Electrokinetic Flow Instability in High Concentration Gradient Microflows

2002 ◽  
Author(s):  
Chuan-Hua Chen ◽  
Juan G. Santiago
Keyword(s):  
Wave Speed ◽  
Flow Instability ◽  
Ionic Concentration ◽  
Qualitative Behavior ◽  
Common Channel ◽  
High Concentration ◽  
Electrokinetic Flow ◽  
Quantitative Properties ◽  
Material Line ◽  
Ongoing Project

This paper documents the scalar imaging of an electrokinetic flow instability that is directly relevant to microfluidic systems that aim to handle and analyze heterogeneous sample streams. The instability occurs in simple T-junctions where two streams of different ionic concentration flow into a common channel. Using neutral dye visualizations, general qualitative behavior of the instability is documented including the formation of a wave in the stream/stream material line that originates at the junction of the two channels and propagates downstream. Several quantitative properties of this phenomenon are measured including wave speed and the extent of the perturbation boundary. This work is part of an ongoing project to identify the physics of this instability and determine the regime of stability, with an ultimate goal of developing methods to either enhance or suppress the instability.

Ground water quality of selected areas of Punjab and Sind Provinces, Pakistan: Chemical and microbiological aspects

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Ionic Concentration ◽  
Chloride Ions ◽  
Potassium Ions ◽  
Ammonium Ions ◽  
High Concentration ◽  
Phosphate Ions ◽  
Sodium Magnesium ◽  
Very High ◽  
Microbiological Aspects

The assessment of groundwater is essential for the estimation of suitability of water for safe use. An attempt has been made to study the groundwater of selected areas of Punjab (Sheikhupura & Sahiwal) and Sindh (Sindh, Jawar Dharki and Dharki), Pakistan. The results indicate that pH, color and odor were all within limits of WHO that is pH ranges 6.5–8.5, colorless and odorless, respectively. The high values of suspended solids were observed in the Sindh-1 and Dharki samples. Microbiologically only Sahiwal and Jawar Dharki were found fit for drinking purpose. Trace metals analysis of Sheikhupura-1 and Sindh-1 showed that values do not fall within limits of WHO for Iron. The ionic concentration analysis showed that high bicarbonate (HCO3-), ions are present in the samples of Sahiwal and Dharki; Sindh-1 and Jawar Dharki samples showed very high concentration for chloride ions, all samples were satisfactory level for sulphate (SO42-), sodium, magnesium and phosphate ions except samples of Sindh-1 and Jawar Dharki. High concentration of calcium and potassium ions was observed in samples of Sindh-1, while all other samples were found fit for drinking purposes in respect of nitrate, nitrite and ammonium ions. The high concentration of Fluoride was found only in Sheikhupura-2 samples.

scholarly journals In vitro surface biocompatibility of high-content silicon-substituted calcium phosphate ceramics

2013 ◽  
Vol 11 (2) ◽  
pp. 140-150 ◽  
Author(s):  
Nasser Mostafa ◽  
Abdallah Shaltout ◽  
Lachezar Radev ◽  
Hassan Hassan
Keyword(s):  
Calcium Phosphate ◽  
Inductively Coupled Plasma ◽  
Energy Dispersive Spectrometer ◽  
Optical Emission ◽  
Ionic Concentration ◽  
Apatite Layer ◽  
High Concentration ◽  
Calcium Phosphate Ceramics ◽  
Porous Microstructure

AbstractThe present work investigates surface biocompatibility of silicon-substituted calcium phosphate ceramics. Different silicon-substituted calcium phosphate ceramic bodies were prepared from co-precipitated powders by sintering at 1300°C. The in vitro bioactivity of the ceramics was assessed in simulated body fluid (SBF) at 37°C for periods up to 4 weeks. The changes in the surface morphology and composition were determined by scanning electron microscopy (SEM) coupled with electron probe microanalysis and energy dispersive spectrometer (EDX). Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to observe the change in ionic concentration of SBF after removal of the samples. The bioactivity of the ceramics increased with an increasing silicate ion substitution in a systematic way. The surface of ceramics with 2.23% silicon substitution was partially covered with apatite layer after one week, while ceramics with 8.1% silicon substitution were completely covered with apatite in the first week. The porous microstructure of high-concentration Si-substituted ceramics helps the dissolution of surface ions and the leaching process. This allows SBF to reach supersaturation in a short time and accelerate the deposition of apatite layer.

