Electric Vector Research Articles

Enhancing Photoluminescence: Photonic Bound States in the Continuum in Si Structures with the Self‐Assembled Ge Nanoislands (Laser Photonics Rev. 15(7)/2021)

The cover image illustrates the photonic crystal slab's eigenmode as demonstrated in article number 2000242 by Sergey Dyakov and co-workers. The cones represent the rotation of the electric vector during one period of electromagnetic oscillations. From this figure, one can determine the symmetry type of this mode and predict the features of the far-field emissivity of quantum emitters at the corresponding frequency.

Plausible multiferroic and magneto-electric behaviour of polycrystalline Bi0.85Gd0.05La0.1FeO3 at room temperature

The structural, magnetic and magneto-electric (ME) properties of polycrystalline BiFeO3 and Bi0.9–xGdxLa0.1FeO3 (x = 0.00 and 0.05) samples have been investigated. X-ray diffraction patterns confirm the formation of single phases in all the samples with ‘R3c’ space group. Magnetic anisotropy and ferroelectric hysteresis behaviour are observed in Bi0.85Gd0.05La0.1FeO3 through magnetization and polarization measurements respectively. In addition, the same compound shows weak ferromagnetism at room temperature with a significantly enhanced remnant magnetization of ~ 23.6emu.mol−1, concomitant with an exchange bias. ME measurements on the compound show a non-linear dependence of magnetic and electric vectors.

Compact explicit matrix representations of the flexoelectric tensor and a graphic method for identifying all of its rotation and reflection symmetries

Flexoelectricity is an electromechanical phenomenon produced in a dielectric material, with or without centrosymmetric microstructure, undergoing a non-uniform strain. It is characterized by the fourth-order flexoelectric tensor, which links the electric polarization vector with the gradient of the second-order strain tensor. Our previous work [H. Le Quang and Q.-C. He, Proc. R. Soc. A 467, 2369 (2011)] solved the fundamental theoretical problem of determining the number and types of all rotational symmetries that the flexoelectric tensor can exhibit. In the present study, compact explicit matrix representations of the flexoelectric tensor are provided so as to facilitate the use of it with any possible rotational symmetry. The number and types of all reflection symmetries that the flexoelectric tensor can have are also determined. To identify the rotational symmetry and reflection symmetry of a given flexoelectric tensor, a simple and efficient graphic method based on the concept of pole figures is presented and illustrated.

Piezoelectric response of energetic composites under an electrostatic excitation

Several high-explosive (HE) crystals are known to be piezoelectric. However, no systematic study has been carried out on how this effect can be utilized. In this paper, we report the results of an analysis on the response of composites consisting of HE crystals and a polymeric binder under electrostatic excitation. The HE crystals considered are 1,3,5-trinitroperhydro-1,3,5-triazine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, pentaerythritol tetranitrate, and ammonium perchlorate. To explore avenues for enhancing the piezoelectric effect, the binder of the composites is taken to be piezoelectric polyvinylidene fluoride. The focus is on the distributions of induced electric field vector and mechanical stress in the microstructures. The effects of crystal–binder volume fraction, HE crystal size, and dielectric constants of the HE crystals are investigated. To further explore the effect, microparticles of lead zirconate titanate piezoelectric ceramic are introduced to some microstructures. For the HE crystals considered here, a coupled electromechanical analysis shows that the microstructural heterogeneities can enhance the local electric fields to as high as 1.34 times the applied E-field, causing the dielectric breakdown field strength of the overall composite to be much lower than the breakdown strengths of the constituents in the microstructure. In addition, the induced stress levels just prior to dielectric breakdown are well below the yield strengths of the respective constituents. As such, controlled dielectric breakdown, rather than mechanical damage, should primarily be used to facilitate hotspot formation, ignition, and chemical reaction. The likelihood of local dielectric breakdown within the HE crystals is systematically quantified as a function of applied electric field, microstructural attributes, and constituent behavior. To gauge the effect of the direct piezoelectric effect, one material case is also subjected to mechanical excitation in the form of compression. Under an applied external stress, the results show that the direct piezoelectric effect can lead to local yielding and thereby serve as a hotspot generation mechanism. On the other hand, the induced E-field is weak and unlikely to serve as a practical or efficient means of effecting hotspots within an energetic material. The analysis points out that simultaneous application of electrostatic excitation and mechanical excitation can also be considered.

