Heterogeneous Electric Field Research Articles

A superlattice interface and S-scheme heterojunction for ultrafast charge separation and transfer in photocatalytic H2 evolution

The rapid recombination of photoinduced charge carriers in semiconductors fundamentally limits their application in photocatalysis. Herein, we report that a superlattice interface and S-scheme heterojunction based on Mn0.5Cd0.5S nanorods can significantly promote ultrafast charge separation and transfer. Specifically, the axially distributed zinc blende/wurtzite superlattice interfaces in Mn0.5Cd0.5S nanorods can redistribute photoinduced charge carriers more effectively when boosted by homogeneous internal electric fields and promotes bulk separation. Accordingly, S-scheme heterojunctions between the Mn0.5Cd0.5S nanorods and MnWO4 nanoparticles can further accelerate the surface separation of charge carriers via a heterogeneous internal electric field. Subsequent capture of the photoelectrons by adsorbed H2O is as fast as several picoseconds which results in a photocatalytic H2 evolution rate of 54.4 mmol·g−1·h−1 without any cocatalyst under simulated solar irradiation. The yields are increased by a factor of ~5 times relative to control samples and an apparent quantum efficiency of 63.1% at 420 nm is measured. This work provides a protocol for designing synergistic interface structure for efficient photocatalysis.

Interfacial Dual‐Modulation via Cationic Electrostatic Shielding and Anionic Preferential Adsorption toward Planar and Reversible Zinc Electrodeposition

AbstractRechargeable aqueous zinc‐ion batteries (ZIBs) with low cost and high safety arouse most promises as next‐generation energy storage configurations. Yet the heterogeneous electric field distributions and interfacial side reactions are considered stumbling roadblocks toward the commercialization of ZIBs. Here, these challenges via cationic electrostatic shielding and anionic preferential adsorption by sodium gluconate (SG) additive are addressed. The polar functional groups (─COO−) of SG anions preferentially anchor to the Zn anode, which can alter Zn2+ migration pathways and restrain side reactions. Moreover, as per the smaller effective reduction potential, the separated cations (Na+) from SG serve as a dynamic armor to provide strong electrostatic shielding effect for uniform Zn2+ deposition on the [002] crystal plane, radically eliminating Zn dendrite growth and promoting anti‐corrosion behaviors of Zn. Consequently, the Zn//Zn symmetric cell with modified electrolyte confers a lifespan of up to 600 h at a high 80% depth of discharge. Furthermore, even under a record‐low negative/positive ratio of 2.11 and lean electrolyte of 30 µL mAh−1, the Zn//VOX full cell remains enhanced capacity retention of 84.37% even after 800 cycles at 1 A g−1. This work develops an interfacial dual‐modulation strategy and provides unique insights to enlighten the practical application of ZIBs.

Relativistic Runaway Electron Avalanches Within Complex Thunderstorm Electric Field Structures

AbstractRelativistic runaway electron avalanches (RREAs) are generally accepted as a source of thunderstorms gamma ray radiation. Avalanches can multiply in the electric field via the relativistic feedback mechanism based on processes with gamma rays and positrons. This study shows that a non‐uniform electric field geometry can lead to the new RREAs multiplication mechanism—“reactor feedback,” due to the exchange of high‐energy particles between different accelerating regions within a thundercloud. A new method for the numerical simulation of RREA dynamics within heterogeneous electric field structures is proposed. Under the assumption that reactor feedback can produce a terrestrial gamma ray flash (TGF), necessary conditions for TGF occurrence in the system with the reactor feedback are derived using the developed analytical description and the numerical simulation. Observable properties of TGFs influenced by the proposed mechanism are discussed.

Simulation Study of Coaxial Treatment Chambers for PEF Pasteurization: A Critical Review

A pulsed electric field (PEF) produces pasteurized liquid foods with fresh and nutritional properties. The treatment chamber is a crucial part of the PEF processing system where a high voltage is applied, producing an electric field to treat the liquid foods. The proper construction of the treatment chamber regulates the distribution of the electrical field inside the treatment zone. Mixing of liquid inside the treatment zone is an effective tool to overcome this heterogeneous effect. The coaxial treatment chamber offers a heterogeneous electric field and temperature distribution inside the treatment zone. A helical insulator inside the coaxial treatment chamber provides a mixing effect. In this research, a numerical simulation was done to measure the electric field in different geometries of treatment chambers at different flow rates. The simulation aimed to optimize the new coaxial treatment chamber design. The modelling findings showed homogeneous electrical field strength in the helical treatment chamber. This study provides new insights for industrial-scale setup using multiple helical chambers in a continuous flow PEF treatment.

