Unrestricted expression of the Drosophila gene patched allows a normal segment polarity.

In the Drosophila embryo, mutations in the segment polarity gene patched (ptc) cause the replacement of the middle region of each segment by a mirror-image duplication of the remaining structures, including the parasegmental border. This gene, which encodes a transmembrane protein, is initially expressed in a generalized way at blastoderm, but later stops being transcribed in cells expressing the engrailed gene, and even later in cells in the middle of the parasegment. The genes engrailed (en) and wingless (wg) are also segment-polarity genes, and they are expressed in adjacent stripes flanking the parasegment borders in the embryo; in ptc mutants wg expression extends anteriorly and an ectopic stripe of en expression is induced. The suggestion has been made that ptc must be transcribed in a specific subset of cells to prevent en expression anterior to the wg-expressing stripe. Here we report that unrestricted expression of ptc from a heat-shock promoter has no adverse effect on development of Drosophila embryos. The heat-shock construct can also rescue ptc mutants, restoring wg expression to its normal narrow stripe. The ectopic en stripe fails to appear, but the normal one remains unaffected. The results imply that, despite its localized requirement, the restricted expression of ptc does not itself allocate positional information.     

Clathrin is a key regulator of basolateral polarity

Clathrin-coated vesicles are vehicles for intracellular trafficking in all nucleated cells, from yeasts to humans. Many studies have demonstrated their essential roles in endocytosis and cellular signalling processes at the plasma membrane. By contrast, very few of their non-endocytic trafficking roles are known, the best characterized being the transport of hydrolases from the Golgi complex to the lysosome. Here we show that clathrin is required for polarity of the basolateral plasma membrane proteins in the epithelial cell line MDCK. Clathrin knockdown depolarized most basolateral proteins, by interfering with their biosynthetic delivery and recycling, but did not affect the polarity of apical proteins. Quantitative live imaging showed that chronic and acute clathrin knockdown selectively slowed down the exit of basolateral proteins from the Golgi complex, and promoted their mis-sorting into apical carrier vesicles. Our results demonstrate a broad requirement for clathrin in basolateral protein trafficking in epithelial cells.     

稳健估计在水准网数据处理中的应用

探讨在观测值含有粗差的情况下,采用稳健估计的方法,分析稳健估计对粗差的抵抗能力,并在此基础上设计稳健估计程序,通过实例对比分析说明稳健估计方法的优越性.     

Field experiment on a robust hierarchical metropolitan quantum cryptography network

A hierarchical metropolitan quantum cryptography network upon the inner-city commercial telecom fiber cables is reported in this paper. The seven-user network contains a four-node backbone net with one node acting as the subnet gateway, a two-user subnet and a single-fiber access link, which is realized by the Faraday-Michelson interferometer set-ups. The techniques of the quantum router, optical switch and trusted relay are assembled here to guarantee the feasibility and expandability of the quantum cryptography network. Five nodes of the network are located in the government departments and the secure keys generated by the quantum key distribution network are utilized to encrypt the instant video, sound, text messages and confidential files transmitting between these bureaus. The whole implementation including the hierarchical quantum cryptographic communication network links and the corresponding application software shows a big step toward the practical user-oriented network with a high security level.     

计算机网络监控管理系统的故障管理模块设计

以实时故障管理为切入点.初步实现了通信网统一的故障管理方式.通过对通信网监控系统故障管理模块的设计, 提出了通信网监控系统故障管理的需求,得出了实现真正的综合网络管理的标准化方法.同时, 本文还分析和研究了故障管理模块的工作原理,分析了故障管理的一般步骤.在对故障管理模块软件实现的基础上, 使用网络分析仪对故障管理模块的工作进行了分析和验证, 证明了方案的可行性.     

CS8900A网络接口模块的设计

随着嵌入式系统和网络技术的飞速发展,在网络上实现数据传输已经变成嵌入式系统研究中一个非常重要的组成部分。CS8900A是Cirrus Logic公司生产的16位以太网控制芯片,文章介绍了该芯片的主要功能特性和工作原理,并结合实际项目简要阐述了如何利用CS8900A通过硬件设计及软件设计实现嵌入式系统的网络互连。     

基于流体网络模块的模块化建模方法

热力系统图形化建模是电站仿真领域中的前沿课题。该文针对热力系统的特点，并考虑实时仿真的要求，进一步完善了流体网络模块的概念，使之物理概念和数学独立性更完整。由此系统地提出了一个基于流体网络模块的模块化建模方法。该方法面向对象的概念更完整，模块划分及连接方法更简单、统一。所介绍的模块化建模方法已在为韩国三星重工（ＳＨＩ）开发的图形建模系统ＧＮＥＴ中得到验证。     

构建园区网健壮体系的比较研究

提出了构建园区网健壮体系的模型,比较和讨论当前运用于园区网主要的安全技术、服务质量(QOS)策略和实际应用技巧,并给出了目前备受困扰的ARP欺骗的解决方法和P2P(端到端)流量控制解决方法,最后设计了一个构建园区网健壮体系的具体方案.     

