Dielectric Breakdown in Chemical Vapor Deposited Hexagonal Boron Nitride

Insulating films are essential in multiple electronic devices because they can provide essential functionalities, such as capacitance effects and electrical fields. Two-dimensional (2D) layered materials have superb electronic, physical, chemical, thermal, and optical properties, and they can be effectively used to provide additional performances, such as flexibility and transparency. 2D layered insulators are called to be essential in future electronic devices, but their reliability, degradation kinetics, and dielectric breakdown (BD) process are still not understood. In this work, the dielectric breakdown process of multilayer hexagonal boron nitride (h-BN) is analyzed on the nanoscale and on the device level, and the experimental results are studied via theoretical models. It is found that under electrical stress, local charge accumulation and charge trapping/detrapping are the onset mechanisms for dielectric BD formation. By means of conductive atomic force microscopy, the BD event was triggered at several locations on the surface of different dielectrics (SiO2, HfO2, Al2O3, multilayer h-BN, and monolayer h-BN); BD-induced hillocks rapidly appeared on the surface of all of them when the BD was reached, except in monolayer h-BN. The high thermal conductivity of h-BN combined with the one-atom-thick nature are genuine factors contributing to heat dissipation at the BD spot, which avoids self-accelerated and thermally driven catastrophic BD. These results point to monolayer h-BN as a sublime dielectric in terms of reliability, which may have important implications in future digital electronic devices.Fil: Jiang, Lanlan. Soochow University; ChinaFil: Shi, Yuanyuan. Soochow University; China. University of Stanford; Estados UnidosFil: Hui, Fei. Soochow University; China. Massachusetts Institute of Technology; Estados UnidosFil: Tang, Kechao. University of Stanford; Estados UnidosFil: Wu, Qian. Soochow University; ChinaFil: Pan, Chengbin. Soochow University; ChinaFil: Jing, Xu. Soochow University; China. University of Texas at Austin; Estados UnidosFil: Uppal, Hasan. University of Manchester; Reino UnidoFil: Palumbo, Félix Roberto Mario. Comisión Nacional de Energía Atómica; Argentina. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lu, Guangyuan. Chinese Academy of Sciences; República de ChinaFil: Wu, Tianru. Chinese Academy of Sciences; República de ChinaFil: Wang, Haomin. Chinese Academy of Sciences; República de ChinaFil: Villena, Marco A.. Soochow University; ChinaFil: Xie, Xiaoming. Chinese Academy of Sciences; República de China. ShanghaiTech University; ChinaFil: McIntyre, Paul C.. University of Stanford; Estados UnidosFil: Lanza, Mario. Soochow University; Chin

Evolution and Formation of Non-Metallic Inclusions during Electroslag Remelting of Ce-Bearing 15Cr-22Ni-1Nb Austenitic Heat-Resistant Steel

The evolution of inclusions in austenitic heat-resistant steel with different Ce content during protective argon gas atmosphere electroslag remelting (ESR) was studied. All oxide inclusions in the Ce-free consumable electrode are MgO·Al2O3. A part of these MgO·Al2O3 inclusions was removed before metal droplets entered the liquid metal pool during the ESR. The soluble oxygen (arising from the reoxidation) reacted with soluble aluminum, calcium, and magnesium in liquid steel to form MgO·Al2O3 and CaO–Al2O3 inclusions in liquid steel. All oxide inclusions in the electrode with 0.016 mass% Ce are Ce2O2S. A portion of these Ce2O2S inclusions was dissociated into soluble oxygen, cerium, and sulfur in liquid steel during the ESR process, whereas the others were removed by absorbing them into molten slag. The oxide inclusions in the liquid metal pool and remelted ingot were Ce2O3, CeAlO3, and Ce2O2S. The CeAlO3 and Ce2O3 inclusions were reoxidation products formed by the chemical reaction between the soluble oxygen, soluble aluminum, and cerium. The oxide inclusions in the electrode with 0.300 mass% Ce are CeS and Ce2O2S. These CeS inclusions were removed by molten slag adsorption during the ESR. A part of these Ce2O2S inclusions was removed by slag adsorption, and the remaining entered into the liquid metal pool. The oxide inclusions in the liquid metal pool and the ingot were Ce2O3 and Ce2O2S. The Ce2O3 inclusions were formed through the chemical reaction between the soluble oxygen and cerium in the liquid metal pool. The Ce2O2S inclusions in the liquid pool originate from reoxidation products during the ESR process and the relics from the electrode

