A new genus and species, Rebouliothallus huolinhensis sp. nov., and two uncertain species, Ricciopsis sp. and Hepaticites sp., are described. The fossils were collected from the Lower Cretaceous Huolinhe Formation of ...A new genus and species, Rebouliothallus huolinhensis sp. nov., and two uncertain species, Ricciopsis sp. and Hepaticites sp., are described. The fossils were collected from the Lower Cretaceous Huolinhe Formation of Huolinhe Basin, northeastern China. The new genus Rebouliothallus was established in the Aytoniaceae family of Marchantiales. Rebouliothallus huolinhensis appears to be quite similar to species of the extant genus Reboulia Raddi. The species is characterized by the relatively large ventral scales. Ventral scales are large, imbricate and arranged in two rows on the ventral surface. Rhizoids are either pegged or smooth. Ricciopsis sp. is characterized by the rosette- forming thallus. Hepaticites sp. shows some similarities to liverworts. Of the forty-nine Early Cretaceous floras of China, only two floras, one from the Huolinhe basin, Inner Mongolia and the other from the Jixi Basin, Heilongjiang Province, contain fossil liverworts. The rare fossil liverwort records in the Early Cretaceous floras of China may be the result of taphonomic bias.展开更多
The uptake of zinc and cadmium by a species of marine diatom Thalassirosira weissflogii and the nutrient variation （ phosphorus and silicon） in the culture medium were estimated when exposed to zinc and cadmium stre...The uptake of zinc and cadmium by a species of marine diatom Thalassirosira weissflogii and the nutrient variation （ phosphorus and silicon） in the culture medium were estimated when exposed to zinc and cadmium stress under controlled laboratory conditions. It was found that low cadmium addition could stimulate the culture to grow with a relatively high rate and exert its toxicity at the elevated concentration. The cellular uptake of zinc and cadmium by the diatom varied in the ranges of 1.21 - 3.75 and 0. 060 - 0. 629 fmol per cell respectively in the whole cultivation period. The mean cellular phosphorus and silicon drawdowns were constant with 0. 26 - 0. 42 and 0. 30 - 0. 46 pmol per cell respectively in those healthy cultures. It is illustrated that the algal cells can adjust some physiological mechanisms to decrease metal accumulation and keep metal homeostasis in the organism. The correlation analysis results further indicate that the cellular cadmium uptake might be closely related with the cellular phosphorus, silicon drawdown and the growth rate of diatom （P 〈0. 05, 0. 001,0. 01 ） ; and the cultures grow better in good conditions, the lower amount of phosphorus, silicon materials are consumed by a single cell to keep a high efficiency of utilization.展开更多
T型三电平变换器在常规调制策略下,存在着严重的内管外管损耗不均的问题。当变换器的调制比低于0.57时,T型三电平变换器的内管温升明显高于外管温升,这个问题在低电压穿越(low voltage ride through, LVRT)运行时更为严峻,将威胁变换器...T型三电平变换器在常规调制策略下,存在着严重的内管外管损耗不均的问题。当变换器的调制比低于0.57时,T型三电平变换器的内管温升明显高于外管温升,这个问题在低电压穿越(low voltage ride through, LVRT)运行时更为严峻,将威胁变换器的长期可靠运行。为此,提出了一种基于损耗优化分布的不连续脉宽调制策略,在空间矢量图的对应区域采用新的开关序列,每相采用钳位到直流侧正极或直流侧负极的钳位方式,进而实现外管内管电流的重新分配。新调制策略采用五段式发波,不仅有效改善了内外管损耗的分布,还能提高变换器整体效率;通过冗余小矢量互补的序列,维持中点电压的平衡;新调制策略具有统一的载波调制实现方式。最后,通过电气-热联合仿真,验证了所提损耗优化分布调制策略的有效性。展开更多
基金supported by the National Basic Research Program of China (973 Program) (no.2012CB822003)the Funds of Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, CAS (No.Y421140303)+2 种基金Specialized Research Fund for the Doctoral Program of Higher Education (Grant 20120211110022)the Fundamental Research Funds for the Central Universities (Grant lzujbky-2015-201)the National Natural Science Foundation of China (Grants 41172022, 41272026 and 41202001)
文摘A new genus and species, Rebouliothallus huolinhensis sp. nov., and two uncertain species, Ricciopsis sp. and Hepaticites sp., are described. The fossils were collected from the Lower Cretaceous Huolinhe Formation of Huolinhe Basin, northeastern China. The new genus Rebouliothallus was established in the Aytoniaceae family of Marchantiales. Rebouliothallus huolinhensis appears to be quite similar to species of the extant genus Reboulia Raddi. The species is characterized by the relatively large ventral scales. Ventral scales are large, imbricate and arranged in two rows on the ventral surface. Rhizoids are either pegged or smooth. Ricciopsis sp. is characterized by the rosette- forming thallus. Hepaticites sp. shows some similarities to liverworts. Of the forty-nine Early Cretaceous floras of China, only two floras, one from the Huolinhe basin, Inner Mongolia and the other from the Jixi Basin, Heilongjiang Province, contain fossil liverworts. The rare fossil liverwort records in the Early Cretaceous floras of China may be the result of taphonomic bias.
基金This work was supported by the National Natural Science Foundation of China under contract No. 40646031； the Foundation of Scientific and Technological Planning Project of Guangdong Province in China under contract Nos 2006B36601005 and 2005B33201007 and the Innovation Program of the Chinese Academy of Sciences under contract No. KZCX3 - SW - 227.
文摘The uptake of zinc and cadmium by a species of marine diatom Thalassirosira weissflogii and the nutrient variation （ phosphorus and silicon） in the culture medium were estimated when exposed to zinc and cadmium stress under controlled laboratory conditions. It was found that low cadmium addition could stimulate the culture to grow with a relatively high rate and exert its toxicity at the elevated concentration. The cellular uptake of zinc and cadmium by the diatom varied in the ranges of 1.21 - 3.75 and 0. 060 - 0. 629 fmol per cell respectively in the whole cultivation period. The mean cellular phosphorus and silicon drawdowns were constant with 0. 26 - 0. 42 and 0. 30 - 0. 46 pmol per cell respectively in those healthy cultures. It is illustrated that the algal cells can adjust some physiological mechanisms to decrease metal accumulation and keep metal homeostasis in the organism. The correlation analysis results further indicate that the cellular cadmium uptake might be closely related with the cellular phosphorus, silicon drawdown and the growth rate of diatom （P 〈0. 05, 0. 001,0. 01 ） ; and the cultures grow better in good conditions, the lower amount of phosphorus, silicon materials are consumed by a single cell to keep a high efficiency of utilization.
文摘T型三电平变换器在常规调制策略下,存在着严重的内管外管损耗不均的问题。当变换器的调制比低于0.57时,T型三电平变换器的内管温升明显高于外管温升,这个问题在低电压穿越(low voltage ride through, LVRT)运行时更为严峻,将威胁变换器的长期可靠运行。为此,提出了一种基于损耗优化分布的不连续脉宽调制策略,在空间矢量图的对应区域采用新的开关序列,每相采用钳位到直流侧正极或直流侧负极的钳位方式,进而实现外管内管电流的重新分配。新调制策略采用五段式发波,不仅有效改善了内外管损耗的分布,还能提高变换器整体效率;通过冗余小矢量互补的序列,维持中点电压的平衡;新调制策略具有统一的载波调制实现方式。最后,通过电气-热联合仿真,验证了所提损耗优化分布调制策略的有效性。
