bluuebunny/crossref_metadata_2025 huggingface dataset:
Derivation of an approximate analytical solution for understanding the response characteristics of the EBS
Authors: Ohi T. , Chiba T. , Nakagawa T. , Takase T. , Nakazawa T. , Akagi Y. , Idemitsu K.
Published: November 2012

To perform a safety assessment for the geological disposal of radioactive waste, it is important to understand the response characteristics of the disposal system. In this study, approximate analytical solutions for steady-state nuclide releases from the engineered barrier system (EBS) of a repository were derived for an orthogonal one-dimensional diffusion model. In these approximate analytical solutions, inventory depletion, decay during migration and the influence of groundwater flow in the excavation damaged zone (EDZ) were considered. These solutions were simplified by the Taylor theorem in order to clearly represent the response characteristics of the EBS. The validity of these solutions was shown by comparison with numerical solutions. The response characteristics of the EBS are useful for identifying target values for important parameters that would have the effect of improving the robustness of system safety. The robustness of the geological disposal system and the reliability of the safety assessment can thus potentially be improved using the approximate analytical solutions.
Modelling Deep Borehole Disposal of Higher Burn-up Spent Nuclear Fuels
Authors: Travis Karl P. , Gibb Fergus G. F. , Hesketh Kevin W.
Published: November 2012

Higher burn-up (> 50 GWd/t) spent nuclear fuels (SNF) present problems for long-term management and disposal in mined repositories, principally because of their higher heat output. Here we present results from heat flow modeling of an alternative scheme for disposing of SNF - deep borehole disposal (DBD). We focus on how temperatures on the outer surface of the containers evolve, affect the melting and re-solidification of the high density support matrix (HDSM) and their consequences for the feasibility of this disposal concept. We conclude that not only is DBD a viable option for higher burn-up SNF, but it could be a practical disposal route for a range of combinations of SNF ages and number of fuel pins per container.
Research of Rock Mass Gas Conductivity with respect to Geological Disposal and the EDZ
Authors: Svoboda Jiri , Smutek Jan
Published: November 2012

The geological disposal of radioactive waste, based on a multi-barrier concept wherein the first barrier consists of the metal waste container and the final barrier the host rock, is widely considered the only viable solution.

Following disposal the risk will remain of the formation of gases due to corrosion and other processes. Research being carried out at the Czech Technical University in Prague (CTU), Centre of Experimental Geotechnics (CEG), the Josef underground laboratory as part of FORGE and other projects focuses on gas migration in underground areas and especially within the EDZ.

The research consists of several stages including the design of gas conductivity equipment destined for in-situ testing and the gas conductivity tests proper. An important part of the research involves the evaluation of a potential correlation between rock mass classification parameters and gas conductivity; a certain degree of correlation was identified in earlier research projects. The discovery of such a correlation would greatly assist in the future design of underground gas storage and deep radioactive waste facilities.
Modeling of the oxic stage in a HLW disposal cell in an argillaceous host rock
Authors: Marsal François , De Windt Laurent , Pellegrini Delphine
Published: November 2012

Determining the redox conditions in the near field of deep underground radioactive waste disposal cells is a key question regarding the performance of metallic components (e.g. waste overpack), which may undergo drastic corrosion processes in oxic conditions. This oxic transient is supposed to be short due notably to the oxygen consumption by corrosion and pyrite oxidation. However, the observed precipitation of Fe(III)-minerals as well as localized corrosion patterns on steel coupons placed during 6 years in a borehole drilled in the Toarcian argillite of Tournemire (France) may suggest that in-situ oxic conditions lasted several years, which is not consistent with reactive transport simulations performed with usual hypotheses (perfect contact between materials, high pyrite accessibility, water saturated conditions). Multicomponent reactive transport simulations considering gas diffusion were performed with the code HYTEC and reproduce correctly the observations made in Tournemire while considering imperfect interfaces and resaturation processes. The model was then applied to a disposal cell for high-level waste (HLW) representative of the design developed in France, putting into evidence the possibility of a redox contrast between the front and back of a disposal cell in an argillaceous medium, as well as a duration of the oxic stage within the cell as long as the ventilation of handling drifts is maintained.
Sensing and Monitoring of Radwaste Storage: A Realtime Online Demonstrator
Authors: Cosentino Luigi , Calì Claudio , De Luca Giovanni , Finocchiaro Paolo , Litrico Pietro , Pappalardo Alfio , Piscopo Massimo , Scirè Carlotta , Scirè Sergio
Published: November 2012

At INFN-LNS we have developed a new kind of gamma mini-sensor, which allowed to implement a prototype array of modular sensors for online monitoring of radioactive waste. The sensors are based on Silicon PhotoMultipliers and scintillating fibers sensitive to gamma radiation, that have to be placed in a repository in shape of a fine grid, around each single waste drum. We simulated the counting response of thin scintillating fibers and verified the results with measurements using radioactive sources. Front-end electronics and an FPGA-based counting system were developed to handle the field data, also implementing data transmission, a graphical user interface and a data storage system. Moreover a test of four sensors in a real radwaste storage site was performed with promising results.
The Importance of Verification and Validation Testing of Engineering Designs in Underground Rock Laboratories
Authors: Scourse Eleanor M. , Kickmaier Wolfgang , McKinley Ian G. , Kawamura Hideki , Stephens Samuel T.
Published: November 2012

