bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of Ni(II) sorption on chlorite - a fracture filling mineral in granites
Authors: Gustafsson Å. , Molera M. , Puigdomenech I. 
Published: April 2011

AbstractChlorite is an Fe(II)-containing phyllosilicate which is often present as a fracture filling mineral in e.g. granitic rocks. It may therefore be significant in influencing redox conditions and sorption processes in granitic groundwaters. The sorption properties of chlorite may therefore be important when modelling the migration of radionuclides under reducing conditions around nuclear waste repositories or in sites contaminated by mining waste.The sorption behaviour of Ni(II) onto a natural chlorite (Karlsborg, Sweden) was investigated using a batch technique. The effects of three different background electrolyte concentrations (0.01 M, 0.1 M and 0.5 M NaClO4), different pH values (ranging from 4 to 11) and different Ni(II) concentrations (10−6 and 10−8 M) were studied under anoxic conditions in a glove-box. Ni(II) solutions were spiked with 63Ni and β-Liquid scintillation counting (LSC) was used to determine the concentration of nickel in the bulk solution, allowing the calculation of solid-water distribution coefficients for the metal ion.The results of the sorption experiments show strong pH dependence at pH > 5, but the sorption is independent of ionic strength. The maximum adsorption is found in the pH range between 7 and 11 with Kd values ≍103 cm3/g. A diffuse double layer model has been used to describe the experimental results.
Product consistency test of fully radioactive high-sodium content borosilicate glass K-26
Authors: Ojovan N.V. , Startceva I.V. , Barinov A.S. , Ojovan M.I. , Bacon D.H. , McGrail B.P. , Vienna J.D. 
Published: April 2011

AbstractChemical durability of fully radioactive, high-sodium borosilicate glass K-26 was evaluated using the product consistency test PCT-A. Examination revealed normalised leaching rates as high as 5.93•10−2, 4.05•10−2 and 2.93•10−2 g/m2•day for sodium, boron and silicon respectively. Data on chemical durability of glass K-26 are consistent with similar composition glasses. These are of particular interest for performance assessment models.
Aqueous Dissolution of Pyrochlore and Zirconolite in F--bearing Solutions
Authors: Zhang Zhaoming , Li Huijun , Vance Eric R. , McLeod Terry , Scales Nicholas 
Published: April 2011

AbstractWe have studied the aqueous durability of pyrochlore-structured yttrium-titanate (Y2Ti2O7) and Nd/Al-bearing zirconolite [(Ca0.8Nd0.2)Zr(Ti1.8Al0.2)O7] in both neutral and acidic solutions, with and without the presence of 0.001 M of NaF. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) were used to characterize the composition, structure and morphology of the pyrochlore (Y2Ti2O7) and zirconolite surfaces, both before and after static dissolution testing at 90 and 150°C for four weeks. The leachates were also analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to estimate the individual elemental releases. The results show that the presence of F- ions only has a significant effect in acidic media on the dissolution behavior of pyrochlore and zirconolite. This detrimental effect is more pronounced for pyrochlore than zirconolite; the Y2Ti2O7 surface was replaced completely by alteration products after dissolution testing at 150°C for 4 weeks in acidic media with 0.001 M fluoride ions.
Rapid Method for ICP-MS Analysos of Plutonium in Sediment Samples
Authors: Greis Christina , Düker Anders , Pettersson Håkan , Karlsson Stefan , Allard Bert 
Published: April 2011

AbstractA rapid and reliable method for quantification of transuranium elements in environmental samples is required from the aspect of emergency preparedness. Determination of these elements in e.g. sediment samples includes three steps: sample dissolution, chemical separation and measurement. Different acids were used for leaching of plutonium, americium and neptunium from contaminated sediment (during heating or microwave digestion). Chemical separation was performed by co-precipitation (with Fe(OH)3 or NdF3), by anion exchange or by liquid-liquid extraction (with tributylphosphate, trioctylamine and thenoyl trifluoroacetone, respectively). The following radioisotopes were quantified by quadrupole ICP-MS equipped with an ultrasonic nebulizer (USN): 237Np, 239Pu, 240Pu, 241Pu, 242Pu and 241Am. Data are only given for 239Pu and 240Pu in this paper. Plutonium was also measured by alpha spectrometry in some samples, as well as 137Cs and 241Am by gamma spectrometry. The agreement between concentrations of plutonium obtained by ICP-MS and alpha spectrometry was good, which demonstrates that a simple and rapid procedure for analysis of plutonium by quadrupole ICP-MS is feasible.
Separation of 137Cs from Acidic Nuclear Waste Simulant via an Engineered Inorganic Ion Exchanger
Authors: Tranter T.J. , Vereshchagina T.A. , Anshits A.G. , Fomenko E. , Aloy A.S. , Sapozhnikova N.V. 
Published: April 2011

