Objective:To investigate mosquitocidal effects of ethanolic extract of(lowers of Tagetes erecta(T.erecta) and its chloroform and petroleum ether soluble fractions against the larvae of Culex quinquefasciatus(Cx.quinqu...Objective:To investigate mosquitocidal effects of ethanolic extract of(lowers of Tagetes erecta(T.erecta) and its chloroform and petroleum ether soluble fractions against the larvae of Culex quinquefasciatus(Cx.quinquefasciatus).Methods:The fresh flowers of T.erecta were extracted in cold with ethanol(5.0 L) and after concentration,the ethanol extract was fractionated with chloroform and petroleum ether to afford a brownish syrupy suspension of ethanol extract(50.0 g),petroleum ether soluble fraction(18.6 g) and chloroform soluble fraction(23.8 g).The larvicidal effect of ethanol extract and their solvent fractions were determined by the standard procedure of WHO against different instars of Cx.quinquefasciatus.Results:Among the tested samples the chloroform soluble fractions showed the highest toxicity and consequently,the lowest LC_(50) values(14.14 μ g/mL,17.06 μ g/mL.36.88 μ g/mL and 75.48 μ g/mL) for all the instars larvae of Cx.quinquefasciatus.The larvae showed comparative tolerance in the course of increasing age and time.Conclusions:It can be concluded that the flowers of T.erecta are very effective natural larvicide and could be useful against Cx.quinquefasciatus.展开更多
Last week, I read news about school bullying with my parents, and it made me feel very sad. School bullying is a serious problem nowadays. It can happen in the classroom or even after school.
In early March,a couple in Jiaxing,Zhejiang Province,grabbed social media headlines by hosting a wedding that only cost 5,000 yuan($690)-a number well below the average cost of weddings in China.
Three-leg Ostrich Oneday,Jack comeshomefrom school witha new notebook.He says to his mum,"t's a prize,mother."His mother says,“A prize? That's good.But how did yougetthat?”"My teacher gave it ...Three-leg Ostrich Oneday,Jack comeshomefrom school witha new notebook.He says to his mum,"t's a prize,mother."His mother says,“A prize? That's good.But how did yougetthat?”"My teacher gave it to me.He asked us how many legs an ostrich has,and Iansweredthree,"Jack says.展开更多
On the morning of 3 July,Zhou Hongwei,Party branch secretary of Huangnidun Village,visited Zhou Wenping’s home to hear the family’s suggestions regarding the village’s plan to install more street lamps and upgrade ...On the morning of 3 July,Zhou Hongwei,Party branch secretary of Huangnidun Village,visited Zhou Wenping’s home to hear the family’s suggestions regarding the village’s plan to install more street lamps and upgrade public water pipelines.After their meeting,Zhou immediately headed to another family for their opinions.展开更多
1初遇,然然是个12岁的女孩,是偌大的心脏重症监护室(cardiac intensive care unit,CICU)角落里一个孤独而特别的存在。当大厅里的小宝宝们因饥饿而哇哇大哭时,她总是乖巧地待在床位上,静静地玩手机或躺着。每个经过她身边的人,都会好奇...1初遇,然然是个12岁的女孩,是偌大的心脏重症监护室(cardiac intensive care unit,CICU)角落里一个孤独而特别的存在。当大厅里的小宝宝们因饥饿而哇哇大哭时,她总是乖巧地待在床位上,静静地玩手机或躺着。每个经过她身边的人,都会好奇地警上一眼,但是看过之后都会迅速收回目光,因为她的外形实在是让人既心疼又害怕。展开更多
Susan:If you were a dinosaur,which dinosaur would you prefer to be?Ed:I'd be a Triceratops(三角龙)for sure!It's the scariest(最恐怖的)one.Susan:The Triceratops isn't the scariest dinosaur!Ed:How can you sa...Susan:If you were a dinosaur,which dinosaur would you prefer to be?Ed:I'd be a Triceratops(三角龙)for sure!It's the scariest(最恐怖的)one.Susan:The Triceratops isn't the scariest dinosaur!Ed:How can you say that?展开更多
The Colorado potato beetle is an important pest of solanaceous plants in the Northern Hemisphere. Better understanding of its physiological responses to temperature stress and their interactions with still-prevalent c...The Colorado potato beetle is an important pest of solanaceous plants in the Northern Hemisphere. Better understanding of its physiological responses to temperature stress and their interactions with still-prevalent chemical control has important implications for the management of this insect. We measured mortality and expression of the Hsp70 heat shock proteins in the Colorado potato beetle larvae exposed to sublethal concentration of the commonly used insecticide imidacloprid, and to supraoptimal temperatures. Both turned out to be significant stress factors, although induction of Hsp70 by imidacloprid observed in the present study was low compared to its induction by the heat. The two factors also interacted with each other. At an extreme temperature of 43 ~C, exposure to a sublethal dose of imidacloprid resulted in a significant rise in larval mortality, which was not observed at an optimal temperature of 25 ~C. Heat-stressed larvae also failed to respond to imidacloprid by producing more Hsp70. These findings suggest that when field rates of insecticides become insufficient for killing the exposed beetles under optimal temperature conditions due to the evolution of resistance in beetle populations, they may still reduce the probability of resistant beetles surviving the heat shock created by using propane flamers as a rescue treatment.展开更多
