Genome evolution in yeasts

Identifying the mechanisms of eukaryotic genome evolution by comparative genomics is often complicated by the multiplicity of events that have taken place throughout the history of individual lineages, leaving only distorted and superimposed traces in the genome of each living organism. The hemiascomycete yeasts, with their compact genomes, similar lifestyle and distinct sexual and physiological properties, provide a unique opportunity to explore such mechanisms. We present here the complete, assembled genome sequences of four yeast species, selected to represent a broad evolutionary range within a single eukaryotic phylum, that after analysis proved to be molecularly as diverse as the entire phylum of chordates. A total of approximately 24,200 novel genes were identified, the translation products of which were classified together with Saccharomyces cerevisiae proteins into about 4,700 families, forming the basis for interspecific comparisons. Analysis of chromosome maps and genome redundancies reveal that the different yeast lineages have evolved through a marked interplay between several distinct molecular mechanisms, including tandem gene repeat formation, segmental duplication, a massive genome duplication and extensive gene loss.     

云南酵母菌的研究Ⅱ:白马雪山自然保护区的酵母菌

 从云南滇西北德钦县的白马雪山自然保护区的不同基物分离到酵母菌224株,经分类鉴定为8属,其中的裂芽酵母属为我国新记录.文中报道了该地区酵母菌的类群和分布以及优势属.     

国立西北工学院工程教育课程体系的演化

目的全面审视抗战时期国立西北工学院与其工程教育的课程体系,为近代中国科学教育史研究提供新线索。方法原始期刊文献分析和考证。结果 1938年,西北工学院在筹建之初,已设有土木、电机、化学、纺织、机械、矿冶6个系,后又增设水利工程和航空工程两个系,开设了投影几何、立体几何、工程数学、应用天文学、应用力学、材料力学、热机学、平面测量、大地测量、地质实习、电工学、河工实验、房屋建筑、污水工程、工程契约与规范等成系统的工程教育课程,并在矿冶、土木、水利、机械等方面尽力结合西北工业实践。结论其课程体系的成熟和完善,迅速提升了西北科学教育的总体水平,标志着西北工程教育体系之形成,从而加快了西方科学教育在中国西北本土化以及整个西北科学教育现代化的进程。     

利用复杂网络来研究tRNA序列的进化

根据点突变和互补复制的进化机制构建tRNA序列相似度平行网络和反平行网络并研究了网络的特征．分析发现当相似度很大时，tRNA基因网络出现了无标度（scale—free）的特征．其次，还比较了平行网络和反平行网络的特征，发现在相同的条件下，反平行网络中的tRNA序列间的关系比平行网络中更密切，它们之间的相似程度更高．这同时说明现代tRNA序列由互补复制机制进化的可能性更大．最后根据点突变和互补复制的进化机制建立了一个粗糙的tRNA进化模型．结果发现模型tRNA相似度网络在0．3≤ε≤0．5条件下，不仅和真实tRNA相似度网络有局部的相似行为，而且网络的整体行为也是相似的．因此现代tRNA序列的合理的进化机制应该是上述两种机制的混合．     

利用复杂网络来研究tRNA序列的进化

根据点突变和互补复制的进化机制构建tRNA序列相似度平行网络和反平行网络并研究了网络的特征.分析发现当相似度很大时,tRNA基因网络出现了无标度(scale-free)的特征.其次,还比较了平行网络和反平行网络的特征,发现在相同的条件下,反平行网络中的tRNA序列间的关系比平行网络中更密切,它们之间的相似程度更高.这同时说明现代tRNA 序列由互补复制机制进化的可能性更大.最后根据点突变和互补复制的进化机制建立了一个粗糙的tRNA进化模型.结果发现模型tRNA相似度网络在0.3≤ξ≤0.5条件下,不仅和真实tRNA相似度网络有局部的相似行为,而且网络的整体行为也是相似的.因此现代tRNA序列的合理的进化机制应该是上述两种机制的混合.     

Application of chemical fractionation and X-ray powder diffraction to study phosphorus speciation in sediments from Lake Hongfeng,China

Based on the techniques of sequential extraction and X-ray powder diffraction (XRD), the distribution characteristics of phosphorus speciation were investigated in 13 sediment samples from Lake Hongfeng, an important drinking water source for Guiyang with a typical karstic limestone environment. The total phosphorus (TP) concentrations in the sediments ranged from 973.36 to 2334.18 mg/kg with a mean concentration of 1635.87 mg/kg (dry weight), and it was evident that the phosphorus level in the sediments was high compared with other eutrophic lakes such as Lake Chaohu and Lake Xihu. The results of the two methods, sequential extraction and XRD, demonstrated the presence of different phosphorus species in the lake sediments. Being compatible with local geophysical characteristics, the results of sequential extraction techniques indicate that the average percentages of dissolved phosphorus (DP), aluminum-bound phosphorus (Al-P), iron-bound phosphorus (Fe-P), calcium-bound phosphorus (Ca-P) and organic phosphorus (OP) in the sediments were 0.40%, 7.06%, 5.07%, 45.48% and 38.49%, respectively. Notably, the concentrations of inorganic phosphorus (IP) were higher than those of OP, and the IP consisted primarily of Ca-P. The high concentrations of Ca-P may temporarily control the release of phosphorus from the sediments because it is a relatively stable, inert and non-bioavailable phosphorus fraction. The results of XRD analysis indicated that, among phosphorus species, AlPO₄ was found in all sediment samples at relatively high concentrations. Moreover, the TP concentrations in the sediments were high; thus the release potential and bioavailability of phosphorus in the sediments was important. Further statistical analyses of the results revealed significant correlations between phosphorus species in the sediments with two extractable principal components and four selectable cluster levels allowing interpretation of possible origins of phosphorus loading and transformation mechanisms of phosphorus species. Furthermore, available remediation measures were briefly assessed for the lake while considering its distinct environmental features.     

