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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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Tsung-Hsiung Wang Syh-Ming Ho Han-Lung Chen Ker-Ming Chen Syh-Ming Liang Aina Hung 《应用聚合物科学杂志》1994,51(3):415-422
The adhesion of polyimide to polyimide was studied by measuring the peel strength of various polyimide–polyimide composites. Different factors such as diffusion of polyamic acid to polyimide substrate, contact angle, wettability, and the thermal expansion coefficient of polyimide films and the presence of siloxane can affect this adhesion and are discussed in this article. © 1994 John Wiley & Sons, Inc. 相似文献
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Nisar Ali Farman Ali Shaukat Saeed Amir Said Zeshan Ali Sheikh Syed Muhammad Salman Muhammad Bilal 《应用聚合物科学杂志》2021,138(24):50646
The incorporation of inorganic nanoparticles into polymers have gained significant attention to improving functional properties. The ultimate nanocomposite behaviors are influenced by many parameters, such as microstructural distribution that are produced during the treatment process. Herein, a hybrid material integrating a modified network into a polyimide PI matrix was produced via the sol–gel method by the reaction of pyromellitic dianhydride, 4, 4-oxydianaline, and 1, 5-diaminonaphthalene to synthesize copolyimides nanocomposite. The modified polyimide and unmodified polyimide silica (SiO2) nanoparticles were incorporated in the polyimide matrix to have polyimide silica nanocomposite. In modified silica nanoparticles, 3-aminopropyltriethosilane was introduced to have better compatibility among inorganic–organic hybrid with similar chemical contact due to their flexible alkyl group. The surface morphology or structure of silica and polyimide was affirmed by scanning electron microscopy, Fourier transforms infrared spectroscopy confirmed the synthesis of pure polyimide, unmodified polyimide, and modified polyimide silica via presence and absence of certain peaks. Thermogravimetric analysis (TGA) results showed high thermal stability of nanocomposites as silica content increases. In contrast to unmodified silica, the modified silica provides more thermal stability to the nanocomposites. Dynamic mechanical analysis was used to investigate the tensile stress of pure polyimide, unmodified, and modified silica nanocomposites. Thermal stability, storage modulus, and moisture absorption of these hybrid materials were improved with silica nanoparticles. The TG mass spectrum confirms the successful synthesis of modified silica networks. The substituted silica nanoparticles show higher mechanical toughness and storage in modified compared to unmodified silica nanocomposite, which exhibits stronger binding attraction between silica nanoparticles and polyimide matrix. 相似文献
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Issues relating to the fabrication of complex multichip modules were investigated from a manufacturability perspective. The use of a preimidized photosensitive polyimide reduces the number of processing steps, thus making it a desirable dielectric material. Factors influencing the polyimide resolution, stress, and feature profile were studied both by experimentation and modeling. Thermal cure cycles for polyimide baking were optimized for solvent resistance, polyimide mechanical properties, and process throughput. Studies were also done on polyimide interactions with metal depositions, including adhesion and polyimide surface damage. Results of this research are shown as embodied in a fabricated 1.4 Gbit/s optical transceiver multichip module. 相似文献
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Zi-Kang Zhu Yong Yang Jie Yin Xin-Yu Wang Yang-Chuan Ke Zong-Neng Qi 《应用聚合物科学杂志》1999,73(11):2063-2068
Organosoluble montmorillonite/polyimide hybrids were prepared using a monomer solution intercalation polymerization method. Montmorillonite was organo-treated with p-aminobenzoic acid and the organosoluble polyimide was based on pyromellitic dianhydride and 4,4′-diamino-3,3′-dimethyldiphenylmethane. The particle size of montmorillonite in the hybrid containing 1 wt % of montmorillonite is about 400 nm. The strength and the toughness of montmorillonite/polyimide hybrids are improved simultaneously when the montmorillonite content is below 5 wt %. The thermal stabilities of montmorillonite/polyimide hybrids are obviously improved and their thermal expansion coefficients are reduced. When the montmorillonite content is below 5 wt %, the montmorillonite/polyimide hybrids are soluble in strong aprotonic polar organic solvents. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2063–2068, 1999 相似文献
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The copper diffusion barrier properties of layered silicate/fluorinated polyimide nanocomposites were analyzed by transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS). It was found that the particles of copper are effectively retarded from penetrating into the polyimide matrix by layered silicates. The diffusion coefficients of layered silicate/polyimide nanocomposites are lower than that of the pure polyimide. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1422–1425, 2004 相似文献
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A continuum-based elastic micromechanics model is developed for silica nanoparticle/polyimide composites with various nanoparticle/polyimide interfacial treatments. The model incorporates the molecular structures of the nanoparticle, polyimide, and interfacial regions, which are determined using a molecular modeling method that involves coarse-grained and reverse-mapping techniques. The micromechanics model includes an effective interface between the polyimide and nanoparticle with properties and dimensions that are determined using the results of molecular dynamics simulations. It is shown that the model can be used to predict the elastic properties of silica nanoparticle/polyimide composites for a large range of nanoparticle radii, 10-10,000 Å. For silica nanoparticle radii above 1000 Å, the predicted properties are equal to those predicted using the standard Mori-Tanaka micromechanical approach, which does not incorporate the molecular structure. It is also shown that the specific silica nanoparticle/polyimide interface conditions have a significant effect on the composite mechanical properties for nanoparticle radii below 1000 Å. 相似文献
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In an atomic force microscopic image of the main‐chain‐ and the side‐chain‐type polyimide surfaces, we have observed a variation of the surface morphology to use the rubbing depths and the rubbing times. On the rubbed polyimide surface, the polymer clusters are aligned in long chains along the rubbing direction. The topology of the polyimide surface is weakly changed at a lower rubbing depth, but it is greatly changed at a deeper rubbing depth. Once the polished string structure is obtained, no considerable changes in the surface topography of the polyimide are visible, although rubbing times are increased from 1 to 8 at constant rubbing depths (0.3 mm). The rubbed polyimide films show optical phase retardation, which was steeply increased with increasing rubbing depth; but it was increased very little with increasing rubbing times. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1728–1734, 2000 相似文献
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The porous polyimide membranes were prepared by a wet phase inversion process based on the organo-soluble polyimide. The influence of coagulation bath composition and casting polymer solution concentration on the morphology of membranes was investigated. A series of spongy-like porous polyimide membranes with different porosity were obtained and characterized. These porous polyimide membranes exhibited excellent thermal stability and dimensional stability with the glass transition temperature of 274 °C and thermal shrinkage less than 1% after stored at 200 °C. All the porous polyimide membranes exhibited good wettability with electrolyte uptake of 190–378% due to their high surface polarity and high porosity. The discharge curves for the lithium-ion cells using porous polyimide membranes as separator displayed relatively flatter voltage plateaus than that for Celgard 2400 membrane and gave the discharge capacity of 129–131 mAh/g. The thermal stable porous polyimide membranes are favorable to be applied as separator in the lithium-ion cell and can be expected to provide excellent battery performance at elevated temperature. 相似文献
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