bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leaching of Actinide-Doped Nuclear Waste Glass in a Tuff-Dominated System
Authors: Bazan Fernando , Rego J. , Aines R. D. 
Published: June 2019

AbstractA laboratory leaching test has been performed as part of a project to evaluate the suitability of tuff rocks at Yucca Mountain, Nevada, as a site for a high-level nuclear waste repository. Glass samples were placed in water inside tuff vessels, and then the tuff vessels were placed in water inside Teflon containers. Glass-component leach rates and migration through the tuff were measured for samples of the ATM- 9actinide glass, which is a PNL 76-68 based glass doped with low levels of 99Tc, 237Np, 238U and 239Pu to simulate wastes. Disc samples of this glass were leached at 90°C for 30, 90, and 183 days inside tuff vessels using a natural groundwater (J-13 well-water) as the leachant. Some samples were held by 304L stainless steel supports to evaluate the effect of this metal on the release rate of glass constituents. At the end of each leaching interval, the J-13 water present inside and outside the rock vessel was analyzed for glass components in solution.On the basis of these analyses, boron, molybdenum, and technetium appear to migrate through the rock at rates that depend on the porosity of each vessel and the time of reaction. The actinide elements (uranium, neptunium, and plutonium) were found only in the inner leachate. Sodium, silicon, and strontium are present in the rock as well as in the J-13 water, and the addition of these elements from the glass could not be determined. Normalized elemental mass loss values for boron, molybdenum, and technetium were calculated using the combined concentrations of the inner and outer leachates and assuming a negligible retention on the rock. The maximum normalized release was 2.3 g/m for technetium. Boron, molybdenum, technetium, and neptunium were released linearly with respect to each other, with boron and molybdenum released at about 85% of the technetium rate, and neptunium at 5-10% of the technetium rate. Plutonium was found at low levels in the inner leachate but was strongly sorbed on the steel and Teflon supports. Neptunium was sorbed to a lesser extent. Future analysis of the tuff vessels will determine whether the actinides were strongly sorbed on the surface of the tuff rock.
Borosilicate Glass Corrosion in the Presence of Steel Corrosion Products
Authors: Bart G. , Zwicky H.U. , Aerne E.T. , Graber TH. , Z'berg D. , Tokiwai M. 
Published: June 2019

AbstractSince 1982, the corrosion behaviour of radioactive high level waste glass and of inactive glasses of the same composition has been studied in the framework of a Japanese-Swedish-Swiss (JSS) project. In addition to granite and backfilling material, the influence of steel corrosion products on glass corrosion has been investigated in experiments of up to one year at 90°C with a sample surface area to leachant volume ratio of 10 m−1. Leachant and steel corrosion products were separated from each other by filtration and analyzed by atomic absorption spectroscopy and γ-spectroscopy. The glass corrosion layers were characterized by optical and scanning electron microscopy and by secondary ion mass spectrometry.It could be shown, that glass corrosion is enhanced by steel corrosion products. The quantity of corroded glass seems to be dependent on the surface area and not on the total amount of steel corrosion products in the system, suggesting a mechanism controlled by silica sorption on the steel corrosion product. If lead oxide is added to the system, glass corrosion is almost to- tally suppressed.
Large Scale Leach Testing of Dwpf Canister Sections
Authors: Bickford Dennis F. , Pellarin Daniel J. 
Published: June 2019

AbstractA Large-Scale Leach Test Facility (LSLTF) has been constructed at the U.S. Department of Energy's Savannah River Laboratory (SRL) to perform static leach tests on 24-inch (610 mm)-diameter canister sections cut from simulated (nonradioactive) waste forms cast under reference conditions. The equipment and test procedures are designed to closely correspond to MCC-l leach test criteria.Less than a factor of 3 increase in leachability results from combined scale-up, glass-cracking, leached surface area estimation, and surface roughness effects. This factor is dominated by surface roughness of saw cut surfaces. The factor is negligible when compared to the 200,000/1 ratio of glass sample masses.The MCC-l, and other small-scale leach tests have been valuable in determining the relative merits of alternative waste form compositions. However, the actual waste glass to be stored in repositories is subject to fracture, devitrification, and container/glass interactions, which are difficult to simulate on a laboratory scale. Large-scale leach tests integrate these and other possible waste form characteristics that are not represented in typical small samples.The facility, equipment, test method and results of one year leach test- ing are discussed. These results substantiate the applicability of small scale test data which precede this work, and the use of small scale tests to simulate leaching of the Defense Waste Processing Facility's borosilicate glass product. Exceptionally good sampling statistics make the large scale data particularly well suited for verification of models of leachability rates.
Structural Changes Around Uranium at the Surface of Waste Glasses Caused by Leaching
Authors: Barrett N.T. , Antonini G.M. , Thornley F.R. , Greaves G.N. , Manara A. 
Published: June 2019

