Redistribution of iron during directional solidification of metallurgical-grade silicon at low growth rate

研究冶金级硅低速定向凝固过程中杂质铁的再分布。采用ICP-MS检测铁的浓度,绘制铁在固相、液相、晶界和晶体生长方向上的浓度示意图。铁浓度在固、液相中具有明显差异。依据质量守恒定理,计算得出溶质边界层约为4 mm,铁的有效分凝系数约为2.98×10~(-4)。在低速凝固条件下,铁容易偏析聚集在晶界。在生长方向上,由于低速凝固,铁浓度在硅锭86%高度以下几乎恒定,不完全符合Scheil方程规律。讨论了对流对铁再分布的影响,对流"死区"对铁再分布具有重要影响。Redistribution of iron during directional solidification of metallurgical-grade silicon(MG-Si) was conducted at low growth rate. Concentrations of iron were examined by ICP-MS and figured in solid and liquid phases, at grain boundary and in growth direction. Concentrations are significantly different between solid and liquid phases. The thickness of the solute boundary layer is about 4 mm verified by mass balance law, and the effective distribution coefficient is 2.98×10~(-4). Iron element easily segregates at grain boundary at low growth rate. In growth direction, concentrations are almost constant until 86% ingot height, and they do not meet the Scheil equation completely, which is caused by the low growth rate. The effect of convection on the redistribution of iron was discussed in detail. Especially, the "dead zone" of convection plays an important role in the iron redistribution.Projects(51334004,51204143)supported by the National Natural Science Foundation of China;; Project(2006L2003)supported by the Scientific Technological Innovation Platform of Fujian Province,Chin

Effects of Low Energy Carbon Ion and Nitrogen Ion Implantation on Germinant Rate, Growth Weight and Peroxidase of Stevia rebaudiana Bertoni

以经过碳、氮 (75× 1 0 14 ke V/ cm2 )离子注入处理后的甜叶菊 (Stevia rebaudianaBertoni)种子为材料 ,研究低能离子注入对甜叶菊萌发率、生长量及过氧化物同工酶的影响。结果表明 :(1 )萌发期处理组的萌发率低于对照 ,萌发延迟 ,幼苗成活率不及对照组 ;萌发后期处理组的相对生长量、过氧化物酶活性高于对照组。 (2 )幼苗移至实验地种植后 ,处理组幼苗长势明显优于未处理组 ,处理组 60 d蕾株比明显高于对照组。 (3)过氧化物酶同工酶谱分析发现 ,对照组具有完整 6条基本带的植株数为 1 2 ,具有完整 B1、B2基本带的植株数为 2 0 ;C+处理组分别为 5和 1 1 ,N+处理组分别为 5和 6。统计发现低能离子的注入影响最大的是同工酶谱 B1、B2带。 N+处理组生物学负效应大于 C+处理组The paper reports the effects of low energy Carbon and Nitrogen ion (75×10 14 keV/cm 2 )implantation into S. rebaudiana seeds.on germinant rate, relative growth weight and peroxidase of S. rebaudiana. The results showed: (1)The seed germinant rates were lower and seeding servival rates and deve lopment speeds were slower in the treated groups than those in the control in the initial period of seed germinating;but in the late period of seed germinating the relative growth weight and peroxidase activity were higher in treated groups than those in the control.(2)When seedings were transplanted into experimental field the growth and development were speeded up in treated groups than that in the control.The rate of flower bud plants were higher in treated groups than that in the control. (3)The isozymogram of peroxidase by PAGE showed that there were 12 plants which had 1～6 basic bands and 20 plants which had B1,B2 bands in the control,but only there were 5 plants and 11 plants, respectively, in C + treated groups,and there were 5 plants and 6 plants, respectively, in N + treated groups. The result also showed there were more negative effects by ion implantation into S. rebaudiana in N + treated groups than those in C + treated groups in the periods of seed germinating and plant growth.国家基金委重大项目资助课题!( 1 9890 30 0

Analysis of the Content of Stevia Sweeteners by Capillary Zone Electrophoresis

本文介绍了一种用毛细管区带电泳法筛选甜菊糖苷突变体的有效方法。根据实验结果 ,优化的电泳条件为 :60mmol/LTris 硼酸缓冲液 (pH 8.0 ) ,柱温 30℃ ,工作电压 2 5kV。优化条件下 ,甜菊苷 (Ste vioside)迁移时间的R .S .D为 0 .45% (1 5次 ) ,且在 7.45× 1 0 - 5～ 1 .74× 1 0 - 2 mol/L的浓度范围内存在良好的线性关系 (r=0 .9994) ,甜菊主要糖苷在 5min内均可实现分离。在优化条件下 ,本实验研究了低能离子注入后甜菊主要糖苷含量变化 ,结果令人满意。This paper introduced an effect capillary zone electrophoresis method for screening of stevia mutation. According to the experimental results, the optimum separation conditions were selected as: 60 mmol/L Tris tetraborate buffer of pH 8.0, 30 ℃ and 25 KV. Under optimum conditions, the R.S.D. of stevioside migration time for 15 runs was 0.45%. The detector response for stevioside was linear over the range of 7.45×10 -5 ～1.74×10 -2 mol/L (r=0.9994). Stevia main sweeteners cound be separated effectively in less than five minutes. This method was applied for determining the variation of stevia main sweeteners after low_energy ions implantation

