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Abstract Seismic and magnetotelluric studies suggest hydrous silicate melts atop the 410 km discontinuity form 30–100 km thick layers. Importantly, in some regions, two layers are observed. These stagnant layers are related to their comparable density to the surrounding mantle, but their formation mechanisms and detailed structures remain unclear. Here we report a large decrease of silicate melt viscosity at ~14 GPa, from 96(5) to 11.7(6) mPa⋅s, as water content increases from 15.5 to 31.8 mol% H₂O. Such low viscosities facilitate rapid segregation of melt, which would typically prevent thick layer accumulation. Our 1D finite element simulations show that continuous dehydration melting of upwelling mantle material produces a primary melt layer above 410 km and a secondary layer at the depth of equal mantle-melt densities. These layers can merge into a single thick layer under low density contrasts or high upwelling rates, explaining both melt doublets and thick single layers. 

Current research on ferroelectric polymers centers predominantly on poly(vinylidene fluoride) (PVDF)–based fluoropolymers because of their superior performance. However, they are considered “forever chemicals” with environmental concerns. We describe a family of rationally designed fluorine-free ferroelectric polymers, featuring a polyoxypropylene main chain and disulfonyl alkyl side chains with a C3 spacer: −SO₂CH₂CHRCH₂SO₂− (R = −H or −CH₃). Both experimental and simulation results demonstrate that strong dipole-dipole interactions between neighboring disulfonyl groups induce ferroelectric ordering in the condensed state, which can be tailored by changing the R group: ferroelectric for R = −H or relaxor ferroelectric for R = −CH₃. At low electric fields, the relaxor polymer exhibits electroactuation and electrocaloric performance comparable with those of state-of-the-art PVDF-based tetrapolymers. 

Abstract Radioactive pertechnetate (TcO₄⁻) from the nuclear fuel cycle presents a severe risk to the environment due to its large solubility in water and non‐complexing nature. By utilizing the chaotropic properties of TcO₄⁻and its nonradioactive surrogate perrhenate (ReO₄⁻) and the principle of chaotropic interactions, a series of quaternary ammonium‐containing polyelectrolyte brush‐grafted silica particles are designed and applied to remove ReO₄⁻from water. These cationic hairy particles (HPs) are synthesized by surface‐initiated atom transfer radical polymerization of 2‐(N,N‐dimethylamino)ethyl methacrylate and subsequent quaternization with various halogen compounds. Dynamic light scattering (DLS) studies showed that the HPs with sufficiently longN‐alkyl andN‐benzyl substituents underwent sharp size reduction transitions in water when titrated with a KReO₄solution, indicating strong chaotropic interactions between the brushes and ReO₄⁻. All the HPs exhibited fast adsorption kinetics; the HPs with longerN‐alkyl andN‐benzyl substituents showed higher capabilities of removing ReO₄⁻than those with shorterN‐alkyls. Moreover, the brush particles with longerN‐substituents displayed a significantly stronger ability in selective adsorption of ReO₄⁻than the particles with shorterN‐substituents in the presence of competing anions, such as F⁻, Cl⁻, NO₃⁻, and SO₄²⁻. This work opens a new avenue to design high‐performance adsorbent materials for TcO₄⁻and ReO₄⁻. 

Heterografted molecular bottlebrushes (MBBs) with side chains composed of poly(n-butyl acrylate) (PnBA) and pH-responsive poly(2-(N,N-diethylamino)ethyl methacrylate) (PDEAEMA, pKa = 7.4) have been shown to be efficient, robust, and responsive emulsifiers. However, it remains unknown how they respond to external stimuli at interfaces. In this work, the shape-changing behavior of six hetero- and homografted MBBs at air–water interfaces in response to pH changes and lateral compression was investigated using a Langmuir–Blodgett trough and atomic force microscopy. At a surface pressure of 0.5 mN m−1, PDEAEMA-containing MBBs showed no worm-globule transitions when the pH was increased from 4.0 to 10.0, at which PDEAEMA becomes insoluble in water. Upon lateral compression at pH 4.0, MBBs with a mole fraction of PDEAEMA side chains (xPDEAEMA) < 0.50 underwent pronounced worm-globule shape transitions; there was an increasing tendency for bottlebrushes to become connected with increasing xPDEAEMA. At xPDEAEMA = 0.76, the molecules remained wormlike even at high compression. These observations were presumably caused by the increased electrostatic repulsion between protonated PDEAEMA side chains in the subphase with increasing xPDEAEMA, hindering the shape change. At pH 10.0, MBBs with xPDEAEMA < 0.50 showed a lower tendency to change their wormlike morphologies upon compression than at pH 4.0. No shape transition was observed when xPDEAEMA > 0.50, attributed to the relatively high affinity toward water and the rigidity of PDEAEMA. This study revealed the shape-changing behavior of amphiphilic pH-responsive MBBs at air–water interfaces, which could be useful for future design of multicomponent MBBs for potential applications. 

Abstract A key challenge in millimeter-wave and terahertz wireless networks is blockage of the line-of-sight path between a base station and a user. User and environmental mobility can lead to blockage of highly directional beams by intervening people or objects, yielding link disruptions and poor quality of service. Here, we propose a solution to this problem which leverages the fact that, in such scenarios, users are likely to be located within the electromagnetic near field of the base station, which opens the possibility to engineer wave fronts for link maintenance. We show that curved beams, carrying data at high bit rates, can realize a link by curving around an intervening obstacle. We develop a model to analyze and experimentally evaluate the bandwidth limitations imposed by the use of self accelerating beams. We also demonstrate that such links employ the full aperture of the transmitter, even those portions which have no direct line of sight to the receiver, emphasizing that ray optics fails to capture the behavior of these near-field wave fronts. This approach, which is ideally suited for use at millimeter-wave and terahertz frequencies, opens vast new possibilities for wave front management in directional wireless networks.