点缺陷光子晶体传播特性的研究

应用平面波展开法数值模拟了空气洞六角晶格结构点缺陷光子晶体的传输特性,得到了传输模式图和波长变化关系,为光子晶体器件的开发提供了理论依据。     

低速~(40)Ar~(17+)离子入射金属Be表面发射的近红外光谱线和X射线谱

用速度不同的(动能EK=272和357keV,速度v=1.14×106和1.72×106m/s)的高电荷态离子40Ar17+分别入射金属Be表面,同时测量这种相互作用过程中产生的近红外光谱线和X射线谱。实验结果表明,在低速范围内(速度小于玻尔速度vBohr=2.19×106m/s),速度较小的40Ar17+离子在到达金属的表面临界距离Rc到进入表面(2—3原子层)的进程中,形成了较多的高激发态Ar原子,其退激辐射较强的光谱线,进而验证了经典过垒模型。     

DFT study and quantitative detection by surface‐enhanced Raman scattering (SERS) of ethyl carbamate

Ethyl carbamate (EC), a potentially toxic compound, is found in alcoholic beverages and fermented foodstuff. A combined experimental and theoretical study of Raman on EC is reported in this work for the first time. The Raman bands observed for EC in solid phase are characteristic for the carbonyl group, C―C, C―H and N―H stretching and deformation vibrations. These spectral features coupled with a pKa study allowed establishing the neutral species of EC present in the aqueous solutions experimentally tested at different concentrations. In addition, by performing a density functional theory study in the gas phase, the calculated geometry, the harmonic vibrational modes, and the Raman scattering activities of EC were found to be in good agreement with our experimental data and helped establish the surface‐enhanced Raman scattering (SERS) behavior and EC adsorption geometry on the silver surfaces. The Raman peak at 1006 cm⁻¹, assigned to the υ_s(CC) + ω(CH) modes, the strongest and best reproducible peak in the SERS spectra, was used for a quantitative evaluation of EC. The limit of detection, which corresponds to a signal‐to‐noise ratio equal to 3, was found to be 2 × 10⁻⁷ M (17.8 µg l⁻¹). SERS spectra obtained by using hydroxylamine hydrochloride‐reduced silver nanoparticles provide a fast and reproducible qualitative and quantitative determination of EC in aqueous solution. Copyright © 2013 John Wiley & Sons, Ltd.     

An Error Analysis for the Finite Element Approximation to the Steady-State Poisson-Nernst-Planck Equations

Poisson-Nernst-Planck equations are a coupled system of nonlinear partial differential equations consisting of the Nernst-Planck equation and the electrostatic Poisson equation with delta distribution sources, which describe the electrodiffusion of ions in a solvated biomolecular system. In this paper, some error bounds for a piecewise finite element approximation to this problem are derived. Several numerical examples including biomolecular problems are shown to support our analysis.     

无菌与带菌盐藻矿质元素含量的比较分析

采用火焰原子吸收光度法分别测定了对数初、中、末期无菌与带菌盐藻细胞及上清液中Mg,Fe,K,Ca,Na,Mn,Zn,Cu,Ni,Cd和Cr的含量。结果表明:(1)该盐藻Mg,Fe,K,Ca和Na的含量在1～10mg.g-1之间,Zn,Cu,Mn和Ni的含量基本在0.1～1 mg.g-1之间,有害金属Cd和Cr的含量极微。(2)无菌与带菌盐藻不同时期矿质元素的变化趋势大致相同,Mg,Fe,K,Ca,Na,Mn和Cu的含量随着培养时间的延长有所下降,Ca下降的最明显;Mg,Fe,K,Ca和Na的含量在上清液中保持稳定,无明显差异,而Cu和Mn含量在对数中后期的上清液中明显增加。(3)无菌与带菌盐藻Mg,K,Cu和Ni的含量差异不大;带菌盐藻的Fe,Ca,Na和Zn的含量在对数中期均显著下降,且低于无菌盐藻;而到对数末期又明显高于无菌盐藻。本实验结果为进一步利用盐藻资源以及深入研究藻菌相互作用机理提供了参考。     

