Marrow mesenchymal stem cells transduced with TPO/FL genes as support for ex vivo expansion of hematopoietic stem/progenitor cells

A new marrow-derived mesenchymal stem cell (hMSC) line that could support expansion of hematopoietic stem/progenitor cells (HSPCs) was developed. Primary hMSCs were infected with retrovirus containing Flt-3 ligand and thrombopoietin genes. CD34+ cells from cord blood were expanded with primary hMSCs or transduced hMSCs. The expansion of total nucleated cells, CD34+ cells and mixed colonies containing erythroid and myeloid cells and megakaryocytes for 2 weeks coculture with transduced hMSCs was remarkably increased. The outputs of long-term culture-initiating cells for 2 and 4 weeks coculture with transduced hMSCs were also largely increased. The expansion rates of HSPCs with transduced hMSCs were unchanged for 6 weeks. In contrast, the expansion rates of HSPCs with primary hMSCs declined drastically through 6 weeks. SCID-repopulating cell expansion with transduced hMSCs for 4 weeks was significantly higher than that of uncultured CD34+ cells and HSPCs expanded with primary hMSCs. Received 21 June 2005; received after revision 30 July 2005; accepted 24 August 2005     

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     

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.     

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。     

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.     

基于动态搜索区域的无线传感器网络小世界特性构建方案

为了减少无线传感器网络节点的能量消耗,以延长无线传感器网络的寿命,首先研究了如何通过在无线传感器网络中构建小世界特性以延长其网络寿命,并着重分析了DAS( directed angulation towards the sink)方案.然后针对DAS方案中临近sink节点区域内的节点能量过快消耗的问题,提出了一种在无线传感器网络中构建小世界特性的新方案——菱形区域方案.该方案根据sensor节点到sink节点距离的大小,动态地改变菱形捷径端点搜索区域的大小,达到构建小世界特性并增强网络抗毁性的目的.理论证明了菱形区域方案在一定条件下较DAS方案既节省能量又能延长网络的寿命.     

采用离散元方法评价集料的骨架结构

为了从细观结构角度深入研究骨架型沥青混合料集料的受力特征,在离散元程序PFC3D内,采用多球相互重叠的方法描述粗集料颗粒的三维不规则形状,并建立了考虑级配特征的集料混合物生成方法.按照集料粒径由大到小的顺序,在PFC3D中对各档集料进行了虚拟的逐级填充,并定量分析了各粒径集料对逐级填充后混合物中集料间隙率、集料之间的接触点数量、接触力等参数的影响.结果表明:集料混合物中,较粗集料受到的接触力大于较细集料;在较粗集料的混合物中,加入大于2.36 mm的较细集料有助于增加集料混合物的接触点数量,降低较粗集料所承担的接触力;粒径4.75 ～9.50 mm集料对接触点数量的增加最为显著;4.75 mm是骨架型沥青混合料的关键粒径.     

Buck型DC-DC变换器中单输入模糊控制器的设计与实现

提出了一种简化的用于数字控制DC-DC变换器的模糊控制算法——单输入模糊控制算法.通过在算法中引入符号距离法,将常规模糊控制算法中的2个输入简化为单个输入,从而使相应的模糊规则条数明显减少.在此基础上,采用FPGA设计了单输入模糊控制器,并进行了系统验证.测试结果表明,在输入电压为2.7～3.5V、输出电压为0.8～1.5V的Buck型DC-DC开关变换器中,系统的建立时间小于150 ms,稳态误差小于10 mV.与常规模糊控制器相比,这种单输入模糊控制器具有设计、调节和硬件实现简单等优势,因而有望在数字控制DC-DC变换器中得到广泛应用.     

Experimental study on multi-point autoignition characteristics and influence factors of diesel spray in a controllable active thermo-atmosphere

Auto-ignition characteristics of high-pressure diesel spray in the controllable active thermo-atmos-phere (CATA) were studied with a high-speed camera video system. Multi-point autoignition phe-nomenon of diesel spray in the CATA was observed and the influence factors of the autoignition were analyzed. The stabilization mechanisms of the spray flame in different coflow temperatures were also discussed. The stabilization of the flames was controlled by different factors: autoignition phenomenon in low coflow temperature and flame spread in high coflow temperature. The test results also show that the autoignition delay depends strongly on the coflow temperature and has nonlinear relationship with the temperature. Autoignition delay decreases by almost 10 ms from 16.9 to 7.1 ms when the coflow temperature increases from 996 to 1048 K and only 4 ms from 1048 to 1101 K. The injection parameters in terms of nozzle diameter, injection pressure and pump speed, have some effects on autoignition delay while these effects depend on the coflow temperature. The significant effect lies in low coflow temperature. The injection parameters influence the autoignition delay because it can shorten the physical delay by improving the spray quality and enlarging the spray angle or penetration rate to im-prove mixture quality.