bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Fumaric Anhydride on Bioadhesive Polymer Compositions
Authors: Santos C.A. , Freedman B.D. , Ghosn S. , Mathiowitz E. 
Published: April 2011

AbstractBioadhesive polymers are useful as drug delivery systems designed to adhere to the gastrointestinal lumen. The interaction between polymer and mucosal tissue influences residence time of the polymeric device and greatly affects the bioavailability of encapsulated drug. Poly(fumaric-co-sebacic anhydride) [P(FA:SA)] demonstrated impressive results in a variety of in vitro and in vivo experiments designed to test bioadhesion of microspheres. Among different molar ratios of P(FA:SA), adhesive measurements increased with increasing fumaric acid (FA) content. Using a modified microbalance technique, P(FA:SA)10:90 yielded a tensile work measurement of 82.99±12.76 nJ (mean±SEM) while that for P(FA:SA)70:30 was 453.23±47.73 nJ. A low molecular weight substance, fumaric anhydride prepolymer (FAPP), the oligomer form of fumaric acid, was incorporated into the microspheres and greatly increased the bioadhesive properties of P(FA:SA) as well as those of the relatively non-bioadhesive polymer poly(caprolactone) (PCL). Tensile work of P(FA:SA)20:80 was 32.95±5.42 nJ, and P(FA:SA)20:80 with 25% FAPP yielded a tensile work measurement of 556.28±113.12 nJ. Adhesion testing with PCL yielded a tensile work measurement of 7.93±1.84 nJ, while that for PCL with 25% FAPP was 1629.54±307.55 nJ. The effect of FA on drug delivery was evaluated in vitro using the P(FA:SA):FAPP blend with the everted intestinal sac technique. A low molecular weight drug (sodium salicylate) encapsulated in P(FA:SA)20:80 passed through the everted intestinal lumen to the interior of the sac to yield a concentration of 11.17±0.93 mg/dL, and drug encapsulated in P(FA:SA)20:80 with 10% FAPP yielded a concentration of 16.25±1.68 mg/dL (P<0.05). Unencapsulated drug passed through the intestinal lumen to yield a concentration of 8.09±-0.36 mg/dL. These experiments demonstrate that fumaric anhydride could be a very important component in bioadhesive polymer systems.
Investigations on the Electrochemical Behavior of Zr-Al-Cu-Ni Bulk Metallic Glass
Authors: Buchholz K. , Gebert A. , Mummert K. , Eckert J. , Schultz L. 
Published: April 2011

AbstractThe passivation behavior of bulk glassy Zr55Al10Cu30Ni5 alloy samples in weakly alkaline sulphate solution (pH = 8) is investigated in comparison to the arc-melted crystalline alloy, to the main alloying component zirconium and to aluminium. Results of potentiodynamic and potentiostatic polarization measurements reveal the formation of a stable passivating surface film on the glassy alloy grown by a high-field mechanism. Auger electron spectroscopic investigations of anodized sample surfaces show that the films formed on the glassy Zr-Al-Cu-Ni alloys exhibit a composition gradient in cross-sectional direction. In 0.001M NaCl electrolytes bulk glassy Zr-Al- Cu-Ni samples are susceptible to pitting corrosion, which is due to the existence of crystalline inclusions.
Glass Formation and Phase Separation In The Vitreloy Type Bulk Metallic Glasses
Authors: Hays Charles C. , Kim Paul , Johnson William L. 
Published: April 2011

AbstractResults of calorimetric, differential thermal analysis, and structural measurements are presented for a series of bulk metallic glass forming compositions in the Zr-Ti-Cu-Ni-Be alloy system. The structural data identify the competing crystalline phases, formed on cooling from the liquid state, for various compositions in the Zr-Ti-X quasi-ternary phase diagram; with the Cu-Ni-Be ratio given by X = Be9Cu5Ni4. For this region of the ndimensional phase space (n=5), the bulk glass forming range is extensive and the calorimetric data exhibit thermal features associated with the occurrence of phase separation in the undercooled liquid state prior to primary crystallization. The topology of the composition manifold is complex; manifest by dramatic changes in crystallization behavior for small changes in the Zr-Ti-X ratio. Alloys with large supercooled liquid regions, Δ, are observed; ΔT≈ 135 K. Zr-Ti-Cu-Ni-Be alloy compositions with eutectic temperatures less than that of pure Al (Tm = 933 K) were also synthesized.
A Relation Between Fragility, Specific Heat, and Shear Modulus Temperature Dependence for Simple Supercooled Liquids
Authors: Granato A. V. 
Published: April 2011

