Structural insight into brassinosteroid perception by BRI1

Brassinosteroids are essential phytohormones that have crucial roles in plant growth and development. Perception of brassinosteroids requires an active complex of BRASSINOSTEROID-INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED KINASE 1 (BAK1). Recognized by the extracellular leucine-rich repeat (LRR) domain of BRI1, brassinosteroids induce a phosphorylation-mediated cascade to regulate gene expression. Here we present the crystal structures of BRI1(LRR) in free and brassinolide-bound forms. BRI1(LRR) exists as a monomer in crystals and solution independent of brassinolide. It comprises a helical solenoid structure that accommodates a separate insertion domain at its concave surface. Sandwiched between them, brassinolide binds to a hydrophobicity-dominating surface groove on BRI1(LRR). Brassinolide recognition by BRI1(LRR) is through an induced-fit mechanism involving stabilization of two interdomain loops that creates a pronounced non-polar surface groove for the hormone binding. Together, our results define the molecular mechanisms by which BRI1 recognizes brassinosteroids and provide insight into brassinosteroid-induced BRI1 activation.     

弹性地基上加热圆板的非线性轴对称自由振动

基于von Karman薄板理论和Hamilton原理,运用假设时间模态法,得到了弹性地基上加热圆板非线性轴对称自由振动的常微分控制方程.考虑不可移简支边界条件,采用打靶法得到了一阶屈曲位形下的前3阶振型的数值结果.结果表明:随地基弹性系数增加,热屈曲临界温度增加;在小振幅的情形下,振型对屈曲构型的影响和地基系数对振型...     

胡卢巴种质资源RAPD遗传多样性分析

在优化随机引物扩增多态性DNA标记（RAPD）反应体系和条件的基础上,利用筛选的多态性引物分析了胡卢巴种质资源的遗传多样性．结果表明,19条RAPD引物显示了40份胡卢巴种质资源的遗传距离为0．02～0．70,来源上变幅从大到小为：宁夏和国外种质间、国外种质间、宁夏种质间、国内其他省份种质间．40份胡卢巴种质资源分为两类,即Ⅰ类包括3份国外种质;Ⅱ类包括37份种质,可大体上分为宁夏、国内其他省份和国外种质3个亚类．     

两株丝状真菌N3、N9的分类鉴定

从一酸奶样品中分离到两株丝状真菌N3、N9,通过形态学观察、ITS序列测定及其系统发育分析,初步确定了N3、N9菌株的分类地位以及与其近缘种之间的生物系统学关系.实验结果表明N3、N9菌株在PDA培养基上形成典型绒状茵落,菌丝体上具有担子茵所特有的锁状联合结构.ITS序列测定及系统发育分析表明N3菌株与灰白侧耳(Pleurotus spodoleucus)同源性最高,N9菌株与佛罗里达侧耳(Pleurotus floridanus)同源性最高.     

蔗渣浆纤维模塑装饰建筑材料的制备与性能

以天然蔗渣浆纤维为原料,利用模塑热压工艺复合成形,得到物理性能优良的纤维模塑装饰建筑材料.借助拉伸性能测试、热重分析、FT-IR等研究了影响该材料力学性能的因素.研究表明:该材料的拉伸性能主要受增强剂和阻燃剂添加量,干燥温度、时间和压力的影响;随着阻燃剂添加量的增加,材料的拉伸性能明显降低;最佳干燥温度为160℃,干燥...     

The effect of nanohybrid materials on the pour-point and viscosity depressing of waxy crude oil

The pipeline transportation of waxy crude oil is a problem both at home and abroad.In this paper,a novel nanohybrid pour-point depressant (PPD) was used to decrease the pour point and viscosity of waxy crude oil.The pour point and apparent viscosity of waxy crude oil was decreased significantly upon addition of the nanohybrid PPD,and the long-term stability of the nanohybrid PPD was superior to that of a conventional ethylene-vinyl acetate copolymer PPD.Polarized optical microscopy and X-ray diffraction were used to study the effect of the nanohybrid PPD on the crystallization of crude oil.Addition of the nanohybrid PPD reduced the amount of wax crystals,prevented their aggregation,and reduced the temperature at which the crude oil started to crystallize.The significant effect of this nanohybrid PPD on the pour point and viscosity depressing of crude oil is of great importance for facilitating the safe,efficient and energy-minimized transportation of waxy crude oil.     

基于MAS/GIS技术的车辆指挥中心及其实现

随着通信技术的发展,车辆的实时监控已经成为十分重要的研究课题。介绍了一个基于CIS／MAS／无线通信的车辆实时监控系统的整体解决方案．并讨论了基于该方案实现的指挥中心软件体系、功能及其实现原理。     

Banach空间二阶非线性脉冲积分微分方程边值问题解的存在性

利用Darbo不动点定理．讨论了二阶非线性脉冲积分微分方程的边值问题,在较弱的条件下得到广解的存在性。     

Effects of Hydrophilic Monomer Types and Level on Polystyrene-Acrylate/montmorillonite Nanocomposite Made by Emulsion Polymerization

1 Results Nanocomposite has attracted more and more interest all over the world.Polystyrene (PS) is a commercialized and mass-productive polymer,continuous research efforts have been devoted to the development of polystyrene/montmorillonite (PS/MMT) nanocomposites[1-2].But the polarity of styrene (St) is too small to intercalate the space between the clay layers.The polarity of hydrophilic monomer is so strong that it can intercalate the MMT easily,the intercalated smectic clays maybe exfoliated by usin...     

船舶浅水航行下沉量数值计算

为求解船舶航行中的下沉量,采用NURBS技术对船体进行曲面重构,并应用基于Rankine源格林函数的一阶面元法构造数学模型,然后结合两者得出船舶下沉量的计算方法.以标准船型KCS为例进行验证,计算值与实验值的最大和最小相对误差分别为-10.32％和-1.84％,与实验情况基本相符,说明该算法具有可行性.