53 resultados para Berkeley Pit
Resumo:
A GaSb crystal incorporated with Mn has been grown by the Bridgman method on the Polizon facility onboard the FOTON-M3 spacecraft. Structural defects and growth striations have been successfully revealed by the chemical etching method. By calculating various parameters of the convection, the striation patterns can be explained, and the critical value of the Taylor number, which characterizes the convective condition of the rotating magnetic field induced azimuthal flow, was shown. The stresses generated during crystal growth can be reflected by the observations of etch pit distribution and other structural defects. Suggestions for improving the space experiment to improve the quality of the crystal are given.
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The defects and the lattice perfection of an AlN (0001) single crystal grown by the physical vapor transport (PVT) method were investigated by wet etching, X-ray diffraction (XRD), and infrared absorption, respectively. A regular hexagonal etch pit density (EPD) of about 4000 cm~(-2) is observed on the (0001) A1 surface of an AlN single crystal. The EPD exhibits a line array along the slip direction of the wurtzite structure, indicating a quite large thermal stress born by the crystal in the growth process. The XRD full width at half maximum (FWHM) of the single crystal is 35 arcsec, suggesting a good lattice perfection. Pronounced infrared absorption peaks are observed at wave numbers of 1790, 1850, 2000, and 3000 cm~(-1), respectively. These absorptions might relate to impurities O, C, Si and their complexes in AlN single crystals.
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A semi-insulating (SI) GaAs single crystal ingot was successfully grown in a recoverable satellite. The two-dimensional distribution of stoichiometry in space-grown SI-GaAs single crystal wafer was studied nondestructively based upon x-ray Band diffraction. The avenge stoichiometry in the space-grown crystal is 0.50007 with mean square deviation of 6 x 10(-6), and shows a better stoichiametric property than the ground-grown SI-GaAs. The average etch pit density (EPD) of dislocations in the crystal revealed by molten KOH is 2.0 x 10(4) cm(-2), and the highest EPD is 3.1 x 10(4) cm(-2). This result indicates that the structural properly of the crystal is quite good.
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Experimentally observed X-ray reflectivity curves show bi-crystal(twin) characteristics. The study revealed that there was defect segregation at the twin boundary. Stress was relaxed at the edge of the boundary. Relaxation of the stress resulted in formation of twin and other defects. As a result of formation of such defects, a defect-free and stress-free zone or low defect density and small stress zone is created around the defects. So a twin model was proposed to explain the experimental results. Stress(mainly thermal stress), chemical stoichiometry deviation and impurities nonhomogeneous distributions are the key factors that cause twins in LEC InP crystal growth. Twins on (111) face in LEC InP crystal were studied. Experimental evidence of above mentioned twin model and suggestions on how to get twin-free LEC InP single crystals will be discussed.
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The effects of in situ annealing treatment in the initial growth stage and In-doping during growth of the GaN on the material properties were investigated. GaN was grown by LP-MOVPE. In situ annealing reduced the full-width at half-maximum (FWHM) of X-ray rocking curves and reduced etch pit density of GaN films. It improved the optical properties of the epilayer. Undoped and In-doped GaN films of initial growth stage were investigated. It was found that morphology and optical properties were improved in In-doped samples. (C) 2000 Elsevier Science B.V. All rights reserved.
