非饱和土石坝渗流分析

传统的渗流分析主要考虑饱和区而忽略非饱和区内的渗流,本文基于饱和-非饱和渗流计算原理,采用有限元法考虑了非饱和区渗流的影响,并以各向同性均质坝和心墙土石坝为算例进行计算分析。算例表明,由于基质吸力产生的虹吸作用,使得浸润线上部的非饱和区内也存在着连续的水流,通过分析这种水流的特点,定性地得出其对土石坝渗流稳定性的影响。     

土地利用动态变化对地表径流的影响——以上海浦东新区为例

结合基于遥感数据获得的土地利用结果与SCS模型,在GIS环境下模拟了上海浦东新区不同阶段的土地利用/覆被变化对地表径流的影响.结果表明:土地利用结构与格局的变化使地表径流深度趋于增大;同时,在浦东新区城市化的不同时期,由土地利用/覆被变化引起的地表平均径流深度变化也不相同.     

注浆法治理公路黄土暗穴病害的试验研究

注浆法是公路工程中治理暗穴的一种新方法.针对湿陷性黄土地区公路工程中大量发育的暗穴病害,通过室内浆液材料物理力学性能试验与工程现场模拟注浆效果试验,分析了以水泥为主剂的注浆材料在不同配合比情况下治理公路工程中暗穴的效果.室内外试验结果分析表明:浆液水灰比在2.5∶1～1.5∶1之间较为适宜;在不影响路基路面的正常压力下有效的加固半径是1.0 m～1.5 m;在特殊情况下为了使浆液快速凝结可以加入一定量的水玻璃作为速凝剂;可以采用二次注浆加强治理的效果.     

汶川8.0级地震后咸阳市群众恐慌情绪行为与控制对策浅析

汶川8.0级地震后,咸阳市出现比较严重的群众恐慌情绪,在查找引发群众恐慌情绪主要事件及行为反应的基础上,分析公众产生恐慌情绪的根源,反思稳定群众恐慌情绪行为的应对措施,对今后应对此类事件的工作提出建议.     

Cd对野茼蒿种子发芽的影响

为了研究重金属Cd在野茼蒿生长初期所产生的毒性效应,本文以野茼蒿种子为实验材料,分别设定了低浓度组(0、0.2、0.5、0.8、1.0和5.0 mg·L-1)和高浓度组(0、10、25、50和100 mg·L-1)2组实验,对在Cd胁迫作用下野茼蒿种子的萌发生长进行了研究.结果表明:在低浓度(＜5 mg·L-1)下,C...     

7种拟除虫菊酯农药对卤虫的急性毒性研究

为了研究7种拟除虫菊酯农药对美国大盐湖卤虫(GSL Artemia)的急性毒性效应,挑选18~24 h内孵出的卤虫,继续培养24 h后得到Ⅱ~Ⅲ龄卤虫无节幼体,将其暴露于所设浓度梯度的拟除虫菊酯溶液中进行24 h急性毒性实验,记录卤虫无节幼体在各浓度溶液中的死亡情况,并将所得数据进行Probit分析。结果表明,卤虫对不同拟除虫菊酯的敏感性相差较大。氯菊酯、氯烯炔菊酯、炔咪菊酯、胺菊酯、联苯菊酯、高效氯氟氰菊酯和溴氰菊酯对卤虫的24 h半致死浓度(24 h-LC50)分别为4.68、14.82、18.12、38.21、>100、>100和>100 mg.L-1。因此,在含有卤虫的盐水环境中,应尽量避免使用毒性较高的氯菊酯,而选择使用联苯菊酯、高效氯氟氰菊酯和溴氰菊酯等毒性较低的农药。     

变化环境下北江下游年径流量的加权马尔可夫链预测

在气候变化和人类活动的影响下,西北江的水文环境发生了重大变化,导致北江下游的来水条件发生变化。采用斯波曼检验（Spearman’s rho test）和Mann-kendall法系统地分析了北江下游的年径流量的变化趋势和变异情况,在此基础上建立了北江下游变化环境下年径流量的加权马尔可夫链预测模型。结果表明：西北江近50年来的大规模联围筑闸、大规模无序采掘河床泥沙等剧烈的人类活动,导致北江下游三水水文站年径流量在1990年左右发生了变异;所建立的加权马尔可夫链预测结果表明,从变异后的序列中统计出来的状态＂转移概率＂矩阵,能准确地反映出环境变化后年径流量之间的关系,所建立的加权马尔可夫链法预测变化环境下的年径流量是可行的,预测效果也比较好;按文章确定的分级标准,依现有的资料信息推断,环境发生变化后,在未来长期过程中,北江下游出现平水年的机会最大,但年际间的丰枯波动概率也不小。这一结果值得水资源管理部门注意。     