AbstractStructural changes occurring at the surface of leached borosilicate glasses containing 3%wt of uranium have been investigated using fluores- cence EXAFS spectroscopy at grazing incidence. X-ray penetration depths between 30 Å and above 1000 Å are possible by varying the incidence angle of the X-ray monochromatic radiation in the vicinity of the critical angle for total external reflection, øc. This enables the surface and bulk structure to be compared. It is found that a local increase in uranium concentration takes place near the surface of the glass during the first 30 minutes of leaching time. Uranium is coordinated with oxygen and other uranium atoms. The local distribution can be modelled by a square planar island structure comprised of uranyl-type units. This structure changes with corrosion time. After 30 minutes of leaching there is evidence of partial removal of the surface layer.
Simulation of Uranium Transport with Variable Temperature and Oxidation Potential: The Computer Program Thcc
Authors: Carnahan C. L. 
Published: June 2019

AbstractA simulator of reactive chemical transport has been constructed with the capabilities of treating variable temperatures and variable oxidation potentials within a single simulation. Homogeneous and heterogeneous chemical reactions are simulated at temperature-dependent equilibrium, and changes of oxidation states of multivalent elements can be simulated during transport. Chemical mass action relations for formation of complexes in the fluid phase are included explicitly within the partial differential equations of transport, and a special algorithm greatly simplifies treatment of reversible precipitation of solid phases. This approach allows direct solution of the complete set of governing equations for concentrations of all aqueous species and solids affected simultaneously by chemical and physical processes. Results of example simulations of transport, along a temperature gradient, of uranium solution species under conditions of varying pH and oxidation potential and with reversible precipitation of uraninite and coffinite are presented. The examples illustrate how inclusion of variable temperature and oxidation potential in numerical simulators can enhance understanding of the chemical mechanisms affecting migration of multivalent waste elements.
Permanent Crystal Lattice Contraction, a Primary Mechanism in Thermally Induced Alteration of Na Bentonite
Authors: Pusch Roland 
Published: June 2019

AbstractThe basic process in thermal transformation of smectite to hydrous mica is generally thought to be a lattice charge change caused by partial replacement of tetrahedral silica by aluminum. This is assumed to yield preferential uptake of potassium with concomitant contraction and loss of expandability of smectite aggregates as well as release of silica that migrates by diffusion from interlayer space into interaggregate voids, where it may form amorphous silica hydrogels and possibly quartz.The latter process was investigated by use of hydrothermal tests of fully water saturated, as well as partly saturated Na-montmorillonite gels, the intention being to identify possible heat-induced changes in expandability on a molecular scale by applying electron microscopy. The gels were exposed to a temperature of 225°C for 18 days in a first test series and the microstructural patterns compared with those of non-heated material.A clear tendency of lattice contraction was observed in the heated clay gels, particularly in the non-saturated one. The microstructure had the form of networks of virtually non-expandable, interwoven dense stacks.A possible physical explanation of the contraction is that the heat caused instability of the interlayer water lattices, yielding dominant interatomic mass forces which caused contraction of the stacks. In connection herewith, silica was released from the smectite lattices and precipitated at the edges of the stacks, which reduced or eliminated the expandability. Minute, precipitated silicic bodies, amorphous as well as crystal-line, appeared in both clays.
Nanomechanical Quantification of Polymer Energy Absorption
Authors: Tweedie Catherine A. , Smith James F. , Van Vliet Krystyn J. 
Published: June 2019

