共查询到20条相似文献,搜索用时 187 毫秒
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紫砂方壶,是紫砂造型中与圆壶、花壶、筋纹壶并列的一大类壶型。方壶造型古朴、形体优美、工艺严谨、气韵生动、技法独特,其整体透露出豪爽、刚劲、正直的阳刚之气,神、气堪比男子。方器造型的特点是方中藏圆,线面挺括平整,轮廓线条分明,给予人们干净利落、明快挺秀之感。整体以直线、横线为主,曲线、细线为辅,器型的中轴线、平衡线要正确、匀挺、富于变化,表现出轮廓分明、平稳庄重的方壶特点。紫砂方壶整体简洁典雅、神形兼备,线条舒展流畅,壶器刚柔相济,性格堪 相似文献
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缠枝纹,又名“转枝纹”、“连枝纹”,是以植物的枝杆或藤蔓作骨架,向上下、左右延伸,形成波线式的二方连续或四方连续,其结构连绵不断,形象委婉多姿,故古人寓意生生不息、万代绵长的美好愿望,从而跻身于中国吉祥纹饰之列。缠枝纹约起源于汉代,盛行于南北朝、隋唐、宋元和明清,广泛用于雕刻、家具、漆器、编织、刺绣、玉器、年画、剪纸、碑刻等工艺美术行业,更是瓷器上最常见的纹样。 相似文献
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Jan Rinkel Simon T. Steiner Dr. Guangkai Bian Rong Chen Prof. Dr. Tiangang Liu Prof. Dr. Jeroen S. Dickschat 《Chembiochem : a European journal of chemical biology》2020,21(4):486-491
The absolute configuration of fusaterpenol (GJ1012E) has been revised by an enantioselective deuteration strategy. A bifunctional enzyme with a terpene synthase and a prenyltransferase domain from Aspergillus brasiliensis was characterised as variediene synthase, and the absolute configuration of its product was elucidated. The uniform absolute configurations of these and structurally related di- and sesterterpenes together with a common stereochemical course for the geminal methyl groups of GGPP unravel a similar conformational fold of the substrate in the active sites of the terpene synthases. For variediene, a thermal reaction observed during GC/MS analysis was studied in detail for which a surprising mechanism was uncovered. 相似文献
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以水合肼-六水合三氯化铁-活性炭为还原体系, 3, 5 二(三氟甲基)溴苯和二苯基次膦酰氯为原料,经格氏反应、硝化和还原合成了含氟和氧膦的二胺,总收率达 50%。并用FTIR、1HNMR和熔点测试技术对其结构进行了鉴定。该反应具有操作简便,条件温和,收率高易于纯化的优点。然后用常规的二步法,使该二胺和 4, 4′ 二胺基二苯醚与六氟异丙叉基 (3, 4 邻苯二甲酸酐)进行共缩聚,并经化学酰亚胺化制得了共缩聚型聚酰亚胺,收率为 93%。该共缩聚型聚酰亚胺在非质子强极性溶剂中均具有良好的溶解性,玻璃化温度 (Tg)大于 250℃,10%的热分解温度(Td)为 519 7℃。实验表明,氧膦的引入提高了聚酰亚胺的附着力。 相似文献
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Abstract The delignification response in cooking and the impact of bleaching on earlywood and latewood were studied. Spruce earlywood and latewood chips were pulped by the kraft process and subsequently treated with one bleaching chemical at a time. In cooking, latewood required a higher alkali charge to reach the same kappa number. No difference in the light absorption coefficient between the different fiber types was observed. After oxygen delignification the earlywood fibers had a higher light absorption coefficient at the same kappa number. The difference in light absorbing material was maintained when bleaching was performed with chlorine dioxide, ozone, and peracetic acid. Hydrogen peroxide decreased the light absorbing structures in the earlywood to the same level as for latewood. The earlywood pulp had a higher brightness at a given kappa number than the latewood. The higher brightness remained through all bleaching operations and was primarily due to a higher light scattering ability. 相似文献
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增塑增韧聚丙烯的制备及其性能研究 总被引:3,自引:0,他引:3
周中玉;潘泳康;唐颂超;王庆海 《中国塑料》2010,24(11):35-38
以液体石蜡作为聚丙烯(PP)的增塑剂,首先将纳米二氧化硅(SiO2)预先分散于液体石蜡中制成纳米溶胶,然后采用双螺杆挤出机将此溶胶与PP熔融共混制备了增塑增韧PP复合材料,研究了液体石蜡和纳米SiO2对PP力学性能和结晶性能的影响。结果表明,经过液体石蜡增塑后,PP的冲击强度可提高90 %;再经过纳米SiO2增韧后,其冲击强度可进一步提高100 %;液体石蜡能够提高PP的结晶度,纳米SiO2能够减小PP的球晶尺寸。 相似文献
