Polarization Effects Research Articles

Evaluation of ion recombination and polarity effect on photon depth dose measurements using mini- and micro-ion chamber.

To investigate the effect of ion recombination ( ) and polarity ( ) correction factors on percentage depth dose (PDD) curves for three ion chambers, using flat and flattening filter free (FFF) beams, across different broad field sizes. A method to assess these effects and their corresponding corrections is proposed. and were evaluated following the IAEA TRS-398 protocol for three ion chambers: PTW Semiflex-3D-31021, PinPoint-3D-31022, and Semiflex-31010. PDD measurements were acquired from dmax to 32cm depth at four voltages (±400V or±300V, and±100V) for field sizes 4×4, 10×10, 20×20, and 40×40 cm2. The values were computed after the correction at each applied voltage. This study aimed to assess the variation of the factors along scanning depths for different field sizes, to evaluate the need for correcting the scanning data. was independent of depth and field size for Semiflex-3D, while it presented an increasing value with depth for the PinPoint-3D. increased with dose rate, i.e., decreased with depth. The variation of this perturbation effect over the PDD range was about 0.1% for flat beams with all three ion chambers. With FFF beams, it was around 0.3% with PinPoint-3D, and 0.8% for 10FFF with Semiflex-3D. A second-order polynomial fit can be determined to directly correct the raw data scanned along the beam axis for both and . can significantly affect the PDD scanning measurements in FFF beams acquired with Semiflex-3D. An error close to 1% at large depths could be present, meaning an error of less than 0.3% relative to the dose at the depth of dmax.

Magnetic Field-Induced Polar Order in Monolayer Molybdenum Disulfide Transistors.

In semiconducting monolayer transition metal dichalcogenides (ML-TMDs), broken inversion symmetry and strong spin-orbit coupling result in spin-valley lock-in effects so that the valley degeneracy may be lifted by external magnetic fields, potentially leading to real-space structural transformation. Here, magnetic field (B)-induced giant electric hysteretic responses to back-gate voltages are reported in ML-MoS2 field-effect transistors (FETs) on SiO2/Si at temperatures <20 K. The observed hysteresis increases with |B| up to 12 T and is tunable by varying the temperature. Raman spectroscopic and scanning tunneling microscopic studies reveal significant lattice expansion with increasing |B| at 4.2 K, and this lattice expansion becomes asymmetric in ML-MoS2 FETs on rigid SiO2/Si substrates, leading to out-of-plane mirror symmetry breaking and the emergence of a tunable out-of-plane ferroelectric-like polar order. This broken symmetry-induced polarization in ML-MoS2 shows typical ferroelectric butterfly hysteresis in piezo-response force microscopy, adding ML-MoS2 to the single-layer material family that exhibits out-of-plane polar order-induced ferroelectricity, which is promising for such technological applications as cryo-temperature ultracompact non-volatile memories, memtransistors, and ultrasensitive magnetic field sensors. Moreover, the polar effect induced by asymmetric lattice expansion may be further generalized to other ML-TMDs and achieved by nanoscale strain engineering of the substrate without magnetic fields.

Photoinduced modulation and the effect of CNT loading on field effect transistor characteristics of CNT/ZnO/PVDF composite.

CNT/ZnO/PVDF polymer composite phototransistor is studied for the effect of CNT loading and the photoinduced modulation on its transfer characteristics. XRD study shows that the induced strain in the composite is due to the addition of CNT to the ZnO/PVDF composite. The percentage of β-phase present in PVDF is estimated through Raman spectroscopy and the composite's spectral response is determined by UV-Vis absorbance spectroscopy. From the DC electrical conductivity study it is found that the percolation threshold for the composites is obtained for 0.3 wt% of CNT, and 0.44 wt % of CNT loading makes the composite conductive. On adding 1 wt% of CNT, the electrical conductivity of the ZnO/PVDF composite increases 40 times (~ 0.2 μS/m). The temperature-dependent DC conductivity shows that the conductivity of the composites changes from variable range hopping (VRH) to band conductance upon an increase in CNT loading above the percolation threshold and exhibits a negative temperature coefficient (NTC). Two terminal photoconductivity studies are done to understand the photo enhancement and sensitivity of all the devices. PE hysteresis studies show that the polarization of the composites increases drastically from 0.05 μC/cm2 below the percolation threshold to 10 - 30 μC/cm2 above the percolation threshold of CNT in the composite. To study the effect of interfacial polarization on photoconductivity, the composite is studied in a three-terminal device format using SiO2 as a gate dielectric. A band diagram analysis of the oxide-composite and CNT/ZnO interface is done to understand the mechanism behind the photoinduced field effect on transfer characteristics and the effect of CNT loading. The switching behavior and decay time under UV illumination are studied to understand the effect of CNT loading and photoinduced polarization. The persistent photoconductivity decreases and the charge collection efficiency of the FET increases as the CNT loading increases.

