Structure of the detoxification catalyst mercuric ion reductase from Bacillus sp. strain RC607

Several hundred million tons of toxic mercurials are dispersed in the biosphere. Microbes can detoxify organo-mercurials and mercury salts through sequential action of two enzymes, organomercury lyase and mercuric ion reductase (MerA). The latter, a homodimer with homology to the FAD-dependent disulphide oxidoreductases, catalyses the reaction NADPH + Hg(II)----NADP+ + H+ + Hg(0), one of the very rare enzymic reactions with metal substrates. Human glutathione reductase serves as a reference molecule for FAD-dependent disulphide reductases and between its primary structure and that of MerA from Tn501 (Pseudomonas), Tn21 (Shigella), p1258 (Staphylococcus) and Bacillus, 25-30% of the residues have been conserved. All MerAs have a C-terminal extension about 15 residues long but have very varied N termini. Although the enzyme from Streptomyces lividans has no addition, from Pseudomonas aeruginosa Tn501 and Bacillus sp. strain RC607 it has one and two copies respectively of a domain of 80-85 residues, highly homologous to MerP, the periplasmic component of proteins encoded by the mer operon. These domains can be proteolytically cleaved off without changing the catalytic efficiency. We report here the crystal structure of MerA from the Gram-positive bacterium Bacillus sp. strain RC607. Analysis of its complexes with nicotinamide dinucleotide substrates and the inhibitor Cd(II) reveals how limited structural changes enable an enzyme to accept as substrate what used to be a dangerous inhibitor. Knowledge of the mode of mercury ligation is a prerequisite for understanding this unique detoxification mechanism.     

渣油加氢微膨胀床反应器中的气液流动状态及床层膨胀率

在常温常压下用模拟渣油和模拟氢气近似模拟了微膨胀床渣油加氢处理反应器内的气液流动状态,考察了催化剂粒径和堆密度、虚拟气液流速以及催化剂装填高度对催化剂床层膨胀率的影响。实验结果表明:大粒径、低堆密度的催化剂床层膨胀率较高;虚拟气速与床层膨胀率关系曲线上存在拐点,拐点值随催化剂装填高度增加而增大;虚拟液体流速对催化剂床层膨胀率影响较小;在工业操作条件下,微膨胀床渣油加氢处理反应器的催化剂床层膨胀率小于10%;催化剂装填高度对床层膨胀率有明显的影响,催化剂装填量较大时,需要采用较高的气油比才能保证催化剂床层处于微膨胀状态。     

货车整车质量辨识方法研究

针对货车整车质量辨识问题,分别对基于车辆纵向动力学和基于运动学的两种整车质量辨别方法进行仿真和实车试验研究。阐述了两种整车质量辨识方法的原理,在TruckSim软件平台上建立车辆模型并在多种工况下基于这两种方法进行仿真分析。根据仿真结果进行实车试验,提出了一种车速冗余计算和加速度计算的方法,利用带时变遗忘因子的递推最小二乘法（RLS）对实车质量进行估计。研究结果表明,所提出的车速冗余计算方法和加速度计算方法准确有效,同时减少换挡次数能够显著提高辨识算法的收敛速度。相比于运动学整车质量辨识算法,基于车辆纵向动力学整车质量辨识算法能够有效地估计货车整车质量,鲁棒性好,估计准确,收敛速度快,具有很好的工程应用价值。     

Programming the magnitude and persistence of antibody responses with innate immunity

Many successful vaccines induce persistent antibody responses that can last a lifetime. The mechanisms by which they do so remain unclear, but emerging evidence indicates that they activate dendritic cells via Toll-like receptors (TLRs). For example, the yellow fever vaccine YF-17D, one of the most successful empiric vaccines ever developed, activates dendritic cells via multiple TLRs to stimulate proinflammatory cytokines. Triggering specific combinations of TLRs in dendritic cells can induce synergistic production of cytokines, which results in enhanced T-cell responses, but its impact on antibody responses remain unknown. Learning the critical parameters of innate immunity that program such antibody responses remains a major challenge in vaccinology. Here we demonstrate that immunization of mice with synthetic nanoparticles containing antigens plus ligands that signal through TLR4 and TLR7 induces synergistic increases in antigen-specific, neutralizing antibodies compared to immunization with nanoparticles containing antigens plus a single TLR ligand. Consistent with this there was enhanced persistence of germinal centres and of plasma-cell responses, which persisted in the lymph nodes for >1.5 years. Surprisingly, there was no enhancement of the early short-lived plasma-cell response relative to that observed with single TLR ligands. Molecular profiling of activated B cells, isolated 7 days after immunization, indicated that there was early programming towards B-cell memory. Antibody responses were dependent on direct triggering of both TLRs on B cells and dendritic cells, as well as on T-cell help. Immunization protected completely against lethal avian and swine influenza virus strains in mice, and induced robust immunity against pandemic H1N1 influenza in rhesus macaques.     

