农田灌溉对亚洲西部地区环境的影响

引言农田灌溉是一种最易提高干旱地区农业产量的方法。灌溉农业与旱作农业相比,谷物产量可提高6倍,根块植物产量可提高4—5倍。因此,农田灌溉在渴望得到更多粮食的干旱地区,可以发挥巨大的作用。农田灌溉使这些地区获得高产稳产,同时减轻了干旱和沙漠化的威胁。     

Irish on the move

Trends in emigration from Ireland over time are reviewed. "During the eighteenth and nineteenth centuries overseas migration to the United States and seasonal harvest migration to Britain were the main types of movement, but over the past 100 years the Irish have developed a special affinity for settling in British towns. Although the outflow was halted for a time during the 1970s, when return migration took over, the 1980s have seen a renewal of the exodus. This time, however, the character of the flow has changed from predominantly low-skill construction and factory workers to embrace better-educated emigrants, including many graduates. This shift reflects Ireland's changing position in the international market for labour."     

爱琴地区新构造正断层带的构造非均匀性

一、引言 本文是对爱琴张性构造区新构造正断层带为期五年的野外调查结果所作的综台与分析(图1)．着重介绍爱琴地区的三个地带．(1)希腊大陆的科林斯地区(图1a)．(2)西土耳其的伊密兹尔地区(图1b)．(3)柯雷特的中部及西部(图1c)．在这三个地带正断层使中生代碳酸岩同第四纪沉积物直接相接，     

Soil bentonite wall protects foundation from thrust faulting: analyses and experiment

When seismic thrust faults emerge on the ground surface,they are particularly damaging to buildings,bridges and lifelines that lie on the rupture path.To protect a structure founded on a rigid raft,a thick diaphragm-type soil bentonite wall(SBW) is installed in front of and near the foundation,at sufficient depth to intercept the propagating fault rupture.Extensive numerical analyses,verified against reduced–scale(1 g) split box physical model tests,reveal that such a wall,thanks to its high deformability and low shear resistance,"absorbs" the compressive thrust of the fault and forces the rupture to deviate upwards along its length.As a consequence,the foundation is left essentially intact.The effectiveness of SBW is demonstrated to depend on the exact location of the emerging fault and the magnitude of the fault offset.When the latter is large,the unprotected foundation experiences intolerable rigid-body rotation even if the foundation structural distress is not substantial.     

椭球面上多边形的面积计算

本文给出了椭球面上多边形面积计算的一种新方法。这个多边形的边可能是大地线、恒向线、大圆线或是它们的组合。     

Enzymatic activity in the rhizosphere of Spartina maritima: potential contribution for phytoremediation of metals

Extracellular enzymatic activity (EEA) of five enzymes (peroxidase, phenol oxidase, beta-glucosidase, beta-N-acetylglucosaminidase and acid phosphatase) was analysed in sediments colonised by Spartina maritima in two salt marshes (Rosário and Pancas) of the Tagus estuary (Portugal) with different characteristics such as sediment parameters and metal contaminant levels. Our aim was a better understanding of the influence of the halophyte on microbial activity in the rhizosphere under different site conditions, and its potential consequences for metal cycling and phytoremediation in salt marshes. Acid phosphatase and beta-N-acetylglucosaminidase presented significantly higher EEA in Rosário than in Pancas, whereas the opposite occurred for peroxidase. This was mainly attributed to differences in organic matter between the two sites. A positive correlation between root biomass and EEA of hydrolases (beta-glucosidase, beta-N-acetylglucosaminidase and acid phosphatase) was found, indicating a possible influence of the halophyte in sediment microbial function. This would potentially affect metal cycling in the rhizosphere through microbial reactions.     

什么是断层陡坎？

近十年来，不断加强对构造活动性的仪器观测和历史记录。人们把注意力集中于根据地质，地貌的记录鉴别和研究古地震上，重要的是识别断层地貌特片，例如，断层陡坎，它可能是某一区域构造活动类型及其活动时间的明显标志。     

法国南部早第三纪成壤层序稳定碳同位素地层学:陆地—海洋相关关系依据

全新世成壤碳酸盐结核和古土壤稳定碳同位素成分可以用于推测古大气ＣＯ２含量,重建古环境条件及使陆相沉积物与海相层序发生关系。由于大洋和大气碳交换的时限较短,因此,土壤碳酸盐中的碳同位素成分保留了大洋ＣＯ２储体的同期变化。然而,时间跨度较大,并且能够提供海相和陆相层序相关关系信息的详细的陆地碳同位素地层资料很少。在对法国南部下第三系陆相层序进行分析时,稳定同位素地层分析方法尤其适用于生物地层资料稀少的地层相关关系分析。这一时期尤其引人注目是因为海洋范围碳同位素记录明显变化,并且含有许多重要的哺乳动物演化事…