贾第虫rDNA的研究

典型的真核生物有四种rRNA（18S、5.8S、28S和5SrRNA）。一般18S、5.8S和28S的基因分别由转录间隔区（ITS）隔开而位于同一个转录单位上构成一个rRNA基因拷贝，多个rRNA基因拷贝串联形成rDNA。rDNA聚集在一起构成核仁组织区（NOR），成为核仁发生的位置。5SrRNA基因除在少数真核生物（如：酵母）中是和18S、28S rRNA基因位于同一个转录单位上外，一般是处在核仁以外的区域。贾第虫一度被认为是现存最原始的真核生物。支持这一观点的一个重要证据之一就是它还不具核仁结构。那么它的rDNA与典型真核生物的相比会有怎样的特点呢？本文在基因组的水平上对贾第虫的rDNA进行了全面调查分析，并对5S rRNA及其相关蛋白进行重点研究，得到如下结果和结论： 1）贾第虫的18S rRNA（1448bp）基因和28S rRNA（2300bp）基因比其他一些真核生物的（一般为1800bp和3400bp）要小的多，甚至比一些原核生物的相应的rRNA基因还要小。不仅如此，其5.8S rRNA基因和28SrRNA基因之间的转录间隔区（ITS2）比典型真核生物的对应区域也要短得多（只有54bp），且GC含量较高。结构预测表明该间隔区不能形成在许多真核生物中所能形成的保守的二级结构。更特别的是，贾第虫基因组中的rRNA基因序列大部分都是不完整的，并且不按照18S-5.8S-28S rRNA基因顺序排列，也没有多个完整拷贝顺序排列的区域。这提示贾第虫rRNA基因可能是以一种不同于典型真核生物的方式聚集的。因此本文认为以上这些特点可能与贾第虫不能形成典型核仁结构有关。 2）本文从贾第虫基因组中鉴定出了5S rRNA基因，并实验验证了其表达及其完整基因序列所编码的5S rRNA具有典型真核生物的T型二级结构，且具有绝大多数保守位点。RT-PCR表明该基因具有转录活性。该结果否定了前人的贾第虫没有5S rRNA的实验结果。并表明贾第虫尽管很原始，但其5S rRNA基因仍然是独立存在的和单独转录的。贾第虫基因组中总共有8个5S rRNA基因拷贝（且其中还有一个拷贝具有15个bp的异常插入）这大大低于一般真核生物的拷贝数。这些5S rRNA基因也不形成串联排列的区域。 我们还在贾第虫中鉴定出在真核生物中唯一与5S rRNA接触的核糖体蛋白L5蛋白并验证了其表达，该序列与其他真核生物的L5蛋白相似性很高，这提示贾第虫在5S rRNA基因转录出核后与L5蛋白结合形成5S RNP的过程可能与典型的真核生物是一致的。此外，我们从贾第虫中鉴定不出符合典型真核生物TFIIIA因子特征的蛋白，这提示贾第虫5S rRNA的转录起始以及转录后出核的机制可能与典型真核生物不同。过去对贾第虫的研究表明高等真核生物里RNA聚合酶III所独有的四个亚基在贾第虫中找不到同源物，而这样不完整的RNA聚合酶III已经可以在贾第虫中完成5S rRNA的转录了，这表明RNA聚合酶III所独有的这些亚基可能是为了完成其他功能而进化出来的。

GaInNAs/GaAs quantum well lasers grown by solid-source molecular beam epitaxy

The growth of GaInNAs/GaAs quantum wells (QW) was investigated by solid-source molecular beam epitaxy. N was introduced by a dc-active plasma source. The effect of growth conditions such as on the N incorporation and photoluminescence (PL) intensity of the QWs has been studied. The PL peak intensity decreased and the PL fun width at half maximum increased with increasing N concentrations. The highest N concentration of 2.6% in a GaInNAs/GaAs QW was obtained, and corresponding to a PL peak wavelength of 1.57 mum at 10K. Rapid thermal annealing at 850degreesC significantly improved the crystal quality of the QWs. An optimum annealing time of 5s at 850degreesC was obtained. A GaInNAs/GaAs SQW laser with the emitting wavelength of 1.2 mum and a high characteristic temperature of 115 K was achieved at room temperature.

