811 resultados para 851
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Spirodilactones are a series of compounds with the structures of spiro-carbon and lactone which result in the special physical and chemical characters of Spirodilactones, In this paper the advance in the methods of synthesis, derivative reaction, chrial resolution, polymer synthesis of the most representative aspects for spirodi-gamma -butylactone and its derivations , were summarized described.
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Chromium hexacyanoferrate (CrHCF) modified grassy carbon electrode (GC) in different electrolytes was studied by cyclic voltammetry and in situ FTIR spectroelectrochemistry. The results indicate that the behavior of CrHCF firm can be understood in term of two structures: Cr1/3Cr(III)Fe(II)(CN), and MCr(III)Fe(II)(CN)(6). Besides,the film exists in amorphous state: the outer layer is porous film, while the inner layer is relatively compact. According to the electrochemical reaction of CrHCF, the lattice can contract and expand with the cations' diffusion.
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The melting behavior of semicrystalline poly(ether ether ketone ketone) (PEEKK) has been studied by differential scanning calorimetry (DSC). When PEEKK is annealed from the amorphous state, it usually shows two melting peaks. The upper melting peaks arise first, and the lower melting peaks are developed later. The upper melting peaks shown in the DSC thermogram are the combination (addition) of three parts: initial crystal formed before scanning; reorganization; and melting-recrystallization of lower melting peaks in the DSC scanning period. In the study of isothermal crystallization kinetics, the Avrami equation was used to analyze the primary process of the isothermal crystallization; the Avrami constant, n, is about 2 for PEEKK from the melt and 1.5 for PEEKK from the glass state. According to the Lauritzen-Hoffman equation, the kinetic parameter of PEEKK from the melt is 851.5 K; the crystallization kinetic parameter of PEEKK is higher than that of PEEK, and suggests the crystallizability of PEEKK is less than that of PEEK. The study of crystallization on PEEKK under nonisothermal conditions is also reported for cooling rates from 2.5 degrees C/min to 40 degrees C/min, and the nonisothermal condition was studied by Mandelkern analysis. The results show the nonisothermal crystallization is different from the isothermal crystallization. (C) 1996 John Wiley & Sons, Inc.
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Quantitative structure-toxicity models were developed that directly link the molecular structures of a et of 50 alkYlated and/or halogenated phenols with their polar narcosis toxicity, expressed as the negative logarithm of the IGC50 (50% growth inhibitor
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本文介绍了高温熔体X射线散射实验装置,溶液径向分布函数计算原理,实验数据处理以及一个径向分布函数测定计算实例。
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We tested the applicability of the random amplified polymorphic deoxyribonucleic acid (RAPD) analysis for identification of three marine fish cell lines FG. SPH, and RSBK and as a possible tool to detect cross-contamination. Sixth commercial 10-mer RAPD primers were tested on the cell lines and on samples collected from individual fish. The results obtained showed that the cell lines could be identified to the correspondent species on the basis of identical Patterns produced by 35-48% of the primers tested. the total mean similarity indices for cell lines versus correspondent species of individual fish ranged from 0.825 to 0.851. indicating the existence of genetic variation in these cell lines in relation to the species of their origin. Also, four primers, which gave a monomorphic hand pattern within species/line, but different among the species/line, were obtained. These primers can be useful for identification of these cell lines and for characterization of the genetic variation of these cell lines in relation to the species of their origin. This supported the use of RAPD analysis as an effective tool in species identification and cross-contamination test among different cell lines.
