Electric Potential Gradient Research Articles

Bacterial proton motive force as an unprecedented target to control antimicrobial resistance.

Novel antibacterial therapies are urgently required to tackle the increasing number of multidrug-resistantpathogens. Identification of new antimicrobial targets is critical to avoid possible cross-resistance issues. Bacterial proton motive force (PMF), an energetic pathway located on the bacterial membrane, crucially regulates various biological possesses such as adenosine triphosphatesynthesis, active transport of molecules, and rotation of bacterial flagella. Nevertheless, the potential of bacterial PMF as an antibacterial target remains largely unexplored. The PMF generally comprises electric potential (ΔΨ) and transmembrane proton gradient (ΔpH). In this review, we present an overview of bacterial PMF, including its functions and characterizations, highlighting the representative antimicrobial agents that specifically target either ΔΨ or ΔpH. At the same time, we also discuss the adjuvant potential of bacterial PMF-targeting compounds. Lastly, we highlight the value of PMF disruptors in preventing the transmission of antibiotic resistance genes.These findings suggest that bacterial PMF represents an unprecedented target, providing a comprehensive approach to controlling antimicrobial resistance.

Results of Long-Term Observations of the Electric Field of the Atmosphere During the Eruption of Volcano Ebeko in the Period 2018‒2020

In order to study the processes of formation of Volume charges in the eruptive clouds of the eruptions of the Ebeko volcano in the period 2018‒2020, observations of the atmospheric electric potential gradient in the city of Severo-Kurilsk were carried out. 179 cases were recorded when the propagation of an eruptive cloud occurred in cloudless or low-cloud conditions and was accompanied by a response in variations of the atmospheric electric potential gradient. Four types of responses in variations of the potential gradient of the electric field of the atmosphere are revealed, it is shown that the type of recorded response is determined by the conditions of propagation of the eruptive cloud relative to the point of registration, and also determined by the relative location of the lower and upper regions of the eruptive cloud at the time of registration of the response. At the same time, the negative volume charge prevails in the eruptive cloud, which is localized in the upper region of the eruptive cloud, the positive volume charge is localized in the lower region. The data of field observations are consistent with the results of numerical modeling.

Electrokinetic Remediation for Textile Wastewater Contaminated Soil

<p>Soil contamination due to industrial activities is very common and discharging of partially treated or untreated textile wastewater into nearby environment in developing countries contaminated soils. The remediation of textile wastewater contaminated soils containing residual organic dyes and inorganic salts is risky. It is required to identify an economic and eco-friendly in-situ remediation technique for the textile wastewater contaminated soil. This paper investigates the effective removal of residual textile dyes and inorganic salts from the soil using electrokinetic remediation. Laboratory scale acrylic reactors were utilized and the soil was collected from the contaminated agricultural site. The experiment was optimized for different electrode combination (Iron-iron, Iron-stainless steel, Iron-aluminium, Iron-graphite), electrode distance (3 cm, 5.5 cm, and 10.5 cm) and electrical potential gradient (3V/cm, 4V/cm, and 5V/cm). Tap water was used as electrolytes in order to prevent further contamination during remediation process. An electroosmotic flow of 256 mL was observed at cathode reservoir for Iron-graphite electrodes and these electrodes removed 93% electrical conductivity and 82% of total organic carbon from soil. It is found that electroosmosis is the dominant mechanism by which residual textile dyes were removed. The proposed remediation technique is found efficient, economic and eco-friendly compared to the existing technologies.</p>

Lightning stroke rates, atmospheric electric potential gradient data, and Schumann resonance data corresponding to the eruption of the Hunga Tonga - Hunga Ha'apai volcano on January 15, 2022

Lightning stroke rates, atmospheric electric potential gradient data, and Schumann resonance data corresponding to the eruption of the Hunga Tonga - Hunga Ha'apai volcano on January 15, 2022

Nanopores as versatile single-molecule tools: From DNA turbines to protein sequencing.