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目的获得具有生物学活性的与导向肽融合表达的重组TRAIL蛋白,提高TRAIL对肿瘤细胞的杀伤作用。方法构建TRAIL与导向多肽PEPHC1的融合基因,克隆入质粒pGEM-3zf(-)中进行测序,序列正确后,亚克隆入表达载体pBV220中,转化大肠杆菌DH5α,温度诱导表达。结果42℃诱导4h,融合基因得到了表达,SDS-PAGE表明目的蛋白占菌体总蛋白的15%以上,以包涵体形式存在。经包涵体洗涤、变性、复性,并经离子交换层析柱纯化后可得到融合蛋白PE-TRAIL,经体外试验证明具有生物学活性。结论成功克隆并表达了具有生物学活性的与导向肽融合表达的重组TRAIL蛋白。 相似文献
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Inorganic nanofillers, CaCO3 and nanoclay, are widely applied to improve the mechanical properties of polypropylene (PP). In general, the use of spherical CaCO3 can enhance the impact strength while the use of layered nanoclay can enhance the modulus and yield stress. With the objective to simultaneously improve the stiffness, strength, and impact strength of PP, in this work a ternary nanocomposite, PP/CaCO3/nanoclay (NCPP), was prepared and its morphology, crystallization, and mechanical behaviors were investigated with a comparison to the binary nanocomposites, PP/CaCO3 (CPP) and PP/nanoclay (NPP). The results showed that in NCPP the nanoclay was extremely exfoliated with a much higher degree than that in NPP, which was possibly because the incorporation of CaCO3 nanoparticles adjusted the matrix viscosity and thus provided a balance between shear stress and molecule diffusion. As a result of this highly exfoliated structure, a substantial increase in modulus and yield stress was attained in NCPP. However, its impact strength was less enhanced. The toughening effects of the CaCO3 particles observed in CPP became ineffective. This difference was ascribed to the fact that in NCPP the crystallization behavior was dominated by the nanoclay and the formation of β‐phase crystallites induced by the CaCO3 particles was inhibited. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
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我国PTA及PX市场供需状况分析 总被引:4,自引:0,他引:4
介绍了国内PTA,PX供需状况,并对市场需求进行了预测。目前,我国PTA生产能力约5 700 kt/ a,PX生产能力约2 000 kt/a,满足不了国内的需求,自给率不足50%。统计预测2010年,PTA需求量约15 000 kt/a,PX需求量约9 800 kt/a。指出国内企业新建PTA装置必须同时考虑原料来源。 相似文献
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In this paper a simple preparative method for isolation and purification of ginkgolides A and B was developed,As starting material,a commercially available standardized ginkgo extract (EGb761,containing 24% flavonoid and 6% terpene trilactones) was used,After a pretreatment step,optimized by the uniform design method ,the concentrated intermediate extract with high content of GA and gb( 90%) was separated into the individual terpenes by preparative liquid chromatography eluted with petroleum ether-ethylacetate,Analysis of products was carried out by means of HPLC-ELSD(evaporative light -scattering detector),The results show that ginkgolides A and B are obtained in higher yield and better purity. 相似文献
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二甲基二烯丙基氯化铵-丙烯酰胺共聚物的合成与结构表征 总被引:4,自引:2,他引:2
用二步法合成了季铵盐阳离子单体N ,N 二甲基二烯丙基氯化铵 (DMDAAC)。第一步 ,向反应瓶中加入 1mol二甲胺的水溶液 ,控制温度 40℃以下 ,滴加 1mol氯丙烯和 1molNaOH水溶液 (其质量分数为 40 % )。滴加完后再反应 2h,分取上层有机相 ;第二步 ,将有机相加入反应瓶中 ,同时加入适量的丙酮 ,控制温度在 30℃以下 ,滴加 1mol氯丙烯 ,反应 4h。过滤、洗涤、干燥得阳离子单体DMDAAC ,总转化率为 63%。以n(DMDAAC)∶n(丙烯酸胺 ) =1∶3在水溶液中共聚 ,合成了阳离子共聚物 [P(DMDAAC AM) ]。反应以分别占单体总质量的 0 5 %的过硫酸钾和亚硫酸氢钠为引发剂 ,反应温度 40℃ ,反应时间 6~ 8h。并利用IR、1HNMR对单体和共聚物进行了结构表征。 相似文献
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以异维生素A酸为原料,二环己基碳酰亚胺(DCC)为脱水剂,4-二甲氨基吡啶(DMAP)为催化剂,设计合成了结构新颖,具有潜在生物活性的化合物4a(异维生素A酸对苯二酯),产率达到87.6%。优化条件为:异维生素A酸与对苯二酚摩尔比为2.02∶1,反应时间4 h,DCC滴加速度为0.5滴/秒。在此条件基础上由维生素A酸、异维生素A酸合成了其它5种双酯。并将4a进一步结构修饰,得到异维生素A酸在人体内代谢氧化物的衍生物,产率达到75.3%。以1H1、3C NMR和MS对它们的结构进行了表征。 相似文献