亚纯函数的正规族

设为F区域D上亚纯函数簇，k∈Z^＋（k≥2），m∈Z^＋，a≠0，b为两有穷复数，c（z）≠0为D上解析函数，Vf∈F，f（z）的零点之级≥m，并且f（z）在区域D上的极点总个数（计算重数）至多为m,f（z）=a→f＇（z）=b，f（z）=0→0→f＇（z）=c（z），f＇（z）=c（z）→｜f^（k）（z）｜≤h，那么F在区域D内正规．     

Sequence and analysis of chromosome 2 of the plant Arabidopsis thaliana

Arabidopsis thaliana (Arabidopsis) is unique among plant model organisms in having a small genome (130-140 Mb), excellent physical and genetic maps, and little repetitive DNA. Here we report the sequence of chromosome 2 from the Columbia ecotype in two gap-free assemblies (contigs) of 3.6 and 16 megabases (Mb). The latter represents the longest published stretch of uninterrupted DNA sequence assembled from any organism to date. Chromosome 2 represents 15% of the genome and encodes 4,037 genes, 49% of which have no predicted function. Roughly 250 tandem gene duplications were found in addition to large-scale duplications of about 0.5 and 4.5 Mb between chromosomes 2 and 1 and between chromosomes 2 and 4, respectively. Sequencing of nearly 2 Mb within the genetically defined centromere revealed a low density of recognizable genes, and a high density and diverse range of vestigial and presumably inactive mobile elements. More unexpected is what appears to be a recent insertion of a continuous stretch of 75% of the mitochondrial genome into chromosome 2.     

Magnetism in Mn and Co doped ZnO bulk samples

Bulk samples with nominal composition Zn0.95Co0.05O and Zn0.92Co0.05Mn0.03O were fabricated by a solid-state reaction method at 600℃.X-ray diffraction experiment showed that the peaks of secondary phase Co3O4 with a cubic structure were visible in both samples,besides the main peaks of wurtzite structure as ZnO.Magnetization measurement indicated that doping Co alone can induce ferromag- netism in ZnO itself,while the introduction of Mn significantly enhances ferromagnetism.However, both samples showed different magnetic behavior at temperatures below 50 K.It was also noted that ferromagnetic coupling interaction was weakened due to the presence of antiferromagnetic Co3O4.     

A New En-/de-coding Scheme of Spreading Time OCDMA

In this paper, we propose a new en-/de-coding scheme of spreading time OCDMA utilizing the dispersion of grating and filter in frequency domain. The key components of the scheme are grating pair, Fourier transformation lens, phase filter etc. The results of design and calculation are shown that the spreading time of input pulse can be up to nanosecond-duration and the phase filter can provide pseudo-noise bursts in time domain. The requirements for Laser and optical detection equipment in the scheme are reduced. So the new scheme proposed by us is effective for OCDMA en-/de-coding of coherent ultra-short pulses.     

基于转矩控制的上坡辅助电控系统

针对车辆坡道起步时加速踏板和制动踏板协同操纵难度大、易引发溜坡事故等问题,提出一种基于电机转矩控制的电动汽车上坡辅助控制方法.建立了车辆坡道起步动力学模型,构建了具备"前馈+反馈"结构的预加载上坡辅助控制算法以保证控制实时性,通过时域分析法揭示了控制参数对系统稳定性、稳态误差和动态性能的影响机理.开发了面向量产纯电动乘用车平台的实车控制系统,分析了整车CAN网络通信架构.综合考虑溜坡距离和乘坐舒适性,通过道路试验确定了最优的控制参数组合,并将试验结果与现有的纯PI调节和负载观测器调节进行了对比分析.结果 表明,预加载上坡辅助控制算法相比于纯PI调节,可以减少11 cm的溜车距离,将溜车距离控制在3 cm以内,有效解决了坡道起步的溜车问题.     

关于亚纯函数的k阶导函数和有理函数(英文)

设f是复平面C内的超越亚纯函数,R是一个有理函数且R(■)0,k是一个正整数.并假设f的零点重级至少为k+1,至多有限个零点例外.则f~((k))-R有无限多个零点.