MPLS在虚拟专用网中的应用

首先阐述了虚拟专用网（VPN）和多协议标记交换（MPLS）技术的概念，又描述了MPLS协议在虚拟专用网建设中的应用。主要就MPLS技术应用于虚拟专用网的优势、MPLSVPN的网络结构、内部机制、工作过程及其完全性做了论述。     

利用DTMF技术实现电力线载波通信

介绍一种基于DTMF编码的电力线载波系统，该系统由双音频（DTMF）编译码芯片HT9200和MT8870、模拟乘法器MC1496和电力线耦合器组成。通过对系统组成原理的介绍，详细论述了系统的设计过程以及为了保证其通信的可靠性而采取的干扰和软件纠错措施。试验证明，该系统充分发挥了DTMF的优良性，是一套低成本的电力线载波数据通信系统。     

鳜传染性脾肾坏死病毒ICR489基因序列分析

报道了鳜鱼传染性脾肾坏死病毒 (ISKNV)的ICR489基因结构及其序列分析。对ISKNVDNAKpnⅠB酶切片段的序列分析结果发现该序列中含有完整的ICR489基因。ISKNVICR489基因完整读码框为 10 11bp ,GC含量为 5 6 97% ,等电点为 6 82 ,编码一个长为 337aa、相对分子质量为 382 70的推定蛋白。结构分析发现该基因起始密码子上游具有启动子元件TATAbox,有反向重复序列可形成茎环 ,并有一段回文序列。ISKNV与其它 3种虹彩病毒 (FV3、RRV和LCDV_1)的ICR489基因氨基酸序列具有一定的同源性 ,但ISKNV与它们的同源性不高 ,序列比较和系统树分析发现ISKNV与蛙病毒属和淋巴囊肿病毒属的病毒都不尽相同     

Production of insulin-like growth factor I (IGF-I) and IGF-binding proteins by rat intestinal stromal cells in vitro

To determine if intestinal stromal cells secrete diffusible factors such as insulin-like growth factors (IGFs) capable of regulating epithelial cell growth in vitro, stromal cells were isolated by enzymatic digestion of rat intestine. Incorporation of [³H]thymidine into DNA and [¹⁴C]leucine into protein of IEC-6 cells, a model intestinal epithelial cell line, was significantly increased (two- to threefold) when the IEC-6 cells were co-cultured with stromal cells, relative to IEC-6 cells grown alone. Medium conditioned by stromal cells stimulated DNA synthesis of IEC-6 cells in a dose-dependent manner. Analysis of the conditioned medium revealed that intestinal stromal cells secreted IGF-I, but little IGF-II, in addition to an M _r 32,000 IGF-binding protein (IGFBP-2) and an IGFBP having M _r∼ 24,000. We conclude that rat intestinal stromal cells secrete one or more diffusible factors, which may include IGF-I and IGFBPs, capable of stimulating proliferation of IEC-6 cells in vitro. Received 25 August 1997; received after revision 7 November 1997; accepted 20 November 1997     

煤基炭材料用作锂离子电池负极

以煤为前驱体，经700－1000℃炭化制得煤基炭材料，用X射线衍射和恒电流法研究了炭材料微晶结构的变化以及放电性能。研究发现，随着热处理温度的增加，煤基炭材料的微晶结构逐渐变得规整，首次放电容量下降。     

Complex zeolite structure solved by combining powder diffraction and electron microscopy

Many industrially important materials, ranging from ceramics to catalysts to pharmaceuticals, are polycrystalline and cannot be grown as single crystals. This means that non-conventional methods of structure analysis must be applied to obtain the structural information that is fundamental to the understanding of the properties of these materials. Electron microscopy might appear to be a natural approach, but only relatively simple structures have been solved by this route. Powder diffraction is another obvious option, but the overlap of reflections with similar diffraction angles causes an ambiguity in the relative intensities of those reflections. Various ways of overcoming or circumventing this problem have been developed, and several of these involve incorporating chemical information into the structure determination process. For complex zeolite structures, the FOCUS algorithm has proved to be effective. Because it operates in both real and reciprocal space, phase information obtained from high-resolution transmission electron microscopy images can be incorporated directly into this algorithm in a simple way. Here we show that by doing so, the complexity limit can be extended much further. The power of this approach has been demonstrated with the solution of the structure of the zeolite TNU-9 (|H9.3|[Al9.3Si182.7O384]; ref. 10) with 24 topologically distinct (Si,Al) atoms and 52 such O atoms. For comparison, ITQ-22 (ref. 11), the most complex zeolite known to date, has 16 topologically distinct (Si,Ge) atoms.     

基于符合变量运算的状态空间方程离散化

针对MATLAB控制系统工具箱中模型转换命令，不能对带符合变量连续状态空间方程进行离散化，提出借助符合数学工具箱中有关符合对象函数构成M文件，自动完成此过程，该方法与常规方法所得结果比较，两者完全一致，证明此方法的正确性和实用性。     

Dissecting the architecture of a quantitative trait locus in yeast

Most phenotypic diversity in natural populations is characterized by differences in degree rather than in kind. Identification of the actual genes underlying these quantitative traits has proved difficult. As a result, little is known about their genetic architecture. The failures are thought to be due to the different contributions of many underlying genes to the phenotype and the ability of different combinations of genes and environmental factors to produce similar phenotypes. This study combined genome-wide mapping and a new genetic technique named reciprocal-hemizygosity analysis to achieve the complete dissection of a quantitative trait locus (QTL) in Saccharomyces cerevisiae. A QTL architecture was uncovered that was more complex than expected. Functional linkages both in cis and in trans were found between three tightly linked quantitative trait genes that are neither necessary nor sufficient in isolation. This arrangement of alleles explains heterosis (hybrid vigour), the increased fitness of the heterozygote compared with homozygotes. It also demonstrates a deficiency in current approaches to QTL dissection with implications extending to traits in other organisms, including human genetic diseases.     

Exome sequencing identifies recurrent somatic RAC1 mutations in melanoma

We characterized the mutational landscape of melanoma, the form of skin cancer with the highest mortality rate, by sequencing the exomes of 147 melanomas. Sun-exposed melanomas had markedly more ultraviolet (UV)-like C>T somatic mutations compared to sun-shielded acral, mucosal and uveal melanomas. Among the newly identified cancer genes was PPP6C, encoding a serine/threonine phosphatase, which harbored mutations that clustered in the active site in 12% of sun-exposed melanomas, exclusively in tumors with mutations in BRAF or NRAS. Notably, we identified a recurrent UV-signature, an activating mutation in RAC1 in 9.2% of sun-exposed melanomas. This activating mutation, the third most frequent in our cohort of sun-exposed melanoma after those of BRAF and NRAS, changes Pro29 to serine (RAC1(P29S)) in the highly conserved switch I domain. Crystal structures, and biochemical and functional studies of RAC1(P29S) showed that the alteration releases the conformational restraint conferred by the conserved proline, causes an increased binding of the protein to downstream effectors, and promotes melanocyte proliferation and migration. These findings raise the possibility that pharmacological inhibition of downstream effectors of RAC1 signaling could be of therapeutic benefit.     

基于符号对象函数的状态反馈调节系统的CAD

针对MATLAB控制系统工具箱中极点配置函数 ,不能完成状态反馈调节系统计算问题 ,提出借助符号数学工具箱中有关符号对象函数 ,构成M文件 ,自动完成设计过程。该方法计算结果与仿真结果比较 ,两者完全一致 ,证明此方法的正确性和实用性