Emodin inhibits tumor cell migration through suppression of the phosphatidylinositol 3-kinase-Cdc42/Rac1 pathway

Enhanced cell migration is one of the underlying mechanisms in cancer invasion and metastasis. Therefore, inhibition of cell migration is considered to be an effective strategy for prevention of cancer metastasis. We found that emodin (3-methyl-1,6,8-trihydroxyanthraquinone), an active component from the rhizome of Rheum palmatum, significantly inhibited epidermal growth factor (EGF)- induced migration in various human cancer cell lines. In the search for the underlying molecular mechanisms, we demonstrated that phosphatidylinositol 3-kinase (PI3K) serves as the molecular target for emodin. In addition, emodin markedly suppressed EGF-induced activation of Cdc42 and Rac1 and the corresponding cytoskeleton changes. Moreover, emodin, but not LY294002, was able to block cell migration in cells transfected with constitutively active (CA)-Cdc42 and CA-Rac1 by interference with the formation of Cdc42/Rac1 and the p21-activated kinase complex. Taken together, data from this study suggest that emodin inhibits human cancer cell migration by suppressing the PI3K-Cdc42/Rac1 signaling pathway.Received 7 February 2005; received after revision 11 March 2005; accepted 18 March 2005     

A model of calcium signaling and degranulation dynamics induced by laser irradiation in mast cells

Recent experiments show that calcium signaling and degranulation dynamics induced by low power laser irradiation in mast cells must rely on extracellular Ca^2＋ influx. An analytical expression of Ca^2＋ flux through TRPV4 cation channel in response to interaction of laser photon energy and extracellular Ca^2＋ is deduced, and a model characterizing dynamics of calcium signaling and degranulation activated by laser irradiation in mast cells is established. The model indicates that the characteristics of calcium signaling and degranulation dynamics are determined by interaction between laser photon energy and Ca^2＋ influx. Extracellular Ca^2＋ concentration is so high that even small photon energy can activate mast cells, thus avoiding the possible injury caused by laser irradiation with shorter wavelengths. The model predicts that there exists a narrow parameter domain of photon energy and extracellular Ca^2＋ concentration of which results in cytosolic Ca^2＋ limit cycle oscillations, and shows that PKC activity is in direct proportion to the frequency of Ca^2＋ oscillations. With the model it is found that sustained and stable maximum plateau of cytosolic Ca^2＋ concentration can get optimal degranulation rate. Furthermore, the idea of introducing the realistic physical energy into model is applicable to modeling other physical signal transduction systems.     

基于等离子体的GTS模型气动减阻研究

为探究等离子体对类厢式货车的气动减阻效果,以GTS模型为研究对象,采用数值仿真的方法,分别研究了当来流风速为20 m/s时,3个位置处等离子体布置角度、激励电压对GTS模型的气动减阻效果并分析其减阻机理,然后进行组合工况的分析.研究结果表明,等离子体是通过诱导近壁面气体定向流动使流动分离点后移、推迟流动的分离,从而减小GTS模型前后压差阻力、降低整车气动阻力系数,等离子体布置的位置在流动分离点后方并且靠近流动分离点.单个位置激励时,等离子体布置在GTS尾部两侧时气动减阻效果最好,最大减阻率为5.09%;组合工况时最大减阻率可达6.01%.当来流风速一定时,等离子体存在最佳布置角度与激励电压.     

Real time observation of the photocleavage of single DNA molecules

A method for real time observation of photo-cleavage of stratched λDNA at single molecular level by a fluorescent microscope coupled with CCD is developed.DNA molecules stained with YOYO-1 are stretched by the mo-lecular combing technique and fixed on a modified slide.Then the Process of Photocleavage and relaxation of DNA under radiation of blue light is observed.We speculate that the conformation change of stretched DNA and the effect of water are likely to facilitate the effect of YOYO photocleav-age DNA molecules.The photocleavage effect of YOYO for stretched DNA may be useful to study DNA elasticity,cancer research as well as the interaction between DNA and dyes.     

