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大肠杆菌CM/PDT抗反馈抑制突变体的构建及其性质
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作者 刘云 王世春 +3 位作者 张学清 刘志红 高波 徐琪寿 《中国生物化学与分子生物学报》 CAS CSCD 北大核心 2002年第5期535-540,共6页
为了获得具有高催化活性且抗反馈抑制的大肠杆菌分支酸变位酶 预苯酸脱水酶 (chorismatemutase prephenatedehydrataseCM PDT) [EC5 .4 .99.5 EC4 .2 .1.5 1],通过相关菌种CM PDT氨基酸序列同源比较 ,寻找高度保守位点 .用定点突变及... 为了获得具有高催化活性且抗反馈抑制的大肠杆菌分支酸变位酶 预苯酸脱水酶 (chorismatemutase prephenatedehydrataseCM PDT) [EC5 .4 .99.5 EC4 .2 .1.5 1],通过相关菌种CM PDT氨基酸序列同源比较 ,寻找高度保守位点 .用定点突变及PCR法构建突变酶M1(缺失 30 4T、30 5G、Q30 6K)、M2 (缺失W 338)、M3(缺失 30 1~ 386位氨基酸 )、M32 9(E32 9A)和M374 (C374A) ,野生型及各突变型基因与pET2 8a(+ )载体连接后 ,表达融合蛋白 .在非变性条件下 ,由TALON金属螯合亲和层析柱纯化野生型和突变体的酶蛋白 .酶活性测定表明 ,突变体M3的PDT活性下降为野生型活性的 2 9% ,但保持了CM活性 .突变体M374保持了CM ,PDT两种酶的活性 ,突变体M1、M2、M32 9的CM ,PDT活性有一定程度的提高 .酶抗反馈抑制作用检测表明 ,突变体M3、M374解除了苯丙氨酸的反馈抑制作用 ,M1、M2、M32 9部分解除了苯丙氨酸的反馈抑制作用 .与含野生型pheA基因的E .coliBL2 1菌株相比 ,含突变基因的E .coliBL2 1菌株对 10mmol L的苯丙氨酸代谢类似物具有强的抗反馈抑制作用 ,其中M1,M2 ,M3对 2 0mmol 展开更多
关键词 大肠杆菌CM/PDT 抗反馈抑制突 构建 性质 分支酸酶/苯酸脱水酶 苯丙氨酸代谢类似物
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催化裂化装置烟机振动问题分析与处理 被引量:1
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作者 程千里 《炼油技术与工程》 CAS 2018年第11期38-40,共3页
中国石化青岛炼油化工有限责任公司2. 90 Mt/a催化裂化装置主风机三机组烟气轮机后支撑轴瓦振动一直偏大(70~76μm波动),有时会超过报警值80μm,烟机入口管线也多次出现焊缝开裂现象。通过分析运行过程中烟机入口管线温度的变化对烟机... 中国石化青岛炼油化工有限责任公司2. 90 Mt/a催化裂化装置主风机三机组烟气轮机后支撑轴瓦振动一直偏大(70~76μm波动),有时会超过报警值80μm,烟机入口管线也多次出现焊缝开裂现象。通过分析运行过程中烟机入口管线温度的变化对烟机振动的影响、焊缝开裂形态,并对烟机机组进行了检修,断定烟机入口管线运行中存在应力过大问题。2015年装置停工大检修期间对烟机入口管线进行改造后,烟机后支撑轴瓦振动测点XC11513数值维持在较好水平,平均维持在48~60μm。与改造前相比,改造后烟机机组后轴瓦振动平均下降25μm,烟机入口管线运行两年多未出现焊缝开裂问题。 展开更多
关键词 催化裂化 烟气轮机 振动 焊缝开裂 管线预变位
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大型门式起重机结构设计对运行啃轨的影响分析 被引量:2
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作者 邹正彪 高伟东 强少华 《起重运输机械》 2017年第6期15-18,共4页
依据门式起重机金属结构受载变形特点,采用刚性腿预变位方式,优化起重机运行机构的承载状态,减小运行机构车轮和轨道的磨损,可提高部件的使用寿命,并对刚性腿预变位的计算方法和制造工艺提出了参考意见。
关键词 门式起重机 刚性腿 预变位 计算方法 制造工艺
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大肠杆菌苯丙氨酸合成途径关键酶基因pheA的克隆与表达 被引量:1
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作者 刘云 梁学颖 +2 位作者 刘志红 刘耀清 徐琪寿 《生物技术通讯》 CAS 1999年第4期250-253,共4页
为了通过基因工程手段来增加苯丙氨酸的生物产量,利用PCR方法从大肠杆菌中克隆了抗反馈抑制突变型及野生型的pheA基因,进行了核苷酸序列分析,并利用高效的原核表达载体PBV220对pheA基因编码的突变型及野生型分支酸... 为了通过基因工程手段来增加苯丙氨酸的生物产量,利用PCR方法从大肠杆菌中克隆了抗反馈抑制突变型及野生型的pheA基因,进行了核苷酸序列分析,并利用高效的原核表达载体PBV220对pheA基因编码的突变型及野生型分支酸变位酶/预苯酸脱水酶(CM/PD)进行了表达。序列分析表明突变型基因碱基第580位由T变为C,相应氨基酸由Val变为Ala,SDS-PAGE图谱扫描分析表明目的蛋白CM/PD的表达量占全菌体蛋白的43%,占上清总蛋白的57%。酶活性测定表明其CM和 PD活性分别提高了 15.5和6.7倍,产酸量也有了一定的提高,为构建产苯丙氨酸的生物工程菌奠定了基础。 展开更多
关键词 抗反馈抑制 分支酸酶/苯酸脱水酶 基因表达
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催裂化装置烟机进出口管道安装及质量控制
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作者 杨航超 《石油化工建设》 2022年第10期69-71,76,共4页
烟气轮机在催化裂化装置能耗方面起着重要作用,而烟气轮机及其进出口管道的安装直接影响着烟气轮机的运行.以陕西靖边工业园区150万t/a催化裂解制乙烯装置烟气轮机进出口管道施工为例,介绍了机组进出口管道安装中的工作内容.
关键词 烟气轮机 无应力配管 预变位 自由管段 对称焊
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催化裂化装置烟机进出口管道施工总结
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作者 杨航超 《石油化工建设》 2022年第5期77-79,共3页
烟气轮机在催化裂化装置能耗方面起着重要作用,而烟气轮机及其进出口管道的安装直接影响着烟气轮机的运行。以陕西靖边工业园区150万t/a催化裂解(DCC)制乙烯装置烟气轮机进出口管道施工为例,介绍了机组进出口管道安装中的工作内容。
关键词 烟气轮机 无应力配管 预变位 自由管段 对称焊
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Five-year oncologic outcomes and prognostic factors for locally advanced low rectal cancer after low anterior resection
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作者 Bo Yao Yadi Wang Na Lu 《The Chinese-German Journal of Clinical Oncology》 CAS 2014年第7期309-315,共7页