AbstractAn engineered ion exchange material has been prepared for the specific purpose of removing radioactive cesium from acidic waste. Separating the fission product 137Cs from the bulk of the nuclear waste stream is often advantageous because, after typical cooling times, this isotope is usually the primary source of gamma radiation dose. The engineered ion exchanger was prepared using ammonium molybdophosphate impregnated into hollow glass crystalline microspheres. The microspheres or cenospheres, are refractory compounds of silica and alumina that are derived from the fly ash produced in coal combustion. This paper describes equilibrium experiments that were conducted with the engineered ion exchanger and a simulated acidic waste solution. These tests indicate that the new material has a high capacity and selectivity for cesium in these matrices.
Dissolution Rate of Colloidal Silica in Highly Alkaline Solution
Authors: Chida Taiji , Niibori Yuichi , Tochiyama Osamu , Mimura Hitoshi , Tanaka Koichi 
Published: April 2011

AbstractFor the performance assessment of the radioactive waste repository, it is important to clarify the dynamic behavior of silica (silicic acid and hydrous or unhydrous silicon dioxides). The behavior of silica would be complicated when cement is used for the construction of the repository, since silica takes various forms due to polymerization, precipitation and dissolution with change of pH or temperature. In order to know the fundamental kinetic property of silica, this study has examined the dissolution rate of colloidal-silica.In the experiment, the concentration of silica in a soluble form was determined by the silicomolybdenum-yellow method. In this study, soluble-silica was defined as silica reacting with molybdate reagent and coloring yellow, and colloidal-silica was defined as silica in liquid phase except for soluble-silica. Colloidal-silica was obtained through the polymerization process, where the pH value of silica solution was brought down from over 10 by HNO3 solution. This study examined dissolution rate of colloidal-silica again by setting to 10 or 13 in pH-value and 288 K, 298 K or 313 K in temperature. In the experimental results, the dissolution reaction of colloidal-silica proceeded linearly with time, when the dissolution of colloidal silica was not restricted by the solubility of silica. To estimate the dissolution rate, we assumed df /dt = k*, where f is the soluble-silica fraction defined as the amount of soluble-silica divided by the silica amount introduced into the sample solution, t the time (s) and k* the rate constant (s-1). The activation energy for the dissolution of the colloidal-silica at pH 13 was estimated to be approximately 80 kJ·mol-1which was similar to that for amorphous silica (solid phase) at pH 13. This suggests the same reaction mechanism for the dissolution of colloidal-silica and amorphous silica in highly alkaline solution.
Evidence for Neptunium Incorporation into Uranium (VI) Phases
Authors: Buck Edgar C. , Hanson Brady D. , Friese Judah I. , Douglas Matt , McNamara Bruce K. 
Published: April 2011

AbstractThis paper examines the ability of electron energy-loss spectroscopy (EELS) combined with transmission electron microscopy (TEM) to detect both low concentrations of Np in a U matrix and to provide evidence for incorporation of Np in U(VI) phases. The case for U(VI) secondary minerals acting as solubility-controlling phases for Np in repository performance assessment models has not been fully established. Direct evidence for incorporation, rather than sorption, continues to be difficult to obtain. Detection of Np with TEM-EELS is hampered by the occurrence of a plural (multiple) scattering event from the more abundant U atoms (U-M5 + U- O4,5), that results in severe overlap on the Np-M5 edge at ∼3665 eV. By examining the energy âgap' between the Np-M5 and Np-M4 edges (184 eV), a method for observing Np independently of the plural scattering event has been established. Clear evidence of Np incorporation into synthetic studtite {(UO2)(O2)(H2O)2](H2O)2} and uranophane {Ca(UO2)2(SiO3OH)2(H2O)5} has been found with TEM-EELS. The EELS technique continues to remain an important tool for examining the potential for transuranic behavior in nuclear waste materials.
Effect of External Gamma Irradiation on Dissolution of the UO2 Matrix
Authors: Jégou C. , Muzeau B. , Broudic V. , Peuget S. , Poulesquen A. , Roudil D. 
Published: April 2011

