This paper studies the status of empty nest only-child families in urban China,using data about these families taken from a 2015 survey conducted by the Institute of Population and Labor Economics,Chinese Academy of S...This paper studies the status of empty nest only-child families in urban China,using data about these families taken from a 2015 survey conducted by the Institute of Population and Labor Economics,Chinese Academy of Social Sciences.Factors that determine the timing of empty nest periods and their duration for only-child parents are also analyzed.The data shows that more than half of the only-child parents surveyed in 2015 lived in empty nests.Some of these parents had been empty-nesters for as many as 25 years.During the life cycle of families,the empty nest status of elderly only-child parents shows different characteristics at different stages,as the only-children begin attending universities,start to work,get married,and have children of their own.There are empty nest periods in only-child families when the only-child leaves the parents for several years and periods when the child returns home and lives with parents for years.The living arrangements of only-child parents depend mainly on changes in the life needs of their only-children.Intergenerational support is focused on meeting the needs of only-children.展开更多
The acute and chronic toxic effects of bifenthrin on Daphnia magna were studied. The results showed that 24 h-EC 50 , 48 h-LC 50 and 96 h-LC 50 of bifenthrin on D. magna were 3.24, 12.40 and 1.40 μg/L r...The acute and chronic toxic effects of bifenthrin on Daphnia magna were studied. The results showed that 24 h-EC 50 , 48 h-LC 50 and 96 h-LC 50 of bifenthrin on D. magna were 3.24, 12.40 and 1.40 μg/L respectively. And the LOEC and NOEC of bifenthrin were 0.02 and 0.004 μg/L respectively. The recovery test of bifenthrin on Daphnia magna was presented. Daphnia magna(F 0 generation) were exposed during 21 d to different bifenthrin concentrations. Offspring(animals from the first and third brood: F 1(1st) and F 1(3rd), respectively) were transferred to a free pesticide medium during a 21 d recovery period. In this recovery study, survival, growth, reproduction(mean total young per female, onset of reproduction and number broods per female) and the intrinsic rate of natural increase (r) were assessed as parameters. Reproduction such as number of young per female as well as length was still reduced in F 1(1st) generation daphnids from parentals(F 0) exposed to the bifenthrin. However F 1(3rd) individuals from parentals exposed to pesticide concentrations were able to restore reproduction when a recovery period of 21 d was allowed, but the length of F 1(3rd) from parentals exposed to the 0.5 and 0.75 μg/L bifenthrin concentration was still significantly effected(P<0.05).展开更多
文摘This paper studies the status of empty nest only-child families in urban China,using data about these families taken from a 2015 survey conducted by the Institute of Population and Labor Economics,Chinese Academy of Social Sciences.Factors that determine the timing of empty nest periods and their duration for only-child parents are also analyzed.The data shows that more than half of the only-child parents surveyed in 2015 lived in empty nests.Some of these parents had been empty-nesters for as many as 25 years.During the life cycle of families,the empty nest status of elderly only-child parents shows different characteristics at different stages,as the only-children begin attending universities,start to work,get married,and have children of their own.There are empty nest periods in only-child families when the only-child leaves the parents for several years and periods when the child returns home and lives with parents for years.The living arrangements of only-child parents depend mainly on changes in the life needs of their only-children.Intergenerational support is focused on meeting the needs of only-children.
文摘The acute and chronic toxic effects of bifenthrin on Daphnia magna were studied. The results showed that 24 h-EC 50 , 48 h-LC 50 and 96 h-LC 50 of bifenthrin on D. magna were 3.24, 12.40 and 1.40 μg/L respectively. And the LOEC and NOEC of bifenthrin were 0.02 and 0.004 μg/L respectively. The recovery test of bifenthrin on Daphnia magna was presented. Daphnia magna(F 0 generation) were exposed during 21 d to different bifenthrin concentrations. Offspring(animals from the first and third brood: F 1(1st) and F 1(3rd), respectively) were transferred to a free pesticide medium during a 21 d recovery period. In this recovery study, survival, growth, reproduction(mean total young per female, onset of reproduction and number broods per female) and the intrinsic rate of natural increase (r) were assessed as parameters. Reproduction such as number of young per female as well as length was still reduced in F 1(1st) generation daphnids from parentals(F 0) exposed to the bifenthrin. However F 1(3rd) individuals from parentals exposed to pesticide concentrations were able to restore reproduction when a recovery period of 21 d was allowed, but the length of F 1(3rd) from parentals exposed to the 0.5 and 0.75 μg/L bifenthrin concentration was still significantly effected(P<0.05).