Objective: The aim of the study is to investigate the longterm oncologic outcomes including local recurrence, distant metastases and overall survival (OS) for patients with low rectal cancer underwent low anterior ... Objective: The aim of the study is to investigate the longterm oncologic outcomes including local recurrence, distant metastases and overall survival (OS) for patients with low rectal cancer underwent low anterior resection (LAR) with total mesorectal excision (TME), and to analyze the prognostic factors for them. Methods: Between January 2001 and December 2009, 147 patients with clinical stage II and III rectal cancers located 3-6 cm from the anal verge underwent LAR with TME without temporary diverting stoma. The median distal resection margin (DRM) was 1.0 (range, 0.3-5) cm. Anastomostic leakage occurred in 29 (19.7%) patients. Thirty patients received surgery alone, 20 patients received preoperative chemoradiotherapy (CRT), 43 patients received postoperative CRT, and adjuvant chemotherapy was administered for 108 patients. The median cycle of adjuvant chemotherapy was 6 (range, 2-20) cycles. The median followup was 74.8 (range, 30.1-146.3) months. Results: In all patients, 5-year recurrence-free survival (RFS), disease-free survival (DFS) and OS were 70.4%, 54.2% and 60.5%, respectively. Forty-three (29.3%) patients suffered local recurrence. Patients received preoperative CRT with a downstaging yp0/1 who had a better 5-year RFS, DFS and OS, which were 100%, 90.9%, and 90.9%, respectively. For patients with pathologic stage Ⅱ and stage Ⅲ, the 5-year RFS, DFS, and OS were 79.2% and 60.1%, 67.9% and 39.1%, 72.1% and 48.2%, respectively. On multivariable analysis, RFS was associated with anostomostic leakage, DFS was associated with anastomostic leakage and pathologic N stage, and OS was associated with anastomostic leakage, pathologic N and T stage. For patients with anastomostic leakage, the 5-year RFS, DFS, and OS were 51.7%, 32.4%, and 38.3%, respectively, which were worse than that for patients without anastomostic leakage, the latter were 75.2%, 59.7%, 65.7%, respectively (P 〈 0.05). DRM and radiotherapy were associated with RFS on univariable analysis (P 〈 0.05), but not on multivariable analysis. Tumor grade was prognostic factors for RFS and OS on univariable analysis, but not on multivariable analysis. The other factors including sex, age, tumor size and adjuvant chemotherapy were not associated with RFS, DFS and OS on univariable analysis. Conclusion: For patients with low rectal caner underwent LAR and TME, the long-term oncologic outcomes were satisfactory for patients with stage yp0/1, but not for patients with pathologic stage II1. Anastomositic leakage negatively affect long-term oncologic outcomes. Radiotherpy, adjuvant chemotherapy and distal resection margin were not associated with long-term outcomes. 展开更多
关键词 low rectal cancer sphincter-preserving surgery long-term outcomes prognostic factors
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Phase Transition Analysis Based Quality Prediction for Multi-phase Batch Processes 被引量:3
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作者 赵露平 赵春晖 高福荣 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2012年第6期1191-1197,共7页