Nanopores offer ample opportunities for studying single biomolecules. I will present some recent examples of nanopore research from my lab: (1) DNA origami turbines powered by nanoscale flow. We demonstrated driven rotary motion of a nanoscale DNA origami turbine which harnesses energy from a water/ion flow generated by a static chemical or electrical potential gradient in a solid-state nanopore. Sustained unidirectional rotary motion of up to 20 revolutions/s were observed. These artificial nano-engines operate autonomously in physiological conditions, converting energy into useful mechanical work. (2) Nanopore-based sequential reading of peptides. We demonstrated a nanopore-based single-molecule peptide reader capable of reliably detecting single amino-acid substitutions within individual peptides. A peptide is linked to a DNA molecule and sequentially pulled through a biological nanopore by a DNA helicase in single amino-acid steps. Stepping ion-current signals enable discrimination of single-amino-acid substitutions in single reads. Notably, we demonstrated the capability to ‘rewind’ peptide reads, obtaining indefinitely many independent reads of the same molecule, yielding an undetectably low read errors. Recently, we expanded this concept to discriminating single post-translational modifications within peptides of mixed charge. These proof-of-concept experiments constitute a promising basis for the development of a single-molecule protein sequencer.

Magnetic potential based formulation for linear and non-linear 3D RF sheath simulation

This paper reports a new numerical scheme to simulate the radio-frequency (RF) induced RF sheath, which is suitable for a large 3D simulation. In the RF sheath boundary model, the tangential component of the electric field () is given by the gradient of a scalar electric field potential. We introduce two additional scalar potentials for the tangential components of the magnetic field, which effectively impose the normal electric displacement (D n ) on the plasma sheath boundary condition via in-homogeneous Neumann boundary condition and constrain the tangential electric field on the surface as curl-free (). In our approach, the non-linear sheath impedance is formulated as a natural extension of the large thickness (or asymptotic) sheath limit (), allowing for handling both asymptotic and non-linear regimes seamlessly. The new scheme is implemented using the Petra-M finite element method analysis framework and is verified with simulations in the literature. The significance of non-linearity is discussed in various plasma conditions. An application of this scheme to asymptotic RF sheath simulation on the WEST ICRF antenna side limiters is also discussed.

A multiphysics-multiscale-multidrive theoretical model for C3S hydration

A multiphysics-multiscale-multidrive model for C 3 S hydration is developed theoretically in this paper. Firstly, the governing equations are formulated with thermo-chemo-electrical coupled fields during C 3 S hydration, including Nernst-Planck equation for ionic diffusion and chemical reaction, conduction equation for heat transfer, and Poisson equation for electrical field. Secondly, the multiscale computations are achieved from the ionic concentrations, electric potential and C–S–H nuclei number at micro-scale level to the heat flow, chemical shrinkage and C–S–H density at macro-scale level. Thirdly, the multidrives (C 3 S dissolution, both C–S–H and CH precipitation, the gradients of ionic concentration, electric potential and chemical activity) are included for physiochemical reactions. In addition, the full process of hydration heat flow and chemical shrinkage is integrated and formulated theoretically during all the five periods. After validation with experimental results, it is confirmed that the present model can characterize well the time evolution of the hydration heat flow, chemical shrinkage, and ionic concentrations. Moreover, the effects of water-to-cement ratios (w/c) and specific surface areas on C 3 S hydration kinetics are investigated by the model, indicating that (a) the drastic increase of initial silicate concentration is captured theoretically, (b) the slight influence of w/c on hydration kinetics is confirmed by the model.

Numerical simulation of repetitive transcranial magnetic stimulation by the smoothed finite element method

This paper presents a series of smoothed finite element methods (SFEM) for repetitive transcranial magnetic stimulation (rTMS) based on the quasi-static electromagnetic equations. The problem domain is first discretized into a set of tetrahedral elements and linear shape functions are used to interpolate the field variables. Then the smoothing domains (SDs) are constructed based on the edges, nodes, and faces of the background mesh. The smoothed gradient of electric potential and smoothed magnetic flux density over each SD are obtained by using the gradient smoothing technique (GST). The generalized smoothed Galerkin weakform is utilized to derive the discretized system equations. Numerical examples, including both spherical and realistic shaped heads, illustrate that the SFEM has the following important characteristics: (1) easier pre-processing; (2) better accuracy; (3) faster convergence; (4) higher computational efficiency.

