Extrinsic Electric Fields Research Articles

High-Performance Electrostrictive Relaxors with Dispersive Endotaxial Nanoprecipitations.

Ultrahigh-precision manufacturing and detection have highlighted the importance of investigating electrostrictive materials with a weak stimulated extrinsic electric field and a simultaneous large hysteresis-free strain. In this study, a new type of electrostrictive relaxor ferroelectric is designed by constructing a complex inhomogeneous local structure to realize excellent electrostrictive properties. A remarkably large electrostrictive coefficient, M33 (8 × 10-16 m2 V-2 ) is achieved. Through a combined atomic-scale scanning transmission electron microscopy and advanced in situ high-energy synchrotron X-ray diffraction analysis, it is observed that such superior electrostrictive properties can be ascribed to a special domain structure that consists of endotaxial nanoprecipitations embedded in a polar matrix at the phase boundary of the rhombohedral/tetragonal/cubic phases. The matrix contributes to the high strain response under the weak extrinsic electric field because of the highly flexible polarization and randomly dispersed endotaxial nanoprecipitations with a nonpolar central region, which provide a strong restoring force that reduces the strain hysteresis. The approach developed in this study is widely applicable to numerous relaxor ferroelectrics, as well as other dielectrics, for further enhancing their electrical properties, such as electrostriction and energy-storage capacity.

Investigation of additives nanoparticles and sphere barriers effects on the fluid flow inside a nanochannel impressed by an extrinsic electric field: A molecular dynamics simulation

In this paper, MD technique was employed to predict the atomic barrier impact on H2O/Copper nanofluid dynamic manner in existence of outer electric subject. To examine the H2O/Copper nanofluid flow, the Copper nanochannel with sphere barriers was simulated. In these MD simulations, the interactions between atoms of atomic structures were explained via Lenard-Jones force fields and Embedded Atom Model. To examine the atomic manner of these structures, physical specification like density, velocity and temperature profiles of H2O/Copper nanofluid reported. MD simulation outcomes display that, these physical specification of H2O/Copper nanofluid within non-optimal nanochannel effected by atomic barriers size transformations. Further, the effects of external electric field magnitude and frequencies variation on dynamical manner of H2O/Cu calculated. Numerically, it is calculated that, highest rate of temp., velocity and density profiles reach to 0.123 atom/Å3, 0.986 Å/ps, and 513 K rates which these theatrical reports can be significant for actual application of nanofluid structures.

Repair of dentine-related lesions without a drill or injection.

For covering the shortages of traditional treatments, a novel and non-invasive system was developed with the simple adaption of nature's own repair process, while an extrinsic electric field was introduced to improve its remineralization kinetics. In an in vivo study, acid-etched rabbit dentine was used to evaluate the remineralization efficacy and safety of the system. The exposed dentine tubules were fully occluded after 5 hours/1.0 mA and 8 hours/0.5 mA of remineralization. After 5 hours of remineralization (1.0 mA), the micro-hardness of the demineralized dentine was fully recovered, equal to native rabbit dentine. Haematoxylin–eosin staining demonstrated no obvious inflammatory reaction. This study provides a feasible solution to realize rapid repair of dentine.

Negative transconductance in multi-layer organic thin-film transistors

Negative transconductance (NTC) refers to the phenomenon of the N-shape transfer characteristic appearing with a current peak and valley. It has been extensively studied in the past few decades due to its applications in logic and memory devices. Here, we observe unique antibipolar transfer characteristics and NTC behavior in multi-layer 2,6-diphenyl anthracene organic thin-film transistors grown on h-BN, which is due to the vertical potential barrier between the charge accumulation region near the substrate and the neutral bulk region under the contacts. The applied extrinsic electric field could effectively modulate the barrier height, resulting in a competition for charge carrier transport between lateral and vertical directions. Based on the NTC and antibipolar properties, a frequency doubler has been fabricated on a single transistor, which provides a new building block for organic logic circuits.