Resumo:
广西壮族自治区是中国多孔菌资源比较丰富的区域之一,本研究对广西主要林区进行了初步调查,并根据形态学研究方法对广西地区的多孔菌进行了系统分类学研究。 结果显示,广西地区的多孔菌共有15科,60属,140种。研究过程中发现两个新种,分别是菌索容氏孔菌Junghuhnia rhizomorpha H.S. Yuan & Y.C. Dai和小孔大孢卧孔菌Megasporoporia microporela X.S. Zhou &Y.C. Dai;发现7个中国新记录种:萨拉氏灵芝Ganoderma sarasinii Steyaert,唐氏胶囊革菌Gloeocystidiellum donkii S.S. Rattan,线浅孔菌Grammothele lineata Berkeley & M.A. Curtis,粉状捷克革菌Jacksonomyces furfurellus (Bres.) Sheng H. Wu & Z.C. Chen,半伏容氏孔菌Junghuhnia separabilima (Pouzar) Ryvarden,非洲纵隔担孔菌Protomerulius africanus (Ryvarden) Ryvarden和日本芮氏孔菌Wrightoporia japonica Núñez & Ryvarden;78种为广西地区新记录种,占该地区已报道种类的55.7%。 依据分类学的研究结果,对广西地区的多孔菌的种类组成和地理成分进行了初步分析,结果显示,优势科为多孔菌科Polyporaceae(33.3%),其次为皱孔菌科Meripilaceae(10%),优势属为多孔菌属Polyporus(7.9%%)和针层孔菌属Phellinus(5.7%);属的地理成分以世界广布属(68.3%)和热带–亚热带分布属(23.3%)为主,种的地理成分以泛热带分布成分(35%)和世界广布种(30%)为主。 经研究表明广西地区共有森林干基腐朽病原多孔菌21种,食用多孔菌菌有5种,药用多孔菌32种,工业用多孔菌17种,多孔菌资源较丰富。 对重要种类木蹄层孔菌Fomes fomentarius (L.:Fr.) Fr.进行了固体培养研究,结果显示木蹄层孔菌的营养菌丝生长最适培养温度为28℃,最适培养pH值为7,最适培养碳源为蔗糖,最适培养氮源为蛋白胨。
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Based on the relativistic chiral effective field theory, we study the effective mass of the Delta-resonance in medium by investigating the self-energy of the Delta-resonance related to the pi N decay channel in symmetric nuclear matter. We find that the effective mass of Delta-resonance decreases evidently with increasing nuclear density rho. In our calculation, we also consider the influence of the shifts of the nucleon mass, pion mass and its decay constant due to the restoration of chiral symmetry in medium. The results are roughly consistent with the data given by Lawrence Berkeley National Laboratory.
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本论文简述了强子介质效应的研究现状,理论方法以及实验探测技术。系统的介绍了相对论平均场理论和手征有效场论。利用相对论平均场研究了Pentaquark的介质效应,利用手征有效场论研究了△(1232)共振态的介质效应。 在密度相关的平均场理论基础上,计算出的Pentaquark的有效质量随核物质密度的增加而减小。一定的Pentaquark含量导致每核子的结合能减小,这使得核物质系统更加稳定。 在手征有效场论的框架下,利用泡利不相容原理对核子传播子的修正,以及核子有效质量在核物质中的改变,通过计算△共振态一阶自能,讨论了△共振态的有效质量和衰变宽度对核物质密度的依赖关系。结果表明:△共振态的有效质量随核物质密度的增加而减小,在正常核密度下为1221MeV,而在3倍正常核密度时为1186MeV,其减小幅度与美国Lawrence Berkeley国家实验室上做的58Ni+Cu(能量为1.97GeV/u)碰撞实验给出的结果大致相符;△粒子的衰变宽度在核物质中的变化主要决定于核子以及△粒子的有效质量的变化
Resumo:
本文用Monte Carlo法模拟计算了30keV和200keV的N~+离子与110keV的Fe~+离子在模拟细胞中的射程分布和径迹结构,并且将110keV Fe~+模拟计算的结果与RBS测量的结果相比较发现计算与测量吻合较好。从计算和实验都说明相当低的能量的重离子不大可能直接作用引起麦胚深层生物效应,它们产生的生物效应很可能是由次级效应造成的。用Monte Carlo法模拟计算30keV和200keV的N~+离子产生的级联离子在模拟细胞中的作用范围,得出其不可能直接在麦胚深层产生生物效应。理论上分析了低能重离子激发特征X射线的机理。针对我们的侧重点,分别讨论了在弱扰动情况和强扰动情况下,特征X射线的激发。用Si(Li)探测器实测了Na、Mg、S、Cl的特征X射线在有机膜中的相对衰减以及与O、K元素的特征X射线能量相当的X射线或轫致辐射在有机膜中的相对衰减,分别得出了它们衰减的数学描述,并把实验得到的不同能量的X射 线在有机膜中质量吸收系数与Berkeley的OCG软件计算出的结果相比相差都小于30%。本工作是国家自然科学基金委重点课题——离子注入生物诱变机理有生物效应研究的一部分。首先搞清了低能重离子在生物材料中的直接作用范围。二、搞清了核-核弹性碰撞产物的级联运动原子的作用范围。三、理论上分析了特征X射线的产生及实验上测量了它们在生物材料中的衰减,基本上搞清了生物材料中某些元素的特征X射线作用范围和强度。四、填补了软X射线穿透有机膜的实验数据
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针对黄土高原蓬勃发展的窖灌农业 ,提出3种水窖配置模式 :峁顶光头式 ;路旁葡萄串式和场、院、凹地单点式。为了高效利用水窖集蓄的雨水资源 ,文中推荐自压微灌、外动力加压微灌、坑灌和水肥穴灌等4种窖水高效利用技术。
