997 resultados para 715


Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文描述了大孔径涂敷柱LBC柱的制备及其对水中痕量有机物的吸附富集技术的研究,LBC柱是一种涂有固定液SE-30的大孔径金属柱,用以直接吸附富集水中痕量有机物,然后热脱附到GDX-502预柱上,用CS_2洗脱并浓缩后注入气相色谱仪进行分析测定。本文还讨论了溶液浓度、柱长度、过柱速度、徐膜厚度对LBC柱吸附富集效率的影响及其本方法的重现性。相对标准偏差小于7%。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Surface structure of the glassy carbon surface modified with cobalt tetraphenyl-porphyrin (CoTPP) by thermal-treatment has been studied by XPS, DTA and TG. During the thermal treatment a bond can be formed between the glassy carbon surface and TPP. Therefore the stability of electrode for the catalysis of dioxygen reduction is improved. Upon thermal treatment at 600 degrees C, FWHM of Co(2p(2/2)) is broadened, the reason is due to overlapping of peaks of multiple states, the spin orbit separation between Co (2p(1/2)) and Co (2p(3/2)) increases to 15.5-16.3eV, which indicated a change from low spin divalent states, the kinetic energy of Co L3VV Auger line and Auger parameter also increase. These changes of central cobalt ion provide a suitable redox potential for Co(III)/Co(II) which is related to the activity for catalysis of dioxygen reduction.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

用质谱化学电离和量子化学方法研究了致癌物质N-亚硝基二甲胺(NDMA)的结构及性质,优化了化学电离质谱中主要离子的构型;探讨了NDMA的质子化合物的形成途径,经NDMA及其质子化合物的静电势计算,阐述了NDMA的可能致癌机理。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文用XPS、DTA和TG分析了四苯基钴卟啉化学修饰电极的热分解行为,它不同于四苯基铁卟啉.由XPS谱图揭示了四苯基钴卟啉与玻璃碳电极之间的相互作用,进而阐述了经热处理的四苯基钴卟啉化学修饰电极的表面结构与电催化稳定性的关系.从Co2p_3/2和2p_(1/2)能级的自旋分裂间距及其Shake-up伴峰,了解经热处理后的四苯基钴卟啉修饰电极中钴自旋态变化,并且从Co的L_3VV俄歇跃迁计算出Co的双电离能,其双电离能与电催化活性有一定关系。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