超临界压力下航空煤油热裂解特性研究

本文介绍了大庆3号煤油在超临界条件下热裂解特性的实验研究。通过改进的煤油二级加热系统以及裂解产物收集和分析系统，研究了煤油在温度 700－1100K，压力 3.5－4.5MPa，以及驻留时间 0.6/1/2.5s 时的热裂解吸热特性。同时实验测量了裂解产物的成分以及裂解混合物的流量随温度、压力、驻留时间的变化。研究发现：裂解特性，如裂解度、化学热沉、裂解产物成分均随裂解温度、驻留时间显著变化，而受压力的影响不大。当裂解度大约 45％时，裂解反应的化学热沉达到最大值，该值随着驻留时间的增大而减小。气相产物的成分分析结果表明随着裂解温度的升高和驻留时间的增大，产物中饱和烃的比重增加，因此反应的吸热能力明显减小。在目前的裂解条件下，可获得的最大化学热沉为0.5MJ/kg，小于美国JP-7燃料的最大热沉0.7 MJ/kg（裂解度60％）。

近贫燃极限甲烷/空气火焰的层流燃烧速度研究

利用微重力条件下向外传播的球形火焰,对贫燃极限附近甲烷/空气预混火焰的层流燃烧速度进行了测量,得到当量比从0.512(本文微重力实验中测定的可燃极限)到0.601范围内的零拉伸层流燃烧速度,并与前人实验数据和使用3种化学反应动力学模型的计算结果进行了比较. 本文实验结果与已有的微重力实验数据非常接近,而其他研究者在常重力实验中得到的数据大多都明显高于微重力实验结果. 不同化学反应机理预测的燃烧速度比微重力实验测量值大得多,这是因为它们主要是用远离可燃极限的燃烧速度校核的

钩藤和蹄叶橐吾的化学成分研究

本论文由三章组成。第一、二章分别报道钩藤、蹄叶橐吾的化学成分研究工作。从两种药用植物中共分离和鉴定了37 个化合物，其中有1 组6 个新的骨架相似的鞘糖脂类同系物及5 个新的倍半萜类化合物。第三章概述了艾里莫芬烷内酯类化合物的研究进展。 第一章报道钩藤(Uncaria rhynchophylla)带钩茎枝乙醇提取物的化学成分。采用正、反相硅胶柱层析等分离方法，运用NMR、MS 等波谱技术共分离鉴定得到22 个化合物，分属于五环三萜类化合物、鞘糖脂类化合物等，其中有1 组6个新的鞘糖脂类化合物同系物，另外有7 个化合物首次从该植物中分离得到。 第二章报道蹄叶橐吾(Ligularia fischeri)根部乙醇提取物化学成分的分离纯化和结构鉴定。通过正、反相硅胶柱层析等分离纯化和MS、NMR 等波谱解析，共分离鉴定得到18 个化合物，其中5 个是新化合物。它们的结构分别确定为3β-acetyl-6β, 8α, 10β-trihydroxyeremophila-7(11)-en-8, 12-olide (23), 3β-acetyl-8β,10β-dihydroxy-6β-(2-methylbutyryloxy)-eremophilenolide (24), 3β-acetyl-6β, 10β-dihydroxyeremophila-7(11), 8(9)-dien-8, 12-olide (25), 3β-acetyl-6β, 10β-dihydroxyeremophila- 7(11), 8(9)-dien-8, 12-olide (26), (3aR, 4R, 5S, 7aS)-2-acetyl-7ahydroxy-3a, 4, 5, 6, 7, 7a-hexahydro-1H-inden-5-yl acetate (27)。这5 个化合物经体外生物活性测试，结果表明化合物23 具有抑制酪氨酸磷酸酯酶的活性, 其IC50 值为1.30 μg/ml。 第三章概述了近二十年来艾里莫芬烷内酯类化合物的研究进展，包括其结构及药理活性两个方面，列举了从23 种植物中分到的114 个艾里莫芬烷内酯类化合物，同时也对其主要生物活性进行了总结。 This dissertation consists of three chapters. The first and second chapters elaborate the phytochemical investigation of Uncaria rhynchophylla and Ligularia fischeri. Thirty-seven compounds, including six new ones, were isolated and identified by spectroscopic methods and X-ray diffraction experiments. The third chapter is a review on the study progress of Eremophilanolides. The first chapter focus on the isolation and identification of chemical constituents from Uncaria rhynchophylla. Twenty-two compounds were isolated from the roots of U. rhynchophylla by repeat column chromatography over normal and reversed phase silica gel. Those compounds mainly belonged pentacyclic triterpenoids and sphingolipids. Among them, a series homologues of six sphingolipids were new compounds and seven compounds were firstly reported in this plant. The second chapter is about the phytochemical investigation of L. fischeri. Eighteen compounds were isolated and identified. Among them, four new erem-ophilanolides and a new dinoreremophilane derivative were characterized as 3β-acetyl-6β, 8α, 10β-trihydroxyeremophila-7(11)-en-8, 12-olide (23), 3β-acetyl-8β, 10β-dihydroxy-6β-(2-methylbutyryloxy)-eremophilenolide (24), 3β-acetyl-6β, 10β-dihydroxyeremophila-7(11), 8(9)-dien-8,12-olide (25), 3β-acetyl-6β, 10α-dihydroxyeremophila- 7(11), 8(9)-dien-8,12-olide (26), (3aR,4R,5S,7aS)-2-acetyl-7a-hydroxy-3a, 4, 5, 6,7, 7a-hexahydro-1H-inden-5-yl acetate (27) by spectroscopic analysis and confirmed by X-ray crystallography analysis. It was revealed that compound 23 has the ability to inhabit the PTP1B in vivo. And its IC50 is 1.30 μg/ml. The third part is a review on the study progress of Eremophilanolides.

