988 resultados para 302-M0004A
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研究了4种不同环氧化度的稀土异戊橡胶(EIR)的生胶、混炼胶及硫化胶性能。结果表明,随着环氧化度(摩尔)从10%增150%,EIR的T_g由-54℃升至-30℃,但它们(除EIR-50外)的混炼行为与稀土异戊橡胶(Ln-IR)相当,混炼胶表面平整光滑。随着环氧化度增加,混炼胶硫化速度加快,硫化平坦区较窄,且具有明显的硫化返原现象;硫化胶的300%定伸应力、拉伸强度、硬度、磨耗等增加,耐20 ̄#机油和气密性明显提高。EIR-50气密性与丁基橡胶相当,油增重与腈橡胶接近;但扯断伸长率和弹性下降,即阻尼性能提高,生热和湿滑性能无明显变化。由100℃热空气老化后EIR硫化胶的300%定伸应力下降表明,EIR属于断链反应为主的热老化历程。
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[La(NO3)(3)(OH2)(2)(OHMe)(bipy).15-crown-5 is monoclinic, P2(1)/n, with a = 11.239(6), b = 19.302(7), c = 14.458(8) Angstrom, beta = 92.47(5)degrees, and D-calc = 1.63 g cm(-3) for Z = 4. In the complex, two nitrogen atoms (from bipy) and nine oxygen atom
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报道了异丙基膦酸单(1一已基一4一乙基)辛酯(PT一2)的正庚烷溶液在硫酸介质中对Sc3+、Fe3+、Lu3+萃取平衡的影响,结果表明,通过控制酸度可以使三种元素分高。确定了Sc3+的萃取机理,低酸度下为阳离子交换反应,高酸度下为溶剂化反应,中等酸度下两种反应并存。研究了饱和萃合物的IR、NMR谱。讨论了温度对萃取平衡的影响,低酸度和高酸度下均为放热反应。
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本文综述了CdTe/CdS和CuInSe_2/CdS薄膜太阳电池的进展,讨论了这两种电池的发展前景。
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用循环伏安法和计时电位法研究了YCl_3-KCl·NaCl熔体中Y~(3+)在钼和镍电极上的电极过程。Y~(3+)的还原是分步反应过程:Y~3+c=Y~(2+),Y~(2+)+2c=Y。Y~(3+)在镍电极上还原后能与镍形成合金,对不同条件下形成的合金组成进行了X射线分析。
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Seed rearing is an important part in large scale clam culture industry. Since the nutritional history affects early development in bivalve, the condition of larval nutrition plays a key role in successful seed rearing. So far, the molecular mechanism of nutrient uptake in bivalve larvae is unclear. As one of the important proteolytic enzymes, cathepsin B of several organisms has been reported to be involved in digestion. We intended to analyze whether cathepsin B is involved in larval nutrient metabolism in the economic bivalve, clam Meretrix meretrix. The full length of M. meretrix cathepsin B (MmeCB) cDNA was cloned, which is 1647 bp with an open reading frame of 1014 bp. The deduced amino acid sequence encoded a preproenzyme of 337 residues with Cys-114, His-282 and Asn-302 composing cathepsin B activity center. The temporal and spatial expressions of MmeCB mRNA were examined from trochophore to post larva stages by whole mount in situ hybridization. In trochophore stage, no detectable signal was found. In the later three stages, MmeCB mRNA was detected in the digestive gland, suggesting a possible role of MmeCB in digestion. Moreover, MmeCB mRNA was also observed in the epidermal cells in D-veligers. Cathepsin B specific inhibitor (CA074 methyl ester) was applied to block the activity of cathepsin B in unfed larvae. The average shell lengths of treated larvae were smaller than that in control groups. The results of mRNA epidermal distribution and inhibitor treatment in D-veligers indicated that MmeCB may be also associated with other pathway of nutrient metabolism in larval epidermis. The overall results in this paper revealed that MmeCB might play a role in larval nutrient metabolism. (C) 2008 Elsevier B.V. All rights reserved.
