Weak Polarization Research Articles

Spin density matrix for and its polarization alignment in * *Supported by the National Natural Science Foundation of China (12247121)

We investigate the spin density matrix of in the Cartesian coordinate system of baryon-antibaryon pairs produced in annihilation. Using the helicity formalism of Jacob and Wick, we derive the expression for the spin-3/2 density matrices. Our analysis is based on the angular distribution of the process in the BESIII experiment. By decomposing the polarization state of particles along different coordinate axes, we examine the polarization dependence of the cross-section. Our results demonstrate that particles exhibit varying degrees of tensor polarization along the x-, y-, and z-axes, as well as weak vector polarization and rank-3 tensor polarization along the y-axis. To the best of our knowledge, this is the first study to calculate the polarization dependence of the cross-section distributions for the annihilation process . Our theoretical predictions are in good agreement with the experimental measurements.

In situ precise construction of surface-activated boron powders: A new strategy to synergistically improve the interface properties and enhance combustion performance of boron

Boron powder (B) is considered to be the most ideal fuel for fuel-rich rocket propellants due to its high calorific value. However, substances such as B2O3 and H3BO3 on the surface of B powder not only reduce the combustion efficiency of B, but also seriously deteriorate the preparation process of hydroxyl-terminated polybutadiene (HTPB)-based propellants, making it difficult for B powder to be used in fuel-rich rockets propellant. Herein, two weak polarity molecules, 1 H, 1 H, 2 H, 2 H-perfluorodecyltrichlorosilane (denoted as PT) and decyltrichlorosilane (denoted as DT), are proposed to be directly anchored on the surface of B powder by chemical bonding to change the surface of B powder. The textural and chemical properties of the B powder and the surface-activated B powders, as well their reaction and combustion performance under different conditions, were studied in detail using various experimental methods. The results show that B@PT and B@DT activated by 1 H, 1 H, 2 H, 2 H-perfluorodecyltrichlorosilane and decyltrichlorosilane respectively have better reaction and combustion performance than B powder. The perfluorodecyltrichlorosilane on the surface of B@PT can release radicals such as CnF2n+2 and CnF2n with strong oxidizing properties during the thermal decomposition process, which can corrode the oxide layer on the surface of B powder and can significantly improve the combustion performance of B powder. This research is expected to enable the large-scale application of B powder in HTPB-based fuel-rich rocket propellants.

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.

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.

Hydration dominates dielectric spectroscopy-based high accuracy quantification of lactose content in cow's milk.

Lactose is a critical factor in the quality of milk and dairy products. Achieving high accuracy and rapid detection of lactose content in cow's milk remains a challenge. Dielectric spectroscopy has emerged as a promising tool for detecting food components. We explored the effect of lactose content on the dielectric spectra of cow's milk and proposed a rapid analytical method for the quantitative determination of lactose content in cow's milk with high accuracy based on dielectric spectra. We obtained the dielectric spectra of 316 cow's milk samples in the frequency range of 20 to 4500 MHz and noticed a strong negative correlation between the lactose content and the value of the dielectric loss factor (ε'') below 1500 MHz. Lactose doesn't affect cow's milk dielectric properties by excluded volume effect but dominates the effect on the dielectric properties of cow's milk by hydration. The support vector regression (SVR) model based on the variable importance in projection (VIP) has the best prediction performance for lactose content. Its root-mean-square error of prediction set (RMSEP) and residual prediction deviation (RPD) is 0.29 g kg-1 and 6.968, respectively, and its prediction performance is better than that of the currently reported near-infrared (NIR) method and other methods. Despite the weak polarity of lactose molecules, its hydration is a significant factor affecting the dielectric properties of milk. This study provides a basis for high accuracy and rapid quantitative detection of lactose in cow's milk based on dielectric spectra. This article is protected by copyright. All rights reserved.

High-Performance Sliding Ferroelectric Transistor Based on Schottky Barrier Tuning

Sliding ferroelectricity associated with interlayer translation is an excellent candidate for ferroelectric device miniaturization. However, the weak polarization gives rise to the poor performance of sliding ferroelectric transistors with a low on/off ratio and a narrow memory window, which restricts its practical application. To address the issue, we propose a facile strategy by regulating the Schottky barrier in sliding ferroelectric semiconductor transistors based on γ-InSe, in which a high performance with a large on/off ratio (106) and a wide memory window (4.5 V) was ultimately acquired. Additionally, the memory window of the device can be further modulated by electrostatic doping or light excitation. These results open up new ways for designing novel ferroelectric devices based on emerging sliding ferroelectricity.