Theoretical analysis of xuv photoabsorption spectra of laser-produced iodine plasmas

The 4d photoabsorption spectra of I2+, I3+, and I4+ have been obtained in the 70-127 eV region with the dual laser-produced plasma technique at time delays ranging from 400 to 520 ns. With decreasing time delay, the dominant contribution to the spectra evolves from the I2+ to the I4+ ions, and each spectrum contains discrete 4d-nf transitions and a broad 4d-epsilon f shape resonance, which are identified with the aid of multiconfiguration Hartree-Fock calculations. The excited states decay by direct autoionization involving 5s or 5p electrons, and rates for the different processes and resulting linewidths were calculated. With increasing ionization, the 4d-epsilon f shape resonance become intense and broader in going from I2+ to I3+, and then vanishes at I5+. In addition, the discrete structure of the calculated spectrum of each ion gradually approaches the corresponding shape resonance position. Based on the assumption of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model, we reproduced spectra which are in good agreement with experiment.

NOx storage-reduction over Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios

A series of Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios were prepared. The NOx storage capacities of these catalysts were measured by isothermal storage at 350 degreesC. It was found that the NOx storage capacity increased with increasing Mg/Al atomic ratios. The catalytic behaviors of Pt/Mg-Al-O and Pt/MgO were studied with storage-reduction cycles at 400 degreesC. Under oxidizing conditions, NOx concentration in the outlet gas gradually increased with time, which indicated the catalysts could store NOx effectively. After a switch from oxidizing conditions to reducing conditions, NOx desorption peak emerged immediately due to the incomplete reduction of stored NOx, which lowered the total NOx conversion. With increasing Mg/Al atomic ratio in the catalysts, NOx conversion increases. Pt/MgO has the highest NOx conversion because of its best activity in the reduction of NOx by C3H6. It seems that with an increasing amount of MgO in the catalysts, the self-poisoning of Pt-sites by adsorbed species during the reaction of NOx with C3H6 may be inhibited effectively.

Unique properties of Ir/ZSM-5 catalyst for NO reduction with CO in the presence of excess oxygen

The reduction of NO with CO in the presence of excess oxygen was investigated over different noble metal catalysts for probing the relationship between catalytic properties and adsorption behaviors. Among the four precious metal catalysts investigated, Ir/ZSM-5 was found to be the only active one for NO reduction with CO under lean conditions. With the decreasing of the Ir content, higher NO conversion and CO selectivity was obtained. Temperature-programmed reaction (TPR) studies of NO/H-2/O-2 and NO/CO/O-2 showed that the Pt/ZSM-5 was active when H-2 was used as the reductant, whereas, the Ir/ZSM-5 was active when CO was the reducing agent. This difference is due to the different mechanisms of the two reactions. Temperature-programmed desorption (TPD) of NO, CO and O-2 showed that NO could dissociate more easily over the Ir/ZSM-5 than on the Pt/ZSM-5, while the oxidation of CO by O-2 proceeded more rapidly on the Pt/ZSM-5 than on the Ir/ZSM-5. The presence of excess O-2 inhibited drastically the dissociation of NO, which is considered as the key step for the NO-CO reaction. The high dissociation rate of NO over the Ir/ZSM-5 is visualized as the key factor for its superior high activity in NO reduction with CO under lean conditions. (C) 2002 Elsevier Science B.V. All rights reserved.

