Electrode Separation Research Articles

Improving Deep Sensitivity of Four-Electrode Focused Impedance Method In Lungs by Varying Electrode Geometries

Bio-Electrical impedance is of special interest in the detection and diagnosis of lung problems, particularly in the low and medium income countries. An age old simple technique employing four electrodes is known as ‘Tetra Polar Impedance Measurement (TPIM)’ but it cannot localize a particular zone of interest region. A new technique named as ‘Focused Impedance Method (FIM)’ was innovated by a Dhaka University group which gives high sensitivity in a localized zone of interest. Previously FIM was used from one side of the thorax which gave a rather limited information from the lungs, from shallow depths only. In order to get information from deeper regions of the lungs a new configuration of electrodes for FIM was proposed by the same group at Dhaka University which placed two electrodes at the front and two electrodes at the back of the thorax in a horizontal plane. It is expected that the degree of depth sensitivity would depend on electrode separation on both the sides. The electrode width may also have an effect. In order to study these quantitatively, COMSOL Multiphysics software was used to simulate the measurements in a rounded rectangular volume to represent a typical thorax, which was filled with isotonic saline. Electrode separations of 5cm, 10cm, 15cm and 20cm were studied while electrode widths studied were 0.15cm, 1cm and 3cm. The work supported the proposed new configuration of electrodes for FIM in that this method gives enhanced sensitivity throughout the depths of a lung and that for a thorax with a cross section of 33cm26cm, an electrode separation between 10cm and 15cm would give optimum results. For electrode width, the ones studied did not give any significant difference, however, the smallest (0.15cm) one appeared to give slightly better results.
 Bangladesh Journal of Medical Physics Vol.15 No.1 2022 P 43-54

Assembly of electric double-layer capacitors with hardwood kraft lignin-based electrodes and separator together with ionic liquid electrolyte

Abstract This study aimed to assemble a high-performance electric double-layer capacitor (EDLC) using a hardwood kraft lignin (HKL)-based separator and HKL-based electrodes, which were fabricated from a nonwoven mat of electrospun HKL fibers. The separator was prepared by the thermostabilization of the mat derived from a mixed dope of HKL, hexamethylenetetramine, and polyethylene glycol (1.66/0.50/0.09, w/w) for electrospinning. Although a mat-type HKL-based electrode containing conductive carbon black (CB) has been reported to be suitable for a commercial cellulosic separator, this electrode was found to be unsuitable for the HKL-based separator because of its rough surface and poor contact with the separator interface. Hence, a powder-type electrode with a smooth surface was fabricated by grinding the mat, followed by casting with a carboxymethyl cellulose aqueous solution, and its EDLC possessed high energy (49 Wh kg−1) and power densities (151 kW kg−1). Moreover, to provide a simple process for electrode fabrication, another mat-type electrode was fabricated by adding CB to the mixed dope, followed by electrospinning, carbonization, and steam activation. The resultant EDLC exhibited excellent electrochemical performance with energy (58 Wh kg−1) and power densities (55 kW kg−1).

Flame detection via active plasma probing

Combustion diagnostics of highly diluted air fuel mixtures are of great importance for reducing the carbon footprint of various types of combustion systems. Flame detection techniques, such as ion sensing and optical diagnostics, have been reported for diagnosing combustion status. In this paper, a flame front detection technique based on active plasma probing is introduced and analyzed. Unlike the conventional ion sensing used in internal combustion engines, a separate electrode gap is used to detect the flame front arrival. Further, the voltage potential across the electrodes of the spark plug probe is modulated actively to be slightly below the breakdown threshold prior to flame arrival. At the arrival of the flame front, the ions in the flame tend to decrease the breakdown voltage threshold and trigger a breakdown event. An optically accessible constant volume combustion vessel is employed to investigate the efficacy of such active plasma probing for the detection of the flame front under quiescent and flow conditions. Three types of fuels are used in the tests, including methane, propane, and DME, with an air fuel ratio sweep (from stoichiometric to extremely lean) for each fuel. Efforts are made to characterize the probing criteria of minimum, yet adequate voltage to succeed in the detection of the arrival and departure of the flame front most sensitively and reliably, for all three types of fuels under various mixture strengths. For comparison, conventional ion current measurements are conducted under identical background conditions to benchmark the efficacy of flame detection. Results show that the active plasma probing can promptly detect the arrival and departure of the flame front, robustly regardless of the fuel type and excess air ratios. The precise control of the detecting voltage is key for reliable flame detection with high sensitivity.