ABSTRACTMechanical characterization of polymeric thin films and small volume structures is critical to device development in industrial applications ranging from low-k dielectric microelectronic packaging films to engineered and natural biological substrata. Although nanoindentation has the potential to quantify mechanical properties of polymeric systems, the established analyses developed for metals and ceramics (eg, calculation of hardness and Young's modulus) do not capture key aspects of viscoelastoplastic deformation and are therefore not quantitatively applicable. Here, we present a set of complementary, nanoscale contact-based experimental approaches that together characterize specific energy absorption as a unique mechanical characteristic of polymers, and provide examples for a set of amorphous polymers.
Strain mapping on gold thin film buckling and silicon blistering
Authors: Goudeau P. , Tamura N. , Parry G. , Colin J. , Coupeau C. , Cleymand F. , Padmore H. 
Published: June 2019

AbstractStress/Strain fields associated with thin film buckling induced by compressive stresses or blistering due to the presence of gas bubbles underneath single crystal surfaces are difficult to measure owing to the microscale dimensions of these structures. In this work, we show that micro Scanning X-ray diffraction is a well suited technique for mapping the strain/stress tensor of these damaged structures.
The Effect of Microstructural Inhomogeneity on Grain Boundary Diffusion Creep
Authors: Rastogi Kanishk , Moldovan Dorel 
Published: June 2019

AbstractStress concentration at grain boundaries (GB), a phenomena arising from microstructural inhomogeneity, is an important factor in determining the mechanical properties of polycrystalline materials. In this study we use mesoscopic simulations to investigate characteristics of the deformation mechanism of grain-boundary diffusion creep (Coble creep) in a polycrystalline material. The stress distribution along the grain boundaries in a polycrystalline solid under externally applied stress is determined and the mechanism of how topological inhomogeneities introduce stress concentrations is investigated. Microstructures with inhomogeneities of various sizes and distributions are considered and their effect on the stress distribution and creep rate is quantified.
Structural Control of Lithium Fluoride Thin Films
Authors: Yazicigil O.G. , Rafik D. , Vorontsov V. , King A.H. 
Published: June 2019

AbstractPolycrystalline lithium fluoride thin films have a number of existing and potential uses, but the optimization of their microstructure has not yet been addressed systematically. We have developed a means of measuring the porosity in LiF films, and a method for performing detailed electron-microscopical studies on this normally beam-sensitive material. These techniques have been applied to assess the structure of LiF films immediately after deposition from the vapor phase, and also after subsequent annealing.
Depth-Dependent Hardness Characterization by Nanoindentation using a Berkovich Indenter with a Rounded Tip
Authors: Kim Ju-Young , Read David T. , Kwon Dongil 
Published: June 2019

AbstractThe height difference Δhb between the ideally sharp Berkovich indenter tip and a Δhb rounded tip was measured by direct observation using atomic force microscopy (AFM). The accuracy of the indirect area function method for measuring h was confirmed. The Δhb indentation size effects (ISE) in (100) single crystal copper, (100) single crystal tungsten, and fused quartz were characterized by applying the ISE model considering the rounded tip effect. The model fits the data these materials well, even though fused quartz does not deform by dislocations. However, a very small value of the ISE characteristic length h' was obtained for fused quartz. The present h' value for (100) copper is 32% larger than a previously-measured value for polycrystalline copper. This may indicate that grain boundaries suppress the dislocation activity envisioned in the ISE model.
Influence of Gas Atmosphere on the Plasticity of Metal Thin Films
Authors: Wübben T. , Dehm G. , Arzt E. 
Published: June 2019

AbstractStresses in thin films are routinely measured by the so-called substrate curvature technique. These experiments are usually carried out in air or under a protective gas atmosphere. In this contribution we describe a new set-up capable of performing substrate curvature measurements under ultra-high vacuum conditions. The advantages are the absence of possible artifacts due to gas/film interactions, better control of gas composition, and the possibility to measure chemical effects on mechanical properties in a controlled way. We present first results that indicate an unexpected sensitivity even of polycrystalline Cu films to the gas environment.
Thermal Expansion of Low Dielectric Constant Thin Films by High-Resolution X-Ray Reflectivity
Authors: Omote Kazuhiko , Ito Yoshiyasu 
Published: June 2019