Lightning stroke rates, atmospheric electric potential gradient data, and Schumann resonance data corresponding to the eruption of the Hunga Tonga - Hunga Ha'apai volcano on January 15, 2022

Lightning stroke rates, atmospheric electric potential gradient data, and Schumann resonance data corresponding to the eruption of the Hunga Tonga - Hunga Ha'apai volcano on January 15, 2022

Uniqueness of Solutions in Thermopiezoelectricity of Nonsimple Materials.

This article presents the theory of thermopiezoelectricity in which the second displacement gradient and the second electric potential gradient are included in the set of independent constitutive variables. This is achieved by using the entropy production inequality proposed by Green and Laws. At first, appropriate thermodynamic restrictions and constitutive equations are obtained, using the well-established Coleman and Noll procedure. Then, the balance equations and the constitutive equations of linear theory are derived, and the mixed initial-boundary value problem is set. For this problem a uniqueness result is established. Next, the basic equations for the isotropic case are derived. Finally, a set of inequalities is obtained for the constant constitutive coefficients of the isotropic case that, on the basis on the previous theorem, ensure the uniqueness of the solution of the mixed initial-boundary value problem.

A theoretical understanding of ionic current through a nanochannel driven by a viscosity gradient

HypothesisDifferent thermodynamic forces owing to the gradient of temperature, electrical potential, or concentration can drive ionic current through charged membranes. It has been recently shown that a viscosity gradient can drive an electrical current through a negatively charged nanochannel (Wiener and Stein, arXiv: 1807.09106). A model description of this phenomenon, based on the Maxwell–Stefan equation will help unravel the dominating physical mechanisms in so-called visco-migration. TheoryTo understand the physical mechanisms underlying this phenomenon, we employed the Maxwell–Stefan equation to develop a 1D model and obtain a relation between the flux of solvents and the driving forces. Viscosity gradients are known to drive transport, but the development of an electrical current has not been theoretically described prior to this work. FindingsOur 1D model shows that the ionic current depends on the ideality of the solvent, though both ideal and non-ideal scenarios demonstrated good agreement with experimental data. We employed the model to understand the impact of solution bulk ionic strength and pH on the drift of ionic species with same reservoirs solution properties. Our modeling results unveiled the significant impact of bulk solution properties on the drift of ions which is in agreement with the experiments. Moreover, we have shown that the diffusion gradient along the nanochannel contributes significantly into driving ionic species if we even apply a small ionic concentration gradient to both reservoirs. Our modeling results may pave the way for finding novel applications for drift of ions in a diffusion gradient, which can be induced by connecting reservoirs of different viscosity fluids.

Control of Electrolyte Filtration through a Charged Porous Layer (Membrane) Using a Combination of Pressure Drop and an External Electric Field

A novel method is proposed for calculating the solvent flux density and electric current density in the process of flow of an electrolyte solution through a charged porous layer (membrane) under the simultaneous action of external pressure and electric potential gradients. The method is based on irreversible thermodynamics and the cell model of an ion-exchange membrane. It is shown that, with the increase in the electrolyte concentration, the total permeability of the porous structure also increases as a result of both barofiltration and electroosmotic transfer of the solvent when both external gradients are co-directional vectors. As for the current density, it also increases with the increasing electrolyte concentration owing to the growth of the streaming current and specific conductivity.

Improvement of performance and sensitivity of 2D and 3D image reconstruction in EIT using EFG forward model

This paper presents a pure element-free Galerkin method (EFGM) forward model for image reconstruction in 2D and 3D electrical impedance tomography (EIT) using an adaptive current injection method. In EIT systems with the adapting current injection method, both static and dynamic images can be reconstructed; however, determination of electrode contact impedances in the complete electrode model is difficult and the Gap model is used. In this paper, in the EIT forward problem a weak form functional based on the Gap model and a pure EFGM approach are developed, and in the EIT inverse problem, Jacobian matrix is computed by the EFGM, and a fast integration technique is introduced to calculate the entries of the Jacobian matrix within an adequate computation time. The influence of increasing the density of nodes at and near the electrodes with steep electric potential gradients on the accuracy of FEM and EFGM forward solutions is investigated, and the performance of the image reconstruction algorithm with the proposed fast integration technique is examined. The numerical results reveal that the proposed EFGM forward model with the fast integration technique has an efficient performance both in terms of mean relative imaging errors and computational time.