Statistical analysis and optimization of fuel cells using the design of experiment

Evidently, paper-based microfluidic devices, including fuel cells, have been proven to power low-power integrated miniaturized devices. However, the harvested energy depends on various design parameters, positioning and other ancillary factors. Herein, design of experiment is used to make a boisterous study of the data used in paper-based microfluidic fuel cell and to make various optimizations and studies of the raw data used in the microbial fuel cell paper. The paper-based microfluidic fuel cell was analysed for two different positioning, horizontal and vertical, and the maximum power outputs were noted. A statistical technique based on full factorial design was used to study the performance of paper-based microfluidic fuel cell. In the microbial fuel cell, a rigorous study was conducted pertaining to the electrode separation, channel variation and absorbent pad stability. In both these cases, the analysis of mean, analysis of variance, signal-to-noise ratio and desirability study were performed. For the paper-based microfluidic fuel cell, the best desirability values for the horizontal and vertical arrangements were measured to be 0.8842 and 0.92768, respectively. For the microbial fuel cell, in the case of 2 mm electrode separation, the present analysis of variance model came out to be significant. Inclusively, this work provides a pathway to realize optimum paper-based microfluidic fuel cell, and such study can be extrapolated to develop other microfluidic devices.

Effects of DC Polarity and Field Uniformity on Breakdown of SF₆ and C₃F₇CN/CO₂ Mixture

To address the issues of greenhouse gases and resultant global warming, there is an urgency to find an electronegative gas to replace SF6 in global power system networks. This article provides an experimental study of various factors on DC breakdown of electronegative gases. Rod-plane geometries with a range of rod diameters (3.5–12.5 mm) and electrode separations (5–55 mm) are used to provide different degrees of field uniformity. SF6 and a 20% C3F7CN / 80% CO2 mixture are tested under pressures ranging between 1 and 5 bar. Breakdown voltages (BDVs) under both polarities rise linearly with gap distance in quasi-uniform fields with the positive being higher. Increasingly nonuniform fields lead to saturation in the case of positive BDV, while in the negative polarity case, the BDV increases linearly. As a result, the two polarities’ BDV magnitudes crossover as field nonuniformity increases. The value at which the negative value exceeds the positive is dependent on the field uniformity, pressure, and gas medium. A simulation based on the streamer criterion model provides a good agreement with experimental results for positive DC breakdown in the range of 2–5 bar. In terms of the insulation characteristics, 20% C3F7CN / 80% CO2 could provide a valuable alternative to SF6 in high-voltage plant for outdoor applications in hot-climate countries and indoor applications in cold-climate countries.

Bio-Physical Modeling of Galvanic Human Body Communication in Electro-Quasistatic Regime.

Human Body Communication (HBC) is an alternative to radio wave-based Wireless Body Area Network (WBAN) because of its wide bandwidth leading to enhanced energy efficiency. Designing Modern HBC devices need the accurate electrical equivalent of the HBC channel for energy efficient communication. The objective of this paper is to present an improved lumped element-based detailed model of Galvanic HBC channel which can be used to explain the dependency of the channel behaviour on the internal body dependent parameters such as electrical properties of skin and muscle tissue layers along with the external parameters such as electrode size, electrode separation, geometrical position of the electrodes and return-path or parasitic capacitances. The model considers the frequency-dependent impedance of skin and muscle tissue layers and the effect of various coupling capacitances between the body and Tx/Rx electrodes to the Earth-Ground. A 2D planar structure of skin and muscle tissue layers is simulated using a Finite Element Method (FEM) tool to prove the validity of the proposed model. The effect of symmetry and asymmetry at the transmitter and receiver ends is also explained using the model. The model become very useful for fast calculation of Galvanic channel response without using any FEM tool. Experimental results show that the galvanic response is not only a function of channel length but also depends on the mismatch at the transmitter and receiver end. In case of a very high mismatch scenario, the channel behavior is dominated by the capacitive HBC, even for a galvanic excitation and termination.