The reverse buffering effects of social support on the relationships between stresses and mental health: a survey of Chinese adults during the COVID-19 lockdown

Background People lived through different types of stresses during the COVID-19 pandemic, and stresses from different sources are believed to associate differently with mental health. Objectives The current study aims to examine the relationship between types of stresses and mental health among the general Chinese adult population, and further explore the moderating role of social support in these relationships. Methods This study was conducted from 1 to 10 February 2020, and 2441 participants were recruited through an online cross-sectional survey from 31 provinces in China. We used multiple linear regression analyses to examine the associations among stresses’ types, social support, and mental health. Results The study revealed that all types of stresses were associated with more mental health symptoms. Stresses from lockdown policy presented stronger associations with mental health symptoms (Beta = 0.387 for depressive symptoms and Beta = 0.385 for post-traumatic stress symptoms (PTSS)) than stresses from pandemic fear (Beta = 0.195 for depressive symptoms and Beta = 0.221 for PTSS). Moreover, greater social support enhanced the positive associations between stresses and mental health symptoms. Conclusions Stresses from lockdown policies during the early stage of the COVID-19 epidemic are worthy of more attention. We urge more interventions are required to reduce the side-effect of lockdown policies, and also discuss implications for mental health promotion

The ABI3-ERF1 module mediates ABA-auxin crosstalk to regulate lateral root emergence

Summary: Abscisic acid (ABA) is involved in lateral root (LR) development, but how ABA signaling interacts with auxin signaling to regulate LR formation is not well understood. Here, we report that ABA-responsive ERF1 mediates the crosstalk between ABA and auxin signaling to regulate Arabidopsis LR emergence. ABI3 is a negative factor in LR emergence and transcriptionally activates ERF1 by binding to its promoter, and reciprocally, ERF1 activates ABI3, which forms a regulatory loop that enables rapid signal amplification. Notably, ABI3 physically interacts with ERF1, reducing the cis element-binding activities of both ERF1 and ABI3 and thus attenuating the expression of ERF1-/ABI3-regulated genes involved in LR emergence and ABA signaling, such as PIN1, AUX1, ARF7, and ABI5, which may provide a molecular rheostat to avoid overamplification of auxin and ABA signaling. Taken together, our findings identify the role of the ABI3-ERF1 module in mediating crosstalk between ABA and auxin signaling in LR emergence

Dihydroartemisinin Exerts Anti-Tumor Activity by Inducing Mitochondrion and Endoplasmic Reticulum Apoptosis and Autophagic Cell Death in Human Glioblastoma Cells

Glioblastoma (GBM) is the most advanced and aggressive form of gliomas. Dihydroartemisinin (DHA) has been shown to exhibit anti-tumor activity in various cancer cells. However, the effect and molecular mechanisms underlying its anti-tumor activity in human GBM cells remain to be elucidated. Our results proved that DHA treatment significantly reduced cell viability in a dose- and time-dependent manner by CCK-8 assay. Further investigation identified that the cell viability was rescued by pretreatment either with Z-VAD-FMK, 3-methyladenine (3-MA) or in combination. Moreover, DHA induced apoptosis of GBM cells through mitochondrial membrane depolarization, release of cytochrome c and activation of caspases-9. Enhanced expression of GRP78, CHOP and eIF2α and activation of caspase 12 were additionally confirmed that endoplasmic reticulum (ER) stress pathway of apoptosis was involved in the cytotoxicity of DHA. DHA-treated GBM cells exhibited the morphological and biochemical changes typical of autophagy. Co-treatment with chloroquine (CQ) significantly induced the above effects. Furthermore, ER stress and mitochondrial dysfunction were involved in the DHA-induced autophagy. Further study revealed that accumulation of reactive oxygen species (ROS) was attributed to the DHA induction of apoptosis and autophagy. The illustration of these molecular mechanisms will present a novel insight for the treatment of human GBM