430 resultados para 1194
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提出了测定微量硫化物的快速亚甲蓝分光光度法。实验结果表明:在硫酸溶液中, K2Cr2O7+对二甲氨基苯胺+S2-迅速显色反应形成亚甲蓝,表观摩尔吸收系数为4.06×104 L·mol-1·cm-1;最大吸收波长为 664 nm;线性范围为 0~0.8 mg/L。实验了采用全差示光 度法直接测定水中硫化物的条件,用于某江水中21.6 μg/L的硫化物测定时,相对标准偏差 为3.2%(n=6);试样的标准加入回收率为95%~110%。
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Polypyrrole film electrode with Co(W2O7)(6)(10-) and CuW12O406- ions were synthesised in aqueous solutions, The electrode possesses a good stability and cyclic voltammetric behavior in weakly acidic or near neutral solutions, The redox of CuW12O406- ion can be catalysed by the polypyrrole film, The ESR measurement of the polypyrrole film with Co(W2O7)(6)(10-) and CuW12O406- ions indicates that the heteropolyanions not only play the role of neutralizing electricity in the polypyrrole film, contrasted with the film containing NO3-, but also Interact with the polypyrrole molecular chain to form some additive compound, The additive compound affects the electric structure elf the polypyrrole film and is unstable at more positive or more negative potentials.
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我们曾提出,电子组态具有共轭性的一对三价稀土离子,在一定条件下,会实现电子转移而产生价态变化.价态变化会明显改变材料的功能特性,因此,研究稀土元素价态变化,对新型功能材料设计具有重要意义.本工作研究了SrF_2:xEu,yTb磷光体中Eu-Tb的价态变化,发现SrF_2中,电子组态共轭的Eu~(3+)与Tb~(3+)在本实验条件下,可以实现电子转移.这一现象的发现有助于了解团相反应中稀土离子价态变化的规律.为寻找共轭稀土离子对之间实现电子转移条件提供了实验依据.
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XPS has extensively been applied to the study of polymers, in which a considerably important topic is the surface phase separations in block copolymers and blends. Copolymers (or blends) will produce a phase separation if their components are in-
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The glutathione peroxidases are essential enzymes of the cellular antioxidant defence system. In the present study, the full-length cDNA sequence encoding an extracellular glutathione peroxidase (designated CfGPx3) was isolated from Zhikong scallop Chlamys farreri. The complete cDNA was of 1194 bp, containing a 5' untranslated region (UTR) of 50 bp, a 3' UTR of 490 bp and an open reading frame (ORF) of 654 bp encoding a polypeptide of 217 amino acids. CfGPx3 possessed all the conserved features critical for the fundamental structure and function of glutathione peroxidase, such as the selenocysteine encoded by stop codon UGA, the GPx signature motif ((96)LGVPCNQFI(103)) and the active site motif ((WNFEKF184)-W-179). The high similarity of CfGPx3 with GPx from other organisms indicated that CfGPx3 should be a new member of the glutathione peroxidase family. By fluorescent quantitative real-time PCR, the CfGPx3 mRNA was universally detected in the tissues of haemocytes, gill, gonad, muscle and hepatopancreas with the highest expression in hepatopancreas. After scallops were challenged by Listonella anguillarum, the expression level of CfGPx3 transcript in haemocytes was significantly up-regulated (P<0.05) at 8 h post challenge. These results suggested that CfGPx3 was potentially involved in the immune response of scallops and perhaps contributed to the protective effects against oxidative stress. (C) 2010 Elsevier Inc. All rights reserved.