基金Supported by a grant from Ministry of Science and Technology,Bangladesh(No.BPROM/SHA-9/B-ANI-PRO/2009/324)
文摘Objective:To investigate mosquitocidal effects of ethanolic extract of(lowers of Tagetes erecta(T.erecta) and its chloroform and petroleum ether soluble fractions against the larvae of Culex quinquefasciatus(Cx.quinquefasciatus).Methods:The fresh flowers of T.erecta were extracted in cold with ethanol(5.0 L) and after concentration,the ethanol extract was fractionated with chloroform and petroleum ether to afford a brownish syrupy suspension of ethanol extract(50.0 g),petroleum ether soluble fraction(18.6 g) and chloroform soluble fraction(23.8 g).The larvicidal effect of ethanol extract and their solvent fractions were determined by the standard procedure of WHO against different instars of Cx.quinquefasciatus.Results:Among the tested samples the chloroform soluble fractions showed the highest toxicity and consequently,the lowest LC_(50) values(14.14 μ g/mL,17.06 μ g/mL.36.88 μ g/mL and 75.48 μ g/mL) for all the instars larvae of Cx.quinquefasciatus.The larvae showed comparative tolerance in the course of increasing age and time.Conclusions:It can be concluded that the flowers of T.erecta are very effective natural larvicide and could be useful against Cx.quinquefasciatus.
文摘Last week, I read news about school bullying with my parents, and it made me feel very sad. School bullying is a serious problem nowadays. It can happen in the classroom or even after school.
文摘In early March,a couple in Jiaxing,Zhejiang Province,grabbed social media headlines by hosting a wedding that only cost 5,000 yuan($690)-a number well below the average cost of weddings in China.
文摘Three-leg Ostrich Oneday,Jack comeshomefrom school witha new notebook.He says to his mum,"t's a prize,mother."His mother says,“A prize? That's good.But how did yougetthat?”"My teacher gave it to me.He asked us how many legs an ostrich has,and Iansweredthree,"Jack says.
文摘On the morning of 3 July,Zhou Hongwei,Party branch secretary of Huangnidun Village,visited Zhou Wenping’s home to hear the family’s suggestions regarding the village’s plan to install more street lamps and upgrade public water pipelines.After their meeting,Zhou immediately headed to another family for their opinions.
基金本文部分内容在以下学术场合报告过,并得到与会者有用的意见:Roundtable on Current Issues in Light Verb Syntax in Chinese(香港2016年5月)、Eleventh Workshop on Formal Syntax and Semantics(台北2016年9月)、“汉语句式问题”国际学术研讨会(武汉2016年10月)、第五届中国句法语义论坛(上海2016年10月)、高丽大学BK21Plus中日语言文化教育研究团座谈会(首尔2016年11月)、第二十一届国际粤方言研讨会(澳门2016年12月）、第二十二届国际粤方言研讨会(香港2017年12月）、不列颠哥伦比亚大学亚洲研究学系（温哥华2018年3月）。2017/18年度在麻省理工学院访问期间,笔者有机会整理资料，增润本文。
文摘1初遇,然然是个12岁的女孩,是偌大的心脏重症监护室(cardiac intensive care unit,CICU)角落里一个孤独而特别的存在。当大厅里的小宝宝们因饥饿而哇哇大哭时,她总是乖巧地待在床位上,静静地玩手机或躺着。每个经过她身边的人,都会好奇地警上一眼,但是看过之后都会迅速收回目光,因为她的外形实在是让人既心疼又害怕。
文摘Susan:If you were a dinosaur,which dinosaur would you prefer to be?Ed:I'd be a Triceratops(三角龙)for sure!It's the scariest(最恐怖的)one.Susan:The Triceratops isn't the scariest dinosaur!Ed:How can you say that?
文摘The Colorado potato beetle is an important pest of solanaceous plants in the Northern Hemisphere. Better understanding of its physiological responses to temperature stress and their interactions with still-prevalent chemical control has important implications for the management of this insect. We measured mortality and expression of the Hsp70 heat shock proteins in the Colorado potato beetle larvae exposed to sublethal concentration of the commonly used insecticide imidacloprid, and to supraoptimal temperatures. Both turned out to be significant stress factors, although induction of Hsp70 by imidacloprid observed in the present study was low compared to its induction by the heat. The two factors also interacted with each other. At an extreme temperature of 43 ~C, exposure to a sublethal dose of imidacloprid resulted in a significant rise in larval mortality, which was not observed at an optimal temperature of 25 ~C. Heat-stressed larvae also failed to respond to imidacloprid by producing more Hsp70. These findings suggest that when field rates of insecticides become insufficient for killing the exposed beetles under optimal temperature conditions due to the evolution of resistance in beetle populations, they may still reduce the probability of resistant beetles surviving the heat shock created by using propane flamers as a rescue treatment.