Numerical Effects on the Prediction of Flow Instabilities in Channels With Sudden-Expansions

2003 ◽  
Author(s):  
S. Patel ◽  
D. Drikakis
Keyword(s):  
Wave Speed ◽  
Flow Instability ◽  
Flow Instabilities ◽  
Computational Investigation ◽  
Third Order ◽  
Order Of Accuracy ◽  
First Order ◽  
Bifurcation Phenomena ◽  
Flow Through ◽  
Stable Flow

We have considered the problem of flow through a suddenly-expanded channel and performed a computational investigation to examine numerical effects on the prediction of flow instability and bifurcation phenomena. The results revealed that the solution of the flow depends on the numerical method employed. We have employed Godunov-type methods in conjunction with first-, second- and third-order accurate interpolation schemes. It is shown that the order of accuracy of the interpolation used in the discretisation of the wave-speed dependent term and averaged part of the intercell flux affects the prediction of the instability. Computations using first-order discretisation for the calculation of the flux components results in symmetric stable flow, whereas second- and third-order discretisations lead to a symmetry-breaking bifurcation.

The Shear and Elongational Flow of Polymer Melts Containing Anisometric Filler Particles; Part I

1984 ◽  
Vol 57 (3) ◽  
pp. 507-522 ◽  
Author(s):  
L. A. Utracki
Keyword(s):  
Yield Stress ◽  
Flow Instability ◽  
Extensional Flow ◽  
Plug Flow ◽  
Dynamic Test ◽  
Melt Processing ◽  
Solid Base ◽  
Transient Effects ◽  
High Concentration ◽  
Simple Method

Abstract There is a dichotomy in the information on flow of anisometric particles. Most of the fundamental studies only consider dilute suspensions in Newtonian liquids, although some authors venture into a semiconcentrated (two-body collision) region and others into pseudoplastic liquids. These publications provide a solid base for understanding the behavior of the high-concentration systems of industrial importance, but without the desirable quantification. The description of these systems is experimental or, at best, qualitative, via simplified constitutive models. At high concentration of anisometric particles, one must consider: yield stress, plug flow, shear segregation, and a change of relaxation spectrum. There is no simple method to correlate the steady-state and dynamic test data. The magnitude of the stress overshoot in transient tests increases with concentration and deformation rate. While the normal stress increases with concentration, the die swell decreases. The yield stress in elongation is larger than that in shear, and the maximum strain at break initially increases with addition of filler, goes through a maximum, and falls to very low values at high loading. The orientation of anisometric particles can be accomplished in converging and diverging, i.e., extensional flow. In a simple shear field, the effect depends on the rate, concentration, and matrix viscosity—in general, shearing causes disorientation of aligned particles. All these effects influence melt processing. For extrusion, the plug flow narrows the range of processing variables, increases the solid-conveying zone, and may lead to flow instability. In injection molding, gating, pattern of orientation (modulated by solidification), and the transient effects depend on the specificity of the rheological behavior of the filled pseudoplastic liquids.

Assessment of Leachate Contamination of Groundwater at Some Waste Disposal Sites in the Southern Guinea Savannah Ecological Zone of Nigeria Using Geoelectric Processes

2021 ◽  
Vol 47 (2) ◽  
pp. 383-392
Author(s):  
M.E. Omale ◽  
E.E. Udensi ◽  
J.J. Musa
Keyword(s):  
Ionic Concentration ◽  
Contaminant Plume ◽  
High Concentration ◽  
Current Electrode ◽  
Contaminant Plumes ◽  
Active Structures ◽  
Electrode Separation ◽  
Profile Line ◽  
Potential Electrode ◽  
Electrical Sounding

