bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Microstructure of ggbfs/OPC Habdened Cement Pastes and Some Effects of Leaching
Authors: Richardson I.G. , Rodger Sally A. , Groves G.W. 
Published: March 2011

ABSTRACTGround granulated blast-furnace slag (ggbfs) /Ordinary Portland cement (OPC) blends are possible materials for use in intermediate and low-level radioactive waste repositories. The microstructural development in neat OPC is described. The effect of increasing the loading of ggbfs on the composition and microstructure of the hardened paste has been examined by a number of techniques, including transmission electron microscopy. The implications for performance are discussed. A ggbfs/OPC 9:1 blend which had been exposed, after normal hydration to aqueous leaching was also examined. Marked changes in the microstructure and composition were observed.
Estimation of Illitization Rate of Smectite from the Thermal History of Murakami Deposit, Japan
Authors: Kamei G. , Arai T. , Yusa Y. , Sasaki N. , Sakuramoto Y. 
Published: March 2011

ABSTRACTThe research on illitization of smectite in the natural environment affords information on the long-term durability of bentonite which is the candidate for buffer material.Murakaml bentonite deposit in central Japan, where the bentonite and rhyolitic intrusive rock were distributed, was surveyed and the lateral variation of smectite to illite in the aureole of the rhyolite was studied.The radiometric ages of some minerals from the intrusive rock and the clay deposit were determined. Comparison of the mineral ages ( obtained by K-Ar, Rb-Sr and fission-track methods ) with closure temperature estimated for the various isotopic systems allowed the thermal history of the area. The age of the intrusion was 7.1± 0.5 Ma(; Mega d'annees), and the cooling rate of the intrusive rock was estimated to be approximately 45 °C/Ma.Sedimentation ages of the clay bed were mostly within the range from 18 to 14 Ma. However, the fission-track age of zircon in the clay containing illite/smectite mixed layers was 6.4±0.4 Ma, which was close to that of the intrusion. The latter value could be explained as the result of annealing of fission-tracks in zircon. The presence of annealing phenomena and the estimated cooling rate concluded that illitization had occured in the period of 3.4 Ma at least under the temperature range from above 240±50 to 105 °C. Illite-smectite mixed layers occured from smectite in the process. The proportion of iliite was about 40 %. Approximately, 29 kcal/mol as a value of activation energy was calculated to the illitization.The hydrogen isotopic ratio ( D/H ) of constitution water of the illite was determined. The values that were calculated for the water, which was related to the illitization, fell within the range of hydrogen isotopic ratios of seawater.
Authigenic Clay Minerals in the Rustler Formation, WIPP Site Area, New Mexico
Authors: Brookins D. G. , Lambert S. J. , Ward D. B. 
Published: March 2011

ABSTRACTTransuranic waste is planned for disposal in the Late Permian evaporites of the Delaware Basin, southeastern New Mexico, at the WIPP Site. The disposal horizon is located in the bedded halite of the Salado Formation, which is overlain by the impure halite-anhydrite (gypsum)-siltstone-mudstone of the Rustler Formation. The Rustler Formation also contains two dolomite members, the Magenta and Culebra, which transmit water. The Culebra Member is suspected to have actively interacted with waters at time(s) from the Late Permian to the present, and it is important to assess the reactivity of these waters in conjunction with WIPP stability.We have investigated the Rb-Sr systematics of clay minerals from the Culebra Member and elsewhere in the Rustler Formation. By separating the less than 0.125 μm size material we are able to deal with presumed true authigenic clay minerals. The authigenic fraction is especially sensitive to chemical and isotopic exchange with waters, and an episodic exposure to a large amount of water will re-set the clay minerals to such a time. Our data yield 259 ± 22 Ma Rb-Sr isochron, which is consistent with the Late Permian age of the Rustler Formation. This age demonstrates that age-determining cations in these clay minerals have preserved their isotopic and chemical integrity since the Late Permian.
Sizing Requirements for Flow-Through Geochemical Tests: Theoretical Considerations and Model Results
Authors: Hoover James D. , Thornton Edward C. 
Published: March 2011

