Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on el...Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on electron microscope meshes according to two size ranges: coarse particles (r>0.5μm) and fine particles (0.5μm>r>0. 1μm) by using a two-stage impactor. It was found that more than seventy percent of the fine particles and about twenty percentof the coarse particles were sulfate-containing particles. These particles were formed mainly through heterogeneousnucleation. The element composition analyses revealed that the atmospheric aerosol particles in Beijing were domi-nated by crustal particles and construction dust.展开更多
With the discovery and further understanding of topoisomerases, it becomes clear that the supercoiling of double stranded DNA plays an important role in DNA replication, RNA transcription and even in the control of ge...With the discovery and further understanding of topoisomerases, it becomes clear that the supercoiling of double stranded DNA plays an important role in DNA replication, RNA transcription and even in the control of gene expression. Although the small circular DNA can be separated by means of density gradient centrifugation or gel electrophoresis and展开更多
Polyurethane elastomers are segmented co-polymers of alternating hard and soft segments which are based on various low molecular weight polyesters, polyethers or polybutadienes that are terminated with hydroxyl groups...Polyurethane elastomers are segmented co-polymers of alternating hard and soft segments which are based on various low molecular weight polyesters, polyethers or polybutadienes that are terminated with hydroxyl groups. The hard segments consist of diisocyanates and chain extenders or cross-linking agents which can be diols展开更多
在减压降温液氮温区(约64K),采用磁缀饰法(即高分辨Bitter图法),分别在熔融织构生长(MTG)的YBa_2Cu_3O_7超导体和射频溅射制备的单晶外延YBa_2Cu_3O_7薄膜上用KYKY-1000 B SEM观察到超导体的磁通分布图,属无序非晶态结构。在MTG超导体...在减压降温液氮温区(约64K),采用磁缀饰法(即高分辨Bitter图法),分别在熔融织构生长(MTG)的YBa_2Cu_3O_7超导体和射频溅射制备的单晶外延YBa_2Cu_3O_7薄膜上用KYKY-1000 B SEM观察到超导体的磁通分布图,属无序非晶态结构。在MTG超导体中得到清晰的孪晶界、层界和晶体缺陷对磁通的钉扎图象。最强的钉扎中心出现在尺寸较大的Y_2BaCuO_5(211)第二相粒子周围。展开更多
文摘Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on electron microscope meshes according to two size ranges: coarse particles (r>0.5μm) and fine particles (0.5μm>r>0. 1μm) by using a two-stage impactor. It was found that more than seventy percent of the fine particles and about twenty percentof the coarse particles were sulfate-containing particles. These particles were formed mainly through heterogeneousnucleation. The element composition analyses revealed that the atmospheric aerosol particles in Beijing were domi-nated by crustal particles and construction dust.
文摘With the discovery and further understanding of topoisomerases, it becomes clear that the supercoiling of double stranded DNA plays an important role in DNA replication, RNA transcription and even in the control of gene expression. Although the small circular DNA can be separated by means of density gradient centrifugation or gel electrophoresis and
基金Project supported by the National Natural Science Foundation of China.
文摘Polyurethane elastomers are segmented co-polymers of alternating hard and soft segments which are based on various low molecular weight polyesters, polyethers or polybutadienes that are terminated with hydroxyl groups. The hard segments consist of diisocyanates and chain extenders or cross-linking agents which can be diols
文摘在减压降温液氮温区(约64K),采用磁缀饰法(即高分辨Bitter图法),分别在熔融织构生长(MTG)的YBa_2Cu_3O_7超导体和射频溅射制备的单晶外延YBa_2Cu_3O_7薄膜上用KYKY-1000 B SEM观察到超导体的磁通分布图,属无序非晶态结构。在MTG超导体中得到清晰的孪晶界、层界和晶体缺陷对磁通的钉扎图象。最强的钉扎中心出现在尺寸较大的Y_2BaCuO_5(211)第二相粒子周围。
