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.

Cloning and expression analysis of a HSP70 gene from Pacific abalone (Haliotis discus hannai)

Heat shock protein 70 (HSP70), the primary member of HSPs that are responsive of thermal stress, is found in all multicellular organisms and functions mostly as molecular chaperon. The inducible HSP70 cDNA cloned from Pacific abalone (Haliotis discus hannai) using rapid amplification of cDNA ends (RACE), was highly homologous to other HSP70 genes. The full-length cDNA of the Pacific abalone HSP70 was 2631 bp, consisting of a 5'-terminal untranslated region (UTR) of 90 bp, a 3'-terminal UTR of 573 by with a canonical polyadenylation signal sequence AATAAA and a poly (A) tail, and an open reading frame of 1968 bp. The HSP70 cDNA encoded a polypeptide of 655 amino acids with an ATPase domain of 382 amino acids, the substrate peptide binding domain of 161 amino acids and a C-terminus domain of 112 amino acids. The temporal expression of HSP70 was measured by semi-quantitative RT-PCR after heat shock and bacterial challenge. Challenge of Pacific abalone with heat shock or the pathogenic bacteria Vibrio anguillarum resulted in a dramatic increase in the expression of HSP70 mRNA level in muscle, followed by a recovery to normal level after 96 h. Unlike the muscle, the levels of HSP70 expression in gills reached the top at 12 h and maintained a relatively high level compared with the control after thermal and bacterial challenge. The upregulated mRNA expression of HSP70 in the abalone following heat shock and infection response indicates that the HSP70 gene is inducible and involved in immune response. (c) 2006 Elsevier Ltd. All rights reserved.

采用普通双绞线远距离传输动力、图像、双向数据的方法

论述了一种在一对普通动力双绞线上实现直流动力、彩色图像和双向数据的远距离实时传输方法,详细介绍了其工作原理、电路设计和试验结果。

随机系统模型参数在线辨识的一种算法及负荷预报

本文提出了一种简化的多变量随机系统状态模型参数在线辨识方法。与最小二乘自适应递推算法比较,不仅需要辨识的参数减少,而且针对一类模型参数缓慢变化的系统,可以通过选择不同的遗忘因子序列来控制参数变化的幅度,解决了电力系统负荷预报中季节模型的老化问题。本方法基于带有随机噪声状态模型的典范型,大大节省了计算机的运算量和存贮容量,适于微处理机的在线应用。

空间情境模型中以观察者为中心的空间关系表征

Human being built and updated the representations of spatial distances and spatial relations between protagonist and the around things in language comprehension. The representations of the spatial relations in egocentric spatial situational models were important in spatial cognition, narrative comprehension and psycholinguistic. Using imagery searching paradigm, Franklin and Tversky (1990) studied the representations of the spatial relations in egocentric spatial situational models and found the standard RT pattern of searching the objects in different directions around the observer (frontcanonical axis constructed spatial representation, as consequence, front-back, right-left directions represents near than other pairs. So from front to back, from back to front, from right to left or from left to right, is quick than other pairs. With the 45-degree count-clockwise rotation of the objects around the body, the geometric distance between them determined the psychological distance between two objects. As a conclusion, the structural natures of the spatial representation determined the nature of spatial relations.