Polarization Pattern Research Articles

Mechanical Writing of Polar Skyrmionic Topological States via Extrinsic Dzyaloshinskii-Moriya-like Flexoelectricity in Ferroelectric Thin Films.

Exploring complex topological structures in condensed matter has shown promising applications in nanotechnology. Although polar topologies such as chiral vortices and skyrmions have been observed in ferroelectric heterostructures, their existence in simple systems has posed challenges due to the absence of intrinsic noncollinear interaction (like Dzyaloshinskii-Moriya interaction in ferromagnetics). Here, we demonstrate that a nanoindentation mechanically switches local polarizations to stable polar topologies, including skyrmions, within a room-temperature PbTiO3 thin film via the flexoelectric effect as a noncollinear (Dzyaloshinskii-Moriya-like) driving force using phase-field simulations. In addition, by moving the indenter, the continuous polarization switching leads to the "writing" of arbitrary polar patterns (such as donut-like skyrmionium). Furthermore, the written topologies can be "erased" by applying a voltage with the same conducted indenter. Therefore, this study shows the writing and erasing process of room-temperature polar topologies in a ferroelectric thin film, which significantly advances their potential applications.

Identifying the Origin of Fast Radio Burst–Associated X-Ray Bursts with X-Ray Polarization

The origin of an extraordinary X-ray burst (XRB) associated with a fast radio burst (FRB) such as FRB 20200428 is still unclear, though several models, such as the emission of a trapped fireball modified by resonant cyclotron scattering, the outflow from a polar trapped-expanding fireball, and the synchrotron radiation of a far-away relativistic shock, have been proposed. To determine which model is true, we study the possible X-ray polarization signature for each model, inspired by the importance of radio polarization in identifying the FRB origin. We first numerically simulate or calculate the XRB spectrum for each model and fit it to the observed data, then compute the corresponding polarization signal based on the fit. We find that these three models predict different polarization patterns in terms of phase/time and energy variations. The differences can be used to test the models with future X-ray polarization observations.

Loop Defects in Honeycomb Photonic Crystals

Herein, the properties of a novel type of photonic cavities, namely, loop defects in honeycomb photonic crystals, are discussed. Features of such defects, in particular far‐field and polarization patterns of their modes, are studied. The robustness of modes to the structural imperfections is discussed in terms of the variation in their frequency, quality factor, and far‐field emission. The predicted effects can be readily observed in state‐of‐the‐art experiments and may lead to potential applications in integrated photonics.

Extrinsic dielectric response due to domain wall motion in ferroelectric BaTiO[formula omitted]

BaTiO3 (BTO) is a prototypical perovskite ferroelectric, whose dielectric permittivity and loss spectra – which are strongly temperature and frequency dependent – include contributions from inhomogeneous polarization patterns, with domain walls (DWs) being the most common types. In order to elucidate how DWs influence dielectric response, we utilized a continuum approach based on the Landau–Ginzburg theory to model field-dependent properties of polydomain tetragonal phase of BTO near room temperature and above. A system with 180∘ DWs was evaluated as a case study, with both position-resolved and volume-averaged dielectric susceptibility and loss computed at different temperatures for a range of applied field frequencies and amplitudes. Our results demonstrate that cooperative dipole fluctuations in the vicinity of the DW provide a large (extrinsic) contribution to the system dielectric response relative to the intrinsic contribution stemming from within the domain. Dynamics of the DW profile fluctuations under applied field can be represented by a combination of breathing and sliding vibrational motions, with each exhibiting distinct dependence on the field frequency and amplitude. The implications of this behavior are important for understanding and improving control of coupled functional properties in ferroelectric materials, including their dielectric, electromechanical, and electrooptical responses. Furthermore, this investigation provides a computational benchmark for future studies and can be readily extended to other topological polarization patterns in ferroelectrics.

Dynamical Manipulation of Polar Topologies from Acoustic Phonon Excitations.

Since the recent discovery of polar topologies, a recurrent question has been how to remotely tune them. Many efforts have focused on the pumping of polar optical phonons from optical methods, but with limited success, as only switching between specific phases has been achieved so far. Additionally, the correlation between optical pulse characteristics and the resulting phase is poorly understood. Here, we propose an alternative approach and demonstrate the deterministic and dynamical tailoring of polar topologies using acoustic phonon excitations. Our second-principles simulations reveal that by pumping specific longitudinal and transverse acoustic phonons, various topological textures can be induced in materials like BaTiO3 or PbTiO3. This method leverages the strong coupling between polarization and strain in these materials, enabling predictable and dynamic control of polar patterns. Our findings open up an alternative possibility for the manipulation of polar textures, suggesting a promising research direction.