Creating Ultrahigh and Long‐Persistent Triboelectric Charge Density on Weak Polar Polymer via Quenching Polarization

AbstractTo achieve high charge density for the triboelectric polymer is a crucial task for fabricating triboelectric nanogenerators (TENGs). This work has developed a quenching polarization (QP) method to create ultrahigh and long‐persistent triboelectric charge on the triboelectric polymer with weak dipole polarity. The Ethylene chlorotrifluoroethylene copolymer (ECTFE) film can reach a charge density of 391 µC m−2 in the vertical contact mode by using this QP treatment, which is 200% higher than the result achieved by the most widely used method of corona polarization. The mechanism of the improvement through QP on the triboelectric properties is studied on the basis of the polarization induced grain refinement and interfacial trapping. The QP‐treated ECTFE can maintain ultra‐high charge density for both solid‐solid and solid‐liquid TENG. More interestingly, the charge induced by QP treatment is so persistent that it produces a recoverable discharging phenomenon for solid‐liquid TENG, which has never been observed before. This QP method provides a different approach for fabricating high‐performance triboelectric materials, while the QP‐induced changes in crystallization and tribo‐charge density can help to complete the physical understanding of the electrification mechanism of triboelectric polymer.

Reflective high-sensitivity polarization change imaging using a dual polarizer structure

In this study, we demonstrate a reflective imaging system in which a dual polarizer structure, consisting of a uniform polarizer and a polarizer on the pixel of a polarization image sensor, enables the detection of weak polarization changes. The uniform polarizer can achieve a high extinction ratio and is used to render the amount of polarization change in a condition that is easily detectable by the polarization image sensor. The polarization image sensor uses two types of polarizers arranged in an orthogonal relationship with each other to obtain complementary signals for polarization rotation. This is also used for differential detection to reduce the in-phase noise components. In the prototype system, the signal characteristics were in close agreement with theoretical considerations. Furthermore, as a demonstration of high-sensitivity polarization rotation imaging, the polarization rotation of a menthol solution in a 150-µm-thick channel was detected.

Manipulation of ferroelectric polarization and light absorption in non-noble metal/Aurivillius ferroelectric hybrid to enhance self-driven photodetection by coupling ferro-pyro-phototronic and plasmonic effect

Aurivillius ferroelectrics materials with layer perovskite structure, spontaneous polarization and ferro-pyro-phototronic effect afford a promising avenue for self-powered photodetectors. Nevertheless, poor photo-response caused by weak remanent polarization and low absorption coefficient hinders their further application. Herein, we demonstrate an excellent self-powered photodetector in nanosheets-assembled Bi microspheres array/Nd-doped Bi4Ti3O12 [Bi3.8Nd0.2Ti3O12] nanofibers heterostructured, which can rationally couple between ferroelectric polarization and ferro-pyro-phototronic effect in Aurivillius ferroelectric Bi3.8Nd0.2Ti3O12 and plasmonic effect in non-noble metal Bi. Firstly, an A-site doping with lanthanoid cation Nd3+ and dimension lowering strategy is proposed to improve the ferroelectric properties by reducing the oxygen vacancy concentration and coercive force field of Bi4Ti3O12 nanofibers through electrospinning method. Furthermore, the Bi nanosheets-assembled microspheres array allowing multiple reflection and scattering of incident light is introduced to enhance the local electromagnetic field and light absorption of Bi3.8Nd0.2Ti3O12. Ultimately, the Bi@Bi3.8Nd0.2Ti3O12 with negatively polarized obtains a superior zero-bias photocurrent of -500 nA under 390 nm laser illumination, which is 195.31 and 22.16 times higher than unpolarized Bi4Ti3O12 and Bi3.8Nd0.2Ti3O12, respectively. Simultaneously, an outstanding detectivity (8.11 ×1011 Jones) and fast photoresponse time (57/114 µs) are correspondingly achieved. Our research provides a reliable way to simultaneously realize large ferroelectric polarization and high light absorption for jointly manipulation of electrons and photons in self-powered optoelectronic devices.

