课程文献中心 更多>>

关键词： cavity ring-down spectroscopy   isotopic partitioning   priming   soil respiration   Spartina alterniflora   Spartina patens  

摘要： Coastal wetlands are commonly exposed to hydrocarbon pollutants derived from extraction disasters like the Deepwater Horizon oil spill. Naturally occurring microbes can degrade oil, but the rate of oil degradation depends heavily on the key chemical and biological factors. The goal of this study was to determine the influence of interactions between marsh plants and nitrogen (N) on the degradation of oil from the Deepwater Horizon oil spill. Oil disappearance was measured with gas chromatography (GC) focusing on the change in C-18 n-alkane-to-phytane ratio of oil, and instantaneous oil degradation rates were measured using an instantaneous carbon isotopic partitioning method. N addition often stimulates oil decomposition in soil slurries, but the effect of N in our mesocosms depended on plant species. N addition accelerated oil degradation in Spartina alterniflora mesocosms but slowed oil degradation in Spartina patens mesocosms. Across all plant and N treatments, oil degradation related to plant root growth. In many ecosystems including marshes, N addition has been shown to diminish root growth by reducing the need for nutrient foraging. Where N addition reduces root growth, N may ultimately exacerbate oxygen scarcity in marsh soils possibly negating or reversing the positive, direct effects that N has on oil degradation. Based on these findings, fertilization strategies that maximize marsh plant root growth will be the most effective at increasing the microbial degradation of oil and will have the greatest potential to mitigate the impacts of oil in marsh ecosystems.

关键词： Enamel insulated wire   Partial discharge   Insulation breakdown voltage   Insulation lifetime  

摘要： Insulation breakdown voltage and insulation lifetime were investigated in straight lines or twisted pairs with polyesterimide-polyamideimide enameled round wires (EI/AIW). The enamel thickness was 50 mu m and the conducting copper radius was 0.50, 0.75, 1.09, and 1.50 mm, respectively. There were many air gaps in a twisted pair therefore, when voltage was applied to the twisted pair, enamel erosion took place in the air gap area because of partial discharge according to Paschen's law. Insulation breakdown voltage and insulation lifetime were highest in the sample of 0.75 mm conductor radius, which was higher than those values for 0.50 mm or 1.09 and 1.55 mm.

关键词： Hatchling orientation   Artificial lighting   Horizon elevation   Marine turtle   Conservation management   Elevation   Industry   Coastal development  

摘要： Marine turtles are threatened globally by increasing coastal development. In particular, increased artificial lighting at the nesting beach has the potential to disrupt turtle breeding success. Few published data exist regarding the behaviour of the flatback turtle Natator depressus, a species endemic to Australia, in response to artificial light. Given the ongoing industrialisation of the Australian coastline, this study is a timely investigation into the orientation of flatback hatchlings exposed to light glow produced by lighting typically used in industrial settings. We recorded the orientation of hatchlings at the nesting beach on Barrow Island, Western Australia, exposed to 3 types of standard lighting-high-pressure sodium vapour (HPS), metal halide (MH), and fluorescent white (FW)-at 3 different intensities. The light array was positioned either behind a high dune (producing a high, dark silhouette;16 degrees elevation), or in a low creek bed (producing a low silhouette and bright horizon;2 degrees elevation). At medium and high light intensities of all 3 light types, hatchlings were significantly less ocean-oriented when exposed to light at 2 degrees elevation compared to 16 degrees elevation. This difference remained with glow from low-intensity MH light;however, there was no significant difference in orientation of hatchlings exposed to low-intensity HPS and FW light glow at either elevation. Our study emphasises the importance of horizon elevation cues in hatchling sea-finding. Since all species of marine turtles show similar sea-finding behaviour, our results have important implications for management of lighting adjacent to turtle nesting beaches in Australia and elsewhere, as coastal development continues.