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作者所在的课题组,自1998年以来从胶州湾海泥中陆续分离了800株海洋放线菌,并从4株放线菌中分离出了12个新结构活性化合物。选择产生新颖抗肿瘤抗生素的海洋放线菌M045和M048,产全霉素的海洋放线菌M095和产蒽醌类化合物的海洋放线菌M097为研究材料,建立了海洋放线菌的遗传转化体系,为海洋放线菌的遗传工程操作及天然化合物组合生物合成奠定了基础。 (1)通过接合转移建立了菌株M045的遗传转化体系。用来源于蓝藻Anacystis nidulans UTEX625的别藻蓝蛋白基因验证了转化体系的有效性。通过PCR及基因组步移方法获得长度为1709bp的部分聚酮合成酶(PKS)基因,分析其同放射菌素基因具有同源性,利用基因中断插入失活该基因,但未获得突变株。因此尝试通过反向遗传学方法,克隆该菌株中新骨架抗肿瘤抗生素——中国霉素的生物合成基因簇,本研究已经构建了该菌株Fosmid基因组文库,对基因组文库的筛选工作正在进行中。 (2)利用PEG-介导的质粒pIJ702转化原生质体和接合转移两种方法均成功获得菌株M048的转化子,其中接合转移率高达10-4。菌株M048来源于高盐的海洋环境,维持原生质体所需渗透压与模式菌株—变铅青链霉菌(Streptomyces lividans)有很大差异,本研究对菌株M048原生质体形成和再生的各种因素进行了优化,获得了渗透压稳定剂蔗糖最佳浓度为0.4M。 质粒pIJ8600整合于菌株M048染色体上,对该转化株的抑菌活性、薄层层析(TLC)以及HPLC-MS进行了分析。结果表明,同野生菌株相比,该转化株对7种受试菌的抑菌活性显著增强,TLC显示差异的化合物条带,HPLC-MS显示化合物组分有差异。因此质粒pIJ8600的整合,引起菌株次级代谢产物生物合成途径的改变,使有抑菌活性的化合物大量累积。 从菌株M048染色体上克隆获得了1196bp的部分PKS基因,通过基因中断插入失活该基因,结果显示M048突变株次级代谢产物抑菌活性增强,HPLC分析发现显著差异。初步分析该PKS基因的中断使菌株体内某些生物合成途径受阻,而大量合成抗菌活性强的chandrananimycin C,或者产生了抑菌活性强的其它化合物。 (3)本研究成功建立了菌株M095的接合转移体系。M095/pIJ8600转化株的生物学活性分析并未发现差异,表明该菌株染色体上的整合位点(attB)是中性(neutral)的。通过PCR以及基因组步移的方法克隆获得了该菌株的部分糖基转移酶基因,该基因中断突变株对4株受试菌的抑菌活性增强,HPLC显示有差异,表明该糖基转移酶基因参与了菌株M095活性次级代谢产物的生物合成过程。 (4)对于菌株M097,用接合转移法成功获得了转化子。实现了别藻蓝蛋白基因的重组表达,并纯化了表达产物,体外试验表明其具有清除羟基自由基能力。结果表明来源于蓝藻的外源基因可以在海洋放线菌体内有效表达和正确折叠,初步验证了本研究所建立的海洋放线菌遗传转化体系的稳定性及有效性。对M097/pIJ8600转化株的生物学活性分析,未发现差异,表明该菌株染色体上的整合位点是中性的。 本论文首次将基因工程技术引入四株海洋放线菌,建立了海洋放线菌自身的基因转移系统,为利用基因工程技术改造海洋放线菌的天然化合物生物合成途径提供了方法。对部分PKS基因中断突变株的生物学活性及化学分析,初步揭示了通过遗传转化方法进行化合物组合生物合成的可行性。
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Nitrous oxide (N2O) emission was measured in a Kobresia humilis meadow and a Potentilla fruticosa meadow in the Qinghai-Tibet Plateau from June 2003 to July 2006. Five treatments were setup in the two alpine meadows. Two bare soil treatments were setup in the K. humilis meadow (BSK) and in the P. fruticosa meadow (BSP) by removing the above- and belowground plant biomass. Three plant community treatments were setup with one in the K. humilis meadow (herbaceous community in the K. humilis meadow-HCK) and two in the P. fruticosa meadow (herbaceous community in the P. fruticosa meadow-HCP, and shrub community in the P. fruticosa meadow-SCP). Nitrous oxide emission from BSP was estimated to be 38.1 +/- 3.6 mu g m(-2) h(-1), significantly higher than from BSK (30.2 +/- 2.8 mu g m(-2) h(-1)) during the whole experiment period. Rates from the two herbaceous blocks (HCK and HCP) were close to 39.5 mu g m(-2) stop h(-1) during the whole experimental period whereas shrub community (SCP) showed significant high emission rates of N2O. Annual rate of N2O emission was estimated to be 356.7 +/- 8.3 and 295.0 +/- 11.6 mg m(-2) year(-1) from the alpine P. fruticosa meadow and from the alpine K. humilis meadow, respectively. These results suggest that alpine meadows in the Qinghai-Tibetan Plateau are an important source of N2O, contributing an average of 0.3 Tg N2O year(-1). We concluded that N2O emission will decrease, due to a predicted vegetation shift from shrubs to grasses imposed by overgrazing.