21世纪中国金融学教学改革与发展战略

国家教育部新世纪教改工程项目《21 世纪中国金融学专业教育教学改革与发展战略研究》, 目前已取得阶段性成果。2001 年8 月16 日至21 日, 承担该项目的中央财经大学、中国人民大学、厦门大学和复旦大学在青海省西宁市举行了成果交流和研讨会。项目主持人、中央财经大学副校长、金融学博士生导师王广谦教授主持了这次会议, 全国所有有金融学博士学位授权点的高校和科研院所都有代表出席大会, 用主持人的话来说, “全国金融学界顶尖级人物基本上都到了”。出席会议的还有教育部高等教育司刘凤泰副司长和杨志坚处长。与会专家学者回顾了近20 年国内外金融业的迅猛发展, 分析了在21 世纪随着经济全球化、金融国际化对我国经济金融带来的机遇和挑战, 以及对我国金融研究、金融学科建设和人才培养带来的冲击,大家认识到, 经过20 年的改革开放和发展, 目前我国在这些领域虽有长足的进步, 但仍远远不能适应形势发展的要求。要想把我国金融学科建设成国际一流学科, 培养出一流的高素质金融专业人才, 还必须进行一系列改革与创新。与会专家教授根据各自的教学实践, 提出了许多具有建设性的意见。研讨会上发言踊跃、气氛热烈, 不时出现不同观念的碰撞和不同观点的交锋, 对推进金融学科建设十分有益。下面将著名专家教授颇具代表性的观点( 按发言顺序) 择要摘发, 以飨读者, 以推动中国金融学科的建设与繁荣

Damage to mangroves from extreme cold in early 2008 in southern China

通讯作者Author for correspondence (E-mail: [email protected])2008年初,我国南方19个省经历了50年一遇的持续低温雨雪冰冻天气。极端气候对华南沿海各省的红树林区造成不同程度的危害。2008年3月,在我国南方各省红树林区的10个代表性地点,对这次寒害造成的红树植物伤害程度进行了系统的调查。结果表明:冬季低温对红树林的影响极为显著,特别是在低纬度的海南、广西和广东湛江,由于极端低温正值夜间退潮,对红树林的影响更为显著;在纬度较高的福建,本地红树种类秋茄(Kandelia obovata)、桐花树(Aegiceras corniculatum)和白骨壤(Avicennia marina)及引种的木榄(Bruguiera gymnorrhiza)等,由于长期适应于冬季较低的气温或在种植前经过抗寒锻炼,具有较强的抗寒能力。各地主要红树植物中,广布种秋茄、桐花树和白骨壤最为耐寒,其耐寒性均大于红树科的木榄、海莲(Bruguiera sexangula)和红海榄(Rhizophora stylosa)。海桑(Sonneratia caseolaris)对温度的敏感性最强,抗寒能力最低,因此,即使在其原产地海南也受到较为严重的寒害,在纬度更高的引种地出现大面积受害甚至全部死亡,而从孟加拉国引种的无瓣海桑(Sonneratia apetala)却显示出一定的抗寒能力。同一地点的红树植物幼苗的抗寒能力低于大树。此次寒害也造成了苗圃场的种苗大量死亡,成熟的植株提前落花落果,这势必会影响后继一两年内红树林的自然更新和人工造林。因此,在未来红树林造林或人工引种中,一定要考虑到红树植物的抗寒能力。国家自然科学基金(30671646和30700092);厦门大学“闽江学者”启动基

EPON中的可控组播技术研究

以太网无源光网络（EPON）以其树形拓扑结构和高达1 Gbit/s的带宽特性而非常适合应用于广播和组播业务（例如IPTV）。文章主要探讨组播业务在EPON中开展的技术可行性,并从安全性和可维护性考虑,对现有的方案进行改进,加入组播源控制和用户权限控制,从而提高了组播控制的精度。同时给出了扩展运行、管理和维护（OAM）协议的设计方案,根据不同的控制方式,提出了动态和静态配置的控制策略,并进行了实验验证

Cloning and Sequencing of the cDNA of UDPG-glucosyltransferase from Stevia rebaudiana

利用与植物次生代谢产物糖基化相关的UDPG糖基转移酶的特征性保守区域 ,设计了同源简并引物 ,以甜菊基因组DNA为模板 ,PCR扩增获得甜菊糖基转移酶基因片段 .根据获得的基因片段设计引物GSTr和GSTf,分别与cDNA文库的T3 和T7通用引物扩增获得全长核苷酸序列的甜菊糖基转移酶基因 ,定名为sudpt 2 ,该基因全长 16 6 2bp ,包括poly(A)和一个 136 2bp的开放阅读框 ,编码 45 4个氨基酸 .与常见的糖基转移酶基因的相似性达 44 %～ 77% ,且具有UDPG糖基转移酶的特征性保守序列 .分子发育进化分析表明 ,此基因为类黄酮糖基转移酶基因家族成员By using two homologous degenerated primers, DNA fragments encoding steviol UDPG glucosyltransferase were amplified from the leaves of Stevia rebaudiana. The DNA fragment with strong homology to known flavonoid glucosyltransferases was used to design two primers to amplify upstream and downstream cDNA of stevia glucosyltransferase. The cDNA of stevia glucosyltransferase sudpg-2 was 1 662 bp in length, with a poly(A) tail and a 1 362 bp open reading frame which encoded 454 deduced amino acid residues. The deduced amimo acids sequence has 40%～60% identity to other plant glucosyltransferase and includes a part of the glucosyltransferase signature sequence. Molecular phylogenic relations of the deduced amino acids sequences with other plant glucosyltransferase suggested that the steviol UDPG glucosyltransferase belongs to family of flavonoid glucosyltransferases