基于OBB层次结构碰撞检测的改进算法

方向包围盒（Oriented bounding box：OBB）的构造以及包围盒的相交测试的计算量都比较大,严重影响了在模拟、仿真的应用,尤其是有变形物体的场景。引入近似凸包的思想提出一种快速构造方向包围盒算法,很大程度上减少了构造方向包围盒（0BB）层次结构的顶点数,改进后的算法在降低构造层次结构时间的同时,对方向包围盒的紧密性代价几乎没有影响,在有些时候还提高了包围盒的紧密性。在包围盒相交测试方面,提留了一种基于筒单羽以爱的相交须刿方击,该算法在检测过程中省去了大量包围盒的相交测试计算,提高了相交测试的速度。最后将两种改进算法联合的碰撞检测框架与常用的基于均值和协方差矩阵的包围盒构造和基于分裂轴的算法进行比较,证明了算法具有高效性。     

茉莉酸受体多功能纳米探针的合成与应用

将巯基丙酸修饰的CdTe量子点和植物激素茉莉酸通过一步法偶联到表面修饰氨基的Fe3O4纳米颗粒表面,合成了一种同时具有荧光信号、磁响应性能和特异性标记植物原生质体中茉莉酸受体的多功能磁性荧光纳米探针. 荧光光谱测试表明该探针保持了CdTe量子点荧光性能,具有荧光强度高,适用体系的pH范围宽,抗光漂白性能好等优点. 磁响应及磁滞回线测试充分说明该探针具有良好的超顺磁性. 使用该探针对绿豆原生质体中茉莉酸受体进行成像,结果表明,该探针对茉莉酸受体具有选择性标记的功能,茉莉酸受体主要存在于原生质体膜上. 该标记方法简单方便,能为茉莉酸信号转导研究提供可视化的信息.     

Catalysis of protein folding by prolyl isomerase

Rates of protein folding reactions vary considerably. Some denatured proteins regain the native conformation within milliseconds or seconds, whereas others refold very slowly in the time range of minutes or hours. Varying folding rates are observed not only for different proteins, but can also be detected for single polypeptide species. This originates from the co-existence of fast- and slow-folding forms of the unfolded protein, which regain the native state with different rates. The proline hypothesis provides a plausible explanation for this heterogeneity. It assumes that the slow-folding molecules possess non-native isomers of peptide bonds between proline and another residue, and that crucial steps in the refolding of the slow-folding molecules are limited in rate by the slow reisomerization of such incorrect proline peptide bonds. Recently the enzyme peptidyl-prolyl cis-trans isomerase (PPIase) was discovered and purified from pig kidney. It catalyses efficiently the cis in equilibrium trans isomerization of proline imidic peptide bonds in oligopeptides. Here we show that it also catalyses slow steps in the refolding of a number of proteins of which fast- and slow-folding species have been observed and where it was suggested that proline isomerization was involved in slow refolding. The efficiency of catalysis depends on the accessibility for the isomerase of the particular proline peptide bonds in the refolding protein chain.     

Glioma cell activation by Alzheimer's peptide Abeta1-42, alpha1-antichymotrypsin,and their mixture

We compared the effects ofAlzheimer's peptide (Abeta1-42), a,-antichymotrypsin (ACT) and an ACT/Abeta1-42 mixture on human glioma DK-MG cells. The solution of Abeta (5 microM) formed by 2-h incubation at room temperature induced tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 levels by 55 and 45%, respectively, and increased gelatinase B activity by 67%, while exposure of cells to the ACT/Abeta1-42 mixture (1:10 molar ratio ACT: Abeta1-42) under the same experimental conditions showed no effect on IL-6 levels or gelatinase B activity, but strongly induced TNF-alpha (by 190%), compared to the controls. Stimulation of the cells with Abeta1-42 alone, but not with ACT, increased by about 20% low-density lipoprotein (LDL) uptake and mRNA levels for LDL receptor and HMG-CoA reductase, while the ACT/Abeta1-42 mixture significantly increased LDL uptake (by 50%), up-regulated mRNA levels for LDL receptor and HMG-CoA reductase by 48 and 63%, respectively, and increased lipid accumulation by about 20-fold. These data suggest a possible new role for Abeta in Alzheimer's disease through its interaction with the inflammatory reactant, ACT.     

The origin of spontaneous activity in the developing auditory system

Spontaneous activity in the developing auditory system is required for neuronal survival as well as the refinement and maintenance of tonotopic maps in the brain. However, the mechanisms responsible for initiating auditory nerve firing in the absence of sound have not been determined. Here we show that supporting cells in the developing rat cochlea spontaneously release ATP, which causes nearby inner hair cells to depolarize and release glutamate, triggering discrete bursts of action potentials in primary auditory neurons. This endogenous, ATP-mediated signalling synchronizes the output of neighbouring inner hair cells, which may help refine tonotopic maps in the brain. Spontaneous ATP-dependent signalling rapidly subsides after the onset of hearing, thereby preventing this experience-independent activity from interfering with accurate encoding of sound. These data indicate that supporting cells in the organ of Corti initiate electrical activity in auditory nerves before hearing, pointing to an essential role for peripheral, non-sensory cells in the development of central auditory pathways.     

Structural parts involved in activation and inactivation of the sodium channel

Structure-function relationships of the sodium channel expressed in Xenopus oocytes have been investigated by the combined use of site-directed mutagenesis and patch-clamp recording. This study provides evidence that the positive charges in segment S4 are involved in the voltage-sensing mechanism for activation of the channel and that the region between repeats III and IV is important for its inactivation.     

引黄工程中的3个地面泵站主厂房钢屋架工程

山西省万家寨引黄工程3个地面泵站主厂房屋架均采用螺栓球钢屋架制作，文章就钢屋架工程的制作施工过程做了较为详尽的介绍。     

Superconductivity at 43 K in SmFeAsO1-xFx

Since the discovery of high-transition-temperature (high-T(c)) superconductivity in layered copper oxides, extensive effort has been devoted to exploring the origins of this phenomenon. A T(c) higher than 40 K (about the theoretical maximum predicted from Bardeen-Cooper-Schrieffer theory), however, has been obtained only in the copper oxide superconductors. The highest reported value for non-copper-oxide bulk superconductivity is T(c) = 39 K in MgB(2) (ref. 2). The layered rare-earth metal oxypnictides LnOFeAs (where Ln is La-Nd, Sm and Gd) are now attracting attention following the discovery of superconductivity at 26 K in the iron-based LaO(1-x)F(x)FeAs (ref. 3). Here we report the discovery of bulk superconductivity in the related compound SmFeAsO(1-x)F(x), which has a ZrCuSiAs-type structure. Resistivity and magnetization measurements reveal a transition temperature as high as 43 K. This provides a new material base for studying the origin of high-temperature superconductivity.