Linking predator and prey behaviour: contrasts between Antarctic fur seals and macaroni penguins at South Georgia

Antarctic fur seals Arctocephalus gazella and macaroni penguins Eudyptes chrysolophus are the two main land-based krill Euphausia superba consumers in the northern Scotia Sea. Using a combination of concurrent at-sea (predator observations, net hauls and multi-frequency acoustics), and land-based (animal tracking and diet analysis) techniques, we examined variability in the foraging ecology of these sympatric top predators during the austral summer and autumn of 2004. Krill availability derived from acoustic surveys was low during summer, increasing in autumn. During the breeding season, krill occurred in 80% of fur seal diet samples, with fish remains in 37% of samples. Penguin diets contained the highest proportion of fish in over 20 years of routine monitoring (46% by mass; particularly the myctophid Electrona antarctica), with krill (33%) and amphipods (Themisto gaudichaudii; 21%) also occurring. When constrained by the need to return and feed their offspring both predator species foraged to the northwest of South Georgia, consistent with an area of high macrozooplankton biomass, but fur seals were apparently more successful at exploiting krill. When unconstrained by chick-rearing (during March) penguins foraged close to the Shag Rocks shelf-break, probably exploiting the high daytime biomass of fish in this area. Penguins and seals are able to respond differently to periods of reduced krill abundance (in terms of variability in diet and foraging behaviour), without detriment to the breeding success of either species. This highlights the importance of myctophid fish as an alternative trophic pathway for land-based predators in the Scotia Sea ecosystem.     

Turbinaria ornata as an herbivory refuge for associate algae

Habitat associations are an integral part of coral reef community structure. Commonly, one organism lives in such close association within or near another that a spatial refuge occurs, whereby one of the organisms provides protection to the other. This is often the result of defenses of the host deterring an associate organism’s consumers. In Moorea, French Polynesia, the range and abundance of the brown macroalga, Turbinaria ornata, have increased drastically since 1980 such that dense aggregations of this macroalga are a dominant component of the backreef habitat. Turbinaria ornata is both mechanically and chemically defended from herbivores. Other species of macroalgae grow within aggregations of Turbinaria and may benefit from these defenses. This study investigates whether aggregations of Turbinaria create a refuge from herbivory for associate macroalgae. When Turbinaria aggregations were removed experimentally, there was a significant increase in the number of associate algal species. Moreover, an herbivory assay using the palatable local alga Acanthophora spicifera identified herbivory as the mechanism for lower diversity on bommies lacking Turbinaria aggregations. The local increase in algal richness due to the refuge from herbivory afforded by Turbinaria may be an important contribution to macroalgal and community dynamics on reefs in Moorea, French Polynesia.     

Antioxidant status, flight performance and sexual signalling in wild-type parrots

During mate choice, individuals are predicted to assess traits that honestly signal the quality of potential partners. Locomotor capacity may be such a trait, potentially signalling condition and ability to resist oxidative damage. In this study, we experimentally manipulated nutritional status: Male wild-type budgerigars, imported from Australia, were provided with either an enhanced (EQ) or reduced quality (RQ) diet varying in vitamin (particularly retinol and α-tocopherol) and mineral levels. Then, we assessed whether this influenced locomotor capacity, i.e. escape flight performance, and sexual attractiveness in male budgerigars Melopsittacus undulatus. Males in the EQ group showed significantly greater total antioxidant capacity and higher blood plasma concentrations of the dietary antioxidants retinol and α-tocopherol, but not carotenoids, than the RQ group. Over 8 weeks of flight training, males on the EQ diet showed significantly greater improvement on the most strenuous flight test than RQ males. In mate choice trials, females preferred EQ over RQ males. EQ males that were relatively fast in escape flight trials were more strongly preferred in the mate preference arena than their RQ competitors. Interestingly, males with high plasma carotenoid levels flew slower and were less attractive than males with low carotenoid levels. This might indicate that carotenoids are not effective antioxidants in birds. Overall, our results show that dietary-derived antioxidants can influence sexual attractiveness and other fitness-related traits through multiple pathways. Locomotor capacity appears to be an honest signal of male condition in birds.