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应用稳定碳、氮同位素比值法和脂肪酸标志分析法,较为系统地研究了贝藻混养系统中滤食性贝类的食物来源,评估了大型藻类对混养系统及滤食性贝类的物质贡献。主要研究结果如下: 1.综述了典型生态系统中大型藻类和滤食性贝类各自的生态学地位和作用,大型藻类与滤食性贝类不仅在水体营养盐方面存在互利关系,二者在物质循环与收支方面同样具有耦合性,大型藻类提供的颗粒态有机质可以为滤食性贝类提供饵料来源。 2.总结了稳定同位素比值法和脂肪酸标志法在海洋生态系统食物来源及食物网分析中的应用,并建立了两种方法的具体操作规程。 3.分析了栉孔扇贝Chlamys farreri和海带Laminaria japonica混养系统中海带碎屑形成及释放不同阶段的生态学特征,评估了碎屑对扇贝的饵料贡献。海带在6周内释放了自身约27%的碳;碎屑形成及释放过程中C:N比值显著下降,同时伴随着旺盛的细菌降解,碎屑中也发现有大量硅藻类和原生动物存在。稳定同位素分析证实海带碎屑是混养期间扇贝的主要食物来源。 4.查明了春季胶州湾潮间带自然分布的长牡蛎Crassostrea gigas、紫贻贝Mytilus galloprovincialis和湾内浅海筏式养殖栉孔扇贝的可能食物来源。湾内栉孔扇贝饵料组成中浮游硅藻类为最主要部分,同时混杂有陆源有机质和细菌类物质;潮间带自然生长的牡蛎和贻贝饵料组成中,浮游植物占86.2-89.0%,种类组成中除硅藻外还包括一定比例的金藻和甲藻类;潮间带繁盛的孔石莼Ulva pertusa藻床为两种贝类提供了8.7-11.0%的补充食物来源。 5.揭示了桑沟湾贝藻混养海区春、夏季栉孔扇贝饵料来源组成情况及其季节变化,评估了海带养殖区碎屑碳量季节变化及海带来源碳对扇贝组织碳的贡献。结果表明,湾内贝藻混养区碎屑碳量为75.52-265.19 μg l-1,其在水体总颗粒态有机碳中的比例为25.6-73.8%。海带来源碎屑碳对栉孔扇贝组织碳的贡献比例为14.1-42.8%,且与水体碎屑碳比例的季节变化存在极显著相关性(F=0.992, P=0.004)。5月份湾外海带养殖区水体碎屑碳量为110.12-144.71 μg l-1,显著高于湾内无海带区(75.52 μg l-1),湾外养殖的扇贝组织中海带来源碳比例为22.0-24.1%,显著高于湾内单养区扇贝(9.6%)。估算结果表明,桑沟湾每年收获的6967吨(总湿重)栉孔扇贝中,海带提供了约57.1吨碳,换算为海带干物质为219.6吨。脂肪酸标志分析结果表明,2月份至8月份硅藻类在扇贝饵料组成中比例逐渐下降,而细菌类比例逐渐升高。整个采样期间,EPA/DHA比例较低,说明扇贝饵料组成中可能包括高DHA含量的组分。
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作者以海湾扇贝胚胎和幼虫为材料,研究了氨氮的毒性影响。氨氮对海湾扇贝胚胎孵化率为EC50为1.97ppm总氨氮(相当于0.094ppm非离子氨)。氨氮对早D形幼虫、平均壳长110μ的D形幼虫和壳顶幼虫的96小时LC50分别为6.33、7.84和5.25总氨氮(相当于0.302、0.374和0.251ppm非离子氨)。氨氮对幼虫生长、眼点发生和变态的EC50分别为4.04、2.10和2.67ppm总氨氮(相当于0.193、0.10和0.127ppm非离子氨)。实验结果表明,海湾扇贝早期D形幼虫对氨氮毒性的耐受力比壳长较大的D形幼虫的耐受力低,但壳顶幼虫的耐受力最低。海湾扇贝在胚胎发育期和幼虫眼点发生与变态期对氨氮的毒性作用非常敏感。
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本研究利用皱纹盘鲍的EST序列进行单核苷酸多态(SNP)标记开发;对等位基因特异性PCR(AS-PCR)方法进行了优化,使之适合SNP基因型分析;对一个作图家系开发基因相关SNP标记,并对标记在子代个体中的分离情况进行了分析,探讨了借助SNP在遗传连锁图谱上定位功能基因的方法。 对大约5800条EST序列进行拼接,共获得含有4条以上序列的contig 150个,在86个含有单碱基突变位点的contigs中发现SNP 302个,碱基置换类型A/G(C/T)、A/C(G/T)、A/T、C/G的位点数目分别为147、90、21、16个。