This study aims at determining the leachate contamination of the groundwater resource at selected domestic wastes disposal sites in Minna, Nigeria for a population about 2.1 million, to locate aquifers and hydraulically active structures by tracing the movement of contaminant plumes and seepages in ground at the selected locations. Resistivity data was collected using a terrameter (SAS4000) while the Vertical Electrical Sounding (VES) mode was deployed using the Schlumberger array to enable investigation of the depth penetration of contaminant plume. The induced polarization (IP) was used to determine the level of contaminant plume. The VES readings measured at 50m intervals along each profile line and 100m inter-profile distance, with a maximum current electrode separation of 200m and potential electrode separation of 30m. There are equal numbers of three and four layers observed on the profile, which has ten VES points. The first layer has a resistivity range between 48.4 Ωm & 428 Ωm and thickness between 0.65m & 3.83m. However, isolated resistivity area such as VES; N5 (287Ωm), N6 (295Ωm) and N8 (428Ωm) also suggested sandy/soil rich in organic matter (humus material/soil). The second and third layer is the fractured basement which has very low resistivity values for most VES (N1–48.5Ωm, N2–38.7Ωm, N3–41.6Ωm, N5–61.5Ωm, N7–49.6Ωm, N8–60.7Ωm, N9–108Ωm and N10–97.6Ωm) that indicated leachate presence and contamination, which results from increased ionic concentration. In conclusion, it was discovered that the study area had high conductivity values for some of the locations using the resitivity determination method. This indicated the presence of water within the study area. It was also concluded that the IP which indicated high concentration of metals caused the lowering of the resisitivity values at some of the locations, thus indicating the presence of metals within the study area.

Ground water quality of selected areas of Punjab and Sind Provinces, Pakistan: Chemical and microbiological aspects

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Ionic Concentration ◽  
Chloride Ions ◽  
Potassium Ions ◽  
Ammonium Ions ◽  
High Concentration ◽  
Phosphate Ions ◽  
Sodium Magnesium ◽  
Very High ◽  
Microbiological Aspects

The assessment of groundwater is essential for the estimation of suitability of water for safe use. An attempt has been made to study the groundwater of selected areas of Punjab (Sheikhupura & Sahiwal) and Sindh (Sindh, Jawar Dharki and Dharki), Pakistan. The results indicate that pH, color and odor were all within limits of WHO that is pH ranges 6.5–8.5, colorless and odorless, respectively. The high values of suspended solids were observed in the Sindh-1 and Dharki samples. Microbiologically only Sahiwal and Jawar Dharki were found fit for drinking purpose. Trace metals analysis of Sheikhupura-1 and Sindh-1 showed that values do not fall within limits of WHO for Iron. The ionic concentration analysis showed that high bicarbonate (HCO3-), ions are present in the samples of Sahiwal and Dharki; Sindh-1 and Jawar Dharki samples showed very high concentration for chloride ions, all samples were satisfactory level for sulphate (SO42-), sodium, magnesium and phosphate ions except samples of Sindh-1 and Jawar Dharki. High concentration of calcium and potassium ions was observed in samples of Sindh-1, while all other samples were found fit for drinking purposes in respect of nitrate, nitrite and ammonium ions. The high concentration of Fluoride was found only in Sheikhupura-2 samples.

Comparative Assessment of Hydrodynamic Models in Slow-Motion Mooring Dynamics

1999 ◽  
Vol 122 (2) ◽  
pp. 109-117 ◽  
Author(s):  
Joa˜o Paulo J. Matsuura ◽  
Kazuo Nishimoto ◽  
Michael M. Bernitsas ◽  
Luis O. Garza-Rios
Keyword(s):  
Parametric Design ◽  
Slow Motion ◽  
Qualitative Behavior ◽  
Nonlinear Stability Analysis ◽  
Hydrodynamic Models ◽  
Steady Current ◽  
Mooring Dynamics ◽  
Ship Hydrodynamic ◽  
Quantitative Properties ◽  
Short Wing

The slow-motion dynamics of a turret mooring system is analyzed and compared for four of the most commonly used ship hydrodynamic maneuvering models. Each of those utilizes a different approach to model and then to calculate or measure the hydrodynamic forces and moment acting on the vessel. The four hydrodynamic maneuvering models are studied first by a physics-based analysis of each model and then by numerically comparing their prediction of equilibria, nonlinear stability analysis, bifurcation sequences, and morphogeneses of turret mooring systems. Catastrophe sets are constructed in two-dimensional parametric design spaces to determine the qualitative behavior of the system, and nonlinear time simulations are used to assess its quantitative properties. Static bifurcations of the principal equilibrium are compared to determine the nature of alternate equilibria. A turret-moored tanker is modeled with anchored catenaries, including nonlinear drag. External excitation is time independent, and for the numerical applications it is limited to steady current. Of the four models used, the Abkowitz and Takashina models show similar qualitative dynamics. The Obokata and Short-Wing models are also qualitatively similar, but very different from the first group. Limited sensitivity analysis pinpoints the source of discrepancy between the two schools of thought. [S0892-7219(00)01401-1]

scholarly journals Hydrogeochemical Characterization and Vulnerability Assessment of Shallow Groundwater in Basement Complex Area, Southwest Nigeria