Heterogeneous Intramolecular Electric Field as a Descriptor of Diels-Alder Reactivity.

External electric fields have proven to be an effective tool in catalysis, on par with pressure and temperature, affecting the thermodynamics and kinetics of a reaction. However, fields in molecules are complicated heterogeneous vector objects, and there is no universal recipe for grasping the exact features of these fields that implicate reactivity. Herein, we demonstrate that topological features of the heterogeneous electric field within the reactant state and of the quantum mechanical electron density-a scalar reporter on the field experienced by the system-can be identified as rigorous descriptors of the reactivity to follow. We scrutinize specifically the Diels-Alder reaction. Its 3D nature and the lack of a singular directionality of charge movement upon barrier crossing make the effect of the electric field not obvious. We show that the electric field topology around the dienophile double bond and the associated changes in the topology of the electron density in this bond are predictors of the reaction barrier. They are also the metrics to rationalize and predict how the external field would inhibit or enhance the reaction. The findings pave the way toward designing external fields for catalysis and reading the reactivity without an explicit mechanistic interrogation, for a variety of reactions.

Combining NanoKnife with M1 oncolytic virus enhances anticancer activity in pancreatic cancer.

NanoKnife, a nonthermal ablation technique also termed irreversible electroporation (IRE), has been adopted in locally advanced pancreatic cancer (LAPC) treatment. However, reversible electroporation (RE) caused by heterogeneous electric field magnitude leads to inadequate ablation and tumor recurrence. Alphavirus M1 has been identified as a novel natural oncolytic virus which is nonpathogenic and with high tumor selectivity. This study evaluated improvements to therapeutic efficacy through combination therapy incorporating NanoKnife and M1 virus. We showed that IRE triggered reactive oxygen species (ROS)-dependent apoptosis in pancreatic cancer cells (PCCs) mediated by phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) pathway suppression. When NanoKnife was combined with M1 virus, the therapeutic efficacy was synergistically enhanced. The combinatorial treatment further inhibited tumor proliferation and prolonged the survival of orthotopic pancreatic cancer (PC)-bearing immunocompetent mice. In depth, NanoKnife enhanced the oncolytic effect of M1 by promoting its infection. The combination turned immune-silent tumors into immune-inflamed tumors characterized by T cell activation. Clinicopathologic analysis of specific M1 oncolytic biomarkers indicated the potential of the combination regimen. The combinatorial therapy represents a promising therapeutic efficacy and may ultimately improve the prognosis of patients with LAPC.

An Improved Electroporator With Continuous Liquid Flow and Double-Exponential Waveform for Liquid Food Pasteurization

Pulsed electric field (PEF) pasteurisation keeps treated liquid food fresh and nutritious compared to traditional thermal pasteurisation. However, PEF adoption is still limited on an industrial scale due to a lack of practical systems. As a result, a great deal of research has gone into overcoming the limitations of the existing systems. Keeping this in mind, the current study contributes to the improvement of the electroporator. The heterogeneous electric field’s distribution raises the temperature of the treated food samples. Liquid laminar flow is a reason for heterogeneous electric field’s distribution in continuous treatment. Hotspots may also be created by using an inefficient high-voltage waveform in addition to the heterogeneous electric field distribution. This study rectifies the heterogeneous distribution by proposing an improved coaxial treatment chamber and double-exponential waveform to replace the exponential-decaying waveform. A static mixer provides an increased mixing, i.e. disrupting the laminar flow, inside the treatment zone. COMSOL based computational model was developed to study flow behaviour and corresponding temperature distribution in the proposed coaxial treatment chamber with sieves. Based on the model, it has been concluded that coaxial electrodes with sieves provide more homogeneous flow properties inside the treatment chamber. The effectiveness of the double-exponential (DE) waveform was validated using MATLAB. A three-stage Marx generator giving the DE waveform was designed and constructed. The performance of the improved treatment chamber together with the DE waveform, known as the electroporator, was studied using chemical and microbial analysis. Untreated, PEF treated, and thermal treated orange samples were stored at 4°C for 9 days before being examined. The lowest microbial growth was observed in both the PEF treated with sieves and thermally treated food samples than the untreated sample. However, treated juices’ visual and chemical colour analysis showed that the PEF-treated sample acquired a brighter appearance than a thermally processed sample. Thus, this study provides significant findings in developing and utilising an electroporator to inactivate microorganisms.

