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991.
目的在植物毛状根和毕赤酵母中表达人碱性成纤维细胞生长因子(Human basic fibroblast growth factor,hbFGF),并对发酵条件进行优化。方法将hbFGF基因分别克隆至表达载体pCAMBIA1301和pPICZα上,构建重组表达质粒pCAMBIA1301-hbFGF和pPICZα-hbFGF。通过发根农杆菌介导,将pCAMBIA1301-hbFGF质粒转入大豆毛状根;采用电转化法将质粒pPICZα-hbFGF转入毕赤酵母X-33菌株,PCR法筛选阳性转化子,诱导表达。筛选高效稳定表达株,发酵培养并优化发酵条件,SDS-PAGE和Western blot分析表达产物,并进行纯化。结果经酶切及测序证明两个重组表达质粒构建正确;经PCR鉴定证明hbFGF基因已整合入大豆毛状根及毕赤酵母基因组中;筛选出了在两种体系中发酵培养的最佳条件;hbFGF在大豆毛状根和毕赤酵母中的表达量分别占总蛋白的31%和42%,且均具有良好的反应原性;经纯化后,均可见相对分子质量约18000的单一条带。结论 hbFGF能够在大豆毛状根和毕赤酵母中高效表达,为其大规模工业化生产奠定了实验基础。 相似文献
992.
Synthesis of Anisotropic Na0.5Bi0.5TiO3 Crystals Using Different Topochemical Microcrystal Conversion Methods
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Wei Zhao Nianqi Liu Kexin Gao Zihao Wang Shimeng Zhang 《International Journal of Applied Ceramic Technology》2016,13(5):871-875
Na0.5Bi0.5TiO3 (NBT) platelets with high aspect ratio were synthesized from Na0.5Bi4.5Ti4O15 (NBIT) precursors via a topochemical microcrystal conversion in molten salt conditions. The effect of the synthesis parameters, such as the molten salt system, synthesis temperature, and the molar ratio of Na2CO3 and NBIT, was investigated. The results showed that NaCl–KCl molten salt environment and excess Na2CO3 played a positive role in the synthesis, square‐shaped NBT was obtained at 950°C in NaCl–KCl molten salt and a TiO2‐free environment, and it was a suitable template candidate to achieve NBT‐based textured ceramics using the reactive template grain growth (RTGG) method. 相似文献
993.
Apolipoprotein A-I (ApoA-I) is functionally involved in the transportation and metabolism of lipids in vertebrates. In this study, two isoforms of apoA-Ib in common carp (Cyprinus carpio L.) were characterized. Sequence comparison and phylogenetic analysis showed that C. carpio ApoA-Ib is relatively conserved within cyprinid fishes. During embryonic development, C. carpio
apoA-Ib was first expressed at the stage of multi-cells, and the highest mRNA level was observed at the stage of optic vesicle. A ubiquitous expression pattern was detected in various tissues with extreme predominance in the liver. Significantly different expression levels were observed between light and heavy body weight groups and also in the compensatory growth test. Seventeen and eight single-nucleotide polymorphisms (SNPs) were identified in matured mRNA of the C. carpio
apoA-Ib.1 and apoA-Ib.2, respectively. Two of these SNPs (apoA-Ib.2-g.183A>T and apoA-Ib.2-g.1753C>T) were significantly associated with body weight and body length in two populations of common carp. These results indicate that apoA-Ib may play an important role in the modulation of growth and development in common carp. 相似文献
994.
过冷流动沸腾在核能、动力、化工等工业领域广泛存在,局部空泡分布特性的准确预测对构建两相流数理模型及两相流动压降和传热特性计算均具有重要意义。实验借助光学探针测量手段研究摇摆条件下圆管内过冷沸腾局部空泡分布特性,并提出多周期同相位叠加方法获得摇摆运动条件下局部瞬时空泡份额。实验结果表明:摇摆条件下圆管内局部空泡分布呈现周期性波动规律,摇摆条件下圆管轴心区及近壁区均会出现局部空泡份额峰值,且流道近壁区局部空泡份额波动幅度最大;与静止条件下不同,摇摆运动周期内过冷沸腾局部空泡份额空间分布形态随时间发生变化;摇摆周期和摇摆角度对过冷沸腾局部空泡分布特性也存在一定影响。 相似文献
995.
996.