Emerging Claudin18.2-targeting Therapy for Systemic Treatment of Gastric Cancer: Seeking Nobility Amidst Danger.

Gastric cancer in advanced stages lacked effective treatment options. claudin18.2 (CLDN18.2) is a membrane protein that is crucial for close junctions in the differentiated epithelial cells of the gastric mucosa, playing a vital role in barrier function, and can be hardly recognized by immune cells due to its polarity pattern. As the polarity of gastric tumor cells changes, claudin18.2 is exposed on the cell surface， resulting in immune system recognition, and making it an ideal target. In this review, we summarized the expression regulation mechanism of claudin18.2 both in normal cells and malignant tumor cells. Besides, we analyzed the available clinical results and potential areas for future research on claudin18.2-positive gastric cancer and claudin18.2-targeting therapy. In conclusion, claudin18.2 is an ideal target for gastric cancer treatment, and the claudin18.2-targeting therapy has changed the treatment pattern of gastric cancer.

Theory of Stimulated Brillouin Scattering in Fibers for Highly Multimode Excitations

Stimulated Brillouin scattering (SBS) is often an unwanted loss mechanism in both active and passive fibers. Highly multimode excitation of fibers has been proposed as a novel route toward efficient SBS suppression. Here, we develop a detailed, quantitative theory which confirms this proposal and elucidates the physical mechanisms involved. Starting from the vector optical and scalar acoustic equations, we derive appropriate nonlinear coupled mode equations for the signal and Stokes modal amplitudes and an analytical formula for the SBS (Stokes) gain with applicable approximations, such as the neglect of shear effects. This allows us to calculate the exponential growth rate of the Stokes power as a function of the distribution of power in a highly multimode signal. The peak value of the gain spectrum across the excited modes determines the SBS threshold—the maximum SBS-limited power that can be sent through the fiber. The theory shows that the peak SBS gain is greatly reduced by highly multimode excitation due to gain broadening and relatively weaker intermodal SBS gain. The inclusion of exact vector optical modes in the calculation is crucial in order to capture the incomplete intermodal coupling due to mismatch of polarization patterns of higher-order modes. We demonstrate that equal excitation of the 160 modes of a commercially available, highly multimode circular step index fiber raises the SBS threshold by a factor of 6.5 and find comparable suppression of SBS in similar fibers with a D-shaped cross section. Published by the American Physical Society 2024

Long-run trends in partisan polarization of climate policy-relevant attitudes across countries

ABSTRACT We summarize long-run trends in partisan polarization of voters’ climate policy-relevant attitudes across 36 countries and multiple decades (1993–2020). We find substantial growth in partisan polarization of these attitudes in the US, other Anglophone countries and much of Western Europe, but not elsewhere. Comparing Western European to Anglophone countries, partisan polarization is more prominent on different climate policy-relevant attitudes, and primarily involves supporters of different party types. Observed partisan polarization patterns are not well explained by changes in either linkage to economic ideology or levels of general societal disagreement on climate policy-relevant questions. Growing partisan polarization does not generally reflect all partisan groups becoming more accepting of climate reform yet diverging because of differing rates of change. Instead, what disagreements there are on these matters have become increasingly tied to party support. Our findings highlight the increasing difficulty of achieving sustained political consensus for effective climate reform across many countries.

Targeting Lactate: An Emerging Strategy for Macrophage Regulation in Chronic Inflammation and Cancer.

Lactate accumulation and macrophage infiltration are pivotal features of both chronic inflammation and cancer. Lactate, once regarded merely as an aftereffect of glucose metabolism, is now gaining recognition for its burgeoning spectrum of biological roles and immunomodulatory significance. Recent studies have evidenced that macrophages display divergent immunophenotypes in different diseases, which play a pivotal role in disease management by modulating macrophage polarization within the disease microenvironment. The specific polarization patterns of macrophages in a high-lactate environment and their contribution to the progression of chronic inflammation and cancer remain contentious. This review presents current evidence on the crosstalk of lactate and macrophage in chronic inflammation and cancer. Additionally, we provide an in-depth exploration of the pivotal yet enigmatic mechanisms through which lactate orchestrates disease pathogenesis, thereby offering novel perspectives to the development of targeted therapeutic interventions for chronic inflammation and cancer.

