Controlled synthesis and diameter-dependent optical properties of Cu nanowire arrays

Using electrochemical deposition, Cu nanowire arrays have been successfully fabricated by home-made polycarbonate ion-track templates. The diameters were well controlled by etching time of templates. The minimum diameter is 15 nm. The morphologies and structures were analyzed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The wires prefer [1 1 0] growth direction due to H ions absorption. The optical properties of Cu nanowire arrays are studied by an ultraviolet/visible/near-infrared spectrophotometer. Two extinction peaks were observed in spectra. The optical mechanism is discussed based on surface plasmon resonance

Time-dependent density-functional calculations for optical spectra of Na-2 and Na-4 clusters

With the frame of the time-dependent local density approximation, an efficient description of the optical response of clusters has been used to study the photo-absorption cross section of Na-2 and Na-4 clusters. It is shown that our calculated results are in good agreement with the experiment. In addition, our calculated spectrum for the Na-4 cluster is in better agreement with experiment than the GW absorption spectrum.

Preparation of silver nanowires in ion-track membranes

Polycarbonate (PC) membranes were irradiated with swift heavy ions and latent tracks were created along the ions' trajectories. Nanopores, diameters between 100 and 500 nm, were obtained after illuminating the membranes with UV light and etching in NaOH solution. Silver nanowires were produced in the etched ion-track membranes by electrochemical deposition. The morphology and crystallinity of the silver nanowires were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Under certain conditions (deposition voltage 25 mV, current density 1-2 mA.cm(-2), temperature 50 degrees C, electrolyte 0.1 mol.L-1 AgNO3), single-crystalline silver nanowires with preferred orientation along the [111] direction can be synthesized.

Optical absorption spectra of Na-5, Na-6 and Na-7 clusters: a theoretical study

In the frame of time-dependent density functional theory, the: dynamical polarizabilities of Na-5, Na-6 and Na-7 clusters are calculated using a time-dependent local density approximation. By using Fourier transformation, the optical absorption spectra of Na-5, Na-6 and Na-7 clusters are obtained from their dynamical polarizabilities. It is shown that experimentally measured optical absorption spectra of Na-5, Na-6 and Na-7 clusters are reproduced in our calculations. Furthermore, the calculations of Na-6 and Na-7 clusters are in good agreement with the results of configuration interaction method. Compared with the three-dimensional structure of Na-6, the calculated optical absorption spectra of Na-6 with the two-dimensional structure are more close to the experimental data.

High-order harmonic generation and multi-photon ionization of Na-2 in laser fields

In this paper high-order harmonic generation (HHG) spectra and the ionization probabilities of various charge states of small cluster Na-2 in the multiphoton regimes are calculated by using time-dependent local density approximation (TDLDA) for one-colour (1064 nm) and two-colour (1064 nm and 532 nm) ultrashort (25 fs) laser pulses. HHG spectra of Na2 have not the large extent of plateaus due to pronounced collective effects of electron dynamics. In addition, the two-colour laser field can result in the breaking of the symmetry and generation of the even order harmonic such as the second order harmonic. The results of ionization probabilities show that a two-colour laser field can increase the ionization probability of higher charge state.

几种不同下垫面地表粗糙度动态变化及其对通量机理模型模拟的影响

在众多地表通量模拟模型和遥感通量反演模型中,空气动力学粗糙度(z0)是一个重要的地表参数．选取代表典型农田的禹城站,代表复杂下垫面的千烟洲站和代表森林下垫面的长白山站3个通量观测站的风速和温度廓线资料,运用最小二乘法拟合迭代,分别计算得到各站点通量塔所在地的零平面位移和空气动力学粗糙度．在此基础上,分别分析不同下垫面的空气动力学粗糙度随作物高度和叶面积指数(LAI)、风向(地形)、风速、摩擦速度等因子的变化．并采用SEBS模型分析地表空气动力学粗糙度动态变化对地表通量计算的影响．结果表明:空气动力学粗糙度随植被特征(如作物高度,叶面积指数等)以及风向、风速和摩擦速度等因子而变化．禹城和长白山站通量塔所在风浪区的空气动力学粗糙度明显随作物生长期植被高度及叶面积指数变化,即先随LAI增加而增加,达到峰值后,随LAI增加而减小;千烟洲叶面积指数变化较小,空气动力学粗糙度随叶面积指数的变化不明显;地形较平坦的禹城和长白山站空气动力学粗糙度随风向变化较小,而地形起伏较大的千烟洲站空气动力学粗糙度随风向变化较大．随着风速的变化,禹城站空气动力学粗糙度没有明显变化,而千烟洲和长白山空气动力学粗糙度表现出随风速增加而减小的趋势．各站空气动力学粗糙度的这种动态变化对模型通量反演有较大影响,通过模型分析, 5月1日～6月3日禹城空气动力学粗糙度日平均值、千烟洲及长白山通量塔空气动力学粗糙度5d平均值与模型所取z0值相比,由于z0的动态变化造成相同时间尺度显热通量H的计算相对误差的绝对值最大可分别达到2．726％,33．802％和18．105％．

