晶格匹配氮化镓和氧化锌基外延薄膜衬底材料ScAlMgO4晶体生长研究

采用提拉法成功生长了氮化镓和氧化锌基外延薄膜晶格匹配的ScAlMgO4单晶衬底材料,晶体呈透明白色,尺寸为Ф30mm×59mm,表面部分沿解理面有裂纹.粉末X射线衍射（XRD）分析表明经1400℃固相反应烧结的原料基本合成了ScAlMgO4多晶相.初步的偏光显微镜观察、晶体的粉末XRD表征、透过光谱和双晶摇摆测试表明晶体具有较好的光学性质和结晶质量.研究表明晶体本身的层状结构、较大的温度梯度和热应力的不均匀性是生长过程中引起晶体开裂的几个主要原因.

稻族的分子系统学研究

稻族（Oryzeae）是禾本科中包含多种经济植物的重要类群，现有大约12个属，广布于全球的热带和温带地区。虽然有证据表明稻族是一个单系类群，但稻族的分类处理和属间系统发育关系以及稻族的生物地理学等方面仍存在许多悬而未决的问题。本研究利用了7个DNA片段，包括2个叶绿体基因片段（trnL和matK）、1个线粒体基因片段（nad1）和4个分布在不同染色体上的核基因片段（Adh1、Adh2、GPA1和Waxy）以及形态性状（87个）重建了稻族的系统发育关系，并在此基础上利用6个DNA片段（trnL、matK、nad1、Adh1、Adh2和GPA1）探讨了稻属基部类群的系统发育关系。同时在系统发育研究的基础上，进一步探讨了稻族物种间的分歧时间及生物地理学问题。主要结果如下： 1.稻族的系统学 多基因和形态性状的分析表明：1）稻族是单系类群可分为两个主要分支，相当于传统的两个亚族，第一个亚族（Zizaniinae）包括稻属﹑假稻属和Porteresia，而第二个亚族（Oryzinae）包括其余8个属。两性花是稻族的原始状态，而单性花多次起源，共起源了3次，因此单性花和两性花的区别不宜作为划分亚族的依据;2）Zizania 与分布在南美的单型属Rhynchoryza关系最近;3）一些单型属（Hydrochloa、Porteresia和Prosphytochloa）的确立得不到分子证据的支持，特别是Hydrochloa，形态证据分析的结果明确不支持建立该单型属;4）形态分析结果支持Zizania 4个种聚为一支，而东亚的一个种（Zizania latifolia）为该属基部类群。 2.稻属基部类群的系统发育关系 多基因系统发育分析表明：1）稻属是一个单系类群;2）所有数据都支持稻属10种染色体组类型各自为单系，包括稻属中最后确定的染色体组类型HK（Oryza schlechteri和Porteresia coarctata）;3）F染色体组与HK和HJ中的H染色体组关系最近，类似于E染色体组与异源四倍体的CD染色体组中的D染色体组关系最近; 4）双亲遗传的核基因和母系遗传的线粒体和叶绿体基因的对比分析表明，HJ染色体组两个物种的母系来源是H，而HK染色体组两个物种母系来源是K。三个染色体组相比较，H分化较早，J次之，K分化最晚;5）在系统发育研究基础上，本研究认为稻属4个复合体的划分是可信的，原来未划分到任何一个复合体中的两个种O. brachyantha和O. schlechteri以及新近归入稻属的Oryza coarctata都应归入O. ridleyi复合体。 3.稻族各谱系的分化时间及其生物地理学意义 利用分子钟及其改进方法对稻族各谱系的起源和分化时间进行了估测，并在此基础上探讨了形成各类群地理分布式样的可能原因。结果表明，稻族在始新世（Eocene）晚期（3640万年前）起源于东南亚随后分为两大支。稻属基部类群G染色体组物种与稻属其他物种在1200万年前分开;稻属中A/B/C/E染色体组类群在700万年前开始分化。 在稻族的第一大支Oryzinae亚族中，稻属和假稻属1400万年前分开后，通过远程扩散及随后的漫长的历史过程形成了目前的分布格局。稻属从东南亚起源并逐渐扩散到非洲、澳洲及美洲;而假稻属则从非洲出发扩散到全球的热带和亚热带地区。这两个属的演化历史非常相似，都是全球广泛分布且起源时间较晚。 在稻族第二大支Zizaniinae亚族中，Zizania是稻族中唯一欧亚-北美间断分布属，与其分布在南美的姊妹群Rhynchoryza在2554万年前分开，这一支可能是先从南美扩散到东亚，然后再从东亚扩散到北美;Zizaniopsis和Luziola两属在南美洲和北美洲都有分布，其分歧时间为2180万年前，这两属具有类似的进化历史，即通过上新世（Pliocene）末期隆起的巴拿马陆桥形成现在的分布格局;Chikusichola与Potamophila/Prosphytochloa这一支从中新世（Miocene）早期（2270万年前）开始分化，由于Chikusichola（分布在东南亚）、Potamophila（澳大利亚）和Prosphytochloa（非洲）相距很远，这3个属的扩散必然与跨洋远距离扩散有关。