Several national programs for geological disposal of higher activity radioactive waste will initiate siting via a call for volunteers. This is probably furthest advanced in Japan (NUMO) and the UK (NDA RWMD). In both these cases, rather than focusing on a reference repository concept, a catalogue of options has been developed. This requires a process to tailor design options to sites and compare particular design/site combinations as part of the site selection process. As has been noted in the longer-running Japanese program, the assessment of options must be as realistic as possible, rather than conservative, as in past nominating approaches to siting. Past demonstration work has focused on feasibility, showing that it is possible to implement a design. Determining practicality, which incorporates many more complex factors, is more difficult. Extensive desk studies can form a basis for such analysis but these must be rigorously tested, which makes full-scale tests in Underground Rock Laboratories (URLs) an essential component of any program. This paper highlights the importance of such demonstration projects and illustrates how they are vital in both improving understanding of the engineered barrier system and stakeholder engagement.
Evaluating the corrosion rate of low alloyed steel in Callovo-Oxfordian clay: towards a complementary EIS, gravimetric and structural study
Authors: Martin Frantz A. , Perrin Stéphane , Bataillon Christian
Published: November 2012

Dedicated integrated experiments have been used to determine in situ the corrosion rate of low alloyed steels in geological repository mockups (90°C, anaerobic, 40 bars, slow synthetic water flux…). Two possible situations have been investigated: the steel can either be in direct contact with the host rock or in a solution rich in clay suspension. Electrochemical Impedance Spectroscopy (EIS), sampling gravimetry and microanalyses have been performed to determine the corrosion rate evolution with the exposure duration of the specimens. Kinetic regime modifications have been linked to structural modifications of the corrosion products interface.
Effect of temperature on the crevice corrosion resistance of Ni-Cr-Mo alloys as engineered barriers in nuclear waste repositories
Authors: Hornus Edgar C. , Mabel Giordano C. , Rodríguez Martín A. , Carranza Ricardo M.
Published: November 2012

Ni-Cr-Mo alloys offer an outstanding corrosion resistance in a wide variety of highly corrosive environments. Alloys 625, C-22, C-22HS and HYBRID-BC1 are considered among candidates as engineered barriers of nuclear repositories. The objective of the present work was to assess the effect of temperature on the crevice corrosion resistance of these alloys. The crevice corrosion repassivation potential (ER,CREV) of the tested alloys was determined by the Potentiodynamic-Galvanostatic-Potentiodynamic (PD-GS-PD) method. Alloy HYBRID-BC1 was the most resistant to chloride-induced crevice corrosion, followed by alloys C-22HS, C-22 and 625. ER,CREV showed a linear decrease with temperature. There is a temperature above which ER,CREV does not decrease anymore, reaching a minimum value. This ER,CREV value is a strong parameter for assessing the localized corrosion susceptibility of a material in a long term timescale, since it is independent of temperature, chloride concentration and geometrical variables such as crevicing mechanism, crevice gap and type of crevice former.
Effect of Alloy Composition on the Localized Corrosion Resistance of Nickel Alloys
Authors: Sosa Haudet Santiago , Rodríguez Martín A. , Carranza Ricardo M.
Published: November 2012

Nickel base alloys are considered among candidate materials for engineered barriers of nuclear repositories. The localized corrosion resistance is a determining factor in the materials selection for this application. This work compares the crevice corrosion resistance of selected nickel base alloys, namely 625, G-30, G-35, C-22, C-22HS and HYBRID-BC1. The crevice corrosion repassivation potential (ER,CREV) of the tested alloys was determined by the Potentiodynamic-Galvanostatic-Potentiodynamic (PD-GS-PD) method. The testing temperature was 60ºC and the chloride concentrations used were 0.1 M, 1 M and 10 M.

A linear relationship between ER,CREV and the logarithm of chloride concentration was found. ER,CREV increased linearly with PREN (Pitting Resistance Equivalent Number) in concentrated chloride solutions. ER,CREV is the sum of three contributions: ECORR*, η and ΔΦ. ECORR* and η increased linearly with PREN, while ΔΦ increased linearly with PREN for concentrated chloride solutions, not showing a definite trend with PREN for the less concentrated solutions.
Identification of the Cathode Reaction Accompanied with Overpack Corrosion
Authors: Otsuka Ichiro , Iida Yoshihisa , Yamaguchi Tetsuji , Kato Osamu , Tateishi Tsuyoshi , Tanaka Tadao
Published: November 2012

Cathode reaction on overpack corrosion in the geological repository environments of radioactive waste was identified from corrosion experiments of carbon steel specimens. Carbon steel specimens were encapsulated in degassed glass ampoules with various solutions which were prepared by distilled water degassed by Ar gas bubbling, and set in a thermostatic bath for several weeks. In the X-ray diffraction and X-ray photochemical spectroscopy, crystalline Fe3O4 and Fe2(OH)2CO3, and amorphous Fe(OH)2 were mainly detected on specimens which were immersed into distilled water, high concentration of sodium hydrogen carbonate solution, and low concentration of sodium hydrogen carbonate solution and sodium sulfate solution, respectively. Only hydrogen gas was detected in a gas phase analysis, indicating that hydrogen generation reaction was the dominant cathode reaction in the anoxic condition expected in geological repository environments.
Topological connectivity analysis of accumulated radiation damage from multiple molecular dynamics recoil cascades
Authors: Foxhall Henry R. , Harding John H. , Travis Karl P.
Published: November 2012

