TETRAKIS(MU-DL-ALANINE-O-O')OCTA-AGUADIERBIUM(III) HEXAPERCHLORATE

The structure of the title compound, [Er-2(C3H7NO2)(4)- (H2O)(8)](ClO4)(6), consists of dimeric [Er-2(DL-alanine)(4)-(H2O)(8)](6+) cations and perchlorate anions. The four alanine molecules act as bridging ligands linking two Er3+ ions through their carboxyl O atoms. Each Er3+ ion is also coordinated by four water molecules to complete eightfold coordination in a square antiprism fashion. The perchlorate anions and the methyl groups of the alanine ligands are disordered.

Construction of AFLP-based genetic linkage map for Zhikong scallop, Chlamys farreri Jones et Preston and mapping of sex-linked markers

Zhikong scallop (Chlamys farreri) is an economically important aquaculture species in China; however, frequent mass mortality seriously affects the development of its industry. Genetic linkage map is useful for genetic improvement and selective breeding of C. farreri. Linkage maps were constructed using an intraspecific F-1 cross and amplified fragment length polymorphism (AFLP) markers. Thirty-two selected AFLP primer combinations produced 545 AFLP markers that were polymorphic in either of the parents and segregated in the progeny. Of these segregating markers, 166 were mapped to 19 linkage groups of the female framework map, covering a total of 1503.9 cM, with an average marker spacing of 10.2 cM; and 197 markers were assigned to 20 linkage groups of the male map, covering a total of 1630.7 cM, with 9.2 cM per marker. A sex-linked marker was mapped on the female map with zero recombination and a LOD of 27.3. The genetic length of C farreri genome was estimated as 1889.0 cM for the female and 1995.9 cM for the male. The coverage of the framework map was calculated as 79.6% for the female and 81.7% for the male. When the triplets and doublets were considered, the observed length of the map was calculated as 1610.2 cM with coverage of 85.2% for the female, and 1880.5 cM with coverage of 94.2% for the male. The genetic maps presented here will serve as a basis for the construction of a high-resolution genetic map and mapping of economically important genes. (C) 2004 Published by Elsevier B.V.

Comparison of photobioreactors for cultivation of Undaria pinnatifida gametophytes

Undaria pinnatifida gametophytes were grown in 2.5 l bubble column and airlift reactor at 25 degreesC and light intensity of 40 mumol m(-2) s(-1) for 6 days. With aeration at 1 l min(-1), the airlift reactor yielded higher growth rate (0.12 mg DW ml(-1) d(-1)) than a bubble column (0.08 mg DW ml(-1) d(-1)). The advantages were related to the more homogeneous fluid dynamic characteristics of the airlift reactor.

Molecular characterizations of oxytetracycline resistant bacteria and their resistance genes from mariculture waters of China

Oxytetracycline-resistant bacteria were isolated from a mariculture farm in China, and accounted for 32.23% and 5.63% of the total culturable microbes of the sea cucumber and the sea urchin rearing waters respectively. Marine vibrios, especially strains related to Vibrio splendidus or V. tasmaniensis, were the most abundant resistant isolates. For oxytetracycline resistance, tet(A), tet(B) and tet(D) genes were detected in both sea cucumber and sea urchin rearing ponds. The dominant resistance type for V. tasmaniensis-like strains was the combination of both tet(A) and tet(B) genes, while the major resistance type for V. splendidus-like strains was a single tet(D) gene. Most of the sea cucumber tet-positive isolates harbored a chloramphenicol-resistance gene, either cat IV or cat II, while only a few sea urchin tet-positive isolates harbored a cat gene, actually cat IV. The coexistence of tet and cat genes in the strains isolated from the mariculture farm studied was helpful in explaining some of the multi-resistance mechanisms. (c) 2006 Elsevier Ltd. All rights reserved.

远程数据库访问系统客户／服务器体系结构模型的设计与实现

远程数据库访问（ＲＤＡ）是ＯＳＩ应用层一个特别应用服务元素（ＳＡＳＥ），是数据库基础标准，是构造分布数据库开放式体系结构的基础．本文遵照国际标准ＲＤＡ模型、服务、协议，研究并给出实现ＲＤＡ客户／服务器体系结构模型、方法与系统原型。

中国南方红土古环境重建中存在的几个问题

随着黄土-古土壤系列在中国北方第四纪古环境演变的成功恢复,对中国南方红土所记录的古环境和全球变化信息的研究也逐渐成为热点。然而,纵观最近10多年来对中国南方红土古环境变化的研究现状,还存在不少问题,一些结论尚难以令人满意,从成因机理上未能给予有力的理论支持。对在风化壳形成机理的认识、风化壳剖面记载环境变化的历史、红土-沉积旋回所反映的古气候变迁、红土和黄土的古环境记录的对比等方面的研究中暴露出的一些问题,本文进行了剖析和讨论。

喀斯特森林雨水的地球化学特征——以贵州茂兰国家级自然保护区为例

贵州茂兰喀斯特原始森林地区25个雨水样品的化学组成研究表明，该区雨水的pH值为4．4～7．2，平均为5．1。雨水样品富NH4^＋、Ca^2＋和SO4^2-、C1^-。NH4^＋是最主要的阳离子，平均值为56．8／μmol／L，占阳离子组成的26％～74％，Ca^2＋次之，平均值为14．8μmol／L，NHg和Ca^2＋之和占了阳离子组成的71％～94％，SO4^2-是最主要的阴离子，平均值为39．2μmol／L，占了阴离子组成的69％～91％，CI一次之，平均值为9．5μmol／L。SO4^2-和C1-占了阴离子组成的71％～96％。与中国其他地区的雨水样品相比，茂兰地区雨水离子含量要低1～2个数量级；物质来源分析表明茂兰地区雨水中溶质主要来源于自然过程的输入，人为活动输入可以忽略不计.