AbstractIt is often said that the fragility and specific heat discontinuity at the glass transition are related characteristic features of glasses. We give a relation between these quantities for simple liquids, and also find that the temperature dependence of the shear modulus should be closely related to these quantities. According to the Interstitialcy Theory, the liquid state shear modulus G = Go, exp (-βc) = Go exp {-γ[(T/To)-l ]}, where Gois the shear modulus at a reference temperature To, which can be taken to be the glass temperature. In these relations, βis the diaelastic shear susceptibility, c is the interstitialcy concentration, T is the temperature, and dc/dT = γ/βTo. It has been proposed by Dyre, Olsen and Christensen that U in the viscosity η = ηo exp (U/kT) be given as the work done in shoving aside particles during a diffusion step, and therefore be proportional to the (liquid state) shear modulus. If so, then combining the above relations, the fragility F = [d log η/d (Tg/T]T=Tg becomes F=(1+γ) log [η (Tg)/ηo], where γ = - (Tg/G)(dG/dT). Then, since δCv, = UF(dc/dT), where UF is the interstitialcy formation energy, one obtains further with reasonable simplifying approximations δCv/Cv∼γG(T)/Goo, where Goo is the zero temperature crystalline shear modulus. For a typical fragile glass γ ∼ 2 (F ∼ 50) with G(Tg)/Goo ∼ 1/2, then δCv/Cv, ⊼ 1, ut close to zero for strong glasses, in fair agreement with available experimental results. The perspective given by the Interstititialcy Theory is then that the fragility is given phenomenologically by the temperature dependence of the shear modulus, or microscopically by the rate of increase of the equilibrium interstitialcy concentration with temperature.
Decomposition in Pd40Ni40P20 Bulk Metallic Glass
Authors: Miller M. K. , Schwarz R. B. , He Yi 
Published: April 2011

AbstractAn atom probe field ion microscope and 3-dimensional atom probe characterization of the solute distribution in a bulk Pd40Ni40P20 metallic glass in the as-cast state and after annealing has been performed. Statistical analysis of the atom probe atom-by-atom data detected the presence of short range ordering in the as-cast alloy. Phase separation at the nanometer level is observed in glassy samples after annealing above the glass-transition temperature. Crystallization proceeds by phase separation into three distinct crystalline phases. Atom probe analysis of the alloy annealed for 1 h at 410°C revealed that the primary nickel phosphide phase contained significant levels of palladium, the palladium-rich Pd3P phosphide phase contained low levels of nickel and there was a small amount of a palladium-nickel solid solution.
Thermochemistry and Kinetics of Gas-Phase Reactions Relevant to the CVD of Coatings: New Data for Process Models
Authors: Allendorf M. D. , Melius C. F. , McDaniel A. H. 
Published: April 2011

AbstractUnderstanding the role of gas-phase reactions is an important step in the development of useful CVD process models. In this article, we review the general types of gas-phase reactions that can occur and discuss quantum-chemistry techniques for predicting their thermochemistry and kinetics. We also describe the use of high-temperature flow reactors to measure gas-phase reaction kinetics. Coupling these theoretical and experimental methods is a powerful approach to the characterization of CVD precursor chemistry. We illustrate this in a discussion of the reaction between BC13and NH3, which is important in the deposition of hexagonal boron nitride coatings.
Temperature Dependence of Wafer Backside Deposition in Single Wafer CVD Reactor
Authors: Wang Q. , Liu Dennis D. , Yeh Jim 
Published: April 2011

AbstractA quantitative experiment was designed to characterize in detail the backside silicon nodule formation (BSNF) on a single wafer reactor. It is found that there are two BSNF related vapor processes. One is the silicon mass transfer between wafer and wafer susceptor, which is controlled by the temperature difference between wafer and the susceptor. The other is the chemical vapor deposition process due to the presence of precursor (trichlorosilane) at the vicinity of the wafer backside. The contributions of these two processes to BSNF, however, have opposite dependencies on wafer temperatures. The silicon mass transfer from susceptor to wafer backside decreased with increasing wafer temperature. The trichlorosilane deposition increases with increasing wafer temperature. The effects of these two processes are also strongly dependent on susceptor configuration. It is found that having a wafer in direct contact with the susceptor could minimize the trichlorosilane deposition process, but silicon mass transfer is still present at the edge of the wafers. This study demonstrates that careful process control and susceptor design are necessary to eliminate wafer backside deposition.
Nitrogen Defect Concentration in Chemical Vapor Deposited Homoepitaxial Diamond at High TemperatureS
Authors: Yan Chih-Shiue , Vohra Yogesh K. 
Published: April 2011

