With reference to the recent achivements about the structure, spectra and kinetics of light_harvesting complex (LHCⅡ) in PSⅡ of higher plants, a four_level model was provided to simulate the energy transfer process ...With reference to the recent achivements about the structure, spectra and kinetics of light_harvesting complex (LHCⅡ) in PSⅡ of higher plants, a four_level model was provided to simulate the energy transfer process from LHC Ⅱ to the reaction center. On the basis of this model, a set of rate equation was established. Analysis of its algebra solution led to a general picture of energy transfer process in LHC Ⅱ of higher plants and the strong interaction among pigment molecules in this process. Based on the spectra, kinetics and biological structural data providing some information of energy transfer path and energy dissipation mechanism, it has been found that energy transfer mainly happened between the pigments whose energy level was most closely adjacent, the loss of energy had a close relation to the process of energy transfer and tended to increase with the decrease of energy level. The protective mechanism of antenna system was also discussed.展开更多
In nature, quadrupeds as horses or cats change their gait to be suited to their motion speed. This fact is very important to realize smooth motion with different gaits. In this article a method of the gait transition ...In nature, quadrupeds as horses or cats change their gait to be suited to their motion speed. This fact is very important to realize smooth motion with different gaits. In this article a method of the gait transition for the quadruped walking machine is proposed. With analyzing the accustomed gaits of quadruped, some standard gaits and the relationships between duty factor and the phasic differences of the legs corresponding to the first leg could be concluded. With this, the gaits transferring could be continuous. Besides, celerity and on line method for generation and modifying gaits is studied, which can make the robot have a smooth motion to adapt the uncharted rough terrain.展开更多
The structures of human telomeric DNA have received much attention due to its significant biological importance.Most studies have focused on G-quadruplex structure formed by short telomeric DNA sequence,but little is ...The structures of human telomeric DNA have received much attention due to its significant biological importance.Most studies have focused on G-quadruplex structure formed by short telomeric DNA sequence,but little is known about the structures of long singlestranded telomeric DNAs.Here,we investigated the structure of DNA with a long sequence of d[AGGG(TTAGGG)6](G6-DNA)and the effect of a single repeat sequence d(TTAGGG)(G01-DNA)on the structure of G6-DNA using sedimentation velocity technique,polyacrylamide gel electrophoresis,circular dichroism spectroscopy,and UV melting experiments.The results suggest that the G6-DNA can form dimers in aqueous solutions and G01-DNA can form additional G-quadruplex structures by binding to G6-DNA.However,G01-DNA has no effect on the structure of DNA with a sequence of d[AGGG(TTAGGG)3](G3-DNA).Our study provides new insights into the structure polymorphism of long human single-stranded telomeric DNA.展开更多
Purple soils are widely distributed in the Sichuan Hilly Basin and are highly susceptible to erosion, especially on the cultivated slopes. Quantitative assessment of the erosion rates is, however, difficult due to sma...Purple soils are widely distributed in the Sichuan Hilly Basin and are highly susceptible to erosion, especially on the cultivated slopes. Quantitative assessment of the erosion rates is, however, difficult due to small size of the plots of the manually-tilled land, the complex land use, and steep hillslopes. ^137Cs and ^210Pbex （excess ^210Pb） tracing techniques were used to investigate the spatial pattern of soil erosion rates associated with slope-land under hoe tillage in Neijiang of the Sichuan Hilly Basin. The ^137Cs and ^210Pbex inventories at the top of the cultivated slope were extremely low, and the highest inventories were found at the bottom of the cultivated slope. By combining the erosion rates estimates provided by both ^137Cs and 21~Pbex measurements, the weighted mean net soil loss from the study slope was estimated to be 3 100 t km^-2 year^-1, which was significantly less than 6 930 t km^-2 year^-1 reported for runoff plots on a 10° cultivated slope at the Suining Station of Soil Erosion. The spatial pattern of soil erosion rates on the steep agricultural land showed that hoe tillage played an important role in soil redistribution along the slope. Also, traditional farming practices had a significant role in reducing soil loss, leading to a lower net erosion rate for the field.展开更多
文摘With reference to the recent achivements about the structure, spectra and kinetics of light_harvesting complex (LHCⅡ) in PSⅡ of higher plants, a four_level model was provided to simulate the energy transfer process from LHC Ⅱ to the reaction center. On the basis of this model, a set of rate equation was established. Analysis of its algebra solution led to a general picture of energy transfer process in LHC Ⅱ of higher plants and the strong interaction among pigment molecules in this process. Based on the spectra, kinetics and biological structural data providing some information of energy transfer path and energy dissipation mechanism, it has been found that energy transfer mainly happened between the pigments whose energy level was most closely adjacent, the loss of energy had a close relation to the process of energy transfer and tended to increase with the decrease of energy level. The protective mechanism of antenna system was also discussed.
