A catalog of M stars has been published from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope data release 7(LAMOST DR7).We cross-matched the LAMOST M catalog with Kepler,Kepler 2(K2)and Transiting Exopla...A catalog of M stars has been published from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope data release 7(LAMOST DR7).We cross-matched the LAMOST M catalog with Kepler,Kepler 2(K2)and Transiting Exoplanet Survey Satellite(TESS)surveys.We obtained the light curves from the Kepler and TESS surveys.We detected 20,047 flare events from 4053 M stars and calculated their durations,amplitudes,and energies.We analyzed the distribution of the flare durations and energies.The distributions of flare duration for Kepler,K2 and TESS peak are at 3–3.5 hr,4–6 hr and 1–1.5 hr,respectively.This may be the result of the different cadences for the three data sets.The highest regions of the flare energies of Kepler,K2 and TESS are 32–32.5,32–32.5 and31–31.5 erg in Log format,respectively.A linear relationship between flare duration and energy emerges from our analysis.The ratio of flare duration to total observational time is approximately 0.2%–0.3%for the Kepler,K2 and TESS surveys.The occurrence rate of a star with a flare event increases from the M0 to M4 subtypes.We also determined the spatial distribution of the flare rate of M stars in the Milky Way.It seems that the flare rate decreases as the vertical height increases.The power index of the flare energies is in the region of 1.53–2.32,which is similar to previous result for solar type star(2.0).Further,we examined the relationship between the flare amplitude and chromospheric intensity.The flare activity increases rapidly with the increase in the HαEW at the lower values(less approximately 2?)and it increases slowly at the higher values.展开更多
We present an ab-initio study of monolayer BaBiO_(3) focused on how to harness the insulator-metal transition through suppression of the charge density wave(CDW)phase in this material.After the determination of the mo...We present an ab-initio study of monolayer BaBiO_(3) focused on how to harness the insulator-metal transition through suppression of the charge density wave(CDW)phase in this material.After the determination of the most stable structure for the freestanding monolayer,we investigate the effects of an applied electric field and of charge doping on the electronic properties of the system.Our results show that external electric fields of the order of 0.1-0.3 V/A are able to stabilize the metallic phase,destroy the CDW phase and,in addition,lead to a metallic metastable phase.On this same footing,we show that hole doping could also suppress the CDW phase and drive the system toward a metallic phase with large electron-phonon coupling.To this end,we also study the dependence of the electron-phonon coupling on hole-doping concentration and show that this could drive the onset of superconductivity.Indeed,low-dimensional BaBiO3 is an extremely flexible material with electronic properties that could be tuned using different and possibly combined external tools such as electric fields and charge doping,paving the way to achieve effective control on the transition from the CDW,to the metallic and then superconducting phase.展开更多
Arterioportal fistulas(APFs)are defined as vascular communications between the systemic arteries and portal circulation.APFs are classified as congenital or acquired,large or small,intrahepatic or extrahepatic,and tra...Arterioportal fistulas(APFs)are defined as vascular communications between the systemic arteries and portal circulation.APFs are classified as congenital or acquired,large or small,intrahepatic or extrahepatic,and traumatic or spontaneous.The consistent abnormal connection may result in severe presinusoidal portal hypertension,leading to gastrointestinal bleeding(GIB),ascites,elevated liver function enzymes,heart failure,diarrhea,and even pancreatitis or hematobilia in some unusual cases.Indeed,less than half reported cases have GIB,predominately caused by variceal rupture.Peptic ulcer bleeding has rarely been reported in the setting of APFs.Herein,we describe a case in which intrahepatic APF manifested as gastric ulcer bleeding,progressive portal thrombosis,and massive ascites,with these symptoms successfully relieved by endovascular treatment.展开更多
基金LAMOST is a National Major Scientific Project built by the Chinese Academy of Sciencesprovided by the National Development and Reform Commission+3 种基金the financial supports obtained from the NSFC No.11963002the fostering project of Guizhou University with No.201911the science research grants from the China Manned Space Project with No.CMS-CSST-2021-B07the Natural Science Foundation of Guizhou Province with No.2022164。
文摘A catalog of M stars has been published from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope data release 7(LAMOST DR7).We cross-matched the LAMOST M catalog with Kepler,Kepler 2(K2)and Transiting Exoplanet Survey Satellite(TESS)surveys.We obtained the light curves from the Kepler and TESS surveys.We detected 20,047 flare events from 4053 M stars and calculated their durations,amplitudes,and energies.We analyzed the distribution of the flare durations and energies.The distributions of flare duration for Kepler,K2 and TESS peak are at 3–3.5 hr,4–6 hr and 1–1.5 hr,respectively.This may be the result of the different cadences for the three data sets.The highest regions of the flare energies of Kepler,K2 and TESS are 32–32.5,32–32.5 and31–31.5 erg in Log format,respectively.A linear relationship between flare duration and energy emerges from our analysis.The ratio of flare duration to total observational time is approximately 0.2%–0.3%for the Kepler,K2 and TESS surveys.The occurrence rate of a star with a flare event increases from the M0 to M4 subtypes.We also determined the spatial distribution of the flare rate of M stars in the Milky Way.It seems that the flare rate decreases as the vertical height increases.The power index of the flare energies is in the region of 1.53–2.32,which is similar to previous result for solar type star(2.0).Further,we examined the relationship between the flare amplitude and chromospheric intensity.The flare activity increases rapidly with the increase in the HαEW at the lower values(less approximately 2?)and it increases slowly at the higher values.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074241,11929401,52120204,and 62004043)the Science and Technology Commission of Shanghai Municipality(Grant Nos.22XD1400900,20501130600,21JC1402700,21JC1402600,and 20QA1401000)+1 种基金the Key Research Project of Zhejiang Laboratory(Grant No.2021PE0AC02)the High-Performance Computing Center,Shanghai Technical Service Center of Science and Engineering Computing,Shanghai University。
文摘We present an ab-initio study of monolayer BaBiO_(3) focused on how to harness the insulator-metal transition through suppression of the charge density wave(CDW)phase in this material.After the determination of the most stable structure for the freestanding monolayer,we investigate the effects of an applied electric field and of charge doping on the electronic properties of the system.Our results show that external electric fields of the order of 0.1-0.3 V/A are able to stabilize the metallic phase,destroy the CDW phase and,in addition,lead to a metallic metastable phase.On this same footing,we show that hole doping could also suppress the CDW phase and drive the system toward a metallic phase with large electron-phonon coupling.To this end,we also study the dependence of the electron-phonon coupling on hole-doping concentration and show that this could drive the onset of superconductivity.Indeed,low-dimensional BaBiO3 is an extremely flexible material with electronic properties that could be tuned using different and possibly combined external tools such as electric fields and charge doping,paving the way to achieve effective control on the transition from the CDW,to the metallic and then superconducting phase.
文摘Arterioportal fistulas(APFs)are defined as vascular communications between the systemic arteries and portal circulation.APFs are classified as congenital or acquired,large or small,intrahepatic or extrahepatic,and traumatic or spontaneous.The consistent abnormal connection may result in severe presinusoidal portal hypertension,leading to gastrointestinal bleeding(GIB),ascites,elevated liver function enzymes,heart failure,diarrhea,and even pancreatitis or hematobilia in some unusual cases.Indeed,less than half reported cases have GIB,predominately caused by variceal rupture.Peptic ulcer bleeding has rarely been reported in the setting of APFs.Herein,we describe a case in which intrahepatic APF manifested as gastric ulcer bleeding,progressive portal thrombosis,and massive ascites,with these symptoms successfully relieved by endovascular treatment.
