Electrical Potential Difference Research Articles

Accurate measurement of electric potentials in biased GaAs compound semiconductors by phase-shifting electron holography.

The innate electric potentials in biased p- and n-type GaAs compound semiconductors and the built-in potential were successfully measured with high accuracy and precision by applying in situ phase-shifting electron holography to a wedge-shaped GaAs specimen. A cryo-focused-ion-beam system was used to prepare the 35°-wedge-shaped specimen with smooth surfaces for a precise measurement. The specimen was biased in a transmission electron microscope, and holograms with high-contrast interference fringes were recorded for the phase-shifting method. A clear phase image around the p-n junction was reconstructed even in a thick region (thickness of ~700 nm) at a spatial resolution of 1 nm and precision of 0.01 rad. The innate electric potentials of the unbiased p- and n-type layers were measured to be 12.96 ± 0.17 V and 14.43 ± 0.19 V, respectively. The built-in potential was determined to be 1.48 ± 0.02 V. In addition, the in situ biasing measurement revealed that the measured electric-potential difference between the p and n regions changed by an amount equal to the voltage applied to the specimen, which indicates that all of the external voltage was applied to the p-n junction and that no voltage loss occurred at the other regions.

Calcium phosphate buffer formed in the mitochondrial matrix during preconditioning supports ΔpH formation and ischemic ATP production and prolongs cell survival –A hypothesis

Ischemic preconditioning makes cells less sensitive to oxygen deprivation. A similar effect can be achieved by increasing the calcium concentration and applying potassium channel openers. A hypothetical mechanism of preconditioning is presented. In the mitochondrial matrix, there is a calcium hydroxide buffer consisting of a few insoluble calcium phosphate minerals. During ischemia, calcium ions stored in the matrix buffer start to leak out, forming an electric potential difference, while hydroxyl ions remain in the matrix, maintaining its pH and the matrix volume. Preconditioning factors increase the matrix buffer capacity. Production of ATP during ischemia might be the relic of a pre-endosymbiotic past.

The effect of electrode shape and arrangement on breakup of dielectric liquid jet in electric field

In this study, the behavior of dielectric liquid jet in the presence of electric field was analyzed and the effects of electrode geometry and electric field direction on surface wave frequency, jet breakup, and produced droplet characteristics were investigated. When a dielectric liquid jet flows through an electric field, three types of electric forces can be imposed on the flow field: electrophoretic, dielectrophoretic, and electrostriction forces. Flow of liquid jet in gaseous surrounding is affected by electrophoretic and dielectrophoretic forces. Considering the direction of electrophoretic force, applying the electric field in the direction of jet flow thickens the jet by decelerating the flow; nevertheless, inverse field increases the diameter of jet by accumulation of liquid in the downstream region of electrodes. Dielectrophoretic force does not depend on field direction and always increases the diameter of liquid jet. Results showed that breakup length is shortened by electric field and applying a 6 kV electric potential difference can reduce the upper limit of breakup length by 27% in comparison with non-electrified case. Furthermore, the electric field increases the production of round droplets and decreases the number of irregular and sharp-edged droplets. Increase in electric field strength usually leads to reduction in droplet size. Besides, parallel–triangular electrodes in direct field and star–triangular electrodes in inverse field are more effective in the production of round droplets. Although smallest droplets are produced using star–triangular arrangement, parallel–triangular electrodes can produce droplets with more homogeneity in size distribution.

Combustion of composite Ni–Al fibers

Thermal, structural and emissive characteristics of the combustion of metal composite Ni-Al fibers in an inert and oxidizing media are studied using high-speed video recording, dynamic spectrometry and Langmuirprobe. The measurements have shown that combustion wave propagates at a velocity of 0.15÷0.3 m/s depending on the pressure and composition of gas media and the maximum process temperature is in the range of 2600÷3720 K. The kinetics of combustion is shown to be controlled by capillary mass transfer in metalmelts. The effects of emission of nonequilibrium gas plasma and the spontaneous electric polarization of reaction wave are found, where the difference in electrical potentials of the condensed and gas-dust phases can exceed (2÷3) 103V.