ABSTRACTA methodology for evaluating test apparatus size requirements has been applied to the sizing of flow-through tests used in the evaluation of coupled reaction and transport processes. The results of the sizing evaluation constrain the apparatus dimensions and test conditions capable of yielding results representative of the processes of interest.The size requirements of flow-through tests involving a system of simplified granite and groundwater were determined in order to demonstrate the feasibility and implications of sizing evaluations. Reaction path simulations were performed using the E03/6 codes at temperatures of 25°C, 100°C, and 200°C. The determination of reaction path as a function of time was then used to obtain minimum column residence time requirements. Simulation results indicate that column lengths required for development of quasistatic equilibrium reaction zones at 200°C are three times smaller than at 100°C, and over 36 times smaller than at 25°C.A range of possible combinations of column dimensions and flow rates for a set of model test conditions exist for a given residence time. The most appropriate combinations depend on the purpose of the test, the process of interest, and factors such as test duration, sampling requirements, and engineering limitations. Size and scale evaluations thus provide a technical basis for the design and construction of flow-through tests, and have profound implications for the interpretation of test results.
Sizing and Scaling Requirements of a Large-Scale Physical Model for Code Validation
Authors: Khaleel R. , Legore T. 
Published: March 2011

ABSTRACTScaling considerations relevant to porous media flow are reviewed. An analysis approach is presented for determining the sizing requirements of a large-scale, hydrology physical model. The physical model will be used to validate performance assessment codes that evaluate the long-term behavior of the repository isolation system. Numerical simulation results for sizing requirements are presented for a porous medium model in which the media properties are spatially uncorrelated.
A Coupled Chemical-Mass Transport Submodel for Predicting Radionuclide Release from an Engineered Barrier System Containing High-Level Waste Glass
Authors: McGrail B. P. , Apted M. J. , Engel D. W. , Liebetrau A. M. 
Published: March 2011

ABSTRACTA mechanistic model describing a dynamic mass balance between the production and consumption of silicic acid was coupled to a near-field mass transport model to predict the dissolution kinetics of a high-level waste glass in a deep geologic repository. The effects of interactions between an iron overpack and the glass are described by a time-dependent precipitation reaction for a ferrous silicate mineral. The kinetic model is used to transform radionuclide concentration-versus-reaction progress values, predicted from a geochemical reaction path computer code, to concentration-versus-time values that are used to calculate the rate of radionuclide release by diffusive mass transfer to the surrounding host rock. The model provides for both solubility-limited and kinetically limited release; the rate-controlling mechanism is dependent on the predicted glass/groundwater chemistry.
Thermodynamic Modeling of Cement/Groundwater Interaction as a Tool For Long-Tern Performance Assessment
Authors: Criscenti Louise J. , Serne R. Jeff 
Published: March 2011

ABSTRACTThe chemical behavior of cement in the natural environment is of interest because cement has been suggested as a means of containing low-level radioactive waste and as a barrier between radioactive-waste containers and the surrounding soil or rock. In the past, either experiments or computer modeling have been used independently to predict how cement will leach in the natural environment. In this study, a geochemical model for cement leaching was developed, and predictions by the model were compared to results from a static leach test. Calcium concentrations and pH were adequately predicted by the model; however, other major leachate constituents, such as Al, Si, and S04, were poorly predicted. Additional experimental data and refinement of the model are both required to better predict the observed leachate concentrations. Accurate prediction of experimental results by a geochemical model would increase confidence in the model for use in long-term performance assessment.
Grouted Waste Leach Tests: Pursuit of Mechanisms and Data for Long-Term Performance Assessment
Authors: Serne R. Jeff 
Published: March 2011

ABSTRACTAt Hanford, low-level liquid nuclear waste is being mixed with cementitious materials (grout) to form leach-resistant solid waste. Prior to grouting each liquid waste, an assessment must be performed to evaluate the long-term environmental impact. These predictions rely upon a diffusioncontrolled release model and short-term laboratory leach data on small grout samples. This paper describes size scale-up and inventory scale-up experiments that evaluate whether diffusion does in fact control the release of contaminants. The results of the volume scale-up test suggest that tests on grout cylinders between the sizes 3 cm dia. by 3 cm length and 30 cm dia. by 29 cm length yield comparable results. These data and other available literature suggest that extrapolation of leach results to large blocks of solidified waste is defensible.The inventory scale-up tests for 125I and selenium show a constant effective diffusivity regardless of the original inventory. This suggests that diffusion processes do in fact control the release of iodide and selenium from grout. The 99Tc effective diffusivities may not remain constant with changes in inventory.
Long-Range Interactions and Rigidity in Surfaces and Lamellar Phases
Authors: Kardar Mehran 
Published: March 2011

