分数量子霍尔效应-1998年诺贝尔物理学奖介绍

1998年10月，三位美国科学家，Daniel Tsui(崔琦，美籍华裔科学家)、Horst Stormer(美国德裔科学家)和Robert Laughlin，因他们在发现分数量子霍尔效应方面所作出的杰出贡献而获得诺贝尔物理学奖。文章力图从物理角度概要介绍分数量子霍尔效应的主要物理现象和机制。

1998洪涝灾害的深层次原因系统分析

１９９８年６月～１９９８年９月长江流域发生特大洪灾，以高水迎峰，上压下顶，峰急水猛，时长量大为特征。分析洪灾形成的主要原因，除气候反常、降雨集中等自然因素外，也存在水土流失，植被减少，围湖造田，河道淤积，水利工程失修、老化，法制观念淡薄，投入问题尖锐，承灾功能脆弱，人口急剧增长，协调失误等深层次的问题。

Observation of the seasonal evolution of the Yellow Sea Cold Water Mass in 1996-1998

We use the hydrographic data obtained during the joint survey of the Yellow Sea by the First Institute of Oceanography, China and the Korea Ocean Research and Development Institute, Korea, to quantify the spatial structures and temporal evolution of the southern Yellow Sea Cold Water Mass (YSCWM). It is indicated that the southern YSCWM is a water mass that develops in summer and decays in fall. In winter, due to the intrusion of the Yellow Sea Warm Current (YSWC), the central area (approximately between 34 degrees N and 35 degrees N, 122 degrees E and 124 degrees E) of the Yellow Sea is mainly occupied by relatively high temperature water (T > 10 degrees C). By contrast, from early summer to fall, under the seasonal thermocline, the central area of Yellow Sea is occupied by cold water (T < 10 degrees C). In summer, the southern YSCWM has two cold cores. One is formed locally southeast of Shandong Peninsula, and the other one has a tongue-like feature occupying the area approximately between 34 degrees N and 37 degrees N, 123 degrees E and 126 degrees E. The bottom layer temperature anomalies from February to July in the cold tongue region, along with the trajectories of the bottom floaters, suggest that the cold water mass in the northeast region has a displacement from the north to the central area of the Yellow Sea during the summer. (c) 2007 Elsevier Ltd. All rights reserved.

The environment effect on fish assemblage structure in waters adjacent to the Changjiang (Yangtze) River estuary (1998-2001)

We collected fish abundance data in the Changjiang (Yangtze River) estuary and adjacent waters in November 1998, May 1999, November 2000, and May 2001. Using the data, we evaluated the characteristics of the fish assemblages at each site and investigated the effect of several environmental factors. We used a multivariate analysis, including community ordination methods such as detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA), and two-way indicator species analysis (TWINSPAN). We analyzed the biological community structure and environmental factors to determine their spatial distributions, temporal dynamics, and seasonal variations. Among the fish species, five exceeded 5% of the total abundance: Harpodon nehereus (42.82%), Benthosema pterotum (13.85%), Setipinna taty (11.64%), Thryssa kammalensis (9.17%) and Apogonichthys lineatus (6.49%). These were separated into four ecological assemblages: hypsithermal-saline, hypsithermal-brackish, hypothermal-brackish, and hypothermal-saline. We evaluated the degree of influence of environmental factors on the fish community. Our analyses suggested that environmental factors including water depth, salinity, turbidity, transparency, nutrient, and suspended matter formed a synthetic spatial gradient between the coastal and pelagic areas. Ecological and environmental factors changed temporally from 1998 to 2001, and drove the fish community succession. The environmental factors driving the fish community structure included bottom temperature, water depth, bottom and surface pH, surface total phosphorous, and bottom dissolved oxygen. This investigation was completed before completion of the Three Gorges Dam; therefore the results of this study provide an important foundation for evaluating the influence of the human activities.