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A novel method for fabrication of nanometer-sized electrodes and tips suitable for scanning electrochemical microscopy (SECM) is reported. A fine etched Pt wire is coated with polyimide, which was produced by polymerization on the Pt surface initiated by heat. This method can prepare electrodes with effective radii varying from a few to hundreds of nanometers. Scanning electron microscopy, cyclic voltammetry, and SECM were used to characterize these electrodes. Well-defined steady-state voltammograms could be obtained in aqueous or in 1,2-dichloroethane solutions. Ibis method produced the nanoelectrodes with exposed Pit on the apex, and they can also be employed as the nanotips for SECM investigations. Different sizes of Pt nanotips made by this method were employed to evaluate the kinetics of the redox reaction of Ru(NH3)6(3+) on the surface of a large Pt electrode by SECM, and the standard rate constant kappa (o) of this system was calculated from the best fit of the SECM approach curve. This result is similar to the values obtained by analysis of the obtained voltammetric data.
Resumo:
A cDNA for a novel T-box containing gene was isolated from the amphioxus Branchiostoma belcheri. A molecular phylogenetic tree constructed from the deduced amino acid sequence of the isolated cDNA indicates that this gene belongs to the T-Brain subfamily. In situ hybridization reveals that the expression is first detected in the invaginating archenteron at the early gastrula stage and this expression is down-regulated at the neurula stage. In early larvae, the expression appears again and transcripts are detected exclusively in the pre-oral pit (wheel organ-Hatschek's pit of the adult). In contrast to the vertebrate counterparts, no transcripts are detected in the brain vesicle or nerve cord throughout the development. These results are interpreted to mean that a role of T-Brain products in vertebrate forebrain development was acquired after the amphioxus was split from the lineage leading to the vertebrates. On the other hand, comparison of the tissue-specific expression domain of T-Brain genes and other genes between amphioxus and vertebrates revealed that the pre-oral pit of amphioxus has several molecular features which are comparable to those of the vertebrate olfactory and hypophyseal placode. (C) 2002 Wiley-Liss, Inc.
Resumo:
Amphioxus Bblhx3 was identified as a LIM-homeobox gene expressed in gastrulae. Structural analysis suggested that it is a member of lhx3 but not of lhx1 gene group. Whole mount in situ hybridization revealed, that expression of Bblhx3 was initiated at the early gastrula stage and continued at least until 10-day larvae. Expression of Bblhx3 first appeared in the vegetal and future dorsal area in initial gastrulae and became restricted to the endoderm during gastrulation. In neurulae and early larvae, Bblhx3 was expressed in the developing neural tube, the notochord and preoral pit lineage. In 10-day larvae, Bblhx3 was expressed only in the preoral pit. This expression pattern is apparently distinct from that of vertebrate lhx3 genes that are not expressed during gastrulation. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.
