P-选择素CR结构域功能的模拟预测

<正>选择素(selectin)与其配体间相互作用介导的细胞粘附在炎症级联反应、肿瘤转移和淋巴细胞归巢等病理、生理过程中起重要作用。其结构组成从远离细胞表面的N-末端到胞内C-末端,依次为:钙型凝集素功能区(Calcium-type lectin domain,Lec),类上皮生长因子功能区(Epidermal Growth Factor-like module,EGF),具有粘附补体蛋白作用的多个重复序列(Consensus Repeats,CRs),跨膜区(Transmembrane,TM)和胞内区

青藏高原东缘青杨（Populus cathayana Rehd.）遗传多样性研究

青杨（Populus cathayana Rehd.）是青杨派杨树的主要树种之一，为我国特有乡土树种，其主要分布区之一是我国的青藏高原，集中分布地带在甘肃省中部及青海省东部，四川省西北部岷江上游和松潘等地区。本研究以青藏高原东缘青杨天然分布区的6个群体143个个体为材料，用AFLP、SSR和叶绿体SSR分子标记分析青杨天然群体的遗传多样性，分析其遗传结构和分化，比较6个群体间遗传多样性的高低和群体间的遗传关系。旨在为青杨基因资源评价、保护与保存、遗传改良策略制定等提供科学理论依据。通过以上研究，得出如下主要研究结果： 1 AFLP分子标记研究结果 采用4对选择性引物对6个青杨天然群体143个个体进行分析，扩增谱带分析共检测到175个位点，其中173个位点表现为多态，多态位点百分率高达98.9%。从整体上表现出较高的遗传多样性，Nei’s基因多样度(h)水平为0.306。从青杨天然群体位点分布来看，有高达20%的位点（32位点）为群体所特有，仅有9.14%的位点（16位点）在所有群体中存在。群体间的遗传分化极大，所有遗传变异中，有48.9%的遗传变异存在于群体间。在个体群丛（Individuals cluster）和主坐标（PCO analysis）分析中，青杨各群体未呈现任何地理模式，Mantel检测也显示各群体间遗传距离与地理距离无明显相关。研究认为，由于地理和空间上大尺度的隔离和地形地貌复杂使得群体间无法进行基因交流，导致群体间遗传分化极大，另外各群体在不同的选择压力下，经历各自独立的进化历程，这些都可能导致群体间遗传距离与地理距离的不相关。 2 SSR分子标记研究结果 在SSR分析中，7个位点在6个青杨天然群体143个个体中共检测到79个等位基因，每位点检测到的等位基因数在5-16之间，平均11.3个，总体上多态位点百分率达100%。平均观察杂合度和期望杂合度分别为0.792和0.802。Hardy-Weinberg平衡检验表明青杨大部分群体都处于非平衡状态，群体大部分位点都是偏离哈迪-温伯格平衡（76.3%），只有23.7%的测验满足哈迪-温伯格平衡。分析青杨天然群体内和群体间的遗传变异，基因分化系数（GST）为0.373，即有62.7%的遗传变异存在群体内，37.3%的遗传变异存在群体间。群体内的遗传变异高于群体间水平。根据各群体遗传距离UPGMA聚类分析，有来自相临分布区、近似气候类型的群体聚在一起的趋势，但Mantel检测反映遗传距离与地理距离间并无明显相关性。 3 cpSSR分子标记研究结果 分析来自青藏高原东缘6个青杨天然群体，所用cpSSR引物中有5对cpSSR引物（CCMP2、CCMP5、SCUO01、SCU03、SCU07）都表现较高的多态性，单个引物检测的片段数都在4以上。5对cpSSR引物共检测片段数26个，组成了12种叶绿体DNA单倍型。各群体的单倍型分布和频率有较大差异，群体单倍型多样性范围为0-0.4926，TS、JZ、PW和SHY群体单倍型多样性高于QHY和LED群体水平。本研究发现，分布在青藏高原东缘的青杨天然群体，群体间不存在共享的单倍型，各群体间存在极大的遗传分化（GST=0.9223）。从青藏高原东缘地区经历的地质历史事件来看，第四纪的冰期气候变迁可能是造成青杨现今遗传结构模式的主要因素之一。根据单倍型在各群体的分布情况，进行青杨群体聚类分析结果，各群体无明显的分组现象，青杨各群体也未呈现任何清晰地理模式。 由于不同分子标记在对群体遗传多样性检测能力与效率上存在差异，所以三种标记检测的青藏高原东缘青杨天然群体遗传多性水平也不尽一致，但在与用同种方法检测其它物种或同一物种不同种源群体比较，三种分子标记方法都揭示了青藏高原东缘青杨天然群体具有中等偏上的遗传多样性水平。结果分析表明，群体间遗传分化极大，这是由于青杨天然群体分布于青藏高原东缘，既有高原又有高山峡谷，由于地理和空间上大尺度的隔离和地形地貌复杂导致了基因流物理上的阻隔。三种分子标记研究结果经Mantel分析检测，遗传距离与地理距离之间都无明显相关性。较为一致的解释是，青杨分布区域地理和空间上大尺度的隔离和和地形地貌复杂导致群体之间不存在均匀扩散现象，另外各群体在不同的选择压力下，经历各自独立的进化历程，这些都可能导致群体间遗传距离与地理距离的不相关。 The wide geographical and climatic distribution of P. cathayana Rehd. indicates that there is a large amount of genetic diversity available, which can be exploited for conservation, breeding programs and afforestation schemes. The results are as follows: 1 Research results of AFLP genetic diversity In present study, genetic diversity was evaluated in the natural populations of P. cathayana originating from southern and eastern edge of the Qinghai-Tibetan Plateau of China by means of AFLP markers. For four primer combinations, a total of 175 bands were obtained, of which 173 (98.9%) were polymorphic. Six natural populations of P. cathayana possessed different levels of genetic diversity, high level of genetic differentiation existed among populations (GST=0.489) of P. cathayana. Individuals cluster and PCO analysis based on Jaccard’s similarity coefficient also showed evident population genetic structure with high level population genetic differentiation. The long evolutionary process coupled with genetic drift within populations, rather than contemporary gene flow, are the major forces shaping genetic structure of P. cathayana populations. Moreover, there is no correspondence between geographical and genetic distances in the populations of P. cathayana, seldom gene exchange among populations and different selection pressures may be the causes. Our finding of different levels of genetic diversity within population and high level of genetic differentiation among populations provided promising condition for further breeding or conservation programs. 