自密实混凝土重力坝浇筑层间稳定性分析研究

自密实混凝土重力坝是用流动性较强的混凝土在堆石之间填充并分层浇筑而成。为了研究浇筑层间的稳定性,采用刚体平衡原理和第三强度理论分别对自密实混凝土重力坝层间的抗滑稳定性和堆石间拉力情况进行了分析研究。结果表明：随着坝体层间堆石相对接触面积α的增大,层间抗滑稳定系数K逐渐增大,但是增加的幅度处在一个稳定的范围之内;随着堆石相对超出高度β的增大,堆石间的拉力逐渐增大,β=15%可以作为自密实混凝土重力坝设计的上限值;地震工况对于坝体层间抗滑稳定系数K和堆石间拉力大小的影响较大,该工况抗滑稳定系数K减小了15%以上,堆石间拉力最大增大约2 MPa。     

海中大桥水中超长灌注桩施工质量控制要点分析

随着国民经济和城市建设的发展,各种跨河跨海大桥越来越多,水中超长灌注桩施工工艺在桥梁施工中也越来越常见,该施工技术操作方便,具有很强的适应性。文章从海口市如意岛项目跨海大桥水中超长灌注桩钻孔平台搭设、钢护筒埋设、泥浆制备、钻孔施工、钢筋笼制作安装、水下混凝土灌注以及后压浆等几个关键环节中,探讨了水中超长灌注桩施工方法和质量控制要点,圆满解决了超长灌注桩施工中水流冲击影响、水中定位难、施工条件限制、钻孔施工倾斜度过大、桩底沉渣层过厚等技术问题,顺利完成了工程建设任务。     

OsMre11 Is Required for Mitosis during Rice Growth and Development

Meiotic recombination 11 (Mre11) is a relatively conserved nuclease in various species. Mre11 plays important roles in meiosis and DNA damage repair in yeast, humans and Arabidopsis, but little research has been done on mitotic DNA replication and repair in rice. Here, it was found that Mre11 was an extensively expressed gene among the various tissues and organs of rice, and loss-of-function of Mre11 resulted in severe defects of vegetative and reproductive growth, including dwarf plants, abnormally developed male and female gametes, and completely abortive seeds. The decreased number of cells in the apical meristem and the appearance of chromosomal fragments and bridges during the mitotic cell cycle in rice mre11 mutant roots revealed an essential role of OsMre11. Further research showed that DNA replication was suppressed, and a large number of DNA strand breaks occurred during the mitotic cell cycle of rice mre11 mutants. The expression of OsMre11 was up-regulated with the treatment of hydroxyurea and methyl methanesulfonate. Moreover, OsMre11 could form a complex with OsRad50 and OsNbs1, and they might function together in non-homologous end joining and homologous recombination repair pathways. These results indicated that OsMre11 plays vital roles in DNA replication and damage repair of the mitotic cell cycle, which ensure the development and fertility of rice by maintaining genome stability.     

Annexin 1 Is a Component of eATP-Induced Cytosolic Calcium Elevation in Arabidopsis thaliana Roots

Extracellular ATP (eATP) has long been established in animals as an important signalling molecule but this is less understood in plants. The identification of Arabidopsis thaliana DORN1 (Does Not Respond to Nucleotides) as the first plant eATP receptor has shown that it is fundamental to the elevation of cytosolic free Ca²⁺ ([Ca²⁺]_cyt) as a possible second messenger. eATP causes other downstream responses such as increase in reactive oxygen species (ROS) and nitric oxide, plus changes in gene expression. The plasma membrane Ca²⁺ influx channels involved in eATP-induced [Ca²⁺]_cyt increase remain unknown at the genetic level. Arabidopsis thaliana Annexin 1 has been found to mediate ROS-activated Ca²⁺ influx in root epidermis, consistent with its operating as a transport pathway. In this study, the loss of function Annexin 1 mutant was found to have impaired [Ca²⁺]_cyt elevation in roots in response to eATP or eADP. Additionally, this annexin was implicated in modulating eATP-induced intracellular ROS accumulation in roots as well as expression of eATP-responsive genes.     

