Construction of Plant Expression Vector of the proBA Gene from Bacillus subtilis Mutant and Analysis of the Salt Tolerance of Transgenic Arabidopsis thaliana

从枯草芽孢杆菌(Bacillussubtilis)抗脯氨酸结构类似物突变株中克隆得到脯氨酸合成途径中的关键酶基因proB(编码γ-谷氨酰胺激酶)和proA(编码谷氨酰胺-γ-半醛脱氢酶),同时设计引物从拟南芥基因组中扩增得到吡咯啉-5-羧酸合成酶B基因(p5csB)的第一个内含子序列,将其分别与proB和proA基因通过PCR拼接后,酶切连接构建得到植物双元表达载体pBI121pro。以LBA4404为介导,采用真空抽滤的方法转化得到转proBA基因拟南芥;第三代的纯合子(T3)通过半巢式PCR的方法验证外源基因已整合到拟南芥基因组中,GUS活性分析表明外源基因在叶片中表达最强,茎部其次,根部最弱;对600mmol.L-1致死浓度NaCl耐受能力的分析表明,转基因拟南芥的平均存活时间(37.8min)明显高于野生型拟南芥(26min)。The genes proB and proA encoding the two enzymes, -GK (-glutamyl kinase) and -GSADH (Glu-5-semialdehyde dehydrogenase), were amplified from the Bacillus subtilis mutant to the proline analogue.The first intron of p5csB gene was also retrieved from Arabidopsis thaliana and linked with proB and proA respectively through PCR. After the endonuclease digestion and fragment ligation, the recombinant plant binary expression vector (pBI121pro) was obtained. The transformation of Arabidopsis thaliana was mediated by Agrobacterium tumfaciens LBA4404 by using the vacuum infiltration method. Half nested PCR was performed to verify the insertion of exotic genes into the genome of T3 homozygous plants. GUS activity assay indicated that the exotic genes were expressed most highly in the leaves, secondly in the stems and least in the roots. The analysis of tolerance to the deadly salt concentration (600 mmolL~(-1) NaCl) showed that the average survival time of transgenic plants (37.8 min) was obviously higher than that of wild type controls (26 min). In this research, the key gene proBA involved in the proline biosynthesis of highly salt-tolerant microorganism were cloned, and after removal of the feedback inhibition, it was, for the first time, transferred into the model plant Arabidopsis thaliana,which is of highly theoretical and practical significance.教育部十五“211”项目和武汉大学科技创新项目资助

Effect of droplet impact on molten pool dynamics in hybrid laser-MIG welding of aluminum alloy

In order to investigate the effect of droplet impact on molten pool dynamics in hybrid laser-MIG (metal inert gas) welding, a three-dimensional mathematical model was developed, and a new approach to simulate the droplet impact was proposed. In the model, the droplet heat and impact under the influence of laser was considered, and the deformation of molten pool was calculated with considering droplet impact and arc pressure. To simplify the model, a modified body heat source model was presented for laser source to take into account multiple reflections and Fresnel absorption. Surface tension, electromagnetic force, and buoyancy were considered to calculate the fluid flow pattern. Furthermore, several dimensionless numbers were used to recognize the importance of the driving forces in molten pool. It was found that molten pool dynamics and final weld bead geometry were strongly affected by the droplet impact. To demonstrate the importance of droplet impact, the temperature, velocity distribution, and the deformation of molten pool were analyzed and compared under different conditions. With considering droplet impact, the penetration was bigger, and the width was smaller. Furthermore, the simulated weld bead geometry was in good agreement with experimental measurement

铝合金激光-MIG复合焊焊缝力学性能研究

对高铁车身用6N01铝合金进行激光-MIG复合焊接实验,并对焊缝力学性能进行了研究.测定了从焊缝区至热影响区及母材的硬度变化,得到了焊缝的抗拉强度及拉伸曲线,拟合出了疲劳寿命趋势线,而且观测了断口形貌并测定了断口成分