2 Research results of SSR genetic diversity In this study, the genetic diversity of P. cathayana was investigated using microsatellite markers. In a total of 150 individuals collected from six natural populations in the southeastern part of the Qinghai-Tibetan Plateau in China, a high level of microsatellite polymorphism was detected. At the seven investigated microsatellite loci, the number of alleles per locus ranged from 5 to 16, with a mean of 11.3, the observed heterozygosities across populations ranged from 0.408 to 0.986, with a mean of 0.792, and the expected heterozygosities across populations ranged from 0.511 to 0.891, with a mean of 0.802. The proportion of genetic differentiation among populations accounted for 37.3% of the whole genetic diversity. The presence of such a high level of genetic diversity could be attributed to the features of the species and the habitats where the sampled populations occur: The southeastern part of the Qinghai-Tibetan Plateau is regarded as the natural distribution and variation center of the genus Populus in China. Variation in environmental conditions and selection pressures in different populations, and topographic dispersal barriers could be factors associated with the high level of genetic differentiation found among populations. The populations possessed significant heterozygosity excesses, which may be due to extensive population mixing at the local scale. The cluster analysis showed that the populations are not strictly grouped according to their geographic distances but the habitat characteristics also influence the divergence pattern. In addition, we suggest that population SHY should be regarded as an ecologically divergent species of P. cathayana. 3 Research results of cpSSR genetic diversity Genetic diversity of six natural populations of P. cathayana originating from the southeastern part of the Qinghai-Tibetan Plateau in China was studied by use of cpSSR markers. Based on 5 pairs of polymorphic primers screened from 12 pairs of primers, twenty-six different length fragments and twelve different kinds of haplotypes were reduced in 143 samples. There were significant variant haplotypes among the populations．There were no shared haplotypes found among populations, analysis of molecular variance indicated that a high proportion of the total genetic variance was attributable to variations among populations (92.23%). The pattern of genetic structure which is associated with spatial separation, variation in environmental conditions and selection pressures in different populations, is also the result of geological historical factor. A molecular phylogenetic tree based on the 12 haplotypes showed that the populations are not strictly grouped according to their geographic distances.