Selective observation of transverse optical phonons of Au modes to evaluate free charge carrier parameters in β -Ga2O3 substrate and homoepitaxial film

Polarized infrared reflectance spectra from β-Ga2O3 (001) unintentionally doped (undoped) and Sn-doped substrates were investigated. Spectra from an undoped homoepitaxial film grown on the Sn-doped substrate were also investigated. By setting the electric field vector of the incident light E parallel to the crystallographic b-axis in the s-polarized configuration, the spectra for pure transverse optical phonons of Au modes were well reproduced by the Drude–Lorentz model. Subsequently, the free-carrier concentrations and carrier mobilities were determined to be in reasonable agreement with those determined by Hall-effect measurements, and at the same time, the film thickness was determined for the homoepitaxial layer. The results ensure the validity of the simplified optical model analyses for any arbitrary surface orientations where the b-axis is parallel to the surface only if no birefringence effects are present by choosing as E//b in s-polarized configuration.

Fabrication of polarization colour filter device via direct Au film imprinting

In this study, Au grating with a subwavelength period was fabricated on low-melting glass via direct imprint lithography. The Au film was imprinted at 425 °C and 5 kN using SiC as a mold. The period, grating depth, and fill factor of the mold were 300 nm, ∼240 nm, and 0.5, respectively. Consequently, Au grating with a pitch, depth, and fill factor of 300 nm, ∼110 nm, and 0.7, respectively, was obtained. The transverse magnetic (TM, electric field vector perpendicular to the grating) spectra at an incident angle of 40° exhibited sharp peaks at a wavelength of 642 nm, and the TM transmittance and extinction ratio were 30% and 12.9 dB, respectively. The maximum extinction ratio was 19.0 dB at a wavelength and incident angle of 1 µm and 60°, respectively. This process is simpler and less expensive than the conventional fabrication processes.

Resonance Raman spectroscopic analysis of the iron–sulfur cluster redox chain of the Ralstonia eutropha membrane‐bound [NiFe]‐hydrogenase

AbstractIron–sulfur (Fe–S) centers are versatile building blocks in biological electron transfer chains because their redox potentials may cover a wide potential range depending on the type of the cluster and the specific protein environment. Resonance Raman (RR) spectroscopy is widely used to analyze structural properties of such cofactors, but it remains still a challenge to disentangle the overlapping signals of metalloproteins carrying several Fe–S centers. In this work, we combined RR spectroscopy with protein engineering and X‐ray crystallography to address this issue on the basis of the oxygen‐tolerant membrane‐bound hydrogenase from Ralstonia eutropha that catalyzes the reversible conversion of hydrogen into protons and electrons. Besides the NiFe‐active site, this enzyme harbors three different Fe–S clusters constituting an electron relay with a distal [4Fe–4S], a medial [3Fe–4S], and an unusual proximal [4Fe–3S] cluster that may carry a hydroxyl ligand in the superoxidized state. RR spectra were measured from protein crystals by varying the crystal orientation with respect to the electric field vector of the incident laser to achieve a preferential RR enhancement for individual Fe–S clusters. In addition to spectral discrimination by selective reduction of the proximal cluster, protein engineering allowed for transforming the proximal and medial cluster into standard cubane‐type [4Fe–4S] centers in the C19G/C120G and P242C variants, respectively. The latter variant was structurally characterized for the first time in this work. Altogether, the entirety of the RR data provided the basis for identifying the vibrational modes characteristic of the various cluster states in this “model” enzyme as a prerequisite for future studies of complex (FeS)‐based electron transfer chains.

