ABSTRACT
We report a memristive switching effect in Pt/CuOx/Si/Pt devices prepared by the rf sputtering technique at room temperature. Differently from other Cu-based metal filament switching systems, a gradual electroforming process, marked by a gradual increase of the device resistance and a gradual decrease of the device capacitance, was observed in the current-voltage and capacitance characteristics. After the gradual electroforming, the devices show a uniform memristive switching behavior. By Auger electron spectroscopy analysis, a model based on the thickness change of the SiOx layer at the CuOx/Si interface and Cu ion migration is proposed for the gradual electroforming and uniform memristive switching, respectively. This work should be meaningful for the preparation of forming-free and homogeneous memristive devices.
ABSTRACT
Brain metastasis (BM) is a major cause of mortality in small-cell lung cancer (SCLC) patients; however, the molecular pathway of SCLC BM remains largely unknown because of a lack of investigation. Here we screen the levels of some candidate-soluble factors in the serum of SCLC patients and find that SCLC patients with high levels of placental growth factor (PLGF) are prone to BM. Using in vitro blood-brain barrier model, we show that PLGF derived from SCLC cells triggers vascular endothelial growth factor receptor-1-Rho-extracellular regulated protein kinase 1/2 signaling axis activation, results in disassembly of tight junction in brain endothelial cells and promotes SCLC cell transendothelial migration. Furthermore, the downregulation of PLGF suppresses SCLC cell metastasis to the brain in an experimental BM model. These data suggest that PLGF is a potential signature of SCLC BM and a prospective therapeutic target for SCLC BM.