Dual-functional CuO/CN for highly efficient solar evaporation and water purification

Sunlight-clean water production from industrial wastewater, domestic sewage, and seawater is a sustainable water purification technology with the potential to solve environmental and energy problems. Semiconductor has good application prospects for photothermal conversion due to its advantages of earth-abundance, nontoxicity, and stability. While, most of its energy is released in the form of radiative relaxation, which leads to a low light-to-heat conversion efficiency. Enhancing its non-radiative relaxation is an effective way to improve light-to-heat conversion efficiency. In this work, heterostructured copper oxide/carbon nitride (CuO/CN) was designed to enhance non-radiative relaxation and thus improve the solar energy-to-thermal energy performance by constructing heterogeneous electric field. Electron paramagnetic resonance spectroscopy, X-ray photoelectron spectroscopy and differential charge density analyses proved the formation of heterogeneous electric fields between CuO and CN. Under the enhanced non-radiative relaxation, CuO/CN has an excellent light absorption range and carrier separation efficiency. The water evaporation rate under sunlight increased from 0.31 to 1.14 kg·m−2·h−1 and photothermal conversion efficiency increased from 19% to 72%. Simultaneously, CuO/CN can remove nearly 100% of the ions in seawater and Chemical Oxygen Demand (COD), Ammonia Nitrogen (NH3-N), Nitrate Nitrogen (NO3-N), and Total Phosphorus (TP) in industrial wastewater to produce clean water. Combined with photo-Fenton-like technology, it can effectively remove organic pollutants and volatile organic compounds (VOCs) from water. This work provides an efficient solar-clean water production technology with excellent pollution decontamination ability, which will be extremely attractive for future life.

Electroporation does not affect human dermal fibroblast proliferation and migration properties directly but indirectly via the secretome

Aesthetic wound healing is often experienced by patients after electrochemotherapy. We hypothesized that pulsed electric fields applied during electrochemotherapy (ECT) or gene electrotransfer (GET) protocols could stimulate proliferation and migration of human cutaneous cells, as described in protocols for electrostimulation of wound healing. We used videomicroscopy to monitor and quantify in real time primary human dermal fibroblast behavior when exposed in vitro to ECT and GET electric parameters, in terms of survival, proliferation and migration in a calibrated scratch wound assay. Distinct electric field intensities were applied to allow gradient in cell electropermeabilization while maintaining reversible permeabilization conditions, in order to mimic in vivo heterogeneous electric field distribution of complex tissues. Neither galvanotaxis nor statistical modification of fibroblast migration were observed in a calibrated scratch wound assay after application of ECT and GET parameters. The only effect on proliferation was observed under the strongest GET conditions, which drastically reduced the number of fibroblasts through induction of mitochondrial stress and apoptosis. Finally, we found that 24 h-conditioned cell culture medium by electrically stressed fibroblasts tended to increase the migration properties of cells that were not exposed to electric field. RT-qPCR array indicated that several growth factor transcripts were strongly modified after electroporation.

The complexity of high-frequency electric fields degrades electrosensory inputs: implications for the jamming avoidance response in weakly electric fish.

