Mechanism of Ionic Diffusion in Dense Bentonite

1988 ◽  
Vol 127 ◽  
Author(s):  
S.C.H. Cheung ◽  
M. N. Gray
Keyword(s):  
Interstitial Water ◽  
Particle Surface ◽  
Free Water ◽  
Clay Particle ◽  
Ionic Diffusion ◽  
Interstitial Free ◽  
New Model ◽  
Compacted Bentonite ◽  
Flow Through ◽  
Through Diffusion

ABSTRACTA new model based on ionic diffusion in surface (bound) and interstitial (free) water in compacted bentonite systems has been developed. The model is supported by data obtained from flow-through diffusion experiments using Cs+, I- and Cl-. The results show that diffusion depends on the charge of the diffusing species: cations are attracted to the clay particle surface, but are not immobilized, whereas anions are repelled from the clay particle surface. Cations diffuse through both surface and interstitial water, and anions diffuse mainly through interstitial water. The clay structure has been found to affect the diffusion of cations and anions.

Measurement of pyruvate and lactate kinetics across the hindlimb and gut of anesthetized dogs

1994 ◽  
Vol 267 (1) ◽  
pp. E174-E182 ◽  
Author(s):  
D. L. Chinkes ◽  
X. J. Zhang ◽  
J. A. Romijn ◽  
Y. Sakurai ◽  
R. R. Wolfe
Keyword(s):  
Free Water ◽  
Whole Body ◽  
Transmembrane Transport ◽  
New Model ◽  
Lactate Kinetics ◽  
Stable Isotopic ◽  
Anesthetized Dogs ◽  
Flow Through ◽  
Lactate And Pyruvate

We have developed a new model to quantify regional pyruvate and lactate transmembrane transport, shunting, exchange, production, and oxidation in vivo. The method is based on the systemic continuous infusion of pyruvate or lactate stable isotopic carbon tracers and the measurement of pyruvate and lactate enrichment and concentration in the artery and vein of that region (e.g., leg or gut), the pyruvate and lactate enrichment of intracellular free water in the tissue as measured by biopsy, and the rate of blood flow through the tissue. The purpose of the experiment was to measure the pyruvate and lactate kinetics in leg muscle and gut in anesthetized dogs (n = 6). The transmembrane transport and degree of shunting of pyruvate and lactate were comparable in muscle and gut. When modified for substrate inflow, interconversion between pyruvate and lactate took place at a rate twice as fast in muscle as in the gut, and production and oxidation of pyruvate was approximately 50% greater in muscle than in the gut. Thus our new model enables quantitation of many aspects of lactate and pyruvate kinetics. We conclude that in anesthetized animals the muscle is the tissue most responsible for whole body peripheral pyruvate and lactate kinetics.

scholarly journals Measurement on Diffusion Coefficients and Isotope Fractionation Factors by a Through-Diffusion Experiment

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 208
Author(s):  
Takuma Hasegawa ◽  
Kotaro Nakata ◽  
Rhys Gwynne
Keyword(s):  
Groundwater Flow ◽  
Diffusion Coefficients ◽  
Isotope Fractionation ◽  
Free Water ◽  
Effective Porosity ◽  
Diffusion Experiment ◽  
Fractionation Factor ◽  
Through Diffusion ◽  
Geological Formations ◽  
Fractionation Factors

For radioactive waste disposal, it is important that local groundwater flow is slow as groundwater flow is the main transport medium for radioactive nuclides in geological formations. When the groundwater flow is very slow, diffusion is the dominant transport mechanism (diffusion-dominant domain). Key pieces of evidence indicating a diffusion-dominant domain are the separation of components and the fractionation of isotopes by diffusion. To prove this, it is necessary to investigate the different diffusion coefficients for each component and the related stable isotope fractionation factors. Thus, in this study, through-diffusion and effective-porosity experiments were conducted on selected artificial materials and natural rocks. We also undertook measurements relating to the isotope fractionation factors of Cl and Br isotopes for natural samples. For natural rock samples, the diffusion coefficients of water isotopes (HDO and H218O) were three to four times higher than those of monovalent anions (Cl−, Br- and NO3−), and the isotope fractionation factor of 37Cl (1.0017–1.0021) was slightly higher than that of free water. It was experimentally confirmed that the isotope fractionation factor of 81Br was approximately 1.0007–1.0010, which is equivalent to that of free water. The enrichment factor of 81Br was almost half that of 37Cl. The effective porosity ratios of HDO and Cl were slightly different, but the difference was not significant compared to the ratio of their diffusion coefficients. As a result, component separation was dominated by diffusion. For artificial samples, the diffusion coefficients and effective porosities of HDO and Cl were almost the same; it was thus difficult to assess the component separation by diffusion. However, isotope fractionation of Cl and Br was confirmed using a through-diffusion experiment. The results show that HDO and Cl separation and isotope fractionation of Cl and Br can be expected in diffusion-dominant domains in geological formations.

