Diffusion of Cs, Np, Am and Co in compacted sand-bentonite mixtures: evidence for surface diffusion of Cs cations

Clay Minerals ◽  
2013 ◽  
Vol 48 (2) ◽  
pp. 411-422 ◽  
Author(s):  
T. Sawaguchi ◽  
T. Yamaguchi ◽  
Y. Iida ◽  
T. Tanaka ◽  
I. Kitagawa
Keyword(s):  
Surface Diffusion ◽  
Pore Water ◽  
Concentration Gradient ◽  
Unit Volume ◽  
Effective Diffusivity ◽  
The Other ◽  
Diffusion Method ◽  
Diffusive Flux ◽  
Diffusive Transport ◽  
Through Diffusion

AbstractWe studied the diffusive transport of Cs, Np, Am and Co in compacted sandbentonite mixtures by using the through-diffusion method. The experiments for Cs were performed under various aqueous compositions. Effective diffusivity (De) values of 4.7×10–10 to 5.9×10–9 m2 s–1 were obtained with a somewhat large variation. Apparent diffusivity (Da) values, on the other hand, showed less variation, ranging from 2.0×10–12 to 6.2×10–12 m2 s–1. The results indicated that diffusive flux was proportional to the concentration gradient on the basis of the amount of Cs in the unit volume of the compacted sand-bentonite mixtures rather than the Cs concentration gradient in pore water. Because the former concentration gradient in the mixtures was nearly equal to that of adsorbed Cs, the diffusion of Cs in the mixtures was probably dominated by the concentration gradient of the Cs adsorbed on the mixtures. In addition, the effective/apparent diffusivity of 237Np(IV) and apparent diffusivity of 241Am(III) and 60Co(II) in the mixtures were determined in 0.3/0.03 mol l–1 (NH4)2CO3/Na2S2O4 solution.

Effective diffusivity of neptunium and plutonium in granite from Inada, Ibaraki, Japan under anaerobic conditions

2002 ◽  
Vol 90 (12) ◽  
Author(s):  
Tetsuji Yamaguchi ◽  
S. Nakayama ◽  
H. Okamoto
Keyword(s):  
Effective Diffusivity ◽  
Diffusion Method ◽  
Anaerobic Conditions ◽  
Through Diffusion ◽  
Effective Diffusivities

SummaryThe effective diffusivities of neptunium and plutonium in Inada granite have been determined using the through–diffusion method. Experiments were performed under anaerobic conditions in the presence of carbonate. The actinides are expected to be present as carbonato or carbonatohydroxo complexes. Effective diffusivity (D

Formation factor measurements in granite in the laboratory – Comparison of through diffusion and electromigration techniques.

2002 ◽  
Vol 757 ◽  
Author(s):  
Martin Löfgren ◽  
Ivars Neretnieks
Keyword(s):  
Direct Current ◽  
Igneous Rock ◽  
Rock Sample ◽  
Effective Diffusivity ◽  
Diffusive Flux ◽  
Formation Factor ◽  
Granite Sample ◽  
Experimental Time ◽  
Large Samples ◽  
Through Diffusion

ABSTRACTTraditionally the effective diffusivity in and the formation factor of intrusive igneous rock have been measured in the laboratory by through diffusion (TD) experiments, which are very time consuming in larger samples with low porosity. In previous work alternating current (AC) has been used to measure the formation factor directly in large samples. In this paper direct current is used to actually transport the tracers through the rock sample in so called through electromigration (TEM) experiments. In these experiments electoosmosis has to be corrected for. The experimental time is reduced substantially when adding an electromigratory flux to the diffusive flux. TD, TEM and AC experiments were performed on a 15 mm thick unweathered granite sample from Laxemar, Sweden. The tracers uranin and iodide were used. The formation factor measured with the three methods varied between 1.2·10-4 - 2.87·10-4.