50个contigs在BLASTx分析后具有匹配(E值小于1E-5),其中的220个SNPs全部为同义cSNPs,位于遗传密码子的第三简并位。粗略估算,皱纹盘鲍核基因组中SNP的平均分布密度不低于1%。 通过扩增DNA pool后产物直接测序共验证了28个SNP。PCR直接测序法操作简单,结果可靠,一次测序可能验证多个位点,有时还可以发现新的突变位点。通过重点研究引物3’端不同错配对PCR扩增的影响,对AS-PCR的引物设计原则及反应条件进行了探讨及优化,发现在AS引物的3’端倒数第二位引入额外的强错配后,AS-PCR检测SNP的特异性会得到很大的提高,从而使AS-PCR可以满足小规模的SNP基因型分析。 根据EST-contig或者单一的EST序列设计PCR引物74组,其中43组可以特异扩增皱纹盘鲍基因组DNA。用这些引物扩增一个作图家系的父母本,并对PCR产物纯化后分别进行双向直接测序,在18个基因片段中发现了86个SNP,其中82个是新SNP,并且绝大多数SNP位于内含子序列中。这些SNP在父母本中的基因型,在多数情形下,是一方为纯合(AA),而另一方为杂合(AB);父母本均为杂合和均为纯合的形式则较少。在父母本中杂合形式的SNP位点,理论上可以在子代中发生分离。 在每个基因的内含子中选择父母本基因型为AA×AB或者AB×AA的SNP位点,设计AS-PCR分型引物并检测123个子代个体的基因型。在对9个基因中的11个SNP位点(包括5个母本标记和6个父本标记)进行子代基因型分析后发现,2个位点不符合孟德尔1:1分离(P < 0.05),符合预期分离比率的9个位点存在较大可能定位于遗传连锁图谱。通过分析两组父母本标记(F142和M142,F459和M459)发现,在根据父母本序列设计SNP分型引物时,可以设计指向同一基因的成对的父母本标记,从而使两个单亲标记可作为一个共同标记使用。
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High-molecular-weight dissolved organic matter (HMW-DOM, > 1,000 Daltons) is actively involved in the global biogeochemical cycling of many elements, but its carbon sources and detailed formation pathways are still not well understood. In this study, we measured bulk stable carbon and nitrogen isotopic ratios, lipid composition, and compound-specific carbon isotopic ratios of HMW-DOM samples collected from four U.S. estuaries (Boston Harbor/Massachusetts Bay, Delaware/Chesapeake Bay, San Diego Bay, and San Francisco Bay). Analytical results show (1) a fraction of HMW-DOM (lipid associated) in estuarine and coastal waters is derived from bacteria and phytoplankton; (2) this fraction of HMW-DOM is formed by various release processes of bacterial membrane components and bacterial reworking of phytoplankton-derived material; (3) this fraction of HMW-DOM is generally present in all samples from different coastal systems despite variable organic matter inputs and environmental conditions, suggesting an important bacterial role in HMW-DOM formation.