AbstractBy introducing high precision sample alignment technique, repeatability of incident angle to the sample surface for x-ray reflectivity (XRR) measurement is achieved to be within 0.3 arcsec. As a result, film thickness and density are possible to be measured repeatability within 0.03% and density within 0.26%. This accuracy realized to detect very small change of thermal expansion of thin films. The coefficient of thermal expansions (CTE) for porous low-k films deposited by CVD method were measured up to 400°C. The obtained values are in the range from 40 to 80 x10-6 K-1 and they are very large compare to that of copper (16-20 x10-6 K-1).
Development of an All-Fiber Coherent Laser Radar for Precision Range and Velocity Measurements
Authors: Pierrottet Diego , Amzajerdian Farzin , Peri Frank 
Published: June 2019

AbstractAn all-fiber coherent laser radar system capable of high-resolution range and line of sight velocity measurements is under development with a goal to aid NASA's new Space Exploration initiative for manned and robotic missions to the Moon and Mars. Precision range and velocity data are key parameters to navigating planetary landing pods to the pre-selected site and achieving autonomous safe soft-landing. By employing a combination of optical heterodyne and linear frequency modulation techniques [1-3] and utilizing state-of-the-art fiber optic technologies, highly efficient, compact and reliable laser radar suitable for operation in a space environment is being developed.The all-fiber coherent laser radar has several important advantages over more conventional pulsed laser altimeters or range finders. One of the advantages of the coherent laser radar is its ability to directly measure the platform velocity by extracting the Doppler shift generated by the platform motion. The Doppler velocity measurement is about two orders of magnitude more accurate than the velocity estimates obtained by laser altimeters using the rate of change in range [4]. Another advantage is continuous-wave operation that allows the use of highly efficient and reliable commercial off-the-shelf fiber optic telecommunication components. This paper will describe the design and operation of this laser radar sensor and discuss its projected performance. A laboratory breadboard system has already been developed as a step toward a flight prototype. The experimental data representing the potentials of this laser radar system will be reported.
Characterization of Exotic Material Heat Sinks for Laser Diode Arrays
Authors: Stephens Edward.F. 
Published: June 2019

AbstractLow duty cycle, high peak power, conductively cooled laser diode arrays have been manufactured for several years by a number of different vendors. Typically these packages have been limited to a few percent duty cycles due to thermal problems that develop in tight bar pitch arrays at higher duty cycles. Traditionally these packages are made from some combination of copper and BeO or Tungsten/copper and BeO. Trade-offs between thermal conductivity and CTE matching are always made when manufacturing these devices. In addition, the manufacturability of the heat sinks plays a critical role in creating a cost effective, high performance solution. In this discussion we examine several different exotic materials that have been manufactured and tested as heat sinks for laser diode arrays.
Associations between Fall Distance, Age, and Trauma Outcomes in Older Adult Patients
Authors: Berg Gina M. , Hervey Ashley M. , Lee Felecia A. , Holmes Sarah , Keuter Kayla R. , Harrison Paul B. 
Published: June 2019

Introduction. Falls are the leading cause of injury death amongolder adults. This study sought to determine if there are differencesbetween fall distance (ground level vs greater than groundlevel) and age (old vs very old) in terms of in-hospital mortality,orthopedic consultations, and neurological consultations.
Methods. A retrospective trauma registry review was conductedof older adult patients (aged > 65 years), admitted to aMidwestern Level I trauma facility (2005 - 2010) due to a fall.Results. Of the 1,064 patients analyzed, the majority fell fromground level compared to greater than ground level (64% and36%, respectively). Median age was 80 years. Fall distance wasnot associated significantly with in-hospital mortality (OR0.88; CI 0.50 - 1.54) or neurological consultations (OR 1.02; CI0.72 - 1.43), but was associated with orthopedic consultations(OR 1.49; CI 1.09 - 2.04). Age was not associated with in-hospitalmortality or neurological or orthopedic consultations.
Conclusions. Fall distance was not associated with in-hospitalmortality or receiving a neurological consultation.However, older adults who fell from greater than groundlevel were more likely to receive orthopedic consultations.There were no differences in in-hospital mortality or receivinga neurological or orthopedic consultation based onage. These findings indicated that as the older adult populationincreases, burden of care will increase for trauma centersand neurological services. KS J Med 2016;9(3):54-57.
Early Outcomes of Cemented versus Cementless Total Knee Arthroplasty
Authors: Shepherd Jeffrey , Chong Alexander C.M. , Cusick Robert P. 
Published: June 2019