ABSTRACTRecently there has been a large effort to understand the statistical and phase behavior of collections of surfaces and membranes. Experimental activity has focused on the behavior of stacked films in lamellar phases of microemulsions. Here I briefly sumnmarize the role of fluctuations and undulations in four classes of films: fluid, hexatic, solid, and charged.
Scaling Behaviour of the Viscoelastic Properties of a Biopolymer System Near the Gel Point
Authors: Axelos M. A. V. , Kolb M. 
Published: March 2011

ABSTRACTRheological measurements have been performed on pectin-calcium systems close to the sol-gel transition. Two different experimental setups - steady state and oscillatory shear measurements - show scaling of the viscoelastic properties. The results of both types of measurements are consistent with each other and with scalar percolation theory.
Dynamics of Concentrated Colloidal Suspensions
Authors: Weitz D. A. , Ye L. , Sheng Ping , Huang J. S. , Pine D. J. , Liu J. , Chaikin P. M. , Pusey P. N. 
Published: March 2011

ABSTRACTWe study the dynamics of concentrated colloidal suspensions by measuring the frequency dependent structure factor, S(q,w), using light scattering techniques. We introduce Diffusing Wave Spectroscopy, which extends dynamic light scattering to the multiple scattering regime, allowing us to study the lower frequency, diffusive modes of S(q,w), which reflect the Brownian motion of the particles. We study the behavior of the higher-frequency, propagating modes of S(q,w), which reflect acoustic waves, using Brillouin scattering. To study S(q,w) at low qa, where q is the scattering vector and a the particle diameter, we use inverted micelles, and find that the interactions between the micelles has a dramatic impact on the speed of sound as the volume fraction of micelles increases. To study S(q,w) at large qa, we use index matched PMMA particles, allowing us to measure the dispersion curve of phonons in a hard sphere colloid system. Together, these results provide a measure of S(q, w) over a wide range of q and of w.
Charge and Size Polydispersity Effects on the Scattering Properties and the High-Frequency Elasticity of Colloids
Authors: D'Aguanno Bruno , Klein Rudolf , Wagner Norman J. 
Published: March 2011

ABSTRACTPolydispersity in charge and in size of colloidal particles strongly influences the static light scattering < I(k) >. These effects are calculated by solving the Ornstein-Zernike integral equation together with the thermodynamically consistent Rogers-Young closure for a multicomponent mixture of up to 10 components. The results for < I(k) > for polydisperse systems show significant differences from results obtained by treating the system as an effective monodisperse one. For <I(k) > a large increase is found at small k as well as a shift in the main peak. Finally, using the above results, high-frequency elastic moduli are predicted for a binary mixture.
Microscopic Processes in Microemulsion Polymerizations
Authors: Candau Francoise 
Published: March 2011

ABSTRACTThe polymerization of acrylamide inside watcr-swollen micellas of Aerosol OT dispersed in toluene has been investigated. Incorporation of acrylamide enhances the interparticular attractive forces as shown by the intensity curves in small angle neutron scattering. It also induces sharp rises in conductivity which were attributed to a percolative process. The percolation threshold is lowered upon increasing the monomer content, reflecting the enhancement of the attractive interactions. In percolating systems, the structure affects the formation of polymer particles. Microscopy experiments show that particle nucleation occurs continuously throughout the polymerization.
Formation of Metal Colloids in Inverse Micelles and Microemulsions
Authors: Wilcoxon Jess P. , Williamson Rod L. 
Published: March 2011

ABSTRACTGold colloidal suspensions are produced from both inverse micelle solutions and microemulsions through both chemical and photolytic reduction of the appropriate salt. A variety of surfactant/solvent combinations yield varying results with respect to metalloid growth kinetics and stability as revealed through dynamic light scattering, small-angle x-ray and neutron scattering, and transmission electron microscopy.
X-Ray Diffraction Studies of Zwitterionic Associating Polymers
Authors: Shen Y. , Safinya C. R. , Fetters L. , Adam M. , Witten T. , Liang K. S. , Chance R. , Stokes J. 
Published: March 2011