Mineralogical Changes of Cement and Bentonite Accompanied ith Their Interactions

2009 ◽  
Vol 1193 ◽  
Author(s):  
Seiichi Hoshino ◽  
Tetsuji Yamaguchi ◽  
Toshikatsu Maeda ◽  
Masayuki Mukai ◽  
Tadao Tanaka ◽  
...  
Keyword(s):  
Tritiated Water ◽  
Effective Diffusivity ◽  
Diffusion Method ◽  
Hardened Cement ◽  
Computational Studies ◽  
Secondary Phases ◽  
Hardened Cement Paste ◽  
Xrd Pattern ◽  
Through Diffusion ◽  
Primary Minerals

AbstractMineralogical changes of cement and bentonite accompanied with their interaction wereexperimentally studied by mixing granulated hardened cement paste and bentonite, and aging the mixture for91 days at 50° C. Mineralogical changes of cement and bentonite were identified by XRD. Hydratedcalcium-silicate phases (C-S-H), Ca(OH)2, ettringite and monosulfate were identified in the unalteredhardened cement. While Ca(OH)2 and monosulfate decreased with aging and disappeared after 91 days,calcite and katoite (Ca3Al2(SiO4)(OH)8) were formed concurrently. Montmorillonite, quartz (and/orchalcedony), clinoptilolite, plagioclase, calcite, analcime and pyrite were identified in the unaltered bentonite.The XRD pattern showed that diffraction intensities of these minerals decreased with aging. It seems thatthese primary minerals dissolved in the course of the alteration. C-S-H appeared in bentonite during the agingas secondary phases, indicating the participation of silicon dissolved from the bentonite and calcium from thecement formed the C-S-H. The formation of C-S-H that had been predicted by previous modeling studieswas confirmed by the present experiments.In addition, diffusivity of tritiated water in mixed specimen with granulated hardened cement andbentonite was determined by a through-diffusion method. The effective diffusivity of tritiated water decreasedwith aging. The result suggests that the mass diffusivity in the interface of cement-bentonite system willdecrease with their interactions. The results of the diffusion experiments are qualitatively consistent with thediffusivity change in cement-bentonite systems predicted by some computational studies.

Diffusive Transport of Carbon Dioxide through USW-G4 Topopah Spring Tuffs

1993 ◽  
Vol 333 ◽  
Author(s):  
M. Sarwar Ali ◽  
Franklin G. King ◽  
Shamsuddin Ilias
Keyword(s):  
Carbon Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Radius ◽  
Effective Diffusivity ◽  
Yucca Mountain ◽  
Effect Of Temperature ◽  
Diffusion Method ◽  
Diffusive Transport

ABSTRACTThe estimation of diffusive transport of gases through tuffs is important in order to assess whether Yucca Mountain is an environmentally safe and acceptable repository for high-level radioactive waste. The purpose of this study is to provide effective diffusivity data which may be used to calculate the amount of diffusion of carbon dioxide through Yucca Mountain tuff layers to the environment. The effective diffusivity of carbon dioxide was measured for tuff samples from five different layers of the USW-G4 drillhole, which is located in the central part of the proposed repository horizon. The tuff samples studied are from the following layers and depths: Vapor Phase (83.6 m), Upper Lithophysal (130.1 m), Middle Nonlithophysal (224.5 m), Lower Lithophysal (243.9 m, 266.9 m, 297.3 m and 335.2 m), and Lower Nonlithophysal (356.3 m and 371.0 m). A steady-state, counter-diffusion method, using gas chromatographic analysis, was used to determine the effective diffusivity of carbon dioxide through tuff samples. Effective diffusivity increased with temperature between 25°C and 125°C for all layers. The effect of temperature on diffusivity correlated well using second-order polynomials. The porosity, specific surface area and mean pore radius were also determined. In general, diffusivity increased with porosity, specific surface area and mean pore radius, but did not correlate well. From the measured data , it appears that the diffusion takes place primarily in the combined Knudsen and bulk diffusion regimes.