The results of sequential large-scale molecular dynamics (MD) simulations of radiation damage cascades in Gd2Ti2O7 and Gd2Zr2O7 are presented. Twelve alpha recoil cascades, each due to a recoil atom with 40 keV of kinetic energy, are performed in both materials and a stark contrast in behaviour observed. Topological connectivity analysis is used to analyse the structural evolution of the two systems. Our results provide important insight into accumulation of disorder in pyrochlore-structured ceramics.
Consistency of the strontium transport parameters in Boom Clay obtained from different types of experiments: accounting for the filter plates
Authors: Aertsens Marc , Govaerts Joan , Maes Norbert , Van Laer Liesbeth
Published: November 2012

In a previous MRS paper, the consistency of migration parameters for strontium (Sr) in Boom Clay, obtained by different types of experiments, was examined. No consistent value could be obtained for the product ηR of the diffusion accessible porosity η and the retardation factor R. Furthermore the nearly flat concentration profile measured in one of the through diffusion experiments could not be explained by the traditional through diffusion model. A reason is that the filter plates confining the clay sample have not been taken into account.

Therefore, for Sr and tritiated water (HTO), the apparent diffusion coefficient and the product ηR in the filters are measured in through diffusion experiments on filter plates.

Taking into account the filter plates, the outlet fluxes and the Sr profiles in the clay of both Sr through diffusion experiments, are described well with (i) the previously estimated Sr apparent diffusion coefficient in the clay of 7 × 10-12 m2/s, (ii) an apparent filter diffusion coefficient in the range 2 × 10-12 m2/s to 5 × 10-11 m2/s (vs. 1 × 10-11 m2/s measured in the filter through diffusion experiments), (iii) a clay capacity factor ηR in the range between 5000 and 22000, and (iv) a filter capacity factor between 0.3 and 0.6 (in agreement with the filter through diffusion measurements). However, using the above parameters, the evolution at the inlet could not be described. So although inconsistency diminished, some inconsistency remains.
An Investigation of Microbial Effect as Biofilm Formation on Radionuclide Migration
Authors: Yoshikawa H. , Kawakita M. , Fujiwara K. , Sato T. , Asano T. , Sasaki Y.
Published: November 2012

It is well discussed about biological effect to high-level radioactive waste (HLW) disposal and known that the biofilm is considered to be the uncertain factor to estimate for migration of radioactive elements. The objective of this research is to estimate the microbial effect of Cs migration in groundwater interacted with rock surface. Specially, we focus on Cs behavior at the rock surface surrounded by biofilm. The most important factor is the Cs sorption and diffusion to the microbe and/or their biofilm. Generation of bio-colloid absorbed with Cs and retardation of Cs by their matrix diffusion in rock will be influenced by these phenomena. We introduce about scenario analysis for biofilm and a simple Cs diffusion test with and without sulfur reducing bacteria (SRB) which is well known as easy to produce biofilm on the rock surface in order to clarify the existence effect of the bacteria at the rock surface. The Cs diffusion experiment, using Desulfovivrio desullfuricans as SRB, indicated that microbial effect was less to through their biofilm in the experimental condition. We consider that Cs is easy to contact the rock surface even if surrounded biofilm and not effect to retardation by matrix diffusion scenario.
Advances in a Bioprocess for the Treatment of Nuclear Waste: Spent Ionic Exchange Resins
Authors: Mosquera Rodríguez León , Pizarro Ramón A.
Published: November 2012

Development of a bioprocess intended to achieve a volume reduction of spent resins (either from research and power reactors) is the main purpose of this research project. Search is constrained to microorganisms that exhibit radioresistance, and which can be cultured in a heavy metal environment with additives of nuclear reactor waters such as boron, lithium and gadolinium compounds.

Bacteria adapted to a radioactive environment were obtained by treating a RA-3 Reactor spent ionic exchange resin sample (kept at Área de Gestión Ezeiza: AGE) with sterile water; microorganisms suspended were isolated, subject to purity controls and characterized.

Experiments performed with these strains include:

-Culture in a mineral-broth having polystyrene as source of both carbon and energy. The strain RMB 1200 gave the highest number of viable cells, then being tested with some aromatic compounds, and with some additives of nuclear reactor waters and other elements found in spent resins.

-An anionic exchange resin sample was heated, yielding a chemical environment resembling to that of radiolysed resins, and then RMB 1200 strain was cultured with this solid.

-A technique to stain polymers was developed in order to find morphological changes caused by microbiological activity. Microscopic examination of cultured polymer samples has been performed.