Determine the Moisture Distribution in Sewage Sludge by Drying Differential

2014 ◽  
Vol 665 ◽  
pp. 404-407 ◽  
Author(s):  
Wan Yu ◽  
Pei Sheng Li
Keyword(s):  
Sewage Sludge ◽  
Interstitial Water ◽  
Bound Water ◽  
Free Water ◽  
High Accuracy ◽  
Moisture Distribution ◽  
Municipal Sewage ◽  
Municipal Sewage Sludge ◽  
Hot Air ◽  
Critical Water Content

Moisture distribution in sewage sludge was considered as the essential of thermal drying. Some methods were given in literatures to test the moisture distribution, but there was no standard method to determine the critical water content between different kinds of water. The municipal sewage sludge was dried by hot air in this work. Based on the drying curve, the derivative of drying rate with respect to dry basis moisture content was brought out to analyze the moisture distribution in sewage sludge. Results show that this method can easily determine the free water, interstitial water, surface water and bound water with a high accuracy. The present work can provide new insight to determine the moisture distribution in sewage sludge, which was still lacking in the literatures.

Low salinity frazil ice generation at the base of a small Antarctic ice shelf

1993 ◽  
Vol 5 (3) ◽  
pp. 309-322 ◽  
Author(s):  
J.-L. Tison ◽  
D. Ronveaux ◽  
R. D. Lorrain
Keyword(s):  
Interstitial Water ◽  
Sea Water ◽  
Freezing Point ◽  
Free Water ◽  
Ice Crystals ◽  
Ice Shelf ◽  
Apparent Contradiction ◽  
Ice Shelves ◽  
Frazil Ice ◽  
Low Salinity

Chemical, isotopic and crystallographic characteristics of marine ice formed at the base of the Hells Gate Ice Shelf, Terra Nova Bay, allow a better understanding of the dynamics of marine ice accretion under small ice shelves. The observed properties of the different types of frazil ice found in the area immediately behind the ice shelf front, result from a progressive evolution of the individual frazil ice crystals initially accreted at the base of the ice-shelf. Basal melting caused by the descending plumes of water masses at a temperature above their local freezing point, initiates partial melting of the frazil ice crystals. This dilutes the interstitial water and initiates chemical sorting effects as diffusion proceeds from the normal sea water in the free water column to the diluted interstitial water in the loose frazil layer. Different environmental conditions will result in contrasting properties. Where the subglacial interface is sculptured with domes or inverted channels, it will favour the accumulation of thick units of frazil ice, in a calm environment, that will be further protected from convection mixing over long time periods. This will result in the formation of orbicular frazil showing c-axes at random, strong dilution and important sorting effects. On the contrary, where no channel or dome exist, or where those are already filled with frazil, rectangular or wave-like banded frazil will form with properties showing interfacial streaming effects induced by water currents. Strong c-axes concentration at a single maximum, less dilution and weaker chemical sorting effects are then observed. These findings provide a tentative explanation for the apparent contradiction between the very low salinity levels detected in marine ice at the base of ice shelves and the comparatively minor salinity fluctuations in sea water profiles near ice shelves.

The flow-through diffusion cell (FTDC) method: a novel approach toin vitro drug release studies

2005 ◽  
Vol 55 (1) ◽  
pp. 12-18 ◽  
Author(s):  
Sunil K Bajpai ◽  
Sutanjay Saxena ◽  
Seema Dubey
Keyword(s):  
Drug Release ◽  
Diffusion Cell ◽  
Novel Approach ◽  
Release Studies ◽  
Flow Through ◽  
Through Diffusion

A Novel Flow through Diffusion Cell for Assessing Drug Transport across the Buccal Mucosa In Vitro

2009 ◽  
Vol 98 (12) ◽  
pp. 4577-4588 ◽  
Author(s):  
Maria L.A.D. Lestari ◽  
Joseph A. Nicolazzo ◽  
Barrie C. Finnin
Keyword(s):  
Buccal Mucosa ◽  
Drug Transport ◽  
Diffusion Cell ◽  
Flow Through ◽  
Through Diffusion
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