Electric Potential Patterns Research Articles

Oscillatory phenomena in electrophysiological networks: The coupling between cell bioelectricity and transcription

Morphogenetic regulation during embryogenesis and regeneration rely on information transfer and coordination between different regions. Here, we explore theoretically the coupling between bioelectrical and transcriptional oscillations at the individual cell and multicellular levels. The simulations, based on a set of ion channels and intercellular gap junctions, show that bioelectrical and transcriptional waves can electrophysiologically couple distant regions of a model network in phase and antiphase oscillatory states that include synchronization phenomena. In this way, different multicellular regionalizations can be encoded by cell potentials that oscillate between depolarized and polarized states, thus allowing a spatio-temporal coding. Because the electric potential patterns characteristic of development and regeneration are correlated with the spatial distributions of signaling ions and molecules, bioelectricity can act as a template for slow biochemical signals following a hierarchy of experimental times. In particular, bioelectrical gradients that couple cell potentials to transcription rates give to each single cell a rough idea of its location in the multicellular ensemble, thus controlling local differentiation processes that switch on and off crucial parts of the genome.

Thermal-damage effects on fracturing evolution of granite under compression-shear loading

Shear-dominant instability disasters in high-temperature conditions pose a significant challenge for deep underground rock projects, necessitating a thorough understanding of rock fracture evolution and the impacts of thermal damage. To investigate how thermal damage influences shear fracturing behavior and geophysical responses, experiments were conducted on thermally-treated granite under compression-shear loading conditions. The detailed failure process was meticulously monitored using integrated acoustic emission (AE), electric potential (EP), and digital image correlation (DIC) techniques. The effects of thermal treatment on the patterns of AEs, EPs, and DIC strain fields during the loading process were analyzed. Micromechanics related to the influence of thermal treatment on mechanical properties and geophysical responses were explored using X-ray diffraction (XRD) and scanning electron microscopy (SEM). By defining damage variables through multiparameter analysis using AE, EP, and DIC, the study delved into predictive insights on the failure process of thermal-damage granite. The results indicate that the physical properties of granite undergo significant changes as the treatment temperature increases, with the peak stress gradually decreasing and the plastic characteristics increasing. These changes can be attributed to thermal damage, which causes internal water escape, expansion of mineral particles, and crack formation. Additionally, increasing the thermal treatment temperature leads to a decrease in both AE and EP intensity, as well as a reduction in the occurrence of high-magnitude AE events, while the cumulative AE count rapidly increases during the plastic stage. Notably, thermal treatment induces significant alterations in mineral composition, intergranular fractures, and the formation of a gradual zigzag crack path, resulting in the intensified development of shear microcracks. This observation is supported by the varying of AE characteristic parameter AF/RA and the analysis of DIC displacement decomposition. Moreover, the three defined damage variables exhibit accelerated growth prior to catastrophic failure, with the order of precursor occurrence observed as AE, DIC, and EP. However, the occurrence of the precursor time for these three geophysical signals becomes earlier with increasing treatment temperature. These research findings shed light on the mechanism of compression-shear failure of thermal-damage rock and provide valuable references for predicting precursors of the shear-dominant instability disasters such as induced earthquakes.

Correcting instructive electric potential patterns in multicellular systems: External actions and endogenous processes

BackgroundTransmembrane electrical potential differences in cells modulate the spatio-temporal distribution of signaling ions and molecules that are instructive for downstream signaling pathways in multicellular systems. The local coupling between bioelectricity and protein transcription patterns allows dynamic subsystems (modules) of cells that share the same bioelectrical state to show similar biochemical downstream processes. MethodsWe simulate theoretically how the integration-segregation pattern formed by the different multicellular modules that define a biosystem can be controlled by multicellular potentials. To this end, we couple together the model equations of the bioelectrical network to those of the genetic network. ResultsThe coupling provided by the intercellular junctions and the external microenvironment allows the restoration of the target bioelectrical pattern by changing the transcription rate of specific ion channels, the post-translational blocking of these channels, and changes in the environmental ionic concentrations. ConclusionsThe simulations show that the single-cell feedback between bioelectrical and transcriptional processes, together with the coupling provided by the intercellular junctions and the environment, can correct large-scale patterns by means of suitable external actions. General significanceThis study provides a theoretical advancement in the understanding of how the multicellular bioelectric coupling may guide repolarizing interventions for regenerating a tissue, with potential implications in biomedicine.

