Helium-bearing superconductor at high pressure

Helium (He) is the most inert noble gas at ambient conditions. It adopts a hexagonal close packed structure (P63/mmc) and remains in the insulating phase up to 32 TPa. In contrast, lithium (Li) is one of the most reactive metals at zero pressure, while its cubic high-pressure phase (Fd-3m) is a weak metallic electride above 475 GPa. Strikingly, a stable compound of Li5He2 (R-3m) was formed by mixing Fd-3m Li with P63/mmc He above 700 GPa. The presence of helium promotes the lattice transformation from Fd-3m Li to Pm-3m Li, and tuns the three-dimensional distributed interstitial electrons into the mixture of zero- and two-dimensional anionic electrons. This significantly increases the degree of metallization at the Fermi level, consequently, the coupling of conductive anionic electrons with the Li-dominated vibrations is the key factor to the formation of superconducting electride Li5He2 with a transition temperature up to 26 K, dynamically stable to pressures down to 210 GPa.Comment: 5 pages, 3 figure

Activation of BNIP3-mediated mitophagy protects against renal ischemia-reperfusion injury

Acute kidney injury (AKI) is a syndrome of abrupt loss of renal functions. The underlying pathological mechanisms of AKI remain largely unknown. BCL2-interacting protein 3 (BNIP3) has dual functions of regulating cell death and mitophagy, but its pathophysiological role in AKI remains unclear. Here, we demonstrated an increase of BNIP3 expression in cultured renal proximal tubular epithelial cells following oxygen-glucose deprivation-reperfusion (OGD-R) and in renal tubules after renal ischemia-reperfusion (IR)-induced injury in mice. Functionally, silencing Bnip3 by specific short hairpin RNAs in cultured renal tubular cells reduced OGD-R-induced mitophagy, and potentiated OGD-R-induced cell death. In vivo, Bnip3 knockout worsened renal IR injury, as manifested by more severe renal dysfunction and tissue injury. We further showed that Bnip3 knockout reduced mitophagy, which resulted in the accumulation of damaged mitochondria, increased production of reactive oxygen species, and enhanced cell death and inflammatory response in kidneys following renal IR. Taken together, these findings suggest that BNIP3-mediated mitophagy has a critical role in mitochondrial quality control and tubular cell survival during AKI

Accurate Steady-State Mathematical Models of Arm and Line Harmonic Characteristics for Modular Multilevel Converter

The analysis of circulating current in modular multilevel converter (MMC) has aroused extensive research interests recently. Most studies on the derivation of harmonic components of circulating current neglect the harmonics in the line currents, but the harmonics evidently distort the line currents in many MMC applications where a circulating path for the dominant third-order harmonic current exists. So far, little research has been done on the model of the harmonics in line currents of MMC and neglecting them inevitably causes large error in the previous analytical expressions of circulating current. To solve these problems, this paper proposes a novel accurate steady-state mathematical model of harmonic components existing both in arm and line currents, and presents the detailed relations between the inner and outer harmonic characteristics of MMC. Thus, the derived instantaneous voltages and currents both in arm and line from the proposed models are far more accurate than the present research. What's more, each existing higher order harmonic is precisely calculated for the first time, filling up the blank of the conventional studies, and providing a better reference for the understanding, designing, and controlling of the MMC engineering applications. The correctness and high accuracy of the proposed models are verified by simulation results in PSCAD/EMTDC.</p