ABSTRACTWe have carried out x-ray scattering studies in melts of a series of linear polyisoprenes with highly polar sulfo-zwitterion groups at one end. The zwitterion end groups cause aggregation in good solvents for polyisoprene. The aggregation number depends strongly on the molecular weight of the polyisoprene tails and on the polarity of the solvent. Molecular mechanics simulations of the interactions between the zwitterion head groups suggest tubelike or diskline structures for the aggregates. Spherical structures are not energetically favorable. High resolution synchrotron x-ray scattering studies were carried out for six different (chain) molecular weights between 2000 and 23,000. For low molecular weights (between 2000 and 4000) a tubular structure is found with the tubes organized on a well-defined, two-dimensional triangular lattice with very large domain sizes >2000Å. A structural phase transition to a cubic (bcc) phase with long range order is observed to occur for molecular weights >10,000. The lattice spacing increase over the molecular range was between 95Å (for MW-2000) and 206Å (for MW-23,000). For the high molecular weight melts, annealing transforms the structure from (bcc) (with long range order) to an (fcc) disordered structure with short range order.
Structure and Properties of Resorcinol-Formaldehyde Gels
Authors: Letts Stephan A. , Buckley Steven R. , Kong Fung-Ming , Lindsay Edward F. , Sattler Margaret L 
Published: March 2011

ABSTRACTThe condensation polymerization of resorcinol and formaldehyde catalized by sodium carbonate produces a sol that aggregates to form a gel. Using viscometry the effect of temperature and catalyst concentration on the sol-gel transition was investigated. At a solids concentration of 3%, gelation occurred in 1500 minutes. The rate of increase in viscosity was a function of both catalyst concentration and temperature. The structure of the gels was studied by freeze-fracture TEM. In the sol phase the RF solutions contain particles of 5 to 20 nm diameter. After gelation the particles form a crosslinked network with a pore structure of 100 nm.
Thermal Property Evolution Toward Effectively Two-Dimensional Substrate-Free Systems
Authors: Geer R. , Stoebe T. , Huang C. C. , Pindak R. , Goodby J. 
Published: March 2011

ABSTRACTA high-resolution differential quasi-adiabatic calorimeter has been developed to investigate the physical properties of freestanding liquid-crystal films. Our recent heat-capacity studies near the smectic-A-hexatic-B transition of both 65OBC and 46OBC freestanding films clearly demonstrate the evolution towards twodimensional limiting behavior in four-layer films. As the film thickness decreases towards four molecular layers, the heatcapacity anomalies first display separate peaks for the surface and interior transitions and then evolve to one dominated by the surface transition.
Electrohydrodynamic Flow in Thick Liquid Crystal Cells
Authors: Van Winkle David H. , Gurung Jit , Biggers Rand 
Published: March 2011

ABSTRACTThe thermal transport across a thick (0.66 cm) liquid crystal cell has been measured versus applied ac voltage and frequency. These measurements are correlated with the optically observed onset of flow and turbulence in cells as identical as practicable to those used for the thermal transport measurements. In addition, the measurements are compared with reported observations in thin cells. The thermal transport across the liquid crystal is characterized by an effective thermal conductivity Kf. It was found that Kf increases with increasing frequency, at constant voltage, to a maximum enhancement at about 40 Hz at room temperature. Optical observations on thick cells indicate that dynamic columnar domains of flowing liquid crystal are the primary mode of heat transport, as determined by correlating the structure and characteristic lifetime of such domains as a function of voltage and frequency. Optical observations at low voltages suggest that Williams Domains do not exist in these thick cells, and that all observed responses are functions of electric field strength, not applied voltage (as in thin Williams Domain cells).
Simple Theory for Persistent-Flexible Liquid Crystal Polymers Beyond the Second Virial Approximation
Authors: Hentschke Reinhard , Herzfeld Judith 
Published: March 2011