Copper Carbonate Hydroxide as Precursor of Interfacial CO in CO2 Electroreduction.

Copper electrodes are especially effective in catalysis of C2 and further multi‐carbon products in the CO2 reduction reaction (CO2RR) and therefore of major technological interest. The reasons for the unparalleled Cu performance in CO2RR are insufficiently understood. Here, the electrode–electrolyte interface was highlighted as a dynamic physical‐chemical system and determinant of catalytic events. Exploiting the intrinsic surface‐enhanced Raman effect of previously characterized Cu foam electrodes, operando Raman experiments were used to interrogate structures and molecular interactions at the electrode–electrolyte interface at subcatalytic and catalytic potentials. Formation of a copper carbonate hydroxide (CuCarHyd) was detected, which resembles the mineral malachite. Its carbonate ions could be directly converted to CO at low overpotential. These and further experiments suggested a basic mode of CO2/carbonate reduction at Cu electrodes interfaces that contrasted previous mechanistic models: the starting point in carbon reduction was not CO2 but carbonate ions bound to the metallic Cu electrode in form of CuCarHyd structures. It was hypothesized that Cu oxides residues could enhance CO2RR indirectly by supporting formation of CuCarHyd motifs. The presence of CuCarHyd patches at catalytic potentials might result from alkalization in conjunction with local electrical potential gradients, enabling the formation of metastable CuCarHyd motifs over a large range of potentials.

Accelerated Osteogenesis of Heterogeneous Electric Potential Gradient on CFO/P(VDF‐TrFE) Membranes

AbstractPiezoelectric biomaterials are considered to be able to mimic the electrophysiological microenvironment of natural bone tissue, thus enhancing the bone regeneration. However, the effects of heterogeneous electric potential gradient of piezoelectric biomaterials on their osteogenic performance still remain elusive, largely because of the challenge of harassing the distribution of electric potential gradient on the surface of piezoelectric biomaterials. This study controls the heterogeneous electric potential gradient on the CoFe2O4/poly(vinylidene fluoride‐trifluoroethylene (CFO/P(VDF‐TrFE)) membrane by using an alternatively positive–negative polarization processing on microscaled straight‐stripe patterned indium tin oxide coated glass (ITO) electrodes. The potential gradient (Δζ) on membranes can be controlled by the stripe width and polarization parameters. Interestingly, Δζshows a significant influence on the cellular osteogenic potential of mesenchymal stem cells (MSCs) and the bone regeneration performance in vivo. The Δζof 0.672 pm/(V*µm) shows the optimal osteogenic performance both in vitro and in vivo, which can be attributed to the boost of integrins α5β1expression as well as the orientated arrangement and contractility of the cytoskeletons via mechanotransduction signaling cascades. This work therefore shows the importance of heterogeneous electric potential and provides a novel strategy to accelerate the osteogenic performances of piezoelectric biomaterials.

Self-diffusiophoresis of Janus particles that release ions

Catalytic Janus swimmers demonstrate a diffusiophoretic motion by self-generating the gradients of concentrations and electric potential. Recent work has focused on simplified cases, such as a release of solely one type of ions or low surface fluxes of ions, with limited theoretical guidance. Here, we consider the experimentally relevant case of particles that release both types of ions, and obtain a simple expression for a particle velocity in the limit of the thin electrostatic diffuse layer. Our approximate expression is very accurate even when ion fluxes and surface potentials are large and allows one to interpret a number of intriguing phenomena, such as the reverse in the direction of the particle motion in response to variations of the salt concentration or self-diffusiophoresis of uncharged particles.