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鱼类细胞培养已成为鱼类病毒学、肿瘤学、毒理学、遗传学和免疫学等研究的重要手段。本文首先从形态、蛋白质(同工酶)和DNA(RAPD分析)三个层次水平对牙鲆鳃细胞系FG、鲈鱼心脏细胞系SPH和真鲷鳍细胞系RSBF的特性进行了分析,并分别与其所对应的原代培养组织作了比较。形态、蛋白质和DNA分析的结果表明:(1) 三株海水鱼细胞系的乳酸脱氢酶(LDH)酶谱彼此明显不同,可作为对它们进行种属鉴定和交叉污染鉴别的有效遗传标记;(2)与所对应的原代培养组织的LDH酶谱相比,细胞系FG的LDH酶谱维持不变,而细胞系SPH和FRSBF的LFH酶酶谱变化较大;(3)与所对应的原代培养细胞的形态相比,细胞系FG的细胞形态没有明显改变,而细胞系SPH和RSBF的细胞形态则发生了明显改变;(4)60个DNA随机引物对三株细胞系及其原代培养组织的RAPD分析表明,有35-48%的引物在细胞系及其原代培养组织之间产生完全相同的RAPD指纹,为这三株细胞系种属来源的鉴别奠定了基础,另有27-32%的引物在细胞系及其原代培养组织之间产生不同的RAPD指纹,表明这三株细胞系中发生了遗传变异;(5)FG、SPH和RSBF三株细胞系与其所来源鱼类个体间的总遗传相似性指数大小为0.825-0.851,这表明了它们之间的同源性,同时为我们采用RAPD技术对其它细胞系进行种属鉴定提供了可供参考的实验数据;(6)筛选得到四个随机引物S-91、S-223、S-228和S-237,分别可参在这三株海水鱼细胞系中扩增得到特异性的彼此明显不同的RAPD指纹,这些特异性RAPD指纹在各细胞系与其原代培养组织之间,以及在细胞系的传代培养过程中是稳定的,因而这四个引物对于这三株细胞系的种属鉴定、交叉污染检测以及监测它们与其来源鱼类个体之间的遗传变异将非常有用。其次,170代以后的FG细胞发生了自发性肿瘤转化,具有了在细胞单层上聚集生长和堆积生长的能力,本文对转化前后细胞的形态、贴壁依赖性(软琼脂克隆形成实验)和遗传物质稳定性(RAPD分析)进行分析的结果表明:FG细胞失去接触抑制和生长的密主抑制,获得在细胞单层上聚集生长和堆积生长能力的同时,也获得了在软琼脂中生的能力(8-14个克隆/10~6个接种细胞);RAPD分析表明,转化前后FG细胞的RAPD指纹发生了明显的变异。因此,FG细胞的自发性肿瘤转化也如哺乳动物细胞一样,包括一系列不断进行的细胞学和遗传学变化,并最终导致其基因组DNA的遗传变异。最后,本文分析了聚乙烯亚胺(PEI)和氯化镍在RSBF细胞中的细胞毒性和基因毒性,结果表明:鱼类细胞系RSBF可作为一个有效的检测水环境中污染的细胞毒性和基因性效应的效应的筛选系统;RAPD分析可作为一个灵敏的非专一性的基因毒性检测终点;PEI对RSBF细胞的高细胞毒性和基因毒性表明,我们在利用PEI作基因载体进行人类基因冶疗和进行鱼类转基因实验时要格外慎重;镍及其化合物可能是导致鱼类肿瘤性疾病的原因之一。
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[目的]以芒果苷和浸膏收率为指标,优化川西獐牙菜的提取工艺。[方法]采用L_(16)(4~5)正交法设计实验,考察乙醇浓度、溶媒比、提取时间、提取次数4个因素对指标值的影响。[结果]最优提取工艺为75%乙醇15倍量回流提取4次,每次印min。[结论]正交实验法用于优化川西獐牙菜的提取,简便易行,预测性好。
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短管兔儿草为典型的高山植物 ,具较强的光合能力 ,但光合效率较低。叶片具有发达的通气贮气组织 ;栅栏组织发达 ,叶绿体基粒片层较少。短管兔儿草光合作用特性易受生长环境因素的影响。低温胁迫使短管兔儿草光合速率、光合量子产额降低。低温下的光照加剧了光合作用受抑制的程度。本研究表明 ,短管兔儿草具较强的抗冻能力 ,是研究植物抗冻机理及筛选抗冻基因的理想材料
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文章首次明确提出黔东南天柱县、锦屏县、黎平县以及相邻的湖南省靖县、会同县、洪江县存在浊积岩型金矿。研究发现,这些金矿均产在加里东皱褶带中,它们产于背斜的轴部,向两翼延伸,形成平行于地层的石英脉;另一种石英脉则充填于褶皱和剪切作用形成的剪切带或断裂带中。这些褶皱和断裂均呈北东方向。黔东南地区的浊积岩型金矿,均赋存于前震旦系下江群浊积岩中,产在板岩、凝灰岩或者在板岩和砂岩交界处。石英脉中金的富集与黄铁矿、毒砂、闪锌矿、方铅矿等密切相关。细脉比宽脉更富集金。断裂交叉处更富含金。石英脉两侧(尤其是顺层石英脉)的蚀变很弱。主要为硅化和绿泥石化。应用RB-SR方法测得石英脉的年龄为370~450Ma,成矿时代应在加里东期或期后。黔东南浊积岩金矿在品位(多数可见明金)、储量和产量方面均很有前景,研究它们具有十分重要的学术价值和经济意义.
