均匀电场对冰晶结构及生长的影响

采用分子动力学模拟方法研究了强度为4.0-40.0 V·nm^-1的均匀电场对过冷水冰晶结构和冰晶生长速率的影响. 文中通过CHILL 算法来识别不同的冰相结构,通过拟合Avrami 公式来得到冰晶生长所需的特征时间. 结果表明,在所施加的电场强度范围内生成的冰相以立方冰为主. 随着电场强度的增加,形成的立方冰的变形程度逐渐增大,冰晶的密度从0.98 g·cm^-3 增加到1.08 g·cm^-3,同时冰晶生长的特征时间从5.153 ns 减小到0.254 ns,冰晶生长的速率逐渐增长. 对水分子的动力学分析表明,冰晶生长速率增加的部分原因是电场能够促进水分子运动到形成冰晶所需要的取向. 此外,对冰相分子形成过程的分析表明缺陷冰分子在冰晶的生长过程中扮演着中间态的角色. 随电场强度的增加,由缺陷冰转变为立方冰的比例增长的速率逐渐提高.     

Wrinkling and Growth Mechanism of CuO Nanowires in Thermal Oxidation of Copper Foil

We report a systematic study on wrinkling and CuO nanowires （NWs） growth in the thermal oxidation of copper foil. Copper foils with thickness of 0.5 mm were thermally oxidized in air at 500℃ for 0.5-10 h. It is found that all the samples have wrinkles and the size of the wrinkles increases with the oxidation time increasing. CuO NWs can grow on both the sidehill and hilltop of wrinkle. The CuO NWs on sidehill are longer and denser than those on hilltop. The growth direction of the CuO NWs on sidehill is not vertical to the substrate but vertical to their growth surfaces. The process of wrinkling and CuO NWs growth can be divided into three stages： undulating, voiding, and cracking. The CuO NWs on both sidehill and hilltop grow at the undulating stage. However, only the CuO NWs on sidehill grow and those on hilltop stop growing at the voiding and cracking stages because of the void in hilltop. The local electric field in a wrinkle at undulating stage was calculated, and it is found that the difference of local electric field strengths between hilltop and sidehill is small, which indicates that the predominant driving force for the diffusion of Cu ion during CuO NWs growth is internal stress.     

Ge_nEu(n=1-13)团簇的结构、电子及磁性质(英文)

利用密度泛函理论在广义梯度近似下研究了GenEu(n=1-13)团簇的生长模式和磁性.结果表明:对于GenEu(n=1-13)团簇的基态结构而言,没有Eu原子陷入笼中.这和SinEu以及其它过渡金属掺杂半导体团簇的生长模式不同.除GeEu团簇外,GenEu(n=2-13)团簇的磁矩均为7μB.团簇的总磁矩与Eu原子的4f轨道磁矩基本相等.Ge、Eu原子间的电荷转移以及Eu原子的5d、6p和6s间的轨道杂化可以增强Eu原子的局域磁矩,却不能增强团簇总磁矩.     

阳极氧化铝模板法可控制备金属纳米线和纳米管阵列的生长机制

利用阳极氧化铝模板(AAO)进行Ni的电化学沉积, 通过在溶液中引入螯合剂控制电解质的有效浓度和电沉积的过电位, 实现了Ni纳米线和纳米管阵列的可控制备. 通过分析电沉积过程中纳米线和纳米管在不同位置生长速率(侧壁(Vw)和底端(Vb))的控制因素, 我们提出了纳米线和纳米管生长的可能机制. 当电解质浓度高而还原电位更负(如-1.5 V)时, 或者当电解质浓度低而还原电位较负(如-0.5 V)时, Vw>Vb, 可以获得Ni纳米管阵列; 当电解质浓度高而还原电位较负(如-0.5 V)时, 或者当电解质浓度低而还原电位更负(如-1.5 V)时, Vw≈Vb, 可以获得Ni纳米线阵列. 这种生长机制适用于多种金属纳米管或者纳米线阵列的可控制备.     

