The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and acetone has been investigated with density functional theory, From the potential energy profile, it can be predicted that the r...The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and acetone has been investigated with density functional theory, From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The presented rule of this reaction： the [2＋2] cycloaddition effect between the πorbital of dimethyl-silylene carbene and the π orbital of π-bonded compounds leads to the formation of a twisty four-membered ring intermediate and a planar four-membered ring product; The unsaturated property of C atom from carbene in the planar four-membered ring product,resulting in the generation of CH3-transfer product and silicic bis-heterocyclic compound.展开更多
The distribution of diatoms from surface sediments of the West Philippine Basin was analyzed, with 68 species and varieties of diatoms from 26 genera identified. Diatom abundance varied spatially, with the absolute ab...The distribution of diatoms from surface sediments of the West Philippine Basin was analyzed, with 68 species and varieties of diatoms from 26 genera identified. Diatom abundance varied spatially, with the absolute abundance of diatoms ranging from 0 to 3.4× 104 frustules/g. The seven tropical pelagic diatoms were Alveus marinus, Azpeitia africana, Azpeitia nodulifera, Hemidiscus cuneiformis, Hernidiscus cuneiformis var. ventricosus, Roperia tesselata and Rhizosolenia bergonii. The relative abundance of these species was greater than 20%, and their distribution pattern in the sediments was overlaid by the flow of the Kuroshio Current. Ethmodiscus rex was present at 159 stations, formed the most abundant and dominant species in the diatomaceous ooze, and thus referred to as Ethmodiscus ooze. Ethmodiscus rex was also a major contributor to primary production in the region. A principal component analysis was employed to explain the relationship between samples and variations in diatom species from the WPB. Four diatom assemblages were distinguished, representing different oceanographic conditions; their spatial distributions were closely related with the North Equatorial Current and Kuroshio Current patterns in the region. These diatom assemblages can therefore be useful in deciphering late Quaternary palaeoceanographic reconstructions of the West Philippine Basin.展开更多
文摘The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and acetone has been investigated with density functional theory, From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The presented rule of this reaction： the [2＋2] cycloaddition effect between the πorbital of dimethyl-silylene carbene and the π orbital of π-bonded compounds leads to the formation of a twisty four-membered ring intermediate and a planar four-membered ring product; The unsaturated property of C atom from carbene in the planar four-membered ring product,resulting in the generation of CH3-transfer product and silicic bis-heterocyclic compound.
基金Supported by the National Natural Science Foundation of China(Nos.41306083,41106076)the Special Fund for Scientific Research Foundation of the Third Institute of Oceanography,State Oceanic Administration,China(Nos.2010002,2013032)
文摘The distribution of diatoms from surface sediments of the West Philippine Basin was analyzed, with 68 species and varieties of diatoms from 26 genera identified. Diatom abundance varied spatially, with the absolute abundance of diatoms ranging from 0 to 3.4× 104 frustules/g. The seven tropical pelagic diatoms were Alveus marinus, Azpeitia africana, Azpeitia nodulifera, Hemidiscus cuneiformis, Hernidiscus cuneiformis var. ventricosus, Roperia tesselata and Rhizosolenia bergonii. The relative abundance of these species was greater than 20%, and their distribution pattern in the sediments was overlaid by the flow of the Kuroshio Current. Ethmodiscus rex was present at 159 stations, formed the most abundant and dominant species in the diatomaceous ooze, and thus referred to as Ethmodiscus ooze. Ethmodiscus rex was also a major contributor to primary production in the region. A principal component analysis was employed to explain the relationship between samples and variations in diatom species from the WPB. Four diatom assemblages were distinguished, representing different oceanographic conditions; their spatial distributions were closely related with the North Equatorial Current and Kuroshio Current patterns in the region. These diatom assemblages can therefore be useful in deciphering late Quaternary palaeoceanographic reconstructions of the West Philippine Basin.
