Abstract. Dinitrogen pentoxide (N 2 O 5 ) and nitryl chloride (ClNO 2 ) are key species in nocturnal tropospheric chemistry and have significant effects on particulate nitrate formation and the following day's photochemistry through chlorine radical production and NO x recycling upon photolysis of ClNO 2 . To better understand the roles of N 2 O 5 and ClNO 2 in the high-aerosol-loading environment of northern China, an intensive field study was carried out at a high-altitude site (Mt. Tai, 1465 m a.s.l.) in the North China Plain (NCP) during the summer of 2014. Elevated ClNO 2 plumes were frequently observed in the nocturnal residual layer with a maximum mixing ratio of 2.1 ppbv (1 min), whilst N 2 O 5 was typically present at very low levels (< 30 pptv), indicating fast heterogeneous N 2 O 5 hydrolysis. Combined analyses of chemical characteristics and backward trajectories indicated that the ClNO 2 -laden air was caused by the transport of NO xrich plumes from the coal-fired industry and power plants in the NCP. The heterogeneous N 2 O 5 uptake coefficient (γ ) and ClNO 2 yield (φ) were estimated from steady-state analysis and observed growth rate of ClNO 2 . The derived γ and φ exhibited high variability, with means of 0.061 ± 0.025 and 0.28 ± 0.24, respectively. These values are higher than those derived from previous laboratory and field studies in other regions and cannot be well characterized by model parameterizations. Fast heterogeneous N 2 O 5 reactions dominated the nocturnal NO x loss in the residual layer over this region and contributed to substantial nitrate formation of up to 17 µg m −3 . The estimated nocturnal nitrate formation rates ranged from 0.2 to 4.8 µg m −3 h −1 in various plumes, with a mean of 2.2 ± 1.4 µg m −3 h −1 . The results demonstrate the significance of heterogeneous N 2 O 5 reactivity and chlorine activation in the NCP, and their unique and universal roles in fine aerosol formation and NO x transformation, and thus their potential impacts on regional haze pollution in northern China.

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Focusing on two-dimensional (2D) Janus MoSSe monolayers, we show that simultaneously existing in-plane and out-of-plane intrinsic electric fields cause Zeeman-and Rashba-type spin splitting, respectively. In MoSSe van der Waals (vdW) structures, intrinsic electric field results in a large interlayer band offset. Therefore, large interlayer band offset, being the driving force for interlayer excitons, endows ultralong lifetimes to excitons and might dissociate excitons into free carriers. In comparison to its parent structure (i.e., MoS 2 ), MoSSe vdW structures are rather appealing for new concepts in light−electricity interconversion. In addition, the Rashba effects could be tuned by changing the interlayer distances due to the competition between the intralayer and interlayer electric field. Due to the large band offset, valley polarization relaxation is markedly reduced, promising enhanced valley polarization and ultralong valley lifetimes. As a result, MoSSe vdW structures harbor strong valley-contrasting physics, making them competitive systems to their parent structures.

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Drug resistance in breast cancer remains a major cause for the failure of chemotherapy. Glucosylceramide synthase (GCS) plays an important role in multidrug resistance (MDR) in breast cancer. P-glycoprotein (P-gp) also confers a cross-resistance of many unrelated drugs. In this study, we studied the MDR effect and potential mechanisms of breast cancer after constructing permanent breast cancer cell lines with GCS knockout by using recombinant vectors targeting GCS (pSUPER-GCSshRNAs). The GCSshRNA stably transfected cells were successfully established and significant lower levels of GCS mRNA and protein expression were confirmed. In in vitro experiments, the GCSshRNA stably transfected cells showed a significantly reduced level of MDR1 and P-gp expression and decreased drug efflux ability. Reduced level of GCS expression conveyed a significant reversal of drug resistance by MTT assay and increased caspase-3 activity. In in vivo experiments by using nude mice with xenograft tumors, a significant inhibition of tumor growth was observed after comparing with the control group. Furthermore, enhanced response of chemotherapy was acquired by reduced expression of GCS as well as MDR1 in vivo. In conclusion, GCSshRNA could efficiently suppress GCS and MDR1 expression in vitro and in vivo and these findings may be used as one of the methods to reverse MDR in breast cancer.