Reducing the negative impact of freezing and thawing cycles on marl by means of the electrokinetical injection of calcium chloride

The purpose of this study was to compensate the negative impact of freezing and thawing cycles on marly soil by means of electrokinetical injection of calcium chloride as a remediation method. Therefore, firstly, the effect of concentration of CaCl2 solution, voltage gradient, and electrokinetic remediation time on the marl improvement was assessed. The electrokinetic remediation tests were conducted for nine different testing scenarios. As the improvement verification criteria, the unconfined compressive strength (UCS), electric potential difference, and drainage were measured. After performing the electrokinetic remediation test, three sets of UCS samples were taken from around anode, cathode, and the in-between. Instantly after that, the UCS of the first set was measured so that the improvement effect might be determined. Afterwards, one and four cycles of freezing and thawing were applied to the second and third sets of samples, respectively, and the UCS loss was measured. After four cycles of freeze-thaw, the concentration of 1.1 kg/lit, i.e. 1.1 kg of CaCl2 powder was dissolved in 1 lit of distilled water, and remediation period of 4 days for all locations in the sample, and the voltage gradient of 2 V/cm near anode and 1 V/cm near cathode and the in-between areas resulted into the highest UCS. It should be mentioned that in all test scenarios, the samples after four freeze-thaw cycles still had an acceptable value of UCS, whilst the natural marl samples provided for the study were demolished only under a small load after one freeze-thaw cycle. Micro-structural analysis was also performed based on XRD and SEM methods and it affirmed the occurrence of chemical modification and the change of the particles into flocculated particles and consequently the improvement of marl after electrokinetic remediation.

Determination of potassium hydrogen phthalate purity by coulometric titration system: Validation study and uncertainty estimation

This paper describes the Coulometry system implemented at National Metrology Institute (NMI) of Colombia for purity certification of potassium hydrogen phthalate (KHP). The system aims to become a primary measurement system. This study includes an evaluation of precision in terms of relative standard deviation (%RSD), and its associated uncertainty by repeatability and end-point detection such as type-A uncertainty; And by electric resistance, time, potential difference and sample mass such as type-B uncertainty sources. The implementation of this system will allow the certification in purity of different reference materials.

Electrically-responsive deformation of polyelectrolyte complex (PEC) fibrous membrane

This study aims at the effect of electro-osmotic flow on a fibrous membrane comprised of assembled oppositely-charged polyelectrolytes and submerged in aqueous ionic solution. As electric field is applied across an edge-clamped circular membrane, it deforms under the action of a transverse force, the origin of which is in focus. Fibers were electrospun from a blend of poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA). A model is presented, which explains and describes the membrane deformation in terms of the ionic strength and pH level of the solution, the membrane geometry and porosity, the ζ-potential and elastic modulus of the membrane, as well as the applied cross-membrane electric potential difference. The model is corroborated by a set of experiments. The dependence of the membrane deformation on the electric potential was found to be rather weak, while the elastic modulus was found to be strongly dependent on the solution pH.

In vitro Methods for the Development and Analysis of Human Primary Airway Epithelia.

Cystic fibrosis (CF) is a chronic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, which encodes for a channel expressed at the apical surface of epithelial tissues. Defective chloride and bicarbonate secretion, arising from CFTR mutations, cause a multi-organ disease. In the airways, impaired ion transport results in a thick mucus, dehydration of the periciliar region and bacterial infections. Over the last years, basic research has sustained a great effort to identify therapies that are able to correct defective CFTR. For this purpose, in vitro cell models have played a key role in the study of mechanisms of the disease and to assess CFTR modulator therapies. Cultures of human primary bronchial epithelia are considered a physiologically relevant disease model due to their ability to maintain most of the morphological and functional characteristics of the airway epithelium in vivo. Despite their value, these cells are limited by the availability of human lung tissue and by the complexity of the culture procedure. However, primary human nasal cells can be considered as an alternative model for the study of CF pathophysiology since they are easier to obtain and recapitulate the properties of bronchial cultures. Over the years, several groups have optimized a protocol with key steps to culture and fully amplify differentiated primary airway epithelia. Our approach provides epithelia monolayers grown on porous filters, characterized by high transepithelial electrical resistance and an electrical potential difference. These parameters are required to perform electrophysiological experiments devoted to the study of ion transport mechanisms in airway epithelia. The aim of this study was to describe different methods to expand and differentiate isolated cells into fully polarized monolayers of airway epithelium, in order to provide an optimized protocol to support physiopathology analysis and to evaluate therapeutic strategies.