Metallurgical manipulation of surface Volta potential in bimetals and cell response of human mesenchymal stem cells

Bioelectricity plays an overriding role in directing cell migration, proliferation, differentiation etc. Tailoring the electro-extracellular environment through metallurgical manipulation could modulate the surrounding cell behaviors. In this study, different electric potential patterns, in terms of Volta potential distribution and gradient, were created on the metallic surface as an electric microenvironment, and their effects on adherent human mesenchymal stem cells were investigated. Periodically and randomly distributed Volta potential pattern, respectively, were generated on the surface through spark plasma sintering of two alternatively stacked dissimilar metals films and of a mixture of metallic powders. Actin cytoskeleton staining demonstrated that the Volta potential pattern strongly affected cell attachment and deformation. The cytoskeletons of cells were observed to elongate along the Volta potential gradient and across the border of adjacent regions with higher and lower potentials. Moreover, the steepest potential gradient resulting from the drastic compositional changes on the periodic borders gave rise to the strongest osteogenic tendency among all the samples. This study suggests that tailoring the Volta potential distribution and gradient of metallic biomaterials via metallurgical manipulation is a promising approach to activate surrounding cells, providing an extra degree of freedom for designing desirable bone-repairing metallic implants.

Interhemispheric Asymmetry of the Thermospheric Neutral Density Response to the 7–9 September 2017 Geomagnetic Storms

AbstractThe thermospheric neutral density response to the 7–9 September 2017 storms is investigated based on the Swarm satellite observations and the thermosphere‐ionosphere‐electrodynamic general circulation model (TIEGCM) simulation. The Swarm data depicted a prominent interhemispheric asymmetry (IHA) in the afternoon sector during the second storm, a feature that was yet explained. Driven by realistic high‐latitude electric potential and electron precipitation patterns, the TIEGCM is able to reproduce the observed storm‐time neutral density response. The TIEGCM simulation reveals that the differences in the traveling atmospheric disturbances (TADs) is largely responsible for the observed IHA in the neutral mass density response at low and middle latitudes, whereas the difference in mean molecular mass between the two hemispheres may contribute to the IHA in neutral density at higher latitudes. The IHAs in TADs and mean molecular mass are attributed to the IHA in Joule heating dissipation on the night and dawn sides.

The Hazard of Electric Field Increment in the Damaged Silicon-Rubber and Porcelain Insulators

In power transmission lines, it is necessary to isolate the inherent voltage parts from each other and from zero potential. An insulator is defined as having a high degree of electrical insulation between the conductors and the brackets. Insulators also allow for mechanical conductivity of the conductor and ground. The presence of a broken insulator can alter the stress distribution. In this paper, the effect of mechanical insulation cracking (chattering) on electric field in two common types of insulators (porcelain and silicone rubber) and electric potential distribution models are analyzed. First, the electric field and electric potential patterns in the solid insulator are examined. In the following, the insulator is assumed to be broken, and the electric field and electric potential patterns for a broken insulator relative to the basic insulator shape are illustrated and compared. The results show that the presence of insulation cracking under dry and environmentally benign conditions affects the stress distribution pattern within and around the insulator. Finally, a comparison between the effect of fracture on the electric field and the potential distribution patterns in different parts of the insulator is discussed in detail.

