Parylene-Coated Polytetrafluoroethylene-Membrane-Based Portable Urea Sensor for Real-Time Monitoring of Urea in Peritoneal Dialysate

A portable urea sensor for use in fast flow conditions was fabricated using porous polytetrafluoroethylene (PTFE) membranes coated with amine-functionalized parylene, parylene-A, by vapor deposition. The urea-hydrolyzing enzyme urease was immobilized on the parylene-A-coated PTFE membranes using glutaraldehyde. The urease-immobilized membranes were assembled in a polydimethylsiloxane (PDMS) fluidic chamber, and a screen-printed carbon three-electrode system was used for electrochemical measurements. The success of urease immobilization was confirmed using scanning electron microscopy, and fourier-transform infrared spectroscopy. The optimum concentration of urease for immobilization on the parylene-A-coated PTFE membranes was determined to be 48 mg/mL, and the optimum number of membranes in the PDMS chamber was found to be eight. Using these optimized conditions, we fabricated the urea biosensor and monitored urea samples under various flow rates ranging from 0.5 to 10 mL/min in the flow condition using chronoamperometry. To test the applicability of the sensor for physiological samples, we used it for monitoring urea concentration in the waste peritoneal dialysate of a patient with chronic renal failure, at a flow rate of 0.5 mL/min. This developed urea biosensor is considered applicable for (portable) applications, such as artificial kidney systems and portable dialysis systems.

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Parylene-Coated PTFE-Membrane-Based Portable Urea Sensor for Use in Fast Flow Conditions

10.20944/preprints201909.0297.v1 ◽

2019 ◽

Author(s):

Min Park ◽

JeeYoung Kim ◽

Kyounghee Kim ◽

Jae-Chul Pyun ◽

Gun Yong Sung

Keyword(s):

Flow Condition ◽

Electrode System ◽

Optimum Concentration ◽

Optimum Number ◽

Flow Conditions ◽

Flow Rates ◽

Ptfe Membrane ◽

Amine Functionalized ◽

Fast Flow ◽

Optimized Conditions

A portable urea sensor for use in the fast flow condition was fabricated using porous polytetrafluoroethylene (PTFE) membranes coated with amine-functionalized parylene, parylene-A, by vapor deposition. To generate a specific electrochemical sensor signal from urea, the urea-hydrolyzing enzyme urease was immobilized on the parylene-A-coated PTFE membranes via chemical crosslinking using glutaraldehyde. The urease-immobilized membranes were assembled in a polydimethylsiloxane (PDMS) fluidic chamber, and a screen-printed carbon three-electrode system was used for electrochemical measurements. The success of urease immobilization was confirmed using fluorescence microscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The optimum concentration of urease for immobilization on the parylene-A-coated PTFE membranes was determined to be 48 mg/mL, and the optimum number of membranes in the PDMS chamber was found to be 8. Using these optimized conditions, we fabricated the urea biosensor and monitored urea samples under various flow rates ranging from 0.5 to 10 mL/min in the flow condition using chronoamperometry. To test the applicability of the sensor for physiological samples, we used it for monitoring urea concentration in the waste peritoneal dialysate of a patient with chronic renal failure, at a flow rate of 0.5 mL/min.

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Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

Geothermal Energy ◽

10.1186/s40517-021-00201-3 ◽

2021 ◽

Vol 9 (1) ◽

Author(s):

Tobias Blanke ◽

Markus Hagenkamp ◽

Bernd Döring ◽

Joachim Göttsche ◽

Vitali Reger ◽

...

Keyword(s):

Reynolds Number ◽

Laminar Flow ◽

Mass Flow ◽

Flow Rate ◽

Heat Exchangers ◽

Circular Ring ◽

Flow Conditions ◽

Flow Rates ◽

Mass Flow Rates ◽

Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

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Temperature log simulations in high-enthalpy boreholes

Geothermal Energy ◽

10.1186/s40517-019-0149-0 ◽

2019 ◽

Vol 7 (1) ◽

Cited By ~ 2

Author(s):

Jia Wang ◽

Fabian Nitschke ◽

Maziar Gholami Korzani ◽

Thomas Kohl

Keyword(s):

