超高层筒体结构模型振动台地震破坏试验研究

就超高层筒体结构在地震作用下的动力特性与破坏反应,对一个1∶50比例的超高层建筑模型进行了微震、强震直至破坏的振动台试验研究。试验通过满足弹性—重力相似条件得到原型结构在地震作用下的动力特性与破坏现象。结果表明,结构的横向二阶以上及竖向一阶振动对结构的抗震安全性起控制作用,结构中上部是抗震薄弱部位,试验破坏现象与实际震害吻合。     

Evidence of habitat structure-generated bottleneck in the recruitment process of the SW Atlantic crab<Emphasis Type="Italic"> Cyrtograpsus angulatus</Emphasis>

Shelters generated by the introduced reef-building polychaete Ficopomatus enigmaticus (Serpulidae) significantly enhance settlement of the crab Cyrtograpsus angulatus (Grapsidae) in a SW Atlantic coastal lagoon (Mar Chiquita, 37°32S; 57°26W; Argentina). However, their ultimate role in recruitment does not appear to be very important, suggesting a habitat-generated bottleneck that occurs between settlement and recruitment. Laboratory and field experiments show that newly settled crabs actively select refuges similar in size. Inside the reefs, decreases in crab density of each newly settled cohort mirror the ratio of decreases in the number of reef refuges of similar sizes, suggesting that habitat fractal structure determines the mortality rate after settlement. Field experiments using artificial shelters show that as crabs increase in size, they move outside reefs. Field tethering of juvenile- and adult-sized crabs without access to refuges showed that juvenile crabs suffer a much higher risk of mortality than adults. Our results show that the availability of small refuges provided by polychaete reefs enhances crab settlement, but, then, due to a decrease in the number of refuges as size increases, produces a demographic bottleneck during recruitment. Thus, independent of settlement intensity, enhanced survivorship in the smallest size classes due to refuge is not transmitted to larger size classes. This is likely one reason why stock-recruitment relationships may not hold in species that use shelters during both recently settled and juvenile life stages. These results provide a good example of why habitat enhancement programs need to incorporate a comprehensive evaluation of the species ontogenic ecology to avoid class size-specific bottlenecks.Communicated by P.W. Sammarco, Chauvin     

Sexual and asexual reproduction of<Emphasis Type="Italic"> Allostichaster capensis</Emphasis> (Echinodermata: Asteroidea) in Golfo Nuevo

Sexual and asexual reproduction of the fissiparous starfish Allostichaster capensis were examined for 24 months at Bahía Kaiser, Golfo Nuevo, Chubut, Argentina. Gonad indices revealed an annual reproductive cycle, with peak development occurring in late winter (August). Spawning occurred in spring (September). Pyloric caeca indices displayed a clear annual cycle and a reciprocal relationship with gonad indices, showing the storage function of pyloric caeca. The starfish population appears to be largely maintained by fission, as only two females were found. A. capensis also showed an annual cycle of fission, with the highest frequency in spring and summer (from November to January), just after spawning. Incidence of fission was correlated with environmental factors such as photoperiod, seawater temperature, and salinity.Communicated by P.W. Sammarco, Chauvin     

Evaluation of oxidation stability of lignite humic substances by DSC induction period measurement

The stability of lignite humic acids and four regenerated humic acids was estimated by employing differential scanning calorimetry. Induction period for the oxidative decomposition of humic matter was calculated from non-isothermal measurements at six different rates of heating. To simulate the gradual evolution history of humic acids, different intensities of oxidation attack by nitric acid on the original lignite was used. Experimental data showed higher stability of natural humic acids in the temperature range where the decomposition step occurred. On the other hand, extrapolation to lower temperatures and calculated kinetic parameters did not correspond to the order observed at higher temperatures. An oscillating trend of calculated parameters of the two proposed parts of stability was observed, which agreed with data concerning regenerated humic acids production. The approach applied in this work represents a rapid and useful method for evaluation of organic matter stability.     

Influence of low temperature on the discharge mechanism of the electric fish Torpedo marmorata and T. ocellata

The influence of low temperature on the discharge of a part of the electric organ, evoked by electrical stimulation of the nerve leading to it, has been studied on in vitro nerve-electric tissue preparations of the fishes Torpedo marmorata or T. ocellata placed into sea water of different temperatures. It has been found that the amplitude of the discharge of the electric tissue made up from serially organized electroplaques sharply decreases at temperatures below 15 °C. The latent period of discharges increases most markedly at lower temperatures (about 10 °C). Experiments have been performed during July and August on fish caught in the Kotor bay of the Southern Adriatic. Questions related to the dissociation of different aspects of the intrinsic mechanism of the discharge generation by temperature, and to the possible significance of this finding with respect to the ecology of this fish, as well as possible adaptation mechanisms involved, are discussed.     