Electric Field Effects During Solidification of the Ternary Oxide Eutectic Al2O3‐YAG‐ZrO2

AbstractLHPG and zone melting solidification of Al2O3‐YAG‐ZrO2:Y eutectic samples is performed in order to investigate intrinsic and extrinsic electric field phenomena. An intrinsic electric field is measured during solidification. Its decay with distance from the interface, and its relaxation with time, show that it is induced by the accumulation of positive electric charges at the solid‐liquid interface, that diffuse away when pulling is stopped. Under extrinsic electric field, a significant modification of the eutectic phase diagram is observed. The charged diffusive boundary layer interacts with the field and the microstructure is impacted. Those observations suggest that the segregating species is zirconium ions.

Bandwidth Improvement of CMOS-APD With Carrier-Acceleration Technique

We present a silicon avalanche photodetector (APD) based on multiple P + /N-well junctions fabricated in standard complementary metal-oxide-semiconductor (CMOS) technology. In order to overcome the photodetection-bandwidth limitation of the CMOS-APD based on P + /N-well junction, carrier-acceleration technique is proposed. With this technique, the photogenerated carriers in the charge-neutral N-well region are accelerated by the extrinsic electric field. To induce the extrinsic electric field inside N-well, the CMOS-APD is designed with multiple junctions to reduce the distance between two different N-well biasing contacts. Its performance is simulated and measured with different bias voltages applied to N-well, and it is demonstrated that the CMOS-APD with the carrier-acceleration technique provides higher photodetection bandwidth.

Distinct electronic structure of the electrolyte gate-induced conducting phase in vanadium dioxide revealed by high-energy photoelectron spectroscopy.

The development of new phases of matter at oxide interfaces and surfaces by extrinsic electric fields is of considerable significance both scientifically and technologically. Vanadium dioxide (VO2), a strongly correlated material, exhibits a temperature-driven metal-to-insulator transition, which is accompanied by a structural transformation from rutile (high-temperature metallic phase) to monoclinic (low-temperature insulator phase). Recently, it was discovered that a low-temperature conducting state emerges in VO2 thin films upon gating with a liquid electrolyte. Using photoemission spectroscopy measurements of the core and valence band states of electrolyte-gated VO2 thin films, we show that electronic features in the gate-induced conducting phase are distinct from those of the temperature-induced rutile metallic phase. Moreover, polarization-dependent measurements reveal that the V 3d orbital ordering, which is characteristic of the monoclinic insulating phase, is partially preserved in the gate-induced metallic phase, whereas the thermally induced metallic phase displays no such orbital ordering. Angle-dependent measurements show that the electronic structure of the gate-induced metallic phase persists to a depth of at least ∼40 Å, the escape depth of the high-energy photoexcited electrons used here. The distinct electronic structures of the gate-induced and thermally induced metallic phases in VO2 thin films reflect the distinct mechanisms by which these states originate. The electronic characteristics of the gate-induced metallic state are consistent with the formation of oxygen vacancies from electrolyte gating.

Third-order electric-field-induced dipolar resonances from patterned barium-strontium-titanate thin-films

Using microwave reflection spectroscopy, the complex permittivities of etch defined, 240 nm thick, (Ba0.6Sr0.4)TiO3, thin films have been measured over the frequency range of (1 to 4) GHz. Anomalous electric-field-induced electro-acoustic resonances were observed and characterized as a function of extrinsic electric field magnitude, ambient temperature, and sample diameter. The real and imaginary parts of the measured permittivities were fit to frequency-dependent functions derived from the Lorentz oscillator model. From these functions, extracted static dielectric constants were found to display excellent agreement with a closed-form expression derived by calculating third-order nonlinear susceptibility from the Landau-Devonshire-Ginzberg model.