基金Supported by the china postdoctoral Science Foundation （No. 20080430362）.
文摘In nature, quadrupeds as horses or cats change their gait to be suited to their motion speed. This fact is very important to realize smooth motion with different gaits. In this article a method of the gait transition for the quadruped walking machine is proposed. With analyzing the accustomed gaits of quadruped, some standard gaits and the relationships between duty factor and the phasic differences of the legs corresponding to the first leg could be concluded. With this, the gaits transferring could be continuous. Besides, celerity and on line method for generation and modifying gaits is studied, which can make the robot have a smooth motion to adapt the uncharted rough terrain.
基金supported by the National Natural Scientific Foundation of China (No.21674107)the Fundamental Research Funds for the Central Universities (No.WK2340000066)
文摘The structures of human telomeric DNA have received much attention due to its significant biological importance.Most studies have focused on G-quadruplex structure formed by short telomeric DNA sequence,but little is known about the structures of long singlestranded telomeric DNAs.Here,we investigated the structure of DNA with a long sequence of d[AGGG(TTAGGG)6](G6-DNA)and the effect of a single repeat sequence d(TTAGGG)(G01-DNA)on the structure of G6-DNA using sedimentation velocity technique,polyacrylamide gel electrophoresis,circular dichroism spectroscopy,and UV melting experiments.The results suggest that the G6-DNA can form dimers in aqueous solutions and G01-DNA can form additional G-quadruplex structures by binding to G6-DNA.However,G01-DNA has no effect on the structure of DNA with a sequence of d[AGGG(TTAGGG)3](G3-DNA).Our study provides new insights into the structure polymorphism of long human single-stranded telomeric DNA.
基金Project supported by the Ministry of Science and Technology of China (No. 2003CB415201)National Natural Science Foundation of China (No. 40671120)+1 种基金the International Atomic Energy Agency (Nos. 12322/RO and UK-12094)the Young Scientist Foundation of Sichuan Province (No.06ZQ026-030)
文摘Purple soils are widely distributed in the Sichuan Hilly Basin and are highly susceptible to erosion, especially on the cultivated slopes. Quantitative assessment of the erosion rates is, however, difficult due to small size of the plots of the manually-tilled land, the complex land use, and steep hillslopes. ^137Cs and ^210Pbex （excess ^210Pb） tracing techniques were used to investigate the spatial pattern of soil erosion rates associated with slope-land under hoe tillage in Neijiang of the Sichuan Hilly Basin. The ^137Cs and ^210Pbex inventories at the top of the cultivated slope were extremely low, and the highest inventories were found at the bottom of the cultivated slope. By combining the erosion rates estimates provided by both ^137Cs and 21~Pbex measurements, the weighted mean net soil loss from the study slope was estimated to be 3 100 t km^-2 year^-1, which was significantly less than 6 930 t km^-2 year^-1 reported for runoff plots on a 10° cultivated slope at the Suining Station of Soil Erosion. The spatial pattern of soil erosion rates on the steep agricultural land showed that hoe tillage played an important role in soil redistribution along the slope. Also, traditional farming practices had a significant role in reducing soil loss, leading to a lower net erosion rate for the field.