Reconstruction of Long-Term Changes in Lake water Chemistry,Zooplankton and Benthos of a Small,Acidified High-Mountain Lake: Magic Modelling and Palaeolimnogical Analysis

Starolesnianske pleso is a small and shallow acid lake in the High Tatra Mountains, situated at 2000 m above sea level, on granitic bedrock, with sparse and thin soil cover. When detailed measurements began in the 1980s Starolesnianske pleso had pH below 5 and only one species of cladoceran zooplankton, the ubiquitous Chydorus sphaericusPalaeolimnological investigations show changes in cladoceran zooplankton and chironomid zoobenthic assemblages since about 1920 and a major change in 1970–1980. The dynamic acidification model MAGIC was used to reconstruct changes in water chemistry over the past 150 years. The results from MAGIC agree well with the sediment record; pH levels gradually decreased from 6.5 in the mid-1800s to about 5.6 in 1920 (first response in biota) to below 5.0 by 1970, and concentrations of inorganic aluminium rose dramatically beginning about 1960. In the 1990s the lake water chemistry showed clear signs of reversal in acidification brought about by a major decline in S deposition.     

Hysteresis in Reversal of Central European Mountain Lakes from Atmospheric Acidification

Extremely high emissions of S and N compounds in Central Europe (both 280 mmol m^-2 yr^-1) declined by 70and 35%, respectively, during the last decade. Decreaseddeposition rates of SO₄ ^-2, NO₃ ^-, and NH₄ ⁺ in the region paralleled emission declines. The reduction in atmospheric inputs of S and N to mountain ecosystemshas resulted in a pronounced reversal of acidification in the Tatra Mountains and Bohemian Forest lakes. Between the 1987–1990and 1997–1999 periods, concentrations of SO₄ ^-2 and NO₃ ^- decreased (average ± standard deviation) by 22±7 and 12±7 mol L^-1, respectively, in theTatra Mountains, and by 19±7 and 15±10 mol L^-1, respectively, in the Bohemian Forest. Their decrease was compensated in part (1) by a decrease in Ca²⁺ + Mg²⁺ (17±7 mol L^-1) and H⁺ (4±6 mol L^-1), and an increase in HCO₃ ^-(10±10 mol L^-1) in the Tatra Mountains lakes, and (2) by a decrease in Al (7±4 mol L^-1), Ca²⁺ + Mg²⁺ (9±6 mol L^-1), and H⁺ (6±5 mol L^-1), in Bohemian Forest lakes. Despite the rapid decline in lake water concentrations of SO₄ ^-2 and NO₃ ^- in response to reduced S and N emissions, their present concentrations in some lakes are higher than predictionsbased on observed concentrations at comparable emission rates during development of acidification. This hysteresis in chemical reversal from acidification has delayed biological recovery of the lakes. The only unequivocal sign of biological recovery hasbeen observed in erné Lake (Bohemian Forest) where a cladoceran species Ceriodaphnia quadrangular has recentlyreached its pre-acidification abundance.     

利用人工降雨手段化汛期特大暴雨灾害为可利用水资源

利用美国1979-1995年NCEP/NCAR再分析及其它格点资料进行分析。发现汛期影响我国特大暴雨及洪涝灾害的，是一支存在于南，北两半球之间的非亚支“宏观气流系统”，它的气流运行具有一定的规律性，因而，对我国的特大暴雨和洪涝灾害，不但可以进行及时的监测和预报，而且可以在这支宏观气流系统的上游地带施行人工影响云雨工程，把空中丰沛水分降到需要雨水的地区，化洪涝灾害为宝贵的水资源。     

天文灾害学刍议(Ⅱ)——天文灾害学研究的意义及其进展

简述了开展天文灾害学研究的意义。已有研究表明 ,一些天文因素对许多自然灾害的孕育有调制作用 ,对一些自然灾害的发生有诱发、触发的作用 ,深入开展天文灾害学研究有理论意义和应用价值。同时作者简要综述了这一交叉研究领域近些年的进展情况。