Determination and analysis of spectral fluorescence cross-sections of bacteria aerosols

Fluorescence cross-sections of single bacteria provide information on the strength of fluorescence response of bacteria for particular excitation conditions and give hints about a possible distinguishability of bacteria by fluorescence techniques. In this report, the fluorescence cross-sections of dry bacteria aerosols are derived from fluorescence spectra by absolute calibration of the measuring system. The fluorescence is measured in a continuous aerosol flow. The aerosol concentration is calculated from microscopic analyses of bacteria samples taken from the aerosol flow. Established calibration methods such as Mie scattering from monodisperse spheres and Raman scattering from water are applied to the same set of fluorescence spectra. The cross-section data obtained are evaluated with regard to their independency from the applied measuring system. The results are compared to data published in the literature. Polarization effects are identified to contribute to the discrepancies between the different datasets.Graphical abstract

Control of ferroelectricity in Ta-doped HfO2 and its non-zero-crossing current–voltage hysteresis behavior

Hafnium oxide (HfO2)-based ferroelectrics are being explored as potential candidates for ferroelectric memory devices due to their highly compatibility with complementary metal-oxide-semiconductor (CMOS) technology. Enhancing the remanent polarization and investigating the underlying mechanism are crucial tasks. In the present study, tantalum (Ta) was introduced as a dopant to induce ferroelectric properties in HfO2, a large portion of orthorhombic phase was recognized in the as-grown Ta:HfO2 without further thermal treatment. The remanent polarization of Ta:HfO2 thin films can be optimized by adjusting the oxygen flow rates during the sputtering process. The influencing factors for enhanced ferroelectric performance include the control of Ta concentration, its valence state, and the presence of singly ionized oxygen vacancies, which are influenced by oxygen addition. Furthermore, the resistive switching behavior showing non-zero crossing current–voltage (I–V) hysteresis is associated with ferroelectricity and the presence of oxygen vacancies. A model has been proposed to explain the ferroelectric resistive switching with non-zero crossing I–V characteristics by considering the role of oxygen vacancies and polarization effects. This model suggests that the oxygen vacancies at the surface layer, along with ferroelectric polarization, play a crucial role in electron transport.

Ageing-Related Macrophage Polarisation in the Trigeminal Ganglion Enhances Incisional Intraoral Pain.

Although macrophage polarisation in the trigeminal ganglion (TG) is crucial in orofacial pain hypersensitivity, the effect of ageing-related changes and their involvement in intra-oral nociception remains unclear. We assessed the effect of ageing-related macrophage polarisation in TG on intra-oral mechanical pain hypersensitivity following palatal mucosal incision using senescence-accelerated mice (SAM)-prone8 (SAMP8) and SAM-resistant 1 (SAMR1). Mechanical head-withdrawal reflex threshold (MHWRT) of the palatal mucosa was measured for 21 days after palatal mucosal incision. On days 3 and 14, the abundance of Iba-1-immunoreactive (IR) cells, CD11c-IR cells (pro-inflammatory macrophages (M1)), C-C motif chemokine ligand 2 (CCL2)-IR M1-macrophages, CD206-IR cells (anti-inflammatory macrophages (M2)) and transforming growth factor-β (TGF-β)-IR M2-macrophages in the TG was analysed. The effect of continuous intra-TG administration of CCL2-neutralising antibody or recombinant-CCL2 on MHWRT was examined. Incision-induced decrease in MHWRT was enhanced in SAMP8 compared with that in SAMR1. On days 3 and 14, the number of CCL2-IR M1-macrophages in TG was increased in SAMP8 compared with that in SAMR1. CCL2-neutralising antibody suppressed, whereas recombinant-CCL2 increased pain hypersensitivity in SAMP8. Mechanical pain hypersensitivity after oral mucosal injury is potentiated and sustained by age-related enhancement of CCL2 signalling via M1-macrophage hyperactivation in TG.