MoS2/NiVFe crystalline/amorphous heterostructure induced electronic modulation for efficient neutral-alkaline hydrogen evolution

MoS2 is attractive for electrocatalytic hydrogen evolution reaction (HER) as an inexpensive transition metal-based electrocatalyst, however, its catalytic performance within a wide pH range is still challenging. Herein, NiVFe layered double hydroxide (LDH) modified MoS2 (MoS2/NiVFe) is developed by a two-step hydrothermal method to form a crystal-amorphous heterostrctural electrocatalyst. The crystal-amorphous heterostrcture is demonstrated to provide a large electrochemically active surface area to enhance the active sites and expedite the electron transfer. More importantly, a strong electronic modulation effect is revealed by XPS and theoretical calculations that electrons in NiVFe-LDH transfer to MoS2, which results in high-valent Ni-site to attract -OH and electron-rich S-site to adsorb -H, significantly reducing the barriers of water splitting. As a result, at 10 mA cm−2 in alkaline and neutral media, the MoS2/NiVFe electrocatalyst exhibits low overpotentials for HER of 78 and 141 mV, respectively. A remarkable activity towards OER is also achieved accompanied with an impressive stability. When applied as both electrodes for overall water separation, it only needs a low cell voltage of 1.47 V for MoS2/NiVFe to provide a current density of 10 mA cm−2 in 1.0 M KOH. This study provides an efficient method for designing MoS2-based electrocatalysts for HER within a broad pH range.

Photovoltaic system DC series arc fault: a case study

<p>Photovoltaic (PV) systems are becoming increasingly popular; however, arc faults on the direct current (DC) side are becoming more widespread as a result of the effects of aging as well as the trend toward higher DC voltage levels, posing severe risk to human safety and system stability. The parallel arc faults present higher level of current as compared with the series arc faults, making it more difficult to spot the series arc. In this paper and for the aim of condition monitoring, the features of a DC series arc fault are analyzed by analysing the arc features, performing model’s simulation in PSCAD, and carrying out experimental studies. Various arc models are simulated and investigated; for low current arcs, the heuristic model is used where a set of parameters established. Moreover, the heuristic model’s simulated arc has been shown to be compatible with the experimental data. The features of arc noise in the electrode separation region and steady-arcing states with varied gap widths are investigated. It has been discovered that after an arc fault occurs, arc noise increases, notably in the frequency range below 50 kHz; where this property is useful for detecting DC series arc faults. Besides that, variations in air gap width are more sensitive to frequencies under 5 kHz.</p>

Voltage–Current Characteristic of Free Burning Arcs in SF₆ Alternative Gas Mixtures

Voltage–current characteristics of free burning arcs in SF6 and air have been known for decades. As the demand for an SF6-free solution is increasing, there is an accompanying need to determine arc parameters in the alternative gases. An unblown arc experiment has been established to determine the voltage–current characteristics of SF6 alternative gases, which have not yet been thoroughly studied. In this experiment, free burning arc measurements were performed in a number of gases under consideration of SF6 alternatives, including CO2 and mixtures of CO2/O2 with and without C4F7N or C5F10O additives at the concentrations of up to 10 %. Measurements were also performed in air and SF6 for comparison. Arc voltage was measured in each gas at pressures ranging from 1- to 5-bar absolute, and electrode separations ranging from 20 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$95 \mathrm {~mm}$ </tex-math></inline-formula> . Voltage–current characteristic measurements for air and SF6 show good agreement with previously published results. A linear relationship of the arc voltage to the arc length is shown as well as the fourth root dependence of the arc voltage on the gas pressure. It was shown that neither the O2 nor the fluorinated additives to CO2 have any significant influence on the voltage–current characteristic. The minimum arc voltage in all measured gases was slightly higher than in SF6, but the arc in SF6 was the least stable and had the highest elongations resulting in high-voltage peaks. The arc voltage in air had a similar minimum value to the CO2-based gases, but the arc was much more stable, resulting in lower effective voltage, especially at low currents.

