scholarly journals Stream tracer breakthrough curve decomposition into mass fractions: A simple framework to analyze and compare conservative solute transport processes

2016 ◽  
Vol 15 (2) ◽  
pp. 140-153 ◽  
Author(s):  
Adam N. Wlostowski ◽  
Michael N. Gooseff ◽  
William B. Bowden ◽  
Wilfred M. Wollheim
Keyword(s):  
Solute Transport ◽  
Breakthrough Curve ◽  
Transport Processes ◽  
Mass Fractions ◽  
Conservative Solute Transport

Claudin Tight Junction Proteins: Novel Aspects in Paracellular Transport

2008 ◽  
Vol 28 (6) ◽  
pp. 577-584 ◽  
Author(s):  
Constanze Will ◽  
Michael Fromm ◽  
Dominik Müller
Keyword(s):  
Tight Junction ◽  
Solute Transport ◽  
Molecular Mechanisms ◽  
Family Members ◽  
Transport Processes ◽  
Paracellular Transport ◽  
Solute Flux ◽  
Solute Fluxes ◽  
Essential Components ◽  
Renal Tubular

Claudins are essential components of the intercellular tight junction and major determinants of paracellular solute fluxes across epithelia and endothelia. Many members of this family display a distinct charge or size specificity, whereas others render the epithelium impermeable to transport. Due to intercellular localization, claudin-mediated transport processes are passive and driven by an electrochemical gradient. In epithelial tissues, claudins exhibit a temporal–spatial expression pattern corresponding with regional and local solute transport profiles. Whereas paracellular transport mechanisms in organs such as intestine and kidney have been extensively investigated, little is known about the molecular mechanisms determining solute transport in the peritoneum, and thus the determinants of peritoneal dialysis. Given the ubiquitous expression of claudins in endothelia and epithelia, it is predictable that claudins also contribute to pore formation and determination in the peritoneum, and that they are involved in solute flux. Therefore, we review the basic characteristics of claudin family members and their function as exemplified in renal tubular transport and give an outlook to what extent claudin family members might be of importance for solute reabsorption across the peritoneal membrane.

Historical development of soil-water physics and solute transport in porous media

2007 ◽  
Vol 7 (1) ◽  
pp. 59-66 ◽  
Author(s):  
D.E. Rolston
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Solute Transport ◽  
Soil Water ◽  
20Th Century ◽  
Water Flow ◽  
Unsaturated Soils ◽  
Transport Processes ◽  
Transport In Porous Media ◽  
Unsaturated Hydraulic Conductivity

The science of soil-water physics and contaminant transport in porous media began a little more than a century ago. The first equation to quantify the flow of water is attributed to Darcy. The next major development for unsaturated media was made by Buckingham in 1907. Buckingham quantified the energy state of soil water based on the thermodynamic potential energy. Buckingham then introduced the concept of unsaturated hydraulic conductivity, a function of water content. The water flux as the product of the unsaturated hydraulic conductivity and the total potential gradient has become the accepted Buckingham-Darcy law. Two decades later, Richards applied the continuity equation to Buckingham's equation and obtained a general partial differential equation describing water flow in unsaturated soils. For combined water and solute transport, it had been recognized since the latter half of the 19th century that salts and water do not move uniformly. It wasn't until the middle of the 20th century that scientists began to understand the complex processes of diffusion, dispersion, and convection and to develop mathematical formulations for solute transport. Knowledge on water flow and solute transport processes has expanded greatly since the early part of the 20th century to the present.

Profiles of water and solute transport along long-loop descending limb: analysis by mathematical model

1987 ◽  
Vol 252 (3) ◽  
pp. F393-F402 ◽  
Author(s):  
J. Taniguchi ◽  
K. Tabei ◽  
M. Imai
Keyword(s):  
Mathematical Model ◽  
Solute Transport ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Species Difference ◽  
Transport Processes ◽  
Similar Amount ◽  
Sodium Potassium ◽  
Water And Solute Transport

We simulated profiles of water and solute transport along the descending limb of the long-loop nephron by a mathematical model based on mass balance equations for water, sodium, potassium, and urea, using phenomenological coefficients reported for hamsters. We assumed that interstitial concentration of sodium, potassium, and urea increased linearly along the descending limb from 150 to 350, from 5 to 50, and from 5 to 300 mM, respectively. Under this condition an increase in osmolality at the end-descending limb was mainly accounted for by the absorption of water. Considerable amounts of potassium and urea were secreted along the descending limb. Sodium was reabsorbed rather than secreted along the descending limb by both diffusion and solvent drag. The secreted amounts of urea and potassium were comparable to those observed by micropuncture studies. The sodium concentration in the lumen was higher than in the interstitium, with the transmural sodium gradient being 15 meq/liter at the hairpin turn. The potassium mass flow rate at the end-descending limb increased by 2.4 times. Large variations in potassium concentration of the delivered fluid scarcely changed the potassium mass flow rate at the end-descending limb. The secretion of urea and potassium and the reabsorption of sodium were increased as a function of delivered flow rate. An increase in corticomedullary urea gradient decreased the net potassium secretion along the descending limb. When the transport parameters for rabbits were used, both reabsorption of sodium and addition of urea were decreased, but a similar amount of potassium was secreted. These analyses indicate that the mathematical model that takes the species difference and internephron heterogeneity into consideration is useful in illustrating the transport processes along the descending limb of Henle's loop under various physiological and pathophysiological conditions.