Results obtained with RMB 1200 include metabolic capabilities to use aromatic carbon sources (benzoate, polyphenols), its growth with polystyrene and resin, and short-term tolerance to several xenobiotics assayed at higher concentration levels than the ones of spent resins.
Development of New Fullerene-based Electron Acceptors for Efficient Organic Photovoltaic Cells
Authors: Matsuo Yutaka
Published: November 2012

This article describes design of fullerene-based electron-accepting materials to obtain high performance in organic thin-film photovoltaic devices. A 1,4-bis(dimethylphenylsilylmethyl)[60]fullerene gives higher open circuit voltage than 1,2-diadduct because of smaller π-conjugated systems, and enables columnar fullerene-core array for high electron mobility and thermal crystallization for ideal phase separation with electron-donor materials. A 56π-electron fullerene derivative possessing the dihydromethano group as the smallest carbon addend does not disrupt fullerene-fullerene contact in solid state, giving high open-circuit voltage without decreasing of short-circuit current density and fill factor.
Plasmonic Solar Cells with Embedded Silver Nanoparticles from Vapor Condensation
Authors: Santbergen Rudi , Tan Hairen , Pfeiffer Tobias , Li Xin , Frijnts Tim , Smets Arno , Schmidt-Ott Andreas , Zeman Miro
Published: November 2012

The use of plasmonic nanoparticles as light scattering elements for light trapping in solar cells is studied. From theoretical considerations it follows that Ag particles with a diameter on the order of 100 nm possess ideal light scattering properties. It is demonstrated that these particles can be fabricated using the selective aerosol deposition technique. Because this newly developed technique provides excellent control over critical parameters such as particle size and surface coverage it is a valuable tool for optimizing plasmonic solar cells. The initial experiments show that embedding Ag particles with a diameter of 180 nm into amorphous silicon solar cells enhances the current output.
Tuning Light Scattering by Periodic Metal Nanoparticle Arrays for Solar Cell Applications
Authors: Payne David N. R. , Temple Tristan L. , Bagnall Darren M.
Published: November 2012

The drive to reduce the thickness of solar cells is putting ever greater demands on light-trapping techniques. Techniques are required to improve absorption of light within the semiconductor, while not adversely affecting the electrical properties of the device. Conventional diffraction gratings can scatter visible and near-infrared photons into large angles, which get trapped in the silicon layer by total internal reflection. However, diffraction gratings typically have large feature sizes and so increase the overall surface area of a solar cell compared to the planar case. A periodic arrangement of metal nanoparticles acts as a diffraction grating, but an over-coated semiconductor will have a similar surface area to a planar layer due a combination of a low particle height and low surface coverage.

Random arrays of identical metal nanoparticles feature Lorentzian scattering peaks that can be tuned by modifying the size and shape of the particle. Periodic arrays have much more complicated scattering peaks, due to the enhancement and suppression of scattering at different wavelengths caused by the constructive and destructive interference between each nanoparticle. In effect the scattering spectrum of the individual nanoparticle is modified by the diffractive orders of the array, and so both parameters must be optimized together.

We have studied periodic arrays of metal nanoparticles fabricated using electron-beam lithography, and characterised their reflectance properties. The optical properties of the fabricated arrays were found to be in good agreement with finite-difference time-domain (FDTD) simulations. Au and Al nanoparticles are found to have a strong scattering effect and Al nanoparticles are also shown to exhibit an anti-reflection effect in combination with scattering. This work is focused on verifying that FDTD simulations can accurately model metal nanoparticle arrays and then extending the simulations to determine the previously unknown transmittance characteristics of metal nanoparticle arrays on silicon.
Synthesis and Magnetic Properties of Cobalt Ferrite Nanoparticles
Authors: Etier Morad F. , Shvartsman Vladimir V. , Stromberg Frank , Landers Joachim , Wende Heiko , Lupascu Doru C.
Published: November 2012

Nanopowders of cobalt iron oxide (CoFe2O4) were successfully fabricated by the co-precipitation method followed by a technique to prevent particle agglomeration. Particle sizes were in the range of 24 to 44 nm. The size of cobalt iron oxide particles decreases with increasing the concentration of the precipitation agent. The crystal structure was confirmed by X-ray diffraction (XRD), the chemical composition by energy dispersive spectroscopy (EDS), and phase changes by thermogravimetric differential thermal analysis (TGA-TDA). The particle morphology was analyzed by scanning electron microscopy (SEM). Magnetic properties were investigated by SQUID magnetometry and Mössbauer spectroscopy. Being nearly monodisperse and non-agglomerated the prepared cobalt iron oxide powders are the base for synthesizing magnetoelectric composites embedded in a ferroelectric BaTiO3 matrix.
High aspect ratio free standing ZnO-magnetostrictive mesoscale cylindrical magnetoelectric core shell composite
Authors: Kaps S. , Mishra Y. K. , Hrkac V. , Greve H. , Kienle L. , Quandt E. , Adelung R.
Published: November 2012

Optimizing magnetic field sensors made by piezoelectric-magnetostrictive composites is a trade off between several parameters. Whereas large structures will cause in principle high electrical currents the mechanical coupling will lead to shear losses and therefore limit the sensitivity of the sensor and make it impossible to measure small magnetic fields. In very small structures the shear losses will decrease but the imperfections in the interfaces become more important and the typically small currents will be disturbed by, e.g., surface conductivity of the piezoelectric material and are thus difficult to measure. The best compromise is a mesoscale sensor which has relatively small losses due to shearing but still high enough electrical currents to work as a good sensor. We will present a setup which allows the use free standing ZnO micro rods as piezoelectric core material which are surrounded by a magnetostrictive layer. Since no clamping is necessary the expansion and contraction of the material is not hindered by a matrix material. The tuning of the relative layer thicknesses can be easily optimized by changing the thickness of the magnetostrictive layer so that an optimum can be achieved for different ZnO micro rods. For the growth of the ZnO a newly developed process will be presented which allows the growth of a large variety of single crystals with different aspect ratios up to needles with several millimeters in length.
Temperature Dependent Thermopower and Resistance Measurements of CNT-MgB2 Composites
Authors: Adu Kofi W. , Jayasingha Ruwantha , Ma Danhao , Sumanasekera Gamini U.
Published: November 2012

