Weak Electric Field Research Articles

Nonlinear and Relaxation Processes in Piezoceramics in the Region of Weak Electric Fields

Nonlinear and Relaxation Processes in Piezoceramics in the Region of Weak Electric Fields

Bidirectional Jump Point Search Path-Planning Algorithm Based on Electricity-Guided Navigation Behavior of Electric Eels and Map Preprocessing.

The electric eel has an organ made up of hundreds of electrocytes, which is called the electric organ. This organ is used to sense and detect weak electric field signals. By sensing electric field signals, the electric eel can identify changes in their surroundings, detect potential prey or other electric eels, and use it for navigation and orientation. Path-finding algorithms are currently facing optimality challenges such as the shortest path, shortest time, and minimum memory overhead. In order to improve the search performance of a traditional A* algorithm, this paper proposes a bidirectional jump point search algorithm (BJPS+) based on the electricity-guided navigation behavior of electric eels and map preprocessing. Firstly, a heuristic strategy based on the electrically induced navigation behavior of electric eels is proposed to speed up the node search. Secondly, an improved jump point search strategy is proposed to reduce the complexity of jump point screening. Then, a new map preprocessing strategy is proposed to construct the relationship between map nodes. Finally, path planning is performed based on the processed map information. In addition, a rewiring strategy is proposed to reduce the number of path inflection points and path length. The simulation results show that the proposed BJPS+ algorithm can generate optimal paths quickly and with less search time when the map is known.

Changes over time in ferroelectricity of nanocomposites containing cellulose combined with [NH4][Zn(HCOO)3

ABSTRACT For the first time, a composite based on a ferroelectric metal-organic framework of [NH4][Zn(HCOO)3] combined with nanocellulose at different cellulose concentrations from 0 to 75 wt% was synthesised to investigate the changes over time in phase transition and ferroelectric switching. A comparative study for fresh samples and the samples after 288 h was conducted. Electrophysical parameters were measured in a temperature range of 140 to 245 K under a weak electric field with an amplitude of 2 V.cm−1 at a frequency of 1 kHz. The results indicated that the increase in cellulose content led to increasing the phase transition temperature from 190.1 to 238.5 K. Besides, the coercive field was also found to increase from 3.78 to 14.12 kV.cm−1 along with the reduction of dielectric permittivity and maximum polarisation. After 288 h, this phase transition decreased significantly over time even to 231.6 K in the case of highest cellulose content (75 wt%). Meanwhile, the coercive field was found to decrease from 14.12 to 10.57 kV.cm−1. Remarkable changes were detected for samples with cellulose content of higher 25 wt%. The weaker interaction between ferroelectric part and cellulose over time due to the softness of cellulose was responsible for the obtained phenomena.

Experimental study on solidification of uranium tailings by microbial grouting combined with electroosmosis

The present microbial reinforcement of rock and soil exhibits limitations, such as uneven reinforcement effectiveness and low calcium carbonate generation rate, resulting in limited solidification strength. This study introduces electroosmosis as a standard microbial grouting reinforcement technique and investigates its solidification effects on microbial-reinforced uranium tailings. The most effective electroosmosis effect on uranium tailings occurs under a potential gradient of 1.25 V/cm. The findings indicate that a weak electric field can effectively promote microbial growth and biological activity and accelerate bacterial metabolism. The largest calcium carbonate production occurred under the gradient of 0.5 V/cm, featuring a good crystal combination and the best cementation effect. Staged electroosmosis and electrode conversion efficiently drive the migration of anions and cations. Under electroosmosis, the cohesion of uranium tailings reinforced by microorganisms increased by 37.3% and 64.8% compared to those reinforced by common microorganisms and undisturbed uranium tailings, respectively. The internal friction angle is also improved, significantly enhancing the uniformity of reinforcement and a denser and stronger microscopic structure. This research demonstrates that MICP technology enhances the solidification effects and uniformity of uranium tailings, providing a novel approach to maintaining the safety and stability of uranium tailings dams.

