bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Methodological Modifications of Determination of Diffusion Coefficients in Compacted Bentonite
Authors: Vopálka Dušan , Filipská Helena , Vokál Antonín
Published: April 2011

The results of 3H, 36Cl and 137Cs diffusion experiments through compacted bentonite using a new design of diffusion cell and a new methodology of diffusion coefficients evaluation are presented. The diffusion cell was made from the stainless steel and enables to connect it directly to the input and/or output reservoirs without any tubing. The evaluation of diffusion coefficients utilizes a compartmental model developed in the environment of the GoldSim transport code. It enables to determine diffusion coefficients for various types of boundary conditions, including also input and output filters. The influence of the diffusion through filters on the determined values of both effective (De) and apparent (Da) diffusion coefficients was numerically demonstrated for the through diffusion method. This effect is most important for Da, the value of which would be underestimated using standard ways of evaluation for neutral and positively charged species, mainly in the case of high effective porosity.

The comparison of standard and the newly developed method of evaluation of diffusion coefficients showed a significant influence of diffusion in filters for HTO. Contrary to the standard method of evaluation, the evaluation taking into account filters showed here no difference between total and effective porosity. The effect of filter resistance was negligible for Cl-, especially at high dry density of compacted bentonite, due to the anion exclusion effect. The numerical model developed enabled to determine Da values of Cs+ from the concentration change in the inlet reservoir.
Testing of a near-field biogeochemical model against data from a large-scale gas generation experiment
Authors: Small J.S. , Nykyri M. , Paaso N. , Hovi U. , Itävaara M. , Sarlin T.
Published: April 2011

A biogeochemical model that represents processes of metal corrosion, microbial degradation of cellulosic waste and mass transfer within a heterogeneous system has been used to represent processes of gas generation in a large-scale (20m3) experiment that has studied degradation of typical nuclear reactor operating waste. The experiment has been in operation for a period of about eight years and has established a pattern of methanogenic gas generation. A “blind testing” approach has been used to develop the model of the experiment using independently derived kinetic data for corrosion and microbial processes. The model correctly represents the anaerobic conditions leading to methane generation during the course of the experiment. The overall rate of gas generation of the experiment is well represented, as is the composition of evolved gases and geochemistry of sampled liquids. The experiment and the model together build confidence in the ability to simulate processes of gas generation and variation in chemical conditions in heterogeneous repository environments.
The JNC Generic URL Research Program - Providing a Knowledge Base to Support both Implementer and Regulator in Japan
Authors: Umeki Hiroyuki , Shimizu Kazuhiko , Seo Toshihiro , Kitamura Akira , Ishikawa Hirohisa
Published: April 2011

In accordance with the R&D framework specified by the Atomic Energy Commission of Japan in 2000 for the implementing phase of HLW disposal, the Japan Nuclear Cycle Development Institute (JNC) continues to be responsible for R&D activities aimed at enhancing the reliability of disposal technologies and safety assessment methodologies and associated databases. JNC has thus been actively promoting technical R&D with a view to contributing to both the implementation of disposal and the formulation of safety regulations.

One of JNC's key roles is to establish and demonstrate site characterization methodologies based on investigations in two purpose-built generic URL (underground research laboratory) projects: one at Mizunami in crystalline rock and the other at Horonobe in sedimentary rock.

Through the surface-based investigations in the Mizunami and Horonobe projects (phase 1), integration of work from different disciplines into a “geosynthesis” has been illustrated and is planned to be developed further in the underground facilities at these sites (phases 2 and 3). These projects also serve for developing and testing the tools and methodologies required for site characterization. Further know-how will be gained through participation in foreign underground laboratory projects, transfer of experience from these projects to Japan and tailoring it to Japanese conditions and requirements.