How many parameters are needed to represent polar sea ice surface patterns and heterogeneity?

Abstract. Sea ice surface patterns encode more information than can be represented solely by the ice fraction. The aim of this paper is thus to establish the importance of using a broader set of surface characterization metrics and to identify a minimal set of such metrics that may be useful for representing sea ice in Earth system models. Large-eddy simulations of the atmospheric boundary layer over various idealized sea ice patterns, with equivalent ice fractions and average floe areas, demonstrate that the spatial organization of ice and water can play a crucial role in determining boundary layer structures. Thus, various methods used to quantify heterogeneity in categorical lattice-based spatial data, such as those used in landscape ecology and Geographic Information System (GIS) studies, are employed here on a set of recently declassified high-resolution sea ice surface images. It is found that, in conjunction with ice fraction, patch density (representing the fragmentation of the surface), the splitting index (representing variability in patch size), and the perimeter–area fractal dimension (representing the tortuosity of the interface) are all required to describe the two-dimensional pattern exhibited by a sea ice surface. For surfaces with anisotropic patterns, the orientation of the surface relative to the mean wind is also needed. Finally, scaling laws are derived for these relevant landscape metrics, allowing for their estimation using aggregated spatial sea ice surface data at any resolution. The methods used in and the results gained from this study represent a first step toward developing further methods for quantifying variability in polar sea ice surfaces and for parameterizing mixed ice–water surfaces in coarse geophysical models.

Novel mechanisms of intestinal flora regulation in high-altitude hypoxia

BackgroundThis study investigates the molecular mechanisms behind firmicutes-mediated macrophage (Mψ) polarization and glycolytic metabolic reprogramming through HIF-1α in response to intrinsic mucosal barrier injury induced by high-altitude hypoxia. MethodsEstablishing a hypoxia mouse model of high altitude, we utilized single-cell transcriptome sequencing to identify key cell types involved in regulating intestinal mucosal barrier damage caused by high-altitude hypoxia. Through proteomic analysis of colonic tissue Mψ and metabolomic analysis of Mψ metabolites, we determined crucial proteins and metabolic pathways influencing intestinal mucosal barrier damage induced by high-altitude hypoxia. Mechanistic validation was conducted using RAW264.7 Mψ in vitro by assessing cell viability with CCK-8 assay following treatment with different metabolites. The hypoxia mouse model was further validated in vivo by transplanting gut microbiota of Firmicutes. Histological examinations through H&E staining assessed colonic cell morphology and structure, while the FITC-dextran assay evaluated intestinal tissue permeability. Hypoxia probe signal intensity in mouse colonic tissue was assessed via metronidazole staining. Various experimental techniques, including flow cytometry, immunofluorescence, ELISA, Western blot, and RT-qPCR, were employed to study the impact of HIF-1α/glycolysis pathway and different gut microbiota metabolites on Mψ polarization. ResultsBioinformatics analysis revealed that single-cell transcriptomics identified Mψ as a key cell type, with their polarization pattern playing a crucial role in the intestinal mucosal barrier damage induced by high-altitude hypoxia. Proteomics combined with metabolomics analysis indicated that HIF-1α and the glycolytic pathway are pivotal proteins and signaling pathways in the intestinal mucosal barrier damage caused by high-altitude hypoxia. In vitro cell experiments demonstrated that activation of the glycolytic pathway by HIF-1α led to a significant upregulation of mRNA levels of IL-1β, IL-6, and TNFα while downregulating mRNA levels of IL-10 and TGFβ, thereby promoting M1 Mψ activation and inhibiting M2 Mψ polarization. Further mechanistic validation experiments revealed that the metabolite butyric acid from Firmicutes bacteria significantly downregulated the protein expression of HIF-1α, GCK, PFK, PKM, and LDH, thus inhibiting the HIF-1α/glycolytic pathway that suppresses M1 Mψ and activates M2 Mψ, consequently alleviating the hypoxic symptoms in RAW264.7 cells. Subsequent animal experiments confirmed that Firmicutes bacteria inhibited the HIF-1α/glycolytic pathway to modulate Mψ polarization, thereby mitigating intestinal mucosal barrier damage in high-altitude hypoxic mice. ConclusionThe study reveals that firmicutes, through the inhibition of the HIF-1α/glycolysis pathway, mitigate Mψ polarization, thereby alleviating intrinsic mucosal barrier injury in high-altitude hypoxia.