Current-induced spin polarization and spin Hall effect in III-V compounds two-dimensional materials

Current-induced spin polarization and spin Hall effect in III-V compounds two-dimensional materials

Differential and integral elastic cross sections for electrons and positrons collisions with carbon dioxide molecules

This study investigates the elastic scattering of electrons and positrons by carbon dioxide (CO2) molecules over a wide energy range from 1 eV to 1 KeV. We have computed differential and integral elastic cross-sections (DCS and ICS) using partial wave analysis and compared the theoretical results with available experimental data. Our findings show a strong correlation with experimental results, particularly at mid to high-energy ranges, validating the employed theoretical frameworks. Additionally, the Sherman function was examined to explore spin polarisation effects during scattering events. This research provides crucial insights for applications in atmospheric physics, materials science, and molecular scattering processes, demonstrating its direct relevance to real-world problems and paving the way for further investigation into particle-molecule interactions.

The coupling effect of polarization and lattice strain on charge transfer between quintuple-layer Al2X3/Al2Y3 (X, Y = O, S, Se, Te; X ≠ Y) interfaces

The electronic properties of two-dimensional (2D) polar semiconductor heterostructures are closely related to the degree of interlayer charge transfer. Taking 2D quintuple-layer (QL)-Al2S3 and QL-Al2O3 semiconductor as examples, we study the electronic properties and interlayer charge transfer of QL-Al2S3/Al2O3 interfaces by first-principles calculations. The driving force of the directional interlayer charge transfer is the polarization electric field. The kinetic process of interface charge transfer is related to the charge (strain) distribution of QL-Al2S3 and QL-Al2O3. By changing the strain distribution of QL-Al2S3/Al2O3 interfaces with same polarization arrangement, the electronic properties and interfacial charge transfer of heterojunctions can be adjusted. Our work is an important indicator for understanding the dynamic process of interlayer charge transfer between 2D polar semiconductors. In addition, we propose one method for regulating the electronic properties of heterojunctions by coupling polarization and lattice strain.

High‐efficiency electromagnetic absorption of HfC–SiCf ceramics with a 3D reticular structure

AbstractThe development of high‐temperature electromagnetic (EM) wave absorbing materials is an important direction for achieving radar stealth in high‐speed aircraft. In this study, HfC–SiCf composite ceramics with 3D reticular structure were synthesized in one‐step using the molten‐salt‐assisted carbon thermal reduction method. During the synthesis process, SiC grew in situ into a fibrous structure with a diameter of 500 nm and lengths ranging from 2 to 30 µm. By adjusting the molar ratio of HfC to SiC, the HfC‐30 mol% SiC (HS30) exhibited the best EM absorption performance at room temperature, with a minimum reflection loss (RLmin) of −31.4 dB at 16.1 GHz and an effective absorption bandwidth (EAB) of 4.6 GHz. The excellent absorption performance was attributed to the 3D reticular structure composed of SiC fibers, HfC bulk, and HfC nanoparticles, which significantly increased the number of pores and heterogeneous interfaces in the material. These microinterfaces induced interface polarization effects, thereby effectively enhancing the EM absorption. As the temperature increased, the EM absorption performance declined. At 900°C, the HS30 sample exhibited an EAB of 1.18 GHz from 12.4 to 13.58 GHz and an RLmin of 22.6 dB at 13.0 GHz. This research provides references for understanding the effects of material composition and structure on EM absorption performance.

Rational Control of Maximum EMI/CPL Intensity and Wavelength of Bora[6]helicene via Polarity and Vibronic Effects.