Resumo:
Bangia fuscopurpurea (Rhodophyta) was cultivated in Putian (Fujian province, China). The characteristics of the life history concerned with cultivation were investigated and the cultivation procedure was presented. The gametophytic phase (thallus) and the sporophytic phase (conchocelis) occurred alternately in the life history of B. fuscopurpurea. Young thalli produced archeospores, and the number depended on the environmental factors. Temperature affected the number of archeospore release and percent of germination, and photo flux density (PFD) mainly affected the time of spore release and germination. Thalli matured from December to February and developed into the conchocelis phase through sexual reproduction. The conchocelis grown in shells had three developmental stages: vegetative conchocelis, conchosporangiall formation and conchospore formation. Pit-connections were present in the first 2 stages but absent after conchospore formation. Vegetative conchocelis and conchosporangial. branches can transform into each other. However, conchospores only developed into the gametophytic phase. Cultivation of B. fuscopurpurea was based on characterization of the life history, consisting of 3 steps: zygotospores collection, indoor cultivation of conchocelis and outdoor cultivation of thalli. Young thalli that developed from conchospores produced numerous archeospores before December. Over 90% of the crop was from the development of archeospores. The results indicated that conchosporelings were a good source of archeospores, and the development of the large quantity of archeospores acted as a more prevailing means to increase the population size. (C) 2008 Elsevier B.V. All rights reserved.
Resumo:
海湾扇贝Argopecten irradian Lamarck于1982年从美国引种到中国,由于具有较快的生长速度和很高的经济效益,海湾扇贝成为中国最主要的养殖贝类之一。近年来海湾扇贝养殖遇到了死亡率高等问题,深入开展海湾扇贝功能基因的研究,尤其是免疫相关基因及其机制研究并在此基础上寻找扇贝疾病防治的有效方法对海湾扇贝的健康养殖十分重要。 对于贝类免疫系统来说,其血细胞在先天性免疫防御中起着重要的作用。当受到外界病原侵染时,贝类血细胞的一个重要免疫反应就是吞噬作用。在吞噬病原过程中,受到病原侵染的贝类还会产生其他多种免疫反应,这些免疫反应将消耗大量的能量(ATP),产能的呼吸链会加速运转,由此也会引发与呼吸链相耦联的活性氧(ROS)的大量产生。这些活性氧具有极强的反应特性,能破坏病原微生物的结构和功能分子,实现对入侵病原的杀灭。利用活性氧对被吞噬的病原进行杀灭,这是吞噬作用消除病原抵御侵染的重要机制。但由于活性氧分子反应的非特异性,它们也会破坏宿主机体细胞内的功能蛋白分子、不饱和脂肪酸分子和核酸等,对细胞造成严重的伤害,进而导致机体生理机能的损伤和免疫系统的破坏。所以,及时消除病原感染机体内过量产生的ROS,维持相关细胞的正常代谢,对提高机体抵抗力和免疫力具有重要的作用。