Gamma decay of the lowly excited states of 189Re

189W activities were produced via the 192Os(n, α) reaction using irradiation of isotopically enriched 192Os metallic powder of ～100 mg/cm2 with 14 MeV neutrons. The X-γ and γ-γ coincidence measurements were made so as to obtain γ rays from 189W decay and its coincidence relations. A new simple decay scheme of 189W including three γ rays of 210.2, 229.6 and 260.2 keV is proposed. Two new levels of 189Re at 470.4 and 489.8 keV are assigned.

He-CO散射截面的量子力学研究

采用精确度较高的密耦方法(Close-Coupling)计算了He-CO碰撞的散射截面,能量从5 meV~70meV,计算结果与M.Keil等的实验结果(64 meV)基本相符.研究表明:势能的零点能位置、势阱深度、势阱位置、排斥势强度以及势能在势阱附近的方向性都对散射截面有较大的影响.

~(189)Re的两个新能级

建议189W一个新的简单衰变纲图。指定189Re能量为470.4keV和489.8keV的2个新能级。改进了先前189Re的能级信息。

重离子径迹模板法合成银纳米线

聚碳酸脂(PC)膜被高能重离子辐照后沿入射离子路径产生潜径迹,把带有潜径迹的膜经紫外光敏化后置于NaOH溶液中进行蚀刻,通过选择蚀刻条件,在PC膜内得到直径从100到500nm导通的核径迹孔.以带有核径迹孔的PC膜为模板,用电化学沉积法制备出不同直径的银纳米线.在特定的实验条件下(沉积电压25mV、电流密度1-2mA·cm~(-2)、温度50℃和电解液为0.1mol·L~(-1)的AgNO_3溶液),获得了沿[111]方向择优取向生长的具有单晶结构的银纳米线.利用扫描电子显微镜(SEM)、X射线衍射(XRD)、透射电子显微镜(TEM)及选区电子衍射(SAED)等手段对银纳米线的形貌和晶体结构特征进行了表征.

弱电流测量中的I-F变换电路

介绍了一种用于弱电流测量中的I-F变换电路,它将输入的电流信号直接变换为脉冲频率输出,然后送入计数器计数和送入计算机处理。并对其电路原理作了较详细的阐述。经过在现场检验和使用,该电路工作稳定可靠,灵敏度高,抗干扰能力强等特点,得到了满意的结果。

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.