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Although single nucleotide polymorphisms (SNPs) are important resources for population genetics, pedigree analysis and genomic mapping, such loci have not been reported in Pacific abalone so far. In this study, a bioinformatics strategy was adopted to discover SNPs within the expressed sequences (ESTs) of Pacific abalone, Haliotis discus hannai, and furthermore, polymerase chain reaction direct sequencing (PCR-DS) and allele-specific PCR (AS-PCR) were used for SNPs detection and genotype scoring respectively. A total of 5893 ESTs were assembled and 302 putative SNPs were identified. The average density of SNPs in ESTs was 1%. Fifty-two sets of sequencing primers were designed from SNPs flanking ESTs to amplify the genomic DNA, and 13 could generate products of expected size. Polymerase chain reaction direct sequencing of the amplification products from pooled DNA samples revealed 40 polymorphic SNP loci. Using a modified tetra-primer AS-PCR, seven mitochondrial and six nuclear SNPs were typed and characterized among 37 wild abalones. In conclusion, it is feasible to discover SNPs from number limited ESTs and the AS-PCR as a simple, robust and reliable assay could be a primary method for small- and medium-scale SNPs detection in abalones as well as other non-model organisms.
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Chitosan (CS) with two different molecular weights was modified by reacting with 4-hydroxyl-5-chloride-1,3-benzene-disulfo-chloride or 2-hydroxyl-5-chloride-1,3-benzene-disulfo-chloride to give new 2-(4(or 2)-hydroxyl-5-chloride-1,3-benzene-di-sulfanimide)-chitosan (2-HCBSAHCS, 2-HCBSALCS, 4-HCBSAHCS, 4-HCBSALCS). The structure of the derivatives was characterized by FT-IR and C-13 NMR spectroscopy. The antioxidant activities of the derivatives were investigated employing various established systems, such as hydroxyl radical ((OH)-O-center dot)/superoxide anion (O-2(radical anion)) scavenging/reducing power and chelating activity. All the derivatives showed stronger scavenging activity on hydroxyl radical than chitosan and ascorbic acid (Vc), and IC50 of 4-HCBSAHCS, 4-HCBSALCS, 2-HCBSAHCS and 2-HCBSALCS was 0.334, 0.302, 0.442, 0.346 mg/mL, respectively. The inhibitory activities of the derivatives toward superoxide radical by the PMS-NADH system were strong. The results showed that the superoxide radical scavenging effect of 2-(4(or 2)-hydroxyl-5-chloride-1,3-benzene-disulfanimide)-chitosan was higher than chitosan. The derivatives had obviously reducing power and slight chelating activity. The data obtained in in vitro models clearly establish the antioxidant potency of 2-(4(or 2)-hydroxyl-5-chloride-1,3-benzene-disulfanimide)-chitosan. (C) 2007 Elsevier Masson SAS. All rights reserved.
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以调查统计的方法研究了高寒草甸匍匐茎植物短穗兔耳草Lagotis brachystachya无性系的生长特征、形态特征以及能量分配规律,研究结果表明:匍匐茎只有1条的短穗兔耳草最多,占60.47%,匍匐茎有4条的短穗兔耳草只占6.98%.在牧草生长盛期,短穗兔耳草无性系的基株高度4.03cm,根长为9.11 cm,叶数为7.98;分株高度0.85 cm,根长2.73 cm,叶数为3.08;匍匐茎的茎生叶数为12.54,长度为15.14 cm,匍匐茎比节间重为2.18 mg/cm,粗度为0.97 mm,不同构件的干质量呈现出基株>匍匐茎>分株>茎生叶的规律.随着匍匐茎数目的增多,短穗兔耳草无性系的基株根长逐渐增加,用于克隆繁殖的能量投资也有增加的趋势,其他参数都没有明显的变化规律.