晚弗拉斯期缺氧事件——弗拉斯-法门阶动物危机的原因？

弗拉斯-法门期(晚泥盆世)动物灭绝事件是显生宙五次主要生物事件中的一次，在此事件中，大约有21％的海洋生物科和50％的生物属消亡，低纬度热带生物礁生态系和浅水海洋动物所受影响最为严重，而高纬度生态系，深水生物和陆地动、植物群仅受到微弱影响，对于该事件的持续时期和最终原因存在广泛分岐。     

美国公众参与理论与实践及其对中国土地整治的借鉴

采用文献分析、对比分析等方法研究美国公众参与理论与实践,以期为中国土地整治公众参与提供借鉴。结果表明:美国公众参与理论比较成熟,联邦及州政府法律要求公众参与规划、决策等,部门、协会等制定了公众参与手册,公众参与技术方法多样且有针对性。中国可借鉴美国公众参与做法,加强土地整治公众参与理论研究,建立健全土地整治公众参与法律制度,编制土地整治公众参与手册,采用多样的公众参与技术方法,从而完善中国土地整治理论,提高土地整治科学性和综合效益。     

Analytic element modeling of embedded multiaquifer domains

An analytic element approach is presented for the modeling of multiaquifer domains embedded in a single-aquifer model. The inside of each domain may consist of an arbitrary number of aquifers separated by leaky layers. The analytic element solution is obtained through a combination of existing single-aquifer and multiaquifer analytic elements and allows for the analytic computation of head and leakage at any point in the aquifer. Along the boundary of an embedded multiaquifer domain, the normal flux is continuous everywhere; continuity of head across the boundary is met exactly at collocations points and approximately, but very accurately, in between. The analytic element solution compares well with an existing exact solution. A hypothetical example with a river intersecting two embedded domains illustrates the practical application of the proposed approach.     

亚洲第四系的主要划分及其岩性和生物地层学意义

这个专题讨论会是作为INQUA亚太地区地层分委员会的第四次国际专题讨论会举办的。1985年,国际地层委员会(ISC)批准了意大利南部Vrica地区的上新世-更新世界线。此后,1987年在渥太华召开的Ⅻ届INQUA大会通过了更新世地层划分分委员会(主席G.M.Richmond)的建议,即把下更新统-中更新统界线暂定在松山-布容极     

影像检查技术——解决管道问题的根本所在

本文简要说明了对于管道质量检测,影像检测技术是相当重要的,是进行管道修复的最重要的技术基础工作。     

CONTROL OF GULLY EROSION USING STIFF GRASSES

Concentrated flow can cause gully formation on sloping lands and in riparian zones. Current practice for riparian gully erosion control involves blocking the gully with a structure comprised of an earthen embankment and a metal or plastic pipe. Measures involving native vegetation would be more attractive for habitat recovery and economic reasons. To test the hypothesis that switchgrass （Panicum virgatum L.） hedges planted at 0.5-m vertical intervals within a gully would control erosion, a series of hedges was established in four concentrated flow channels. Two of the channels were previously eroded trapezoidal channels cut into compacted fill in an outdoor laboratory. The other two channels were natural gullies located at the edge of floodplain fields adjacent to an incised stream. While vegetation was dormant, artificial runoff events were created in the two laboratory gullies and one of the natural gullies using synthetic trapezoidal-shaped hydrographs with peak discharge rates of approximately 0.03, 0.07, and 0.16 m3/s. During these tests flow depth, velocity, turbidity, and soil pore water pressures were monitored. The fourth gully was subjected to a series of natural runoff events over a five-month period with peaks up to 0.09 m3/s. Flow depths in all tests were generally 〈 0.3 m, and flow velocities varied spatially and exceeded 2.0 m/s at the steepest points of the gullies. Erosion rates were negligible for controlled flow experiments, but natural flows in the fourth gully resulted in 1 m ofthalweg degradation, destroying the central portions of the grass hedges, most likely due to the highly erodible nature of the soils at this site. Geotechnical modeling of soil steps reinforced with switchgrass roots showed factors of safety 〉 1 for step heights 〈 0.5 m, but instability was indicated for step heights 〉1 m, consistent with the experimental observations.     

东昆仑南带中元古代晚期—新元古代早期叠层石组合的发现

东昆仑南带加嗡门地区碳酸盐岩地层中发现的中元古代晚期-新元古代早期叠层石组合以大型锥叠层石及其相关的分子Conophyton garganicus var. inkeni,C. cf. ressoti Menchikov, Jacutophyton f. 和Conicodomenia cf. longotenuia等最丰富, 并与Baicalia共生, 故可视之为Conophyton-Baicalia组合.这叠层石组合可以与天山、华北等地蓟县系中部-青白口系中部叠层石组合对比,尤其酷似于天山地区蓟县系的爱尔基干组合和华北蓟县系的闪坡岭叠层石组合,而显著有别于华南地块.它还可以与南乌拉尔、西伯利亚、北美、北非和阿拉斯加半岛等地区的中里菲界上部--上里菲界下部层位中的叠层石组合对比.加嗡门叠层石组合的时限为距今1 300～850 Ma,大致为蓟县纪中期-青白口纪中期或中里菲晚期-晚里菲早期.东昆仑南带存在前寒武纪微地块,当时此微地块的古地理和古环境与天山、华北、西伯利亚和阿拉斯加半岛等地区的前寒武纪地块相似,均位于低纬度区,其上均广泛发育适宜叠层石繁育的温暖陆表海,它们可能共同处于罗迪尼亚超大陆的低纬度大陆边缘部位,与华南地块的不同.这对本区和东昆仑地层和大地构造研究,以及对罗迪尼亚超大陆重建提供了新的古生物约束.     

Post-fire recovery of Puya raimondii,vegetation and birds in the puna of Huascarán National Park,Perú

A large fire of 233 ha in Huascarán National Park in Peru provided an opportunity to compare plant and bird responses in burned and nearby unburned zones of the puna. Heights and live diameters of flagship Puya raimondii rosettes(assigned to four broad developmental phases), plant communities(66 species in 24 families and nine growth forms) and bird communities(77 species in six trophic guilds) were monitored after the fire. Although no mortality was observed, Puya raimondii plants were affected...     

Influence of reclamation works on the marine environment in a semi-enclosed bay

1Introduction GamakBay,anegg shapedseasurfaceareaofap proximately112km2,isasemi enclosedshallowwaterareawithameandepthof9mandhasbotheastandsouthchannelstoreceiveseawaterfromoutside(seeFig.1).Similarscalesoftidalwavesalmostsimultane ouslyenterorexitthrough…