. Research that is focused on seed characteristics and their contribution to the spread of plants may be a key to precluding spread of cutleaf teasel in the field. Field studies were conducted to determine the viability and germinability of seeds after flowering, seedling emergence patterns, and seed persistence. Flowering (60% of anthesis) was observed under natural conditions on July 24, 2004, and July 16, 2005. Seeds harvested 12 d after flowering exhibited 43% viability and 2.5% germination. Seed weight and viability were greatest 30 d after flowering, but germination was < 32%. Seedling emergence was monitored over a 12-mo period with the greatest emergence in April and October with 33% of seeds germinating. Seed persistence was evaluated over a 3-yr period under field conditions. Up to 84% of the germinated seeds had germinated during the first year, with 6% of seeds remaining viable after 3 yr. Although seed persistence was relatively short, the rapid development of seeds following flowering as well as seedling emergence in both fall and spring suggests management practices are needed throughout the year to restrict reestablishment spread of cutleaf teasel.
Leptin Therapy Reverses Hyperglycemia in Mice With Streptozotocin-Induced Diabetes, Independent of Hepatic Leptin Signaling
Authors: Denroche Heather C. , Levi Jasna , Wideman Rhonda D. , Sequeira Roveena M. , Huynh Frank K. , Covey Scott D. , Kieffer Timothy J. 
Published: April 2011

OBJECTIVE
Leptin therapy has been found to reverse hyperglycemia and prevent mortality in several rodent models of type 1 diabetes. Yet the mechanism of leptin-mediated reversal of hyperglycemia has not been fully defined. The liver is a key organ regulating glucose metabolism and is also a target of leptin action. Thus we hypothesized that exogenous leptin administered to mice with streptozotocin (STZ)-induced diabetes reverses hyperglycemia through direct action on hepatocytes.

RESEARCH DESIGN AND METHODS
After the induction of diabetes in mice with a high dose of STZ, recombinant mouse leptin was delivered at a supraphysiological dose for 14 days by an osmotic pump implant. We characterized the effect of leptin administration in C57Bl/6J mice with STZ-induced diabetes and then examined whether leptin therapy could reverse STZ-induced hyperglycemia in mice in which hepatic leptin signaling was specifically disrupted.

RESULTS
Hyperleptinemia reversed hyperglycemia and hyperketonemia in diabetic C57Bl/6J mice and dramatically improved glucose tolerance. These effects were associated with reduced plasma glucagon and growth hormone levels and dramatically enhanced insulin sensitivity, without changes in glucose uptake by skeletal muscle. Leptin therapy also ameliorated STZ-induced hyperglycemia and hyperketonemia in mice with disrupted hepatic leptin signaling to a similar extent as observed in wild-type littermates with STZ-induced diabetes.

CONCLUSIONS
These observations reveal that hyperleptinemia reverses the symptoms of STZ-induced diabetes in mice and that this action does not require direct leptin signaling in the liver.
A Synthesis of Best Evidence for the Restoration of Upper-Extremity Function in People with Tetraplegia
Authors: Kalsi-Ryan Sukhvinder , Verrier Mary C. 
Published: April 2011

Purpose: Because upper-limb function represents overall function for individuals with tetraplegia, the restoration of upper-extremity function is exceedingly important for this population. The purpose of this review was to identify interventions that optimize upper-limb function after tetraplegia based on best available evidence. Methods: A search of MEDLINE, AMED, and PubMed with the search terms “hand function AND tetraplegia” and “upper limb function AND tetraplegia” found 384 articles. After elimination of duplicates and review of titles and abstracts, 43 studies were found to be applicable. Study quality of all applicable studies was assessed with a modified version of the Scottish Intercollegiate Guidelines Network for Cohort Studies methodology. Results: The applicable studies were organized into three categories: conventional therapies (CT), electrical stimulation therapies (ES), and surgical interventions (SI). The proportion of papers in each category that presented with sufficient methodological quality to contribute to best evidence was as follows: CT: 0/2; ES: 10/21; SI: 6/20. Conclusions: ES therapies are beneficial as assistive technologies and as therapeutic intervention in the subacute phase of recovery. SIs are suitable for individuals who meet very specific criteria for tendon-transfer surgery. Further clinical trials are warranted for ES and SI therapies to substantiate prescription of therapeutics.
Les pêches en mer Caspienne
Authors: Carré François 
Published: April 2011

La quasi totalité des 550 000 tonnes de poissons capturées en Caspienne, en 1971, le furent par l'U.R.S.S. Après des difficultés sérieuses rencontrées de 1940 à 1960, la production a retrouvé un niveau élevé, mais avec un changement profond dans la nature des arrivages : les poissons de qualité ont décliné fortement (alose, gardon), sauf lorsqu'ils sont l'objet d'une pisciculture intensive (esturgeon), et l'essentiel des prises est maintenant constitué de petits pélagiques, les clupéonelles ou kil'ka. Ces transformations proviennent vraisemblablement de la baisse du niveau de la mer, des grands barrages réalisés sur les fleuves tributaires et de la pollution croissante.
La pêche se présente sous deux formes : activité côtière et fluviale avec des sennes et des filets fixes qui capturent la totalité des espèces de qualité, elle est alors l'œuvre des kolkhozes en U.R.S.S. et d'une société nationale en Iran ; pêche industrielle qui porte sur le kil'ka, elle est pratiquée par l'U.R.S.S. seule, à l'aide de gros navires congélateurs, parfois d'usines flottantes à farine de poisson, qui sont armés dans les six principaux ports de pêche : Astrahan', Gur'ev, Bautino, Krasnovodsk, Baku-Gousany et Mahadkala.
Sur les côtes, la grande région pour les débarquements et le traitement du poisson demeure le delta de la Volga, avec des productions spécialisées et réputées (caviar) et les industries annexes de la pêche. Pourtant, sous l'effet du développement de la capture du kil'ka dans le centre et le sud de la mer, les rives méridionales, sauf en Iran, connaissent une activité croissante, comme en témoigne l'ouverture du nouveau port de pêche de Gousany près de Baku.