As online content continues to grow, so does the spread of hate speech. We identify and examine challenges faced by online automatic approaches for hate speech detection in text. Among these ...difficulties are subtleties in language, differing definitions on what constitutes hate speech, and limitations of data availability for training and testing of these systems. Furthermore, many recent approaches suffer from an interpretability problem-that is, it can be difficult to understand why the systems make the decisions that they do. We propose a multi-view SVM approach that achieves near state-of-the-art performance, while being simpler and producing more easily interpretable decisions than neural methods. We also discuss both technical and practical challenges that remain for this task.
Electromagnetic metastructures stand for the artificial structures with a characteristic size smaller than the wavelength, which may efficiently manipulate the states of light. However, their ...applications are often restricted by the bandwidth of the electromagnetic response of the metastructures. It is therefore essential to reassert the principles in constructing broadband electromagnetic metastructures. Herein, after summarizing the conventional approaches for achieving broadband electromagnetic functionality, some recent developments in realizing broadband electromagnetic response by dispersion compensation, nonresonant effects, and several trade‐off approaches are reviewed, followed by some perspectives for the future development of broadband metamaterials. It is anticipated that broadband metastructures will have even more substantial applications in optoelectronics, energy harvesting, and information technology.
Broadband electromagnetic response is often required in the applications of metastructures. It is therefore important to reassess the principles of constructing broadband electromagnetic metastructures. Some recent developments in realizing broadband electromagnetic response by dispersion compensation, nonresonant effects, and some trade‐off approaches are reviewed. Perspectives are given on the development of broadband metastructured materials.
A freely tunable polarization rotator for broadband terahertz waves is demonstrated using a three‐rotating‐layer metallic grating structure, which can conveniently rotate the polarization of a ...linearly polarized terahertz wave to any desired direction with nearly perfect conversion efficiency. This low‐cost, high‐efficiency, and freely tunable device has potential applications as material analysis, wireless communication, and THz imaging.
Stimuli‐responsive and active materials promise radical advances for many applications. In particular, soft magnetic materials offer precise, fast, and wireless actuation together with versatile ...functionality, while liquid crystal elastomers (LCEs) are capable of large reversible and programmable shape‐morphing with high work densities in response to various environmental stimuli, e.g., temperature, light, and chemical solutions. Integrating the orthogonal stimuli‐responsiveness of these two kinds of active materials could potentially enable new functionalities and future applications. Here, magnetic microparticles (MMPs) are embedded into an LCE film to take the respective advantages of both materials without compromising their independent stimuli‐responsiveness. This composite material enables reconfigurable magnetic soft miniature machines that can self‐adapt to a changing environment. In particular, a miniature soft robot that can autonomously alter its locomotion mode when it moves from air to hot liquid, a vine‐like filament that can sense and twine around a support, and a light‐switchable magnetic spring are demonstrated. The integration of LCEs and MMPs into monolithic structures introduces a new dimension in the design of soft machines and thus greatly enhances their use in applications in complex environments, especially for miniature soft robots, which are self‐adaptable to environmental changes while being remotely controllable.
A liquid crystal elastomer material with embedded ferromagnetic microparticles takes advantage of both magnetic and thermal stimuli‐responsiveness. Such a monolithic soft material enables reconfigurable magnetic soft miniature machines that self‐adapt to changing environmental conditions. The hybrid material introduces a multi‐modal actuation and physical intelligence capability for wireless soft machines.
Spinal sensory transmission is under descending biphasic modulation, and descending facilitation is believed to contribute to chronic pain. Descending modulation from the brainstem rostral ...ventromedial medulla (RVM) has been the most studied, whereas little is known about direct corticospinal modulation. Here, we found that stimulation in the anterior cingulate cortex (ACC) potentiated spinal excitatory synaptic transmission and this modulation is independent of the RVM. Peripheral nerve injury enhanced the spinal synaptic transmission and occluded the ACC-spinal cord facilitation. Inhibition of ACC reduced the enhanced spinal synaptic transmission caused by nerve injury. Finally, using optogenetics, we showed that selective activation of ACC-spinal cord projecting neurons caused behavioral pain sensitization, while inhibiting the projection induced analgesic effects. Our results provide strong evidence that ACC stimulation facilitates spinal sensory excitatory transmission by a RVM-independent manner, and that such top-down facilitation may contribute to the process of chronic neuropathic pain.
Highly selective and direct electroreductive ring‐opening carboxylation of epoxides with CO2 in an undivided cell is reported. This reaction shows broad substrate scopes within styrene oxides under ...mild conditions, providing practical and scalable access to important synthetic intermediate β‐hydroxy acids. Mechanistic studies show that CO2 functions not only as a carboxylative reagent in this reaction but also as a promoter to enable efficient and chemoselective transformation of epoxides under additive‐free electrochemical conditions. Cathodically generated α‐radical and α‐carbanion intermediates lead to the regioselective formation of α‐carboxylation products.
Highly selective and direct electroreductive ring‐opening carboxylation of epoxides with CO2 in an undivided cell to yield synthetically important β‐hydroxy acids is described. CO2 functions not only as a carboxylative reagent in this reaction but also as a promoter to enable efficient and chemoselective transformation of epoxides under additive‐free electrochemical conditions.
The usage of elemental sulfur (S8) for constructing sulfur‐containing polymers is of great significance in terms of sulfur resource utilization or fabrication of high‐performance polymers. Currently, ...the random disassembly of S8 hinders its direct use in the precise synthesis of sulfur‐containing polymers. Herein, we provide an effective strategy for controlling the dismantlement of S8 to synthesize polydisulfides, a promising category of dynamic bonds containing polymers. In this strategy, the completely alternating copolymerization of one sulfur atom, which is orderly derived from S8, with episulfides is achieved with MTBD (7‐methyl‐1,5,7‐triazabicyclo4.4.0dec‐5‐ene) as catalyst and PPNSbF6 (PPN+ is bis(triphenylphosphine)iminium) as cocatalyst. Delightedly, the living‐ polymerization feature, and the good monomer compatibility allows for the access to diverse polydisulfides. Furthermore, the density functional theory (DFT) was employed to elaborate the copolymerization process.
A strategy for controlling the orderly disassembly of elemental sulfur (S8) in the presence of MTBD (a hindered organic base) and PPNSbF6 (an ammonium salt) is described for constructing polydisulfides by copolymerizing with episulfides. The “living polymerization” feature and good monomer compatibility of this copolymerization allows for the access to diverse polydisulfides with well‐defined structures and excellent optical properties.
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