Helicon等离子体源的研制

本论文设计建造了全新的Helicon等离子体源，用于近代物理所加速器强流束等离子体中和和聚焦研究。等离子密度峰值可达到3.9×1013cm－3。采用朗谬尔四探针诊断方法系统研究了该等离子体源的特性。在等离子体源基础上，将扩散区代之以引出系统和束流测量系统，建成了Helicon离子源。 Helicon源的特点是等离子体密度高，均匀性好，在离子源技术，等离子体物理研究，材料加工以及航空推进等方面有着广泛的应用。但是国内在Helicon源的研究方面尚处于空白，国际上对其基本原理和工作机制至今还不太清楚，一台新Helicon离子源从设计建造到实验调试，都处于半经验状态，没有完整的理论可循。本论文设计建造的Helicon等离子体源是在低射频功率、低磁感应强度下产生高密度的等离子体。通过对放电管、天线、射频源、和高频耦合电路等各参数的反复调节和优化，在以氩气为中性气体、1200W射频功率和200Gs磁感应强度下，获得等离子体密度峰值达到3.9×1013cm－3。并对等离子体特性随各参数的变化关系进行了系统的实验研究，研究结果表明：（1）等离子体密度随射频源功率增加而增大并渐趋饱和，在300-600W时出现跳跃，说明离子源由放电模式转变为Helicon模式；（2）随磁感应强度增加，等离子体密度出现极值，需要寻求二者的最佳匹配；（3）当中性气体为氩气时，等离子体密度最大；（4）等离子体中心密度最高，沿轴向衰减较快，但径向分布均匀，实验验证了Helicon源离子均匀分布的特性，初步估计该等离子体横向能量较大，但还需要进一步研究。本文在Helicon等离子体源的基础上，去掉扩散区加上引出系统和束流测量系统，设计建造了一台Helicon离子源。进行了初步的束流引出实验，在输入功率为200W时，获得引出束流1mA。发现并解决了额外功率在等离子体电极上的损耗、溅射等问题，在以后的工作中将通过模拟计算对引出系统进行进一步优化，以取得较好的引出束流结果

Low-temperature heat capacities and standard molar enthalpy of formation of aspirin

Molar heat capacities (C-p,C-m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of Cp, vs. T was established in the light of the low-temperature heat capacity measurements and least square fitting method. The corresponding function is as follows: for 78 Kless than or equal toTless than or equal to383 K, C-p,C-m/J mol(-1) K-1=19.086X(4)+15.951X(3)-5.2548X(2)+90.192X+176.65, [X=(T-230.50/152.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {DeltaH(T)-DeltaH(298.15)} and {S-T-S-298.15}, were derived.

长白山北坡水甲虫多样性与环境因子的关系

为了解水甲虫多样性与环境的关系,于2004—2006年每年6—10月在长白山北坡采集不同环境条件下水甲虫标本,共发现水甲虫8科38属70种。研究发现不同的环境,水甲虫的种类、数量、个体大小明显不同。通过多元回归分析发现:水甲虫Shannon-Wiener多样性指数与海拔(r=0.507)、底泥有机质含量(r=0.638)和全磷含量(r=0.668)成明显正相关,与水电导率(r=-0.470)、水深度(r=-0.461)和水pH值(r=-0.470)负相关显著;均匀度指数与底泥有机质含量(r=0.542)和全磷含量(r=0.489)正相关显著;物种数与海拔(r=0.590)、底泥有机质含量(r=0.593)和全磷含量(r=0.618)成正相关,与水深度(r=-0.636)、水电导率(r=-0.558)、水pH值(r=-0.535)成显著负相关。环境因子影响水甲虫的分布,但人类是最终决定因素,了解水甲虫多样性与环境的关系,有助于揭示生物-环境-人类三者之间的关系,为生态系统和生物多样性的修复和保护提供服务。

干扰与植被关系研究的特点和面临的挑战

生态学家在全球、区域、局地、景观、生态系统、植被、种群、物种等各个尺度研究干扰的生态作用。就植被与干扰的关系而言 ,生态学家一方面关注植被对干扰的适应 ,另一方面关注干扰对植物种群、群落、生态系统的结构、过程和功能的再调节。综合干扰作用和受干扰生态系统的恢复是干扰与植被关系研究的重要组成部分。干扰的生态作用研究面临诸多挑战 ,诸如背景局限、比较局限、方法局限、认知局限。目前 ,大多数的相关研究是为资料 (即为相关综合提供例证研究 )、实证(即检测已存在的理论和假说 )和实践 (即为特定的生态恢复提供依据 )而开展的。对植物干扰适应机制的高度的理论概括和对干扰状况下全球植被动态进行预测是目前研究干扰的生态作用的生态学家面临的最大挑战