The determinants of heat-shock element-directed lacZ expression in Saccharomyces cerevisiae.

Heat-shock induction of heat-shock protein genes is due to a specific promoter element (the heat-shock element, HSE). This study used lacZ under HSE control (HSE-lacZ) to characterize HSE activity in Saccharomyces cerevisiae cells of different physiological states and differing genetic backgrounds. In batch fermentations HSE-lacZ induction by heat shock was maximal in exponential growth, and showed marked decline with the approach to stationary phase. Expression in the absence of heat shock was unaffected by growth phase, indicating that the growth-dependent expression of many yeast heat-shock genes uses promoter elements in addition to the HSE. Heat-induced expression was strongly influenced by the temperature at which cultures were grown. While basal, uninduced expression was constant during growth at different temperatures to 30 degrees C, induction by transfer to 39 degrees C was reduced by increases in growth temperature as low as 18-24 degrees C. Maximal HSE-lacZ induction (30- to 50-fold) was in cultures grown at low temperatures (18-24 degrees C), then heat shocked at 39 degrees C. Ethanol was a poor inducer. Mutations having little effect on HSE-lacZ expression included a respiratory petite; ubi4 (which inactivates the poly-ubiquitin gene); also ubc4 and ubc5 (which each inactivate one of the ubiquitin ligases involved in degradation of aberrant protein). pep4-3 increased both basal and induced beta-galactosidase about two-fold, probably because of slower turnover of this enzyme in pep4-3 strains.     

从76届SEG年会看综合物化探技术的发展方向

文中在介绍76届SEG年会的展商、展台及会场专题报告与论文发布情况的基础上，阐述了参加本届SEG年会的体会，指出了重磁电技术发展的四个趋势：向海洋勘探技术方向发展、向复杂区综合勘探技术方向发展、向三维联合处理和三维可视化解释技术发展、向直接圈定和检测油气方向发展。     

基于SolidWorks的螺杆压缩机机体三维建模设计

应用SolidWorks软件,建立了螺杆压缩机机体三维实体模型.对螺杆压缩机机体的内、外螺旋面的建模进行了分析和研究,提出了建立分段螺旋面模型的基本思路和方法.     

离子液体催化C_5馏分中二烯烃的聚合反应

合成了多种基于1-丁基-3-甲基咪唑阳离子的离子液体,并作为裂解C5馏分中混合二烯烃聚合反应的介质。考察了离子液体种类、反应温度、反应时间和添加Lew is酸对混合二烯烃聚合反应的影响。实验结果表明,以硝酸根为阴离子的离子液体对混合二烯烃的聚合反应具有一定的阻聚作用;以六氟磷酸根为阴离子的离子液体能明显促进混合二烯烃的聚合反应,提高二聚物的含量;添加Lew is酸(质量分数为1%的ZnCl2)的离子液体对混合二烯烃的聚合反应具有更明显的促进作用,其效果仅次于酸性氯铝酸类离子液体,反应温度以30℃以下为宜,温度过高将促使二聚物进一步聚合,形成三聚物乃至多聚物,降低二聚物的含量。     

溶胶-凝胶法制备磷钨酸-硅胶催化合成苹果酯

采用溶胶-凝胶法制备了一系列磷钨酸-硅胶催化剂(PW/SG),考察了该催化剂催化乙酰乙酸乙酯与乙二醇液相缩合制备苹果酯的反应性能。实验结果表明,PW质量分数为40%时的PW/SG催化剂表现出最佳的催化活性;40%PW/SG催化剂制备苹果酯的最佳工艺条件为:n(乙酰乙酸乙酯)∶n(乙二醇)=1∶1.2,催化剂用量占反应物质量的0.36%,带水剂环己烷用量占反应物体积的30%,反应温度383K,反应时间90min;在此条件下,乙酰乙酸乙酯的转化率可达95.5%,苹果酯的选择性大于97%;催化剂稳定性实验表明,经5次重复使用,40%PW/SG催化剂的活性基本保持不变,乙酰乙酸乙酯转化率稳定在95.0%左右。     

