计算多个费曼图的不变振幅平方的Mathematica软件

利用Mathematica符号处理系统,发展了一种用于直接计算多个费曼图不变振幅平方的软件。利用该软件,用户仅需要根据费曼规则,输入所有有贡献的图的振幅,即可求出粒子过程的不变振幅平方。     

二项风险模型中破产概率上界的估计

目的对二项风险模型中的破产概率的指数上界进行了有效估计。方法主要运用离散的5阶凸随机序的极值分布的理论。结果在离散的5阶凸随机序意义下,获得了破产概率的指数上界的估计。结论模拟结果非常接近精确的指数上界。     

Glutamine stimulates translation of uncoupling protein 2mRNA

Uncoupling protein 2 (UCP2) belongs to a family of transporters/exchangers of the mitochondrial inner membrane. Using cell lines representing natural sites of UCP2 expression (macrophages, colonocytes, pancreatic beta cells), we show that UCP2 expression is stimulated by glutamine at physiological concentrations. This control is exerted at the translational level. We demonstrate that the upstream open reading frame (ORF1) in the 5’ untranslated region (5’UTR) of the UCP2 mRNA is required for this stimulation to take place. Cloning of the 5’ UTR of the UCP2 mRNA in front of a GFP cDNA resulted in a reporter gene with which GFP expression could be induced by glutamine. An effect of glutamine on translation of a given mRNA has not been identified before, and this is the first evidence for a link between UCP2 and glutamine, an amino acid oxidized by immune cells or intestinal epithelium and playing a role in the control of insulin secretion. Received 26 January 2007; received after revision 16 April 2007; accepted 8 May 2007 C. Hurtaud, C. Gelly: These authors contributed equally to this work.     

Influence of temperature on taste perception

Daily experience tells us that temperature has a strong influence on how we taste. Despite the longstanding interest of many specialists in this aspect of taste, we are only starting to understand the molecular mechanisms underlying the temperature dependence of different taste modalities. Recent research has led to the identification of some strong thermosensitive molecules in the taste transduction pathway. The cold activation of the epithelial Na⁺ channel and the heat activation of the taste variant of the vanilloid receptor (TRPV1t) may underlie the temperature dependence of salt responses. Heat activation of the transient receptor potential channel TRPM5 explains the enhancement of sweet taste perception by warm temperatures. Current development of methods to study taste cell physiology will help to determine the contribution of other temperature-sensitive events in the taste transduction pathways. Vice versa, the analysis of the thermodynamic properties of these events may assist to unveil the nature of several taste processes. Received 29 August 2006; received after revision 5 October 2006; accepted 20 November 2006     

弹性体变形分析的符号表达式系统

从一般的弹性体变形理论出发,利用Mathematica系统,初步建立了弹性体变形分析的符号表达式系统．该系统可以自动地完成弹性体变形理论各种张量及方程的推导过程,给出相应的精确符号表达式;自动地完成指定符号表达式的数值化与图形化过程     

Cr(Ⅵ)氧化5-溴水杨基荧光酮光度法测定微量Cr

在硫酸介质中,Ｃｒ（Ⅵ）将５－溴水杨基荧光酮（５－ＢＳＡＦ）氧化成最大吸收峰为４９４ｎｍ的有色产物,其表观摩尔吸光系数为３．６７×１０４Ｌ／（ｍｏｌ·ｃｍ）,Ｃｒ（Ⅵ）量在０～１５ｍｇ／２５Ｌ范围内服从比耳定律。用此法测定了电镀废液中微量Ｃｒ,回收率为９８．５％～１０３％,相对标准偏差为２．６％     

通过数据交换在CATIA V5中创建工程图

介绍了在CATIA V5中创建符合中国国家标准(GB)规定的图框和标题栏的几种方法,重点讨论了共享AutoCAD的DXF数据文件的创建方法,该法具有简便、实用、高效的特点.通过它创建一系列CATDrawing样板文件对规范CATIA V5工程图纸、进行产品数据管理(PDM)和提高绘图效率具有现实意义.文中介绍的滑块零件从3D实体造型到2D工程图生成的应用实例可为读者利用CATIA V5进行零件或产品工程图设计提供参考.     

注射H5N1亚型禽流感抗体鸡的血清抗体水平消长规律监测

为了解H5N1亚型禽流感纯化抗体(IgG)在鸡体内消长规律,用血凝抑制试验检测了不同注射时间分离的血清样品。结果表明IgG接种后第1至5天,血清抗体滴度恒定在24~26,第8天为23~24,第10天以后几乎检测不到抗体。上述数据表明注射滴度为29的抗体液1mL可有效保护肉鸡免受禽流感病毒的感染,有效期为8天。     

新型三杆五自由度虚轴机床五坐标加工数学模型

研制了一种新型三杆五自由度虚轴机床,建立了五坐标加工数学模型·利用刀具轴线与加工轨迹上曲面法向量的关系及三杆虚轴机床平动的特性,确定了三驱动杆的长度及两驱动轴的转角·该表达式为显式,形式简单,计算量小,易于实现机床五坐标加工的实时控制·另外给出了机床运动学正解及雅可比矩阵·正解及雅可比矩阵为显式,为机床的灵巧性分析、速度分析及误差补偿提供了条件·这种虚轴机床可以实现复杂形面的五坐标加工·     

含多个手性中心的麻黄碱衍生物的合成

首次利用天然麻黄碱作为亲核试剂与手性5－烷氧基－3,4－二卤－2（5H）－呋喃酮反应,得到了含多个手性中心的麻黄碱衍生物5－（S）－烷氧基－4－麻黄碱基－3－卤－2（5H）－呋喃酮,产率70％－80％。所有化合物均经IR,^1HNMR,MS以及元素分析得到确证,为室温下方便地制备含多个手性中心的麻黄碱衍生物化合物提供了一条可能的新途径。