Application of environmentally friendly potassium oleate modified wollastonite in carbon black/natural rubber composites

AbstractCarbon black uses nonrenewable resources (e.g., petroleum and natural gas) as raw materials, which not only causes dust pollution, but also has poor wet traction and high‐heat generation of rubber. Wollastonite is a polar filler, it requires surface modification to improve its hydrophobicity. In this paper, potassium oleate was introduced as an environment‐friendly modifier to decrease the polarity of the wollastonite, and a series of properties of the rubber composites with modified wollastonite replacing different parts of carbon black were studied. The experimental results show that the interfacial contact angle of the modified wollastonite changes from 0° to 51°, resulting in a weaker polarity. When 10 phr PO‐modified wollastonite were used to replace 10 phr carbon black filled with natural rubber, the processing safety is better, the Payne effect is effectively weakened and the rolling resistance is reduced, the tensile product reached 15573.98, which was 12.95% higher than that of the composites filled with full carbon black, resulting in the best comprehensive properties. This study verified the feasibility of replacing part of carbon black with potassium oleate modified wollastonite to prepare “green tire,” reduce the consumption of fossil energy, promote sustainable development, and provide reference for actual industrial production.

Three-dimensional mode multiplexer based on adiabatic-tapered waveguides forming vertical directional couplers over C + L band and beyond.

We present a mode multiplexer based on vertical directional couplers that are formed by adiabatic-tapered waveguides. We design and fabricate the device via the micro-fabrication processing to (de)multiplex the E11, E21, and E12 modes from the few-mode bus waveguide. Our experimental device shows a coupling ratio higher than 98.6% and 97.0% for the E21 and E12 modes, respectively, over the C + L band and beyond. The modal cross talk of this device can be lower than -17.1 dB, -18.4 dB, and -15.1 dB caused by the unintended E11, E21, and E12 modes, respectively. This mode multiplexer can work over a broader wavelength range with weak polarization sensitivity, which could be used in the mode-division-multiplexing systems where mode (de)multiplexing is required in the expanded communication wavelength window other than the C-band.

Phthalimide Ligand Coordination as a Critical “Key” for Constructing Chlorine–Platinum–Nitrogen Single-Site Catalysts for Effective Acetylene Hydrochlorination

Owing to the low dispersion and deficiency of active species in Pt catalysts, Pt-complexes catalysts (Pt–Lx/SAC–IPA) were synthesized using 2-propanol (IPA) solvent via ligand coordination strategy. The IPA, which exhibits a low boiling point and weak polarity, promotes the dispersion of Pt species. Further, the introduction of phthalimide ligand (L1) modulates the electronic properties of active metals, thereby constructing the single-site-dispersed Cl–Pt–N local structure bearing Pt(II) (presumably the active center of the reaction). Concurrently, the enhanced adsorption and activation performances of the catalyst toward an HCl reactant, as well as its weakened performances toward a C2H2 reactant, improve its anticoking performance and lower the reaction energy barrier. Therefore, the most active Pt–L1/SAC–IPA catalyst achieves an outstanding performance comparable with that of the standard Au/activated carbon (AC)–aqua regia (AR) catalyst, and it is reasonable to conclude that the L1 ligand functioned as a critical “key” in the Pt-based catalytic acetylene hydrochlorination.

Red emission from InGaN active layer grown on nanoscale InGaN pseudosubstrates

We demonstrated nanoplatelet In x Ga1−x N pseudosubstrates with In content varying from 0 to 0.3 on low-dislocation-density GaN substrates. These nanoplatelets efficiently relax in-plane strain, thus allowing for the use of a thick active layer to reduce built-in polarization. The 15 nm thick InGaN active layers grown under the same conditions on these nanoplatelets showed a remarkable cathodoluminescence redshift from 460 to 617 nm, suggesting enhanced In incorporation efficiency in InGaN nanoplatelets with higher In content. Moreover, the 617 nm-emitting sample presented an imperceptible blueshift under excitation-power-dependent photoluminescence, indicating a weak polarization field introduced by the high-In-content pseudosubstrates and the thick active layer.

BN-Doped Carbon Nanotubes and Nanoribbons as Nonlinear-Optical Functional Materials for Application in Second-Order Nonlinear Optics

Pure carbon-based nanomaterials with good π conjugation and thermal stability, e.g., nanotubes and nanoribbons, have long served as promising conjugated materials for application in second-order nonlinear-optical (NLO) devices but suffer from two inherent structural problems: weak polarity (or even nonpolarity) and high chemical reactivity ascribed to zigzag edge states. In the present work, boron nitride (BN) chains are used to divide carbon nanotubes and nanoribbons, forming a functional block to tune the electronic structure, and thus induce charge redistribution or modify the molecular energy gap for second-order NLO materials or integrated electronic materials. A balance between the electronic kinetic stability and second-order NLO properties is established by structural manipulation. The strong second-order NLO responses in the visible and near-infrared regions make these hybridized carbon-based molecules potential NLO materials for applications in biological nonlinear optics. The application of BN to tune the electronic structure of carbon nanomaterials paves a path for fabricating nanoelectronic and nano-NLO devices.