大型多协议服务器的优化网络调度模块设计

针对多服务器中协议过多,没有形成统一调度方式,传统的网络调度模块存在延迟与冲突的问题。提出一种用于多协议服务器的网络调度模块设计方法。研究了多协议服务器的特征,详细论述了该网络调度模块硬件和软件设计过程,针对多协议造成的网络调度模型发生混乱的问题,运用一种分层约束方法,对不同的底层协议进行分析。实现不同协议服务器的前端测试设备参数约束 ,再引入一种数据融合方法对多协议服务器外扩FLASH、SRAM、SDRAM存储器芯片和网络控制芯片DM8168进行融合,保证调度的一致性.系统测试结果表明:该模块可以较好的完成多协议服务器的任务调度,网络模块的吞吐量与传统的调度方法提高了13%,模块延迟与冲突下降了5%     

基于轻量化卷积神经网络的改进模型与验证

卷积神经网络随着深度和结果复杂度的不断增加,其参数量和计算量大大制约了它的应用场景,本文在SueezeNet网络结构基础上引用分组卷积并采用Channel-shuffel来解决分组卷积后的信息不流通问题。以减少原有网络结构的的参数量提高网络运行效率。在ORL数据集的验证表现也表明,在网络参数减少的情况下分类精度和收敛效率并不会有降低甚至略有提高。可以体现分组卷积在结构轻量化上的有效性。     

A protein with several possible membrane-spanning domains encoded by the Drosophila segment polarity gene patched

The patterning of cells in insect segments requires the exchange of information between cells, which in Drosophila depends on the activity of members of the segment-polarity class of genes. Here we report the molecular characterization of one such gene, patched. We find that patched encodes a large protein with several possible membrane-spanning domains and is expressed in a complex pattern during embryogenesis.     

基于图论的青海公路网鲁棒性研究

针对青海公路的实际情况构建了基于图论的青海公路网,提出了重要节点、重要路段的评估方法并确定了重要节点、重要路段TOP10。对重要节点和路段分别进行了蓄意攻击仿真实验,并随机选取相同数量的节点和路段进行了随机攻击仿真实验,对比结果验证了评估方法的有效性,由此得出了增强整个路网鲁棒性的方法。     

Regulation of segment polarity genes in the Drosophila blastoderm by fushi tarazu and even skipped

During the late cellular blastoderm stage of Drosophila embryo-genesis the segmentation genes engrailed, en, and wingless, wg, become expressed in two series of 14 stripes which will subsequently coincide with the anterior and posterior limits of each parasegment. Previous studies have shown that the establishment of the pattern of en stripes depends upon the activity of the homoeobox-containing pair-rule genes fushi tarazu, ftz and even skipped, eve. Here we show that these two genes also control the spatial expression of wg. Whereas ftz and eve behave as activators of en we find that both genes are required to repress wg expression, so that wg becomes expressed only in the narrow stripes of cells which come to separate the ftz and eve bands at the end of the blastoderm stage. In contrast, we propose that the precise positioning of the en stripes depends upon signals generated in a combinatorial manner by the overlaps between the ftz or eve domains and those of other pair rule genes, specifically odd paired, opa and paired, prd.     

RecBCD enzyme is a DNA helicase with fast and slow motors of opposite polarity

Helicases are molecular motors that move along and unwind double-stranded nucleic acids. RecBCD enzyme is a complex helicase and nuclease, essential for the major pathway of homologous recombination and DNA repair in Escherichia coli. It has sets of helicase motifs in both RecB and RecD, two of its three subunits. This rapid, highly processive enzyme unwinds DNA in an unusual manner: the 5'-ended strand forms a long single-stranded tail, whereas the 3'-ended strand forms an ever-growing single-stranded loop and short single-stranded tail. Here we show by electron microscopy of individual molecules that RecD is a fast helicase acting on the 5'-ended strand and RecB is a slow helicase acting on the 3'-ended strand on which the single-stranded loop accumulates. Mutational inactivation of the helicase domain in RecB or in RecD, or removal of the RecD subunit, altered the rates of unwinding or the types of structure produced, or both. This dual-helicase mechanism explains how the looped recombination intermediates are generated and may serve as a general model for highly processive travelling machines with two active motors, such as other helicases and kinesins.     