Demonstration of Weak Polarization Electric Field III‐N LEDs based on Polar Plane

AbstractA strong polarization electric field (PEF) in III‐nitride semiconductors has adverse effects on the performance of III‐N light‐emitting diodes (LEDs). However, to reduce the PEF of III‐N LEDs based on the polar plane (c‐plane) remains a big challenge. Here, a weak PEF blue LED on c‐plane GaN with an InGaN/AlGaN superlattices (SLs) quantum barrier and InGaN quantum well grown by metal‐organic chemical vapor deposition is proposed. The InGaN/SLs multiple quantum wells (MQWs) show a significant reduction of PEF compared with traditional InGaN/GaN MQWs. A low electric field of 0.5 MV cm−1 is obtained, which is confirmed by power‐dependent photoluminescence (PL) and time‐resolved PL measurements. The proposed LEDs with InGaN/AlGaN SLs barriers present a low efficiency droop, a great wavelength stability, and a high −3 dB E‐O modulation bandwidth up to 1.01 GHz. This work demonstrates the role of InGaN/AlGaN SLs barriers in reducing the PEF of III‐N LEDs and provides a feasible technical route to achieve the weak PEF LEDs on c‐plane, which can be expanded and applied to the preparation of high‐performance, long wavelength, and deep UV III‐N LEDs.

Conformational Fluctuations and Induced Orientation of a Protein, Its Solvation Shell, and Bulk Water in Weak Non-Unfolding External Electric Fields.

Extreme external electric fields have been reported to disrupt the tertiary structure of stably folded proteins; however, the effects of weaker electric fields on many biomolecules, especially net-uncharged proteins, and on the surrounding aqueous environment have been rarely discussed. To explore these effects at the atomic level, here, we have used molecular dynamics simulations to estimate rotational motion and induced structural fluctuations in the model protein ubiquitin and its hydration layer due to applied non-unfolding electrostatic fields. When exposed to weak electric fields of up to 0.2 V nm-1, ubiquitin displayed competition between internal structure-maintaining molecular interactions and the external orienting force, which disrupted the local structure in certain regions of the protein. Moreover, relative to hydration water, bulk water showed a greater tendency to align with the electric field, indicating that the presence of protein caused hydration water to acquire rotational mobility different from that in a pure-water system. The differential influence of the applied electric field on the hydration and bulk water surrounding ubiquitin will be common to almost all (nonmembrane) biomacromolecules. Our findings highlight the importance of local dipoles and their electric polarizability even in net-uncharged biomolecules.

Lasing in Zn-doped GaAs nanowires on an iron film

In this work, we demonstrate optically pumped lasing in highly Zn-doped GaAs nanowires (NWs) lying on an iron film. The conically shaped NWs are first covered with an 8 nm thick Al2O3 film to prevent atmospheric oxidation and mitigate band-bending effects. Multimode and single-mode lasing have been observed for NWs with a length greater or smaller than 2 μm, respectively. Finite difference time domain calculations reveal a weak electric field enhancement in the Al2O3 layer at the NW/iron film interface for the lasing modes. The high Zn acceptor concentration in the NWs provides enhanced radiative efficiency and enables lasing on the iron film despite plasmonic losses. Our results open avenues for integrating NW lasers on ferromagnetic substrates to achieve new functionalities, such as magnetic field-induced modulation.

Microscopic derivation of Ginzburg–Landau theory and the BCS critical temperature shift in general external fields

We consider the Bardeen–Cooper–Schrieffer (BCS) free energy functional with weak and macroscopic external electric and magnetic fields and derive the Ginzburg–Landau functional. We also provide an asymptotic formula for the BCS critical temperature as a function of the external fields. This extends our previous results in Deuchert et al. (Microscopic derivation of Ginzburg-Landau theory and the BCS critical temperature shift in a weak homogeneous magnetic field, PMP 4(1), 1–89 (2023)) for the constant magnetic field to general magnetic fields with a nonzero magnetic flux through the unit cell.

Enhanced germination and electrotactic behaviour of Phytophthora palmivora zoospores in weak electric fields

Soil-dwelling microorganisms use a variety of chemical and physical signals to navigate their environment. Plant roots produce endogenous electric fields which result in characteristic current profiles. Such electrical signatures are hypothesised to be used by pathogens and symbionts to track and colonise plant roots. The oomycete pathogen Phytophthora palmivora generates motile zoospores which swim towards the positive pole when exposed to an external electric field in vitro. Here, we provide a quantitative characterization of their electrotactic behaviour in 3D. We found that a weak electric field (0.7–1.0 V cm−1) is sufficient to induce an accumulation of zoospore at the positive pole, without affecting their encystment rate. We also show that the same external electric field increases the zoospore germination rate and orients the germ tube’s growth. We conclude that several early stages of the P. palmivora infection cycle are affected by external electric fields. Taken together, our results are compatible with the hypothesis that pathogens use plant endogenous electric fields for host targeting.