This experience represents an important knowledge base, which is obviously important for the implementer but is also needed by the regulator, in order to assess how key site characteristics are derived and what uncertainties are associated with this process.
Sorption of Selenium (IV) on Mineral Mixtures: Role of Minor Phases in the Modelling Part
Authors: Charlotte Hurel , Nicolas Marmier
Published: April 2011

Sorption processes have been largely studied and modelled by considering single mineral surfaces (iron oxides, clay etc). In the case of a complex surface such as claystone, it seems important to be able to predict the behaviour of the radioactive elements in contact with the natural site. The modelling part becomes very complex if the whole minerals composing the geological media have to be taken into account. In that way, this study aims at testing various mineral mixtures, to identify the most reactive phase controlling the adsorption processes, in order to get a “simplified” system for a model calculation. Various mineral assemblages (goethite, pyrite, calcite and montmorillonite) were studied here, in contact with an anionic specie (selenium). Experiments were carried out using single, binary, ternary or quaternary solid mixtures, in order to evaluate the major reactive mineral phase. A surface complexation model was then considered to fit the experimental data. Stoichiometries and constants were extracted using FITEQL by fitting experimental results obtained on single solid in NaNO3, and used in a predictive calculation with PHREEQC for mixtures in synthetic grounwater. By doing this, we wanted to verify if the assumption that surface reactivity of single minerals keeps the same in a different environment can be used for predictive calculations.

Results obtained have shown that the presence of calcite and pyrite does not influence the total amount of selenium adsorbed. Then a simplified model was proposed, taking into account only the major phase responsible for the sorption of Se.
Selenium Sorption in a Sedimentary rock/saline Groundwater System and Spectroscopic Evidence
Authors: Xia X. , Kamei G. , Iijima K. , Shibata M. , Ohnuki T. , Kozai N.
Published: April 2011

Sorption of selenium (Se) was studied by batch technique by using sedimentary rock samples andcorresponding saline groundwater from Horonobe underground research laboratory (URL)site under reducing condition. Spectroscopic analyses were performed by X-ray absorption near-edge structure (XANES) afterthe sorption experiments to identify the oxidation states of Se on the sedimentary rock. It issuggested thatthe dominant parameters affecting the Se sorption are iron-bearing minerals, especially exchangeable Fe and pyrite, and organic matters. Most of the Se sorbed on the sedimentary rock was Se(0) inthe case of natural saline groundwater, at least at relatively high Se concentration, while only part of the Se was Se(0) in caseof the synthetic groundwater, which contains no organic matters. Incorporationinto pyrite could be the sorption mechanism of Se(0).
The Sorption of Thorium and Americium onto Fresh and Degraded Ordinary Portland Cement and onto Green Tuff
Authors: Cowper Mark M. , Baker Sarah , Chambers Adam V. , Heath Timothy G. , Mihara Morihiro , Williams Stephen J.
Published: April 2011

The sorption of thorium and americium has been measured onto crushed samples of freshordinary Portland cement (OPC), degraded OPC (DOPC) and green tuff under a range of aqueous conditions as part of research into the disposal of TRU waste in Japan. Sorption onto OPC was measured from deionised water,3 mol dm−3sodium nitrate solution and simulated seawater, and onto DOPC from demineralised water; all solutions were pre-equilibrated with the relevant cement. Sorption onto tuff was measured from pre-equilibrated deionised water, 3 mol dm−3sodium nitrate solution, simulated seawater, OPC leachate and 1 mol dm−3ammonium hydroxide solution. RDvalues were determined from the amount of thorium or americium remaining in solution after centrifugation, 0.45 μm filtration and 10,000 nominal molecular weight cut-off (NMWCO) filtration. Centrifugation gave lower RDvalues than filtration. MeanRDvalues for sorption onto OPC and DOPC were in the range 4 × 104to ≥1 × 106cm3g−1for thorium, and 3 ×103to ≥1 × 105cm3g−1for americium, after filtration through 10,000 NMWCO filters. Mean RDvalues for thorium sorption onto tuff increased from2 × 103cm3g−1in tuff-equilibrated deionised water, to ≥ 4 × 106cm3g−1from ammonium hydroxide solution (10,000 NMWCO-filtration). A similar trend was seen for10,000 NMWCO-iltered americium samples where mean RDvalues increased from 4 × 103cm3g−1in deionised water to 1 × 105cm3g−1in ammonium hydroxide solution.
Modelling uranium leaching from agricultural soils to groundwater as a criterion for comparison with complementary safety indicators
Authors: Jacques D. , Šimůnek J. , Mallants D. , van Genuchten M.Th.
Published: April 2011