Electric field‐induced polarization of charged cell surface proteins does not determine the direction of galvanotaxis

Galvanotaxis, that is, migration induced by DC electric fields, is thought to play a significant role in development and wound healing, however, the mechanisms by which extrinsic electric fields orchestrate intrinsic motility responses are unknown. Using mammalian cell lines (3T3, HeLa, and CHO cells), we tested one prevailing hypothesis, namely, that electric fields polarize charged cell surface molecules, and that these polarized molecules drive directional motility. Negatively charged sialic acids, which contribute the bulk of cell surface charge, redistribute preferentially to the surface facing the direction of motility, as measured by labeling with fluorescent wheat germ agglutinin. We treated cells with neuraminidase to remove sialic acids; as expected, this decreased total cell surface charge. We also changed cell surface charge independent of sialic acid moieties, by conjugating cationic avidin to the surface of live cells. Neuraminidase inhibited the electric field-induced directional polarization of membrane ruffling and alpha4 integrin, while avidin treatment actually reversed the directional polarization of sialic acids. Neuraminidase treatment inhibited directionality but did not alter speed of motility. Surprisingly, avidin treatment did not significantly alter either directionality or speed of motility. Thus, our results demonstrate that electric field-induced polarization of charged species indeed occurs. However, polarization of the bulk of charged cell surface proteins is neither necessary nor sufficient to cause motility, thus contradicting the second part of our hypothesis. Because neuraminidase inhibited directional motility, we also conclude that sialic acids are required constituents of some cell surface molecule(s) through which electric fields mount a polarized transmembrane response.

Ab Initio Quantum Mechanical Study of Metal Substitution in Analogues of Rubredoxin: Implications for Redox Potential Control

Substitution of different metals into the redox sites of metalloproteins is a means of studying the structure of the native protein and of varying the redox properties of the protein. The implicit assumption is often made that metal substitution changes only intrinsic properties of the redox site such as the ionization potential without altering the surrounding protein or solvent. However, if this is not true, structural studies of metal-substituted proteins will not reflect the native protein and the differences in redox potential upon metal substitution will not be simply the differences in ionization potential of the redox sites because of perturbations in the extrinsic electric field. Here, we present an ab initio unrestricted Hartree−Fock quantum mechanical study of metal substitution in the [M(SCH3)4)]2-/1- analogue, where M = Fe, Co, Ni, and Zn, of the protein rubredoxin. Variations in several physical properties were determined and compared to experimental data. Upon metal substitution, only minor variations in geometry, atomic spin, and atom-centered partial charges of the redox site are observed. However, significant variation is found in the energies of reduction, on the order of 100−1000 mV. This indicates that when such substitutions are made into an Fe−S metalloprotein, little change will occur in the interactions between the metal site and the surrounding protein and thus the surrounding protein structure and the resultant electric field will not change. Thus, the structure is relevant to the native protein and the redox properties are mainly determined by the variations in the intrinsic ionization potential of the metal site and not the extrinsic field of the surrounding protein and solvent.

Oxide Film Formation on Metals and Alloys by Thermal, Electrochemical and Plasma Oxidation and Prediction of Resulting Structures

AbstractMulticomponent oxide films are needed to meet the increasing demands of the electronics industry. Three main methods that involve oxidation of a metallic substrate are thermal, anodic and plasma oxidation. Today we do not have an adequate fundamental physical-chemical model of how multicomponent oxides evolve on alloys under these oxidizing conditions to design a wide range of materials for electronic devices. The three methods will be discussed in terms of physical/chemical parameters that influence the chemical nature and structure of the resulting oxides. By using surface studies of the oxidation behavior of numerous metals and alloys we have been able to delineate the factors which are most important to the oxide formation process and provide insight into the prediction of oxide layer structures. The electrochemical processes that occur during the materials reaction with a chosen environment will be used to discuss the physical and chemical mechanisms involved. Intrinsic and extrinsic electric fields will be shown to influence the chemical and structural nature of the resulting oxide structures. Examples will be presented from a number of metal and alloy systems that have been examined in our laboratory. These include Al, Ti, Zr, Nb, Mn, Cu and Ni and some of their selected alloys. The models that have developed from these studies are providing some predictive power in how the complex oxide overlayer will be chemically speciated and on its structure.