Solvent polarity control as an efficient methodology to regulate the chiroptical properties, including spectral shape, width, intensity, wavelength, etc., has emerged as a novel frontier in optical materials design. However, the underling relationship connecting polarity to the optical property remains unclear. Herein, using state-of-the-art computations and the FC|VG model, the solvent effect on the chiroptical properties of bora[6]helicene was accurately and systematically computed to shed light on this issue. It is found that the vibronic coupling is crucial in explaining the spectral shape, width, and relative intensity of different peaks. Moreover, the intensity and position of the emission (EMI) and circularly polarized luminescence (CPL) are closely related to the polarity of the solvent. Intriguingly, we got a series of good linear relationships between polarity and EMI|CPL (|r| ≥ 0.95). Thus, this parameter can be used as a potential descriptor to estimate the intensity and position of EMI|CPL, leading to new strategies for designing fully colored fluorescent materials.

Comparing the effects of anodal and cathodal transcranial direct current stimulation of primary motor cortex at varying intensities on motor learning in healthy young adults.

Inconsistent results are observed in the effects of transcranial direct current stimulation (tDCS) with different montages on motor learning. This study aimed to compare the effects of anodal and cathodal tDCS (c-tDCS) over primary motor cortex (M1) at different intensities on motor learning in healthy young adults. The participants were randomly divided into: (1) 1mA M1 c-tDCS, (2) 1mA M1 anodal tDCS (a-tDCS), (3) 2mA M1 c-tDCS, (4) 2mA M1 a-tDCS and (5) M1 sham tDCS groups. The groups received 20-min stimulation with serial reaction time task (SRTT) incidentally, while the tDCS was turned off after 30 s in the sham tDCS group. Response time (RT) and error rate (ER) during SRTT were assessed prior, during and 72 h after the intervention. The results of the paired t-test indicated that online learning occurred in all groups (p< 0.05), except in M1 c-tDCS (1mA) (p> 0.05). One-way ANOVA analysis also indicated that there were differences in offline learning (RT (F(DF) =5.19(4); p< 0.001; and ER (F(DF) =9(4), p< 0.0001) among groups, with more offline learning in 1mA M1 a-tDCS, 2mA M1 c-tDCS and 2mA M1 a-tDCS groups (p< 0.05). On the other hand, the 1mA M1 c-tDCS group did not indicate any consolidation effect or even a trend toward negative offline learning. M1 a-tDCS with different intensities and also 2mA M1 c-tDCS may be helpful for the enhancement of motor learning in young healthy adults. This study enhances our understanding of tDCS intensity and polarity effects on motor learning, with potential for optimizing therapeutic protocols.

When Disagreement Becomes Uncivil on Social Media: The Role of Passive Receiving and Active Expression of Incivility in Influencing Political Polarization

Exposure to cross-cutting viewpoints may not always play the deliberative role it is supposed to. This study uses both panel survey and social media data to examine how disagreement can trigger incivility, including exposure to and expression of incivility, and further elicit emotions and influence polarization. Results from the two-wave panel survey indicate that cross-cutting exposure has a polarizing effect first through promoting exposure to uncivil messages and expression of uncivil opinions, then through negative emotions. Notably, cross-cutting exposure can indirectly reduce polarization by first encouraging expression of uncivil opinions and then eliciting positive emotions, highlighting the importance of active expression. Analysis of data from the Hong Kong-based discussion forum HKDisc demonstrates that cross-cutting exposure is positively related to exposure to uncivil messages, and exposure to and expression of incivility predict polarization regardless of whether positive or negative emotions are detected in the uncivil content. This study provides empirical evidence of the effects of cross-cutting exposure and incivility on polarization at the individual and collective levels.

Rationally designed photothermal-pyroelectric Fe0.9Ni0.1S2/ZnSnO3 Z-scheme heterojunction for promoting electrical charge polarization towards optimized photocatalytic H2 evolution and intermolecular N-N coupling reaction