Removal of Organic Pollutants Via Electrochemical Oxidation Near Anodes During Electrokinetic Remediation: Proof of Concept

This study designed a practical approach of separating electrodes chambers to prove the influence of electrochemical oxidation on pyrene removal during electrokinetic (EK) remediation. The anode and cathode electrodes were arranged in two independent soil chambers, and the soil chambers were connected by salt bridges. Salt bridges electrokinetic (SBEK) remediation avoided acid–base neutralization and facilitated the intensity of the current. The results showed that 99.5% of pyrene was removed within 7 days in anodic chamber. The removal rate of pyrene was ∼99.6–99.9% at SBEK1 anode and 29.5–36.2% at SBEK1 cathode after 42 days. The changes in current, pH, and redox potential values indicated that an efficient “oxidizer” was formed in the anode chamber. Compared with conventional EK remediation, SBEK can take place under a suitable oxidizing condition because of increasing current intensity and decreasing soil pH in the anode chamber. Furthermore, SBEK with electrode polarity reversal test had better decontamination efficiency of pyrene than fixed electrodes. Removal rate of pyrene increased to 62.9% after 14 days with polarity reversal; correspondingly, the energy consumption of SBEK test was ∼13 times higher than that of the conventional EK test. The novel application of separated electrodes chambers appears to be a viable strategy for removing organic pollutants.

Mechanically Tuned Thermopower of Single‐Molecule Junctions

AbstractIn this paper, the tuning of the thermopower with single‐molecule junctions of fullerene (C60), 4,4′‐bipyridine (BPY), and p‐phenylenediamine (PPD) using scanning tunneling microscopy (STM)‐based break junction technique is demonstrated. Single‐molecule junctions are prepared in a nanogap between a Au‐STM tip and a Au(111) electrode. Upon applying a temperature difference across the junction, a thermoelectric voltage is generated across it. By mechanically controlling the tip–electrode separation distance, the thermoelectric voltage of the junction is tuned. The absolute value of the thermopower decreases with decreasing tip–electrode separation distance for BPY and PPD, while it increases for C60. Atomistic simulations of the junction illustrate how this arises from shifts in the conduction orbital energies induced by the mechanical compression of the junctions.

Investigation of Pt/Fe-N-C Hybrids Towards ORR in Acidic Environment

Polymer electrolyte membrane fuel cells (PEMFCs) are recognized as one of the renewable energy sources in portable, automobile, and stationary applications. Currently, both low temperature (LT) and high temperature (HT) PEMFCs use platinum group metal (PGM) based catalysts for oxygen reduction reaction (ORR) containing usually Pt nanoparticles on carbon black. To reduce the total cost of PEMFC stack, worldwide researchers have considerable attention to find an inexpensive alternative catalyst. Recently, metal-nitrogen-carbon (M-N-C) compounds such as Fe-N-Cs are the most promising PGM-free catalysts for ORR. However, they suffer from insufficient volumetric activity and electrochemical stability in PEMFCs. [1,2] Xiao et al. have proven an improved electrochemical stability of Pt-Fe-N-C electrocatalysts consisting of atomically dispersed Pt and Fe atoms or Pt-Fe alloy nanoparticles in comparison with Fe-N-C only. [3] Mechler et al. have reported that the addition of 1-2 wt.% Pt in hybrid Pt/Fe-N-C catalyst performs well with an increased stability in LT-PEMFCs. [4] Liao et al. have recently shown better ORR activity of Pt/Fe-N-C than Pt/C. [5] With the overriding goal of reducing LT- and HT-PEMFC production costs, Pt/Fe-N-C activity, selectivity and stability with systematically reducing the Pt-content has not been investigated yet. In this study, Pt/Fe-N-C hybrids are synthesized using PMF-011904 from Pajarito Powder (USA) as catalyst support and wet-chemically precipitated Pt nanoparticles with targeted Pt-contents of 40, 5, 1 and 0 wt.%. First, ICP mass spectrometry is used for Pt quantification along all catalysts, and transmission electron microscopy is carried out to investigate morphology and Pt nanoparticle diameter and distribution on the Fe-N-C catalyst. Second, ORR activity and selectivity is investigated by rotating ring disc electrode (RRDE) experiments in 0.1 mol L-1 HClO4, and electrochemical surface area of Pt is calculated by hydrogen underpotential deposition and CO stripping voltammetry. Last, accelerated stress testing (AST) is performed with 5,000 triangle potential cycles between 0.6–1.5 VRHE to evaluate the catalyst stability. Figure 1 shows the initial ORR curves during the RRDE experiments. The mass activities of 40, 5 and 1 wt.% Pt/Fe-N-C determined at 0.9 VRHE are 222.5 ± 41.2 A gPt -1, 170.8 ± 80.4 A gPt -1 and 49.0 ± 8.6 A gPt -1, respectively. Thus, the mass activity depends on Pt-content in the hybrid catalyst strongly. In addition, the other electrochemical characterization results are also going to be discussed in terms of catalyst selectivity, stability and the correlation with morphological aspects during the presentation. Figure 1 ORR curves in O2-saturated 0.1 mol L-1 HClO4 electrolyte with rotation speed of 1,600 rpm and scan rate of 5 mV s-1 (averaged results of three separate electrodes per each catalyst).[1] Y. He, S. Liu, C. Priest, Q.Shi , G. Wu, Chem. Soc. Rev. 2020, 11, 3484–3524.[2] T. Reshetenko, A. Serov, M. Odgaard, G. Randolf, L. Osmieri, A. Kulikovsky, Electrochem. Commun. 2020, 118, 106795.[3] F. Xiao, G.-L. Xu, C.-J. Sun, I. Hwang, M. Xu, H.-W. Wu, Z. Wei, X. Pan, K. Amine, M. Shao, Nano Energy 2020, 77, 10592.[4] A. K. Mechler, N. R. Sahraie, V. Armel, A. Zitolo, M. T. Sougrati, J. N. Schwämmlein, D. J. Jones, F. Jaouen, J. Electrochem. Soc. 2018, 165, F1084.[5] W. Liao, S. Zhou, Z. Wang, F. Liu, H. Pan, T. Xie, Q. Wang, ChemCatChem 2021, 13, 23, 4925-4930. Figure 1