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Iain S. Donnison, Donal M. O Sullivan, Ann Thomas, Peter Canter, Beverley Moore, Ian Armstead, Howard Thomas, Keith J. Edwards and Ian P. King (2005). Construction of a Festuca pratensis BAC library for map-based cloning in Festulolium substitution lines. Theoretical and Applied Genetics, 110 (5) pp.846-851 Sponsorship: BBSRC;BBSRC RAE2008
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New applications of genetic data to questions of historical biogeography have revolutionized our understanding of how organisms have come to occupy their present distributions. Phylogenetic methods in combination with divergence time estimation can reveal biogeographical centres of origin, differentiate between hypotheses of vicariance and dispersal, and reveal the directionality of dispersal events. Despite their power, however, phylogenetic methods can sometimes yield patterns that are compatible with multiple, equally well-supported biogeographical hypotheses. In such cases, additional approaches must be integrated to differentiate among conflicting dispersal hypotheses. Here, we use a synthetic approach that draws upon the analytical strengths of coalescent and population genetic methods to augment phylogenetic analyses in order to assess the biogeographical history of Madagascar's Triaenops bats (Chiroptera: Hipposideridae). Phylogenetic analyses of mitochondrial DNA sequence data for Malagasy and east African Triaenops reveal a pattern that equally supports two competing hypotheses. While the phylogeny cannot determine whether Africa or Madagascar was the centre of origin for the species investigated, it serves as the essential backbone for the application of coalescent and population genetic methods. From the application of these methods, we conclude that a hypothesis of two independent but unidirectional dispersal events from Africa to Madagascar is best supported by the data.
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PURPOSE: Malignant ureteral obstruction often necessitates chronic urinary diversion and is associated with high rates of failure with traditional ureteral stents. We evaluated the outcomes of a metallic stent placed for malignant ureteral obstruction and determined the impact of risk factors previously associated with increased failure rates of traditional stents. MATERIALS AND METHODS: Patients undergoing placement of the metallic Resonance® stent for malignant ureteral obstruction at an academic referral center were identified retrospectively. Stent failure was defined as unplanned stent exchange or nephrostomy tube placement for signs or symptoms of recurrent ureteral obstruction (recurrent hydroureteronephrosis or increasing creatinine). Predictors of time to stent failure were assessed using Cox regression. RESULTS: A total of 37 stents were placed in 25 patients with malignant ureteral obstruction. Of these stents 12 (35%) were identified to fail. Progressive hydroureteronephrosis and increasing creatinine were the most common signs of stent failure. Three failed stents had migrated distally and no stents required removal for recurrent infection. Patients with evidence of prostate cancer invading the bladder at stent placement were found to have a significantly increased risk of failure (HR 6.50, 95% CI 1.45-29.20, p = 0.015). Notably symptomatic subcapsular hematomas were identified in 3 patients after metallic stent placement. CONCLUSIONS: Failure rates with a metallic stent are similar to those historically observed with traditional polyurethane based stents in malignant ureteral obstruction. The invasion of prostate cancer in the bladder significantly increases the risk of failure. Patients should be counseled and observed for subcapsular hematoma formation with this device.