Introduction. Total knee arthroplasty (TKA) has been provento be very effective for long-term pain relief in the degenerativeknee. Few studies have investigated short-term clinicaland functional outcomes between the cemented and cementlessTKA. The specific aim of this study was to assess the potentialdifference of functional outcomes in the early postoperativeperiod between these two surgical options usingthe Knee Society Score (KSS) and range of motion (ROM).
Methods. A total of 164 knees that had undergone TKA by a singlesurgeon at a single institution between 2007 and 2010 were reviewed.Three different TKA prosthetic designs (cruciate retaining(CR), posterior stabilized (PS) and cruciate substituting (CS))were included. Data collection included patient demographics,pre- and post-operative ROM, and pre- and post-operative KSSat each visit (1.5 months, 3 months, and 12 months). Two separateKSS scores were assigned: functional score and clinical score.
Results. Sixty-seven knees underwent cemented TKA and 97knees underwent cementless TKA. No significant differencewas recognized in either age or body mass index for thesetwo TKA groups. The cementless group showed a significantearly ROM improvement after 1.5 months post-operative (p <0.05), while the cemented group showed ROM improvementonly after three months post-operative. No significant differencewas detected in terms of KSS between the cemented andcementless TKA groups at each measured time period. Bothgroups showed marked KSS improvement (cemented: 135%,cementless: 125%) after 1.5 months post-operative and theKSS seemed to be stabilized after three months post-operativefor both groups (cemented: p = 0.36; cementless: p = 0.07).
Conclusions. There was a significant early ROM improvementfor the cementless TKA group compared to the cementedTKA group, but no statistical significant difference was notedin KSS in the early post-operative period when comparing cementedand cementless TKA groups. The findings provide evidencethat cementless TKA patients can undergo an identicalpost-operative protocol to cemented TKA, without concernsabout implant stability or function. KS J Med 2016;9(4):93-98.
Una aproximación estratégica para la puesta en marcha de una revista académica en línea
Authors: Canella Rubén , Gegunde Horacio , Galosi Carla , Tsuji Teresa , Michelini Gabriela 
Published: June 2019

La puesta en marcha de una revista académica en línea presupone varios niveles de articulación. La revista constituye un sistema complejo, en el que operan actores heterogéneos como universidades, centros de investigación e institutos, así como también se dirige a públicos diversos, como miembros de la misma comunidad científica, estudiantes y la sociedad en general. La puesta en línea del material, en el marco de la Web 2.0, implica también un intercambio constante entre los partícipes de todo el proceso de elaboración. El desafío de poner en marcha una revista académica llevó a la realización de un diagnóstico previo a la creación de la publicación producto de la colaboración entre la Universidad de La Coruña, la UNLZ, y el Centro Iberoamericano de Estudios en Comunicación Información y Desarrollo (CIECID). Para cumplir el objetivo, se aplicó a una situación concreta del método RAPC, una de las herramientas metodológicas nacidas de la Nueva Teoría Estratégica (NTE), y propuesta recientemente por Rafael Alberto Pérez. El interés en estaherramienta metodológica radica en que permite realizar un análisis de la situación estratégica sin fragmentar el sistema objeto de estudio y así establecer un diagnostico. De este modo, en el artículo se identifican y visualizan los actores y los públicos y los flujos de comunicación aplicados en el campo, a partir del modelo y las herramientas conceptuales, metodológicas e instrumentales propuestos por la NTE para la puesta en funcionamiento de una revista científica de carácter interuniversitario e internacional.