Single-crystal silver nanowires: Preparation and Surface-enhanced Raman Scattering (SERS) property

Ordered Ag nanowire arrays with high aspect ratio and high density self-supporting Ag nanowire patterns were successfully prepared using potentiostatic electrodeposition within the confined nanochannels of a commercial porous anodic aluminium oxide (AAO) template. X-ray diffraction and selected area electron diffraction analysis show that the as-synthesized samples have preferred (220) orientation. Transmission electron microscopy and scanning electron microscopy investigation reveal that large-area and ordered Ag nanowire arrays with smooth surface and uniform diameter were synthesized. Surface-enhanced Raman Scattering (SERS) spectra show that the Ag nanowire arrays as substrates have high SERS activity.     

任意模式电耦合波导耦合器的CST仿真

在已有的任意模式波导耦合器理论推导的基础上,找到了用数字仿真软件CST(Cormputer Simulation Technology)实现此过程的方法,给出了具体的仿真步骤.求解过程用CST微波工作室的本征模求解器和参数扫描功能.通过仿真例子,验证了此方法的正确性.     

Growth and characterization of ZnO films on (11-20) sapphire substrates by atomic layer deposition using DEZn and N2O

Zinc oxide (ZnO) films were grown on (11-20) sapphire substrates at 600 °C by atomic layer deposition (ALD) using diethylzinc (DEZn) and nitrous oxide (N₂O). A ZnO buffer layer was deposited at low temperature (LT) prior to the growth of a bulk ZnO film for a typical growth run. In some cases, buffer-layer annealing or post-annealing treatments were employed to optimize ZnO growth. Based on the experimental results of X-ray diffractometry (XRD) and transmission electron microscopy (TEM), all the as-grown ZnO films were found to show c-axis preferred orientation with co-existence of <1-100>_ZnO∥<1-100>_sapphire and <11-20>_ZnO∥<1-100>_sapphire relationships in the (0001)ZnO/(11-20)sapphire hetero-interface. Typical room temperature (RT) photoluminescence (PL) spectrum of the as-grown ZnO film shows only near band edge (NBE) emissions without defect luminescence. ZnO films with improved quality were achieved by post-annealing or buffer-layer annealing treatments. In particular, buffer-layer annealing was found to improve the crystalline and optical properties of a ZnO film substantially.     

提高九顶山铜钼矿钼回收率的研究

通过对选矿厂原有浮选工艺及矿石性质的研究,查明钼回收率低的原因及寻找合适的选矿工艺。为此,本文提出了增加磨矿细度并添加适量黄药的浮选工艺。工业生产结果表明,该工艺能适应所处理的矿石性质.指标得到明显改善。钼精矿品位从32.19%提高到42.80%,钼回收率从21.16%提高到72.72%。     

In vitro Characterization of Enzymes Involved in the Synthesis of Nonproteinogenic Residue (2S,3S)‐β‐Methylphenylalanine in Glycopeptide Antibiotic Mannopeptimycin

Mannopeptimycin, a potent drug lead, has superior activity against difficult‐to‐treat multidrug‐resistant Gram‐positive pathogens such as methicillin‐resistant Staphylococcus aureus (MRSA). (2S,3S)‐β‐Methylphenylalanine is a residue in the cyclic hexapeptide core of mannopeptimycin, but the synthesis of this residue is far from clear. We report here on the reaction order and the stereochemical course of reaction in the formation of (2S,3S)‐β‐methylphenylalanine. The reaction is executed by the enzymes MppJ and TyrB, an S‐adenosyl methionine (SAM)‐dependent methyltransferase and an (S)‐aromatic‐amino‐acid aminotransferase, respectively. Phenylpyruvic acid is methylated by MppJ at its benzylic position at the expense of one equivalent of SAM. The resulting β‐methyl phenylpyruvic acid is then converted to (2S,3S)‐β‐methylphenylalanine by TyrB. MppJ was further determined to be regioselective and stereoselective in its catalysis of the formation of (3S)‐β‐methylphenylpyruvic acid. The binding constant (K_D) of MppJ versus SAM is 26 μM . The kinetic constants with respect to k_{cat Ppy} and K_{M Ppy}, and k_{cat SAM} and K_{M SAM} are 0.8 s^?1 and 2.5 mM , and 8.15 s^?1 and 0.014 mM , respectively. These results suggest SAM has higher binding affinity for MppJ than Ppy, and the C? C bond formation in βmPpy might be the rate‐limiting step, as opposed to the C? S bond breakage in SAM.     

