Expression and activity of a multixenobiotic resistance system in the Pacific oyster Crassostrea gigas

The multidrug resistance (MDR) mechanism corresponds to a defence system relying on the expression of high molecular membrane proteins that can actively lower the intracellular concentration of a wide variety of toxins, thus maintaining them below their toxic level. Using RT-PCR, expression levels of a gene belonging to the class I of mammalian mdr genes, has been assessed in different developmental stages of the oyster Crassostrea gigas. While no expression was found in the oocyte or the trocophore stage, a rise of mRNA content was observed from the veliger stage to the juvenile stage, thus indicating the induction of the system as the animal is developing in the environment. The incubation of gill fragments in the dye rhodamine B and subsequent measurements of intracellular fluorescence using a microplate reader indicates that the system can effectively decrease the accumulation of the test compound in a competitive manner with known inhibitors or environmental contaminants as observed in vertebrate cells. The oyster MXR system is thus becoming active in adult oyster and could be of importance in environmentally contaminated areas.     

河口污染沉积物中重金属释放与迁移的围隔生态系研究

利用围隔式生态实验装置研究了加拿大False河口污染沉积物中重金属Pb、Zn、Cd、Cu在海水环境中的行为。实验模拟了 4种环境条件 :( 1)高生产力 ;( 2 )低生产力 ;( 3 )高悬浮物含量 ;( 4 )还原环境。结果表明 ,污染沉积物中重金属在海水环境中的行为既取决于元素自身性质 ,亦受外界环境条件制约。还原环境能抑制重金属的释放 ,有助于体系中原有的重金属清除出水柱。低生产力条件下 ,Pb、Zn表现出释放行为 ,而高生产力和高悬浮物含量条件下 ,Pb、Zn表现出先释放后迁移 ,而Cd、Cu则呈现出相反的图象。研究了实验期间 4种重金属释放与迁移的净通量 ,表明氧化条件下Cu、Zn净释放通量比Cd、Pb高 1～ 2个量级。研究表明 ,添加粘土及向还原环境倾倒均有助于减轻污染沉积物倾倒后重金属的二次污染     

亚马孙河及其河口区中颗粒有机碳的来源和运移

本文将碳同位素比值用于研究亚马孙河及其主要支流中颗粒有机碳(POC)的来源,同时也探讨了河流POC向海洋环境的输送,在亚马孙河上游POC的碳同位索值δ¹³C(-24.5——28.0‰)较之在其中下游的相应值(-27.9——30.1‰)要重一些一般来说,其支流POC的同位素组成要比在亚马孙河主航道中测得的值要轻一些由碳同位素数据证明,亚马孙河主航道中POC的主要来源是陆地物质,而不是河生生物,在亚马孙河口区和淡水舌中观测到POC的同位素组成有很大的变化范围(-17.5——28.4‰),这被认为是河流的POC与海洋的POC在该区域中混合作用的结果.由同位素数据可计算出河流有机碎屑沿平行于河流航道方向向海可搬运至距河口290km处,而沿亚马孙河淡水舌方向在河口西北方向1100km处仍可看到河流POC的稳定同位素信号.     

与辐射对流过程有关的热带环流:用全球谱模式所作的数值试验

一、引 言 在热带地区,太阳辐射和云辐射的互相作用过程对于数值天气预报来说是头等重要的。1983年 6月 WCRP的报告指出,目前的数值试验确认:时间平均热带环流的模拟(热带环流的时间平稳模拟)对对流和对流与辐射的相互作用是十分敏感的。这些物理过程的主要作用是通过加强的水分循环使对流加热加强,而水分循环的加强是由热带地区的水汽供应的增加和降水率的增加所造成的。 这篇文章描述了欧洲中期天气预报中心全球谱模式两个旬积分的结果。其目的是为了确定在热带地区的对流加热和降水率对辐射的作用。每一个模式的积分是从1979年 6月 11日格林威治时间12点的初始状态开始的,并且适用于若干天以后发生的印度夏季风迅速加强的时期。     

对地球大气和表面研究的卫星数据处理和分析软件系统

一、引 言 在地球科学发展中现在正出现两个重要的趋势。一个是传统的研究地球部分的定向学科的方法。它正慢慢地让位於更全面的多学科的方法,该方法把地球和大气看成是一个动态的综合系统。另一个是空间观测方法,或更确切地说是卫星遥感,它正成为地球科学各学科如:海洋学、气象学、生物学、地质学和地球物理学的标准研究工具。 鉴于这种趋势,加州空间研究所一直都在开发卫星数据处理和分析软件系统,来支持多学科的及综合研究计划。该系统叫做OASIS(海洋大气卫星图象系统),它有助於处理地球的大气和表面(陆地和海洋)的科研及教学活动的开展。     

SOME CORRELATIONS BETWEEN THE GEOLOGY OF CHINA PROPER AND THE GEOLOGY OF MONGOLIA

During the summer of 1930 we had. thanks to the Central Asiatic Expedition led by Dr. R.C. Andrews, a splendid opportunity for studying the geological formations of SE. Gobi, along the Kalgan-Urga trail, South and     

Maneuvering modeling and simulation of AUV dynamic systems with Euler-Rodriguez quaternion method

The purpose of this study is to develop maneuvering models and systems of a simulator to improve the motion performance of autonomous underwater vehicles (AUVs) at the preliminary design stages in advance. The AUVs simulation systems based on the standard submarine equations of motion in six-degree-of-freedom (6-DOF) integrated with the Euler-Rodriguez quaternion method for representing singularity-free AUV attitude and time-saving calculation, and with a nonlinear control model for maneuvering and depth control simulations, time-marching in the fourth-order Runge-Kutta scheme. For validation of the simulation codes, results of the ISiMI AUV open-loop tests including turning test and zigzag test as well as an AUV simulator on the basis of Euler-angle method were used to compare with the quaternion-based AUV simulator. The computational results from the proposed simulator agree well with those from both the ISiMI AUV experiments and the Euler-angle based simulations. Additionally, a new maneuvering procedure, namely "put-out" was implemented to test directional stability for a large-scale AUV in the proposed AUV simulator that can be considered for vehicles in space as well as in constrained planes.     

Benthic recovery during open sea fish farming abatement in Western Mediterranean, Spain

Fish farming is an important source of organic matter input in coastal waters, which contributes to eutrophication. In this study, the macrofaunal benthic community was studied after the cessation of fish farming with the aim of improving our understanding of benthic succession and sediment recovery in a marine ecosystem. The results showed that the best environmental variables for assessing organic pollution were acid-volatile sulfides (AVS) and redox potential. Succession and recovery was best explained by macrofaunal analysis based on community composition as well as on trophic groups. The patterns of recovery differed between each impacted station. For this reason, succession could not be accurately predicted due to the unique environmental parameters and the singular community functional structure of each location. The Azti Marine Benthic Index (AMBI) proved its validity for assessing pollution but did not distinguish between successional stages.     

Modified Joint Distribution of Wave Heights and Periods

The modified versions of the linear theoretical model of Longuet-Higgins (1983) are derived in this work and also compared with the laboratory experiments carried out in MARINTEK. The main feature of modifications is to replace the mean frequency in the formulation with the peak frequency of the wave spectrum. These two alternative forms of joint distributions are checked in three typical random sea states characterized by the initial wave steepness. In order to further explore the properties of these models, the associated marginal distributions of wave heights and wave periods are also researched with the observed statistics and some encouraging results are obtained.