两种不同穗型水稻品种灌浆期间物质生产特性的比较

选用直立穗型水稻品种辽粳 32 6和弯曲穗品种奥羽 316 ,在相同栽培条件下 ,比较两品种灌浆期间物质生产与分配、群体生长率 (CGR)、净同化率 (NAR)及与物质生产密切相关的叶绿素含量、叶面积指数 (LAl)、比叶重等指标。结果表明 ,和弯曲穗品种奥羽 316相比 ,直立穗品种辽粳 32 6在灌浆后期仍能保持较强的物质生产能力 ,其抽穗后生产的干物质量占其生物产量的 5 3.77% ,比其经济产量高出 12 %。灌浆期间 ,直立穗品种辽粳 32 6的比叶重较高 ,叶绿素含量较高 ,LAI下降较慢 ,各项生理指标优于弯曲穗品种奥羽 316。抽穗后 ,直立穗品种辽粳 32 6具有比弯曲穗品种奥羽 316更强的生产能力 ,因而更符合高产栽培的需要。

栽培模式、施氮和品种对冬小麦冠层结构和产量的影响

在黄土高原南部半湿润易旱区土垫旱耕人为土上进行大田试验,研究氮肥、品种和栽培模式对冬小麦叶面积指数(LAI)和透光率(DIFN)及产量的影响。结果表明,小麦生长过程中LAI先增大后减小,在开花期最大,成熟期最小,施氮能够显著增加LAI;DIFN的变化规律与LAI相反。不同品种间LAI和DIFN差异显著。全程覆膜和覆膜150 d的LAI极显著大于常规栽培、集雨面栽培和三密一稀栽培模式,DIFN与此相反;施氮后籽粒产量极显著增加。在不同栽培模式下,以全程覆膜、覆膜150 d和集雨面栽培模式的产量较高,但从维持土壤质量角度考虑,则覆膜150 d和集雨面2种栽培模式优于其它几种栽培模式;从冠层结构特征分析,这2种栽培模式更有利于增加群体光合能力。

基于MODIS数据的中国陆面制图:方法软件和数据产品(英文)

本文介绍一个自动处理MODIS1B数据并生产覆盖全中国陆面产品的软件系统。该算法改进了LAI(MOD15),土地覆被分类(MOD12),云检测(MOD35),陆面反射率(MOD09)和气溶胶(MOD04)产品。这些算法的输入数据都是本地获取的参数,能够有效降低其带来的不确定性。产生的部分新产品是NASA标准产品中没有的,包括森林火烧迹地和PAR。数据处理系统运行于中国科学院资源与环境数据中心。

基于景观尺度过程模型的长白山净初级生产力空间分布影响因素分析

对长白山自然保护区的净初级生产力(NPP)的空间分布格局进行了模拟,对它们与环境因子和植被因子间的相互关系进行了分析.结果表明,1995年NPP的模拟值平均为0.680kgC·m-2·年-1,变幅为0.105～1.241kgC·m-2·年-1(82.1%),其中阔叶红松林的NPP最高(1.084kgC·m-2·年-1).环境条件决定了长白山植被年NPP空间分布的大趋势.土壤含水量对NPP的限制最大,呈负相关关系(R=-0.65),长白山植物生长一般不存在水分不足的问题.植被的NPP与LAI高度正相关(R=

基于遥感和地面数据的景观尺度生态系统生产力的模拟

描述了一个反映系统碳循环和水循环的景观尺度生态系统生产力过程模型(EPPML).该模型以遥感图像作为数据源,从中获取影响植被生产力的重要变量———叶面积指数(LAI);主要对景观尺度生态系统的净初级生产力(NPP)和蒸散量的空间分布格局和时间动态进行模拟;用地理信息系统(GIS)手段对空间数据进行处理、分析和显示,从而实现将植物生理生态研究的结果从小尺度向中尺度进行拓展和转换.本研究用EPPML对1995年长白山自然保护区的植被生产力进行了模拟,结果表明,EPPML可以比较准确地模拟该保护区主要植被的NP

基于3S的自然植被光能利用率的时空分布特征的模拟

光能利用率(LUE)直接影响植被各层中的能量分布和光合速率,在确定环境对光合和地上部生长分配的综合限制上十分有价值,是衡量系统功能的一个重要指标。本研究以遥感图像(TM)作为数据源,获取了影响植被LUE的重要变量———叶面积指数(LAI);用程序语言编写了描述系统碳循环和水循环的景观尺度生态系统生产力过程模型(EPPML),对长白山自然保护区的太阳总辐射、净初级生产力(NPP)和LUE等的季节动态和空间分布进行了模拟;并用地理信息系统(GIS)手段对空间数据进行处理、分析和显示,从而实现了将植物生理生态研