Structures of voltage-gated sodium channels

Ion Channels In “excitable” cells, like neurons and muscle cells, a difference in electrical potential is used to transmit signals across the cell membrane. This difference is regulated by opening or closing ion channels in the cell membrane. For example, mutations in human voltage-gated sodium (Nav) channels are associated with disorders such as chronic pain, epilepsy, and cardiac arrhythmia. Pan et al. report the high-resolution structure of a human Nav channel, and Shen et al. report the structures of an insect Nav channel bound to the toxins that cause pufferfish and shellfish poisoning in humans. Together, the structures give insight into the molecular basis of sodium ion permeation and provide a path toward structure-based drug discovery. Science , this issue p. [eaau2486][1], p. [eaau2596][2] [1]: /lookup/doi/10.1126/science.aau2486 [2]: /lookup/doi/10.1126/science.aau2596

Numerical Simulation of a Two-Phase Flow for the Acrylonitrile Electrolytic Adiponitrile Process in a Vertical/Horizontal Electrolysis Cell

This paper investigated the effect of oxygen holdup on the current density distribution over the electrode of a vertical/horizontal electrolysis cell with a two-dimensional Eulerian–Eulerian two-phase flow model in the acrylonitrile (AN) electrolytic adiponitrile (ADN) process. The physical models consisted of a vertical/horizontal electrolysis cell 10 mm wide and 600 mm long. The electrical potential difference between the anode and cathode was fixed at 5 V, which corresponded to a uniform current density j = 0.4 A/cm2 without any bubbles released from the electrodes. The effects of different inlet electrolyte velocities (vin = 0.4, 0.6, 1.0 and 1.5 m/s) on the void fraction and the current density distributions were discussed in detail. It is shown that, for a given applied voltage, as the electrolyte velocity is increased, the gas diffusion layer thickness decreased and this resulted in the decrease of the gas void fraction and increase of the corresponding current density; for a given velocity, the current density for a vertical cell was higher than that for a horizontal cell. Furthermore, assuming the release of uniform mass flux for the oxygen results in overestimation of the total gas accumulation mass flow rate by 2.8% and 5.8% and it will also result in underestimation of the current density by 0.3% and 2.4% for a vertical cell and a horizontal cell, respectively. The results of this study can provide useful information for the design of an ADN electrolysis cell.

Enhanced voltage generation through electrolyte flow on liquid-filled surfaces

The generation of electrical voltage through the flow of an electrolyte over a charged surface may be used for energy transduction. Here, we show that enhanced electrical potential differences (i.e., streaming potential) may be obtained through the flow of salt water on liquid-filled surfaces that are infiltrated with a lower dielectric constant liquid, such as oil, to harness electrolyte slip and associated surface charge. A record-high figure of merit, in terms of the voltage generated per unit applied pressure, of 0.043 mV Pa−1 is obtained through the use of the liquid-filled surfaces. In comparison with air-filled surfaces, the figure of merit associated with the liquid-filled surface increases by a factor of 1.4. These results lay the basis for innovative surface charge engineering methodology for the study of electrokinetic phenomena at the microscale, with possible application in new electrical power sources.

Electromagnetic flow rate measurement in molten tin circulating in a closed-loop test system

Flow rate measurement in molten metals at elevated temperatures is still a challenging task in metallurgie application. Due to the opaqueness and chemical aggressiveness of such melts, non-contact and non-invasive electromagnetic methods are of special interest. In order to develop and to test such methods under controllable laboratory conditions, during the last years at TU Ilmenau we have built up and instrumented the test facility TINTELO (tin test loop). TINTELO is a closed loop facility made of stainless steel in which molten tin at a temperature up to 350°C circulates in the horizontal plane. The flow is driven by an electromagnetic pump based on rotating permanent magnets. The rotation frequency of the pump can be fixed at up to 60 Hz providing a mass flow rate of 17.5 kg/s which corresponds to a Reynolds number of Re = 2·105. TINTELO is instrumented with both a Lorentz force flowmeter and a wall potential flowmeter. The Lorentz force flowmeter measures the force which the electrical conducting moving molten tin exerts on a system of permanent magnets arranged outside of the loop. This force is the counter force to the well-known braking Lorentz force that is proportional to the melt flow rate. Moreover, the wall potential flowmeter records the electric potential difference between two electrodes inserted in the conducting wall of the loop. This potential difference, induced by the moving melt when interacting with an externally applied magnetic field, is proportional to melt velocity. In this paper we present the design and the instrumentation of TINTELO, the calibration methods for the used flowmeters and first results of the flow rate test measurements.

