The paracellular claudin channel of the thick ascending limb (TAL) of Henle is critical for Ca++ reabsorption in the kidney. Genome‐wide association studies (GWASs) have identified claudin‐14 associated with hypercalciuric nephrolithiasis. Here, we show that claudin‐14 promoter activity and transcript are exclusively localized in the TAL. Under normal dietary condition, claudin‐14 proteins are suppressed by two microRNA molecules (miR‐9 and miR‐374). Both microRNAs directly target the 3′‐UTR of claudin‐14 mRNA; induce its mRNA decay and translational repression in a synergistic manner. Through physical interaction, claudin‐14 blocks the paracellular cation channel made of claudin‐16 and ‐19, critical for Ca++ reabsorption in the TAL. The transcript and protein levels of claudin‐14 are upregulated by high Ca++ diet, while downregulated by low Ca++ diet. Claudin‐14 knockout animals develop hypermagnesaemia, hypomagnesiuria, and hypocalciuria under high Ca++ dietary condition. MiR‐9 and miR‐374 transcript levels are regulated by extracellular Ca++ in a reciprocal manner as claudin‐14. The Ca++ sensing receptor (CaSR) acts upstream of the microRNA‐claudin‐14 axis. Together, these data have established a key regulatory role for claudin‐14 in renal Ca++ homeostasis.

body motion monitoring, covering subtle and large-strain ranges.Capacitive strain sensor has a simple structure with two electrodes separated by a dielectric material. Metals [19] and semiconductors [20] can be used as electrodes for constructing capacitive sensors. However, these electrode materials have poor mechanical properties, limiting the sensing range of capacitive strain sensors. [21] To solve the problem, geometrical engineering of rigid materials into buckled, [22][23][24] wrinkled, [16,25] and kirigami [26] forms is widely employed. For example, Someya's group shaped gold film into a wrinkled form for developing capacitive strain sensors, with a stretchability up to 140%. [16] In addition to the geometrical engineering, the usage of intrinsic stretchable materials as electrode for soft capacitive strain sensors is the other strategy widely adopted. These intrinsic stretchable materials include liquid metal, [27] nanomaterial/elastomer composites, [28] and conductive textiles. [29] Dickey and co-workers developed a liquid-metal-based capacitive strain sensor having a high stretchability (≈100%). [8] A capacitive strain sensor using conductive textile electrode was developed by Walsh's group, with a stretchability of 100% and a sensitivity of 1.23. [29] Cohen et al. reported a carbon nanotube (CNT)/elastomer-based capacitive sensor, owning a stretchability of 100% and a sensitivity of 0.99. [7] Although the above strategies can provide capacitive sensors with high stretchability, most of the electrode materials are not intrinsically self-healable. To fully mimic the functionality of human skin, the self-healability for sensory devices is highly demanded. [30] Hydrogels which consist of 3D networks with large quantity of water or ionic liquid have been proposed as electrode materials for soft electronics, due to their large stretchability, self-healability, and biocompatibility. [31,32] For sensing applications, hydrogel-based resistive strain sensors have been widely studied. [33][34][35][36] These devices have achieved large sensing limits, but the hydrogels have relatively long self-healing time and low self-healing efficiency. [33,36,37] Additionally, some of them needs external heating to accelerate the self-healing process. [35,38] Through the dynamic complexing interaction between metal ion and OH group, polyvinyl alcohol (PVA) based hydrogel has been investigated as active materials for constructing sensors. [39,40] CNT/PVA-based resistive strain Capacitive strain sensors could become an important component of electronic skin (E-skin) due to their low hysteresis and high linearity. However, to fully mimic the functionality of human skin, a capacitive strain sensor should be stretchable and self-healable. The development of such a sensor is limited by electrode materials which generally lack self-healability and/or stretchability. A highly stretchable and self-healing MXene (Ti 3 C 2 T x )/polyvinyl alcohol (PVA) hydrogel electrode is developed for use in capacitive strain sensors for E-skin. The...

No abstract

Fe‐based oxides have been seldom reported as electrocatalysts for the hydrogen evolution reaction (HER), limited by their weak intrinsic activity and conductivity. Herein, phosphorus doping modulation is used to construct inverse spinel P‐Fe3O4 with dual active sites supported on iron foam (P‐Fe3O4/IF) for alkaline HER with an extremely low overpotential of 138 mV at 100 mA cm−2. The obtained inverse spinel Fe–O–P derived from controllable phosphorization can provide an octahedral Fe site and O atom, which bring about the unusual dissociation mechanisms of two water molecules to greatly accelerate the proton supply in alkaline media. Meanwhile, the ΔGH of the P atom in Fe–O–P as an active site is theoretically calculated to be 0.01 eV. Notably, the NiFe LDH/IF(+)||P‐Fe3O4/IF(−) couple achieves an onset potential of 1.47 V (vs RHE) for overall water splitting, with excellent stability for more than 1000 h at a current density of 1000 mA cm−2, and even for 25 000 s at 10 000 mA cm−2 in 6.0 m KOH at 60 °C. The excellent catalyst stability and low‐cost merits of P‐Fe3O4/IF may hold promise for industrial hydrogen production. This work may reveal a new design strategy of earth‐abundant materials for large‐scale water splitting.

No abstract