Reinterpreting published tDCS results in terms of a cranial and cervical nerve co-stimulation mechanism.

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation method that has been used to alter cognition in hundreds of experiments. During tDCS, a low-amplitude current is delivered via scalp electrodes to create a weak electric field in the brain. The weak electric field causes membrane polarization in cortical neurons directly under the scalp electrodes. It is generally assumed that this mechanism causes the observed effects of tDCS on cognition. However, it was recently shown that some tDCS effects are not caused by the electric field in the brain but rather via co-stimulation of cranial and cervical nerves in the scalp that also have neuromodulatory effects that can influence cognition. This peripheral nerve co-stimulation mechanism is not controlled for in tDCS experiments that use the standard sham condition. In light of this new evidence, results from previous tDCS experiments could be reinterpreted in terms of a peripheral nerve co-stimulation mechanism. Here, we selected six publications that reported tDCS effects on cognition and attributed the effects to the electric field in the brain directly under the electrode. We then posed the question: given the known neuromodulatory effects of cranial and cervical nerve stimulation, could the reported results also be understood in terms of tDCS peripheral nerve co-stimulation? We present our re-interpretation of these results as a way to stimulate debate within the neuromodulation field and as a food-for-thought for researchers designing new tDCS experiments.

Enhanced photocatalytic performance of Co3(PO4)2/Ag3PO4 immobilized on SiC: The synergistic effects and mechanism

Co3(PO4)2/Ag3PO4 (CoPi/AgP) were immobilized onto SiC nanowires through co-precipitation. Compared with Ag3PO4, the photoactivity and photostability of CoPi/AgP/SiC were significantly enhanced, while the cost was reduced because of the low demand for expensive Ag3PO4. Under visible light, Ag3PO4/SiC loaded with 0.5%Co3(PO4)2 achieved an apparent methyl orange (MO) degradation rate constant of 1.77 times higher than Ag3PO4 and 7.49 times higher than Ag3PO4/SiC. Moreover, after five reuses, Ag3PO4/SiC loaded with 0.5%Co3(PO4)2 maintained its photocatalytic activity at 87%, whereas pure Ag3PO4 retained only 32.5%. The synergistic action of the Z-scheme Ag3PO4/SiC heterojunction and Co3(PO4)2 cocatalyst led to enhanced photoactivity and stability. The weak internal electric field induced in Co3(PO4)2/Ag3PO4 significantly increased the intensity of the main internal electric field in Ag3PO4/SiC, resulting in a rapid interfacial transfer, prolonged lifetime, and strong redox ability of the photoinduced charge carriers. This mechanism demonstrates a positive effect on charge separation, oxidative reaction kinetics, and the formation of·OH of the Co3(PO4)2 hole cocatalyst. Density functional theory (DFT) calculations and active species trapping experiments confirmed the Z-scheme electron transfer pathway. Consequently, this study provides a low-cost method to construct a novel immobilized photocatalyst with high activity and stability for the efficient degradation of organic pollutants under visible light.

Soft actuators based on piezoelectric composites for nanoscale self-bending

Nano/microscale objects would be far less damaged by soft actuators than rigid actuators in the mechanical nano/micromanipulation, but the precision of most soft actuators cannot meet the requirements. In this work, a kind of soft actuators which can realize nanoscale self-bending are developed on the basis of lead zirconate titanate (PZT)/shape memory polyurethane (SMPU) composites. The self-bending ability is the result of the weak polarization electric fields produced by the combination of the microstructures of particulate composites and the fringe effect of electric fields. However, unlike common piezoelectric actuators, strong polarization electric fields would weaken the actuation ability (self-bending ability). The PZT/SMPU actuators are able to generate nanoscale self-bending displacements with the maximum error of ± 8 nm in a common condition without controlling any environmental parameter. This work provides a helpful reference for the design of soft self-bending actuators based on piezoelectric particulate composites.