Emergence and transformation of polar skyrmion lattices via flexoelectricity

As analogies to magnetic skyrmions, polar skyrmions in ferroelectric superlattices and multilayers have garnered widespread attention for their non-trivial topology and novel properties like negative capacitance and nonlinear optical effect. So far, they have only been theoretically predicted to be able to assemble ordered hexagonal skyrmion lattices (SkLs) in ferroelectric thin films. Here, based on phase-field simulations, we report the critical roles of flexoelectricity playing in the stabilization and transformation of polar SkLs. Different polar SkL patterns can emerge in the ferroelectric thin films, including tetragonal-SkL, and hexagonal-SkLs with diverse orientations, as summarized by phase diagrams. These emergent SkL states are attributed to the material anisotropy modified by the flexoelectric effect. Interestingly, we further found that the hexagonal-SkLs can be rotated by applying strain gradient or in-plane electric field to the films. Moreover, a nonreciprocal bending response of tetragonal-SkL is also induced by the flexoelectric effect. Our results provide useful guidelines for the implementation of polar skyrmion lattices in experiments.

Wealth polarization in western countries

This paper delves into the dynamics of wealth distribution across various countries, utilizing innovative methodologies to uncover patterns of wealth polarization and its determinants. Wealth, distinct from income, reflects long-term economic resources and serves as a crucial indicator of economic well-being. Employing the "relative distribution" method and Recentered Influence Function (RIF) regression, this study examines changes in wealth distribution and the factors driving wealth polarization across eight European countries, Australia, and the United States.The analysis reveals significant heterogeneity in wealth distribution trends among countries, with disparities observed over time. Wealth polarization, akin to income polarization, emerges as a phenomenon distinct from traditional measures of inequality, shedding light on the concentration of wealth within societies. Household composition, demographic factors, and socioeconomic characteristics significantly influence wealth polarization, echoing patterns observed in income polarization studies.The findings underscore the multifaceted nature of wealth distribution dynamics and highlight the need for comprehensive policy interventions to address wealth inequality and polarization. Policy measures such as progressive taxation, regulatory reforms, and asset-building programs for marginalized communities are crucial in fostering equitable wealth distribution and creating inclusive societies.

Efficient completely polarization-encoded binocular structured light 3D measurement method for metallic objects

In practical 3D measurement applications, stereo vision assisted with phase shift patterns is intensively studied and widely used for its high precision and excellent noise resilience. While aiming to improve matching efficiency, excessive projection patterns or unreliable algorithms may be introduced as a side effect. We propose a completely polarization-encoded phase shift (CPPS) method to overcome the above challenges. In our method, the Stokes parameter S1 of the polarization patterns is encoded. Compared to the traditional fringe patterns, our method can reduce the number of projected patterns to improve the measurement efficiency. Therefore, the exact constraints can be realized without additional patterns. Experimental results show that the CPPS method reduces the matching time by 76.6% while reducing the number of fringe patterns by half.

Textile omnidirectional antenna for wearable WiFi-7 applications using higher order modes

In WiFi 7 (IEEE 802.11be), Multiple Input Multiple Output (MIMO) technology plays a crucial role in enhancing throughput. This combination enables numerous applications for wearable WiFi devices. For instance, WiFi can be utilized for tracking and fall detection purposes. Additionally, wearable devices used in gaming, vital signal monitoring, and tracking can benefit from the implementation of wearable MIMO antennas. Despite the demand for wearable WiFi antennas, specifically in the new 6 GHz band, a significant gap exists in the investigation of antennas that are completely made of textile, are low profile, and provide vertical polarization and omnidirectional patterns. Addressing this gap, in this paper, a wearable planar antenna is introduced, which is specifically designed to offer an omnidirectional pattern and linear polarization. To ensure its practicality and ease of use, the antenna utilizes lightweight and wearable textile material. The design details and performance of the proposed antenna are presented. The antenna covers all three bands of WiFi, namely, 2.4 GHz, 5 GHz, and 6 GHz bands. The 10-dB return loss bandwidth is 2.4 GHz–2.5 GHz, and 4.6 GHz–7.2 GHz. The maximum Specific Absorption Rate (SAR) for an input power of 500 mW is calculated at 1.053 W/Kg for a 2 mm air gap between the antenna and tissue surface. The size of the antenna is given by a circular area of π × (50 mm)2, and a thickness of 6 mm.

Observation of Antiferroelectric Domain Walls in a Uniaxial Hyperferroelectric.