Heat Transfer ◽

Temperature Distribution ◽

Temperature Gradient ◽

Flow Rate ◽

Fluid Loss ◽

Flow Conditions ◽

Flow Rates ◽

High Enthalpy ◽

Fluid Losses ◽

Lateral Heat

Abstract Temperature logs have important applications in the geothermal industry such as the estimation of the static formation temperature (SFT) and the characterization of fluid loss from a borehole. However, the temperature distribution of the wellbore relies on various factors such as wellbore flow conditions, fluid losses, well layout, heat transfer mechanics within the fluid as well as between the wellbore and the surrounding rock formation, etc. In this context, the numerical approach presented in this paper is applied to investigate the influencing parameters/uncertainties in the interpretation of borehole logging data. To this end, synthetic temperature logs representing different well operation conditions were numerically generated using our newly developed wellbore simulator. Our models account for several complex operation scenarios resulting from the requirements of high-enthalpy wells where different flow conditions, such as mud injection with- and without fluid loss and shut-in, occur in the drill string and the annulus. The simulation results reveal that free convective heat transfer plays an important role in the earlier evolution of the shut-in-time temperature; high accuracy SFT estimation is only possible when long-term shut-in measurements are used. Two other simulation scenarios for a well under injection conditions show that applying simple temperature correction methods on the non-shut-in temperature data could lead to large errors for SFT estimation even at very low injection flow rates. Furthermore, the magnitude of the temperature gradient increase depends on the flow rate, the percentage of fluid loss and the lateral heat transfer between the fluid and the rock formation. As indicated by this study, under low fluid losses (< 30%) or relatively higher flow rates (> 20 L/s), the impact of flow rate and the lateral heat transfer on the temperature gradient increase can be ignored. These results provide insights on the key factors influencing the well temperature distribution, which are important for the choice of the drilling data to estimate SFT and the design of the inverse modeling scheme in future studies to determine an accurate SFT profile for the high-enthalpy geothermal environment.

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Carotid Bifurcation Hemodynamics in Older Adults: Effect of Measured Versus Assumed Flow Waveform

Journal of Biomechanical Engineering ◽

10.1115/1.4001265 ◽

2010 ◽

Vol 132 (7) ◽

Cited By ~ 27

Author(s):

Yiemeng Hoi ◽

Bruce A. Wasserman ◽

Edward G. Lakatta ◽

David A. Steinman

Keyword(s):

Magnetic Resonance ◽

Older Adult ◽

Blood Flow Rate ◽

Carotid Bifurcation ◽

Flow Waveform ◽

Flow Conditions ◽

Flow Rates ◽

Relative Residence Time ◽

Contrast Magnetic Resonance ◽

Dynamics Models

Recent work has illuminated differences in carotid artery blood flow rate dynamics of older versus young adults. To what degree flow waveform shape, and indeed the use of measured versus assumed flow rates, affects the simulated hemodynamics of older adult carotid bifurcations has not been elucidated. Image-based computational fluid dynamics models of N=9 normal, older adult carotid bifurcations were reconstructed from magnetic resonance angiography. Subject-specific hemodynamics were computed by imposing each individual’s inlet and outlet flow rates measured by cine phase-contrast magnetic resonance imaging or by imposing characteristic young and older adult flow waveform shapes adjusted to cycle-averaged flow rates measured or allometrically scaled to the inlet and outlet areas. Despite appreciable differences in the measured versus assumed flow conditions, the locations and extents of low wall shear stress and elevated relative residence time were broadly consistent; however, the extent of elevated oscillatory shear index was substantially underestimated, more by the use of assumed cycle-averaged flow rates than the assumed flow waveform shape. For studies of individual vessels, use of a characteristic flow waveform shape is likely sufficient, with some benefit offered by scaling to measured cycle-averaged flow rates. For larger-scale studies of many vessels, ranking of cases according to presumed hemodynamic or geometric risk is robust to the assumed flow conditions.

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Rapid flow in multilayer microfluidic paper-based analytical devices

Lab on a Chip ◽

10.1039/c7lc01300k ◽

2018 ◽

Vol 18 (5) ◽

pp. 793-802 ◽

Cited By ~ 46

Author(s):

Robert B. Channon ◽

Michael P. Nguyen ◽

Alexis G. Scorzelli ◽

Elijah M. Henry ◽

John Volckens ◽

...

Keyword(s):

Single Layer ◽

Sequential Injection ◽

Stripping Analysis ◽

Flow Rates ◽

Rapid Flow ◽

Paper Device ◽

Fast Flow

Multilayer paper devices are used to generate fast flow rates (1.56 cm s−1) which are 145-fold quicker than classical single-layer paper device designs. These self-pumping devices are demonstrated for the sequential injection stripping analysis of cadmium.

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USE OF HEMODIALYSIS IN THE TREATMENT OF QUINIDINE POISONING

PEDIATRICS ◽

10.1542/peds.52.1.95 ◽

1973 ◽

Vol 52 (1) ◽

pp. 95-99

Author(s):

Ekkehard W. Reimold ◽

Walter J. Reynolds ◽

David E. Fixler ◽

LaVerne McElroy

Keyword(s):

Blood Flow ◽

Glomerular Filtration Rate ◽

Glomerular Filtration ◽

Treatment Period ◽

Filtration Rate ◽

Renal Excretion ◽

Artificial Kidney ◽

Flow Rates ◽

Urine Acidification ◽

Forced Diuresis

Hemodialysis was used in addition to forced diuresis in the treatment of quinidine poisoning of a 3-year-old girl. The estimated retained dose of quinidine was 1,600 mg. During a 36-hour treatment period the patient excreted through the kidneys 768.1 mg quinidine (21.3 mg/hr). Hemodialysis almost doubled the quinidine elimination by removing 145 mg in eight hours (18.1 mg/hr): renal excretion, 55%; hemodialysis, 45%. The quinidine elimination with dialysis is high when high blood flow rates through the artificial kidney can be maintained. Adequate glomerular filtration rate and urine acidification are necessary for high renal excretion of quinidine.