Electric field modulation effect and mechanism on n-alkanes fuel pyrolysis: A ReaxFF MD and DFT study

To promote the fuel utilization efficiency in the aviation and space transport, the electric field was selected as an efficiency method to modify the fuel pyrolysis rate. This work investigated the surrogate fuel component n-alkane (n-pentane, n-heptane and n-decane) pyrolysis process under the electric field. The three n-alkanes pyrolysis rate and reaction pathway were analyzed. And the reaction mechanism under the electric field was discussed by the bond cracking potential energy (PES), system thermal motion and energy. The molecular dynamics results showed the n-alkanes pyrolysis was modulated by the electric field strength, which promotion in weak electric field and inhibition in strong field. The species transformation net was complicated and selective while the conversion flux was reduced by the strong field. The field improved the molecule polarization and deformation to result in the edged carbon bond and H bond dissociation with lower energy barriers. Analyzing the molecular motion and system energy, the intermolecular distance was elongated, and interaction energy was reduced, which caused to the decrease of collision frequency under the field. The contribution of electric field to the single molecule decomposition and inhibition molecules motion worked together on the global n-alkane pyrolysis. This work supplied a theory support to the promoting fuel utilization using the electric energy.

Self-sustaining conducting state and bipolar ionizing Gunn domains in pulse avalanche GaAs diodes

Domain instability in nonequilibrium electron-hole plasma leads to the formation of narrow moving regions of the ionizing electric field—collapsing Gunn domains. In pulse power electronics devices based on gallium arsenide, impact ionization in collapsing domains acts as an efficient mechanism for the generation of nonequilibrium carriers at low voltages and weak average electric fields.

Relaxation features of own photoconductivity in p-GaSe single crystals

The effects of the electric field, temperature, and initial value of the dark resistivity on the relaxation processes of intrinsic photoconductivity in single crystals of gallium monoselenide (p-GaSe) are studied. It is shown that although in all the samples under study, in the processes of establishment and disappearance of photoconductivity, the process of attachment of nonequilibrium charge carriers by attracting and repulsive centers in weak and stronger electric fields is, accordingly, inevitable, however, in samples of high-resistivity crystals, it is also necessary to take into account the significant influence of random macroscopic defects caused by layering.

Frequency-domain analysis of membrane polarization in two-compartment model neurons with weak alternating electric fields.

Transcranial alternating current stimulation (tACS) is widely used in studying brain functions and the treatment of neuropsychiatric diseases in a frequency-specific manner. However, how tACS works on neuronal activity has been poorly understood. In this paper, we use linear system analysis to investigate how weak alternating electric fields (EFs) affect the membrane polarization of neurons in the frequency domain. Two biophysically realistic conductance-based two-compartment models of cortical pyramidal neurons are developed to simulate subthreshold membrane polarization with weak alternating EFs. We linearize the original nonlinear models at the stable equilibrium points and further simplify them to the two- or three-dimensional linear systems. Thus, we calculate the transfer functions of the low-dimensional linear models to model neuronal polarization patterns. Based on the transfer functions, we compute the amplitude- and phase-frequency characteristics to describe the relationship between weak EFs and membrane polarization. We also computed the parameters (gain, zeros, and poles) and structures (the number of zeros and poles) of transfer functions to reveal how neuronal intrinsic properties affect the parameters and structure of transfer functions and thus the frequency-dependent membrane polarization with alternating EFs. We find that the amplitude and phase of membrane polarization both strongly depended on EF frequency, and these frequency responses are modulated by the intrinsic properties of neurons. The compartment geometry, internal coupling conductance, and ionic currents (except Ih) affect the frequency-dependent polarization by mainly changing the gain and pole of transfer functions. Larger gain contributes to larger amplitude-frequency characteristics. The closer the pole is to the imaginary axis, the lower phase-frequency characteristics. However, Ih changes the structure of transfer function in the dendrite by introducing a new pair of zero-pole points, which decrease the amplitude at low frequencies and thus lead to a visible resonance. These results highlight the effects of passive properties and active ion currents on subthreshold membrane polarization with alternating EFs in the frequency domain, which provide an explainable connection of how intrinsic properties of neurons modulate the neuronal input-output functions with weak EF stimulation.