AbstractLeaching experiments were done on UO2 pellets doped with alpha-emitters (238/239Pu, 1500 - year batch), in the presence of an external gamma irradiation source (A60Co = 260 Ci, γ dose rate = 650 Gy h−1). The effects of α and γ radiation and the nature of the cover gas (air or Ar + 4% H2) on water radiolysis, and on oxidizing dissolution of the UO2 matrix, are quantified and discussed. The cover gas clearly has a major role in the effect of γ radiolysis. The dissolution rate in an aerated medium is 83 mg m−2 d−1 compared with only 6 mg m−2 d−1 in Ar + 4% H2. The rate drop is accompanied by a reduction of about four orders of magnitude in the hydrogen peroxide concentrations in the homogeneous solution. The UO2 alteration rate under gamma radiation in Ar + 4% H2 is comparable to the rate obtained in the presence of alpha radiolysis alone for the doped UO2 pellets with the highest alpha activities (4.75 × 108 Bq/g UO2, 15 - year batch).
Radiolytic Corrosion of238Pu-doped UO2Pellets in 5 M NaCl Solution
Authors: Kelm M. , Bohnert E. 
Published: April 2011

AbstractDeaerated 5 M NaCl solution is alpha-irradiated up to 700 days in the presence of UO2pellets. Experiments are conducted with238Pu-doped pellets in pure brine and with undoped UO2pellets in a238Pu containing brine. The long-lived radiolysis products H2, O2and ClO3-are formed in all cases proportional to the dose applied on the solution and with yields corresponding to 200, 80 and 7 nMol/(L*Gy).The U concentrations increase with time but do not exceed about 10−4Mol/L thus indicating Uranium to be solubility limited. Moreover, the rinse solutions of the vessels at the end of the experiments contain up to one order of magnitude more U than found in the solutions. The total amounts of mobilized U deviate by less than a factor 10 from each other regardless of the large ratio of surface dose rates (ratio up to 2300) or mean dose rates (ratio up to 100), applied while the reference experiment (UO2pellet in pure brine) yields only some 10−7Mol/L U which is over 3 orders of magnitude lower than observed in experiments with radiation present.The simulation of the radiation chemical processes using a kinetic reaction model can reasonably reproduce the findings of the experiments with respect to the formation of H2and O2and give the order of magnitude for the concentrations of chlorine species and of oxidized UO2.
Valencies of Mn impurities in ZnO
Authors: Petit L. , Schulthess T. C. , Svane A. , Temmerman W.M. , Szotek Z. 
Published: April 2011

AbstractWe use the self-interaction corrected (SIC) local spin-density (LSD) approximation to investigate the groundstate valency configuration of Mn impurities in p-type ZnO. In Zn1−xMnxO, we find the localized Mn2+ configuration to be preferred energetically. When codoping Zn1−xMnxO with N, we find that four d-states stay localized at the Mn site, while the remaining d-electron charge transfers into the hole states at the top of the valence bands. If the Mn concentration [Mn] is equal to the N concentration [N], this results in a scenario without carriers to mediate long range order. If on the other hand [N] is larger than [Mn], the N impurity band is not entirely filled, and carrier mediated ferromagnetism becomes theoretically possible.
Terahertz measurements of the Photoactive Protein Bacteriorhodopsin mutant D96N: M and P states
Authors: Chen J.-Y. , Knab J. R. , Cerne J. , Hillebrecht J. R. , Birge R. R. , Markelz A. G. 
Published: April 2011