纯镍与304不锈钢激光异种焊接的工艺及其接头的组织性能

采用高密度Nd：YAG固态连续激光器对N6纯镍和304奥氏体不锈钢进行了焊接工艺实验,探究了激光功率和离焦量对焊缝成形的影响。对接头进行了拉伸强度和硬度的测试,并结合光学显微镜（OM）、扫描电镜（SEM）、能谱分析仪（EDS）等手段分析了接头的微观组织。结果表明：N6纯镍一侧热影响区晶粒长大明显,焊缝区靠近两侧熔合线附近为向焊缝中心区域生长的柱状晶,焊缝中心区域存在细小的胞晶区域;N6热影响区的显微硬度最低,焊缝的显微硬度介于N6镍母材和304不锈钢母材之间;接头拉伸断裂位置在焊缝区,抗拉强度达到N6纯镍母材的90%以上,可以满足实际情况下的使用要求。拉伸断口表现为准解理断裂

Comparative study of hybrid laser-MIG leading configuration on porosity in aluminum alloy bead-on-plate welding

Laser-metal inert gas (MIG) welding is a promising welding technology, which presents many attractive properties. However, porosity still remains a serious problem in laser-MIG welding of aluminum. In this experimental study, the effect of leading configuration on porosity formation and distribution in laser-MIG bead-on-plate welding of A7N01 alloy was investigated. Experiments on arc current, welding speed, and arc configuration were performed comparatively for two leading configurations, respectively. The welds were analyzed with X-ray photographs and cross-section observations. Pores in laser-MIG-welded samples were mainly keyhole-induced. The concept of porosity area fraction was used to evaluate the severity of pore defect. The maximum porosity area fraction presented at different arc currents in the two leading configurations (in laser leading welding, it is 150 A, while in arc leading welding, it is 110 A). With welding speed increasing, porosity area fraction decreased. Bubble escape condition was deduced and used to discuss the probable mechanism of the effect of leading configuration on pore formation. The results showed that leading configuration was considerable in porosity minimization and prevention

植物模式标本的考证与数字化:以中国国家植物标本馆为例

模式标本是最重要的植物标本,是确定植物学名的依据,是植物分类学家从事植物系统分类研究必不可少的科学材料,也是开展专科专属研究、编写国家或地方植物志、进行植物区系调查研究、开发利用和保护植物资源的重要基本资料。但模式标本的人为和自然毁损难以避免,模式标本及其标签信息的数字化使得模式标本的形态、地理分布、采集等主要信息得到最大限度的永久保存,可以极大地方便模式标本信息的共享,可以为科学研究人员或相关人员提供植物形态、地理分布、历史变迁等多方面的信息。本文以中国科学院植物研究所国家植物标本馆维管束植物模式标本数字化建设为例,详细介绍了规范化整理模式标本的方法、模式标本数字化的操作流程,并通过大量实例介绍了模式标本考订的过程、常见问题的处理方法等,以期为其他单位开展模式标本数字化建设提供经验

用于生命之树重建的数据集

由中国科学院计算机网络信息中心、中国科学院植物研究所、深圳市中国科学院仙湖植物园"三方两地"共同合作研究建设的"达尔文树"——分子数据分析应用环境(DarwinTree——Molecular Data Analysis and Application Environment),从中国陆地植物发育系统框架的研究出发,逐步推动解决生命之树构建过程中存在的技术难题,探索利用基因和基因组信息构建生命之树的策略和方法,研究和开发DNA序列信息自动采集和生命之树自动生成技术(Automatic Reconstruction of The Tree of Life),建立生命之树信息平台及其利用体系,为最终在我国建立具有国际影响的,能很好地兼容物种分类、地理分布、形态性状、化石信息以及DNA信息的物种库(Species Bank)创造条件。DarwinTree旨在为科研人员提供数据和分析并举的工作平台,该平台将承担数据汇集和面向实际科研工作应用的双重作用。本文发布的数据集包括:(1)DarwinTree基础数据集:来自国际公共序列数据的标记处理得到的分子标记数据及其与任意阶元物种分类名称对应的统计数据集;(2)DarwinTree自测序数据集:面向中国陆地植物研究的补充测序序列数据;(3)DarwinTree中国维管植物进化数据集:已构建的中国维管植物属系统发育树的数据(Generic tree of Chinese vascular plants)