In order to establish an HPLC-MS/MS method for detecting progesterone in raw milk,raw milk was extracted with methanol,and then determined by HPLC-MS/MS after the purification with a C18 solid phase extraction column....In order to establish an HPLC-MS/MS method for detecting progesterone in raw milk,raw milk was extracted with methanol,and then determined by HPLC-MS/MS after the purification with a C18 solid phase extraction column. Qualitative determination was performed according to retention time and selective ion abundance ratio,and quantification was performed by external standard method. The results showed that progesterone had a good linear relation in the range of0. 1-5. 0 ng/ml,with a correlation coefficient of 0. 999 9. The detection limit of the established method was 0. 02 μg/kg,and the quantification limit was0. 04 μg/kg. In the standard addition range of 0. 1-5. 0 ng/ml,the recovery ranged from 79. 6% to 105. 1%,with relative standard deviation≤8. 9%. Compared with the industry standard,the detection limit and the quantification limit of the established method are significantly reduced,and the sensitivity of the method is enhanced,so this method is suitable for the detection of progesterone residue in fresh milk in pastures.展开更多
The most widely used area of intelligent education supported by mobile technology is language learning. From the perspective of cognition, this study starts from the study of the second language theory and proposes th...The most widely used area of intelligent education supported by mobile technology is language learning. From the perspective of cognition, this study starts from the study of the second language theory and proposes the design idea of the "three rounds and three stages" teaching mode of the college English wisdom classroom from the perspective of the third language learning, and explores the implementation process. Finally, the paper analyzes the actual effect of the teaching model of the English-language classroom of College English English, and proposes corresponding suggestions.展开更多
RNA-dependent RNA polymerase(RdRp),also known as nsp12,is a key comp on ent in the syn thesis of viral ribonucleic acid(RNA)and is considered the primary target of nucleoside analog(NA)inhibitors.A recent publication ...RNA-dependent RNA polymerase(RdRp),also known as nsp12,is a key comp on ent in the syn thesis of viral ribonucleic acid(RNA)and is considered the primary target of nucleoside analog(NA)inhibitors.A recent publication by Kabinger et al.reported the unique molecular mechanisms of molnupiravir on inducing RNA mutations by RdRp during replication of SARS-CoV-2.^(1) As an oral broad-spectrum NA an tiviral age nt,moln upiravir has bee n prove n with considerable potential for the prevention and treatment of Corona Virus Disease 2019(COVID-19)(Fig.1).^(2)展开更多
基金Supported by Science and Technology Open Cooperation Project of Henan Province(162106000017)Science and Technology People-benefiting Plan Project of Henan Province(152207110004)+1 种基金Major Science and Technology Program of Henan Province(16110051020)Puyang Science and Technology Plan Project(160215)
文摘In order to establish an HPLC-MS/MS method for detecting progesterone in raw milk,raw milk was extracted with methanol,and then determined by HPLC-MS/MS after the purification with a C18 solid phase extraction column. Qualitative determination was performed according to retention time and selective ion abundance ratio,and quantification was performed by external standard method. The results showed that progesterone had a good linear relation in the range of0. 1-5. 0 ng/ml,with a correlation coefficient of 0. 999 9. The detection limit of the established method was 0. 02 μg/kg,and the quantification limit was0. 04 μg/kg. In the standard addition range of 0. 1-5. 0 ng/ml,the recovery ranged from 79. 6% to 105. 1%,with relative standard deviation≤8. 9%. Compared with the industry standard,the detection limit and the quantification limit of the established method are significantly reduced,and the sensitivity of the method is enhanced,so this method is suitable for the detection of progesterone residue in fresh milk in pastures.
文摘The most widely used area of intelligent education supported by mobile technology is language learning. From the perspective of cognition, this study starts from the study of the second language theory and proposes the design idea of the "three rounds and three stages" teaching mode of the college English wisdom classroom from the perspective of the third language learning, and explores the implementation process. Finally, the paper analyzes the actual effect of the teaching model of the English-language classroom of College English English, and proposes corresponding suggestions.
文摘准确进行周期识别对于合理认识水文变异规律、开展中长期水文模拟预报、水安全评价等具有重要的意义.本文通过滑动改变周期长度和初相位,构造出多组模拟周期序列,并以相关系数作为模拟周期序列与原始序列拟合精度的判别指标,选择拟合程度最好的模拟周期作为最优周期识别结果,从而提出水文序列滑动周期识别方法.理论和公式推导表明:相关系数可表征水文序列中的周期波动程度,相关系数越大,说明拟合精度越高,对应的周期变异越显著.统计试验结果显示:相比于常用的周期识别方法,文中方法的周期识别效率更高,且在各因素影响下也最具稳定性和可靠性.最后,文中方法应用于澜沧江流域21个站的年降雨量序列进行周期识别,结果显示该流域的降雨周期存在多时间尺度特征,北部和中部的降雨周期长度较短,多数在2~5 a左右,而南部的降雨周期5~10 a居多,个别站点的周期长度达到了18 a.
基金This work was supported by the grants from the NSFC(Nos.81773890,21772131,82073997)the Fundamental Research Funds of Science&Technology Department of Sichuan Province(No.2021YFS0044)Project First-Class Disciplines Development supported by CDUTCM.
文摘RNA-dependent RNA polymerase(RdRp),also known as nsp12,is a key comp on ent in the syn thesis of viral ribonucleic acid(RNA)and is considered the primary target of nucleoside analog(NA)inhibitors.A recent publication by Kabinger et al.reported the unique molecular mechanisms of molnupiravir on inducing RNA mutations by RdRp during replication of SARS-CoV-2.^(1) As an oral broad-spectrum NA an tiviral age nt,moln upiravir has bee n prove n with considerable potential for the prevention and treatment of Corona Virus Disease 2019(COVID-19)(Fig.1).^(2)