A Study on the Cathode Materials Recovery Process Using Various Wet Chemistry

Demand for lithium-ion batteries (LIBs) has increased dramatically over the years due to the rapid market expansion of electric vehicles. Current commercial lithium ion batteries mainly contain nickel, cobalt, manganese metal oxides, lithium, phosphates, aluminum, copper, graphite, organic electrolytes and other chemicals. Therefore, the recycling and reuse of used lithium-ion batteries at the end of their useful life are of great interest by many researchers. However, due to the high energy density, high safety and low price of lithium-ion batteries, the difference and variety are large, which poses great difficulties in recycling waste lithium-ion batteries. Lithium ion batteries recycling typically involves both physical and chemical processes. Physical processes typically include pretreatment and direct recovery of electrode materials. These processes typically include decomposition, crushing, screening, magnetic separation, washing, heat treatment, etc. As shown in Figure 1, chemical processes can generally be divided into pyrometallurgical and hydrometallurgical processes which include leaching, separation, extraction and chemical/electrochemical precipitation. Recently, recycling technologies for lithium secondary batteries through a direct regeneration process have been attracting attention. Directly regeneration technique has the advantages of short recovery route, low energy consumption, eco-friendly compared to pyrometallurgical and hydrometallurgical processes. In order to recover the cathode active material from the separated electrode plate, a process for separating the PVDF binder and the cathode active material is required. In general, N-methyl-2-pyrrolidone (NMP) is the most common solvent for the manufacture of cathode electrodes in the battery industry. Although ~99% of the solvent used in electrode manufacturing is recovered, it is however limited in several countries due to negative environmental impacts.In this study, the cathode materials were separated electrode from used lithium ion cell using various wet-chemistry. Chemical, structural, and electrochemical characteristics of the cathode materials and substrate were investigated. Figure 1

Enhanced ammonia-rich solution production and electrode separation using magnetic nickel-loaded carbon black in flow-electrode electrochemical deionization (FEED)

Carbon materials with abundant micropores and large specific capacitance (e.g., activated carbon, AC) are usually considered to be ideal candidates for flow-electrode capacitive deionization and are now widely employed to the ammonia recovery from wastewater. However, the microporous structure endows AC with a strong adsorption capacity toward ammonia nitrogen, which greatly reduces the recovery efficiency (the storage of ammonia nitrogen in the electrolyte). In this study, magnetic nickel-loaded carbon black (Ni0-CB) particles were simply synthesized by impregnating Ni onto the surface of the carbon black (CB) particles, endowing no <50 % of electrical energy savings and increasing ammonia recovery efficiency by ~20 % in comparison to AC. When charging, Na+ and NH4+ were migrated to the cathode, with the conversion of NH4+ into NH3 was accelerated due to the higher pH of Ni-CB systems. The excellent electrical conductivity of the CB body and compensation of the conductivity of Ni greatly decreased the electrical energy consumption. Followed by reverse discharge, Na+ and less NH4+ would be turned back into the spacer chamber; the adsorption toward NH3 was effectively reduced due to the abundant mesopores of CB. Thus, NH3 was more likely to be retained in the electrolyte. In addition, the superior magnetic features of Ni-CBs realized the rapid separation of the CB and ammonia-rich solution. The introduction of magnetic Ni-CB in flow-electrode electrochemical deionization technology realized the improved ammonia-rich solution production from wastewater and the recycling of carbon particles without additional solid–liquid separation (i.e., filtration, settlement).