The temperature dependent resistance R(T) and thermopower S(T) of sintered single wall carbon nanotubes (SWCNT) and magnesium diboride (MgB2) composites containing 5wt%, 10wt%, and 15wt% of SWCNTs have been measured and compared to their pure counterparts. The thermopower of both MgB2 (in the normal state) and SWCNT remain positive over the entire temperature range (10K to 300K) with room temperature values being ∼ 8μV/K and 57μV/K, respectively. The thermopower of the sintered composites decreased with decreasing temperature and switched from positive to negative near 70K. The superconducting critical temperature (Tc) of the samples ranges from 38K-41K. The room-temperature resistance ratio (RRR) is seen to depend on the sample composition. The temperature width (ΔT) is observed to increase with increasing SWCNT concentration. The normal state resistance data were fitted with the generalized Block-Grüneisen function obtaining Debye temperature of ∼ 900K.
Pathway of Porous Silicon Formation Inside Si Nanowires Throughout Metal Assisted Etching
Authors: Tonkikh Alexander A. , Geyer Nadine , Fuhrmann Bodo , Leipner Hartmut S. , Werner Peter
Published: November 2012

The selective formation of porous silicon in nanowires is observed in Si/Ge epitaxial layers along Ge layers grown by molecular beam epitaxy on a Si(100) substrate after metal-assisted chemical etching in aqueous HF-H2O2 solution. We assume that Ge layers serve as channels for a hole current out of the semiconductor to sustain the dissolution reaction. The tunnelling of holes through the potential barrier at the semiconductor surface is assumed to be the dominating mechanism of the hole transfer to the electrolyte.
Reversible Degradation of Photoluminescence in Si/SiGe Three Dimensional Nanostructures
Authors: Modi Nikhil , Tsybeskov Leonid , Lockwood David J. , Wu Xiao Z. , Baribeau Jean Marc
Published: November 2012

We report the degradation of low temperature photoluminescence (PL) from Si/SiGe three-dimensional cluster morphology nanostructures under continuous photoexcitation. The PL intensity initially decreases slowly for about 15 minutes, and then decreases rapidly, until only ∼ 10% of the original PL intensity remains. A complete recovery of the PL requires restoring the sample temperature to ∼ 300K. We propose that a slow accumulation of charge in SiGe clusters enhances the rate of Auger recombination and results in the observed PL degradation.
Large-area patterned magnetic nanostructures by self-assembling of polystyrene nanospheres
Authors: Tiberto Paola , Boarino Luca , Celegato Federica , Barrera Gabriele , Coisson Marco , De Leo Natascia , Vinai Franco
Published: November 2012

In this work, dot and anti-dot structures in Co, Ni, Ni80Fe20, Fe50Pd50, Fe73.5Cu1Nb3Si13.5B9 and Fe78B13Si9 thin films have been produced by means of nanosphere lithography. Two multi-step processes have been followed and will be here described. The first one directly exploits polystyrene nanosheres (PN) as a mask to fabricate arrays of magnetic nanoholes and dots. In the second case, the nanospheres are used to design a polymeric mask of a photoresist subsequently used to pattern a magnetic nanostructure on a film. Advantages and disadvantages of the two lithographical techniques will be here highlighted. In both processes, the dimension and mutual distance of the patterns are dependent on the starting PN diameter (in the interval 500-800 nm). Samples microstructure has been studied by means of SEM and AFM microscopy. Room-temperature hysteresis loops have been measured by an AGFM (Alternating Gradient Field Magnetometer). MFM microscopy has been exploited to study the magnetic domain pattern. All produced systems have been observed to display tunable microstructure and, consequently, various magnetic properties for application.
Microemulsion Synthesis of Iron Core/Iron Oxide Shell Magnetic Nanoparticles and Their Physicochemical Properties
Authors: Kekalo Katsiaryna , Koo Katherine , Zeitchick Evan , Baker Ian
Published: November 2012

Iron magnetic nanoparticles were synthesized under an inert atmosphere via the reaction between FeCl3 and NaBH4 in droplets of water in a microemulsion consisting of octane with cetyl trimethylammonium bromide and butanol as surfactants. A thin Fe3O4 layer was produced on the iron nanoparticles using slow, controlled oxidation at room temperature. A silica shell was deposited on the Fe3O4 using 3-aminopropyltrimethoxysilane following the method of Zhang et al. [Mater. Sci. Eng. C 30 (2010) 92–97]. The structure and chemistry of the resulting nanoparticles were studied using variety of methods and their magnetic properties were determined. The diameter of the iron core was typically 8-16 nm, while the thickness of the Fe3O4 shell was 2-3 nm. The presence of the silica layer was confirmed using Fourier transform infra-red spectroscopy and the number of NH2-groups on each nanoparticle was determined based on colorimetric tests using ortho-phthalaldehyde.
Short-term Cytotoxic and Inflammatory Responses of Human Monocytes to Stainless Steel Fibre Networks
Authors: Spear Rose L. , Brooks Roger A. , Markaki Athina E.
Published: November 2012