Removal of Hazardous Cationic Salt Pollutants During Electrochemical Treatment from Contaminated Mixed Heterogeneous Saline Soil

Salt-affected soils are found mainly in arid and semiarid regions. In these areas, weak precipitation rate causes salt accumulation at high level on the soil surfaces, leading to drastic modifications in soil properties, affecting hence the environment, human health and civil engineering infrastructure and facilities. This research aimed to study the performance of the electrochemical treatment on removal of hazardous cationic salt including sodium, potassium and magnesium cations. The novelty of this work lies in the investigation of the potential of electroosmosis phenomenon as a driving vector in the removal of cationic hazardous salt during its regularized path toward the cathodic area. Therefore, a controlled-permanent analysis of contaminated catholyte water over processing time was achieved, in order to understand the evolution of contaminant removal during treatment time via the electroosmosis process. For this purpose, five relevant indices were evaluated, including electric current, electroosmotic flow, pH, electrical conductivity and cationic hazardous salt removal efficiency. Experimental tests were conducted in laboratory-designed cell using different electric potential difference for a total period of 8 days. Owing to the electroosmosis phenomenon, salt contaminants migrated and accumulated in the catholyte chamber, facilitating thereby their removal. Among these contaminants, sodium and potassium exhibit the highest decontamination efficiency with a rate of 88 and 85%, respectively. Magnesium ions show moderate removal with a percentage of 53%, due to the pH gradient, degree of hydration, ionic valence and mobility. The results demonstrate that the electrochemical treatment may be an efficient method for remediation of saline low-permeable heterogeneous soils.

Elasticity solution of the bending of beams with the flexoelectric and piezoelectric effects

This paper studies the bending behavior of a nanosclae elastic beam with flexoelectric and piezoelectric effects. Based on a two-dimensional theory of piezoelectricity and flexoelectricity, an exact elasticity solution is derived when applied transverse mechanical loading and/or electric potential difference between the top and bottom surfaces are prescribed. Obtained results may apply to not only pure piezoelectric beams without flexoelectricity only if setting all flexoelectric coefficients to zero but also beams of isotropic material with flexoelectricity only if setting all piezoelectric coefficients to zero. The solution can be taken as a benchmark solution of related models of beams as actuators, generators, etc. The influences of piezoelectricity and flexoelectricity on the transverse deflection, stress distribution and electric polarization are analyzed. Flexoelectricity plays a crucial role in altering bending deflection, electric polarization for a single homogeneous simply supported beam. The deflection and electric polarization of a beam with both piezoelectric and flexoelectric effects are not the sum of the corresponding ones of a purely piezoelectric beam and a purely flexoelectric beam.

Compelling Rejuvenated Catalytic Performance in Metallic Glasses.

Metallic glasses (MGs) with the metastable nature and random atomic packing structure have attracted large attention in the catalytic family due to their superior catalytic performance. In contrast, their crystalline counterparts are restricted by the highly ordered packing structure, fewer surface active sites, and crystallographic defects for catalytic activity. The uncertainty of the different catalytic mechanisms and the intrinsic characteristics correlated to MGs and their crystalline counterparts become a major impediment to promote their catalytic efficiencies and widespread applications. Herein, it is reported that the excellent catalytic behavior in Fe-based MGs goes through a detrimental effect with the partial crystallization, but receives a compelling rejuvenation in the full crystallization. Further investigation reveals that multiphase intermetallics with electric potential differences in fully crystallized alloys facilitate the formation of galvanic cells. More importantly, extensively reduced grain boundaries due to grain growth greatly weaken electron trapping and promote inner electron transportation. The relatively homogenous grain-boundary corrosion in the intermetallics contributes to well-separated phases after reaction, leading to refreshment of the surface active sites, thereby quickly activating hydrogen peroxide and rapidly degrading organic pollutants. The exploration of catalytic mechanisms in the crystalline counterparts of MGs provides significant insights into revolutionize novel catalysts.

Multifunctional polyaniline hybrid nanofiber with YVO4 (Er2%;Yb8%)

We synthesized electrospun nanofibers based on polyaniline (PAni) and orthovanadate from Yttrium co-doped with Erbium and Ytterbium [YVO4 (Er2%, Yb8%)]. We evaluated the association of the electrical and thermal properties of PAni with the upconversion (UC) effect due to the orthovanadate. We characterized the material by UV–Vis Spectroscopy, Fourier transform infrared (FTIR), Impedance Spectroscopy and Photoluminescence. Initially, we obtained polyaniline by emulsion polymerization in presence of surfactant, sodium dodecyl sulfate, yttrium orthovanadate and polyvinyl alcohol, resulting in a homogeneous dark green color solution. When we subjected the solution to a 14 kV constant electric potential difference applied between a 12 mm diameter needle (cathode) and a collecting plate (anode) 12 cm apart, the material deposited in the form of fibers. SEM results show that these fibers presented an average diameter of (89 ± 40) nm. On the other hand, when excited with radiation of wavelength λ = 980 nm (2.5 W) the material emitted radiation in the visible region with characteristic peaks at 525, 543 and 553 nm. The emission of intense green light is characteristic of UC effect. Due to photothermal characteristic of PAni the sample was heated, reaching temperatures close to 100 °C without suffering degradation. Measurements of photoluminescence showed that when exposed to HCl vapor, the material presented an increase of almost 100% in the intensity of light emitted in the UC effect, as well as a reduction of its electrical impedance from the order of GΩ to 900 KΩ, in a reversible process. These results are suggestive that these composite fibers appear as a promising active material for the sensing of acid vapors.