Spin-Valued Four Bosons Electrodynamics

Electromagnetism is based on electric charge and spin. The study here corresponds to understand on spin effects at a vectorial electrodynamics. Its scenario is a non-linear abelian electromagnetism where the electric charge is transmitted through a four bosons quadruplet, constituted by the usual photon, massive photon and charged massive photons. These four bosons intermediate the charge exchange ΔQ = 0, ±1.The spin is introduced at first principles. A spintronics Lagrangian for four vector fields is performed. Considering that spin is a space-time physical entity derived from Lorentz Group, these vector fields are associated to Lorentz Group, as Lie algebra valued. Similarly to non-abelian gauge theories where Aμ≡ Aμ,ata, one introduces the relationship Aμ≡ Aμ,κλΣκλ where (Σκλ)αβ is the Lorentz Group generator. Thus, based on three fundamentals which are light invariance, electric charge conservation law and vector fields Lie algebra valued through Lorentz Group generators, one derives a spin-valued four vectorial electrodynamics. It is given by the fields quadruplet Aμ1 ≡ {Aμ, Uμ, Vμ±} where Aμ means the usual photon, Uμ a massive photon and Vμ± massive charged photons. Two novelties appear. The first one is that, new terms are developed into usual four bosons electromagnetism. They contribute to Lagrangian, equations of motion, Noether theorem. The second one is that the equations of motion derive a renormalizable spin coupling with the electric and magnetic fields.There is a spin-1 electrodynamics to be investigated. A neutral electromagnetism is mandatory to be analyzed. Something beyond dipole, quadrupole and so on. Understand the role of spin in the electrical and magnetic properties of particles. A spin vectorial expression S--> is obtained. It adds EM interactions not depending on electric charge and with spin interactions through electric dipole and magnetic moments.

The variation of the electric field along optic fiber for null Cartan and pseudo-null frames

In this paper, we introduce new frame and new transformation associated with combined Korteweg–de Vries–modified Korteweg–de Vries (KdV–mKdV) equation, the mKdV and the KdV equations with respect to the null Cartan frame in Minkowski 3-space. Direction of the state of polarization of monochromatic linear polarized light wave traveling in the optic fiber is given by the direction of electric field vector. We show that the electric field vector [Formula: see text] can be expressed as a linear combination of null Cartan frame apparatus using this new transformation in Minkowski 3-space. Later, we study rotation of the polarization plane along optic fiber according to null Cartan frame and Frenet frame of pseudo-null curve in Minkowski 3-space. Finally, we obtain Lorentz force equations via null and pseudo null electromagnetic curves.

Element Differential Method for Solving Linear and Nonlinear Electromagnetic Problems

A novel numerical method named element differential method (EDM) is first presented to solve linear and nonlinear static electromagnetic problems. The main idea of this method is to use the direct differentiation formulation of the shape functions of Lagrange isoparametric elements to evaluate geometry and physical variables. A new collocation method is proposed to establish the system of equations, in which the governing equation is collocated at the internal nodes of the elements, the continuity conditions of tangential component of magnetic field intensity and normal component of electric displacement vector are collocated at interface nodes between elements, and Neumann boundary conditions are collocated at outer surface nodes. Compared with the finite element method, there is no need to use any variational or energy principles to establish the system of equations and there is no requirement for integral evaluation. The derived spatial derivatives can be directly substituted into the static electromagnetic governing equations and the boundary conditions to form the final system of algebraic equations. Three 2D numerical examples are used to verify the correctness and effectiveness of the presented method for solving linear and nonlinear static electromagnetic problems.

