水位波动对长江中下游湖泊湖滨带底质环境的影响

以长江中下游湖泊为对象，研究了水位波动对湖滨带底质环境的影响．结果表明，底质环境参数沿高程梯度变化明显．底质含水率沿高程梯度增加而减小，pH值沿高程梯度变化不大，有机质、总氮和总磷沿高程梯度呈先增大后减小的趋势．底质环境参数的季节变化也较大．分析表明，水位波动幅度、淹没深度、高水位持续时间等对湖滨带底质环境有较大影响．在中等波动幅度下，底质参数沿高程的变异系数最大，表明此时湖滨带底质异质性较高．夏季湖滨带淹没时间越长、淹没深度越大，底质养分流失越快．高水位持续时间越长，底质pH值变化就越大、营养盐流失越快．本研究结果可为湖滨带生态修复及管理提供依据

Experimental study on competitive interaction among reef-building coral Turbinaria peltata,Rhizoclonium sp. and rabbitfish Siganus guttatus

本研究通过120 d的室内培养实验研究了盾形陀螺珊瑚(TurbInArIA PElTATA)、根枝藻(rHIzOClOnIuM SP.)和点斑篮子鱼(SIgAnuS guTTATuS)之间的相互作用关系.结果显示,高质量浓度的nO-3(5.00~10.00 Mg/dM3)刺激了丝状绿藻根枝藻在缸内的爆发式生长,在实验27 d时根枝藻在缸壁的面积覆盖率达到90.5%,藻丝长度为10~15 CM.在海藻的胁迫作用下,盾形陀螺珊瑚的PSⅡ最大光化学量子产量(f V/f M)均值逐渐从0.712降至0.626,降幅为10.7%~13.5%.放入4尾4~6 CM长的点斑篮子鱼后,实验缸壁根枝藻的面积覆盖率在2d内从90.5%下降至10.0%.但解除根枝藻胁迫后盾形陀螺珊瑚的f V/f M值并没有明显变化,与对照组的差异也不显著;随着海藻胁迫因子的消除,盾形陀螺珊瑚的f V/f M值逐渐升高,并在第120天时恢复至初始状态.本研究结果从珊瑚光合作用效率的角度验证了啃食者的存在确能缓解富营养化对造礁珊瑚的不利影响,为“下行控制假说“提供了新的证据.A 120 days experiment was conducted in the aquarium to study competitive interaction among reef-building coral Turbinaria peltata,green macroalgae Rhizoclonium sp.and rabbitfish Siganus guttatus.The results showed that high concentration of NO-3( 5.00 ~10.00mg/dm3) stimulated the explosive growth of filamentous Rhizoclonium sp.,which covered 90.5% of aquarium wall on the 27thday.The length of algal filament ranged from 10cm to 15cm.Some polyps of T.peltata were covered by algae or were continuously touched and squeezed by algal filament under the action of water flow.In the meantime,the mean F v / F m gradually declined from 0.712 to 0.626 under the stress.The addition of 4 rabbitfish sharply reduced the coverage of filamentous macroalgae from 90.5 % to 10.0 % level in 2 days,but the F v / F m of T.peltata didn't recover fast.However,as the stress on the algae disappeared,T.peltata F v / F m gradually returned back to initial state on day 120.The study verifies that the grazers indeed alleviate the negative effects of eutrophication on corals and it provides a new evidence for the "top-down control"of herbivores.国家海洋局第三海洋研究所基本科研业务费资助项目(海三科2011033); 国家海洋公益性行业科研专项资助项目(201105012); 厦门海洋研究开发院共建专项资助项

大连极紫外相干光源

先进光源的发展在前沿科学研究中发挥的作用越来越重要。近十年来,飞速发展的自由电子激光技术为科学家们提供了探索未知世界、发现新科学规律和实现技术变革的重要工具。建成的大连极紫外(EUV)相干光源的运行波段为50~150nm,单脉冲能量大于100μJ,且可提供10-12 s和10-13 s量级的超快激光脉冲,是我国第一台自由电子激光用户装置,并且是国际上唯一运行在极紫外波段的自由电子激光用户装置,在世界范围内为用户提供具有高峰值亮度和超短脉冲的极紫外激光。大连EUV相干光源是由国家自然科学基金委资助、由中国科学院大连化学物理研究所和上海应用物理研究所共同承担的重大科学仪器研制项目,目标是打造一个以先进极紫外光源为核心、主要用于能源基础科学研究的光子科学平台

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies