Molecular dynamics and control following excitation with an ultra-short intense laser pulse

Vibronic excitations of the tri-atomic molecule OClO (A(2)A(2)(nu(1), nu(2), nu(3)) <-- (XB1)-B-2 (0, 0, 0)) with weak and strong ultra-short laser fields are studied within full quantum wavepacket dynamics in hyperspherical coordinates. Different dynamics is observed following excitation with laser pulses of different intensities. With a strong laser pulse, many vibrational states are excited and a spatially more localised wavepacket arises. The numerical results show that the population of different vibrational states of the wavepacket on the excited potential energy surface is altered by the intensity of the laser pulse. The numerical results also suggest a related effect on the phase of the wavepacket. These interesting phenomena can be understood by an analysis of the corresponding results for two model diatomic molecules. The possible physical mechanisms of control of chemical processes using strong laser fields are discussed. (C) 2004 Elsevier B.V. All rights reserved.

Molybdenum containing surface complex for olefin epoxidation

Silica-supported molybdenum surface complexes were prepared by the reaction between (N=) Mo(OtBu)(3) and silica via displacement of the tert-butoxy ligands for siloxyls from the silica surface. The structure of the surface molybdenum complexes was well defined by in-situ FT-IR, elemental analysis, H-1 NMR and C-13 CP/MAS NMR techniques. The surface complexes could undergo alcoholysis reaction with CD3OD and CH3OH in the same way as free (N =) Mo(OtBu)(3) and they show high catalytic activity and selectivity in olefin epoxidation. Initial rates up to 24.9 mmol epoxide (mmol Mo)(-1) min(-1) were achieved in the epoxidation of cyclohexene using TBHP as oxidant.

旱农区不同种植模式作物最佳补灌时期和适宜补灌量研究

对不同种植模式作物进行补灌的产量及水分效应研究表明 ,在自然降雨基础上补灌 45 mm和 90 mm水 ,各种植模式的产量及水分利用效率均较对照大幅度提高。初步确定出在作物生长前期降雨较多的丰水年 ,三种种植模式的适宜补灌定额为 90 mm。三种种植模式中作物的最佳补灌时期及适宜补灌量分别为 :单作小麦播前沟灌 8mm,孕穗期补灌 82mm;单作地膜玉米在大喇叭口期一次补灌 90 mm;带田小麦播前沟灌 4mm,拔节期和孕穗期各补灌 19mm,带田地膜玉米在拔节期和大喇叭口期各补灌 2 4 mm。该结论适宜于北方旱地农田推广应用。

沈阳市建成区植被环境效益分析

以基于GIS为基础的城市植被分析软件———CITYgreen的要求对沈阳市建成区进行调查,并统计分析,获得沈阳市建成区绿色覆盖现状,各用地类型植被的环境效益以及沈阳市建成区的总体环境效益。结果表明,沈阳市建成区的绿色覆盖(树冠与草地之和)率以绿化类用地最高;植被净化效益的主体为树木覆盖,植被环境效益与树冠覆盖比呈现正相关关系,单位面积的净化效益以绿化用地最高,商业金融用地最低;建成区总碳贮存为199 485.4t,每年的碳存留为879.6478t,O3的去除量为71 283.89kg,SO2的去除量为22 163.97kg,NO2的去除量为40 876.3kg,PM10的去除量为61 494.02kg,CO的去除量为8 149.331kg。该文还对提高环境质量提出建议。

生态空间理论与景观异质性

概述生态空间理论的若干主要方面：尺度、空间格局、景观异质性、镶嵌与生态交错带以及干扰与景观动态等。生态空间理论是景观评价、管理和生态规划的重要基础，对于区域可持续发展和生物多样性保护等方面的研究都具有重要的指导意义。

生物有机肥对小油菜生长及品质的影响

在小油菜上进行施用生物有机肥、有机无机配合施肥、三元肥的田间对比试验。结果表明,单施生物有机肥比单施无机三元肥的小油菜中硝酸盐和亚硝酸盐含量分别降低36.17%和21.77%;种植后土壤中有机质比单施无机三元肥提高11.12%。油菜生产中施用生物有机肥可以提高作物品质,提高土壤有机质含量,培肥地力,与三元肥配合施用不会造成明显减产。

