The colony-forming Phaeocystis species are causative agents of dense bloom occurrences incoastal waters worldwide. It is difficult to separate them because of the different morphologies associated with their colonial ...The colony-forming Phaeocystis species are causative agents of dense bloom occurrences incoastal waters worldwide. It is difficult to separate them because of the different morphologies associated with their colonial stages. In this study we applied molecular approaches to analyze the genetic variation of Phaeocystis globosa and Phaeocystis pouchetii from several geographic regions, and to assist in tracing the dispersal of bloom-forming Phaeocystis species in coastal waters of China. The sequences of the internal transcribed spacers (ITS1 and ITS2) of rDNA and the 5. 8S ribosomal RNA gene of Phaeocystis strains were determined. Sequence comparison shows that P.globosa was the most divergent to P. pouchetii, exhibiting sequence divergence higher than 0.08. However, lower genetic divergences existed between strains of P. globosa. The sequence comparison of the Phaeocystis rDNA ITS clearly shows that the species isolated from the southeast coast of China is identified as P. globosa rather than P. cf. pouchetii or other species. Furthermore, the significance of rDNA variation in distinct global populations of P. globosa suggested it might have had sufficient time to accumulate detectable mutations at the rDNA locus, supporting the hypothesis of ancient dispersal of P .globosa to many areas, meaning that P. globosa blooms in the coastal waters of China are endemic rather than a newly introduced species or a foreign source. Finally, based on the high divergent region of rDNA ITS, a pair of species-specific primers for P. globosa were designed, they could be useful to detect the presence of this species in mixed plankton assemblages or flagellate stages that are recognized with diffculties by means of conventional microscopy.展开更多
The crystal structure of tetrakis[(pyrrol-1-yl)methyl]methane was determined by X-ray diffraction measurement, and the result shows that it belongs to monoclinic crystal system, space group is P2 1/n, with a=0.9284(3...The crystal structure of tetrakis[(pyrrol-1-yl)methyl]methane was determined by X-ray diffraction measurement, and the result shows that it belongs to monoclinic crystal system, space group is P2 1/n, with a=0.9284(3) nm, b=1.0950(6) nm, c=1.8749(8) nm; α=γ= 90.00(4)°, β=103.63(3)°, V=1.8523(14) nm 3, Z=4, ρ calcd. =1.192 kg/m 3, μ=0.072 nm -1 , F(000)=712, R 1=0.0854, wR 2=0.1884. It has been found that the molecules exist in two enantiomeric states. Enantioselective self-assemblies such as one-dimensional molecular stacks in a single handedness, homochiral monolayers and a chiral superlattice are specified in this racemic crystal. In addition, a simple technique is advocated to distinguish chiral states from tetrahedral molecules in the solid state. The present R/S nomenclature of the tetracooradinated carbon centers is used solely for its convenience to distinguish the two enantiomeric states, but not used to determine the absolute configurations.展开更多
The optoelectronic telescope has two sets of control systems: azimuth one and elevation one, and both are driven by PWM power amplifier with high efficiency and wide speed regulation range. The diagram of the azimuth ...The optoelectronic telescope has two sets of control systems: azimuth one and elevation one, and both are driven by PWM power amplifier with high efficiency and wide speed regulation range. The diagram of the azimuth control system is demonstrated, the nonlinear factors is analyzed at low speed, and some related experiments are carried out. The results show that the positioning error with unipolar is 86 codes(106.21″), while 18 codes (22.23″) is with bipolar PWM driver.展开更多
Formate and acetate are ubiquitous in the troposphere. Their occurrence is closely related to processes in the biosphere and contributes to an understanding of carbon biogeochemical cycles. A 43-year record of formate...Formate and acetate are ubiquitous in the troposphere. Their occurrence is closely related to processes in the biosphere and contributes to an understanding of carbon biogeochemical cycles. A 43-year record of formate and acetate in an ice core from Glacier 1 (43?6′N, 86?9′E) at Urumqi river head, Tianshan, west China was investigated. Fluctuating between 22.7 ng·g-1 and 2830.7 ng·g-1, acetate concentration averages 373.2 ?376.1 ng·g-1 (mean ?1s, N = 541) and is the highest anion in the record. Next to acetate, the concentration for formate varies between 2.1 ng·g-1 and 795.5 ng·g-1 and averages 61.1 ?89.0 ng·g-1 (N = 541). The formate to acetate ratio averages 0.22 ?0.25 (N = 541), indicating that the chief source is from fossil fuel combustion, coal burning in particular. The two species co-varied in the past four decades and exhibited periods of high concentration from the early 1960s to the middle of 1970s and from the early 1980s to the middle of 1990s, separated by a time of the lower concentration between 1975—1980. These variations may reflect the local/regional anthropogenic pollution to the atmosphere as well as the economic development of northwestern China.展开更多