Over-the-Air Array Calibration of mmWave Phased Array in Beam-Steering Mode Based on Measured Complex Signals

Accurate knowledge of initial complex excitation coefficients for phased-array elements is essential to ensure accurate array performance. In the literature, many array calibration algorithms have been proposed for this purpose, which generally requires customized phase setting for individual phase shifters connected to array elements. In this article, a new array calibration method is proposed for phased array operating in beam-steering mode only, that is, phase shifts of elements are only simultaneously set according to the beam-steering directions, and therefore, there is no need for dedicated individual element phase tuning. The proposed method requires a minimum number of complex-signal measurements in principle, which enables fast measurement. Furthermore, it is found that the performance of the proposed method is determined by the beam-steering matrix, whose condition number is mainly ruled by the beam-steering angle interval. The proposed method is numerically simulated and experimentally validated in a millimeter-wave (mmWave) phased-array antenna-in-package (AiP) platform at 28 GHz. The proposed method presents good agreement with the well-known rotating element electric field vector (REV) array calibration method, with an amplitude error and phase error within ±0.5 dB and ±5°, respectively. Furthermore, the reconstructed array pattern with the proposed method offers excellent match with the measured array pattern.

Review on the physical basis of wave–particle duality: Conceptual connection between quantum mechanics and the Maxwell theory

A well-known mystery in quantum mechanics is wave–particle duality: Is an electron a point mass or a physical wave? What is the physical meaning of its wave function? About a hundred years ago, there was a famous debate between Bohr and Einstein on this topic. Their question is still open today. This paper reviews a new theoretical framework to address this problem. Here, it is hypothesized that both photons and electrons are quantized excitation waves of the vacuum, the physical properties of which can be modeled based on the Maxwell theory. Using the method of Helmholtz decomposition, one can show that the wave function of the particle is associated with an electric vector potential called “ Z”, which plays the role of basic field for the excitation wave. Using this framework, the quantum wave equations can be derived based on a quantization of the Maxwell theory. This work suggests that, the quantum wave function truly represents a physical wave; the wave packet looks like a “particle” only in the macroscopic view. Because the vacuum excitation obeys the principle of all-or-none, the probability of detecting this “particle” is related to the wave function as suggested in the Copenhagen interpretation.

Physical optics approach to wave diffraction by a perfect electromagnetic conductor half-plane

The scattering of electromagnetic plane waves by a perfect electromagnetic conductor is investigated. The method of physical optics is used for the analysis of the problem. The reflected fields by a whole-plane are taken into account. The surface electric and magnetic current densities are constructed with the aid of the incident wave and the reflected field from the whole-surface. The scattering integrals are obtained for the electric and magnetic vector potentials. The scattered electric and magnetic fields are expressed in terms of the vector potentials. The scattering integrals are evaluated asymptotically for large values of the wave-number. Some numerical results are given.

15 Use of Bioelectric Impedance Analysis in Burn Patients: A Pilot Study

Abstract Introduction Bioelectric Impedance Analysis (BIA) is a rapid, non-invasive, and inexpensive technology based on electrical conductivity. BIA assesses body composition, fluid shifts, and phase angle, an electrical force vector where smaller values suggest cellular injury. Our objective was to use BIA to longitudinally track the clinical status of burn patients. We hypothesized that BIA would detect progressive decreases in muscle mass throughout the patient’s hospital course and that low phase angle values would correlate with severity of injury. Methods A cohort study of 10 patients from January 1, 2020 to March 13, 2020 was performed at an ABA-verified burn center. Patient and burn characteristics and laboratory data were collected. BIA measurements were performed daily for the first 10 days of admission and then twice weekly until discharge. The primary outcome was to detect changes in body composition. The secondary objectives were to detect differences between low and high-risk patients in terms of water composition and phase angle. Patients with APACHE II > 15, measured at burn unit admission, were considered high risk for burn injury related morbidity and mortality. Results BIA detected a statistically significant negative correlation between time spent hospitalized and leg lean mass (LM) (r2=0.56, P< 0.0001), right arm LM (r2=0.52, P< 0.0001) and left leg LM (r2=0.57, P< 0.0001), and positive correlation between body fat mass (BFM) and time spent hospitalized (r2=0.50, P=0.0004). Water composition (volume of extracellular water (ECW) per total body water (TBW)) negatively correlated with low-risk patients: right arm (r2=0.51, P< 0.0001), left arm (0.71, P< 0.001), thorax (0.66, P< 0.0001), right leg (0.74, P< 0.0001), left leg (0.35, P=0.002). Full body phase angle increased with low-risk patients over their hospital course (r2=0.62, P< 0.0001), while phase angle decreased with high-risk patients (r2=0.71, P=0.0006). Full body phase angle differentiated high risk patients (P< 0.0001), and phase angle of thorax differentiated between patients with and without inhalation injury (P=0.002). Conclusions Our study demonstrates that BIA measures changes in body composition and fluid shifts, identifies inhalation injury, and correlates with severity of injury in hospitalized burn patients. This pilot study included a limited number of participants with varying anatomic injuries presenting unique measurement challenges. Regardless, our preliminary data justifies a larger prospective study to confirm these results and correlate them with clinical outcomes.

Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron

Context. Supermassive black holes in the centres of radio-loud active galactic nuclei (AGN) can produce collimated relativistic outflows (jets). Magnetic fields are thought to play a key role in the formation and collimation of these jets, but the details are much debated. Aims. We study the innermost jet morphology and magnetic field strength in the AGN 3C 345 with an unprecedented resolution using images obtained within the framework of the key science programme on AGN polarisation of the Space VLBI mission RadioAstron. Methods. We observed the flat spectrum radio quasar 3C 345 at 1.6 GHz on 2016 March 30 with RadioAstron and 18 ground-based radio telescopes in full polarisation mode. Results. Our images, in both total intensity and linear polarisation, reveal a complex jet structure at 300 μas angular resolution, corresponding to a projected linear scale of about 2 pc or a few thousand gravitational radii. We identify the synchrotron self-absorbed core at the jet base and find the brightest feature in the jet 1.5 mas downstream of the core. Several polarised components appear in the Space VLBI images that cannot be seen from ground array-only images. Except for the core, the electric vector position angles follow the local jet direction, suggesting a magnetic field perpendicular to the jet. This indicates the presence of plane perpendicular shocks in these regions. Additionally, we infer a minimum brightness temperature at the largest (u, v)-distances of 1.1 × 1012 K in the source frame, which is above the inverse Compton limit and an order of magnitude larger than the equipartition value. This indicates locally efficient injection or re-acceleration of particles in the jet to counter the inverse Compton cooling or the geometry of the jet creates significant changes in the Doppler factor, which has to be > 11 to explain the high brightness temperatures.

ПЕРЕМАГНИЧИВАНИЕ И НЕОДНОРОДНЫЙ МАГНИТОЭЛЕКТРИЧЕСКИЙ ЭФФЕКТ В НАНОРАЗМЕРНОЙ ДВУХСЛОЙНОЙ ФЕРРОМАГНИТНОЙ ПЛЕНКЕ С КОМБИНИРОВАННОЙ ОДНООСНОЙ И КУБИЧЕСКОЙ АНИЗОТРОПИЕЙ В СЛОЯХ

A numerical study of the magnetization reversal of a two-layer exchange-coupled ferromagnetic plate of finite dimensions, which has a combined uniaxial anisotropy (of the "easy axis" type for the upper layer and «easy plane» for the lower one) and cubic anisotropy with orientation [111]. It is shown that, in the presence of cubic anisotropy, the ground state of magnetization turns out to be uniform in the plane of the film. However, there is discontinuity at the interface between the film layers. This inhomogeneity can lead to the appearance of electric polarization due to the magnetoelectric effect. The electric polarization vector in this case lies in the plane of the film. Its modulus increases with increasing cubic anisotropy. In addition, with an increase in cubic anisotropy, a hysteresis of electrical polarization is observed.