The aim of the current work was to examine the human monocyte response to 444 ferritic stainless steel fibre networks. 316L austenitic fibre networks, of the same fibre volume fraction, were used as control surfaces. Fluorescence and scanning electron microscopies suggest that the cells exhibited a good degree of attachment and penetration throughout both networks. Lactate Dehydrogenase (LDH) and TNF-α releases were used as indicators of cytotoxicity and inflammatory responses respectively. LDH release indicated similar levels of monocyte viability when in contact with the 444 and 316L fibre networks. Both networks elicited a low level secretion of TNF-α, which was significantly lower than that of the positive control wells containing zymosan. Collectively, the results suggest that 444 ferritic and 316L austenitic networks induced similar cytotoxic and inflammatory responses from human monocytes.
Temperature Response of Magnetostrictive/Piezoelectric Polymer Magnetoelectric Laminates
Authors: Gutiérrez Jon , Lasheras Andoni , Barandiarán Jose Manuel , Vilas Jose Luis , San Sebastián María , León Luis Manuel
Published: November 2012

The temperature effect on the magnetoelectric response of hybrid magnetostrictive/piezoelectric laminated composites in the range from room temperature up to 85 ºC is presented. The samples analyzed consisted of alternating, stacked, layers of a magnetostrictive amorphous metal, and a piezoelectric polymer, bonded to each other with an epoxy. The maximum magnetoelectric effect was observed when the composites were driven at their electromechanical resonance. First, we present results on the fabricability of the laminated composite sensor consisting on Vitrovac 4040® (Fe39Ni39Mo4Si6B12) as the magnetostrictive amorphous component and two different piezoelectric polymers: poly(vinylidene fluoride) (PVDF) and 2,6(β-CN)APB/ODPA (poli 2,6) polyimide, a new type of high temperature piezoelectric polymer. At room temperature induced magnetoelectric voltages of 79.6 and 0.35 V/cm.Oe were measured when using PVDF and poli 2,6 polyimide respectively as the piezoelectric components. When heating, we have observed that the magnetoelectric response of the PVDF-containing device quickly decayed to about 5 V/cm.Oe, while for the poli 2,6- containing one it remained almost constat. We discuss the advantage of using this new piezoelectric polymer due to its good performance at high temperatures, making these magnetoelectric laminate composites suitable for high temperature applications.
Improved Cardiomyocyte Functions of Carbon Nanofiber Cardiac Patches
Authors: Stout David A. , Raimondo Emilia , Webster Thomas J.
Published: November 2012

The objective of the present in vitro research was to determine cardiomyocyte functions on poly-lactic-co-glycolic acid (50:50 (PLA:PGA); PLGA) with greater amounts of carbon nanofibers (CNFs) using an in vitro electrical stimulation system for myocardial tissue engineering applications. The addition of CNFs can increase the conductivity and strength of pure PLGA. For this reason, different PLGA: CNF ratios (100:0, 75:25, 50:50, 25:75, 0:100 wt%) were created where conductivity and cytocompatibility properties under electrical stimulation with human cardiomyocytes were determined. Results showed that PLGA:CNF materials were conductive and that conductivity increased with greater amounts of PLGA added, from 0 S.m-1 for 100:0 wt% (pure PLGA) to 6.5x10-3 S.m-1 for 0:100 wt% (pure CNFs) materials. Furthermore, results indicated that cardiomyocyte cell density increased with continuous electrical stimulation (rectangular, 2 nm, 5 V/cm, 1 Hz) after 1, 3, and 5 days as well as a slight increase in Troponin I excretion compared to non-electrically stimulated normal cardiomyocyte cell functions. This study, thus, provides an alternative conductive scaffold using nanotechnology which should be further explored for numerous cardiovascular applications.
Nickel Multi-walled Carbon Nanotube Composite Electrode for Hydrogen Generation
Authors: Kalra Nitin , Santhanam Kalathur , Olney David
Published: November 2012

The electrochemical decomposition of water is an attractive method, however, the performance of the electrodes and efficiencies are of great concern in its large scale production. In this context, we wish to report here the superior performance of Ni-multiwalled carbon nanotube composite as cathode in the decomposition of water. The current voltage curves recorded with this electrode in different media showed a significant electrocatalysis in the reduction of hydrogen ion; the background electrolysis is shifted in the anodic direction. The nanocomposite composition has been found to be crucial in the efficient production of hydrogen. A coulombic efficiency of about 68% has been obtained at this electrode with a hydrogen production rate of 130L/m2 d. This electrode is more efficient than the 316L stainless steel (composition in percentage: C 0.019, Cr 17.3, Mo 2.04, Ni 11.3, Mn 1.04, N 0.041, Fe bulk) cathode that produces 10 ml/h at an area of 20 cm2 (5L/m2.h) (2). The results obtained with different electrolytes, performance variation with electrode composition, and current densities will be presented. The trials carried out using solar panel instead of DC power source showed similar hydrogen production rates and efficiencies.
Utilisation of gyrolite with impure Cd2+ ions in cement stone
Authors: Eisinas Anatolijus , Baltakys Kestutis , Siauciunas Raimundas
Published: November 2012