Low- and Mid-Latitude Ionospheric Response to the 2013 St. Patrick’s Day Geomagnetic Storm in the American Sector: Global Ionosphere Thermosphere Model Simulation

In this study, the low-and mid-latitude ionospheric response to the main phase of the 2013 St. Patrick’s Day geomagnetic storm in the American sector on the dayside has been investigated using the ground-based measurements and the Global Ionosphere Thermosphere Model (GITM). First, it is found that the observed ionospheric response can be well reproduced by GITM when it is driven by the electric potential and electron precipitation patterns derived from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) technique. The AMIE-driven GITM simulation also significantly improves the data-model comparison as compared with the simulation driven by the high-latitude empirical models. Second, it is found that the transport process associated with the neutral wind is largely responsible for the observed ionospheric response. Specifically, the traveling atmospheric disturbances (TADs) propagating from the opposite hemisphere play an important role in the formation of the negative storm phase at low and middle latitudes. Third, it is found that the asymmetric negative storm phases occurred at the nominal equatorial ionization anomaly (EIA) peak region in the afternoon sector are mainly attributed to the interaction of the TADs launched in different hemispheres with different phase speeds. Specifically, stronger Joule heating deposited in the northern hemisphere (NH) generates TADs with faster phase speeds than those launched in the southern hemisphere (SH). Consequently, the locations where the TADs originated from the different hemispheres interact are asymmetric about the geomagnetic equator, leading to the formation of asymmetric ionospheric negative storm phases. This study highlights the importance of accurately specifying high-latitude electrodynamic forcings in global I-T simulations and provides a new insight into the cause of the interhemispheric asymmetry phenomena during geomagnetic storms.

Analysis of electro-osmotic flow by lattice Boltzmann simulation and Helmholtz-Smoluchowski formula

Numerical study of electro-osmotic flow (EOF) and theoretical exploration of relationship between EOF and electrical double layer (EDL) are carried out in the present work. Under the Poisson-Boltzmann and Debye-Hückel approximations, the analytic solution of electric potential, net charge, and flow pattern can be derived. The numerical results obtained by Poisson-Nernst-Planck (PNP) and Navier-Stokes equations are compared with the analytic solution and the solution based on the Helmholtz-Smoluchowski formula. Also, this article provides a clearer view on nondimensionalization applied on lattice Boltzmann method with different differential equation.

The numerical analysis on the variation of electric potential, electric current and Lorentz force with its influence on buoyancy-driven conjugate heat transfer and fluid flow using OpenFOAM

The development of electric potential, electric current and Lorentz force in the presence of the magnetic field in the fluid/solid domain is studied numerically. Moreover, the significance of the magnetic field and its orientation on the pattern of electric potential, electric current and the direction of the Lorentz force is observed in the enclosure. The buoyancy-driven conjugate heat transfer and fluid flow solver with Magnetohydrodynamics (MHD) is developed in open source CFD tool OpenFOAM. The buoyancy force in the enclosure is altered by varying the Rayleigh number of Ra = 104, 105, 106, at the fixed Prandtl number of Pr = 0.02. The magnetic field is imposed in the x-direction (Bx) and y-direction (By) measured by Hartmann number of Ha = 0–100. The conjugate thermal and electromagnetic coupling is considered for the fluid-wall interface in the present analysis and includes the wall thickness within the computational domain. The orientation of the magnetic field shows the asymmetric (for Bx) and symmetric pattern (for By) of an electric potential distribution in the enclosure, and hence electric current. The detailed analysis of temperature iso-surface, isotherms, streamlines, and Nusselt number variations, etc in the presence of magnetic field are discussed in detail.

Abstract 1933: Tissue print Vmem imaging: Visualizing bioelectric signatures in cancer

