Water and Solute Flux Measurement

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.

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Correction of Eddy Covariance Based Crop ET Considering the Heat Flux Source Area

Atmosphere ◽

10.3390/atmos12020281 ◽

2021 ◽

Vol 12 (2) ◽

pp. 281

Author(s):

Stuart L. Joy ◽

José L. Chávez

Keyword(s):

Heat Flux ◽

Eddy Covariance ◽

Agricultural Land ◽

Flux Measurement ◽

Source Area ◽

Mean Bias Error ◽

Bias Error ◽

Crop Water ◽

The Past ◽

Measurement Results

Eddy covariance (EC) systems are being used to measure sensible heat (H) and latent heat (LE) fluxes in order to determine crop water use or evapotranspiration (ET). The reliability of EC measurements depends on meeting certain meteorological assumptions; the most important of such are horizontal homogeneity, stationarity, and non-advective conditions. Over heterogeneous surfaces, the spatial context of the measurement must be known in order to properly interpret the magnitude of the heat flux measurement results. Over the past decades, there has been a proliferation of ‘heat flux source area’ (i.e., footprint) modeling studies, but only a few have explored the accuracy of the models over heterogeneous agricultural land. A composite ET estimate was created by using the estimated footprint weights for an EC system in the upwind corner of four fields and separate ET estimates from each of these fields. Three analytical footprint models were evaluated by comparing the composite ET to the measured ET. All three models performed consistently well, with an average mean bias error (MBE) of about −0.03 mm h−1 (−4.4%) and root mean square error (RMSE) of 0.09 mm h−1 (10.9%). The same three footprint models were then used to adjust the EC-measured ET to account for the fraction of the footprint that extended beyond the field of interest. The effectiveness of the footprint adjustment was determined by comparing the adjusted ET estimates with the lysimetric ET measurements from within the same field. This correction decreased the absolute hourly ET MBE by 8%, and the RMSE by 1%.

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On the use of plume models to estimate the flux in volcanic gas plumes

Nature Communications ◽

10.1038/s41467-021-22159-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Julia Woitischek ◽

Nicola Mingotti ◽

Marie Edmonds ◽

Andrew W. Woods

Keyword(s):

Electrochemical Sensors ◽

Measurement Techniques ◽

Flux Measurement ◽

Hydrothermal Systems ◽

Mount Etna ◽

Volcanic Gas ◽

Gas Flux ◽

Convective Structures ◽

Video Images ◽

Villarrica Volcano

AbstractMany of the standard volcanic gas flux measurement approaches involve absorption spectroscopy in combination with wind speed measurements. Here, we present a new method using video images of volcanic plumes to measure the speed of convective structures combined with classical plume theory to estimate volcanic fluxes. We apply the method to a nearly vertical gas plume at Villarrica Volcano, Chile, and a wind-blown gas plume at Mount Etna, Italy. Our estimates of the gas fluxes are consistent in magnitude with previous reported fluxes obtained by spectroscopy and electrochemical sensors for these volcanoes. Compared to conventional gas flux measurement techniques focusing on SO2, our new model also has the potential to be used for sulfur-poor plumes in hydrothermal systems because it estimates the H2O flux.

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Heat flux measurement at the initial phase of normal shock wave reflection using the sensor on anisotropic thermoelements

Journal of Physics Conference Series ◽

10.1088/1742-6596/1697/1/012225 ◽

2020 ◽

Vol 1697 ◽

pp. 012225

Author(s):

P A Popov ◽

V A Sakharov ◽

S A Poniaev ◽

N A Monakhov ◽

M A Kotov

Keyword(s):

Shock Wave ◽

Heat Flux ◽

Initial Phase ◽

Wave Reflection ◽

Flux Measurement ◽

Normal Shock ◽

Shock Wave Reflection ◽

Normal Shock Wave ◽

Heat Flux Measurement

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Gradient heat flux measurement in study of condensation at inner surface of the tube

Journal of Physics Conference Series ◽

10.1088/1742-6596/1683/2/022018 ◽

2020 ◽

Vol 1683 ◽

pp. 022018

Author(s):