This study examined the adsorption capacity of gyrolite for Cd2+ ions in acidic and alkaline solutions and the influence of this compound on the hydration of ordinary Portland cement (OPC). In addition, this paper presents the utilisation scheme of gyrolite with impure Cd2+ ions in the cement stone. It was determined that the Cd(NO3)2 solution substitution isomorphism is typical of gyrolite because ∼33% (in solution at a pH of 5·96) and ∼22% (in solution at a pH of 8·70) of Cd2+ ions participate in the substitution/chemical reaction (gyrolite-Ca0 + Cd2+≤ftrightarrow gyrolite-Cd0 + Ca2+), whereas the rest of these ions are present in gyrolite according to an additional interaction. It was estimated that the addition of adsorbents substituted with Cd2+ ions had no substantial effect on the mineralogical composition of OPC samples. It was also noted that Cd2+ ions were bound in the cement stone under all experimental conditions.
Biological ensemble modeling to evaluate potential futures of living marine resources
Authors: Gårdmark Anna , Lindegren Martin , Neuenfeldt Stefan , Blenckner Thorsten , Heikinheimo Outi , Müller-Karulis Bärbel , Niiranen Susa , Tomczak Maciej T. , Aro Eero , Wikström Anders , Möllmann Christian
Published: November 2012

Natural resource management requires approaches to understand and handle sources of uncertainty in future responses of complex systems to human activities. Here we present one such approach, the “biological ensemble modeling approach,” using the Eastern Baltic cod (Gadus morhua callarias) as an example. The core of the approach is to expose an ensemble of models with different ecological assumptions to climate forcing, using multiple realizations of each climate scenario. We simulated the long‐term response of cod to future fishing and climate change in seven ecological models ranging from single‐species to food web models. These models were analyzed using the “biological ensemble modeling approach” by which we (1) identified a key ecological mechanism explaining the differences in simulated cod responses between models, (2) disentangled the uncertainty caused by differences in ecological model assumptions from the statistical uncertainty of future climate, and (3) identified results common for the whole model ensemble. Species interactions greatly influenced the simulated response of cod to fishing and climate, as well as the degree to which the statistical uncertainty of climate trajectories carried through to uncertainty of cod responses. Models ignoring the feedback from prey on cod showed large interannual fluctuations in cod dynamics and were more sensitive to the underlying uncertainty of climate forcing than models accounting for such stabilizing predator–prey feedbacks. Yet in all models, intense fishing prevented recovery, and climate change further decreased the cod population. Our study demonstrates how the biological ensemble modeling approach makes it possible to evaluate the relative importance of different sources of uncertainty in future species responses, as well as to seek scientific conclusions and sustainable management solutions robust to uncertainty of food web processes in the face of climate change.
Experimental evidence for an ideal free distribution in a breeding population of a territorial songbird
Authors: Haché Samuel , Villard Marc-André , Bayne Erin M.
Published: November 2012

According to the ideal despotic distribution (IDD), dominant individuals gain a fitness advantage by acquiring territories that are of higher quality, thereby forcing other individuals into lower quality habitat. In contrast, the ideal free distribution (IFD) predicts that local density is a function of habitat quality, but that individuals achieve the same fitness in different habitat types as a result of density‐dependent variation in territory size. Although the IFD represents an alternative, population dynamics of territorial species are generally expected to be driven by an IDD. We tested the predictions of IFD and IDD by monitoring the demographic response of the Ovenbird (Seiurus aurocapilla) to selection harvesting (30–40% tree removal) during the first five years postharvest in five pairs of 25‐ha study plots, each comprising a control (undisturbed) and a treatment (harvested plot). In the first year following harvesting, Ovenbird territory size increased in treatment plots relative to controls, whereas density, productivity per unit area, and the abundance of litter invertebrates decreased. Treatment effects declined consistently as stands regenerated, and most effects were no longer significant by the fifth year postharvest. However, there was no treatment effect on daily nest survival rate nor on per capita productivity. These results are consistent with the IFD, whereby similar per capita productivity is achieved across habitat types through density adjustments facilitated by changes in territory size. To our knowledge, this is the first study providing evidence for an IFD in a territorial bird species.
Vegetation and soil carbon‐13 isoscapes for South America: integrating remote sensing and ecosystem isotope measurements
Authors: Powell Rebecca L. , Yoo Eun-Hye , Still Christopher J.
Published: November 2012