AbstractHomoepitaxial diamond films were grown on polished single crystal {100} oriented natural type Ila diamond circular substrates using high density microwave plasma chemical vapor deposition (MPCVD). Twelve homoepitaxial diamond films were grown under a variety of substrate temperatures (1000 C-2000 C), methane concentration (1% - 3% in hydrogen gas) and processing pressure(60 - 150 torr). Electron paramagnetic resonance (EPR) studies demonstrate that nitrogen is largely incorporated as singly substitutional impurity (P1-center) and nitrogen's concentration is in the range of 10 -100 parts per million. Nitrogen's concentration also shows a systematic decrease with increasing substrate temperatures. The temperature variation of nitrogen at high temperatures is discussed within a model where single substitutional nitrogen aggregates to form nitrogen defects which are not EPR active.
Surface Phenomena of the Thin Diamond-Like Carbon Films
Authors: Polyakov V. I. , Rukovishnikov A. I. , Khomich A. V. , Druz B. L. , Kania D. , Hayes A. , Prelas M. A. , Tompson R. V. , Ghosh T. K. , Loyalka S. K. 
Published: April 2011

AbstractDiamond-like carbon films (DLC) 10–40 nm thick were deposited on quartz substrates on an interdigitated planar array of 20 μm Ni electrodes already prepared by lithographic techniques. The influence of the adsorbed molecules onte electrical properties of the thin DLC films was investigated. Current and capacitance-voltage characteristics were examined. Charge-based deep level transient spectroscopy (Q-DLTS) was used for study of adsorption and desorption processes. The strong sensitivity of Q-DLTS spectra to the presence of the vapor water and isopropyl alcohol was found. For example, the Q-DLTS signal for some deposited DLC film was changed more then in order in presence of the water vapor. Such strong surface phenomena of the thin DLC films may be exploited in novel gas sensor devices.
Effect of Processing Parameters on the Chemistry of Magnetron Sputtered Ti-Al Thin Films
Authors: Kale A. S. , Seal J S. , Beaulieu K. , Sundaram K. B. 
Published: April 2011

AbstractTitanium-aluminum alloys are proved to be a viable candidate material in the field of structural coatings due to their high temperature creep and oxidation resistance in addition to being a lightweight material. In the present paper, we study the effect of applied power on the mechanical properties and surface chemistry of dc-magnetron sputtered Ti3AI thin films. While SEM and XRD investigate the structure and morphology of the deposited films, XPS and AES proved to be an essential tool for studying the surface chemistry and detailed chemical bonding information of the Ti3AI thin films. Glancing angle XPS and Auger depth profiling were carried out to study the chemistry at a few layers beneath the surface to monitor the changes in the stoichiometry of Ti3AI films. Microhardness measurements indicate an increase in the thin film hardness with increased sputtering power. These data were further compared to thin films deposited under liquid N2 temperatures.
Optical Properties and Corrosion Resistance of Durable Silver Coatings
Authors: Fuqua P. D. , Barrie J. D. 
Published: April 2011

AbstractThere is a need in the optics community for highly reflective mirrors that do not degrade in harsh environments. While silver can be a highly efficient reflector of visible light, it suffers from poor resistance to corrosive atmospheric gases. Here, we investigate a durable silver coating scheme, in which silver is sputter deposited between very thin layers of nichrome nitride. Excellent corrosion resistance is achieved with a silicon nitride overcoat. Samples were exposed to a variety of atmospheres and it was found that the nichrome nitride dramatically increased corrosion resistance when compared to bare silver or silicon nitride coated silver. Similar results were found when electrochemical impedance spectroscopy was used to evaluate samples. The enhanced corrosion resistance is achieved even when the thickness of the nichrome nilTide adhesion layer is too thin to be considered continuous.
Cesium Sorption on Tonalite and Mica Gneiss
Authors: Siitari-Kauppi M. , Hölttä P. , Pinnioja S. , Lindberg A. 
Published: April 2011