Naturally occurring radionuclides can also end up in soils and groundwater due to human practices, such as application of certain fertilizers in agriculture. Many mineral fertilizers, particularly (super)phosphates, contain small amounts of 238U and 230Th which eventually may be leached from agricultural soils to underlying water resources. Field soils that receive P-fertilizers accumulate U and Th and their daughter nuclides, which eventually may leach to groundwater. Our objective was to numerically assess U migration in soils. Calculations were based on a new reactive transport model, HP1, which accounts for interactions between U and organic matter, phosphate, and carbonate. Solid phase interactions were simulated using a surface complexation module. Furthermore, all geochemical processes were coupled with a model accounting for dynamic changes in the soil water content and the water flux. The capabilities of the code in calculating natural U fluxes to groundwater were illustrated using a semi-synthetic 200-year long time series of climatological data for Belgium. Based on an average fertilizer application, the input of phosphate and uranium in the soil was defined. This paper discusses calculated U distributions in the soil profile as well as calculated U fluxes leached from a 100-cm deep soil profile. The calculated long-term leaching rates originating from fertilization are significantly higher after 200 years than estimated release rates from lowlevel nuclear waste repositories.
The Electrochemistry of Copper in Aqueous Sulphide Solutions
Authors: Smith J. , Qin Z. , King F. , Werme L. , Shoesmith D.W.
Published: April 2011

Using a variety of electrochemical and surface analytical techniques, the mechanism and kinetics of Cu corrosion in anoxic, aqueous, sulphide-containing environments are being investigated. Under these conditions ([S]total = 10−4 to 3 ×10−3 mol/L), the anodicgrowth ofa film (XRD identifies Cu2S/Cu1.8S as major/minor phases, respectively) is supported by the cathodic reduction of water thereby destabilizing the copper surface. For more oxidizing conditions, the subsequent growth of a partially passivating film is observed. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry at rotating disc electrodes show film growth occurringwith negligible dissolution and under partial SH- transport control. Current-potentialrelationships as a function of [S]total give Tafel slopes of ∼ (40 mV)−1 suggesting reaction occurs via a 2step process: Aninitial rapid adsorption of SH- leading to an equilibrium surface concentration, followed by a rate determining electron transfer to form a sulphide film. It is proposed thatfilm growth propagates via transport of CuI through the film to the solution interface. The primary goal of this research is the development of a mathematical model which can be used to assess the performance of copper nuclear waste canisters in granitic repositories.
Deep Disposal of Eurobitum Bituminised Waste: Scoping Calculations of Nitrate Release
Authors: Weetjens Eef , Sillen Xavier , Valcke Elie
Published: April 2011

The Eurobitum bituminised waste produced by the former EUROCHEMIC reprocessing plant in Mol-Dessel (Belgium) contains a lot of salts, mainly NaNO3. This NaNO3 may possibly affect significantly the evolution of a radwaste repository through redox and ion exchange reactions with Boom Clay, which in Belgium is studied as a reference host formation. Yet, the leaching behaviour of NaNO3 from the Eurobitum and its migration in the Boom Clay is rather unclear. Therefore, some scoping numerical calculations have been performed. In a first phase, we calculated the water flux towards the disposal gallery to assess the timescale of the saturation process of the disposal galleries. In a second phase, the leaching rate of NaNO3 out of the drums is compared with its diffusive removal through the Boom Clay.

The water flux to the gallery was calculated at approximately 100 ml/day per metre gallery, based on the natural pressure gradient observed around the HADES Underground Research Laboratory. Different approaches were elaborated to find a NaNO3 source term for the diffusion calculations. For various ways of characterising the nitrate release, the numerical calculations generally show that the NaNO3 concentrations in the first decimetres of Boom Clay will not be much higher than 1 M. Moreover, a sensitivity analysis showed that if the nitrate is released from the bituminised waste product within 10 000 years, the Boom Clay controls the concentration profiles; if the release is slower, the source term has a more pronounced effect on the near field concentrations.
Ageing of Eurobitum Bituminised Radioactive Waste under Gamma Irradiation
Authors: Rorif Fabian , Valcke Elie , Boven Patrick , Ooms Hans , Peeters Jozef , Smets Steven
Published: April 2011