Sensory systems encode environmental information that is necessary for adaptive behavioural choices, and thus greatly influence the evolution of animal behaviour and the underlying neural circuits. Here, we evaluate how the quality of sensory information impacts the jamming avoidance response (JAR) in weakly electric fish. To sense their environment, these fish generate an oscillating electric field: the electric organ discharge (EOD). Nearby fish with similar EOD frequencies perform the JAR to increase the difference between their EOD frequencies, i.e. their difference frequency (DF). The fish determines the sign of the DF: when it has a lower frequency (DF > 0), EOD frequency is decreased and vice versa. We study the sensory basis of the JAR in two species: Apteronotus leptorhynchus have a high frequency (ca 1000 Hz), spatio-temporally heterogeneous electric field, whereas Eigenmannia sp. have a low frequency (ca 300 Hz), spatially uniform field. We show that the increased complexity of the Apteronotus field decreases the reliability of sensory cues used to determine the DF. Interestingly, Apteronotus responds to all JAR stimuli by increasing EOD frequency, having lost the neural pathway that produces JAR-related decreases in EOD frequency. Our results suggest that electric field complexity may have influenced the evolution of the JAR by degrading the related sensory information.

Formation and control of secondary nanostructures in electro-hydrodynamic patterning of ultra-thin films

Based on a computational model involving finite element method, we report the morphological evolution and pattern formation process in a thin polymer film subject to an externally imposed periodically varying heterogeneous DC electric field, induced by topographically patterned top electrode. Quasi-steady state morphology is observed to depend on remnant liquid layer after the evolution of primary structures. The dynamics of remnant layer de-wetting that essentially is dictated by electrode assembly, fluid properties, and initial film thickness, results in formation of intermediate secondary structures. The possibility of controlling these structures is explored by varying periodicity of the stamp/top electrode, applied potential and initial liquid volume. At a fixed operating condition, critical periodicity is identified for stable secondary structure formation that may lead to ordered nano-patterns for diverse applications.

An In Situ and In Silico Evaluation of Biophysical Effects of 27 MHz Electromagnetic Whole Body Humans Exposure Expressed by the Limb Current.

Objectives The aim was to evaluate correlations between biophysical effects of 27 MHz electromagnetic field exposure in humans (limb induced current (LIC)) and (1) parameters of affecting heterogeneous electric field and (2) body anthropometric properties, in order to improve the evaluation of electromagnetic environmental hazards. Methods Biophysical effects of exposure were studied in situ by measurements of LIC in 24 volunteers (at the ankle) standing near radio communication rod antenna and in silico in 4 numerical body phantoms exposed near a model of antenna. Results Strong, positive, statistically significant correlations were found in all exposure scenarios between LIC and body volume index (body height multiplied by mass) (r > 0.7; p < 0.001). The most informative exposure parameters, with respect to the evaluation of electromagnetic hazards by measurements (i.e., the ones strongest correlated with LIC), were found to be the value of electric field (unperturbed field, in the absence of body) in front of the chest (50 cm from body axis) or the maximum value in space occupied by human. Such parameters were not analysed in previous studies. Conclusions Exposed person's body volume and electric field strength in front of the chest determine LIC in studied exposure scenarios, but their wider applicability needs further studies.

Modulated corona nanosecond discharge in air under ambient pressure

A unique type of corona discharge-modulated corona nanosecond discharge-has been obtained, the parameters of which have been determined in a geometric system of electrodes with a sharply heterogeneous electric field in air under ambient pressure and natural humidity.

Overlapping of the Diffuse Double Layer in the Vicinity of the Microporous Electrode