野大豆和栽培大豆抗盐分子标记的研究

野大豆群体3和群体4属盐渍群体，其个体有的是抗盐的，有的是敏感的，有的是中等抗盐的，本文通过随机扩增多态性DNA (RAPD)和DNA扩增指纹(DAF)分析野大豆群体抗盐性与分子标记之间的关系，从而更好地研究野大豆群体的盐适应机理。通过12个RAPD引物和3个DAF引物扩增发现：引物OPF05，OPF19和OPH02的扩增产物中有与抗盐性可能相关的特异标记，分别是OPF05_(213);OPF19_(4361);OPF19_(1727);OPF19_(1400);OPF19_(700);OPH02_(1350)。这些特异标记在所研究的抗盐植株中都存在;在敏感型植株中都不存在;在中等抗盐植株中有的存在，有的不存在。以上表明野大豆群体的抗盐性与RAPD分子标记有一定的相关性。为进一步研究抗盐性的特异标记，本文对栽培大豆抗盐品种Morgan和文丰七号的特异DAF标记片断8-27_(240) (Zhong et al., 1997)进行了克隆测序，测序结果通过BLASTn程序与基因库中的基因序列进行同源比较，发现上的DNA序列中的19组（每组大约二十到三十个碱基）序列与基因库中的其它基因相应序列有很高的同源性，几乎全部100%同源。尤其目的序列第15个碱基到第33个碱基（共19个碱基）之间的序列与基因库中的25个基因的相应序列的同源性全部是100%，并且与之相比的基因大多来自动物和人。因而推测其有可能是保守区，而不是编码区。进一步用DNASIS软件分析其碱基组成(A/T含量是64.9%，G/C含量是35.1%)并进行翻译，结果同样表明此序列可能是一调控序列并非编码区。至于这段序列是否与抗盐紧密相关，这有待于以后把此序列转到敏感型植株中然后检测其抗性来验证。 本文还通过RAPD分析野大豆群体3和群体4的多态性，发现群体3的多态性明显高于群体4。野大豆群体3的抗盐性大于群体4早已通过生理指标的鉴定，至于多态性与抗盐性之间是否有必然联系，还需进一步研究讨论。利用RAPD数据，通过MEGA软件中的NJ计算遗传距离的方法对群体3和4进行聚类分析，研究野大豆群体间及群体内个体间的亲缘及进化关系，探讨野大豆群体盐适应机理的分子起源。