C-type lectins are a superfamily of carbohydrate-recognition proteins which play crucial roles in the innate immunity. In this study, the gene of a C-type lectin with multiple carbohydrate-recognition domains (CRDs) from scallop Chlamys farreri (designated as Cflec-3) was cloned by rapid amplification of cDNA ends (RACE) approach based on expression sequence tag (EST) analysis. The full-length cDNA of Cflec-3 was of 2256 bp. The open reading frame encoded a polypeptide of 516 amino acids, including a signal sequence and three CRDs. The deduced amino acid sequence of Cflec-3 showed high similarity to members of C-type lectin superfamily. By fluorescent quantitative real-time PCR, the Cflec-3 mRNA was mainly detected in hepatopancreas, adductor, mantle, and marginally in gill, gonad and hemocytes of healthy scallops. After scallops were challenged by Listonella anguillarum, the mRNA level of Cflec-3 in hemocytes was up-regulated and was significantly higher than that of blank at 8 h and 12 h post-challenge. The function of Cflec-3 was investigated by recombination and expression of the cDNA fragment encoding its mature peptide in Escherichia coli BL21 (DE3)-pLysS. The recombined Cflec-3 (rCflec-3) agglutinated Gram-negative bacteria Pseudomonas stutzeri. The agglutinating activity was calcium-dependent and could be inhibited by D-mannose. These results collectively suggested that Cflec-3 was involved in the immune response against microbe infection and contributed to nonself-recognition and clearance of bacterial pathogens in scallop. (C) 2009 Elsevier Ltd. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone contributing to the folding, maintenance of structural integrity and proper regulation of a subset of cytosolic proteins. The full-length cDNA of Zhikong scallop Chlamysfarreri HSP90 (designated CfHSP90) was cloned by EST and rapid RACE techniques. It was of 2710 bp, including an open reading frame (ORF) of 2181 bp encoding a polypeptide of 726 amino acids with all the five HSP90 family signatures. BLAST analysis revealed that the CfHSP90 gene shared high similarity with other known HSP90 genes. Fluorescent real-time quantitative RT-PCR was used to examine the expression pattern of CfHSP90 mRNA in haemocytes of scallops exposed to Cd2+, Pb2+ and Cu2+ for 10 and 20 days, respectively. All the three heavy metals could induce CfHSP90 expression. There was a clear dose-dependent expression pattern of CfHSP90 after heavy metals exposure for 10 days or 20 days. Different concentrations of the same metal resulted in different effects on CfHSP90 expression. The results indicated that CfHSP90 responded to various heavy metal stresses with a dose-dependent expression pattern as well as exposure time effect, and could be used as a molecular biomarker in a heavy metal polluted environment. (c) 2007 Elsevier Inc. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A pollen record of core PC-1 from the northern Okinawa Trough, East China Sea (ECS), provides information on vegetation and climate changes since 24 cal. kaBP. A total of 103 samples were palynologically analyzed at 8 cm intervals with a time resolution of 230 a. Four pollen zones are recognized: zone I (812-715 cm, 24.2-21.1 cal. kaBP), zone II (715-451 cm, 21.1-15.2 cal. kaBP), zone III (451-251 cm, 15.2-10.8 cal. kaBP), zone IV (251-0 cm, 10.8-0.3 cal. kaBP), corresponding to Late MIS 3, Last Glacial Maximum (LGM), deglaciation and Holocene, respectively. The LGM is characterized by the dominance of herbs, mainly Artemisia, and high pollen influx, implying an open vegetation on the exposed continental shelf and a cool and dry climate. The deglaciation is a climate warming stage with Pinus percentage increased and Artemisia percentage decreased and a rapid sea-level rise. The Holocene is characterized by predominance of tree pollen with rapid increase in Castanea-Castanopsis indicating the development of mixed evergreen and deciduous broad-leaved forest and a warm, humid climate. Low pollen influx during the Holocene probably implies submergence of the continental shelf and retreat of the pollen source area. The vegetation indicated by pollen assemblage found in this upper zone is consistent with the present vegetation found in Kyushu, Japan. Originating from the humid mountain area of North Luzon of the Philippines, Tasmania and New Zealand, Phyllocladus with sporadic occurrence throughout PC-1 core probably suggests the influence of Palaeo-Kuroshio Current or intense summer monsoon. The observed changes in Pinus and Herbs percentage indicate fluctuations of the sea level, and high Pinus percentage corresponds to high sea level. Spectrum analysis of the pollen percentage record reveals many millennial-scale periodicities, such as periodicities of 6.8, 3.85 2.2, 1.6 ka.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Based on the Navier-Stokes equation, an equation describing the Langmuir circulation is derived by a perturbation method when the influences of Coriolis force and buoyancy force are both considered. The approach used in the analysis is similar to the works carried out by Craik and Leibovich [J. Fluid Mech. 73 (1976) 401], Leibovich [J. Fluid Mech. 79 (1977) 715] and Huang [J. Fluid Mech. 91 (1979) 191]. Potential applications of the equation proposed are discussed in the area of Antarctic circumpolar current.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

