Hg~(2+)、Cd~(2+)及其联合胁迫对伊乐藻的生长及POD和SOD活性的影响

利用水族箱实验研究了伊乐藻的现存量以及POD和SOD活性在Hg2+、Cd2+及其联合胁迫下的响应特点.结果表明:Hg2+和Cd2+对伊乐藻的联合毒性大于单一的毒性;在Hg2+20μmol.L-1,或Cd2+80μmol.L-1,或Hg2++Cd2+50μmol.L-1([Hg2+]/[Cd2+]=1/4)时,植物现存量增加的百分比与金属离子浓度负相关;高于上述浓度时,植物现存量减少的速率明显降低.POD和SOD活性的变化趋势相似,在6 h时,其活性在低于40μmol.L-1的Hg2+、或160μmol.L

Deep mixing for excavation support: Design issues

Deep mixing is effectively used in excavations both in conjunction with and in substitution of traditional techniques, where it results in more economical and convenient solutions for the stability of the system and the prevention of seepage. Deep mixed walls constructed as part of a soldier pile and tie-backs system act also as temporary support, prevent seepage like a sheet pile wall, but require a lower amount of steel. The deep mixed treatment can also contribute to the stability of the wall system against deep-seated failures. Although deep mixing is currently used for excavation control in numerous projects, no standard procedure has been developed and the different applications have not been evaluated. As this technique emerges as a more economical and effective alternative to traditional excavation shoring, there is a need for guidelines describing proven procedures for evaluation of design, analysis and construction. This paper presents comparisons in the design of excavation support using deep mixing and other traditional techniques. Issues important for design, analysis, and construction of deep mixed excavation walls are also discussed.

A method for individual identification of echolocation signals in free-ranging finless porpoises carrying data loggers

Echolocation click events of a free-ranging juvenile and an adult finless porpoise (Neophocaena phocaenoides) were recorded with an acoustic data logger. Additionally, dive depth and swim speed of the juvenile were recorded with a behavior data logger. Echoes of echolocation signals from the water surface were clearly detected in shallow dives approximately less than 2 m. The delay time between a surface echo and a direct signal corresponded with the two-way transmission time for the animal's depth, indicating that the signals originated from the animal wearing the data loggers. The finless porpoises produced echolocation signals frequently and were thought to be able to detect their depth by listening to echoes from the water surface. (C) 2000 Acoustical Society of America. [S0001-4966(00)01609-X].

Synthesis of composite AIN powder mixed with sintering additives by the Lanxide method

Composite AlN powder, mixed with the sintering additive Y2O3, was synthesized by the direct nitridation of molten Al-Mg-Y alloys. The character of products was determined by means of electron microscopy, X-ray diffraction, granularmetric analysis and chemical composition analysis etc. The results show that the nitridation rate of the raw alloys is higher, and the nitridation products axe porous enough to be easily crushed. Composite AlN powder, obtained by the Lanxide method, has excellent characters such as high purity, especially low oxygen content, and narrow well-distributed grain size and so on.

Processing network models of energy/environment systems

Processing networks are a variant of the standard linear programming network model which are especially useful for optimizing industrial energy/environment systems. Modelling advantages include an intuitive diagrammatic representation and the ability to incorporate all forms of energy and pollutants in a single integrated linear network model. Added advantages include increased speed of solution and algorithms supporting formulation. The paper explores their use in modelling the energy and pollution control systems in large industrial plants. The pollution control options in an ethylene production plant are analyzed as an example. PROFLOW, a computer tool for the formulation, analysis, and solution of processing network models, is introduced.

认证字典及其在PKI中的应用研究

认证字典是一类重要的数据结构,它在众多研究领域都具有重要的理论和应用价值.文中介绍了认证字典的基本概念和原理,引入了时间约束,给出了一种新的认证字典分类方法.从认证字典在PKI中的应用出发,分析了其实现技术;并简单地分析和比较了基于不同认证字典实现的证书撤销方案.

Corrosion inhibition of carbon steel in tetra-n-butylammonium bromide aqueous solution by benzotriazole and Na3PO4

The corrosion inhibition behavior of benzotriazole, Na3PO4 and their mixture on carbon steel in 20 wt.% (0.628 mol l(-1)) tetra-n-butylammonium bromide aerated aqueous solution was investigated by weight-loss test, potentiodynamic polarization measurement, electrochemical impedance spectroscopy and scanning electron microscope/energy dispersive X-ray techniques. The inhibition action of BTA or SP or inhibitors mixture on the corrosion of carbon steel is mainly due to the inhibition of anodic process of corrosion. The results revealed that inhibitors mixtures have shown synergistic effects at lower concentration of inhibitors. At 2 g l(-1) BTA and 2 g l(-1) SP showed optimum enhanced inhibition compared with their individual effects.