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Changling fault depression is a compound fault depression complicated by interior fault, with faults in the west and overlap in the west. North of Changling fault depression show NNE strike while south is NW strike. Changling fault depression has undergone twochasmic stage which control the development and distribution of volcanic rock, one depression stage, later inversion and uplift stage which control the formation of natural gas reservoir, and basin atrophic stage. The main boundary faults and main faults in Changling fault depression control three volcanic cycles and the distribution of volcanic rock. Seismic reflection characteristic and logging response characteristic of volcanic rock in study area are obvious, and the distribution characteristic, volcanic cycle and active stage of volcanic rock can be revealed by seismic attribute, conventional logging data can distinguish clastic rock from volcanic rock or distinguish partial different types of volcanic rock. The reservoir property of rhyolite and volcanic tuff are the best. Favorable volcanic reservoir can be preserved in deep zone. Imaging logging and frequency decompostion technology of seismic data act as effective role in the study of reservoir physical property and gas-bearing properties of volcanic rock.. Hydrocarbon gas in study area is high and over mature coal type gas, the origin of CO2 is complex, it is either inorganic origin or organic origin, or mixing origin. Hydrocarbon gas is mainly originate from Shahezi formation and Yingcheng formation source rocks, CO2 is mainly mantle source gas. Hydrocarbon has the characteristics of continuous accumulation with two charging peak. The first peak represent liquid hydrocarbon accumulation time, The second peak stand for the accumulation time of gaseous hydrocarbon.CO2 accumulate approximately in Neocene. The source rock distribution range, volcanic rock and favorable reservoir facies, distribution characteristic of deep fault (gas source fault) and late inversion structure are the major factors to control gas reservoir formation and distribution. All the results show that these traps that consist of big inherited paleo uplift(paleo slope), stratigraphic overlap and thinning out, volcanic rock, are the most advantageous target zone.
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Rubinstein, W. (2002). Jewish Top Wealth-Holders in Britain, 1809-1909. Jewish Historical Studies. 37, pp.133-161. RAE2008
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Dissertação de Mestrado apresentada à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências da Comunicação, com especialização em Marketing e Comunicação Estratégica.
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Growth/differentiation factor 5 (GDF5) and glial cell line-derived neurotrophic factor (GDNF) are neurotrophic factors that promote the survival of midbrain dopaminergic neurons in vitro and in vivo. Both factors have potent neurotrophic and neuroprotective effects in rat models of Parkinson's disease (PD), and may represent promising new therapies for PD. The aim of the present study was to investigate the endogenous expression and function of GDF5 and GDNF in the nigrostriatal dopaminergic system during development and in rat models of PD. Examination of the temporal expression patterns of endogenous GDF5, GDNF, and their respective receptors, in the developing and adult nigrostriatal dopaminergic system suggest that these factors play important roles in promoting the survival and maturation of midbrain dopaminergic neurons during the period of postnatal programmed cell death. The relative levels of GDF5 and GDNF mRNAs in the midbrain and striatum, and their individual temporal expression patterns during development, suggest that their modes of actions are quite distinct in vivo. Furthermore, the sustained expression of GDF5, GDNF, and their receptors into adulthood suggest roles for these factors in the continued support and maintenance of mature nigrostriatal dopaminergic neurons. The present study found that endogenous GDF5, GDNF, and their receptors are differentially expressed in two 6-hydroxydopamine-induced lesion adult rat models of PD. In both terminal and axonal lesion models of PD, GDF5 mRNA levels in the striatum increased at 10 days post-lesion, while GDNF mRNA levels in the nigrostriatal system decreased at 10 and 28 days post-lesion. Thus, despite the fact that exogenous GDF5 and GDNF have similar effects on midbrain dopaminergic neurons in vitro and in vivo, their endogenous responses to a neurotoxic injury are quite distinct. These results highlight the importance of studying the temporal dynamic changes in neurotrophic factor expression during development and in animal models of PD.
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We show that "commodity currency" exchange rates have surprisingly robust power in predicting global commodity prices, both in-sample and out-of-sample, and against a variety of alternative benchmarks. This result is of particular interest to policy makers, given the lack of deep forward markets in many individual commodities, and broad aggregate commodity indices in particular. We also explore the reverse relationship (commodity prices forecasting exchange rates) but find it to be notably less robust. We offer a theoretical resolution, based on the fact that exchange rates are strongly forward-looking, whereas commodity price fluctuations are typically more sensitive to short-term demand imbalances. © 2010 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology.
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This paper concerns the development and validation (using an oil/water system) of a finite volume computer model of the continuous casting process for steel flat products. The emphasis is on hydrodynamic aspects and in particular the dynamic behaviour of the metal/slag interface. Instability and wave action encourage the entrainment of inclusions into the melt affecting product quality. To track the interface between oil and water a new implicit algorithm was developed, called the Counter Diffusion Method. To prevent excessive damping, a time-filtered version of the k-e model, was found necessary, with appropriate density stratification terms representing interface turbulence damping.