Removal of NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> by radical injection

Removal of NOx(DeNOx, NOx is the total of NO and NO2) from flue gas by radical injection has been investigated .the discharge characteristics were examined and the steady streamer corona was acquired hy adjusting the nozzle gases properly. It was Found that an increase in the voltage resulted in a decrease in the NO concentration and the concentration of the NO2 increased at tow voltages but decreased as the voltage rose to a certain level. The DeNOx efficiency increased as the applied voltage rose and reached a maximum of 70% when the voltage approached the breakdown voltage. The hypothetical mechanism of NOx removal suggested that the radicals formed in the discharge process converted the NO and NO2 into acidic species. The Monte Carlo method was used to calculate the rate coefficients and the productivity of the radicals, and then the concentrations of both NO and NO2 and the DeNOx effielencies were calculated with chemical kinetics. The calculated DeNOx efficiencies were coalparable with the experimental DeNOx efficiencies at low voltages, but were lower at high voltages.     

旅游数字足迹研究：热点与展望

在疫情蔓延、经济下行的背景下,开展旅游数字足迹研究,分析预测旅游消费行为,是推进旅游消费发展、推动国际国内经济"双循环"的重要基础工作.作为旅游信息化领域的新兴话题,旅游数字足迹是游客在通讯网络、互联网和物联网等泛在网络上留下的海量电子痕迹,真实反映了游客选择偏好和深层次的行为规律.国内外学者对这方面的研究已取得一定成果,但仍处于探索阶段.鉴于此,本研究辨析了旅游数字足迹的定义、类型和相关概念,阐明了旅游数字足迹的数据来源、特征和应用,分析了旅游数字足迹在游客人口特征、游客人格预测和游客行为分析领域的热点问题.最后,从理论体系构建、数据来源和预测方法精度等问题出发,对旅游数字足迹领域未来的研究方向进行了展望,为持续激发旅游消费潜力、推动旅游消费规模增长提供理论参考.     

土工带加筋垫层中筋带应力的研究

对玻塑土工带加筋垫层中筋带应力的发挥进行研究。设计了8种不同筋带布置的加筋垫层并进行载荷试验,测得各种加筋垫层地基的变形曲线、极限承载力及极限平衡时垫层内筋带的应力值。对数据进行分析后发现,筋带应力的大小是影响加筋垫层力学性质的决定因素。筋带应力的发挥与筋带布置参数首层加筋距、加筋距、加筋密度、加筋层数等有很大的关系。对加筋垫层的作用原理进行理论分析后,提出使筋带应力充分发挥的筋带布置方案。     

一种提高检测效率的V-detector优化算法的设计

实值阴性选择算法V-detector在产生检测器时不能确保检测器具有较大的覆盖范围,其结果是检测器集合中的检测器数量过多,检测效率较低。为提高检测效率,提出了V-detector优化算法,一方面,通过合理确定检测器的中心点位置及检测半径,扩展了检测器的覆盖范围;另一方面,优化算法采用假设检验的判定方法判断检测器集合对非自体空间的覆盖率。假设检验融合到检测器集合的生成进程中,在确保检测器集合满足覆盖率要求的条件下,减少了检测器集合中的检测器数量。实验结果表明,与原算法相比,优化算法使检测器集合中检测器的数量大幅度下降,检测效率得到提高。     

模式集成代数

在全局模式多数据库系统中模式集成是一个非常重要的问题·为解决面向对象多数据库系统的模式集成,提出了一套集成代数,主要包括５类集成操作:合并操作类,相交操作类,聚合操作类,概括操作类和特化操作类·它们对其他类型的多数据库系统的模式集成也具有一定的普遍意义·     

基于压缩感知的实时在线目标追踪

在正负样本区域随机抽取了不同尺度下图像的局部二值模式(LBP)特征,将高维的特征信息投射到低秩的压缩域,并据此建立了表观模型.使用一个随机稀疏测量矩阵来压缩前景和背景目标.将追踪问题转化成为了一个使用朴素贝叶斯分类器的二元分类问题.所提方法可以较快速、实时地在线追踪目标,同时解决了目标尺度变化、遮挡问题.