AbstractWe use terahertz (THz) spectroscopy as a biomaterials characterization tool. Previously we have shown a strong contrast between the THz dielectric response for wild type (WT) and D96N mutant of bacteriorhodopsin. In those studies we observed a large increase in the THz absorbance of WT with excitation to thermally captured photo-intermediates whereas no such increase in absorbance was observed for the mutant D96N. These results suggest that the THz response is sensitive to structural changes and relative flexibility of biomolecules. However the photo-intermediate populations of the WT and D96N samples were not equivalent in those measurements. While the WT samples had relaxed (bR), M and P state intermediates present, the D96N samples had only bR and M states. Here we present terahertz absorbance measurements of D96N as a function of M and P state populations at room temperature. The THz response is constant for intermediate states populations up to 23% M state and up to 30% P state. These results verify that there is a fundamental difference in the conformational dynamics as measured by THz dielectric response for a single residue mutation.
Fast Simulation Protocol for Protein Structural Transitions: Modeling of the Relationship of Structure and Function
Authors: Setty Arun K. , Zuckerman D. M. 
Published: April 2011

AbstractAn approach is developed to study the dynamics of protein conformational transitions in depth. A computational (Monte Carlo) approach based on a united residue model is used. Unbiased transitions between the Apo and Holo conformations/states of calmodulin are observed at the rate of 1 per day per processor. A series of models of increasing complexity is studied, accounting for hydrophobic interactions and calcium binding. Details of the transitional region and structural information about intermediate states are obtained. Statistically converged ensembles of transitions are obtained in a reasonable real time period.
Teaching Corporate Culture – an Engineer's Survival Guide
Authors: Savage Richard N. 
Published: April 2011

AbstractThe transition from new engineering graduate to successful member of corporate America is a difficult journey. Often the skills required are not part of a student's traditional undergraduate education. At Cal Poly, we have integrated a new course into our existing Senior Project curriculum which enables students to develop the professional skills necessary to become an effective member of any corporation. Key skills such as communication, problem solving and project management are practiced through active learning techniques. These as well as other topics studied are required for ABET certification.The new course investigates the mission and values that are at the foundation of any corporation's culture. It challenges students to evaluate their own personal leadership potential. Organization structures along with the roles and responsibilities of Engineering, Marketing, Sales, Operations, Finance and Executive management are studied along with the interdisciplinary nature of engineering and technology. The rigors and metrics of a typical product development methodology are explored along with the concepts of program management and the protection of intellectual property. Business models are studied which enable students to evaluate the impact engineering can have on a company's financial success. Moreover, the students learn that they are members of a global community with environmental and social responsibilities. The impact of technology on society can be profound and students are challenged to consider difficult ethical issues as well as exciting career opportunities.
Flame spray synthesis of tin oxide nanoparticles for gas sensing
Authors: Sahm Thorsten , Mädler Lutz , Gurlo Alexander , Barsan Nicolae , Pratsinis Sotiris E. , Weimar Udo 
Published: April 2011

ABSTRACTTin oxide nanoparticles for gas sensing application have been synthesized with an aerosol method. The particles were manufactured with the versatile Flame spray Pyrolysis (FSP) method producing highly crystalline powders with closely controlled a primary particle and crystallite size of 10 nm and 17 nm. The single crystalline particles were only slightly aggregated and directly used for thick film sensor deposition by drop coating and screen printing.The flame made SnO2 nanoparticles showed high and rapidresponse to reducing gases such as propanal and CO.
Room Temperature Hydrogen Gas Sensitivity of Nanocrystalline-Doped Tin Oxide Sensor Incorporated into MEMS Device
Authors: Shukla Satyajit , Agrawal Rajnikant , Ludwig Lawrence , Cho Hyoung , Seal Sudipta 
Published: April 2011

ABSTRACTNanocrystalline indium oxide (In2O3)-doped tin oxide (SnO2) thin film sensor has been sol-gel dip-coated on a microelectromechanical systems (MEMS) device. The micro-sensor device is successfully utilized to sense ppm level H2 at room temperature with high sensitivity. The chamber pressure has no pronounce effect on the room temperature H2 sensitivity.
In2O3 nanowire mat devices as high performance NO2 gas sensors
Authors: Zhang Daihua , Liu Zuqin , Zhou Chongwu 
Published: April 2011

ABSTRACTA high sensitive and reliable In2O3 nanowire mat devices are fabricated. Detection of NO2 gas down to ppb levels was achieved. This represents orders-of-magnitude improvement over previously reported metal oxide film or nanowire/nanobelt sensors. Furthermore, this simple device shows certain selectivity to NO2 with other common chemicals such as NH3, O2, CO and H2 around.
Themodynamic and Kinetic Principles for Electrochemical Gas Sensors Based on Solid Ionic Conductors
Authors: Tsagarakis Evangelos D. , Weppner Werner 
Published: April 2011