Abstract Work in models of embryonic development shows that membrane voltage, or resting potential (Vmem), regulates cell behaviors that are disrupted in cancer, including proliferation, migration, apoptosis, homeostasis, and cell-cell signaling. Normal cells and tissues maintain stereotypical patterns of Vmem and these patterns are recognizable in Vmem Imaging as bioelectric signatures. In embryonic tissues, cells that are relatively undifferentiated are usually less negative (depolarized) than fully differentiated cells, and different cell lineages have characteristic bioelectric signatures. Recently, the development of innovative imaging technologies using Voltage Sensitive Dyes (VSDs) allows the visualization of Vmem in living cells and tissues. In culture, Vmem Imaging using VSDs can readily differentiate between sister breast cancer cell lines of low and high metastatic potential (EpH4 and EpH4.2, respectively). Although the cultures are identical in bright field images, Vmem Imaging shows a dramatically more heterogeneous bioelectric signature for EpH4.2 than for EpH4 cells, consistent with reduced gap junctional communication. One of the challenges of Vmem Imaging has been the limited thickness of tissue that can be analyzed using the VSDs (about 50 microns). To overcome this limitation, we have combined innovative Tissue Print technologies with Vmem Imaging in order to visualize patterns of electric potential in living cancer cells obtained from human surgical specimens. Tissue Prints are touch preps that transfer a thin layer of viable cells to a nitrocellulose membrane as an oriented imprint; biomarkers identified on these tissues prints can be mapped back to the source tissue to establish pathology and gene expression correlations. Tissue Print Vmem Imaging of radical prostatectomy specimens shows differentiation of bioelectric signatures between cancer and adjacent benign tissue and between cancer of different grades (Gleason pattern 3 and pattern 4). Such differences in bioelectric signatures represent unexplored cancer phenotypes that are made accessible by Tissue Print Vmem Imaging technologies. Citation Format: Dany S. Adams, Brian H. Tracey, Larry Takiff, James Kearns, Stephen P. Naber, Sandra M. Gaston. Tissue print Vmem imaging: Visualizing bioelectric signatures in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1933.

SuperDARN Evidence for Convection‐Driven Lagrangian Coherent Structures in the Polar Ionosphere

AbstractPolar cap patches are large sporadic enhancements of plasma density on the scale of hundreds of kilometers, which can impact the performance of Global Navigation Satellite Systems. Lagrangian Coherent Structures (LCSs) are ridges that show areas of maximal separation in a time‐evolving flow. Previous work based on modeled ionospheric flow showed that LCSs exist in the ionosphere and are barriers governing patch formation. In this work, we identify the first data‐driven LCSs in the high‐latitude ionosphere using Super Dual Auroral Radar Network (SuperDARN) ion convection fields. The LCSs found using the Ionosphere‐Thermosphere Algorithm for LCSs are compared during geomagnetically quiet and active periods. The shape of the LCS is found to be dependent on the electric potential pattern. A consistent two‐cell pattern results in a W‐shaped LCS, but when the two‐cell pattern breaks down, the LCS loses this characteristic shape. The changes in the electric potential, and thus the LCS, are likely due to changes in the interplanetary magnetic field. A comparison between LCSs obtained from empirical models and data reveal that the data‐driven LCSs are poleward of and have a shorter longitudinal span than the model‐based LCSs. A comparison of the LCS location and the formation of a polar cap patch on 17 March 2015 showed that the center of the patch developed from plasma on the main LCS ridge, and this is confirmed with a separate polar cap patch event from 26 September 2011.

Thermal analysis and electro-elastic response of multilayered spherical vessels

A striking correlation of control aims with temperature variation and mechanical deflections promotes the use of smart materials in structural health monitoring applications of laminated structures. To maintain the whole structure in a consistent situation, performing its desired function, and to remove the thermal stresses and degradation associated with the operational circumstances, the assembled smart counterparts should be considered. In this study we explore the transient characteristics of laminated spherical vessels made of functionally graded materials (FGMs) with piezoelectric substrates exposed to mechanical, electrical, and thermal shocks. The material properties of the pyroelectric media are constant, and the host shell is made of isotropic and FGMs, of which the material properties, encompassing thermal and mechanical agents, are assumed to be graded through the thickness. In light of the energy balance among different sub-layers, it is plausible to reconsider the design of the system aiming at extension of the operational life of the constituent materials. In the context of transient analysis, the direct and converse piezoelectric effects and the operational evaluation of the FG vessels are semi-analytically scrutinized in order to present the dynamic perturbations in the corresponding elements. Qualitative patterns of stresses, electric potential, and temperature graphs for different material parameters are calculated and presented graphically in order to clarify the effect of the grading index of material properties, electric and thermal motivations, and geometry of the laminated shell. The data acquired from the proposed concept not only display the behavior of the FG host shell subjected to judiciously varied working conditions, but also can skillfully predict the sensory and actuatory outputs of the embedded smart layers, presenting a highly efficient tool for structural health monitoring and damage detection.