水肥耦合条件下春小麦叶片的光合作用

采用312-D最优饱和设计,在辽宁西部半干旱区进行了田间春小麦光合作用试验研究．结果表明:叶片光合速率与籽粒产量正相关．水肥单因子对叶片光合速率影响的大小顺序是,氮>水>磷．交互耦合作用对叶片光合速率影响的大小顺序为:氮与水耦合>氮与磷耦合>磷与水耦合．水肥耦合促进叶片光合速率提高的主要原因是:扩大了叶面积、提高了叶片蒸腾速率、增大了叶片气孔导度、提高了胞内水浓度、降低了胞内二氧化碳浓度．单叶光合速率高于7．5×10-3μmol／s的水肥优化管理方案是:施氮量为323．4-399．9 kg／hm2、施磷量为65．8-105．7 kg／hm2、灌水量为276．1-353．2 mm．

土壤氧化还原酶催化动力学研究进展

土壤氧化还原酶是存在于土壤中的一种重要酶类,参与土壤中为数众多的重要生物化学反应,与土壤中有机物质的转化、腐殖质的形成以及土壤肥力变化密切相关.其催化反应的动力学研究常用来阐明其催化过程的特性、酶的本质属性及其对环境变化的响应等.研究土壤氧化还原酶动力学特征对探讨其来源、性质及影响因素,对进一步调控多种营养元素参与的反应过程有重要意义.文中概述了土壤氧化还原酶动力学研究的理论基础,综述了土壤氧化还原酶催化动力学研究的进展和影响因素,并对今后的研究提出了几点建议.

基于非均匀DCT的量化索引调制隐写

基于量化索引调制(QIM)的隐写技术正日益受到隐写分析的威胁。该文将通常在DCT域隐写的做法改为在非均匀DCT域进行,将参数作为密钥,提出了一种NDCT-QIM图像隐写方法。由于在攻击者猜测的域中,嵌入信号具有扩散性,NDCT-QIM方法不利于隐写分析对隐写特征的检测,分析和实验表明,它能够更好地抵御基于梯度能量、直方图及小波统计特征等常用统计量的隐写分析,增强了隐写的隐蔽性。

温度对Ti_(45)Zr_(35)Ni_(20)合金电化学贮氢性能的影响

采用真空熔炼法制备了Ti45Zr35Ni20合金,研究了合金在不同温度下的电化学贮氢性能。结果表明,Ti45Zr35-Ni20电极的电化学性能随着温度而变化,温度从323 K升高到343 K时,电极的活化次数从22次减少到8次,放电容量从86.1 mAh/g增到135.0 mAh/g,快速放电能力也有所提高,然而,高温使电极的循环稳定性显著下降,自放电率增大。

Hydrogenation of phenol in scCO(2) over carbon nanofiber supported Rh catalyst

A catalyst of Rh nanoparticles supported on a carbon nanofiber, 5 wt.% Rh/CNF, with an average size of 2-3 nm has been prepared by a method of incipient wetness impregnation. The catalyst presented a high activity in the ring hydrogenation of phenol in a medium of supercritical CO2 (scCO(2)) at a low temperature of 323 K. The presence of compressed CO2 retards hydrogenation of cyclohexanone to cyclohexanol under the reaction conditions used, and this is beneficial for the formation of cyclohexanone, increasing the selectivity to cyclohexanone.

In Situ Preparation and Luminescent Properties of CeF3 and CeF3:Tb3+ Nanoparticles and Transparent CeF3:Tb3+/PMMA Nanocomposites in the Visible Spectral Range

CeF3 and CeF3:Tb3+ nanoparticles were prepared by reverse microemulsion with a functional monomer, methyl methacrylate (MMA), as the oil phase, and CeF3:Tb3+/poly (methyl methacrylate) (PMMA) nanocomposites were obtained via polymerization of the MMA monomer. The nanoparticles and nanocomposites have been well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), low- and high-resolution transmission electron microscope (TEM), selected-area electron diffraction (SAED), thermogravimetric analysis (TGA), UV/vis transmission spectra, photoluminescence excitation, and emission spectra and luminescence decays. The well-crystallized CeF3 and CeF3:Tb3+ nanoparticles are spherical with a mean diameter of 15 nm. They show the characteristic emission of Ce3+ 5d-4f (313 nm, D-2-F-2(5/2); 323 nm, D-2-F-2(7/2)) and Tb3+ D-5(4)-F-7(J) (J = 6-3, with D-5(4)-F-7(5) green emission at 541 nm as the strongest one) transitions, respectively.