Developing a photocatalytic composite system that can couple hydrogen (H2) evolution and benzylamine (BA) oxidation is a challenging task, especially while avoiding sacrificial agents and value-added chemicals. Here, a practical approach is reported to develop a photothermal-pyroelectric-Fe0.9Ni0.1S2/ZnSnO3 photocatalytic system with core–shell and Z-scheme heterostructure via hydrothermal and annealing methods. Although Fe0.9Ni0.1S2 nanoparticles (NPs) could convert most of near-infrared (NIR) light energy into heat energy to drive the pyroelectric effect of ZnSnO3, it also results in temperature fluctuations (ΔT) in the system, causing natural polarization and thermoelectric effects under the condensed water circulation. As a result, the as-designed Fe0.9Ni0.1S2/ZnSnO3-2 composites could yield up to 7.194 mmol g-1h−1 with exceptional photocatalytic H2 evolution under simulated sunlight. This result is 5.41 and 4.92-fold those of Fe0.9Ni0.1S2 and ZnSnO3, respectively, with 16.66 % apparent quantum yield (AQY) under 365 nm monochromatic light. At the same time, the composites could also oxidize BA and yield up to 6.640 mmol g-1h-1n-benzylidene benzylamine (NBBA) with a 90.2 % selectivity. Due to the synergistic effect of Z-scheme’s built-in electric field and photothermal-pyroelectric of Fe0.9Ni0.1S2/ZnSnO3, the surface charges released on them could direct the charge transfer pathways and restrain their recombination with accelerated electron transfer kinetics, thus extending the carrier lifetime. This work offers a new perspective for designing electrical charge polarized by the photothermal-pyroelectric effect, which can enhance H2 evolution and BA oxidation concurrently.

Analysis and study of digital economy level measurement index

PurposeThis study aims to assess the level of development of the digital economy by constructing a comprehensive measurement system. It explores regional differences within China’s digital economy, highlighting the varying degrees of digital infrastructure, industrialization, governance and innovation capabilities across provinces.Design/methodology/approachA multidimensional analytical framework including digital infrastructure, industrialization, digitization, governance and innovation was developed. Entropy methods were used to calculate the weights of each dimension. The coupled coordination degree model and the Tobit model with random effects panel are applied to analyze the current situation, discrepancies and influencing factors.FindingsThis study reveals significant regional differences in the development of China’s digital economy, characterized by a pattern of “strong in the east, weak in the west; high in the south, low in the north.” This geographical imbalance exacerbates the “polarization effect” and the “siphon effect,” where resources and growth tend to concentrate in already developed areas, further intensifying regional inequalities. The development of the digital economy is driven by principles of innovation, coordination and sharing, which facilitate the creation and dissemination of new technologies and collaboration across different sectors. However, this progress is also constrained by considerations of environmental sustainability (green) and economic openness.Originality/valueThis paper contributes to the body of knowledge by providing a novel multidimensional measurement system for the level of digital economy development. The unique application of the coupled coordination degree model and Tobit model to analyze regional differences and influencing factors provides insights into the dynamics of China’s digital economy.

Electromigration in Cu–Cu joints: Measurement of activation energy and polarity effect

Electromigration (EM) has been a pivotal reliability challenge for interconnects, but there are only few studies on EM in Cu–Cu joints. In this work, accelerated EM tests for the Cu–Cu joints were conducted at three temperatures (150 °C, 179 °C, and 208 °C) and the temperature-dependent failures were discussed. The polarity effect of the grain growth behaviors at the bonding interfaces was observed at the opposite electron flows, which may be attributed to the difference in EM-build-up stress conditions and the divergence in atomic fluxes. Moreover, the activation energy (Ea) extrapolated from the three EM temperatures was derived as 0.9 eV. As compared to the solder joints with same dimensions, the Cu–Cu joints possess more than ten times of time-to-failures (TTFs) under the same EM condition.

Political polarization and corruption: A theoretical and empirical review

Notwithstanding the considerable scholarly and public attention that political polarization and corruption have attracted in recent years and the important mechanisms through which the former may influence the latter, research in this area remains limited and inconclusive. This article offers a comprehensive theoretical and empirical synthesis of the current state of research in this domain. It finds that a large fraction of the apparent contradictions can be attributed to the conceptual inconsistencies and ambiguity surrounding political polarization. The types of polarization that have an inherently hostile and uncivil element (usually referred to as affective or pernicious polarization) undermine democratic accountability, which leads to more corruption. The role of ideological polarization among parties and the general population is more complex: it may boost accountability and decrease corruption but can also contribute to the aforementioned harmful forms of polarization and enhance the role of partisan bias in public opinion formation, thereby increasing corruption. The overall effect of ideological polarization on corruption may depend on the nature and the degree of the former, as well as on mitigating contextual factors. The two may create a vicious circle as corruption also increases political polarization via various channels.