基于鲁棒神经网络的水下机器人运动控制

针对水下机器人神经网络控制中系统响应速度慢及对噪声较敏感的问题,依据变结构控制理论,提出了一种基于鲁棒神经网络的水下机器人控制方法E利用指数趋近律,推导出神经网络参数的镇定算法,并采用标准误差反向传播(EBP)算法最小化目标函数,最后在水下综合探测机器人仿真平台上进行了试验研究E试验结果表明,该控制方法对神经网络学习率的改变和外界扰动有很强的鲁棒性,大大降低了机器人机械传动系统的磨损,且能够保证神经网络快速、稳定地学习,从而满足实时性控制的要求,具有较高的理论和实用价值.     

缓解中断风险的应急供应链网络鲁棒优化

突发事件造成供应链环境的不确定,节点企业普遍暴露在风险下,任一节点失效会导致整个供应链服务水平降低。文章主要研究供应链网络中断风险下的鲁棒优化设计,将应急策略融入供应链网络设计中,建立了基于多场景、多时段、单一产品的鲁棒混合整数规划模型。通过算例对模型的有效性进行验证,探讨了决策者的风险态度和可变性权重对供应链网络设计的影响。文章从鲁棒性的角度研究中断供应链,为兼具效益和风险的供应链网络设计提供了一种有效的方法。     

一种具有可靠性的IPv6主动网络的动态主机配置模式

针对IPv6主动网络管理复杂、参数配置繁琐的特点,提出一种具有可靠性的IPv6主动网络动态主机配置模式,可实现对接入网络的主动节点以及从一个子网移动到另一个子网的主动节点网络参数的自动配置.     

PTK7/CCK-4 is a novel regulator of planar cell polarity in vertebrates

In addition to the apical-basal polarity pathway operating in epithelial cells, a planar cell polarity (PCP) pathway establishes polarity within the plane of epithelial tissues and is conserved from Drosophila to mammals. In Drosophila, a 'core' group of PCP genes including frizzled (fz), flamingo/starry night, dishevelled (dsh), Van Gogh/strabismus and prickle, function to regulate wing hair, bristle and ommatidial polarity. In vertebrates, the PCP pathway regulates convergent extension movements and neural tube closure, as well as the orientation of stereociliary bundles of sensory hair cells in the inner ear. Here we show that a mutation in the mouse protein tyrosine kinase 7 (PTK7) gene, which encodes an evolutionarily conserved transmembrane protein with tyrosine kinase homology, disrupts neural tube closure and stereociliary bundle orientation, and shows genetic interactions with a mutation in the mouse Van Gogh homologue vangl2. We also show that PTK7 is dynamically localized during hair cell polarization, and that the Xenopus homologue of PTK7 is required for neural convergent extension and neural tube closure. These results identify PTK7 as a novel regulator of PCP in vertebrates.     

Drosophila Stardust is a partner of Crumbs in the control of epithelial cell polarity.

The polarized architecture of epithelial cells depends on the highly stereotypic distribution of cellular junctions and other membrane-associated protein complexes. In epithelial cells of the Drosophila embryo, three distinct domains subdivide the lateral plasma membrane. The most apical one comprises the subapical complex (SAC). It is followed by the zonula adherens (ZA) and, further basally, by the septate junction. A core component of the SAC is the transmembrane protein Crumbs, the cytoplasmic domain of which recruits the PDZ-protein Discs Lost into the complex. Cells lacking crumbs or the functionally related gene stardust fail to organize a continuous ZA and to maintain cell polarity. Here we show that stardust provides an essential component of the SAC. Stardust proteins colocalize with Crumbs and bind to the carboxy-terminal amino acids of its cytoplasmic tail. We introduce two different Stardust proteins here: one MAGUK protein, characterized by a PDZ domain, an SH3 domain and a guanylate kinase domain; and a second isoform comprising only the guanylate kinase domain. The Stardust proteins represent versatile candidates as structural and possibly regulatory constituents of the SAC, a crucial element in the control of epithelial cell polarity.