Multi-Electrode Architecture Modeling and Optimization for Homogeneous Electroporation of Large Volumes of Tissue

Electroporation is a phenomenon that consists of increasing the permeability of the cell membrane by means of high-intensity electric field application. Nowadays, its clinical application to cancer treatment is one of the most relevant branches within the many areas of electroporation. In this area, it is essential to apply homogeneous treatments to achieve complete removal of tumors and avoid relapse. It is necessary to apply an optimized transmembrane potential at each point of the tissue by means of a homogenous electric field application and appropriated electric field orientation. Nevertheless, biological tissues are composed of wide variety, heterogeneous and anisotropic structures and, consequently, predicting the applied electric field distribution is complex. Consequently, by applying the parallel-needle electrodes and single-output generators, homogeneous and predictable treatments are difficult to obtain, often requiring several repositioning/application processes that may leave untreated areas. This paper proposes the use of multi-electrode structure to apply a wide range of electric field vectors to enhance the homogeneity of the treatment. To achieve this aim, a new multi-electrode parallel-plate configuration is proposed to improve the treatment in combination with a multiple-output generator. One method for optimizing the electric field pattern application is studied, and simulation and experimental results are presented and discussed, proving the feasibility of the proposed approach.

A new radio-frequency acoustic method for remote study of liquids

In the present work, a novel study method of conductive liquids has been proposed. It is based on a discovered phenomenon of radiofrequency anisotropy of electrolyte solution, which arises in response to mechanical excitation of the solution. The phenomenon was observed during the development of a radiofrequency polarimetric contactless cardiograph. The electric field vector rotates after its transition through the pericardial region due to the acceleration changes of blood. Numerous in vitro experiments with monochromatic and impulse acoustic waves always induced the polarization rotation of the RF wave passing through an electrolyte solution. The response obtained from the solutions on acoustic excitation of the Heaviside function form demonstrates the effect of a solution “memory”. The dynamics of this process resembles the spin glasses magnetization. We hypothesized that there was a magnetic moment change within the solution, and the possible reason for it is an appearance of electromagnetic impulse caused by the same acoustic excitation. In a further experiment, we really captured a suspected electrical potential. Given that, we can declare at least three new physical effects never observed before for an electrolyte solution. The study method itself may provide broad options for remote measurement of the electrolyte solution parameters.

Method to Enhance Directional Propagation of Circularly Polarized Antennas by Making Near-Electric Field Phase More Uniform

A new approach to significantly increase the uniformity in aperture phase distribution, through time synchronization in the near-electric field, of circularly polarized (CP) antennas is presented. The method uses the phase of the CP electric field vectors, obtained through full-wave numerical simulations, and does not rely on any approximation such as ray tracing. The near-field data is post-processed to extract the relative phase difference that exists due to the unsynchronized rotations of the electric field vectors in a plane parallel to the antenna aperture. The phase delay is compensated with a thin time-synchronizing metasurface (TSM) that has a 2-D array of time-delay cells. The method is demonstrated with a prototype made of a two-port patch antenna, which is fed through a hybrid junction, and a TSM that is placed at one wavelength spacing above the patch. When TSM is used with patch antenna, its uniform phase area increases manifold thus increasing far-field directivity from 6.8 to 22 dBic.

Nonparaxial scalar diffraction theory modifications for improved efficiency estimation

Using the nonparaxial scalar diffraction equations to estimate the diffraction efficiency of multiple orders of a sinusoidal reflection grating, we compare the results of transverse electric (TE) and transverse magnetic (TM) vector wave simulations for a reflective surface on glass. Modifications are presented that enable the nonparaxial scalar solution to approximate simulation results in each order to within 1% to 2% across a 0 to 90 deg range of incidence angles when the diffracted power is predominantly carried in the first several orders, up to the fourth order. The accuracy of simulations in this regime is particularly important for surface scattering where individual spatial frequencies typically have amplitudes much less than a hundred nanometers. A substantial reduction in the error between vector simulations and scalar estimation of diffraction efficiency is demonstrated with the following modifications: (1) an obliquity factor correction for the specular order based on a first-order power conservation criterion, (2) a “cutoff” factor modifying the obliquity factor as the diffracted angle approaches 90 deg for each order, and (3) nonuniform unallocated power distribution near the low-order cutoffs. The second and third modifications are applied to higher diffraction orders for extending the range of applicable grating heights up to 200 nm (peak-to-valley), periods down to twice the wavelength, and slopes up to 0.2 (root mean square).