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Prediction of Droplet Production Speed by Measuring the Droplet Spacing Fluctuations in a Flow-Focusing Microdroplet Generator

Micromachines ◽

10.3390/mi10120812 ◽

2019 ◽

Vol 10 (12) ◽

pp. 812 ◽

Cited By ~ 1

Author(s):

Wen Zeng ◽

Dong Xiang ◽

Hai Fu

Keyword(s):

Fluid Flow ◽

Efficient Method ◽

Immiscible Fluids ◽

Droplet Generation ◽

Flow Focusing ◽

Flow Conditions ◽

Flow Rates ◽

Wide Range ◽

Droplet Production ◽

Monodisperse Droplets

In a flow-focusing microdroplet generator, by changing the flow rates of the two immiscible fluids, production speed can be increased from tens to thousands of droplets per second. However, because of the nonlinearity of the flow-focusing microdroplet generator, the production speed of droplets is difficult to quantitatively study for the typical flow-focusing geometry. In this paper, we demonstrate an efficient method that can precisely predict the droplet production speed for a wide range of fluid flow rates. While monodisperse droplets are formed in the flow-focusing microchannel, droplet spacing as a function of time was measured experimentally. We discovered that droplet spacing changes periodically with time during each process of droplet generation. By comparing the frequency of droplet spacing fluctuations with the droplet production speed, precise predictions of droplet production speed can be obtained for different flow conditions in the flow-focusing microdroplet generator.

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Assessment of LID practices for restoring pre-development runoff regime in an urbanized catchment in southern Finland

Water Science & Technology ◽

10.2166/wst.2015.129 ◽

2015 ◽

Vol 71 (10) ◽

pp. 1485-1491 ◽

Cited By ~ 30

Author(s):

Mingfu Guan ◽

Nora Sillanpää ◽

Harri Koivusalo

Keyword(s):

Low Impact Development ◽

Urban Runoff ◽

Flow Conditions ◽

Runoff Generation ◽

Flow Rates ◽

Storm Water Management Model ◽

Runoff Regime ◽

Reduction Effect ◽

Development Levels ◽

Negative Impacts

This study quantifies the effects of common stormwater management techniques on urban runoff generation. Simulated flow rates for different low impact development (LID) scenarios were compared with observed flow rates during different urban construction phases in a catchment (12.3 ha) that was developed from natural forest to a residential area over a monitoring period of 5 years. The Storm Water Management Model (SWMM) was calibrated and validated against the observed flow rates in the fully developed catchment conditions, and it was then applied to parameterize the LID measures and produce scenarios of their hydrological impacts. The results from the LID scenarios were compared with the observed flow rates in the pre-development and the partially developed catchment conditions. The results show that LID controls reduce urban runoff towards the flow conditions in the partially developed catchment, but the reduction effect diminishes during large rainfall events. The hydrographs with LID are still clearly different from the observed pre-development levels. Although the full restoration of pre-development flow conditions was not feasible, a combination of several measures controlling both volumes and retention times of storm runoff appeared to be effective for managing the stormwater runoff and mitigating the negative impacts of urban development.

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Polymorph Selection of ROY by Flow-Driven Crystallization

Crystals ◽

10.3390/cryst9070351 ◽

2019 ◽

Vol 9 (7) ◽

pp. 351 ◽

Cited By ~ 4

Author(s):

Ziemecka ◽

Gokalp ◽

Stroobants ◽

Brau ◽

Maes ◽

...

Keyword(s):

Radial Flow ◽

Outer Edge ◽

Local Concentration ◽

Equilibrium Flow ◽

Confined Space ◽

Flow Conditions ◽

Flow Rates ◽

Polymorph Selection ◽

Displacement Pattern ◽

Selection Of

The selection of polymorphs of the organic compound 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, ROY, is studied experimentally in the confined space between two horizontal glass plates when an acetone solution of ROY of variable concentration is injected at a variable flow rate into water. Depending on the local concentration within the radial flow, a polymorph selection is observed such that red prisms are favored close to the injection center while yellow needles are the preferred polymorph close to the edge of the injected ROY domain. At larger flow rates, a buoyancy-driven instability induces stripes at the outer edge of the displacement pattern, in which specific polymorphs are seen to crystallize. Our results evidence the possibility of a selection of ROY polymorph structures in out-of-equilibrium flow conditions.

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