Dynamics simulation of the effect of cosolvent on the solubility and tackifying behavior of PDMS tackifier in supercritical CO2 fracturing fluid

Due to the low viscosity of supercritical carbon dioxide (SC-CO2) fracturing fluid, the method of adding tackifier is generally chosen to improve its sand carrying ability. Recently, siloxane-based tackifier has been widely utilized because of low cohesive energy and good viscosity building properties, but cosolvents are somehow needed to be added in the system to improve its solubility in SC-CO2. In this study, polydimethylsiloxane (PDMS)- a widely used siloxane polymer- was selected as the object tackifier. First, the effects of the addition of cosolvents such as ethanol, acetic acid, cyclohexane and toluene on dissolution behaviors of PDMS in SC-CO2 fracturing fluid were investigated by molecular dynamics simulation. Moreover, the solubilization effects of polar and nonpolar cosolvents on PDMS in SC-CO2 fracturing fluid were studied by comparing the binding energy, cohesive energy density and radial distribution function between solvent-solvent and between solvent-solute. The simulation results showed that cyclohexane could improve the solubility parameters of SC-CO2 the most at the same cosolvent concentration, and SC-CO2 was more uniformly distributed in the system. Meanwhile, the interactions between toluene and SC-CO2 was the strongest, and SC-CO2 was generally uniformly distributed in the system. However, ethanol and acetic acid performed poorly because they could produce hydrogen bonds with certain directionality and saturation. It was revealed that the mechanism of using cosolvents to improve the solubility of PDMS in SC-CO2 was based on the equilibrium of intermolecular forces between CO2 and PDMS, between CO2 and cosolvent, and between PDMS and cosolvent. When the siloxane-based tackifier was a nonpolar material, cyclohexane was recommended as the cosolvent. If the siloxane-based tackifier itself had some weak polarity, toluene was more suitable.

X-ray sensitive selenium-containing Ru complexes sensitize nasopharyngeal carcinoma cells for radio/chemotherapy.

Radiotherapy has been extensively applied to cancer therapy in clinical trials. However, radiation resistance and dose limitation generally hamper the efficacy of radiotherapy. There is an urgent need for radiosensitizers with high efficiency and safety to enhance the anti-tumor effect of radiotherapy. In this paper, a selenium-containing (Se) ruthenium (Ru) complex (RuSe) was designed as a radiosensitizer to synergistically augment the killing effect of radiotherapy on nasopharyngeal carcinoma cells. In this system, the heavy atomic effect of Ru enhances the photoelectron production triggered by X-rays, thus inducing a burst of reactive oxygen species (ROS). In addition, Se atoms with a strong polarization property were introduced into the ligand of the metal complex to enhance the tumor chemo/radiotherapy effect. Consequently, RuC with a weak atomic polarization effect, as a comparison for RuSe, was also rationally explored to elucidate the role of Se atoms on chemo/radiotherapy sensitization. Indeed, compared with RuC, RuSe at a sub-toxic dose was able to potentiate the lethality of radiotherapy after preconditioning with cancer cells, by inducing ROS over-production, decreasing the mitochondrial membrane potential, and arresting the cell cycle at the sub-G1 phase. Furthermore, upon radiation, RuSe was superior to RuC, by inducing apoptotic cell death by activating caspase-3, -8, and -9. In summary, this study not only demonstrates an effective and safe strategy for the application of RuSe complexes to the cancer-targeted chemo/radiotherapy of human cancers, but also sheds light on the potential mechanisms of such Se-containing drugs as efficient radiotherapy sensitizers.

Crosslinking modification and hydrogen bonding synergy to achieve high breakdown strength and energy density of PMMA-co-GMA/PVDF dielectric composite films.

Polymer-based dielectric materials have been used in film capacitors due to their rapid charge-discharge rate, lightness, and low cost. Nevertheless, the energy storage properties of these dielectric films were limited by their weak polarization ability and low discharge energy density. Herein, the solution casting method was used to prepare all-organic crosslinked composite films using linear methyl methacrylate-co-glycidyl methacrylate (MG) as the matrix and ferroelectric poly(vinylidene fluoride) (PVDF) as the organic filler. The crosslinked MG networks can enhance the breakdown strength, restrain dielectric loss, and keep high discharge efficiency. What's more, the presence of PVDF can compensate for the low electrical displacement, improve the permittivity, and overcome the brittleness of the crosslinked films. The optimal all-organic crosslinked dielectric film exhibited an ultrahigh breakdown strength of 800 MV m-1 and a high efficiency of 77.4%. The maximum energy density of the composite film reached up to 12.1 J cm-3, which was nearly 120% higher than the energy density of 5.6 J cm-3 of the pure MG film. The enhancement in energy storage properties is ascribed to the synergistic effects of chemical crosslinking and hydrogen bonding. This study offers a feasible method for all-organic polymer films to fabricate energy storage equipment.