从海洋动植物中寻找和筛选具有药用价值的活性先导化合物是海洋药物研发极为重要的理论基础研究。基于中国东南热带和亚热带沿海海域丰富的生物资源,本工作以化学分析和生物活性筛选为导向,以黄海海域习见的绿藻束生刚毛藻、南海三亚附近海域的圆裂短足软珊瑚、海绵Pseudoceratina sp.及广西沿海滩涂的盐生植物海刀豆四种海洋生物为样品,应用现代分析和检测手段对其次生代谢产物及其生物活性进行较系统的研究。 综合利用现代色谱手段和波谱技术,从上述目标生物样品中共分离并结构鉴定化合物74个,其中新化合物10个,新天然产物1个,这一新发现原则性结果,属国内外首次报道。1.对黄海海域束生刚毛藻C. fascicularis的化学成分及其生物活性进行了首次研究,从中得到叶绿素类新化合物Porphyrinolactone 1和新天然产物 20-Chlor-(132-S)-hydroxyphaeophytin a 2,在避光条件下对叶绿素类化合物进行体外NF-κB活性抑制筛选实验, 结果表明化合物1-6对NF-κB都有显著的抑制活性;对叶绿素类化合物首次进行体外蛋白酶体ChT-L的抑制活性实验筛选,化合物2和4对蛋白酶体ChT-L表现出显著的抑制活性,在浓度为50μM时,抑制率分别为70%和73.5%,并对其立体构型和生物活性的构效关系进行探讨;首次从该属得到环阿尔廷三萜类化合物7—12;对所得化合物7—15在浓度为1μg/mL时对肿瘤细胞部分靶蛋白酶的抑制活性测定结果表明,这些化合物对不同的靶蛋白酶表现出较强的抑制活性。2. 从南海圆裂短足软珊瑚中发现孕甾及其糖苷类新化合物22—27。3. 南海海绵Pseudoceratina sp.中发现溴代酪氨酸生物碱类新化合物41—42,组胺酸生物碱类新化合物43,并对其生源关系进行探讨。4. 首次对海刀豆C. maritime的化学成分进行研究,发现紫檀素类化合物61—63,异黄酮4个64—67;对该类化合物61—67首次进行NF-κB和蛋白酶体ChT-L的抑制活性筛选,其中化合物63表现出较强的NF-κB的抑制活性。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

以褐藻裙带菜(Undaria pinnatifida)、萱藻(Scytosiphon lomentarius)、海蒿子(Sargassum confusum)、叉开网地藻(Dictyopteris divaricata)、海带(Laminaria japonica)、囊藻(Colpomenia sinuosa)、鼠尾藻(Sargassum thunbergii)、水云(Ectocarpus confervoides)为材料,对其色素-蛋白质复合物的分离技术及其特性进行了系统研究。通过对裙带菜色素-蛋白质复合物分离技术及其影响因素的研究,确立了褐藻的PAGE分离方法。采用Tris-Gly电泳分离系统,以非离子去污剂DMG或DIG为增溶剂(DMG: Chl=20: 1, DIG: Chl=50: 1, 4 ℃增溶1 h),10%的分离胶浓度,丙烯酰胺与甲叉双丙烯酰胺的比例为30: 0.8,从裙带菜中成功地分离出8条含色素的蛋白质复合物带。采用Anderson命名系统,以高等植物菠菜为参照,将其命名为CPIa, CPI, CPa, LHC_1, LHC_2, LHC_3, LHC_4和LHC_5。游离色素较少。通过对三种褐藻的色素-蛋白质复合物的表观分子量测定、光谱学研究以及对裙带菜色素-蛋白质复合物的多肽组成分析,揭示了褐藻各种色素-蛋白质复合物的特征。CPIa是褐藻分子量较大的PSI复合物,为墨角藻黄素-叶绿素 a/c-蛋白质复合物。CPI是褐藻的PSI核心复合物,为P700-叶绿素 a-蛋白质复合物。CPa是褐藻的PSII复合物,为墨角藻黄素-叶绿素 a/c-蛋白质复合物。其余5条为捕光色素-蛋白质复合物,LHC_1和LHC_3是墨角藻黄素-叶绿素 a/c-蛋白质复合物,LHC_2, LHC_4和LHC_5是叶绿素 a/c-蛋白质复合物。根据裙带菜色素-蛋白质复合物的多肽分析结果并与高等植物比较,提出褐藻PSI和PSII的结构模型。褐藻PSI和PSII的反应中心多肽与高等植物相同,捕光复合物明显区别。褐藻LHCI和LHCII的多肽组成相同,都是由单一的20 kDa多肽组成。褐藻叶状体、叶绿体、类囊体膜和PSI复合物的77 K 荧光发射光谱具有特异性,缺少高等植物PSI特征的730 nm 荧光峰。叶状体的77 K 荧光发射光谱按荧光主峰的波长分为两种类型,一种类型的荧光主峰在690 nm,另一种类型的在705-720 nm。三种褐藻PSI复合物的77 K 荧光发射光谱相同,有两个分别们于680 nm和715 nm 的发射峰。褐藻的77 K 荧光特异是由PSI的结构决定的。根据褐藻PSI复合物的荧光特性以及去污剂增溶动力学分析结果,推动F715来自褐藻核心色素-蛋白质复合物,F680来源于PSI复合物中的捕光复合物。褐藻PSI复合物中缺少高等植物发射730 nm 荧光的LHCIb复合物的能量传递模型。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

