Ziyang County, Shaanxi Province, China is a world known selenium（Se）-enriched area, and a severe selenosis incident was reported in Naore Village during the 1990 s. This study investigated the geochemical characteri...Ziyang County, Shaanxi Province, China is a world known selenium（Se）-enriched area, and a severe selenosis incident was reported in Naore Village during the 1990 s. This study investigated the geochemical characteristics of Se and its fractions in Se-enriched rocks from Ziyang. Se distribution is uneven, ranging from 0.23 to 57.00 μg/g（17.29±15.52 μg/g）. Se content is higher in slate than chert, and even lower in carbonate rocks. Cd, As and V are enriched but Pb is depleted in Se-enriched strata. Se has different correlations both with TS（total sulfur）（R^2=0.59 for chert） and TC（total carbon）（R^2=0.77 for slate, R^2=0.87 for carbonate）. Se has significant positive correlations with V（r=0.65）, As（r=0.485）, Cd（r=0.459） and Pb（r=0.405）. The Se level correlates with mineral content, positively with pyrite, chlorite and illite, negatively with albite. Se associated with sulfide/selenide and elemental Se are the predominant fractions of total recovered Se, suggesting that a reducing environment and the formation of sulfides were significant to Se deposition during its geochemical cycle. Although low concentration of bio-available Se（average 5.62%±3.69%） may reduce the risk of Se poisoning in the target area, utilization of Se-rich rock as natural fertilizer should be restricted.展开更多
The reaction of a variety of aldoximes with perfluoroalkanosulfonyl fluoride in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene（DBU） in dichloromethane smoothly generated the corresponding nitriles in 70%-95% yie...The reaction of a variety of aldoximes with perfluoroalkanosulfonyl fluoride in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene（DBU） in dichloromethane smoothly generated the corresponding nitriles in 70%-95% yields.展开更多
Data mining technology and association rule mining can be important technologies to deal with a large amount of accumulated data in the medical field,and can reflect the value of large medical data.According to the ch...Data mining technology and association rule mining can be important technologies to deal with a large amount of accumulated data in the medical field,and can reflect the value of large medical data.According to the characteristics of large medical data,aiming at the problem that the traditional Apriori algorithm scans the database too long and generates too many candidate itemsets,a method of digital mapping and sorting of itemsets is proposed.The method of the base model and generation model was used to generate superset,which can improve the efficiency of superset generation and pruning.By using open source framework Hadoop and transplanting the improved algorithm to the Hadoop platform combined with the MapReduce framework,the idea of parallel improvement was introduced based on database partition.Experimental results show that it solves the redundancy of large-scale data sets and makes Apriori algorithm have good parallel scalability.Finally,an example was given to demonstrate the possibility of improving the algorithm.展开更多
基金supported by the Foundation of China Geological Survey(Nos.12120113087100,12120113022600)the Basic Scientific Research of the Institute of Geophysical Geochemical Exploration,Chinese Academy of Geological Sciences(No.WHS201302)
文摘Ziyang County, Shaanxi Province, China is a world known selenium（Se）-enriched area, and a severe selenosis incident was reported in Naore Village during the 1990 s. This study investigated the geochemical characteristics of Se and its fractions in Se-enriched rocks from Ziyang. Se distribution is uneven, ranging from 0.23 to 57.00 μg/g（17.29±15.52 μg/g）. Se content is higher in slate than chert, and even lower in carbonate rocks. Cd, As and V are enriched but Pb is depleted in Se-enriched strata. Se has different correlations both with TS（total sulfur）（R^2=0.59 for chert） and TC（total carbon）（R^2=0.77 for slate, R^2=0.87 for carbonate）. Se has significant positive correlations with V（r=0.65）, As（r=0.485）, Cd（r=0.459） and Pb（r=0.405）. The Se level correlates with mineral content, positively with pyrite, chlorite and illite, negatively with albite. Se associated with sulfide/selenide and elemental Se are the predominant fractions of total recovered Se, suggesting that a reducing environment and the formation of sulfides were significant to Se deposition during its geochemical cycle. Although low concentration of bio-available Se（average 5.62%±3.69%） may reduce the risk of Se poisoning in the target area, utilization of Se-rich rock as natural fertilizer should be restricted.
基金the National Natural Science Foundation of China (No. 21362022) for financial support
文摘The reaction of a variety of aldoximes with perfluoroalkanosulfonyl fluoride in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene（DBU） in dichloromethane smoothly generated the corresponding nitriles in 70%-95% yields.
基金the national natural science foundation of China([2018]61741124)the science planning project of Guizhou province(Guizhou science and technology cooperation platform talent[2018]no.5781)What’s more,we thank the anonymous reviewers sincerely for their significant and valuable feedback.
文摘Data mining technology and association rule mining can be important technologies to deal with a large amount of accumulated data in the medical field,and can reflect the value of large medical data.According to the characteristics of large medical data,aiming at the problem that the traditional Apriori algorithm scans the database too long and generates too many candidate itemsets,a method of digital mapping and sorting of itemsets is proposed.The method of the base model and generation model was used to generate superset,which can improve the efficiency of superset generation and pruning.By using open source framework Hadoop and transplanting the improved algorithm to the Hadoop platform combined with the MapReduce framework,the idea of parallel improvement was introduced based on database partition.Experimental results show that it solves the redundancy of large-scale data sets and makes Apriori algorithm have good parallel scalability.Finally,an example was given to demonstrate the possibility of improving the algorithm.