Ui-Jin Chung Jong-Keuk Park Nong-Moon Hwang Ho-Yong Lee Doh-Yeon Kim 《Journal of the American Ceramic Society》2002,85(12):3076-3080
Pb(Mg1/3 Nb2/3 )O3 -35 mol% PbTiO3 (PMN-35PT) specimens with a 5 mol% excess PbO were prepared by excessive heat treatment at 1150°C to induce abnormal grain growth. Through electron backscatter diffraction analysis and the observation of a three-dimensional morphology, the abnormally grown PMN-35PT grains were found to be twinned crystals with penetration characteristics. The morphology of the PMN-35PT twinned crystal was crystallographically analyzed. The abnormal grain growth of PMN-35PT is suggested to be due to preferential growth at the reentrant angles formed by twins. 相似文献
997.
Guo-Dong Zhan Yuichi Ikuhara Mamoru Mitomo Rong-Jun Xie Taketo Sakuma Amiya K. Mukherjee 《Journal of the American Ceramic Society》2002,85(2):430-436
The microstructures of fine-grained β-SiC materials with α-SiC seeds annealed either with or without uniaxial pressure at 1900°C for 4 h in an argon atmosphere were investigated using analytical electron microscopy and high-resolution electron microscopy (HREM). An applied annealing pressure can greatly retard phase transformation and grain growth. The material annealed with pressure consisted of fine grains with β-SiC as a major phase. In contrast, the microstructure in the material annealed without pressure consisted of elongated grains with half α-SiC. Energy-dispersive X-ray analysis showed no differences in the amount of segregation of aluminum and oxygen atoms at grain boundaries, but did show a significant difference in the segregation of yttrium atoms at grain boundaries along SiC grains for the two materials. The increased segregation of yttrium ions at grain boundaries caused by the applied pressure might be the reason for the retarded phase transformation and grain growth. HREM showed a thin secondary phase of 1 nm at the grain boundary interface for both materials. The development of a composite grain consisting of a mixture of β/α polytypes during annealing was a feature common to both materials. The possible mechanisms for grain growth and phase transformation are discussed. 相似文献
998.
Curtis Scott Mary Kaliszewski Charles Greskovich Lionel Levinson 《Journal of the American Ceramic Society》2002,85(5):1275-1280
In a given batch more than 30%–40% of polycrystalline, MgO-doped Al2 O3 tubes were converted into single crystals of sapphire by abnormal grain growth (AGG) in the solid state at 1880°C. Most crystals grew 4–10-cm in length in tubes with wall thicknesses of 1/2 and 3/4 mm and outer diameters of 5 and 7 mm, respectively, and had their c -axes oriented ∼ 90° and 45° to the tube axis. Initiation of AGG was associated with low values of bulk MgO concentration near 50 ppm. The unconverted tubes did not develop centimeter-size crystals but instead exhibited millimeter-size grains. The different grain structures in converted and unconverted tubes may be related to nonuniform concentration of MgO in the extruded tubes. The growth front of the migrating crystal boundary was typically nonuniformly shaped, and the interface between the single crystal and the polycrystalline matrix was composed of many "curved" boundary segments indicative of classical AGG in a single-phase material. The average velocities of many migrating crystal boundaries were quite high and reached ∼1.5 cm/h. The average grain boundary mobility at 1880°C was calculated as 2 × 10−10 m3 /(N·s), representing the highest value reported so far in Al2 O3 and within a factor of 2.5 of the calculated intrinsic mobility. Under similar experimental conditions sapphire crystals did not grow when a codopant of CaO, La2 O3 , or ZrO2 was added in concentrations of several hundred ppm. 相似文献
999.
Thomas C. Farmer Corinne L. Carpenter Michael F. Doherty 《American Institute of Chemical Engineers》2016,62(9):3505-3514
This article is motivated by a remarkable observation reported recently by Myerson, Trout, and co‐workers that continuous crystallization is capable of producing metastable polymorphs in stable steady‐state operation. We explain why this phenomenon occurs and give simple design rules for reproducing it in other polymorphic systems. A linear stability analysis gives simple functions of parameters for which one can continuously produce thermodynamically metastable products based only on the relative polymorph dynamics. We demonstrate agreement with two sets of experimental data; L‐glutamic acid grown from aqueous solution and p‐aminobenzoic acid also grown from aqueous solution. For many polymorphic compounds, engineering a process to produce a desired polymorph is as simple as finding a reasonable operating point for the continuous mixed‐suspension mixed‐product removal crystallization process (temperature, residence time, initial supersaturation, etc.) according to the rules reported in this article. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3505–3514, 2016 相似文献
1000.