Introduction A microporous electrode with nm-sized micropores on the surface is an attractive subject in electrochemistry. Some experimental results show the physicochemical properties of microporous electrodes are not explained only in terms of the surface area. We have an interest in the electrical double layer in the narrow space. When the size of the micropore on the electrode is smaller than the diffuse part of the electrical double layer, the diffuse double layer show overlap across the pore. This overlapping of the diffuse double layer cannot be estimated on the one dimension model, such as Gouy–Chapman (GC) theory for planar electrodes. We propose a model of the diffuse double layers in the vicinity of micropores on the basis of the Poisson-Boltzmann equation without any complicated assumptions. This calculation shows essential features of the diffuse double layer on the electrode with micropores. The size dependence, the permittivity dependence, the potential dependence, and the electrolyte concentration dependence of the diffuse double layer and also the differential capacitance of the electrode with micropores are discussed.Model The model is described with a cylindrical coordinate. The electrode was assumed as a conductor with an equipotential surface. The diameter of a pore on the electrode was varied from 0.2 to 5 nm. To avoid singular points in the calculation, the radius of the corners was assumed to be 50 pm in the geometry of this model. The solution phase contains a 1:1 electrolyte. In the solution phase, the Poisson–Boltzmann equation was applied to obtain the profile of the electric potential. In this calculation, the relative permittivity was set to be from 10 to 78. The nonlinear Poisson–Boltzmann equation was numerically solved by the finite element method. The differential capacitance of the double layer was estimated from the dependence of the total charge on the electrode surface on the surface potential.Results and discussion The calculated potential profile showed the overlapping of the diffuse double layer in the micropore. The electric field in the micropore is weaker than that outside of the micropore, that is, the overlapped diffuse double layer provides the mild electric field. Assuming that the thickness of the diffuse double layer is the division of the surface potential by the gradient of the potential at the electrode surface, the degree of the overlapping can express qualitatively. When the size of the micropore on the electrode is smaller than the thickness of the diffuse double layer, the calculated capacitance agrees with the GC capacitance at the planner electrode. On the other hand, when the size of the micropore on the electrode is larger than the thickness of the diffuse double layer, the double layer capacitance converges on the GC capacitance at the microporous electrode. This means that the surface area of micropore becomes effective only at thinner diffuse double layers. The change of the thickness of the diffuse double layer in the micropore causes the strong dependence of the capacitance on the potential and the electrolyte concentration compared with the situation of planar electrode. The characteristic features of microporous electrodes would be originated from the heterogeneous electric field caused by the overlapping of the diffuse double layer.

Non-ultraviolet-based patterning of polymer structures by optically induced electrohydrodynamic instability

We report here an approach to rapidly construct organized formations of micron-scale pillars from a thin polydimethylsiloxane (PDMS) film by optically induced electrohydrodynamic instability (OEHI). In OEHI, a heterogeneous electric field is induced across two thin fluidic layers by stimulating a photoconductive thin film in a parallel-plate capacitor configuration with visible light. We demonstrated that this OEHI method could control nucleation sites of pillars formed by electrohydrodynamic instability. To investigate this phenomenon, a tangential electric force component is assumed to have arisen from the surface polarization charge and is introduced into the traditional perfect dielectric model for PDMS films. Numerical simulation results showed that this tangential electric force played an important role in OEHI.

Pattern formation in thin polymer films by spatially modulated electric fields

We present a theoretical model and experimental data describing the response of a thin liquid polymer film to a heterogeneous electric field. The theory predicts two different regimes separated by a distinct boundary: in one regime the film is characterized by steady-state low amplitude surface modulations following the periodicity of the electric field, in the other regime the film breaks up into pillars centered around the region of highest field strength. The theoretical analysis describes the film destabilization in terms of two dimensionless variables, which fully describe the low amplitude limit. The corresponding experimental system was realized with a photo-structured epoxy resin covering the top electrode and thin polystyrene films that were destabilized by the applied electric field and characterized by AFM after quenching. Theoretical and experimental results allow us to determine the destabilization conditions and to identify the experimental variables that characterize film destabilization. The theoretical framework provides a tool for the experimentalist to predict in detail the structures generated by film destabilization, thereby enabling a new way of ‘soft-lithography’.

Optical Band Splitting and Electronic Perturbations of the Heme Chromophore in Cytochrome c at Room Temperature Probed by Visible Electronic Circular Dichroism Spectroscopy

