剪切对聚烯烃结晶行为的影响——高分子结晶过程中中介相的研究

本论文通过POM、DSC、WXRD和SR-SAXS等一系列技术手段分别对剪切场下的等规立构聚丙烯（iPP）和间规立构聚丙烯（sPP）均聚物、乙烯-辛烯共聚物（PEcO）以及iPP/PEcO共混物的结晶结构和结晶动力学过程进行了系统研究。 剪切不能改变sPP的晶型，但能使得（200）晶面发生取向，同时，剪切导致片晶结构发生明显的取向。对剪切场下不同辛烯含量的PEcO的结晶研究发现：剪切对广角测试范围的结构影响较小，对小角测试范围的结构影响较大，说明乙烯-辛烯共聚物熔体在一定尺度范围的结构是比较稳定的。通过对iPP/PEcO共混物体系的研究，发现剪切速率的提高减少了结晶诱导时间，但剪切速率的变化以及共混物中组分的变化对球晶的生长速率没有明显影响。剪切可以诱导共混物中的iPP形成β晶型，并且含量随着剪切速率的增大而提高。剪切使得共混物中iPP结晶的微晶和片晶均发生了取向，片晶取向随着共混物中弹性体含量的增加而增大。 通过对剪切场下均聚物、共聚物以及共混物的结晶行为研究，发现剪切对于聚烯烃微晶尺寸、片晶厚度以及长周期有较小影响，但对微晶和片晶的取向有一定影响，对片晶的取向影响尤其显著。

Investigation on isothermal and non-isothermal crystallization kinetics of poly (epsilon-caprolactone)

The crystallization kinetics and the development of lamellar structure during the isothermal crystallization of poly (epsilon-caprolactone) (PCL) were investigated by means of differential scanning calorimetry (DSC) and real-time synchrotron small angle X-ray scattering (SR-SAXS) techniques, respectively. The Avrami analysis was performed to obtain the kinetics parameters. The value of Avrami index, n, is about 3, demonstrating a three-dimensional spherulitic growth on heterogeneous nuclei in the process of isothermal crystallization. The activation energy and the surface free energy of chain folding for isothermal crystallization were determined according to the Arrhenius equation and Hoffman-Lauritzen theory, respectively. In the process of nonisothermal crystallization of PCL, the value of Avrami index, n, is about 4, which demonstrates a three-dimensional spherulitic growth on homogeneous nuclei. In addition, lamellar parameters were obtained from the analysis of SR-SAXS data.

Influence of heat treatment on spectroscopic properties of Er3+ in multicomponent ZrF4-ZnF2-AlF3-YF3-MF2 (M = Ca, Sr, Ba) based glass

Er3+ doped multicomponent fluoride based glass was prepared. These precursor fluoride glass samples were then heated using different schedules. Crystalline phase particles were successfully precipitated in the multicomponent fluoride glass samples after heat treatment. The influence of heat treatment on the spectroscopic properties of Er3+ in multicomponent fluoride based glass samples were discussed. Small changes of the Judd-Ofelt parameters Omega(i) (i = 2,4,6) were found in multicomponent fluoride glass samples before and after heat treatment compared to oxyfluoride telluride glass. Preparation conditions used to produce transparent multicomponent fluoride glass ceramics doped with rare-earth ions are discussed. (c) 2007 Elsevier B.V. All rights reserved.

Nd：（La，Sr）（Al，Ta）O3晶体的生长及光谱性能的研究

应用中频感应提拉法生长了新型的Nd：（La，Sr）（Al，Ta）O3（Nd^3＋：LSAT）晶体。运用电感耦合等离子体原子发射光谱仪（ICPAES）测定Nd^3＋离子在Nd^3＋：LSAT晶体中的分凝系数为0．587。X射线粉末衍射（XRPD）测试结果表明Nd^3＋：LSAT晶体与LSAT晶体同构。研究了不同退火条件对晶体光谱性能的影响。分析了Nd^3＋：LSAT晶体的光谱性能，Nd^3＋：LSAT晶体的荧光寿命为290μs。比较了Nd^3＋：LSAT和Nd^3＋：YAG，Nd^3＋：YVO3等晶体的光谱

在Sr～2+α_BBO单晶衬底上生长β_BBO薄膜的研究

Crystalline beta-BBO thin films were successfully prepared on (001)-oriented Sr2+-doped alpha-BBO substrates by using liquid phase epitaxy, pulsed laser deposition and vapor transport equilibration techniques. The films were characterized by X-ray diffraction and X-ray rocking curve. The present results manifest that the beta-BBO thin films grown on Sr2+-doped alpha-BBO substrates have larger degree of orientation f value and smaller X-ray rocking curve FWHM than the ones grown on other reported substrates. Compared with other substrates, alpha-BBO has the similar structure, the same UV cutoff and the same chemical properties to beta-BBO. These results reveal that Sr2+-doped alpha-BBO single crystal may be a promising substrate proper to the growth of beta-BBO films.