ABSTRACTKhokhlov and Semenov (KS) have proposed a theory for long persistent chains that quite accurately describes the liquid crystalline behavior of dilute solutions of long homogeneous bend-elastic macromolecules. By replacing their second virial description of excluded volume effects with Lee's generalization of the Carnahan-Starling equation, results are obtained which are valid over a wider range of polymer concentrations. Comparison of the calculated order parameter and equation of state with experimental data for Poly(γ-benzyl-L-glutamate) yields good agreement for large polymer axial ratios, where rigid particle theories deviate strongly from experimental results. In addition, we show how this approach to persistent flexibility can be connected to a recent model for translational order in lyotropic liquid crystals.
Weighted-Density Theory of Phase Transitions in Fluids Composed of Anisotropic Particles
Authors: Marko J. F. , Curtin W. A. 
Published: March 2011

ABSTRACTA nonperturbative approach to the density-functional description of phase transitions in fluids composed of anisotropic particles is presented. The theory is exact to second order in functional perturbation theory, and at higher orders satisfies all sum rules derived from density derivatives of the two-point direct correlations. We have applied this theory to orientational and translational freezing of hard ellipsoids, and we find that the description of the structure of crystalline phases is improved in comparison to the commonly used second-order theory. For the case of orientational freezing, it is found that the higher-order contributions do not modify the predictions of the second-order theory, and that accurate liquid structure appears to be the key factor leading to improved description of the nematic phase.
Modulated Phases in Amphiphilic Monolayers at the Water/Air Interface
Authors: Andelman David 
Published: March 2011

ABSTRACTRecently, modulated phases of insoluble monolayers of fatty acids and phospholipids spread on the water/air interface have been observed by fluorescence microscopy experiments. We propose a theoretical explanation of this observation by including electrostatic (dipolar) interactions in the total free energy calculation for the monolayer. Dipoles can originate from two sources: neutral amphiphiles have a permanent dipole and charged amphiphiles have an induced one. Modulated phases are found to be stable in two different limits: close to the liquid-gas transition and at low temperatures. Several phases with stripe and hexagonal symmetry are predicted and the phase transitions between them are calculated.
Surface Adsorption Studied by Optical SHG: Soluble Monolayers at the Air/Water Interface
Authors: Vogel Viola , Mullin C. S. , Shen Y. R. , Kim M. W. 
Published: March 2011

ABSTRACTOptical second harmonic generation (SHG) is applied to investigate the structure of the interfacial layer of soluble surfactants adsorbed to the air/water interface.
Nuclear Reaction Analysis Studies on the Interface Formation in Polymer Mixtures
Authors: Steiner Ullrich , Chaturvedi Kumar , Zak Omer , Krausch Georg , Schatz Günther , Klein Jacob 
Published: March 2011

ABSTRACTWe have measured the composition profile between two polymer phases above and below their critical temperature for phase separation Tc, using the 2H(3He,4He)1H nuclear reaction in a direct profiling technique. Above Tc, we verify the “thtrmodynamic slowing down” effects on interdiffusion close to the critical point. Pelow Tc, we find that the width of the interface grows with time to a finite limiting value. The variation of this limiting value, as Tc, is approached from below is in good agreement with the predictions of mean-field theories. The time dependence of the initial interfacial broadening below Tc has been found to be significantly slower than t1/2.
Influence of Cationic Interactions on Fatty Acid Monolayers Studied by Ellipsometry
Authors: Kim Mahn Won , Sauer Bryan B. , Yu Hyuk , Yazdanian Mehran , Zografi George 
Published: March 2011

ABSTRACTOptical properties of fatty acid monolayers were measured as a function of surface density and under the influence of cations in the aqueous substrate. The monolayer behavior of pentadecanoic acid (C15) on an aqueous solution of HCl at pH=2.0 was studied. The change in the ellipsometric phase angle δΔ was mildly affected by increases in surface density at constant orientation but strongly influenced by the liquid-expanded/solid phase transition presumably due to a change in conformation.The increase in the ellipsometric phase angle 6Δ with chain length C15, C16, C18, and C22 was attributed to an increase in thickness of fatty acids at the air/water interface. Separating the effect of optical density of head groups, the refractive indices calculated from the chain length data were independent of ionic environment. The magnitude of δΔ for fatty acids on aqueous substrates increased in the order HCl, CdCl2, and PbCl2. This was due to an increase in the refractive index of fatty acid head groups caused by association of divalent cations. Ellipsometry was also found to be a useful technique to monitor in-situ the degree of divalent cation association.