Ferroelectric domain walls are a rich source of emergent electronic properties and unusual polar order. Recent studies show that the configuration of ferroelectric walls can go well beyond the conventional Ising-type structure. Néel-, Bloch-, and vortex-like polar patterns have been observed, displaying strong similarities with the spin textures at magnetic domain walls. Here, the discovery of antiferroelectric domain walls in the uniaxial ferroelectric Pb5Ge3O11 is reported. Highly mobile domain walls with an alternating displacement of Pb atoms are resolved, resulting in a cyclic 180° flip of dipole direction within the wall. Density functional theory calculations show that Pb5Ge3O11 is hyperferroelectric, allowing the system to overcome the depolarization fields that usually suppress the antiparallel ordering of dipoles along the longitudinal direction. Interestingly, the antiferroelectric walls observed under the electron beam are energetically more costly than basic head-to-head or tail-to-tail walls. The results suggest a new type of excited domain-wall state, expanding previous studies on ferroelectric domain walls into the realm of antiferroic phenomena.

Theory of paraxial optical skyrmions

Vector light beams, characterized by a spatially varying polarization, can exhibit localized structures reminiscent of the skyrmions familiar from the study of magnetic media. We present a theory of such skyrmions within paraxial optics, exploiting mathematical analogies with the study of superfluids, especially the A phase of superfluid He 3 . The key feature is the skyrmion field, which, together with the underlying skyrmion vector potential, determines the properties of the skyrmions and, more generally, the polarization structure of every paraxial vector beam. In addition to structures with integer skyrmion numbers, we find polarization patterns with non-integer skyrmion numbers; these seem to have no analogue in other fields of physics.

Dynamics of Polar Vortex Crystallization.

Vortex crystals are commonly observed in ultrathin ferroelectrics. However, a clear physical picture of origin of this topological state is currently lacking. Here, we show that vortex crystallization in ultrathin Pb(Zr_{0.4},Ti_{0.6})O_{3} films stems from the softening of a phonon mode and can be described as a Z_{2}×SU(1) symmetry-breaking transition. This result sheds light on the topology of the polar vortex patterns and bridges polar vortices with smectic phases, spin spirals, and other modulated states. Finally, we predict a resonant switching of the vortex tube orientation driven by midinfrared laser light which could enable new technologies.

From Optimism to Concern: Unveiling Sentiments and Perceptions Surrounding ChatGPT on Twitter

Artificial intelligence (AI) technologies, as a product of processes aimed at imitating human intelligence through computers and software, affect our daily lives in various aspects, including cultural, technological, and economic. The advent of ChatGPT, developed by OpenAI, signifies a pivotal AI advancement in human language comprehension and generation, heralding profound implications across societal, economic, and cultural dimensions. However, a notable gap exists in scholarly literature concerning the examination of perceptions and discussions surrounding ChatGPT. This study aims to address this gap by analyzing Twitter conversations, comprising 1.1 million tweets containing “ChatGPT” or “#ChatGPT” between December 1 2022 and June 1 2023, with geolocation data. Employing a text as data approach encompassing text, sentiment, and semantic network analyses, sentiment polarity and lexical patterns were explained, while semantic network analysis revealed central expressions and prominent themes in Twitter discussions. The study highlights the social effects of AI technologies from the perspective of Twitter users and reveals the sentimental tendency and themes in tweets with geographical and economic dimensions. The findings reflect the prevalence of positive sentiment and hype toward ChatGPT while there are also concerns regarding privacy, cybersecurity, and misuse of AI tools. More importantly, content generation, technical aspects, business applications, educational use, and competitors are among the main themes of ChatGPT-related discussions on Twitter.

Taiwanese Support for Self-Defense after the Russo–Ukrainian War

What impact does the Russo–Ukrainian War have on Taiwanese citizens’ attitudes toward the country’s self-defense? We used seven waves of representative surveys by the Institute for National Defense and Security Research between September 2021 and March 2023 (n = 10,869) in Taiwan. We tested two major hypotheses: that support for self-defense should increase for all citizens after the Ukraine crisis; and that the effect should be visible only among certain partisans. Using two surveys fielded before and after the Russian invasion, respectively, we found that support for war did not change significantly. Instead, we found a pattern of polarization based on partisanship. Subsequent analyses using seven waves reached the same conclusion. The partisan hypothesis also received additional support from a robustness test. Overall, the paper highlights the importance of context in studying public reactions to security threats. Policy and theoretical implications were discussed at the end of the paper.