Effect of Cl- on photosynthetic bicarbonate uptake in two cyanobacteria Microcystis aeruginosa and Synechocystis PCC6803

Photosynthetic inorganic carbon utilization was investigated in two cyanobacteria Microcystis aeruginosa and Synechocystis PCC6803 grown in standing culture. Photosynthetic rates for the two algae reached about 10 times the theoretical CO₂ supply rate at low dissolved inorganic carbon (DIC) of 100 μmol/L, and the rates were unaffected by the addition of 20 mmol/L Na⁺, indicating that the two algae possessed Na+-independent HCO^-₃ utilization for photosynthesis under low DIC. Their photo- synthetic rates at low DIC were inhibited by higher Cl^- and the degrees of inhibition were increased with the rise of CI^- concentration, and in the presence of Diphenylamine-2-carboxylate (DPC), a reported Cl^- channel inhibitor, the rates decreased by 74%－82%, implying that putative DPC-sensitive Cl^- channels participate in Na+-independent HCO₃^- uptake for photosynthesis. The experiment of intracellular 14C-DIC accumulation for photosynthesis showed that internal DIC pools decreased by about 80% with 200 μmol/L DPC and by 64%－70% with 100 mmol/L Cl^-. The experiment of chlorophyll a fluorescence quenching showed that initial rates and extents of fluorescence quenching obviously decreased with 200 μmol/L DPC or 100 mmol/L Cl^-. The two experiments gave further evidence that putative DPC-sen- sitive Cl^- channels participate in Na+-independent HCO^-₃ uptake for photosynthesis in the two algae grown in standing culture.     

Analysis of sedimentary-geomorphologic variation and the living environment of hominids at the Shuidonggou Paleolithic site

Shuidonggou is one of the most important Upper Paleolithic sites in North China. Due to the presence of rich human remains, animal fossils, abundant sporopollen and unique geological sequence, it is the type site for Late Pleistocene to Holocene human occupation and environmental change in the Ningxia-lnner Mongolia region. Many scholars suggest that the site should be named the ＂Shuidong- gou Formation＂ of Late Pleistocene in North China. Dating results indicate that ancient human activities at the site took place 30-24 ka （Marine Isotope Stage [MIS] 3）. The climate at that time was warmer and moister than present day, and adequate precipitation led to the formation of water pack depressions where broad-leaf trees and sparse forest vegetations, as well as herbivorous animals flourished, making the area suitable for early human hunting, gathering and survival. The Neolithic human occupation happened 9-5 ka at the site, while similar environmental conditions with MIS3 occurred. The absence of human activity record in the region during the Last Glacial Maximum （MIS2） suggests that the environment was too harsh for humans to live there.     

A water-soluble fluorescence resonance energy transfer probe for hypochlorous acid and its application to cell imaging

A water-soluble fluorescence resonance energy transfer (FRET) probe for hypochlorous acid (HOCl), dansyl rhodamine B piperazinoacetohydrazide, was designed, synthesized and characterized. The dansyl moiety in the probe acted as a FRET donor and the rhodamine moiety acted as a FRET acceptor. The two moieties were connected by a HOCl-cleavable active bond, and cleavage of this linker decreased the FRET efficiency and increased the fluorescence intensity of the donor at 501 nm. The water solubility of the prob...     

钢筋混凝土靶体侵彻破坏响应及其原位测试技术研究

为研究弹体在钢筋混凝土中的侵彻过程,本文研制了格栅测试系统,主要由格栅电缆、LED灯、电源和高速相机等组成.依附靶体中的钢筋,格栅电缆被制作成棋盘式格栅网,按一定间距预埋于靶体之中,并与电源和LED灯组成回路.运动中的弹体切断附近的格栅电缆,对应的LED灯将熄灭,进而表征了格栅电缆的破坏状态,并由高速相机进行记录.结合格栅的分布,实时原位测试弹体的侵彻轨迹、速度和侵彻深度.基于此,本文测试了弹体的速度变化和最终的侵深,并结合经验公式、直接测量进行了校验,论证了格栅测试方法的有效性.