Antibacterial Activity of Thujaoccidentalis,ThujaorientalisandChamaecyparisobtusa

2017 ◽  
Vol 8 (03) ◽  
Author(s):  
Kyoung- Sun Seo ◽  
Seong Woo Jin ◽  
Seongkyu Choi ◽  
Kyeong Won Yun
Keyword(s):  
Staphylococcus Aureus ◽  
Antibacterial Activity ◽  
Antibacterial Agent ◽  
Methanol Extract ◽  
The Other ◽  
Diffusion Method ◽  
E Coli ◽  
Agar Diffusion ◽  
Agar Diffusion Method ◽  
Crude Methanol Extract

The antibacterial activity of three Cupressaceae plants (Thujaoccidentalis,ThujaorientalisandChamaecyparisobtusa) was tested against three bacteria using the agar diffusion method. The ether and ethylacetate fraction of crude methanol extract from the three plants showed potent antibacterial activity against the tested microorganisms. The result showed that Staphylococcus aureus revealed the most sensitivity among the tested bacteria. Thujaoccidentalisether fraction and Thujaorientalis hexane fraction exhibited the highest antibacterial activity against Staphylococcus aureus. E. coli was shown the highest MIC values compared to the other two tested bacteria, which indicates the lowest antibacterial activity against the bacterium. This study promises an interesting future for designing a potentially active antibacterial agent from the three Cupressaceae plants.

Effective, Shortened Drying of Agar-Gelcasting Al2O3 Tube Through Immersing in Acetone

2021 ◽  
Author(s):  
Ramnaree Kaemkit ◽  
Supawan Vichaphund ◽  
Anukorn Phureungrat ◽  
Methee Promsawat ◽  
Suksawat Sirijarukul ◽  
...  
Keyword(s):  
Cross Section ◽  
Concentration Gradient ◽  
Water Concentration ◽  
Drying Shrinkage ◽  
The Other ◽  
Air Drying ◽  
Al2o3 Tube ◽  
Acetone Water ◽  
Porous Microstructure ◽  
Glass Tubes

Abstract A liquid drying agent, i.e. acetone, was employed for allowing the faster drying of Al2O3 tubes fabricated by agar gelcasting than the conventional air drying. The mixture of Al2O3 slurry and agar solution was separately prepared and then mixed prior to molding out of a set of warmed glass tubes. After the mixture transformed into gelled tube, the gelled tube was demolded and then immersed in acetone at different periods of time from 0 to 50 h. The immersed periods of 50 h led to the acetone replacement for water being inside of the gelling tube by 74 wt.% and then shortened the drying period to be 25 min. On the other hand, the conventional air drying spent 420 min drying completely. After drying, the immersed tubes possessed spherical cross section; whereas, no immersed tubes showed the deformation of cross section. The shortened drying was in line with the smaller drying shrinkage (4.7%), broader pore-size distribution and higher porous microstructure, comparing to the conventional air drying. The mechanism of acetone replacement for water was attributed to the acetone-water concentration gradient creating their inter-diffusion.

scholarly journals Quantifying Asymmetric Wave Breaking and Two-Way Transport

2004 ◽  
Vol 61 (22) ◽  
pp. 2735-2748 ◽  
Author(s):  
Noboru Nakamura
Keyword(s):  
Wave Breaking ◽  
Polar Vortex ◽  
Effective Diffusivity ◽  
The Other ◽  
Stratospheric Polar Vortex ◽  
Air Masses ◽  
Rossby Wave Breaking ◽  
Advection Diffusion Equation ◽  
Extratropical Tropopause ◽  
Asymmetric Wave

Abstract Effective diffusivity calculated from a scalar field that obeys the advection–diffusion equation has proved useful for estimating the permeability of unsteady boundaries of air masses such as the edge of the stratospheric polar vortex and the extratropical tropopause. However, the method does not discriminate the direction of transport—whereas some material crosses the boundary from one side to the other, some material does so in the other direction—yet the extant method concerns only the net transport. In this paper, the diagnostic is extended to allow partitioning of fluxes of mass and tracer into opposing directions. This is accomplished by discriminating the regions of “inward” and “outward” wave breaking with the local curvature of the tracer field. The utility of the new method is demonstrated for nonlinear Kelvin– Helmholtz instability and Rossby wave breaking in the stratosphere using a numerically generated tracer. The method successfully quantifies two-way transport and hence the direction of wave breaking—the predominantly equatorward breaking of Rossby waves in the extratropical middle stratosphere, for example. Isolated episodes of mixing are identified well, particularly by the mass flux that primarily arises from the tracer filaments. Comparison of different transport schemes suggests that the results are reasonably robust under a varying subgrid representation of the model.

scholarly journals Optimization of cutting conditions using artificial neural networks and the Edgeworth-Pareto method for CNC face-milling operations on high-strength grade-H steel