Medullary electrosensory processing in the little skate

1. Previous studies have demonstrated that the resting activity of electrosensory ALLN fibers is modulated by the animal's own respiratory activity and that all fibers innervating a single ampullary cluster are modulated with the same amplitude and phase relationship to ventilation. We demonstrate that ALLN fibers in the skate are modulated in this common-mode manner bilaterally, regardless of receptor group, orientation, or position of the receptor pore on the body surface (Fig. 2). 2. Ascending efferent neurons (AENs), which project to the electrosensory midbrain from the DON, are modulated through a much smaller portion of their dynamic range. AENs give larger responses to an extrinsic local electric field than to the respiratory driving, indicating that a mechanism exists for suppressing ventilatory electrosensory reafference. 3. In paralyzed animals no modulation of resting activity or of responses of extrinsic electric fields could be observed with respect to the animal's respiratory motor commands in the absence of electrosensory reafference. 4. Cells of the dorsal granular ridge (DGR) project to medullary AENs via the DON molecular layer. A majority of proprioceptive DGR neurons are modulated by ventilatory activity, however, in a given fish the modulation is not in the same phase relationship to ventilation among DGR units. 5. The modulation of AENs during respiration was increased following transection of the contralateral ALLN (Fig. 9). Resting activity and responses to excitatory stimuli were inhibited by simultaneous stimulation of the transected contralateral ALLN indicating that a common-mode rejection mechanism is mediated via the commissural interconnections of the DONs.

Experimental measurements of field effects on dielectronic recombination cross sections and Rydberg product-state distributions.

Experimental details are presented for the measurement of the effects of extrinsic electric fields on cross sections and Rydberg product-state distributions for dielectronic recombination of ${\mathrm{Mg}}^{+}$ with electrons. A new type of Rydberg state detector is described. Experimental results for dielectronic recombination in the presence of fields are presented for three field values, and these results are compared with theoretical calculations.

Steady growth cone currents revealed by a novel circularly vibrating probe: a possible mechanism underlying neurite growth.

The rate and direction of neurite growth have been shown in a number of studies to be determined by the distribution of adhesive sites on the growth cone. Recent evidence showing that the application of extrinsic electric fields can redistribute membrane molecules and alter both the rate and direction of neurite growth have raised the question whether endogenous electric fields might be produced by steady currents in growth cones. To investigate this question, we have devised a novel circularly vibrating microprobe capable of measuring current densities in the range of 5 nA/cm2 (near the theorectical limit of sensitivity), with a spatial resolution of 2 micron. The design of this device and the development of a novel algorithm for computing current vectors on-line is described. Using this probe we have found that cultured goldfish retinal ganglion cell growth cones generate steady inward currents at their tips. The measured currents, in the range of 10-100 nA/cm2, appear to flow into the filopodia at their tips and back outward near the junctures of the filopodia and the growth cone. The currents appear to be produced only during active growth. Ion substitution experiments support the conclusion that the majority of this current is carried by Ca2+ ions, which we postulate flow through a population of activated voltage-sensitive Ca2+ channels located on the filopodial tips. Calculation of the transmembrane current density (4 X 10(-6) nA/cm2) leads to an estimate of channel density (10 channels/micron2) in close agreement with the measured density of Ca2+ channels in other systems. The assumption that calcium channel proteins are conveyed to nerve terminals by active transport, whereas sodium channel proteins are conveyed passively by a slower somatofugal diffusion process [Strichartz et al, 1984], would explain why developing neurons tend to display Ca2+-sensitive electrogenesis at their growing tips, and Na+-sensitive action potentials later in development. In order to gain some insight into the possible role of these steady growth currents, we estimated the membrane depolarization and axial voltage gradient they produce. It is likely that the currents produce sufficient membrane depolarization (approximately equal to 4 mV) to cause autogenous activation of ion channel permeabilities. Similarly, the axial voltage gradient (approximately equal to 4 mV/cm) would be expected to move intracytoplasmic vesicles by electrophoresis at a rate (20-40 microns/hr) very close to that at which the filopodia are observed to grow.(ABSTRACT TRUNCATED AT 400 WORDS)