AbstractDifferent approaches for measuring the interaction between radionuclides and rock matrix are needed to test the compatibility of transport models and retardation experiments. In this work sorption of cesium (134Cs) was studied on unaltered mica gneiss, and on unaltered, moderately altered and strongly altered tonalite. The crushed rock samples were sieved into seven fractions from 0. 1 mm to 3.15 mm. The mass distribution ratio values for each fraction was determined using the static batch method. Cesium sorption onto different minerals was demonstrated using digital image analysis in order to interpret thin section autoradiographs. The autoradiographic method based on irradiation-induced luminescence properties in feldspars was applied in order to estimate the alteration of tonalites.Cesium sorption on moderately altered and strongly altered tonalite was stronger than on unaltered rocks owing to larger specific surface areas and the composition of alteration minerals. Strongest sorption was found on biotite. Mass distribution ratio, Rd, values of 0.3–1.1 m3·kg−1 for unaltered rocks and 0.9–3.4 m3·kg−1 for altered rocks were determined. Moderate dependence on surface area was found for mica gneiss after I and 3 days sorption time. For strongly altered tonalite only slight dependence on surface area was found. Research-articled -values increased as a function of sorption time due to diffusion into the particles. Higher increase in values for larger diameter particles indicated the availability of internal specific surface areas.
Sorption of Radionuclides Onto Cement Materials Altered by Hydrothermal Reaction
Authors: Sugiyama D. , Fujita T. 
Published: April 2011

AbstractThe sorption of radionuclides onto cement materials is a very important parameter when considering the release of radionuclides from radioactive wastes. Once the composition or crystallinity of the constituent minerals of a cement material is changed by alteration in the disposal environment, its sorption ability might be affected. In this study, the effect of hydrothermal alteration on the sorption properties of two cement grouts and Calcium Silicate Hydrogels (CSH-gels) is investigated by using the batch sorption technique. In the case of strontium (a model cation) sorption, the distribution ratio for Ordinary Portland Cement (OPC) and OPC/Blast Furnace Slag blended cement (OPC/BFS) decreased as the alteration temperature increased. This is mainly caused by the decrease of sorption onto CSH-gel which is a constituent of cement materials. In the case of selenium (selenite, a model anion) sorption, the distributionratio decreased as the alteration temperature increased for OPC treated in both distilled water and groundwater, and for OPC/BFS in groundwater. This is attributed to the decomposition of ettringite which sorbs anions. The distribution ratio for OPC/BFS in distilled water increased as the alteration temperature increased, although ettringite decomposed. This is attributed to the formation of monosulphate which also sorbs anions. These results show that the hydrothermal alteration of cement mineral phases in a disposal environment may cause changes which could increase or decrease the sorption of radionuclides onto cements depending on the cement composition and radionuclide speciation.
Purification of Alkaline Waste Solutions from Np and Pu
Authors: Guelis A. V. , Shilov V. P. , Krot N. N. 
Published: April 2011

AbstractCoprecipitation of Np and Pu with Co(OH)3 and Fe(OH)3, obtained by the Method of Appearing Reagents from Co(NH3)6 Cl3, K2FeO4, and Na2[Fe(CN)5NO]2H2O from alkaline solutions and from simulants of Hanford Site tank wastes has been studied. Removal of Np and Pu from pH 10.5 to 0.4 M NaOH is semiquantitative with decontamination factors of 80 to 400. The presence of EDTA and HEDTA interferes with the precipitation of Co(OH)3 and Fe(OH)3. The deleterious effect of EDTA was eliminated by Ca2 addition at a 1:1 molar ratio of Ca2:EDTA. The deleterious effect of HEDTA was eliminated by the addition of 0.11 M excess precursor Co(NH3)6Cl3 to increase the content of carrier Co(OH)3.
Formulation, Testing, and Structural Characterization of High-Zirconium High-Level Waste Glasses
Authors: McKeown David A. , Muller Isabelle S. , Buechele Andrew C. , Pegg Ian L. , Kendziora Christopher A. , Scales Charles R. 
Published: April 2011

AbstractA range of compositions of high-zirconia borosilicate glasses were formulated and their structures investigated by a combination of techniques. These compositions have potential applications for high-level nuclear waste storage in combination with advanced reprocessing methods. Raman and Zr EXAFS data were collected for a series of glasses spanning a range of zirconia concentrations. The Raman spectra indicate that Zr acts as a silicate network modifier, where the silicate tetrahedral network depolymerizes as the zirconia content increases. Zr EXAFS analysis indicates that Zr is found in octahedral sites, and to a minor extent, sevencoordinated sites. As the zirconia content increases, the fraction of seven-coordinated Zr-sites increases; this may be the cause of ZrO2 baddeleyite crystallization that was observed in some Zr-rich glasses investigated.
Inventories of Iodine-129 and Cesium-137 in the Gaps and Grain Boundaries of LWR Spent Fuels
Authors: Gray W. J. 
Published: April 2011