Simple rose model of water in constant electric field.

A simple two-dimensional statistical mechanical water model, called the rose model, was used in this work. We studied how a homogeneous constant electric field affects the properties of water. The rose model is a very simple model that helps explain the anomalous properties of water. Rose water molecules are represented as two-dimensional Lennard-Jones disks with potentials for orientation-dependent pairwise interactions mimicking formations of hydrogen bonds. The original model is modified by addition of charges for interaction with the electric field. We studied what kind of influence the electric field strength has on the model's properties. To determine the structure and thermodynamics of the rose model under the influence of the electric field we used Monte Carlo simulations. Under the influence of a weak electric field the anomalous properties and phase transitions of the water do not change. On the other hand, the strong fields shift the phase transition points as well as the position of the density maximum.

Effects of temperature and microwave on the stability of the blast effector complex APikL2A/sHMA25 as determined by molecular dynamics analyses.

Magnaporthe oryzae is the causal agent of rice blast, and understanding how abiotic stress affects the resistance of plants to this disease is useful for designing disease control strategies. In this paper, the effects of temperature and microwave irradiation on the effector complex comprising APikL2A from M. oryzae and sHMA25 from foxtail millet were investigated by molecular dynamics simulations using the GROMACS software package. While the structure of APikL2A/sHMA25 remained relatively stable in a temperature range of 290K (16.85°C) to 320K (46.85°C), the concave shape of the temperature-dependent binding free energy curve indicated that there was maximum binding affinity between APikL2A and sHMA25 at 300K-310K. This coincided with the optimum infectivity temperature, thus suggesting that coupling of the two polypeptides may play a role in the infection process. A strong oscillating electric field destroyed the structure of APikL2A/sHMA25, although it was stable and not susceptible to weak electric fields.

Light‐Responsive Springs from Electropatterned Liquid Crystal Polymer Networks

AbstractFuture robotic systems will have to adapt their operation to dynamic environments and therefore their development will require the use of active soft components. Bioinspired approaches toward novel actuation materials for active components rely on integrating molecular machines in soft matter, and ensuring that their nanoscale movement is amplified to the macroscale, where mechanically relevant motion is generated. This approach is successfully used in the design of photoresponsive soft springs and other mechanically active materials. Here, this study reports on a new approach where the operation of photoswitches and chiral liquid crystals are combined with an original and mask‐free microscopic patterning method to generate helix‐based movement at the macroscale, including light‐driven winding and unwinding accompanied with inversion of handedness. The microscopic patterning is the result of the unique organization of cholesteric liquid crystals under weak electric field. At a higher level, the pitch and the handedness of the active springs are defined by the imprinted pattern and the angle at which the spring ribbons are cut in the material. These findings are likely to enable soft and responsive robotic systems, and they show how transmission of molecular operation into macroscale functional movement is enabled by materials design across multiple hierarchical levels.

Using Electric Field to Improve the Effect of Microbial-Induced Carbonate Precipitation

The precipitation of calcium carbonate induced by Sporosarcina pasteurii (S. pasteurii) has garnered considerable attention as a novel rock and soil reinforcement technique. The content and structure of calcium carbonate produced through this reaction play a crucial role in determining the rocks’ and soil’s reinforcement effects in the later stages. Different potential gradients were introduced during the bacterial culture process to enhance the performance of the cementation and mineralization reactions of the bacterial solution to investigate the effects of electrification on the physical and chemical characteristics, such as the growth and reproduction of S. pasteurii. The results demonstrate that the concentration, activity, and number of viable bacteria of S. pasteurii were substantially enhanced under an electric field, particularly the weak electric field generated by 0.5 V/cm. The increased number of bacteria provides more nucleation sites for calcium carbonate deposition. Moreover, as the urease activity increased, the calcium carbonate content generated under an electric potential gradient of 0.5 V/cm surpassed that of other potential gradient groups. The growth rate increased by 9.78% compared to the calcium carbonate induced without electrification. Significantly, the suitable electric field enhances the crystal morphology of calcium carbonate and augments its quantity, thereby offering a novel approach for utilizing MICP in enhancing soil strength, controlling water pollution, and mitigating seepage. These findings elevate the applicability of microbial mineralization in engineering practices.