The extent of the physico-chemical processes of concern in the study on the acceptability of the Belgian Eurobitum bituminised waste for underground disposal will depend on the degree ofageing of the bituminous matrix. Therefore, the ageing of non-radioactive simulates of Eurobitum under gamma irradiation was studied both in the presence and absence of oxygen. Chemical changes in the bitumen structure were measured in the mid-infrared region with the attenuated total reflectance infrared technique (ATR/FTIR) and evaluation of the peaks at 1700 cm−1 (C=O) and 1600 cm−1 (C=C). Even for the highest total absorbed doses (∼800 kGy at ∼150 Gy/h), the effect of the irradiation in Eurobitum was found to be small and was, in any case, smaller than for samples heated for three hours at 130°C in air.
Synthesis and characterisation of transition metal substituted barium hollandite ceramics
Authors: Hyatt Neil C. , Stennett Martin C. , Fiddy Steven G. , Wellings Jayne S. , Dutton Sian S. , Maddrell Ewan R. , Connelly Andrew J. , Lee William E.
Published: April 2011

A range of transition metal bearing hollandite phases, formulated Ba1.2B1.2Ti6.8O16 (B2+ = Mg, Co, Ni, Zn, Mn) and Ba1.2B2.4Ti5.6O16 (B3+ = Al, Cr, Fe) were prepared using an alkoxide - nitrate route. X-ray powder diffraction demonstrated the synthesis of single phase materials for all compositions except B = Mn. The processing conditions required to produce > 95 % dense ceramics were determined for all compositions, except B = Mg for which the maximum density obtained was > 93 %. Analysis of transition metal K-edge XANES data confirmed the presence of the targeted transition metal oxidation state for all compositions except B = Mn, where the overall oxidation state was found to be Mn3+. The K-edge EXAFS data of Ba1.2B1.2Ti6.8O16 (B = Ni and Co) were successfully analysed using a crystallographic model of the hollandite structure, with six oxygen atoms present in the first co-ordination shell at a distance of ca. 2.02Å. Analysis of Fe K-edge EXAFS data of Ba1.2B2.4Ti5.4O16 revealed a reduced co-ordination shell of five oxygens at ca. 1.99Å.
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

Nd-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

Technetium 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

Experiments 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

In 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

Existing 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

The 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

FePt 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

We 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

Carbon 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

We 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

We 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

The 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

The 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

Many 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.
Proactive Coping in Community-Dwelling Older Australians
Authors: Sougleris Christina , Ranzijn Rob
Published: April 2011

This article reports on a study of older community-dwelling Australian adults which aimed to test whether a relatively unexplored construct, proactive coping, could have a role in purpose in life, personal growth, and life satisfaction. A total of 109 women and 115 men (Mean age = 75.04 yrs, SD = 6.66) completed a questionnaire containing Greenglass et al.'s (1999) Proactive Coping Inventory, the Purpose in Life and Personal Growth ***sub-scales of Ryff's (1989) Psychological Well-being Scales, and the Satisfaction with Life Scale (Diener et al., 1985). The results of hierarchical multiple regression analyses indicated that proactive coping was a highly significant predictor of all three measures of well-being, after controlling for age and health. The effect on personal growth and purpose in life was particularly strong. Proactive coping does seem to be an important variable in the psychological well-being of older adults. However, the correlational nature of the design, and the likelihood of some conceptual overlap between the well-being variables, suggest that these inferences can only be tentative. Designing psychological interventions to improve proactive coping may help to improve quality of life at older ages. There is a need for experimental research to further explore the causal influence of proactive coping and for further theoretical work to determine the exact nature of proactive coping.
Verbal Abuse in the Army of the Cumberland: William Rosecrans' Acid Tongue as a Major Factor in the Union Defeat at the Battle of Chickamauga
Authors: Loges Max
Published: April 2011

Recent studies suggest that verbal abuse and harassment are relatively common in the workplace. These same studies show that such abuse decreases worker satisfaction, undermines relationships, and distracts workers from functioning as team members committed to common goals. This study examines a classic example of verbal abuse and harassment in the workplace—that of Union Civil War General William Rosecrans toward his subordinates during a campaign conducted in Tennessee during 1863. It can, in fact, be argued that Rosecrans' abusive language was a major factor in the Union defeat at the Battle of Chickamauga in September of 1863.
Relating the Nursing Paradigm to Practice: A Teaching Strategy
Authors: Duff Elsie
Published: April 2011