基金This study was supported by the National Natural Science Foundation of China under contract No. 39970063the Natural Science Foundation of Guangdong Province, China under contract No. 001213the Red-tide Key Project of the Natural Science Foundatio
文摘The colony-forming Phaeocystis species are causative agents of dense bloom occurrences incoastal waters worldwide. It is difficult to separate them because of the different morphologies associated with their colonial stages. In this study we applied molecular approaches to analyze the genetic variation of Phaeocystis globosa and Phaeocystis pouchetii from several geographic regions, and to assist in tracing the dispersal of bloom-forming Phaeocystis species in coastal waters of China. The sequences of the internal transcribed spacers (ITS1 and ITS2) of rDNA and the 5. 8S ribosomal RNA gene of Phaeocystis strains were determined. Sequence comparison shows that P.globosa was the most divergent to P. pouchetii, exhibiting sequence divergence higher than 0.08. However, lower genetic divergences existed between strains of P. globosa. The sequence comparison of the Phaeocystis rDNA ITS clearly shows that the species isolated from the southeast coast of China is identified as P. globosa rather than P. cf. pouchetii or other species. Furthermore, the significance of rDNA variation in distinct global populations of P. globosa suggested it might have had sufficient time to accumulate detectable mutations at the rDNA locus, supporting the hypothesis of ancient dispersal of P .globosa to many areas, meaning that P. globosa blooms in the coastal waters of China are endemic rather than a newly introduced species or a foreign source. Finally, based on the high divergent region of rDNA ITS, a pair of species-specific primers for P. globosa were designed, they could be useful to detect the presence of this species in mixed plankton assemblages or flagellate stages that are recognized with diffculties by means of conventional microscopy.
基金the National Natural Science Foundation of China(No.6 0 1710 0 8) and Shanghai Science and TechnologyCom mittee(No.0 2 14 nm0 0 5 )
文摘The crystal structure of tetrakis[(pyrrol-1-yl)methyl]methane was determined by X-ray diffraction measurement, and the result shows that it belongs to monoclinic crystal system, space group is P2 1/n, with a=0.9284(3) nm, b=1.0950(6) nm, c=1.8749(8) nm; α=γ= 90.00(4)°, β=103.63(3)°, V=1.8523(14) nm 3, Z=4, ρ calcd. =1.192 kg/m 3, μ=0.072 nm -1 , F(000)=712, R 1=0.0854, wR 2=0.1884. It has been found that the molecules exist in two enantiomeric states. Enantioselective self-assemblies such as one-dimensional molecular stacks in a single handedness, homochiral monolayers and a chiral superlattice are specified in this racemic crystal. In addition, a simple technique is advocated to distinguish chiral states from tetrahedral molecules in the solid state. The present R/S nomenclature of the tetracooradinated carbon centers is used solely for its convenience to distinguish the two enantiomeric states, but not used to determine the absolute configurations.
基金Natural Science Foundation from Science & Technology Department of Jilin Province(HJ2003013)
文摘The optoelectronic telescope has two sets of control systems: azimuth one and elevation one, and both are driven by PWM power amplifier with high efficiency and wide speed regulation range. The diagram of the azimuth control system is demonstrated, the nonlinear factors is analyzed at low speed, and some related experiments are carried out. The results show that the positioning error with unipolar is 86 codes(106.21″), while 18 codes (22.23″) is with bipolar PWM driver.
基金This work was joint-supported by the National Natural Science Foundation of China(Grant No.40073035)Chinese Academy of Sciences(Grant No.CAS 2002-43)Tianshan Glaciological Station.
文摘Formate and acetate are ubiquitous in the troposphere. Their occurrence is closely related to processes in the biosphere and contributes to an understanding of carbon biogeochemical cycles. A 43-year record of formate and acetate in an ice core from Glacier 1 (43?6′N, 86?9′E) at Urumqi river head, Tianshan, west China was investigated. Fluctuating between 22.7 ng·g-1 and 2830.7 ng·g-1, acetate concentration averages 373.2 ?376.1 ng·g-1 (mean ?1s, N = 541) and is the highest anion in the record. Next to acetate, the concentration for formate varies between 2.1 ng·g-1 and 795.5 ng·g-1 and averages 61.1 ?89.0 ng·g-1 (N = 541). The formate to acetate ratio averages 0.22 ?0.25 (N = 541), indicating that the chief source is from fossil fuel combustion, coal burning in particular. The two species co-varied in the past four decades and exhibited periods of high concentration from the early 1960s to the middle of 1970s and from the early 1980s to the middle of 1990s, separated by a time of the lower concentration between 1975—1980. These variations may reflect the local/regional anthropogenic pollution to the atmosphere as well as the economic development of northwestern China.