ABSTRACTSeveral concepts can be applied for gas detection using solid ionic conductors. The fundamental characteristics and the essential variables for proper design of electrochemical cells are analyzed in terms of the sensing principle applied. The principal properties for materials as components of electrochemical devices are being illustrated. Employment of dynamic method allows implementation of the Fourier coefficients to generate a complex plane plot representation. This can be particularly useful for extracting information regarding the selectivity of an electrochemical cell to multiple gas species. Moreover, modeling the system response upon a periodical perturbation can be beneficial on understanding the individual processes and optimizing the overall performance.
Rational Synthesis and Optimization of Multifunctional Solid-State Gas Sensors
Authors: Schwank Johannes , Korotcenkov Ghenadii 
Published: April 2011

ABSTRACTA new approach is discussed for the rational synthesis and development of optimized multifunctional solid-state gas sensors. Multifunctionality—the incorporation of multiple types of reactivities into a material, such as acid and/or base functionalities, oxidation and/or reduction functionalities, etc.—isa requirement in many gas sensing applications. The front end of many gas sensors contains catalytic layers, so that optimization of catalysts and optimization of gas sensors can be carried out in a synergistic fashion.Multifunctionality presents unique challenges to rational catalyst and sensor systems development because the overall performance of the material is a convolution of the performance of the various subcomponents, and optimization of these individual subcomponents in isolation does not necessarily lead to optimal, or even acceptable, overall performance. A major obstacle to dealing with these difficulties is the inherent complexity of heterogeneous systems prepared by traditional approaches, which makes it difficult to unambiguously identify the compositions and morphologies of the local active sites and their interactions. Further complicating the problem is the requirement to function in environments that can vary on both short and long time scales. A key to understanding, controlling, and optimizing these materials is the ability to produce and study well-defined sensor materials with well-defined composition and morphology, with the flexibility to vary the composition easily without jeopardizing the structural uniformity.The development of new or improved materials for gas sensor applications requires a search for novel and innovative approaches to the nano-scale design of these materials. The use of the technology of surface modification by successive ionic layer deposition (SILD) method is such an innovative approach that will be discussed in this paper.
Surface Plasma Treatment and Sensibilization of Tin Dioxide Films for Enhancement of Gas Sensitivity and Selectivity
Authors: Dmitriev Serghei V. , Brinzari Vladimir I. , Korotcenkov Ghenadii S. 
Published: April 2011

ABSTRACTResults of investigation aimed at the improvement of gas sensitive characteristics of tin dioxide thin film's based gas sensors through their treatment in high frequent (HF) oxygen plasma and sensibilization by means of doping are presented.Tin dioxide thin films were deposited from alcohol solutions of SnCl45H2O by means of chemical spray pyrolysis method on alumina substrate at the temperatures in the range from 400 to 500°C. The thickness of films was varied in the range 20–100 nm.Surface treatment of obtained tin dioxide layers was carried out in pure oxygen plasma at room temperature and 3-4 times increase of the resistance and gas sensitivity was obtained at that. These parameters' changing is discussed from the point of view of thin film's stoichiometry alteration, for control of which there were used IR and SIMS measurements. Obtained results are compared with results of the film's high temperature (∼600oC) thermal annealing on air.To increase thin film's gas sensitivity and selectivity the doping with Pd and Cu was applied. Doping was carried out also through chemical spray pyrolysis method from the solutions of corresponding compounds of Pd and Cu. Such modification of SnO2 surface hasallowed to increasing sensitivity to H2 up to 5.103 rel. units (high selectivity) at the simultaneous shift of sensitivity maximum from 350 to 150°C. Doping with Cu has allowed to increasing 4-5 times sensitivity and selectivity toward CH4 and C3H8 gases in air and reducing operating temperatures from 500–520°C to 350–370°C.It is concluded that combination of HF oxygen plasma tin dioxide film' treatment and its surface sensibilization is an effective way to considerably improvement of gas sensitive and selective characteristics of tin dioxide based thin film gas sensors (TFGS).