原子核145Tb和157Yb的高自旋态能级结构研究

本论文分为两部分：1）利用能量为165 Mev的飞束流，通过熔合蒸发反应118Sn（32S，1p4n），用12套BGO（AC）HPGe探测器进行了γ射线的激发函数、X-γ-t和γ-γ-t符合测量。首次建立了由50个能级、81条γ跃迁组成的145Tb的高自旋态能级纲图。基于邻近N＝80同中子素能级结构的系统性，用弱祸合模型对145Tb的低位能级结构进行了解释。145Tb的低位能级可以看成是由一个hll尼价质子与偶偶核芯144Gd的2＋，4＋和3-激发态祸合而成。通过粒子一核芯相互作用计算很好地再现了145Tb的低位激发态。通过比较可知，（πh11/2⑧v-22+，4+）和（πh11/2×3-）多重态的激发能与相应核芯的激发态能量相差不大，这说明价质子与核芯的相互作用比较弱。本工作在多粒子壳模型组态基础上对145Th的更高激发态进行了深入讨论。为了使实验能级的组态指定更为直接方便，采用了参数无关的半经验壳模型计算。其结果清楚地揭示了球形核多准粒子的激发特性。通过与计算结果比较，明确地指定了晕态能级和部分非晕态能级的组态。 2）利用能量为90MeV的16O束流，通过144Sm（16O，3n）反应，用11套BGO（AC）HPGe探测器进行了长时间的γ-γ-t符合测量。基于γ-γ符合关系、γ射线的各向异性度和DCO系数的测量结果，首次建立了157Yb的高自旋能级纲图。确定了157Yb的13／2+同质异能态的激发能为530 keV。此同质异能态已经被前人指定，其激发能却一直未知。观测到了157Yb的vi13/2龙转动带。157Yb能级纲图中的角动量较低部分显示了轻微扁椭与长椭形变之间的共存。随着角动量增加，157Yb的vi13/2带逐渐损失其集体性，其能级结构演变为具有准振动的激发样式，最后被单粒子激发所取代。用TRs模型计算了157Yb的vi13/2转动带随着角动量增加的形状演变。计算结果很好地再现了实验观测。本工作表明，157Yb不但在核素图上连接了基态为球形（N＜87）和有明显长椭球形变（N＞87）的2组同位素，而且同时具有这2组同位素的结构性质。

Preparation of Mn substituted La-hexaaluminate catalysts by using supercritical drying

LaMnxAl12-xO19 catalysts were prepared from NH4OH and metal nitrates solutions. Supercritical drying (SCD) and conventional oven drying (CD) methods were used to extract the water in the hydrogel. The effects of drying methods on properties of the catalysts were investigated by means of TEM, N-2-adsorption, thermogravimetry (TG)-differential thermal analysis (DTA) and X-ray diffraction. SCD method is beneficial to maintain high surface area and improving catalytic activity for methane combustion of the catalyst. The specific surface area and pore volume of LaMn1Al11O19 catalyst prepared by SCD method are 28 m(2)/g and 0.23 cm(3)/g, respectively, and the ignition of methane could be carried out at 450degreesC. However, those of the CD catalyst prepared from the same precursor are 15 m(2)/g, 0.11 cm(3)/g and 530 degreesC, respectively. Suitable Mn content (0 less than or equal to x less than or equal to 2) could promote the formation of LaMnAl11O19 hexaaluminate, while further addition of Mn (2 less than or equal to x less than or equal to 6) cause the formation of LaMnO3. (C) 2003 Elsevier B.V All rights reserved.

基于决策树的科尔沁沙地土地利用/覆盖变化监测

以科尔沁沙地西缘内蒙古翁牛特旗为对象,利用3个时相(1989、1999和2007年,分别表示三北防护林体系工程建设近10年、20年和30年)Landsat ETM/TM数据,采用决策树分类方法对该区土地利用/覆盖动态变化进行监测。结果表明:基于决策树分类方法进行遥感影像分类的总体精度能达到89.4%以上,Kappa系数达到0.84以上;近20年,草地和耕地是主要土地利用类型(两项合计占64%以上),林业用地比重为4.8%~5.3%,面积较少;各土地类型面积变化大小依次为耕地>未利用土地>林地>居民及建设用地>水域>草地。

农林复合系统种间关系研究进展

种间相互作用在很大程度上决定了农林复合系统的生产力和可持续性,理解种间相互作用是经营和管理农林复合系统的关键。地上部分相互作用主要包括复合系统组分对光的竞争与互利、小气候的改变对系统生产力的影响;地下部分相互作用主要包括复合系统组分对水分和养分资源的竞争与互利、固氮树种对系统生产力的影响以及化感作用。今后需加强不同立地条件下的不同农林复合系统种间关系的比较、农林复合系统组分的空间分布格局、化感作用以及农林复合系统种间关系模型等研究。

沈阳城市森林植被结构和植物多样性研究

<正>1引言城市森林植被结构包括林地布局、林地类型、植物种类组成、树木胸径结构等方面:植物多样性包括物种丰富度、多样性指数和物种均匀度指数等内容。城市森林植被结构和植物多样性水平影响到城市森林的功能和健康,影响到城市森林的可持续管理。

Gelatin multilayer assembled on the poly(L-lactic acid) surface for better cytocompatibility

Gelatin multilayers were assembled on PLLA substrate at pH 3, 5, and 7, which was below, around, and above the isoelectric point of the amphoteric polymer, using the layer-by-layer assembly technique. The multilayer deposition on the PLLA substrate was monitored by X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. The XPS, water contact angle, and atomic force microscopy data indicated that the layer thickness, surface hydrophicity, and surface morphology of the gelatin multilayers assembled strongly depended on the pH at which the layers were deposited