Batch processes are usually involved with multiple phases in the time domain and many researches on process monitoring as well as quality prediction have been done using phase information. However, few of them conside... Batch processes are usually involved with multiple phases in the time domain and many researches on process monitoring as well as quality prediction have been done using phase information. However, few of them consider phase transitions, though they exit widely in batch processes and have non-ignorable impacts on product qualities. In the present work, a phase-based partial least squares (PLS) method utilizing transition information is proposed to give both online and offline quality predictions. First, batch processes are divided into several phases using regression parameters other than prior process knowledge. Then both steady phases and transitions which have great influences on qualities are identified as critical-to-quality phases using statistical methods. Finally, based on the analysis of different characteristics of transitions and steady phases, an integrated algorithm is developed for quality prediction. The application to an injection molding process shows the effectiveness of the proposed algorithm in comparison with the traditional MPLS method and the phase-based PLS method. 展开更多
关键词 MULTI-PHASE TRANSITION partial least squares quality prediction batch process
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Regression Equations for Predicting the Effect of Tine Width on Draught and Soil Translocation in Moderately Fine Textured Soil 被引量:1
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作者 Seth Idowu Manuwa Olugboyega Cornelius Ademosun Adebola Adesina 《Journal of Environmental Science and Engineering(B)》 2012年第6期820-825,共6页
Experiments were conducted in an indoor soil bin filled with sandy clay loam soil. Tests were carried out with tillage tines to study the effect tool width on soil disturbance and draught. Depth of operation was held ... Experiments were conducted in an indoor soil bin filled with sandy clay loam soil. Tests were carried out with tillage tines to study the effect tool width on soil disturbance and draught. Depth of operation was held constant at 35 mm and then at 70 mm while speed was varied at three levels of 1.0, 3.6 and 9.0 km/h. The widths of the tines tested were 10, 20, 31, 40, 51, 88, 126, 163 and 200 mm. The cone penetration resistance of the soil varied from 400 to 600 kPa. Draught was measured with a load cell while soil disturbance was measured with a profile meter and meter rule. Draught increased at a decreasing rate with tine width. Quadratic models best fitted the data points with high R2 values. The increase in draught was affected by the forward speed since higher draught values were obtained at higher speed. Results show that the parameters of soil disturbance increased with increase in tine width, except height of ridge (hr), which did not show any specific trend. The specific draught was highest (10.63 N/cm) with tine T20 while Tine T1 had the least specific draught of 5.2 N/cm. 展开更多
关键词 Soil bin tillage tines DRAUGHT soil disturbance parameters rake angle forward speed regression analysis
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Effects of pre-compression on formation of dynamic precipitates and creep anisotropy of hot-extruded AZ91−2Y magnesium alloy
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作者 Wei LI Huang HUANG +4 位作者 Wei-ying HUANG Jian CHEN Sheng-de ZHANG Zhen-yu XIAO Wei QIU 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2022年第11期3550-3562,共13页