S Z Sapozhnikov ◽

V Y Mityakov ◽

A Y Babich ◽

E R Zainullina

Keyword(s):

Heat Flux ◽

Flux Measurement ◽

Heat Flux Measurement ◽

Inner Surface

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Fabrication of Gum Arabic-Graphene (GGA) Modified Polyphenylsulfone (PPSU) Mixed Matrix Membranes: A Systematic Evaluation Study for Ultrafiltration (UF) Applications

Membranes ◽

10.3390/membranes11070542 ◽

2021 ◽

Vol 11 (7) ◽

pp. 542

Author(s):

Alaa Mashjel Ali ◽

Khalid T. Rashid ◽

Ali Amer Yahya ◽

Hasan Sh. Majdi ◽

Issam K. Salih ◽

...

Keyword(s):

Fourier Transforms ◽

Thermal Characteristics ◽

Gum Arabic ◽

Evaluation Study ◽

Membrane Properties ◽

Systematic Evaluation ◽

Mixed Matrix Membranes ◽

Solute Flux ◽

Xrd Patterns ◽

Modified Graphene

In the current work, a Gum, Arabic-modified Graphene (GGA), has been synthesized via a facile green method and employed for the first time as an additive for enhancement of the PPSU ultrafiltration membrane properties. A series of PPSU membranes containing very low (0–0.25) wt.% GGA were prepared, and their chemical structure and morphology were comprehensively investigated through atomic force microscopy (AFM), Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Besides, thermogravimetric analysis (TGA) was harnessed to measure thermal characteristics, while surface hydrophilicity was determined by the contact angle. The PPSU-GGA membrane performance was assessed through volumetric flux, solute flux, and retention of sodium alginate solution as an organic polysaccharide model. Results demonstrated that GGA structure had been successfully synthesized as confirmed XRD patterns. Besides, all membranes prepared using low GGA content could impart enhanced hydrophilic nature and permeation characteristics compared to pristine PPSU membranes. Moreover, greater thermal stability, surface roughness, and a noticeable decline in the mean pore size of the membrane were obtained.

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Simulation of S-Entropy Production during the Transport of Non-Electrolyte Solutions in the Double-Membrane System

Entropy ◽

10.3390/e22040463 ◽

2020 ◽

Vol 22 (4) ◽

pp. 463

Author(s):

Andrzej Ślęzak ◽

Wioletta M. Bajdur ◽

Kornelia M. Batko ◽

Radomir Šcurek

Keyword(s):

Entropy Production ◽

Transport Theory ◽

Membrane System ◽

Electrolyte Solutions ◽

Solute Flux ◽

Initial Moment ◽

Hydraulic Permeability ◽

Transport Parameters ◽

Double Membrane ◽

Solute Permeability

Using the classical Kedem–Katchalsky’ membrane transport theory, a mathematical model was developed and the original concentration volume flux (Jv), solute flux (Js) characteristics, and S-entropy production by Jv, ( ( ψ S ) J v ) and by Js ( ( ψ S ) J s ) in a double-membrane system were simulated. In this system, M1 and Mr membranes separated the l, m, and r compartments containing homogeneous solutions of one non-electrolytic substance. The compartment m consists of the infinitesimal layer of solution and its volume fulfills the condition Vm → 0. The volume of compartments l and r fulfills the condition Vl = Vr → ∞. At the initial moment, the concentrations of the solution in the cell satisfy the condition Cl < Cm < Cr. Based on this model, for fixed values of transport parameters of membranes (i.e., the reflection (σl, σr), hydraulic permeability (Lpl, Lpr), and solute permeability (ωl, ωr) coefficients), the original dependencies Cm = f(Cl − Cr), Jv = f(Cl − Cr), Js = f(Cl − Cr), ( Ψ S ) J v = f(Cl − Cr), ( Ψ S ) J s = f(Cl − Cr), Rv = f(Cl − Cr), and Rs = f(Cl − Cr) were calculated. Each of the obtained features was specially arranged as a pair of parabola, hyperbola, or other complex curves.

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