The prediction of solute transport in surcharged manholes using CFD

2007 ◽  
Vol 55 (4) ◽  
pp. 57-64 ◽  
Author(s):  
S.D. Lau ◽  
V.R. Stovin ◽  
I. Guymer
Keyword(s):  
Solute Transport ◽  
Laboratory Data ◽  
Transport Processes ◽  
Relevant Parameter ◽  
Computationally Efficient ◽  
Engineering Structures ◽  
Advection Dispersion ◽  
Hydraulic Regime ◽  
Wide Range ◽  
Discrete Phase

Solute transport processes occur within a wide range of water engineering structures, and urban drainage engineers increasingly rely on modelling tools to represent the transport of dissolved materials. The models take as input representative travel time and dispersion characteristics for key system components, and these generally have to be identified via field or laboratory measurements. Computational Fluid Dynamics (CFD) has the potential to reveal the underlying hydraulic processes that control solute transport, and to provide a generic means of identifying relevant parameter values. This paper reports on a study that has been undertaken to evaluate the feasibility of utilising a CFD-based approach to modelling solute transport. Discrete phase modelling has been adopted, as this is computationally efficient and robust when compared with the time-dependent solution of the advection–dispersion equation. Simulation results are compared with published laboratory data characterising the dispersion effects of surcharged manholes, focusing specifically on an 800 mm diameter laboratory manhole for a flowrate of 0.002 m3/s and a range of surcharge depths. Preliminary indications are that the CFD results adequately replicate the measured downstream temporal concentration profiles, and that a threshold surcharge depth, corresponding to a change in hydraulic regime within the manhole, can also be identified.

Water flow and solute transport processes in the unsaturated zone

1986 ◽  
Vol 22 (9S) ◽  
pp. 89S-108S ◽  
Author(s):  
D. R. Nielsen ◽  
M. Th. Van Genuchten ◽  
J. W. Biggar
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Unsaturated Zone ◽  
Transport Processes

scholarly journals A Mathematical Model for Transport in Poroelastic Materials with Variable Volume:Derivation, Lie Symmetry Analysis, and Examples

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 396
Author(s):  
Roman Cherniha ◽  
Joanna Stachowska-Pietka ◽  
Jacek Waniewski
Keyword(s):  
Solute Transport ◽  
Lie Symmetry ◽  
Transport Processes ◽  
Experimental Investigations ◽  
One Dimensional ◽  
Poroelastic Media ◽  
Poroelastic Materials ◽  
Dimensional Version ◽  
The One ◽  
Symmetry Method

Fluid and solute transport in poroelastic media is studied. Mathematical modeling of such transport is a complicated problem because of the volume change of the specimen due to swelling or shrinking and the transport processes are nonlinearly linked. The tensorial character of the variables adds also substantial complication in both theoretical and experimental investigations. The one-dimensional version of the theory is less complex and may serve as an approximation in some problems, and therefore, a one-dimensional (in space) model of fluid and solute transport through a poroelastic medium with variable volume is developed and analyzed. In order to obtain analytical results, the Lie symmetry method is applied. It is shown that the governing equations of the model admit a non-trivial Lie symmetry, which is used for construction of exact solutions. Some examples of the solutions are discussed in detail.

scholarly journals Effects of Cemented Porous Media on Temporal Mixing Behavior of Conservative Solute Transport

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1204 ◽  
Author(s):  
Zhi Dou ◽  
Xueyi Zhang ◽  
Zhou Chen ◽  
Yun Yang ◽  
Chao Zhuang ◽  
...  
Keyword(s):  
Porous Media ◽  
Solute Transport ◽  
Preferential Flow ◽  
Early Stage ◽  
Pore Space ◽  
Negative Influence ◽  
Velocity Variation ◽  
Scalar Dissipation ◽  
Mixing Behavior ◽  
Conservative Solute Transport

The cementation of porous media leads to the variation of the pore space and heterogeneity of the porous media. In this study, four porous media (PM1, PM2, PM3, and PM4) with the different radii of solid grains were generated to represent the different cementation degrees of the porous media. The direct simulations of flow and conservative solute transport in PM1–4 were conducted to investigate the influence of the cemented porous media and Peclet number (Pe) on the temporal mixing behavior. Two metrics, scalar dissipation rates (SDR) and dilution index, were employed to quantify the temporal mixing behavior. It was found that the spatial velocity variability of the flow field was enhanced as cementation degree increased. The results of the coefficient of velocity variation ( C V U ) increased from 0.943 to 2.319 for PM1–4. A network consisted of several preferential flow paths was observed in PM1–4. The preferential flow enhanced the mixing of the conservative solute but had a negative influence on the mixing of the solute plume when the cemented solid grains formed several groups, and there were some stagnant regions where the flow was almost immobile. As the Pe increased, for PM1–3, the exponent of the best-fitting power law of the global SDR decreased. At the case of Pe = 400, the slope of the global SDR reduced to around −1.9. In PM4 where the preferential flow was enhanced by the cemented solid grains, the slope of the global SDR increased as the Pe increased. The global SDR results indicated that the temporal mixing behavior followed a Fickian scaling ( S D R ∝ p v − 1.5 ) in the early stage (Pv < 0.05), while the mixing behavior turned to be non-Fickian in the late stage. The transition time from the Fickian scaling to the non-Fickian scaling was found to be sensitive to the cementation degree of the porous media.

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