N掺杂TiO_2纳米管阵列的制备与性质研究

本文采用阳极氧化法制备了孔径为60-80nm,孔壁厚约为20-30nm的高有序度TiO2纳米管。将制备的TiO2纳米管经表面酸化后在浓氨水中浸泡,并于氮气气氛中进行退火处理,以实现TiO2纳米管的N掺杂。利用SEM、XRD、Raman和XPS对样品的形貌与结构进行了研究。结果显示,掺N后不会破坏阳极氧化形成的高有序纳度米管阵列,而且N的引入促进了TiO2纳米管在低温下由锐钛矿相向金红石相的转变。N掺杂样品的XPS中出现了结合能位于399.7 eV的峰,该峰来源于TiO2的间隙氮杂质,显示此方法在TiO2纳米管中实现了有效的N的掺杂。     

网络虚拟仪器的通讯技术研究

网络技术拓展了虚拟仪器的使用范围 ,使之能通过局域网或Internet实现远程测控的功能 ,构成网络化虚拟仪器。文章就网络化虚拟仪器中的网络通讯技术进行了研究 ,提出了一种混合结构的网络模型 ;对嵌入式测试服务器进行了设计 ,解决两个服务器重构的问题 ;用LabVIEW和Java分别对客户端虚拟仪器进行了设计 ,并解决了网络通讯中的数据重组和数据移植问题。     

Spiking Behavior in Chua's Circuit

Chua ＇s circuit with a slow-fast effect is established under certain parameter conditions. The dynamics of this slow- fast system is investigated. A spiking phenomenon can be observed in the numerical simulation. By introducing slow-fast analysis and a generalized Jacobian matrix at the non-smooth boundaries, the bifurcation mechanism for the periodic spiking solution, different from the smooth case, is discussed.     

聚丙烯/抗老化剂复合体系的γ-射线辐照降解研究

研究了聚丙烯(PP)及含有受阻酚类抗氧剂和受阻胺类光稳定剂复合体系的PP复合物经过γ-射线辐照后发生的结构变化及抗老化剂所起作用。实验利用红外光谱(FTIR)和示差扫描量热法(DSC)对PP的结构变化进行了系统表征。研究结果表明,当辐照剂量较小(50 kGy)时,纯PP及其复合物体系均未发生明显降解;当辐照剂量较大(≥50 kGy)时,PP及其复合物的羰基指数迅速提高,二者的结晶温度和熔融温度大幅度降低,说明PP发生了严重降解。在相同γ-射线辐照剂量条件下(≥50 kGy),PP复合物的羰基指数高于纯PP,而结晶温度以及熔融温度低于纯PP,表明高辐照剂量下抗老化剂复合物的存在不但没有阻止聚丙烯的降解,反而加快了降解的速率。     

增强的UV-B辐射对高粱幼苗光合和抗氧化系统的影响

由于臭氧层逐渐变薄,到达地球表面UV-B辐射不断增加,因UV-B辐射改变的太阳光谱将会对陆地植物造成不同程度的伤害。本试验以高粱龙杂5为材料,对二叶一心高粱进行四种剂量UV-B处理,恢复2 d采用光合仪测定光合参数,并取样测定抗氧化酶活性。随着UV-B剂量的升高,高粱叶片褐化损伤加重,植株矮化,鲜重和干重显著降低;花青素含量显著升高,叶绿素和类胡萝卜素含量显著减少,净光合速率和叶绿素荧光参数显著下降。同时,随UV-B剂量升高,高粱幼苗气孔导度、胞间CO₂浓度和蒸腾速率表现为“降-升-降”变化;POD和CAT活性呈现“降-升-降”变化;SOD和GR活性呈现“降-升”变化,APX和GPX呈现“升-降-升”变化。在供试的四种剂量中,UV-B处理6 h(相当2.4 J·m-2)的高粱幼苗净光合急剧下降,其他光合指标以及抗氧化酶活性也表现出明显转折。结果表明,增强的UV-B辐射直接导致高粱光合色素、净光合速率和叶绿素荧光参数的改变;高粱抗氧化系统对高、低剂量UV-B响应机制不同, 其中 ASA-GSH循环对低剂量UV-B反应更敏感,高剂量UV-B辐射不仅破坏高粱光合作用,而且启动植物酶促和非酶抗氧化系统,导致叶片褐化坏死,植株生物量累积减少、株高矮化,甚至死亡。