HfO 2 -based ferroelectric film has shown great potential for the application of ferroelectric memory due to its great advantages as compared to traditional ferroelectrics. However, the origin of the ferroelectricity of the HfO 2 -based ferroelectric film is still under debate. In this work, by performing ab initial molecular dynamics calculation, the phase stability and the polarization switching behavior of HfO 2 were systematically studied to illuminate the intrinsic origin its ferroelectricity. Results show that, under different inplane constraints and room temperature, the out-of-plane polarized orthorhombic ferroelectric phase Pca2 1 is always the metastable phase of HfO 2 . As driven by the out-of-plane electric field, HfO 2 exhibits linear dielectric behavior or antiferroelectric behavior with the ferroelectric−tetragonal−ferroelectric phase transformation under in-plane compression. With the tensile strain condition, the nonferroelectric HfO 2 could be transformed to be the out-of-plane polarized orthorhombic ferroelectric phase, which shows good ferroelectricity under a periodic electric field. The triggered phase transformation and ferroelectricity as modulated by the epitaxial constraint as found in this work were verified by a recent experiment and should be the intrinsic origin of the ferroelectricity of HfO 2 -based films.

Patients with chronic kidney disease (CKD) are characterized by a gradual loss of kidney function over time. A number of studies have indicated that tubule interstitial fibrosis (TIF) is associated with the occurrence and development of CKD. The aim of the present study was to investigate the effect of quercetin treatment on the fibrosis of renal tubular epithelial cells and to determine whether the anti-fibrotic effects of quercetin are achieved via microRNA (miR)-21. Human tubular epithelial HK-2 cells were cultured with transforming growth factor (TGF)-β to induce fibrosis and the expression of fibrotic markers collagen I, fibronectin, α-smooth muscle actin (SMA) and epithelial-cadherin were measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. Cells were treated with 7.5, 15 or 30 mg/ml quercetin, following which fibrosis and miR-21 expression were evaluated. Quercetin-treated cells were transfected with miR-21 mimics and the expression of fibrotic markers was examined using RT-qPCR. Finally, the expression of fibrosis-associated miR-21 target genes, phosphatase and tensin homolog (PTEN) and TIMP Metallopeptidase Inhibitor 3 (TIMP3), was measured in cells treated with quercetin with or without miR-21 mimics using RT-qPCR, western blotting and immunocytochemistry. The results revealed that TGF-β treatment induced a significant increase in the expression of fibrotic markers in HK-2 cells, while quercetin treatment partially inhibited the fibrosis of HK-2 cells. Furthermore, quercetin treatment significantly inhibited TGF-β-induced miR-21 upregulation and transfection with miR-21 mimics reversed the anti-fibrotic effects of quercetin. Quercetin treatment markedly upregulated PTEN and TIMP3 expression, whereas transfection with miR-21 mimics reversed this effect. The results of the present study suggest that quercetin is able to alleviate TGF-β-induced fibrosis in HK-2 cells via suppressing the miR-21 and upregulating PTEN and TIMP3. Quercetin may have potential as an anti-fibrotic treatment for patients with renal fibrosis.

Flexible HZO ferroelectric films with superior ferroelectricity, retention and fatigue endurance under multiple harsh conditions.

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