O2-是生物体内产生的第一种活性氧分子,其他的活性氧分子也是由它衍生而来,消除过量O2-是消除过量活性氧危害的第一步也是关键一步。生物体内,超氧化物歧化酶(SOD)是催化O2-发生歧化反应,消除O2-的关键酶。 首先,本文通过RACE方法获得了海湾扇贝SOD家族全部三种基因的cDNA全长并对其进行了序列的生物信息学分析,海湾扇贝AiCuZnSOD全长cDNA为1047个碱基,其中开放阅读框为459个碱基,编码152个氨基酸,与栉孔扇贝Chlamys farreri的CuZnSOD相似度为77.5%,与长牡蛎Crassostrea gigas的相似度为75%,与人的相似度为74.7%。AiMnSOD全长cDNA为1207个碱基,其中开放阅读框为678个碱基,编码226个氨基酸,序列比对结果发现AiMnSOD的氨基酸序列与虾夷扇贝Mizuhopecten yessoensis和皱纹盘鲍Haliotis discus hannai的相似度分别为85%和78.4%,与哺乳动物相似度也在68%~72%之间。AiECSOD全长cDNA为893个碱基,其中开放阅读框为657个碱基,编码218个氨基酸。AiECSOD与其它物种ECSOD相似度比较低。与线虫Brugia pahangi的相似度为27.9%,与疟蚊Anopheles gambiae的相似度为31.4%,与斑马鱼Danio rerio的相似度为27.8%,与人的相似度也只有28.6%,与同是贝类的长牡蛎ECSOD也只有28.1%的相似性。主要原因是AiECSOD的信号肽和肝磷脂结合区域在各物种中无同源性。 其次,采用qRT-PCR(quantitative real time PCR)方法分析三种SOD基因在不同组织中的表达情况,结果表明三种SOD基因的组织表达有所差异。AiCuZnSOD基因在鳃中表达水平最高,其次是血细胞和性腺,在外套膜、闭壳肌和肝胰脏表达水平较低。AiMnSOD基因在鳃中表达水平最高,其次是外套膜,在血细胞、性腺,而在肝胰脏和闭壳肌表达较弱。AiECSOD基因在血细胞中表达水平最高,其次是肝胰脏,在鳃、闭壳肌表达水平较低,而性腺和外套膜没有检测到。同时,采用qRT-PCR对鳗弧菌Vibrio angullarum感染后海湾扇贝血细胞中三种SOD基因mRNA表达变化进行了检测。AiCuZnSOD表达量在各个时间段没有显著差异(P > 0.05)。AiMnSOD的表达量在1.5 h时略有下降,在3 h时达到最高表达量,是空白组(0h)的3倍(P < 0.01),从6 h到24 h表达量逐渐下降,24 h时表达量是空白组的1.6倍,24 h到48 h又稍有升高。AiECSOD的表达量在1.5 h时有所下降,是空白组的0.3倍(P < 0.05),随后逐渐升高,在12 h时达到最高表达量,是空白组(0h)的4.5倍(P < 0.01),从24 h到48 h表达量逐渐下降并恢复到空白组的水平。在对照组,各个时间点没有显著差异(P > 0.05)。在鳗弧菌感染后,海湾扇贝三种SOD的表达并不一致,且差异比较显著。AiCuZnSOD被认为是构成性表达基因,其受外界刺激的影响最小,AiMnSOD和AiECSOD受刺激后表达上调比较明显。 第三,采用Genome-walking的方法得到了海湾扇贝三种SOD基因的基因组全长和近端启动子序列并对其进行了相关分析。AiCuZnSOD的基因组序列全长为4279bp,包含有4个外显子和3个内含子。AiMnSOD的基因组序列全长为10692bp,包含有4个外显子和3个内含子。AiECSOD的基因组序列全长为5276bp,包含有5个外显子和4个内含子。三种基因外显子和内含子的结合处序列遵循-AT/GT-原则。我们把海湾扇贝SOD家族的三个基因的近端启动子进行了比较分析。发现三种SOD在靠近起始密码子的位置都有Oct-1结合位点。三种SOD共有的转录位点有:Oct-1、C/EBPalp、Oct2.1、Sp-1和GATA-1。AiCuZnSOD和AiMnSOD共有的转录位点有:ICSBP、Ftz、TATA-box、C/EBPbeta和Antp。AiCuZnSOD和AiECSOD共有的转录位点有:AP-1和NFκB。AiMnSOD和AiECSOD共有的转录位点有:GR和ER。AiCuZnSOD独有的位点有:SRF、YY-1和NF-1。AiMnSOD独有的位点有:HNF-1、Hb、MEB、NF-muE1、Pit-1a和Eve。AiECSOD独有的位点有:CREB、RATA-alph、Kruppel-like和AP-3。 此外,通过构建原核表达载体,本研究对AiCuZnSOD和AiECSOD基因进行了体外重组表达,并对纯化的重组蛋白进行了酶活分析。酶活分析表明,重组AiCuZnSOD蛋白有较高的酶活和稳定性。 最后,我们对海湾扇贝三种SOD基因的部分区域,包括启动子、编码区,部分内含子区域进行了SNP检测,并对SOD基因部分SNP位点多态性和鳗弧菌敏感性进行了相关分析。三种SOD基因中,我们共发现了59个SNP位点,其中AiECSOD的SNP位点最多,特别是在启动子区,AiCuZnSOD和AiMnSOD多态性较低。其中AiCuZnSOD启动子区的-1739 T-C 位点的基因型和等位基因,AiECSOD启动子区的-498 A-T和-267 G-A等位基因频率,AiECSOD的第一个外显子38 Thr-Lys的多态性在敏感和抗菌群体中存在显著差异(P < 0.05)。