BaLiF_3∶Eu,Gd中Gd~(3+)→Eu~(2+)的能量传递

研究了 Ba Li F3中 Gd3+和 Eu2 +的光谱性质及 Gd3+对 Eu2 +的能量传递过程 ,讨论了传递机理 .Gd3+的含量 (物质的量分数 )为 0 .3 %时 ,传递效率最高 ,传递几率 PSA=1 .3 5× 1 0 5s- 1 .当 Gd3+的含量高于 0 .3 %时 ,由于 Gd3+ 和 Eu2 + 竞争吸收 Gd3+ 占优势 ,增加 Gd3+ 含量 ,竞争吸收比相应增加 ,Eu2 + 自身吸收光子数目减少 ,发射强度降低

蓝紫色ZnO-Al_2O_3-SiO_2长余辉陶瓷

通过高温固相法首次合成并报道了兰紫色ZnO Al2O3 SiO2长余辉陶瓷,系统地研究了其发光和缺陷性质。在强度0.6mW·cm-2,主峰254nm的UVP紫外灯下激发15min,然后关闭激发源,样品发射兰紫色长余辉。撤去激发源以后5s,余辉初始强度为230mcd·m-2,色坐标为(0.1292,0.0984)。暗视场中,8h以后余辉仍然肉眼可辨。样品的紫外可见发射和不同时间的余辉发射光谱显示:荧光发射位于390nm,来源于基质的自致发光;而余辉有两个发射峰,主峰位于390nm,肩峰位于520nm。这表明样品中存在两种余辉发射中心。由余辉衰减曲线可以看出,这两种余辉发光都由一个快过程和一个慢过程组成。其中,慢过程决定了材料的长余辉时间。从时间依赖的余辉强度倒数曲线可以看出,余辉强度与时间成反比,这表明余辉发光的机理为电子空穴复合过程。热释光谱显示:样品分别在92和250℃附近出现两个宽的热释峰,说明材料中至少存在两种具有不同陷阱深度的电子或空穴缺陷中心。

玻璃化转变在室温附近的一种新型梳状聚合物的合成和表征——侧链分子量为550的聚乙二醇单甲醚

以分子量为550的聚乙二醇单甲醚为侧链，苯乙烯/马来酸酐共聚物为骨架，合成了苯乙烯/马来酸酐共聚物多缩乙二醇酯，用红外光谱、元素分析、DSC、热失重等方法，对合成条件、产物结构和性能进行了研究。结果表明：反应严格按照反应方程进行，精制产物是非晶的梳状聚合物。玻璃化温度为30.68℃，分解温度为120℃。对动态力学性能及其锂盐复合物离子导电性进行研究表明α转变温度和β转变温度分别是28℃和-47.7℃。电导率与温度的依赖关系符合VTF方程。室温电导率最高可达4.2×10-5S/cm。

辐射法研制功能高分子膜离子选择电极活性材料

用辐射接枝工艺合成了功能高分子膜活性材料,并对其进行了表征,测定了以此为活性材料的离子选择电极性能。结果发现,硫酸根电极在10~(-1)—10~(-3)mol/L Na_2SO_4溶液中响应时间<70s,斜率为52mV/PSO_4~(2-);氯离子电极的线性范围1×10~(-1)—2×10~(-4)mol/L,检测下限为8×10~(-5)mol/L,稳定性好,寿命长,响应时间<5s,内阻<60kΩ,抗毒化能力强。从稀土离子选择电极中发现,以辐射接枝工艺合成的材料比化学法合成的好,前者斜率为53 mV/PGd,后者斜率为46 mV/PGd;预辐照接枝工艺合成的材料比共辐照接枝工艺的好些。

聚萘的裂解色谱研究

聚萘是一种新型的高分子,掺杂后具有导电性能,是一种导电聚合物。本文用裂解色谱法(PGC)研究了它的热裂解行为,分离鉴定了主要和特征裂解产物,并在此基础上,对其分子链结构和裂解机理进行了讨论。 实验部分 (一)样品 聚萘(PN):由本实验室直接从萘合成,使用前在100℃下真空热处理48小时加以提纯。 (二)仪器和实验条件 裂解器:美同CDS Py-ro-Probe 190型(丝式);裂解温度300-800℃,裂解时间5s。色谱仪:北分厂-2305E型,氢火焰离子化检

溶剂对聚乙炔合成及性能的影响

聚乙快的不稳定性及难以加工影响了其应用.最近,Naarmann通过陈化在硅油中的Ti(OBu)_4~-AlEt_3催化体系及加入不同量的Li-(n-Bu)制得了拉伸后电导率达10~5S/cm的聚乙炔膜,此膜的电导和形态在空气中几个月几乎不发生改变.我们曾报导用加热的甲苯-Ti(OBu)_4~--AlEt_3催化体系合成高性能聚乙炔膜.本文进一步讨论不同溶剂对高性能聚乙炔(HPPA)合成及性能的影响.