PEG接枝氧化石墨烯的制备与细胞成像

通过酯化反应将不同分子量的聚乙二醇（PEG）接枝到氧化石墨烯（GO）表面,得到系列GO-PEG。利用傅里叶变换红外光谱（FTIR）、拉曼光谱（Raman）、扫描电子显微镜（SEM）对GO-PEG的结构和形貌进行了表征,用热重分析（TGA）测定了GO-PEG中PEG的接枝量。SEM结果表明GO-PEG的剥离程度高于GO。GO-PEG在磷酸盐缓冲溶液中具有良好的分散稳定性,稳定性与接枝量呈正相关。GO-PEG通过非共价键合作用对荧光素（Flu）的负载量可达1.75mg·mg^-1,且负载量受接枝量影响;另外,GO-PEG对Flu的释放行为具有pH值触发药物释放性能。将接枝PEG的端羟基与Flu共价键合,所得GO-PEG₆₀₀₀-Flu荧光探针实现了对HepG₂细胞的成像。     

Proteomic analysis of the Arabidopsis thaliana cell wall

With the completion of the Arabidopsis genome, many hypothetical proteins have been predicted without any information on their expression, subcellular localisation and function. We have performed proteomic analysis of proteins sequentially extracted from enriched Arabidopsis cell wall fractions and separated by two-dimensional gel electrophoresis (2-DE). The proteins were identified by peptide mass fingerprinting using matrix-assisted laser desorption/ionisation-time of flight (MALDI-TOF) mass spectrometry and genomic database searches. This is part of a targeted exercise to establish the entire Arabidopsis secretome database. We report evidence for new proteins of unknown function whose existence had been predicted from genomic sequences and, furthermore, localise them to the cell wall. In addition, we observed an unexpected presence in the cell wall preparations of proteins whose known biochemical activity has never been associated with this compartment hitherto. We discuss the implications of these findings and present results suggesting a possible involvement of cell wall kinases in plant responses to pathogen attack.     

钪对Al—6Mg—Zr合金焊接抗腐蚀的影响

采用中性盐雾试验和剥落腐蚀等方法研究了微量稀土元素Sc对Al—6Mg—Zr合金焊接接头耐蚀性能的影响，并用金相显微镜和透射电子显微镜观察合金焊接接头的微观组织、探讨其腐蚀机理。结果表明，添加了Sc元素后的Al—6Mg—Sc—Zr合金焊接接头比Al—6Mg—Zr合金具有更好的耐蚀性能。研究认为，添加Sc元素能有效地细化晶粒，形成的Al3(Sc，Zr)第二杷能强烈地阻止位错和亚晶界的运动，提高了合金的再结晶温度，从而使合金组织中的β(Mg5Al8，Mg2Al3)沉淀相分布均匀、呈弥散分布，最终使合金的腐蚀敏感性降低。     

过渡金属催化的有机硼酸与不饱和键的加成反应

概述了过渡金属催化的有机硼酸与不饱和键的加成反应,包括铑催化、镍催化、钯催化三部分内容.     

(HAlNH)n(n=1～6)簇的结构、红外光谱和热力学性质的研究

用自洽场理论(HF)和密度泛函理论(DFT)的B3LYP方法,在6-31G水平上研究了HAlNH的低聚物(HAlNH)~n(n=1～6)簇的几何构型、电子结构、红外光谱和化学热力学性质,并比较了(HAlNH)~n和(ClAlNH)~n两种低聚物对应结构中化学键强弱,分析了引起(AlN)~n骨架结构发生变化的原因。结果表明,(HAlNH)~n簇的基态结构为C~s(n=1),D~2~h(n=2),D~3~h(n=3),T~d(n=4),C~s(n=5)和D~3~d(n=6)对称点群。HAlNH基态结构中,Al-N键是三重键。在D~2~h(n=2)和D~3~h(n=3)结构中,所有Al-N键均为二重键。在T~d(n=4)和D~3~d(n=6)中,Al-N键为正常单键,而在C~s(n=5)结构中含有三种Al-N键：单键、双键和混合键。振动频率计算表明,结构a～f均为基态稳定结构。热力学计算给出的稳定性顺序为：f>d>e>c>b>a。     