藏羚(Pantholops hodgsoni)是青藏高原特有物种,隶属于偶蹄木牛科山羊亚科藏羚属~([1-4]),主要分布于中国境内的青海、西藏、新疆三省区交界处的高寒荒漠化草原、高寒草原和高寒草甸地区,海拔一般在4 100-5 00m之间,生存环境十分恶劣,目前已处于濒危状态。国际社会对藏羚羊的保护高度关注,但由于缺乏对该物种的科学认识,保护措施只能以反盗猎和打击藏羚羊绒及其制品的走私贸易为主~([4])。我们在青海省重大科技攻关项目和中国科学院知识创新工程项目的资助下,开展了藏羚羊种群生物学及保护措施的研究,并于2002年7月至12月先后3次在可可西里国家级自然保护区进行考察,发现保护区救护的1只名叫爱羚的雄性藏羚在人工饲养条件下生长良好,已达到性成熟状态。该结果意味着人工驯养可能性在藏羚的保护实践中发挥重要作用。现将考察报告如下。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper studied the reproductive strategies of Kobresia humilis in alpine meadow about its sexual reproduction ,vegetative reproduction and reproductive efforts respectively. The results show that the seed output of Kobresia humilis is 715. 5per unit (m2) . The germination is above 60 % in fit condition ,while only about 3 % in field. There is only 16. 13 % seed which get into seed bank and remain vitality till grass greening. So the seedling is only 3. 46 per unit (m2) in field.But the new ramets of Kobresia humilis are 711. 34 unit (m2 ) from vegetative reproduction. In addition ,vegetative reproductive effort is more than sexual reproductive effort . It constitutes 93. 5 % of all reproductive efforts. Therefore ,the main reproductive strategy of Kobresia humilis is vegetative reproduction ,and sexual reproduction is secondary in alpine condition.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文设计并实现了一种生成式的CAPP系统-S_3PTCAPP。主要用于回转体零件的计算机辅助工艺设计。整个系统采用专家系统的思想,分为输入、基本加工方法、调头与装卡、工具工装查询与输出5个子系统。用框架结构、和宣言型语义网作为领域知识的主要表示方法。在推理方法上采用了数据驱动控制、目标驱动控制、生成与测试广义混合推理等几种方法。对输入输出模块分别采用了用户适应类、用户适应类与系统适应类综合二种接口类型。全部程序是在PC/XT机上,用 turbo-prolog 语言实现的。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

以五龙金矿为例,在同一剖面上采集了不同成矿阶段的含金石英脉和近矿蚀变岩样品,.根据矿物流体包裹体和蚀变岩成分地的测定结果,系统地讨论了不同成矿阶段流体包裹体成(K^+、Na^+、Ca^+、CO2等)和不同蚀变岩成分(K2O、Na2O、CaO1、MgO、CO2等)的变化规律,结果表明,从第二成矿阶段到第四成矿阶段,流体中的Na^+、Ca^+、Mg^+含量有明显的升高的趋势,K^+ 含量降低,蚀变岩中,K2O由远离矿体的原岩到靠近矿体的蚀变岩其含量增加,而Na2O、CaO、MgO逐渐降低,这种流体包裹体和蚀变岩中的某些相应成分的变化特征,应该是流体-岩石相互作用的结果。