Accelerated speciation in colour-polymorphic birds

Colour polymorphism exemplifies extreme morphological diversity within populations. It is taxonomically widespread but generally rare. Theory suggests that where colour polymorphism does occur, processes generating and maintaining it can promote speciation but the generality of this claim is unclear. Here we confirm, using species-level molecular phylogenies for five families of non-passerine birds, that colour polymorphism is associated with accelerated speciation rates in the three groups in which polymorphism is most prevalent. In all five groups, colour polymorphism is lost at a significantly greater rate than it is gained. Thus, the general rarity and phylogenetic dispersion of colour polymorphism is accounted for by a combination of higher speciation rate and higher transition rate from polymorphism to monomorphism, consistent with theoretical models where speciation is driven by fixation of one or more morphs. This is corroborated by evidence from a species-level molecular phylogeny of passerines, incorporating 4,128 (66.5%) extant species, that polymorphic species tend to be younger than monomorphic species. Our results provide empirical support for the general proposition, dating from classical evolutionary theory, that colour polymorphism can increase speciation rates.     

岩土工程中的系统工程问题

讨论了系统工程的特点，分析了岩土工程的学科系统是由多个学科组成，并且相互交叉和融合，具有系统工程的整体性，层次性，相关性，动态性等典型特点，提出了岩土工程的研究方法，即应用系统工程的原理和方法进行研究，是岩土工程研究的最好方法。以三峡工程永久船闸陡高边坡为例，讨论了岩土工程的学科系统，研究内容，研究步骤，得出了几点结论。     

Evidence for ecology's role in speciation

A principal challenge in testing the role of natural selection in speciation is to connect the build-up of reproductive isolation between populations to divergence of ecologically important traits. Demonstrations of 'parallel speciation', or assortative mating by selective environment, link ecology and isolation, but the phenotypic traits mediating isolation have not been confirmed. Here we show that the parallel build-up of mating incompatibilities between stickleback populations can be largely accounted for by assortative mating based on one trait, body size, which evolves predictably according to environment. In addition to documenting the influence of body size on reproductive isolation for stickleback populations spread across the Northern Hemisphere, we have confirmed its importance through a new experimental manipulation. Together, these results suggest that speciation may arise largely as a by-product of ecological differences and divergent selection on a small number of phenotypic traits.     

中风患者口腔念珠菌负荷的研究

目的:研究不同时期中风患者口腔念珠菌的负荷变化。方法:采用舌印记法和漱口水法收集43位中风患者在急性期、出院期及出院后半年的口腔微生物样本进行培养分析。结果:急性期中风患者口腔念珠菌负荷明显增高。急性期中风患者口腔念珠菌负荷明显高于出院及出院后半年中风患者口腔念珠菌负荷(P0.05)。伴随刷牙困难及佩带活动义齿的中风患者的口腔念珠菌负荷较高(P0.05)。结论:中风患者口腔念珠菌负荷与不同时期中风患者的身体功能的水平有密切的联系。     

化工原理教学中突出工程思维的培养

化工原理是一门实践性、工程性很强的应用课程。教学实践中应注重培养学生的工程思维、工程意识、分析工程问题、解决工程问题的能力。本文从工程研究方法的角度探讨对学生工程思维的培养问题。     

化工原理教学中学生工程技术能力的培养

化工原理是培养化工类学生工程技术能力的主要课程,本文总结化工原理的教学实践经验,对如何做好该课程的教学工作,提高学生的工程技术观进行了初步的探讨.     

初论工科研究生工程技术研究能力的培养

根据科学技术发展的历史和现状，论证了工程技术在国民经济发展中的重要作用；通过分析国外理工院校研究生的培养现状和我国经济建设对人才的需求，提出了以培养工程技术研究能力为重点的工科研究生培养目标以及相应的若干措施。     

Rapid evolution in response to high-temperature selection

Temperature is an important environmental factor affecting all organisms, and there is ample evidence from comparative physiology that species and even conspecific populations can adapt genetically to different temperature regimes. But the effect of these adaptations on fitness and the rapidity of their evolution is unknown, as is the extent to which they depend on pre-existing genetic variation rather than new mutations. We have begun a study of the evolutionary adaptation of Escherichia coli to different temperature regimes, taking advantage of the large population sizes and short generation times in experiments on this bacterial species. We report significant improvement in temperature-specific fitness of lines maintained at 42 degrees C for 200 generations (about one month). These changes in fitness are due to selection on de novo mutations and show that some biological systems can evolve rapidly in response to changes in environmental factors such as temperature.     

Host shift to an invasive plant triggers rapid animal hybrid speciation

Speciation in animals is almost always envisioned as the split of an existing lineage into an ancestral and a derived species. An alternative speciation route is homoploid hybrid speciation in which two ancestral taxa give rise to a third, derived, species by hybridization without a change in chromosome number. Although theoretically possible it has been regarded as rare and hence of little importance in animals. On the basis of molecular and chromosomal evidence, hybridization is the best explanation for the origin of a handful of extant diploid bisexual animal taxa. Here we report the first case in which hybridization between two host-specific animals (tephritid fruitflies) is clearly associated with the shift to a new resource. Such a hybrid host shift presents an ecologically robust scenario for animal hybrid speciation because it offers a potential mechanism for reproductive isolation through differential adaptation to a new ecological niche. The necessary conditions for this mechanism of speciation are common in parasitic animals, which represent much of animal diversity. The frequency of homoploid hybrid speciation in animals may therefore be higher than previously assumed.