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萜类化合物具有可观的经济价值,但是目前的生产过程复杂、产量低。酿酒酵母甲羟戊酸途径为萜类化合物的合成提供直接前体,因此酿酒酵母细胞具有合成异源萜类化合物的天然优势。对酿酒酵母甲羟戊酸途径的清晰认识是对其进行有效利用的基础,本文从代谢途径、关键酶的特点和全局调控机制3个方面对该途径进行了介绍。从代谢途径的构建和优化、模块与底盘细胞的适配、模块构建及组装方式的角度概述了酿酒酵母细胞异源合成单萜、倍半烯萜、二萜、三萜类化合物的研究进展。指出实现酿酒酵母高效合成萜类化合物所需要解决的基础问题是对酿酒酵母甲羟戊酸途径进行更为全面了解和对萜类化合物的天然代谢途径进行明确解析;另外,合成生物学的进一步发展也将为此提供应用基础。 相似文献
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明代德化瓷塑大师、瓷圣何朝宗的瓷塑艺术具有独特和永恒的艺术魅力,它达到了中国古代瓷塑艺术成就的高峰。何朝宗鬼斧神工的瓷塑艺术将宗教精神、人生哲学、审美情趣融入德化的白瓷,创造出了一件件不朽的瓷塑艺术品,他的艺术风格一直影响到数百年后的今天。现存福建泉州海交馆的何朝宗瓷塑艺术代表作品《渡海观音》,就是一尊何氏精湛的雕塑艺术语言和艺术家心目中的“世上独一无二的艺术珍品”。何朝宗的瓷塑艺术凝铸着一个时代的智慧,它将永恒的闪耀着灿烂的光辉。 相似文献
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1胶原纤维巴西Novaprom胶原纤维是以精选的牛皮内剖层(真皮)组织提取的,它不同于明胶或明胶的衍生物。它的生产是在严格控制的时间和温度范围内进行的,从而确保其主要成分──胶原蛋白的活性不变,并以天然纤维的形式存在。它在肉制品中的结构呈纤维状而不是一般的胶冻,因而这种结构是非常稳定的,是不可逆的。它是很好的功能性动物纤维蛋白,在肉制品及鱼糜制品等相关的食品中得到广泛的应用。2胶原纤维的性能及相关指标(1)蛋白质含量:胶原纤维中的动物蛋白质(M×6.25)高达98%,含有人体必需的氨基酸。(2)吸水、持水性:胶原纤维结构良好,呈矩… 相似文献
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玻璃纤维池窑拉丝生产线配合料的制备中,原料是形成优质玻璃液的基础,因此可以说配合料的稳定性、均匀性和准确性对玻璃纤维的质量起着决定的作用.生产实践证明:组分和粒度均匀的配合料,不但能强化玻璃液的熔化和澄清过程,而且还能减少或消除影响玻璃质量的各种弊病.所以认真拟定玻璃纤维原料的成分和选择玻璃纤维的种类和化学性质:严格控制进厂原料化学成分、粒度和水份;做好原料的分堆、存放、加工、称量、混合、输送是优质配合料制备不可缺少的手段,这也是做好玻璃纤维池窑配合料的基本任务. 相似文献
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1前言 随着池窑生产的发展,原有的浸润剂在快速浸润性和快速浸透性方面无法得到满足.意大利DSM公司聚酯乳液是公认的喷射纱浸润剂最好的成膜剂.本项目的目的是研制出能工业化生产的与DSM公司产品质量相当的聚酯乳液,替代进口,节约外汇,满足我国池窑发展需要,争创良好的经济社会效益. 相似文献
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苯乙烯是重要的石油化工原料。本文介绍了国内外苯乙烯生产的发展概况,合成乙苯,苯乙烯所用的催化剂种类,并就苯乙烯生产及催化剂的发展趋势提出了自己的观点。 相似文献
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责任是人应主动承担的角色义务和对其因过失所造成后果应承担的责罚.有两层涵义:一是义务;二是后果.责任心是个体自觉做好分内事务和履行道德义务的心理倾向,是个性心理品质成分中自我特征维度上的重要内容.责任心具有两个方面的涵义:一是角色分内职责;二是角色道德义务.责任心是一种通过责任认知、责任个性和责任适应的动态形式表现出来的静态品质,责任心是责任心过程结构与责任心关系结构相互制约、相互影响的统一体. 相似文献
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The variation of the Au 4f binding energy of Au clusters with the cluster size has been established by measuring the binding energies of clusters whose size distributions were independently determined by HREM and STM. The binding energy increases significantly when the cluster size is less than 2 nm. Au-Cu bimetallic clusters of the composition Cu3Au have been deposited for the first time on carbon substrates. The shifts in the core level binding energies of the bimetallic clusters show the effect of alloying in the case of large clusters, but show effects of both alloying and cluster size in the case of the small clusters. The interaction of CO with Cu3Au clusters is stronger than with a bulk Cu metal. The interaction of CO with small Cu clusters also seems to be stronger than with bulk Cu or with large Cu clusters. 相似文献
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Emmanuel Ginsburger Fernand Pla Christian Fonteix Silvère Massebeuf Philippe Swaels 《Chemical engineering science》2003,58(19):4493-4514