We have measured the electronic circular dichroism (ECD) of the ferri- and ferro-states of several natural cytochrome c derivatives (horse heart, chicken, bovine, and yeast) and the Y67F mutant of yeast in the region between 300 and 750 nm. Thus, we recorded the ECD of the B- and Q-band region as well as the charge-transfer band at ∼695 nm. The B-band region of the ferri-state displays a nearly symmetric couplet at the B 0-position that overlaps with a couplet 790 cm −1 higher in energy, which we assigned to a vibronic side-band transition. For the ferro-state, the couplet is greatly reduced, but still detectable. The B-band region is dominated by a positive Cotton effect at energies lower than B 0 that is attributed to a magnetically allowed iron→heme charge-transfer transition as earlier observed for nitrosyl myoglobin and hemoglobin. The Q-band region of the ferri-state is poorly resolved, but displays a pronounced positive signal at higher wavenumbers. This must result from a magnetically allowed transition, possibly from the methionine ligand to the d xy-hole of Fe 3+. For the ferro-state, the spectra resolve the vibronic structure of the Q v-band. A more detailed spectral analysis reveals that the positively biased spectrum can be understood as a superposition of asymmetric couplets of split Q 0 and Q v-states. Substantial qualitative and quantitative differences between the respective B-state and Q-state ECD spectra of yeast and horse heart cytochrome c can clearly be attributed to the reduced band splitting in the former, which results from a less heterogeneous internal electric field. Finally, we investigated the charge-transfer band at 695 nm in the ferri-state spectrum and found that it is composed of at least three bands, which are assignable to different taxonomic substates. The respective subbands differ somewhat with respect to their Kuhn anisotropy ratio and their intensity ratios are different for horse and yeast cytochrome c. Our data therefore suggests different substate populations for these proteins, which is most likely assignable to a structural heterogeneity of the distal Fe-M80 coordination of the heme chromophore.

Molecular characterization of Yarrowia lipolytica and Candida zeylanoides isolated from poultry.

Yeast isolates from raw and processed poultry products were characterized using PCR amplification of the internally transcribed spacer (ITS) 5.8S ribosomal DNA region (ITS-PCR), restriction analysis of amplified products, randomly amplified polymorphic DNA (RAPD) analysis, and pulsed-field gel electrophoresis (PFGE). ITS-PCR resulted in single fragments of 350 and 650 bp, respectively, from eight strains of Yarrowia lipolytica and seven strains of Candida zeylanoides. Digestion of amplicons with HinfI and HaeIII produced two fragments of 200 and 150 bp from Y. lipolytica and three fragments of 350, 150, and 100 bp from C. zeylanoides, respectively. Although these fragments showed species-specific patterns and confirmed species identification, characterization did not enable intraspecies typing. Contour-clamped heterogeneous electric field PFGE separated chromosomal DNA of Y. lipolytica into three to five bands, most larger than 2 Mbp, whereas six to eight bands in the range of 750 to 2,200 bp were obtained from C. zeylanoides. Karyotypes of both yeasts showed different polymorphic patterns among strains. RAPD analysis, using enterobacterial repetitive intergenic sequences as primers, discriminated between strains within the same species. Cluster analysis of patterns formed groups that correlated with the source of isolation. For ITS-PCR, extraction of DNA by boiling yeast cells was successfully used.

Special pleochroism in the far-infrared spectra of ferroelectric triglycine sulfate

A special dichroism is observed in the far-infrared spectra of triglycine sulfate crystals. The absorption of a few peculiar lines is dependent on the orientation of the sample surface while, indeed, the infrared electric vector is kept in a constant direction. A significant broadening of some lines in a plate cut perpendicular to the axis is explained by a heterogeneous electric field in the surface layer. New lines appearing only in a plate cut parallel may be interpreted either by a loss of symmetry in the surface parallel to the binary C2 axis or by more classic arguments derived from the complexity introduced by a high absorption index in a very anisotropic crystal. This dichroism is observed in reflectivity and, when transmission is considered, for some lines the dichroism is limited to very thin samples in good accordance with a surface layer explanation, while for other lines it is still observed for thick samples.

Design types and performances of preparative polyacrylamide gel electrophoresis apparatus

AbstractThe designs of both gel and elution chambers in preparative electrophoresis apparatuses are key elements for their performance. The present paper describes four types of designs which were developed by the author to alleviate the shortcomings found in the preceding designs. Performance tests, using human hemoglobin (Hb), partially purified haptoglobin 2‐1 type (Hp 2‐1), and bis‐albumin‐containing serum, show that insufficient dissipation of Joule heat and a heterogeneous electric field cause curvature and slant of the sample zones, and that only a chamber of optimal shape and size leads to minimal dilution, giving a good resolution. Moreover, notch, angle, and rim (Fig. 5), designed to support the gel, and tapering of the elution chamber to minimize its volume, are also important ministructures for the performance of the instrument. Unoptimal sets of these structures also cause concave sample bands and result in bad resolution and excessive dilution. These findings emphasize that in scaling up the apparatus, the structure must be designed on the basis of the detailed fundamental experiments from macrostructure to microstructure by using models of actual size.