(2R，3R)-和(2S，3S)-2-(4-羟基-3-甲氧基)-3-羟甲基-1，4-苯并二氧六环-6-醛的对映选择性合成

1,4-苯并二氧六环木脂素类天然产物多数具有增加胆碱乙酰化酶和抗肝毒等活性 ,其活性主要源于 1 ,4-苯并二氧六环官能团 [1] . 1 ,4-苯并二氧六环木脂素的消旋全合成已有报道 [2 ] ,但其不对称合成还是空白[3] .我们发展了一条对映选择性合成 1 ,4-苯并二氧六环木脂素的简捷有效的路线 .基于前面的工作 [4 ] ,我们发现 1 ,4-苯并二氧六环醛类衍生物是合成此类天然产物的关键中间体 ,选择 2 - (4-羟基- 3-甲氧基 ) - 3-羟甲基 - 1 ,4-苯并二氧六环 - 6-醛 (1 )作为目标分子 ,其合成路线如下 :Reagents and conditions:( ) Me OH,H2 SO4,9…     

C_nAl_m~+(n=1～12,m=1,2)团簇几何结构特征与稳定性的量子化学研究

采用密度泛函理论(DFT)的B3LYP方法,在6-311++G**水平上对CnAlm+(n=1～12,m=1,2)团簇的几何和电子结构进行了理论计算,讨论了混合团簇的结构与成键特征,以及振动频率与电荷转移.结果表明,CnAl+团簇的基态结构分别为Al原子与Cn链端基配位形成的直线或折线状结构,以及Al原子与Cn环上1个C原子端位相连或打开Cn环与2个C原子相连形成的环状结构;分子总的平均键长随着n的增大逐渐趋于定值0.138nm.CnAl+2团簇基态结构可以看作是两个较小的Cn/2Al+分子碎片通过端位C原子相互结合形成CcoreAlshell的直线或顺式与反式折线状结构;分子总的平均键长随着n的增大逐渐趋于定值0.141nm.通过对基态结构的能量分析,得到了CnAl+和CnAl+2团簇的稳定性信息.     

Transport behavior of humic acid-modified nano-hydroxyapatite in saturated packed column: effects of Cu, ionic strength, and ionic composition

The surfaces of nano-hydroxyapatite (nHAP) used for contaminated soil and groundwater remediation may be modified to render nHAP highly mobile in the subsurface. Humic acid (HA) is widely used to modify and stabilize colloid suspensions. In this work, column experiments were conducted to determine the effects of contaminant (e.g., Cu) concentration, ionic strength (IS), and ion composition (IC) on the transport behavior of HA-modified nHAP in saturated packed columns. IS and nature of the cation had strong effects on the deposition of nHAP, and the effect was greater for divalent than for monovalent cations. Divalent cations have a greater capacity to screen the surface charge of nHAP, and Ca(2+) bridges the HA-modified nHAP colloidal particles, which causes greater deposition. Moreover, Cu(2+) had a greater effect on the transport behavior than Ca(2+) due to their strong exchange with Ca(2+) of nHAP and its surface complexation with nHAP. The relative travel distance L(T), of the injected HA-modified nHAP colloids, ranges from less than one to several meters at varying Cu concentrations, ISs, and ICs in saturated packed columns. The results are crucial to evaluate the efficacy of nHAP on the remediation of contaminated soil and groundwater environments.     

(MN)nHm(M=Ga,In; n=1-4; m=1, 2)团簇的结构与稳定性

采用密度泛函理论(DFT)的B3LYP方法, 在6-31G**和Lanl2dz水平上分别对(MN)nHm(M=Ga, In; n=1-4; m=1, 2)进行了优化和振动频率计算. 得到了上述团簇的最稳定构型、H原子的结合能以及它们的能隙. 结果表明, (MN)nH(M=Ga, In; n=1-4)的基态构型均为双重态, (MN)nH2(M=Ga, In; n=1-4)的基态构型均为单重态; 当氢的个数为1时, 加在N原子上比加在M(M=Ga, In)原子上稳定, 如有N3单元, 那么加在N3单元两侧的构型是相同的, 且它是最稳定的; 当氢的个数为2时, 除n=1外, 分别加在两个N原子上的构型是最稳定的, 如有N3单元, 那么分别加在N3单元分离最远的两个N原子的构型是最稳定的. GaNH、(GaN)3H 和InNH的结合能和能隙都很大, 说明这些团簇都有很高的稳定性.     

实用的步进电机驱动电路

概述 步进电机是一种将电脉冲转化为角位移的执行机构,可以通过控制脉冲个数来控制角位移量,从而达到准确定位的目的;同时可以通过控制脉冲频率来控制电机转动的速度和加速度,从而达到调速的目的.