中国暖温带森林群落多样性若干问题的研究

中国暖温带落叶阔叶林区维管植物共158科，931属，近4000种（含亚种，变种和变型），种子植物l3l科，877属，3770余种。暖温带植物区系有很强的温带性质，各类温带成分共548属，而各类热带成分仅226属，热带成分与温带成分(R/T)的比率为0．31。运用TWINSPAN和DCA对全国34个植物区系进行了数量分类排序，结果反映了一个地区的植物区系性质主要取决于其所在地的地理位置，同时也受山地海拔高度的强烈影响这一植物区系的基本特征。 根据暖温带森林植物的特点，修订了Raunkiear生活型系统。暖温带森林植物以地面芽植物(H)占较大的优势，占暖温带全部种类的33.9%;其次是地下芽(G)植物，占l 9.7%;全部高位芽植物占27.5%，绝大部分为落叶阔叶高位芽植物。主要由这些生活型组成的暖温带植物生活型总谱基本反映了暖温带夏季温暖多雨、冬季寒冷干旱的中纬度地区地面芽植物群落气候特征。 暖温带森林植被类型主要有7个植被亚型，约50个群系。辽东栎群落是典型的地带性森林群落。应用TWINSPAN和DCA程序将68块暖温带部分地区辽东栎群落样地和83块北京山区辽东栎群落样地分别划分为1 5个和14个群落类型。用物种丰富度指数、Simpson指数、多样性奇测法、Shannon-Wiene r指数、Pielou均匀度指数，Heip均匀度指数、AIatalo均匀度指数等常用的多样性测度方法，分别对暖温带和北京山区辽东栎群落的多样性进行了测度，结果发现，多样性作为一个整体与DCA第1轴有很大的相关关系：暖温带辽东栎群落多样性指数与DCA第1轴的复相关系数为0.7左右，北京山区较高，为0.8左右。多样性的空间特征为：随海拔的升高和纬度的降低，多样性指数呈上升趋势，反映了水热条件在辽东栎水平分布范围内、人类活动和水分因子在辽东栎垂直分布范围内对群落多样性的影响;不同群落之间多样性指数由低到高的顺序为：灌丛、辽东栎萌生丛、辽东栎林、辽东栎纯林、混交林，符合群落演替过程中多样性的动态规律。 对秦岭主峰太白山海拔1400-1600m之间植被类型和物种多样性进行了研究，在划分的1 5种群落类型中，以位于海拔1500-2300m之间的落叶阅叶混交林和栎类混交林的群落多样性最高，在海拔2300-3600m之间，群落多样性趋于单调下降，反映了热量的不足在这一海拔高度范围成为多样性的主要限制因子。

微卫星DNA分析证明异种克隆大熊猫重构胚的核来自大熊猫供体

建立了一种从早期囊胚中提取DNA以进行核内和核外DNA分析的方法。用这种方法从异种克隆大熊猫重构胚中提取总DNA,以大熊猫特异的微卫星DNA引物成功地扩增出了微卫星座位g~(010)。PCR产物双向测序表明,2个重构胚与大熊猫供体对照序列完全一致。结果证明该异种大熊猫重构胚的核的确来自大熊猫供体细胞核。

Lycojapodine A, a Novel Alkaloid from Lycopodium japonicum

Lycojapodine A, a novel C16N-type Lycopodium alkaloid with an unprecedented 6/6/6/7 tetracyclic ring system, was isolated from the club moss Lycopodium japonicum. The structure and relative stereochemistry were elucidated on the basis of spectroscopic dat

沉水植物对沉积物中磷赋存形态影响的初步研究

采用磷的分级方法研究苦草移植后生长过程中沉积物不同的磷赋存形态(NH4ClP,BDP,NaOHP和HClP)以及总磷的变化,同时结合野外人工恢复的水草区域采样的结果,进一步分析了野外条件下沉水植物狐尾藻(MyriophyllumspicatumL.)对磷赋存形态的影响,结果表明,沉水植物能够有效的降低沉积物中磷的含量,而且水生植物对磷的不同赋存形态的影响并不相同,其中,BDP是受沉水植物影响最为明显的磷赋存形态.

U19/Eaf2 Binds to and Stabilizes von Hippel-Lindau Protein

Studies have firmly established a key regulatory role for the tumor suppressor pVHL in the regulation of the vascular system and normal spermatogenesis. Here, we report that knockout of the newly identified tumor suppressor U19/Eaf2 also caused vascular system abnormalities and aspermatogenesis, suggesting a potential link between U19/Eaf2 and pVHL. Coimmunoprecipitation and in vitro binding assays showed an association between U19/Eaf2 and pVHL, whereas deletion mutagenesis revealed the requirement of the NH2 terminus of U19/Eaf2 and both the alpha and beta domains of pVHL for this binding. U19/Eaf2 stabilizes pVHL, as shown by protein stability and pulse-chase studies. Testes and mouse embryonic fibroblasts (MEF) derived from U19/Eaf2 knockout mice expressed reduced levels of pVHL, indicating that full in vivo expression of pVHL indeed requires U19/Eaf2. As expected, U19/Eaf2 knockout MEF cells exhibited an increased level and activity of hypoxia-inducible factor 1 alpha (HIF1 alpha), a protein typically regulated via a pVHL-mediated degradation pathway. Furthermore, angiogenesis in a Matrigel plug assay was significantly increased in U19/Eaf2 knockout mice. The above observations argue that U19/Eaf2 can modulate HIF1 alpha and angiogenesis, possibly via direct binding and stabilization of pVHL. [Cancer Res 2009;69(6):2599-606]