Challenges associated with near‐Earth nightside current

AbstractEvery magnetic field of solar and planetary space environments is associated with a current of differentially flowing charged particles. Electric potential patterns in geospace and near other planets are also closely linked with currents. Close to the Earth, particularly in the near‐Earth nightside magnetosphere, several current systems wax and wane during periods of space weather activity. The velocity‐dependent drift, energization, and loss processes in this region complicate current system evolution. There is a discrepancy about the magnitude, timing, and location of these currents, however, and this Commentary pitches the case for a concerted community effort to resolve this issue.

Comparison study of ring current simulations with and without bubble injections

AbstractFor many years, stand‐alone ring current models have been successfully producing storm time ring current enhancements without specifying explicit localized transient injections along their outer boundaries. However, both observations and simulations have suggested that the frequent burst flows or bubble injections can contribute substantially to the storm time ring current energy. In this paper, we investigate the difference in the spatial and temporal development of the ring current distribution with and without bubble injections using the Rice Convection Model‐Equilibrium. The comparison study indicates that the simulation with bubble effects smoothed out along geosynchronous orbit can predict approximately the same large‐scale ring current pressure distribution and electric potential pattern as the simulation with bubble effects included. Our results suggest that the increase of the hot plasma population along geosynchronous orbit can be envisaged as an integrated effect of bubble injections from the near‐Earth plasma sheet. However, the observed fluctuations in the plasma population and electric field can only be captured when the mesoscale injections are included in the simulation. We also confirmed again that adiabatic convection of fully populated flux tubes cannot inject the ring current from the middle plasma sheet. The paper provides a justification for using stand‐alone ring current models in the inner magnetosphere to simulate magnetic storms, without explicit consideration of bubbles and magnetic buoyancy effects inside geosynchronous orbit.

Cation-induced EHD流れに及ぼす電圧印加パターンの影響

Cation-induced EHD流れに及ぼす電圧印加パターンの影響

Electroosmotic flow of a power-law fluid through an asymmetrical slit microchannel with gradually varying wall shape and wall potential

• Non-parallel electroosmotic flow of power-law fluid in a microchannel. • Lubrication theory for slowly varying channel height and wall potential. • Linear superposition of forces invalidated by asymmetry of channel. • Nonlinear interaction between wall undulation and wall charge modulation. • Flow-rate sensitive to phase shift of wall patterns and power-law index. This study aims to investigate electroosmotic flow of a power-law fluid through a slit channel with walls asymmetrically patterned with periodic variations in shape and zeta potential. On taking into account the near-wall depletion layer, the present problem is simplified on the basis of the lubrication approximation, and through the use of the Helmholtz–Smoluchowski slip boundary condition. Nonlinear equations are to be solved for two unknown functions of axial dependence, one being the induced pressure gradient, and another being an undetermined stress component. An efficient numerical scheme is devised in this work to solve the nonlinear problem. Results are generated to check whether the principle of linear superposition of forces, for electrokinetic flow of a non-Newtonian fluid in the presence of a Newtonian depletion layer, is still applicable to flow in an asymmetric channel. It is also found that phase shifts between the geometrical and electric potential patterns on the two walls may lead to qualitatively disparate effects, depending on the power-law behavior index of the fluid and the applied pressure gradient.