The creep anisotropy behavior under different stresses at 180℃ of hot-extruded AZ91−2Y magnesium alloy with pre-compression(PC)and without pre-compression(NPC)was studied.Microstructure,texture and mechanical propert... The creep anisotropy behavior under different stresses at 180℃ of hot-extruded AZ91−2Y magnesium alloy with pre-compression(PC)and without pre-compression(NPC)was studied.Microstructure,texture and mechanical properties of the alloy were examined by scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),transmission electron microscopy(TEM)and tensile creep tests.The results revealed that the creep resistance was proportional to the volume fraction of spherical Mg_(17)Al_(12) precipitates.The dynamic precipitation of large volume fraction of lamellar Mg_(17)Al_(12) in NPC samples leads to the basaláañslip as the dominant creep mechanism,and the NPC samples have obvious anisotropy.In the PC samples,dynamic precipitation of large volume fraction of spherical Mg_(17)Al_(12) has inhibitory effect on the basaláañslip.The pyramidalác+añslip and twinning improve the creep anisotropy resistance significantly. 展开更多
关键词 magnesium alloy creep anisotropy pre-compression twin DISLOCATION
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Influence of Deformation on Light Particles as a Probe of Nuclear Dissipation for a Neutron-Deficient ^178Pb System
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作者 YE Wei 《Communications in Theoretical Physics》 SCIE CAS CSCD 2006年第4期687-690,共4页
Using a diffusion model we investigate deformation effects on the sensitivity of different light particles to nuclear dissipation for a rather neutron-deficlent ^178Pb system. Galculations show that deformation signif... Using a diffusion model we investigate deformation effects on the sensitivity of different light particles to nuclear dissipation for a rather neutron-deficlent ^178Pb system. Galculations show that deformation significantly increases the sensitivity of neutron emission to dissipation strength, and that this effect becomes stronger with increasing deformation. 展开更多
关键词 deformation effect isospin effect pre-scission particle multiplicity nuclear dissipation PROBE diffusion model
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Experimental and analytical studies on the deformability of a precast RC shear wall involving bolted connections 被引量:3
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作者 SUN Jian QIU HongXing +1 位作者 YANG Yuan LU Bo 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2015年第8期1439-1448,共10页
To study the deformability and ductility of an innovative precast shear wall joined by bolted connections,experimental tests were conducted on two test walls under monotonic and cyclic loading,respectively;subsequentl... To study the deformability and ductility of an innovative precast shear wall joined by bolted connections,experimental tests were conducted on two test walls under monotonic and cyclic loading,respectively;subsequently,theoretical analysis was performed on the deformation performance of the shear wall assembly.The test results confirmed the favorable deformability and ductility of the specimens.The top displacement of the shear wall assembly was analytically decomposed into several constituent parts,the theoretical formulae of which were subsequently deduced.The compositional analysis demonstrated that the top displacement of the test wall was primarily induced by the elastic deformation of the upper wall panel(UWP),the relative slippages within the bolted connections,and the flexural deformation within the plastic region of the UWP,while the constituent part contributed by the deformation in the connecting steel frame can be neglected. 展开更多
关键词 precast shear wall bolted connections DEFORMABILITY analytical formulae
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