Lipids of sulfate-reducing bacteria and sulfur-oxidizing bacteria found in the Dongsheng uranium deposit

U-bearing sandstones from the Dongsheng deposit in Ordos Basin contain abundant C15-C18 fatty acids. The fatty acids may have been derived from modern and ancient organisms including organisms from the intervals of U mineralization. A certain amount of i15:0, a15:0, a17:0 fatty acids coexist with small amounts of i17:1ω7c and 10me16:0, characteristic biomarkers of Desulfovibrio and Desulfobacter sp., respectively. This indicates the existence of sulfate-reducing bacteria (SRB) in the sandstones. The presence of sulfur-oxidizing bacteria (SOB), such as Beggiatoa and Thioploca, is indicated by significant amounts of 16:1ω7c and 18:1ω7c fatty acids. The existence of the SRB in the deposit, as inferred from the fatty acids, is consistent with results from fossilized microorganisms and isotopic compositions of ore-stage pyrite. This suggests that the environment may have been favorable for the SRB to grow since ore formation (9.8-22 Ma). The bacteria may have degraded hydrocarbons directly, or indirectly utilized hydrocarbons degraded by oxic microbes in the deposits. This process may have produced 12C-rich calcite and prominent baseline humps of unresolved complex mixtures (UCM), and 25-demethylated hopanes and tricyclic terpanes. The existence of sulfur-oxidizing bacteria and sulfate-reducing bacteria in the deposit may have resulted in bacterial sulfate reduction to sulfide, re-oxidization of the sulfide to sulfate and subsequent reduction of the sulfate to sulfide. This assertion is supported by ore-stage pyrite with δ34S values as low as-39.2‰, and the lightest sulfate (about 11‰) measured during the Phanerozoic, a difference of more than 46‰.     

宋词创作观念矛盾与词文学美学体征的变化

作为一代文学之胜的宋词发展流变是一个充满矛盾同时也是充满了活力的进程:在审美观念上,虽然雅化潮流成为一种强势往前推进,但是,俗词的创作传播作为一种源于市井民间的活力涵养着词的生命肌体;理性上的拒斥与实践的热衷这一心理矛盾使宋词从政治教化的重负中逃逸出来,保持一种感性鲜活的审美品质;执着悲哀与超越悲哀两极的情感趋向冲撞对流衍化出宋词丰富多采的审美形态;在性别上,一种整合了双性特点的的抒情范式使宋词具有了更为隽永的滋味;文体上虽有尊体与破体之辩,但在创作实践中,词的破体而行却为词带来了多元多姿的审美风貌;风格上婉约与豪放的消长变化这组过去探讨的最多的矛盾则更多的和以上五组矛盾有着密切的关联。     

Guest Editorial： Special Issue on Parameterized Complexity

<正>Dedication.This Special Issue on Parameterized Complexity of Tsinghua Science and Technology is a tribute to the influential contributions of Jianer Chen to parameterized complexity algorithmics.It is an occasion to celebrate the many important contributions to this new and prospering branch of theoretical computer science made by Jianer Chen,as he reaches the ripe young age of 60.Happy birthday,Jianer,from     

对市场细分的新思考

在营销活动中，如何对市场进行有效的细分始终是值得我们重点研究的课题。文章针对企业市场细分过程中存在的两极分化的现象，提出了企业在细分市场时要配合运用市场泛化的策略，以达到有效细分市场的目的。     

利用CFD技术研究叶片斜度对贯流风机性能的影响

为了考察贯流风机多结构参数同时变化对其内部流场的影响,引出与多结构参数联系紧密的叶片斜度,文章利用CFD技术对不同叶片斜度的贯流风机进行非稳态数值模拟,考察流量系数、风机效率及总压系数的变化情况,并用焓差法风量实验验证模拟结果的正确性。结果表明,叶片斜度对风机性能影响显著,通过优化叶片斜度,可以使其流场内偏心涡移向蜗舌,进口段脱落涡减少,出口流速增大,风机性能得到提升。     

高等数学课程设置的多样化研究

由于专业和学生之间存在差异,在高等数学课程设置上必须实行多样化。具体说来,把高等数学的学习内容分为三个模块:基础模块、拓展模块(基地班)和应用模块,实践表明,这种多样化的高等数学课程设置取得了较好的教学效果。     

限定性范围副词的再分类及其与N(P)组合分析

通过语言事实的考察,对双音节限定性范围副词的再分类及其与名词或名词短语的组合问题进行分析和探讨,以揭示它们在句法功能上的共性与差异性。     

分散H∞低阶控制器在不确定电力系统中的应用

提出了一种新的方法为具有不确定性的实际电力系统设计分散鲁棒H∞阻尼控制器。采用多胞型模型将系统运行状态的各种变化描述为以若干个典型运行参数为顶点的凸集。分散H∞控制器的设计可以归结为基于同伦参数法的两个线性矩阵不等式的求解问题。所提的方法可以得出较低阶的鲁棒控制器，具有工程实用性。将其与系统模型降阶法相结合，可进一步减轻计算负担，进而适用于实际电力系统的控制器求解。算法分别用于SVC的分散附加阻尼控制器和19机IEEE标准测试系统的PSS设计。算例结果表明，分散控制器相互协调，不但显著地提升系统的阻尼比，使其具有良好的抗干扰能力，且对于严重故障后产生的持续振荡具有很好的抑制作用。     

Sequence similarity analysis of non-self CTL epitopes and mouse proteins using sequence alignment

This research analyzed amino acid sequence similarity between non-self T cell epitopes recognized by mouse antibodies and mouse proteins. Using sequence alignment,we found that only 8 of 1 108 epitopes are highly similar to mouse protein sequences. The result shows that non-self T cell epitopes are not similar or have little similarity to mouse protein sequences. Furthermore,reviewing the related literature,we also found that the eight epitopes would trigger immune responses in some particular environment,which are ignored by T cells in normal condition. The result suggests that no or low-similarity peptide vaccines can reduce the chance of collateral cross-reactions and enhance the antigen-specific immune response to vaccine.     

整体观与科学——中国传统思维整体观的现实意义

科学的发展使得机械论的整体观完全落伍,新的整体观正在兴起,从可分离分割的、整体是部分的结果的机械整体观转变为不可分离的、部分依赖整体才能存在的新整体观。这种整体观正是东方思维下的整体观。中国传统思维上的"天人合一"的整体观在科学中逐渐呈现出它的现实意义。