16-O-去甲基乌头碱的生物转化及电喷雾质谱研究

采用乌头碱和人肠内细菌体外温孵的方法,探讨乌头碱在肠内的生物转化规律.乌头类生物碱在ESI正离子模式条件下形成质子化分子[M+H]+,利用离子阱电喷雾串联质谱和傅立叶离子回旋共振电喷雾串联质谱方法可以直接分析乌头碱的转化产物.本文首次报道了乌头碱在人肠内菌群环境中产生16-O-去甲基乌头碱,16-O-去甲基乌头碱可进一步被肠内细菌转化,通过脱乙酰基、脱苯甲酰基、脱甲基、脱羟基以及酯化反应,产生新型的单酯型、双酯型和20余种脂类生物碱等转化产物.

Starburst substituted hexaazatriphenylene compounds: synthesis, photophysical and electrochemical properties

Starburst-substituted hexaazatriphenylene Compounds have been designed and synthesized by introducing various peripheral aryl substituents to the central heterocyclic core. The effects of various substituent groups on the photophysical and electrochemical properties of the substituted hexaazatriphenylene have been investigated. Significant red-shifts of the absorption peak (from 413 nm to 530 nm) and emission peak (from 432 nm to 700 nm) were observed when the electron-donating ability of the aryl substituents was increased, corresponding to a decrease in the band gap from 2.90 eV to 2.05 eV. Introducing bulky substituents with weak electron-donating ability enhances the fluorescence quantum yield from 23% to 87%. In contrast, incorporating aryl substituents with strong electron-donating ability decreases the fluorescence quantum yield.

Investigation on preparation and fluorescence properties of oxy-fluoride glass co-doped with Er3+ and Yb3+

The glass sample based on the composition of 45PbF(2)-45GeO(2)-10WO(3) co-doped with Yb3+/Er3+ was prepared by the fusion method in two steps: melted at 950 degreesC for 20 similar to 25 min then annealed at 380 degreesC for 4 h. Through the V-prism it is found that the refractive index of host glass and the sample are 1.517 and 1.65 respectively. The transmittance was observed by using the ultraviolet-visible-infrared spectrometer in the wavelength range from 0.35 to 2.5mum. The transmittaitce of the host glass is beyond 73%. That of the sample is beyond 50% and there are characteristic absorption peaks of rare-earth ions. The emission spectrum was measured by using the Hitachi F-4500 fluorescent spectrometer pumped by 980 nm semiconductor laser. There are a strong emission peak at 530 nm and a weak peak at 650 nm.

Surface-enhanced Raman scattering studies on aggregated silver nanoplates in aqueous solution

Four different sizes of citrate-protected silver nanoplates with the corresponding in-plane dipole resonance band at 530, 619, 778, and 858 nm, respectively, are synthesized for surface-enhanced Raman scattering (SERS) study. Their aggregation behaviors are monitored by use of UV-vis spectroscopy. During the aggregation process, a marked red shift of the in-plane dipole resonance of silver nanoplates is observed, whereas other resonance modes of them only have small alterations in the site or intensity. Aggregated silver nanoplates can serve as active SERS substrates with an enhancement factor of about 4.5 x 10(5) using 2-aminothiophenol as a probing molecule. The SERS performance of silver nanoplates is even superior to the commonly used Lee-Meisel silver colloid, making them very attractive for SERS applications.

Polyimides derived from 3,3 '-bis(N-aminophthalimide)

A novel diamine, 3,3'-bis(N-aminophthalimide) (BAPI), was prepared from 3,3'-bis(N-phenylphthalimide). Its structure was determined via IR, H-1 NMR, N-15 NMR, elemental analysis, and single-crystal X-ray diffraction analysis. A series of homo- and copolyimides were synthesized by a conventional one-step method in p-chlorophenol. The characteristic IR absorption bands of hydrazine-based imide groups were near 1780, 1750, 1350, 1100, and 730 cm(-1). The polymers showed good solubility in polar aprotic solvents and phenols at room temperature. The temperatures of 5% weight loss (T-5%) of the polyimides ranged from 495 to 530 degrees C in air. DMTA analyses indicated that the glass-transition temperatures (Tgs) of the polyimides were in the range 371-432 degrees C. These polymers had cutoff wavelengths between 350 and 400 nm. The polyimide films of 6FDA/BAPI and 4,4'-HQPDA/BAPI were colorless; other films were pale yellow or yellow.

Syntheses of biphenyl polyimides via nickel-catalyzed coupling polymerization of bis(chlorophthalimide)s

A facile method for the synthesis of biphenyl polyimides, which involves the nickel-catalyzed coupling of aromatic dichlorides containing imide structure in the presence of zinc and triphenylphosphine, has been developed. The polymerizations proceeded smoothly under mild conditions and produced biphenyl polyimides with inherent viscosities of 0.13-0.98 dL/g. The polymerizations of bis(4-chlorophthalimide)s with bulky side substituents gave high molecular weight polymers. Low molecular weight polymers from bis(4-chlorophthalimide)s containing rigid diamine moieties and bis(3-chlorophthalimide)s were obtained because of the formations of polymer precipitate and cyclic oligoimides, respectively. The effects of various factors, such as amount of catalyst, solvent volume, ligand, reaction temperature, and time, on the polymerization were studied. The random copolymerization of two bis(chlorophthalimide)s in varying proportions produced medium molecular weight material. The TgS of prepared polyimides were observed at 245-311 degreesC, and the thermogravimetry of polymers showed 10% weight loss in nitrogen at 470-530 degreesC.