超临界CO2萃取天然产品的特性研究

结合溶解度参数研究了超临界ＣＯ２的溶剂功能和提高溶剂强度的途径。同时综述了超临界ＣＯ２加工天然产品过程中的各种影响因素，讨论了克服生物母体束缚作用，提高天然产品萃取率与选择性的各种措施。     

不同摩擦副中Si3N4陶瓷摩擦磨损特性研究

奥氏体不锈钢1Cr18Ni9Ti是难切削材料之一。本研究采用一种销盘试验机,模似陶瓷刀具实际切削加工时使用状况,考察了Si_3N_4/不锈钢摩擦副的摩擦学性能,并着重考察了与不锈钢对磨时Si_3N_4陶瓷的磨损特性。作为比较,对Si_3N_4/45号钢摩擦副的摩擦磨损性能也进行了较为详细的考察。试验结果表明,相同试验条件下,Si_3N_4/不锈钢中Si_3N_4,陶瓷的磨损率比Si_3N_4/45~#钢摩擦副中Si_3N_4的磨损率约大2个数量级。润滑剂对两种摩擦副摩擦磨损性能的影响也有很大差别。借助扫描电镜,X光电子能谱,俄歇电子能谱等多种分析手段对Si_3N_4陶瓷的磨损机理进行了分析,并对两种摩擦副中Si_3N_4磨损率的差别作了讨论。     

非接触式地表水电导率检测系统

将电容耦合非接触电导检测技术应用于地表水电导率检测,研制了非接触式地表水电导率测量传感器,建立了一种新型非接触式检测系统.利用有限元仿真的方法建立了传感器的仿真模型,对传感器结构参数的优化进行了研究,并分析了该系统的抗杂质干扰能力.系统测试结果表明,将该检测系统应用于地表水电导率检测是可行的.该系统具有传感器结构简单、电极非接触和抗杂质干扰能力强等特点,可以满足地表水电导率野外长期在线实时检测的要求.     

Measurement of solid concentration using Terahertz technique

Terahertz（THz） technique is a new measurement technique that has emerged in recent years.For the measurement of solid concentration,a radiation attenuation method and a phase delay method were developed,which are based on the Beer-Lambert law.Experimental work was carried out on a terahertz time-domain spectroscopy system（THz-TDS）.Results obtained verify that the terahertz technique may provide a possible new solution to the problem of solid concentration measurement and the two proposed measurement methods are effective.Experiment results also indicate that the phase delay method is more accurate than the radiation attenuation method and the size of the particles affects the measurement results of both methods.     

基于 Tikhonov 和 TV 混合正则化的接地 网电阻抗成像算法研究

电阻抗成像技术(EIT)是解决接地网腐蚀定位问题的方法之一,为了改善接地网 EIT 逆问题的病态性,提高求解稳定 性以及重建图像清晰度,提出了经典吉洪诺夫正则化(Tikhonov)和全变差正则化(TV)相结合的混合正则化(Tikhonov-TV)接地 网成像算法。 首先,在循环测量原理的基础上,创新地借助 COMSOL 与 MATLAB 联合仿真求取接地网 EIT 正问题模型电压数 据;其次,在理论分析基础上,通过 Tikhonov-TV 正则化的 EIT 算法分别求解基于先验拓扑信息和未知拓扑信息的两种接地网逆 问题模型的场域电阻率分布;最后仿真和实验对比了 Tikhonov、TV 以及 Tikhonov-TV 3 种正则化算法的接地网 EIT 重建图像,并 采用电阻率均方误差(Resistivity MSE)和截线电阻率曲线图来衡量图像质量,实验得出基于先验拓扑信息的 1 处和 2 处腐蚀情 况下 Resistivity MSE 分别达到 1. 27×10 -15 和 1. 59×10 -15 ,电阻率均方误差最小。 结果表明,提出的 Tikhonov-TV 正则化算法有效 地改善了 EIT 逆问题的病态性,收敛性能最优,重建图像效果优于 Tikhonov 和 TV 正则化算法。