AbstractPerformance assessment calculations that support geologic disposal of spent nuclear fuel in a potential repository at Yucca Mountain, Nevada, are based in part on the assumption that 2% of the total inventories of 135Cs, 129I, and 99Tc are located in the gap and grain-boundary regions where they could dissolve rapidly if the spent fuel were to be contacted by groundwater. Actual measured values reported here for a few light-water reactor (LWR) spent fuels show that the combined gap and grain-boundary inventories of 129I approximately equaled the fission-gas release fractions. For 137Cs, the combined gap and grain-boundary inventories were approximately one third of the fission-gas release fractions. These measured values can be used to replace the 2% estimate and thus reduce the uncertainties in the calculations.
Multi-Scale Near-Field Thermohydrologic Analysis of Alternative Designs for the Potential Repository at Yucca Mountain
Authors: Buscheck T. A. , Gansemer J. , Nitao J. J. , Delorenzo T. H. 
Published: April 2011

AbstractA multi-scale, thermohydrologic (TH) modeling methodology has been developed that integrates the results from 1-, 2-, and 3-D drift-scale models and a 3-D mountain-scale model to calculate the near-field TH variables affecting the performance of the engineered barrier system (EBS) of the potential repository at Yucca Mountain. This information was used by Total System Performance Assessment—Viability Assessment (TSPA-VA) and is being used by the ongoing TSPA, supporting the License Application Design Selection, to assess waste-package (WP) corrosion, waste-form dissolution, and radionuclide transport in the EBS. Line-load WP spacing, which places WPs nearly end to end in widely spaced drifts, results in more locally intensive and uniform heating along drifts, causing hotter, drier, and more uniform conditions on WPs than point-load spacing, which is used in the VA design. Backfilling drifts with a granular material with coarse, well-sorted, nonporous grains (e.g., a coarse quartz sand) results in a large, persistent reduction in RH on WPs; point-load spacing allows only the medium-to-high-heat-output WPs to benefit from RH reduction, but line-load spacing enables all WPs to benefit.
Radionuclide Migration Analysis Using A Discrete Fracture Network Model
Authors: IJIRI Y. , SAWADA A. , WEBB E.K. , WATARI S. , HATANAKA K. , UCHIDA M. , ISHIGURO K. , UMEKI H. , DERSHOWITZ W.S. 
Published: April 2011

AbstractThis paper describes an approach for assessing the geosphere performance of nuclear waste disposal in fractured rock. In this approach, a three-dimensional heterogeneous channelnetwork model is constructed using a stochastic discrete fracture network (DFN) code. Radionuclide migration in the channel-network model is solved using the Laplace transform Galerkin finite element method, taking into account advection-dispersion in a fracture network, matrix diffusion, sorption in the rock matrix as well as radioactive chain decay. Preliminary radionuclide migration analysis was performed for fifty realizations of a synthetic block-scale DFN model. The total radionuclide release from all packages in the repository was estimated from the statistics of the results of fifty realizations under the hypothesis of ergodicity. The interpretation of the result of the three-dimensional network model by a combination of simpler one-dimensional parallel plate models is also discussed.
Impact of Ionic Strength on Colloid Mobility in Saturated And Unsaturated Porous Media
Authors: Gamerdinger A. P. , Kaplan D. I. , H. J. H. 
Published: April 2011

AbstractA model system consisting of well-characterized quartz sand, negatively charged carboxyl-modified latex microspheres, and synthetic J- 13 groundwater was used as a first-step in defining limiting conditions for colloid transport at the proposed Yucca Mountain Repository for radioactive waste. Colloid (280-nm diameter) and tracer (bromide) transport was determined using column methods under steady-state flow conditions for both saturated and unsaturated moisture conditions. Experiments were conducted at three water contents (13%, 70%, and 100% saturated) and four ionic strengths (deionized water, and 0.1 x, 1x, and 10x the ionic strength of J-13 groundwater, which has an ionic strength of 0.0116). Colloid mobility in the 13% saturated columns was appreciably less than in the 70% and 100% saturated columns, whereas colloid mobility in the 70% and 100% saturated columns were quite similar. Ionic strength had a significant impact on colloid retention, becoming more pronounced in the drier systems. Colloids were mobile in deionized water and the 0.1x J-13 groundwater. Retention was approximately 20% in lx J-13 groundwater and 100% in the 10x J-13 groundwater. Compared with the 70% and 100% saturated conditions, colloid mobility decreased for the 10% saturated condition, with greater than 50% retention for the 1x J-13 groundwater system. As observed for the 70% and 100% saturated conditions, colloids in the 10x J-13 solution were essentially immobile. Colloid mobility is greatly affected by the ionic strength of the soil solution and this effect is moisture saturation dependent.