Spectroscopic properties of Nd3+:(La,Sr)(Al,Ta)O-3 crystal

A new laser crystal Nd3+:(La, Sr)(Al, Ta)O-3 (abbreviated as Nd3+:LSAT) has been grown by the conventional Czochralski method. The absorption and luminescence spectra of trivalent neodymium in Nd3+:LSAT crystal were measured at room temperature. The value of absorption and emission cross-section was calculated. The Judd-Ofelt analysis was applied to the crystal to get the phenomenological parameters (Omega(i), i = 2,4,6), the line strengths, the radiative transition rates, the branching ratios and the radiative lifetime. (C) 2006 Elsevier B.V. All rights reserved.

气相传输平衡法在Sr^2＋：α-BBO衬底上制备β-BBO薄膜的研究

采用气相传输平衡技术在掺Sr^2＋的α-BBO（001）衬底上制备了β-BBO薄膜，研究了粉料配比、VTE处理温度以及恒温时间对薄膜质量的影响。结果表明，在适当的粉料配比、VTE处理温度以及恒温时间下，在Sr^2＋：α-BBO晶片表层制备呈c轴高度择优取向的、没有第二相物质的β-BBO薄膜，其双晶摇摆曲线半峰宽值FWHM为1000＂，显示出β-BBO薄膜较好的结晶质量。并对气相传输平衡技术制备β-BBO薄膜的机理进行了初步的探讨。

剪接因子SR-蛋白特异的激酶—SRPK1的发现

<正> 1977年,当美国麻省理工学院的PhillipSharp和冷泉港实验室的Richard Roberts分别领导的两个研究小组在研究腺病毒(adenov-irus)和其mRNA之间的杂种分子发现了基因割裂(split)现象时,他们立刻感到诺贝尔已带着他的遗产敲开了他们的心扉。果然,一个新的称为RNA剪接Splicing的研究领域从此诞生了,16年后,随着这一领域的不断开拓,当时这一发现的领导者Phillip Sharp和Richard Roberts终于于1993年分享了诺贝尔

利用水生植物清除水体中放射性物质的研究 (Ⅲ)水生植物对Sr~(90)、Y~(91)、Cs~(137)、Ce~(144)的积累、释放及Ca对Sr~(90)吸收的影响

5种水生植物对所用4种放射性同位素都有一定的清除能力,其清除能力的大小不仅取决于生物的种类,而且还取决于生物本身代谢率的高低。试验结果:去污率高的可达80%,积累系数最高可达1,500;水体中含Ca量的多少对生物吸收积累放射性物质的多少有一定的影响;生物在积累放射性物质之后,转移到无放射性物质的水体中将释放出原积累的一部分放射性物质。

利用水生植物清除水体中放射性物质的研究(Ⅰ)——水生植物对Sr~(90)的吸收积累和清除能力

<正> 原子能和平利用事业的广泛开展,水体中容易受到放射性物貭的沾染,尤其是核武器的試驗,使水体中的放射性本底逐漸增高。如何清除水体中放射性物貭沾染,是一个必需解决的重要問题。水生植物对放射性物貭具有吸收和积累的能力,在許多文献中已有报导。为了利用水生植物的这个特性来清除水体中放射性沾染,我們对九种水生植物进行了試驗。

Oscillatory change of SR-protein kinase activities during oocyte maturation meiosis in fish

The SR-protein kinase activity was analyzed and the cytological changes were observed during oocyte maturation in bisexual transparent color crucian carp ( Carassius auratus color variety). The results revealed that the SR-protein kinase activity was sensitive to the artificially induced spawning hormones, and the change of oscillatory activity was similar to that of the maturation-promoting factor (MPF) kinase that regulates meiotic cell cycle in fish.

New observations on the pressure dependence of luminescence from Eu2+-doped MF2 (M = Ca, Sr, Ba) fluorides

The luminescence from Eu2+ ions in MF2 (M = Ca, Sr, Ba) fluorides has been investigated under the pressure range of 0-8 GPa. The emission band originating from the 4f(6)5d(1) -> 4f(7) transition of Eu2+ ions in CaF2 and SrF2 shows the red-shift as increasing pressure with pressure coefficients of -17 meV/GPa for CaF2 and -18 meV/GPa for SrF2. At atmospheric pressure, the emission spectrum of BaF2:Eu2+ comprises two peaks at 2.20 and 2.75 eV from the impurity trapped exciton (ITE) and the self-trapped exciton (STE), respectively. As the pressure is increased, both emission peaks shift to higher energies, and the shifting rate is slowed by the phase transition from the cubic to orthorhombic phase at 4 GPa. Due to the phase transition at 4-5 GPa pressure, the ITE emission disappears gradually, and the STE emission is gradually replaced by the 4f(6)5d(1) -> 4f(7) transition of Eu2+. Above 5 GPa, the pressure behavior of the 4f(6)5d(1) -> 4f(7) transition of EU2+ in BaF2: EU2+ is the same as the normal emission of Eu2+ in CaF2 and SrF2 phosphors.