The clarity of nights is the major factor that should be carefully considered for optical/infrared astronomical observatories in site-testing campaigns.Cloud coverage is directly related to the amount of time availabl...The clarity of nights is the major factor that should be carefully considered for optical/infrared astronomical observatories in site-testing campaigns.Cloud coverage is directly related to the amount of time available for scientific observations at observatories.In this article,we report on the results of detailed night-time cloud statistics and continuous observing time derived from ground-based all-sky cameras(ASCs)at the Muztagh-ata site from 2017to 2021.Results obtained from acquisition data show that the proportion of the annual observing time at the Muztagh-ata site is 65%,and the best period with the least cloud coverage and longer continuous observing time is from September to February.We made a comparison of the monthly mean observing nights obtained from our ASC and CLARA data set,and results show that the discrepancy between them may depend on the cloud top heights.On average,this site can provide 175 clear nights and 169 nights with at least 4 hr of continuous observing time per year.展开更多
A transition metal-free synthesis of β-(pyridin-2-yl)-methyl ketones,using(pyridin-2-yl)methyl alcohols and ketones through the 2-pyridinylmethyl borrowing strategy,has been disclosed.This approach provides an effici...A transition metal-free synthesis of β-(pyridin-2-yl)-methyl ketones,using(pyridin-2-yl)methyl alcohols and ketones through the 2-pyridinylmethyl borrowing strategy,has been disclosed.This approach provides an efficient,available and environmentally benign access,leading to alkylation products with broad functional group tolerance and excellent yields.Meanwhile,the selective cleavage of unactivated C(sp^(3))-C(sp^(3))bonds of common secondary alcohols was achieved with high atom economy.展开更多
基金supported by the Chinese Academy of Sciences (CAS) “Light of West China”Program (No.2022_XBQNXZ_014)the Xinjiang Natural Science Foundation (Grant No.2022D01A357)+2 种基金the Joint Research Fund in Astronomy under a cooperative agreement between the National Natural Science Foundation of China (NSFC)and the CAS (Grant No.U2031209)the NSFC (Grant Nos.11873081,11603065,and 12073047)resource sharing platform construction project of Xinjiang Uygur Autonomous Region (No.PT2306)。
文摘The clarity of nights is the major factor that should be carefully considered for optical/infrared astronomical observatories in site-testing campaigns.Cloud coverage is directly related to the amount of time available for scientific observations at observatories.In this article,we report on the results of detailed night-time cloud statistics and continuous observing time derived from ground-based all-sky cameras(ASCs)at the Muztagh-ata site from 2017to 2021.Results obtained from acquisition data show that the proportion of the annual observing time at the Muztagh-ata site is 65%,and the best period with the least cloud coverage and longer continuous observing time is from September to February.We made a comparison of the monthly mean observing nights obtained from our ASC and CLARA data set,and results show that the discrepancy between them may depend on the cloud top heights.On average,this site can provide 175 clear nights and 169 nights with at least 4 hr of continuous observing time per year.
基金the financial support provided by the National Natural Science Foundation of China(21801209 and 21801210)the Fundamental Research Funds for the Central Universities(SWU118117,SWU118028 and XDJK2019AA003)+1 种基金the Venture&Innovation Support Program for Chongqing Overseas Returnees(cx2018085)the Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0130).
文摘A transition metal-free synthesis of β-(pyridin-2-yl)-methyl ketones,using(pyridin-2-yl)methyl alcohols and ketones through the 2-pyridinylmethyl borrowing strategy,has been disclosed.This approach provides an efficient,available and environmentally benign access,leading to alkylation products with broad functional group tolerance and excellent yields.Meanwhile,the selective cleavage of unactivated C(sp^(3))-C(sp^(3))bonds of common secondary alcohols was achieved with high atom economy.