In this paper, we report our multiwavelength observations of the C4.2 circularribbon flare in active region (AR) 12434 on 2015 October 16. The short-lived flare was associated with positive magnetic polarities and a negative polarity inside, as revealed by the photospheric line-of-sight magnetograms. Such magnetic pattern is strongly indicative of a magnetic null point and spine-fan configuration in the corona. The flare was triggered by the eruption of a mini-filament residing in the AR, which produced the inner flare ribbon (IFR) and the southern part of a closed circular flare ribbon (CFR). When the eruptive filament reached the null point, it triggered null point magnetic reconnection with the ambient open field and generated the bright CFR and a blowout jet. Raster observations of the Interface Region Imaging Spectrograph (IRIS ) show plasma upflow at speed of 35−120 km s −1 in the Fe xxi 1354.09Å line (log T ≈ 7.05) and downflow at speed of 10−60 km s −1 in the Si iv 1393.77Å line (log T ≈ 4.8) at certain locations of the CFR and IFR during the impulsive phase of flare, indicating explosive chromospheric evaporation. Coincidence of the single HXR source at 12−25 keV with the IFR and calculation based on the thick-target model suggest that the explosive evaporation was most probably driven by nonthermal electrons.

It has been reported that there are multiple mechanisms by which bufalin could exert its antimetastatic effect. HIF-1α has been reported to be involved in tumor migration and invasion by regulating EMT. However, it is not known whether bufalin could exert the antimetastatic effect by modulating HIF-1α expression in hepatocellular carcinoma. In the present study, we aimed to evaluate the antimetastatic potential of bufalin in vivo and in vitro. Our results demonstrated that the liver/lung metastases were significantly reduced in bufalin-treated mice, as tested in the orthotopic transplanted and tail vein injection tumor models. Furthermore, the epithelial-to-mesenchymal transition (EMT) was inhibited in bufalin-treated tumors, as reflected the upregulation of E-cadherin, and downregulation of N-cadherin, vimentin, Snail. Similar results were observed in SMMC7721 cells treated with bufalin. Moreover, the transforming growth factor-β1 (TGF-β1)-induced EMT was also abrogated by bufalin. Mechanistically, our study demonstrated that hypoxia-inducible factor-1α (HIF-1α) played an important role in the antimetastatic effect of bufalin in hepatocellular carcinoma. Importantly, HIF-1α expression may be regulated through the inhibition of the PI3K/AKT/mTOR pathway. Taken together, our results suggest that bufalin suppresses hepatic tumor invasion and metastasis and that this process may be related to the PI3K/AKT/mTOR/ HIF-1α axis.

We have explored the relationship between hard X-ray (HXR) emissions and Doppler velocities caused by the chromospheric evaporation in two X1.6 class solar flares on 2014 September 10 and October 22, respectively. Both events display double ribbons and Interface Region Imaging Spectrograph (IRIS) slit is fixed on one of their ribbons from the flare onset. The explosive evaporations are detected in these two flares. The coronal line of Fe XXI 1354.09Å shows blue shifts, but chromospheric line of C I 1354.29Å shows red shifts during the impulsive phase. The chromospheric evaporation tends to appear at the front of flare ribbon. Both Fe XXI and C I display their Doppler velocities with a 'increase-peak-decrease' pattern which is well related to the 'rising-maximumdecay' phase of HXR emissions. Such anti-correlation between HXR emissions and Fe XXI Doppler shifts, and correlation with C I Doppler shifts indicate the electron-driven evaporation in these two flares.

In this paper, we report our multiwavelength observations of a partial filament eruption event in NOAA active region 11283 on 2011 September 8. A magnetic null point and the corresponding spine and separatrix surface are found in the active region. Beneath the null point, a sheared arcade supports the filament along the highly complex and fragmented polarity inversion line. After being activated, the sigmoidal filament erupted and split into two parts. The major part rose at the speeds of 90−150 km s −1 before reaching the maximum apparent height of ∼115 Mm. Afterwards, it returned to the solar surface in a bumpy way at the speeds of 20−80 km s −1 . The rising and falling motions were clearly observed in the extreme-ultravoilet (EUV), UV, and Hα wavelengths. The failed eruption of the main part was associated with an M6.7 flare with a single hard X-ray source. The runaway part of the filament, however, separated from and rotated around the major part for ∼1 turn at the eastern leg before escaping from the corona, probably along large-scale open magnetic field lines. The ejection of the runaway part resulted in a very faint coronal mass ejection (CME) that propagated at an apparent speed of 214 km s −1 in the outer corona. The filament eruption also triggered transverse kink-mode oscillation of the adjacent coronal loops in the same AR. The amplitude and period of the oscillation were 1.6 Mm and 225 s. Our results are important for understanding the mechanisms of partial filament eruptions and provide new constraints to theoretical models. The multiwavelength observations also shed light on space weather prediction.Subject headings: Sun: corona -Sun: coronal mass ejections (CMEs) -Sun: flares -Sun: filaments Online-only material: animations, color figures -22 -4. The runaway part, however, separated from and rotated around the major part for ∼1 turn before escaping outward from the corona at the speeds of 125−255 km s −1 , probably along the large-scale open magnetic field lines as evidenced by the PFSS modelling and the type III radio burst. The ejected part of the filament led to a faint CME. The angular width and apparent speed of the CME in the FOV of C2 are 37 • and 214 km s −1 . The propagation directions of the escaping filament observed by SDO/AIA and STA/EUVI are consistent with those of the CME observed by LASCO/C2 and STA/COR1, respectively. 5. The partial filament eruption also triggered transverse oscillation of the neighbouring coronal loops in the same AR. The amplitude and period of the kink-mode oscillation were 1.6 Mm and 225 s. We also performed diagnostics of the plasma density and temperature of the oscillating loops.The authors thank the referee for valuable suggestions and comments to improve the quality of this article. We gratefully acknowledge for inspiring and constructive discussions. SDO is a mission of NASA's Living With a Star Program. AIA and HMI data are courtesy of the NASA/SDO science teams. STEREO/SECCHI data are provided by a consortium of US,