国际综合大洋钻探计划IODP323白令海航次介绍

国际综合大洋钻探计划IODP323航次于2009年7月6日开始至9月4日结束在白令海实施。该航次的主要科学目标

Lanxide技术合成含烧结助剂的复合AIN粉体

高纯度的氮气中，以Al-Mg-Y合金为母合金，利用Lanxide技术合成了含烧结助剂 Y_2O_3的复合AIN粉体．通过扫描电镜、X射线衍射、粒径分析及化学成分分析等检测手段对氮化产物进行表征．实验结果表明，合金氮化反应完全，氮化产物疏松易于粉化．粉化后获得的复合AIN粉体具有纯度高，氧杂质含量低，粒度细小等优点。

半干旱区沙质草地关键生态系统过程对水肥添加的响应

制约半干旱区生态系统恢复的主要因素是什么？一直是生态学界争论的问题，水分或养分或二者的联合限制是现存的3种观点，但是利用野外实验结合生态化学计量比，分析和判断半干旱区自然生态系统生产力恢复的限制因子还未见报道。 本论文以科尔沁沙地东南缘退耕后自然恢复的沙质草地为研究对象，通过析因设计的水、氮、磷添加实验，研究与碳循环、氮循环、磷循环等有关的生态系统关键过程，及其对人为干扰（灌溉和施肥）及全球变化（气候变化和氮沉降）的响应。从2004年到2005年采用3因素2水平析因设计进行水（0, 80mm）、氮（0, 20 g N m-2 yr-1）、磷（0, 10 g P2O5 m-2 yr-1）添加实验。2005年增加了0、2.5、5、7.5、10、30、40 g N m-2 yr-1的氮梯度添加实验。通过两年的实验，得出主要结论如下： 1）该沙质草地生态系统生产力主要受氮素养分的限制，水分与磷素并不是主要限制因素。施氮量达到7.5 g N m-2 yr-1时生物量明显提高，当氮素添加量达到40 g N m-2 yr-1时，生产力最高为1607.3 g m-2，但是并未找出氮肥添加量的上限。禾本科生物量与Shannon-Wiener多样性指数间呈指数负相关，拟合方程为：y = 1318.3e-0.2421x（R2 = 0.6887）。 2）添加水增加了土壤CO2排放速率，而施氮肥的影响并不明显。在较干旱的年份（降水量低于450 mm）干旱期（4月15日-6月15日）添加磷肥明显抑制了土壤呼吸，而在较湿润的年份（降水量高于450 mm）干旱期添加磷肥则显著增加了土壤呼吸。土壤呼吸与表层0-10 cm土壤含水量存在显著的正相关关系；土壤呼吸与土壤温度之间呈显著的指数正相关（R2 = 0.6798），拟合方程为：y = 0.1832e0.1299x。 3）氮素添加对半干旱区沙质草地生态系统氮有效性具有明显的增强作用，可提高土壤氮的矿化速率。该沙质草生态系统土壤有效氮主要由NO3--N组成，并具有明显的季节变化，NH4+-N和NO3--N含量在表层0-10 cm有高于10-20 cm的趋势。植物地上部分和凋落物的C:N比极低。土壤全量的C:N比明显受添加水的影响，与氮、磷添加无关。 4）添加磷素改善了半干旱区沙质草地生态系统土壤磷的有效性，添加氮和水则没有影响。0-10 cm层土壤相对有效磷有高于10-20 cm层的趋势，这说明土壤中的有效磷淋溶作用不强或者是植物主要利用了表土层10 cm以下的土壤有效磷。第一次提出P:N比的概念，利用相对有效磷和相对矿质氮的比值作为土壤相对P:N比，相对P:N比与生物量、ANPP、非禾本科ANPP之间呈显著的线性相关关系。相对P:N比与生物量的线性负相关程度最高，拟合方程为：y = -52.333x + 1356.2（R2 = 0.7263）。 5）水、肥添加对该沙质草地土壤含水量的影响并不显著，不同处理之间以及相同处理的不同层次之间土壤含水量的差异主要源自土壤的空间异质性。根据2005年4-7月的土壤含水量的方差分析结果，可以将表层0-10 cm划分为多变层，10-30 cm划分为过渡层，30-100 cm划分为稳变层。单独添加磷肥或水磷结合可以显著降低白草的蒸腾速率，而且添加磷肥可以抵消添加氮肥所导致的蒸腾速率增加。 6）添加水提高了物种丰富度和均匀度，而施氮肥降低了物种丰富度和均匀度，施磷肥也相应地增加了物种丰富度和均匀度，但幅度不大。本项研究的结果不支持单调上升格局，多样性与生产力呈负相关关系，单调下降和单峰关系两种格局都存在。10-20 cm土层相对矿质氮与物种丰富度、Shannon-Wiener指数、Shannon-Wiener均匀度指数均呈显著的负相关关系。物种丰富度与土壤相对矿质氮之间负相关关系最显著，可以用幂函数进行拟合方程：y = 348.58x-2.1236（n = 8; R2 = 0.8576）。 综合以上的研究结果，建议适量施用氮肥，加速退化沙质草地生态系统生产力的恢复；干旱年份辅以磷肥，以降低温室气体的排放速率。