Effects of dielectric particles on non-oxidative coupling of methane in a dielectric barrier discharge plasma reactor

A dielectric barrier discharge (DBD) plasma reactor was employed for non-oxidative coupling of methane. The coupling reaction in the DBD plasma bed was conducted near atmospheric pressure and room temperature. In the bed, dielectric materials such as ordered mesoporous silica (KIT-6), sea sand silica, and α-Al2O3 were employed. This non-catalytic reaction system could successfully activate CH bond to produce methyl radicals and light hydrocarbons without additional thermal energy and oxidant molecules. The gap distance between dielectric particles was determined by their sizes, which was experimentally shown. The effects of gap distance were found significant on the conversion and the selectivity. The existence of maximum conversion at a specific gap distance was experimentally observed and could be described successfully by using a newly developed concept of micro-electrodes. Based on the concept, the minimum threshold electric potential difference between the dielectric particles could be successfully estimated, where the conversion was shown to be maximized. Furthermore, it seemed quite possible to control the compositions of ethane, ethylene, and acetylene by properly adjusting the size or the gap distance of particles.

Structure of the human voltage-gated sodium channel Nav1.4 in complex with β1.

Voltage-gated sodium (Nav) channels, which are responsible for action potential generation, are implicated in many human diseases. Despite decades of rigorous characterization, the lack of a structure of any human Nav channel has hampered mechanistic understanding. Here, we report the cryo-electron microscopy structure of the human Nav1.4-β1 complex at 3.2-Å resolution. Accurate model building was made for the pore domain, the voltage-sensing domains, and the β1 subunit, providing insight into the molecular basis for Na+ permeation and kinetic asymmetry of the four repeats. Structural analysis of reported functional residues and disease mutations corroborates an allosteric blocking mechanism for fast inactivation of Nav channels. The structure provides a path toward mechanistic investigation of Nav channels and drug discovery for Nav channelopathies.

Electromotive Force versus Electrical Potential Difference: Approaching (but Not Yet at) Equilibrium

One of the most elusive concepts in electrochemistry is that of electromotive force (EMF). Often students, and even instructors, mistakenly take it as “electric potential difference” (EPD) or “voltage difference”. To clarify this issue properly, here we demonstrate an activity that was conducted with readily available and inexpensive resources. We employ the widely known Daniell Cell slightly modified to meet our need of measuring EMF and EPD. The key of the demonstration is to connect to the cell a potentiometer, which is an element that provides a controllable variable resistance. When the slider of the potentiometer is set to the maximum resistance, only negligible charge circulates, which brings the system to a partial equilibrium at which the potential annotated is exactly equivalent to the electromotive force. This is equivalent to opening the circuit of the cell. Upon turning the slider toward lower resistances, charge circulates with the electromotive force no longer measurable because the electro...

Aplikasi Geolistrik pada Pemetaan Daerah Intrusi Air Laut di Pantai Candidasa

To know the magnitude of sea water intrusion that occurred in Candidasa area need to be mapping by using Geo-electric Method. Geo-electric method is one Geophysical method that works by injecting an electric current into the ground and then measured the potential difference it generates. Based on the data of electric current and potential difference, resistivity will be obtained in the research area. The result of sea water intrusion mapping in Candi Dasa beach area indicates that sea water intrusion has occurred but not yet on the status of conspiracy. If groundwater extraction is not restricted, the level of intrusion will continue to increase. Contour resistivity indicates that there has been a sea water intrusion in the Candidasa Tourism Area in a mild status in the southeast area at a depth of 5-10 m. The measured rock resistivity values in the study sites ranged from 0.35 to 1800 ohm.m, the seawater intrusion criteria occurred at a resistivity of 0.5 - 30 ohm.m. The results of the study are expected to give policyholders input on sea water intrusion in Candidasa Tourism area so that appropriate policy steps can be taken.