Auxin and Root Gravitropism: Addressing Basic Cellular Processes by Exploiting a Defined Growth Response

Root architecture and growth are decisive for crop performance and yield, and thus a highly topical research field in plant sciences. The root system of the model plant Arabidopsis thaliana is the ideal system to obtain insights into fundamental key parameters and molecular players involved in underlying regulatory circuits of root growth, particularly in responses to environmental stimuli. Root gravitropism, directional growth along the gravity, in particular represents a highly sensitive readout, suitable to study adjustments in polar auxin transport and to identify molecular determinants involved. This review strives to summarize and give an overview into the function of PIN-FORMED auxin transport proteins, emphasizing on their sorting and polarity control. As there already is an abundance of information, the focus lies in integrating this wealth of information on mechanisms and pathways. This overview of a highly dynamic and complex field highlights recent developments in understanding the role of auxin in higher plants. Specifically, it exemplifies, how analysis of a single, defined growth response contributes to our understanding of basic cellular processes in general.     

分子筛辅助人参须根粉快速制备人参皂苷Rg5的工艺研究

利用多功能改进型索氏提取器为提取工具,以人参须根粉为原料,盐酸为催化剂,分子筛辅助下高效制备了稀有人参皂苷Rg5,并通过单因素实验优化了工艺条件。实验结果表明：当以30 mL的甲醇为溶剂、加入0.3 g 4 A分子筛、于65 ℃提取4 h时,人参总皂苷的提取率达到10.2%,稀有人参皂苷Rg5的得率达到3.20%,与传统索氏提取器相比可以显著提高人参皂苷Rg5的制备效率。分子筛辅助下利用多功能改进型索氏提取器从人参须根粉提取制备稀有人参皂苷Rg5,不仅得率较高,而且操作简单快捷,是一种快速制备人参皂苷Rg5的工艺方法。     

排桩式波浪能发电装置附近流场特性研究

基于雷诺时均Navier-Stokes方程和k?ω湍流模型,研究单排桩式振荡水柱式波浪能发电装置在规则波作用下的桩基附近流场特性. 通过物理模型实验验证所建数值波浪水槽的准确性. 模拟规则波作用下装置附近的流场特性,分析装置附近的涡特征以及其对装置附近泥沙冲刷情况的潜在影响. 结果表明,测试工况下,在桩式振荡水柱装置桩柱体的桩基附近观察到马蹄涡和尾涡现象,马蹄涡强度随着Keulegan–Carpenter（KC）数的增大而减小,尾涡强度随着KC数的增大而增大. 马蹄涡因强度过小,在模拟的KC数范围内不是装置桩基泥沙冲刷的主要因素,高强度的尾涡很可能成为装置桩基附近泥沙起动、输运和冲刷的重要影响因素.     

敞口管型桩压入对既有受荷桩基承载性状影响

基于经典桩侧摩阻力公式和圆孔扩张理论,优化考虑土压力系数、土塞增长率、扩孔塑性半径等问题,计算新增管桩的植入对在役桩承载性状的影响. 对比分析有限元的软件与理论计算结果,发现管型桩贯入引致的桩间土挤土效应,使在役桩侧摩阻力在一定深度范围内增加,且桩长越长、桩间距越小,贡献越明显. 新增桩与在役桩的距离小于3倍桩径,会形成局部群桩效应,使群桩协同工作时的桩顶沉降增加;距离大于6倍桩径,管型桩压入对既有桩侧摩阻力、群桩协同工作效应的影响较小.     

加芯搅拌桩芯桩定位限垂技术的研发与应用

为控制水泥土加芯搅拌桩的芯桩贯入质量,研发了一种基于芯桩定位导向架的定位限垂挑臂装置,并通过采用不同材质、不同尺寸的方法,反复摸索、实施,分析得出了芯桩定位导向架的定位限垂挑臂装置的最优方案。同时,通过运用数据比对、图表说明的方法,有效验证了加芯搅拌桩芯桩定位限垂挑臂装置对于现场施工的重要作用。在新疆地区23450 根加芯搅拌桩工程中进行首次应用,实践表明研发的定位限垂技术可有效控制芯桩贯入的定位和垂直度,提高施工效率。该定位限垂技术经济效益良好,可为今后新疆地区特殊软基处理以及加芯搅拌桩施工提供参考价值。     

电缆化配电系统高频谐振频移方法

为解决电缆化配电网高频谐振问题,提出了一种基于配电网阻抗重构的高频谐振频移方法。首先,分析了电缆化配电网高次谐波源与高频谐振的产生机理。其次,给出了电缆化配电网阻抗重构的高频谐振频移方法,并比较不同无源阻抗重构后的频移及谐振峰抑制效果。然后,结合实际工程案例,利用系统函数绘出伯德图与根轨迹评价该方法对高频谐振治理效果以及系统稳定性的影响,验证了基于电缆化配电网阻抗重构的高频谐振频移方法的有效性,最后研究了无源阻抗参数变化对配电网高频谐振的影响。