中国第一口超千米深水钻井液技术

LW3-1-1探井位于中国南海珠江口盆地，作业水深1480m，完钻井深为3843m，地层以大套灰色泥岩和页岩为主，具有强水敏性．要求钻井液具有良好的流变性、润滑性、抑制性，良好的抗盐、抗钙、抗高温和抗低温能力，以及强的天然气水合物抑制能力。该井采用了PFMX钻井液体系，钻井周期为49d，介绍了钻井液工艺及现场应用情况。PFMX体系表现出很多油基钻井液的优点，如好的润滑性、高的钻进速率、膜效应、强的井眼稳定及页岩抑制性，解决了强水敏性地层的井壁稳定等问题，还解决了深水钻井中遇到的挑战，如低的破裂压力梯度、天然气永合物、浅层水流、深水低温等问题，满足了该区块作业需要。     

Thermal properties and crystalline structure of liquid crystalline poly(ethylene terephthalate‐co‐2(3)‐chloro‐1,4‐phenylene terephthalate)

Thermal properties and crystalline structure of liquid crystalline (LC) poly(ethylene terephthalate‐co‐2(3)‐chloro‐1,4‐phenylene terephthalate) [copoly(ET/CPT)] were investigated using differential scanning calorimetry (DSC), thermogravimetry (TGA), limiting oxygen index (LOI) measurement, electron dispersive X‐ray analysis (EDX), X‐ray diffractometry, and infrared spectrometry (IR). The thermal transition temperatures of copoly(ET/CPT) were changed with the composition. Copoly(ET/CPT) showed two thermal decomposition steps and the residues at 700°C and LOI values of copoly(ET/CPT) were almost proportional to its chlorine content. The activation energy of thermal decomposition of LC units was very low compared to that of poly(ethylene terephthalate)(PET) units. Crystal structure of copoly(ET/CPT) (20/80) was of triclinic system with the lattice constants of a = 9.98 A?, b = 8.78 A?, c = 12.93 A?, α = 97.4°, β = 96.1°, and γ = 90.8°, which is very close to that of poly(chloro‐p‐phenylene terephthlate) (PCPT) with the lattice constants of a = 9.51 A?, b = 8.61 A?, c = 12.73 A?, α = 96.8°, β = 95.4°, and γ = 90.8°. When copoly(ET/CPT)(50/50) was annealed at 220°C in vacuum, crystallization induced sequential reordering (CISR) was not observed but the heat of fusion was slightly increased due to the increase of the trans isomer content in PET units. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1286–1294, 2002; DOI 10.1002/app.10451     

Low-cycle fatigue behavior of Sn-Ag, Sn-Ag-Cu, and Sn-Ag-Cu-Bi lead-free solders

Low-cycle fatigue (LCF) tests on as-cast Sn-3.5Ag, Sn-3Ag-0.5Cu, Sn-3Ag-0.5Cu-1Bi, and Sn-3Ag-0.5Cu-3Bi solders was carried out using a noncontact strain-controlled system at 20°C with a constant frequency of 0.1 Hz. The addition of Cu does not significantly affect the fatigue life of eutectic Sn-Ag solder. However, the fatigue life was significantly reduced with the addition of Bi. The LCF behavior of all solders followed the Coffin-Manson relationship. The fatigue life of the present solders is dominated by the fracture ductility and can be described by the ductility-modified Coffin-Manson’s relationship. Steps at the boundaries of dendrite phases were the initiation sites for microcracks for Sn-3.5Ag, Sn-3Ag-0.5Cu, and Sn-3Ag-0.5Cu-1Bi solders, while for Sn-3Ag-0.5Cu-3Bi solder, cracks initiated along both the dendrite boundaries and subgrain boundaries in the dendrite phases. The linking of these cracks and the propagation of cracks inside the specimen occurred both transgranularly through eutectic phases and intergranularly along dendrite boundaries or subgrain boundaries.