Radiative flow of nanofluid past a convected vertical Riga plate with activation energy and nonlinear heat generation

This article presents an analysis of the radiative flow of nanofluid past a convected vertical Riga plate with activation energy and nonlinear heat generation. A Riga plate is a surface-mounted electromagnetic actuator with a spanwise aligned array of alternating electrodes and permanent magnets. The aforementioned rheological model is formulated in the way of the nonlinear partial differential equations (PDEs). The system of nonlinear coupled ordinary differential equations (ODEs) is obtained from the modeled nonlinear PDEs by incorporating valid similarity transformations. The system of ODEs is then figured out by the reliable shooting method. The effects of mixed convection, modified Hartmann number, Biot number, thermophoresis, Eckert number, reaction rate, the width of magnets and electrodes, and Lewis and Prandtl numbers on the velocity, temperature, and concentration profiles are investigated graphically and numerically. It is found that the speed of the fluid can be managed with the separation of magnets and electrodes. Further, the concentration of nanofluid is significantly enhanced in the presence of activation energy. Also, the nonlinear exponential index parameter of heat generation declines the temperature of the fluid. Further, it is found that in the presence of thermal radiation, viscous dissipation, and nonlinear heat generation, the Nusselt number increases averagely by about 11.3%.

Comparison of Positive Electrode Separation by Electrical Pulsed Discharge in Underwater and Air Environments

This study presents a novel method to separate positive electrode active materials (PEAMs) and aluminum (Al) foil from positive electrodes (PEs) to enable more effective recycling processes. A pulsed current was applied to a PE sample that was prepared by manual dismantlement of spent lithium-ion batteries (LiBs). Joule heating caused the temperature of the Al foil to increase to be above the melting points of adhesion included in the PEAMs. The influence of the surrounding medium of the PE sample on the delamination phenomenon was investigated. PEAMs were peeled from the Al foil in water and air environments. High-speed visible imaging was employed to discuss separation processes. Differences in the size of the separated PEAMs and the amount of residual PEAM on the surface of the Al foil occurred due to the influence of the medium filled in the voids inside the PEAM layer.

Normal pacing function with normal impedance trends despite evident lead fracture in an implantable defibrillator – What is the mechanism?

A 63-year-old lady with a high-grade atrioventricular (AV) block and a structurally normal heart underwent permanent pacemaker implantation (dual chamber, Medtronic Ltd) 8 years back. On follow up, she had a recurrence of syncope after 3 years. The device interrogation at that time had revealed ventricular tachycardia (VT) for which she underwent implantable cardioverter defibrillator (ICD, Medtronic Ltd, Egida DR, DF1) upgradation at another center (electrograms not available). Now, she presents with episodes of presyncope after another 5 years. The Echocardiography was unremarkable. The ICD was interrogated & there was a stored ventricular fibrillation (VF) episode. But the electrograms suggested noise over a true VF electrogram noted in both near and far-field. In all probability, the VF was not a true one which might have arisen from some lead noise or from an electromagnetic interference (EMI). Fluoroscopy revealed an evident lead fracture near the superior vena cava (SVC) coil. The stored electrogram (EGM) characteristics also suggested possible lead noise rather than a true VF. She was advised for lead revision. Interestingly, all pacing parameters were normal along with normal impedance despite the evident lead fracture. This happened due to the ICD lead arrangements as there are separate electrodes for the SVC/RV coil and pacing. While the SVC coil was damaged, the pacing electrodes remained unaffected. Since the patient has no episode of true VT/NSVT and the echocardiography was normal, she was managed temporarily by changing the pacemaker to asynchronous (DOO) mode.