2018 ◽  
Vol 7 (1) ◽  
pp. 72-103 ◽  
Author(s):  
A.J. Adewumi ◽  
A.Y.B. Anifowose ◽  
F.O. Olabode ◽  
T.A. Laniyan
Keyword(s):  
Major Ions ◽  
Shallow Groundwater ◽  
Mean Value ◽  
Ionic Concentration ◽  
Water Type ◽  
High Concentration ◽  
Drastic Model ◽  
Groundwater Samples ◽  
Southwest Nigeria ◽  
Hydrogeochemical Characterization

Abstract Thirty-five (35) groundwater samples from Owo area were analyzed for physicochemical parameters. Results show that the mean value of pH is 6.32, TDS is 208.92 mg/l, temperature is 28.77°C, EC is 545.16 μs/cm; TH is 111.09 mg/l, SO4 is 71.73 mg/l, Cl is 0.07 mg/l, HCO3 is 14.09 mg/l, Na is 25.06 mg/l, Ca is 37.07 mg/l, K is 24.36 mg/l and Mg is 4.41 mg/l. The results were compared to the WHO and NDSQW standards. All parameters were within the permissible limit except EC in well OW6 and K is above the stipulated standards in 69% of the total samples. The high concentration of K is linked to the use of NPK fertilizer in the area for agricultural purposes. The groundwater belongs to Ca-Na-K-SO4 and Na-Ca-SO4 water type respectively. The ionic concentration in the groundwater is due to the dissolution of the rock that makes up the aquifer. Plagioclase and silicate-bearing rocks are the sources of major ions in the water. SAR, PI, RSBC and KR reveals that groundwater in the area is good for irrigation purpose. DRASTIC model further revealed that groundwater in the area is less vulnerable to contamination under the current environmental conditions.

Electrokinetic Microflow Instability With Conductivity Gradients

2003 ◽  
Author(s):  
Chuan-Hua Chen ◽  
Hao Lin ◽  
Sanjiva K. Lele ◽  
Juan G. Santiago
Keyword(s):  
Electric Field ◽  
Convective Instability ◽  
Flow Instability ◽  
Microfluidic Channels ◽  
Charge Accumulation ◽  
Electrokinetic Flow ◽  
Dc Electric Field ◽  
Bulk Charge ◽  
First Time ◽  
And Diffusion

We have experimentally identified and quantified an electrokinetic flow instability that occurs in DC-electric-field driven microfluidic channels with significant conductivity gradients. We have, for the first time, developed a physical model for this instability which captures the interactions between bulk charge accumulation, electromigration, convection, and diffusion. A linear stability analysis based on this model captures key physics of this convective instability with a threshold electric field. The model and experiments show conductivity gradients and their associated bulk charge accumulation are crucial for such instabilities.

Cytomembrane Preservation in Tissue Dehydrated Only With Glutaraldehyde and Epon 812 Resin

1973 ◽  
Vol 31 ◽  
pp. 320-321
Author(s):  
Daniel C. Pease
Keyword(s):  
Diffraction Pattern ◽  
X Ray Diffraction ◽  
High Concentration ◽  
Unpublished Study ◽  
X Ray ◽  
Sectioned Material

A previous study demonstrated that tissue could be successfully infiltrated with 50% glutaraldehyde, and then subsequently polymerized with urea to create an embedment which retained cytomembrane lipids in sectioned material. As a result, the 180-190 Å periodicity characteristic of fresh, mammalian myelin was preserved in sections, as was a brilliant birefringence, and the capacity to bind OsO4 vapor in the hydrophobic bilayers. An associated (unpublished) study, carried out in co-operation with Drs. C.K. Akers and D.F. Parsons, demonstrated that the high concentration of glutaraldehyde (and urea) did not significantly alter the X-ray diffraction pattern of aldehyde-fixed, myelin. Thus, by itself, 50% glutaraldehyde has little effect upon cytomembrane systems and can be used with confidence for the first stages of dehydration.

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