用于射频泄漏抑制的相位共轭电路设计

针对方向回溯天线中射频泄漏对相位共轭性能及波束指向性能影响的问题,提出了基于平衡结构的二次混频相位共轭结构,实现射频泄漏抑制。分析了传统相位共轭(phase-conjugating,PON)阵列中射频-中频(radio frequency-intermediate frequency,RF-IF)隔离度对相位共轭性能影响;并针对传统PON阵列射频泄漏抑制较差的问题,设计了基于平衡结构的阻性场效应管(field effect transistor,FET)混频电路来提高射频泄漏抑制指标和相位共轭性能;进一步设计了平衡型的二次混频相位共轭结构,利用跟踪锁相环和同相正交(in-phase/quadrature,IQ)调制结构促进RF-IF隔离。仿真结果表明,本文设计的平衡型二次混频相位共轭电路射频泄漏的抑制高于40 dB,且具有在射频输入功率低至-80 d Bm时,保持约4 dBm的稳定共轭信号输出。     

走出对领导者智商与情商的认识误区

当前人们对领导者智商和情商认识上有诸多错谬之处,通过对当前人们错误认识的分析,对于人们正确地理解领导者综合素质,提高领导能力具有一定的现实意义。     

Computing motif correlations in proteins

Protein motifs, which are specific regions and conserved regions, are found by comparing multiple protein sequences. These conserved regions in general play an important role in protein functions and protein folds, for example, for their binding properties or enzymatic activities. The aim here is to find the existence correlations of protein motifs. The knowledge of protein motif/domain sharing should be important in shedding new light on the biologic functions of proteins and offering a basis in analyzing the evolution in the human genome or other genomes. The protein sequences used here are obtained from the PIR-NREF database and the protein motifs are retrieved from the PROSITE database. We apply data mining approach to discover the occurrence correlations of motif in protein sequences. The correlation of motifs mined can be used in evolution analyses and protein structure prediction. We discuss the latter, i.e., protein structure prediction in this study. The correlations mined are stored and maintained in a database system. The database is now available at http://bioinfo.csie.ncu.edu.tw/ProMotif/.     

Effect of two broad-spectrum antibiotics on activity and stability of continuous nitrifying system

A 13 amino acid sequence, CRVARGDWNDNYC, originated from disintegrin eristostatin, was introduced into an inactive human proinsulin molecule between the B29 and A2 sites to replace proinsulin C-peptide by molecular cloning techniques. The constructed Arg-Gly-Asp (RGD)-proinsulin gene was cloned into a temperature-inducible vector pBV220 and expressed in Escherichia coli. The expressed RGD-proinsulin was refolded and purified by Sephadex G50 and DEAE-Sephadex A25 separations. The chemical identity was confirmed by both amino acid composition and mass spectrometry analyses. This RGD-proinsulin showed an inhibitory activity of adenosine 5′-diphosphate-induced human platelet aggregation with an IC₅₀ value of 200 nM. Its insulin receptor binding activity remained as low as 0.03% with native insulin as a control, and its insulin immune activity retained 27.6% compared with proinsulin.     

异亮氨酸拉链结构对可溶性CD40L生物学活性的影响

CD40配基(CD40L)为TNF超家族中的一员，瞬时表达于激活的CD4^ 的T淋巴细胞上．自然状态下膜上三聚体的CD40L通过和CD40受体(CD40R)结合，在免疫监视和肿瘤免疫中发挥作用．以PCR方法从peDNA3-CD40L质粒上扩增得到编码CD40L基因的胞外部分sCD40L，并将该片段插入大肠杆菌表达质粒pET30a上，构建得到大肠杆菌表达质粒pET30a-sCD40L；同时，在sCD40L的N端融合了异亮氨酸拉链(Isoleucine Zipper，IZ)结构，构建得到表达质粒pET30a-IZ-sCD40L．表达质粒在大肠杆菌中表达，得到可溶性的重组人CD40L和IZ-CD40L．SDS-PAGE分析结果表明重组人rhsCD40L和IZ-rhsCD40L在相应分子质量位置都有明显的条带产生，并得到Western blotting的确认．非SDS-PAGE电泳结果显示，异亮氨酸拉链结构有利于rhsCD40L蛋白形成聚合体结构．B细胞增殖实验和人骨髓瘤细胞株XG2凋亡实验结果都表明，异亮氨酸拉链结构提高了rhsCD40L的生物学活性．     