A kinetic-mechanistic study of cyanide degradation which can be contained in mining tailings dams using a divided electrolytic cell

Cyanidation is considered the most employed process to recover precious metals such as silver and gold. However, cyanide containing wastes can be hazardous for the environment. Therefore, the soil electroremediation technique was systematically studied to eliminate/degrade the cyanide contained in mining tailing dams using an electrolytic cell with cationic separator and cheap-stable carbon electrodes. The extent and kinetics of cyanide degradation was firstly analyzed in synthetic solutions using the electrolytic cell at different current density, ionic conductivity, and cyanide concentration. The electrolytic system was also evaluated for the treatment of a sample obtained from a mining tailing dam containing cyanide. The results revealed that 100 % of cyanide can be degraded from synthetic solutions containing 200 ppm CN– at 60 A/m2, 0.25 M NaOH and room temperature. It was also found that 100 % of cyanide can be degraded from the real samples obtained from a Mexican mining tailing dam. The kinetic analysis revealed that cyanide degradation can occur through two pathways: a) in the case of tests containing 500 and 800 ppm NaCN, the rate determining step of the cyanide degradation to cyanate species follows a first order reaction with respect to the cyanide ions, and b) when the tests are carried out with 200 ppm NaCN, the same first order reaction controls the process kinetics from 0 to 30 min, while at t > 60 min, the rate determining step for cyanide degradation is modified and limited by the occurrence of parasite reactions. The proposed mechanism for cyanide degradation is also consistent with the thermodynamic calculations. The results also revealed that complete cyanide electro-degradation can be achieved with a current efficiency of 100 %.

Optimization of electrode excitation in a microfluidic bio-cell sorter with trapezoidal electrodes for blood cell separation

Blood cell separation from bio-samples is an important task in health diagnosis and more challenges lies when cells of smaller size or cells with same size but different types need to be isolated. Integration of microelectrodes in the microchannel of microfluidic devices is an interesting method to produce non-uniform electric field which can be utilized for separating the biological cells. This paper presents computational analysis and simulations for separation of blood cells in a microfluidic device design with rectangular and trapezoidal electrodes array (TEA) to interrogate influence of focusing on separation trajectories of the red blood cells (RBCs) and platelets (PLTs). The effect of electrode voltage for focusing and separation is investigated. Efficient separation can be achieved by either low focusing-low separation (LF-LS) or high focusing-high separation (HF-HS) electrode voltages. The proposed microfluidic chip design can pave path to development of efficient blood cell separation device with less complicated fabrication steps.

Geology and Correlative Analysis of Borehole Logs with Geo-electric Sections of Some Parts of Ibadan, Southwestern Nigeria

The property of rocks varies from one geological location to another or even disappears laterally, and these properties are important factors in determining groundwater quantity. This makes this research work focused on the correlative analysis of lithologies and borehole logs with geo-electric sections in the basement terrain of Ibadan, southwestern Nigeria, using Borehole logging and geophysical electrical method. Twenty-two vertical electrical sounding stations and borehole Logsare acquired within the study area with a maximum Schlumberger electrode separation of 100m. The data are interpreted qualitatively and quantitatively by partial curve matching and computer iteration to obtain the first-order geo-electric model parameters. The results of the geo-electric investigation reveal some lithological Layers such as topsoil, clay, weathered laterite basement, and fresh basement. At the same time, those from boreholes include topsoil, loamy soil, friable brown soil, clayey-sand, sandy-clay, laterite weathered basement/saprolite, and Fresh Basement. Electrical resistivity and borehole logs correlation revealed: poor, poor-moderate and moderate-perfect correlations based on a comparison between the number of lithological layers encountered from both vertical electrical sounding derived lithology and those from borehole and depth of occurrence. The depth of water struck grouped into three 0 - 45 m, 45 - 70 m, and 50 - 100 m to bring out the most favourable depth of aquifer potential while three yields categories 0.5-2 lt/s; 2 - 4lt/s and 4 -12 lt/s are observed with the above depth classification respectively. Good yielding fractures increase with depth in the quartzite regions but decrease with depth in both gneisses and the schist rock bodies. The correlations between geo-electric sections and borehole logs have shown that the geoelectric section obtained from the vertical electric section cannot totally be substituted for borehole logging but can serve as alternative means of classifying the sub-surface lithologies in the absence of borehole logging.