Nursing science is a topic students and faculty view with skepticism. The interchangeable terms and the need to understand the contextual nature of nursing philosophy lead to feelings of anxiety and confusion. Students question the relevance of learning nursing science in relation to practice. The analogy of a building is used to explain how nursing philosophy relates to practice. The foundation of the building forms the paradigm of the nursing domain, the outside walls represent conceptual models, the interior walls symbolize theories and the detailed décor characterizes nursing observations and practice, connecting abstract theory to concrete nursing knowledge. The analogy of interrelated concepts may help students gain an understanding of nursing science, which is essential to further knowledge development in nursing.
Speaking Up: Contextualizing Women's Voices and Gatekeepers' Reactions in Promoting Women's Empowerment in Rural India
Authors: Baily Supriya
Published: April 2011

This article deepens the understanding of the impact empowerment programs have for women on their social environment, and more specifically on the men in the community, who may or may not be supportive of such endeavors. Gathering evidence from one case in rural India, it addresses how powerholders and gatekeepers reacted to the increased use of women's voices as they interacted as members of a group, within the broader community, and as the women recognized their own increase in value to the community.
What Matters for Marginalized Girls and Boys in Bangladesh: A Capabilities Approach for Understanding Educational Well-Being and Empowerment
Authors: Dejaeghere Joan , Lee Soo Kyoung
Published: April 2011

Ensuring the education of marginalized children has become an important agenda in order to reach the goals of universal primary education and gender equality. Education policies and projects aiming to target marginalized children often do so on the basis of demographic variables, such as sex, ethnicity, poverty and geography. We argue that this approach to defining marginality does not sufficiently address underlying discriminatory conditions and norms that perpetuate inequalities. In this article, we employed a capabilities approach as an analytical frame to understand what girls and boys in a rural district in Bangladesh reason affects their educational well-being and empowerment. We draw on critical feminist perspectives of empowerment to illustrate how gendered inequalities are perpetuated in the structures and norms in communities and schools. We argue that specific conditions can differentially marginalize or empower, and these conditions have persistent gendered patterns. Conditions of a safe, supportive, and quality educational environment foster possibilities for empowerment and well-being, and conversely, a lack of these conditions can marginalize children from achieving well-being through education.
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.
Drosophila Insulin Pathway Mutants Affect Visual Physiology and Brain Function Besides Growth, Lipid, and Carbohydrate Metabolism
Authors: Murillo-Maldonado Juan M. , Sánchez-Chávez Gustavo , Salgado Luis M. , Salceda Rocío , Riesgo-Escovar Juan R.
Published: April 2011

OBJECTIVE

Type 2 diabetes is the most common form of diabetes worldwide. Some of its complications, such as retinopathy and neuropathy, are long-term and protracted, with an unclear etiology. Given this problem, genetic model systems, such as in flies where type 2 diabetes can be modeled and studied, offer distinct advantages.

RESEARCH DESIGN AND METHODS

We used individual flies in experiments: control and mutant individuals with partial loss-of-function insulin pathway genes. We measured wing size and tested body weight for growth phenotypes, the latter by means of a microbalance. We studied total lipid and carbohydrate content, lipids by a reaction in single fly homogenates with vanillin-phosphoric acid, and carbohydrates with an anthrone-sulfuric acid reaction. Cholinesterase activity was measured using the Ellman method in head homogenates from pooled fly heads, and electroretinograms with glass capillary microelectrodes to assess performance of central brain activity and retinal function.

RESULTS

Flies with partial loss-of-function of insulin pathway genes have significantly reduced body weight, higher total lipid content, and sometimes elevated carbohydrate levels. Brain function is impaired, as is retinal function, but no clear correlation can be drawn from nervous system function and metabolic state.

CONCLUSIONS

These studies show that flies can be models of type 2 diabetes. They weigh less but have significant lipid gains (obese); some also have carbohydrate gains and compromised brain and retinal functions. This is significant because flies have an open circulatory system without microvasculature and can be studied without the complications of vascular defects.