Nonlinear Phase-Field Modeling of Lithium Dendritic Growth during Electrodeposition

Lithium batteries have been widely used, but the growth of lithium dendrites does lead to some hazards, such as internal short circuit, thermal runaway and even explosion. In paper, a nonlinear phase field model combined with Butler-Volmer expression was developed to study dendrite growth during electrodeposition. Two types of initial electrode-electrolyte interface are applied in numerical simulations. Results show that the cation concentration enrichment occurs near the dendritic tip due to the electromigration, and the curve of the growth velocity versus time follows a simple power law relation, indicating that the stability of the dendritic array originating from initial electrode-electrolyte interface can be broken with the applied electrical potential increasing. Moreover, we found that applied electric potential gradient can strongly influence the dendritic growth velocity and the dendritic growth during electrodeposition is less relative to the surface tension anisotropy.

Electric Fields Enhance Ice Formation from Water Vapor by Decreasing the Nucleation Energy Barrier

Video images of ice formation from moist air under temperature and electric potential gradients reveal that ambient electricity enhances ice production rates while changing the habit of ice particles formed under low supersaturation. The crystals formed under an electric field are needles and dendrites instead of the isometric ice particles obtained within a Faraday cage. Both a non-classical mechanism and classical nucleation theory independently explain the observed mutual feedback between ice formation and its electrification. The elongated shapes result from electrostatic repulsion at the crystal surfaces, opposing the attractive intermolecular forces and thus lowering the ice-air interfacial tension. The video images allow for the estimation of ice particle dimensions, weight, and speed within the electric field. Feeding this data on standard equations from electrostatics shows that the ice surface charge density attains 0.62–1.25 × 10−6 C·m−2, corresponding to 73–147 kV·m−1 potential gradients, reaching the range measured within thunderstorms. The present findings contribute to a better understanding of natural and industrial processes involving water phase change by acknowledging the presence and effects of the pervasive electric fields in the ambient environment.

Electromigration of protons and zero valent iron oxidation: A physico-chemical insight to model the kinetics of fenton-like process

To describe correctly the kinetics of Fenton-like process with zero valent iron, it is imperative to determine the rate of Fe2+ formation by ZVI oxidation at fairly acidic pH. With this purpose, experiments of ZVI oxidation were carried out in a well-stirred reactor in which air or N2 was bubbled through an aqueous solution at pH 2.5, 3 and 4 and 25 °C for 10,800 s. To mimic the Fenton-like process, the experiments were repeated at pH 3 and two different initial concentrations of H2O2. The results without H2O2 revealed that the rate-limiting step of Fe2+ formation is the electromigration of protons through an iron oxide barrier layer of negligible thickness. The solution of the Nernst-Planck equation was able to describe the flux of protons involved in the reduction half-reaction of ZVI oxidation. From the rate of protons consumption and the stoichiometry of the overall redox reaction, a rate expression for Fe2+ formation was obtained. A novel detailed kinetic model for the Fenton-like process with ZVI involving 20 species and 55 reactions was suggested. The only tuned parameters were the effective diffusivity of protons times the electric potential gradient, and the rate constant of precipitation of iron ion species. The results of species concentrations in the experiments with H2O2, and a large set of independent data of concentration of major species in reactors where powder iron and steel plates were immersed in aqueous acidic solution with and without H2O2, support both the rate equation for the Fe2+ formation and the Fenton-like kinetic model.

Transcranial stimulation analysis using the smoothed finite element method

This paper presents a series of smoothed finite element methods (SFEM) for transcranial stimulation simulations. The problem domain is first discretized into a set of four-node tetrahedral elements, and linear shape functions are employed to interpolate the field variables. Then, the smoothing domains are further formed in conjunction with the nodes, edges or faces of elements. In order to improve the accuracy of low-order interpolation, the magnetic flux density and gradient of electric potential are smoothed using the gradient smoothing technique (GST) over each smoothing domain. Based on the generalized smoothed Galerkin weakform, the discretized system equations are finally obtained. Numerical examples, including transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) problems, demonstrate that the SFEM possesses the following important properties: (1) better accuracy; (2) faster convergence; (3) higher computational efficiency; (4) more robust in transcranial stimulation simulations.