The carbon isotope composition (δ13C) of terrestrial vegetation and soils is required for a diverse set of research, including carbon cycle studies that utilize global atmospheric CO2 and δ13C data, as well as studies of animal migration and food web dynamics where the δ13C of plants and soils is imparted to animal tissues. We present δ13C maps for South America that correspond roughly to the year 2000, based upon predictions of the abundance and distribution of C3 and C4 vegetation, along with empirical measures of the δ13C of plant leaf and soil endmembers. Our approach relies upon the near‐universal restriction of C4 photosynthesis to the herbaceous growth form and the differing performance of C3 and C4 grasses in various climates, along with land‐cover and crop‐type distributions. Specifically, we predict the percentage cover of C3 and C4 vegetation in each 5‐minute grid cell (∼10 km) based on input gridded layers of vegetation growth form fractional cover, crop‐area/crop‐type distributions, and a high spatial resolution climate data. We develop a consistent set of rules to harmonize the different data layers. The δ13C of vegetation in South America is then estimated based on the C3/C4 composition in each land grid cell, assuming constant mean values for closed C3 tropical forest (−32.3‰), open C3 forest ecosystems (−29.0‰), C3 herbaceous cover (−26.7‰) and C4 herbaceous cover (−12.5‰). In addition to using the mean isotope values, we also incorporate the measured standard deviation for each category. Soil δ13C is estimated for the C4‐favored climate regions of South America using two, largely independent approaches: one that is derived from our vegetation δ13C prediction and one that is based on a previously published relationship between fractional woody cover and the δ13C of soil organic carbon. Finally, we present preliminary maps of relative uncertainty in the estimates of vegetation growth form, generated by integrating global measures of accuracy with local measures of neighborhood variability. These maps demonstrate that the highest uncertainty is found in savanna ecosystems, which contain the most heterogeneous vegetation cover and structure along with a high percentage of C4 grass cover.
Arterial Erectile Dysfunction and Peripheral Arterial Disease: Reliability of a New Phenotype of Endothelial Progenitor Cells and Endothelial Microparticles
Authors: Condorelli Rosita A. , Calogero Aldo E. , Vicari Enzo , di Pino Luigi , Giacone Filippo , Mongioì Laura , la Vignera Sandro
Published: November 2012

Abstract: The aim of this study was to evaluate whether the blood concentrations of a new immunophenotype of circulating late endothelial progenitor cells (EPC) and endothelial microparticles (EMP) varies in patients with arterial erectile dysfunction (aED) and abnormalities in other arterial districts. To accomplish this, cavernous artery peak systolic velocity (PSV), acceleration time (AT), and intima‐media thickness (IMT) were determined after intracavernous administration of alprostadil by echo‐color Doppler in 80 consecutive patients (age range, 50–75 years). Fifteen patients had aED alone (group A) and served as controls; 22 had aED plus atheroma plaques and/or increased IMT of the common carotid artery (group B); 20 had aED plus lower limb artery abnormalities (group C); and 23 had aED plus carotid and lower limb artery abnormalities (group D). EPC and EMP blood concentrations were evaluated by flow cytometry. Blood mononuclear cells with the immunophenotype CD45neg/CD34pos/CD144pos were defined as EPCs, whereas CD45neg/CD144pos/annexin Vposcells were defined as EMPs. Group B and C patients had a similar PSV, AT, and IMT at the level of the cavernous arteries. Their PSV values were significantly lower and mean values of AT and IMT significantly higher compared with group A patients. Patients of group D had a significantly lower PSV and significantly higher AT and IMT compared with all other groups. As far as serum concentrations of EPCs and EMPs, group D patients had significantly higher EPC and EMP mean values compared with all other groups. Group B and C patients had similar EPC and EMP values. This study showed that a more generalized peripheral atherosclerotic process is associated with a more severe penile artery insufficiency and endothelial dysfunction. Moreover, this study confirms the diagnostic reliability of the immunophenotype of EPCs and EMPs chosen in the clinical practice.
Effect of a 60‐Day Oral Gavage of a Crude Alkaloid Extract From Chromolaena odorata Leaves on Hormonal and Spermatogenic Indices of Male Rats
Authors: Yakubu Musa T.
Published: November 2012

Abstract: The present study was aimed at investigating the effects of the crude alkaloids isolated from Chromolaena odorata leaves on the hormonal and spermatogenic indices of male rats. The alkaloids obtained from C odorata leaves using standard methods were administered to male rats for 60 days at the doses of 250, 500, and 1000 mg/kg body weight. Thin‐layer chromatographic analysis of the alkaloid mixture produced 8 spots, 3 of which were alkaloids with Rf values of 0.41, 0.49, and 0.55 as confirmed by the formation of orange color and creamy precipitates with both Dragendorff and Mayer reagents, respectively. The alkaloids were represented in the extract by a yield of 20.28 g, corresponding to a percentage yield of 90.05% of the total extract of 22.52 g. The final body weights of both the control and alkaloid‐treated animals increased significantly (P < .05) compared with their respective body weights before treatment. The alkaloids significantly decreased (P < .05) the testes–body weight ratio; the concentrations of testicular total protein, glycogen, sialic acid, and cholesterol; and the activities of γ‐glutamyl transferase, acid phosphatase, and alkaline phosphatase. The serum luteinizing hormone and follicle‐stimulating hormone levels, as well as testicular and serum testosterone levels, also decreased significantly (P < .05). There were decreases in the sperm count, motility, and density, as well as morphological changes in the sperm cells. The pH and whitish‐gray color of the semen were not significantly affected. All of the doses of the alkaloids increased the total mean number of sperm cell abnormalities, with the secondary type predominating over the primary sperm cell abnormality. The alterations in the levels of the hormones and secretory and synthetic constituents of the testes and the spermatotoxic effects by the alkaloids from C odorata leaves may be due to nonavailability or deprivation of testosterone to the target organ. This lack of testosterone may have consequential effects on the reproductive process of the male rat.