Relative retention of the fibroblast growth factors FGF-1 and FGF-2 on strong cation-exchange sorbents

The isocratic retention of two heparin-binding fibroblast growth factors, FGF-1 (acidic FGF) and FGF-2 (basic FGF), was compared on a set of six preparative strong cation-exchange adsorbents. The FGFs comprise a solute pair that are structurally equivalent, yet differ in protein parameters of potential importance in cation-exchange chromatography, such as isoelectric point, net charge, and the number and distribution of basic amino acids. The cation-exchange adsorbents comprise a diverse set of materials in common use for protein purification, with physical and chemical properties that have been characterized and described previously. Isocratic k' values for the two proteins obtained on each adsorbent at several different [NaCl] are compared with one another and with corresponding data for hen egg lysozyme, which is also strongly retained on cation-exchangers. Of the six adsorbents examined, three showed strong retention of both FGFs, with equivalent k' values for FGF-1 and FGF-2. Three others, which showed weaker overall retention for the FGF pair, showed much larger retention differences between FGF-1 and FGF-2. The trends in retention order among the stationary phases are very similar to those seen previously with other unrelated proteins. However, retention differences between the two FGFs, and between the FGFs and lysozyme, do not correlate well with simple charge properties such as net charge, indicating, as in some previous studies, the importance of local regions on the protein surface in determining retention. These observations are interpreted in terms of the structural features of the proteins and the physicochemical properties of the adsorbents.     

碳纳米管的最新制备技术及生长机理

结合笔者的工作综述了碳纳米管的制备技术及生长机理的最新研究进展，重点介绍了近两年来碳纳米管制备的进展情况，包括传统制备方法的改进（电弧放电法、化学气相沉积法和激光蒸发法）、新型制备技术、特殊结构的碳纳米管制备；同时探讨了碳纳米管的各种生长机理；最后提出了碳纳米管制备技术和生长机理的发展方向。     

Chromatographic separation and mass spectrometric identification of positional isomers of polyethylene glycol-modified growth hormone-releasing factor (1-29)

A one-step chromatographic method capable of separating all isomers of polyethylene glycol (PEG)-growth hormone-releasing factor (GRF) (1-29) conjugates was developed. The unmodified GRF (1-29) and seven different isomers of PEG-GRF (1-29) conjugates were separated by using a simple reversed-phase HPLC method depending on the differences of hydrophobicity due to the number and site of PEG attachment. The PEGylation sites of all isomers of PEG-GRF (1-29) conjugates were identified by determining the molecular masses of the Lys-C digested fragments with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This study is a first report for the separation of all PEG-conjugate isomers and would be useful for further studies to find the promising conjugate by evaluating biological activity and stability of each isomer.     

Electrovectorial Effects of Electrically Polarized Hydroxyapatite on Biological Phenomena

Electrically polarized hydroxyapatite ceramics have chemical, physical, and biological effects upon their surrounding constituents in vivo as well as in vitro as electrets, independent solids irradiating electrostatic force. Using the polarized hydroxyapatite, we have observed that crystal growth from a simulated body fluid can be accelerated or decelerated, and microorganisms can be manipulated on the surfaces of hydroxyapatite, depending upon the electric signs.     

用双还原法制备三角形银纳米片及其光学性能

在硼氢化钠和柠檬酸三钠共存的体系中还原硝酸银, 以聚乙烯吡咯烷酮(PVP)为表面活性剂和保护剂, 水浴加热制备得到三角形银纳米片, 用X射线衍射(XRD)、透射电子显微镜(TEM)、紫外-可见(UV-Vis)吸收光谱、表面增强拉曼散射(SERS)光谱对其进行了表征. 结果表明: 三角形银纳米片产物为立方相金属银, 边长为(100±40) nm, 厚度为(10±5) nm; 产物表现出与球形银纳米粒子完全不同的吸收光谱; 柠檬酸根在银晶核不同晶面的选择吸附、PVP的包覆作用及Ag(111)晶面的层错对产物的形成起决定作用; 与球形纳米颗粒相比, 三角形银纳米片膜对吡啶(Py)分子有显著的SERS活性.     

ZnO Nanobelts and Hollow Microspheres Grown on Cu Foil

ZnO nanobelts, hollow microspheres, and urchins have been prepared on copper foil via a simply low temperature evaporation route. The microstructure, morphologies, and photolu-minescence of the ZnO nanostructures were studied with X-ray diffraction, Raman spectra, scanning electron microscopy and photoluminescence spectra. The width of the nanobelts was about 500 nm and the length was longer than 10μm. The diameter of the hollow microspheres was between 5 and 10μm. A possible growth mechanism of the nanobelts, microspheres and urchins was proposed. The photoluminescence spectrum exhibited strong deep level energy emissions and a weak near band edge emission. These ZnO nanostructures on a copper substrate have the advantages of naturally good adhesion and electrical connection between the ZnO nanostructures and the conductive substrate.