2019 ◽  
Vol 105 (5-6) ◽  
pp. 2151-2165 ◽  
Author(s):  
Adel Taha Abbas ◽  
Danil Yurievich Pimenov ◽  
Ivan Nikolaevich Erdakov ◽  
Tadeusz Mikolajczyk ◽  
Mahmoud Sayed Soliman ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Unit Volume ◽  
High Strength ◽  
Face Milling ◽  
Production Costs ◽  
The Other ◽  
Cutting Conditions ◽  
Milling Operations ◽  
Artificial Neural ◽  
Pareto Method

Abstract Computer Numerical Control (CNC) face milling is commonly used to manufacture products from high-strength grade-H steel in both the automotive and the construction industry. The various milling operations for these components have key performance indicators: accuracy, surface roughness (Ra), and machining time for removal of a unit volume min/cm3 (Tm). The specified surface roughness values for machining each component is achieved based on the prototype specifications. However, poor adherence to specifications can result in the rejection of the machined parts, implying extra production costs and raw material wastage. An algorithm using an artificial neural network (ANN) with the Edgeworth-Pareto method is presented in this paper to optimize the cutting parameter in CNC face-milling operations. The set of parameters are adjusted to improve surface roughness and minimal unit-volume material removal rates, thereby reducing production costs and improving accuracy. An ANN algorithm is designed in Matlab, based on a 3–10-1 Multi-Layer Perceptron (MLP), which predicts the Ra of the workpiece surface to an accuracy of ± 5.78% within the range of the experimental angular spindle speed, feed rate, and cutting depth. An unprecedented Pareto frontier for Ra and Tm was obtained for the finished grade-H steel workpiece using an ANN algorithm that was then used to determine optimized cutting conditions. Depending on the production objective, one or the other of two sets of optimum machining conditions can be used: the first one sets a minimum cutting power, while the other sets a maximum Tm with a slight increase (under 5%) in milling costs.

scholarly journals Electronic Measurement of Changes in the Volume of Pore Water During Testing of Soil Samples

1971 ◽  
Vol 8 (2) ◽  
pp. 341-345 ◽  
Author(s):  
R. J. Mitchell ◽  
K. N. Burn
Keyword(s):  
Pore Water ◽  
Volume Change ◽  
Force Transducer ◽  
Soil Samples ◽  
The Other ◽  
Triaxial Testing ◽  
The Core ◽  
Electronic Measurement ◽  
Electronic Recording ◽  
Visual Reading

Two systems are described for electronic recording of changes in the volume of pore water for triaxial testing of soils: one using a miniature force transducer to measure by direct weighing; the other based upon a float system connected to the core of a differential transformer. Both systems provide measurement of volume change at least as accurately as may be obtained by visual reading of burettes graduated to 0.1 cm3, i.e. to ± 0.05 cm3.

scholarly journals Interpretive criteria to differentiate low- and high-level mupirocin resistance in Staphylococcus aureus

2007 ◽  
Vol 56 (7) ◽  
pp. 937-939 ◽  
Author(s):  
Naira Elane Moreira de Oliveira ◽  
Ana Paula Couto Marques Cardozo ◽  
Elizabeth de Andrade Marques ◽  
Kátia Regina Netto dos Santos ◽  
Marcia Giambiagi deMarval
Keyword(s):  
Staphylococcus Aureus ◽  
High Resistance ◽  
The Other ◽  
Diffusion Method ◽  
Disc Diffusion ◽  
Disc Diffusion Method ◽  
Zone Diameter ◽  
Resistant Strains ◽  
Mupirocin Resistance ◽  
High Level

Meticillin-resistant Staphylococcus aureus isolates were classified into three mupirocin susceptibility groups by the disc diffusion method using 5 and 200 μg mupirocin discs. The zone diameter observed for a 5 μg disc distinguished MupS from the resistant strains (either MupRL or MupRH). On the other hand, a 200 μg disc distinguished the high-resistance MupRH strains from the other two (MupS or MupRL). Thus, the concomitant use of 5 and 200 μg mupirocin discs allowed the clear distinction among the three mupirocin susceptibility groups, MupS, MupRL or MupRH.

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