Establishment and Optimization of HPLC-MS/MS for Detection of Progesterone Residue in Raw Milk

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.

Risk factors associated with Salmonella in dairy cattle farms in Henan and Hubei provinces,China

A cross-sectional study was conducted to evaluate the risk factors associated with the Salmonella infection status of dairy herds in Henan and Hubei provinces,China.Herds were assigned a Salmonella status based on the isolation of Salmonella from fecal samples obtained from adult lactating dairy cows.Information on potential biosecurity risk factors was collected using a questionnaire template via a 15-min face-to-face interview with dairy cattle producers from May 2020 to March 2021.The questionnaire consisted of 23 questions across two broad categories of potential biosecurity risk factors:farm and biosecurity managemental factors.A total of 48 farms were surveyed.In all(100%,48/48)of the surveyed farms,although sick animals were separated from healthy animals using fencing,there were no strict quarantine protocols for newly introduced animals.Mixed species rearing was practiced in 35.4%(17/48)of the farms.Feces were removed more than once a day in 45.8%(22/48)of the farms,whereas the remainder(54.2%,26/48)only removed animal feces once a day.A total of 29.2%(14/48)of the farms were located<2 km from other livestock farms.The use of personal protective equipment was consistently performed on all farms,with a major-ity of the workers on most farms(81.3%,39/48)always disinfecting footwear before entering production areas.A significant association between Salmonella-positive status and the high frequency of the presence of wildlife(birds and rodents in sheds and feed storage places)was recorded(OR:11.9,95%Cl:1.7,84.1,p=0.013).Fortunately,no farms shared farm equipment with other farms.The study highlights the occurrence of wildlife as a risk factor for the presence of Salmonella in investigated dairy herds.There is a need to institute appropriate on-farm control measures for wild birds and rodents to control the potential spread of Salmonella in dairy production systems.

Intelligent Teaching Design Management of College English from the Perspective of Educational Ecology

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.

Longitudinal gut fungal alterations and potential fungal biomarkers for the progression of primary liver disease

Liver disease,a major health concern worldwide,is a serious and progressive disorder.Herein,we not only established a mouse model of DEN+CCl4-induced primary liver disease but also collected clinical human samples to investigate longitudinal alterations in the gut mycobiome.As liver disease advanced,gut integrity was disrupted,and the mycobiota was disturbed in the mouse models.The metabolites associated with hepatocellular carcinoma(HCC)differed from those associated with the cirrhotic phase as follows:levels of stercobilin and aflatoxin B1 dialcohol were reduced,while levels of triterpenoids,bafilomycin A1,and DHEA were increased in the HCC group.The abundance of the phylum Chytridiomycota increased as the chronic liver disease progressed and was then replaced by the phylum Ascomycota in HCC.Based on the results from clinical human samples,the genus Candida(Ascomycota)(in humans)and the genus Kazachstania(Ascomycota)(in mice)occupied a dominant position in the HCC group,while other fungi were depleted.The increased abundance of C.albicans and depletion of S.cerevisiae may be hallmarks of the progression of liver cirrhosis to early HCC.Moreover,the administration of C.albicans and S.cerevisiae in the LC-HCC progression could accelerate or retard the progression of HCC.Therefore,gut fungi have the potential to serve as a noninvasive clinical biomarker and even a treatment method.

Highly efficient three-dimensional solar evaporator for zero liquid discharge desalination of high-salinity brine

Solar-driven interfacial evaporation is a promising technology for freshwater production from seawater,but salt accumulation on the evaporator surface hinders its performance and sustainability.In this study,we report a simple and green strategy to fabricate a three-dimensional porous graphene spiral roll(3GSR)that enables highly efficient solar evaporation,salt collection,and water production from near-saturated brine with zero liquid discharge(ZLD).The 3GSR design facilitates energy recovery,radial brine transport,and directional salt crystallization,thereby resulting in an ultrahigh evaporation rate of 9.05 kg m^(-2) h^(-1) in 25 wt%brine under 1-sun illumina-tion for 48 h continuously.Remarkably,the directional salt crystallization on its outer surface not only enlarges the evaporation area but also achieves an ultrahigh salt collection rate of 2.92 kg m^(-2) h^(-1),thus enabling ZLD desalination.Additionally,3GSR exhibits a record-high water production rate of 3.14 kg m^(-2) h^(-1) in an outdoor test.This innovative solution offers a highly efficient and continuous solar desalination method for water production and ZLD brine treatment,which has great implications for addressing global water scarcity and environmental issues arising from brine disposal.

基于相关系数的水文序列滑动周期识别方法

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.

A novel model of molnupiravir against SARS-CoV-2 replication: accumulated RNA mutations to induce error catastrophe

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)