This work deals with modelling of emulsion polymerization processes using batch and semi-batch reactors. Specific attention is paid to copolymerization of the system styrene/butyl acrylate.The main key parameters of the model are identified on the basis of batch experimental data in order to describe the complete sketch of emulsion polymerization. The model is then used to simulate, under several operating conditions, the polymerization rate, the global monomers conversion, the number and weight average molecular weights as well as the particle size distribution and the glass transition temperature. Then, the model is generalized to the use of semi-batch processes and validated for this application. 相似文献
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《国际聚合物材料杂志》2012,61(1-4):113-122
Abstract Kinetics and mechanisms of oxidation of 6 acetals by molecular oxygen and ozone in liquid phase have been studied. Reaction with molecular oxygen (70°C, 15–16 hr) leads to the formation monoethers of the corresponding glycols with 68–90% selectivity. Salts of metals and complexes with crown-ethers have increased the reaction rate significally. Ozone have reacted with acetals with formation similar products. The mechanisms of intermediate stages have been proposed. 相似文献
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This study aimed to investigate the structural features, antioxidant activity, tyrosinase inhibitory effect, and mechanism of proanthocyanidins from leaf and fruit of Leucaena leucocephala. MALDI-TOF-MS, thiolysis coupled with HPLC-ESI-MS, and 13C-NMR confirmed that these proanthocyanidins were complex mixtures of propelargonidins, procyanidins, and prodelphinidins. (Epi)catechin, (epi)gallocatechin, (epi)catechin gallate, and (epi)gallocatechin gallate were the main constitutive units. The findings obtained from enzyme analysis revealed that the proanthocyanidins had inhibitory effects on both monophenolase and diphenolase of tyrosinase. The IC50 values of leaf and fruit proanthocyanidins were 73.5?±?2.7 and 52.3?±?3.5 µg/mL for monophenolase activity, and 27.2?±?1.4 and 16.1?±?1.1 µg/mL for diphenolase activity, respectively. The inhibition of diphenolase by proanthocyanidins were proved to be reversible and mixed type. In addition, it was also found from various antioxidant methods that the proanthocyanidins in leaf and fruit possessed potent DPPH radical scavenging activity with IC50 values of 103.4?±?0.8 and 87.8?±?1.1 µg/mL, ABTS radical scavenging activity with IC50 values of 72.9?±?0.4 and 65.7?±?0.9 µg/mL, and ferric reducing antioxidant power with FRAP values of 3.74?±?0.03 and 4.02?±?0.15?mmol AAE/g, respectively. The results obtained suggested that the proanthocyanidins from leaf and fruit of L. leucocephala might have the potential to be exploited as natural tyrosinase inhibitors and antioxidants. 相似文献
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塑料挤出机螺杆,机筒耐磨损,耐腐蚀的强化与应用 总被引:4,自引:0,他引:4
对塑料挤出机,注塑机螺杆,机筒的磨损,腐蚀原因及提高螺杆,机筒耐磨损,耐腐蚀的方法、制造与应用作了较详尽的介绍。 相似文献