关键词： 地铁车站   反应位移法   抗震分析  

摘要： 随着地下结构建设规模的不断扩大,地铁车站的抗震问题已逐步成为地铁建设中新的焦点,而与工程设计相应的地震响应计算方法仍不够成熟。运用反应位移法对典型地铁车站结构进行地震响应计算分析,并评价其抗震性能,最后得出基于反应位移法计算的地下车站与地震中车站破坏形式比较相符,运用反应位移法计算抗震可以满足设计要求。

关键词： 地铁   影响分析   防护措施  

摘要： 结合武汉地铁2号线北延线受地形地貌及城市规划等因素影响,不可避免的跨越马家湖的情况,分析了桥梁施工建设对马家湖的影响,并提出了针对性的防护措施,结果表明:施工期间对马家湖影响可以得到有效控制,施工结束后环境影响会逐渐消失。

关键词： 食管癌细胞   RNA干扰   MDC1基因   细胞周期相关蛋白   放射敏感性   MDC1  

摘要： 目的：利用RNA干扰技术降低食管癌细胞ECA109中MDC1基因表达，观察照射后细胞周期和放射敏感性变化并探讨相关机制。方法针对MDC1mRNA序列设计合成3对有效干扰序列和阴性对照序列，与载体pSIH1？H1？copGFP形成重组质粒，RT？PCR和蛋白印迹法测定MDC1mRNA和蛋白水平表达。克隆形成实验检测细胞放射敏感性，流式细胞术检测细胞周期，蛋白印迹法检测CHK1、CHK2蛋白表达，激光共聚焦显微镜观察细胞核内MDC1斑点数量。单因素方差分析组间差别。结果成功构建 pMDC1？shRNA 质粒并感染 ECA109细胞，获得稳定转染细胞 ECA109M。ECA109M细胞MDC1mRNA、蛋白表达水平低于ECA109N、ECA109细胞（ P＝0．032、P＝0．041）。5 Gy照射后 ECA109M 细胞 G2＋M 期比例低于 ECA109N、ECA109（P＝0．026）。5 Gy 照射后 ECA109、ECA109N、ECA109M细胞中CHK1和CHK2蛋白表达相近（P＝0．345和P＝0．451），ECA109M 细胞CHK2T68蛋白表达低于ECA109、ECA109N细胞（ P＝0．012）。 ECA109细胞D0值为3．06 Gy，SF2值为0．91；ECA109N、ECA109M细胞的D0值分别为2．90、1．88 Gy；SF2值分别为0．89、0．84（ P＝0．021；P＝0．037）。结论 RNA干扰降低MDC1蛋白表达后可以降低细胞周期相关蛋白的表达，解除细胞周期阻滞，增强食管癌细胞ECA109的放射敏感性。

关键词： 兼容   自动检定线   接触电阻   丢帧   测量误差  

摘要： 针对现有自动化检定线适用于单一计量设备的情况,本文以实现兼容检定单相电能表、三相电能表、用电信息采集终端为目标,并保证自动检定线检定结论的准确可靠。通过对比三相电能表检定台体和人工检定台体的测量误差,分析接触电阻与丢帧对兼容电能表与用电信息采集终端自动检定线测量误差的影响,并提出了改善措施。

关键词： 计算几何   重力式结构   稳定性分析   自动化  

摘要： 针对重力式结构设计中进行多荷载工况、多设计方案的稳定性计算时,各种组合情况下的重力作用效应计算费时费力的问题提出基于计算几何学的计算方法,该算法将重力作用效应的计算问题简化。对重力式结构的设计断面,首先判断其凸凹性,然后利用水位线将其分解为多个子多边形,再根据子多边形内是否存在凹点计算子多边形面积、质心,最后汇总计算原设计断面的面积、质心和重力作用效应,进而得到稳定性指标。根据该算法编制了一套计算机程序,将其应用于株洲二线船闸项目的闸室计算,得到了良好的效果。

关键词： 膨胀叶丝   工艺气体温度   饱和蒸汽加入量   烟碱   焦油  

摘要： 从降低卷烟焦油、烟碱量的角度出发,分析不同工艺条件下膨胀叶丝常规化学成分及烟气成分。发现试验条件下,在饱和蒸汽加入量一定,工艺气体温度较高时,膨胀叶丝烟气成分中焦油、烟碱量和CO量较低;工艺气体温度相同的条件下,焦油量、烟碱量和CO量在蒸汽加入量600kg/h时最低。