The co-crystal of iron(II) complex hydrate with hydroxybenzoic acid: [Fe(Phen)<Subscript>3</Subscript>]Cl(p-hydroxybenzoate).2(p-hydroxybenzoic acid).7H<Subscript>2</Subscript>O

Crystal of [Fe(Phen)₃]Cl(PHB).2(PHBH).7H₂O (1) is triclinic, space group P-1 with a = 12.0388(11) ?, b = 15.5286(14) ?, c = 15.7794(14) ?, α = 89.759(2)°, β = 75.818(2)°, γ = 71.900(2)° and Z = 2, (phen = phenanthroline, PHBH = p-hydroxybenzoic acid, PHB = p-hydroxybenzoate anion). The phen in adjacent Fe(phen)₃ ²⁺ cations are π–π interacted forming offset face to face (OFF) motifs. Juxtaposition of four phen ligands from two cations encapsulate an R₂ ²(8) dimeric unit of H-bonded PHBH molecules within a centrosymmetric box froming a filled aryl box motif (FAB). Alternation of OFF and FAB motifs form {OFF⋯FAB}∞ strands. The Fe(phen)₃ ²⁺ cation engages its phen ligands in π–π and/or CH–π interactions with two crystalographically different PHBH molecules and one PHB anion. Seven water molecules and a chloride anion per iron(II) trisphenanthroline cation fill empty spaces in the structure forming a hydrophilic cluster. Extensive intermolecular H-bond interactions occur between water molecules, chloride anions, PHBH molecules, and PHB anions. Thermal analysis of (1) was done under N_2(g). The TG, and dTG curves revealed the expected mass losses. All associated processes are endothermic as shown in the DSC curve.     

Hydrogen bonding patterns in bis(pyrimethamine hydrogen sulfate) monohydrate

The crystal structure of the compound bis [2,4-diamino-5-(p-chlorophenyl)-6-ethyl pyrimidinium hydrogen sulfate] monohydrate was studied by X-ray diffraction methods. The compound crystallises in orthorhombic system, space group P2₁2₁2₁, a=18.531(2) ?, b=16.190(2) ?, c=10.777(2) ?, V=3233.3(8), Z=4. The asymmetric unit shows the presence of two crystallographically independent pyrimethamine molecules, two hydrogen sulfate anions, and a water molecule. The hydrogen sulfate anions form a cyclic hydrogen bonded motif R₂ ²(8) with the 2-amino pyrimidine of the respective protonated pyrimethamine cations, through N–H···O hydrogen bonds. Thus the sulfate anions mimic the role of carboxylate anions observed in many aminopyrimidine-carboxylate interactions. This motif self assembles through DDAA array of quadruple hydrogen bonds, N–H···Cl, O–H···O and C–H···O hydrogen bonds.Supplementary material CCDC-293607 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 IEZ, UK; fax: C44 (0) 1223-336033; e-mail: deposit@ccdc.cam.ac.uk].     

参照零模型的符号社交网络理论研究

 结构平衡理论和地位理论是社交网络领域的重要理论,可以用来分析同时具有正向和负向连边的社交符号网络。提出了3种新的随机断边重连零模型,基于随机断边重连和符号随机置乱两大类零模型,对符号社交网络的地位理论和结构平衡理论进行了系统研究。发现基于零模型不但可以验证两种理论在实证网络中的准确性,还能揭示正边、负边拓扑结构和连边符号相关性对于整个网络性质的影响。提出了一个新框架,研究能否将有向符号网络转化为无向符号网络,发现目前常用的将有向符号网络转化成无向符号网络的方法在有些情况下对于研究社交网络理论是不合适的,存在着信息损失;讨论了非符号有向网络中的势能理论。     

一种基于透视变换的球面纹理映射方法

分析了传统的纹理映射方法在球面映射中的不足之处,提出了一种运用透视变换原理的纹理映射新方法,并实现了球表面的纹理映射,较好地解决了在球面两极处的走样问题,透视变换纹理映射方法还可应用到其它不可展曲面以及多面体表面映射同一纹理图案的问题