Photo‐Curable Fluorinated High‐k Polyimide Dielectrics by Polar Side Substitution Effect for Low‐Voltage Operating Flexible Printed Electronics

AbstractPolyimide‐based dielectric films are widely used in various thin film devices including organic field‐effect transistors (OFETs) owing to their promising thermal/chemical stability, mechanical flexibility, and insulating properties. On the other hand, considerable attention is paid to lowering the process temperature to allow coating on plastic substrates because high‐temperature annealing (≈200 °C) is usually required to convert precursors to polyimide films with those excellent properties. In addition, polyimide‐based dielectric films have low dielectric constants (k) (&lt;4). Therefore, modifying the k properties of polyimide is a critical issue for applications as an insulating thin film for practical transistors. This paper reports a new type of polyimide‐based gate dielectric comprising methacryloyl moiety (PI‐MA) as a side chain for photo‐pattern/processability and high‐k properties. This study shows that the photocured PI‐MA thin films show excellent insulating properties (leakage current densities &lt; 10−8 A cm⁻2 at 4 MV cm⁻1) and high‐k properties (≈8) even without a post‐annealing process. Finally, the use of PI‐MA in printed field‐effect transistors results in high performance with low‐voltage operation (within 5 V) and integrated logic‐gate devices (NOT, NAND, and NOR gates).

Triggering Asymmetric Layer Displacement Polarization and Redox Dual-Sites Activation by Inside-Out Anion Substitution for Efficient CO2 Photoreduction.

Sluggish bulk charge transfer and barren catalytic sites severely hinder the CO2 photoreduction process. Seeking strategies for accelerating charge dynamics and activating reduction and oxidation sites synchronously presents a huge challenge. Herein, an inside-out chlorine (Cl) ions substitution strategy on the layered polar Bi4O5Br2 is proposed for achieving layer structure-dependent polarization effect and redox dual-sites activation. Cl ions in the bulk phase shrink the halogen layer interspace by 8‰, triggering asymmetric [Bi4O5]2+ layer displacement polarization, prolonging the average photocharge lifetime to 201.8ps. Meanwhile, surface substituted Cl ions enhance the electron-donating capability of neighboring Bi atoms, activating the intrinsic Bi reduction sites, and increasing H2O molecule adsorption on nearby intrinsic O oxidation site (cal. by 0.105eV), also self-donating as an alien oxidation site. Besides, Cl upshifts the p-band center closer to the Fermi level, facilitating the reactant adsorption. Therefore, the energy barrier for CO2 activation and rate-limiting *COOH intermediate formation steps are significantly decreased. Without cocatalysts and sacrificial reagents, inside-out Cl-substituted Bi4O5Br2 delivers a remarkable CO2-to-CO photoreduction rate of 50.18µmol g-1 h-1, being one of the state-of-the-art catalysts. This finding offers insights into exploiting polarization at the molecular-level and enhances understanding of catalytic site activation.

Understanding ultrafast rechargeable Al/graphite battery by visualizing phase separation

Al/graphite batteries (ABs) using ionic liquid electrolytes exhibit exceptionally fast charging and cycling stability. However, the mechanisms underlying their high rate capabilities remains elusive. In this study, in situ optical microscopy is employed to investigate the intercalation dynamics of single-flake graphite in ABs. Observations reveal that surface reaction limitations, rather than AlCl4− mass transfer, primarily govern performance in the graphite cathode. During charging under varying current densities, the ABs display distinct phase separation behaviour with an intercalation wave morphology, indicating that surface reactions restrict the intercalation process. This finding explains the ultrafast recharge capability of ABs, where active sites in graphite become nearly fully intercalated with AlCl4− at high current densities. Additionally, slight rate performance loss occurs due to increasing ohmic and charge transfer polarisation (ηohm and ηct) at higher current densities. To address this limitation, we propose increasing the cut-off voltage as a straightforward and effective method to mitigate these polarization effects. This study offers valuable insights into the electrochemical behaviour of rechargeable secondary ion batteries by visualising their phase separation.