DNA polymorphism of the plankton community and its relationships to species composition in the Three Gorges Reservoir Region of the Yangtze River

We examined DNA polymorphism of the plankton community in the Three Gorges Reservoir Region of Yangtze River and studied its relationships to species composition. Samples of the plankton community were collected from nine sampling sites and analyzed by random amplified polymorphic DNA (RAPD). Nine of 60 screened primers generated a total of 88 observable 180 to 1400 by bands, all of which were polymorphic. Cluster analysis of the resulting binary format from DNA banding patterns grouped the target communities into three clusters. The topology of the constructed diagram from species composition data was generally similar to that based on RAPD markers.

The Yangtze River dolphin or baiji (Lipotes vexillifer): population status and conservation issues in the Yangtze River, China

1. Baiji were sighted 17 times during three recent simultaneous multi-vessel surveys in the Yangtze River, China (November 4-10, 1997; December 4-9, 1998; October 31-November 5, 1999). There were 11 sightings in 1997 (consisting of 17 animals), five in 1998 (seven animals), and two in 1999 (four animals). It was concluded that 13 individuals Could be considered as a minimum number of the baiji currently in the Yangtze River. 2. An annual rate of population decrease was roughly estimated as 10%. From the body sizes observed, the proportions of old, adult and immature individuals were approximately estimated at 57, 26, and 17% respectively. 3. Baiji showed a significant attraction to confluences and sand bars with large eddies. The present distribution range of the baiji is less than 1400 km in length in the Yangtze main river. Distances between the two nearest groups of baiji appear to be increasing. 4. Two typical sightings are described, in which surfacing and movements of baiji were recorded. Baiji were often found swimming together with finless porpoise. In the surveys they occurred in the same group in 63% of occurrences. Interactions between baiji and finless porpoise are described and discussed. 5. Human activities are the main threats to the baiji. Illegal electrical fishing accounted for 40% of known mortalities during the 1990s. Engineering explosions for maintaining navigation channels have become another main cause of baiji deaths. The last hope of saving the species may be to translocate the remaining baiji into a semi-captive reserve. known as the 'Baiji Semi-natural Reserve'. Copyright (C) 2003 John Wiley Sons, Ltd.

InAs/GaAs quantum-dot superluminescent diodes with 110 nm bandwidth

Broadband superluminescent diodes are fabricated by using InAs/GaAs self-assembled quantum dots as an active region. The devices exhibited properties of 110 run bandwidth with the centre of 1.1 mu m and above 30 mW output under pulse injection at room temperature.

Epitaxial growth of SiC on complex substrates

Epitaxial growth of SiC on complex substrates was carried out at substrate temperature from 1200 degreesC to 1400 degreesC. Three kinds of new complex substrates, c-plane sapphire, AlN/sapphire, and GaN/AlN/sapphire, were used in this study. We obtained a growth rate in the range of 1-6 mum/h. Thick (6 mum) SIC epitaxial layers with no cracks were successfully obtained on AlN/sapphire and GaN/AlN/sapphire substrates. X-ray diffraction patterns have confirmed that single-crystal SiC was obtained on these complex substrates. Analysis of optical transmission spectra of the SIC grown on sapphire substrates shows the lowest-energy gap near 2.2 eV, which is the value for cubic SiC. The undoped SIC showed n-type electrical conductivity. (C) 2001 Elsevier Science B.V. All rights reserved.

AlGaInP visible quantum well lasers for information technology

650 nm-range AlGaInP multi-quantum well (MQW) laser diodes grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) have been studied and the results are presented in this paper. Threshold current density of broad area contact laser diodes can be as low as 350 A/cm(2). Laser diodes with buried-ridge strip waveguide structures were made, threshold currents and differential efficiencies are (22-40) mA and (0.2-0.7) mW/mA, respectively. Typical output power for the laser diodes is 5 mW, maximum output power of 15 mW has been obtained. Their operation temperature can be up to 90 degrees C under power of 5 mW. After operating under 90 degrees C and 5 mW for 72 hrs, the average increments for the threshold currents of the lasers at 25 degrees C and the operation currents at 5 mW (at 25 degrees C) are (2-3) mA and (3-5) mA, respectively. Reliability tests showed that no obvious degradation was observed after 1400 hours of CW operation under 50 degrees C and 2.5 mW.