The influence of IMF clock angle timescales on the morphology of ionospheric convection

AbstractWe exploit a database of high‐latitude ionospheric electric potential patterns, derived from radar observations of plasma convection in the Northern Hemisphere from the years 2000–2006, to investigate the timescales of interplanetary magnetic field (IMF) control of ionospheric convection and associated magnetospheric dynamics. We parameterize the convection observations by IMF clock angle, θ (the angle between geocentric solar magnetic (GSM) north and the projection of the IMF vector onto the GSM Y‐Z plane), and by an IMF timescale, τB (the length of time that a similar clock angle has been maintained prior to the convection observations being made). We find that the nature of the ionospheric convection changes with IMF clock angle, as expected from previous time‐averaged studies, and that for τB∼30 min, the convection patterns closely resemble their time‐averaged counterparts. However, as τB increases we find that the convection evolves away from the time‐averaged patterns to reveal modified characteristic flow features. We discuss these findings in terms of solar wind‐magnetosphere‐ionosphere coupling and consider their implications for understanding the time‐dependent nature of magnetospheric dynamics.

Analytical model of light-emitting diode with patterned contact

In this paper we develop an analytical model for the light-emitting diode (LED) with the metal p-contact patterned as an array of thin strips. The model is based on conformal mapping approach and accounts for the overlapped fringing electric fields created by the adjacent strips. We derive analytical expressions for the electric potential, current injected into the LED active region and power of light extracted via the openings in the pattern. Spatial distribution of electric potential and LED radiation pattern are calculated. Further investigations are necessary to elucidate the contribution of the side walls of the strips on the LED output performance.

Creation of a Human Head Phantom for Testing of Electroencephalography Equipment and Techniques

We have designed and fabricated an anatomically accurate human head phantom that is capable of generating realistic electric scalp potential patterns. This phantom was developed for performance evaluation of new electroencephalography (EEG) caps, hardware, and measurement techniques that are designed for environments high in electromagnetic and mechanical noise. The phantom was fabricated using conductive composite materials that mimic the electrical and mechanical properties of scalp, skull, and brain. The phantom prototype was calibrated and testing was conducted using a 32-electrode EEG cap. Test results show that the phantom is able to generate diverse scalp potential patterns using a finite number of dipole antennas internal to the phantom. This phantom design could provide a valuable test platform for wearable EEG technology.

Ionospheric and thermospheric variations associated with prompt penetration electric fields

This paper presents a comprehensive modeling investigation of ionospheric and thermospheric variations during a prompt penetration electric field (PPEF) event that took place on 9 November 2004, using the Thermosphere‐Ionosphere‐Mesosphere Electrodynamic General Circulation Model (TIMEGCM). The simulation results reveal complex latitudinal and longitudinal/local‐time variations in vertical ion drift in the middle‐ and low‐latitude regions owing to the competing influences of electric fields and neutral winds. It is found that electric fields are the dominant driver of vertical ion drift at the magnetic equator; at midlatitudes, however, vertical ion drift driven by disturbance meridional winds exceeds that driven by electric fields. The temporal evolution of the UT‐latitude electron density profile from the simulation depicts clearly a super‐fountain effect caused by the PPEF, including the initial slow‐rise of the equatorial F‐layer peak height, the split of the F‐layer peak density, and the subsequent downward diffusion of the density peaks along magnetic field lines. Correspondingly, low‐latitude total electron content (TEC) becomes bifurcated around the magnetic equator. The O/N2column density ratio, on the other hand, shows very little variations during this PPEF event, excluding composition change as a potential mechanism for the TEC variations. By using realistic, time‐dependent, high‐latitude electric potential and auroral precipitation patterns to drive the TIMEGCM, the model is able to successfully reproduce the large vertical ion drift of ∼120 m/s over the Jicamarca incoherent radar (IS) in Peru, which is the largest daytime ion drift ever recorded by the radar. The simulation results are validated with several key observations from IS radars, ground GPS‐TEC network, and the TIMED‐GUVI O/N2column density ratio. The model‐data intercomparison also reveals some deficiencies in the TIMEGCM, particularly the limitations imposed by its upper boundary height as well as the prescribed O+ flux.