PD Characteristics and Parameter Extraction for EPR Cable Terminal in EMUs With Spike Defect at Low Temperature

Ethylene propylene rubber (EPR) cable terminals are widely used in high-speed railway trains. In the alpine environment, partial discharge (PD) and even breakdown failures caused by spike defects frequently occur in EPR cable terminals. To study the discharge development of cable terminals with spike defects in alpine regions, EPR cable terminal test samples with spike defects were made, and a low-temperature PD test system was built to simulate the environmental conditions in alpine regions. The characteristics of the lower PD spectrum were analyzed, and the influence mechanism of low temperature on the discharge activity was analyzed combined with the scanning electron microscope (SEM) scan. The research results show that the discharge development of the terminal spike defect can be divided into three stages: S1~S3. In S1 stage, the degree of PD at –30°C is weaker than that at 20°C dues to the low diffusion ability and weak polarization effect of carriers. In S2 and S3 stages, with the continuous discharge, low temperature makes the deterioration tolerance of ethylene propylene rubber material decrease more seriously, which promotes the development of discharge. The discharge phase interval is larger and the discharge activity is more intense at –30°C than at 20°C, and the breakdown time point is 11.6% earlier. By studying the characteristics of the spectrum, it is found that the deviation of PD φ- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q_ave</i> spectrum at –30°C from positive to negative is an important signal before the critical breakdown of cable insulation, which can provide a reference for judging the severity of terminal spike defects at low temperature.

All-organic lead-free thermochromic and dielectric switchable epoxy microcomposites from singly incorporating leuco dye microcapsules for advanced encryption

In this study, an all-organic lead-free thermochromic and dielectric switchable epoxy microcomposite (TEP) is presented from singly incorporating leuco dye microcapsule materials (LDM) into the epoxy matrix. TEP can simultaneously adjust the color and permittivity in response to temperature between 30 °C and 70 °C. Moreover, the switchable dielectric behavior of TEP can be manipulated by LDMs content and voltage frequency. The switchable dielectric behavior of TEP permittivity is proposed to originate from the inner interfacial polarizations in LDMs triggered by the order-disorder phase transition. Before the phase transition, the molecules in LDMs are in ordered and compact arrays with restricted mobility, which can hardly undergo transportations and reorientations, leading to the weak interfacial polarization strength at the inner surfaces of LDMs and the low permittivity of TEP. After the phase transition, the molecules in LDMs are liberated with enhanced intermolecular distances and mobility, facilitating the inner interfacial polarization in LDMs and leading to the high permittivity of TEP. The correlation between the switchable dielectric behavior and the order-disorder phase transition is furtherly verified based on the Lichtenecker’s mixing model. This study unlocks a novel function of switchable permittivity for the LDM materials and provides an innovative strategy for designing the thermochromic and dielectric switchable smart materials.

Maxwell–Wagner polarization engineering in ferroelectric photovoltaic effect

Ferroelectric photovoltaic cells have attracted particular interest owing to their potential applications in the green energy field. But there are two drawbacks: weak polarization and wide bandgap, which make them suffer from the limitation of energy conversion efficiency. In this study, the key issue is solved in Ag2O nanoparticle-dispersed Bi5Ti3FeO15 composites. In order to clarify the mechanism, performances of the bandgap, polarization-dependent J–V curves, dielectric response, and switchable photocurrents were investigated. The Maxwell–Wagner polarization effect is confirmed by permittivity Cole–Cole plots with two or more semicircles overlapping. The spatial polarization gradient matrices can reduce the effective mass of the electron–hole pairs and further promote their separation via the Maxwell–Wagner polarization effect. The synchronous mobility of the separated carriers is enhanced. An improved ferroelectric photovoltaics is achieved in Bi5Ti3FeO15⋅3%Ag2O composites, and the key parameters are as follows: VOC ∼ −3.1 V, energy converse efficiency 9.2 × 10−4%. Furthermore, this work shows the first step toward polarization gradient composites for application in ferroelectric photovoltaic cells.